poppler/JArithmeticDecoder.h

//========================================================================
//
// JArithmeticDecoder.h
//
// Arithmetic decoder used by the JBIG2 and JPEG2000 decoders.
//
// Copyright 2002-2004 Glyph & Cog, LLC
//
//========================================================================

//========================================================================
//
// Modified under the Poppler project - http://poppler.freedesktop.org
//
// All changes made under the Poppler project to this file are licensed
// under GPL version 2 or later
//
// Copyright (C) 2018 Albert Astals Cid <aacid@kde.org>
//
// To see a description of the changes please see the Changelog file that
// came with your tarball or type make ChangeLog if you are building from git
//
//========================================================================

#ifndef JARITHMETICDECODER_H
#define JARITHMETICDECODER_H

class Stream;

//------------------------------------------------------------------------
// JArithmeticDecoderStats
//------------------------------------------------------------------------

class JArithmeticDecoderStats {
public:

  JArithmeticDecoderStats(int contextSizeA);
  ~JArithmeticDecoderStats();
  JArithmeticDecoderStats(const JArithmeticDecoderStats &) = delete;
  JArithmeticDecoderStats& operator=(const JArithmeticDecoderStats &) = delete;
  JArithmeticDecoderStats *copy();
  void reset();
  int getContextSize() { return contextSize; }
  void copyFrom(JArithmeticDecoderStats *stats);
  void setEntry(unsigned int cx, int i, int mps);

private:

  unsigned char *cxTab;		// cxTab[cx] = (i[cx] << 1) + mps[cx]
  int contextSize;

  friend class JArithmeticDecoder;
};

//------------------------------------------------------------------------
// JArithmeticDecoder
//------------------------------------------------------------------------

class JArithmeticDecoder {
public:

  JArithmeticDecoder();
  ~JArithmeticDecoder();
  JArithmeticDecoder(const JArithmeticDecoder &) = delete;
  JArithmeticDecoder& operator=(const JArithmeticDecoder &) = delete;

  void setStream(Stream *strA)
    { str = strA; dataLen = 0; limitStream = false; }
  void setStream(Stream *strA, int dataLenA)
    { str = strA; dataLen = dataLenA; limitStream = true; }

  // 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(unsigned int context, JArithmeticDecoderStats *stats);

  // Decode eight bits.
  int decodeByte(unsigned int context, JArithmeticDecoderStats *stats);

  // Returns false for OOB, otherwise sets *<x> and returns true.
  bool decodeInt(int *x, JArithmeticDecoderStats *stats);

  unsigned int decodeIAID(unsigned int codeLen,
		   JArithmeticDecoderStats *stats);

  void resetByteCounter() { nBytesRead = 0; }
  unsigned int getByteCounter() { return nBytesRead; }

private:

  unsigned int readByte();
  int decodeIntBit(JArithmeticDecoderStats *stats);
  void byteIn();

  static unsigned int qeTab[47];
  static int nmpsTab[47];
  static int nlpsTab[47];
  static int switchTab[47];

  unsigned int buf0, buf1;
  unsigned int c, a;
  int ct;

  unsigned int prev;			// for the integer decoder

  Stream *str;
  unsigned int nBytesRead;
  int dataLen;
  bool limitStream;
};

#endif