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//========================================================================
//
// 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, 2021 Albert Astals Cid <aacid@kde.org>
// Copyright (C) 2019 Volker Krause <vkrause@kde.org>
// Copyright (C) 2020 Even Rouault <even.rouault@spatialys.com>
//
// 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:
explicit 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);
bool isValid() const { return cxTab != nullptr; }
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 const unsigned int qeTab[47];
static const int nmpsTab[47];
static const int nlpsTab[47];
static const 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