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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 | |
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 | |
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 | } |