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
fifo_alloc(unsigned int size)28 struct 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
fifo_free(struct fifo * fifo)43 void fifo_free(struct fifo *fifo)
44 {
45 free(fifo->buffer);
46 free(fifo);
47 }
48
fifo_put(struct fifo * fifo,void * buffer,unsigned int len)49 unsigned 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
fifo_get(struct fifo * fifo,void * buf,unsigned int len)72 unsigned 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