92 lines
3.2 KiB
Solidity
92 lines
3.2 KiB
Solidity
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// Brought from https://github.com/aragon/aragonOS/blob/v4.3.0/contracts/common/SafeERC20.sol
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// Adapted to use pragma ^0.5.8 and satisfy our linter rules
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pragma solidity ^0.5.8;
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import "./ERC20.sol";
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library SafeERC20 {
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// Before 0.5, solidity has a mismatch between `address.transfer()` and `token.transfer()`:
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// https://github.com/ethereum/solidity/issues/3544
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bytes4 private constant TRANSFER_SELECTOR = 0xa9059cbb;
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/**
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* @dev Same as a standards-compliant ERC20.transfer() that never reverts (returns false).
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* Note that this makes an external call to the token.
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*/
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function safeTransfer(ERC20 _token, address _to, uint256 _amount) internal returns (bool) {
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bytes memory transferCallData = abi.encodeWithSelector(
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TRANSFER_SELECTOR,
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_to,
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_amount
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);
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return invokeAndCheckSuccess(address(_token), transferCallData);
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}
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/**
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* @dev Same as a standards-compliant ERC20.transferFrom() that never reverts (returns false).
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* Note that this makes an external call to the token.
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*/
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function safeTransferFrom(ERC20 _token, address _from, address _to, uint256 _amount) internal returns (bool) {
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bytes memory transferFromCallData = abi.encodeWithSelector(
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_token.transferFrom.selector,
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_from,
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_to,
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_amount
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);
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return invokeAndCheckSuccess(address(_token), transferFromCallData);
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}
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/**
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* @dev Same as a standards-compliant ERC20.approve() that never reverts (returns false).
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* Note that this makes an external call to the token.
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*/
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function safeApprove(ERC20 _token, address _spender, uint256 _amount) internal returns (bool) {
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bytes memory approveCallData = abi.encodeWithSelector(
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_token.approve.selector,
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_spender,
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_amount
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);
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return invokeAndCheckSuccess(address(_token), approveCallData);
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}
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function invokeAndCheckSuccess(address _addr, bytes memory _calldata) private returns (bool) {
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bool ret;
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assembly {
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let ptr := mload(0x40) // free memory pointer
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let success := call(
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gas, // forward all gas
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_addr, // address
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0, // no value
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add(_calldata, 0x20), // calldata start
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mload(_calldata), // calldata length
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ptr, // write output over free memory
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0x20 // uint256 return
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)
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if gt(success, 0) {
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// Check number of bytes returned from last function call
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switch returndatasize
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// No bytes returned: assume success
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case 0 {
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ret := 1
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}
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// 32 bytes returned: check if non-zero
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case 0x20 {
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// Only return success if returned data was true
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// Already have output in ptr
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ret := eq(mload(ptr), 1)
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}
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// Not sure what was returned: don't mark as success
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default { }
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}
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}
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return ret;
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}
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}
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