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