Add HashFunction interface (w/ Poseidon & Sha256)

utils.go

@@ -0,0 +1,25 @@
+package arbo
+
+import "math/big"
+
+// SwapEndianness swaps the order of the bytes in the byte slice.
+func SwapEndianness(b []byte) []byte {
+	o := make([]byte, len(b))
+	for i := range b {
+		o[len(b)-1-i] = b[i]
+	}
+	return o
+}
+
+// BigIntToBytes converts a *big.Int into a byte array in Little-Endian
+func BigIntToBytes(bi *big.Int) []byte {
+	var b [32]byte
+	copy(b[:], SwapEndianness(bi.Bytes()))
+	return b[:]
+}
+
+// BytesToBigInt converts a byte array in Little-Endian representation into
+// *big.Int
+func BytesToBigInt(b []byte) *big.Int {
+	return new(big.Int).SetBytes(SwapEndianness(b))
+}