atomic.c
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1 /*
2  * Copyright (c) 2012 Ronald S. Bultje <rsbultje@gmail.com>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include "atomic.h"
22 
23 #if !HAVE_ATOMICS_NATIVE
24 
25 #if HAVE_PTHREADS
26 
27 #include <pthread.h>
28 
29 static pthread_mutex_t atomic_lock = PTHREAD_MUTEX_INITIALIZER;
30 
31 int avpriv_atomic_int_get(volatile int *ptr)
32 {
33  int res;
34 
35  pthread_mutex_lock(&atomic_lock);
36  res = *ptr;
37  pthread_mutex_unlock(&atomic_lock);
38 
39  return res;
40 }
41 
42 void avpriv_atomic_int_set(volatile int *ptr, int val)
43 {
44  pthread_mutex_lock(&atomic_lock);
45  *ptr = val;
46  pthread_mutex_unlock(&atomic_lock);
47 }
48 
49 int avpriv_atomic_int_add_and_fetch(volatile int *ptr, int inc)
50 {
51  int res;
52 
53  pthread_mutex_lock(&atomic_lock);
54  *ptr += inc;
55  res = *ptr;
56  pthread_mutex_unlock(&atomic_lock);
57 
58  return res;
59 }
60 
61 void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval)
62 {
63  void *ret;
64  pthread_mutex_lock(&atomic_lock);
65  ret = *ptr;
66  if (*ptr == oldval)
67  *ptr = newval;
68  pthread_mutex_unlock(&atomic_lock);
69  return ret;
70 }
71 
72 #elif !HAVE_THREADS
73 
74 int avpriv_atomic_int_get(volatile int *ptr)
75 {
76  return *ptr;
77 }
78 
79 void avpriv_atomic_int_set(volatile int *ptr, int val)
80 {
81  *ptr = val;
82 }
83 
84 int avpriv_atomic_int_add_and_fetch(volatile int *ptr, int inc)
85 {
86  *ptr += inc;
87  return *ptr;
88 }
89 
90 void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval)
91 {
92  if (*ptr == oldval) {
93  *ptr = newval;
94  return oldval;
95  }
96  return *ptr;
97 }
98 
99 #else
100 
101 #error "Threading is enabled, but there is no implementation of atomic operations available"
102 
103 #endif /* HAVE_PTHREADS */
104 
105 #endif /* !HAVE_MEMORYBARRIER && !HAVE_SYNC_VAL_COMPARE_AND_SWAP && !HAVE_MACHINE_RW_BARRIER */
106 
107 #ifdef TEST
108 #include "avassert.h"
109 
110 int main(void)
111 {
112  volatile int val = 1;
113  int res;
114 
115  res = avpriv_atomic_int_add_and_fetch(&val, 1);
116  av_assert0(res == 2);
117  avpriv_atomic_int_set(&val, 3);
118  res = avpriv_atomic_int_get(&val);
119  av_assert0(res == 3);
120 
121  return 0;
122 }
123 #endif
int avpriv_atomic_int_get(volatile int *ptr)
Load the current value stored in an atomic integer.
Definition: atomic.c:74
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
HMTX pthread_mutex_t
Definition: os2threads.h:38
void avpriv_atomic_int_set(volatile int *ptr, int val)
Store a new value in an atomic integer.
Definition: atomic.c:79
simple assert() macros that are a bit more flexible than ISO C assert().
ret
Definition: avfilter.c:821
int avpriv_atomic_int_add_and_fetch(volatile int *ptr, int inc)
Add a value to an atomic integer.
Definition: atomic.c:84
void * avpriv_atomic_ptr_cas(void *volatile *ptr, void *oldval, void *newval)
Atomic pointer compare and swap.
Definition: atomic.c:90
static av_always_inline int pthread_mutex_unlock(pthread_mutex_t *mutex)
Definition: os2threads.h:104
static av_always_inline int pthread_mutex_lock(pthread_mutex_t *mutex)
Definition: os2threads.h:97
int main(int argc, char **argv)
Definition: main.c:22