1 files changed, 61 insertions, 19 deletions

diff --git a/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol b/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
index 0e5b87aa4..6497d3c7a 100644
--- a/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
+++ b/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
@@ -1,45 +1,90 @@
-pragma solidity ^0.4.18;
+/*
 
-import { Token } from "../Token/Token.sol";
+  Copyright 2018 ZeroEx Intl.
 
-contract ERC20Token is Token {
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
 
-    function transfer(address _to, uint _value)
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
+
+import "./IERC20Token.sol";
+
+contract ERC20Token is IERC20Token {
+
+    string constant INSUFFICIENT_BALANCE = "Insufficient balance to complete transfer.";
+    string constant INSUFFICIENT_ALLOWANCE = "Insufficient allowance to complete transfer.";
+    string constant OVERFLOW = "Transfer would result in an overflow.";
+
+    mapping (address => uint256) balances;
+    mapping (address => mapping (address => uint256)) allowed;
+
+    uint256 public totalSupply;
+
+    function transfer(address _to, uint256 _value)
         public
         returns (bool)
     {
-        require(balances[msg.sender] >= _value && balances[_to] + _value >= balances[_to]);
+        require(
+            balances[msg.sender] >= _value,
+            INSUFFICIENT_BALANCE
+        );
+        require(
+            balances[_to] + _value >= balances[_to],
+            OVERFLOW
+        );
         balances[msg.sender] -= _value;
         balances[_to] += _value;
-        Transfer(msg.sender, _to, _value);
+        emit Transfer(msg.sender, _to, _value);
         return true;
     }
 
-    function transferFrom(address _from, address _to, uint _value)
+    function transferFrom(address _from, address _to, uint256 _value)
         public
         returns (bool)
     {
-        require(balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to] + _value >= balances[_to]);
+        require(
+            balances[_from] >= _value,
+            INSUFFICIENT_BALANCE
+        );
+        require(
+            allowed[_from][msg.sender] >= _value,
+            INSUFFICIENT_ALLOWANCE
+        );
+        require(
+            balances[_to] + _value >= balances[_to],
+            OVERFLOW
+        );
         balances[_to] += _value;
         balances[_from] -= _value;
         allowed[_from][msg.sender] -= _value;
-        Transfer(_from, _to, _value);
+        emit Transfer(_from, _to, _value);
         return true;
     }
 
-    function approve(address _spender, uint _value)
+    function approve(address _spender, uint256 _value)
         public
         returns (bool)
     {
         allowed[msg.sender][_spender] = _value;
-        Approval(msg.sender, _spender, _value);
+        emit Approval(msg.sender, _spender, _value);
         return true;
     }
 
     function balanceOf(address _owner)
-        public
-        view
-        returns (uint)
+        public view
+        returns (uint256)
     {
         return balances[_owner];
     }
@@ -47,12 +92,9 @@ contract ERC20Token is Token {
     function allowance(address _owner, address _spender)
         public
         view
-        returns (uint)
+        returns (uint256)
     {
         return allowed[_owner][_spender];
     }
-
-    mapping (address => uint) balances;
-    mapping (address => mapping (address => uint)) allowed;
-    uint public totalSupply;
 }
+