filter/source/graphicfilter/egif/giflzwc.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
  21 #include <tools/stream.hxx>
  22 #include "giflzwc.hxx"
  23 #include <array>
  24
  25
  26 class GIFImageDataOutputStream
  27 {
  28 private:
  29
  30     void        FlushBlockBuf();
  31     inline void FlushBitsBufsFullBytes();
  32
  33     SvStream&   rStream;
  34     std::array<sal_uInt8, 255>
  35                     pBlockBuf;
  36     sal_uInt8       nBlockBufSize;
  37     sal_uInt32      nBitsBuf;
  38     sal_uInt16      nBitsBufSize;
  39
  40 public:
  41
  42                 GIFImageDataOutputStream( SvStream & rGIF, sal_uInt8 nLZWDataSize );
  43                 ~GIFImageDataOutputStream();
  44
  45     inline void WriteBits( sal_uInt16 nCode, sal_uInt16 nCodeLen );
  46 };
  47
  48
  49 inline void GIFImageDataOutputStream::FlushBitsBufsFullBytes()
  50 {
  51     while (nBitsBufSize>=8)
  52     {
  53         if( nBlockBufSize==255 )
  54             FlushBlockBuf();
  55
  56         pBlockBuf[nBlockBufSize++] = static_cast<sal_uInt8>(nBitsBuf);
  57         nBitsBuf >>= 8;
  58         nBitsBufSize -= 8;
  59     }
  60 }
  61
  62
  63 inline void GIFImageDataOutputStream::WriteBits( sal_uInt16 nCode, sal_uInt16 nCodeLen )
  64 {
  65     if( nBitsBufSize+nCodeLen>32 )
  66         FlushBitsBufsFullBytes();
  67
  68     nBitsBuf |= static_cast<sal_uInt32>(nCode) << nBitsBufSize;
  69     nBitsBufSize = nBitsBufSize + nCodeLen;
  70 }
  71
  72
  73 GIFImageDataOutputStream::GIFImageDataOutputStream( SvStream & rGIF, sal_uInt8 nLZWDataSize ) :
  74         rStream(rGIF), nBlockBufSize(0), nBitsBuf(0), nBitsBufSize(0)
  75 {
  76     rStream.WriteUChar( nLZWDataSize );
  77 }
  78
  79
  80 GIFImageDataOutputStream::~GIFImageDataOutputStream()
  81 {
  82     WriteBits(0,7);
  83     FlushBitsBufsFullBytes();
  84     FlushBlockBuf();
  85     rStream.WriteUChar( 0 );
  86 }
  87
  88
  89 void GIFImageDataOutputStream::FlushBlockBuf()
  90 {
  91     if( nBlockBufSize )
  92     {
  93         rStream.WriteUChar( nBlockBufSize );
  94         rStream.WriteBytes(pBlockBuf.data(), nBlockBufSize);
  95         nBlockBufSize = 0;
  96     }
  97 }
  98
  99
 100 struct GIFLZWCTreeNode
 101 {
 102
 103     GIFLZWCTreeNode*    pBrother;       // next node which has the same father
 104     GIFLZWCTreeNode*    pFirstChild;    // first
 105     sal_uInt16          nCode;          // the code for the string of pixel values which comes about
 106     sal_uInt16          nValue;         // the pixel value
 107 };
 108
 109
 110 GIFLZWCompressor::GIFLZWCompressor()
 111     : pPrefix(nullptr), nDataSize(0), nClearCode(0),
 112       nEOICode(0), nTableSize(0), nCodeSize(0)
 113 {
 114 }
 115
 116
 117 GIFLZWCompressor::~GIFLZWCompressor()
 118 {
 119     if (pIDOS!=nullptr) EndCompression();
 120 }
 121
 122
 123 void GIFLZWCompressor::StartCompression( SvStream& rGIF, sal_uInt16 nPixelSize )
 124 {
 125     if( pIDOS )
 126         return;
 127
 128     sal_uInt16 i;
 129
 130     nDataSize = nPixelSize;
 131
 132     if( nDataSize < 2 )
 133         nDataSize=2;
 134
 135     nClearCode=1<<nDataSize;
 136     nEOICode=nClearCode+1;
 137     nTableSize=nEOICode+1;
 138     nCodeSize=nDataSize+1;
 139
 140     pIDOS.reset(new GIFImageDataOutputStream(rGIF,static_cast<sal_uInt8>(nDataSize)));
 141     pTable.reset(new GIFLZWCTreeNode[4096]);
 142
 143     for (i=0; i<4096; i++)
 144     {
 145         pTable[i].pBrother = pTable[i].pFirstChild = nullptr;
 146         pTable[i].nCode = i;
 147         pTable[i].nValue = static_cast<sal_uInt8>( i );
 148     }
 149
 150     pPrefix = nullptr;
 151     pIDOS->WriteBits( nClearCode,nCodeSize );
 152 }
 153
 154 void GIFLZWCompressor::Compress(sal_uInt8* pSrc, sal_uInt32 nSize)
 155 {
 156     if( !pIDOS )
 157         return;
 158
 159     GIFLZWCTreeNode* p;
 160     sal_uInt16 i;
 161     sal_uInt8 nV;
 162
 163     if( !pPrefix && nSize )
 164     {
 165         pPrefix=&pTable[*pSrc++];
 166         nSize--;
 167     }
 168
 169     while( nSize )
 170     {
 171         nSize--;
 172         nV=*pSrc++;
 173         for( p=pPrefix->pFirstChild; p!=nullptr; p=p->pBrother )
 174         {
 175             if (p->nValue==nV)
 176                 break;
 177         }
 178
 179         if( p)
 180             pPrefix=p;
 181         else
 182         {
 183             pIDOS->WriteBits(pPrefix->nCode,nCodeSize);
 184
 185             if (nTableSize==4096)
 186             {
 187                 pIDOS->WriteBits(nClearCode,nCodeSize);
 188
 189                 for (i=0; i<nClearCode; i++)
 190                     pTable[i].pFirstChild=nullptr;
 191
 192                 nCodeSize=nDataSize+1;
 193                 nTableSize=nEOICode+1;
 194             }
 195             else
 196             {
 197                 if(nTableSize==static_cast<sal_uInt16>(1<<nCodeSize))
 198                     nCodeSize++;
 199
 200                 p=&pTable[nTableSize++];
 201                 p->pBrother=pPrefix->pFirstChild;
 202                 pPrefix->pFirstChild=p;
 203                 p->nValue=nV;
 204                 p->pFirstChild=nullptr;
 205             }
 206
 207             pPrefix=&pTable[nV];
 208         }
 209     }
 210 }
 211
 212 void GIFLZWCompressor::EndCompression()
 213 {
 214     if( pIDOS )
 215     {
 216         if( pPrefix )
 217             pIDOS->WriteBits(pPrefix->nCode,nCodeSize);
 218
 219         pIDOS->WriteBits( nEOICode,nCodeSize );
 220         pTable.reset();
 221         pIDOS.reset();
 222     }
 223 }
 224
 225 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */