michael@0: // Compress/RangeCoder/RangeCoderBit.h
michael@0: 
michael@0: #ifndef __COMPRESS_RANGECODER_BIT_H
michael@0: #define __COMPRESS_RANGECODER_BIT_H
michael@0: 
michael@0: #include "RangeCoder.h"
michael@0: 
michael@0: namespace NCompress {
michael@0: namespace NRangeCoder {
michael@0: 
michael@0: const int kNumBitModelTotalBits  = 11;
michael@0: const UInt32 kBitModelTotal = (1 << kNumBitModelTotalBits);
michael@0: 
michael@0: const int kNumMoveReducingBits = 2;
michael@0: 
michael@0: const int kNumBitPriceShiftBits = 6;
michael@0: const UInt32 kBitPrice = 1 << kNumBitPriceShiftBits;
michael@0: 
michael@0: class CPriceTables
michael@0: {
michael@0: public:
michael@0:   static UInt32 ProbPrices[kBitModelTotal >> kNumMoveReducingBits];
michael@0:   static void Init();
michael@0:   CPriceTables();
michael@0: };
michael@0: 
michael@0: template <int numMoveBits>
michael@0: class CBitModel
michael@0: {
michael@0: public:
michael@0:   UInt32 Prob;
michael@0:   void UpdateModel(UInt32 symbol)
michael@0:   {
michael@0:     /*
michael@0:     Prob -= (Prob + ((symbol - 1) & ((1 << numMoveBits) - 1))) >> numMoveBits;
michael@0:     Prob += (1 - symbol) << (kNumBitModelTotalBits - numMoveBits);
michael@0:     */
michael@0:     if (symbol == 0)
michael@0:       Prob += (kBitModelTotal - Prob) >> numMoveBits;
michael@0:     else
michael@0:       Prob -= (Prob) >> numMoveBits;
michael@0:   }
michael@0: public:
michael@0:   void Init() { Prob = kBitModelTotal / 2; }
michael@0: };
michael@0: 
michael@0: template <int numMoveBits>
michael@0: class CBitEncoder: public CBitModel<numMoveBits>
michael@0: {
michael@0: public:
michael@0:   void Encode(CEncoder *encoder, UInt32 symbol)
michael@0:   {
michael@0:     /*
michael@0:     encoder->EncodeBit(this->Prob, kNumBitModelTotalBits, symbol);
michael@0:     this->UpdateModel(symbol);
michael@0:     */
michael@0:     UInt32 newBound = (encoder->Range >> kNumBitModelTotalBits) * this->Prob;
michael@0:     if (symbol == 0)
michael@0:     {
michael@0:       encoder->Range = newBound;
michael@0:       this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits;
michael@0:     }
michael@0:     else
michael@0:     {
michael@0:       encoder->Low += newBound;
michael@0:       encoder->Range -= newBound;
michael@0:       this->Prob -= (this->Prob) >> numMoveBits;
michael@0:     }
michael@0:     if (encoder->Range < kTopValue)
michael@0:     {
michael@0:       encoder->Range <<= 8;
michael@0:       encoder->ShiftLow();
michael@0:     }
michael@0:   }
michael@0:   UInt32 GetPrice(UInt32 symbol) const
michael@0:   {
michael@0:     return CPriceTables::ProbPrices[
michael@0:       (((this->Prob - symbol) ^ ((-(int)symbol))) & (kBitModelTotal - 1)) >> kNumMoveReducingBits];
michael@0:   }
michael@0:   UInt32 GetPrice0() const { return CPriceTables::ProbPrices[this->Prob >> kNumMoveReducingBits]; }
michael@0:   UInt32 GetPrice1() const { return CPriceTables::ProbPrices[(kBitModelTotal - this->Prob) >> kNumMoveReducingBits]; }
michael@0: };
michael@0: 
michael@0: 
michael@0: template <int numMoveBits>
michael@0: class CBitDecoder: public CBitModel<numMoveBits>
michael@0: {
michael@0: public:
michael@0:   UInt32 Decode(CDecoder *decoder)
michael@0:   {
michael@0:     UInt32 newBound = (decoder->Range >> kNumBitModelTotalBits) * this->Prob;
michael@0:     if (decoder->Code < newBound)
michael@0:     {
michael@0:       decoder->Range = newBound;
michael@0:       this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits;
michael@0:       if (decoder->Range < kTopValue)
michael@0:       {
michael@0:         decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte();
michael@0:         decoder->Range <<= 8;
michael@0:       }
michael@0:       return 0;
michael@0:     }
michael@0:     else
michael@0:     {
michael@0:       decoder->Range -= newBound;
michael@0:       decoder->Code -= newBound;
michael@0:       this->Prob -= (this->Prob) >> numMoveBits;
michael@0:       if (decoder->Range < kTopValue)
michael@0:       {
michael@0:         decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte();
michael@0:         decoder->Range <<= 8;
michael@0:       }
michael@0:       return 1;
michael@0:     }
michael@0:   }
michael@0: };
michael@0: 
michael@0: }}
michael@0: 
michael@0: #endif