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 #ifdef __KERNEL__
  25
  26 #include <linux/kernel.h>
  27 #include <linux/spinlock.h>
  28
  29 struct kfifo {
  30         unsigned char *buffer;  /* the buffer holding the data */
  31         unsigned int size;      /* the size of the allocated buffer */
  32         unsigned int in;        /* data is added at offset (in % size) */
  33         unsigned int out;       /* data is extracted from off. (out % size) */
  34         spinlock_t *lock;       /* protects concurrent modifications */
  35 };
  36
  37 extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
  38                                 unsigned int __nocast gfp_mask, spinlock_t *lock);
  39 extern struct kfifo *kfifo_alloc(unsigned int size, unsigned int __nocast gfp_mask,
  40                                  spinlock_t *lock);
  41 extern void kfifo_free(struct kfifo *fifo);
  42 extern unsigned int __kfifo_put(struct kfifo *fifo,
  43                                 unsigned char *buffer, unsigned int len);
  44 extern unsigned int __kfifo_get(struct kfifo *fifo,
  45                                 unsigned char *buffer, unsigned int len);
  46
  47 /**
  48  * __kfifo_reset - removes the entire FIFO contents, no locking version
  49  * @fifo: the fifo to be emptied.
  50  */
  51 static inline void __kfifo_reset(struct kfifo *fifo)
  52 {
  53         fifo->in = fifo->out = 0;
  54 }
  55
  56 /**
  57  * kfifo_reset - removes the entire FIFO contents
  58  * @fifo: the fifo to be emptied.
  59  */
  60 static inline void kfifo_reset(struct kfifo *fifo)
  61 {
  62         unsigned long flags;
  63
  64         spin_lock_irqsave(fifo->lock, flags);
  65
  66         __kfifo_reset(fifo);
  67
  68         spin_unlock_irqrestore(fifo->lock, flags);
  69 }
  70
  71 /**
  72  * kfifo_put - puts some data into the FIFO
  73  * @fifo: the fifo to be used.
  74  * @buffer: the data to be added.
  75  * @len: the length of the data to be added.
  76  *
  77  * This function copies at most 'len' bytes from the 'buffer' into
  78  * the FIFO depending on the free space, and returns the number of
  79  * bytes copied.
  80  */
  81 static inline unsigned int kfifo_put(struct kfifo *fifo,
  82                                      unsigned char *buffer, unsigned int len)
  83 {
  84         unsigned long flags;
  85         unsigned int ret;
  86
  87         spin_lock_irqsave(fifo->lock, flags);
  88
  89         ret = __kfifo_put(fifo, buffer, len);
  90
  91         spin_unlock_irqrestore(fifo->lock, flags);
  92
  93         return ret;
  94 }
  95
  96 /**
  97  * kfifo_get - gets some data from the FIFO
  98  * @fifo: the fifo to be used.
  99  * @buffer: where the data must be copied.
 100  * @len: the size of the destination buffer.
 101  *
 102  * This function copies at most 'len' bytes from the FIFO into the
 103  * 'buffer' and returns the number of copied bytes.
 104  */
 105 static inline unsigned int kfifo_get(struct kfifo *fifo,
 106                                      unsigned char *buffer, unsigned int len)
 107 {
 108         unsigned long flags;
 109         unsigned int ret;
 110
 111         spin_lock_irqsave(fifo->lock, flags);
 112
 113         ret = __kfifo_get(fifo, buffer, len);
 114
 115         /*
 116          * optimization: if the FIFO is empty, set the indices to 0
 117          * so we don't wrap the next time
 118          */
 119         if (fifo->in == fifo->out)
 120                 fifo->in = fifo->out = 0;
 121
 122         spin_unlock_irqrestore(fifo->lock, flags);
 123
 124         return ret;
 125 }
 126
 127 /**
 128  * __kfifo_len - returns the number of bytes available in the FIFO, no locking version
 129  * @fifo: the fifo to be used.
 130  */
 131 static inline unsigned int __kfifo_len(struct kfifo *fifo)
 132 {
 133         return fifo->in - fifo->out;
 134 }
 135
 136 /**
 137  * kfifo_len - returns the number of bytes available in the FIFO
 138  * @fifo: the fifo to be used.
 139  */
 140 static inline unsigned int kfifo_len(struct kfifo *fifo)
 141 {
 142         unsigned long flags;
 143         unsigned int ret;
 144
 145         spin_lock_irqsave(fifo->lock, flags);
 146
 147         ret = __kfifo_len(fifo);
 148
 149         spin_unlock_irqrestore(fifo->lock, flags);
 150
 151         return ret;
 152 }
 153
 154 #else
 155 #warning "don't include kernel headers in userspace"
 156 #endif /* __KERNEL__ */
 157 #endif