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// BitmDecoder.h -- the Most Significant Bit of byte is First
#ifndef __BITM_DECODER_H
#define __BITM_DECODER_H
#include "../IStream.h"
namespace NBitm {
const unsigned kNumBigValueBits = 8 * 4;
const unsigned kNumValueBytes = 3;
const unsigned kNumValueBits = 8 * kNumValueBytes;
const UInt32 kMask = (1 << kNumValueBits) - 1;
template<class TInByte>
class CDecoder
{
unsigned m_BitPos;
UInt32 m_Value;
public:
TInByte m_Stream;
bool Create(UInt32 bufferSize) { return m_Stream.Create(bufferSize); }
void SetStream(ISequentialInStream *inStream) { m_Stream.SetStream(inStream);}
void ReleaseStream() { m_Stream.ReleaseStream();}
void Init()
{
m_Stream.Init();
m_BitPos = kNumBigValueBits;
Normalize();
}
UInt64 GetProcessedSize() const { return m_Stream.GetProcessedSize() - (kNumBigValueBits - m_BitPos) / 8; }
void Normalize()
{
for (;m_BitPos >= 8; m_BitPos -= 8)
m_Value = (m_Value << 8) | m_Stream.ReadByte();
}
UInt32 GetValue(unsigned numBits) const
{
// return (m_Value << m_BitPos) >> (kNumBigValueBits - numBits);
return ((m_Value >> (8 - m_BitPos)) & kMask) >> (kNumValueBits - numBits);
}
void MovePos(unsigned numBits)
{
m_BitPos += numBits;
Normalize();
}
UInt32 ReadBits(unsigned numBits)
{
UInt32 res = GetValue(numBits);
MovePos(numBits);
return res;
}
void AlignToByte() { MovePos((32 - m_BitPos) & 7); }
};
}
#endif
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