bsnes/snesreader/unrar/model.hpp

#ifndef _RAR_PPMMODEL_
#define _RAR_PPMMODEL_

#include "coder.hpp"
#include "suballoc.hpp"

const int MAX_O=64;                   /* maximum allowed model order */

const int INT_BITS=7, PERIOD_BITS=7, TOT_BITS=INT_BITS+PERIOD_BITS,
					INTERVAL=1 << INT_BITS, BIN_SCALE=1 << TOT_BITS, MAX_FREQ=124;

#ifndef STRICT_ALIGNMENT_REQUIRED
#pragma pack(1)
#endif

struct SEE2_CONTEXT
{ // SEE-contexts for PPM-contexts with masked symbols
	ushort Summ;
	byte Shift, Count;
	void init(int InitVal)
	{
		Summ=InitVal << (Shift=PERIOD_BITS-4);
		Count=4;
	}
	uint getMean()
	{
		uint RetVal=SHORT16(Summ) >> Shift;
		Summ -= RetVal;
		return RetVal+(RetVal == 0);
	}
	void update()
	{
		if (Shift < PERIOD_BITS && --Count == 0)
		{
			Summ += Summ;
			Count=3 << Shift++;
		}
	}
};


class ModelPPM;
struct PPM_CONTEXT;

struct STATE
{
	byte Symbol;
	byte Freq;
	PPM_CONTEXT* Successor;
};

struct FreqData
{
	ushort SummFreq;
	STATE _PACK_ATTR * Stats;
};

struct PPM_CONTEXT
{
		ushort NumStats;
		union
		{
			FreqData U;
			STATE OneState;
		};

		PPM_CONTEXT* Suffix;
		inline void encodeBinSymbol(ModelPPM *Model,int symbol);  // MaxOrder:
		inline void encodeSymbol1(ModelPPM *Model,int symbol);    //  ABCD    context
		inline void encodeSymbol2(ModelPPM *Model,int symbol);    //   BCD    suffix
		inline void decodeBinSymbol(ModelPPM *Model);  //   BCDE   successor
		inline bool decodeSymbol1(ModelPPM *Model);    // other orders:
		inline bool decodeSymbol2(ModelPPM *Model);    //   BCD    context
		inline void update1(ModelPPM *Model,STATE* p); //    CD    suffix
		inline void update2(ModelPPM *Model,STATE* p); //   BCDE   successor
		void rescale(ModelPPM *Model);
		inline PPM_CONTEXT* createChild(ModelPPM *Model,STATE* pStats,STATE& FirstState);
		inline SEE2_CONTEXT* makeEscFreq2(ModelPPM *Model,int Diff);
};

#ifndef STRICT_ALIGNMENT_REQUIRED
#ifdef _AIX
#pragma pack(pop)
#else
#pragma pack()
#endif
#endif

const uint UNIT_SIZE=Max(sizeof(PPM_CONTEXT),sizeof(RAR_MEM_BLK));
const uint FIXED_UNIT_SIZE=12;

/*
inline PPM_CONTEXT::PPM_CONTEXT(STATE* pStats,PPM_CONTEXT* ShorterContext):
				NumStats(1), Suffix(ShorterContext) { pStats->Successor=this; }
inline PPM_CONTEXT::PPM_CONTEXT(): NumStats(0) {}
*/

template <class T>
inline void _PPMD_SWAP(T& t1,T& t2) { T tmp=t1; t1=t2; t2=tmp; }


class ModelPPM
{
	private:
		friend struct PPM_CONTEXT;

		/*_PACK_ATTR*/ SEE2_CONTEXT SEE2Cont[25][16], DummySEE2Cont;

		struct PPM_CONTEXT *MinContext, *MedContext, *MaxContext;
		STATE* FoundState;      // found next state transition
		int NumMasked, InitEsc, OrderFall, MaxOrder, RunLength, InitRL;
		byte CharMask[256], NS2Indx[256], NS2BSIndx[256], HB2Flag[256];
		byte EscCount, PrevSuccess, HiBitsFlag;
		ushort BinSumm[128][64];               // binary SEE-contexts

		RangeCoder Coder;
		SubAllocator SubAlloc;

		void RestartModelRare();
		void StartModelRare(int MaxOrder);
		inline PPM_CONTEXT* CreateSuccessors(bool Skip,STATE* p1);

		inline void UpdateModel();
		inline void ClearMask();
		friend class Unpack;
	public:
		ModelPPM();
    void CleanUp(); // reset PPM variables after data error
		bool DecodeInit(Unpack *UnpackRead,int &EscChar);
		int DecodeChar();
};

#endif