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// QuantumDecoder.cpp
#include "StdAfx.h"
#include "../../Common/Defs.h"
#include "QuantumDecoder.h"
namespace NCompress {
namespace NQuantum {
static const unsigned kNumLenSymbols = 27;
static const unsigned kMatchMinLen = 3;
static const unsigned kNumSimplePosSlots = 4;
static const unsigned kNumSimpleLenSlots = 6;
static const UInt16 kUpdateStep = 8;
static const UInt16 kFreqSumMax = 3800;
static const unsigned kReorderCountStart = 4;
static const unsigned kReorderCount = 50;
void CModelDecoder::Init(unsigned numItems)
{
NumItems = numItems;
ReorderCount = kReorderCountStart;
for (unsigned i = 0; i < numItems; i++)
{
Freqs[i] = (UInt16)(numItems - i);
Vals[i] = (Byte)i;
}
Freqs[numItems] = 0;
}
unsigned CModelDecoder::Decode(CRangeDecoder *rc)
{
UInt32 threshold = rc->GetThreshold(Freqs[0]);
unsigned i;
for (i = 1; Freqs[i] > threshold; i++);
rc->Decode(Freqs[i], Freqs[(size_t)i - 1], Freqs[0]);
unsigned res = Vals[--i];
do
Freqs[i] += kUpdateStep;
while (i--);
if (Freqs[0] > kFreqSumMax)
{
if (--ReorderCount == 0)
{
ReorderCount = kReorderCount;
for (i = 0; i < NumItems; i++)
Freqs[i] = (UInt16)(((Freqs[i] - Freqs[(size_t)i + 1]) + 1) >> 1);
for (i = 0; i < NumItems - 1; i++)
for (unsigned j = i + 1; j < NumItems; j++)
if (Freqs[i] < Freqs[j])
{
UInt16 tmpFreq = Freqs[i];
Byte tmpVal = Vals[i];
Freqs[i] = Freqs[j];
Vals[i] = Vals[j];
Freqs[j] = tmpFreq;
Vals[j] = tmpVal;
}
do
Freqs[i] = (UInt16)(Freqs[i] + Freqs[(size_t)i + 1]);
while (i--);
}
else
{
i = NumItems - 1;
do
{
Freqs[i] >>= 1;
if (Freqs[i] <= Freqs[(size_t)i + 1])
Freqs[i] = (UInt16)(Freqs[(size_t)i + 1] + 1);
}
while (i--);
}
}
return res;
}
void CDecoder::Init()
{
m_Selector.Init(kNumSelectors);
unsigned i;
for (i = 0; i < kNumLitSelectors; i++)
m_Literals[i].Init(kNumLitSymbols);
unsigned numItems = (_numDictBits == 0 ? 1 : (_numDictBits << 1));
const unsigned kNumPosSymbolsMax[kNumMatchSelectors] = { 24, 36, 42 };
for (i = 0; i < kNumMatchSelectors; i++)
m_PosSlot[i].Init(MyMin(numItems, kNumPosSymbolsMax[i]));
m_LenSlot.Init(kNumLenSymbols);
}
HRESULT CDecoder::CodeSpec(const Byte *inData, size_t inSize, UInt32 outSize)
{
if (inSize < 2)
return S_FALSE;
CRangeDecoder rc;
rc.Stream.SetStreamAndInit(inData, inSize);
rc.Init();
while (outSize != 0)
{
if (rc.Stream.WasExtraRead())
return S_FALSE;
unsigned selector = m_Selector.Decode(&rc);
if (selector < kNumLitSelectors)
{
Byte b = (Byte)((selector << (8 - kNumLitSelectorBits)) + m_Literals[selector].Decode(&rc));
_outWindow.PutByte(b);
outSize--;
}
else
{
selector -= kNumLitSelectors;
unsigned len = selector + kMatchMinLen;
if (selector == 2)
{
unsigned lenSlot = m_LenSlot.Decode(&rc);
if (lenSlot >= kNumSimpleLenSlots)
{
lenSlot -= 2;
unsigned numDirectBits = (unsigned)(lenSlot >> 2);
len += ((4 | (lenSlot & 3)) << numDirectBits) - 2;
if (numDirectBits < 6)
len += rc.Stream.ReadBits(numDirectBits);
}
else
len += lenSlot;
}
UInt32 dist = m_PosSlot[selector].Decode(&rc);
if (dist >= kNumSimplePosSlots)
{
unsigned numDirectBits = (unsigned)((dist >> 1) - 1);
dist = ((2 | (dist & 1)) << numDirectBits) + rc.Stream.ReadBits(numDirectBits);
}
unsigned locLen = len;
if (len > outSize)
locLen = (unsigned)outSize;
if (!_outWindow.CopyBlock(dist, locLen))
return S_FALSE;
outSize -= locLen;
len -= locLen;
if (len != 0)
return S_FALSE;
}
}
return rc.Finish() ? S_OK : S_FALSE;
}
HRESULT CDecoder::Code(const Byte *inData, size_t inSize,
ISequentialOutStream *outStream, UInt32 outSize,
bool keepHistory)
{
try
{
_outWindow.SetStream(outStream);
_outWindow.Init(keepHistory);
if (!keepHistory)
Init();
HRESULT res = CodeSpec(inData, inSize, outSize);
HRESULT res2 = _outWindow.Flush();
return res != S_OK ? res : res2;
}
catch(const CLzOutWindowException &e) { return e.ErrorCode; }
catch(...) { return S_FALSE; }
}
HRESULT CDecoder::SetParams(unsigned numDictBits)
{
if (numDictBits > 21)
return E_INVALIDARG;
_numDictBits = numDictBits;
if (!_outWindow.Create((UInt32)1 << _numDictBits))
return E_OUTOFMEMORY;
return S_OK;
}
}}
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