Function newContext

driver_unix.go:109–176

(sampleRate int, channelCount int, format mux.Format, bufferSizeInBytes int)

}

func newContext(sampleRate int, channelCount int, format mux.Format, bufferSizeInBytes int) (*context, chan struct{}, error) {
	c := &context{
		channelCount: channelCount,
		cond:         sync.NewCond(&sync.Mutex{}),
		mux:          mux.New(sampleRate, channelCount, format),
		ready:        make(chan struct{}),
	}
	theContext = c

	go func() {
		defer close(c.ready)

		// Open a default ALSA audio device for blocking stream playback
		type openError struct {
			device string
			err    C.int
		}
		var openErrs []openError
		var found bool

		for _, name := range deviceCandidates() {
			cname := C.CString(name)
			defer C.free(unsafe.Pointer(cname))
			if err := C.snd_pcm_open(&c.handle, cname, C.SND_PCM_STREAM_PLAYBACK, 0); err < 0 {
				openErrs = append(openErrs, openError{
					device: name,
					err:    err,
				})
				continue
			}
			found = true
			break
		}
		if !found {
			var msgs []string
			for _, e := range openErrs {
				msgs = append(msgs, fmt.Sprintf("%q: %s", e.device, C.GoString(C.snd_strerror(e.err))))
			}
			c.err.TryStore(fmt.Errorf("oto: ALSA error at snd_pcm_open: %s", strings.Join(msgs, ", ")))
			return
		}

		// TODO: Should snd_pcm_hw_params_set_periods be called explicitly?
		const periods = 2
		var periodSize C.snd_pcm_uframes_t
		if bufferSizeInBytes != 0 {
			periodSize = C.snd_pcm_uframes_t(bufferSizeInBytes / (channelCount * 4 * periods))
		} else {
			periodSize = C.snd_pcm_uframes_t(1024)
		}
		bufferSize := periodSize * periods
		if err := c.alsaPcmHwParams(sampleRate, channelCount, &bufferSize, &periodSize); err != nil {
			c.err.TryStore(err)
			return
		}

		go func() {
			buf32 := make([]float32, int(periodSize)*channelCount)