mirror of
https://github.com/libretro/scummvm.git
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135 lines
3.5 KiB
C++
135 lines
3.5 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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*/
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#include "common/scummsys.h"
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#include "zvision/lzss_read_stream.h"
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namespace ZVision {
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LzssReadStream::LzssReadStream(Common::SeekableReadStream *source, bool stream, uint32 decompressedSize)
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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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_readCursor(0) {
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// Clear the window to null
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memset(_window, 0, blockSize);
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// Reserve space in the destination buffer
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// TODO: Make a better guess
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if (decompressedSize == npos) {
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decompressedSize = source->size();
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}
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_destination.reserve(decompressedSize);
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if (stream)
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decompressBytes(blockSize);
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else
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decompressAll();
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}
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void LzssReadStream::decompressBytes(uint32 numberOfBytes) {
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uint32 bytesRead = 0;
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while (!_source->eos() && bytesRead <= 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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byte mask = 1;
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for (uint32 i = 0; i < 8; i++) {
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if ((flagbyte & mask) == mask)
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{
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byte data = _source->readByte();
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bytesRead++;
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if (_source->eos())
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break;
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_window[_windowCursor] = data;
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_destination.push_back(data);
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// Increment and wrap the window cursor
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_windowCursor = (_windowCursor + 1) & 0xFFF;
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}
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else
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{
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byte low = _source->readByte();
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bytesRead++;
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if (_source->eos())
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break;
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byte high = _source->readByte();
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bytesRead++;
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if (_source->eos())
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break;
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uint16 length = (high & 0xF) + 2;
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uint16 offset = low | ((high & 0xF0)<<4);
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for(byte j = 0; j <= length; j++)
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{
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byte temp = _window[(offset + j) & 0xFFF];
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_window[_windowCursor] = temp;
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_destination.push_back(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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}
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void LzssReadStream::decompressAll() {
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decompressBytes(_source->size());
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}
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bool LzssReadStream::eos() const {
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// Make sure that we've read all of the source
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return _readCursor >= _destination.size() && _source->eos();
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}
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uint32 LzssReadStream::read(void *dataPtr, uint32 dataSize) {
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// Check if there are enough bytes available
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// If not, keep decompressing until we have enough bytes or until we reach EOS
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while (dataSize > _destination.size() - _readCursor) {
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// Check if we can read any more data from source
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if (_source->eos()) {
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dataSize = _destination.size() - _readCursor;
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break;
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}
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decompressBytes(blockSize);
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}
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memcpy(dataPtr, _destination.begin() + _readCursor, dataSize);
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_readCursor += dataSize;
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return dataSize;
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}
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uint32 LzssReadStream::currentSize() const {
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return _destination.size();
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}
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} // End of namespace ZVision
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