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118 lines
4.6 KiB
C++
118 lines
4.6 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* $URL$
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* $Id$
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*
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*/
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#ifndef CINE_UNPACK_H
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#define CINE_UNPACK_H
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#include "common/scummsys.h"
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namespace Cine {
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/**
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* A LZ77 style decompressor for Delphine's data files
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* used in at least Future Wars and Operation Stealth.
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* @note Works backwards in the source and destination buffers.
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* @warning Having the source and destination in the same buffer when unpacking can cause errors!
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*/
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class CineUnpacker {
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public:
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/**
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* Unpacks packed data from the source buffer to the destination buffer.
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* @note You may call this on already unpacked data but then source length must be equal to destination length.
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* @warning The source and destination should not point to the same buffer. If they do, errors may occur!
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* @param src Pointer to the source buffer.
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* @param srcLen Length of the source buffer.
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* @param dst Pointer to the destination buffer.
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* @param dstLen Length of the destination buffer.
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* @return True if no errors were detected in the source data and unpacking was successful, otherwise false.
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*/
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bool unpack(const byte *src, uint srcLen, byte *dst, uint dstLen);
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private:
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/**
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* Reads an unsigned big endian 32-bit integer from the source stream and goes backwards 4 bytes.
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* @return If the operation is valid, an unsigned big endian 32-bit integer read from the source stream.
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* @return If the operation is invalid, zero.
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* @note Sets internal error state if the read operation would be out of source bounds.
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*/
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uint32 readSource();
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/**
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* Shifts the current internal 32-bit chunk to the right by one.
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* Puts input carry into internal chunk's topmost (i.e. leftmost) bit.
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* @return The least significant bit that was shifted out from the chunk.
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*/
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uint rcr(bool inputCarry);
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/**
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* Get the next bit from the source stream.
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* @note Changes the bit position in the source stream.
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* @return The next bit from the source stream.
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*/
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uint nextBit();
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/**
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* Get bits from the source stream.
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* @note Changes the bit position in the source stream.
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* @param numBits Number of bits to read from the source stream.
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* @return Integer value consisting of the bits read from the source stream (In range [0, (2 ** numBits) - 1]).
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* @return Later the bit was read from the source, the less significant it is in the return value.
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*/
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uint getBits(uint numBits);
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/**
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* Copy raw bytes from the input stream and write them to the destination stream.
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* This is used when no adequately long match is found in the sliding window.
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* @note Sets internal error state if the operation would be out of bounds.
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* @param numBytes Amount of bytes to copy from the input stream
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*/
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void unpackRawBytes(uint numBytes);
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/**
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* Copy bytes from the sliding window in the destination buffer.
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* This is used when a match of two bytes or longer is found.
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* @note Sets internal error state if the operation would be out of bounds.
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* @param offset Offset in the sliding window
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* @param numBytes Amount of bytes to copy
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*/
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void copyRelocatedBytes(uint offset, uint numBytes);
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private:
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uint32 _crc; //!< Error-detecting code (This should be zero after successful unpacking)
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uint32 _chunk32b; //!< The current internal 32-bit chunk of source data
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byte *_dst; //!< Pointer to the current position in the destination buffer
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const byte *_src; //!< Pointer to the current position in the source buffer
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// These are used for detecting errors (e.g. out of bounds issues) during unpacking
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bool _error; //!< Did an error occur during unpacking?
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const byte *_srcBegin; //!< Source buffer's beginning
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const byte *_srcEnd; //!< Source buffer's end
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byte *_dstBegin; //!< Destination buffer's beginning
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byte *_dstEnd; //!< Destination buffer's end
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};
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} // End of namespace Cine
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#endif
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