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