/*
 * Copyright (c) 2000 Paycounter, Inc.
 * Author: Alfred Perlstein <alfred@paycounter.com>, <alfred@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	$FreeBSD$
 */

/* Try to pull in native atomic type */
#include <machine/atomic.h>

/* if not available, simulate using mutexes */
#ifndef HAVE_ATOMIC_TYPE
#include <sys/mutex.h>

struct atomic {
	struct mtx	at_mtx;
	long		at_cnt;
};

/*
 * constructor must be called on any instantiated atomic struct
 */
static __inline void
atomic_init(struct atomic *a)
{

	mtx_init(&a->at_mtx, "atomic", MTX_DEF);
	a->at_cnt = 0;
}

/*
 * destructor, must be called when freeing an atomic struct
 */
static __inline void
atomic_destroy(struct atomic *a)
{

	mtx_destroy(&a->at_mtx);
}

/*
 * add 1 to an atomic counter
 */
static __inline void
atomic_inc(struct atomic *a)
{

	mtx_enter(&a->at_mtx, MTX_DEF);
	a->at_cnt++;
	mtx_exit(&a->at_mtx, MTX_DEF);
}

/*
 * subtract 1 and return true if it goes to zero
 */
static __inline int
atomic_dec_tstz(struct atomic *a)
{
	long	ref;

	mtx_enter(&a->at_mtx, MTX_DEF);
	ref = --(a->at_cnt);
	mtx_exit(&a->at_mtx, MTX_DEF);
	return (ref == 0);
}
#endif