Move constants and utils to package, apply small fixes

babyjub/helpers.go

@@ -1,40 +1,9 @@
 package babyjub
 
 import (
-	"bytes"
-	"encoding/hex"
-	"fmt"
-	"math/big"
-	"strings"
-
 	"github.com/dchest/blake512" // I have personally reviewed that this module doesn't do anything suspicious
 )
 
-// SwapEndianness swaps the endianness of the value encoded in xs.  If xs is
-// Big-Endian, the result will be Little-Endian and viceversa.
-func SwapEndianness(xs []byte) []byte {
-	ys := make([]byte, len(xs))
-	for i, b := range xs {
-		ys[len(xs)-1-i] = b
-	}
-	return ys
-}
-
-// BigIntLEBytes encodes a big.Int into an array in Little-Endian.
-func BigIntLEBytes(v *big.Int) [32]byte {
-	le := SwapEndianness(v.Bytes())
-	res := [32]byte{}
-	copy(res[:], le)
-	return res
-}
-
-// SetBigIntFromLEBytes sets the value of a big.Int from a Little-Endian
-// encoded value.
-func SetBigIntFromLEBytes(v *big.Int, leBuf []byte) *big.Int {
-	beBuf := SwapEndianness(leBuf)
-	return v.SetBytes(beBuf)
-}
-
 // Blake512 performs the blake-512 hash over the buffer m.  Note that this is
 // the original blake from the SHA3 competition and not the new blake2 version.
 func Blake512(m []byte) []byte {
@@ -42,47 +11,3 @@ func Blake512(m []byte) []byte {
 	h.Write(m[:])
 	return h.Sum(nil)
 }
-
-// Hex is a byte slice type that can be marshalled and unmarshaled in hex
-type Hex []byte
-
-// MarshalText encodes buf as hex
-func (buf Hex) MarshalText() ([]byte, error) {
-	return []byte(hex.EncodeToString(buf)), nil
-}
-
-// String encodes buf as hex
-func (buf Hex) String() string {
-	return hex.EncodeToString(buf)
-}
-
-// HexEncode encodes an array of bytes into a string in hex.
-func HexEncode(bs []byte) string {
-	return fmt.Sprintf("0x%s", hex.EncodeToString(bs))
-}
-
-// HexDecode decodes a hex string into an array of bytes.
-func HexDecode(h string) ([]byte, error) {
-	if strings.HasPrefix(h, "0x") {
-		h = h[2:]
-	}
-	return hex.DecodeString(h)
-}
-
-// HexDecodeInto decodes a hex string into an array of bytes (dst), verifying
-// that the decoded array has the same length as dst.
-func HexDecodeInto(dst []byte, h []byte) error {
-	if bytes.HasPrefix(h, []byte("0x")) {
-		h = h[2:]
-	}
-	if len(h)/2 != len(dst) {
-		return fmt.Errorf("expected %v bytes in hex string, got %v", len(dst), len(h)/2)
-	}
-	n, err := hex.Decode(dst, h)
-	if err != nil {
-		return err
-	} else if n != len(dst) {
-		return fmt.Errorf("expected %v bytes when decoding hex string, got %v", len(dst), n)
-	}
-	return nil
-}