From 20ee1ae65e57ef7d60404277162c84c572c6bb10 Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Mon, 21 Jul 2014 20:38:43 +0200
Subject: [PATCH] Refactored CALLDATALOAD to use big int

* Added BigMin
---
 ethchain/vm.go    | 14 +++++++++-----
 ethutil/big.go    | 19 +++++++++++--------
 ethutil/common.go | 12 +++++++-----
 3 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/ethchain/vm.go b/ethchain/vm.go
index 34ecd95b71..a9bed1eca9 100644
--- a/ethchain/vm.go
+++ b/ethchain/vm.go
@@ -503,13 +503,17 @@ func (vm *Vm) RunClosure(closure *Closure) (ret []byte, err error) {
 			vm.Printf(" => %v", vm.vars.Value)
 		case CALLDATALOAD:
 			require(1)
-			offset := stack.Pop().Int64()
+			var (
+				offset  = stack.Pop()
+				data    = make([]byte, 32)
+				lenData = big.NewInt(int64(len(closure.Args)))
+			)
 
-			data := make([]byte, 32)
-			if big.NewInt(int64(len(closure.Args))).Cmp(big.NewInt(offset)) >= 0 {
-				l := int64(math.Min(float64(offset+32), float64(len(closure.Args))))
+			if lenData.Cmp(offset) >= 0 {
+				length := new(big.Int).Add(offset, ethutil.Big32)
+				length = ethutil.BigMin(length, lenData)
 
-				copy(data, closure.Args[offset:l])
+				copy(data, closure.Args[offset.Int64():length.Int64()])
 			}
 
 			vm.Printf(" => 0x%x", data)
diff --git a/ethutil/big.go b/ethutil/big.go
index 7af6f74145..ec263b8188 100644
--- a/ethutil/big.go
+++ b/ethutil/big.go
@@ -4,14 +4,6 @@ import (
 	"math/big"
 )
 
-var BigInt0 *big.Int = big.NewInt(0)
-
-// True
-var BigTrue *big.Int = big.NewInt(1)
-
-// False
-var BigFalse *big.Int = big.NewInt(0)
-
 // Big pow
 //
 // Returns the power of two big integers
@@ -73,3 +65,14 @@ func BigMax(x, y *big.Int) *big.Int {
 
 	return x
 }
+
+// Big min
+//
+// Returns the minimum size big integer
+func BigMin(x, y *big.Int) *big.Int {
+	if x.Cmp(y) >= 0 {
+		return y
+	}
+
+	return x
+}
diff --git a/ethutil/common.go b/ethutil/common.go
index 2fd031a20a..cbd94e7add 100644
--- a/ethutil/common.go
+++ b/ethutil/common.go
@@ -58,9 +58,11 @@ func CurrencyToString(num *big.Int) string {
 
 // Common big integers often used
 var (
-	Big1   = big.NewInt(1)
-	Big2   = big.NewInt(2)
-	Big0   = big.NewInt(0)
-	Big32  = big.NewInt(32)
-	Big256 = big.NewInt(0xff)
+	Big1     = big.NewInt(1)
+	Big2     = big.NewInt(2)
+	Big0     = big.NewInt(0)
+	BigTrue  = Big1
+	BigFalse = Big0
+	Big32    = big.NewInt(32)
+	Big256   = big.NewInt(0xff)
 )