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https://github.com/scummvm/scummvm.git
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102 lines
2.8 KiB
C++
102 lines
2.8 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 modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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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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*
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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, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "common/scummsys.h"
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#include "zvision/file/lzss_read_stream.h"
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namespace ZVision {
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LzssReadStream::LzssReadStream(Common::SeekableReadStream *source)
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: _source(source),
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// It's convention to set the starting cursor position to blockSize - 16
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_windowCursor(0x0FEE),
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_eosFlag(false) {
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// All values up to _windowCursor inits by 0x20
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memset(_window, 0x20, _windowCursor);
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memset(_window + _windowCursor, 0, BLOCK_SIZE - _windowCursor);
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}
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uint32 LzssReadStream::decompressBytes(byte *destination, uint32 numberOfBytes) {
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uint32 destinationCursor = 0;
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while (destinationCursor < numberOfBytes) {
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byte flagbyte = _source->readByte();
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if (_source->eos())
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break;
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uint mask = 1;
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for (int i = 0; i < 8; ++i) {
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if ((flagbyte & mask) == mask) {
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byte data = _source->readByte();
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if (_source->eos()) {
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return destinationCursor;
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}
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_window[_windowCursor] = data;
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destination[destinationCursor++] = data;
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// Increment and wrap the window cursor
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_windowCursor = (_windowCursor + 1) & 0xFFF;
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} else {
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byte low = _source->readByte();
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if (_source->eos()) {
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return destinationCursor;
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}
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byte high = _source->readByte();
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if (_source->eos()) {
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return destinationCursor;
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}
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uint16 length = (high & 0xF) + 2;
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uint16 offset = low | ((high & 0xF0) << 4);
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for (int j = 0; j <= length; ++j) {
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byte temp = _window[(offset + j) & 0xFFF];
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_window[_windowCursor] = temp;
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destination[destinationCursor++] = temp;
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_windowCursor = (_windowCursor + 1) & 0xFFF;
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}
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}
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mask = mask << 1;
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}
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}
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return destinationCursor;
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}
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bool LzssReadStream::eos() const {
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return _eosFlag;
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}
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uint32 LzssReadStream::read(void *dataPtr, uint32 dataSize) {
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uint32 bytesRead = decompressBytes(static_cast<byte *>(dataPtr), dataSize);
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if (bytesRead < dataSize) {
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// Flag that we're at EOS
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_eosFlag = true;
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}
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return dataSize;
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}
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} // End of namespace ZVision
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