    /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
    /*
     * This file is part of the LibreOffice project.
     *
     * This Source Code Form is subject to the terms of the Mozilla Public
     * License, v. 2.0. If a copy of the MPL was not distributed with this
     * file, You can obtain one at http://mozilla.org/MPL/2.0/.
     *
     * This file incorporates work covered by the following license notice:
     *
     *   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 .
     */

    #include "lzwdecom.hxx"
    #include <sal/log.hxx>
    #include <tools/stream.hxx>
    #include <algorithm>
    #include <set>

    LZWDecompressor::LZWDecompressor()
        : pIStream(nullptr)
        , nTableSize(0)
        , bEOIFound(false)
        , bInvert(false)
        , bFirst(true)
        , nOldCode(0)
        , pOutBufData(nullptr)
        , nOutBufDataLen(0)
        , nInputBitsBuf(0)
        , nInputBitsBufSize(0)
    {
        for (sal_uInt16 i=0; i<MAX_TABLE_SIZE; i++)
        {
            pTable[i].nPrevCode=0;
            pTable[i].nDataCount=1;
            pTable[i].nData=static_cast<sal_uInt8>(i);
        }
    }

    LZWDecompressor::~LZWDecompressor()
    {
    }

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

        nTableSize=258;

        bEOIFound=false;

        nOutBufDataLen=0;

        pIStream->ReadUChar( nInputBitsBuf );

        nInputBitsBufSize=8;

        if ( bFirst )
        {
            bInvert = nInputBitsBuf == 1;
            bFirst = 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==nullptr) return 0;

        nCount=0;
        for (;;) {

            if (pIStream->GetError()) break;

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

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

            if (bEOIFound) 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->ReadUChar( 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)
    {
        if (nTableSize >= MAX_TABLE_SIZE)
        {
            //It might be possible to force emit a 256 to flush the buffer and try
            //to continue later?
            SAL_WARN("filter.tiff", "Too much data at scanline");
            bEOIFound = true;
            return;
        }

        unsigned char aSeenIndexes[MAX_TABLE_SIZE] = {0};
        while (pTable[nCodeFirstData].nDataCount>1)
        {
            if (aSeenIndexes[nCodeFirstData])
            {
                SAL_WARN("filter.tiff", "Loop in chain");
                bEOIFound = true;
                return;
            }
            aSeenIndexes[nCodeFirstData] = 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=true;
            }
        }
        else if (nCode<nTableSize)
            AddToTable(nOldCode,nCode);
        else if (nCode==nTableSize)
            AddToTable(nOldCode,nOldCode);
        else
        {
            bEOIFound=true;
        }

        if (bEOIFound)
            return;

        nOldCode=nCode;

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

    /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

↑ V730 Not all members of a class are initialized inside the constructor. Consider inspecting: pOutBuf.