From 0b50802d52cdb7e5560ea6ff3a453b7378e3d5f7 Mon Sep 17 00:00:00 2001
From: Dave Collins <davec@conformal.com>
Date: Tue, 29 Aug 2017 20:40:19 -0500
Subject: [PATCH] btcjson/rpcserver: Encode witness stack as slice.

The modifies the encoding of witness stacks in JSON responses to use a
slice of strings instead of a single space-separated string for
compatibility with Core.
---
 btcjson/chainsvrresults.go | 14 +++++++-------
 rpcserver.go               | 39 +++++++++++++++++++-------------------
 2 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/btcjson/chainsvrresults.go b/btcjson/chainsvrresults.go
index 9af1d3994..33d54d385 100644
--- a/btcjson/chainsvrresults.go
+++ b/btcjson/chainsvrresults.go
@@ -317,7 +317,7 @@ type Vin struct {
 	Vout      uint32     `json:"vout"`
 	ScriptSig *ScriptSig `json:"scriptSig"`
 	Sequence  uint32     `json:"sequence"`
-	Witness   string     `json:"txinwitness"`
+	Witness   []string   `json:"txinwitness"`
 }
 
 // IsCoinBase returns a bool to show if a Vin is a Coinbase one or not.
@@ -335,9 +335,9 @@ func (v *Vin) HasWitness() bool {
 func (v *Vin) MarshalJSON() ([]byte, error) {
 	if v.IsCoinBase() {
 		coinbaseStruct := struct {
-			Coinbase string `json:"coinbase"`
-			Sequence uint32 `json:"sequence"`
-			Witness  string `json:"witness,omitempty"`
+			Coinbase string   `json:"coinbase"`
+			Sequence uint32   `json:"sequence"`
+			Witness  []string `json:"witness,omitempty"`
 		}{
 			Coinbase: v.Coinbase,
 			Sequence: v.Sequence,
@@ -351,7 +351,7 @@ func (v *Vin) MarshalJSON() ([]byte, error) {
 			Txid      string     `json:"txid"`
 			Vout      uint32     `json:"vout"`
 			ScriptSig *ScriptSig `json:"scriptSig"`
-			Witness   string     `json:"txinwitness"`
+			Witness   []string   `json:"txinwitness"`
 			Sequence  uint32     `json:"sequence"`
 		}{
 			Txid:      v.Txid,
@@ -389,7 +389,7 @@ type VinPrevOut struct {
 	Txid      string     `json:"txid"`
 	Vout      uint32     `json:"vout"`
 	ScriptSig *ScriptSig `json:"scriptSig"`
-	Witness   string     `json:"txinwitness"`
+	Witness   []string   `json:"txinwitness"`
 	PrevOut   *PrevOut   `json:"prevOut"`
 	Sequence  uint32     `json:"sequence"`
 }
@@ -423,7 +423,7 @@ func (v *VinPrevOut) MarshalJSON() ([]byte, error) {
 			Txid      string     `json:"txid"`
 			Vout      uint32     `json:"vout"`
 			ScriptSig *ScriptSig `json:"scriptSig"`
-			Witness   string     `json:"txinwitness"`
+			Witness   []string   `json:"txinwitness"`
 			PrevOut   *PrevOut   `json:"prevOut,omitempty"`
 			Sequence  uint32     `json:"sequence"`
 		}{
diff --git a/rpcserver.go b/rpcserver.go
index 602e793b9..db4dece8a 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -629,6 +629,23 @@ func handleDebugLevel(s *rpcServer, cmd interface{}, closeChan <-chan struct{})
 	return "Done.", nil
 }
 
+// witnessToHex formats the passed witness stack as a slice of hex-encoded
+// strings to be used in a JSON response.
+func witnessToHex(witness wire.TxWitness) []string {
+	// Ensure nil is returned when there are no entries versus an empty
+	// slice so it can properly be omitted as necessary.
+	if len(witness) == 0 {
+		return nil
+	}
+
+	result := make([]string, 0, len(witness))
+	for _, wit := range witness {
+		result = append(result, hex.EncodeToString(wit))
+	}
+
+	return result
+}
+
 // createVinList returns a slice of JSON objects for the inputs of the passed
 // transaction.
 func createVinList(mtx *wire.MsgTx) []btcjson.Vin {
@@ -638,7 +655,7 @@ func createVinList(mtx *wire.MsgTx) []btcjson.Vin {
 		txIn := mtx.TxIn[0]
 		vinList[0].Coinbase = hex.EncodeToString(txIn.SignatureScript)
 		vinList[0].Sequence = txIn.Sequence
-		vinList[0].Witness = witnessToSring(txIn.Witness)
+		vinList[0].Witness = witnessToHex(txIn.Witness)
 		return vinList
 	}
 
@@ -658,29 +675,13 @@ func createVinList(mtx *wire.MsgTx) []btcjson.Vin {
 		}
 
 		if mtx.HasWitness() {
-			vinEntry.Witness = witnessToSring(txIn.Witness)
+			vinEntry.Witness = witnessToHex(txIn.Witness)
 		}
 	}
 
 	return vinList
 }
 
-// witnessToSring formats the passed witness stack as a string to be used
-// within a JSON response. The witness is encoded as a single string with
-// spaces separating each witness element.
-func witnessToSring(witness wire.TxWitness) string {
-	var b bytes.Buffer
-	for i, wit := range witness {
-		if i > 0 {
-			b.WriteString(" ")
-		}
-
-		b.WriteString(hex.EncodeToString(wit))
-	}
-
-	return b.String()
-}
-
 // createVoutList returns a slice of JSON objects for the outputs of the passed
 // transaction.
 func createVoutList(mtx *wire.MsgTx, chainParams *chaincfg.Params, filterAddrMap map[string]struct{}) []btcjson.Vout {
@@ -2852,7 +2853,7 @@ func createVinListPrevOut(s *rpcServer, mtx *wire.MsgTx, chainParams *chaincfg.P
 		}
 
 		if len(txIn.Witness) != 0 {
-			vinEntry.Witness = witnessToSring(txIn.Witness)
+			vinEntry.Witness = witnessToHex(txIn.Witness)
 		}
 
 		// Add the entry to the list now if it already passed the filter