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