Contract Source Code:

/**
Matic network contracts
*/

pragma solidity ^0.5.2;


contract IERC721Receiver {
    /**
     * @notice Handle the receipt of an NFT
     * @dev The ERC721 smart contract calls this function on the recipient
     * after a `safeTransfer`. This function MUST return the function selector,
     * otherwise the caller will revert the transaction. The selector to be
     * returned can be obtained as `this.onERC721Received.selector`. This
     * function MAY throw to revert and reject the transfer.
     * Note: the ERC721 contract address is always the message sender.
     * @param operator The address which called `safeTransferFrom` function
     * @param from The address which previously owned the token
     * @param tokenId The NFT identifier which is being transferred
     * @param data Additional data with no specified format
     * @return bytes4 `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
     */
    function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data)
    public returns (bytes4);
}

interface IERC20 {
    function transfer(address to, uint256 value) external returns (bool);

    function approve(address spender, uint256 value) external returns (bool);

    function transferFrom(address from, address to, uint256 value) external returns (bool);

    function totalSupply() external view returns (uint256);

    function balanceOf(address who) external view returns (uint256);

    function allowance(address owner, address spender) external view returns (uint256);

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title IERC165
 * @dev https://eips.ethereum.org/EIPS/eip-165
 */
interface IERC165 {
    /**
     * @notice Query if a contract implements an interface
     * @param interfaceId The interface identifier, as specified in ERC-165
     * @dev Interface identification is specified in ERC-165. This function
     * uses less than 30,000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

contract IERC721 is IERC165 {
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    function balanceOf(address owner) public view returns (uint256 balance);
    function ownerOf(uint256 tokenId) public view returns (address owner);

    function approve(address to, uint256 tokenId) public;
    function getApproved(uint256 tokenId) public view returns (address operator);

    function setApprovalForAll(address operator, bool _approved) public;
    function isApprovedForAll(address owner, address operator) public view returns (bool);

    function transferFrom(address from, address to, uint256 tokenId) public;
    function safeTransferFrom(address from, address to, uint256 tokenId) public;

    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory data) public;
}

library SafeMath {
    /**
     * @dev Multiplies two unsigned integers, reverts on overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);

        return c;
    }

    /**
     * @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Adds two unsigned integers, reverts on overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }

    /**
     * @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
     * reverts when dividing by zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}

contract ContractReceiver {
    /// @dev Function that is called when a user or another contract wants to transfer funds.
    /// @param _from Transaction initiator, analogue of msg.sender
    /// @param _value Number of tokens to transfer.
    /// @param _data Data containig a function signature and/or parameters
    function tokenFallback(address _from, uint256 _value, bytes memory _data)
        public;
}

interface IGovernance {
    function update(address target, bytes calldata data) external;
}

contract Governable {
    IGovernance public governance;

    constructor(address _governance) public {
        governance = IGovernance(_governance);
    }

    modifier onlyGovernance() {
        require(
            msg.sender == address(governance),
            "Only governance contract is authorized"
        );
        _;
    }
}

contract IWithdrawManager {
    function createExitQueue(address token) external;

    function verifyInclusion(
        bytes calldata data,
        uint8 offset,
        bool verifyTxInclusion
    ) external view returns (uint256 age);

    function addExitToQueue(
        address exitor,
        address childToken,
        address rootToken,
        uint256 exitAmountOrTokenId,
        bytes32 txHash,
        bool isRegularExit,
        uint256 priority
    ) external;

    function addInput(
        uint256 exitId,
        uint256 age,
        address utxoOwner,
        address token
    ) external;

    function challengeExit(
        uint256 exitId,
        uint256 inputId,
        bytes calldata challengeData,
        address adjudicatorPredicate
    ) external;
}

contract Registry is Governable {
    // @todo hardcode constants
    bytes32 private constant WETH_TOKEN = keccak256("wethToken");
    bytes32 private constant DEPOSIT_MANAGER = keccak256("depositManager");
    bytes32 private constant STAKE_MANAGER = keccak256("stakeManager");
    bytes32 private constant VALIDATOR_SHARE = keccak256("validatorShare");
    bytes32 private constant WITHDRAW_MANAGER = keccak256("withdrawManager");
    bytes32 private constant CHILD_CHAIN = keccak256("childChain");
    bytes32 private constant STATE_SENDER = keccak256("stateSender");
    bytes32 private constant SLASHING_MANAGER = keccak256("slashingManager");

    address public erc20Predicate;
    address public erc721Predicate;

    mapping(bytes32 => address) public contractMap;
    mapping(address => address) public rootToChildToken;
    mapping(address => address) public childToRootToken;
    mapping(address => bool) public proofValidatorContracts;
    mapping(address => bool) public isERC721;

    enum Type {Invalid, ERC20, ERC721, Custom}
    struct Predicate {
        Type _type;
    }
    mapping(address => Predicate) public predicates;

    event TokenMapped(address indexed rootToken, address indexed childToken);
    event ProofValidatorAdded(address indexed validator, address indexed from);
    event ProofValidatorRemoved(address indexed validator, address indexed from);
    event PredicateAdded(address indexed predicate, address indexed from);
    event PredicateRemoved(address indexed predicate, address indexed from);
    event ContractMapUpdated(bytes32 indexed key, address indexed previousContract, address indexed newContract);

    constructor(address _governance) public Governable(_governance) {}

    function updateContractMap(bytes32 _key, address _address) external onlyGovernance {
        emit ContractMapUpdated(_key, contractMap[_key], _address);
        contractMap[_key] = _address;
    }

    /**
     * @dev Map root token to child token
     * @param _rootToken Token address on the root chain
     * @param _childToken Token address on the child chain
     * @param _isERC721 Is the token being mapped ERC721
     */
    function mapToken(
        address _rootToken,
        address _childToken,
        bool _isERC721
    ) external onlyGovernance {
        require(_rootToken != address(0x0) && _childToken != address(0x0), "INVALID_TOKEN_ADDRESS");
        rootToChildToken[_rootToken] = _childToken;
        childToRootToken[_childToken] = _rootToken;
        isERC721[_rootToken] = _isERC721;
        IWithdrawManager(contractMap[WITHDRAW_MANAGER]).createExitQueue(_rootToken);
        emit TokenMapped(_rootToken, _childToken);
    }

    function addErc20Predicate(address predicate) public onlyGovernance {
        require(predicate != address(0x0), "Can not add null address as predicate");
        erc20Predicate = predicate;
        addPredicate(predicate, Type.ERC20);
    }

    function addErc721Predicate(address predicate) public onlyGovernance {
        erc721Predicate = predicate;
        addPredicate(predicate, Type.ERC721);
    }

    function addPredicate(address predicate, Type _type) public onlyGovernance {
        require(predicates[predicate]._type == Type.Invalid, "Predicate already added");
        predicates[predicate]._type = _type;
        emit PredicateAdded(predicate, msg.sender);
    }

    function removePredicate(address predicate) public onlyGovernance {
        require(predicates[predicate]._type != Type.Invalid, "Predicate does not exist");
        delete predicates[predicate];
        emit PredicateRemoved(predicate, msg.sender);
    }

    function getValidatorShareAddress() public view returns (address) {
        return contractMap[VALIDATOR_SHARE];
    }

    function getWethTokenAddress() public view returns (address) {
        return contractMap[WETH_TOKEN];
    }

    function getDepositManagerAddress() public view returns (address) {
        return contractMap[DEPOSIT_MANAGER];
    }

    function getStakeManagerAddress() public view returns (address) {
        return contractMap[STAKE_MANAGER];
    }

    function getSlashingManagerAddress() public view returns (address) {
        return contractMap[SLASHING_MANAGER];
    }

    function getWithdrawManagerAddress() public view returns (address) {
        return contractMap[WITHDRAW_MANAGER];
    }

    function getChildChainAndStateSender() public view returns (address, address) {
        return (contractMap[CHILD_CHAIN], contractMap[STATE_SENDER]);
    }

    function isTokenMapped(address _token) public view returns (bool) {
        return rootToChildToken[_token] != address(0x0);
    }

    function isTokenMappedAndIsErc721(address _token) public view returns (bool) {
        require(isTokenMapped(_token), "TOKEN_NOT_MAPPED");
        return isERC721[_token];
    }

    function isTokenMappedAndGetPredicate(address _token) public view returns (address) {
        if (isTokenMappedAndIsErc721(_token)) {
            return erc721Predicate;
        }
        return erc20Predicate;
    }

    function isChildTokenErc721(address childToken) public view returns (bool) {
        address rootToken = childToRootToken[childToken];
        require(rootToken != address(0x0), "Child token is not mapped");
        return isERC721[rootToken];
    }
}

/**
 * @title ERC20 interface
 * @dev see https://eips.ethereum.org/EIPS/eip-20
 */

/**
 * @title SafeMath
 * @dev Unsigned math operations with safety checks that revert on error
 */

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://eips.ethereum.org/EIPS/eip-20
 * Originally based on code by FirstBlood:
 * https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 *
 * This implementation emits additional Approval events, allowing applications to reconstruct the allowance status for
 * all accounts just by listening to said events. Note that this isn't required by the specification, and other
 * compliant implementations may not do it.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowed;

    uint256 private _totalSupply;

    /**
     * @dev Total number of tokens in existence
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev Gets the balance of the specified address.
     * @param owner The address to query the balance of.
     * @return A uint256 representing the amount owned by the passed address.
     */
    function balanceOf(address owner) public view returns (uint256) {
        return _balances[owner];
    }

    /**
     * @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];
    }

    /**
     * @dev Transfer token to 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) {
        _transfer(msg.sender, 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) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev Transfer tokens from one address to another.
     * Note that while this function emits an Approval event, this is not required as per the specification,
     * and other compliant implementations may not emit the event.
     * @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) {
        _transfer(from, to, value);
        _approve(from, msg.sender, _allowed[from][msg.sender].sub(value));
        return true;
    }

    /**
     * @dev Increase the amount of tokens that an owner allowed to a spender.
     * approve should be called when _allowed[msg.sender][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
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param addedValue The amount of tokens to increase the allowance by.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowed[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner allowed to a spender.
     * approve should be called when _allowed[msg.sender][spender] == 0. To decrement
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowed[msg.sender][spender].sub(subtractedValue));
        return true;
    }

    /**
     * @dev Transfer token for a specified addresses
     * @param from The address to transfer from.
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     */
    function _transfer(address from, address to, uint256 value) internal {
        require(to != address(0));

        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value);
        emit Transfer(from, to, value);
    }

    /**
     * @dev Internal function that mints an amount of the token and assigns it to
     * an account. This encapsulates the modification of balances such that the
     * proper events are emitted.
     * @param account The account that will receive the created tokens.
     * @param value The amount that will be created.
     */
    function _mint(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.add(value);
        _balances[account] = _balances[account].add(value);
        emit Transfer(address(0), account, value);
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account.
     * @param account The account whose tokens will be burnt.
     * @param value The amount that will be burnt.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Approve an address to spend another addresses' tokens.
     * @param owner The address that owns the tokens.
     * @param spender The address that will spend the tokens.
     * @param value The number of tokens that can be spent.
     */
    function _approve(address owner, address spender, uint256 value) internal {
        require(spender != address(0));
        require(owner != address(0));

        _allowed[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account, deducting from the sender's allowance for said account. Uses the
     * internal burn function.
     * Emits an Approval event (reflecting the reduced allowance).
     * @param account The account whose tokens will be burnt.
     * @param value The amount that will be burnt.
     */
    function _burnFrom(address account, uint256 value) internal {
        _burn(account, value);
        _approve(account, msg.sender, _allowed[account][msg.sender].sub(value));
    }
}

contract WETH is ERC20 {
    event Deposit(address indexed dst, uint256 wad);
    event Withdrawal(address indexed src, uint256 wad);

    function deposit() public payable;

    function withdraw(uint256 wad) public;

    function withdraw(uint256 wad, address user) public;
}

interface IDepositManager {
    function depositEther() external payable;
    function transferAssets(
        address _token,
        address _user,
        uint256 _amountOrNFTId
    ) external;
    function depositERC20(address _token, uint256 _amount) external;
    function depositERC721(address _token, uint256 _tokenId) external;
}

library RLPReader {
    uint8 constant STRING_SHORT_START = 0x80;
    uint8 constant STRING_LONG_START  = 0xb8;
    uint8 constant LIST_SHORT_START   = 0xc0;
    uint8 constant LIST_LONG_START    = 0xf8;
    uint8 constant WORD_SIZE = 32;

    struct RLPItem {
        uint len;
        uint memPtr;
    }

    struct Iterator {
        RLPItem item;   // Item that's being iterated over.
        uint nextPtr;   // Position of the next item in the list.
    }

    /*
    * @dev Returns the next element in the iteration. Reverts if it has not next element.
    * @param self The iterator.
    * @return The next element in the iteration.
    */
    function next(Iterator memory self) internal pure returns (RLPItem memory) {
        require(hasNext(self));

        uint ptr = self.nextPtr;
        uint itemLength = _itemLength(ptr);
        self.nextPtr = ptr + itemLength;

        return RLPItem(itemLength, ptr);
    }

    /*
    * @dev Returns true if the iteration has more elements.
    * @param self The iterator.
    * @return true if the iteration has more elements.
    */
    function hasNext(Iterator memory self) internal pure returns (bool) {
        RLPItem memory item = self.item;
        return self.nextPtr < item.memPtr + item.len;
    }

    /*
    * @param item RLP encoded bytes
    */
    function toRlpItem(bytes memory item) internal pure returns (RLPItem memory) {
        uint memPtr;
        assembly {
            memPtr := add(item, 0x20)
        }

        return RLPItem(item.length, memPtr);
    }

    /*
    * @dev Create an iterator. Reverts if item is not a list.
    * @param self The RLP item.
    * @return An 'Iterator' over the item.
    */
    function iterator(RLPItem memory self) internal pure returns (Iterator memory) {
        require(isList(self));

        uint ptr = self.memPtr + _payloadOffset(self.memPtr);
        return Iterator(self, ptr);
    }

    /*
    * @param item RLP encoded bytes
    */
    function rlpLen(RLPItem memory item) internal pure returns (uint) {
        return item.len;
    }

    /*
    * @param item RLP encoded bytes
    */
    function payloadLen(RLPItem memory item) internal pure returns (uint) {
        return item.len - _payloadOffset(item.memPtr);
    }

    /*
    * @param item RLP encoded list in bytes
    */
    function toList(RLPItem memory item) internal pure returns (RLPItem[] memory) {
        require(isList(item));

        uint items = numItems(item);
        RLPItem[] memory result = new RLPItem[](items);

        uint memPtr = item.memPtr + _payloadOffset(item.memPtr);
        uint dataLen;
        for (uint i = 0; i < items; i++) {
            dataLen = _itemLength(memPtr);
            result[i] = RLPItem(dataLen, memPtr); 
            memPtr = memPtr + dataLen;
        }

        return result;
    }

    // @return indicator whether encoded payload is a list. negate this function call for isData.
    function isList(RLPItem memory item) internal pure returns (bool) {
        if (item.len == 0) return false;

        uint8 byte0;
        uint memPtr = item.memPtr;
        assembly {
            byte0 := byte(0, mload(memPtr))
        }

        if (byte0 < LIST_SHORT_START)
            return false;
        return true;
    }

    /** RLPItem conversions into data types **/

    // @returns raw rlp encoding in bytes
    function toRlpBytes(RLPItem memory item) internal pure returns (bytes memory) {
        bytes memory result = new bytes(item.len);
        if (result.length == 0) return result;
        
        uint ptr;
        assembly {
            ptr := add(0x20, result)
        }

        copy(item.memPtr, ptr, item.len);
        return result;
    }

    // any non-zero byte is considered true
    function toBoolean(RLPItem memory item) internal pure returns (bool) {
        require(item.len == 1);
        uint result;
        uint memPtr = item.memPtr;
        assembly {
            result := byte(0, mload(memPtr))
        }

        return result == 0 ? false : true;
    }

    function toAddress(RLPItem memory item) internal pure returns (address) {
        // 1 byte for the length prefix
        require(item.len == 21);

        return address(toUint(item));
    }

    function toUint(RLPItem memory item) internal pure returns (uint) {
        require(item.len > 0 && item.len <= 33);

        uint offset = _payloadOffset(item.memPtr);
        uint len = item.len - offset;

        uint result;
        uint memPtr = item.memPtr + offset;
        assembly {
            result := mload(memPtr)

            // shfit to the correct location if neccesary
            if lt(len, 32) {
                result := div(result, exp(256, sub(32, len)))
            }
        }

        return result;
    }

    // enforces 32 byte length
    function toUintStrict(RLPItem memory item) internal pure returns (uint) {
        // one byte prefix
        require(item.len == 33);

        uint result;
        uint memPtr = item.memPtr + 1;
        assembly {
            result := mload(memPtr)
        }

        return result;
    }

    function toBytes(RLPItem memory item) internal pure returns (bytes memory) {
        require(item.len > 0);

        uint offset = _payloadOffset(item.memPtr);
        uint len = item.len - offset; // data length
        bytes memory result = new bytes(len);

        uint destPtr;
        assembly {
            destPtr := add(0x20, result)
        }

        copy(item.memPtr + offset, destPtr, len);
        return result;
    }

    /*
    * Private Helpers
    */

    // @return number of payload items inside an encoded list.
    function numItems(RLPItem memory item) private pure returns (uint) {
        if (item.len == 0) return 0;

        uint count = 0;
        uint currPtr = item.memPtr + _payloadOffset(item.memPtr);
        uint endPtr = item.memPtr + item.len;
        while (currPtr < endPtr) {
           currPtr = currPtr + _itemLength(currPtr); // skip over an item
           count++;
        }

        return count;
    }

    // @return entire rlp item byte length
    function _itemLength(uint memPtr) private pure returns (uint) {
        uint itemLen;
        uint byte0;
        assembly {
            byte0 := byte(0, mload(memPtr))
        }

        if (byte0 < STRING_SHORT_START)
            itemLen = 1;
        
        else if (byte0 < STRING_LONG_START)
            itemLen = byte0 - STRING_SHORT_START + 1;

        else if (byte0 < LIST_SHORT_START) {
            assembly {
                let byteLen := sub(byte0, 0xb7) // # of bytes the actual length is
                memPtr := add(memPtr, 1) // skip over the first byte
                
                /* 32 byte word size */
                let dataLen := div(mload(memPtr), exp(256, sub(32, byteLen))) // right shifting to get the len
                itemLen := add(dataLen, add(byteLen, 1))
            }
        }

        else if (byte0 < LIST_LONG_START) {
            itemLen = byte0 - LIST_SHORT_START + 1;
        } 

        else {
            assembly {
                let byteLen := sub(byte0, 0xf7)
                memPtr := add(memPtr, 1)

                let dataLen := div(mload(memPtr), exp(256, sub(32, byteLen))) // right shifting to the correct length
                itemLen := add(dataLen, add(byteLen, 1))
            }
        }

        return itemLen;
    }

    // @return number of bytes until the data
    function _payloadOffset(uint memPtr) private pure returns (uint) {
        uint byte0;
        assembly {
            byte0 := byte(0, mload(memPtr))
        }

        if (byte0 < STRING_SHORT_START) 
            return 0;
        else if (byte0 < STRING_LONG_START || (byte0 >= LIST_SHORT_START && byte0 < LIST_LONG_START))
            return 1;
        else if (byte0 < LIST_SHORT_START)  // being explicit
            return byte0 - (STRING_LONG_START - 1) + 1;
        else
            return byte0 - (LIST_LONG_START - 1) + 1;
    }

    /*
    * @param src Pointer to source
    * @param dest Pointer to destination
    * @param len Amount of memory to copy from the source
    */
    function copy(uint src, uint dest, uint len) private pure {
        if (len == 0) return;

        // copy as many word sizes as possible
        for (; len >= WORD_SIZE; len -= WORD_SIZE) {
            assembly {
                mstore(dest, mload(src))
            }

            src += WORD_SIZE;
            dest += WORD_SIZE;
        }

        // left over bytes. Mask is used to remove unwanted bytes from the word
        uint mask = 256 ** (WORD_SIZE - len) - 1;
        assembly {
            let srcpart := and(mload(src), not(mask)) // zero out src
            let destpart := and(mload(dest), mask) // retrieve the bytes
            mstore(dest, or(destpart, srcpart))
        }
    }
}

contract Ownable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    constructor () internal {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), _owner);
    }

    /**
     * @return the address of the owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner());
        _;
    }

    /**
     * @return true if `msg.sender` is the owner of the contract.
     */
    function isOwner() public view returns (bool) {
        return msg.sender == _owner;
    }

    /**
     * @dev Allows the current owner to relinquish control of the contract.
     * It will not be possible to call the functions with the `onlyOwner`
     * modifier anymore.
     * @notice Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @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 {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0));
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

contract ProxyStorage is Ownable {
    address internal proxyTo;
}

contract ChainIdMixin {
  bytes constant public networkId = hex"3A99";
  uint256 constant public CHAINID = 15001;
}

contract RootChainHeader {
    event NewHeaderBlock(
        address indexed proposer,
        uint256 indexed headerBlockId,
        uint256 indexed reward,
        uint256 start,
        uint256 end,
        bytes32 root
    );
    // housekeeping event
    event ResetHeaderBlock(address indexed proposer, uint256 indexed headerBlockId);
    struct HeaderBlock {
        bytes32 root;
        uint256 start;
        uint256 end;
        uint256 createdAt;
        address proposer;
    }
}

contract RootChainStorage is ProxyStorage, RootChainHeader, ChainIdMixin {
    bytes32 public heimdallId;
    uint8 public constant VOTE_TYPE = 2;

    uint16 internal constant MAX_DEPOSITS = 10000;
    uint256 public _nextHeaderBlock = MAX_DEPOSITS;
    uint256 internal _blockDepositId = 1;
    mapping(uint256 => HeaderBlock) public headerBlocks;
    Registry internal registry;
}

contract IStakeManager {
    // validator replacement
    function startAuction(uint256 validatorId, uint256 amount) external;

    function confirmAuctionBid(
        uint256 validatorId,
        uint256 heimdallFee,
        bool acceptDelegation,
        bytes calldata signerPubkey
    ) external;

    function transferFunds(
        uint256 validatorId,
        uint256 amount,
        address delegator
    ) external returns (bool);

    function delegationDeposit(
        uint256 validatorId,
        uint256 amount,
        address delegator
    ) external returns (bool);

    function stake(
        uint256 amount,
        uint256 heimdallFee,
        bool acceptDelegation,
        bytes calldata signerPubkey
    ) external;

    function unstake(uint256 validatorId) external;

    function totalStakedFor(address addr) external view returns (uint256);

    function supportsHistory() external pure returns (bool);

    function stakeFor(
        address user,
        uint256 amount,
        uint256 heimdallFee,
        bool acceptDelegation,
        bytes memory signerPubkey
    ) public;

    function checkSignatures(
        uint256 blockInterval,
        bytes32 voteHash,
        bytes32 stateRoot,
        address proposer,
        bytes memory sigs
    ) public returns (uint256);

    function updateValidatorState(uint256 validatorId, int256 amount) public;

    function ownerOf(uint256 tokenId) public view returns (address);

    function slash(bytes memory slashingInfoList) public returns (uint256);

    function validatorStake(uint256 validatorId) public view returns (uint256);

    function epoch() public view returns (uint256);

    function withdrawalDelay() public view returns (uint256);
}

interface IRootChain {
    function slash() external;

    function submitHeaderBlock(bytes calldata data, bytes calldata sigs)
        external;

    function getLastChildBlock() external view returns (uint256);

    function currentHeaderBlock() external view returns (uint256);
}

contract RootChain is RootChainStorage, IRootChain {
    using SafeMath for uint256;
    using RLPReader for bytes;
    using RLPReader for RLPReader.RLPItem;

    modifier onlyDepositManager() {
        require(msg.sender == registry.getDepositManagerAddress(), "UNAUTHORIZED_DEPOSIT_MANAGER_ONLY");
        _;
    }

    function submitHeaderBlock(bytes calldata data, bytes calldata sigs) external {
        (address proposer, uint256 start, uint256 end, bytes32 rootHash, bytes32 accountHash, uint256 _borChainID) = abi
            .decode(data, (address, uint256, uint256, bytes32, bytes32, uint256));
        require(CHAINID == _borChainID, "Invalid bor chain id");

        require(_buildHeaderBlock(proposer, start, end, rootHash), "INCORRECT_HEADER_DATA");

        // check if it is better to keep it in local storage instead
        IStakeManager stakeManager = IStakeManager(registry.getStakeManagerAddress());
        uint256 _reward = stakeManager.checkSignatures(
            end.sub(start).add(1),
            /**  
                prefix 01 to data 
                01 represents positive vote on data and 00 is negative vote
                malicious validator can try to send 2/3 on negative vote so 01 is appended
             */
            keccak256(abi.encodePacked(bytes(hex"01"), data)),
            accountHash,
            proposer,
            sigs
        );

        require(_reward != 0, "Invalid checkpoint");
        emit NewHeaderBlock(proposer, _nextHeaderBlock, _reward, start, end, rootHash);
        _nextHeaderBlock = _nextHeaderBlock.add(MAX_DEPOSITS);
        _blockDepositId = 1;
    }

    function updateDepositId(uint256 numDeposits) external onlyDepositManager returns (uint256 depositId) {
        depositId = currentHeaderBlock().add(_blockDepositId);
        // deposit ids will be (_blockDepositId, _blockDepositId + 1, .... _blockDepositId + numDeposits - 1)
        _blockDepositId = _blockDepositId.add(numDeposits);
        require(
            // Since _blockDepositId is initialized to 1; only (MAX_DEPOSITS - 1) deposits per header block are allowed
            _blockDepositId <= MAX_DEPOSITS,
            "TOO_MANY_DEPOSITS"
        );
    }

    function getLastChildBlock() external view returns (uint256) {
        return headerBlocks[currentHeaderBlock()].end;
    }

    function slash() external {
        //TODO: future implementation
    }

    function currentHeaderBlock() public view returns (uint256) {
        return _nextHeaderBlock.sub(MAX_DEPOSITS);
    }

    function _buildHeaderBlock(
        address proposer,
        uint256 start,
        uint256 end,
        bytes32 rootHash
    ) private returns (bool) {
        uint256 nextChildBlock;
        /*
    The ID of the 1st header block is MAX_DEPOSITS.
    if _nextHeaderBlock == MAX_DEPOSITS, then the first header block is yet to be submitted, hence nextChildBlock = 0
    */
        if (_nextHeaderBlock > MAX_DEPOSITS) {
            nextChildBlock = headerBlocks[currentHeaderBlock()].end + 1;
        }
        if (nextChildBlock != start) {
            return false;
        }

        HeaderBlock memory headerBlock = HeaderBlock({
            root: rootHash,
            start: nextChildBlock,
            end: end,
            createdAt: now,
            proposer: proposer
        });

        headerBlocks[_nextHeaderBlock] = headerBlock;
        return true;
    }

    // Housekeeping function. @todo remove later
    function setNextHeaderBlock(uint256 _value) public onlyOwner {
        require(_value % MAX_DEPOSITS == 0, "Invalid value");
        for (uint256 i = _value; i < _nextHeaderBlock; i += MAX_DEPOSITS) {
            delete headerBlocks[i];
        }
        _nextHeaderBlock = _value;
        _blockDepositId = 1;
        emit ResetHeaderBlock(msg.sender, _nextHeaderBlock);
    }

    // Housekeeping function. @todo remove later
    function setHeimdallId(string memory _heimdallId) public onlyOwner {
        heimdallId = keccak256(abi.encodePacked(_heimdallId));
    }
}

contract StateSender is Ownable {
    using SafeMath for uint256;

    uint256 public counter;
    mapping(address => address) public registrations;

    event NewRegistration(
        address indexed user,
        address indexed sender,
        address indexed receiver
    );
    event RegistrationUpdated(
        address indexed user,
        address indexed sender,
        address indexed receiver
    );
    event StateSynced(
        uint256 indexed id,
        address indexed contractAddress,
        bytes data
    );

    modifier onlyRegistered(address receiver) {
        require(registrations[receiver] == msg.sender, "Invalid sender");
        _;
    }

    function syncState(address receiver, bytes calldata data)
        external
        onlyRegistered(receiver)
    {
        counter = counter.add(1);
        emit StateSynced(counter, receiver, data);
    }

    // register new contract for state sync
    function register(address sender, address receiver) public {
        require(
            isOwner() || registrations[receiver] == msg.sender,
            "StateSender.register: Not authorized to register"
        );
        registrations[receiver] = sender;
        if (registrations[receiver] == address(0)) {
            emit NewRegistration(msg.sender, sender, receiver);
        } else {
            emit RegistrationUpdated(msg.sender, sender, receiver);
        }
    }
}

contract Lockable is Governable {
    bool public locked;

    modifier onlyWhenUnlocked() {
        require(!locked, "Is Locked");
        _;
    }

    constructor(address _governance) public Governable(_governance) {}

    function lock() external onlyGovernance {
        locked = true;
    }

    function unlock() external onlyGovernance {
        locked = false;
    }
}

contract DepositManagerHeader {
    event NewDepositBlock(address indexed owner, address indexed token, uint256 amountOrNFTId, uint256 depositBlockId);
    event MaxErc20DepositUpdate(uint256 indexed oldLimit, uint256 indexed newLimit);

    struct DepositBlock {
        bytes32 depositHash;
        uint256 createdAt;
    }
}

contract DepositManagerStorage is ProxyStorage, Lockable, DepositManagerHeader {
    Registry public registry;
    RootChain public rootChain;
    StateSender public stateSender;

    mapping(uint256 => DepositBlock) public deposits;

    address public childChain;
    uint256 public maxErc20Deposit = 100 * (10**18);
}

contract DepositManager is DepositManagerStorage, IDepositManager, IERC721Receiver, ContractReceiver {
    using SafeMath for uint256;

    modifier isTokenMapped(address _token) {
        require(registry.isTokenMapped(_token), "TOKEN_NOT_SUPPORTED");
        _;
    }

    modifier isPredicateAuthorized() {
        require(uint8(registry.predicates(msg.sender)) != 0, "Not a valid predicate");
        _;
    }

    constructor() public Lockable(address(0x0)) {}

    // deposit ETH by sending to this contract
    function() external payable {
        depositEther();
    }

    function updateMaxErc20Deposit(uint256 maxDepositAmount) public onlyGovernance {
        require(maxDepositAmount != 0);
        emit MaxErc20DepositUpdate(maxErc20Deposit, maxDepositAmount);
        maxErc20Deposit = maxDepositAmount;
    }

    function transferAssets(
        address _token,
        address _user,
        uint256 _amountOrNFTId
    ) external isPredicateAuthorized {
        address wethToken = registry.getWethTokenAddress();
        if (registry.isERC721(_token)) {
            IERC721(_token).transferFrom(address(this), _user, _amountOrNFTId);
        } else if (_token == wethToken) {
            WETH t = WETH(_token);
            t.withdraw(_amountOrNFTId, _user);
        } else {
            require(IERC20(_token).transfer(_user, _amountOrNFTId), "TRANSFER_FAILED");
        }
    }

    function depositERC20(address _token, uint256 _amount) external {
        depositERC20ForUser(_token, msg.sender, _amount);
    }

    function depositERC721(address _token, uint256 _tokenId) external {
        depositERC721ForUser(_token, msg.sender, _tokenId);
    }

    function depositBulk(
        address[] calldata _tokens,
        uint256[] calldata _amountOrTokens,
        address _user
    )
        external
        onlyWhenUnlocked // unlike other deposit functions, depositBulk doesn't invoke _safeCreateDepositBlock
    {
        require(_tokens.length == _amountOrTokens.length, "Invalid Input");
        uint256 depositId = rootChain.updateDepositId(_tokens.length);
        Registry _registry = registry;

        for (uint256 i = 0; i < _tokens.length; i++) {
            // will revert if token is not mapped
            if (_registry.isTokenMappedAndIsErc721(_tokens[i])) {
                IERC721(_tokens[i]).transferFrom(msg.sender, address(this), _amountOrTokens[i]);
            } else {
                require(
                    IERC20(_tokens[i]).transferFrom(msg.sender, address(this), _amountOrTokens[i]),
                    "TOKEN_TRANSFER_FAILED"
                );
            }
            _createDepositBlock(_user, _tokens[i], _amountOrTokens[i], depositId);
            depositId = depositId.add(1);
        }
    }

    /**
     * @dev Caches childChain and stateSender (frequently used variables) from registry
     */
    function updateChildChainAndStateSender() public {
        (address _childChain, address _stateSender) = registry.getChildChainAndStateSender();
        require(
            _stateSender != address(stateSender) || _childChain != childChain,
            "Atleast one of stateSender or childChain address should change"
        );
        childChain = _childChain;
        stateSender = StateSender(_stateSender);
    }

    function depositERC20ForUser(
        address _token,
        address _user,
        uint256 _amount
    ) public {
        require(_amount <= maxErc20Deposit, "exceed maximum deposit amount");
        require(IERC20(_token).transferFrom(msg.sender, address(this), _amount), "TOKEN_TRANSFER_FAILED");
        _safeCreateDepositBlock(_user, _token, _amount);
    }

    function depositERC721ForUser(
        address _token,
        address _user,
        uint256 _tokenId
    ) public {
        IERC721(_token).transferFrom(msg.sender, address(this), _tokenId);
        _safeCreateDepositBlock(_user, _token, _tokenId);
    }

    // @todo: write depositEtherForUser
    function depositEther() public payable {
        address wethToken = registry.getWethTokenAddress();
        WETH t = WETH(wethToken);
        t.deposit.value(msg.value)();
        _safeCreateDepositBlock(msg.sender, wethToken, msg.value);
    }

    /**
   * @notice This will be invoked when safeTransferFrom is called on the token contract to deposit tokens to this contract
     without directly interacting with it
   * @dev msg.sender is the token contract
   * _operator The address which called `safeTransferFrom` function on the token contract
   * @param _user The address which previously owned the token
   * @param _tokenId The NFT identifier which is being transferred
   * _data Additional data with no specified format
   * @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
   */
    function onERC721Received(
        address, /* _operator */
        address _user,
        uint256 _tokenId,
        bytes memory /* _data */
    ) public returns (bytes4) {
        // the ERC721 contract address is the message sender
        _safeCreateDepositBlock(
            _user,
            msg.sender,
            /* token */
            _tokenId
        );
        return 0x150b7a02;
    }

    // See https://github.com/ethereum/EIPs/issues/223
    function tokenFallback(
        address _user,
        uint256 _amount,
        bytes memory /* _data */
    ) public {
        _safeCreateDepositBlock(
            _user,
            msg.sender,
            /* token */
            _amount
        );
    }

    function _safeCreateDepositBlock(
        address _user,
        address _token,
        uint256 _amountOrToken
    ) internal onlyWhenUnlocked isTokenMapped(_token) {
        _createDepositBlock(
            _user,
            _token,
            _amountOrToken,
            rootChain.updateDepositId(1) /* returns _depositId */
        );
    }

    function _createDepositBlock(
        address _user,
        address _token,
        uint256 _amountOrToken,
        uint256 _depositId
    ) internal {
        deposits[_depositId] = DepositBlock(keccak256(abi.encodePacked(_user, _token, _amountOrToken)), now);
        stateSender.syncState(childChain, abi.encode(_user, _token, _amountOrToken, _depositId));
        emit NewDepositBlock(_user, _token, _amountOrToken, _depositId);
    }

    // Housekeeping function. @todo remove later
    function updateRootChain(address _rootChain) public onlyOwner {
        rootChain = RootChain(_rootChain);
    }
}