1 files changed, 161 insertions, 0 deletions
diff --git a/soundout/alsaout.c b/soundout/alsaout.c
new file mode 100644
index 0000000..0658206
--- /dev/null
+++ b/soundout/alsaout.c
@@ -0,0 +1,161 @@
+#include "alsaout.h"
+#include <stdbool.h>
+#include <stdatomic.h>
+#include <stdlib.h>
+#include <sys/eventfd.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <poll.h>
+#include <asoundlib.h>
+
+enum {
+  BUF_FRAMES = 1024,
+};
+
+struct alsaout_state {
+  struct sound_state ss;
+  sound_callback cbfunc;
+  void *userptr;
+  snd_pcm_t *apcm;
+  int fd_event;
+  int fds_space;
+  struct pollfd *fds;
+  bool paused;
+  bool terminate;
+  atomic_flag cb_flag;
+  bool thread_valid;
+  pthread_t alsa_thread;
+  int16_t buf[BUF_FRAMES*2];
+};
+
+static void *alsaout_thread(void *ptr) {
+  struct alsaout_state *as = ptr;
+  for (;;) {
+    as->fds[0] = (struct pollfd) {
+      .fd = as->fd_event,
+      .events = POLLIN,
+    };
+    int fd_cnt = 1;
+    fd_cnt += snd_pcm_poll_descriptors(
+        as->apcm, as->fds + 1, as->fds_space - 1
+    );
+    int err = poll(as->fds, fd_cnt, -1);
+    if (err <= 0) {
+      continue;
+    }
+    if (as->terminate) return 0;
+    if (as->fds[0].revents) {
+      uint64_t eventdata;
+      ssize_t t = read(as->fd_event, &eventdata, sizeof(eventdata));
+      (void)t;
+    }
+    unsigned short event;
+    if (snd_pcm_poll_descriptors_revents(
+        as->apcm, as->fds + 1, fd_cnt - 1, &event) < 0) continue;
+    if (!event) continue;
+    snd_pcm_sframes_t frames = snd_pcm_avail_update(as->apcm);
+    if (frames <= 0) continue;
+    while (frames) {
+      snd_pcm_sframes_t genframes = frames;
+      if (genframes > BUF_FRAMES) genframes = BUF_FRAMES;
+      while (atomic_flag_test_and_set_explicit(
+          &as->cb_flag, memory_order_acquire));
+      if (as->paused) {
+        atomic_flag_clear_explicit(&as->cb_flag, memory_order_release);
+        break;
+      }
+      as->cbfunc(as->userptr, as->buf, genframes);
+      atomic_flag_clear_explicit(&as->cb_flag, memory_order_release);
+      frames -= genframes;
+      if (snd_pcm_state(as->apcm) == SND_PCM_STATE_XRUN) {
+        err = snd_pcm_prepare(as->apcm);
+      }
+      snd_pcm_sframes_t written = snd_pcm_writei(as->apcm, as->buf, genframes);
+      if (written < 0) {
+        snd_pcm_prepare(as->apcm);
+      }
+    }
+  }
+}
+
+static void alsaout_pause(struct sound_state *ss, int pause, int flush) {
+  struct alsaout_state *as = (struct alsaout_state *)ss;
+  
+  as->paused = pause;
+  if (!pause && flush) {
+    snd_pcm_drop(as->apcm);
+    snd_pcm_prepare(as->apcm);
+    snd_pcm_start(as->apcm);
+  } else {
+    snd_pcm_pause(as->apcm, pause);
+  }
+  while (atomic_flag_test_and_set_explicit(
+      &as->cb_flag, memory_order_acquire));
+  atomic_flag_clear_explicit(&as->cb_flag, memory_order_release);
+  uint64_t event = 1;
+  ssize_t t = write(as->fd_event, &event, sizeof(event));
+  (void)t;
+}
+
+static void alsaout_free(struct sound_state *ss) {
+  if (!ss) return;
+  struct alsaout_state *as = (struct alsaout_state *)ss;
+  if (as->thread_valid) {
+    as->terminate = true;
+    uint64_t event = 1;
+    ssize_t t = write(as->fd_event, &event, sizeof(event));
+    (void)t;
+    pthread_join(as->alsa_thread, 0);
+  }
+  if (as->fd_event != -1) {
+    close(as->fd_event);
+  }
+  if (as->fds) free(as->fds);
+  if (as->apcm) {
+    snd_pcm_close(as->apcm);
+  }
+  free(as);
+}
+
+struct sound_state *alsaout_init(
+  const char *clientname, unsigned srate,
+  sound_callback cbfunc, void *userptr) {
+  (void)clientname;
+  struct alsaout_state *as = malloc(sizeof(*as));
+  if (!as) goto err;
+  *as = (struct alsaout_state) {
+    .ss = {
+      .pause = alsaout_pause,
+      .free = alsaout_free,
+      .apiname = "ALSA",
+    },
+    .cbfunc = cbfunc,
+    .userptr = userptr,
+    .fd_event = -1,
+    .cb_flag = ATOMIC_FLAG_INIT,
+    .paused = true,
+  };
+  if (snd_pcm_open(&as->apcm, "default", SND_PCM_STREAM_PLAYBACK, 0)) {
+    goto err;
+  }
+  as->fd_event = eventfd(0, EFD_CLOEXEC);
+  if (as->fd_event < 0) goto err;
+  as->fds_space = snd_pcm_poll_descriptors_count(as->apcm) + 1;
+  as->fds = malloc(sizeof(*as->fds) * as->fds_space);
+  if (!as->fds) goto err;
+  if (snd_pcm_set_params(
+      as->apcm,
+      SND_PCM_FORMAT_S16, SND_PCM_ACCESS_RW_INTERLEAVED, 2, srate, 1,
+      1000*1000/60)) {
+    goto err;
+  }
+  if (pthread_create(&as->alsa_thread, 0, alsaout_thread, as)) {
+    goto err;
+  }
+  as->thread_valid = true;
+  return &as->ss;
+
+err:
+  alsaout_free(&as->ss);
+  return 0;
+}