From 5ad07e1892a08e8485d0ba6752eeb67fbd4182b2 Mon Sep 17 00:00:00 2001
From: Chen Yi-Cyuan <emn178@gmail.com>
Date: Mon, 30 Oct 2017 09:58:52 +0800
Subject: [PATCH] improve mum performance and reduce gas cost

---
 contracts/math/SafeMath.sol | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/contracts/math/SafeMath.sol b/contracts/math/SafeMath.sol
index 47b7db51b..05ad6ee17 100644
--- a/contracts/math/SafeMath.sol
+++ b/contracts/math/SafeMath.sol
@@ -7,8 +7,11 @@ pragma solidity ^0.4.11;
  */
 library SafeMath {
   function mul(uint256 a, uint256 b) internal constant returns (uint256) {
+    if (a == 0) {
+      return 0;
+    }
     uint256 c = a * b;
-    assert(a == 0 || c / a == b);
+    assert(c / a == b);
     return c;
   }