goodies/source/filter.vcl/itiff/lzwdecom.cxx

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  30
  31 // MARKER(update_precomp.py): autogen include statement, do not remove
  32 #include "precompiled_goodies.hxx"
  33
  34 #include "lzwdecom.hxx"
  35
  36 LZWDecompressor::LZWDecompressor()
  37 {
  38     USHORT i;
  39
  40     pTable=new LZWTableEntry[4096];
  41     pOutBuf=new BYTE[4096];
  42     for (i=0; i<4096; i++)
  43     {
  44         pTable[i].nPrevCode=0;
  45         pTable[i].nDataCount=1;
  46         pTable[i].nData=(BYTE)i;
  47     }
  48     pIStream=NULL;
  49     bFirst = TRUE;
  50     nOldCode = 0;
  51 }
  52
  53
  54 LZWDecompressor::~LZWDecompressor()
  55 {
  56     delete[] pOutBuf;
  57     delete[] pTable;
  58 }
  59
  60
  61 void LZWDecompressor::StartDecompression(SvStream & rIStream)
  62 {
  63     pIStream=&rIStream;
  64
  65     nTableSize=258;
  66
  67     bEOIFound=FALSE;
  68
  69     nOutBufDataLen=0;
  70
  71     *pIStream >> nInputBitsBuf;
  72
  73     nInputBitsBufSize=8;
  74
  75     if ( bFirst )
  76     {
  77         bInvert = nInputBitsBuf == 1;
  78         bFirst = FALSE;
  79     }
  80
  81     if ( bInvert )
  82         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 );
  83 }
  84
  85
  86 ULONG LZWDecompressor::Decompress(BYTE * pTarget, ULONG nMaxCount)
  87 {
  88     ULONG nCount;
  89
  90     if (pIStream==NULL) return 0;
  91
  92     nCount=0;
  93     for (;;) {
  94
  95         if (pIStream->GetError()) break;
  96
  97         if (((ULONG)nOutBufDataLen)>=nMaxCount) {
  98             nOutBufDataLen = nOutBufDataLen - (USHORT)nMaxCount;
  99             nCount+=nMaxCount;
 100             while (nMaxCount>0) {
 101                 *(pTarget++)=*(pOutBufData++);
 102                 nMaxCount--;
 103             }
 104             break;
 105         }
 106
 107         nMaxCount-=(ULONG)nOutBufDataLen;
 108         nCount+=nOutBufDataLen;
 109         while (nOutBufDataLen>0) {
 110             *(pTarget++)=*(pOutBufData++);
 111             nOutBufDataLen--;
 112         }
 113
 114         if (bEOIFound==TRUE) break;
 115
 116         DecompressSome();
 117
 118     }
 119
 120     return nCount;
 121 }
 122
 123
 124 USHORT LZWDecompressor::GetNextCode()
 125 {
 126     USHORT nBits,nCode;
 127
 128     if      (nTableSize<511)  nBits=9;
 129     else if (nTableSize<1023) nBits=10;
 130     else if (nTableSize<2047) nBits=11;
 131     else                      nBits=12;
 132
 133     nCode=0;
 134     do {
 135         if (nInputBitsBufSize<=nBits)
 136         {
 137             nCode=(nCode<<nInputBitsBufSize) | nInputBitsBuf;
 138             nBits = nBits - nInputBitsBufSize;
 139             *pIStream >> nInputBitsBuf;
 140             if ( bInvert )
 141                 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 );
 142             nInputBitsBufSize=8;
 143         }
 144         else
 145         {
 146             nCode=(nCode<<nBits) | (nInputBitsBuf>>(nInputBitsBufSize-nBits));
 147             nInputBitsBufSize = nInputBitsBufSize - nBits;
 148             nInputBitsBuf&=0x00ff>>(8-nInputBitsBufSize);
 149             nBits=0;
 150         }
 151     } while (nBits>0);
 152
 153     return nCode;
 154 }
 155
 156
 157 void LZWDecompressor::AddToTable(USHORT nPrevCode, USHORT nCodeFirstData)
 158 {
 159     while (pTable[nCodeFirstData].nDataCount>1)
 160         nCodeFirstData=pTable[nCodeFirstData].nPrevCode;
 161
 162     pTable[nTableSize].nPrevCode=nPrevCode;
 163     pTable[nTableSize].nDataCount=pTable[nPrevCode].nDataCount+1;
 164     pTable[nTableSize].nData=pTable[nCodeFirstData].nData;
 165
 166     nTableSize++;
 167 }
 168
 169
 170 void LZWDecompressor::DecompressSome()
 171 {
 172     USHORT i,nCode;
 173
 174     nCode=GetNextCode();
 175     if (nCode==256) {
 176         nTableSize=258;
 177         nCode=GetNextCode();
 178         if (nCode==257) { bEOIFound=TRUE; return; }
 179     }
 180     else if (nCode<nTableSize) AddToTable(nOldCode,nCode);
 181     else if (nCode==nTableSize) AddToTable(nOldCode,nOldCode);
 182     else { bEOIFound=TRUE; return; }
 183
 184     nOldCode=nCode;
 185
 186     nOutBufDataLen=pTable[nCode].nDataCount;
 187     pOutBufData=pOutBuf+nOutBufDataLen;
 188     for (i=0; i<nOutBufDataLen; i++) {
 189         *(--pOutBufData)=pTable[nCode].nData;
 190         nCode=pTable[nCode].nPrevCode;
 191     }
 192 }
 193
 194
 195