core/ASCOfficePDFReader/JArithmeticDecoder.h

#ifndef _JARITHMETICDECODER_H
#define _JARITHMETICDECODER_H

class Stream;

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

class JArithmeticDecoderStats 
{
public:

	JArithmeticDecoderStats(int nContextSize);
	~JArithmeticDecoderStats();
	JArithmeticDecoderStats *Copy();
	void Reset();
	int GetContextSize() 
	{ 
		return m_nContextSize; 
	}
	void CopyFrom(JArithmeticDecoderStats *pStats);
	void SetEntry(unsigned int unCx, int nIndex, int nMPS);

private:

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

	friend class JArithmeticDecoder;
};

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

class JArithmeticDecoder 
{
public:

	JArithmeticDecoder();
	~JArithmeticDecoder();

	void SetStream(Stream *pStream)
    { 
		m_pStream      = pStream; 
		m_nDataSize    = 0; 
		m_bLimitStream = FALSE; 
	}
	void SetStream(Stream *pStream, int nDataSize)
    { 
		m_pStream      = pStream; 
		m_nDataSize    = nDataSize; 
		m_bLimitStream = TRUE; 
	}

	// Íà÷èíàåì äåêîäèðîâàòü íîâûé ïîòîê. Çàïîëíÿåì áóôôåð è çàïóñêàåì INITDEC.
	void Start();

	// Çàíîâî äåêîäèðóåì ïðåðâûííûé ïîòîê. Çàíîâî çàïîëíÿåì áóôôåð, íî íå çàïóñêàåì INITDEC. (Èñïîëüçóåòñÿ â  ïîòîêàõ JPEG 2000, ãäå
	// äàííûå ìîãóò áûòü ðàçäåëåíû íà áëîêè.)
	void Restart(int nDataSize);

	// ×èòàåì îñòàâøèåñÿ äàííûå â ïîòîêå.
	void Cleanup();

	// Äåêîäèðóåì îäèí áèò.
	int DecodeBit(unsigned int unContext, JArithmeticDecoderStats *pStats);

	// Äåêîäèðóåì îäèí áàéò.
	int DecodeByte(unsigned int unContext, JArithmeticDecoderStats *pStats);

	BOOL DecodeInt(int *pnValue, JArithmeticDecoderStats *pStats);

	unsigned int DecodeIAID(unsigned int unCodeLen, JArithmeticDecoderStats *pStats);

private:

	unsigned int ReadByte();
	int DecodeIntBit(JArithmeticDecoderStats *pStats);
	void ByteIn();

private:

	static unsigned int arrunQeTable[47];
	static int          arrnNMPSTable[47];
	static int          arrnNLPSTable[47];
	static int          arrnSwitchTable[47];

	unsigned int m_unBuffer0;
	unsigned int m_unBuffer1;
	unsigned int m_unC;
	unsigned int m_unA;
	int          m_nCT;

	unsigned int m_unPrev;

	Stream      *m_pStream;
	int          m_nDataSize;
	BOOL         m_bLimitStream;
};

#endif /* _JARITHMETICDECODER_H */