BIP0144+wire: add a MessageEncoding variant for serialization/deserialization

This commit modifies the existing wire.Message interface to introduce a
new MessageEncoding variant which dictates the exact encoding to be
used when serializing and deserializing messages. Such an option is now
necessary due to the segwit soft-fork package, as btcd will need to be
able to optionally encode transactions/blocks without witness data to
un-upgraded peers.

Two new functions have been introduced: ReadMessageWithEncodingN and
WriteMessageWithEncodingN which wrap BtcDecode/BtcEncode with the
desired encoding format.

wire/msgping_test.go

@@ -50,6 +50,7 @@ func TestPing(t *testing.T) {
 func TestPingBIP0031(t *testing.T) {
 	// Use the protocol version just prior to BIP0031Version changes.
 	pver := BIP0031Version
+	enc := BaseEncoding
 
 	nonce, err := RandomUint64()
 	if err != nil {
@@ -72,14 +73,14 @@ func TestPingBIP0031(t *testing.T) {
 
 	// Test encode with old protocol version.
 	var buf bytes.Buffer
-	err = msg.BtcEncode(&buf, pver)
+	err = msg.BtcEncode(&buf, pver, enc)
 	if err != nil {
 		t.Errorf("encode of MsgPing failed %v err <%v>", msg, err)
 	}
 
 	// Test decode with old protocol version.
 	readmsg := NewMsgPing(0)
-	err = readmsg.BtcDecode(&buf, pver)
+	err = readmsg.BtcDecode(&buf, pver, enc)
 	if err != nil {
 		t.Errorf("decode of MsgPing failed [%v] err <%v>", buf, err)
 	}
@@ -106,14 +107,14 @@ func TestPingCrossProtocol(t *testing.T) {
 
 	// Encode with latest protocol version.
 	var buf bytes.Buffer
-	err = msg.BtcEncode(&buf, ProtocolVersion)
+	err = msg.BtcEncode(&buf, ProtocolVersion, BaseEncoding)
 	if err != nil {
 		t.Errorf("encode of MsgPing failed %v err <%v>", msg, err)
 	}
 
 	// Decode with old protocol version.
 	readmsg := NewMsgPing(0)
-	err = readmsg.BtcDecode(&buf, BIP0031Version)
+	err = readmsg.BtcDecode(&buf, BIP0031Version, BaseEncoding)
 	if err != nil {
 		t.Errorf("decode of MsgPing failed [%v] err <%v>", buf, err)
 	}
@@ -129,10 +130,11 @@ func TestPingCrossProtocol(t *testing.T) {
 // versions.
 func TestPingWire(t *testing.T) {
 	tests := []struct {
-		in   MsgPing // Message to encode
-		out  MsgPing // Expected decoded message
-		buf  []byte  // Wire encoding
-		pver uint32  // Protocol version for wire encoding
+		in   MsgPing         // Message to encode
+		out  MsgPing         // Expected decoded message
+		buf  []byte          // Wire encoding
+		pver uint32          // Protocol version for wire encoding
+		enc  MessageEncoding // Message encoding format
 	}{
 		// Latest protocol version.
 		{
@@ -140,6 +142,7 @@ func TestPingWire(t *testing.T) {
 			MsgPing{Nonce: 123123}, // 0x1e0f3
 			[]byte{0xf3, 0xe0, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00},
 			ProtocolVersion,
+			BaseEncoding,
 		},
 
 		// Protocol version BIP0031Version+1
@@ -148,6 +151,7 @@ func TestPingWire(t *testing.T) {
 			MsgPing{Nonce: 456456}, // 0x6f708
 			[]byte{0x08, 0xf7, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00},
 			BIP0031Version + 1,
+			BaseEncoding,
 		},
 
 		// Protocol version BIP0031Version
@@ -156,6 +160,7 @@ func TestPingWire(t *testing.T) {
 			MsgPing{Nonce: 0},      // No nonce for pver
 			[]byte{},               // No nonce for pver
 			BIP0031Version,
+			BaseEncoding,
 		},
 	}
 
@@ -163,7 +168,7 @@ func TestPingWire(t *testing.T) {
 	for i, test := range tests {
 		// Encode the message to wire format.
 		var buf bytes.Buffer
-		err := test.in.BtcEncode(&buf, test.pver)
+		err := test.in.BtcEncode(&buf, test.pver, test.enc)
 		if err != nil {
 			t.Errorf("BtcEncode #%d error %v", i, err)
 			continue
@@ -177,7 +182,7 @@ func TestPingWire(t *testing.T) {
 		// Decode the message from wire format.
 		var msg MsgPing
 		rbuf := bytes.NewReader(test.buf)
-		err = msg.BtcDecode(rbuf, test.pver)
+		err = msg.BtcDecode(rbuf, test.pver, test.enc)
 		if err != nil {
 			t.Errorf("BtcDecode #%d error %v", i, err)
 			continue
@@ -196,18 +201,20 @@ func TestPingWireErrors(t *testing.T) {
 	pver := ProtocolVersion
 
 	tests := []struct {
-		in       *MsgPing // Value to encode
-		buf      []byte   // Wire encoding
-		pver     uint32   // Protocol version for wire encoding
-		max      int      // Max size of fixed buffer to induce errors
-		writeErr error    // Expected write error
-		readErr  error    // Expected read error
+		in       *MsgPing        // Value to encode
+		buf      []byte          // Wire encoding
+		pver     uint32          // Protocol version for wire encoding
+		enc      MessageEncoding // Message encoding format
+		max      int             // Max size of fixed buffer to induce errors
+		writeErr error           // Expected write error
+		readErr  error           // Expected read error
 	}{
 		// Latest protocol version with intentional read/write errors.
 		{
 			&MsgPing{Nonce: 123123}, // 0x1e0f3
 			[]byte{0xf3, 0xe0, 0x01, 0x00},
 			pver,
+			BaseEncoding,
 			2,
 			io.ErrShortWrite,
 			io.ErrUnexpectedEOF,
@@ -218,7 +225,7 @@ func TestPingWireErrors(t *testing.T) {
 	for i, test := range tests {
 		// Encode to wire format.
 		w := newFixedWriter(test.max)
-		err := test.in.BtcEncode(w, test.pver)
+		err := test.in.BtcEncode(w, test.pver, test.enc)
 		if err != test.writeErr {
 			t.Errorf("BtcEncode #%d wrong error got: %v, want: %v",
 				i, err, test.writeErr)
@@ -228,7 +235,7 @@ func TestPingWireErrors(t *testing.T) {
 		// Decode from wire format.
 		var msg MsgPing
 		r := newFixedReader(test.max, test.buf)
-		err = msg.BtcDecode(r, test.pver)
+		err = msg.BtcDecode(r, test.pver, test.enc)
 		if err != test.readErr {
 			t.Errorf("BtcDecode #%d wrong error got: %v, want: %v",
 				i, err, test.readErr)