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| 1 // Compress/RangeCoderBit.h | |
| 2 | |
| 3 #ifndef __COMPRESS_RANGE_CODER_BIT_H | |
| 4 #define __COMPRESS_RANGE_CODER_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 = 4; | |
| 15 | |
| 16 const int kNumBitPriceShiftBits = 4; | |
| 17 const UInt32 kBitPrice = 1 << kNumBitPriceShiftBits; | |
| 18 | |
| 19 extern UInt32 ProbPrices[kBitModelTotal >> kNumMoveReducingBits]; | |
| 20 | |
| 21 template <int numMoveBits> | |
| 22 class CBitModel | |
| 23 { | |
| 24 public: | |
| 25 UInt32 Prob; | |
| 26 void UpdateModel(UInt32 symbol) | |
| 27 { | |
| 28 /* | |
| 29 Prob -= (Prob + ((symbol - 1) & ((1 << numMoveBits) - 1))) >> numMoveBits; | |
| 30 Prob += (1 - symbol) << (kNumBitModelTotalBits - numMoveBits); | |
| 31 */ | |
| 32 if (symbol == 0) | |
| 33 Prob += (kBitModelTotal - Prob) >> numMoveBits; | |
| 34 else | |
| 35 Prob -= (Prob) >> numMoveBits; | |
| 36 } | |
| 37 public: | |
| 38 void Init() { Prob = kBitModelTotal / 2; } | |
| 39 }; | |
| 40 | |
| 41 template <int numMoveBits> | |
| 42 class CBitEncoder: public CBitModel<numMoveBits> | |
| 43 { | |
| 44 public: | |
| 45 void Encode(CEncoder *encoder, UInt32 symbol) | |
| 46 { | |
| 47 /* | |
| 48 encoder->EncodeBit(this->Prob, kNumBitModelTotalBits, symbol); | |
| 49 this->UpdateModel(symbol); | |
| 50 */ | |
| 51 UInt32 newBound = (encoder->Range >> kNumBitModelTotalBits) * this->Prob; | |
| 52 if (symbol == 0) | |
| 53 { | |
| 54 encoder->Range = newBound; | |
| 55 this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits; | |
| 56 } | |
| 57 else | |
| 58 { | |
| 59 encoder->Low += newBound; | |
| 60 encoder->Range -= newBound; | |
| 61 this->Prob -= (this->Prob) >> numMoveBits; | |
| 62 } | |
| 63 if (encoder->Range < kTopValue) | |
| 64 { | |
| 65 encoder->Range <<= 8; | |
| 66 encoder->ShiftLow(); | |
| 67 } | |
| 68 } | |
| 69 UInt32 GetPrice(UInt32 symbol) const | |
| 70 { | |
| 71 return ProbPrices[(this->Prob ^ ((-(int)symbol)) & (kBitModelTotal - 1)) >>
kNumMoveReducingBits]; | |
| 72 } | |
| 73 UInt32 GetPrice0() const { return ProbPrices[this->Prob >> kNumMoveReducingBit
s]; } | |
| 74 UInt32 GetPrice1() const { return ProbPrices[(this->Prob ^ (kBitModelTotal - 1
)) >> kNumMoveReducingBits]; } | |
| 75 }; | |
| 76 | |
| 77 | |
| 78 template <int numMoveBits> | |
| 79 class CBitDecoder: public CBitModel<numMoveBits> | |
| 80 { | |
| 81 public: | |
| 82 UInt32 Decode(CDecoder *decoder) | |
| 83 { | |
| 84 UInt32 newBound = (decoder->Range >> kNumBitModelTotalBits) * this->Prob; | |
| 85 if (decoder->Code < newBound) | |
| 86 { | |
| 87 decoder->Range = newBound; | |
| 88 this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits; | |
| 89 if (decoder->Range < kTopValue) | |
| 90 { | |
| 91 decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte(); | |
| 92 decoder->Range <<= 8; | |
| 93 } | |
| 94 return 0; | |
| 95 } | |
| 96 else | |
| 97 { | |
| 98 decoder->Range -= newBound; | |
| 99 decoder->Code -= newBound; | |
| 100 this->Prob -= (this->Prob) >> numMoveBits; | |
| 101 if (decoder->Range < kTopValue) | |
| 102 { | |
| 103 decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte(); | |
| 104 decoder->Range <<= 8; | |
| 105 } | |
| 106 return 1; | |
| 107 } | |
| 108 } | |
| 109 }; | |
| 110 | |
| 111 }} | |
| 112 | |
| 113 #endif | |
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Chromium Code Reviews
Issue 624713003:
Keep only base/extractor.[cc|h]. (Closed)
Base URL: https://chromium.googlesource.com/external/omaha.git@master