3.13

7zip/Compress/PPMD/PPMDDecode.h

@@ -0,0 +1,139 @@
+// Decode.h
+// This code is based on Dmitry Shkarin's PPMdH code
+
+#pragma once
+
+#ifndef __COMPRESS_PPM_PPMD_DECODE_H
+#define __COMPRESS_PPM_PPMD_DECODE_H
+
+#include "PPMDContext.h"
+
+namespace NCompress {
+namespace NPPMD {
+
+struct CDecodeInfo: public CInfo
+{
+  void DecodeBinSymbol(NRangeCoder::CDecoder *rangeDecoder)
+  {
+    PPM_CONTEXT::STATE& rs = MinContext->oneState();                   
+    WORD& bs = GetBinSumm(rs, MinContext->Suffix->NumStats);
+    if (rangeDecoder->DecodeBit(bs, TOT_BITS) == 0) 
+    {
+      FoundState = &rs;
+      rs.Freq += (rs.Freq < 128);
+      bs += UINT16(INTERVAL-GET_MEAN(bs,PERIOD_BITS,2));
+      PrevSuccess = 1;
+      RunLength++;
+    } 
+    else 
+    {
+      bs -= UINT16(GET_MEAN(bs,PERIOD_BITS,2));
+      InitEsc = ExpEscape[bs >> 10];
+      NumMasked = 1;                        
+      CharMask[rs.Symbol] = EscCount;
+      PrevSuccess = 0;                      
+      FoundState = NULL;
+    }
+  }
+
+  void DecodeSymbol1(NRangeCoder::CDecoder *rangeDecoder)
+  {
+    PPM_CONTEXT::STATE* p = 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, MinContext->Stats->Freq, MinContext->SummFreq);
+      (FoundState = p)->Freq=(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(NRangeCoder::CDecoder *rangeDecoder)
+  {
+    int count, hiCnt, i = MinContext->NumStats - NumMasked;
+    UINT32 freqSum;
+    SEE2_CONTEXT* psee2c = makeEscFreq2(i, freqSum);
+    PPM_CONTEXT::STATE* ps[256], ** pps = ps, * p = 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 += freqSum;     
+      NumMasked = MinContext->NumStats;
+    }
+  }
+
+  int DecodeSymbol(NRangeCoder::CDecoder *rangeDecoder)
+  {
+    if (MinContext->NumStats != 1)                        
+      DecodeSymbol1(rangeDecoder);
+    else                                
+      DecodeBinSymbol(rangeDecoder);
+    while ( !FoundState ) 
+    {
+      do 
+      {
+        OrderFall++;                
+        MinContext = MinContext->Suffix;
+        if ( !MinContext )          
+          return -1;
+      } 
+      while (MinContext->NumStats == NumMasked);
+      DecodeSymbol2(rangeDecoder);    
+    }
+    BYTE symbol = FoundState->Symbol;
+    NextContext();
+    return symbol;
+  }
+};
+
+}}
+
+#endif