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Source at commit 358 created 13 years 11 months ago. By azimutz, Comment tweaking... | |
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1 | /*␊ |
2 | * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.␊ |
3 | *␊ |
4 | * @APPLE_LICENSE_HEADER_START@␊ |
5 | * ␊ |
6 | * Portions Copyright (c) 1999-2003 Apple Computer, Inc. All Rights␊ |
7 | * Reserved. This file contains Original Code and/or Modifications of␊ |
8 | * Original Code as defined in and that are subject to the Apple Public␊ |
9 | * Source License Version 2.0 (the "License"). You may not use this file␊ |
10 | * except in compliance with the License. Please obtain a copy of the␊ |
11 | * License at http://www.apple.com/publicsource and read it before using␊ |
12 | * this file.␊ |
13 | * ␊ |
14 | * The Original Code and all software distributed under the License are␊ |
15 | * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER␊ |
16 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,␊ |
17 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,␊ |
18 | * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT. Please see the␊ |
19 | * License for the specific language governing rights and limitations␊ |
20 | * under the License.␊ |
21 | * ␊ |
22 | * @APPLE_LICENSE_HEADER_END@␊ |
23 | */␊ |
24 | /**************************************************************␊ |
25 | LZSS.C -- A Data Compression Program␊ |
26 | ***************************************************************␊ |
27 | 4/6/1989 Haruhiko Okumura␊ |
28 | Use, distribute, and modify this program freely.␊ |
29 | Please send me your improved versions.␊ |
30 | PC-VAN SCIENCE␊ |
31 | NIFTY-Serve PAF01022␊ |
32 | CompuServe 74050,1022␊ |
33 | ␊ |
34 | **************************************************************/␊ |
35 | /*␊ |
36 | * lzss.c - Package for decompressing lzss compressed objects␊ |
37 | *␊ |
38 | * Copyright (c) 2003 Apple Computer, Inc.␊ |
39 | *␊ |
40 | * DRI: Josh de Cesare␊ |
41 | */␊ |
42 | ␊ |
43 | #include <sl.h>␊ |
44 | ␊ |
45 | #define N 4096 /* size of ring buffer - must be power of 2 */␊ |
46 | #define F 18 /* upper limit for match_length */␊ |
47 | #define THRESHOLD 2 /* encode string into position and length␊ |
48 | if match_length is greater than this */␊ |
49 | #define NIL N /* index for root of binary search trees */␊ |
50 | ␊ |
51 | int␊ |
52 | decompress_lzss(u_int8_t *dst, u_int8_t *src, u_int32_t srclen)␊ |
53 | {␊ |
54 | /* ring buffer of size N, with extra F-1 bytes to aid string comparison */␊ |
55 | u_int8_t text_buf[N + F - 1];␊ |
56 | u_int8_t *dststart = dst;␊ |
57 | u_int8_t *srcend = src + srclen;␊ |
58 | int i, j, k, r, c;␊ |
59 | unsigned int flags;␊ |
60 | ␊ |
61 | dst = dststart;␊ |
62 | srcend = src + srclen;␊ |
63 | for (i = 0; i < N - F; i++)␊ |
64 | text_buf[i] = ' ';␊ |
65 | r = N - F;␊ |
66 | flags = 0;␊ |
67 | for ( ; ; ) {␊ |
68 | if (((flags >>= 1) & 0x100) == 0) {␊ |
69 | if (src < srcend) c = *src++; else break;␊ |
70 | flags = c | 0xFF00; /* uses higher byte cleverly */␊ |
71 | } /* to count eight */␊ |
72 | if (flags & 1) {␊ |
73 | if (src < srcend) c = *src++; else break;␊ |
74 | *dst++ = c;␊ |
75 | text_buf[r++] = c;␊ |
76 | r &= (N - 1);␊ |
77 | } else {␊ |
78 | if (src < srcend) i = *src++; else break;␊ |
79 | if (src < srcend) j = *src++; else break;␊ |
80 | i |= ((j & 0xF0) << 4);␊ |
81 | j = (j & 0x0F) + THRESHOLD;␊ |
82 | for (k = 0; k <= j; k++) {␊ |
83 | c = text_buf[(i + k) & (N - 1)];␊ |
84 | *dst++ = c;␊ |
85 | text_buf[r++] = c;␊ |
86 | r &= (N - 1);␊ |
87 | }␊ |
88 | }␊ |
89 | }␊ |
90 | ␊ |
91 | return dst - dststart;␊ |
92 | }␊ |
93 |