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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 "common/debug.h"
#include "common/endian.h"
#include "common/util.h"
#include "access/decompress.h"
namespace Access {
void LzwDecompressor::decompress(byte *source, byte *dest) {
_source = source;
byte litByte = 0;
uint16 oldCode = 0;
uint16 copyLength, maxCodeValue, code, nextCode, lastCode;
byte *copyBuf = new byte[8192];
struct { uint16 code; byte value; } codeTable[8192];
memset(codeTable, 0, sizeof(codeTable));
_codeLength = 9;
nextCode = 258;
maxCodeValue = 512;
copyLength = 0;
_sourceBitsLeft = 8;
while (1) {
code = getCode();
if (code == 257)
break;
if (code == 256) {
_codeLength = 9;
nextCode = 258;
maxCodeValue = 512;
lastCode = getCode();
oldCode = lastCode;
litByte = lastCode;
*dest++ = litByte;
} else {
lastCode = code;
if (code >= nextCode) {
lastCode = oldCode;
copyBuf[copyLength++] = litByte;
}
while (lastCode > 255) {
copyBuf[copyLength++] = codeTable[lastCode].value;
lastCode = codeTable[lastCode].code;
}
litByte = lastCode;
copyBuf[copyLength++] = lastCode;
while (copyLength > 0)
*dest++ = copyBuf[--copyLength];
codeTable[nextCode].value = lastCode;
codeTable[nextCode].code = oldCode;
nextCode++;
oldCode = code;
if (nextCode >= maxCodeValue && _codeLength <= 12) {
_codeLength++;
maxCodeValue <<= 1;
}
}
}
delete[] copyBuf;
}
uint16 LzwDecompressor::getCode() {
const byte bitMasks[9] = {
0x00, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0x0FF
};
byte resultBitsLeft = _codeLength;
byte resultBitsPos = 0;
uint16 result = 0;
byte currentByte = *_source;
byte currentBits = 0;
// Get bits of current byte
while (resultBitsLeft) {
if (resultBitsLeft < _sourceBitsLeft) {
// we need less than we have left
currentBits = (currentByte >> (8 - _sourceBitsLeft)) & bitMasks[resultBitsLeft];
result |= (currentBits << resultBitsPos);
_sourceBitsLeft -= resultBitsLeft;
resultBitsLeft = 0;
} else {
// we need as much as we have left or more
resultBitsLeft -= _sourceBitsLeft;
currentBits = currentByte >> (8 - _sourceBitsLeft);
result |= (currentBits << resultBitsPos);
resultBitsPos += _sourceBitsLeft;
// Go to next byte
_source++;
_sourceBitsLeft = 8;
if (resultBitsLeft) {
currentByte = *_source;
}
}
}
return result;
}
uint32 decompressDBE(byte *source, byte **dest) {
uint32 destSize = READ_LE_UINT32(source + 4);
*dest = new byte[destSize];
debug(1, "decompressDBE() destSize = %d", destSize);
LzwDecompressor dec;
dec.decompress(source + 16, *dest);
debug(1, "decompressDBE() ok");
return destSize;
}
} // End of namespace Access
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