fifo.c

/*
 * 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 <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "fifo.h"

struct fifo *fifo_alloc(unsigned int size)
{
	struct fifo *fifo;

	fifo = malloc(sizeof(struct fifo));
	if (!fifo)
		return NULL;

	fifo->buffer = malloc(size);
	fifo->size = size;
	fifo->in = fifo->out = 0;

	return fifo;
}

void fifo_free(struct fifo *fifo)
{
	free(fifo->buffer);
	free(fifo);
}

unsigned int fifo_put(struct fifo *fifo, void *buffer, unsigned int len)
{
	unsigned int l;

	len = min(len, fifo_room(fifo));

	/* 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);

	/*
	 * Ensure that we add the bytes to the fifo -before-
	 * we update the fifo->in index.
	 */

	fifo->in += len;

	return len;
}

unsigned int fifo_get(struct fifo *fifo, void *buf, unsigned int len)
{
	len = min(len, fifo->in - fifo->out);

	if (buf) {
		unsigned int l;

		/*
		 * first get the data from fifo->out until the end of the buffer
		 */
		l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
		memcpy(buf, fifo->buffer + (fifo->out & (fifo->size - 1)), l);

		/*
		 * then get the rest (if any) from the beginning of the buffer
		 */
		memcpy(buf + l, fifo->buffer, len - l);
	}

	fifo->out += len;

	if (fifo->in == fifo->out)
		fifo->in = fifo->out = 0;

	return len;
}