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// QuantumDecoder.h
#ifndef __COMPRESS_QUANTUM_DECODER_H
#define __COMPRESS_QUANTUM_DECODER_H
#include "../../Common/MyCom.h"
#include "LzOutWindow.h"
namespace NCompress {
namespace NQuantum {
class CBitDecoder
{
UInt32 Value;
bool _extra;
const Byte *_buf;
const Byte *_bufLim;
public:
void SetStreamAndInit(const Byte *inData, size_t inSize)
{
_buf = inData;
_bufLim = inData + inSize;
Value = 0x10000;
_extra = false;
}
bool WasExtraRead() const { return _extra; }
bool WasFinishedOK() const
{
return !_extra && _buf == _bufLim;
}
UInt32 ReadBit()
{
if (Value >= 0x10000)
{
Byte b;
if (_buf >= _bufLim)
{
b = 0xFF;
_extra = true;
}
else
b = *_buf++;
Value = 0x100 | b;
}
UInt32 res = (Value >> 7) & 1;
Value <<= 1;
return res;
}
UInt32 ReadStart16Bits()
{
// we use check for extra read in another code.
UInt32 val = ((UInt32)*_buf << 8) | _buf[1];
_buf += 2;
return val;
}
UInt32 ReadBits(unsigned numBits) // numBits > 0
{
UInt32 res = 0;
do
res = (res << 1) | ReadBit();
while (--numBits);
return res;
}
};
class CRangeDecoder
{
UInt32 Low;
UInt32 Range;
UInt32 Code;
public:
CBitDecoder Stream;
void Init()
{
Low = 0;
Range = 0x10000;
Code = Stream.ReadStart16Bits();
}
bool Finish()
{
// do all streams use these two bits at end?
if (Stream.ReadBit() != 0) return false;
if (Stream.ReadBit() != 0) return false;
return Stream.WasFinishedOK();
}
UInt32 GetThreshold(UInt32 total) const
{
return ((Code + 1) * total - 1) / Range; // & 0xFFFF is not required;
}
void Decode(UInt32 start, UInt32 end, UInt32 total)
{
UInt32 high = Low + end * Range / total - 1;
UInt32 offset = start * Range / total;
Code -= offset;
Low += offset;
for (;;)
{
if ((Low & 0x8000) != (high & 0x8000))
{
if ((Low & 0x4000) == 0 || (high & 0x4000) != 0)
break;
Low &= 0x3FFF;
high |= 0x4000;
}
Low = (Low << 1) & 0xFFFF;
high = ((high << 1) | 1) & 0xFFFF;
Code = ((Code << 1) | Stream.ReadBit());
}
Range = high - Low + 1;
}
};
const unsigned kNumLitSelectorBits = 2;
const unsigned kNumLitSelectors = (1 << kNumLitSelectorBits);
const unsigned kNumLitSymbols = 1 << (8 - kNumLitSelectorBits);
const unsigned kNumMatchSelectors = 3;
const unsigned kNumSelectors = kNumLitSelectors + kNumMatchSelectors;
const unsigned kNumSymbolsMax = kNumLitSymbols; // 64
class CModelDecoder
{
unsigned NumItems;
unsigned ReorderCount;
UInt16 Freqs[kNumSymbolsMax + 1];
Byte Vals[kNumSymbolsMax];
public:
void Init(unsigned numItems);
unsigned Decode(CRangeDecoder *rc);
};
class CDecoder:
public IUnknown,
public CMyUnknownImp
{
CLzOutWindow _outWindow;
unsigned _numDictBits;
CModelDecoder m_Selector;
CModelDecoder m_Literals[kNumLitSelectors];
CModelDecoder m_PosSlot[kNumMatchSelectors];
CModelDecoder m_LenSlot;
void Init();
HRESULT CodeSpec(const Byte *inData, size_t inSize, UInt32 outSize);
public:
MY_UNKNOWN_IMP
HRESULT Code(const Byte *inData, size_t inSize,
ISequentialOutStream *outStream, UInt32 outSize,
bool keepHistory);
HRESULT SetParams(unsigned numDictBits);
CDecoder(): _numDictBits(0) {}
virtual ~CDecoder() {}
};
}}
#endif
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