include/linux/kfifo.h

   1 /*
   2  * A simple kernel FIFO implementation.
   3  *
   4  * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  *
  20  */
  21 #ifndef _LINUX_KFIFO_H
  22 #define _LINUX_KFIFO_H
  23
  24 #include <linux/kernel.h>
  25 #include <linux/spinlock.h>
  26
  27 struct kfifo {
  28         unsigned char *buffer;  /* the buffer holding the data */
  29         unsigned int size;      /* the size of the allocated buffer */
  30         unsigned int in;        /* data is added at offset (in % size) */
  31         unsigned int out;       /* data is extracted from off. (out % size) */
  32         spinlock_t *lock;       /* protects concurrent modifications */
  33 };
  34
  35 extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
  36                                 gfp_t gfp_mask, spinlock_t *lock);
  37 extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask,
  38                                  spinlock_t *lock);
  39 extern void kfifo_free(struct kfifo *fifo);
  40 extern unsigned int __kfifo_put(struct kfifo *fifo,
  41                                 const unsigned char *buffer, unsigned int len);
  42 extern unsigned int __kfifo_get(struct kfifo *fifo,
  43                                 unsigned char *buffer, unsigned int len);
  44
  45 /**
  46  * __kfifo_reset - removes the entire FIFO contents, no locking version
  47  * @fifo: the fifo to be emptied.
  48  */
  49 static inline void __kfifo_reset(struct kfifo *fifo)
  50 {
  51         fifo->in = fifo->out = 0;
  52 }
  53
  54 /**
  55  * kfifo_reset - removes the entire FIFO contents
  56  * @fifo: the fifo to be emptied.
  57  */
  58 static inline void kfifo_reset(struct kfifo *fifo)
  59 {
  60         unsigned long flags;
  61
  62         spin_lock_irqsave(fifo->lock, flags);
  63
  64         __kfifo_reset(fifo);
  65
  66         spin_unlock_irqrestore(fifo->lock, flags);
  67 }
  68
  69 /**
  70  * kfifo_put - puts some data into the FIFO
  71  * @fifo: the fifo to be used.
  72  * @buffer: the data to be added.
  73  * @len: the length of the data to be added.
  74  *
  75  * This function copies at most @len bytes from the @buffer into
  76  * the FIFO depending on the free space, and returns the number of
  77  * bytes copied.
  78  */
  79 static inline unsigned int kfifo_put(struct kfifo *fifo,
  80                                 const unsigned char *buffer, unsigned int len)
  81 {
  82         unsigned long flags;
  83         unsigned int ret;
  84
  85         spin_lock_irqsave(fifo->lock, flags);
  86
  87         ret = __kfifo_put(fifo, buffer, len);
  88
  89         spin_unlock_irqrestore(fifo->lock, flags);
  90
  91         return ret;
  92 }
  93
  94 /**
  95  * kfifo_get - gets some data from the FIFO
  96  * @fifo: the fifo to be used.
  97  * @buffer: where the data must be copied.
  98  * @len: the size of the destination buffer.
  99  *
 100  * This function copies at most @len bytes from the FIFO into the
 101  * @buffer and returns the number of copied bytes.
 102  */
 103 static inline unsigned int kfifo_get(struct kfifo *fifo,
 104                                      unsigned char *buffer, unsigned int len)
 105 {
 106         unsigned long flags;
 107         unsigned int ret;
 108
 109         spin_lock_irqsave(fifo->lock, flags);
 110
 111         ret = __kfifo_get(fifo, buffer, len);
 112
 113         /*
 114          * optimization: if the FIFO is empty, set the indices to 0
 115          * so we don't wrap the next time
 116          */
 117         if (fifo->in == fifo->out)
 118                 fifo->in = fifo->out = 0;
 119
 120         spin_unlock_irqrestore(fifo->lock, flags);
 121
 122         return ret;
 123 }
 124
 125 /**
 126  * __kfifo_len - returns the number of bytes available in the FIFO, no locking version
 127  * @fifo: the fifo to be used.
 128  */
 129 static inline unsigned int __kfifo_len(struct kfifo *fifo)
 130 {
 131         return fifo->in - fifo->out;
 132 }
 133
 134 /**
 135  * kfifo_len - returns the number of bytes available in the FIFO
 136  * @fifo: the fifo to be used.
 137  */
 138 static inline unsigned int kfifo_len(struct kfifo *fifo)
 139 {
 140         unsigned long flags;
 141         unsigned int ret;
 142
 143         spin_lock_irqsave(fifo->lock, flags);
 144
 145         ret = __kfifo_len(fifo);
 146
 147         spin_unlock_irqrestore(fifo->lock, flags);
 148
 149         return ret;
 150 }
 151
 152 #endif