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/*

 * A simple kernel FIFO implementation.

 *

 * Copyright (C) 2004 Stelian Pop <stelian@popies.net>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program 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 General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 *

 */

#ifndef _LINUX_KFIFO_H

#define _LINUX_KFIFO_H

#ifdef __KERNEL__

#include <linux/kernel.h>

#include <linux/spinlock.h>

struct kfifo {

        unsigned char *buffer;  /* the buffer holding the data */

        unsigned int size;      /* the size of the allocated buffer */

        unsigned int in;        /* data is added at offset (in % size) */

        unsigned int out;       /* data is extracted from off. (out % size) */

        spinlock_t *lock;       /* protects concurrent modifications */

};

extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,

                                gfp_t gfp_mask, spinlock_t *lock);

extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask,

                                 spinlock_t *lock);

extern void kfifo_free(struct kfifo *fifo);

extern unsigned int __kfifo_put(struct kfifo *fifo,

                                unsigned char *buffer, unsigned int len);

extern unsigned int __kfifo_get(struct kfifo *fifo,

                                unsigned char *buffer, unsigned int len);

/**

 * __kfifo_reset - removes the entire FIFO contents, no locking version

 * @fifo: the fifo to be emptied.

 */

static inline void __kfifo_reset(struct kfifo *fifo)

{

        fifo->in = fifo->out = 0;

}

/**

 * kfifo_reset - removes the entire FIFO contents

 * @fifo: the fifo to be emptied.

 */

static inline void kfifo_reset(struct kfifo *fifo)

{

        unsigned long flags;

        spin_lock_irqsave(fifo->lock, flags);

        __kfifo_reset(fifo);

        spin_unlock_irqrestore(fifo->lock, flags);

}

/**

 * kfifo_put - puts some data into the FIFO

 * @fifo: the fifo to be used.

 * @buffer: the data to be added.

 * @len: the length of the data to be added.

 *

 * This function copies at most @len bytes from the @buffer into

 * the FIFO depending on the free space, and returns the number of

 * bytes copied.

 */

static inline unsigned int kfifo_put(struct kfifo *fifo,

                                     unsigned char *buffer, unsigned int len)

{

        unsigned long flags;

        unsigned int ret;

        spin_lock_irqsave(fifo->lock, flags);

        ret = __kfifo_put(fifo, buffer, len);

        spin_unlock_irqrestore(fifo->lock, flags);

        return ret;

}

/**

 * kfifo_get - gets some data from the FIFO

 * @fifo: the fifo to be used.

 * @buffer: where the data must be copied.

 * @len: the size of the destination buffer.

 *

 * This function copies at most @len bytes from the FIFO into the

 * @buffer and returns the number of copied bytes.

 */

static inline unsigned int kfifo_get(struct kfifo *fifo,

                                     unsigned char *buffer, unsigned int len)

{

        unsigned long flags;

        unsigned int ret;

        spin_lock_irqsave(fifo->lock, flags);

        ret = __kfifo_get(fifo, buffer, len);

        /*

         * optimization: if the FIFO is empty, set the indices to 0

         * so we don't wrap the next time

         */

        if (fifo->in == fifo->out)

                fifo->in = fifo->out = 0;

        spin_unlock_irqrestore(fifo->lock, flags);

        return ret;

}

/**

 * __kfifo_len - returns the number of bytes available in the FIFO, no locking version

 * @fifo: the fifo to be used.

 */

static inline unsigned int __kfifo_len(struct kfifo *fifo)

{

        return fifo->in - fifo->out;

}

/**

 * kfifo_len - returns the number of bytes available in the FIFO

 * @fifo: the fifo to be used.

 */

static inline unsigned int kfifo_len(struct kfifo *fifo)

{

        unsigned long flags;

        unsigned int ret;

        spin_lock_irqsave(fifo->lock, flags);

        ret = __kfifo_len(fifo);

        spin_unlock_irqrestore(fifo->lock, flags);

        return ret;

}

#else

#warning "don't include kernel headers in userspace"

#endif /* __KERNEL__ */

#endif