github.com/klaytn/klaytn@v1.12.1/contracts/feepayer/fee_payer_test.sol (about)

     1  // Copyright 2019 The klaytn Authors
     2  // This file is part of the klaytn library.
     3  //
     4  // The klaytn library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The klaytn library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the klaytn library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  pragma solidity >0.8.0;
    18  
    19  contract FeePayer {
    20      function GetFeePayerDirect() public returns (address) {
    21          assembly {
    22              if iszero(call(gas(), 0x0a, 0, 0, 0, 12, 20)) {
    23                invalid()
    24              }
    25              return(0, 32)
    26          }
    27      }
    28  
    29      function feePayer() internal returns (address addr) {
    30          assembly {
    31              let freemem := mload(0x40)
    32              let start_addr := add(freemem, 12)
    33              if iszero(call(gas(), 0x0a, 0, 0, 0, start_addr, 20)) {
    34                invalid()
    35              }
    36              addr := mload(freemem)
    37          }
    38      }
    39  
    40      function GetFeePayer() public returns (address) {
    41          return feePayer();
    42      }
    43  }