//========================================================================

//

// JArithmeticDecoder.h

//

// Arithmetic decoder used by the JBIG2 and JPEG2000 decoders.

//

// Copyright 2002-2004 Glyph & Cog, LLC

//

//========================================================================

#ifndef JARITHMETICDECODER_H

#define JARITHMETICDECODER_H

#include <aconf.h>

#include "gtypes.h"

class Stream;

//------------------------------------------------------------------------

// JArithmeticDecoderStats

//------------------------------------------------------------------------

class JArithmeticDecoderStats {

public:

  JArithmeticDecoderStats(int contextSizeA);

  ~JArithmeticDecoderStats();

  JArithmeticDecoderStats *copy();

  void reset();

  int getContextSize() { return contextSize; }

  void copyFrom(JArithmeticDecoderStats *stats);

  void setEntry(Guint cx, int i, int mps);

private:

  Guchar *cxTab;    // cxTab[cx] = (i[cx] << 1) + mps[cx]

  int contextSize;

  friend class JArithmeticDecoder;

};

//------------------------------------------------------------------------

// JArithmeticDecoder

//------------------------------------------------------------------------

class JArithmeticDecoder {

public:

  JArithmeticDecoder();

  ~JArithmeticDecoder();

  void setStream(Stream *strA)

    { str = strA; dataLen = 0; limitStream = gFalse; }

  void setStream(Stream *strA, int dataLenA)

    { str = strA; dataLen = dataLenA; limitStream = gTrue; }

  // Start decoding on a new stream.  This fills the byte buffers and

  // runs INITDEC.

  void start();

  // Restart decoding on an interrupted stream.  This refills the

  // buffers if needed, but does not run INITDEC.  (This is used in

  // JPEG 2000 streams when codeblock data is split across multiple

  // packets/layers.)

  void restart(int dataLenA);

  // Read any leftover data in the stream.

  void cleanup();

  // Decode one bit.

  int decodeBit(Guint context, JArithmeticDecoderStats *stats);

  // Decode eight bits.

  int decodeByte(Guint context, JArithmeticDecoderStats *stats);

  // Returns false for OOB, otherwise sets *<x> and returns true.

  GBool decodeInt(int *x, JArithmeticDecoderStats *stats);

  Guint decodeIAID(Guint codeLen,

       JArithmeticDecoderStats *stats);

  void resetByteCounter() { nBytesRead = 0; }

  Guint getByteCounter() { return nBytesRead; }

private:

  Guint readByte();

  int decodeIntBit(JArithmeticDecoderStats *stats);

  void byteIn();

  static Guint qeTab[47];

  static int nmpsTab[47];

  static int nlpsTab[47];

  static int switchTab[47];

  Guint buf0, buf1;

  Guint c, a;

  int ct;

  Guint prev;     // for the integer decoder

  Stream *str;

  Guint nBytesRead;

  int dataLen;

  GBool limitStream;

  Guchar readBuf[32];

  int readBufNext;

  int readBufLength;

};

#endif