mirror of
https://github.com/libretro/scummvm.git
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151 lines
3.6 KiB
C++
151 lines
3.6 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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*
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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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*
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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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*/
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#include "common/debug.h"
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#include "common/endian.h"
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#include "common/util.h"
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#include "access/decompress.h"
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namespace Access {
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void LzwDecompressor::decompress(byte *source, byte *dest) {
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_source = source;
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byte litByte = 0;
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uint16 oldCode = 0;
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uint16 copyLength, maxCodeValue, code, nextCode, lastCode;
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byte *copyBuf = new byte[8192];
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struct { uint16 code; byte value; } codeTable[8192];
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memset(codeTable, 0, sizeof(codeTable));
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_codeLength = 9;
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nextCode = 258;
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maxCodeValue = 512;
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copyLength = 0;
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_sourceBitsLeft = 8;
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while (1) {
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code = getCode();
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if (code == 257)
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break;
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if (code == 256) {
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_codeLength = 9;
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nextCode = 258;
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maxCodeValue = 512;
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lastCode = getCode();
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oldCode = lastCode;
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litByte = lastCode;
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*dest++ = litByte;
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} else {
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lastCode = code;
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if (code >= nextCode) {
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lastCode = oldCode;
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copyBuf[copyLength++] = litByte;
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}
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while (lastCode > 255) {
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copyBuf[copyLength++] = codeTable[lastCode].value;
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lastCode = codeTable[lastCode].code;
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}
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litByte = lastCode;
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copyBuf[copyLength++] = lastCode;
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while (copyLength > 0)
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*dest++ = copyBuf[--copyLength];
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codeTable[nextCode].value = lastCode;
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codeTable[nextCode].code = oldCode;
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nextCode++;
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oldCode = code;
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if (nextCode >= maxCodeValue && _codeLength <= 12) {
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_codeLength++;
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maxCodeValue <<= 1;
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}
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}
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}
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delete[] copyBuf;
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}
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uint16 LzwDecompressor::getCode() {
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const byte bitMasks[9] = {
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0x00, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0x0FF
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};
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byte resultBitsLeft = _codeLength;
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byte resultBitsPos = 0;
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uint16 result = 0;
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byte currentByte = *_source;
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byte currentBits = 0;
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// Get bits of current byte
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while (resultBitsLeft) {
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if (resultBitsLeft < _sourceBitsLeft) {
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// we need less than we have left
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currentBits = (currentByte >> (8 - _sourceBitsLeft)) & bitMasks[resultBitsLeft];
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result |= (currentBits << resultBitsPos);
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_sourceBitsLeft -= resultBitsLeft;
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resultBitsLeft = 0;
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} else {
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// we need as much as we have left or more
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resultBitsLeft -= _sourceBitsLeft;
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currentBits = currentByte >> (8 - _sourceBitsLeft);
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result |= (currentBits << resultBitsPos);
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resultBitsPos += _sourceBitsLeft;
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// Go to next byte
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_source++;
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_sourceBitsLeft = 8;
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if (resultBitsLeft) {
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currentByte = *_source;
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}
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}
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}
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return result;
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}
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uint32 decompressDBE(byte *source, byte **dest) {
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uint32 destSize = READ_LE_UINT32(source + 4);
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*dest = new byte[destSize];
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debug(1, "decompressDBE() destSize = %d", destSize);
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LzwDecompressor dec;
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dec.decompress(source + 16, *dest);
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debug(1, "decompressDBE() ok");
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return destSize;
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}
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} // End of namespace Access
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