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engines/startrek/lzss.cpp

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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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ * $URL: https://scummvm-startrek.googlecode.com/svn/trunk/lzss.cpp $
+ * $Id: lzss.cpp 18 2010-12-17 01:22:54Z clone2727 $
+ *
+ */
+
+#include "common/textconsole.h"
+#include "common/memstream.h"
+#include "common/util.h"
+
+#include "startrek/lzss.h"
+
+namespace StarTrek {
+
+Common::SeekableReadStream *decodeLZSS(Common::SeekableReadStream *indata, uint32 uncompressedSize) {
+	uint32 N = 0x1000; /* History buffer size */
+	byte *histbuff = new byte[N](); /* History buffer */
+	uint32 outstreampos = 0;
+	uint32 bufpos = 0;
+	byte *outLzssBufData = (byte *)malloc(uncompressedSize);
+
+	for (;;) {
+		byte flagbyte = indata->readByte();
+
+		if (indata->eos())
+			break;
+
+		for (byte i = 0; i < 8; i++) {
+			if ((flagbyte & (1 << i)) == 0) {
+				uint32 offsetlen = indata->readUint16LE();
+
+				if (indata->eos())
+					break;
+
+				uint32 length = (offsetlen & 0xF) + 3;
+				uint32 offset = (bufpos - (offsetlen >> 4)) & (N - 1);
+				for (uint32 j = 0; j < length; j++) {
+					byte tempa = histbuff[(offset + j) & (N - 1)];
+					outLzssBufData[outstreampos++] = tempa;
+					histbuff[bufpos] = tempa;
+					bufpos = (bufpos + 1) & (N - 1);
+				}
+			} else {
+				byte tempa = indata->readByte();
+
+				if (indata->eos())
+					break;
+
+				outLzssBufData[outstreampos++] = tempa;
+				histbuff[bufpos] = tempa;
+				bufpos = (bufpos + 1) & (N - 1);
+			}
+		}
+	}
+
+	delete[] histbuff;
+
+	if (outstreampos != uncompressedSize)
+		error("Size mismatch in LZSS decompression; expected %d bytes, got %d bytes", uncompressedSize, outstreampos);
+
+	return new Common::MemoryReadStream(outLzssBufData, uncompressedSize, DisposeAfterUse::YES);
+}
+
+} // End of namespace StarTrek
+