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/* Copyright (C) 2017 the mpv developers
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "osdep/semaphore.h"
#ifdef MP_SEMAPHORE_EMULATION
#include <unistd.h>
#include <poll.h>
#include <limits.h>
#include <sys/time.h>
#include <errno.h>
#include <common/common.h>
#include "io.h"
#include "timer.h"
int mp_sem_init(mp_sem_t *sem, int pshared, unsigned int value)
{
if (pshared) {
errno = ENOSYS;
return -1;
}
if (value > INT_MAX) {
errno = EINVAL;
return -1;
}
if (mp_make_wakeup_pipe(sem->wakeup_pipe) < 0)
return -1;
sem->count = 0;
mp_mutex_init(&sem->lock);
return 0;
}
int mp_sem_wait(mp_sem_t *sem)
{
return mp_sem_timedwait(sem, -1);
}
int mp_sem_trywait(mp_sem_t *sem)
{
int r = -1;
mp_mutex_lock(&sem->lock);
if (sem->count == 0) {
char buf[1024];
ssize_t s = read(sem->wakeup_pipe[0], buf, sizeof(buf));
if (s > 0 && s <= INT_MAX - sem->count) // can't handle overflows correctly
sem->count += s;
}
if (sem->count > 0) {
sem->count -= 1;
r = 0;
}
mp_mutex_unlock(&sem->lock);
if (r < 0)
errno = EAGAIN;
return r;
}
int mp_sem_timedwait(mp_sem_t *sem, int64_t until)
{
while (1) {
if (!mp_sem_trywait(sem))
return 0;
int timeout = 0;
if (until == -1) {
timeout = -1;
} else if (until >= 0) {
timeout = (until - mp_time_ns()) / MP_TIME_MS_TO_NS(1);
timeout = MPCLAMP(timeout, 0, INT_MAX);
} else {
assert(false && "Invalid mp_time value!");
}
struct pollfd fd = {.fd = sem->wakeup_pipe[0], .events = POLLIN};
int r = poll(&fd, 1, timeout);
if (r < 0)
return -1;
if (r == 0) {
errno = ETIMEDOUT;
return -1;
}
}
}
int mp_sem_post(mp_sem_t *sem)
{
if (write(sem->wakeup_pipe[1], &(char){0}, 1) == 1)
return 0;
// Actually we can't handle overflow fully correctly, because we can't
// check sem->count atomically, while still being AS-safe.
errno = EOVERFLOW;
return -1;
}
int mp_sem_destroy(mp_sem_t *sem)
{
close(sem->wakeup_pipe[0]);
close(sem->wakeup_pipe[1]);
mp_mutex_destroy(&sem->lock);
return 0;
}
#endif
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