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
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
|
/* 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 2
* 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, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
/***************************************************************************
** decomp.c
**
** Routines that deal with AGI version 3 specific features.
** The original LZW code is from DJJ, October 1989, p.86.
** It has been modified to handle AGI compression.
**
** (c) 1997 Lance Ewing
***************************************************************************/
#include "agi/agi.h"
#include "agi/lzw.h"
#include "common/textconsole.h"
namespace Agi {
class LZWDecoder {
private:
enum {
MAXBITS = 12,
TABLE_SIZE = 18041, // strange number
START_BITS = 9
};
int32 BITS, MAX_VALUE, MAX_CODE;
uint32 *prefixCode;
uint8 *appendCharacter;
uint8 *decodeStack;
int32 inputBitCount; // Number of bits in input bit buffer
uint32 inputBitBuffer;
public:
LZWDecoder();
~LZWDecoder();
void lzwExpand(uint8 *in, uint8 *out, int32 len);
private:
int setBits(int32 value);
uint8 *decodeString(uint8 *buffer, uint32 code);
uint32 inputCode(uint8 **input);
};
LZWDecoder::LZWDecoder() {
decodeStack = (uint8 *)calloc(1, 8192);
prefixCode = (uint32 *)malloc(TABLE_SIZE * sizeof(uint32));
appendCharacter = (uint8 *)malloc(TABLE_SIZE * sizeof(uint8));
inputBitCount = 0; // Number of bits in input bit buffer
inputBitBuffer = 0L;
}
LZWDecoder::~LZWDecoder() {
free(decodeStack);
free(prefixCode);
free(appendCharacter);
}
/**
* Adjust the number of bits used to store codes to the value passed in.
*/
int LZWDecoder::setBits(int32 value) {
if (value == MAXBITS)
return true;
BITS = value;
MAX_VALUE = (1 << BITS) - 1;
MAX_CODE = MAX_VALUE - 1;
return false;
}
/**
* Return the string that the code taken from the input buffer
* represents. The string is returned as a stack, i.e. the characters are
* in reverse order.
*/
uint8 *LZWDecoder::decodeString(uint8 *buffer, uint32 code) {
uint32 i;
for (i = 0; code > 255;) {
*buffer++ = appendCharacter[code];
code = prefixCode[code];
if (i++ >= 4000) {
error("lzw: error in code expansion");
}
}
*buffer = code;
return buffer;
}
/**
* Return the next code from the input buffer.
*/
uint32 LZWDecoder::inputCode(uint8 **input) {
uint32 r;
while (inputBitCount <= 24) {
inputBitBuffer |= (uint32) * (*input)++ << inputBitCount;
inputBitCount += 8;
}
r = (inputBitBuffer & 0x7FFF) % (1 << BITS);
inputBitBuffer >>= BITS;
inputBitCount -= BITS;
return r;
}
/**
* Uncompress the data contained in the input buffer and store
* the result in the output buffer. The fileLength parameter says how
* many bytes to uncompress. The compression itself is a form of LZW that
* adjusts the number of bits that it represents its codes in as it fills
* up the available codes. Two codes have special meaning:
*
* code 256 = start over
* code 257 = end of data
*/
void LZWDecoder::lzwExpand(uint8 *in, uint8 *out, int32 len) {
int32 c, lzwnext, lzwnew, lzwold;
uint8 *s, *end;
LZWDecoder d;
setBits(START_BITS); // Starts at 9-bits
lzwnext = 257; // Next available code to define
end = (uint8 *)(out + (uint32)len);
lzwold = inputCode(&in); // Read in the first code
c = lzwold;
lzwnew = inputCode(&in);
while ((out < end) && (lzwnew != 0x101)) {
if (lzwnew == 0x100) {
// Code to "start over"
lzwnext = 258;
setBits(START_BITS);
lzwold = inputCode(&in);
c = lzwold;
*out++ = (char)c;
lzwnew = inputCode(&in);
} else {
if (lzwnew >= lzwnext) {
// Handles special LZW scenario
*decodeStack = c;
s = decodeString(decodeStack + 1, lzwold);
} else
s = decodeString(decodeStack, lzwnew);
// Reverse order of decoded string and
// store in out buffer
c = *s;
while (s >= decodeStack)
*out++ = *s--;
if (lzwnext > MAX_CODE)
setBits(BITS + 1);
prefixCode[lzwnext] = lzwold;
appendCharacter[lzwnext] = c;
lzwnext++;
lzwold = lzwnew;
lzwnew = inputCode(&in);
}
}
}
void lzwExpand(uint8 *in, uint8 *out, int32 len) {
LZWDecoder d;
d.lzwExpand(in, out, len);
}
} // End of namespace Agi
|
