AOO410/main/filter/source/graphicfilter/itiff/lzwdecom.cxx

/**************************************************************
 * 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * 
 *************************************************************/



// MARKER(update_precomp.py): autogen include statement, do not remove
#include "precompiled_filter.hxx"

#include "lzwdecom.hxx"

LZWDecompressor::LZWDecompressor()
{
	sal_uInt16 i;

	pTable=new LZWTableEntry[4096];
	pOutBuf=new sal_uInt8[4096];
	for (i=0; i<4096; i++)
	{
		pTable[i].nPrevCode=0;
		pTable[i].nDataCount=1;
		pTable[i].nData=(sal_uInt8)i;
	}
	pIStream=NULL;
	bFirst = sal_True;
	nOldCode = 0;
}


LZWDecompressor::~LZWDecompressor()
{
	delete[] pOutBuf;
	delete[] pTable;
}


void LZWDecompressor::StartDecompression(SvStream & rIStream)
{
	pIStream=&rIStream;

	nTableSize=258;

	bEOIFound=sal_False;

	nOutBufDataLen=0;

	*pIStream >> nInputBitsBuf;

	nInputBitsBufSize=8;

	if ( bFirst )
	{
		bInvert = nInputBitsBuf == 1;
		bFirst = sal_False;
	}

	if ( bInvert )
		nInputBitsBuf = ( ( nInputBitsBuf & 1 ) << 7 ) | ( ( nInputBitsBuf & 2 ) << 5 ) | ( ( nInputBitsBuf & 4 ) << 3 ) | ( ( nInputBitsBuf & 8 ) << 1 ) | ( ( nInputBitsBuf & 16 ) >> 1 ) | ( ( nInputBitsBuf & 32 ) >> 3 ) | ( ( nInputBitsBuf & 64 ) >> 5 ) | ( (nInputBitsBuf & 128 ) >> 7 );
}


sal_uLong LZWDecompressor::Decompress(sal_uInt8 * pTarget, sal_uLong nMaxCount)
{
	sal_uLong nCount;

	if (pIStream==NULL) return 0;

	nCount=0;
	for (;;) {

		if (pIStream->GetError()) break;

		if (((sal_uLong)nOutBufDataLen)>=nMaxCount) {
			nOutBufDataLen = nOutBufDataLen - (sal_uInt16)nMaxCount;
			nCount+=nMaxCount;
			while (nMaxCount>0) {
				*(pTarget++)=*(pOutBufData++);
				nMaxCount--;
			}
			break;
		}

		nMaxCount-=(sal_uLong)nOutBufDataLen;
		nCount+=nOutBufDataLen;
		while (nOutBufDataLen>0) {
			*(pTarget++)=*(pOutBufData++);
			nOutBufDataLen--;
		}

		if (bEOIFound==sal_True) break;

		DecompressSome();

	}

	return nCount;
}


sal_uInt16 LZWDecompressor::GetNextCode()
{
	sal_uInt16 nBits,nCode;

	if      (nTableSize<511)  nBits=9;
	else if (nTableSize<1023) nBits=10;
	else if (nTableSize<2047) nBits=11;
	else                      nBits=12;

	nCode=0;
	do {
		if (nInputBitsBufSize<=nBits)
		{
			nCode=(nCode<<nInputBitsBufSize) | nInputBitsBuf;
			nBits = nBits - nInputBitsBufSize;
			*pIStream >> nInputBitsBuf;
			if ( bInvert )
				nInputBitsBuf = ( ( nInputBitsBuf & 1 ) << 7 ) | ( ( nInputBitsBuf & 2 ) << 5 ) | ( ( nInputBitsBuf & 4 ) << 3 ) | ( ( nInputBitsBuf & 8 ) << 1 ) | ( ( nInputBitsBuf & 16 ) >> 1 ) | ( ( nInputBitsBuf & 32 ) >> 3 ) | ( ( nInputBitsBuf & 64 ) >> 5 ) | ( (nInputBitsBuf & 128 ) >> 7 );
			nInputBitsBufSize=8;
		}
		else
		{
			nCode=(nCode<<nBits) | (nInputBitsBuf>>(nInputBitsBufSize-nBits));
			nInputBitsBufSize = nInputBitsBufSize - nBits;
			nInputBitsBuf&=0x00ff>>(8-nInputBitsBufSize);
			nBits=0;
		}
	} while (nBits>0);

	return nCode;
}


void LZWDecompressor::AddToTable(sal_uInt16 nPrevCode, sal_uInt16 nCodeFirstData)
{
	while (pTable[nCodeFirstData].nDataCount>1)
		nCodeFirstData=pTable[nCodeFirstData].nPrevCode;

	pTable[nTableSize].nPrevCode=nPrevCode;
	pTable[nTableSize].nDataCount=pTable[nPrevCode].nDataCount+1;
	pTable[nTableSize].nData=pTable[nCodeFirstData].nData;

	nTableSize++;
}


void LZWDecompressor::DecompressSome()
{
	sal_uInt16 i,nCode;

	nCode=GetNextCode();
	if (nCode==256) {
		nTableSize=258;
		nCode=GetNextCode();
		if (nCode==257) { bEOIFound=sal_True; return; }
	}
	else if (nCode<nTableSize) AddToTable(nOldCode,nCode);
	else if (nCode==nTableSize) AddToTable(nOldCode,nOldCode);
	else { bEOIFound=sal_True; return; }

	nOldCode=nCode;

	nOutBufDataLen=pTable[nCode].nDataCount;
	pOutBufData=pOutBuf+nOutBufDataLen;
	for (i=0; i<nOutBufDataLen; i++) {
		*(--pOutBufData)=pTable[nCode].nData;
		nCode=pTable[nCode].nPrevCode;
	}
}