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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() {
if (_src < _srcBegin || _src + 4 > _srcEnd) {
_error = true;
return 0; // The source pointer is out of bounds, returning a default value
}
uint32 value = READ_BE_UINT32(_src);
_src -= 4;
return value;
}
uint CineUnpacker::rcr(bool inputCarry) {
uint outputCarry = (_chunk32b & 1);
_chunk32b >>= 1;
if (inputCarry) {
_chunk32b |= 0x80000000;
}
return outputCarry;
}
uint CineUnpacker::nextBit() {
uint carry = rcr(false);
// Normally if the chunk becomes zero then the carry is one as
// the end of chunk marker is always the last to be shifted out.
if (_chunk32b == 0) {
_chunk32b = readSource();
_crc ^= _chunk32b;
carry = rcr(true); // Put the end of chunk marker in the most significant bit
}
return carry;
}
uint CineUnpacker::getBits(uint numBits) {
uint c = 0;
while (numBits--) {
c <<= 1;
c |= nextBit();
}
return c;
}
void CineUnpacker::unpackRawBytes(uint numBytes) {
if (_dst >= _dstEnd || _dst - numBytes + 1 < _dstBegin) {
_error = true;
return; // Destination pointer is out of bounds for this operation
}
while (numBytes--) {
*_dst = (byte)getBits(8);
--_dst;
}
}
void CineUnpacker::copyRelocatedBytes(uint offset, uint numBytes) {
if (_dst + offset >= _dstEnd || _dst - numBytes + 1 < _dstBegin) {
_error = true;
return; // Destination pointer is out of bounds for this operation
}
while (numBytes--) {
*_dst = *(_dst + offset);
--_dst;
}
}
bool CineUnpacker::unpack(const byte *src, uint srcLen, byte *dst, uint dstLen) {
// Initialize variables used for detecting errors during unpacking
_error = false;
_srcBegin = src;
_srcEnd = src + srcLen;
_dstBegin = dst;
_dstEnd = dst + dstLen;
// Initialize other variables
_src = _srcBegin + srcLen - 4;
uint32 unpackedLength = readSource(); // Unpacked length in bytes
_dst = _dstBegin + unpackedLength - 1;
_crc = readSource();
_chunk32b = readSource();
_crc ^= _chunk32b;
while (_dst >= _dstBegin && !_error) {
/*
Bits => Action:
0 0 => unpackRawBytes(3 bits + 1) i.e. unpackRawBytes(1..8)
1 1 1 => unpackRawBytes(8 bits + 9) i.e. unpackRawBytes(9..264)
0 1 => copyRelocatedBytes(8 bits, 2) i.e. copyRelocatedBytes(0..255, 2)
1 0 0 => copyRelocatedBytes(9 bits, 3) i.e. copyRelocatedBytes(0..511, 3)
1 0 1 => copyRelocatedBytes(10 bits, 4) i.e. copyRelocatedBytes(0..1023, 4)
1 1 0 => copyRelocatedBytes(12 bits, 8 bits + 1) i.e. copyRelocatedBytes(0..4095, 1..256)
*/
if (!nextBit()) { // 0...
if (!nextBit()) { // 0 0
uint numBytes = getBits(3) + 1;
unpackRawBytes(numBytes);
} else { // 0 1
uint numBytes = 2;
uint offset = getBits(8);
copyRelocatedBytes(offset, numBytes);
}
} else { // 1...
uint c = getBits(2);
if (c == 3) { // 1 1 1
uint numBytes = getBits(8) + 9;
unpackRawBytes(numBytes);
} else if (c < 2) { // 1 0 x
uint numBytes = c + 3;
uint offset = getBits(c + 9);
copyRelocatedBytes(offset, numBytes);
} else { // 1 1 0
uint numBytes = getBits(8) + 1;
uint offset = getBits(12);
copyRelocatedBytes(offset, numBytes);
}
}
}
return !_error && (_crc == 0);
}
} // End of namespace Cine
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