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 <stdio.h>
23#include <stdlib.h>
24#include <string.h>
25
26#include "fifo.h"
27
28struct fifo *fifo_alloc(unsigned int size)
29{
30	struct fifo *fifo;
31
32	fifo = malloc(sizeof(struct fifo));
33	if (!fifo)
34		return NULL;
35
36	fifo->buffer = malloc(size);
37	fifo->size = size;
38	fifo->in = fifo->out = 0;
39
40	return fifo;
41}
42
43void fifo_free(struct fifo *fifo)
44{
45	free(fifo->buffer);
46	free(fifo);
47}
48
49unsigned int fifo_put(struct fifo *fifo, void *buffer, unsigned int len)
50{
51	unsigned int l;
52
53	len = min(len, fifo_room(fifo));
54
55	/* first put the data starting from fifo->in to buffer end */
56	l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
57	memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
58
59	/* then put the rest (if any) at the beginning of the buffer */
60	memcpy(fifo->buffer, buffer + l, len - l);
61
62	/*
63	 * Ensure that we add the bytes to the fifo -before-
64	 * we update the fifo->in index.
65	 */
66
67	fifo->in += len;
68
69	return len;
70}
71
72unsigned int fifo_get(struct fifo *fifo, void *buf, unsigned int len)
73{
74	len = min(len, fifo->in - fifo->out);
75
76	if (buf) {
77		unsigned int l;
78
79		/*
80		 * first get the data from fifo->out until the end of the buffer
81		 */
82		l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
83		memcpy(buf, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
84
85		/*
86		 * then get the rest (if any) from the beginning of the buffer
87		 */
88		memcpy(buf + l, fifo->buffer, len - l);
89	}
90
91	fifo->out += len;
92
93	if (fifo->in == fifo->out)
94		fifo->in = fifo->out = 0;
95
96	return len;
97}
98