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#ifndef __COMPRESSION_BITCODER_H
#define __COMPRESSION_BITCODER_H
#include "RangeCoder.h"
namespace NCompression {
namespace NArithmetic {
const int kNumBitModelTotalBits = 11;
const UINT32 kBitModelTotal = (1 << kNumBitModelTotalBits);
const int kNumMoveReducingBits = 2;
class CPriceTables
{
public:
UINT32 m_StatePrices[kBitModelTotal >> kNumMoveReducingBits];
CPriceTables();
};
extern CPriceTables g_PriceTables;
/////////////////////////////
// CBitModel
template <int aNumMoveBits>
class CBitModel
{
public:
UINT32 m_Probability;
void UpdateModel(UINT32 aSymbol)
{
/*
m_Probability -= (m_Probability + ((aSymbol - 1) & ((1 << aNumMoveBits) - 1))) >> aNumMoveBits;
m_Probability += (1 - aSymbol) << (kNumBitModelTotalBits - aNumMoveBits);
*/
if (aSymbol == 0)
m_Probability += (kBitModelTotal - m_Probability) >> aNumMoveBits;
else
m_Probability -= (m_Probability) >> aNumMoveBits;
}
public:
void Init() { m_Probability = kBitModelTotal / 2; }
};
template <int aNumMoveBits>
class CBitEncoder: public CBitModel<aNumMoveBits>
{
public:
void Encode(CRangeEncoder *aRangeEncoder, UINT32 aSymbol)
{
aRangeEncoder->EncodeBit(this->m_Probability, kNumBitModelTotalBits, aSymbol);
this->UpdateModel(aSymbol);
}
UINT32 GetPrice(UINT32 aSymbol) const
{
return g_PriceTables.m_StatePrices[
(((this->m_Probability - aSymbol) ^ ((-(int)aSymbol))) & (kBitModelTotal - 1)) >> kNumMoveReducingBits];
}
};
template <int aNumMoveBits>
class CBitDecoder: public CBitModel<aNumMoveBits>
{
public:
UINT32 Decode(CRangeDecoder *aRangeDecoder)
{
UINT32 aNewBound = (aRangeDecoder->m_Range >> kNumBitModelTotalBits) * this->m_Probability;
if (aRangeDecoder->m_Code < aNewBound)
{
aRangeDecoder->m_Range = aNewBound;
this->m_Probability += (kBitModelTotal - this->m_Probability) >> aNumMoveBits;
if (aRangeDecoder->m_Range < kTopValue)
{
aRangeDecoder->m_Code = (aRangeDecoder->m_Code << 8) | aRangeDecoder->m_Stream.ReadByte();
aRangeDecoder->m_Range <<= 8;
}
return 0;
}
else
{
aRangeDecoder->m_Range -= aNewBound;
aRangeDecoder->m_Code -= aNewBound;
this->m_Probability -= (this->m_Probability) >> aNumMoveBits;
if (aRangeDecoder->m_Range < kTopValue)
{
aRangeDecoder->m_Code = (aRangeDecoder->m_Code << 8) | aRangeDecoder->m_Stream.ReadByte();
aRangeDecoder->m_Range <<= 8;
}
return 1;
}
}
};
}}
#endif
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