lib/kfifo.c

   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
  22 #include <common.h>
  23 #include <malloc.h>
  24 #include <kfifo.h>
  25 #include <errno.h>
  26
  27 /**
  28  * kfifo_init - allocates a new FIFO using a preallocated buffer
  29  * @buffer: the preallocated buffer to be used.
  30  * @size: the size of the internal buffer, this have to be a power of 2.
  31  * @gfp_mask: get_free_pages mask, passed to kmalloc()
  32  * @lock: the lock to be used to protect the fifo buffer
  33  *
  34  * Do NOT pass the kfifo to kfifo_free() after use! Simply free the
  35  * &struct kfifo with free().
  36  */
  37 struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size)
  38 {
  39         struct kfifo *fifo;
  40
  41         fifo = malloc(sizeof(struct kfifo));
  42         if (!fifo)
  43                 return NULL;
  44
  45         fifo->buffer = buffer;
  46         fifo->size = size;
  47         fifo->in = fifo->out = 0;
  48
  49         return fifo;
  50 }
  51
  52 /**
  53  * kfifo_alloc - allocates a new FIFO and its internal buffer
  54  * @size: the size of the internal buffer to be allocated.
  55  * @gfp_mask: get_free_pages mask, passed to kmalloc()
  56  * @lock: the lock to be used to protect the fifo buffer
  57  *
  58  * The size will be rounded-up to a power of 2.
  59  */
  60 struct kfifo *kfifo_alloc(unsigned int size)
  61 {
  62         unsigned char *buffer;
  63         struct kfifo *ret;
  64
  65         buffer = malloc(size);
  66         if (!buffer)
  67                 return NULL;
  68
  69         ret = kfifo_init(buffer, size);
  70
  71         if (!ret)
  72                 free(buffer);
  73
  74         return ret;
  75 }
  76
  77 /**
  78  * kfifo_free - frees the FIFO
  79  * @fifo: the fifo to be freed.
  80  */
  81 void kfifo_free(struct kfifo *fifo)
  82 {
  83         free(fifo->buffer);
  84         free(fifo);
  85 }
  86
  87 /**
  88  * kfifo_put - puts some data into the FIFO, no locking version
  89  * @fifo: the fifo to be used.
  90  * @buffer: the data to be added.
  91  * @len: the length of the data to be added.
  92  *
  93  * This function copies at most @len bytes from the @buffer into
  94  * the FIFO depending on the free space, and returns the number of
  95  * bytes copied.
  96  *
  97  */
  98 unsigned int kfifo_put(struct kfifo *fifo,
  99                          unsigned char *buffer, unsigned int len)
 100 {
 101         unsigned int l;
 102
 103         len = min(len, fifo->size - fifo->in + fifo->out);
 104
 105         /* first put the data starting from fifo->in to buffer end */
 106         l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
 107         memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
 108
 109         /* then put the rest (if any) at the beginning of the buffer */
 110         memcpy(fifo->buffer, buffer + l, len - l);
 111
 112         fifo->in += len;
 113
 114         return len;
 115 }
 116
 117 /**
 118  * kfifo_get - gets some data from the FIFO, no locking version
 119  * @fifo: the fifo to be used.
 120  * @buffer: where the data must be copied.
 121  * @len: the size of the destination buffer.
 122  *
 123  * This function copies at most @len bytes from the FIFO into the
 124  * @buffer and returns the number of copied bytes.
 125  *
 126  * Note that with only one concurrent reader and one concurrent
 127  * writer, you don't need extra locking to use these functions.
 128  */
 129 unsigned int kfifo_get(struct kfifo *fifo,
 130                          unsigned char *buffer, unsigned int len)
 131 {
 132         unsigned int l;
 133
 134         len = min(len, fifo->in - fifo->out);
 135
 136         /* first get the data from fifo->out until the end of the buffer */
 137         l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
 138         memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
 139
 140         /* then get the rest (if any) from the beginning of the buffer */
 141         memcpy(buffer + l, fifo->buffer, len - l);
 142
 143         fifo->out += len;
 144
 145         return len;
 146 }
 147
 148 void kfifo_putc(struct kfifo *fifo, unsigned char c)
 149 {
 150         *(fifo->buffer + (fifo->in & (fifo->size - 1))) = c;
 151         fifo->in++;
 152         if (fifo->in - fifo->out > fifo->size)
 153                 fifo->out++;
 154 }
 155
 156 unsigned int kfifo_getc(struct kfifo *fifo, unsigned char *c)
 157 {
 158         if (fifo->in == fifo->out)
 159                 return -1;
 160
 161         *c = *(fifo->buffer + (fifo->out & (fifo->size - 1)));
 162         fifo->out++;
 163
 164         return 0;
 165 }
 166