Initial commit

engines/groovie/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/>.
+ *
+ */
+
+#include "groovie/lzss.h"
+
+namespace Groovie {
+
+#define OUT_BUFF_SIZE 131072
+#define COMP_THRESH 3 // Compression not attempted if string to be compressed is less than 3 long
+
+LzssReadStream::LzssReadStream(Common::ReadStream *indata, uint8 lengthmask, uint8 lengthbits) {
+	/*
+	TODO: Nasty hack. Make a buffer bigger than I'll ever need... probably.
+	What should *really* happen is I should define a whole new type of stream
+	that gets lzss decompressed on the fly
+	*/
+	_outLzssBufData = (uint8 *)malloc(OUT_BUFF_SIZE);
+	_size = decodeLZSS(indata, lengthmask, lengthbits);
+	_pos = 0;
+}
+
+LzssReadStream::~LzssReadStream() {
+	free(_outLzssBufData);
+}
+
+uint32 LzssReadStream::decodeLZSS(Common::ReadStream *in, uint8 lengthmask, uint8 lengthbits) {
+	uint32 N = 1 << (16 - lengthbits); /* History buffer size */
+	byte *histbuff = new byte[N](); /* History buffer */
+	uint32 outstreampos = 0;
+	uint32 bufpos = 0;
+
+	while (!in->eos()) {
+		byte flagbyte = in->readByte();
+		for (uint32 i = 1; i <= 8; i++) {
+			if (!in->eos()) {
+				if ((flagbyte & 1) == 0) {
+					uint32 offsetlen = in->readUint16LE();
+					if (offsetlen == 0) {
+						break;
+					}
+					uint32 length = (offsetlen & lengthmask) + COMP_THRESH;
+					uint32 offset = (bufpos - (offsetlen >> lengthbits)) & (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 = in->readByte();
+					if (in->eos()) {
+						break;
+					}
+					_outLzssBufData[outstreampos++] = tempa;
+					histbuff[bufpos] = tempa;
+					bufpos = (bufpos + 1) & (N - 1);
+				}
+				flagbyte = flagbyte >> 1;
+			}
+		}
+	}
+	delete[] histbuff;
+	return outstreampos;
+}
+
+bool LzssReadStream::eos() const {
+	return _pos >= _size;
+}
+
+uint32 LzssReadStream::read(void *buf, uint32 size) {
+	if (size > _size - _pos)
+		size = _size - _pos;
+
+	memcpy(buf, &_outLzssBufData[_pos], size);
+	_pos += size;
+
+	return size;
+}
+
+} // End of Groovie namespace