4.63

CPP/7zip/Compress/PpmdDecode.h

@@ -0,0 +1,154 @@
+// PpmdDecode.h
+// This code is based on Dmitry Shkarin's PPMdH code
+
+#ifndef __COMPRESS_PPMD_DECODE_H
+#define __COMPRESS_PPMD_DECODE_H
+
+#include "PpmdContext.h"
+
+namespace NCompress {
+namespace NPpmd {
+
+class CRangeDecoderVirt
+{
+public:
+  virtual UInt32 GetThreshold(UInt32 total) = 0;
+  virtual void Decode(UInt32 start, UInt32 size) = 0;
+  virtual UInt32 DecodeBit(UInt32 size0, UInt32 numTotalBits) = 0;
+};
+
+typedef NRangeCoder::CDecoder CRangeDecoderMy;
+
+class CRangeDecoder:public CRangeDecoderVirt, public CRangeDecoderMy
+{
+  UInt32 GetThreshold(UInt32 total) { return CRangeDecoderMy::GetThreshold(total); }
+  void Decode(UInt32 start, UInt32 size) { CRangeDecoderMy::Decode(start, size); }
+  UInt32 DecodeBit(UInt32 size0, UInt32 numTotalBits) { return CRangeDecoderMy::DecodeBit(size0, numTotalBits); }
+};
+
+struct CDecodeInfo: public CInfo
+{
+  void DecodeBinSymbol(CRangeDecoderVirt *rangeDecoder)
+  {
+    PPM_CONTEXT::STATE& rs = MinContext->oneState();
+    UInt16& bs = GetBinSumm(rs, GetContextNoCheck(MinContext->Suffix)->NumStats);
+    if (rangeDecoder->DecodeBit(bs, TOT_BITS) == 0)
+    {
+      FoundState = &rs;
+      rs.Freq = (Byte)(rs.Freq + (rs.Freq < 128 ? 1: 0));
+      bs = (UInt16)(bs + INTERVAL - GET_MEAN(bs, PERIOD_BITS, 2));
+      PrevSuccess = 1;
+      RunLength++;
+    }
+    else
+    {
+      bs = (UInt16)(bs - GET_MEAN(bs, PERIOD_BITS, 2));
+      InitEsc = ExpEscape[bs >> 10];
+      NumMasked = 1;
+      CharMask[rs.Symbol] = EscCount;
+      PrevSuccess = 0;
+      FoundState = NULL;
+    }
+  }
+
+  void DecodeSymbol1(CRangeDecoderVirt *rangeDecoder)
+  {
+    PPM_CONTEXT::STATE* p = GetStateNoCheck(MinContext->Stats);
+    int i, count, hiCnt;
+    if ((count = rangeDecoder->GetThreshold(MinContext->SummFreq)) < (hiCnt = p->Freq))
+    {
+      PrevSuccess = (2 * hiCnt > MinContext->SummFreq);
+      RunLength += PrevSuccess;
+      rangeDecoder->Decode(0, p->Freq); // MinContext->SummFreq);
+      (FoundState = p)->Freq = (Byte)(hiCnt += 4);
+      MinContext->SummFreq += 4;
+      if (hiCnt > MAX_FREQ)
+        rescale();
+      return;
+    }
+    PrevSuccess = 0;
+    i = MinContext->NumStats - 1;
+    while ((hiCnt += (++p)->Freq) <= count)
+      if (--i == 0)
+      {
+        HiBitsFlag = HB2Flag[FoundState->Symbol];
+        rangeDecoder->Decode(hiCnt, MinContext->SummFreq - hiCnt); // , MinContext->SummFreq);
+        CharMask[p->Symbol] = EscCount;
+        i = (NumMasked = MinContext->NumStats)-1;
+        FoundState = NULL;
+        do { CharMask[(--p)->Symbol] = EscCount; } while ( --i );
+        return;
+      }
+    rangeDecoder->Decode(hiCnt - p->Freq, p->Freq); // , MinContext->SummFreq);
+    update1(p);
+  }
+
+
+  void DecodeSymbol2(CRangeDecoderVirt *rangeDecoder)
+  {
+    int count, hiCnt, i = MinContext->NumStats - NumMasked;
+    UInt32 freqSum;
+    SEE2_CONTEXT* psee2c = makeEscFreq2(i, freqSum);
+    PPM_CONTEXT::STATE* ps[256], ** pps = ps, * p = GetStateNoCheck(MinContext->Stats)-1;
+    hiCnt = 0;
+    do
+    {
+      do { p++; } while (CharMask[p->Symbol] == EscCount);
+      hiCnt += p->Freq;
+      *pps++ = p;
+    }
+    while ( --i );
+    
+    freqSum += hiCnt;
+    count = rangeDecoder->GetThreshold(freqSum);
+    
+    p = *(pps = ps);
+    if (count < hiCnt)
+    {
+      hiCnt = 0;
+      while ((hiCnt += p->Freq) <= count)
+        p=*++pps;
+      rangeDecoder->Decode(hiCnt - p->Freq, p->Freq); // , freqSum);
+      
+      psee2c->update();
+      update2(p);
+    }
+    else
+    {
+      rangeDecoder->Decode(hiCnt, freqSum - hiCnt); // , freqSum);
+      
+      i = MinContext->NumStats - NumMasked;
+      pps--;
+      do { CharMask[(*++pps)->Symbol] = EscCount; } while ( --i );
+      psee2c->Summ = (UInt16)(psee2c->Summ + freqSum);
+      NumMasked = MinContext->NumStats;
+    }
+  }
+
+  int DecodeSymbol(CRangeDecoderVirt *rangeDecoder)
+  {
+    if (MinContext->NumStats != 1)
+      DecodeSymbol1(rangeDecoder);
+    else
+      DecodeBinSymbol(rangeDecoder);
+    while ( !FoundState )
+    {
+      do
+      {
+        OrderFall++;
+        MinContext = GetContext(MinContext->Suffix);
+        if (MinContext == 0)
+          return -1;
+      }
+      while (MinContext->NumStats == NumMasked);
+      DecodeSymbol2(rangeDecoder);
+    }
+    Byte symbol = FoundState->Symbol;
+    NextContext();
+    return symbol;
+  }
+};
+
+}}
+
+#endif