source/libs/poppler/poppler-src/poppler/JArithmeticDecoder.h

   1 //========================================================================
   2 //
   3 // JArithmeticDecoder.h
   4 //
   5 // Arithmetic decoder used by the JBIG2 and JPEG2000 decoders.
   6 //
   7 // Copyright 2002-2004 Glyph & Cog, LLC
   8 //
   9 //========================================================================
  10
  11 #ifndef JARITHMETICDECODER_H
  12 #define JARITHMETICDECODER_H
  13
  14 #ifdef USE_GCC_PRAGMAS
  15 #pragma interface
  16 #endif
  17
  18 #include "goo/gtypes.h"
  19
  20 class Stream;
  21
  22 //------------------------------------------------------------------------
  23 // JArithmeticDecoderStats
  24 //------------------------------------------------------------------------
  25
  26 class JArithmeticDecoderStats {
  27 public:
  28
  29   JArithmeticDecoderStats(int contextSizeA);
  30   ~JArithmeticDecoderStats();
  31   JArithmeticDecoderStats *copy();
  32   void reset();
  33   int getContextSize() { return contextSize; }
  34   void copyFrom(JArithmeticDecoderStats *stats);
  35   void setEntry(Guint cx, int i, int mps);
  36
  37 private:
  38
  39   Guchar *cxTab;                // cxTab[cx] = (i[cx] << 1) + mps[cx]
  40   int contextSize;
  41
  42   friend class JArithmeticDecoder;
  43 };
  44
  45 //------------------------------------------------------------------------
  46 // JArithmeticDecoder
  47 //------------------------------------------------------------------------
  48
  49 class JArithmeticDecoder {
  50 public:
  51
  52   JArithmeticDecoder();
  53   ~JArithmeticDecoder();
  54
  55   void setStream(Stream *strA)
  56     { str = strA; dataLen = 0; limitStream = gFalse; }
  57   void setStream(Stream *strA, int dataLenA)
  58     { str = strA; dataLen = dataLenA; limitStream = gTrue; }
  59
  60   // Start decoding on a new stream.  This fills the byte buffers and
  61   // runs INITDEC.
  62   void start();
  63
  64   // Restart decoding on an interrupted stream.  This refills the
  65   // buffers if needed, but does not run INITDEC.  (This is used in
  66   // JPEG 2000 streams when codeblock data is split across multiple
  67   // packets/layers.)
  68   void restart(int dataLenA);
  69
  70   // Read any leftover data in the stream.
  71   void cleanup();
  72
  73   // Decode one bit.
  74   int decodeBit(Guint context, JArithmeticDecoderStats *stats);
  75
  76   // Decode eight bits.
  77   int decodeByte(Guint context, JArithmeticDecoderStats *stats);
  78
  79   // Returns false for OOB, otherwise sets *<x> and returns true.
  80   GBool decodeInt(int *x, JArithmeticDecoderStats *stats);
  81
  82   Guint decodeIAID(Guint codeLen,
  83                    JArithmeticDecoderStats *stats);
  84
  85   void resetByteCounter() { nBytesRead = 0; }
  86   Guint getByteCounter() { return nBytesRead; }
  87
  88 private:
  89
  90   Guint readByte();
  91   int decodeIntBit(JArithmeticDecoderStats *stats);
  92   void byteIn();
  93
  94   static Guint qeTab[47];
  95   static int nmpsTab[47];
  96   static int nlpsTab[47];
  97   static int switchTab[47];
  98
  99   Guint buf0, buf1;
 100   Guint c, a;
 101   int ct;
 102
 103   Guint prev;                   // for the integer decoder
 104
 105   Stream *str;
 106   Guint nBytesRead;
 107   int dataLen;
 108   GBool limitStream;
 109 };
 110
 111 #endif