/*
   * 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