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// Compress/RangeCoder/RangeCoderBit.h
#ifndef __COMPRESS_RANGECODER_BIT_H
#define __COMPRESS_RANGECODER_BIT_H
#include "RangeCoder.h"
namespace NCompress {
namespace NRangeCoder {
const int kNumBitModelTotalBits = 11;
const UInt32 kBitModelTotal = (1 << kNumBitModelTotalBits);
const int kNumMoveReducingBits = 2;
const int kNumBitPriceShiftBits = 6;
const UInt32 kBitPrice = 1 << kNumBitPriceShiftBits;
class CPriceTables
{
public:
static UInt32 ProbPrices[kBitModelTotal >> kNumMoveReducingBits];
static void Init();
CPriceTables();
};
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 CPriceTables::ProbPrices[
(((this->Prob - symbol) ^ ((-(int)symbol))) & (kBitModelTotal - 1)) >> kNumMoveReducingBits];
}
UInt32 GetPrice0() const { return CPriceTables::ProbPrices[this->Prob >> kNumMoveReducingBits]; }
UInt32 GetPrice1() const { return CPriceTables::ProbPrices[(kBitModelTotal - this->Prob) >> 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
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