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 2009 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /*
28 * Zero-length encoding. This is a fast and simple algorithm to eliminate
29 * runs of zeroes. Each chunk of compressed data begins with a length byte, b.
30 * If b < n (where n is the compression parameter) then the next b + 1 bytes
31 * are literal values. If b >= n then the next (256 - b + 1) bytes are zero.
32 */
33 #include <sys/types.h>
34 #include <sys/sysmacros.h>
35
36 size_t
zle_compress(void * s_start,void * d_start,size_t s_len,size_t d_len,int n)37 zle_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
38 {
39 uchar_t *src = s_start;
40 uchar_t *dst = d_start;
41 uchar_t *s_end = src + s_len;
42 uchar_t *d_end = dst + d_len;
43
44 while (src < s_end && dst < d_end - 1) {
45 uchar_t *first = src;
46 uchar_t *len = dst++;
47 if (src[0] == 0) {
48 uchar_t *last = src + (256 - n);
49 while (src < MIN(last, s_end) && src[0] == 0)
50 src++;
51 *len = src - first - 1 + n;
52 } else {
53 uchar_t *last = src + n;
54 if (d_end - dst < n)
55 break;
56 while (src < MIN(last, s_end) - 1 && (src[0] | src[1]))
57 *dst++ = *src++;
58 if (src[0])
59 *dst++ = *src++;
60 *len = src - first - 1;
61 }
62 }
63 return (src == s_end ? dst - (uchar_t *)d_start : s_len);
64 }
65
66 int
zle_decompress(void * s_start,void * d_start,size_t s_len,size_t d_len,int n)67 zle_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
68 {
69 uchar_t *src = s_start;
70 uchar_t *dst = d_start;
71 uchar_t *s_end = src + s_len;
72 uchar_t *d_end = dst + d_len;
73
74 while (src < s_end && dst < d_end) {
75 int len = 1 + *src++;
76 if (len <= n) {
77 while (len-- != 0)
78 *dst++ = *src++;
79 } else {
80 len -= n;
81 while (len-- != 0)
82 *dst++ = 0;
83 }
84 }
85 return (dst == d_end ? 0 : -1);
86 }
87