vcl/source/filter/igif/decode.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  *
   9  * This file incorporates work covered by the following license notice:
  10  *
  11  *   Licensed to the Apache Software Foundation (ASF) under one or more
  12  *   contributor license agreements. See the NOTICE file distributed
  13  *   with this work for additional information regarding copyright
  14  *   ownership. The ASF licenses this file to you under the Apache
  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 #include "decode.hxx"
  21
  22 #include <rtl/alloc.h>
  23
  24 struct GIFLZWTableEntry
  25 {
  26     GIFLZWTableEntry*   pPrev;
  27     GIFLZWTableEntry*   pFirst;
  28     sal_uInt8               nData;
  29 };
  30
  31 GIFLZWDecompressor::GIFLZWDecompressor(sal_uInt8 cDataSize)
  32     : pBlockBuf(nullptr)
  33     , nInputBitsBuf(0)
  34     , nOutBufDataLen(0)
  35     , nInputBitsBufSize(0)
  36     , bEOIFound(false)
  37     , nDataSize(cDataSize)
  38     , nBlockBufSize(0)
  39     , nBlockBufPos(0)
  40 {
  41     nClearCode = 1 << nDataSize;
  42     nEOICode = nClearCode + 1;
  43     nTableSize = nEOICode + 1;
  44     nCodeSize = nDataSize + 1;
  45     nOldCode = 0xffff;
  46     pOutBufData = pOutBuf.data() + 4096;
  47
  48     pTable.reset( new GIFLZWTableEntry[ 4098 ] );
  49
  50     for (sal_uInt16 i = 0; i < nTableSize; ++i)
  51     {
  52         pTable[i].pPrev = nullptr;
  53         pTable[i].pFirst = pTable.get() + i;
  54         pTable[i].nData = (sal_uInt8) i;
  55     }
  56
  57     memset(pTable.get() + nTableSize, 0, sizeof(GIFLZWTableEntry) * (4098 - nTableSize));
  58 }
  59
  60 GIFLZWDecompressor::~GIFLZWDecompressor()
  61 {
  62 }
  63
  64 Scanline GIFLZWDecompressor::DecompressBlock( sal_uInt8* pSrc, sal_uInt8 cBufSize,
  65                                             sal_uLong& rCount, bool& rEOI )
  66 {
  67     sal_uLong   nTargetSize = 4096;
  68     sal_uLong   nCount = 0;
  69     sal_uInt8*  pTarget = static_cast<sal_uInt8*>(rtl_allocateMemory( nTargetSize ));
  70     sal_uInt8*  pTmpTarget = pTarget;
  71
  72     nBlockBufSize = cBufSize;
  73     nBlockBufPos = 0;
  74     pBlockBuf = pSrc;
  75
  76     while( ProcessOneCode() )
  77     {
  78         nCount += nOutBufDataLen;
  79
  80         if( nCount > nTargetSize )
  81         {
  82             sal_uLong   nNewSize = nTargetSize << 1;
  83             sal_uLong   nOffset = pTmpTarget - pTarget;
  84             sal_uInt8*  pTmp = static_cast<sal_uInt8*>(rtl_allocateMemory( nNewSize ));
  85
  86             memcpy( pTmp, pTarget, nTargetSize );
  87             rtl_freeMemory( pTarget );
  88
  89             nTargetSize = nNewSize;
  90             pTmpTarget = ( pTarget = pTmp ) + nOffset;
  91         }
  92
  93         memcpy( pTmpTarget, pOutBufData, nOutBufDataLen );
  94         pTmpTarget += nOutBufDataLen;
  95         pOutBufData += nOutBufDataLen;
  96         nOutBufDataLen = 0;
  97
  98         if ( bEOIFound )
  99             break;
 100     }
 101
 102     rCount = nCount;
 103     rEOI = bEOIFound;
 104
 105     return pTarget;
 106 }
 107
 108 bool GIFLZWDecompressor::AddToTable( sal_uInt16 nPrevCode, sal_uInt16 nCodeFirstData )
 109 {
 110     if( nTableSize < 4096 )
 111     {
 112         GIFLZWTableEntry* pE = pTable.get() + nTableSize;
 113         pE->pPrev = pTable.get() + nPrevCode;
 114         pE->pFirst = pE->pPrev->pFirst;
 115         GIFLZWTableEntry *pEntry = pTable[nCodeFirstData].pFirst;
 116         if (!pEntry)
 117             return false;
 118         pE->nData = pEntry->nData;
 119         nTableSize++;
 120
 121         if ( ( nTableSize == (sal_uInt16) (1 << nCodeSize) ) && ( nTableSize < 4096 ) )
 122             nCodeSize++;
 123     }
 124     return true;
 125 }
 126
 127 bool GIFLZWDecompressor::ProcessOneCode()
 128 {
 129     sal_uInt16              nCode;
 130     bool                bRet = false;
 131     bool                bEndOfBlock = false;
 132
 133     while( nInputBitsBufSize < nCodeSize )
 134     {
 135         if( nBlockBufPos >= nBlockBufSize )
 136         {
 137             bEndOfBlock = true;
 138             break;
 139         }
 140
 141         nInputBitsBuf |= ( (sal_uLong) pBlockBuf[ nBlockBufPos++ ] ) << nInputBitsBufSize;
 142         nInputBitsBufSize += 8;
 143     }
 144
 145     if ( !bEndOfBlock )
 146     {
 147         // fetch code from input buffer
 148         nCode = sal::static_int_cast< sal_uInt16 >(
 149             ( (sal_uInt16) nInputBitsBuf ) & ( ~( 0xffff << nCodeSize ) ));
 150         nInputBitsBuf >>= nCodeSize;
 151         nInputBitsBufSize = nInputBitsBufSize - nCodeSize;
 152
 153         if ( nCode < nClearCode )
 154         {
 155             bool bOk = true;
 156             if ( nOldCode != 0xffff )
 157                 bOk = AddToTable(nOldCode, nCode);
 158             if (!bOk)
 159                 return false;
 160         }
 161         else if ( ( nCode > nEOICode ) && ( nCode <= nTableSize ) )
 162         {
 163             if ( nOldCode != 0xffff )
 164             {
 165                 bool bOk;
 166                 if ( nCode == nTableSize )
 167                     bOk = AddToTable( nOldCode, nOldCode );
 168                 else
 169                     bOk = AddToTable( nOldCode, nCode );
 170                 if (!bOk)
 171                     return false;
 172             }
 173         }
 174         else
 175         {
 176             if ( nCode == nClearCode )
 177             {
 178                 nTableSize = nEOICode + 1;
 179                 nCodeSize = nDataSize + 1;
 180                 nOldCode = 0xffff;
 181                 nOutBufDataLen = 0;
 182             }
 183             else
 184                 bEOIFound = true;
 185
 186             return true;
 187         }
 188
 189         nOldCode = nCode;
 190
 191         if (nCode >= 4096)
 192             return false;
 193
 194         // write character(/-sequence) of code nCode in the output buffer:
 195         GIFLZWTableEntry* pE = pTable.get() + nCode;
 196         do
 197         {
 198             if (pOutBufData == pOutBuf.data()) //can't go back past start
 199                 return false;
 200             nOutBufDataLen++;
 201             *(--pOutBufData) = pE->nData;
 202             pE = pE->pPrev;
 203         }
 204         while( pE );
 205
 206         bRet = true;
 207     }
 208
 209     return bRet;
 210 }
 211
 212 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */