#include <sys/time.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>

static double
ts(void)
{
  static struct timeval last;
  struct timeval now, dt;
  if (last.tv_sec == 0) {
    gettimeofday(&last, NULL);
  }
  gettimeofday(&now, NULL);
  timersub(&now, &last, &dt);
  last = now;
  return dt.tv_sec * 1000.0 + dt.tv_usec / 1000.0;
}

int
main(int argc, char * argv[])
{
  int r;
  snd_pcm_t * pcm;
  snd_pcm_uframes_t buffer_size, period_size;
  char silence[88200] = {0};

  if (argc != 2) {
    return 1;
  }

  r = snd_pcm_open(&pcm, "default", SND_PCM_STREAM_PLAYBACK, 0);
  assert(r == 0);

  r = snd_pcm_set_params(pcm, SND_PCM_FORMAT_S16_LE,
                         SND_PCM_ACCESS_RW_INTERLEAVED, 2, 44100, 1,
                         atoi(argv[1]) * 1000);
  assert(r == 0);

  r = snd_pcm_get_params(pcm, &buffer_size, &period_size);
  assert(r == 0);
  fprintf(stderr, "%.2f: buffer_size = %u, period_size = %u\n",
          ts(), (unsigned) buffer_size, (unsigned) period_size);
  assert(buffer_size <= sizeof(silence) / 4);

  for (;;) {
    snd_pcm_sframes_t avail, wrote = 0;

    snd_pcm_wait(pcm, -1);

    avail = snd_pcm_avail_update(pcm);
    if (avail == -EPIPE) {
      snd_pcm_recover(pcm, -EPIPE, 0);
      avail = snd_pcm_avail_update(pcm);
    }
    if (avail > 0) {
      wrote = snd_pcm_writei(pcm, silence, avail);
    }
    fprintf(stderr, "%.2f: avail = %d, wrote = %d\n", ts(), (int) avail, (int) wrote);
  }

  return 0;
}