/*
 * Copyright (c) 2020 François Tigeot <ftigeot@wolfpond.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 unmodified, 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 ``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 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.
 */

#ifndef _LINUX_REFCOUNT_H_
#define _LINUX_REFCOUNT_H_

#include <linux/atomic.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/kernel.h>

typedef struct refcount_struct {
        atomic_t refs;
} refcount_t;

#define REFCOUNT_SATURATED      (INT_MIN / 2)

static inline void
refcount_set(refcount_t *r, unsigned int n)
{
        atomic_set(&r->refs, n);
}

static inline bool
refcount_dec_and_test(refcount_t *r)
{
        return atomic_dec_and_test(&r->refs);
}

static inline void
refcount_inc(refcount_t *r)
{
        int old_value = atomic_fetchadd_int(&r->refs.counter, 1);

        if (old_value <= 0)
                refcount_set(r, REFCOUNT_SATURATED);
}

#endif  /* _LINUX_REFCOUNT_H_ */