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
|
/* 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.
*
*/
#ifndef CINE_UNPACK_H
#define CINE_UNPACK_H
#include "common/scummsys.h"
namespace Cine {
/**
* A LZ77 style decompressor for Delphine's data files
* used in at least Future Wars and Operation Stealth.
* @note Works backwards in the source and destination buffers.
* @warning Having the source and destination in the same buffer when unpacking can cause errors!
*/
class CineUnpacker {
public:
/**
* Unpacks packed data from the source buffer to the destination buffer.
* @note You may call this on already unpacked data but then source length must be equal to destination length.
* @warning The source and destination should not point to the same buffer. If they do, errors may occur!
* @param src Pointer to the source buffer.
* @param srcLen Length of the source buffer.
* @param dst Pointer to the destination buffer.
* @param dstLen Length of the destination buffer.
* @return True if no errors were detected in the source data and unpacking was successful, otherwise false.
*/
bool unpack(const byte *src, uint srcLen, byte *dst, uint dstLen);
private:
/**
* Reads an unsigned big endian 32-bit integer from the source stream and goes backwards 4 bytes.
* @return If the operation is valid, an unsigned big endian 32-bit integer read from the source stream.
* @return If the operation is invalid, zero.
* @note Sets internal error state if the read operation would be out of source bounds.
*/
uint32 readSource();
/**
* Shifts the current internal 32-bit chunk to the right by one.
* Puts input carry into internal chunk's topmost (i.e. leftmost) bit.
* @return The least significant bit that was shifted out from the chunk.
*/
uint rcr(bool inputCarry);
/**
* Get the next bit from the source stream.
* @note Changes the bit position in the source stream.
* @return The next bit from the source stream.
*/
uint nextBit();
/**
* Get bits from the source stream.
* @note Changes the bit position in the source stream.
* @param numBits Number of bits to read from the source stream.
* @return Integer value consisting of the bits read from the source stream (In range [0, (2 ** numBits) - 1]).
* @return Later the bit was read from the source, the less significant it is in the return value.
*/
uint getBits(uint numBits);
/**
* Copy raw bytes from the input stream and write them to the destination stream.
* This is used when no adequately long match is found in the sliding window.
* @note Sets internal error state if the operation would be out of bounds.
* @param numBytes Amount of bytes to copy from the input stream
*/
void unpackRawBytes(uint numBytes);
/**
* Copy bytes from the sliding window in the destination buffer.
* This is used when a match of two bytes or longer is found.
* @note Sets internal error state if the operation would be out of bounds.
* @param offset Offset in the sliding window
* @param numBytes Amount of bytes to copy
*/
void copyRelocatedBytes(uint offset, uint numBytes);
private:
uint32 _crc; ///< Error-detecting code (This should be zero after successful unpacking)
uint32 _chunk32b; ///< The current internal 32-bit chunk of source data
byte *_dst; ///< Pointer to the current position in the destination buffer
const byte *_src; ///< Pointer to the current position in the source buffer
// These are used for detecting errors (e.g. out of bounds issues) during unpacking
bool _error; ///< Did an error occur during unpacking?
const byte *_srcBegin; ///< Source buffer's beginning
const byte *_srcEnd; ///< Source buffer's end
byte *_dstBegin; ///< Destination buffer's beginning
byte *_dstEnd; ///< Destination buffer's end
};
} // End of namespace Cine
#endif
|
