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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/utility/lzss_read_stream.h"
namespace ZVision {
LzssReadStream::LzssReadStream(Common::SeekableReadStream *source)
: _source(source),
// It's convention to set the starting cursor position to blockSize - 16
_windowCursor(0x0FEE),
_eosFlag(false) {
// Clear the window to null
memset(_window, 0, BLOCK_SIZE);
}
uint32 LzssReadStream::decompressBytes(byte *destination, uint32 numberOfBytes) {
uint32 destinationCursor = 0;
while (destinationCursor < numberOfBytes) {
byte flagbyte = _source->readByte();
if (_source->eos())
break;
uint mask = 1;
for (int i = 0; i < 8; ++i) {
if ((flagbyte & mask) == mask) {
byte data = _source->readByte();
if (_source->eos()) {
return destinationCursor;
}
_window[_windowCursor] = data;
destination[destinationCursor++] = data;
// Increment and wrap the window cursor
_windowCursor = (_windowCursor + 1) & 0xFFF;
} else {
byte low = _source->readByte();
if (_source->eos()) {
return destinationCursor;
}
byte high = _source->readByte();
if (_source->eos()) {
return destinationCursor;
}
uint16 length = (high & 0xF) + 2;
uint16 offset = low | ((high & 0xF0) << 4);
for (int j = 0; j <= length; ++j) {
byte temp = _window[(offset + j) & 0xFFF];
_window[_windowCursor] = temp;
destination[destinationCursor++] = temp;
_windowCursor = (_windowCursor + 1) & 0xFFF;
}
}
mask = mask << 1;
}
}
return destinationCursor;
}
bool LzssReadStream::eos() const {
return _eosFlag;
}
uint32 LzssReadStream::read(void *dataPtr, uint32 dataSize) {
uint32 bytesRead = decompressBytes(static_cast<byte *>(dataPtr), dataSize);
if (bytesRead < dataSize) {
// Flag that we're at EOS
_eosFlag = true;
}
return dataSize;
}
} // End of namespace ZVision
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