Properly stream wav files+reduce effect of oto bug

wav_streamer.go

@@ -0,0 +1,92 @@
+package wavy
+
+import (
+	"io"
+	"os"
+	"sync"
+
+	"github.com/go-audio/wav"
+)
+
+var _ io.ReadSeeker = &WavStreamer{}
+
+type WavStreamer struct {
+	F        *os.File
+	Dec      *wav.Decoder
+	Pos      int64
+	PCMStart int64
+
+	//TODO: This is currently needed because of https://github.com/hajimehoshi/oto/issues/171
+	//We should be able to delete once its resolved
+	mutex sync.Mutex
+}
+
+func (ws *WavStreamer) Read(outBuf []byte) (bytesRead int, err error) {
+
+	ws.mutex.Lock()
+	bytesRead, err = ws.Dec.PCMChunk.Read(outBuf)
+	ws.Pos += int64(bytesRead)
+	ws.mutex.Unlock()
+
+	return bytesRead, err
+}
+
+func (ws *WavStreamer) Seek(offset int64, whence int) (int64, error) {
+
+	ws.mutex.Lock()
+	defer ws.mutex.Unlock()
+
+	n, err := ws.Dec.Seek(offset, whence)
+	if err != nil {
+		return n, err
+	}
+
+	//The underlying parser can not seek back, so in that case we have to rewind the decoder
+	//then seek forward.
+	if n < ws.Pos {
+
+		err = ws.Dec.Rewind()
+		if err != nil {
+			return 0, err
+		}
+
+		//Anything before PCMStart is not valid sound, so the minimum seek back we allow is till PCMStart.
+		if n >= ws.PCMStart {
+
+			n, err = ws.Dec.Seek(offset, whence)
+			if err != nil {
+				return n, err
+			}
+		} else {
+			n = ws.PCMStart
+		}
+	}
+
+	ws.Pos = n
+	return n, err
+}
+
+func (ws *WavStreamer) Size() int64 {
+	return ws.Dec.PCMLen()
+}
+
+func NewWavStreamer(f *os.File, wavDec *wav.Decoder) (*WavStreamer, error) {
+
+	err := wavDec.FwdToPCM()
+	if err != nil {
+		return nil, err
+	}
+
+	currPos, err := wavDec.Seek(0, 1)
+	if err != nil {
+		return nil, err
+	}
+
+	return &WavStreamer{
+		F:        f,
+		Dec:      wavDec,
+		Pos:      currPos,
+		PCMStart: currPos,
+		mutex:    sync.Mutex{},
+	}, nil
+}