1 files changed, 123 insertions, 0 deletions
diff --git a/common/big.go b/common/big.go
new file mode 100644
index 000000000..750b28f85
--- /dev/null
+++ b/common/big.go
@@ -0,0 +1,123 @@
+package common
+
+import "math/big"
+
+// Big pow
+//
+// Returns the power of two big integers
+func BigPow(a, b int) *big.Int {
+	c := new(big.Int)
+	c.Exp(big.NewInt(int64(a)), big.NewInt(int64(b)), big.NewInt(0))
+
+	return c
+}
+
+// Big
+//
+// Shortcut for new(big.Int).SetString(..., 0)
+func Big(num string) *big.Int {
+	n := new(big.Int)
+	n.SetString(num, 0)
+
+	return n
+}
+
+// BigD
+//
+// Shortcut for new(big.Int).SetBytes(...)
+func Bytes2Big(data []byte) *big.Int {
+	n := new(big.Int)
+	n.SetBytes(data)
+
+	return n
+}
+func BigD(data []byte) *big.Int { return Bytes2Big(data) }
+
+func String2Big(num string) *big.Int {
+	n := new(big.Int)
+	n.SetString(num, 0)
+	return n
+}
+
+func BitTest(num *big.Int, i int) bool {
+	return num.Bit(i) > 0
+}
+
+// To256
+//
+// "cast" the big int to a 256 big int (i.e., limit to)
+var tt256 = new(big.Int).Lsh(big.NewInt(1), 256)
+var tt256m1 = new(big.Int).Sub(new(big.Int).Lsh(big.NewInt(1), 256), big.NewInt(1))
+var tt255 = new(big.Int).Lsh(big.NewInt(1), 255)
+
+func U256(x *big.Int) *big.Int {
+	//if x.Cmp(Big0) < 0 {
+	//		return new(big.Int).Add(tt256, x)
+	//	}
+
+	x.And(x, tt256m1)
+
+	return x
+}
+
+func S256(x *big.Int) *big.Int {
+	if x.Cmp(tt255) < 0 {
+		return x
+	} else {
+		// We don't want to modify x, ever
+		return new(big.Int).Sub(x, tt256)
+	}
+}
+
+func FirstBitSet(v *big.Int) int {
+	for i := 0; i < v.BitLen(); i++ {
+		if v.Bit(i) > 0 {
+			return i
+		}
+	}
+
+	return v.BitLen()
+}
+
+// Big to bytes
+//
+// Returns the bytes of a big integer with the size specified by **base**
+// Attempts to pad the byte array with zeros.
+func BigToBytes(num *big.Int, base int) []byte {
+	ret := make([]byte, base/8)
+
+	if len(num.Bytes()) > base/8 {
+		return num.Bytes()
+	}
+
+	return append(ret[:len(ret)-len(num.Bytes())], num.Bytes()...)
+}
+
+// Big copy
+//
+// Creates a copy of the given big integer
+func BigCopy(src *big.Int) *big.Int {
+	return new(big.Int).Set(src)
+}
+
+// Big max
+//
+// Returns the maximum size big integer
+func BigMax(x, y *big.Int) *big.Int {
+	if x.Cmp(y) <= 0 {
+		return y
+	}
+
+	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
+}