github.com/0xPolygon/supernets2-node@v0.0.0-20230711153321-2fe574524eaa/test/contracts/uniswap/v2/UniswapV2ERC20.sol (about)

     1  pragma solidity =0.5.16;
     2  
     3  import './IUniswapV2ERC20.sol';
     4  import './SafeMath.sol';
     5  
     6  contract UniswapV2ERC20 is IUniswapV2ERC20 {
     7      using SafeMath for uint;
     8  
     9      string public constant name = 'Uniswap V2';
    10      string public constant symbol = 'UNI-V2';
    11      uint8 public constant decimals = 18;
    12      uint  public totalSupply;
    13      mapping(address => uint) public balanceOf;
    14      mapping(address => mapping(address => uint)) public allowance;
    15  
    16      bytes32 public DOMAIN_SEPARATOR;
    17      // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    18      bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    19      mapping(address => uint) public nonces;
    20  
    21      event Approval(address indexed owner, address indexed spender, uint value);
    22      event Transfer(address indexed from, address indexed to, uint value);
    23  
    24      constructor() public {
    25          uint chainId;
    26          assembly {
    27              chainId := chainid
    28          }
    29          DOMAIN_SEPARATOR = keccak256(
    30              abi.encode(
    31                  keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'),
    32                  keccak256(bytes(name)),
    33                  keccak256(bytes('1')),
    34                  chainId,
    35                  address(this)
    36              )
    37          );
    38      }
    39  
    40      function _mint(address to, uint value) internal {
    41          totalSupply = totalSupply.add(value);
    42          balanceOf[to] = balanceOf[to].add(value);
    43          emit Transfer(address(0), to, value);
    44      }
    45  
    46      function _burn(address from, uint value) internal {
    47          balanceOf[from] = balanceOf[from].sub(value);
    48          totalSupply = totalSupply.sub(value);
    49          emit Transfer(from, address(0), value);
    50      }
    51  
    52      function _approve(address owner, address spender, uint value) private {
    53          allowance[owner][spender] = value;
    54          emit Approval(owner, spender, value);
    55      }
    56  
    57      function _transfer(address from, address to, uint value) private {
    58          balanceOf[from] = balanceOf[from].sub(value);
    59          balanceOf[to] = balanceOf[to].add(value);
    60          emit Transfer(from, to, value);
    61      }
    62  
    63      function approve(address spender, uint value) external returns (bool) {
    64          _approve(msg.sender, spender, value);
    65          return true;
    66      }
    67  
    68      function transfer(address to, uint value) external returns (bool) {
    69          _transfer(msg.sender, to, value);
    70          return true;
    71      }
    72  
    73      function transferFrom(address from, address to, uint value) external returns (bool) {
    74          if (allowance[from][msg.sender] != uint(-1)) {
    75              allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
    76          }
    77          _transfer(from, to, value);
    78          return true;
    79      }
    80  
    81      function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
    82          require(deadline >= block.timestamp, 'UniswapV2: EXPIRED');
    83          bytes32 digest = keccak256(
    84              abi.encodePacked(
    85                  '\x19\x01',
    86                  DOMAIN_SEPARATOR,
    87                  keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonces[owner]++, deadline))
    88              )
    89          );
    90          address recoveredAddress = ecrecover(digest, v, r, s);
    91          require(recoveredAddress != address(0) && recoveredAddress == owner, 'UniswapV2: INVALID_SIGNATURE');
    92          _approve(owner, spender, value);
    93      }
    94  }