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// Archive/Cab/LZXBitDecoder.h
#ifndef __ARCHIVE_CAB_LZXBITDECODER_H
#define __ARCHIVE_CAB_LZXBITDECODER_H
#include "CabInBuffer.h"
namespace NArchive {
namespace NCab {
namespace NLZX {
namespace NBitStream {
const int kNumBigValueBits = 8 * 4;
const int kNumValueBits = 17;
const int kBitDecoderValueMask = (1 << kNumValueBits) - 1;
class CDecoder
{
protected:
CInBuffer m_Stream;
UInt32 m_BitPos;
UInt32 m_Value;
public:
bool Create(UInt32 bufferSize) { return m_Stream.Create(bufferSize); }
void SetStream(ISequentialInStream *s) { m_Stream.SetStream(s); }
void ReleaseStream() { m_Stream.ReleaseStream(); }
void Init(Byte reservedSize, UInt32 numBlocks)
{
m_Stream.Init(reservedSize, numBlocks);
}
UInt64 GetProcessedSize() const
{ return m_Stream.GetProcessedSize() - (kNumBigValueBits - m_BitPos) / 8; }
UInt32 GetBitPosition() const
{ return UInt32(m_Stream.GetProcessedSize() * 8 - (kNumBigValueBits - m_BitPos)); }
void Init()
{
m_BitPos = kNumBigValueBits;
Normalize();
}
void Normalize()
{
for (;m_BitPos >= 16; m_BitPos -= 16)
{
Byte b0 = m_Stream.ReadByte();
Byte b1 = m_Stream.ReadByte();
m_Value = (m_Value << 8) | b1;
m_Value = (m_Value << 8) | b0;
}
}
UInt32 GetValue(UInt32 numBits)
{
return ((m_Value >> ((32 - kNumValueBits) - m_BitPos)) & kBitDecoderValueMask) >>
(kNumValueBits - numBits);
}
void MovePos(UInt32 numBits)
{
m_BitPos += numBits;
Normalize();
}
UInt32 ReadBits(UInt32 numBits)
{
UInt32 res = GetValue(numBits);
MovePos(numBits);
return res;
}
UInt32 ReadBitsBig(UInt32 numBits)
{
UInt32 numBits0 = numBits / 2;
UInt32 numBits1 = numBits - numBits0;
UInt32 res = ReadBits(numBits0) << numBits1;
return res + ReadBits(numBits1);
}
Byte DirectReadByte()
{
if (m_BitPos == kNumBigValueBits)
return m_Stream.ReadByte();
Byte res;
switch(m_BitPos)
{
case 0:
res = Byte(m_Value >> 16);
break;
case 8:
res = Byte(m_Value >> 24);
break;
case 16:
res = Byte(m_Value);
break;
case 24:
res = Byte(m_Value >> 8);
break;
}
m_BitPos += 8;
return res;
}
HRESULT ReadBlock(UInt32 &uncompressedSize, bool &dataAreCorrect)
{ return m_Stream.ReadBlock(uncompressedSize, dataAreCorrect); }
};
}}}}
#endif
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