diff options
Diffstat (limited to 'engines/zvision/file/lzss_read_stream.cpp')
-rw-r--r-- | engines/zvision/file/lzss_read_stream.cpp | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/engines/zvision/file/lzss_read_stream.cpp b/engines/zvision/file/lzss_read_stream.cpp new file mode 100644 index 0000000000..ca10af7d72 --- /dev/null +++ b/engines/zvision/file/lzss_read_stream.cpp @@ -0,0 +1,103 @@ +/* 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/file/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) { + // All values up to _windowCursor inits by 0x20 + memset(_window, 0x20, _windowCursor); + memset(_window + _windowCursor, 0, BLOCK_SIZE - _windowCursor); +} + +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 |