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https://github.com/libretro/scummvm.git
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100 lines
2.9 KiB
C++
100 lines
2.9 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* $URL$
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* $Id$
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*
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*/
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#include "groovie/lzss.h"
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#define OUT_BUFF_SIZE 131072
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#define COMP_THRESH 3 // Compression not attempted if string to be compressed is less than 3 long
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LzssReadStream::LzssReadStream(Common::ReadStream *indata, uint8 lengthmask, uint8 lengthbits) {
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/*
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TODO: Nasty hack. Make a buffer bigger than I'll ever need... probably.
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What should *really* happen is I should define a whole new type of stream
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that gets lzss decompressed on the fly
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*/
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_outLzssBufData = (uint8 *)malloc(OUT_BUFF_SIZE);
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_size = decodeLZSS(indata, lengthmask, lengthbits);
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_pos = 0;
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}
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LzssReadStream::~LzssReadStream() {
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free(_outLzssBufData);
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}
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uint32 LzssReadStream::decodeLZSS(Common::ReadStream *in, uint8 lengthmask, uint8 lengthbits) {
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uint32 N = 1 << (16 - lengthbits); /* History buffer size */
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byte *histbuff = new byte[N]; /* History buffer */
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memset(histbuff, 0, N);
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uint32 outstreampos = 0;
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uint32 bufpos = 0;
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while (!in->eos()) {
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byte flagbyte = in->readByte();
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for (uint32 i = 1; i <= 8; i++) {
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if (!in->eos()) {
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if ((flagbyte & 1) == 0) {
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uint32 offsetlen = in->readUint16LE();
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if (offsetlen == 0) {
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break;
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}
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uint32 length = (offsetlen & lengthmask) + COMP_THRESH;
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uint32 offset = (bufpos - (offsetlen >> lengthbits)) & (N - 1);
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for (uint32 j = 0; j < length; j++) {
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byte tempa = histbuff[(offset + j) & (N - 1)];
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_outLzssBufData[outstreampos++] = tempa;
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histbuff[bufpos] = tempa;
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bufpos = (bufpos + 1) & (N - 1);
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}
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} else {
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byte tempa = in->readByte();
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if (in->eos()) {
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break;
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}
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_outLzssBufData[outstreampos++] = tempa;
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histbuff[bufpos] = tempa;
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bufpos = (bufpos + 1) & (N - 1);
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}
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flagbyte = flagbyte >> 1;
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}
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}
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}
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delete[] histbuff;
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return outstreampos;
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}
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bool LzssReadStream::eos() const {
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return _pos >= _size;
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}
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uint32 LzssReadStream::read(void *buf, uint32 size) {
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if (size > _size - _pos)
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size = _size - _pos;
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memcpy(buf, &_outLzssBufData[_pos], size);
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_pos += size;
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return size;
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}
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