release/src-rt-6.x/linux/linux-2.6/scripts/squashfs/lzma/C/7zip/Compress/RangeCoder/RangeCoderBit.h

   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