ZVISION: Create class for decompressing and reading LZSS

2 files changed, 209 insertions, 0 deletions

diff --git a/engines/zvision/lzss_read_stream.cpp b/engines/zvision/lzss_read_stream.cpp
new file mode 100644
index 0000000000..69b49c596c
--- /dev/null
+++ b/engines/zvision/lzss_read_stream.cpp
@@ -0,0 +1,134 @@
+/* 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) {
+	// 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();
+		byte mask = 1;
+
+		for (uint32 i = 0; i < 8; i++) {
+			if (!_source->eos()) {
+				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 {
+	// Make sure that we've read all of the source
+	return _readCursor >= _destination.size() && _source->eos();
+}
+
+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()) {
+			dataSize = _destination.size() - _readCursor;
+			break;
+		}
+
+		decompressBytes(blockSize);
+	}
+
+	memcpy(dataPtr, _destination.begin() + _readCursor, dataSize);
+	_readCursor += dataSize;
+
+	return dataSize;
+}
+
+uint32 LzssReadStream::currentSize() const {
+	return _destination.size();
+}
+
+} // End of namespace ZVision
diff --git a/engines/zvision/lzss_read_stream.h b/engines/zvision/lzss_read_stream.h
new file mode 100644
index 0000000000..7e6511a5a9
--- /dev/null
+++ b/engines/zvision/lzss_read_stream.h
@@ -0,0 +1,75 @@
+/* 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.
+*
+*/
+
+#ifndef ZVISION_LZSS_STREAM_H
+#define ZVISION_LZSS_STREAM_H
+
+#include "common/types.h"
+#include "common/stream.h"
+#include "common/memstream.h"
+#include "common/array.h"
+
+namespace ZVision {
+
+class LzssReadStream : public Common::ReadStream {
+public:
+	/**
+	 * A class that decompresses LZSS data and implements ReadStream for easy access 
+	 * to the decompiled data. It can either decompress all the data in the beginning 
+	 * or decompress as needed by read().
+	 *
+	 * @param source              The source data
+	 * @param stream			  Decompress the data as needed (true) or all at once (false)
+	 * @param decompressedSize    The size of the decompressed data. If npos, the class will choose a size and grow as needed
+	 */
+	LzssReadStream(Common::SeekableReadStream *source, bool stream = true, uint32 decompressedSize = npos);
+
+public:
+	static const uint32 npos = 0xFFFFFFFFu;
+	static const uint16 blockSize = 0x1000u;
+
+private:
+	Common::SeekableReadStream *_source;
+	Common::Array<char> _destination;
+	char _window[blockSize];
+	uint16 _windowCursor;
+	uint32 _readCursor;
+
+public:
+	bool eos() const;
+	uint32 read(void *dataPtr, uint32 dataSize);
+	uint32 currentSize() const;
+
+private:
+	/**
+	 * Decompress the next <numberOfBytes> from the source stream. Or until EOS
+	 *
+	 * @param numberOfBytes    How many bytes to decompress. This is a count of source bytes, not destination bytes
+	 */
+	void decompressBytes(uint32 numberOfBytes);
+	/** Decompress all of the source stream. */
+	void decompressAll();
+};
+
+}
+
+#endif