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#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;
}
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