ETH Price: $1,820.94 (+0.79%)

Transaction Decoder

Block:
19521480 at Mar-26-2024 10:11:59 PM +UTC
Transaction Fee:
0.00434078059634295 ETH $7.90
Gas Used:
125,449 Gas / 34.60195455 Gwei

Emitted Events:

404 WETH9.Transfer( src=0x44f9469D0d5393d3a01A0D4Fa14FE7713c1aD1f7, dst=[Receiver] ZeroEx, wad=163050299247593064 )
405 Dragon.Transfer( from=[Sender] 0xbadced52d63e67d830ebf142edfe98656c3b3652, to=0x44f9469D0d5393d3a01A0D4Fa14FE7713c1aD1f7, value=10230886924963358336155 )
406 0x44f9469d0d5393d3a01a0d4fa14fe7713c1ad1f7.0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67( 0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67, 0x000000000000000000000000def1c0ded9bec7f1a1670819833240f027b25eff, 0x000000000000000000000000def1c0ded9bec7f1a1670819833240f027b25eff, 00000000000000000000000000000000000000000000022a9e13ecb12d7e649b, fffffffffffffffffffffffffffffffffffffffffffffffffdbcba9de0d37998, 0000000000000000000000000000000000000000010577050fa296184f21a35c, 0000000000000000000000000000000000000000000000c302d03450e67bc608, fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe5069 )
407 WETH9.Withdrawal( src=[Receiver] ZeroEx, wad=163050299247593064 )

Account State Difference:

  Address   Before After State Difference Code
0x419c4dB4...8D9fDA05E
0x44f9469D...13c1aD1f7
(Uniswap V3: DRGN 2)
(Titan Builder)
5.427684285960236257 Eth5.427684411409236257 Eth0.000000125449
0xBAdCed52...56c3B3652
0.006333700559224796 Eth
Nonce: 24
0.16504321921047491 Eth
Nonce: 25
0.158709518651250114
0xC02aaA39...83C756Cc2 3,014,507.644711335306172627 Eth3,014,507.481661036058579563 Eth0.163050299247593064

Execution Trace

ZeroEx.803ba26d( )
  • UniswapV3Feature.sellTokenForEthToUniswapV3( encodedPath=0x419C4DB4B9E25D6DB2AD9691CCB832C8D9FDA05E002710C02AAA39B223FE8D0A0E5C4F27EAD9083C756CC2, sellAmount=10230886924963358336155, minBuyAmount=158158790270165250, recipient=0x0000000000000000000000000000000000000000 ) => ( buyAmount=163050299247593064 )
    • Uniswap V3: DRGN 2.128acb08( )
      • WETH9.transfer( dst=0xDef1C0ded9bec7F1a1670819833240f027b25EfF, wad=163050299247593064 ) => ( True )
      • Dragon.balanceOf( _owner=0x44f9469D0d5393d3a01A0D4Fa14FE7713c1aD1f7 ) => ( balance=2612886521848177291516125 )
      • ZeroEx.fa461e33( )
        • UniswapV3Feature.uniswapV3SwapCallback( amount0Delta=10230886924963358336155, amount1Delta=-163050299247593064, data=0x000000000000000000000000419C4DB4B9E25D6DB2AD9691CCB832C8D9FDA05E000000000000000000000000C02AAA39B223FE8D0A0E5C4F27EAD9083C756CC20000000000000000000000000000000000000000000000000000000000002710000000000000000000000000BADCED52D63E67D830EBF142EDFE98656C3B3652 )
          • Dragon.transferFrom( _from=0xBAdCed52d63E67d830ebF142edFE98656c3B3652, _to=0x44f9469D0d5393d3a01A0D4Fa14FE7713c1aD1f7, _value=10230886924963358336155 ) => ( True )
          • Dragon.balanceOf( _owner=0x44f9469D0d5393d3a01A0D4Fa14FE7713c1aD1f7 ) => ( balance=2623117408773140649852280 )
          • WETH9.withdraw( wad=163050299247593064 )
            • ETH 0.163050299247593064 ZeroEx.CALL( )
            • ETH 0.163050299247593064 0xbadced52d63e67d830ebf142edfe98656c3b3652.CALL( )
              File 1 of 4: ZeroEx
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
              import "./migrations/LibBootstrap.sol";
              import "./features/Bootstrap.sol";
              import "./storage/LibProxyStorage.sol";
              import "./errors/LibProxyRichErrors.sol";
              /// @dev An extensible proxy contract that serves as a universal entry point for
              ///      interacting with the 0x protocol.
              contract ZeroEx {
                  // solhint-disable separate-by-one-line-in-contract,indent,var-name-mixedcase
                  using LibBytesV06 for bytes;
                  /// @dev Construct this contract and register the `Bootstrap` feature.
                  ///      After constructing this contract, `bootstrap()` should be called
                  ///      to seed the initial feature set.
                  constructor() public {
                      // Temporarily create and register the bootstrap feature.
                      // It will deregister itself after `bootstrap()` has been called.
                      Bootstrap bootstrap = new Bootstrap(msg.sender);
                      LibProxyStorage.getStorage().impls[bootstrap.bootstrap.selector] =
                          address(bootstrap);
                  }
                  // solhint-disable state-visibility
                  /// @dev Forwards calls to the appropriate implementation contract.
                  fallback() external payable {
                      bytes4 selector = msg.data.readBytes4(0);
                      address impl = getFunctionImplementation(selector);
                      if (impl == address(0)) {
                          _revertWithData(LibProxyRichErrors.NotImplementedError(selector));
                      }
                      (bool success, bytes memory resultData) = impl.delegatecall(msg.data);
                      if (!success) {
                          _revertWithData(resultData);
                      }
                      _returnWithData(resultData);
                  }
                  /// @dev Fallback for just receiving ether.
                  receive() external payable {}
                  // solhint-enable state-visibility
                  /// @dev Get the implementation contract of a registered function.
                  /// @param selector The function selector.
                  /// @return impl The implementation contract address.
                  function getFunctionImplementation(bytes4 selector)
                      public
                      view
                      returns (address impl)
                  {
                      return LibProxyStorage.getStorage().impls[selector];
                  }
                  /// @dev Revert with arbitrary bytes.
                  /// @param data Revert data.
                  function _revertWithData(bytes memory data) private pure {
                      assembly { revert(add(data, 32), mload(data)) }
                  }
                  /// @dev Return with arbitrary bytes.
                  /// @param data Return data.
                  function _returnWithData(bytes memory data) private pure {
                      assembly { return(add(data, 32), mload(data)) }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./errors/LibBytesRichErrorsV06.sol";
              import "./errors/LibRichErrorsV06.sol";
              library LibBytesV06 {
                  using LibBytesV06 for bytes;
                  /// @dev Gets the memory address for a byte array.
                  /// @param input Byte array to lookup.
                  /// @return memoryAddress Memory address of byte array. This
                  ///         points to the header of the byte array which contains
                  ///         the length.
                  function rawAddress(bytes memory input)
                      internal
                      pure
                      returns (uint256 memoryAddress)
                  {
                      assembly {
                          memoryAddress := input
                      }
                      return memoryAddress;
                  }
                  /// @dev Gets the memory address for the contents of a byte array.
                  /// @param input Byte array to lookup.
                  /// @return memoryAddress Memory address of the contents of the byte array.
                  function contentAddress(bytes memory input)
                      internal
                      pure
                      returns (uint256 memoryAddress)
                  {
                      assembly {
                          memoryAddress := add(input, 32)
                      }
                      return memoryAddress;
                  }
                  /// @dev Copies `length` bytes from memory location `source` to `dest`.
                  /// @param dest memory address to copy bytes to.
                  /// @param source memory address to copy bytes from.
                  /// @param length number of bytes to copy.
                  function memCopy(
                      uint256 dest,
                      uint256 source,
                      uint256 length
                  )
                      internal
                      pure
                  {
                      if (length < 32) {
                          // Handle a partial word by reading destination and masking
                          // off the bits we are interested in.
                          // This correctly handles overlap, zero lengths and source == dest
                          assembly {
                              let mask := sub(exp(256, sub(32, length)), 1)
                              let s := and(mload(source), not(mask))
                              let d := and(mload(dest), mask)
                              mstore(dest, or(s, d))
                          }
                      } else {
                          // Skip the O(length) loop when source == dest.
                          if (source == dest) {
                              return;
                          }
                          // For large copies we copy whole words at a time. The final
                          // word is aligned to the end of the range (instead of after the
                          // previous) to handle partial words. So a copy will look like this:
                          //
                          //  ####
                          //      ####
                          //          ####
                          //            ####
                          //
                          // We handle overlap in the source and destination range by
                          // changing the copying direction. This prevents us from
                          // overwriting parts of source that we still need to copy.
                          //
                          // This correctly handles source == dest
                          //
                          if (source > dest) {
                              assembly {
                                  // We subtract 32 from `sEnd` and `dEnd` because it
                                  // is easier to compare with in the loop, and these
                                  // are also the addresses we need for copying the
                                  // last bytes.
                                  length := sub(length, 32)
                                  let sEnd := add(source, length)
                                  let dEnd := add(dest, length)
                                  // Remember the last 32 bytes of source
                                  // This needs to be done here and not after the loop
                                  // because we may have overwritten the last bytes in
                                  // source already due to overlap.
                                  let last := mload(sEnd)
                                  // Copy whole words front to back
                                  // Note: the first check is always true,
                                  // this could have been a do-while loop.
                                  // solhint-disable-next-line no-empty-blocks
                                  for {} lt(source, sEnd) {} {
                                      mstore(dest, mload(source))
                                      source := add(source, 32)
                                      dest := add(dest, 32)
                                  }
                                  // Write the last 32 bytes
                                  mstore(dEnd, last)
                              }
                          } else {
                              assembly {
                                  // We subtract 32 from `sEnd` and `dEnd` because those
                                  // are the starting points when copying a word at the end.
                                  length := sub(length, 32)
                                  let sEnd := add(source, length)
                                  let dEnd := add(dest, length)
                                  // Remember the first 32 bytes of source
                                  // This needs to be done here and not after the loop
                                  // because we may have overwritten the first bytes in
                                  // source already due to overlap.
                                  let first := mload(source)
                                  // Copy whole words back to front
                                  // We use a signed comparisson here to allow dEnd to become
                                  // negative (happens when source and dest < 32). Valid
                                  // addresses in local memory will never be larger than
                                  // 2**255, so they can be safely re-interpreted as signed.
                                  // Note: the first check is always true,
                                  // this could have been a do-while loop.
                                  // solhint-disable-next-line no-empty-blocks
                                  for {} slt(dest, dEnd) {} {
                                      mstore(dEnd, mload(sEnd))
                                      sEnd := sub(sEnd, 32)
                                      dEnd := sub(dEnd, 32)
                                  }
                                  // Write the first 32 bytes
                                  mstore(dest, first)
                              }
                          }
                      }
                  }
                  /// @dev Returns a slices from a byte array.
                  /// @param b The byte array to take a slice from.
                  /// @param from The starting index for the slice (inclusive).
                  /// @param to The final index for the slice (exclusive).
                  /// @return result The slice containing bytes at indices [from, to)
                  function slice(
                      bytes memory b,
                      uint256 from,
                      uint256 to
                  )
                      internal
                      pure
                      returns (bytes memory result)
                  {
                      // Ensure that the from and to positions are valid positions for a slice within
                      // the byte array that is being used.
                      if (from > to) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.FromLessThanOrEqualsToRequired,
                              from,
                              to
                          ));
                      }
                      if (to > b.length) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.ToLessThanOrEqualsLengthRequired,
                              to,
                              b.length
                          ));
                      }
                      // Create a new bytes structure and copy contents
                      result = new bytes(to - from);
                      memCopy(
                          result.contentAddress(),
                          b.contentAddress() + from,
                          result.length
                      );
                      return result;
                  }
                  /// @dev Returns a slice from a byte array without preserving the input.
                  ///      When `from == 0`, the original array will match the slice.
                  ///      In other cases its state will be corrupted.
                  /// @param b The byte array to take a slice from. Will be destroyed in the process.
                  /// @param from The starting index for the slice (inclusive).
                  /// @param to The final index for the slice (exclusive).
                  /// @return result The slice containing bytes at indices [from, to)
                  function sliceDestructive(
                      bytes memory b,
                      uint256 from,
                      uint256 to
                  )
                      internal
                      pure
                      returns (bytes memory result)
                  {
                      // Ensure that the from and to positions are valid positions for a slice within
                      // the byte array that is being used.
                      if (from > to) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.FromLessThanOrEqualsToRequired,
                              from,
                              to
                          ));
                      }
                      if (to > b.length) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.ToLessThanOrEqualsLengthRequired,
                              to,
                              b.length
                          ));
                      }
                      // Create a new bytes structure around [from, to) in-place.
                      assembly {
                          result := add(b, from)
                          mstore(result, sub(to, from))
                      }
                      return result;
                  }
                  /// @dev Pops the last byte off of a byte array by modifying its length.
                  /// @param b Byte array that will be modified.
                  /// @return result The byte that was popped off.
                  function popLastByte(bytes memory b)
                      internal
                      pure
                      returns (bytes1 result)
                  {
                      if (b.length == 0) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanZeroRequired,
                              b.length,
                              0
                          ));
                      }
                      // Store last byte.
                      result = b[b.length - 1];
                      assembly {
                          // Decrement length of byte array.
                          let newLen := sub(mload(b), 1)
                          mstore(b, newLen)
                      }
                      return result;
                  }
                  /// @dev Tests equality of two byte arrays.
                  /// @param lhs First byte array to compare.
                  /// @param rhs Second byte array to compare.
                  /// @return equal True if arrays are the same. False otherwise.
                  function equals(
                      bytes memory lhs,
                      bytes memory rhs
                  )
                      internal
                      pure
                      returns (bool equal)
                  {
                      // Keccak gas cost is 30 + numWords * 6. This is a cheap way to compare.
                      // We early exit on unequal lengths, but keccak would also correctly
                      // handle this.
                      return lhs.length == rhs.length && keccak256(lhs) == keccak256(rhs);
                  }
                  /// @dev Reads an address from a position in a byte array.
                  /// @param b Byte array containing an address.
                  /// @param index Index in byte array of address.
                  /// @return result address from byte array.
                  function readAddress(
                      bytes memory b,
                      uint256 index
                  )
                      internal
                      pure
                      returns (address result)
                  {
                      if (b.length < index + 20) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsTwentyRequired,
                              b.length,
                              index + 20 // 20 is length of address
                          ));
                      }
                      // Add offset to index:
                      // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
                      // 2. Account for size difference between address length and 32-byte storage word (subtract 12 from index)
                      index += 20;
                      // Read address from array memory
                      assembly {
                          // 1. Add index to address of bytes array
                          // 2. Load 32-byte word from memory
                          // 3. Apply 20-byte mask to obtain address
                          result := and(mload(add(b, index)), 0xffffffffffffffffffffffffffffffffffffffff)
                      }
                      return result;
                  }
                  /// @dev Writes an address into a specific position in a byte array.
                  /// @param b Byte array to insert address into.
                  /// @param index Index in byte array of address.
                  /// @param input Address to put into byte array.
                  function writeAddress(
                      bytes memory b,
                      uint256 index,
                      address input
                  )
                      internal
                      pure
                  {
                      if (b.length < index + 20) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsTwentyRequired,
                              b.length,
                              index + 20 // 20 is length of address
                          ));
                      }
                      // Add offset to index:
                      // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
                      // 2. Account for size difference between address length and 32-byte storage word (subtract 12 from index)
                      index += 20;
                      // Store address into array memory
                      assembly {
                          // The address occupies 20 bytes and mstore stores 32 bytes.
                          // First fetch the 32-byte word where we'll be storing the address, then
                          // apply a mask so we have only the bytes in the word that the address will not occupy.
                          // Then combine these bytes with the address and store the 32 bytes back to memory with mstore.
                          // 1. Add index to address of bytes array
                          // 2. Load 32-byte word from memory
                          // 3. Apply 12-byte mask to obtain extra bytes occupying word of memory where we'll store the address
                          let neighbors := and(
                              mload(add(b, index)),
                              0xffffffffffffffffffffffff0000000000000000000000000000000000000000
                          )
                          // Make sure input address is clean.
                          // (Solidity does not guarantee this)
                          input := and(input, 0xffffffffffffffffffffffffffffffffffffffff)
                          // Store the neighbors and address into memory
                          mstore(add(b, index), xor(input, neighbors))
                      }
                  }
                  /// @dev Reads a bytes32 value from a position in a byte array.
                  /// @param b Byte array containing a bytes32 value.
                  /// @param index Index in byte array of bytes32 value.
                  /// @return result bytes32 value from byte array.
                  function readBytes32(
                      bytes memory b,
                      uint256 index
                  )
                      internal
                      pure
                      returns (bytes32 result)
                  {
                      if (b.length < index + 32) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsThirtyTwoRequired,
                              b.length,
                              index + 32
                          ));
                      }
                      // Arrays are prefixed by a 256 bit length parameter
                      index += 32;
                      // Read the bytes32 from array memory
                      assembly {
                          result := mload(add(b, index))
                      }
                      return result;
                  }
                  /// @dev Writes a bytes32 into a specific position in a byte array.
                  /// @param b Byte array to insert <input> into.
                  /// @param index Index in byte array of <input>.
                  /// @param input bytes32 to put into byte array.
                  function writeBytes32(
                      bytes memory b,
                      uint256 index,
                      bytes32 input
                  )
                      internal
                      pure
                  {
                      if (b.length < index + 32) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsThirtyTwoRequired,
                              b.length,
                              index + 32
                          ));
                      }
                      // Arrays are prefixed by a 256 bit length parameter
                      index += 32;
                      // Read the bytes32 from array memory
                      assembly {
                          mstore(add(b, index), input)
                      }
                  }
                  /// @dev Reads a uint256 value from a position in a byte array.
                  /// @param b Byte array containing a uint256 value.
                  /// @param index Index in byte array of uint256 value.
                  /// @return result uint256 value from byte array.
                  function readUint256(
                      bytes memory b,
                      uint256 index
                  )
                      internal
                      pure
                      returns (uint256 result)
                  {
                      result = uint256(readBytes32(b, index));
                      return result;
                  }
                  /// @dev Writes a uint256 into a specific position in a byte array.
                  /// @param b Byte array to insert <input> into.
                  /// @param index Index in byte array of <input>.
                  /// @param input uint256 to put into byte array.
                  function writeUint256(
                      bytes memory b,
                      uint256 index,
                      uint256 input
                  )
                      internal
                      pure
                  {
                      writeBytes32(b, index, bytes32(input));
                  }
                  /// @dev Reads an unpadded bytes4 value from a position in a byte array.
                  /// @param b Byte array containing a bytes4 value.
                  /// @param index Index in byte array of bytes4 value.
                  /// @return result bytes4 value from byte array.
                  function readBytes4(
                      bytes memory b,
                      uint256 index
                  )
                      internal
                      pure
                      returns (bytes4 result)
                  {
                      if (b.length < index + 4) {
                          LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                              LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsFourRequired,
                              b.length,
                              index + 4
                          ));
                      }
                      // Arrays are prefixed by a 32 byte length field
                      index += 32;
                      // Read the bytes4 from array memory
                      assembly {
                          result := mload(add(b, index))
                          // Solidity does not require us to clean the trailing bytes.
                          // We do it anyway
                          result := and(result, 0xFFFFFFFF00000000000000000000000000000000000000000000000000000000)
                      }
                      return result;
                  }
                  /// @dev Writes a new length to a byte array.
                  ///      Decreasing length will lead to removing the corresponding lower order bytes from the byte array.
                  ///      Increasing length may lead to appending adjacent in-memory bytes to the end of the byte array.
                  /// @param b Bytes array to write new length to.
                  /// @param length New length of byte array.
                  function writeLength(bytes memory b, uint256 length)
                      internal
                      pure
                  {
                      assembly {
                          mstore(b, length)
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibBytesRichErrorsV06 {
                  enum InvalidByteOperationErrorCodes {
                      FromLessThanOrEqualsToRequired,
                      ToLessThanOrEqualsLengthRequired,
                      LengthGreaterThanZeroRequired,
                      LengthGreaterThanOrEqualsFourRequired,
                      LengthGreaterThanOrEqualsTwentyRequired,
                      LengthGreaterThanOrEqualsThirtyTwoRequired,
                      LengthGreaterThanOrEqualsNestedBytesLengthRequired,
                      DestinationLengthGreaterThanOrEqualSourceLengthRequired
                  }
                  // bytes4(keccak256("InvalidByteOperationError(uint8,uint256,uint256)"))
                  bytes4 internal constant INVALID_BYTE_OPERATION_ERROR_SELECTOR =
                      0x28006595;
                  // solhint-disable func-name-mixedcase
                  function InvalidByteOperationError(
                      InvalidByteOperationErrorCodes errorCode,
                      uint256 offset,
                      uint256 required
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          INVALID_BYTE_OPERATION_ERROR_SELECTOR,
                          errorCode,
                          offset,
                          required
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibRichErrorsV06 {
                  // bytes4(keccak256("Error(string)"))
                  bytes4 internal constant STANDARD_ERROR_SELECTOR = 0x08c379a0;
                  // solhint-disable func-name-mixedcase
                  /// @dev ABI encode a standard, string revert error payload.
                  ///      This is the same payload that would be included by a `revert(string)`
                  ///      solidity statement. It has the function signature `Error(string)`.
                  /// @param message The error string.
                  /// @return The ABI encoded error.
                  function StandardError(string memory message)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          STANDARD_ERROR_SELECTOR,
                          bytes(message)
                      );
                  }
                  // solhint-enable func-name-mixedcase
                  /// @dev Reverts an encoded rich revert reason `errorData`.
                  /// @param errorData ABI encoded error data.
                  function rrevert(bytes memory errorData)
                      internal
                      pure
                  {
                      assembly {
                          revert(add(errorData, 0x20), mload(errorData))
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../errors/LibProxyRichErrors.sol";
              library LibBootstrap {
                  /// @dev Magic bytes returned by the bootstrapper to indicate success.
                  ///      This is `keccack('BOOTSTRAP_SUCCESS')`.
                  bytes4 internal constant BOOTSTRAP_SUCCESS = 0xd150751b;
                  using LibRichErrorsV06 for bytes;
                  /// @dev Perform a delegatecall and ensure it returns the magic bytes.
                  /// @param target The call target.
                  /// @param data The call data.
                  function delegatecallBootstrapFunction(
                      address target,
                      bytes memory data
                  )
                      internal
                  {
                      (bool success, bytes memory resultData) = target.delegatecall(data);
                      if (!success ||
                          resultData.length != 32 ||
                          abi.decode(resultData, (bytes4)) != BOOTSTRAP_SUCCESS)
                      {
                          LibProxyRichErrors.BootstrapCallFailedError(target, resultData).rrevert();
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibProxyRichErrors {
                  // solhint-disable func-name-mixedcase
                  function NotImplementedError(bytes4 selector)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("NotImplementedError(bytes4)")),
                          selector
                      );
                  }
                  function InvalidBootstrapCallerError(address actual, address expected)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InvalidBootstrapCallerError(address,address)")),
                          actual,
                          expected
                      );
                  }
                  function InvalidDieCallerError(address actual, address expected)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InvalidDieCallerError(address,address)")),
                          actual,
                          expected
                      );
                  }
                  function BootstrapCallFailedError(address target, bytes memory resultData)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("BootstrapCallFailedError(address,bytes)")),
                          target,
                          resultData
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../migrations/LibBootstrap.sol";
              import "../storage/LibProxyStorage.sol";
              import "./IBootstrap.sol";
              /// @dev Detachable `bootstrap()` feature.
              contract Bootstrap is
                  IBootstrap
              {
                  // solhint-disable state-visibility,indent
                  /// @dev The ZeroEx contract.
                  ///      This has to be immutable to persist across delegatecalls.
                  address immutable private _deployer;
                  /// @dev The implementation address of this contract.
                  ///      This has to be immutable to persist across delegatecalls.
                  address immutable private _implementation;
                  /// @dev The deployer.
                  ///      This has to be immutable to persist across delegatecalls.
                  address immutable private _bootstrapCaller;
                  // solhint-enable state-visibility,indent
                  using LibRichErrorsV06 for bytes;
                  /// @dev Construct this contract and set the bootstrap migration contract.
                  ///      After constructing this contract, `bootstrap()` should be called
                  ///      to seed the initial feature set.
                  /// @param bootstrapCaller The allowed caller of `bootstrap()`.
                  constructor(address bootstrapCaller) public {
                      _deployer = msg.sender;
                      _implementation = address(this);
                      _bootstrapCaller = bootstrapCaller;
                  }
                  /// @dev Bootstrap the initial feature set of this contract by delegatecalling
                  ///      into `target`. Before exiting the `bootstrap()` function will
                  ///      deregister itself from the proxy to prevent being called again.
                  /// @param target The bootstrapper contract address.
                  /// @param callData The call data to execute on `target`.
                  function bootstrap(address target, bytes calldata callData) external override {
                      // Only the bootstrap caller can call this function.
                      if (msg.sender != _bootstrapCaller) {
                          LibProxyRichErrors.InvalidBootstrapCallerError(
                              msg.sender,
                              _bootstrapCaller
                          ).rrevert();
                      }
                      // Deregister.
                      LibProxyStorage.getStorage().impls[this.bootstrap.selector] = address(0);
                      // Self-destruct.
                      Bootstrap(_implementation).die();
                      // Call the bootstrapper.
                      LibBootstrap.delegatecallBootstrapFunction(target, callData);
                  }
                  /// @dev Self-destructs this contract.
                  ///      Can only be called by the deployer.
                  function die() external {
                      if (msg.sender != _deployer) {
                          LibProxyRichErrors.InvalidDieCallerError(msg.sender, _deployer).rrevert();
                      }
                      selfdestruct(msg.sender);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "./LibStorage.sol";
              /// @dev Storage helpers for the proxy contract.
              library LibProxyStorage {
                  /// @dev Storage bucket for proxy contract.
                  struct Storage {
                      // Mapping of function selector -> function implementation
                      mapping(bytes4 => address) impls;
                      // The owner of the proxy contract.
                      address owner;
                  }
                  /// @dev Get the storage bucket for this contract.
                  function getStorage() internal pure returns (Storage storage stor) {
                      uint256 storageSlot = LibStorage.getStorageSlot(
                          LibStorage.StorageId.Proxy
                      );
                      // Dip into assembly to change the slot pointed to by the local
                      // variable `stor`.
                      // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                      assembly { stor_slot := storageSlot }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev Common storage helpers
              library LibStorage {
                  /// @dev What to bit-shift a storage ID by to get its slot.
                  ///      This gives us a maximum of 2**128 inline fields in each bucket.
                  uint256 private constant STORAGE_SLOT_EXP = 128;
                  /// @dev Storage IDs for feature storage buckets.
                  ///      WARNING: APPEND-ONLY.
                  enum StorageId {
                      Proxy,
                      SimpleFunctionRegistry,
                      Ownable,
                      TokenSpender,
                      TransformERC20
                  }
                  /// @dev Get the storage slot given a storage ID. We assign unique, well-spaced
                  ///     slots to storage bucket variables to ensure they do not overlap.
                  ///     See: https://solidity.readthedocs.io/en/v0.6.6/assembly.html#access-to-external-variables-functions-and-libraries
                  /// @param storageId An entry in `StorageId`
                  /// @return slot The storage slot.
                  function getStorageSlot(StorageId storageId)
                      internal
                      pure
                      returns (uint256 slot)
                  {
                      // This should never overflow with a reasonable `STORAGE_SLOT_EXP`
                      // because Solidity will do a range check on `storageId` during the cast.
                      return (uint256(storageId) + 1) << STORAGE_SLOT_EXP;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev Detachable `bootstrap()` feature.
              interface IBootstrap {
                  /// @dev Bootstrap the initial feature set of this contract by delegatecalling
                  ///      into `target`. Before exiting the `bootstrap()` function will
                  ///      deregister itself from the proxy to prevent being called again.
                  /// @param target The bootstrapper contract address.
                  /// @param callData The call data to execute on `target`.
                  function bootstrap(address target, bytes calldata callData) external;
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibCommonRichErrors {
                  // solhint-disable func-name-mixedcase
                  function OnlyCallableBySelfError(address sender)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("OnlyCallableBySelfError(address)")),
                          sender
                      );
                  }
                  function IllegalReentrancyError()
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("IllegalReentrancyError()"))
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibOwnableRichErrors {
                  // solhint-disable func-name-mixedcase
                  function OnlyOwnerError(
                      address sender,
                      address owner
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("OnlyOwnerError(address,address)")),
                          sender,
                          owner
                      );
                  }
                  function TransferOwnerToZeroError()
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("TransferOwnerToZeroError()"))
                      );
                  }
                  function MigrateCallFailedError(address target, bytes memory resultData)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("MigrateCallFailedError(address,bytes)")),
                          target,
                          resultData
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibSimpleFunctionRegistryRichErrors {
                  // solhint-disable func-name-mixedcase
                  function NotInRollbackHistoryError(bytes4 selector, address targetImpl)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("NotInRollbackHistoryError(bytes4,address)")),
                          selector,
                          targetImpl
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibSpenderRichErrors {
                  // solhint-disable func-name-mixedcase
                  function SpenderERC20TransferFromFailedError(
                      address token,
                      address owner,
                      address to,
                      uint256 amount,
                      bytes memory errorData
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("SpenderERC20TransferFromFailedError(address,address,address,uint256,bytes)")),
                          token,
                          owner,
                          to,
                          amount,
                          errorData
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibTransformERC20RichErrors {
                  // solhint-disable func-name-mixedcase,separate-by-one-line-in-contract
                  function InsufficientEthAttachedError(
                      uint256 ethAttached,
                      uint256 ethNeeded
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InsufficientEthAttachedError(uint256,uint256)")),
                          ethAttached,
                          ethNeeded
                      );
                  }
                  function IncompleteTransformERC20Error(
                      address outputToken,
                      uint256 outputTokenAmount,
                      uint256 minOutputTokenAmount
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("IncompleteTransformERC20Error(address,uint256,uint256)")),
                          outputToken,
                          outputTokenAmount,
                          minOutputTokenAmount
                      );
                  }
                  function NegativeTransformERC20OutputError(
                      address outputToken,
                      uint256 outputTokenLostAmount
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("NegativeTransformERC20OutputError(address,uint256)")),
                          outputToken,
                          outputTokenLostAmount
                      );
                  }
                  function TransformerFailedError(
                      address transformer,
                      bytes memory transformerData,
                      bytes memory resultData
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("TransformerFailedError(address,bytes,bytes)")),
                          transformer,
                          transformerData,
                          resultData
                      );
                  }
                  // Common Transformer errors ///////////////////////////////////////////////
                  function OnlyCallableByDeployerError(
                      address caller,
                      address deployer
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("OnlyCallableByDeployerError(address,address)")),
                          caller,
                          deployer
                      );
                  }
                  function InvalidExecutionContextError(
                      address actualContext,
                      address expectedContext
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InvalidExecutionContextError(address,address)")),
                          actualContext,
                          expectedContext
                      );
                  }
                  enum InvalidTransformDataErrorCode {
                      INVALID_TOKENS,
                      INVALID_ARRAY_LENGTH
                  }
                  function InvalidTransformDataError(
                      InvalidTransformDataErrorCode errorCode,
                      bytes memory transformData
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InvalidTransformDataError(uint8,bytes)")),
                          errorCode,
                          transformData
                      );
                  }
                  // FillQuoteTransformer errors /////////////////////////////////////////////
                  function IncompleteFillSellQuoteError(
                      address sellToken,
                      uint256 soldAmount,
                      uint256 sellAmount
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("IncompleteFillSellQuoteError(address,uint256,uint256)")),
                          sellToken,
                          soldAmount,
                          sellAmount
                      );
                  }
                  function IncompleteFillBuyQuoteError(
                      address buyToken,
                      uint256 boughtAmount,
                      uint256 buyAmount
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("IncompleteFillBuyQuoteError(address,uint256,uint256)")),
                          buyToken,
                          boughtAmount,
                          buyAmount
                      );
                  }
                  function InsufficientTakerTokenError(
                      uint256 tokenBalance,
                      uint256 tokensNeeded
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InsufficientTakerTokenError(uint256,uint256)")),
                          tokenBalance,
                          tokensNeeded
                      );
                  }
                  function InsufficientProtocolFeeError(
                      uint256 ethBalance,
                      uint256 ethNeeded
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InsufficientProtocolFeeError(uint256,uint256)")),
                          ethBalance,
                          ethNeeded
                      );
                  }
                  function InvalidERC20AssetDataError(
                      bytes memory assetData
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InvalidERC20AssetDataError(bytes)")),
                          assetData
                      );
                  }
                  function InvalidTakerFeeTokenError(
                      address token
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("InvalidTakerFeeTokenError(address)")),
                          token
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibWalletRichErrors {
                  // solhint-disable func-name-mixedcase
                  function WalletExecuteCallFailedError(
                      address wallet,
                      address callTarget,
                      bytes memory callData,
                      uint256 callValue,
                      bytes memory errorData
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("WalletExecuteCallFailedError(address,address,bytes,uint256,bytes)")),
                          wallet,
                          callTarget,
                          callData,
                          callValue,
                          errorData
                      );
                  }
                  function WalletExecuteDelegateCallFailedError(
                      address wallet,
                      address callTarget,
                      bytes memory callData,
                      bytes memory errorData
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          bytes4(keccak256("WalletExecuteDelegateCallFailedError(address,address,bytes,bytes)")),
                          wallet,
                          callTarget,
                          callData,
                          errorData
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/AuthorizableV06.sol";
              import "../errors/LibSpenderRichErrors.sol";
              import "./IAllowanceTarget.sol";
              /// @dev The allowance target for the TokenSpender feature.
              contract AllowanceTarget is
                  IAllowanceTarget,
                  AuthorizableV06
              {
                  // solhint-disable no-unused-vars,indent,no-empty-blocks
                  using LibRichErrorsV06 for bytes;
                  /// @dev Execute an arbitrary call. Only an authority can call this.
                  /// @param target The call target.
                  /// @param callData The call data.
                  /// @return resultData The data returned by the call.
                  function executeCall(
                      address payable target,
                      bytes calldata callData
                  )
                      external
                      override
                      onlyAuthorized
                      returns (bytes memory resultData)
                  {
                      bool success;
                      (success, resultData) = target.call(callData);
                      if (!success) {
                          resultData.rrevert();
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./interfaces/IAuthorizableV06.sol";
              import "./errors/LibRichErrorsV06.sol";
              import "./errors/LibAuthorizableRichErrorsV06.sol";
              import "./OwnableV06.sol";
              // solhint-disable no-empty-blocks
              contract AuthorizableV06 is
                  OwnableV06,
                  IAuthorizableV06
              {
                  /// @dev Only authorized addresses can invoke functions with this modifier.
                  modifier onlyAuthorized {
                      _assertSenderIsAuthorized();
                      _;
                  }
                  // @dev Whether an address is authorized to call privileged functions.
                  // @param 0 Address to query.
                  // @return 0 Whether the address is authorized.
                  mapping (address => bool) public override authorized;
                  // @dev Whether an address is authorized to call privileged functions.
                  // @param 0 Index of authorized address.
                  // @return 0 Authorized address.
                  address[] public override authorities;
                  /// @dev Initializes the `owner` address.
                  constructor()
                      public
                      OwnableV06()
                  {}
                  /// @dev Authorizes an address.
                  /// @param target Address to authorize.
                  function addAuthorizedAddress(address target)
                      external
                      override
                      onlyOwner
                  {
                      _addAuthorizedAddress(target);
                  }
                  /// @dev Removes authorizion of an address.
                  /// @param target Address to remove authorization from.
                  function removeAuthorizedAddress(address target)
                      external
                      override
                      onlyOwner
                  {
                      if (!authorized[target]) {
                          LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetNotAuthorizedError(target));
                      }
                      for (uint256 i = 0; i < authorities.length; i++) {
                          if (authorities[i] == target) {
                              _removeAuthorizedAddressAtIndex(target, i);
                              break;
                          }
                      }
                  }
                  /// @dev Removes authorizion of an address.
                  /// @param target Address to remove authorization from.
                  /// @param index Index of target in authorities array.
                  function removeAuthorizedAddressAtIndex(
                      address target,
                      uint256 index
                  )
                      external
                      override
                      onlyOwner
                  {
                      _removeAuthorizedAddressAtIndex(target, index);
                  }
                  /// @dev Gets all authorized addresses.
                  /// @return Array of authorized addresses.
                  function getAuthorizedAddresses()
                      external
                      override
                      view
                      returns (address[] memory)
                  {
                      return authorities;
                  }
                  /// @dev Reverts if msg.sender is not authorized.
                  function _assertSenderIsAuthorized()
                      internal
                      view
                  {
                      if (!authorized[msg.sender]) {
                          LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.SenderNotAuthorizedError(msg.sender));
                      }
                  }
                  /// @dev Authorizes an address.
                  /// @param target Address to authorize.
                  function _addAuthorizedAddress(address target)
                      internal
                  {
                      // Ensure that the target is not the zero address.
                      if (target == address(0)) {
                          LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.ZeroCantBeAuthorizedError());
                      }
                      // Ensure that the target is not already authorized.
                      if (authorized[target]) {
                          LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetAlreadyAuthorizedError(target));
                      }
                      authorized[target] = true;
                      authorities.push(target);
                      emit AuthorizedAddressAdded(target, msg.sender);
                  }
                  /// @dev Removes authorizion of an address.
                  /// @param target Address to remove authorization from.
                  /// @param index Index of target in authorities array.
                  function _removeAuthorizedAddressAtIndex(
                      address target,
                      uint256 index
                  )
                      internal
                  {
                      if (!authorized[target]) {
                          LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetNotAuthorizedError(target));
                      }
                      if (index >= authorities.length) {
                          LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.IndexOutOfBoundsError(
                              index,
                              authorities.length
                          ));
                      }
                      if (authorities[index] != target) {
                          LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.AuthorizedAddressMismatchError(
                              authorities[index],
                              target
                          ));
                      }
                      delete authorized[target];
                      authorities[index] = authorities[authorities.length - 1];
                      authorities.pop();
                      emit AuthorizedAddressRemoved(target, msg.sender);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./IOwnableV06.sol";
              interface IAuthorizableV06 is
                  IOwnableV06
              {
                  // Event logged when a new address is authorized.
                  event AuthorizedAddressAdded(
                      address indexed target,
                      address indexed caller
                  );
                  // Event logged when a currently authorized address is unauthorized.
                  event AuthorizedAddressRemoved(
                      address indexed target,
                      address indexed caller
                  );
                  /// @dev Authorizes an address.
                  /// @param target Address to authorize.
                  function addAuthorizedAddress(address target)
                      external;
                  /// @dev Removes authorizion of an address.
                  /// @param target Address to remove authorization from.
                  function removeAuthorizedAddress(address target)
                      external;
                  /// @dev Removes authorizion of an address.
                  /// @param target Address to remove authorization from.
                  /// @param index Index of target in authorities array.
                  function removeAuthorizedAddressAtIndex(
                      address target,
                      uint256 index
                  )
                      external;
                  /// @dev Gets all authorized addresses.
                  /// @return authorizedAddresses Array of authorized addresses.
                  function getAuthorizedAddresses()
                      external
                      view
                      returns (address[] memory authorizedAddresses);
                  /// @dev Whether an adderss is authorized to call privileged functions.
                  /// @param addr Address to query.
                  /// @return isAuthorized Whether the address is authorized.
                  function authorized(address addr) external view returns (bool isAuthorized);
                  /// @dev All addresseses authorized to call privileged functions.
                  /// @param idx Index of authorized address.
                  /// @return addr Authorized address.
                  function authorities(uint256 idx) external view returns (address addr);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              interface IOwnableV06 {
                  /// @dev Emitted by Ownable when ownership is transferred.
                  /// @param previousOwner The previous owner of the contract.
                  /// @param newOwner The new owner of the contract.
                  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
                  /// @dev Transfers ownership of the contract to a new address.
                  /// @param newOwner The address that will become the owner.
                  function transferOwnership(address newOwner) external;
                  /// @dev The owner of this contract.
                  /// @return ownerAddress The owner address.
                  function owner() external view returns (address ownerAddress);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibAuthorizableRichErrorsV06 {
                  // bytes4(keccak256("AuthorizedAddressMismatchError(address,address)"))
                  bytes4 internal constant AUTHORIZED_ADDRESS_MISMATCH_ERROR_SELECTOR =
                      0x140a84db;
                  // bytes4(keccak256("IndexOutOfBoundsError(uint256,uint256)"))
                  bytes4 internal constant INDEX_OUT_OF_BOUNDS_ERROR_SELECTOR =
                      0xe9f83771;
                  // bytes4(keccak256("SenderNotAuthorizedError(address)"))
                  bytes4 internal constant SENDER_NOT_AUTHORIZED_ERROR_SELECTOR =
                      0xb65a25b9;
                  // bytes4(keccak256("TargetAlreadyAuthorizedError(address)"))
                  bytes4 internal constant TARGET_ALREADY_AUTHORIZED_ERROR_SELECTOR =
                      0xde16f1a0;
                  // bytes4(keccak256("TargetNotAuthorizedError(address)"))
                  bytes4 internal constant TARGET_NOT_AUTHORIZED_ERROR_SELECTOR =
                      0xeb5108a2;
                  // bytes4(keccak256("ZeroCantBeAuthorizedError()"))
                  bytes internal constant ZERO_CANT_BE_AUTHORIZED_ERROR_BYTES =
                      hex"57654fe4";
                  // solhint-disable func-name-mixedcase
                  function AuthorizedAddressMismatchError(
                      address authorized,
                      address target
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          AUTHORIZED_ADDRESS_MISMATCH_ERROR_SELECTOR,
                          authorized,
                          target
                      );
                  }
                  function IndexOutOfBoundsError(
                      uint256 index,
                      uint256 length
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          INDEX_OUT_OF_BOUNDS_ERROR_SELECTOR,
                          index,
                          length
                      );
                  }
                  function SenderNotAuthorizedError(address sender)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          SENDER_NOT_AUTHORIZED_ERROR_SELECTOR,
                          sender
                      );
                  }
                  function TargetAlreadyAuthorizedError(address target)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          TARGET_ALREADY_AUTHORIZED_ERROR_SELECTOR,
                          target
                      );
                  }
                  function TargetNotAuthorizedError(address target)
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          TARGET_NOT_AUTHORIZED_ERROR_SELECTOR,
                          target
                      );
                  }
                  function ZeroCantBeAuthorizedError()
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return ZERO_CANT_BE_AUTHORIZED_ERROR_BYTES;
                  }
              }
              /*
                Copyright 2019 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./interfaces/IOwnableV06.sol";
              import "./errors/LibRichErrorsV06.sol";
              import "./errors/LibOwnableRichErrorsV06.sol";
              contract OwnableV06 is
                  IOwnableV06
              {
                  /// @dev The owner of this contract.
                  /// @return 0 The owner address.
                  address public override owner;
                  constructor() public {
                      owner = msg.sender;
                  }
                  modifier onlyOwner() {
                      _assertSenderIsOwner();
                      _;
                  }
                  /// @dev Change the owner of this contract.
                  /// @param newOwner New owner address.
                  function transferOwnership(address newOwner)
                      public
                      override
                      onlyOwner
                  {
                      if (newOwner == address(0)) {
                          LibRichErrorsV06.rrevert(LibOwnableRichErrorsV06.TransferOwnerToZeroError());
                      } else {
                          owner = newOwner;
                          emit OwnershipTransferred(msg.sender, newOwner);
                      }
                  }
                  function _assertSenderIsOwner()
                      internal
                      view
                  {
                      if (msg.sender != owner) {
                          LibRichErrorsV06.rrevert(LibOwnableRichErrorsV06.OnlyOwnerError(
                              msg.sender,
                              owner
                          ));
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibOwnableRichErrorsV06 {
                  // bytes4(keccak256("OnlyOwnerError(address,address)"))
                  bytes4 internal constant ONLY_OWNER_ERROR_SELECTOR =
                      0x1de45ad1;
                  // bytes4(keccak256("TransferOwnerToZeroError()"))
                  bytes internal constant TRANSFER_OWNER_TO_ZERO_ERROR_BYTES =
                      hex"e69edc3e";
                  // solhint-disable func-name-mixedcase
                  function OnlyOwnerError(
                      address sender,
                      address owner
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          ONLY_OWNER_ERROR_SELECTOR,
                          sender,
                          owner
                      );
                  }
                  function TransferOwnerToZeroError()
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return TRANSFER_OWNER_TO_ZERO_ERROR_BYTES;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/interfaces/IAuthorizableV06.sol";
              /// @dev The allowance target for the TokenSpender feature.
              interface IAllowanceTarget is
                  IAuthorizableV06
              {
                  /// @dev Execute an arbitrary call. Only an authority can call this.
                  /// @param target The call target.
                  /// @param callData The call data.
                  /// @return resultData The data returned by the call.
                  function executeCall(
                      address payable target,
                      bytes calldata callData
                  )
                      external
                      returns (bytes memory resultData);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/errors/LibOwnableRichErrorsV06.sol";
              import "../errors/LibWalletRichErrors.sol";
              import "./IFlashWallet.sol";
              /// @dev A contract that can execute arbitrary calls from its owner.
              contract FlashWallet is
                  IFlashWallet
              {
                  // solhint-disable no-unused-vars,indent,no-empty-blocks
                  using LibRichErrorsV06 for bytes;
                  // solhint-disable
                  /// @dev Store the owner/deployer as an immutable to make this contract stateless.
                  address public override immutable owner;
                  // solhint-enable
                  constructor() public {
                      // The deployer is the owner.
                      owner = msg.sender;
                  }
                  /// @dev Allows only the (immutable) owner to call a function.
                  modifier onlyOwner() virtual {
                      if (msg.sender != owner) {
                          LibOwnableRichErrorsV06.OnlyOwnerError(
                              msg.sender,
                              owner
                          ).rrevert();
                      }
                      _;
                  }
                  /// @dev Execute an arbitrary call. Only an authority can call this.
                  /// @param target The call target.
                  /// @param callData The call data.
                  /// @param value Ether to attach to the call.
                  /// @return resultData The data returned by the call.
                  function executeCall(
                      address payable target,
                      bytes calldata callData,
                      uint256 value
                  )
                      external
                      payable
                      override
                      onlyOwner
                      returns (bytes memory resultData)
                  {
                      bool success;
                      (success, resultData) = target.call{value: value}(callData);
                      if (!success) {
                          LibWalletRichErrors
                              .WalletExecuteCallFailedError(
                                  address(this),
                                  target,
                                  callData,
                                  value,
                                  resultData
                              )
                              .rrevert();
                      }
                  }
                  /// @dev Execute an arbitrary delegatecall, in the context of this puppet.
                  ///      Only an authority can call this.
                  /// @param target The call target.
                  /// @param callData The call data.
                  /// @return resultData The data returned by the call.
                  function executeDelegateCall(
                      address payable target,
                      bytes calldata callData
                  )
                      external
                      payable
                      override
                      onlyOwner
                      returns (bytes memory resultData)
                  {
                      bool success;
                      (success, resultData) = target.delegatecall(callData);
                      if (!success) {
                          LibWalletRichErrors
                              .WalletExecuteDelegateCallFailedError(
                                  address(this),
                                  target,
                                  callData,
                                  resultData
                              )
                              .rrevert();
                      }
                  }
                  // solhint-disable
                  /// @dev Allows this contract to receive ether.
                  receive() external override payable {}
                  // solhint-enable
                  /// @dev Signal support for receiving ERC1155 tokens.
                  /// @param interfaceID The interface ID, as per ERC-165 rules.
                  /// @return hasSupport `true` if this contract supports an ERC-165 interface.
                  function supportsInterface(bytes4 interfaceID)
                      external
                      pure
                      returns (bool hasSupport)
                  {
                      return  interfaceID == this.supportsInterface.selector ||
                              interfaceID == this.onERC1155Received.selector ^ this.onERC1155BatchReceived.selector ||
                              interfaceID == this.tokenFallback.selector;
                  }
                  ///  @dev Allow this contract to receive ERC1155 tokens.
                  ///  @return success  `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
                  function onERC1155Received(
                      address, // operator,
                      address, // from,
                      uint256, // id,
                      uint256, // value,
                      bytes calldata //data
                  )
                      external
                      pure
                      returns (bytes4 success)
                  {
                      return this.onERC1155Received.selector;
                  }
                  ///  @dev Allow this contract to receive ERC1155 tokens.
                  ///  @return success  `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
                  function onERC1155BatchReceived(
                      address, // operator,
                      address, // from,
                      uint256[] calldata, // ids,
                      uint256[] calldata, // values,
                      bytes calldata // data
                  )
                      external
                      pure
                      returns (bytes4 success)
                  {
                      return this.onERC1155BatchReceived.selector;
                  }
                  /// @dev Allows this contract to receive ERC223 tokens.
                  function tokenFallback(
                      address, // from,
                      uint256, // value,
                      bytes calldata // value
                  )
                      external
                      pure
                  {}
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/interfaces/IOwnableV06.sol";
              /// @dev A contract that can execute arbitrary calls from its owner.
              interface IFlashWallet {
                  /// @dev Execute an arbitrary call. Only an authority can call this.
                  /// @param target The call target.
                  /// @param callData The call data.
                  /// @param value Ether to attach to the call.
                  /// @return resultData The data returned by the call.
                  function executeCall(
                      address payable target,
                      bytes calldata callData,
                      uint256 value
                  )
                      external
                      payable
                      returns (bytes memory resultData);
                  /// @dev Execute an arbitrary delegatecall, in the context of this puppet.
                  ///      Only an authority can call this.
                  /// @param target The call target.
                  /// @param callData The call data.
                  /// @return resultData The data returned by the call.
                  function executeDelegateCall(
                      address payable target,
                      bytes calldata callData
                  )
                      external
                      payable
                      returns (bytes memory resultData);
                  /// @dev Allows the puppet to receive ETH.
                  receive() external payable;
                  /// @dev Fetch the immutable owner/deployer of this contract.
                  /// @return owner_ The immutable owner/deployer/
                  function owner() external view returns (address owner_);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/AuthorizableV06.sol";
              /// @dev A contract with a `die()` function.
              interface IKillable {
                  function die() external;
              }
              /// @dev Deployer contract for ERC20 transformers.
              ///      Only authorities may call `deploy()` and `kill()`.
              contract TransformerDeployer is
                  AuthorizableV06
              {
                  /// @dev Emitted when a contract is deployed via `deploy()`.
                  /// @param deployedAddress The address of the deployed contract.
                  /// @param nonce The deployment nonce.
                  /// @param sender The caller of `deploy()`.
                  event Deployed(address deployedAddress, uint256 nonce, address sender);
                  /// @dev Emitted when a contract is killed via `kill()`.
                  /// @param target The address of the contract being killed..
                  /// @param sender The caller of `kill()`.
                  event Killed(address target, address sender);
                  // @dev The current nonce of this contract.
                  uint256 public nonce = 1;
                  // @dev Mapping of deployed contract address to deployment nonce.
                  mapping (address => uint256) public toDeploymentNonce;
                  /// @dev Create this contract and register authorities.
                  constructor(address[] memory authorities) public {
                      for (uint256 i = 0; i < authorities.length; ++i) {
                          _addAuthorizedAddress(authorities[i]);
                      }
                  }
                  /// @dev Deploy a new contract. Only callable by an authority.
                  ///      Any attached ETH will also be forwarded.
                  function deploy(bytes memory bytecode)
                      public
                      payable
                      onlyAuthorized
                      returns (address deployedAddress)
                  {
                      uint256 deploymentNonce = nonce;
                      nonce += 1;
                      assembly {
                          deployedAddress := create(callvalue(), add(bytecode, 32), mload(bytecode))
                      }
                      toDeploymentNonce[deployedAddress] = deploymentNonce;
                      emit Deployed(deployedAddress, deploymentNonce, msg.sender);
                  }
                  /// @dev Call `die()` on a contract. Only callable by an authority.
                  function kill(IKillable target)
                      public
                      onlyAuthorized
                  {
                      target.die();
                      emit Killed(address(target), msg.sender);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev Basic interface for a feature contract.
              interface IFeature {
                  // solhint-disable func-name-mixedcase
                  /// @dev The name of this feature set.
                  function FEATURE_NAME() external view returns (string memory name);
                  /// @dev The version of this feature set.
                  function FEATURE_VERSION() external view returns (uint256 version);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/interfaces/IOwnableV06.sol";
              // solhint-disable no-empty-blocks
              /// @dev Owner management and migration features.
              interface IOwnable is
                  IOwnableV06
              {
                  /// @dev Emitted when `migrate()` is called.
                  /// @param caller The caller of `migrate()`.
                  /// @param migrator The migration contract.
                  /// @param newOwner The address of the new owner.
                  event Migrated(address caller, address migrator, address newOwner);
                  /// @dev Execute a migration function in the context of the ZeroEx contract.
                  ///      The result of the function being called should be the magic bytes
                  ///      0x2c64c5ef (`keccack('MIGRATE_SUCCESS')`). Only callable by the owner.
                  ///      The owner will be temporarily set to `address(this)` inside the call.
                  ///      Before returning, the owner will be set to `newOwner`.
                  /// @param target The migrator contract address.
                  /// @param newOwner The address of the new owner.
                  /// @param data The call data.
                  function migrate(address target, bytes calldata data, address newOwner) external;
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev Basic registry management features.
              interface ISimpleFunctionRegistry {
                  /// @dev A function implementation was updated via `extend()` or `rollback()`.
                  /// @param selector The function selector.
                  /// @param oldImpl The implementation contract address being replaced.
                  /// @param newImpl The replacement implementation contract address.
                  event ProxyFunctionUpdated(bytes4 indexed selector, address oldImpl, address newImpl);
                  /// @dev Roll back to a prior implementation of a function.
                  /// @param selector The function selector.
                  /// @param targetImpl The address of an older implementation of the function.
                  function rollback(bytes4 selector, address targetImpl) external;
                  /// @dev Register or replace a function.
                  /// @param selector The function selector.
                  /// @param impl The implementation contract for the function.
                  function extend(bytes4 selector, address impl) external;
                  /// @dev Retrieve the length of the rollback history for a function.
                  /// @param selector The function selector.
                  /// @return rollbackLength The number of items in the rollback history for
                  ///         the function.
                  function getRollbackLength(bytes4 selector)
                      external
                      view
                      returns (uint256 rollbackLength);
                  /// @dev Retrieve an entry in the rollback history for a function.
                  /// @param selector The function selector.
                  /// @param idx The index in the rollback history.
                  /// @return impl An implementation address for the function at
                  ///         index `idx`.
                  function getRollbackEntryAtIndex(bytes4 selector, uint256 idx)
                      external
                      view
                      returns (address impl);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              /// @dev Feature that allows spending token allowances.
              interface ITokenSpender {
                  /// @dev Transfers ERC20 tokens from `owner` to `to`.
                  ///      Only callable from within.
                  /// @param token The token to spend.
                  /// @param owner The owner of the tokens.
                  /// @param to The recipient of the tokens.
                  /// @param amount The amount of `token` to transfer.
                  function _spendERC20Tokens(
                      IERC20TokenV06 token,
                      address owner,
                      address to,
                      uint256 amount
                  )
                      external;
                  /// @dev Gets the maximum amount of an ERC20 token `token` that can be
                  ///      pulled from `owner`.
                  /// @param token The token to spend.
                  /// @param owner The owner of the tokens.
                  /// @return amount The amount of tokens that can be pulled.
                  function getSpendableERC20BalanceOf(IERC20TokenV06 token, address owner)
                      external
                      view
                      returns (uint256 amount);
                  /// @dev Get the address of the allowance target.
                  /// @return target The target of token allowances.
                  function getAllowanceTarget() external view returns (address target);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              interface IERC20TokenV06 {
                  // solhint-disable no-simple-event-func-name
                  event Transfer(
                      address indexed from,
                      address indexed to,
                      uint256 value
                  );
                  event Approval(
                      address indexed owner,
                      address indexed spender,
                      uint256 value
                  );
                  /// @dev send `value` token to `to` from `msg.sender`
                  /// @param to The address of the recipient
                  /// @param value The amount of token to be transferred
                  /// @return True if transfer was successful
                  function transfer(address to, uint256 value)
                      external
                      returns (bool);
                  /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
                  /// @param from The address of the sender
                  /// @param to The address of the recipient
                  /// @param value The amount of token to be transferred
                  /// @return True if transfer was successful
                  function transferFrom(
                      address from,
                      address to,
                      uint256 value
                  )
                      external
                      returns (bool);
                  /// @dev `msg.sender` approves `spender` to spend `value` tokens
                  /// @param spender The address of the account able to transfer the tokens
                  /// @param value The amount of wei to be approved for transfer
                  /// @return Always true if the call has enough gas to complete execution
                  function approve(address spender, uint256 value)
                      external
                      returns (bool);
                  /// @dev Query total supply of token
                  /// @return Total supply of token
                  function totalSupply()
                      external
                      view
                      returns (uint256);
                  /// @dev Get the balance of `owner`.
                  /// @param owner The address from which the balance will be retrieved
                  /// @return Balance of owner
                  function balanceOf(address owner)
                      external
                      view
                      returns (uint256);
                  /// @dev Get the allowance for `spender` to spend from `owner`.
                  /// @param owner The address of the account owning tokens
                  /// @param spender The address of the account able to transfer the tokens
                  /// @return Amount of remaining tokens allowed to spent
                  function allowance(address owner, address spender)
                      external
                      view
                      returns (uint256);
                  /// @dev Get the number of decimals this token has.
                  function decimals()
                      external
                      view
                      returns (uint8);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "../transformers/IERC20Transformer.sol";
              import "../external/IFlashWallet.sol";
              /// @dev Feature to composably transform between ERC20 tokens.
              interface ITransformERC20 {
                  /// @dev Defines a transformation to run in `transformERC20()`.
                  struct Transformation {
                      // The deployment nonce for the transformer.
                      // The address of the transformer contract will be derived from this
                      // value.
                      uint32 deploymentNonce;
                      // Arbitrary data to pass to the transformer.
                      bytes data;
                  }
                  /// @dev Raised upon a successful `transformERC20`.
                  /// @param taker The taker (caller) address.
                  /// @param inputToken The token being provided by the taker.
                  ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                  /// @param outputToken The token to be acquired by the taker.
                  ///        `0xeee...` implies ETH.
                  /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                  /// @param outputTokenAmount The amount of `outputToken` received by the taker.
                  event TransformedERC20(
                      address indexed taker,
                      address inputToken,
                      address outputToken,
                      uint256 inputTokenAmount,
                      uint256 outputTokenAmount
                  );
                  /// @dev Raised when `setTransformerDeployer()` is called.
                  /// @param transformerDeployer The new deployer address.
                  event TransformerDeployerUpdated(address transformerDeployer);
                  /// @dev Replace the allowed deployer for transformers.
                  ///      Only callable by the owner.
                  /// @param transformerDeployer The address of the trusted deployer for transformers.
                  function setTransformerDeployer(address transformerDeployer)
                      external;
                  /// @dev Deploy a new flash wallet instance and replace the current one with it.
                  ///      Useful if we somehow break the current wallet instance.
                  ///      Anyone can call this.
                  /// @return wallet The new wallet instance.
                  function createTransformWallet()
                      external
                      returns (IFlashWallet wallet);
                  /// @dev Executes a series of transformations to convert an ERC20 `inputToken`
                  ///      to an ERC20 `outputToken`.
                  /// @param inputToken The token being provided by the sender.
                  ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                  /// @param outputToken The token to be acquired by the sender.
                  ///        `0xeee...` implies ETH.
                  /// @param inputTokenAmount The amount of `inputToken` to take from the sender.
                  /// @param minOutputTokenAmount The minimum amount of `outputToken` the sender
                  ///        must receive for the entire transformation to succeed.
                  /// @param transformations The transformations to execute on the token balance(s)
                  ///        in sequence.
                  /// @return outputTokenAmount The amount of `outputToken` received by the sender.
                  function transformERC20(
                      IERC20TokenV06 inputToken,
                      IERC20TokenV06 outputToken,
                      uint256 inputTokenAmount,
                      uint256 minOutputTokenAmount,
                      Transformation[] calldata transformations
                  )
                      external
                      payable
                      returns (uint256 outputTokenAmount);
                  /// @dev Internal version of `transformERC20()`. Only callable from within.
                  /// @param callDataHash Hash of the ingress calldata.
                  /// @param taker The taker address.
                  /// @param inputToken The token being provided by the taker.
                  ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                  /// @param outputToken The token to be acquired by the taker.
                  ///        `0xeee...` implies ETH.
                  /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                  /// @param minOutputTokenAmount The minimum amount of `outputToken` the taker
                  ///        must receive for the entire transformation to succeed.
                  /// @param transformations The transformations to execute on the token balance(s)
                  ///        in sequence.
                  /// @return outputTokenAmount The amount of `outputToken` received by the taker.
                  function _transformERC20(
                      bytes32 callDataHash,
                      address payable taker,
                      IERC20TokenV06 inputToken,
                      IERC20TokenV06 outputToken,
                      uint256 inputTokenAmount,
                      uint256 minOutputTokenAmount,
                      Transformation[] calldata transformations
                  )
                      external
                      payable
                      returns (uint256 outputTokenAmount);
                  /// @dev Return the current wallet instance that will serve as the execution
                  ///      context for transformations.
                  /// @return wallet The wallet instance.
                  function getTransformWallet()
                      external
                      view
                      returns (IFlashWallet wallet);
                  /// @dev Return the allowed deployer for transformers.
                  /// @return deployer The transform deployer address.
                  function getTransformerDeployer()
                      external
                      view
                      returns (address deployer);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              /// @dev A transformation callback used in `TransformERC20.transformERC20()`.
              interface IERC20Transformer {
                  /// @dev Called from `TransformERC20.transformERC20()`. This will be
                  ///      delegatecalled in the context of the FlashWallet instance being used.
                  /// @param callDataHash The hash of the `TransformERC20.transformERC20()` calldata.
                  /// @param taker The taker address (caller of `TransformERC20.transformERC20()`).
                  /// @param data Arbitrary data to pass to the transformer.
                  /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                  function transform(
                      bytes32 callDataHash,
                      address payable taker,
                      bytes calldata data
                  )
                      external
                      returns (bytes4 success);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../fixins/FixinCommon.sol";
              import "../errors/LibOwnableRichErrors.sol";
              import "../storage/LibOwnableStorage.sol";
              import "../migrations/LibBootstrap.sol";
              import "../migrations/LibMigrate.sol";
              import "./IFeature.sol";
              import "./IOwnable.sol";
              import "./SimpleFunctionRegistry.sol";
              /// @dev Owner management features.
              contract Ownable is
                  IFeature,
                  IOwnable,
                  FixinCommon
              {
                  // solhint-disable
                  /// @dev Name of this feature.
                  string public constant override FEATURE_NAME = "Ownable";
                  /// @dev Version of this feature.
                  uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                  /// @dev The deployed address of this contract.
                  address immutable private _implementation;
                  // solhint-enable
                  using LibRichErrorsV06 for bytes;
                  constructor() public {
                      _implementation = address(this);
                  }
                  /// @dev Initializes this feature. The intial owner will be set to this (ZeroEx)
                  ///      to allow the bootstrappers to call `extend()`. Ownership should be
                  ///      transferred to the real owner by the bootstrapper after
                  ///      bootstrapping is complete.
                  /// @return success Magic bytes if successful.
                  function bootstrap() external returns (bytes4 success) {
                      // Set the owner to ourselves to allow bootstrappers to call `extend()`.
                      LibOwnableStorage.getStorage().owner = address(this);
                      // Register feature functions.
                      SimpleFunctionRegistry(address(this))._extendSelf(this.transferOwnership.selector, _implementation);
                      SimpleFunctionRegistry(address(this))._extendSelf(this.owner.selector, _implementation);
                      SimpleFunctionRegistry(address(this))._extendSelf(this.migrate.selector, _implementation);
                      return LibBootstrap.BOOTSTRAP_SUCCESS;
                  }
                  /// @dev Change the owner of this contract.
                  ///      Only directly callable by the owner.
                  /// @param newOwner New owner address.
                  function transferOwnership(address newOwner)
                      external
                      override
                      onlyOwner
                  {
                      LibOwnableStorage.Storage storage proxyStor = LibOwnableStorage.getStorage();
                      if (newOwner == address(0)) {
                          LibOwnableRichErrors.TransferOwnerToZeroError().rrevert();
                      } else {
                          proxyStor.owner = newOwner;
                          emit OwnershipTransferred(msg.sender, newOwner);
                      }
                  }
                  /// @dev Execute a migration function in the context of the ZeroEx contract.
                  ///      The result of the function being called should be the magic bytes
                  ///      0x2c64c5ef (`keccack('MIGRATE_SUCCESS')`). Only callable by the owner.
                  ///      Temporarily sets the owner to ourselves so we can perform admin functions.
                  ///      Before returning, the owner will be set to `newOwner`.
                  /// @param target The migrator contract address.
                  /// @param data The call data.
                  /// @param newOwner The address of the new owner.
                  function migrate(address target, bytes calldata data, address newOwner)
                      external
                      override
                      onlyOwner
                  {
                      if (newOwner == address(0)) {
                          LibOwnableRichErrors.TransferOwnerToZeroError().rrevert();
                      }
                      LibOwnableStorage.Storage storage stor = LibOwnableStorage.getStorage();
                      // The owner will be temporarily set to `address(this)` inside the call.
                      stor.owner = address(this);
                      // Perform the migration.
                      LibMigrate.delegatecallMigrateFunction(target, data);
                      // Update the owner.
                      stor.owner = newOwner;
                      emit Migrated(msg.sender, target, newOwner);
                  }
                  /// @dev Get the owner of this contract.
                  /// @return owner_ The owner of this contract.
                  function owner() external override view returns (address owner_) {
                      return LibOwnableStorage.getStorage().owner;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../errors/LibCommonRichErrors.sol";
              import "../errors/LibOwnableRichErrors.sol";
              import "../features/IOwnable.sol";
              /// @dev Common feature utilities.
              contract FixinCommon {
                  using LibRichErrorsV06 for bytes;
                  /// @dev The caller must be this contract.
                  modifier onlySelf() virtual {
                      if (msg.sender != address(this)) {
                          LibCommonRichErrors.OnlyCallableBySelfError(msg.sender).rrevert();
                      }
                      _;
                  }
                  /// @dev The caller of this function must be the owner.
                  modifier onlyOwner() virtual {
                      {
                          address owner = IOwnable(address(this)).owner();
                          if (msg.sender != owner) {
                              LibOwnableRichErrors.OnlyOwnerError(
                                  msg.sender,
                                  owner
                              ).rrevert();
                          }
                      }
                      _;
                  }
                  /// @dev Encode a feature version as a `uint256`.
                  /// @param major The major version number of the feature.
                  /// @param minor The minor version number of the feature.
                  /// @param revision The revision number of the feature.
                  /// @return encodedVersion The encoded version number.
                  function _encodeVersion(uint32 major, uint32 minor, uint32 revision)
                      internal
                      pure
                      returns (uint256 encodedVersion)
                  {
                      return (major << 64) | (minor << 32) | revision;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "./LibStorage.sol";
              /// @dev Storage helpers for the `Ownable` feature.
              library LibOwnableStorage {
                  /// @dev Storage bucket for this feature.
                  struct Storage {
                      // The owner of this contract.
                      address owner;
                  }
                  /// @dev Get the storage bucket for this contract.
                  function getStorage() internal pure returns (Storage storage stor) {
                      uint256 storageSlot = LibStorage.getStorageSlot(
                          LibStorage.StorageId.Ownable
                      );
                      // Dip into assembly to change the slot pointed to by the local
                      // variable `stor`.
                      // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                      assembly { stor_slot := storageSlot }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../errors/LibOwnableRichErrors.sol";
              library LibMigrate {
                  /// @dev Magic bytes returned by a migrator to indicate success.
                  ///      This is `keccack('MIGRATE_SUCCESS')`.
                  bytes4 internal constant MIGRATE_SUCCESS = 0x2c64c5ef;
                  using LibRichErrorsV06 for bytes;
                  /// @dev Perform a delegatecall and ensure it returns the magic bytes.
                  /// @param target The call target.
                  /// @param data The call data.
                  function delegatecallMigrateFunction(
                      address target,
                      bytes memory data
                  )
                      internal
                  {
                      (bool success, bytes memory resultData) = target.delegatecall(data);
                      if (!success ||
                          resultData.length != 32 ||
                          abi.decode(resultData, (bytes4)) != MIGRATE_SUCCESS)
                      {
                          LibOwnableRichErrors.MigrateCallFailedError(target, resultData).rrevert();
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../fixins/FixinCommon.sol";
              import "../storage/LibProxyStorage.sol";
              import "../storage/LibSimpleFunctionRegistryStorage.sol";
              import "../errors/LibSimpleFunctionRegistryRichErrors.sol";
              import "../migrations/LibBootstrap.sol";
              import "./IFeature.sol";
              import "./ISimpleFunctionRegistry.sol";
              /// @dev Basic registry management features.
              contract SimpleFunctionRegistry is
                  IFeature,
                  ISimpleFunctionRegistry,
                  FixinCommon
              {
                  // solhint-disable
                  /// @dev Name of this feature.
                  string public constant override FEATURE_NAME = "SimpleFunctionRegistry";
                  /// @dev Version of this feature.
                  uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                  /// @dev The deployed address of this contract.
                  address private immutable _implementation;
                  // solhint-enable
                  using LibRichErrorsV06 for bytes;
                  constructor() public {
                      _implementation = address(this);
                  }
                  /// @dev Initializes this feature, registering its own functions.
                  /// @return success Magic bytes if successful.
                  function bootstrap()
                      external
                      returns (bytes4 success)
                  {
                      // Register the registration functions (inception vibes).
                      _extend(this.extend.selector, _implementation);
                      _extend(this._extendSelf.selector, _implementation);
                      // Register the rollback function.
                      _extend(this.rollback.selector, _implementation);
                      // Register getters.
                      _extend(this.getRollbackLength.selector, _implementation);
                      _extend(this.getRollbackEntryAtIndex.selector, _implementation);
                      return LibBootstrap.BOOTSTRAP_SUCCESS;
                  }
                  /// @dev Roll back to a prior implementation of a function.
                  ///      Only directly callable by an authority.
                  /// @param selector The function selector.
                  /// @param targetImpl The address of an older implementation of the function.
                  function rollback(bytes4 selector, address targetImpl)
                      external
                      override
                      onlyOwner
                  {
                      (
                          LibSimpleFunctionRegistryStorage.Storage storage stor,
                          LibProxyStorage.Storage storage proxyStor
                      ) = _getStorages();
                      address currentImpl = proxyStor.impls[selector];
                      if (currentImpl == targetImpl) {
                          // Do nothing if already at targetImpl.
                          return;
                      }
                      // Walk history backwards until we find the target implementation.
                      address[] storage history = stor.implHistory[selector];
                      uint256 i = history.length;
                      for (; i > 0; --i) {
                          address impl = history[i - 1];
                          history.pop();
                          if (impl == targetImpl) {
                              break;
                          }
                      }
                      if (i == 0) {
                          LibSimpleFunctionRegistryRichErrors.NotInRollbackHistoryError(
                              selector,
                              targetImpl
                          ).rrevert();
                      }
                      proxyStor.impls[selector] = targetImpl;
                      emit ProxyFunctionUpdated(selector, currentImpl, targetImpl);
                  }
                  /// @dev Register or replace a function.
                  ///      Only directly callable by an authority.
                  /// @param selector The function selector.
                  /// @param impl The implementation contract for the function.
                  function extend(bytes4 selector, address impl)
                      external
                      override
                      onlyOwner
                  {
                      _extend(selector, impl);
                  }
                  /// @dev Register or replace a function.
                  ///      Only callable from within.
                  ///      This function is only used during the bootstrap process and
                  ///      should be deregistered by the deployer after bootstrapping is
                  ///      complete.
                  /// @param selector The function selector.
                  /// @param impl The implementation contract for the function.
                  function _extendSelf(bytes4 selector, address impl)
                      external
                      onlySelf
                  {
                      _extend(selector, impl);
                  }
                  /// @dev Retrieve the length of the rollback history for a function.
                  /// @param selector The function selector.
                  /// @return rollbackLength The number of items in the rollback history for
                  ///         the function.
                  function getRollbackLength(bytes4 selector)
                      external
                      override
                      view
                      returns (uint256 rollbackLength)
                  {
                      return LibSimpleFunctionRegistryStorage.getStorage().implHistory[selector].length;
                  }
                  /// @dev Retrieve an entry in the rollback history for a function.
                  /// @param selector The function selector.
                  /// @param idx The index in the rollback history.
                  /// @return impl An implementation address for the function at
                  ///         index `idx`.
                  function getRollbackEntryAtIndex(bytes4 selector, uint256 idx)
                      external
                      override
                      view
                      returns (address impl)
                  {
                      return LibSimpleFunctionRegistryStorage.getStorage().implHistory[selector][idx];
                  }
                  /// @dev Register or replace a function.
                  /// @param selector The function selector.
                  /// @param impl The implementation contract for the function.
                  function _extend(bytes4 selector, address impl)
                      private
                  {
                      (
                          LibSimpleFunctionRegistryStorage.Storage storage stor,
                          LibProxyStorage.Storage storage proxyStor
                      ) = _getStorages();
                      address oldImpl = proxyStor.impls[selector];
                      address[] storage history = stor.implHistory[selector];
                      history.push(oldImpl);
                      proxyStor.impls[selector] = impl;
                      emit ProxyFunctionUpdated(selector, oldImpl, impl);
                  }
                  /// @dev Get the storage buckets for this feature and the proxy.
                  /// @return stor Storage bucket for this feature.
                  /// @return proxyStor age bucket for the proxy.
                  function _getStorages()
                      private
                      pure
                      returns (
                          LibSimpleFunctionRegistryStorage.Storage storage stor,
                          LibProxyStorage.Storage storage proxyStor
                      )
                  {
                      return (
                          LibSimpleFunctionRegistryStorage.getStorage(),
                          LibProxyStorage.getStorage()
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "./LibStorage.sol";
              /// @dev Storage helpers for the `SimpleFunctionRegistry` feature.
              library LibSimpleFunctionRegistryStorage {
                  /// @dev Storage bucket for this feature.
                  struct Storage {
                      // Mapping of function selector -> implementation history.
                      mapping(bytes4 => address[]) implHistory;
                  }
                  /// @dev Get the storage bucket for this contract.
                  function getStorage() internal pure returns (Storage storage stor) {
                      uint256 storageSlot = LibStorage.getStorageSlot(
                          LibStorage.StorageId.SimpleFunctionRegistry
                      );
                      // Dip into assembly to change the slot pointed to by the local
                      // variable `stor`.
                      // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                      assembly { stor_slot := storageSlot }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
              import "../errors/LibSpenderRichErrors.sol";
              import "../fixins/FixinCommon.sol";
              import "../migrations/LibMigrate.sol";
              import "../external/IAllowanceTarget.sol";
              import "../storage/LibTokenSpenderStorage.sol";
              import "./ITokenSpender.sol";
              import "./IFeature.sol";
              import "./ISimpleFunctionRegistry.sol";
              /// @dev Feature that allows spending token allowances.
              contract TokenSpender is
                  IFeature,
                  ITokenSpender,
                  FixinCommon
              {
                  // solhint-disable
                  /// @dev Name of this feature.
                  string public constant override FEATURE_NAME = "TokenSpender";
                  /// @dev Version of this feature.
                  uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                  /// @dev The implementation address of this feature.
                  address private immutable _implementation;
                  // solhint-enable
                  using LibRichErrorsV06 for bytes;
                  constructor() public {
                      _implementation = address(this);
                  }
                  /// @dev Initialize and register this feature. Should be delegatecalled
                  ///      into during a `Migrate.migrate()`.
                  /// @param allowanceTarget An `allowanceTarget` instance, configured to have
                  ///        the ZeroeEx contract as an authority.
                  /// @return success `MIGRATE_SUCCESS` on success.
                  function migrate(IAllowanceTarget allowanceTarget) external returns (bytes4 success) {
                      LibTokenSpenderStorage.getStorage().allowanceTarget = allowanceTarget;
                      ISimpleFunctionRegistry(address(this))
                          .extend(this.getAllowanceTarget.selector, _implementation);
                      ISimpleFunctionRegistry(address(this))
                          .extend(this._spendERC20Tokens.selector, _implementation);
                      ISimpleFunctionRegistry(address(this))
                          .extend(this.getSpendableERC20BalanceOf.selector, _implementation);
                      return LibMigrate.MIGRATE_SUCCESS;
                  }
                  /// @dev Transfers ERC20 tokens from `owner` to `to`. Only callable from within.
                  /// @param token The token to spend.
                  /// @param owner The owner of the tokens.
                  /// @param to The recipient of the tokens.
                  /// @param amount The amount of `token` to transfer.
                  function _spendERC20Tokens(
                      IERC20TokenV06 token,
                      address owner,
                      address to,
                      uint256 amount
                  )
                      external
                      override
                      onlySelf
                  {
                      IAllowanceTarget spender = LibTokenSpenderStorage.getStorage().allowanceTarget;
                      // Have the allowance target execute an ERC20 `transferFrom()`.
                      (bool didSucceed, bytes memory resultData) = address(spender).call(
                          abi.encodeWithSelector(
                              IAllowanceTarget.executeCall.selector,
                              address(token),
                              abi.encodeWithSelector(
                                  IERC20TokenV06.transferFrom.selector,
                                  owner,
                                  to,
                                  amount
                              )
                          )
                      );
                      if (didSucceed) {
                          resultData = abi.decode(resultData, (bytes));
                      }
                      if (!didSucceed || !LibERC20TokenV06.isSuccessfulResult(resultData)) {
                          LibSpenderRichErrors.SpenderERC20TransferFromFailedError(
                              address(token),
                              owner,
                              to,
                              amount,
                              resultData
                          ).rrevert();
                      }
                  }
                  /// @dev Gets the maximum amount of an ERC20 token `token` that can be
                  ///      pulled from `owner` by the token spender.
                  /// @param token The token to spend.
                  /// @param owner The owner of the tokens.
                  /// @return amount The amount of tokens that can be pulled.
                  function getSpendableERC20BalanceOf(IERC20TokenV06 token, address owner)
                      external
                      override
                      view
                      returns (uint256 amount)
                  {
                      return LibSafeMathV06.min256(
                          token.allowance(owner, address(LibTokenSpenderStorage.getStorage().allowanceTarget)),
                          token.balanceOf(owner)
                      );
                  }
                  /// @dev Get the address of the allowance target.
                  /// @return target The target of token allowances.
                  function getAllowanceTarget()
                      external
                      override
                      view
                      returns (address target)
                  {
                      return address(LibTokenSpenderStorage.getStorage().allowanceTarget);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./errors/LibRichErrorsV06.sol";
              import "./errors/LibSafeMathRichErrorsV06.sol";
              library LibSafeMathV06 {
                  function safeMul(uint256 a, uint256 b)
                      internal
                      pure
                      returns (uint256)
                  {
                      if (a == 0) {
                          return 0;
                      }
                      uint256 c = a * b;
                      if (c / a != b) {
                          LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                              LibSafeMathRichErrorsV06.BinOpErrorCodes.MULTIPLICATION_OVERFLOW,
                              a,
                              b
                          ));
                      }
                      return c;
                  }
                  function safeDiv(uint256 a, uint256 b)
                      internal
                      pure
                      returns (uint256)
                  {
                      if (b == 0) {
                          LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                              LibSafeMathRichErrorsV06.BinOpErrorCodes.DIVISION_BY_ZERO,
                              a,
                              b
                          ));
                      }
                      uint256 c = a / b;
                      return c;
                  }
                  function safeSub(uint256 a, uint256 b)
                      internal
                      pure
                      returns (uint256)
                  {
                      if (b > a) {
                          LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                              LibSafeMathRichErrorsV06.BinOpErrorCodes.SUBTRACTION_UNDERFLOW,
                              a,
                              b
                          ));
                      }
                      return a - b;
                  }
                  function safeAdd(uint256 a, uint256 b)
                      internal
                      pure
                      returns (uint256)
                  {
                      uint256 c = a + b;
                      if (c < a) {
                          LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                              LibSafeMathRichErrorsV06.BinOpErrorCodes.ADDITION_OVERFLOW,
                              a,
                              b
                          ));
                      }
                      return c;
                  }
                  function max256(uint256 a, uint256 b)
                      internal
                      pure
                      returns (uint256)
                  {
                      return a >= b ? a : b;
                  }
                  function min256(uint256 a, uint256 b)
                      internal
                      pure
                      returns (uint256)
                  {
                      return a < b ? a : b;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibSafeMathRichErrorsV06 {
                  // bytes4(keccak256("Uint256BinOpError(uint8,uint256,uint256)"))
                  bytes4 internal constant UINT256_BINOP_ERROR_SELECTOR =
                      0xe946c1bb;
                  // bytes4(keccak256("Uint256DowncastError(uint8,uint256)"))
                  bytes4 internal constant UINT256_DOWNCAST_ERROR_SELECTOR =
                      0xc996af7b;
                  enum BinOpErrorCodes {
                      ADDITION_OVERFLOW,
                      MULTIPLICATION_OVERFLOW,
                      SUBTRACTION_UNDERFLOW,
                      DIVISION_BY_ZERO
                  }
                  enum DowncastErrorCodes {
                      VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT32,
                      VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT64,
                      VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT96
                  }
                  // solhint-disable func-name-mixedcase
                  function Uint256BinOpError(
                      BinOpErrorCodes errorCode,
                      uint256 a,
                      uint256 b
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          UINT256_BINOP_ERROR_SELECTOR,
                          errorCode,
                          a,
                          b
                      );
                  }
                  function Uint256DowncastError(
                      DowncastErrorCodes errorCode,
                      uint256 a
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          UINT256_DOWNCAST_ERROR_SELECTOR,
                          errorCode,
                          a
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
              import "./IERC20TokenV06.sol";
              library LibERC20TokenV06 {
                  bytes constant private DECIMALS_CALL_DATA = hex"313ce567";
                  /// @dev Calls `IERC20TokenV06(token).approve()`.
                  ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                  /// @param token The address of the token contract.
                  /// @param spender The address that receives an allowance.
                  /// @param allowance The allowance to set.
                  function compatApprove(
                      IERC20TokenV06 token,
                      address spender,
                      uint256 allowance
                  )
                      internal
                  {
                      bytes memory callData = abi.encodeWithSelector(
                          token.approve.selector,
                          spender,
                          allowance
                      );
                      _callWithOptionalBooleanResult(address(token), callData);
                  }
                  /// @dev Calls `IERC20TokenV06(token).approve()` and sets the allowance to the
                  ///      maximum if the current approval is not already >= an amount.
                  ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                  /// @param token The address of the token contract.
                  /// @param spender The address that receives an allowance.
                  /// @param amount The minimum allowance needed.
                  function approveIfBelow(
                      IERC20TokenV06 token,
                      address spender,
                      uint256 amount
                  )
                      internal
                  {
                      if (token.allowance(address(this), spender) < amount) {
                          compatApprove(token, spender, uint256(-1));
                      }
                  }
                  /// @dev Calls `IERC20TokenV06(token).transfer()`.
                  ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                  /// @param token The address of the token contract.
                  /// @param to The address that receives the tokens
                  /// @param amount Number of tokens to transfer.
                  function compatTransfer(
                      IERC20TokenV06 token,
                      address to,
                      uint256 amount
                  )
                      internal
                  {
                      bytes memory callData = abi.encodeWithSelector(
                          token.transfer.selector,
                          to,
                          amount
                      );
                      _callWithOptionalBooleanResult(address(token), callData);
                  }
                  /// @dev Calls `IERC20TokenV06(token).transferFrom()`.
                  ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                  /// @param token The address of the token contract.
                  /// @param from The owner of the tokens.
                  /// @param to The address that receives the tokens
                  /// @param amount Number of tokens to transfer.
                  function compatTransferFrom(
                      IERC20TokenV06 token,
                      address from,
                      address to,
                      uint256 amount
                  )
                      internal
                  {
                      bytes memory callData = abi.encodeWithSelector(
                          token.transferFrom.selector,
                          from,
                          to,
                          amount
                      );
                      _callWithOptionalBooleanResult(address(token), callData);
                  }
                  /// @dev Retrieves the number of decimals for a token.
                  ///      Returns `18` if the call reverts.
                  /// @param token The address of the token contract.
                  /// @return tokenDecimals The number of decimals places for the token.
                  function compatDecimals(IERC20TokenV06 token)
                      internal
                      view
                      returns (uint8 tokenDecimals)
                  {
                      tokenDecimals = 18;
                      (bool didSucceed, bytes memory resultData) = address(token).staticcall(DECIMALS_CALL_DATA);
                      if (didSucceed && resultData.length == 32) {
                          tokenDecimals = uint8(LibBytesV06.readUint256(resultData, 0));
                      }
                  }
                  /// @dev Retrieves the allowance for a token, owner, and spender.
                  ///      Returns `0` if the call reverts.
                  /// @param token The address of the token contract.
                  /// @param owner The owner of the tokens.
                  /// @param spender The address the spender.
                  /// @return allowance_ The allowance for a token, owner, and spender.
                  function compatAllowance(IERC20TokenV06 token, address owner, address spender)
                      internal
                      view
                      returns (uint256 allowance_)
                  {
                      (bool didSucceed, bytes memory resultData) = address(token).staticcall(
                          abi.encodeWithSelector(
                              token.allowance.selector,
                              owner,
                              spender
                          )
                      );
                      if (didSucceed && resultData.length == 32) {
                          allowance_ = LibBytesV06.readUint256(resultData, 0);
                      }
                  }
                  /// @dev Retrieves the balance for a token owner.
                  ///      Returns `0` if the call reverts.
                  /// @param token The address of the token contract.
                  /// @param owner The owner of the tokens.
                  /// @return balance The token balance of an owner.
                  function compatBalanceOf(IERC20TokenV06 token, address owner)
                      internal
                      view
                      returns (uint256 balance)
                  {
                      (bool didSucceed, bytes memory resultData) = address(token).staticcall(
                          abi.encodeWithSelector(
                              token.balanceOf.selector,
                              owner
                          )
                      );
                      if (didSucceed && resultData.length == 32) {
                          balance = LibBytesV06.readUint256(resultData, 0);
                      }
                  }
                  /// @dev Check if the data returned by a non-static call to an ERC20 token
                  ///      is a successful result. Supported functions are `transfer()`,
                  ///      `transferFrom()`, and `approve()`.
                  /// @param resultData The raw data returned by a non-static call to the ERC20 token.
                  /// @return isSuccessful Whether the result data indicates success.
                  function isSuccessfulResult(bytes memory resultData)
                      internal
                      pure
                      returns (bool isSuccessful)
                  {
                      if (resultData.length == 0) {
                          return true;
                      }
                      if (resultData.length == 32) {
                          uint256 result = LibBytesV06.readUint256(resultData, 0);
                          if (result == 1) {
                              return true;
                          }
                      }
                  }
                  /// @dev Executes a call on address `target` with calldata `callData`
                  ///      and asserts that either nothing was returned or a single boolean
                  ///      was returned equal to `true`.
                  /// @param target The call target.
                  /// @param callData The abi-encoded call data.
                  function _callWithOptionalBooleanResult(
                      address target,
                      bytes memory callData
                  )
                      private
                  {
                      (bool didSucceed, bytes memory resultData) = target.call(callData);
                      if (didSucceed && isSuccessfulResult(resultData)) {
                          return;
                      }
                      LibRichErrorsV06.rrevert(resultData);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "./LibStorage.sol";
              import "../external/IAllowanceTarget.sol";
              /// @dev Storage helpers for the `TokenSpender` feature.
              library LibTokenSpenderStorage {
                  /// @dev Storage bucket for this feature.
                  struct Storage {
                      // Allowance target contract.
                      IAllowanceTarget allowanceTarget;
                  }
                  /// @dev Get the storage bucket for this contract.
                  function getStorage() internal pure returns (Storage storage stor) {
                      uint256 storageSlot = LibStorage.getStorageSlot(
                          LibStorage.StorageId.TokenSpender
                      );
                      // Dip into assembly to change the slot pointed to by the local
                      // variable `stor`.
                      // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                      assembly { stor_slot := storageSlot }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              import "../errors/LibTransformERC20RichErrors.sol";
              import "../fixins/FixinCommon.sol";
              import "../migrations/LibMigrate.sol";
              import "../external/IFlashWallet.sol";
              import "../external/FlashWallet.sol";
              import "../storage/LibTransformERC20Storage.sol";
              import "../transformers/IERC20Transformer.sol";
              import "../transformers/LibERC20Transformer.sol";
              import "./ITransformERC20.sol";
              import "./ITokenSpender.sol";
              import "./IFeature.sol";
              import "./ISimpleFunctionRegistry.sol";
              /// @dev Feature to composably transform between ERC20 tokens.
              contract TransformERC20 is
                  IFeature,
                  ITransformERC20,
                  FixinCommon
              {
                  /// @dev Stack vars for `_transformERC20Private()`.
                  struct TransformERC20PrivateState {
                      IFlashWallet wallet;
                      address transformerDeployer;
                      uint256 takerOutputTokenBalanceBefore;
                      uint256 takerOutputTokenBalanceAfter;
                  }
                  // solhint-disable
                  /// @dev Name of this feature.
                  string public constant override FEATURE_NAME = "TransformERC20";
                  /// @dev Version of this feature.
                  uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                  /// @dev The implementation address of this feature.
                  address private immutable _implementation;
                  // solhint-enable
                  using LibSafeMathV06 for uint256;
                  using LibRichErrorsV06 for bytes;
                  constructor() public {
                      _implementation = address(this);
                  }
                  /// @dev Initialize and register this feature.
                  ///      Should be delegatecalled by `Migrate.migrate()`.
                  /// @param transformerDeployer The trusted deployer for transformers.
                  /// @return success `LibMigrate.SUCCESS` on success.
                  function migrate(address transformerDeployer) external returns (bytes4 success) {
                      ISimpleFunctionRegistry(address(this))
                          .extend(this.getTransformerDeployer.selector, _implementation);
                      ISimpleFunctionRegistry(address(this))
                          .extend(this.createTransformWallet.selector, _implementation);
                      ISimpleFunctionRegistry(address(this))
                          .extend(this.getTransformWallet.selector, _implementation);
                      ISimpleFunctionRegistry(address(this))
                          .extend(this.setTransformerDeployer.selector, _implementation);
                      ISimpleFunctionRegistry(address(this))
                          .extend(this.transformERC20.selector, _implementation);
                      ISimpleFunctionRegistry(address(this))
                          .extend(this._transformERC20.selector, _implementation);
                      createTransformWallet();
                      LibTransformERC20Storage.getStorage().transformerDeployer = transformerDeployer;
                      return LibMigrate.MIGRATE_SUCCESS;
                  }
                  /// @dev Replace the allowed deployer for transformers.
                  ///      Only callable by the owner.
                  /// @param transformerDeployer The address of the trusted deployer for transformers.
                  function setTransformerDeployer(address transformerDeployer)
                      external
                      override
                      onlyOwner
                  {
                      LibTransformERC20Storage.getStorage().transformerDeployer = transformerDeployer;
                      emit TransformerDeployerUpdated(transformerDeployer);
                  }
                  /// @dev Return the allowed deployer for transformers.
                  /// @return deployer The transform deployer address.
                  function getTransformerDeployer()
                      public
                      override
                      view
                      returns (address deployer)
                  {
                      return LibTransformERC20Storage.getStorage().transformerDeployer;
                  }
                  /// @dev Deploy a new wallet instance and replace the current one with it.
                  ///      Useful if we somehow break the current wallet instance.
                  ///      Anyone can call this.
                  /// @return wallet The new wallet instance.
                  function createTransformWallet()
                      public
                      override
                      returns (IFlashWallet wallet)
                  {
                      wallet = new FlashWallet();
                      LibTransformERC20Storage.getStorage().wallet = wallet;
                  }
                  /// @dev Executes a series of transformations to convert an ERC20 `inputToken`
                  ///      to an ERC20 `outputToken`.
                  /// @param inputToken The token being provided by the sender.
                  ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                  /// @param outputToken The token to be acquired by the sender.
                  ///        `0xeee...` implies ETH.
                  /// @param inputTokenAmount The amount of `inputToken` to take from the sender.
                  ///        If set to `uint256(-1)`, the entire spendable balance of the taker
                  ///        will be solt.
                  /// @param minOutputTokenAmount The minimum amount of `outputToken` the sender
                  ///        must receive for the entire transformation to succeed. If set to zero,
                  ///        the minimum output token transfer will not be asserted.
                  /// @param transformations The transformations to execute on the token balance(s)
                  ///        in sequence.
                  /// @return outputTokenAmount The amount of `outputToken` received by the sender.
                  function transformERC20(
                      IERC20TokenV06 inputToken,
                      IERC20TokenV06 outputToken,
                      uint256 inputTokenAmount,
                      uint256 minOutputTokenAmount,
                      Transformation[] memory transformations
                  )
                      public
                      override
                      payable
                      returns (uint256 outputTokenAmount)
                  {
                      return _transformERC20Private(
                          keccak256(msg.data),
                          msg.sender,
                          inputToken,
                          outputToken,
                          inputTokenAmount,
                          minOutputTokenAmount,
                          transformations
                      );
                  }
                  /// @dev Internal version of `transformERC20()`. Only callable from within.
                  /// @param callDataHash Hash of the ingress calldata.
                  /// @param taker The taker address.
                  /// @param inputToken The token being provided by the taker.
                  ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                  /// @param outputToken The token to be acquired by the taker.
                  ///        `0xeee...` implies ETH.
                  /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                  ///        If set to `uint256(-1)`, the entire spendable balance of the taker
                  ///        will be solt.
                  /// @param minOutputTokenAmount The minimum amount of `outputToken` the taker
                  ///        must receive for the entire transformation to succeed. If set to zero,
                  ///        the minimum output token transfer will not be asserted.
                  /// @param transformations The transformations to execute on the token balance(s)
                  ///        in sequence.
                  /// @return outputTokenAmount The amount of `outputToken` received by the taker.
                  function _transformERC20(
                      bytes32 callDataHash,
                      address payable taker,
                      IERC20TokenV06 inputToken,
                      IERC20TokenV06 outputToken,
                      uint256 inputTokenAmount,
                      uint256 minOutputTokenAmount,
                      Transformation[] memory transformations
                  )
                      public
                      override
                      payable
                      onlySelf
                      returns (uint256 outputTokenAmount)
                  {
                      return _transformERC20Private(
                          callDataHash,
                          taker,
                          inputToken,
                          outputToken,
                          inputTokenAmount,
                          minOutputTokenAmount,
                          transformations
                      );
                  }
                  /// @dev Private version of `transformERC20()`.
                  /// @param callDataHash Hash of the ingress calldata.
                  /// @param taker The taker address.
                  /// @param inputToken The token being provided by the taker.
                  ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                  /// @param outputToken The token to be acquired by the taker.
                  ///        `0xeee...` implies ETH.
                  /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                  ///        If set to `uint256(-1)`, the entire spendable balance of the taker
                  ///        will be solt.
                  /// @param minOutputTokenAmount The minimum amount of `outputToken` the taker
                  ///        must receive for the entire transformation to succeed. If set to zero,
                  ///        the minimum output token transfer will not be asserted.
                  /// @param transformations The transformations to execute on the token balance(s)
                  ///        in sequence.
                  /// @return outputTokenAmount The amount of `outputToken` received by the taker.
                  function _transformERC20Private(
                      bytes32 callDataHash,
                      address payable taker,
                      IERC20TokenV06 inputToken,
                      IERC20TokenV06 outputToken,
                      uint256 inputTokenAmount,
                      uint256 minOutputTokenAmount,
                      Transformation[] memory transformations
                  )
                      private
                      returns (uint256 outputTokenAmount)
                  {
                      // If the input token amount is -1, transform the taker's entire
                      // spendable balance.
                      if (inputTokenAmount == uint256(-1)) {
                          inputTokenAmount = ITokenSpender(address(this))
                              .getSpendableERC20BalanceOf(inputToken, taker);
                      }
                      TransformERC20PrivateState memory state;
                      state.wallet = getTransformWallet();
                      state.transformerDeployer = getTransformerDeployer();
                      // Remember the initial output token balance of the taker.
                      state.takerOutputTokenBalanceBefore =
                          LibERC20Transformer.getTokenBalanceOf(outputToken, taker);
                      // Pull input tokens from the taker to the wallet and transfer attached ETH.
                      _transferInputTokensAndAttachedEth(
                          inputToken,
                          taker,
                          address(state.wallet),
                          inputTokenAmount
                      );
                      // Perform transformations.
                      for (uint256 i = 0; i < transformations.length; ++i) {
                          _executeTransformation(
                              state.wallet,
                              transformations[i],
                              state.transformerDeployer,
                              taker,
                              callDataHash
                          );
                      }
                      // Compute how much output token has been transferred to the taker.
                      state.takerOutputTokenBalanceAfter =
                          LibERC20Transformer.getTokenBalanceOf(outputToken, taker);
                      if (state.takerOutputTokenBalanceAfter > state.takerOutputTokenBalanceBefore) {
                          outputTokenAmount = state.takerOutputTokenBalanceAfter.safeSub(
                              state.takerOutputTokenBalanceBefore
                          );
                      } else if (state.takerOutputTokenBalanceAfter < state.takerOutputTokenBalanceBefore) {
                          LibTransformERC20RichErrors.NegativeTransformERC20OutputError(
                              address(outputToken),
                              state.takerOutputTokenBalanceBefore - state.takerOutputTokenBalanceAfter
                          ).rrevert();
                      }
                      // Ensure enough output token has been sent to the taker.
                      if (outputTokenAmount < minOutputTokenAmount) {
                          LibTransformERC20RichErrors.IncompleteTransformERC20Error(
                              address(outputToken),
                              outputTokenAmount,
                              minOutputTokenAmount
                          ).rrevert();
                      }
                      // Emit an event.
                      emit TransformedERC20(
                          taker,
                          address(inputToken),
                          address(outputToken),
                          inputTokenAmount,
                          outputTokenAmount
                      );
                  }
                  /// @dev Return the current wallet instance that will serve as the execution
                  ///      context for transformations.
                  /// @return wallet The wallet instance.
                  function getTransformWallet()
                      public
                      override
                      view
                      returns (IFlashWallet wallet)
                  {
                      return LibTransformERC20Storage.getStorage().wallet;
                  }
                  /// @dev Transfer input tokens from the taker and any attached ETH to `to`
                  /// @param inputToken The token to pull from the taker.
                  /// @param from The from (taker) address.
                  /// @param to The recipient of tokens and ETH.
                  /// @param amount Amount of `inputToken` tokens to transfer.
                  function _transferInputTokensAndAttachedEth(
                      IERC20TokenV06 inputToken,
                      address from,
                      address payable to,
                      uint256 amount
                  )
                      private
                  {
                      // Transfer any attached ETH.
                      if (msg.value != 0) {
                          to.transfer(msg.value);
                      }
                      // Transfer input tokens.
                      if (!LibERC20Transformer.isTokenETH(inputToken)) {
                          // Token is not ETH, so pull ERC20 tokens.
                          ITokenSpender(address(this))._spendERC20Tokens(
                              inputToken,
                              from,
                              to,
                              amount
                          );
                      } else if (msg.value < amount) {
                           // Token is ETH, so the caller must attach enough ETH to the call.
                          LibTransformERC20RichErrors.InsufficientEthAttachedError(
                              msg.value,
                              amount
                          ).rrevert();
                      }
                  }
                  /// @dev Executs a transformer in the context of `wallet`.
                  /// @param wallet The wallet instance.
                  /// @param transformation The transformation.
                  /// @param transformerDeployer The address of the transformer deployer.
                  /// @param taker The taker address.
                  /// @param callDataHash Hash of the calldata.
                  function _executeTransformation(
                      IFlashWallet wallet,
                      Transformation memory transformation,
                      address transformerDeployer,
                      address payable taker,
                      bytes32 callDataHash
                  )
                      private
                  {
                      // Derive the transformer address from the deployment nonce.
                      address payable transformer = LibERC20Transformer.getDeployedAddress(
                          transformerDeployer,
                          transformation.deploymentNonce
                      );
                      // Call `transformer.transform()` as the wallet.
                      bytes memory resultData = wallet.executeDelegateCall(
                          // The call target.
                          transformer,
                          // Call data.
                          abi.encodeWithSelector(
                              IERC20Transformer.transform.selector,
                              callDataHash,
                              taker,
                              transformation.data
                          )
                      );
                      // Ensure the transformer returned the magic bytes.
                      if (resultData.length != 32 ||
                          abi.decode(resultData, (bytes4)) != LibERC20Transformer.TRANSFORMER_SUCCESS
                      ) {
                          LibTransformERC20RichErrors.TransformerFailedError(
                              transformer,
                              transformation.data,
                              resultData
                          ).rrevert();
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "./LibStorage.sol";
              import "../external/IFlashWallet.sol";
              /// @dev Storage helpers for the `TokenSpender` feature.
              library LibTransformERC20Storage {
                  /// @dev Storage bucket for this feature.
                  struct Storage {
                      // The current wallet instance.
                      IFlashWallet wallet;
                      // The transformer deployer address.
                      address transformerDeployer;
                  }
                  /// @dev Get the storage bucket for this contract.
                  function getStorage() internal pure returns (Storage storage stor) {
                      uint256 storageSlot = LibStorage.getStorageSlot(
                          LibStorage.StorageId.TransformERC20
                      );
                      // Dip into assembly to change the slot pointed to by the local
                      // variable `stor`.
                      // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                      assembly { stor_slot := storageSlot }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
              library LibERC20Transformer {
                  using LibERC20TokenV06 for IERC20TokenV06;
                  /// @dev ETH pseudo-token address.
                  address constant internal ETH_TOKEN_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
                  /// @dev Return value indicating success in `IERC20Transformer.transform()`.
                  ///      This is just `keccak256('TRANSFORMER_SUCCESS')`.
                  bytes4 constant internal TRANSFORMER_SUCCESS = 0x13c9929e;
                  /// @dev Transfer ERC20 tokens and ETH.
                  /// @param token An ERC20 or the ETH pseudo-token address (`ETH_TOKEN_ADDRESS`).
                  /// @param to The recipient.
                  /// @param amount The transfer amount.
                  function transformerTransfer(
                      IERC20TokenV06 token,
                      address payable to,
                      uint256 amount
                  )
                      internal
                  {
                      if (isTokenETH(token)) {
                          to.transfer(amount);
                      } else {
                          token.compatTransfer(to, amount);
                      }
                  }
                  /// @dev Check if a token is the ETH pseudo-token.
                  /// @param token The token to check.
                  /// @return isETH `true` if the token is the ETH pseudo-token.
                  function isTokenETH(IERC20TokenV06 token)
                      internal
                      pure
                      returns (bool isETH)
                  {
                      return address(token) == ETH_TOKEN_ADDRESS;
                  }
                  /// @dev Check the balance of an ERC20 token or ETH.
                  /// @param token An ERC20 or the ETH pseudo-token address (`ETH_TOKEN_ADDRESS`).
                  /// @param owner Holder of the tokens.
                  /// @return tokenBalance The balance of `owner`.
                  function getTokenBalanceOf(IERC20TokenV06 token, address owner)
                      internal
                      view
                      returns (uint256 tokenBalance)
                  {
                      if (isTokenETH(token)) {
                          return owner.balance;
                      }
                      return token.balanceOf(owner);
                  }
                  /// @dev RLP-encode a 32-bit or less account nonce.
                  /// @param nonce A positive integer in the range 0 <= nonce < 2^32.
                  /// @return rlpNonce The RLP encoding.
                  function rlpEncodeNonce(uint32 nonce)
                      internal
                      pure
                      returns (bytes memory rlpNonce)
                  {
                      // See https://github.com/ethereum/wiki/wiki/RLP for RLP encoding rules.
                      if (nonce == 0) {
                          rlpNonce = new bytes(1);
                          rlpNonce[0] = 0x80;
                      } else if (nonce < 0x80) {
                          rlpNonce = new bytes(1);
                          rlpNonce[0] = byte(uint8(nonce));
                      } else if (nonce <= 0xFF) {
                          rlpNonce = new bytes(2);
                          rlpNonce[0] = 0x81;
                          rlpNonce[1] = byte(uint8(nonce));
                      } else if (nonce <= 0xFFFF) {
                          rlpNonce = new bytes(3);
                          rlpNonce[0] = 0x82;
                          rlpNonce[1] = byte(uint8((nonce & 0xFF00) >> 8));
                          rlpNonce[2] = byte(uint8(nonce));
                      } else if (nonce <= 0xFFFFFF) {
                          rlpNonce = new bytes(4);
                          rlpNonce[0] = 0x83;
                          rlpNonce[1] = byte(uint8((nonce & 0xFF0000) >> 16));
                          rlpNonce[2] = byte(uint8((nonce & 0xFF00) >> 8));
                          rlpNonce[3] = byte(uint8(nonce));
                      } else {
                          rlpNonce = new bytes(5);
                          rlpNonce[0] = 0x84;
                          rlpNonce[1] = byte(uint8((nonce & 0xFF000000) >> 24));
                          rlpNonce[2] = byte(uint8((nonce & 0xFF0000) >> 16));
                          rlpNonce[3] = byte(uint8((nonce & 0xFF00) >> 8));
                          rlpNonce[4] = byte(uint8(nonce));
                      }
                  }
                  /// @dev Compute the expected deployment address by `deployer` at
                  ///      the nonce given by `deploymentNonce`.
                  /// @param deployer The address of the deployer.
                  /// @param deploymentNonce The nonce that the deployer had when deploying
                  ///        a contract.
                  /// @return deploymentAddress The deployment address.
                  function getDeployedAddress(address deployer, uint32 deploymentNonce)
                      internal
                      pure
                      returns (address payable deploymentAddress)
                  {
                      // The address of if a deployed contract is the lower 20 bytes of the
                      // hash of the RLP-encoded deployer's account address + account nonce.
                      // See: https://ethereum.stackexchange.com/questions/760/how-is-the-address-of-an-ethereum-contract-computed
                      bytes memory rlpNonce = rlpEncodeNonce(deploymentNonce);
                      return address(uint160(uint256(keccak256(abi.encodePacked(
                          byte(uint8(0xC0 + 21 + rlpNonce.length)),
                          byte(uint8(0x80 + 20)),
                          deployer,
                          rlpNonce
                      )))));
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../ZeroEx.sol";
              import "../features/IOwnable.sol";
              import "../features/TokenSpender.sol";
              import "../features/TransformERC20.sol";
              import "../external/AllowanceTarget.sol";
              import "./InitialMigration.sol";
              /// @dev A contract for deploying and configuring the full ZeroEx contract.
              contract FullMigration {
                  // solhint-disable no-empty-blocks,indent
                  /// @dev Features to add the the proxy contract.
                  struct Features {
                      SimpleFunctionRegistry registry;
                      Ownable ownable;
                      TokenSpender tokenSpender;
                      TransformERC20 transformERC20;
                  }
                  /// @dev Parameters needed to initialize features.
                  struct MigrateOpts {
                      address transformerDeployer;
                  }
                  /// @dev The allowed caller of `deploy()`.
                  address public immutable deployer;
                  /// @dev The initial migration contract.
                  InitialMigration private _initialMigration;
                  /// @dev Instantiate this contract and set the allowed caller of `deploy()`
                  ///      to `deployer`.
                  /// @param deployer_ The allowed caller of `deploy()`.
                  constructor(address payable deployer_)
                      public
                  {
                      deployer = deployer_;
                      // Create an initial migration contract with this contract set to the
                      // allowed deployer.
                      _initialMigration = new InitialMigration(address(this));
                  }
                  /// @dev Deploy the `ZeroEx` contract with the full feature set,
                  ///      transfer ownership to `owner`, then self-destruct.
                  /// @param owner The owner of the contract.
                  /// @param features Features to add to the proxy.
                  /// @return zeroEx The deployed and configured `ZeroEx` contract.
                  /// @param migrateOpts Parameters needed to initialize features.
                  function deploy(
                      address payable owner,
                      Features memory features,
                      MigrateOpts memory migrateOpts
                  )
                      public
                      returns (ZeroEx zeroEx)
                  {
                      require(msg.sender == deployer, "FullMigration/INVALID_SENDER");
                      // Perform the initial migration with the owner set to this contract.
                      zeroEx = _initialMigration.deploy(
                          address(uint160(address(this))),
                          InitialMigration.BootstrapFeatures({
                              registry: features.registry,
                              ownable: features.ownable
                          })
                      );
                      // Add features.
                      _addFeatures(zeroEx, owner, features, migrateOpts);
                      // Transfer ownership to the real owner.
                      IOwnable(address(zeroEx)).transferOwnership(owner);
                      // Self-destruct.
                      this.die(owner);
                  }
                  /// @dev Destroy this contract. Only callable from ourselves (from `deploy()`).
                  /// @param ethRecipient Receiver of any ETH in this contract.
                  function die(address payable ethRecipient)
                      external
                      virtual
                  {
                      require(msg.sender == address(this), "FullMigration/INVALID_SENDER");
                      // This contract should not hold any funds but we send
                      // them to the ethRecipient just in case.
                      selfdestruct(ethRecipient);
                  }
                  /// @dev Deploy and register features to the ZeroEx contract.
                  /// @param zeroEx The bootstrapped ZeroEx contract.
                  /// @param owner The ultimate owner of the ZeroEx contract.
                  /// @param features Features to add to the proxy.
                  /// @param migrateOpts Parameters needed to initialize features.
                  function _addFeatures(
                      ZeroEx zeroEx,
                      address owner,
                      Features memory features,
                      MigrateOpts memory migrateOpts
                  )
                      private
                  {
                      IOwnable ownable = IOwnable(address(zeroEx));
                      // TokenSpender
                      {
                          // Create the allowance target.
                          AllowanceTarget allowanceTarget = new AllowanceTarget();
                          // Let the ZeroEx contract use the allowance target.
                          allowanceTarget.addAuthorizedAddress(address(zeroEx));
                          // Transfer ownership of the allowance target to the (real) owner.
                          allowanceTarget.transferOwnership(owner);
                          // Register the feature.
                          ownable.migrate(
                              address(features.tokenSpender),
                              abi.encodeWithSelector(
                                  TokenSpender.migrate.selector,
                                  allowanceTarget
                              ),
                              address(this)
                          );
                      }
                      // TransformERC20
                      {
                          // Register the feature.
                          ownable.migrate(
                              address(features.transformERC20),
                              abi.encodeWithSelector(
                                  TransformERC20.migrate.selector,
                                  migrateOpts.transformerDeployer
                              ),
                              address(this)
                          );
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../ZeroEx.sol";
              import "../features/IBootstrap.sol";
              import "../features/SimpleFunctionRegistry.sol";
              import "../features/Ownable.sol";
              import "./LibBootstrap.sol";
              /// @dev A contract for deploying and configuring a minimal ZeroEx contract.
              contract InitialMigration {
                  /// @dev Features to bootstrap into the the proxy contract.
                  struct BootstrapFeatures {
                      SimpleFunctionRegistry registry;
                      Ownable ownable;
                  }
                  /// @dev The allowed caller of `deploy()`. In production, this would be
                  ///      the governor.
                  address public immutable deployer;
                  /// @dev The real address of this contract.
                  address private immutable _implementation;
                  /// @dev Instantiate this contract and set the allowed caller of `deploy()`
                  ///      to `deployer_`.
                  /// @param deployer_ The allowed caller of `deploy()`.
                  constructor(address deployer_) public {
                      deployer = deployer_;
                      _implementation = address(this);
                  }
                  /// @dev Deploy the `ZeroEx` contract with the minimum feature set,
                  ///      transfers ownership to `owner`, then self-destructs.
                  ///      Only callable by `deployer` set in the contstructor.
                  /// @param owner The owner of the contract.
                  /// @param features Features to bootstrap into the proxy.
                  /// @return zeroEx The deployed and configured `ZeroEx` contract.
                  function deploy(address payable owner, BootstrapFeatures memory features)
                      public
                      virtual
                      returns (ZeroEx zeroEx)
                  {
                      // Must be called by the allowed deployer.
                      require(msg.sender == deployer, "InitialMigration/INVALID_SENDER");
                      // Deploy the ZeroEx contract, setting ourselves as the bootstrapper.
                      zeroEx = new ZeroEx();
                      // Bootstrap the initial feature set.
                      IBootstrap(address(zeroEx)).bootstrap(
                          address(this),
                          abi.encodeWithSelector(this.bootstrap.selector, owner, features)
                      );
                      // Self-destruct. This contract should not hold any funds but we send
                      // them to the owner just in case.
                      this.die(owner);
                  }
                  /// @dev Sets up the initial state of the `ZeroEx` contract.
                  ///      The `ZeroEx` contract will delegatecall into this function.
                  /// @param owner The new owner of the ZeroEx contract.
                  /// @param features Features to bootstrap into the proxy.
                  /// @return success Magic bytes if successful.
                  function bootstrap(address owner, BootstrapFeatures memory features)
                      public
                      virtual
                      returns (bytes4 success)
                  {
                      // Deploy and migrate the initial features.
                      // Order matters here.
                      // Initialize Registry.
                      LibBootstrap.delegatecallBootstrapFunction(
                          address(features.registry),
                          abi.encodeWithSelector(
                              SimpleFunctionRegistry.bootstrap.selector
                          )
                      );
                      // Initialize Ownable.
                      LibBootstrap.delegatecallBootstrapFunction(
                          address(features.ownable),
                          abi.encodeWithSelector(
                              Ownable.bootstrap.selector
                          )
                      );
                      // De-register `SimpleFunctionRegistry._extendSelf`.
                      SimpleFunctionRegistry(address(this)).rollback(
                          SimpleFunctionRegistry._extendSelf.selector,
                          address(0)
                      );
                      // Transfer ownership to the real owner.
                      Ownable(address(this)).transferOwnership(owner);
                      success = LibBootstrap.BOOTSTRAP_SUCCESS;
                  }
                  /// @dev Self-destructs this contract. Only callable by this contract.
                  /// @param ethRecipient Who to transfer outstanding ETH to.
                  function die(address payable ethRecipient) public virtual {
                      require(msg.sender == _implementation, "InitialMigration/INVALID_SENDER");
                      selfdestruct(ethRecipient);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
              import "../errors/LibTransformERC20RichErrors.sol";
              import "./Transformer.sol";
              import "./LibERC20Transformer.sol";
              /// @dev A transformer that transfers tokens to arbitrary addresses.
              contract AffiliateFeeTransformer is
                  Transformer
              {
                  // solhint-disable no-empty-blocks
                  using LibRichErrorsV06 for bytes;
                  using LibSafeMathV06 for uint256;
                  using LibERC20Transformer for IERC20TokenV06;
                  /// @dev Information for a single fee.
                  struct TokenFee {
                      // The token to transfer to `recipient`.
                      IERC20TokenV06 token;
                      // Amount of each `token` to transfer to `recipient`.
                      // If `amount == uint256(-1)`, the entire balance of `token` will be
                      // transferred.
                      uint256 amount;
                      // Recipient of `token`.
                      address payable recipient;
                  }
                  uint256 private constant MAX_UINT256 = uint256(-1);
                  /// @dev Create this contract.
                  constructor()
                      public
                      Transformer()
                  {}
                  /// @dev Transfers tokens to recipients.
                  /// @param data ABI-encoded `TokenFee[]`, indicating which tokens to transfer.
                  /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                  function transform(
                      bytes32, // callDataHash,
                      address payable, // taker,
                      bytes calldata data
                  )
                      external
                      override
                      returns (bytes4 success)
                  {
                      TokenFee[] memory fees = abi.decode(data, (TokenFee[]));
                      // Transfer tokens to recipients.
                      for (uint256 i = 0; i < fees.length; ++i) {
                          uint256 amount = fees[i].amount;
                          if (amount == MAX_UINT256) {
                              amount = LibERC20Transformer.getTokenBalanceOf(fees[i].token, address(this));
                          }
                          if (amount != 0) {
                              fees[i].token.transformerTransfer(fees[i].recipient, amount);
                          }
                      }
                      return LibERC20Transformer.TRANSFORMER_SUCCESS;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../errors/LibTransformERC20RichErrors.sol";
              import "./IERC20Transformer.sol";
              /// @dev Abstract base class for transformers.
              abstract contract Transformer is
                  IERC20Transformer
              {
                  using LibRichErrorsV06 for bytes;
                  /// @dev The address of the deployer.
                  address public immutable deployer;
                  /// @dev The original address of this contract.
                  address private immutable _implementation;
                  /// @dev Create this contract.
                  constructor() public {
                      deployer = msg.sender;
                      _implementation = address(this);
                  }
                  /// @dev Destruct this contract. Only callable by the deployer and will not
                  ///      succeed in the context of a delegatecall (from another contract).
                  /// @param ethRecipient The recipient of ETH held in this contract.
                  function die(address payable ethRecipient)
                      external
                      virtual
                  {
                      // Only the deployer can call this.
                      if (msg.sender != deployer) {
                          LibTransformERC20RichErrors
                              .OnlyCallableByDeployerError(msg.sender, deployer)
                              .rrevert();
                      }
                      // Must be executing our own context.
                      if (address(this) != _implementation) {
                          LibTransformERC20RichErrors
                              .InvalidExecutionContextError(address(this), _implementation)
                              .rrevert();
                      }
                      selfdestruct(ethRecipient);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibMathV06.sol";
              import "../errors/LibTransformERC20RichErrors.sol";
              import "../vendor/v3/IExchange.sol";
              import "./Transformer.sol";
              import "./LibERC20Transformer.sol";
              /// @dev A transformer that fills an ERC20 market sell/buy quote.
              contract FillQuoteTransformer is
                  Transformer
              {
                  using LibERC20TokenV06 for IERC20TokenV06;
                  using LibERC20Transformer for IERC20TokenV06;
                  using LibSafeMathV06 for uint256;
                  using LibRichErrorsV06 for bytes;
                  /// @dev Whether we are performing a market sell or buy.
                  enum Side {
                      Sell,
                      Buy
                  }
                  /// @dev Transform data to ABI-encode and pass into `transform()`.
                  struct TransformData {
                      // Whether we aer performing a market sell or buy.
                      Side side;
                      // The token being sold.
                      // This should be an actual token, not the ETH pseudo-token.
                      IERC20TokenV06 sellToken;
                      // The token being bought.
                      // This should be an actual token, not the ETH pseudo-token.
                      IERC20TokenV06 buyToken;
                      // The orders to fill.
                      IExchange.Order[] orders;
                      // Signatures for each respective order in `orders`.
                      bytes[] signatures;
                      // Maximum fill amount for each order. This may be shorter than the
                      // number of orders, where missing entries will be treated as `uint256(-1)`.
                      // For sells, this will be the maximum sell amount (taker asset).
                      // For buys, this will be the maximum buy amount (maker asset).
                      uint256[] maxOrderFillAmounts;
                      // Amount of `sellToken` to sell or `buyToken` to buy.
                      // For sells, this may be `uint256(-1)` to sell the entire balance of
                      // `sellToken`.
                      uint256 fillAmount;
                  }
                  /// @dev Results of a call to `_fillOrder()`.
                  struct FillOrderResults {
                      // The amount of taker tokens sold, according to balance checks.
                      uint256 takerTokenSoldAmount;
                      // The amount of maker tokens sold, according to balance checks.
                      uint256 makerTokenBoughtAmount;
                      // The amount of protocol fee paid.
                      uint256 protocolFeePaid;
                  }
                  /// @dev The Exchange ERC20Proxy ID.
                  bytes4 private constant ERC20_ASSET_PROXY_ID = 0xf47261b0;
                  /// @dev Maximum uint256 value.
                  uint256 private constant MAX_UINT256 = uint256(-1);
                  /// @dev The Exchange contract.
                  IExchange public immutable exchange;
                  /// @dev The ERC20Proxy address.
                  address public immutable erc20Proxy;
                  /// @dev Create this contract.
                  /// @param exchange_ The Exchange V3 instance.
                  constructor(IExchange exchange_)
                      public
                      Transformer()
                  {
                      exchange = exchange_;
                      erc20Proxy = exchange_.getAssetProxy(ERC20_ASSET_PROXY_ID);
                  }
                  /// @dev Sell this contract's entire balance of of `sellToken` in exchange
                  ///      for `buyToken` by filling `orders`. Protocol fees should be attached
                  ///      to this call. `buyToken` and excess ETH will be transferred back to the caller.
                  /// @param data_ ABI-encoded `TransformData`.
                  /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                  function transform(
                      bytes32, // callDataHash,
                      address payable, // taker,
                      bytes calldata data_
                  )
                      external
                      override
                      returns (bytes4 success)
                  {
                      TransformData memory data = abi.decode(data_, (TransformData));
                      // Validate data fields.
                      if (data.sellToken.isTokenETH() || data.buyToken.isTokenETH()) {
                          LibTransformERC20RichErrors.InvalidTransformDataError(
                              LibTransformERC20RichErrors.InvalidTransformDataErrorCode.INVALID_TOKENS,
                              data_
                          ).rrevert();
                      }
                      if (data.orders.length != data.signatures.length) {
                          LibTransformERC20RichErrors.InvalidTransformDataError(
                              LibTransformERC20RichErrors.InvalidTransformDataErrorCode.INVALID_ARRAY_LENGTH,
                              data_
                          ).rrevert();
                      }
                      if (data.side == Side.Sell && data.fillAmount == MAX_UINT256) {
                          // If `sellAmount == -1 then we are selling
                          // the entire balance of `sellToken`. This is useful in cases where
                          // the exact sell amount is not exactly known in advance, like when
                          // unwrapping Chai/cUSDC/cDAI.
                          data.fillAmount = data.sellToken.getTokenBalanceOf(address(this));
                      }
                      // Approve the ERC20 proxy to spend `sellToken`.
                      data.sellToken.approveIfBelow(erc20Proxy, data.fillAmount);
                      // Fill the orders.
                      uint256 singleProtocolFee = exchange.protocolFeeMultiplier().safeMul(tx.gasprice);
                      uint256 ethRemaining = address(this).balance;
                      uint256 boughtAmount = 0;
                      uint256 soldAmount = 0;
                      for (uint256 i = 0; i < data.orders.length; ++i) {
                          // Check if we've hit our targets.
                          if (data.side == Side.Sell) {
                              // Market sell check.
                              if (soldAmount >= data.fillAmount) {
                                  break;
                              }
                          } else {
                              // Market buy check.
                              if (boughtAmount >= data.fillAmount) {
                                  break;
                              }
                          }
                          // Ensure we have enough ETH to cover the protocol fee.
                          if (ethRemaining < singleProtocolFee) {
                              LibTransformERC20RichErrors
                                  .InsufficientProtocolFeeError(ethRemaining, singleProtocolFee)
                                  .rrevert();
                          }
                          // Fill the order.
                          FillOrderResults memory results;
                          if (data.side == Side.Sell) {
                              // Market sell.
                              results = _sellToOrder(
                                  data.buyToken,
                                  data.sellToken,
                                  data.orders[i],
                                  data.signatures[i],
                                  data.fillAmount.safeSub(soldAmount).min256(
                                      data.maxOrderFillAmounts.length > i
                                      ? data.maxOrderFillAmounts[i]
                                      : MAX_UINT256
                                  ),
                                  singleProtocolFee
                              );
                          } else {
                              // Market buy.
                              results = _buyFromOrder(
                                  data.buyToken,
                                  data.sellToken,
                                  data.orders[i],
                                  data.signatures[i],
                                  data.fillAmount.safeSub(boughtAmount).min256(
                                      data.maxOrderFillAmounts.length > i
                                      ? data.maxOrderFillAmounts[i]
                                      : MAX_UINT256
                                  ),
                                  singleProtocolFee
                              );
                          }
                          // Accumulate totals.
                          soldAmount = soldAmount.safeAdd(results.takerTokenSoldAmount);
                          boughtAmount = boughtAmount.safeAdd(results.makerTokenBoughtAmount);
                          ethRemaining = ethRemaining.safeSub(results.protocolFeePaid);
                      }
                      // Ensure we hit our targets.
                      if (data.side == Side.Sell) {
                          // Market sell check.
                          if (soldAmount < data.fillAmount) {
                              LibTransformERC20RichErrors
                                  .IncompleteFillSellQuoteError(
                                      address(data.sellToken),
                                      soldAmount,
                                      data.fillAmount
                                  ).rrevert();
                          }
                      } else {
                          // Market buy check.
                          if (boughtAmount < data.fillAmount) {
                              LibTransformERC20RichErrors
                                  .IncompleteFillBuyQuoteError(
                                      address(data.buyToken),
                                      boughtAmount,
                                      data.fillAmount
                                  ).rrevert();
                          }
                      }
                      return LibERC20Transformer.TRANSFORMER_SUCCESS;
                  }
                  /// @dev Try to sell up to `sellAmount` from an order.
                  /// @param makerToken The maker/buy token.
                  /// @param takerToken The taker/sell token.
                  /// @param order The order to fill.
                  /// @param signature The signature for `order`.
                  /// @param sellAmount Amount of taker token to sell.
                  /// @param protocolFee The protocol fee needed to fill `order`.
                  function _sellToOrder(
                      IERC20TokenV06 makerToken,
                      IERC20TokenV06 takerToken,
                      IExchange.Order memory order,
                      bytes memory signature,
                      uint256 sellAmount,
                      uint256 protocolFee
                  )
                      private
                      returns (FillOrderResults memory results)
                  {
                      IERC20TokenV06 takerFeeToken =
                          _getTokenFromERC20AssetData(order.takerFeeAssetData);
                      uint256 takerTokenFillAmount = sellAmount;
                      if (order.takerFee != 0) {
                          if (takerFeeToken == makerToken) {
                              // Taker fee is payable in the maker token, so we need to
                              // approve the proxy to spend the maker token.
                              // It isn't worth computing the actual taker fee
                              // since `approveIfBelow()` will set the allowance to infinite. We
                              // just need a reasonable upper bound to avoid unnecessarily re-approving.
                              takerFeeToken.approveIfBelow(erc20Proxy, order.takerFee);
                          } else if (takerFeeToken == takerToken){
                              // Taker fee is payable in the taker token, so we need to
                              // reduce the fill amount to cover the fee.
                              // takerTokenFillAmount' =
                              //   (takerTokenFillAmount * order.takerAssetAmount) /
                              //   (order.takerAssetAmount + order.takerFee)
                              takerTokenFillAmount = LibMathV06.getPartialAmountCeil(
                                  order.takerAssetAmount,
                                  order.takerAssetAmount.safeAdd(order.takerFee),
                                  sellAmount
                              );
                          } else {
                              //  Only support taker or maker asset denominated taker fees.
                              LibTransformERC20RichErrors.InvalidTakerFeeTokenError(
                                  address(takerFeeToken)
                              ).rrevert();
                          }
                      }
                      // Clamp fill amount to order size.
                      takerTokenFillAmount = LibSafeMathV06.min256(
                          takerTokenFillAmount,
                          order.takerAssetAmount
                      );
                      // Perform the fill.
                      return _fillOrder(
                          order,
                          signature,
                          takerTokenFillAmount,
                          protocolFee,
                          makerToken,
                          takerFeeToken == takerToken
                      );
                  }
                  /// @dev Try to buy up to `buyAmount` from an order.
                  /// @param makerToken The maker/buy token.
                  /// @param takerToken The taker/sell token.
                  /// @param order The order to fill.
                  /// @param signature The signature for `order`.
                  /// @param buyAmount Amount of maker token to buy.
                  /// @param protocolFee The protocol fee needed to fill `order`.
                  function _buyFromOrder(
                      IERC20TokenV06 makerToken,
                      IERC20TokenV06 takerToken,
                      IExchange.Order memory order,
                      bytes memory signature,
                      uint256 buyAmount,
                      uint256 protocolFee
                  )
                      private
                      returns (FillOrderResults memory results)
                  {
                      IERC20TokenV06 takerFeeToken =
                          _getTokenFromERC20AssetData(order.takerFeeAssetData);
                      // Compute the default taker token fill amount.
                      uint256 takerTokenFillAmount = LibMathV06.getPartialAmountCeil(
                          buyAmount,
                          order.makerAssetAmount,
                          order.takerAssetAmount
                      );
                      if (order.takerFee != 0) {
                          if (takerFeeToken == makerToken) {
                              // Taker fee is payable in the maker token.
                              // Adjust the taker token fill amount to account for maker
                              // tokens being lost to the taker fee.
                              // takerTokenFillAmount' =
                              //  (order.takerAssetAmount * buyAmount) /
                              //  (order.makerAssetAmount - order.takerFee)
                              takerTokenFillAmount = LibMathV06.getPartialAmountCeil(
                                  buyAmount,
                                  order.makerAssetAmount.safeSub(order.takerFee),
                                  order.takerAssetAmount
                              );
                              // Approve the proxy to spend the maker token.
                              // It isn't worth computing the actual taker fee
                              // since `approveIfBelow()` will set the allowance to infinite. We
                              // just need a reasonable upper bound to avoid unnecessarily re-approving.
                              takerFeeToken.approveIfBelow(erc20Proxy, order.takerFee);
                          } else if (takerFeeToken != takerToken) {
                              //  Only support taker or maker asset denominated taker fees.
                              LibTransformERC20RichErrors.InvalidTakerFeeTokenError(
                                  address(takerFeeToken)
                              ).rrevert();
                          }
                      }
                      // Clamp to order size.
                      takerTokenFillAmount = LibSafeMathV06.min256(
                          order.takerAssetAmount,
                          takerTokenFillAmount
                      );
                      // Perform the fill.
                      return _fillOrder(
                          order,
                          signature,
                          takerTokenFillAmount,
                          protocolFee,
                          makerToken,
                          takerFeeToken == takerToken
                      );
                  }
                  /// @dev Attempt to fill an order. If the fill reverts, the revert will be
                  ///      swallowed and `results` will be zeroed out.
                  /// @param order The order to fill.
                  /// @param signature The order signature.
                  /// @param takerAssetFillAmount How much taker asset to fill.
                  /// @param protocolFee The protocol fee needed to fill this order.
                  /// @param makerToken The maker token.
                  /// @param isTakerFeeInTakerToken Whether the taker fee token is the same as the
                  ///        taker token.
                  function _fillOrder(
                      IExchange.Order memory order,
                      bytes memory signature,
                      uint256 takerAssetFillAmount,
                      uint256 protocolFee,
                      IERC20TokenV06 makerToken,
                      bool isTakerFeeInTakerToken
                  )
                      private
                      returns (FillOrderResults memory results)
                  {
                      // Track changes in the maker token balance.
                      uint256 initialMakerTokenBalance = makerToken.balanceOf(address(this));
                      try
                          exchange.fillOrder
                              {value: protocolFee}
                              (order, takerAssetFillAmount, signature)
                          returns (IExchange.FillResults memory fillResults)
                      {
                          // Update maker quantity based on changes in token balances.
                          results.makerTokenBoughtAmount = makerToken.balanceOf(address(this))
                              .safeSub(initialMakerTokenBalance);
                          // We can trust the other fill result quantities.
                          results.protocolFeePaid = fillResults.protocolFeePaid;
                          results.takerTokenSoldAmount = fillResults.takerAssetFilledAmount;
                          // If the taker fee is payable in the taker asset, include the
                          // taker fee in the total amount sold.
                          if (isTakerFeeInTakerToken) {
                              results.takerTokenSoldAmount =
                                  results.takerTokenSoldAmount.safeAdd(fillResults.takerFeePaid);
                          }
                      } catch (bytes memory) {
                          // Swallow failures, leaving all results as zero.
                      }
                  }
                  /// @dev Extract the token from plain ERC20 asset data.
                  ///      If the asset-data is empty, a zero token address will be returned.
                  /// @param assetData The order asset data.
                  function _getTokenFromERC20AssetData(bytes memory assetData)
                      private
                      pure
                      returns (IERC20TokenV06 token)
                  {
                      if (assetData.length == 0) {
                          return IERC20TokenV06(address(0));
                      }
                      if (assetData.length != 36 ||
                          LibBytesV06.readBytes4(assetData, 0) != ERC20_ASSET_PROXY_ID)
                      {
                          LibTransformERC20RichErrors
                              .InvalidERC20AssetDataError(assetData)
                              .rrevert();
                      }
                      return IERC20TokenV06(LibBytesV06.readAddress(assetData, 16));
                  }
              }
              /*
                Copyright 2019 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./LibSafeMathV06.sol";
              import "./errors/LibRichErrorsV06.sol";
              import "./errors/LibMathRichErrorsV06.sol";
              library LibMathV06 {
                  using LibSafeMathV06 for uint256;
                  /// @dev Calculates partial value given a numerator and denominator rounded down.
                  ///      Reverts if rounding error is >= 0.1%
                  /// @param numerator Numerator.
                  /// @param denominator Denominator.
                  /// @param target Value to calculate partial of.
                  /// @return partialAmount Partial value of target rounded down.
                  function safeGetPartialAmountFloor(
                      uint256 numerator,
                      uint256 denominator,
                      uint256 target
                  )
                      internal
                      pure
                      returns (uint256 partialAmount)
                  {
                      if (isRoundingErrorFloor(
                              numerator,
                              denominator,
                              target
                      )) {
                          LibRichErrorsV06.rrevert(LibMathRichErrorsV06.RoundingError(
                              numerator,
                              denominator,
                              target
                          ));
                      }
                      partialAmount = numerator.safeMul(target).safeDiv(denominator);
                      return partialAmount;
                  }
                  /// @dev Calculates partial value given a numerator and denominator rounded down.
                  ///      Reverts if rounding error is >= 0.1%
                  /// @param numerator Numerator.
                  /// @param denominator Denominator.
                  /// @param target Value to calculate partial of.
                  /// @return partialAmount Partial value of target rounded up.
                  function safeGetPartialAmountCeil(
                      uint256 numerator,
                      uint256 denominator,
                      uint256 target
                  )
                      internal
                      pure
                      returns (uint256 partialAmount)
                  {
                      if (isRoundingErrorCeil(
                              numerator,
                              denominator,
                              target
                      )) {
                          LibRichErrorsV06.rrevert(LibMathRichErrorsV06.RoundingError(
                              numerator,
                              denominator,
                              target
                          ));
                      }
                      // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
                      //       ceil(a / b) = floor((a + b - 1) / b)
                      // To implement `ceil(a / b)` using safeDiv.
                      partialAmount = numerator.safeMul(target)
                          .safeAdd(denominator.safeSub(1))
                          .safeDiv(denominator);
                      return partialAmount;
                  }
                  /// @dev Calculates partial value given a numerator and denominator rounded down.
                  /// @param numerator Numerator.
                  /// @param denominator Denominator.
                  /// @param target Value to calculate partial of.
                  /// @return partialAmount Partial value of target rounded down.
                  function getPartialAmountFloor(
                      uint256 numerator,
                      uint256 denominator,
                      uint256 target
                  )
                      internal
                      pure
                      returns (uint256 partialAmount)
                  {
                      partialAmount = numerator.safeMul(target).safeDiv(denominator);
                      return partialAmount;
                  }
                  /// @dev Calculates partial value given a numerator and denominator rounded down.
                  /// @param numerator Numerator.
                  /// @param denominator Denominator.
                  /// @param target Value to calculate partial of.
                  /// @return partialAmount Partial value of target rounded up.
                  function getPartialAmountCeil(
                      uint256 numerator,
                      uint256 denominator,
                      uint256 target
                  )
                      internal
                      pure
                      returns (uint256 partialAmount)
                  {
                      // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
                      //       ceil(a / b) = floor((a + b - 1) / b)
                      // To implement `ceil(a / b)` using safeDiv.
                      partialAmount = numerator.safeMul(target)
                          .safeAdd(denominator.safeSub(1))
                          .safeDiv(denominator);
                      return partialAmount;
                  }
                  /// @dev Checks if rounding error >= 0.1% when rounding down.
                  /// @param numerator Numerator.
                  /// @param denominator Denominator.
                  /// @param target Value to multiply with numerator/denominator.
                  /// @return isError Rounding error is present.
                  function isRoundingErrorFloor(
                      uint256 numerator,
                      uint256 denominator,
                      uint256 target
                  )
                      internal
                      pure
                      returns (bool isError)
                  {
                      if (denominator == 0) {
                          LibRichErrorsV06.rrevert(LibMathRichErrorsV06.DivisionByZeroError());
                      }
                      // The absolute rounding error is the difference between the rounded
                      // value and the ideal value. The relative rounding error is the
                      // absolute rounding error divided by the absolute value of the
                      // ideal value. This is undefined when the ideal value is zero.
                      //
                      // The ideal value is `numerator * target / denominator`.
                      // Let's call `numerator * target % denominator` the remainder.
                      // The absolute error is `remainder / denominator`.
                      //
                      // When the ideal value is zero, we require the absolute error to
                      // be zero. Fortunately, this is always the case. The ideal value is
                      // zero iff `numerator == 0` and/or `target == 0`. In this case the
                      // remainder and absolute error are also zero.
                      if (target == 0 || numerator == 0) {
                          return false;
                      }
                      // Otherwise, we want the relative rounding error to be strictly
                      // less than 0.1%.
                      // The relative error is `remainder / (numerator * target)`.
                      // We want the relative error less than 1 / 1000:
                      //        remainder / (numerator * denominator)  <  1 / 1000
                      // or equivalently:
                      //        1000 * remainder  <  numerator * target
                      // so we have a rounding error iff:
                      //        1000 * remainder  >=  numerator * target
                      uint256 remainder = mulmod(
                          target,
                          numerator,
                          denominator
                      );
                      isError = remainder.safeMul(1000) >= numerator.safeMul(target);
                      return isError;
                  }
                  /// @dev Checks if rounding error >= 0.1% when rounding up.
                  /// @param numerator Numerator.
                  /// @param denominator Denominator.
                  /// @param target Value to multiply with numerator/denominator.
                  /// @return isError Rounding error is present.
                  function isRoundingErrorCeil(
                      uint256 numerator,
                      uint256 denominator,
                      uint256 target
                  )
                      internal
                      pure
                      returns (bool isError)
                  {
                      if (denominator == 0) {
                          LibRichErrorsV06.rrevert(LibMathRichErrorsV06.DivisionByZeroError());
                      }
                      // See the comments in `isRoundingError`.
                      if (target == 0 || numerator == 0) {
                          // When either is zero, the ideal value and rounded value are zero
                          // and there is no rounding error. (Although the relative error
                          // is undefined.)
                          return false;
                      }
                      // Compute remainder as before
                      uint256 remainder = mulmod(
                          target,
                          numerator,
                          denominator
                      );
                      remainder = denominator.safeSub(remainder) % denominator;
                      isError = remainder.safeMul(1000) >= numerator.safeMul(target);
                      return isError;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibMathRichErrorsV06 {
                  // bytes4(keccak256("DivisionByZeroError()"))
                  bytes internal constant DIVISION_BY_ZERO_ERROR =
                      hex"a791837c";
                  // bytes4(keccak256("RoundingError(uint256,uint256,uint256)"))
                  bytes4 internal constant ROUNDING_ERROR_SELECTOR =
                      0x339f3de2;
                  // solhint-disable func-name-mixedcase
                  function DivisionByZeroError()
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return DIVISION_BY_ZERO_ERROR;
                  }
                  function RoundingError(
                      uint256 numerator,
                      uint256 denominator,
                      uint256 target
                  )
                      internal
                      pure
                      returns (bytes memory)
                  {
                      return abi.encodeWithSelector(
                          ROUNDING_ERROR_SELECTOR,
                          numerator,
                          denominator,
                          target
                      );
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev Interface to the V3 Exchange.
              interface IExchange {
                  /// @dev V3 Order structure.
                  struct Order {
                      // Address that created the order.
                      address makerAddress;
                      // Address that is allowed to fill the order.
                      // If set to 0, any address is allowed to fill the order.
                      address takerAddress;
                      // Address that will recieve fees when order is filled.
                      address feeRecipientAddress;
                      // Address that is allowed to call Exchange contract methods that affect this order.
                      // If set to 0, any address is allowed to call these methods.
                      address senderAddress;
                      // Amount of makerAsset being offered by maker. Must be greater than 0.
                      uint256 makerAssetAmount;
                      // Amount of takerAsset being bid on by maker. Must be greater than 0.
                      uint256 takerAssetAmount;
                      // Fee paid to feeRecipient by maker when order is filled.
                      uint256 makerFee;
                      // Fee paid to feeRecipient by taker when order is filled.
                      uint256 takerFee;
                      // Timestamp in seconds at which order expires.
                      uint256 expirationTimeSeconds;
                      // Arbitrary number to facilitate uniqueness of the order's hash.
                      uint256 salt;
                      // Encoded data that can be decoded by a specified proxy contract when transferring makerAsset.
                      // The leading bytes4 references the id of the asset proxy.
                      bytes makerAssetData;
                      // Encoded data that can be decoded by a specified proxy contract when transferring takerAsset.
                      // The leading bytes4 references the id of the asset proxy.
                      bytes takerAssetData;
                      // Encoded data that can be decoded by a specified proxy contract when transferring makerFeeAsset.
                      // The leading bytes4 references the id of the asset proxy.
                      bytes makerFeeAssetData;
                      // Encoded data that can be decoded by a specified proxy contract when transferring takerFeeAsset.
                      // The leading bytes4 references the id of the asset proxy.
                      bytes takerFeeAssetData;
                  }
                  /// @dev V3 `fillOrder()` results.`
                  struct FillResults {
                      // Total amount of makerAsset(s) filled.
                      uint256 makerAssetFilledAmount;
                      // Total amount of takerAsset(s) filled.
                      uint256 takerAssetFilledAmount;
                      // Total amount of fees paid by maker(s) to feeRecipient(s).
                      uint256 makerFeePaid;
                      // Total amount of fees paid by taker to feeRecipients(s).
                      uint256 takerFeePaid;
                      // Total amount of fees paid by taker to the staking contract.
                      uint256 protocolFeePaid;
                  }
                  /// @dev Fills the input order.
                  /// @param order Order struct containing order specifications.
                  /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
                  /// @param signature Proof that order has been created by maker.
                  /// @return fillResults Amounts filled and fees paid by maker and taker.
                  function fillOrder(
                      Order calldata order,
                      uint256 takerAssetFillAmount,
                      bytes calldata signature
                  )
                      external
                      payable
                      returns (FillResults memory fillResults);
                  /// @dev Returns the protocolFeeMultiplier
                  /// @return multiplier The multiplier for protocol fees.
                  function protocolFeeMultiplier()
                      external
                      view
                      returns (uint256 multiplier);
                  /// @dev Gets an asset proxy.
                  /// @param assetProxyId Id of the asset proxy.
                  /// @return proxyAddress The asset proxy registered to assetProxyId.
                  ///         Returns 0x0 if no proxy is registered.
                  function getAssetProxy(bytes4 assetProxyId)
                      external
                      view
                      returns (address proxyAddress);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
              import "../errors/LibTransformERC20RichErrors.sol";
              import "./Transformer.sol";
              import "./LibERC20Transformer.sol";
              /// @dev A transformer that transfers tokens to the taker.
              contract PayTakerTransformer is
                  Transformer
              {
                  // solhint-disable no-empty-blocks
                  using LibRichErrorsV06 for bytes;
                  using LibSafeMathV06 for uint256;
                  using LibERC20Transformer for IERC20TokenV06;
                  /// @dev Transform data to ABI-encode and pass into `transform()`.
                  struct TransformData {
                      // The tokens to transfer to the taker.
                      IERC20TokenV06[] tokens;
                      // Amount of each token in `tokens` to transfer to the taker.
                      // `uint(-1)` will transfer the entire balance.
                      uint256[] amounts;
                  }
                  /// @dev Maximum uint256 value.
                  uint256 private constant MAX_UINT256 = uint256(-1);
                  /// @dev Create this contract.
                  constructor()
                      public
                      Transformer()
                  {}
                  /// @dev Forwards tokens to the taker.
                  /// @param taker The taker address (caller of `TransformERC20.transformERC20()`).
                  /// @param data_ ABI-encoded `TransformData`, indicating which tokens to transfer.
                  /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                  function transform(
                      bytes32, // callDataHash,
                      address payable taker,
                      bytes calldata data_
                  )
                      external
                      override
                      returns (bytes4 success)
                  {
                      TransformData memory data = abi.decode(data_, (TransformData));
                      // Transfer tokens directly to the taker.
                      for (uint256 i = 0; i < data.tokens.length; ++i) {
                          // The `amounts` array can be shorter than the `tokens` array.
                          // Missing elements are treated as `uint256(-1)`.
                          uint256 amount = data.amounts.length > i ? data.amounts[i] : uint256(-1);
                          if (amount == MAX_UINT256) {
                              amount = data.tokens[i].getTokenBalanceOf(address(this));
                          }
                          if (amount != 0) {
                              data.tokens[i].transformerTransfer(taker, amount);
                          }
                      }
                      return LibERC20Transformer.TRANSFORMER_SUCCESS;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
              import "../errors/LibTransformERC20RichErrors.sol";
              import "./Transformer.sol";
              import "./LibERC20Transformer.sol";
              /// @dev A transformer that wraps or unwraps WETH.
              contract WethTransformer is
                  Transformer
              {
                  using LibRichErrorsV06 for bytes;
                  using LibSafeMathV06 for uint256;
                  using LibERC20Transformer for IERC20TokenV06;
                  /// @dev Transform data to ABI-encode and pass into `transform()`.
                  struct TransformData {
                      // The token to wrap/unwrap. Must be either ETH or WETH.
                      IERC20TokenV06 token;
                      // Amount of `token` to wrap or unwrap.
                      // `uint(-1)` will unwrap the entire balance.
                      uint256 amount;
                  }
                  /// @dev The WETH contract address.
                  IEtherTokenV06 public immutable weth;
                  /// @dev Maximum uint256 value.
                  uint256 private constant MAX_UINT256 = uint256(-1);
                  /// @dev Construct the transformer and store the WETH address in an immutable.
                  /// @param weth_ The weth token.
                  constructor(IEtherTokenV06 weth_)
                      public
                      Transformer()
                  {
                      weth = weth_;
                  }
                  /// @dev Wraps and unwraps WETH.
                  /// @param data_ ABI-encoded `TransformData`, indicating which token to wrap/umwrap.
                  /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                  function transform(
                      bytes32, // callDataHash,
                      address payable, // taker,
                      bytes calldata data_
                  )
                      external
                      override
                      returns (bytes4 success)
                  {
                      TransformData memory data = abi.decode(data_, (TransformData));
                      if (!data.token.isTokenETH() && data.token != weth) {
                          LibTransformERC20RichErrors.InvalidTransformDataError(
                              LibTransformERC20RichErrors.InvalidTransformDataErrorCode.INVALID_TOKENS,
                              data_
                          ).rrevert();
                      }
                      uint256 amount = data.amount;
                      if (amount == MAX_UINT256) {
                          amount = data.token.getTokenBalanceOf(address(this));
                      }
                      if (amount != 0) {
                          if (data.token.isTokenETH()) {
                              // Wrap ETH.
                              weth.deposit{value: amount}();
                          } else {
                              // Unwrap WETH.
                              weth.withdraw(amount);
                          }
                      }
                      return LibERC20Transformer.TRANSFORMER_SUCCESS;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./IERC20TokenV06.sol";
              interface IEtherTokenV06 is
                  IERC20TokenV06
              {
                  /// @dev Wrap ether.
                  function deposit() external payable;
                  /// @dev Unwrap ether.
                  function withdraw(uint256 amount) external;
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              interface ITestSimpleFunctionRegistryFeature {
                  function testFn() external view returns (uint256 id);
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              contract TestCallTarget {
                  event CallTargetCalled(
                      address context,
                      address sender,
                      bytes data,
                      uint256 value
                  );
                  bytes4 private constant MAGIC_BYTES = 0x12345678;
                  bytes private constant REVERTING_DATA = hex"1337";
                  fallback() external payable {
                      if (keccak256(msg.data) == keccak256(REVERTING_DATA)) {
                          revert("TestCallTarget/REVERT");
                      }
                      emit CallTargetCalled(
                          address(this),
                          msg.sender,
                          msg.data,
                          msg.value
                      );
                      bytes4 rval = MAGIC_BYTES;
                      assembly {
                          mstore(0, rval)
                          return(0, 32)
                      }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              contract TestDelegateCaller {
                  function executeDelegateCall(
                      address target,
                      bytes calldata callData
                  )
                      external
                  {
                      (bool success, bytes memory resultData) = target.delegatecall(callData);
                      if (!success) {
                          assembly { revert(add(resultData, 32), mload(resultData)) }
                      }
                      assembly { return(add(resultData, 32), mload(resultData)) }
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibMathV06.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              import "../src/vendor/v3/IExchange.sol";
              import "./TestMintableERC20Token.sol";
              contract TestFillQuoteTransformerExchange {
                  struct FillBehavior {
                      // How much of the order is filled, in taker asset amount.
                      uint256 filledTakerAssetAmount;
                      // Scaling for maker assets minted, in 1e18.
                      uint256 makerAssetMintRatio;
                  }
                  uint256 private constant PROTOCOL_FEE_MULTIPLIER = 1337;
                  using LibSafeMathV06 for uint256;
                  function fillOrder(
                      IExchange.Order calldata order,
                      uint256 takerAssetFillAmount,
                      bytes calldata signature
                  )
                      external
                      payable
                      returns (IExchange.FillResults memory fillResults)
                  {
                      require(
                          signature.length != 0,
                          "TestFillQuoteTransformerExchange/INVALID_SIGNATURE"
                      );
                      // The signature is the ABI-encoded FillBehavior data.
                      FillBehavior memory behavior = abi.decode(signature, (FillBehavior));
                      uint256 protocolFee = PROTOCOL_FEE_MULTIPLIER * tx.gasprice;
                      require(
                          msg.value == protocolFee,
                          "TestFillQuoteTransformerExchange/INSUFFICIENT_PROTOCOL_FEE"
                      );
                      // Return excess protocol fee.
                      msg.sender.transfer(msg.value - protocolFee);
                      // Take taker tokens.
                      TestMintableERC20Token takerToken = _getTokenFromAssetData(order.takerAssetData);
                      takerAssetFillAmount = LibSafeMathV06.min256(
                          order.takerAssetAmount.safeSub(behavior.filledTakerAssetAmount),
                          takerAssetFillAmount
                      );
                      require(
                          takerToken.getSpendableAmount(msg.sender, address(this)) >= takerAssetFillAmount,
                          "TestFillQuoteTransformerExchange/INSUFFICIENT_TAKER_FUNDS"
                      );
                      takerToken.transferFrom(msg.sender, order.makerAddress, takerAssetFillAmount);
                      // Mint maker tokens.
                      uint256 makerAssetFilledAmount = LibMathV06.getPartialAmountFloor(
                          takerAssetFillAmount,
                          order.takerAssetAmount,
                          order.makerAssetAmount
                      );
                      TestMintableERC20Token makerToken = _getTokenFromAssetData(order.makerAssetData);
                      makerToken.mint(
                          msg.sender,
                          LibMathV06.getPartialAmountFloor(
                              behavior.makerAssetMintRatio,
                              1e18,
                              makerAssetFilledAmount
                          )
                      );
                      // Take taker fee.
                      TestMintableERC20Token takerFeeToken = _getTokenFromAssetData(order.takerFeeAssetData);
                      uint256 takerFee = LibMathV06.getPartialAmountFloor(
                          takerAssetFillAmount,
                          order.takerAssetAmount,
                          order.takerFee
                      );
                      require(
                          takerFeeToken.getSpendableAmount(msg.sender, address(this)) >= takerFee,
                          "TestFillQuoteTransformerExchange/INSUFFICIENT_TAKER_FEE_FUNDS"
                      );
                      takerFeeToken.transferFrom(msg.sender, order.feeRecipientAddress, takerFee);
                      fillResults.makerAssetFilledAmount = makerAssetFilledAmount;
                      fillResults.takerAssetFilledAmount = takerAssetFillAmount;
                      fillResults.makerFeePaid = uint256(-1);
                      fillResults.takerFeePaid = takerFee;
                      fillResults.protocolFeePaid = protocolFee;
                  }
                  function encodeBehaviorData(FillBehavior calldata behavior)
                      external
                      pure
                      returns (bytes memory encoded)
                  {
                      return abi.encode(behavior);
                  }
                  function protocolFeeMultiplier()
                      external
                      pure
                      returns (uint256)
                  {
                      return PROTOCOL_FEE_MULTIPLIER;
                  }
                  function getAssetProxy(bytes4)
                      external
                      view
                      returns (address)
                  {
                      return address(this);
                  }
                  function _getTokenFromAssetData(bytes memory assetData)
                      private
                      pure
                      returns (TestMintableERC20Token token)
                  {
                      return TestMintableERC20Token(LibBytesV06.readAddress(assetData, 16));
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              contract TestMintableERC20Token {
                  mapping(address => uint256) public balanceOf;
                  mapping(address => mapping(address => uint256)) public allowance;
                  function transfer(address to, uint256 amount)
                      external
                      virtual
                      returns (bool)
                  {
                      return transferFrom(msg.sender, to, amount);
                  }
                  function approve(address spender, uint256 amount)
                      external
                      virtual
                      returns (bool)
                  {
                      allowance[msg.sender][spender] = amount;
                      return true;
                  }
                  function mint(address owner, uint256 amount)
                      external
                      virtual
                  {
                      balanceOf[owner] += amount;
                  }
                  function burn(address owner, uint256 amount)
                      external
                      virtual
                  {
                      require(balanceOf[owner] >= amount, "TestMintableERC20Token/INSUFFICIENT_FUNDS");
                      balanceOf[owner] -= amount;
                  }
                  function transferFrom(address from, address to, uint256 amount)
                      public
                      virtual
                      returns (bool)
                  {
                      if (from != msg.sender) {
                          require(
                              allowance[from][msg.sender] >= amount,
                              "TestMintableERC20Token/INSUFFICIENT_ALLOWANCE"
                          );
                          allowance[from][msg.sender] -= amount;
                      }
                      require(balanceOf[from] >= amount, "TestMintableERC20Token/INSUFFICIENT_FUNDS");
                      balanceOf[from] -= amount;
                      balanceOf[to] += amount;
                      return true;
                  }
                  function getSpendableAmount(address owner, address spender)
                      external
                      view
                      returns (uint256)
                  {
                      return balanceOf[owner] < allowance[owner][spender]
                          ? balanceOf[owner]
                          : allowance[owner][spender];
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/transformers/IERC20Transformer.sol";
              import "./TestMintableERC20Token.sol";
              import "./TestTransformerHost.sol";
              contract TestFillQuoteTransformerHost is
                  TestTransformerHost
              {
                  function executeTransform(
                      IERC20Transformer transformer,
                      TestMintableERC20Token inputToken,
                      uint256 inputTokenAmount,
                      bytes calldata data
                  )
                      external
                      payable
                  {
                      if (inputTokenAmount != 0) {
                          inputToken.mint(address(this), inputTokenAmount);
                      }
                      // Have to make this call externally because transformers aren't payable.
                      this.rawExecuteTransform(transformer, bytes32(0), msg.sender, data);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "../src/transformers/IERC20Transformer.sol";
              import "../src/transformers/LibERC20Transformer.sol";
              contract TestTransformerHost {
                  using LibERC20Transformer for IERC20TokenV06;
                  using LibRichErrorsV06 for bytes;
                  function rawExecuteTransform(
                      IERC20Transformer transformer,
                      bytes32 callDataHash,
                      address taker,
                      bytes calldata data
                  )
                      external
                  {
                      (bool _success, bytes memory resultData) =
                          address(transformer).delegatecall(abi.encodeWithSelector(
                              transformer.transform.selector,
                              callDataHash,
                              taker,
                              data
                          ));
                      if (!_success) {
                          resultData.rrevert();
                      }
                      require(
                          abi.decode(resultData, (bytes4)) == LibERC20Transformer.TRANSFORMER_SUCCESS,
                          "TestTransformerHost/INVALID_TRANSFORMER_RESULT"
                      );
                  }
                  // solhint-disable
                  receive() external payable {}
                  // solhint-enable
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/ZeroEx.sol";
              import "../src/features/IBootstrap.sol";
              import "../src/migrations/FullMigration.sol";
              contract TestFullMigration is
                  FullMigration
              {
                  address public dieRecipient;
                  // solhint-disable-next-line no-empty-blocks
                  constructor(address payable deployer) public FullMigration(deployer) {}
                  function die(address payable ethRecipient) external override {
                      dieRecipient = ethRecipient;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/ZeroEx.sol";
              import "../src/features/IBootstrap.sol";
              import "../src/migrations/InitialMigration.sol";
              contract TestInitialMigration is
                  InitialMigration
              {
                  address public bootstrapFeature;
                  address public dieRecipient;
                  // solhint-disable-next-line no-empty-blocks
                  constructor(address deployer) public InitialMigration(deployer) {}
                  function callBootstrap(ZeroEx zeroEx) external {
                      IBootstrap(address(zeroEx)).bootstrap(address(this), new bytes(0));
                  }
                  function bootstrap(address owner, BootstrapFeatures memory features)
                      public
                      override
                      returns (bytes4 success)
                  {
                      success = InitialMigration.bootstrap(owner, features);
                      // Snoop the bootstrap feature contract.
                      bootstrapFeature = ZeroEx(address(uint160(address(this))))
                          .getFunctionImplementation(IBootstrap.bootstrap.selector);
                  }
                  function die(address payable ethRecipient) public override {
                      dieRecipient = ethRecipient;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/migrations/LibMigrate.sol";
              import "../src/features/IOwnable.sol";
              contract TestMigrator {
                  event TestMigrateCalled(
                      bytes callData,
                      address owner
                  );
                  function succeedingMigrate() external returns (bytes4 success) {
                      emit TestMigrateCalled(
                          msg.data,
                          IOwnable(address(this)).owner()
                      );
                      return LibMigrate.MIGRATE_SUCCESS;
                  }
                  function failingMigrate() external returns (bytes4 success) {
                      emit TestMigrateCalled(
                          msg.data,
                          IOwnable(address(this)).owner()
                      );
                      return 0xdeadbeef;
                  }
                  function revertingMigrate() external pure {
                      revert("OOPSIE");
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
              import "../src/transformers/IERC20Transformer.sol";
              import "../src/transformers/LibERC20Transformer.sol";
              import "./TestMintableERC20Token.sol";
              contract TestMintTokenERC20Transformer is
                  IERC20Transformer
              {
                  struct TransformData {
                      IERC20TokenV06 inputToken;
                      TestMintableERC20Token outputToken;
                      uint256 burnAmount;
                      uint256 mintAmount;
                      uint256 feeAmount;
                  }
                  event MintTransform(
                      address context,
                      address caller,
                      bytes32 callDataHash,
                      address taker,
                      bytes data,
                      uint256 inputTokenBalance,
                      uint256 ethBalance
                  );
                  function transform(
                      bytes32 callDataHash,
                      address payable taker,
                      bytes calldata data_
                  )
                      external
                      override
                      returns (bytes4 success)
                  {
                      TransformData memory data = abi.decode(data_, (TransformData));
                      emit MintTransform(
                          address(this),
                          msg.sender,
                          callDataHash,
                          taker,
                          data_,
                          data.inputToken.balanceOf(address(this)),
                          address(this).balance
                      );
                      // "Burn" input tokens.
                      data.inputToken.transfer(address(0), data.burnAmount);
                      // Mint output tokens.
                      if (LibERC20Transformer.isTokenETH(IERC20TokenV06(address(data.outputToken)))) {
                          taker.transfer(data.mintAmount);
                      } else {
                          data.outputToken.mint(
                              taker,
                              data.mintAmount
                          );
                          // Burn fees from output.
                          data.outputToken.burn(taker, data.feeAmount);
                      }
                      return LibERC20Transformer.TRANSFORMER_SUCCESS;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/fixins/FixinCommon.sol";
              contract TestSimpleFunctionRegistryFeatureImpl1 is
                  FixinCommon
              {
                  function testFn()
                      external
                      pure
                      returns (uint256 id)
                  {
                      return 1337;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/fixins/FixinCommon.sol";
              contract TestSimpleFunctionRegistryFeatureImpl2 is
                  FixinCommon
              {
                  function testFn()
                      external
                      pure
                      returns (uint256 id)
                  {
                      return 1338;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/features/TokenSpender.sol";
              contract TestTokenSpender is
                  TokenSpender
              {
                  modifier onlySelf() override {
                      _;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "./TestMintableERC20Token.sol";
              contract TestTokenSpenderERC20Token is
                  TestMintableERC20Token
              {
                  event TransferFromCalled(
                      address sender,
                      address from,
                      address to,
                      uint256 amount
                  );
                  // `transferFrom()` behavior depends on the value of `amount`.
                  uint256 constant private EMPTY_RETURN_AMOUNT = 1337;
                  uint256 constant private FALSE_RETURN_AMOUNT = 1338;
                  uint256 constant private REVERT_RETURN_AMOUNT = 1339;
                  function transferFrom(address from, address to, uint256 amount)
                      public
                      override
                      returns (bool)
                  {
                      emit TransferFromCalled(msg.sender, from, to, amount);
                      if (amount == EMPTY_RETURN_AMOUNT) {
                          assembly { return(0, 0) }
                      }
                      if (amount == FALSE_RETURN_AMOUNT) {
                          return false;
                      }
                      if (amount == REVERT_RETURN_AMOUNT) {
                          revert("TestTokenSpenderERC20Token/Revert");
                      }
                      return true;
                  }
                  function setBalanceAndAllowanceOf(
                      address owner,
                      uint256 balance,
                      address spender,
                      uint256 allowance_
                  )
                      external
                  {
                      balanceOf[owner] = balance;
                      allowance[owner][spender] = allowance_;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/features/TransformERC20.sol";
              contract TestTransformERC20 is
                  TransformERC20
              {
                  // solhint-disable no-empty-blocks
                  constructor()
                      TransformERC20()
                      public
                  {}
                  modifier onlySelf() override {
                      _;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/transformers/Transformer.sol";
              import "../src/transformers/LibERC20Transformer.sol";
              contract TestTransformerBase is
                  Transformer
              {
                  function transform(
                      bytes32,
                      address payable,
                      bytes calldata
                  )
                      external
                      override
                      returns (bytes4 success)
                  {
                      return LibERC20Transformer.TRANSFORMER_SUCCESS;
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/transformers/LibERC20Transformer.sol";
              contract TestTransformerDeployerTransformer {
                  address payable public immutable deployer;
                  constructor() public payable {
                      deployer = msg.sender;
                  }
                  modifier onlyDeployer() {
                      require(msg.sender == deployer, "TestTransformerDeployerTransformer/ONLY_DEPLOYER");
                      _;
                  }
                  function die()
                      external
                      onlyDeployer
                  {
                      selfdestruct(deployer);
                  }
                  function isDeployedByDeployer(uint32 nonce)
                      external
                      view
                      returns (bool)
                  {
                      return LibERC20Transformer.getDeployedAddress(deployer, nonce) == address(this);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "./TestMintableERC20Token.sol";
              contract TestWeth is
                  TestMintableERC20Token
              {
                  function deposit()
                      external
                      payable
                  {
                      this.mint(msg.sender, msg.value);
                  }
                  function withdraw(uint256 amount)
                      external
                  {
                      require(balanceOf[msg.sender] >= amount, "TestWeth/INSUFFICIENT_FUNDS");
                      balanceOf[msg.sender] -= amount;
                      msg.sender.transfer(amount);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/transformers/IERC20Transformer.sol";
              import "./TestMintableERC20Token.sol";
              import "./TestTransformerHost.sol";
              import "./TestWeth.sol";
              contract TestWethTransformerHost is
                  TestTransformerHost
              {
                  // solhint-disable
                  TestWeth private immutable _weth;
                  // solhint-enable
                  constructor(TestWeth weth) public {
                      _weth = weth;
                  }
                  function executeTransform(
                      uint256 wethAmount,
                      IERC20Transformer transformer,
                      bytes calldata data
                  )
                      external
                      payable
                  {
                      if (wethAmount != 0) {
                          _weth.deposit{value: wethAmount}();
                      }
                      // Have to make this call externally because transformers aren't payable.
                      this.rawExecuteTransform(transformer, bytes32(0), msg.sender, data);
                  }
              }
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "../src/fixins/FixinCommon.sol";
              import "../src/ZeroEx.sol";
              contract TestZeroExFeature is
                  FixinCommon
              {
                  event PayableFnCalled(uint256 value);
                  event NotPayableFnCalled();
                  function payableFn()
                      external
                      payable
                  {
                      emit PayableFnCalled(msg.value);
                  }
                  function notPayableFn()
                      external
                  {
                      emit NotPayableFnCalled();
                  }
                  // solhint-disable no-empty-blocks
                  function unimplmentedFn()
                      external
                  {}
                  function internalFn()
                      external
                      onlySelf
                  {}
              }
              

              File 2 of 4: WETH9
              // Copyright (C) 2015, 2016, 2017 Dapphub
              
              // This program is free software: you can redistribute it and/or modify
              // it under the terms of the GNU General Public License as published by
              // the Free Software Foundation, either version 3 of the License, or
              // (at your option) any later version.
              
              // This program is distributed in the hope that it will be useful,
              // but WITHOUT ANY WARRANTY; without even the implied warranty of
              // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
              // GNU General Public License for more details.
              
              // You should have received a copy of the GNU General Public License
              // along with this program.  If not, see <http://www.gnu.org/licenses/>.
              
              pragma solidity ^0.4.18;
              
              contract WETH9 {
                  string public name     = "Wrapped Ether";
                  string public symbol   = "WETH";
                  uint8  public decimals = 18;
              
                  event  Approval(address indexed src, address indexed guy, uint wad);
                  event  Transfer(address indexed src, address indexed dst, uint wad);
                  event  Deposit(address indexed dst, uint wad);
                  event  Withdrawal(address indexed src, uint wad);
              
                  mapping (address => uint)                       public  balanceOf;
                  mapping (address => mapping (address => uint))  public  allowance;
              
                  function() public payable {
                      deposit();
                  }
                  function deposit() public payable {
                      balanceOf[msg.sender] += msg.value;
                      Deposit(msg.sender, msg.value);
                  }
                  function withdraw(uint wad) public {
                      require(balanceOf[msg.sender] >= wad);
                      balanceOf[msg.sender] -= wad;
                      msg.sender.transfer(wad);
                      Withdrawal(msg.sender, wad);
                  }
              
                  function totalSupply() public view returns (uint) {
                      return this.balance;
                  }
              
                  function approve(address guy, uint wad) public returns (bool) {
                      allowance[msg.sender][guy] = wad;
                      Approval(msg.sender, guy, wad);
                      return true;
                  }
              
                  function transfer(address dst, uint wad) public returns (bool) {
                      return transferFrom(msg.sender, dst, wad);
                  }
              
                  function transferFrom(address src, address dst, uint wad)
                      public
                      returns (bool)
                  {
                      require(balanceOf[src] >= wad);
              
                      if (src != msg.sender && allowance[src][msg.sender] != uint(-1)) {
                          require(allowance[src][msg.sender] >= wad);
                          allowance[src][msg.sender] -= wad;
                      }
              
                      balanceOf[src] -= wad;
                      balanceOf[dst] += wad;
              
                      Transfer(src, dst, wad);
              
                      return true;
                  }
              }
              
              
              /*
                                  GNU GENERAL PUBLIC LICENSE
                                     Version 3, 29 June 2007
              
               Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
               Everyone is permitted to copy and distribute verbatim copies
               of this license document, but changing it is not allowed.
              
                                          Preamble
              
                The GNU General Public License is a free, copyleft license for
              software and other kinds of works.
              
                The licenses for most software and other practical works are designed
              to take away your freedom to share and change the works.  By contrast,
              the GNU General Public License is intended to guarantee your freedom to
              share and change all versions of a program--to make sure it remains free
              software for all its users.  We, the Free Software Foundation, use the
              GNU General Public License for most of our software; it applies also to
              any other work released this way by its authors.  You can apply it to
              your programs, too.
              
                When we speak of free software, we are referring to freedom, not
              price.  Our General Public Licenses are designed to make sure that you
              have the freedom to distribute copies of free software (and charge for
              them if you wish), that you receive source code or can get it if you
              want it, that you can change the software or use pieces of it in new
              free programs, and that you know you can do these things.
              
                To protect your rights, we need to prevent others from denying you
              these rights or asking you to surrender the rights.  Therefore, you have
              certain responsibilities if you distribute copies of the software, or if
              you modify it: responsibilities to respect the freedom of others.
              
                For example, if you distribute copies of such a program, whether
              gratis or for a fee, you must pass on to the recipients the same
              freedoms that you received.  You must make sure that they, too, receive
              or can get the source code.  And you must show them these terms so they
              know their rights.
              
                Developers that use the GNU GPL protect your rights with two steps:
              (1) assert copyright on the software, and (2) offer you this License
              giving you legal permission to copy, distribute and/or modify it.
              
                For the developers' and authors' protection, the GPL clearly explains
              that there is no warranty for this free software.  For both users' and
              authors' sake, the GPL requires that modified versions be marked as
              changed, so that their problems will not be attributed erroneously to
              authors of previous versions.
              
                Some devices are designed to deny users access to install or run
              modified versions of the software inside them, although the manufacturer
              can do so.  This is fundamentally incompatible with the aim of
              protecting users' freedom to change the software.  The systematic
              pattern of such abuse occurs in the area of products for individuals to
              use, which is precisely where it is most unacceptable.  Therefore, we
              have designed this version of the GPL to prohibit the practice for those
              products.  If such problems arise substantially in other domains, we
              stand ready to extend this provision to those domains in future versions
              of the GPL, as needed to protect the freedom of users.
              
                Finally, every program is threatened constantly by software patents.
              States should not allow patents to restrict development and use of
              software on general-purpose computers, but in those that do, we wish to
              avoid the special danger that patents applied to a free program could
              make it effectively proprietary.  To prevent this, the GPL assures that
              patents cannot be used to render the program non-free.
              
                The precise terms and conditions for copying, distribution and
              modification follow.
              
                                     TERMS AND CONDITIONS
              
                0. Definitions.
              
                "This License" refers to version 3 of the GNU General Public License.
              
                "Copyright" also means copyright-like laws that apply to other kinds of
              works, such as semiconductor masks.
              
                "The Program" refers to any copyrightable work licensed under this
              License.  Each licensee is addressed as "you".  "Licensees" and
              "recipients" may be individuals or organizations.
              
                To "modify" a work means to copy from or adapt all or part of the work
              in a fashion requiring copyright permission, other than the making of an
              exact copy.  The resulting work is called a "modified version" of the
              earlier work or a work "based on" the earlier work.
              
                A "covered work" means either the unmodified Program or a work based
              on the Program.
              
                To "propagate" a work means to do anything with it that, without
              permission, would make you directly or secondarily liable for
              infringement under applicable copyright law, except executing it on a
              computer or modifying a private copy.  Propagation includes copying,
              distribution (with or without modification), making available to the
              public, and in some countries other activities as well.
              
                To "convey" a work means any kind of propagation that enables other
              parties to make or receive copies.  Mere interaction with a user through
              a computer network, with no transfer of a copy, is not conveying.
              
                An interactive user interface displays "Appropriate Legal Notices"
              to the extent that it includes a convenient and prominently visible
              feature that (1) displays an appropriate copyright notice, and (2)
              tells the user that there is no warranty for the work (except to the
              extent that warranties are provided), that licensees may convey the
              work under this License, and how to view a copy of this License.  If
              the interface presents a list of user commands or options, such as a
              menu, a prominent item in the list meets this criterion.
              
                1. Source Code.
              
                The "source code" for a work means the preferred form of the work
              for making modifications to it.  "Object code" means any non-source
              form of a work.
              
                A "Standard Interface" means an interface that either is an official
              standard defined by a recognized standards body, or, in the case of
              interfaces specified for a particular programming language, one that
              is widely used among developers working in that language.
              
                The "System Libraries" of an executable work include anything, other
              than the work as a whole, that (a) is included in the normal form of
              packaging a Major Component, but which is not part of that Major
              Component, and (b) serves only to enable use of the work with that
              Major Component, or to implement a Standard Interface for which an
              implementation is available to the public in source code form.  A
              "Major Component", in this context, means a major essential component
              (kernel, window system, and so on) of the specific operating system
              (if any) on which the executable work runs, or a compiler used to
              produce the work, or an object code interpreter used to run it.
              
                The "Corresponding Source" for a work in object code form means all
              the source code needed to generate, install, and (for an executable
              work) run the object code and to modify the work, including scripts to
              control those activities.  However, it does not include the work's
              System Libraries, or general-purpose tools or generally available free
              programs which are used unmodified in performing those activities but
              which are not part of the work.  For example, Corresponding Source
              includes interface definition files associated with source files for
              the work, and the source code for shared libraries and dynamically
              linked subprograms that the work is specifically designed to require,
              such as by intimate data communication or control flow between those
              subprograms and other parts of the work.
              
                The Corresponding Source need not include anything that users
              can regenerate automatically from other parts of the Corresponding
              Source.
              
                The Corresponding Source for a work in source code form is that
              same work.
              
                2. Basic Permissions.
              
                All rights granted under this License are granted for the term of
              copyright on the Program, and are irrevocable provided the stated
              conditions are met.  This License explicitly affirms your unlimited
              permission to run the unmodified Program.  The output from running a
              covered work is covered by this License only if the output, given its
              content, constitutes a covered work.  This License acknowledges your
              rights of fair use or other equivalent, as provided by copyright law.
              
                You may make, run and propagate covered works that you do not
              convey, without conditions so long as your license otherwise remains
              in force.  You may convey covered works to others for the sole purpose
              of having them make modifications exclusively for you, or provide you
              with facilities for running those works, provided that you comply with
              the terms of this License in conveying all material for which you do
              not control copyright.  Those thus making or running the covered works
              for you must do so exclusively on your behalf, under your direction
              and control, on terms that prohibit them from making any copies of
              your copyrighted material outside their relationship with you.
              
                Conveying under any other circumstances is permitted solely under
              the conditions stated below.  Sublicensing is not allowed; section 10
              makes it unnecessary.
              
                3. Protecting Users' Legal Rights From Anti-Circumvention Law.
              
                No covered work shall be deemed part of an effective technological
              measure under any applicable law fulfilling obligations under article
              11 of the WIPO copyright treaty adopted on 20 December 1996, or
              similar laws prohibiting or restricting circumvention of such
              measures.
              
                When you convey a covered work, you waive any legal power to forbid
              circumvention of technological measures to the extent such circumvention
              is effected by exercising rights under this License with respect to
              the covered work, and you disclaim any intention to limit operation or
              modification of the work as a means of enforcing, against the work's
              users, your or third parties' legal rights to forbid circumvention of
              technological measures.
              
                4. Conveying Verbatim Copies.
              
                You may convey verbatim copies of the Program's source code as you
              receive it, in any medium, provided that you conspicuously and
              appropriately publish on each copy an appropriate copyright notice;
              keep intact all notices stating that this License and any
              non-permissive terms added in accord with section 7 apply to the code;
              keep intact all notices of the absence of any warranty; and give all
              recipients a copy of this License along with the Program.
              
                You may charge any price or no price for each copy that you convey,
              and you may offer support or warranty protection for a fee.
              
                5. Conveying Modified Source Versions.
              
                You may convey a work based on the Program, or the modifications to
              produce it from the Program, in the form of source code under the
              terms of section 4, provided that you also meet all of these conditions:
              
                  a) The work must carry prominent notices stating that you modified
                  it, and giving a relevant date.
              
                  b) The work must carry prominent notices stating that it is
                  released under this License and any conditions added under section
                  7.  This requirement modifies the requirement in section 4 to
                  "keep intact all notices".
              
                  c) You must license the entire work, as a whole, under this
                  License to anyone who comes into possession of a copy.  This
                  License will therefore apply, along with any applicable section 7
                  additional terms, to the whole of the work, and all its parts,
                  regardless of how they are packaged.  This License gives no
                  permission to license the work in any other way, but it does not
                  invalidate such permission if you have separately received it.
              
                  d) If the work has interactive user interfaces, each must display
                  Appropriate Legal Notices; however, if the Program has interactive
                  interfaces that do not display Appropriate Legal Notices, your
                  work need not make them do so.
              
                A compilation of a covered work with other separate and independent
              works, which are not by their nature extensions of the covered work,
              and which are not combined with it such as to form a larger program,
              in or on a volume of a storage or distribution medium, is called an
              "aggregate" if the compilation and its resulting copyright are not
              used to limit the access or legal rights of the compilation's users
              beyond what the individual works permit.  Inclusion of a covered work
              in an aggregate does not cause this License to apply to the other
              parts of the aggregate.
              
                6. Conveying Non-Source Forms.
              
                You may convey a covered work in object code form under the terms
              of sections 4 and 5, provided that you also convey the
              machine-readable Corresponding Source under the terms of this License,
              in one of these ways:
              
                  a) Convey the object code in, or embodied in, a physical product
                  (including a physical distribution medium), accompanied by the
                  Corresponding Source fixed on a durable physical medium
                  customarily used for software interchange.
              
                  b) Convey the object code in, or embodied in, a physical product
                  (including a physical distribution medium), accompanied by a
                  written offer, valid for at least three years and valid for as
                  long as you offer spare parts or customer support for that product
                  model, to give anyone who possesses the object code either (1) a
                  copy of the Corresponding Source for all the software in the
                  product that is covered by this License, on a durable physical
                  medium customarily used for software interchange, for a price no
                  more than your reasonable cost of physically performing this
                  conveying of source, or (2) access to copy the
                  Corresponding Source from a network server at no charge.
              
                  c) Convey individual copies of the object code with a copy of the
                  written offer to provide the Corresponding Source.  This
                  alternative is allowed only occasionally and noncommercially, and
                  only if you received the object code with such an offer, in accord
                  with subsection 6b.
              
                  d) Convey the object code by offering access from a designated
                  place (gratis or for a charge), and offer equivalent access to the
                  Corresponding Source in the same way through the same place at no
                  further charge.  You need not require recipients to copy the
                  Corresponding Source along with the object code.  If the place to
                  copy the object code is a network server, the Corresponding Source
                  may be on a different server (operated by you or a third party)
                  that supports equivalent copying facilities, provided you maintain
                  clear directions next to the object code saying where to find the
                  Corresponding Source.  Regardless of what server hosts the
                  Corresponding Source, you remain obligated to ensure that it is
                  available for as long as needed to satisfy these requirements.
              
                  e) Convey the object code using peer-to-peer transmission, provided
                  you inform other peers where the object code and Corresponding
                  Source of the work are being offered to the general public at no
                  charge under subsection 6d.
              
                A separable portion of the object code, whose source code is excluded
              from the Corresponding Source as a System Library, need not be
              included in conveying the object code work.
              
                A "User Product" is either (1) a "consumer product", which means any
              tangible personal property which is normally used for personal, family,
              or household purposes, or (2) anything designed or sold for incorporation
              into a dwelling.  In determining whether a product is a consumer product,
              doubtful cases shall be resolved in favor of coverage.  For a particular
              product received by a particular user, "normally used" refers to a
              typical or common use of that class of product, regardless of the status
              of the particular user or of the way in which the particular user
              actually uses, or expects or is expected to use, the product.  A product
              is a consumer product regardless of whether the product has substantial
              commercial, industrial or non-consumer uses, unless such uses represent
              the only significant mode of use of the product.
              
                "Installation Information" for a User Product means any methods,
              procedures, authorization keys, or other information required to install
              and execute modified versions of a covered work in that User Product from
              a modified version of its Corresponding Source.  The information must
              suffice to ensure that the continued functioning of the modified object
              code is in no case prevented or interfered with solely because
              modification has been made.
              
                If you convey an object code work under this section in, or with, or
              specifically for use in, a User Product, and the conveying occurs as
              part of a transaction in which the right of possession and use of the
              User Product is transferred to the recipient in perpetuity or for a
              fixed term (regardless of how the transaction is characterized), the
              Corresponding Source conveyed under this section must be accompanied
              by the Installation Information.  But this requirement does not apply
              if neither you nor any third party retains the ability to install
              modified object code on the User Product (for example, the work has
              been installed in ROM).
              
                The requirement to provide Installation Information does not include a
              requirement to continue to provide support service, warranty, or updates
              for a work that has been modified or installed by the recipient, or for
              the User Product in which it has been modified or installed.  Access to a
              network may be denied when the modification itself materially and
              adversely affects the operation of the network or violates the rules and
              protocols for communication across the network.
              
                Corresponding Source conveyed, and Installation Information provided,
              in accord with this section must be in a format that is publicly
              documented (and with an implementation available to the public in
              source code form), and must require no special password or key for
              unpacking, reading or copying.
              
                7. Additional Terms.
              
                "Additional permissions" are terms that supplement the terms of this
              License by making exceptions from one or more of its conditions.
              Additional permissions that are applicable to the entire Program shall
              be treated as though they were included in this License, to the extent
              that they are valid under applicable law.  If additional permissions
              apply only to part of the Program, that part may be used separately
              under those permissions, but the entire Program remains governed by
              this License without regard to the additional permissions.
              
                When you convey a copy of a covered work, you may at your option
              remove any additional permissions from that copy, or from any part of
              it.  (Additional permissions may be written to require their own
              removal in certain cases when you modify the work.)  You may place
              additional permissions on material, added by you to a covered work,
              for which you have or can give appropriate copyright permission.
              
                Notwithstanding any other provision of this License, for material you
              add to a covered work, you may (if authorized by the copyright holders of
              that material) supplement the terms of this License with terms:
              
                  a) Disclaiming warranty or limiting liability differently from the
                  terms of sections 15 and 16 of this License; or
              
                  b) Requiring preservation of specified reasonable legal notices or
                  author attributions in that material or in the Appropriate Legal
                  Notices displayed by works containing it; or
              
                  c) Prohibiting misrepresentation of the origin of that material, or
                  requiring that modified versions of such material be marked in
                  reasonable ways as different from the original version; or
              
                  d) Limiting the use for publicity purposes of names of licensors or
                  authors of the material; or
              
                  e) Declining to grant rights under trademark law for use of some
                  trade names, trademarks, or service marks; or
              
                  f) Requiring indemnification of licensors and authors of that
                  material by anyone who conveys the material (or modified versions of
                  it) with contractual assumptions of liability to the recipient, for
                  any liability that these contractual assumptions directly impose on
                  those licensors and authors.
              
                All other non-permissive additional terms are considered "further
              restrictions" within the meaning of section 10.  If the Program as you
              received it, or any part of it, contains a notice stating that it is
              governed by this License along with a term that is a further
              restriction, you may remove that term.  If a license document contains
              a further restriction but permits relicensing or conveying under this
              License, you may add to a covered work material governed by the terms
              of that license document, provided that the further restriction does
              not survive such relicensing or conveying.
              
                If you add terms to a covered work in accord with this section, you
              must place, in the relevant source files, a statement of the
              additional terms that apply to those files, or a notice indicating
              where to find the applicable terms.
              
                Additional terms, permissive or non-permissive, may be stated in the
              form of a separately written license, or stated as exceptions;
              the above requirements apply either way.
              
                8. Termination.
              
                You may not propagate or modify a covered work except as expressly
              provided under this License.  Any attempt otherwise to propagate or
              modify it is void, and will automatically terminate your rights under
              this License (including any patent licenses granted under the third
              paragraph of section 11).
              
                However, if you cease all violation of this License, then your
              license from a particular copyright holder is reinstated (a)
              provisionally, unless and until the copyright holder explicitly and
              finally terminates your license, and (b) permanently, if the copyright
              holder fails to notify you of the violation by some reasonable means
              prior to 60 days after the cessation.
              
                Moreover, your license from a particular copyright holder is
              reinstated permanently if the copyright holder notifies you of the
              violation by some reasonable means, this is the first time you have
              received notice of violation of this License (for any work) from that
              copyright holder, and you cure the violation prior to 30 days after
              your receipt of the notice.
              
                Termination of your rights under this section does not terminate the
              licenses of parties who have received copies or rights from you under
              this License.  If your rights have been terminated and not permanently
              reinstated, you do not qualify to receive new licenses for the same
              material under section 10.
              
                9. Acceptance Not Required for Having Copies.
              
                You are not required to accept this License in order to receive or
              run a copy of the Program.  Ancillary propagation of a covered work
              occurring solely as a consequence of using peer-to-peer transmission
              to receive a copy likewise does not require acceptance.  However,
              nothing other than this License grants you permission to propagate or
              modify any covered work.  These actions infringe copyright if you do
              not accept this License.  Therefore, by modifying or propagating a
              covered work, you indicate your acceptance of this License to do so.
              
                10. Automatic Licensing of Downstream Recipients.
              
                Each time you convey a covered work, the recipient automatically
              receives a license from the original licensors, to run, modify and
              propagate that work, subject to this License.  You are not responsible
              for enforcing compliance by third parties with this License.
              
                An "entity transaction" is a transaction transferring control of an
              organization, or substantially all assets of one, or subdividing an
              organization, or merging organizations.  If propagation of a covered
              work results from an entity transaction, each party to that
              transaction who receives a copy of the work also receives whatever
              licenses to the work the party's predecessor in interest had or could
              give under the previous paragraph, plus a right to possession of the
              Corresponding Source of the work from the predecessor in interest, if
              the predecessor has it or can get it with reasonable efforts.
              
                You may not impose any further restrictions on the exercise of the
              rights granted or affirmed under this License.  For example, you may
              not impose a license fee, royalty, or other charge for exercise of
              rights granted under this License, and you may not initiate litigation
              (including a cross-claim or counterclaim in a lawsuit) alleging that
              any patent claim is infringed by making, using, selling, offering for
              sale, or importing the Program or any portion of it.
              
                11. Patents.
              
                A "contributor" is a copyright holder who authorizes use under this
              License of the Program or a work on which the Program is based.  The
              work thus licensed is called the contributor's "contributor version".
              
                A contributor's "essential patent claims" are all patent claims
              owned or controlled by the contributor, whether already acquired or
              hereafter acquired, that would be infringed by some manner, permitted
              by this License, of making, using, or selling its contributor version,
              but do not include claims that would be infringed only as a
              consequence of further modification of the contributor version.  For
              purposes of this definition, "control" includes the right to grant
              patent sublicenses in a manner consistent with the requirements of
              this License.
              
                Each contributor grants you a non-exclusive, worldwide, royalty-free
              patent license under the contributor's essential patent claims, to
              make, use, sell, offer for sale, import and otherwise run, modify and
              propagate the contents of its contributor version.
              
                In the following three paragraphs, a "patent license" is any express
              agreement or commitment, however denominated, not to enforce a patent
              (such as an express permission to practice a patent or covenant not to
              sue for patent infringement).  To "grant" such a patent license to a
              party means to make such an agreement or commitment not to enforce a
              patent against the party.
              
                If you convey a covered work, knowingly relying on a patent license,
              and the Corresponding Source of the work is not available for anyone
              to copy, free of charge and under the terms of this License, through a
              publicly available network server or other readily accessible means,
              then you must either (1) cause the Corresponding Source to be so
              available, or (2) arrange to deprive yourself of the benefit of the
              patent license for this particular work, or (3) arrange, in a manner
              consistent with the requirements of this License, to extend the patent
              license to downstream recipients.  "Knowingly relying" means you have
              actual knowledge that, but for the patent license, your conveying the
              covered work in a country, or your recipient's use of the covered work
              in a country, would infringe one or more identifiable patents in that
              country that you have reason to believe are valid.
              
                If, pursuant to or in connection with a single transaction or
              arrangement, you convey, or propagate by procuring conveyance of, a
              covered work, and grant a patent license to some of the parties
              receiving the covered work authorizing them to use, propagate, modify
              or convey a specific copy of the covered work, then the patent license
              you grant is automatically extended to all recipients of the covered
              work and works based on it.
              
                A patent license is "discriminatory" if it does not include within
              the scope of its coverage, prohibits the exercise of, or is
              conditioned on the non-exercise of one or more of the rights that are
              specifically granted under this License.  You may not convey a covered
              work if you are a party to an arrangement with a third party that is
              in the business of distributing software, under which you make payment
              to the third party based on the extent of your activity of conveying
              the work, and under which the third party grants, to any of the
              parties who would receive the covered work from you, a discriminatory
              patent license (a) in connection with copies of the covered work
              conveyed by you (or copies made from those copies), or (b) primarily
              for and in connection with specific products or compilations that
              contain the covered work, unless you entered into that arrangement,
              or that patent license was granted, prior to 28 March 2007.
              
                Nothing in this License shall be construed as excluding or limiting
              any implied license or other defenses to infringement that may
              otherwise be available to you under applicable patent law.
              
                12. No Surrender of Others' Freedom.
              
                If conditions are imposed on you (whether by court order, agreement or
              otherwise) that contradict the conditions of this License, they do not
              excuse you from the conditions of this License.  If you cannot convey a
              covered work so as to satisfy simultaneously your obligations under this
              License and any other pertinent obligations, then as a consequence you may
              not convey it at all.  For example, if you agree to terms that obligate you
              to collect a royalty for further conveying from those to whom you convey
              the Program, the only way you could satisfy both those terms and this
              License would be to refrain entirely from conveying the Program.
              
                13. Use with the GNU Affero General Public License.
              
                Notwithstanding any other provision of this License, you have
              permission to link or combine any covered work with a work licensed
              under version 3 of the GNU Affero General Public License into a single
              combined work, and to convey the resulting work.  The terms of this
              License will continue to apply to the part which is the covered work,
              but the special requirements of the GNU Affero General Public License,
              section 13, concerning interaction through a network will apply to the
              combination as such.
              
                14. Revised Versions of this License.
              
                The Free Software Foundation may publish revised and/or new versions of
              the GNU General Public License from time to time.  Such new versions will
              be similar in spirit to the present version, but may differ in detail to
              address new problems or concerns.
              
                Each version is given a distinguishing version number.  If the
              Program specifies that a certain numbered version of the GNU General
              Public License "or any later version" applies to it, you have the
              option of following the terms and conditions either of that numbered
              version or of any later version published by the Free Software
              Foundation.  If the Program does not specify a version number of the
              GNU General Public License, you may choose any version ever published
              by the Free Software Foundation.
              
                If the Program specifies that a proxy can decide which future
              versions of the GNU General Public License can be used, that proxy's
              public statement of acceptance of a version permanently authorizes you
              to choose that version for the Program.
              
                Later license versions may give you additional or different
              permissions.  However, no additional obligations are imposed on any
              author or copyright holder as a result of your choosing to follow a
              later version.
              
                15. Disclaimer of Warranty.
              
                THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
              APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
              HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
              OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
              THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
              PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
              IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
              ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
              
                16. Limitation of Liability.
              
                IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
              WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
              THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
              GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
              USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
              DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
              PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
              EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
              SUCH DAMAGES.
              
                17. Interpretation of Sections 15 and 16.
              
                If the disclaimer of warranty and limitation of liability provided
              above cannot be given local legal effect according to their terms,
              reviewing courts shall apply local law that most closely approximates
              an absolute waiver of all civil liability in connection with the
              Program, unless a warranty or assumption of liability accompanies a
              copy of the Program in return for a fee.
              
                                   END OF TERMS AND CONDITIONS
              
                          How to Apply These Terms to Your New Programs
              
                If you develop a new program, and you want it to be of the greatest
              possible use to the public, the best way to achieve this is to make it
              free software which everyone can redistribute and change under these terms.
              
                To do so, attach the following notices to the program.  It is safest
              to attach them to the start of each source file to most effectively
              state the exclusion of warranty; and each file should have at least
              the "copyright" line and a pointer to where the full notice is found.
              
                  <one line to give the program's name and a brief idea of what it does.>
                  Copyright (C) <year>  <name of author>
              
                  This program is free software: you can redistribute it and/or modify
                  it under the terms of the GNU General Public License as published by
                  the Free Software Foundation, either version 3 of the License, or
                  (at your option) any later version.
              
                  This program is distributed in the hope that it will be useful,
                  but WITHOUT ANY WARRANTY; without even the implied warranty of
                  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
                  GNU General Public License for more details.
              
                  You should have received a copy of the GNU General Public License
                  along with this program.  If not, see <http://www.gnu.org/licenses/>.
              
              Also add information on how to contact you by electronic and paper mail.
              
                If the program does terminal interaction, make it output a short
              notice like this when it starts in an interactive mode:
              
                  <program>  Copyright (C) <year>  <name of author>
                  This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
                  This is free software, and you are welcome to redistribute it
                  under certain conditions; type `show c' for details.
              
              The hypothetical commands `show w' and `show c' should show the appropriate
              parts of the General Public License.  Of course, your program's commands
              might be different; for a GUI interface, you would use an "about box".
              
                You should also get your employer (if you work as a programmer) or school,
              if any, to sign a "copyright disclaimer" for the program, if necessary.
              For more information on this, and how to apply and follow the GNU GPL, see
              <http://www.gnu.org/licenses/>.
              
                The GNU General Public License does not permit incorporating your program
              into proprietary programs.  If your program is a subroutine library, you
              may consider it more useful to permit linking proprietary applications with
              the library.  If this is what you want to do, use the GNU Lesser General
              Public License instead of this License.  But first, please read
              <http://www.gnu.org/philosophy/why-not-lgpl.html>.
              
              */

              File 3 of 4: Dragon
              pragma solidity ^0.4.18;
              
              // File: zeppelin-solidity/contracts/math/SafeMath.sol
              
              /**
               * @title SafeMath
               * @dev Math operations with safety checks that throw on error
               */
              library SafeMath {
                function mul(uint256 a, uint256 b) internal pure returns (uint256) {
                  if (a == 0) {
                    return 0;
                  }
                  uint256 c = a * b;
                  assert(c / a == b);
                  return c;
                }
              
                function div(uint256 a, uint256 b) internal pure returns (uint256) {
                  // assert(b > 0); // Solidity automatically throws when dividing by 0
                  uint256 c = a / b;
                  // assert(a == b * c + a % b); // There is no case in which this doesn't hold
                  return c;
                }
              
                function sub(uint256 a, uint256 b) internal pure returns (uint256) {
                  assert(b <= a);
                  return a - b;
                }
              
                function add(uint256 a, uint256 b) internal pure returns (uint256) {
                  uint256 c = a + b;
                  assert(c >= a);
                  return c;
                }
              }
              
              // File: zeppelin-solidity/contracts/ownership/Ownable.sol
              
              /**
               * @title Ownable
               * @dev The Ownable contract has an owner address, and provides basic authorization control
               * functions, this simplifies the implementation of "user permissions".
               */
              contract Ownable {
                address public owner;
              
              
                event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
              
              
                /**
                 * @dev The Ownable constructor sets the original `owner` of the contract to the sender
                 * account.
                 */
                function Ownable() public {
                  owner = msg.sender;
                }
              
              
                /**
                 * @dev Throws if called by any account other than the owner.
                 */
                modifier onlyOwner() {
                  require(msg.sender == owner);
                  _;
                }
              
              
                /**
                 * @dev Allows the current owner to transfer control of the contract to a newOwner.
                 * @param newOwner The address to transfer ownership to.
                 */
                function transferOwnership(address newOwner) public onlyOwner {
                  require(newOwner != address(0));
                  OwnershipTransferred(owner, newOwner);
                  owner = newOwner;
                }
              
              }
              
              // File: zeppelin-solidity/contracts/token/ERC20Basic.sol
              
              /**
               * @title ERC20Basic
               * @dev Simpler version of ERC20 interface
               * @dev see https://github.com/ethereum/EIPs/issues/179
               */
              contract ERC20Basic {
                uint256 public totalSupply;
                function balanceOf(address who) public view returns (uint256);
                function transfer(address to, uint256 value) public returns (bool);
                event Transfer(address indexed from, address indexed to, uint256 value);
              }
              
              // File: zeppelin-solidity/contracts/token/BasicToken.sol
              
              /**
               * @title Basic token
               * @dev Basic version of StandardToken, with no allowances.
               */
              contract BasicToken is ERC20Basic {
                using SafeMath for uint256;
              
                mapping(address => uint256) balances;
              
                /**
                * @dev transfer token for a specified address
                * @param _to The address to transfer to.
                * @param _value The amount to be transferred.
                */
                function transfer(address _to, uint256 _value) public returns (bool) {
                  require(_to != address(0));
                  require(_value <= balances[msg.sender]);
              
                  // SafeMath.sub will throw if there is not enough balance.
                  balances[msg.sender] = balances[msg.sender].sub(_value);
                  balances[_to] = balances[_to].add(_value);
                  Transfer(msg.sender, _to, _value);
                  return true;
                }
              
                /**
                * @dev Gets the balance of the specified address.
                * @param _owner The address to query the the balance of.
                * @return An uint256 representing the amount owned by the passed address.
                */
                function balanceOf(address _owner) public view returns (uint256 balance) {
                  return balances[_owner];
                }
              
              }
              
              // File: zeppelin-solidity/contracts/token/ERC20.sol
              
              /**
               * @title ERC20 interface
               * @dev see https://github.com/ethereum/EIPs/issues/20
               */
              contract ERC20 is ERC20Basic {
                function allowance(address owner, address spender) public view returns (uint256);
                function transferFrom(address from, address to, uint256 value) public returns (bool);
                function approve(address spender, uint256 value) public returns (bool);
                event Approval(address indexed owner, address indexed spender, uint256 value);
              }
              
              // File: zeppelin-solidity/contracts/token/StandardToken.sol
              
              /**
               * @title Standard ERC20 token
               *
               * @dev Implementation of the basic standard token.
               * @dev https://github.com/ethereum/EIPs/issues/20
               * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
               */
              contract StandardToken is ERC20, BasicToken {
              
                mapping (address => mapping (address => uint256)) internal allowed;
              
              
                /**
                 * @dev Transfer tokens from one address to another
                 * @param _from address The address which you want to send tokens from
                 * @param _to address The address which you want to transfer to
                 * @param _value uint256 the amount of tokens to be transferred
                 */
                function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
                  require(_to != address(0));
                  require(_value <= balances[_from]);
                  require(_value <= allowed[_from][msg.sender]);
              
                  balances[_from] = balances[_from].sub(_value);
                  balances[_to] = balances[_to].add(_value);
                  allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
                  Transfer(_from, _to, _value);
                  return true;
                }
              
                /**
                 * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
                 *
                 * Beware that changing an allowance with this method brings the risk that someone may use both the old
                 * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
                 * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
                 * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
                 * @param _spender The address which will spend the funds.
                 * @param _value The amount of tokens to be spent.
                 */
                function approve(address _spender, uint256 _value) public returns (bool) {
                  allowed[msg.sender][_spender] = _value;
                  Approval(msg.sender, _spender, _value);
                  return true;
                }
              
                /**
                 * @dev Function to check the amount of tokens that an owner allowed to a spender.
                 * @param _owner address The address which owns the funds.
                 * @param _spender address The address which will spend the funds.
                 * @return A uint256 specifying the amount of tokens still available for the spender.
                 */
                function allowance(address _owner, address _spender) public view returns (uint256) {
                  return allowed[_owner][_spender];
                }
              
                /**
                 * approve should be called when allowed[_spender] == 0. To increment
                 * allowed value is better to use this function to avoid 2 calls (and wait until
                 * the first transaction is mined)
                 * From MonolithDAO Token.sol
                 */
                function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
                  allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
                  Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
                  return true;
                }
              
                function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
                  uint oldValue = allowed[msg.sender][_spender];
                  if (_subtractedValue > oldValue) {
                    allowed[msg.sender][_spender] = 0;
                  } else {
                    allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
                  }
                  Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
                  return true;
                }
              
              }
              
              // File: contracts/Dragon.sol
              
              /**
               * @title Dragon
               * @dev DistributableToken contract is based on a simple initial supply token, with an API for the owner to perform bulk distributions.
               *      transactions to the distributeTokens function should be paginated to avoid gas limits or computational time restrictions. 
               */
              contract Dragon is StandardToken, Ownable {
                  string public constant name = "Dragon";
                  string public constant symbol = "DRGN";
                  uint8 public constant decimals = 18;
                  uint256 public constant INITIAL_SUPPLY = 433494437 * (10 ** uint256(decimals));
              
                  //prevent duplicate distributions
                  mapping (address => bool) distributionLocks;
              
                  /**
                   * @dev Constructor that gives msg.sender all of existing tokens.
                   */
                  function Dragon() {
                      totalSupply = INITIAL_SUPPLY;
                      balances[msg.sender] = INITIAL_SUPPLY;
                  }
              
                  /**
                   * @dev Distribute tokens to multiple addresses in a single transaction
                   *
                   * @param addresses A list of addresses to distribute to
                   * @param values A corresponding list of amounts to distribute to each address
                   */
                  function anailNathrachOrthaBhaisIsBeathaDoChealDeanaimh(address[] addresses, uint256[] values) onlyOwner public returns (bool success) {
                      require(addresses.length == values.length);
                      for (uint i = 0; i < addresses.length; i++) {
                          require(!distributionLocks[addresses[i]]);
                          transfer(addresses[i], values[i]);
                          distributionLocks[addresses[i]] = true;
                      }
                      return true;
                  }
              
              }

              File 4 of 4: UniswapV3Feature
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity >=0.6.5 <0.9;
              interface IERC20Token {
                  event Transfer(address indexed from, address indexed to, uint256 value);
                  event Approval(address indexed owner, address indexed spender, uint256 value);
                  /// @dev send `value` token to `to` from `msg.sender`
                  /// @param to The address of the recipient
                  /// @param value The amount of token to be transferred
                  /// @return True if transfer was successful
                  function transfer(address to, uint256 value) external returns (bool);
                  /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
                  /// @param from The address of the sender
                  /// @param to The address of the recipient
                  /// @param value The amount of token to be transferred
                  /// @return True if transfer was successful
                  function transferFrom(address from, address to, uint256 value) external returns (bool);
                  /// @dev `msg.sender` approves `spender` to spend `value` tokens
                  /// @param spender The address of the account able to transfer the tokens
                  /// @param value The amount of wei to be approved for transfer
                  /// @return Always true if the call has enough gas to complete execution
                  function approve(address spender, uint256 value) external returns (bool);
                  /// @dev Query total supply of token
                  /// @return Total supply of token
                  function totalSupply() external view returns (uint256);
                  /// @dev Get the balance of `owner`.
                  /// @param owner The address from which the balance will be retrieved
                  /// @return Balance of owner
                  function balanceOf(address owner) external view returns (uint256);
                  /// @dev Get the allowance for `spender` to spend from `owner`.
                  /// @param owner The address of the account owning tokens
                  /// @param spender The address of the account able to transfer the tokens
                  /// @return Amount of remaining tokens allowed to spent
                  function allowance(address owner, address spender) external view returns (uint256);
                  /// @dev Get the number of decimals this token has.
                  function decimals() external view returns (uint8);
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./IERC20Token.sol";
              interface IEtherToken is IERC20Token {
                  /// @dev Wrap ether.
                  function deposit() external payable;
                  /// @dev Unwrap ether.
                  function withdraw(uint256 amount) external;
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              import "./errors/LibRichErrorsV06.sol";
              import "./errors/LibSafeMathRichErrorsV06.sol";
              library LibSafeMathV06 {
                  function safeMul(uint256 a, uint256 b) internal pure returns (uint256) {
                      if (a == 0) {
                          return 0;
                      }
                      uint256 c = a * b;
                      if (c / a != b) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.MULTIPLICATION_OVERFLOW,
                                  a,
                                  b
                              )
                          );
                      }
                      return c;
                  }
                  function safeDiv(uint256 a, uint256 b) internal pure returns (uint256) {
                      if (b == 0) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.DIVISION_BY_ZERO,
                                  a,
                                  b
                              )
                          );
                      }
                      uint256 c = a / b;
                      return c;
                  }
                  function safeSub(uint256 a, uint256 b) internal pure returns (uint256) {
                      if (b > a) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.SUBTRACTION_UNDERFLOW,
                                  a,
                                  b
                              )
                          );
                      }
                      return a - b;
                  }
                  function safeAdd(uint256 a, uint256 b) internal pure returns (uint256) {
                      uint256 c = a + b;
                      if (c < a) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.ADDITION_OVERFLOW,
                                  a,
                                  b
                              )
                          );
                      }
                      return c;
                  }
                  function max256(uint256 a, uint256 b) internal pure returns (uint256) {
                      return a >= b ? a : b;
                  }
                  function min256(uint256 a, uint256 b) internal pure returns (uint256) {
                      return a < b ? a : b;
                  }
                  function safeMul128(uint128 a, uint128 b) internal pure returns (uint128) {
                      if (a == 0) {
                          return 0;
                      }
                      uint128 c = a * b;
                      if (c / a != b) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.MULTIPLICATION_OVERFLOW,
                                  a,
                                  b
                              )
                          );
                      }
                      return c;
                  }
                  function safeDiv128(uint128 a, uint128 b) internal pure returns (uint128) {
                      if (b == 0) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.DIVISION_BY_ZERO,
                                  a,
                                  b
                              )
                          );
                      }
                      uint128 c = a / b;
                      return c;
                  }
                  function safeSub128(uint128 a, uint128 b) internal pure returns (uint128) {
                      if (b > a) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.SUBTRACTION_UNDERFLOW,
                                  a,
                                  b
                              )
                          );
                      }
                      return a - b;
                  }
                  function safeAdd128(uint128 a, uint128 b) internal pure returns (uint128) {
                      uint128 c = a + b;
                      if (c < a) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256BinOpError(
                                  LibSafeMathRichErrorsV06.BinOpErrorCodes.ADDITION_OVERFLOW,
                                  a,
                                  b
                              )
                          );
                      }
                      return c;
                  }
                  function max128(uint128 a, uint128 b) internal pure returns (uint128) {
                      return a >= b ? a : b;
                  }
                  function min128(uint128 a, uint128 b) internal pure returns (uint128) {
                      return a < b ? a : b;
                  }
                  function safeDowncastToUint128(uint256 a) internal pure returns (uint128) {
                      if (a > type(uint128).max) {
                          LibRichErrorsV06.rrevert(
                              LibSafeMathRichErrorsV06.Uint256DowncastError(
                                  LibSafeMathRichErrorsV06.DowncastErrorCodes.VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT128,
                                  a
                              )
                          );
                      }
                      return uint128(a);
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibRichErrorsV06 {
                  // bytes4(keccak256("Error(string)"))
                  bytes4 internal constant STANDARD_ERROR_SELECTOR = 0x08c379a0;
                  /// @dev ABI encode a standard, string revert error payload.
                  ///      This is the same payload that would be included by a `revert(string)`
                  ///      solidity statement. It has the function signature `Error(string)`.
                  /// @param message The error string.
                  /// @return The ABI encoded error.
                  function StandardError(string memory message) internal pure returns (bytes memory) {
                      return abi.encodeWithSelector(STANDARD_ERROR_SELECTOR, bytes(message));
                  }
                  /// @dev Reverts an encoded rich revert reason `errorData`.
                  /// @param errorData ABI encoded error data.
                  function rrevert(bytes memory errorData) internal pure {
                      assembly {
                          revert(add(errorData, 0x20), mload(errorData))
                      }
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibSafeMathRichErrorsV06 {
                  // bytes4(keccak256("Uint256BinOpError(uint8,uint256,uint256)"))
                  bytes4 internal constant UINT256_BINOP_ERROR_SELECTOR = 0xe946c1bb;
                  // bytes4(keccak256("Uint256DowncastError(uint8,uint256)"))
                  bytes4 internal constant UINT256_DOWNCAST_ERROR_SELECTOR = 0xc996af7b;
                  enum BinOpErrorCodes {
                      ADDITION_OVERFLOW,
                      MULTIPLICATION_OVERFLOW,
                      SUBTRACTION_UNDERFLOW,
                      DIVISION_BY_ZERO
                  }
                  enum DowncastErrorCodes {
                      VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT32,
                      VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT64,
                      VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT96,
                      VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT128
                  }
                  function Uint256BinOpError(BinOpErrorCodes errorCode, uint256 a, uint256 b) internal pure returns (bytes memory) {
                      return abi.encodeWithSelector(UINT256_BINOP_ERROR_SELECTOR, errorCode, a, b);
                  }
                  function Uint256DowncastError(DowncastErrorCodes errorCode, uint256 a) internal pure returns (bytes memory) {
                      return abi.encodeWithSelector(UINT256_DOWNCAST_ERROR_SELECTOR, errorCode, a);
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2020 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              interface IOwnableV06 {
                  /// @dev Emitted by Ownable when ownership is transferred.
                  /// @param previousOwner The previous owner of the contract.
                  /// @param newOwner The new owner of the contract.
                  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
                  /// @dev Transfers ownership of the contract to a new address.
                  /// @param newOwner The address that will become the owner.
                  function transferOwnership(address newOwner) external;
                  /// @dev The owner of this contract.
                  /// @return ownerAddress The owner address.
                  function owner() external view returns (address ownerAddress);
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibCommonRichErrors {
                  function OnlyCallableBySelfError(address sender) internal pure returns (bytes memory) {
                      return abi.encodeWithSelector(bytes4(keccak256("OnlyCallableBySelfError(address)")), sender);
                  }
                  function IllegalReentrancyError(bytes4 selector, uint256 reentrancyFlags) internal pure returns (bytes memory) {
                      return
                          abi.encodeWithSelector(
                              bytes4(keccak256("IllegalReentrancyError(bytes4,uint256)")),
                              selector,
                              reentrancyFlags
                          );
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              library LibOwnableRichErrors {
                  function OnlyOwnerError(address sender, address owner) internal pure returns (bytes memory) {
                      return abi.encodeWithSelector(bytes4(keccak256("OnlyOwnerError(address,address)")), sender, owner);
                  }
                  function TransferOwnerToZeroError() internal pure returns (bytes memory) {
                      return abi.encodeWithSelector(bytes4(keccak256("TransferOwnerToZeroError()")));
                  }
                  function MigrateCallFailedError(address target, bytes memory resultData) internal pure returns (bytes memory) {
                      return abi.encodeWithSelector(bytes4(keccak256("MigrateCallFailedError(address,bytes)")), target, resultData);
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/src/IERC20Token.sol";
              import "@0x/contracts-erc20/src/IEtherToken.sol";
              import "../vendor/IUniswapV3Pool.sol";
              import "../migrations/LibMigrate.sol";
              import "../fixins/FixinCommon.sol";
              import "../fixins/FixinTokenSpender.sol";
              import "./interfaces/IFeature.sol";
              import "./interfaces/IUniswapV3Feature.sol";
              /// @dev VIP uniswap fill functions.
              contract UniswapV3Feature is IFeature, IUniswapV3Feature, FixinCommon, FixinTokenSpender {
                  /// @dev Name of this feature.
                  string public constant override FEATURE_NAME = "UniswapV3Feature";
                  /// @dev Version of this feature.
                  uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 1, 0);
                  /// @dev WETH contract.
                  IEtherToken private immutable WETH;
                  /// @dev UniswapV3 Factory contract address prepended with '0xff' and left-aligned.
                  bytes32 private immutable UNI_FF_FACTORY_ADDRESS;
                  /// @dev UniswapV3 pool init code hash.
                  bytes32 private immutable UNI_POOL_INIT_CODE_HASH;
                  /// @dev Minimum size of an encoded swap path:
                  ///      sizeof(address(inputToken) | uint24(fee) | address(outputToken))
                  uint256 private constant SINGLE_HOP_PATH_SIZE = 20 + 3 + 20;
                  /// @dev How many bytes to skip ahead in an encoded path to start at the next hop:
                  ///      sizeof(address(inputToken) | uint24(fee))
                  uint256 private constant PATH_SKIP_HOP_SIZE = 20 + 3;
                  /// @dev The size of the swap callback data.
                  uint256 private constant SWAP_CALLBACK_DATA_SIZE = 128;
                  /// @dev Minimum tick price sqrt ratio.
                  uint160 internal constant MIN_PRICE_SQRT_RATIO = 4295128739;
                  /// @dev Minimum tick price sqrt ratio.
                  uint160 internal constant MAX_PRICE_SQRT_RATIO = 1461446703485210103287273052203988822378723970342;
                  /// @dev Mask of lower 20 bytes.
                  uint256 private constant ADDRESS_MASK = 0x00ffffffffffffffffffffffffffffffffffffffff;
                  /// @dev Mask of lower 3 bytes.
                  uint256 private constant UINT24_MASK = 0xffffff;
                  /// @dev Construct this contract.
                  /// @param weth The WETH contract.
                  /// @param uniFactory The UniswapV3 factory contract.
                  /// @param poolInitCodeHash The UniswapV3 pool init code hash.
                  constructor(IEtherToken weth, address uniFactory, bytes32 poolInitCodeHash) public {
                      WETH = weth;
                      UNI_FF_FACTORY_ADDRESS = bytes32((uint256(0xff) << 248) | (uint256(uniFactory) << 88));
                      UNI_POOL_INIT_CODE_HASH = poolInitCodeHash;
                  }
                  /// @dev Initialize and register this feature.
                  ///      Should be delegatecalled by `Migrate.migrate()`.
                  /// @return success `LibMigrate.SUCCESS` on success.
                  function migrate() external returns (bytes4 success) {
                      _registerFeatureFunction(this.sellEthForTokenToUniswapV3.selector);
                      _registerFeatureFunction(this.sellTokenForEthToUniswapV3.selector);
                      _registerFeatureFunction(this.sellTokenForTokenToUniswapV3.selector);
                      _registerFeatureFunction(this._sellTokenForTokenToUniswapV3.selector);
                      _registerFeatureFunction(this._sellHeldTokenForTokenToUniswapV3.selector);
                      _registerFeatureFunction(this.uniswapV3SwapCallback.selector);
                      return LibMigrate.MIGRATE_SUCCESS;
                  }
                  /// @dev Sell attached ETH directly against uniswap v3.
                  /// @param encodedPath Uniswap-encoded path, where the first token is WETH.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function sellEthForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 minBuyAmount,
                      address recipient
                  ) public payable override returns (uint256 buyAmount) {
                      // Wrap ETH.
                      WETH.deposit{value: msg.value}();
                      return
                          _swap(
                              encodedPath,
                              msg.value,
                              minBuyAmount,
                              address(this), // we are payer because we hold the WETH
                              _normalizeRecipient(recipient)
                          );
                  }
                  /// @dev Sell a token for ETH directly against uniswap v3.
                  /// @param encodedPath Uniswap-encoded path, where the last token is WETH.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of ETH to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @return buyAmount Amount of ETH bought.
                  function sellTokenForEthToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address payable recipient
                  ) public override returns (uint256 buyAmount) {
                      buyAmount = _swap(
                          encodedPath,
                          sellAmount,
                          minBuyAmount,
                          msg.sender,
                          address(this) // we are recipient because we need to unwrap WETH
                      );
                      WETH.withdraw(buyAmount);
                      // Transfer ETH to recipient.
                      (bool success, bytes memory revertData) = _normalizeRecipient(recipient).call{value: buyAmount}("");
                      if (!success) {
                          revertData.rrevert();
                      }
                  }
                  /// @dev Sell a token for another token directly against uniswap v3.
                  /// @param encodedPath Uniswap-encoded path.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function sellTokenForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address recipient
                  ) public override returns (uint256 buyAmount) {
                      buyAmount = _swap(encodedPath, sellAmount, minBuyAmount, msg.sender, _normalizeRecipient(recipient));
                  }
                  /// @dev Sell a token for another token directly against uniswap v3. Internal variant.
                  /// @param encodedPath Uniswap-encoded path.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for payer.
                  /// @param payer The address to pull the sold tokens from.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function _sellTokenForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address recipient,
                      address payer
                  ) public override onlySelf returns (uint256 buyAmount) {
                      buyAmount = _swap(encodedPath, sellAmount, minBuyAmount, payer, _normalizeRecipient(recipient, payer));
                  }
                  /// @dev Sell a token for another token directly against uniswap v3.
                  ///      Private variant, uses tokens held by `address(this)`.
                  /// @param encodedPath Uniswap-encoded path.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function _sellHeldTokenForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address recipient
                  ) public override onlySelf returns (uint256 buyAmount) {
                      buyAmount = _swap(encodedPath, sellAmount, minBuyAmount, address(this), _normalizeRecipient(recipient));
                  }
                  /// @dev The UniswapV3 pool swap callback which pays the funds requested
                  ///      by the caller/pool to the pool. Can only be called by a valid
                  ///      UniswapV3 pool.
                  /// @param amount0Delta Token0 amount owed.
                  /// @param amount1Delta Token1 amount owed.
                  /// @param data Arbitrary data forwarded from swap() caller. An ABI-encoded
                  ///        struct of: inputToken, outputToken, fee, payer
                  function uniswapV3SwapCallback(int256 amount0Delta, int256 amount1Delta, bytes calldata data) external override {
                      IERC20Token token0;
                      IERC20Token token1;
                      address payer;
                      {
                          uint24 fee;
                          // Decode the data.
                          require(data.length == SWAP_CALLBACK_DATA_SIZE, "UniswapFeature/INVALID_SWAP_CALLBACK_DATA");
                          assembly {
                              let p := add(36, calldataload(68))
                              token0 := calldataload(p)
                              token1 := calldataload(add(p, 32))
                              fee := calldataload(add(p, 64))
                              payer := calldataload(add(p, 96))
                          }
                          (token0, token1) = token0 < token1 ? (token0, token1) : (token1, token0);
                          // Only a valid pool contract can call this function.
                          require(
                              msg.sender == address(_toPool(token0, fee, token1)),
                              "UniswapV3Feature/INVALID_SWAP_CALLBACK_CALLER"
                          );
                      }
                      // Pay the amount owed to the pool.
                      if (amount0Delta > 0) {
                          _pay(token0, payer, msg.sender, uint256(amount0Delta));
                      } else if (amount1Delta > 0) {
                          _pay(token1, payer, msg.sender, uint256(amount1Delta));
                      } else {
                          revert("UniswapV3Feature/INVALID_SWAP_AMOUNTS");
                      }
                  }
                  // Executes successive swaps along an encoded uniswap path.
                  function _swap(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address payer,
                      address recipient
                  ) private returns (uint256 buyAmount) {
                      if (sellAmount != 0) {
                          require(sellAmount <= uint256(type(int256).max), "UniswapV3Feature/SELL_AMOUNT_OVERFLOW");
                          // Perform a swap for each hop in the path.
                          bytes memory swapCallbackData = new bytes(SWAP_CALLBACK_DATA_SIZE);
                          while (true) {
                              bool isPathMultiHop = _isPathMultiHop(encodedPath);
                              bool zeroForOne;
                              IUniswapV3Pool pool;
                              {
                                  (IERC20Token inputToken, uint24 fee, IERC20Token outputToken) = _decodeFirstPoolInfoFromPath(
                                      encodedPath
                                  );
                                  pool = _toPool(inputToken, fee, outputToken);
                                  zeroForOne = inputToken < outputToken;
                                  _updateSwapCallbackData(swapCallbackData, inputToken, outputToken, fee, payer);
                              }
                              (int256 amount0, int256 amount1) = pool.swap(
                                  // Intermediate tokens go to this contract.
                                  isPathMultiHop ? address(this) : recipient,
                                  zeroForOne,
                                  int256(sellAmount),
                                  zeroForOne ? MIN_PRICE_SQRT_RATIO + 1 : MAX_PRICE_SQRT_RATIO - 1,
                                  swapCallbackData
                              );
                              {
                                  int256 _buyAmount = -(zeroForOne ? amount1 : amount0);
                                  require(_buyAmount >= 0, "UniswapV3Feature/INVALID_BUY_AMOUNT");
                                  buyAmount = uint256(_buyAmount);
                              }
                              if (!isPathMultiHop) {
                                  // Done.
                                  break;
                              }
                              // Continue with next hop.
                              payer = address(this); // Subsequent hops are paid for by us.
                              sellAmount = buyAmount;
                              // Skip to next hop along path.
                              encodedPath = _shiftHopFromPathInPlace(encodedPath);
                          }
                      }
                      require(minBuyAmount <= buyAmount, "UniswapV3Feature/UNDERBOUGHT");
                  }
                  // Pay tokens from `payer` to `to`, using `transferFrom()` if
                  // `payer` != this contract.
                  function _pay(IERC20Token token, address payer, address to, uint256 amount) private {
                      if (payer != address(this)) {
                          _transferERC20TokensFrom(token, payer, to, amount);
                      } else {
                          _transferERC20Tokens(token, to, amount);
                      }
                  }
                  // Update `swapCallbackData` in place with new values.
                  function _updateSwapCallbackData(
                      bytes memory swapCallbackData,
                      IERC20Token inputToken,
                      IERC20Token outputToken,
                      uint24 fee,
                      address payer
                  ) private pure {
                      assembly {
                          let p := add(swapCallbackData, 32)
                          mstore(p, inputToken)
                          mstore(add(p, 32), outputToken)
                          mstore(add(p, 64), and(UINT24_MASK, fee))
                          mstore(add(p, 96), and(ADDRESS_MASK, payer))
                      }
                  }
                  // Compute the pool address given two tokens and a fee.
                  function _toPool(
                      IERC20Token inputToken,
                      uint24 fee,
                      IERC20Token outputToken
                  ) private view returns (IUniswapV3Pool pool) {
                      // address(keccak256(abi.encodePacked(
                      //     hex"ff",
                      //     UNI_FACTORY_ADDRESS,
                      //     keccak256(abi.encode(inputToken, outputToken, fee)),
                      //     UNI_POOL_INIT_CODE_HASH
                      // )))
                      bytes32 ffFactoryAddress = UNI_FF_FACTORY_ADDRESS;
                      bytes32 poolInitCodeHash = UNI_POOL_INIT_CODE_HASH;
                      (IERC20Token token0, IERC20Token token1) = inputToken < outputToken
                          ? (inputToken, outputToken)
                          : (outputToken, inputToken);
                      assembly {
                          let s := mload(0x40)
                          let p := s
                          mstore(p, ffFactoryAddress)
                          p := add(p, 21)
                          // Compute the inner hash in-place
                          mstore(p, token0)
                          mstore(add(p, 32), token1)
                          mstore(add(p, 64), and(UINT24_MASK, fee))
                          mstore(p, keccak256(p, 96))
                          p := add(p, 32)
                          mstore(p, poolInitCodeHash)
                          pool := and(ADDRESS_MASK, keccak256(s, 85))
                      }
                  }
                  // Return whether or not an encoded uniswap path contains more than one hop.
                  function _isPathMultiHop(bytes memory encodedPath) private pure returns (bool isMultiHop) {
                      return encodedPath.length > SINGLE_HOP_PATH_SIZE;
                  }
                  // Return the first input token, output token, and fee of an encoded uniswap path.
                  function _decodeFirstPoolInfoFromPath(
                      bytes memory encodedPath
                  ) private pure returns (IERC20Token inputToken, uint24 fee, IERC20Token outputToken) {
                      require(encodedPath.length >= SINGLE_HOP_PATH_SIZE, "UniswapV3Feature/BAD_PATH_ENCODING");
                      assembly {
                          let p := add(encodedPath, 32)
                          inputToken := shr(96, mload(p))
                          p := add(p, 20)
                          fee := shr(232, mload(p))
                          p := add(p, 3)
                          outputToken := shr(96, mload(p))
                      }
                  }
                  // Skip past the first hop of an encoded uniswap path in-place.
                  function _shiftHopFromPathInPlace(bytes memory encodedPath) private pure returns (bytes memory shiftedEncodedPath) {
                      require(encodedPath.length >= PATH_SKIP_HOP_SIZE, "UniswapV3Feature/BAD_PATH_ENCODING");
                      uint256 shiftSize = PATH_SKIP_HOP_SIZE;
                      uint256 newSize = encodedPath.length - shiftSize;
                      assembly {
                          shiftedEncodedPath := add(encodedPath, shiftSize)
                          mstore(shiftedEncodedPath, newSize)
                      }
                  }
                  // Convert null address values to alternative address.
                  function _normalizeRecipient(
                      address recipient,
                      address alternative
                  ) private pure returns (address payable normalizedRecipient) {
                      return recipient == address(0) ? payable(alternative) : payable(recipient);
                  }
                  // Convert null address values to msg.sender.
                  function _normalizeRecipient(address recipient) private view returns (address payable normalizedRecipient) {
                      return _normalizeRecipient(recipient, msg.sender);
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev Basic interface for a feature contract.
              interface IFeature {
                  /// @dev The name of this feature set.
                  function FEATURE_NAME() external view returns (string memory name);
                  /// @dev The version of this feature set.
                  function FEATURE_VERSION() external view returns (uint256 version);
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/interfaces/IOwnableV06.sol";
              /// @dev Owner management and migration features.
              interface IOwnableFeature is IOwnableV06 {
                  /// @dev Emitted when `migrate()` is called.
                  /// @param caller The caller of `migrate()`.
                  /// @param migrator The migration contract.
                  /// @param newOwner The address of the new owner.
                  event Migrated(address caller, address migrator, address newOwner);
                  /// @dev Execute a migration function in the context of the ZeroEx contract.
                  ///      The result of the function being called should be the magic bytes
                  ///      0x2c64c5ef (`keccack('MIGRATE_SUCCESS')`). Only callable by the owner.
                  ///      The owner will be temporarily set to `address(this)` inside the call.
                  ///      Before returning, the owner will be set to `newOwner`.
                  /// @param target The migrator contract address.
                  /// @param newOwner The address of the new owner.
                  /// @param data The call data.
                  function migrate(address target, bytes calldata data, address newOwner) external;
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev Basic registry management features.
              interface ISimpleFunctionRegistryFeature {
                  /// @dev A function implementation was updated via `extend()` or `rollback()`.
                  /// @param selector The function selector.
                  /// @param oldImpl The implementation contract address being replaced.
                  /// @param newImpl The replacement implementation contract address.
                  event ProxyFunctionUpdated(bytes4 indexed selector, address oldImpl, address newImpl);
                  /// @dev Roll back to a prior implementation of a function.
                  /// @param selector The function selector.
                  /// @param targetImpl The address of an older implementation of the function.
                  function rollback(bytes4 selector, address targetImpl) external;
                  /// @dev Register or replace a function.
                  /// @param selector The function selector.
                  /// @param impl The implementation contract for the function.
                  function extend(bytes4 selector, address impl) external;
                  /// @dev Retrieve the length of the rollback history for a function.
                  /// @param selector The function selector.
                  /// @return rollbackLength The number of items in the rollback history for
                  ///         the function.
                  function getRollbackLength(bytes4 selector) external view returns (uint256 rollbackLength);
                  /// @dev Retrieve an entry in the rollback history for a function.
                  /// @param selector The function selector.
                  /// @param idx The index in the rollback history.
                  /// @return impl An implementation address for the function at
                  ///         index `idx`.
                  function getRollbackEntryAtIndex(bytes4 selector, uint256 idx) external view returns (address impl);
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              /// @dev VIP uniswap v3 fill functions.
              interface IUniswapV3Feature {
                  /// @dev Sell attached ETH directly against uniswap v3.
                  /// @param encodedPath Uniswap-encoded path, where the first token is WETH.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function sellEthForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 minBuyAmount,
                      address recipient
                  ) external payable returns (uint256 buyAmount);
                  /// @dev Sell a token for ETH directly against uniswap v3.
                  /// @param encodedPath Uniswap-encoded path, where the last token is WETH.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of ETH to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @return buyAmount Amount of ETH bought.
                  function sellTokenForEthToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address payable recipient
                  ) external returns (uint256 buyAmount);
                  /// @dev Sell a token for another token directly against uniswap v3.
                  /// @param encodedPath Uniswap-encoded path.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function sellTokenForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address recipient
                  ) external returns (uint256 buyAmount);
                  /// @dev Sell a token for another token directly against uniswap v3. Internal variant.
                  /// @param encodedPath Uniswap-encoded path.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for payer.
                  /// @param payer The address to pull the sold tokens from.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function _sellTokenForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address recipient,
                      address payer
                  ) external returns (uint256 buyAmount);
                  /// @dev Sell a token for another token directly against uniswap v3.
                  ///      Private variant, uses tokens held by `address(this)`.
                  /// @param encodedPath Uniswap-encoded path.
                  /// @param sellAmount amount of the first token in the path to sell.
                  /// @param minBuyAmount Minimum amount of the last token in the path to buy.
                  /// @param recipient The recipient of the bought tokens. Can be zero for sender.
                  /// @return buyAmount Amount of the last token in the path bought.
                  function _sellHeldTokenForTokenToUniswapV3(
                      bytes memory encodedPath,
                      uint256 sellAmount,
                      uint256 minBuyAmount,
                      address recipient
                  ) external returns (uint256 buyAmount);
                  /// @dev The UniswapV3 pool swap callback which pays the funds requested
                  ///      by the caller/pool to the pool. Can only be called by a valid
                  ///      UniswapV3 pool.
                  /// @param amount0Delta Token0 amount owed.
                  /// @param amount1Delta Token1 amount owed.
                  /// @param data Arbitrary data forwarded from swap() caller. An ABI-encoded
                  ///        struct of: inputToken, outputToken, fee, payer
                  function uniswapV3SwapCallback(int256 amount0Delta, int256 amount1Delta, bytes calldata data) external;
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../errors/LibCommonRichErrors.sol";
              import "../errors/LibOwnableRichErrors.sol";
              import "../features/interfaces/IOwnableFeature.sol";
              import "../features/interfaces/ISimpleFunctionRegistryFeature.sol";
              /// @dev Common feature utilities.
              abstract contract FixinCommon {
                  using LibRichErrorsV06 for bytes;
                  /// @dev The implementation address of this feature.
                  address internal immutable _implementation;
                  /// @dev The caller must be this contract.
                  modifier onlySelf() virtual {
                      if (msg.sender != address(this)) {
                          LibCommonRichErrors.OnlyCallableBySelfError(msg.sender).rrevert();
                      }
                      _;
                  }
                  /// @dev The caller of this function must be the owner.
                  modifier onlyOwner() virtual {
                      {
                          address owner = IOwnableFeature(address(this)).owner();
                          if (msg.sender != owner) {
                              LibOwnableRichErrors.OnlyOwnerError(msg.sender, owner).rrevert();
                          }
                      }
                      _;
                  }
                  constructor() internal {
                      // Remember this feature's original address.
                      _implementation = address(this);
                  }
                  /// @dev Registers a function implemented by this feature at `_implementation`.
                  ///      Can and should only be called within a `migrate()`.
                  /// @param selector The selector of the function whose implementation
                  ///        is at `_implementation`.
                  function _registerFeatureFunction(bytes4 selector) internal {
                      ISimpleFunctionRegistryFeature(address(this)).extend(selector, _implementation);
                  }
                  /// @dev Encode a feature version as a `uint256`.
                  /// @param major The major version number of the feature.
                  /// @param minor The minor version number of the feature.
                  /// @param revision The revision number of the feature.
                  /// @return encodedVersion The encoded version number.
                  function _encodeVersion(
                      uint32 major,
                      uint32 minor,
                      uint32 revision
                  ) internal pure returns (uint256 encodedVersion) {
                      return (uint256(major) << 64) | (uint256(minor) << 32) | uint256(revision);
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-erc20/src/IERC20Token.sol";
              import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
              /// @dev Helpers for moving tokens around.
              abstract contract FixinTokenSpender {
                  // Mask of the lower 20 bytes of a bytes32.
                  uint256 private constant ADDRESS_MASK = 0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff;
                  /// @dev Transfers ERC20 tokens from `owner` to `to`.
                  /// @param token The token to spend.
                  /// @param owner The owner of the tokens.
                  /// @param to The recipient of the tokens.
                  /// @param amount The amount of `token` to transfer.
                  function _transferERC20TokensFrom(IERC20Token token, address owner, address to, uint256 amount) internal {
                      require(address(token) != address(this), "FixinTokenSpender/CANNOT_INVOKE_SELF");
                      assembly {
                          let ptr := mload(0x40) // free memory pointer
                          // selector for transferFrom(address,address,uint256)
                          mstore(ptr, 0x23b872dd00000000000000000000000000000000000000000000000000000000)
                          mstore(add(ptr, 0x04), and(owner, ADDRESS_MASK))
                          mstore(add(ptr, 0x24), and(to, ADDRESS_MASK))
                          mstore(add(ptr, 0x44), amount)
                          let success := call(gas(), and(token, ADDRESS_MASK), 0, ptr, 0x64, ptr, 32)
                          let rdsize := returndatasize()
                          // Check for ERC20 success. ERC20 tokens should return a boolean,
                          // but some don't. We accept 0-length return data as success, or at
                          // least 32 bytes that starts with a 32-byte boolean true.
                          success := and(
                              success, // call itself succeeded
                              or(
                                  iszero(rdsize), // no return data, or
                                  and(
                                      iszero(lt(rdsize, 32)), // at least 32 bytes
                                      eq(mload(ptr), 1) // starts with uint256(1)
                                  )
                              )
                          )
                          if iszero(success) {
                              returndatacopy(ptr, 0, rdsize)
                              revert(ptr, rdsize)
                          }
                      }
                  }
                  /// @dev Transfers ERC20 tokens from ourselves to `to`.
                  /// @param token The token to spend.
                  /// @param to The recipient of the tokens.
                  /// @param amount The amount of `token` to transfer.
                  function _transferERC20Tokens(IERC20Token token, address to, uint256 amount) internal {
                      require(address(token) != address(this), "FixinTokenSpender/CANNOT_INVOKE_SELF");
                      assembly {
                          let ptr := mload(0x40) // free memory pointer
                          // selector for transfer(address,uint256)
                          mstore(ptr, 0xa9059cbb00000000000000000000000000000000000000000000000000000000)
                          mstore(add(ptr, 0x04), and(to, ADDRESS_MASK))
                          mstore(add(ptr, 0x24), amount)
                          let success := call(gas(), and(token, ADDRESS_MASK), 0, ptr, 0x44, ptr, 32)
                          let rdsize := returndatasize()
                          // Check for ERC20 success. ERC20 tokens should return a boolean,
                          // but some don't. We accept 0-length return data as success, or at
                          // least 32 bytes that starts with a 32-byte boolean true.
                          success := and(
                              success, // call itself succeeded
                              or(
                                  iszero(rdsize), // no return data, or
                                  and(
                                      iszero(lt(rdsize, 32)), // at least 32 bytes
                                      eq(mload(ptr), 1) // starts with uint256(1)
                                  )
                              )
                          )
                          if iszero(success) {
                              returndatacopy(ptr, 0, rdsize)
                              revert(ptr, rdsize)
                          }
                      }
                  }
                  /// @dev Transfers some amount of ETH to the given recipient and
                  ///      reverts if the transfer fails.
                  /// @param recipient The recipient of the ETH.
                  /// @param amount The amount of ETH to transfer.
                  function _transferEth(address payable recipient, uint256 amount) internal {
                      if (amount > 0) {
                          (bool success, ) = recipient.call{value: amount}("");
                          require(success, "FixinTokenSpender::_transferEth/TRANSFER_FAILED");
                      }
                  }
                  /// @dev Gets the maximum amount of an ERC20 token `token` that can be
                  ///      pulled from `owner` by this address.
                  /// @param token The token to spend.
                  /// @param owner The owner of the tokens.
                  /// @return amount The amount of tokens that can be pulled.
                  function _getSpendableERC20BalanceOf(IERC20Token token, address owner) internal view returns (uint256) {
                      return LibSafeMathV06.min256(token.allowance(owner, address(this)), token.balanceOf(owner));
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.5;
              pragma experimental ABIEncoderV2;
              import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
              import "../errors/LibOwnableRichErrors.sol";
              library LibMigrate {
                  /// @dev Magic bytes returned by a migrator to indicate success.
                  ///      This is `keccack('MIGRATE_SUCCESS')`.
                  bytes4 internal constant MIGRATE_SUCCESS = 0x2c64c5ef;
                  using LibRichErrorsV06 for bytes;
                  /// @dev Perform a delegatecall and ensure it returns the magic bytes.
                  /// @param target The call target.
                  /// @param data The call data.
                  function delegatecallMigrateFunction(address target, bytes memory data) internal {
                      (bool success, bytes memory resultData) = target.delegatecall(data);
                      if (!success || resultData.length != 32 || abi.decode(resultData, (bytes4)) != MIGRATE_SUCCESS) {
                          LibOwnableRichErrors.MigrateCallFailedError(target, resultData).rrevert();
                      }
                  }
              }
              // SPDX-License-Identifier: Apache-2.0
              /*
                Copyright 2023 ZeroEx Intl.
                Licensed under the Apache License, Version 2.0 (the "License");
                you may not use this file except in compliance with the License.
                You may obtain a copy of the License at
                  http://www.apache.org/licenses/LICENSE-2.0
                Unless required by applicable law or agreed to in writing, software
                distributed under the License is distributed on an "AS IS" BASIS,
                WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                See the License for the specific language governing permissions and
                limitations under the License.
              */
              pragma solidity ^0.6.12;
              interface IUniswapV3Pool {
                  /// @notice Swap token0 for token1, or token1 for token0
                  /// @dev The caller of this method receives a callback in the form of IUniswapV3SwapCallback#uniswapV3SwapCallback
                  /// @param recipient The address to receive the output of the swap
                  /// @param zeroForOne The direction of the swap, true for token0 to token1, false for token1 to token0
                  /// @param amountSpecified The amount of the swap, which implicitly configures the swap as exact input (positive),
                  /// or exact output (negative)
                  /// @param sqrtPriceLimitX96 The Q64.96 sqrt price limit. If zero for one, the price cannot be less than this
                  /// value after the swap. If one for zero, the price cannot be greater than this value after the swap
                  /// @param data Any data to be passed through to the callback
                  /// @return amount0 The delta of the balance of token0 of the pool, exact when negative, minimum when positive
                  /// @return amount1 The delta of the balance of token1 of the pool, exact when negative, minimum when positive
                  function swap(
                      address recipient,
                      bool zeroForOne,
                      int256 amountSpecified,
                      uint160 sqrtPriceLimitX96,
                      bytes calldata data
                  ) external returns (int256 amount0, int256 amount1);
              }