ERC165合约是IERC165的标准实现。ERC165提供了本合约是否实现了IERC165接口的查询。如果需要额外支持其他interface,可在目标合约内重写supportsInterface(bytes4)方法。
[openzeppelin]:v4.8.3,[forge-std]:v1.5.6
ERC165合约是IERC165的标准实现。ERC165提供了本合约是否实现了IERC165接口的查询。如果需要额外支持其他interface,可在目标合约内重写supportsInterface(bytes4)
方法。
继承ERC165成为一个可调用合约:
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;
import "openzeppelin-contracts/contracts/utils/introspection/ERC165.sol";
interface ICustomizedInterface {
error CustomizedError();
event CustomizedEvent(uint n);
function viewFunction(address addr) external view returns (address);
function pureFunction(uint n) external pure returns (uint);
function externalFunction(uint[] calldata nums, address[] calldata addrs) external;
}
contract MockERC165 is ERC165, ICustomizedInterface {
uint _totalSum;
uint _totalNumberOfAddress;
// implementation of ICustomizedInterface
function viewFunction(address addr) external view returns (address){
if (addr == msg.sender) {
return addr;
}
return address(1024);
}
function pureFunction(uint n) external pure returns (uint){
return n + 1;
}
function externalFunction(uint[] calldata nums, address[] calldata addrs) external {
for (uint i; i < nums.length; ++i) {
_totalSum += nums[i];
}
_totalNumberOfAddress = addrs.length;
}
// override supportsInterface(bytes4) of IERC165
function supportsInterface(bytes4 interfaceId) public view override returns (bool) {
return interfaceId == type(ICustomizedInterface).interfaceId || super.supportsInterface(interfaceId);
}
}
同时该合约实现了一个自定义interface——ICustomizedInterface。
全部foundry测试合约:
通过定义interfaceId作为interface的唯一标记。IERC165主要解决了目标合约已实现接口的检测问题——IERC165的实现合约提供了自身已实现interface的查询功能并且可以被其他继承ERC165Checker
的合约识别。
具体详情参见:https://eips.ethereum.org/EIPS/eip-165
注:IERC165中要求方法supportsInterface(bytes4)
的gas消耗必须小于30000 gas。
interfaceId为interface的标识,有3种方法可以求得一个interface的interfaceId:
type(interface).interfaceId
。以ICustomizedInterface为例:bytes4 interfaceIdICustomizedInterface = type(ICustomizedInterface).interfaceId;
bytes4 interfaceIdICustomizedInterface = ICustomizedInterface.viewFunction.selector
^ ICustomizedInterface.pureFunction.selector
^ ICustomizedInterface.externalFunction.selector;
bytes4 interfaceIdICustomizedInterface = bytes4(keccak256('viewFunction(address)'))
^ bytes4(keccak256('pureFunction(uint256)'))
^ bytes4(keccak256('externalFunction(uint256[],address[])'));
对外提供本合约是否实现了传入interfaceId标识的interface的查询功能。
function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
// 如果传入的interfaceId为IERC165的interfaceId返回true,否则返回false
return interfaceId == type(IERC165).interfaceId;
}
注:ERC165只支持对interface IERC165的确认查询,如果需要额外支持其他interface,可在目标合约内重写该方法。具体例子可见后面的foundry测试代码。
contract ERC165Test is Test {
MockERC165 me = new MockERC165();
function test_SupportsInterface_IERC165() external {
// way 1: from function selector
bytes4 interfaceIdIERC165 = IERC165.supportsInterface.selector;
assertTrue(me.supportsInterface(interfaceIdIERC165));
// way 2: from hash result of function signature
interfaceIdIERC165 = bytes4(keccak256('supportsInterface(bytes4)'));
assertTrue(me.supportsInterface(interfaceIdIERC165));
// way 3: from type(interface).interfaceId
interfaceIdIERC165 = type(IERC165).interfaceId;
assertTrue(me.supportsInterface(interfaceIdIERC165));
// not support
bytes4 interfaceIdNotSupport = 0xffffffff;
assertFalse(me.supportsInterface(interfaceIdNotSupport));
}
function test_SupportsInterface_ICustomizedInterface() external {
// way 1: from XOR of all function selectors in the interface
bytes4 interfaceIdICustomizedInterface = ICustomizedInterface.viewFunction.selector
^ ICustomizedInterface.pureFunction.selector
^ ICustomizedInterface.externalFunction.selector;
assertTrue(me.supportsInterface(interfaceIdICustomizedInterface));
// way 2: from XOR of all hash result of function signature
interfaceIdICustomizedInterface = bytes4(keccak256('viewFunction(address)'))
^ bytes4(keccak256('pureFunction(uint256)'))
^ bytes4(keccak256('externalFunction(uint256[],address[])'));
assertTrue(me.supportsInterface(interfaceIdICustomizedInterface));
// way 3: from type(interface).interfaceId
interfaceIdICustomizedInterface = type(ICustomizedInterface).interfaceId;
assertTrue(me.supportsInterface(interfaceIdICustomizedInterface));
// not support
bytes4 interfaceIdNotSupport = ICustomizedInterface.pureFunction.selector
^ ICustomizedInterface.externalFunction.selector;
assertFalse(me.supportsInterface(interfaceIdNotSupport));
}
function test_SupportsInterface_Gas() external {
// for type(IERC165).interfaceId
uint startGas = gasleft();
me.supportsInterface(type(IERC165).interfaceId);
uint endGas = gasleft();
assertLt(startGas - endGas, 30000);
// for type(ICustomizedInterface).interfaceId
startGas = gasleft();
me.supportsInterface(type(ICustomizedInterface).interfaceId);
endGas = gasleft();
assertLt(startGas - endGas, 30000);
}
}
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