138 lines
3.1 KiB
Go
138 lines
3.1 KiB
Go
// Fenrir console screen reader.
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// Copyright (c) 2026 Storm Dragon
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// SPDX-License-Identifier: GPL-3.0-or-later
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package sound
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import (
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"context"
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"errors"
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"fmt"
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"syscall"
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"time"
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"github.com/jfreymuth/pulse"
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)
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const audioPeriod = 5 * time.Millisecond
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const pcmTimeout = 500 * time.Millisecond
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type pcmOutput interface {
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write([]float32) (int, error)
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prepare() error
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drain() error
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close()
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}
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func (s *Service) start_pcm(pcm pcmOutput) {
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drained := make(chan error, 1)
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s.closeBackend = pcm.close
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s.drainBackend = func(ctx context.Context) error {
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select {
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case err := <-drained:
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return err
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case <-ctx.Done():
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return ctx.Err()
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case <-s.done:
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return nil
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}
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}
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s.workers.Go(func() {
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err := s.run_pcm(pcm)
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drained <- err
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if err != nil && !s.closed.Load() {
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select {
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case s.errors <- fmt.Errorf("ALSA playback: %w", err):
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default:
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}
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}
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})
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}
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func (s *Service) run_pcm(pcm pcmOutput) error {
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// Pace even a virtual PCM such as ALSA's null sink. No busy silence loop,
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// and the same cancellation and cue priority apply to both audio drivers.
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tick := time.NewTicker(audioPeriod)
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defer tick.Stop()
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samples := make([]float32, int(int64(sampleRate*2)*int64(audioPeriod)/int64(time.Second)))
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for {
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select {
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case <-s.done:
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return nil
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case <-tick.C:
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}
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count, err := s.read_samples(samples)
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if err == pulse.EndOfData {
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ctx, cancel := context.WithTimeout(context.Background(), pcmTimeout)
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defer cancel()
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return s.drain_pcm(ctx, pcm)
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}
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if err != nil {
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return err
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}
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if err := s.write_pcm(pcm, samples[:count]); err != nil {
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return err
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}
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}
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}
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func (s *Service) write_pcm(pcm pcmOutput, samples []float32) error {
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ctx, cancel := context.WithTimeout(context.Background(), pcmTimeout)
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defer cancel()
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for len(samples) > 0 {
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select {
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case <-s.done:
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return nil
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case <-ctx.Done():
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return fmt.Errorf("PCM write stalled: %w", ctx.Err())
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default:
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}
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count, err := pcm.write(samples)
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if count < 0 || count > len(samples) || count%2 != 0 {
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return fmt.Errorf("invalid PCM sample count %d", count)
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}
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samples = samples[count:]
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switch {
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case errors.Is(err, syscall.EPIPE), errors.Is(err, syscall.ESTRPIPE):
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// prepare drops the broken buffer without snd_pcm_resume/recover's
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// potentially blocking suspend retry loop. Bound repeated failures.
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if err := pcm.prepare(); err != nil {
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return err
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}
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case err != nil && !errors.Is(err, syscall.EAGAIN) && !errors.Is(err, syscall.EINTR):
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return err
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case err == nil && count > 0:
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continue
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}
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if err := s.wait_pcm(ctx); err != nil {
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return err
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}
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}
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return nil
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}
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func (s *Service) drain_pcm(ctx context.Context, pcm pcmOutput) error {
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for {
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err := pcm.drain()
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if !errors.Is(err, syscall.EAGAIN) && !errors.Is(err, syscall.EINTR) {
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return err
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}
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if err := s.wait_pcm(ctx); err != nil {
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return err
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}
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}
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}
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func (s *Service) wait_pcm(ctx context.Context) error {
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timer := time.NewTimer(audioPeriod)
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defer timer.Stop()
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select {
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case <-s.done:
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return context.Canceled
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case <-ctx.Done():
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return ctx.Err()
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case <-timer.C:
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return nil
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}
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}
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