include/vlc_atomic.h

   1 /*****************************************************************************
   2  * vlc_atomic.h:
   3  *****************************************************************************
   4  * Copyright (C) 2010 Rémi Denis-Courmont
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program 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
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20
  21 #ifdef __cplusplus
  22 # error Not implemented in C++.
  23 #endif
  24
  25 #ifndef VLC_ATOMIC_H
  26 # define VLC_ATOMIC_H
  27
  28 /**
  29  * \file
  30  * Atomic operations do not require locking, but they are not very powerful.
  31  */
  32
  33 # include <assert.h>
  34 # include <stdatomic.h>
  35 # include <vlc_common.h>
  36
  37 typedef struct vlc_atomic_rc_t {
  38     atomic_uintptr_t refs;
  39 } vlc_atomic_rc_t;
  40
  41 /** Init the RC to 1 */
  42 static inline void vlc_atomic_rc_init(vlc_atomic_rc_t *rc)
  43 {
  44     atomic_init(&rc->refs, 1);
  45 }
  46
  47 /** Increment the RC */
  48 static inline void vlc_atomic_rc_inc(vlc_atomic_rc_t *rc)
  49 {
  50     uintptr_t prev = atomic_fetch_add_explicit(&rc->refs, 1, memory_order_relaxed);
  51     vlc_assert(prev);
  52     VLC_UNUSED(prev);
  53 }
  54
  55 /** Decrement the RC and return true if it reaches 0 */
  56 static inline bool vlc_atomic_rc_dec(vlc_atomic_rc_t *rc)
  57 {
  58     uintptr_t prev = atomic_fetch_sub_explicit(&rc->refs, 1, memory_order_acq_rel);
  59     vlc_assert(prev);
  60     return prev == 1;
  61 }
  62
  63 #endif