rtmp: split MessageWriter into single handlers per chunk stream

internal/rtmp/base/messagewriter.go

@@ -4,62 +4,46 @@ import (
 	"io"
 )
 
-// MessageWriter is a message writer.
-type MessageWriter struct {
-	w                                   io.Writer
-	chunkMaxBodyLen                     int
-	lastMessageStreamIDPerChunkStreamID map[byte]uint32
+type messageWriterChunkStream struct {
+	mw                  *MessageWriter
+	lastMessageStreamID *uint32
 }
 
-// NewMessageWriter instantiates a MessageWriter.
-func NewMessageWriter(w io.Writer) *MessageWriter {
-	return &MessageWriter{
-		w:                                   w,
-		chunkMaxBodyLen:                     128,
-		lastMessageStreamIDPerChunkStreamID: make(map[byte]uint32),
-	}
-}
-
-// SetChunkSize sets the chunk size.
-func (mw *MessageWriter) SetChunkSize(v int) {
-	mw.chunkMaxBodyLen = v
-}
-
-// Write writes a Message.
-func (mw *MessageWriter) Write(msg *Message) error {
+func (wc *messageWriterChunkStream) write(msg *Message) error {
 	bodyLen := len(msg.Body)
 	pos := 0
-	first := true
+	firstChunk := true
 
 	for {
 		chunkBodyLen := bodyLen - pos
-		if chunkBodyLen > mw.chunkMaxBodyLen {
-			chunkBodyLen = mw.chunkMaxBodyLen
+		if chunkBodyLen > wc.mw.chunkSize {
+			chunkBodyLen = wc.mw.chunkSize
 		}
 
-		if first {
-			first = false
+		if firstChunk {
+			firstChunk = false
 
-			if v, ok := mw.lastMessageStreamIDPerChunkStreamID[msg.ChunkStreamID]; !ok || v != msg.MessageStreamID {
+			if wc.lastMessageStreamID == nil || *wc.lastMessageStreamID != msg.MessageStreamID {
 				err := Chunk0{
 					ChunkStreamID:   msg.ChunkStreamID,
 					Type:            msg.Type,
 					MessageStreamID: msg.MessageStreamID,
 					BodyLen:         uint32(bodyLen),
 					Body:            msg.Body[pos : pos+chunkBodyLen],
-				}.Write(mw.w)
+				}.Write(wc.mw.w)
 				if err != nil {
 					return err
 				}
 
-				mw.lastMessageStreamIDPerChunkStreamID[msg.ChunkStreamID] = msg.MessageStreamID
+				v := msg.MessageStreamID
+				wc.lastMessageStreamID = &v
 			} else {
 				err := Chunk1{
 					ChunkStreamID: msg.ChunkStreamID,
 					Type:          msg.Type,
 					BodyLen:       uint32(bodyLen),
 					Body:          msg.Body[pos : pos+chunkBodyLen],
-				}.Write(mw.w)
+				}.Write(wc.mw.w)
 				if err != nil {
 					return err
 				}
@@ -68,7 +52,7 @@ func (mw *MessageWriter) Write(msg *Message) error {
 			err := Chunk3{
 				ChunkStreamID: msg.ChunkStreamID,
 				Body:          msg.Body[pos : pos+chunkBodyLen],
-			}.Write(mw.w)
+			}.Write(wc.mw.w)
 			if err != nil {
 				return err
 			}
@@ -81,3 +65,35 @@ func (mw *MessageWriter) Write(msg *Message) error {
 		}
 	}
 }
+
+// MessageWriter is a message writer.
+type MessageWriter struct {
+	w            io.Writer
+	chunkSize    int
+	chunkStreams map[byte]*messageWriterChunkStream
+}
+
+// NewMessageWriter instantiates a MessageWriter.
+func NewMessageWriter(w io.Writer) *MessageWriter {
+	return &MessageWriter{
+		w:            w,
+		chunkSize:    128,
+		chunkStreams: make(map[byte]*messageWriterChunkStream),
+	}
+}
+
+// SetChunkSize sets the maximum chunk size.
+func (mw *MessageWriter) SetChunkSize(v int) {
+	mw.chunkSize = v
+}
+
+// Write writes a Message.
+func (mw *MessageWriter) Write(msg *Message) error {
+	cs, ok := mw.chunkStreams[msg.ChunkStreamID]
+	if !ok {
+		cs = &messageWriterChunkStream{mw: mw}
+		mw.chunkStreams[msg.ChunkStreamID] = cs
+	}
+
+	return cs.write(msg)
+}