av/stream/flac: working on cleaning up decode code

stream/flac/decode.go

@@ -90,7 +90,8 @@ func (ws *writeSeeker) Seek(offset int64, whence int) (int64, error) {
 // Decode takes buf, a slice of FLAC, and decodes to WAV. If complete decoding
 // fails, an error is returned.
 func Decode(buf []byte) ([]byte, error) {
-	// Lex and decode the FLAC into a stream to hold audio and properties.
+
+	// Lex the FLAC into a stream to hold audio and it's properties.
 	r := bytes.NewReader(buf)
 	stream, err := flac.Parse(r)
 	if err != nil {
@@ -99,17 +100,30 @@ func Decode(buf []byte) ([]byte, error) {
 
 	// Create WAV encoder and pass writeSeeker that will store output WAV.
 	ws := &writeSeeker{}
-	enc := wav.NewEncoder(ws, int(stream.Info.SampleRate), int(stream.Info.BitsPerSample), int(stream.Info.NChannels), wavFormat)
+	sr := int(stream.Info.SampleRate)
+	bps := int(stream.Info.BitsPerSample)
+	nc := int(stream.Info.NChannels)
+	enc := wav.NewEncoder(ws, sr, bps, nc, wavFormat)
 	defer enc.Close()
 
+	// Decode FLAC into frames of samples
+	intBuf := &audio.IntBuffer{
+		Format:         &audio.Format{NumChannels: nc, SampleRate: sr},
+		SourceBitDepth: bps,
+	}
+	return decodeFrames(stream, intBuf, enc, ws)
+}
+
+//
+func decodeFrames(s *flac.Stream, intBuf *audio.IntBuffer, e *wav.Encoder, ws *writeSeeker) ([]byte, error) {
 	var data []int
 	for {
-		// Decode FLAC audio samples.
-		frame, err := stream.ParseNext()
-		if err != nil {
+		frame, err := s.ParseNext()
+
+		// If we've reached the end of the stream then we can output the writeSeeker's buffer.
 		if err == io.EOF {
-				break
-			}
+			return ws.Bytes(), nil
+		} else if err != nil {
 			return nil, err
 		}
 
@@ -120,18 +134,9 @@ func Decode(buf []byte) ([]byte, error) {
 				data = append(data, int(subframe.Samples[i]))
 			}
 		}
-		buf := &audio.IntBuffer{
-			Format: &audio.Format{
-				NumChannels: int(stream.Info.NChannels),
-				SampleRate:  int(stream.Info.SampleRate),
-			},
-			Data:           data,
-			SourceBitDepth: int(stream.Info.BitsPerSample),
-		}
-		if err := enc.Write(buf); err != nil {
+		intBuf.Data = data
+		if err := e.Write(intBuf); err != nil {
 			return nil, err
 		}
 	}
-
-	return ws.Bytes(), nil
 }