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mirror of https://github.com/mpv-player/mpv synced 2024-12-18 21:06:00 +00:00
mpv/osdep/atomic.h
wm4 e7e06a47a0 demux: support for some kinds of timed metadata
This makes ICY title changes show up at approximately the correct time,
even if the demuxer buffer is huge. (It'll still be wrong if the stream
byte cache contains a meaningful amount of data.)

It should have the same effect for mid-stream metadata changes in e.g.
OGG (untested).

This is still somewhat fishy, but in parts due to ICY being fishy, and
FFmpeg's metadata change API being somewhat fishy. For example, what
happens if you seek? With FFmpeg AVFMT_EVENT_FLAG_METADATA_UPDATED and
AVSTREAM_EVENT_FLAG_METADATA_UPDATED we hope that FFmpeg will correctly
restore the correct metadata when the first packet is returned.

If you seke with ICY, we're out of luck, and some audio will be
associated with the wrong tag until we get a new title through ICY
metadata update at an essentially random point (it's mostly inherent to
ICY). Then the tags will switch back and forth, and this behavior will
stick with the data stored in the demuxer cache. Fortunately, this can
happen only if the HTTP stream is actually seekable, which it usually is
not for ICY things. Seeking doesn't even make sense with ICY, since you
can't know the exact metadata location. Basically ICY metsdata sucks.

Some complexity is due to a microoptimization: I didn't want additional
atomic accesses for each packet if no timed metadata is used. (It
probably doesn't matter at all.)
2018-04-18 01:17:42 +03:00

103 lines
4.0 KiB
C

/*
* This file is part of mpv.
* Copyright (c) 2013 Stefano Pigozzi <stefano.pigozzi@gmail.com>
*
* mpv is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* mpv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef MP_ATOMIC_H
#define MP_ATOMIC_H
#include <inttypes.h>
#include "config.h"
#if HAVE_STDATOMIC
#include <stdatomic.h>
typedef _Atomic float mp_atomic_float;
typedef _Atomic int64_t mp_atomic_int64;
#else
// Emulate the parts of C11 stdatomic.h needed by mpv.
typedef struct { unsigned long v; } atomic_ulong;
typedef struct { int v; } atomic_int;
typedef struct { unsigned int v; } atomic_uint;
typedef struct { _Bool v; } atomic_bool;
typedef struct { long long v; } atomic_llong;
typedef struct { uint_least32_t v; } atomic_uint_least32_t;
typedef struct { unsigned long long v; } atomic_ullong;
typedef struct { float v; } mp_atomic_float;
typedef struct { int64_t v; } mp_atomic_int64;
#define ATOMIC_VAR_INIT(x) \
{.v = (x)}
#define memory_order_relaxed 1
#define memory_order_seq_cst 2
#define atomic_load_explicit(p, e) atomic_load(p)
#include <pthread.h>
extern pthread_mutex_t mp_atomic_mutex;
#define atomic_load(p) \
({ __typeof__(p) p_ = (p); \
pthread_mutex_lock(&mp_atomic_mutex); \
__typeof__(p_->v) v_ = p_->v; \
pthread_mutex_unlock(&mp_atomic_mutex); \
v_; })
#define atomic_store(p, val) \
({ __typeof__(val) val_ = (val); \
__typeof__(p) p_ = (p); \
pthread_mutex_lock(&mp_atomic_mutex); \
p_->v = val_; \
pthread_mutex_unlock(&mp_atomic_mutex); })
#define atomic_fetch_op(a, b, op) \
({ __typeof__(a) a_ = (a); \
__typeof__(b) b_ = (b); \
pthread_mutex_lock(&mp_atomic_mutex); \
__typeof__(a_->v) v_ = a_->v; \
a_->v = v_ op b_; \
pthread_mutex_unlock(&mp_atomic_mutex); \
v_; })
#define atomic_fetch_add(a, b) atomic_fetch_op(a, b, +)
#define atomic_fetch_and(a, b) atomic_fetch_op(a, b, &)
#define atomic_fetch_or(a, b) atomic_fetch_op(a, b, |)
#define atomic_exchange(p, new) \
({ __typeof__(p) p_ = (p); \
pthread_mutex_lock(&mp_atomic_mutex); \
__typeof__(p_->v) res_ = p_->v; \
p_->v = (new); \
pthread_mutex_unlock(&mp_atomic_mutex); \
res_; })
#define atomic_compare_exchange_strong(p, old, new) \
({ __typeof__(p) p_ = (p); \
__typeof__(old) old_ = (old); \
__typeof__(new) new_ = (new); \
pthread_mutex_lock(&mp_atomic_mutex); \
int res_ = p_->v == *old_; \
if (res_) { \
p_->v = new_; \
} else { \
*old_ = p_->v; \
} \
pthread_mutex_unlock(&mp_atomic_mutex); \
res_; })
#endif /* else HAVE_STDATOMIC */
#endif