path: root/std/StandardToken.sol

pragma solidity >0.4.21;

import "./Token.sol";

contract StandardToken is Token {
    uint256 supply;
    mapping (address => uint256) balance;
    mapping (address =>
        mapping (address => uint256)) m_allowance;

    constructor(address _initialOwner, uint256 _supply) public {
        supply = _supply;
        balance[_initialOwner] = _supply;
    }

    function balanceOf(address _account) constant public returns (uint) {
        return balance[_account];
    }

    function totalSupply() constant public returns (uint) {
        return supply;
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        return doTransfer(msg.sender, _to, _value);
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        if (m_allowance[_from][msg.sender] >= _value) {
            if (doTransfer(_from, _to, _value)) {
                m_allowance[_from][msg.sender] -= _value;
            }
            return true;
        } else {
            return false;
        }
    }

    function doTransfer(address _from, address _to, uint _value) internal returns (bool success) {
        if (balance[_from] >= _value && balance[_to] + _value >= balance[_to]) {
            balance[_from] -= _value;
            balance[_to] += _value;
            emit Transfer(_from, _to, _value);
            return true;
        } else {
            return false;
        }
    }

    function approve(address _spender, uint256 _value) public returns (bool success) {
        m_allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) constant public returns (uint256) {
        return m_allowance[_owner][_spender];
    }
}