Contract Source Code:
// SPDX-License-Identifier: MIT
pragma solidity ^0.5.16;
contract ArcProxy {
/**
* @dev Emitted when the implementation is upgraded.
* @param implementation Address of the new implementation.
*/
event Upgraded(address indexed implementation);
/**
* @dev Emitted when the administration has been transferred.
* @param previousAdmin Address of the previous admin.
* @param newAdmin Address of the new admin.
*/
event AdminChanged(address previousAdmin, address newAdmin);
/**
* @dev Storage slot with the admin of the contract.
* This is the keccak-256 hash of "eip1967.proxy.admin" subtracted by 1, and is
* validated in the constructor.
*/
/* solium-disable-next-line */
bytes32 internal constant ADMIN_SLOT = 0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;
/**
* @dev Storage slot with the address of the current implementation.
* This is the keccak-256 hash of "eip1967.proxy.implementation" subtracted by 1, and is
* validated in the constructor.
*/
/* solium-disable-next-line */
bytes32 internal constant IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
/**
* @dev Modifier to check whether the `msg.sender` is the admin.
* If it is, it will run the function. Otherwise, it will delegate the call
* to the implementation.
*/
modifier ifAdmin() {
if (msg.sender == _admin()) {
_;
} else {
_fallback();
}
}
/**
* Contract constructor.
* @param _logic address of the initial implementation.
* @param _admin Address of the proxy administrator.
* @param _data Data to send as msg.data to the implementation to initialize the proxied contract.
* It should include the signature and the parameters of the function to be called, as described in
* https://solidity.readthedocs.io/en/v0.4.24/abi-spec.html#function-selector-and-argument-encoding.
* This parameter is optional, if no data is given the initialization call to proxied contract will be skipped.
*/
constructor(
address _logic,
address _admin,
bytes memory _data
)
public
payable
{
assert(
IMPLEMENTATION_SLOT == bytes32(
uint256(keccak256("eip1967.proxy.implementation")) - 1
)
);
_setImplementation(_logic);
if (_data.length > 0) {
/* solium-disable-next-line */
(bool success,) = _logic.delegatecall(_data);
/* solium-disable-next-line */
require(success);
}
assert(
ADMIN_SLOT == bytes32(
uint256(keccak256("eip1967.proxy.admin")) - 1
)
);
_setAdmin(_admin);
}
/**
* @dev Fallback function.
* Implemented entirely in `_fallback`.
*/
function () external payable {
_fallback();
}
/**
* @dev fallback implementation.
* Extracted to enable manual triggering.
*/
function _fallback() internal {
_delegate(_implementation());
}
/**
* @dev Delegates execution to an implementation contract.
* This is a low level function that doesn't return to its internal call site.
* It will return to the external caller whatever the implementation returns.
* @param implementation Address to delegate.
*/
function _delegate(address implementation) internal {
/* solium-disable-next-line */
assembly {
// Copy msg.data. We take full control of memory in this inline assembly
// block because it will not return to Solidity code. We overwrite the
// Solidity scratch pad at memory position 0.
calldatacopy(0, 0, calldatasize)
// Call the implementation.
// out and outsize are 0 because we don't know the size yet.
let result := delegatecall(gas, implementation, 0, calldatasize, 0, 0)
// Copy the returned data.
returndatacopy(0, 0, returndatasize)
switch result
// delegatecall returns 0 on error.
case 0 { revert(0, returndatasize) }
default { return(0, returndatasize) }
}
}
/**
* Returns whether the target address is a contract
* @dev This function will return false if invoked during the constructor of a contract,
* as the code is not actually created until after the constructor finishes.
* @param account address of the account to check
* @return whether the target address is a contract
*/
function isContract(address account) internal view returns (bool) {
uint256 size;
// XXX Currently there is no better way to check if there is a contract in an address
// than to check the size of the code at that address.
// See https://ethereum.stackexchange.com/a/14016/36603
// for more details about how this works.
// TODO Check this again before the Serenity release, because all addresses will be
// contracts then.
/* solium-disable-next-line */
assembly { size := extcodesize(account) }
return size > 0;
}
/**
* @dev Returns the current implementation.
* @return Address of the current implementation
*/
function _implementation() internal view returns (address impl) {
bytes32 slot = IMPLEMENTATION_SLOT;
/* solium-disable-next-line */
assembly {
impl := sload(slot)
}
}
/**
* @dev Upgrades the proxy to a new implementation.
* @param newImplementation Address of the new implementation.
*/
function _upgradeTo(address newImplementation) internal {
_setImplementation(newImplementation);
emit Upgraded(newImplementation);
}
/**
* @dev Sets the implementation address of the proxy.
* @param newImplementation Address of the new implementation.
*/
function _setImplementation(address newImplementation) internal {
require(
isContract(newImplementation),
"Cannot set a proxy implementation to a non-contract address"
);
bytes32 slot = IMPLEMENTATION_SLOT;
/* solium-disable-next-line */
assembly {
sstore(slot, newImplementation)
}
}
/**
* @return The address of the proxy admin.
*/
function admin() external ifAdmin returns (address) {
return _admin();
}
/**
* @return The address of the implementation.
*/
function implementation() external ifAdmin returns (address) {
return _implementation();
}
/**
* @dev Changes the admin of the proxy.
* Only the current admin can call this function.
* @param newAdmin Address to transfer proxy administration to.
*/
function changeAdmin(address newAdmin) external ifAdmin {
require(
newAdmin != address(0),
"Cannot change the admin of a proxy to the zero address"
);
emit AdminChanged(_admin(), newAdmin);
_setAdmin(newAdmin);
}
/**
* @dev Upgrade the backing implementation of the proxy.
* Only the admin can call this function.
* @param newImplementation Address of the new implementation.
*/
function upgradeTo(address newImplementation) external ifAdmin {
_upgradeTo(newImplementation);
}
/**
* @dev Upgrade the backing implementation of the proxy and call a function
* on the new implementation.
* This is useful to initialize the proxied contract.
* @param newImplementation Address of the new implementation.
* @param data Data to send as msg.data in the low level call.
* It should include the signature and the parameters of the function to be called, as described in
* https://solidity.readthedocs.io/en/v0.4.24/abi-spec.html#function-selector-and-argument-encoding.
*/
function upgradeToAndCall(
address newImplementation,
bytes calldata data
)
external
payable
ifAdmin
{
_upgradeTo(newImplementation);
/* solium-disable-next-line */
(bool success,) = newImplementation.delegatecall(data);
/* solium-disable-next-line */
require(success);
}
/**
* @return The admin slot.
*/
function _admin() internal view returns (address adm) {
bytes32 slot = ADMIN_SLOT;
/* solium-disable-next-line */
assembly {
adm := sload(slot)
}
}
/**
* @dev Sets the address of the proxy admin.
* @param newAdmin Address of the new proxy admin.
*/
function _setAdmin(address newAdmin) internal {
bytes32 slot = ADMIN_SLOT;
/* solium-disable-next-line */
assembly {
sstore(slot, newAdmin)
}
}
}