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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 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 "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 */
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;
}
} // End of Groovie namespace
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