From 0a0f8c58a277a5ea1002bb2fe282d3afe7da93c4 Mon Sep 17 00:00:00 2001
From: Manuel Araoz <manuelaraoz@gmail.com>
Date: Thu, 13 Oct 2016 15:33:25 -0300
Subject: [PATCH] StandardToken first version

---
 contracts/SafeMath.sol                        | 28 +++++++++++++
 .../{BaseToken.sol => StandardToken.sol}      | 41 ++++++++++---------
 2 files changed, 49 insertions(+), 20 deletions(-)
 create mode 100644 contracts/SafeMath.sol
 rename contracts/{BaseToken.sol => StandardToken.sol} (58%)

diff --git a/contracts/SafeMath.sol b/contracts/SafeMath.sol
new file mode 100644
index 000000000..2d4bebf77
--- /dev/null
+++ b/contracts/SafeMath.sol
@@ -0,0 +1,28 @@
+pragma solidity ^0.4.0;
+
+/**
+ * Math operations with safety checks
+ */
+contract SafeMath {
+  function safeMul(uint a, uint b) internal returns (uint) {
+    uint c = a * b;
+    assert(a == 0 || c / a == b);
+    return c;
+  }
+
+  function safeSub(uint a, uint b) internal returns (uint) {
+    assert(b <= a);
+    return a - b;
+  }
+
+  function safeAdd(uint a, uint b) internal returns (uint) {
+    uint c = a + b;
+    assert(c>=a && c>=b);
+    return c;
+  }
+
+  function assert(bool assertion) internal {
+    if (!assertion) throw;
+  }
+}
+
diff --git a/contracts/BaseToken.sol b/contracts/StandardToken.sol
similarity index 58%
rename from contracts/BaseToken.sol
rename to contracts/StandardToken.sol
index c3fdc8134..3d3c3e1d0 100644
--- a/contracts/BaseToken.sol
+++ b/contracts/StandardToken.sol
@@ -1,42 +1,43 @@
 pragma solidity ^0.4.0;
 
-// Everything throws instead of returning false on failure.
 import './ERC20.sol';
+import './SafeMath.sol';
 
 /**
- * ERC 20 token
+ * ERC20 token
  *
  * https://github.com/ethereum/EIPs/issues/20
  * Based on code by FirstBlood:
  * https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
  */
-contract BaseToken is ERC20 {
+contract StandardToken is ERC20, SafeMath {
 
   mapping(address => uint256) balances;
   mapping (address => mapping (address => uint256)) allowed;
   uint256 public totalSupply;
 
-
   function transfer(address _to, uint256 _value) returns (bool success) {
-    if (balances[msg.sender] >= _value &&
-        balances[_to] + _value > balances[_to]) {
-      balances[msg.sender] -= _value;
-      balances[_to] += _value;
-      Transfer(msg.sender, _to, _value);
-      return true;
-    } else { return false; }
+    if (balances[msg.sender] < _value) {
+      throw;
+    } 
+    balances[msg.sender] = safeSub(balances[msg.sender], _value);
+    balances[_to] = safeAdd(balances[_to], _value);
+    Transfer(msg.sender, _to, _value);
+    return true;
   }
 
   function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
-    if (balances[_from] >= _value &&
-        allowed[_from][msg.sender] >= _value &&
-        balances[_to] + _value > balances[_to]) {
-      balances[_to] += _value;
-      balances[_from] -= _value;
-      allowed[_from][msg.sender] -= _value;
-      Transfer(_from, _to, _value);
-      return true;
-    } else { return false; }
+    var _allowance = allowed[_from][msg.sender];
+    if (balances[_from] < _value ||
+        _allowance < _value)) {
+      throw;
+    }
+
+    balances[_to] = safeAdd(balances[_to], _value);
+    balances[_from] = safeSub(balances[_from], _value);
+    allowed[_from][msg.sender] = safeSub(_allowance, _value);
+    Transfer(_from, _to, _value);
+    return true;
   }
 
   function balanceOf(address _owner) constant returns (uint256 balance) {