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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);
}
}
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