packages/contracts/contracts/tokens/ERC20Token.sol


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51

pragma solidity 0.4.11;

import "./../base/Token.sol";

contract ERC20Token is Token {

    uint constant MAX_UINT = 2**256 - 1;

    function transfer(address _to, uint _value) returns (bool) {
        require(balances[msg.sender] >= _value && balances[_to] + _value >= balances[_to]); 
        balances[msg.sender] -= _value;
        balances[_to] += _value;
        Transfer(msg.sender, _to, _value);
        return true;
    }

    /// @dev ERC20 transferFrom, modified such that an allowance of MAX_UINT represents an unlimited allowance. See https://github.com/ethereum/EIPs/issues/717
    /// @param _from Address to transfer from.
    /// @param _to Address to transfer to.
    /// @param _value Amount to transfer.
    /// @return Success of transfer.
    function transferFrom(address _from, address _to, uint _value) returns (bool) {
        uint allowance = allowed[_from][msg.sender];
        require(balances[_from] >= _value && allowance >= _value && balances[_to] + _value >= balances[_to]); 
        balances[_to] += _value;
        balances[_from] -= _value;
        if (allowance < MAX_UINT) {
            allowed[_from][msg.sender] -= _value;
        }
        Transfer(_from, _to, _value);
        return true;
    }

    function balanceOf(address _owner) constant returns (uint) {
        return balances[_owner];
    }

    function approve(address _spender, uint _value) returns (bool) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) constant returns (uint) {
        return allowed[_owner][_spender];
    }

    mapping (address => uint) balances;
    mapping (address => mapping (address => uint)) allowed;
    uint public totalSupply;
}