Refactored CALLDATALOAD to use big int

* Added BigMin

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)

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
+}

ethutil/common.go

@@ -61,6 +61,8 @@ var (
 	Big1     = big.NewInt(1)
 	Big2     = big.NewInt(2)
 	Big0     = big.NewInt(0)
+	BigTrue  = Big1
+	BigFalse = Big0
 	Big32    = big.NewInt(32)
 	Big256   = big.NewInt(0xff)
 )