ERC20Lib.sol

import "../SafeMathLib.sol";

library ERC20Lib {
  using SafeMathLib for uint;

  struct TokenStorage {
    mapping (address => uint) balances;
    mapping (address => mapping (address => uint)) allowed;
    uint totalSupply;
  }

  event Transfer(address indexed from, address indexed to, uint value);
  event Approval(address indexed owner, address indexed spender, uint value);
  
  function init(TokenStorage storage self, uint _initial_supply) {
    self.totalSupply = _initial_supply;
    self.balances[msg.sender] = _initial_supply;
  }
  
  function transfer(TokenStorage storage self, address _to, uint _value) returns (bool success) {
    self.balances[msg.sender] = self.balances[msg.sender].minus(_value);
    self.balances[_to] = self.balances[_to].plus(_value);
    Transfer(msg.sender, _to, _value);
    return true;
  }

  function transferFrom(TokenStorage storage self, address _from, address _to, uint _value) returns (bool success) {
    var _allowance = self.allowed[_from][msg.sender];

    self.balances[_to] = self.balances[_to].plus(_value);
    self.balances[_from] = self.balances[_from].minus(_value);
    self.allowed[_from][msg.sender] = _allowance.minus(_value);
    Transfer(_from, _to, _value);
    return true;
  }

  function balanceOf(TokenStorage storage self, address _owner) constant returns (uint balance) {
    return self.balances[_owner];
  }

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

  function allowance(TokenStorage storage self, address _owner, address _spender) constant returns (uint remaining) {
    return self.allowed[_owner][_spender];
  }
}