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
|
/* 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.
*
* $URL$
* $Id$
*
*/
#include "common/endian.h"
#include "cine/unpack.h"
namespace Cine {
uint32 CineUnpacker::readSource() {
if (_src < _srcBegin || _src + 4 > _srcEnd) {
_error = true;
return 0; // The source pointer is out of bounds, returning a default value
}
uint32 value = READ_BE_UINT32(_src);
_src -= 4;
return value;
}
uint CineUnpacker::rcr(bool inputCarry) {
uint outputCarry = (_chunk32b & 1);
_chunk32b >>= 1;
if (inputCarry) {
_chunk32b |= 0x80000000;
}
return outputCarry;
}
uint CineUnpacker::nextBit() {
uint carry = rcr(false);
// Normally if the chunk becomes zero then the carry is one as
// the end of chunk marker is always the last to be shifted out.
if (_chunk32b == 0) {
_chunk32b = readSource();
_crc ^= _chunk32b;
carry = rcr(true); // Put the end of chunk marker in the most significant bit
}
return carry;
}
uint CineUnpacker::getBits(uint numBits) {
uint c = 0;
while (numBits--) {
c <<= 1;
c |= nextBit();
}
return c;
}
void CineUnpacker::unpackRawBytes(uint numBytes) {
if (_dst >= _dstEnd || _dst - numBytes + 1 < _dstBegin) {
_error = true;
return; // Destination pointer is out of bounds for this operation
}
while (numBytes--) {
*_dst = (byte)getBits(8);
--_dst;
}
}
void CineUnpacker::copyRelocatedBytes(uint offset, uint numBytes) {
if (_dst + offset >= _dstEnd || _dst - numBytes + 1 < _dstBegin) {
_error = true;
return; // Destination pointer is out of bounds for this operation
}
while (numBytes--) {
*_dst = *(_dst + offset);
--_dst;
}
}
bool CineUnpacker::unpack(const byte *src, uint srcLen, byte *dst, uint dstLen) {
// Initialize variables used for detecting errors during unpacking
_error = false;
_srcBegin = src;
_srcEnd = src + srcLen;
_dstBegin = dst;
_dstEnd = dst + dstLen;
// Initialize other variables
_src = _srcBegin + srcLen - 4;
uint32 unpackedLength = readSource(); // Unpacked length in bytes
_dst = _dstBegin + unpackedLength - 1;
_crc = readSource();
_chunk32b = readSource();
_crc ^= _chunk32b;
while (_dst >= _dstBegin && !_error) {
/*
Bits => Action:
0 0 => unpackRawBytes(3 bits + 1) i.e. unpackRawBytes(1..9)
1 1 1 => unpackRawBytes(8 bits + 9) i.e. unpackRawBytes(9..264)
0 1 => copyRelocatedBytes(8 bits, 2) i.e. copyRelocatedBytes(0..255, 2)
1 0 0 => copyRelocatedBytes(9 bits, 3) i.e. copyRelocatedBytes(0..511, 3)
1 0 1 => copyRelocatedBytes(10 bits, 4) i.e. copyRelocatedBytes(0..1023, 4)
1 1 0 => copyRelocatedBytes(12 bits, 8 bits + 1) i.e. copyRelocatedBytes(0..4095, 1..256)
*/
if (!nextBit()) { // 0...
if (!nextBit()) { // 0 0
uint numBytes = getBits(3) + 1;
unpackRawBytes(numBytes);
} else { // 0 1
uint numBytes = 2;
uint offset = getBits(8);
copyRelocatedBytes(offset, numBytes);
}
} else { // 1...
uint c = getBits(2);
if (c == 3) { // 1 1 1
uint numBytes = getBits(8) + 9;
unpackRawBytes(numBytes);
} else if (c < 2) { // 1 0 x
uint numBytes = c + 3;
uint offset = getBits(c + 9);
copyRelocatedBytes(offset, numBytes);
} else { // 1 1 0
uint numBytes = getBits(8) + 1;
uint offset = getBits(12);
copyRelocatedBytes(offset, numBytes);
}
}
}
return !_error && (_crc == 0);
}
} // End of namespace Cine
|
