/*
 * This file is part of FFmpeg.
 *
 * FFmpeg 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.
 *
 * FFmpeg 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 FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef AVUTIL_REFCOUNT_H
#define AVUTIL_REFCOUNT_H

#include <stdint.h>

/**
 * A thread-safe reference counter.
 *
 * Unlike most libav* structs, sizeof(AVRefcount) IS a part of the public ABI
 * and so it can be embedded directly in other structs.
 *
 * None of its fields should be accessed directly by the caller, always use the
 * av_refcount_*() functions.
 */
typedef struct AVRefcount {
    void   (*_internal0)(void *);
    void    *_internal1;
    intmax_t _internal2;
} AVRefcount;

/**
 * Initialize an AVRefcount to a reference count of 1. This function MUST be
 * called on an AVRefcount before doing anything else with it.
 *
 * @param free The callback to be invoked when the counter reaches zero. May be
 *             NULL, then nothing is called.
 * @param opaque arbitrary user data that will be passed to the free() callback.
 */
void av_refcount_init(AVRefcount *rc, void (*free)(void *opaque),
                      void *opaque);

/**
 * Increase the reference count by 1.
 */
void av_refcount_inc(AVRefcount *rc);

/**
 * Decrease the reference count by 1.
 *
 * @return
 * - 0 when the new reference count is 0. If a free() callback was passed to
 *   av_refcount_init(), it has been invoked.
 * - a positive value when the new reference count is non-zero
 *
 * @note the return value is the new reference count, which may be useful for
 * debugging, but this is not guaranteed by the API and the callers MUST NOT
 * rely on this
 */
unsigned int av_refcount_dec(AVRefcount *rc);

/**
 * Check whether the caller is the exclusive owner of the reference.
 * @return
 * - a positive number if the reference count is exactly 1
 * - zero otherwise
 */
int av_refcount_exclusive(AVRefcount *rc);

#endif /* AVUTIL_REFCOUNT_H */