diff options
Diffstat (limited to 'engines/groovie/lzss.cpp')
-rw-r--r-- | engines/groovie/lzss.cpp | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/engines/groovie/lzss.cpp b/engines/groovie/lzss.cpp new file mode 100644 index 0000000000..750625d70d --- /dev/null +++ b/engines/groovie/lzss.cpp @@ -0,0 +1,99 @@ +/* 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. + * + * $URL$ + * $Id$ + * + */ + +#include "groovie/lzss.h" + +#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 */ + memset(histbuff, 0, N); + 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; +} |