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644 lines
16 KiB
C++
644 lines
16 KiB
C++
/****************************************************************************
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* This file is part of PPMd project *
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* Written and distributed to public domain by Dmitry Shkarin 1997, *
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* 1999-2000 *
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* Contents: model description and encoding/decoding routines *
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****************************************************************************/
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static const int MAX_O=64; /* maximum allowed model order */
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const uint TOP=1 << 24, BOT=1 << 15;
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template <class T>
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inline void _PPMD_SWAP(T& t1,T& t2) { T tmp=t1; t1=t2; t2=tmp; }
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inline RARPPM_CONTEXT* RARPPM_CONTEXT::createChild(ModelPPM *Model,RARPPM_STATE* pStats,
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RARPPM_STATE& FirstState)
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{
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RARPPM_CONTEXT* pc = (RARPPM_CONTEXT*) Model->SubAlloc.AllocContext();
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if ( pc )
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{
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pc->NumStats=1;
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pc->OneState=FirstState;
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pc->Suffix=this;
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pStats->Successor=pc;
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}
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return pc;
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}
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ModelPPM::ModelPPM()
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{
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MinContext=NULL;
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MaxContext=NULL;
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MedContext=NULL;
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}
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void ModelPPM::RestartModelRare()
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{
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int i, k, m;
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memset(CharMask,0,sizeof(CharMask));
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SubAlloc.InitSubAllocator();
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InitRL=-(MaxOrder < 12 ? MaxOrder:12)-1;
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MinContext = MaxContext = (RARPPM_CONTEXT*) SubAlloc.AllocContext();
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if (MinContext == NULL)
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throw std::bad_alloc();
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MinContext->Suffix=NULL;
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OrderFall=MaxOrder;
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MinContext->U.SummFreq=(MinContext->NumStats=256)+1;
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FoundState=MinContext->U.Stats=(RARPPM_STATE*)SubAlloc.AllocUnits(256/2);
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if (FoundState == NULL)
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throw std::bad_alloc();
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for (RunLength=InitRL, PrevSuccess=i=0;i < 256;i++)
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{
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MinContext->U.Stats[i].Symbol=i;
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MinContext->U.Stats[i].Freq=1;
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MinContext->U.Stats[i].Successor=NULL;
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}
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static const ushort InitBinEsc[]={
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0x3CDD,0x1F3F,0x59BF,0x48F3,0x64A1,0x5ABC,0x6632,0x6051
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};
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for (i=0;i < 128;i++)
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for (k=0;k < 8;k++)
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for (m=0;m < 64;m += 8)
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BinSumm[i][k+m]=BIN_SCALE-InitBinEsc[k]/(i+2);
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for (i=0;i < 25;i++)
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for (k=0;k < 16;k++)
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SEE2Cont[i][k].init(5*i+10);
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}
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void ModelPPM::StartModelRare(int MaxOrder)
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{
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int i, k, m ,Step;
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EscCount=1;
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/*
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if (MaxOrder < 2)
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{
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memset(CharMask,0,sizeof(CharMask));
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OrderFall=ModelPPM::MaxOrder;
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MinContext=MaxContext;
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while (MinContext->Suffix != NULL)
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{
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MinContext=MinContext->Suffix;
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OrderFall--;
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}
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FoundState=MinContext->U.Stats;
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MinContext=MaxContext;
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}
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else
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*/
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{
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ModelPPM::MaxOrder=MaxOrder;
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RestartModelRare();
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NS2BSIndx[0]=2*0;
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NS2BSIndx[1]=2*1;
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memset(NS2BSIndx+2,2*2,9);
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memset(NS2BSIndx+11,2*3,256-11);
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for (i=0;i < 3;i++)
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NS2Indx[i]=i;
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for (m=i, k=Step=1;i < 256;i++)
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{
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NS2Indx[i]=m;
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if ( !--k )
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{
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k = ++Step;
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m++;
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}
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}
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memset(HB2Flag,0,0x40);
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memset(HB2Flag+0x40,0x08,0x100-0x40);
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DummySEE2Cont.Shift=PERIOD_BITS;
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}
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}
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void RARPPM_CONTEXT::rescale(ModelPPM *Model)
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{
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int OldNS=NumStats, i=NumStats-1, Adder, EscFreq;
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RARPPM_STATE* p1, * p;
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for (p=Model->FoundState;p != U.Stats;p--)
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_PPMD_SWAP(p[0],p[-1]);
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U.Stats->Freq += 4;
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U.SummFreq += 4;
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EscFreq=U.SummFreq-p->Freq;
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Adder=(Model->OrderFall != 0);
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U.SummFreq = (p->Freq=(p->Freq+Adder) >> 1);
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do
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{
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EscFreq -= (++p)->Freq;
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U.SummFreq += (p->Freq=(p->Freq+Adder) >> 1);
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if (p[0].Freq > p[-1].Freq)
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{
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RARPPM_STATE tmp=*(p1=p);
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do
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{
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p1[0]=p1[-1];
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} while (--p1 != U.Stats && tmp.Freq > p1[-1].Freq);
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*p1=tmp;
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}
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} while ( --i );
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if (p->Freq == 0)
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{
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do
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{
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i++;
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} while ((--p)->Freq == 0);
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EscFreq += i;
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if ((NumStats -= i) == 1)
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{
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RARPPM_STATE tmp=*U.Stats;
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do
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{
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tmp.Freq-=(tmp.Freq >> 1);
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EscFreq>>=1;
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} while (EscFreq > 1);
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Model->SubAlloc.FreeUnits(U.Stats,(OldNS+1) >> 1);
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*(Model->FoundState=&OneState)=tmp; return;
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}
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}
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U.SummFreq += (EscFreq -= (EscFreq >> 1));
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int n0=(OldNS+1) >> 1, n1=(NumStats+1) >> 1;
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if (n0 != n1)
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U.Stats = (RARPPM_STATE*) Model->SubAlloc.ShrinkUnits(U.Stats,n0,n1);
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Model->FoundState=U.Stats;
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}
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inline RARPPM_CONTEXT* ModelPPM::CreateSuccessors(bool Skip,RARPPM_STATE* p1)
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{
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RARPPM_STATE UpState;
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RARPPM_CONTEXT* pc=MinContext, * UpBranch=FoundState->Successor;
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RARPPM_STATE * p, * ps[MAX_O], ** pps=ps;
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if ( !Skip )
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{
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*pps++ = FoundState;
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if ( !pc->Suffix )
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goto NO_LOOP;
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}
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if ( p1 )
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{
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p=p1;
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pc=pc->Suffix;
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goto LOOP_ENTRY;
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}
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do
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{
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pc=pc->Suffix;
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if (pc->NumStats != 1)
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{
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if ((p=pc->U.Stats)->Symbol != FoundState->Symbol)
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do
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{
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p++;
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} while (p->Symbol != FoundState->Symbol);
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}
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else
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p=&(pc->OneState);
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LOOP_ENTRY:
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if (p->Successor != UpBranch)
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{
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pc=p->Successor;
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break;
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}
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// We ensure that PPM order input parameter does not exceed MAX_O (64),
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// so we do not really need this check and added it for extra safety.
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// See CVE-2017-17969 for details.
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if (pps>=ps+ASIZE(ps))
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return NULL;
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*pps++ = p;
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} while ( pc->Suffix );
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NO_LOOP:
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if (pps == ps)
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return pc;
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UpState.Symbol=*(byte*) UpBranch;
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UpState.Successor=(RARPPM_CONTEXT*) (((byte*) UpBranch)+1);
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if (pc->NumStats != 1)
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{
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if ((byte*) pc <= SubAlloc.pText)
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return(NULL);
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if ((p=pc->U.Stats)->Symbol != UpState.Symbol)
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do
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{
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p++;
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} while (p->Symbol != UpState.Symbol);
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uint cf=p->Freq-1;
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uint s0=pc->U.SummFreq-pc->NumStats-cf;
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UpState.Freq=1+((2*cf <= s0)?(5*cf > s0):((2*cf+3*s0-1)/(2*s0)));
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}
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else
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UpState.Freq=pc->OneState.Freq;
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do
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{
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pc = pc->createChild(this,*--pps,UpState);
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if ( !pc )
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return NULL;
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} while (pps != ps);
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return pc;
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}
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inline void ModelPPM::UpdateModel()
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{
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RARPPM_STATE fs = *FoundState, *p = NULL;
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RARPPM_CONTEXT *pc, *Successor;
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uint ns1, ns, cf, sf, s0;
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if (fs.Freq < MAX_FREQ/4 && (pc=MinContext->Suffix) != NULL)
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{
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if (pc->NumStats != 1)
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{
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if ((p=pc->U.Stats)->Symbol != fs.Symbol)
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{
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do
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{
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p++;
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} while (p->Symbol != fs.Symbol);
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if (p[0].Freq >= p[-1].Freq)
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{
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_PPMD_SWAP(p[0],p[-1]);
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p--;
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}
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}
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if (p->Freq < MAX_FREQ-9)
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{
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p->Freq += 2;
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pc->U.SummFreq += 2;
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}
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}
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else
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{
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p=&(pc->OneState);
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p->Freq += (p->Freq < 32);
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}
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}
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if ( !OrderFall )
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{
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MinContext=MaxContext=FoundState->Successor=CreateSuccessors(TRUE,p);
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if ( !MinContext )
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goto RESTART_MODEL;
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return;
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}
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*SubAlloc.pText++ = fs.Symbol;
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Successor = (RARPPM_CONTEXT*) SubAlloc.pText;
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if (SubAlloc.pText >= SubAlloc.FakeUnitsStart)
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goto RESTART_MODEL;
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if ( fs.Successor )
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{
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if ((byte*) fs.Successor <= SubAlloc.pText &&
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(fs.Successor=CreateSuccessors(FALSE,p)) == NULL)
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goto RESTART_MODEL;
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if ( !--OrderFall )
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{
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Successor=fs.Successor;
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SubAlloc.pText -= (MaxContext != MinContext);
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}
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}
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else
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{
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FoundState->Successor=Successor;
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fs.Successor=MinContext;
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}
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s0=MinContext->U.SummFreq-(ns=MinContext->NumStats)-(fs.Freq-1);
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for (pc=MaxContext;pc != MinContext;pc=pc->Suffix)
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{
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if ((ns1=pc->NumStats) != 1)
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{
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if ((ns1 & 1) == 0)
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{
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pc->U.Stats=(RARPPM_STATE*) SubAlloc.ExpandUnits(pc->U.Stats,ns1 >> 1);
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if ( !pc->U.Stats )
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goto RESTART_MODEL;
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}
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pc->U.SummFreq += (2*ns1 < ns)+2*((4*ns1 <= ns) & (pc->U.SummFreq <= 8*ns1));
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}
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else
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{
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p=(RARPPM_STATE*) SubAlloc.AllocUnits(1);
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if ( !p )
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goto RESTART_MODEL;
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*p=pc->OneState;
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pc->U.Stats=p;
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if (p->Freq < MAX_FREQ/4-1)
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p->Freq += p->Freq;
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else
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p->Freq = MAX_FREQ-4;
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pc->U.SummFreq=p->Freq+InitEsc+(ns > 3);
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}
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cf=2*fs.Freq*(pc->U.SummFreq+6);
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sf=s0+pc->U.SummFreq;
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if (cf < 6*sf)
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{
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cf=1+(cf > sf)+(cf >= 4*sf);
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pc->U.SummFreq += 3;
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}
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else
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{
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cf=4+(cf >= 9*sf)+(cf >= 12*sf)+(cf >= 15*sf);
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pc->U.SummFreq += cf;
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}
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p=pc->U.Stats+ns1;
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p->Successor=Successor;
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p->Symbol = fs.Symbol;
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p->Freq = cf;
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pc->NumStats=++ns1;
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}
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MaxContext=MinContext=fs.Successor;
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return;
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RESTART_MODEL:
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RestartModelRare();
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EscCount=0;
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}
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// Tabulated escapes for exponential symbol distribution
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static const byte ExpEscape[16]={ 25,14, 9, 7, 5, 5, 4, 4, 4, 3, 3, 3, 2, 2, 2, 2 };
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#define GET_MEAN(SUMM,SHIFT,ROUND) ((SUMM+(1 << (SHIFT-ROUND))) >> (SHIFT))
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inline void RARPPM_CONTEXT::decodeBinSymbol(ModelPPM *Model)
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{
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RARPPM_STATE& rs=OneState;
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Model->HiBitsFlag=Model->HB2Flag[Model->FoundState->Symbol];
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ushort& bs=Model->BinSumm[rs.Freq-1][Model->PrevSuccess+
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Model->NS2BSIndx[Suffix->NumStats-1]+
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Model->HiBitsFlag+2*Model->HB2Flag[rs.Symbol]+
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((Model->RunLength >> 26) & 0x20)];
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if (Model->Coder.GetCurrentShiftCount(TOT_BITS) < bs)
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{
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Model->FoundState=&rs;
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rs.Freq += (rs.Freq < 128);
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Model->Coder.SubRange.LowCount=0;
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Model->Coder.SubRange.HighCount=bs;
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bs = GET_SHORT16(bs+INTERVAL-GET_MEAN(bs,PERIOD_BITS,2));
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Model->PrevSuccess=1;
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Model->RunLength++;
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}
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else
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{
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Model->Coder.SubRange.LowCount=bs;
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bs = GET_SHORT16(bs-GET_MEAN(bs,PERIOD_BITS,2));
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Model->Coder.SubRange.HighCount=BIN_SCALE;
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Model->InitEsc=ExpEscape[bs >> 10];
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Model->NumMasked=1;
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Model->CharMask[rs.Symbol]=Model->EscCount;
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Model->PrevSuccess=0;
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Model->FoundState=NULL;
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}
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}
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inline void RARPPM_CONTEXT::update1(ModelPPM *Model,RARPPM_STATE* p)
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{
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(Model->FoundState=p)->Freq += 4;
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U.SummFreq += 4;
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if (p[0].Freq > p[-1].Freq)
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{
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_PPMD_SWAP(p[0],p[-1]);
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Model->FoundState=--p;
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if (p->Freq > MAX_FREQ)
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rescale(Model);
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}
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}
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inline bool RARPPM_CONTEXT::decodeSymbol1(ModelPPM *Model)
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{
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Model->Coder.SubRange.scale=U.SummFreq;
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RARPPM_STATE* p=U.Stats;
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int i, HiCnt;
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int count=Model->Coder.GetCurrentCount();
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if (count>=(int)Model->Coder.SubRange.scale)
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return(false);
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if (count < (HiCnt=p->Freq))
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{
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Model->PrevSuccess=(2*(Model->Coder.SubRange.HighCount=HiCnt) > Model->Coder.SubRange.scale);
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Model->RunLength += Model->PrevSuccess;
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(Model->FoundState=p)->Freq=(HiCnt += 4);
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U.SummFreq += 4;
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if (HiCnt > MAX_FREQ)
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rescale(Model);
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Model->Coder.SubRange.LowCount=0;
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return(true);
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}
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else
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if (Model->FoundState==NULL)
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return(false);
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Model->PrevSuccess=0;
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i=NumStats-1;
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while ((HiCnt += (++p)->Freq) <= count)
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if (--i == 0)
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{
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Model->HiBitsFlag=Model->HB2Flag[Model->FoundState->Symbol];
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Model->Coder.SubRange.LowCount=HiCnt;
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Model->CharMask[p->Symbol]=Model->EscCount;
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i=(Model->NumMasked=NumStats)-1;
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Model->FoundState=NULL;
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do
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{
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Model->CharMask[(--p)->Symbol]=Model->EscCount;
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} while ( --i );
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Model->Coder.SubRange.HighCount=Model->Coder.SubRange.scale;
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return(true);
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}
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Model->Coder.SubRange.LowCount=(Model->Coder.SubRange.HighCount=HiCnt)-p->Freq;
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update1(Model,p);
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return(true);
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}
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inline void RARPPM_CONTEXT::update2(ModelPPM *Model,RARPPM_STATE* p)
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{
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(Model->FoundState=p)->Freq += 4;
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U.SummFreq += 4;
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if (p->Freq > MAX_FREQ)
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rescale(Model);
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Model->EscCount++;
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Model->RunLength=Model->InitRL;
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}
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inline RARPPM_SEE2_CONTEXT* RARPPM_CONTEXT::makeEscFreq2(ModelPPM *Model,int Diff)
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{
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RARPPM_SEE2_CONTEXT* psee2c;
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if (NumStats != 256)
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{
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psee2c=Model->SEE2Cont[Model->NS2Indx[Diff-1]]+
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(Diff < Suffix->NumStats-NumStats)+
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2*(U.SummFreq < 11*NumStats)+4*(Model->NumMasked > Diff)+
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Model->HiBitsFlag;
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Model->Coder.SubRange.scale=psee2c->getMean();
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}
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else
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{
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psee2c=&Model->DummySEE2Cont;
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Model->Coder.SubRange.scale=1;
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}
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return psee2c;
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}
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inline bool RARPPM_CONTEXT::decodeSymbol2(ModelPPM *Model)
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{
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int count, HiCnt, i=NumStats-Model->NumMasked;
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RARPPM_SEE2_CONTEXT* psee2c=makeEscFreq2(Model,i);
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RARPPM_STATE* ps[256], ** pps=ps, * p=U.Stats-1;
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HiCnt=0;
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do
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{
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do
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{
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p++;
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} while (Model->CharMask[p->Symbol] == Model->EscCount);
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HiCnt += p->Freq;
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|
// We do not reuse PPMd coder in unstable state, so we do not really need
|
|
// this check and added it for extra safety. See CVE-2017-17969 for details.
|
|
if (pps>=ps+ASIZE(ps))
|
|
return false;
|
|
|
|
*pps++ = p;
|
|
} while ( --i );
|
|
Model->Coder.SubRange.scale += HiCnt;
|
|
count=Model->Coder.GetCurrentCount();
|
|
if (count>=(int)Model->Coder.SubRange.scale)
|
|
return(false);
|
|
p=*(pps=ps);
|
|
if (count < HiCnt)
|
|
{
|
|
HiCnt=0;
|
|
while ((HiCnt += p->Freq) <= count)
|
|
{
|
|
pps++;
|
|
if (pps>=ps+ASIZE(ps)) // Extra safety check.
|
|
return false;
|
|
p=*pps;
|
|
}
|
|
Model->Coder.SubRange.LowCount = (Model->Coder.SubRange.HighCount=HiCnt)-p->Freq;
|
|
psee2c->update();
|
|
update2(Model,p);
|
|
}
|
|
else
|
|
{
|
|
Model->Coder.SubRange.LowCount=HiCnt;
|
|
Model->Coder.SubRange.HighCount=Model->Coder.SubRange.scale;
|
|
i=NumStats-Model->NumMasked;
|
|
pps--;
|
|
do
|
|
{
|
|
pps++;
|
|
if (pps>=ps+ASIZE(ps)) // Extra safety check.
|
|
return false;
|
|
Model->CharMask[(*pps)->Symbol]=Model->EscCount;
|
|
} while ( --i );
|
|
psee2c->Summ += Model->Coder.SubRange.scale;
|
|
Model->NumMasked = NumStats;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
|
|
inline void ModelPPM::ClearMask()
|
|
{
|
|
EscCount=1;
|
|
memset(CharMask,0,sizeof(CharMask));
|
|
}
|
|
|
|
|
|
|
|
|
|
// reset PPM variables after data error allowing safe resuming
|
|
// of further data processing
|
|
void ModelPPM::CleanUp()
|
|
{
|
|
SubAlloc.StopSubAllocator();
|
|
SubAlloc.StartSubAllocator(1);
|
|
StartModelRare(2);
|
|
}
|
|
|
|
|
|
bool ModelPPM::DecodeInit(Unpack *UnpackRead,int &EscChar,byte *hcppm)
|
|
{
|
|
int MaxOrder=UnpackRead->GetChar();
|
|
bool Reset=(MaxOrder & 0x20)!=0;
|
|
|
|
int MaxMB;
|
|
if (Reset)
|
|
{
|
|
MaxMB=UnpackRead->GetChar();
|
|
if (MaxMB>128) return(false);
|
|
}
|
|
else
|
|
if (SubAlloc.GetAllocatedMemory()==0)
|
|
return(false);
|
|
if (MaxOrder & 0x40)
|
|
EscChar=UnpackRead->GetChar();
|
|
Coder.InitDecoder(UnpackRead);
|
|
if (Reset)
|
|
{
|
|
MaxOrder=(MaxOrder & 0x1f)+1;
|
|
if (MaxOrder>16)
|
|
MaxOrder=16+(MaxOrder-16)*3;
|
|
if (MaxOrder==1)
|
|
{
|
|
SubAlloc.StopSubAllocator();
|
|
return(false);
|
|
}
|
|
SubAlloc.SetHeapStartFixed(hcppm);
|
|
SubAlloc.StartSubAllocator(MaxMB+1);
|
|
StartModelRare(MaxOrder);
|
|
}
|
|
return(MinContext!=NULL);
|
|
}
|
|
|
|
|
|
int ModelPPM::DecodeChar()
|
|
{
|
|
if ((byte*)MinContext <= SubAlloc.pText || (byte*)MinContext>SubAlloc.HeapEnd)
|
|
return(-1);
|
|
if (MinContext->NumStats != 1)
|
|
{
|
|
if ((byte*)MinContext->U.Stats <= SubAlloc.pText || (byte*)MinContext->U.Stats>SubAlloc.HeapEnd)
|
|
return(-1);
|
|
if (!MinContext->decodeSymbol1(this))
|
|
return(-1);
|
|
}
|
|
else
|
|
MinContext->decodeBinSymbol(this);
|
|
Coder.Decode();
|
|
while ( !FoundState )
|
|
{
|
|
ARI_DEC_NORMALIZE(Coder.code,Coder.low,Coder.range,Coder.UnpackRead);
|
|
do
|
|
{
|
|
OrderFall++;
|
|
MinContext=MinContext->Suffix;
|
|
if ((byte*)MinContext <= SubAlloc.pText || (byte*)MinContext>SubAlloc.HeapEnd)
|
|
return(-1);
|
|
} while (MinContext->NumStats == NumMasked);
|
|
if (!MinContext->decodeSymbol2(this))
|
|
return(-1);
|
|
Coder.Decode();
|
|
}
|
|
int Symbol=FoundState->Symbol;
|
|
if (!OrderFall && (byte*) FoundState->Successor > SubAlloc.pText)
|
|
MinContext=MaxContext=FoundState->Successor;
|
|
else
|
|
{
|
|
UpdateModel();
|
|
if (EscCount == 0)
|
|
ClearMask();
|
|
}
|
|
ARI_DEC_NORMALIZE(Coder.code,Coder.low,Coder.range,Coder.UnpackRead);
|
|
return(Symbol);
|
|
}
|