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comparison engine/core/vfs/dat/lzssdecoder.cpp @ 0:4a0efb7baf70

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* Datasets becomes the new trunk and retires after that :-)
author mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
date Sun, 29 Jun 2008 18:44:17 +0000
parents
children 90005975cdbb
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-1:000000000000 0:4a0efb7baf70
1 /***************************************************************************
2 * Copyright (C) 2005-2006 by the FIFE Team *
3 * http://www.fifengine.de *
4 * This file is part of FIFE. *
5 * *
6 * FIFE is free software; you can redistribute it and/or modify *
7 * it under the terms of the GNU General Public License as published by *
8 * the Free Software Foundation; either version 2 of the License, or *
9 * (at your option) any later version. *
10 * *
11 * This program is distributed in the hope that it will be useful, *
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of *
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
14 * GNU General Public License for more details. *
15 * *
16 * You should have received a copy of the GNU General Public License *
17 * along with this program; if not, write to the *
18 * Free Software Foundation, Inc., *
19 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA *
20 ***************************************************************************/
21
22 // Standard C++ library includes
23 #include <algorithm>
24
25 // 3rd party library includes
26
27 // FIFE includes
28 #include "vfs/raw/rawdata.h"
29 #include "util/base/exception.h"
30
31 #include "lzssdecoder.h"
32
33 // just a quick&dirty wrapper around anchorites implementation - needs to be replaced with our own LZSS implementation
34 namespace FIFE {
35
36 LZSSDecoder::LZSSDecoder() {}
37 LZSSDecoder::~LZSSDecoder() {}
38
39
40 void LZSSDecoder::decode(RawData* input, uint8_t* output, const uint32_t outputsize) {
41
42 m_outindex = 0;
43 m_outlen = outputsize;
44
45 while (m_outindex < outputsize) {
46 uint16_t blockdesc = input->read16Big();
47 uint16_t bytesToRead = blockdesc & 0x7fff;
48
49 if (blockdesc & 0x8000) { // uncompressed
50 input->readInto(output + m_outindex, bytesToRead);
51 m_outindex += bytesToRead;
52 } else {
53 // Allocate +2 bytes so that on corrupt data the LZSS
54 // decoder won't crash the input buffer.
55 std::vector<uint8_t> indata(bytesToRead + 2);
56 input->readInto(&indata[0], bytesToRead);
57 LZSSDecode(&indata[0], bytesToRead, output);
58 // Note outindex is advanced inside LZSSDecode.
59 }
60
61 }
62 }
63
64 void LZSSDecoder::LZSSDecode(uint8_t* in , long len, uint8_t* out) {
65 const long c_nRingBufferSize = 4096;
66 const long c_nMatchLengthUpperLimit = 18;
67 const long c_nThreshold = 2;
68
69 char buffer[c_nRingBufferSize + c_nMatchLengthUpperLimit - 1];
70 int ibuf = 0;
71 int c;
72
73 int i;
74 int j;
75 int k;
76 int r;
77
78 unsigned int flags;
79
80 for (i = 0; i < c_nRingBufferSize - c_nMatchLengthUpperLimit; i++) {
81 buffer[i] = ' ';
82 }
83
84 r = c_nRingBufferSize - c_nMatchLengthUpperLimit;
85 flags = 0;
86 while ( ibuf < len ) {
87 if (((flags >>= 1) & 256) == 0) {
88 c = in[ibuf++];
89 flags = c | 0xff00;/* uses higher byte cleverly to count eight */
90 }
91
92 if (flags & 1) {
93 c = in[ibuf++];
94 out[m_outindex++] = c;
95
96 buffer[r++] = c;
97 r &= (c_nRingBufferSize - 1);
98 } else {
99 i = in[ibuf++];
100 j = in[ibuf++];
101
102 i |= ((j & 0xf0) << 4);
103 j = (j & 0x0f) + c_nThreshold;
104
105 for (k = 0; k <= j; k++) {
106 c = buffer[(i + k) & (c_nRingBufferSize - 1)];
107
108 out[m_outindex++] = c;
109
110 buffer[r++] = c;
111 r &= (c_nRingBufferSize - 1);
112 }
113 }
114 }
115 }
116
117
118 }