add travis, add go.mod go.sum, update babyjub hex encoders to avoid

importing go-iden3

babyjub/helpers.go

@@ -1,8 +1,13 @@
 package babyjub
 
 import (
-	"github.com/dchest/blake512" // I have personally reviewed that this module doesn't do anything suspicious
+	"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
@@ -37,3 +42,47 @@ 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
+}