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