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 /*#pragma ident "%Z%%M% %I% %E% SMI"*/
28
29 /*
30 * We keep our own copy of this algorithm for 2 main reasons:
31 * 1. If we didn't, anyone modifying common/os/compress.c would
32 * directly break our on disk format
33 * 2. Our version of lzjb does not have a number of checks that the
34 * common/os version needs and uses
35 * In particular, we are adding the "feature" that compress() can
36 * take a destination buffer size and return -1 if the data will not
37 * compress to d_len or less.
38 */
39
40 #define MATCH_BITS 6
41 #define MATCH_MIN 3
42 #define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
43 #define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
44 #define LEMPEL_SIZE 256
45
46 /*ARGSUSED*/
47 static int
lzjb_decompress(void * s_start,void * d_start,size_t s_len,size_t d_len,int n)48 lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
49 {
50 unsigned char *src = s_start;
51 unsigned char *dst = d_start;
52 unsigned char *d_end = (unsigned char *)d_start + d_len;
53 unsigned char *cpy, copymap = 0;
54 int copymask = 1 << (NBBY - 1);
55
56 while (dst < d_end) {
57 if ((copymask <<= 1) == (1 << NBBY)) {
58 copymask = 1;
59 copymap = *src++;
60 }
61 if (copymap & copymask) {
62 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
63 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
64 src += 2;
65 if ((cpy = dst - offset) < (unsigned char *)d_start)
66 return (-1);
67 while (--mlen >= 0 && dst < d_end)
68 *dst++ = *cpy++;
69 } else {
70 *dst++ = *src++;
71 }
72 }
73 return (0);
74 }
75