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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.
*
* $URL$
* $Id$
*
*/
#include "common/endian.h"
#include "cine/unpack.h"
namespace Cine {
uint32 CineUnpacker::readSource() {
uint32 value = READ_BE_UINT32(_src);
_src -= 4;
return value;
}
int CineUnpacker::rcr(int CF) {
int rCF = (_chk & 1);
_chk >>= 1;
if (CF) {
_chk |= 0x80000000;
}
return rCF;
}
int CineUnpacker::nextBit() {
int CF = rcr(0);
if (_chk == 0) {
_chk = readSource();
_crc ^= _chk;
CF = rcr(1);
}
return CF;
}
uint16 CineUnpacker::getBits(byte numBits) {
uint16 c = 0;
while (numBits--) {
c <<= 1;
c |= nextBit();
}
return c;
}
void CineUnpacker::unpackHelper1(byte numBits, byte addCount) {
uint16 count = getBits(numBits) + addCount + 1;
_datasize -= count;
while (count--) {
*_dst = (byte)getBits(8);
--_dst;
}
}
void CineUnpacker::copyRelocatedBytes(uint16 offset, uint16 numBytes) {
_datasize -= numBytes;
while (numBytes--) {
*_dst = *(_dst + offset);
--_dst;
}
}
bool CineUnpacker::unpack(byte *dst, const byte *src, int srcLen) {
_src = src + srcLen - 4;
_datasize = readSource();
_dst = dst + _datasize - 1;
_crc = readSource();
_chk = readSource();
_crc ^= _chk;
do {
if (!nextBit()) {
if (!nextBit()) {
unpackHelper1(3, 0);
} else {
uint16 numBytes = 2;
uint16 offset = getBits(8);
copyRelocatedBytes(offset, numBytes);
}
} else {
uint16 c = getBits(2);
if (c == 3) {
unpackHelper1(8, 8);
} else if (c < 2) { // c == 0 || c == 1
uint16 numBytes = c + 3;
uint16 offset = getBits(c + 9);
copyRelocatedBytes(offset, numBytes);
} else { // c == 2
uint16 numBytes = getBits(8) + 1;
uint16 offset = getBits(12);
copyRelocatedBytes(offset, numBytes);
}
}
} while (_datasize > 0 && _src >= src - 4);
return _crc == 0;
}
} // End of namespace Cine
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