mirror of https://github.com/status-im/EIPs.git
Update cache to use explicit return values of 32 byte length
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@ -36,11 +36,11 @@ For this standard, an *interface* is a set of [function selectors as calculated
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We define the interface identifier as the XOR of all function selectors in the interface. This code example shows how to calculate an interface identifier:
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```solidity
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pragma solidity ^0.4.19;
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pragma solidity ^0.4.20;
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interface Solidity101 {
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function hello() public pure;
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function world(int) public pure;
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function hello() external pure;
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function world(int) external pure;
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}
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contract Selector {
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@ -58,7 +58,7 @@ Note: interfaces do not permit optional functions, therefore, the interface iden
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A contract that is compliant with ERC-165 shall implement the following interface (referred as `ERC165.sol`):
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```solidity
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pragma solidity ^0.4.19;
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pragma solidity ^0.4.20;
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interface ERC165 {
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/// @notice Query if a contract implements an interface
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@ -113,7 +113,7 @@ Also [the ENS](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-137.md) alr
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Following is a caching contract that detects which interfaces other contracts implement. From @fulldecent and @jbaylina.
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```solidity
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pragma solidity ^0.4.19;
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pragma solidity ^0.4.20;
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contract ERC165Cache {
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bytes4 constant InvalidID = 0xffffffff;
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@ -139,25 +139,42 @@ contract ERC165Cache {
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}
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function determineInterfaceImplementationStatus(address _contract, bytes4 _interfaceId) internal view returns (ImplStatus) {
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if (noThrowCall(_contract, InvalidID)) return ImplStatus.No;
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if (!noThrowCall(_contract, ERC165ID)) return ImplStatus.No;
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if (noThrowCall(_contract, _interfaceId)) return ImplStatus.Yes;
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uint256 success;
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uint256 result;
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(success, result) = noThrowCall(_contract, ERC165ID);
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if ((success==0)||(result==0)) {
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return ImplStatus.No;
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}
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(success, result) = noThrowCall(_contract, InvalidID);
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if ((success==0)||(result!=0)) {
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return ImplStatus.No;
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}
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(success, result) = noThrowCall(_contract, _interfaceId);
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if ((success==1)&&(result==1)) {
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return ImplStatus.Yes;
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}
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return ImplStatus.No;
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}
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function noThrowCall(address _contract, bytes4 _interfaceId) internal view returns (bool result) {
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function noThrowCall(address _contract, bytes4 _interfaceId) constant internal returns (uint256 success, uint256 result) {
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bytes4 erc165ID = ERC165ID;
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assembly {
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let x := mload(0x40) // Find empty storage location using "free memory pointer"
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mstore(x, erc165ID) // Place signature at begining of empty storage
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mstore(add(x, 0x04), _interfaceId) // Place first argument directly next to signature
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staticcall(30000, // 30k gas
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_contract, // To addr
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x, // Inputs are stored at location x
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0x8, // Inputs are 8 byes long
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x, // Store output over input (saves space)
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0x20) // Outputs are 32 bytes long
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pop // Discard call return value
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success := staticcall(
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30000, // 5k gas
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_contract, // To addr
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x, // Inputs are stored at location x
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0x8, // Inputs are 8 byes long
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x, // Store output over input (saves space)
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0x20) // Outputs are 32 bytes long
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result := mload(x) // Load the result
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}
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}
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