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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.
*
*/
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "kfifo.h"
/*
* min()/max() macros that also do
* strict type-checking.. See the
* "unnecessary" pointer comparison.
*/
#define min(x,y) ({ \
typeof(x) _x = (x); \
typeof(y) _y = (y); \
(void) (&_x == &_y); \
_x < _y ? _x : _y; })
#define max(x,y) ({ \
typeof(x) _x = (x); \
typeof(y) _y = (y); \
(void) (&_x == &_y); \
_x > _y ? _x : _y; })
/**
* kfifo_init - allocates a new FIFO using a preallocated buffer
* @buffer: the preallocated buffer to be used.
* @size: the size of the internal buffer, this have to be a power of 2.
*
* Do NOT pass the kfifo to kfifo_free() after use! Simply free the
* &struct kfifo with kfree().
*/
struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size)
{
struct kfifo *fifo;
/* size must be a power of 2 */
fifo = malloc(sizeof(struct kfifo));
if (!fifo) {
errno = ENOMEM;
return NULL;
}
fifo->buffer = buffer;
fifo->size = size;
fifo->in = fifo->out = 0;
return fifo;
}
/**
* kfifo_alloc - allocates a new FIFO and its internal buffer
* @size: the size of the internal buffer to be allocated.
*
* The size will be rounded-up to a power of 2.
*/
struct kfifo *kfifo_alloc(unsigned int size)
{
unsigned char *buffer;
struct kfifo *ret;
/*
* round up to the next power of 2, since our 'let the indices
* wrap' tachnique works only in this case.
*/
if (size & (size - 1)) {
// size = roundup_pow_of_two(size);
}
buffer = malloc(size);
if (!buffer) {
errno = ENOMEM;
return 0;
}
ret = kfifo_init(buffer, size);
if (!ret)
free(buffer);
return ret;
}
/**
* kfifo_free - frees the FIFO
* @fifo: the fifo to be freed.
*/
void kfifo_free(struct kfifo *fifo)
{
free(fifo->buffer);
free(fifo);
}
/**
* __kfifo_put - puts some data into the FIFO, no locking version
* @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.
*
* Note that with only one concurrent reader and one concurrent
* writer, you don't need extra locking to use these functions.
*/
unsigned int __kfifo_put(struct kfifo *fifo,
unsigned char *buffer, unsigned int len)
{
unsigned int l;
len = min(len, fifo->size - fifo->in + fifo->out);
/* first put the data starting from fifo->in to buffer end */
l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
/* then put the rest (if any) at the beginning of the buffer */
memcpy(fifo->buffer, buffer + l, len - l);
fifo->in += len;
return len;
}
/**
* __kfifo_get - gets some data from the FIFO, no locking version
* @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.
*
* Note that with only one concurrent reader and one concurrent
* writer, you don't need extra locking to use these functions.
*/
unsigned int __kfifo_get(struct kfifo *fifo,
unsigned char *buffer, unsigned int len)
{
unsigned int l;
len = min(len, fifo->in - fifo->out);
/* first get the data from fifo->out until the end of the buffer */
l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
/* then get the rest (if any) from the beginning of the buffer */
memcpy(buffer + l, fifo->buffer, len - l);
fifo->out += len;
return len;
}
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