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Annotation of elwix/tools/oldlzma/SRC/7zip/Compress/RangeCoder/RangeCoderBit.h, revision 1.1

1.1     ! misho       1: // Compress/RangeCoder/RangeCoderBit.h
        !             2: 
        !             3: #ifndef __COMPRESS_RANGECODER_BIT_H
        !             4: #define __COMPRESS_RANGECODER_BIT_H
        !             5: 
        !             6: #include "RangeCoder.h"
        !             7: 
        !             8: namespace NCompress {
        !             9: namespace NRangeCoder {
        !            10: 
        !            11: const int kNumBitModelTotalBits  = 11;
        !            12: const UInt32 kBitModelTotal = (1 << kNumBitModelTotalBits);
        !            13: 
        !            14: const int kNumMoveReducingBits = 2;
        !            15: 
        !            16: const int kNumBitPriceShiftBits = 6;
        !            17: const UInt32 kBitPrice = 1 << kNumBitPriceShiftBits;
        !            18: 
        !            19: class CPriceTables
        !            20: {
        !            21: public:
        !            22:   static UInt32 ProbPrices[kBitModelTotal >> kNumMoveReducingBits];
        !            23:   static void Init();
        !            24:   CPriceTables();
        !            25: };
        !            26: 
        !            27: template <int numMoveBits>
        !            28: class CBitModel
        !            29: {
        !            30: public:
        !            31:   UInt32 Prob;
        !            32:   void UpdateModel(UInt32 symbol)
        !            33:   {
        !            34:     /*
        !            35:     Prob -= (Prob + ((symbol - 1) & ((1 << numMoveBits) - 1))) >> numMoveBits;
        !            36:     Prob += (1 - symbol) << (kNumBitModelTotalBits - numMoveBits);
        !            37:     */
        !            38:     if (symbol == 0)
        !            39:       Prob += (kBitModelTotal - Prob) >> numMoveBits;
        !            40:     else
        !            41:       Prob -= (Prob) >> numMoveBits;
        !            42:   }
        !            43: public:
        !            44:   void Init() { Prob = kBitModelTotal / 2; }
        !            45: };
        !            46: 
        !            47: template <int numMoveBits>
        !            48: class CBitEncoder: public CBitModel<numMoveBits>
        !            49: {
        !            50: public:
        !            51:   void Encode(CEncoder *encoder, UInt32 symbol)
        !            52:   {
        !            53:     /*
        !            54:     encoder->EncodeBit(this->Prob, kNumBitModelTotalBits, symbol);
        !            55:     this->UpdateModel(symbol);
        !            56:     */
        !            57:     UInt32 newBound = (encoder->Range >> kNumBitModelTotalBits) * this->Prob;
        !            58:     if (symbol == 0)
        !            59:     {
        !            60:       encoder->Range = newBound;
        !            61:       this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits;
        !            62:     }
        !            63:     else
        !            64:     {
        !            65:       encoder->Low += newBound;
        !            66:       encoder->Range -= newBound;
        !            67:       this->Prob -= (this->Prob) >> numMoveBits;
        !            68:     }
        !            69:     if (encoder->Range < kTopValue)
        !            70:     {
        !            71:       encoder->Range <<= 8;
        !            72:       encoder->ShiftLow();
        !            73:     }
        !            74:   }
        !            75:   UInt32 GetPrice(UInt32 symbol) const
        !            76:   {
        !            77:     return CPriceTables::ProbPrices[
        !            78:       (((this->Prob - symbol) ^ ((-(int)symbol))) & (kBitModelTotal - 1)) >> kNumMoveReducingBits];
        !            79:   }
        !            80:   UInt32 GetPrice0() const { return CPriceTables::ProbPrices[this->Prob >> kNumMoveReducingBits]; }
        !            81:   UInt32 GetPrice1() const { return CPriceTables::ProbPrices[(kBitModelTotal - this->Prob) >> kNumMoveReducingBits]; }
        !            82: };
        !            83: 
        !            84: 
        !            85: template <int numMoveBits>
        !            86: class CBitDecoder: public CBitModel<numMoveBits>
        !            87: {
        !            88: public:
        !            89:   UInt32 Decode(CDecoder *decoder)
        !            90:   {
        !            91:     UInt32 newBound = (decoder->Range >> kNumBitModelTotalBits) * this->Prob;
        !            92:     if (decoder->Code < newBound)
        !            93:     {
        !            94:       decoder->Range = newBound;
        !            95:       this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits;
        !            96:       if (decoder->Range < kTopValue)
        !            97:       {
        !            98:         decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte();
        !            99:         decoder->Range <<= 8;
        !           100:       }
        !           101:       return 0;
        !           102:     }
        !           103:     else
        !           104:     {
        !           105:       decoder->Range -= newBound;
        !           106:       decoder->Code -= newBound;
        !           107:       this->Prob -= (this->Prob) >> numMoveBits;
        !           108:       if (decoder->Range < kTopValue)
        !           109:       {
        !           110:         decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte();
        !           111:         decoder->Range <<= 8;
        !           112:       }
        !           113:       return 1;
        !           114:     }
        !           115:   }
        !           116: };
        !           117: 
        !           118: }}
        !           119: 
        !           120: #endif