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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 "config.h"
22 #include "atomic.h"
23 
24 #if !HAVE_ATOMICS_NATIVE
25 
26 #if HAVE_PTHREADS
27 
28 #include <pthread.h>
29 
30 static pthread_mutex_t atomic_lock = PTHREAD_MUTEX_INITIALIZER;
31 
32 int avpriv_atomic_int_get(volatile int *ptr)
33 {
34  int res;
35 
36  pthread_mutex_lock(&atomic_lock);
37  res = *ptr;
38  pthread_mutex_unlock(&atomic_lock);
39 
40  return res;
41 }
42 
43 void avpriv_atomic_int_set(volatile int *ptr, int val)
44 {
45  pthread_mutex_lock(&atomic_lock);
46  *ptr = val;
47  pthread_mutex_unlock(&atomic_lock);
48 }
49 
50 int avpriv_atomic_int_add_and_fetch(volatile int *ptr, int inc)
51 {
52  int res;
53 
54  pthread_mutex_lock(&atomic_lock);
55  *ptr += inc;
56  res = *ptr;
57  pthread_mutex_unlock(&atomic_lock);
58 
59  return res;
60 }
61 
62 void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval)
63 {
64  void *ret;
65  pthread_mutex_lock(&atomic_lock);
66  ret = *ptr;
67  if (*ptr == oldval)
68  *ptr = newval;
69  pthread_mutex_unlock(&atomic_lock);
70  return ret;
71 }
72 
73 #elif !HAVE_THREADS
74 
75 int avpriv_atomic_int_get(volatile int *ptr)
76 {
77  return *ptr;
78 }
79 
80 void avpriv_atomic_int_set(volatile int *ptr, int val)
81 {
82  *ptr = val;
83 }
84 
85 int avpriv_atomic_int_add_and_fetch(volatile int *ptr, int inc)
86 {
87  *ptr += inc;
88  return *ptr;
89 }
90 
91 void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval)
92 {
93  if (*ptr == oldval) {
94  *ptr = newval;
95  return oldval;
96  }
97  return *ptr;
98 }
99 
100 #else /* HAVE_THREADS */
101 
102 /* This should never trigger, unless a new threading implementation
103  * without correct atomics dependencies in configure or a corresponding
104  * atomics implementation is added. */
105 #error "Threading is enabled, but there is no implementation of atomic operations available"
106 
107 #endif /* HAVE_PTHREADS */
108 
109 #endif /* !HAVE_ATOMICS_NATIVE */
110 
111 #ifdef TEST
112 #include "avassert.h"
113 
114 int main(void)
115 {
116  volatile int val = 1;
117  int res;
118 
119  res = avpriv_atomic_int_add_and_fetch(&val, 1);
120  av_assert0(res == 2);
121  avpriv_atomic_int_set(&val, 3);
122  res = avpriv_atomic_int_get(&val);
123  av_assert0(res == 3);
124 
125  return 0;
126 }
127 #endif