wire: add TxWitness JSON (Un)marshal

wire/msgtx.go

@@ -6,6 +6,8 @@ package wire
 
 import (
 	"bytes"
+	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -309,6 +311,36 @@ func (t TxWitness) SerializeSize() int {
 	return n
 }
 
+// MarshalJSON serialises the structure as a JSON appropriate value.
+//
+// NOTE: The 2D byte array is encoded as an array of hex strings.
+func (t TxWitness) MarshalJSON() ([]byte, error) {
+	var hexStrings []string
+	for _, b := range t {
+		hexStrings = append(hexStrings, hex.EncodeToString(b))
+	}
+	return json.Marshal(hexStrings)
+}
+
+// UnmarshalJSON parses a JSON value as a TxWitness.
+func (t *TxWitness) UnmarshalJSON(data []byte) error {
+	var hexStrings []string
+	if err := json.Unmarshal(data, &hexStrings); err != nil {
+		return err
+	}
+
+	*t = make([][]byte, len(hexStrings))
+	for i, hexString := range hexStrings {
+		decoded, err := hex.DecodeString(hexString)
+		if err != nil {
+			return err
+		}
+		(*t)[i] = decoded
+	}
+
+	return nil
+}
+
 // TxOut defines a bitcoin transaction output.
 type TxOut struct {
 	Value    int64