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/* Ppmd7Dec.c -- PPMdH Decoder↩
2017-04-03 : Igor Pavlov : Public domain↩
This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */↩
↩
#include "Precomp.h"↩
↩
#include "Ppmd7.h"↩
↩
#define kTopValue (1 << 24)↩
↩
Bool Ppmd7z_RangeDec_Init(CPpmd7z_RangeDec *p)↩
{↩
unsigned i;↩
p->Code = 0;↩
p->Range = 0xFFFFFFFF;↩
if (IByteIn_Read(p->Stream) != 0)↩
return False;↩
for (i = 0; i < 4; i++)↩
p->Code = (p->Code << 8) | IByteIn_Read(p->Stream);↩
return (p->Code < 0xFFFFFFFF);↩
}↩
↩
#define GET_Ppmd7z_RangeDec CPpmd7z_RangeDec *p = CONTAINER_FROM_VTBL(pp, CPpmd7z_RangeDec, vt);↩
↩
static UInt32 Range_GetThreshold(const IPpmd7_RangeDec *pp, UInt32 total)↩
{↩
GET_Ppmd7z_RangeDec↩
return p->Code / (p->Range /= total);↩
}↩
↩
static void Range_Normalize(CPpmd7z_RangeDec *p)↩
{↩
if (p->Range < kTopValue)↩
{↩
p->Code = (p->Code << 8) | IByteIn_Read(p->Stream);↩
p->Range <<= 8;↩
if (p->Range < kTopValue)↩
{↩
p->Code = (p->Code << 8) | IByteIn_Read(p->Stream);↩
p->Range <<= 8;↩
}↩
}↩
}↩
↩
static void Range_Decode(const IPpmd7_RangeDec *pp, UInt32 start, UInt32 size)↩
{↩
GET_Ppmd7z_RangeDec↩
p->Code -= start * p->Range;↩
p->Range *= size;↩
Range_Normalize(p);↩
}↩
↩
static UInt32 Range_DecodeBit(const IPpmd7_RangeDec *pp, UInt32 size0)↩
{↩
GET_Ppmd7z_RangeDec↩
UInt32 newBound = (p->Range >> 14) * size0;↩
UInt32 symbol;↩
if (p->Code < newBound)↩
{↩
symbol = 0;↩
p->Range = newBound;↩
}↩
else↩
{↩
symbol = 1;↩
p->Code -= newBound;↩
p->Range -= newBound;↩
}↩
Range_Normalize(p);↩
return symbol;↩
}↩
↩
void Ppmd7z_RangeDec_CreateVTable(CPpmd7z_RangeDec *p)↩
{↩
p->vt.GetThreshold = Range_GetThreshold;↩
p->vt.Decode = Range_Decode;↩
p->vt.DecodeBit = Range_DecodeBit;↩
}↩
↩
↩
#define MASK(sym) ((signed char *)charMask)[sym]↩
↩
int Ppmd7_DecodeSymbol(CPpmd7 *p, const IPpmd7_RangeDec *rc)↩
{↩
size_t charMask[256 / sizeof(size_t)];↩
if (p->MinContext->NumStats != 1)↩
{↩
CPpmd_State *s = Ppmd7_GetStats(p, p->MinContext);↩
unsigned i;↩
UInt32 count, hiCnt;↩
if ((count = rc->GetThreshold(rc, p->MinContext->SummFreq)) < (hiCnt = s->Freq))↩
{↩
Byte symbol;↩
rc->Decode(rc, 0, s->Freq);↩
p->FoundState = s;↩
symbol = s->Symbol;↩
Ppmd7_Update1_0(p);↩
return symbol;↩
}↩
p->PrevSuccess = 0;↩
i = p->MinContext->NumStats - 1;↩
do↩
{↩
if ((hiCnt += (++s)->Freq) > count)↩
{↩
Byte symbol;↩
rc->Decode(rc, hiCnt - s->Freq, s->Freq);↩
p->FoundState = s;↩
symbol = s->Symbol;↩
Ppmd7_Update1(p);↩
return symbol;↩
}↩
}↩
while (--i);↩
if (count >= p->MinContext->SummFreq)↩
return -2;↩
p->HiBitsFlag = p->HB2Flag[p->FoundState->Symbol];↩
rc->Decode(rc, hiCnt, p->MinContext->SummFreq - hiCnt);↩
PPMD_SetAllBitsIn256Bytes(charMask);↩
MASK(s->Symbol) = 0;↩
i = p->MinContext->NumStats - 1;↩
do { MASK((--s)->Symbol) = 0; } while (--i);↩
}↩
else↩
{↩
UInt16 *prob = Ppmd7_GetBinSumm(p);↩
if (rc->DecodeBit(rc, *prob) == 0)↩
{↩
Byte symbol;↩
*prob = (UInt16)PPMD_UPDATE_PROB_0(*prob);↩
symbol = (p->FoundState = Ppmd7Context_OneState(p->MinContext))->Symbol;↩
Ppmd7_UpdateBin(p);↩
return symbol;↩
}↩
*prob = (UInt16)PPMD_UPDATE_PROB_1(*prob);↩
p->InitEsc = PPMD7_kExpEscape[*prob >> 10];↩
PPMD_SetAllBitsIn256Bytes(charMask);↩
MASK(Ppmd7Context_OneState(p->MinContext)->Symbol) = 0;↩
p->PrevSuccess = 0;↩
}↩
for (;;)↩
{↩
CPpmd_State *ps[256], *s;↩
UInt32 freqSum, count, hiCnt;↩
CPpmd_See *see;↩
unsigned i, num, numMasked = p->MinContext->NumStats;↩
do↩
{↩
p->OrderFall++;↩
if (!p->MinContext->Suffix)↩
return -1;↩
p->MinContext = Ppmd7_GetContext(p, p->MinContext->Suffix);↩
}↩
while (p->MinContext->NumStats == numMasked);↩
hiCnt = 0;↩
s = Ppmd7_GetStats(p, p->MinContext);↩
i = 0;↩
num = p->MinContext->NumStats - numMasked;↩
do↩
{↩
int k = (int)(MASK(s->Symbol));↩
hiCnt += (s->Freq & k);↩
ps[i] = s++;↩
i -= k;↩
}↩
while (i != num);↩
↩
see = Ppmd7_MakeEscFreq(p, numMasked, &freqSum);↩
freqSum += hiCnt;↩
count = rc->GetThreshold(rc, freqSum);↩
↩
if (count < hiCnt)↩
{↩
Byte symbol;↩
CPpmd_State **pps = ps;↩
for (hiCnt = 0; (hiCnt += (*pps)->Freq) <= count; pps++);↩
s = *pps;↩
rc->Decode(rc, hiCnt - s->Freq, s->Freq);↩
Ppmd_See_Update(see);↩
p->FoundState = s;↩
symbol = s->Symbol;↩
Ppmd7_Update2(p);↩
return symbol;↩
}↩
if (count >= freqSum)↩
return -2;↩
rc->Decode(rc, hiCnt, freqSum - hiCnt);↩
see->Summ = (UInt16)(see->Summ + freqSum);↩
do { MASK(ps[--i]->Symbol) = 0; } while (i != 0);↩
}↩
}↩