1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /*
28 * We keep our own copy of this algorithm for 2 main reasons:
29 * 1. If we didn't, anyone modifying common/os/compress.c would
30 * directly break our on disk format
31 * 2. Our version of lzjb does not have a number of checks that the
32 * common/os version needs and uses
33 * In particular, we are adding the "feature" that compress() can
34 * take a destination buffer size and return -1 if the data will not
35 * compress to d_len or less.
36 */
37
38 #define MATCH_BITS 6
39 #define MATCH_MIN 3
40 #define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
41 #define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
42 #define LEMPEL_SIZE 256
43
44 /*ARGSUSED*/
45 static int
lzjb_decompress(void * s_start,void * d_start,size_t s_len __unused,size_t d_len,int n __unused)46 lzjb_decompress(void *s_start, void *d_start, size_t s_len __unused,
47 size_t d_len, int n __unused)
48 {
49 unsigned char *src = s_start;
50 unsigned char *dst = d_start;
51 unsigned char *d_end = (unsigned char *)d_start + d_len;
52 unsigned char *cpy, copymap = 0;
53 int copymask = 1 << (NBBY - 1);
54
55 while (dst < d_end) {
56 if ((copymask <<= 1) == (1 << NBBY)) {
57 copymask = 1;
58 copymap = *src++;
59 }
60 if (copymap & copymask) {
61 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
62 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
63 src += 2;
64 if ((cpy = dst - offset) < (unsigned char *)d_start)
65 return (-1);
66 while (--mlen >= 0 && dst < d_end)
67 *dst++ = *cpy++;
68 } else {
69 *dst++ = *src++;
70 }
71 }
72 return (0);
73 }
74