ffmpeg/libavutil/atomic.c

   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