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