1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
|
/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include "common/endian.h"
#include "common/util.h"
#include "ultima/shared/core/lzw.h"
namespace Ultima {
namespace Shared {
void LZW::decompress(Common::ReadStream *source, Common::WriteStream *dest) {
int32 destSize = source->readUint32LE();
_source = source;
_currentByte = source->readByte();
byte litByte = 0;
uint16 oldCode = 0;
uint16 copyLength, maxCodeValue, code, nextCode, lastCode;
byte *copyBuf = new byte[8192];
struct {
uint16 code; byte value;
} codeTable[8192];
memset(codeTable, 0, sizeof(codeTable));
_codeLength = 9;
nextCode = 258;
maxCodeValue = 512;
copyLength = 0;
_sourceBitsLeft = 8;
for (;;) {
code = getCode();
if (code == 257)
break;
if (code == 256) {
_codeLength = 9;
nextCode = 258;
maxCodeValue = 512;
lastCode = getCode();
oldCode = lastCode;
litByte = lastCode;
dest->writeByte(litByte);
} else {
lastCode = code;
if (code >= nextCode) {
lastCode = oldCode;
copyBuf[copyLength++] = litByte;
}
while (lastCode > 255) {
copyBuf[copyLength++] = codeTable[lastCode].value;
lastCode = codeTable[lastCode].code;
}
litByte = lastCode;
copyBuf[copyLength++] = lastCode;
while (copyLength > 0)
dest->writeByte(copyBuf[--copyLength]);
codeTable[nextCode].value = lastCode;
codeTable[nextCode].code = oldCode;
nextCode++;
oldCode = code;
if (nextCode >= maxCodeValue && _codeLength <= 12) {
_codeLength++;
maxCodeValue <<= 1;
}
}
}
delete[] copyBuf;
assert(dest->pos() == destSize);
}
uint16 LZW::getCode() {
const byte bitMasks[9] = {
0x00, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0x0FF
};
byte resultBitsLeft = _codeLength;
byte resultBitsPos = 0;
uint16 result = 0;
byte currentByte = _currentByte;
byte currentBits = 0;
// Get bits of current byte
while (resultBitsLeft) {
if (resultBitsLeft < _sourceBitsLeft) {
// we need less than we have left
currentBits = (currentByte >> (8 - _sourceBitsLeft)) &bitMasks[resultBitsLeft];
result |= (currentBits << resultBitsPos);
_sourceBitsLeft -= resultBitsLeft;
resultBitsLeft = 0;
} else {
// we need as much as we have left or more
resultBitsLeft -= _sourceBitsLeft;
currentBits = currentByte >> (8 - _sourceBitsLeft);
result |= (currentBits << resultBitsPos);
resultBitsPos += _sourceBitsLeft;
// Go to next byte
_currentByte = _source->readByte();
_sourceBitsLeft = 8;
if (resultBitsLeft) {
currentByte = _currentByte;
}
}
}
return result;
}
} // End of namespace Shared
} // End of namespace Ultima
|
