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/* 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.
*
*/
#include "common/scummsys.h"
#include "zvision/lzss_read_stream.h"
namespace ZVision {
LzssReadStream::LzssReadStream(Common::SeekableReadStream *source, bool stream, uint32 decompressedSize)
: _source(source),
// It's convention to set the starting cursor position to blockSize - 16
_windowCursor(0x0FEE),
_readCursor(0),
_eosFlag(false) {
// Clear the window to null
memset(_window, 0, blockSize);
// Reserve space in the destination buffer
// TODO: Make a better guess
if (decompressedSize == npos) {
decompressedSize = source->size();
}
_destination.reserve(decompressedSize);
if (stream)
decompressBytes(blockSize);
else
decompressAll();
}
void LzssReadStream::decompressBytes(uint32 numberOfBytes) {
uint32 bytesRead = 0;
while (!_source->eos() && bytesRead <= numberOfBytes) {
byte flagbyte = _source->readByte();
if (_source->eos())
break;
byte mask = 1;
for (uint32 i = 0; i < 8; i++) {
if ((flagbyte & mask) == mask)
{
byte data = _source->readByte();
bytesRead++;
if (_source->eos())
break;
_window[_windowCursor] = data;
_destination.push_back(data);
// Increment and wrap the window cursor
_windowCursor = (_windowCursor + 1) & 0xFFF;
}
else
{
byte low = _source->readByte();
bytesRead++;
if (_source->eos())
break;
byte high = _source->readByte();
bytesRead++;
if (_source->eos())
break;
uint16 length = (high & 0xF) + 2;
uint16 offset = low | ((high & 0xF0)<<4);
for(byte j = 0; j <= length; j++)
{
byte temp = _window[(offset + j) & 0xFFF];
_window[_windowCursor] = temp;
_destination.push_back(temp);
_windowCursor = (_windowCursor + 1) & 0xFFF;
}
};
mask = mask << 1;
}
}
}
void LzssReadStream::decompressAll() {
decompressBytes(_source->size());
}
bool LzssReadStream::eos() const {
return _eosFlag;
}
uint32 LzssReadStream::read(void *dataPtr, uint32 dataSize) {
// Check if there are enough bytes available
// If not, keep decompressing until we have enough bytes or until we reach EOS
while (dataSize > _destination.size() - _readCursor) {
// Check if we can read any more data from source
if (_source->eos()) {
// Shorten the dataSize to what we have left and flag that we're at EOS
dataSize = _destination.size() - _readCursor;
_eosFlag = true;
break;
}
decompressBytes(blockSize);
}
if (dataSize > 0) {
memcpy(dataPtr, _destination.begin() + _readCursor, dataSize);
_readCursor += dataSize;
}
return dataSize;
}
uint32 LzssReadStream::currentSize() const {
return _destination.size();
}
} // End of namespace ZVision
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