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Diffstat (limited to 'CPP/7zip/Compress/RangeCoderBit.h')
-rwxr-xr-x | CPP/7zip/Compress/RangeCoderBit.h | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/CPP/7zip/Compress/RangeCoderBit.h b/CPP/7zip/Compress/RangeCoderBit.h new file mode 100755 index 00000000..566cdd41 --- /dev/null +++ b/CPP/7zip/Compress/RangeCoderBit.h @@ -0,0 +1,113 @@ +// Compress/RangeCoderBit.h + +#ifndef __COMPRESS_RANGE_CODER_BIT_H +#define __COMPRESS_RANGE_CODER_BIT_H + +#include "RangeCoder.h" + +namespace NCompress { +namespace NRangeCoder { + +const int kNumBitModelTotalBits = 11; +const UInt32 kBitModelTotal = (1 << kNumBitModelTotalBits); + +const int kNumMoveReducingBits = 4; + +const int kNumBitPriceShiftBits = 4; +const UInt32 kBitPrice = 1 << kNumBitPriceShiftBits; + +extern UInt32 ProbPrices[kBitModelTotal >> kNumMoveReducingBits]; + +template <int numMoveBits> +class CBitModel +{ +public: + UInt32 Prob; + void UpdateModel(UInt32 symbol) + { + /* + Prob -= (Prob + ((symbol - 1) & ((1 << numMoveBits) - 1))) >> numMoveBits; + Prob += (1 - symbol) << (kNumBitModelTotalBits - numMoveBits); + */ + if (symbol == 0) + Prob += (kBitModelTotal - Prob) >> numMoveBits; + else + Prob -= (Prob) >> numMoveBits; + } +public: + void Init() { Prob = kBitModelTotal / 2; } +}; + +template <int numMoveBits> +class CBitEncoder: public CBitModel<numMoveBits> +{ +public: + void Encode(CEncoder *encoder, UInt32 symbol) + { + /* + encoder->EncodeBit(this->Prob, kNumBitModelTotalBits, symbol); + this->UpdateModel(symbol); + */ + UInt32 newBound = (encoder->Range >> kNumBitModelTotalBits) * this->Prob; + if (symbol == 0) + { + encoder->Range = newBound; + this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits; + } + else + { + encoder->Low += newBound; + encoder->Range -= newBound; + this->Prob -= (this->Prob) >> numMoveBits; + } + if (encoder->Range < kTopValue) + { + encoder->Range <<= 8; + encoder->ShiftLow(); + } + } + UInt32 GetPrice(UInt32 symbol) const + { + return ProbPrices[(this->Prob ^ ((-(int)symbol)) & (kBitModelTotal - 1)) >> kNumMoveReducingBits]; + } + UInt32 GetPrice0() const { return ProbPrices[this->Prob >> kNumMoveReducingBits]; } + UInt32 GetPrice1() const { return ProbPrices[(this->Prob ^ (kBitModelTotal - 1)) >> kNumMoveReducingBits]; } +}; + + +template <int numMoveBits> +class CBitDecoder: public CBitModel<numMoveBits> +{ +public: + UInt32 Decode(CDecoder *decoder) + { + UInt32 newBound = (decoder->Range >> kNumBitModelTotalBits) * this->Prob; + if (decoder->Code < newBound) + { + decoder->Range = newBound; + this->Prob += (kBitModelTotal - this->Prob) >> numMoveBits; + if (decoder->Range < kTopValue) + { + decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte(); + decoder->Range <<= 8; + } + return 0; + } + else + { + decoder->Range -= newBound; + decoder->Code -= newBound; + this->Prob -= (this->Prob) >> numMoveBits; + if (decoder->Range < kTopValue) + { + decoder->Code = (decoder->Code << 8) | decoder->Stream.ReadByte(); + decoder->Range <<= 8; + } + return 1; + } + } +}; + +}} + +#endif |