1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
|
/* Ppmd8Dec.c -- PPMdI Decoder
2010-04-16 : Igor Pavlov : Public domain
This code is based on:
PPMd var.I (2002): Dmitry Shkarin : Public domain
Carryless rangecoder (1999): Dmitry Subbotin : Public domain */
#include "Precomp.h"
#include "Ppmd8.h"
#define kTop (1 << 24)
#define kBot (1 << 15)
Bool Ppmd8_RangeDec_Init(CPpmd8 *p)
{
unsigned i;
p->Low = 0;
p->Range = 0xFFFFFFFF;
p->Code = 0;
for (i = 0; i < 4; i++)
p->Code = (p->Code << 8) | p->Stream.In->Read(p->Stream.In);
return (p->Code < 0xFFFFFFFF);
}
static UInt32 RangeDec_GetThreshold(CPpmd8 *p, UInt32 total)
{
return p->Code / (p->Range /= total);
}
static void RangeDec_Decode(CPpmd8 *p, UInt32 start, UInt32 size)
{
start *= p->Range;
p->Low += start;
p->Code -= start;
p->Range *= size;
while ((p->Low ^ (p->Low + p->Range)) < kTop ||
(p->Range < kBot && ((p->Range = (0 - p->Low) & (kBot - 1)), 1)))
{
p->Code = (p->Code << 8) | p->Stream.In->Read(p->Stream.In);
p->Range <<= 8;
p->Low <<= 8;
}
}
#define MASK(sym) ((signed char *)charMask)[sym]
int Ppmd8_DecodeSymbol(CPpmd8 *p)
{
size_t charMask[256 / sizeof(size_t)];
if (p->MinContext->NumStats != 0)
{
CPpmd_State *s = Ppmd8_GetStats(p, p->MinContext);
unsigned i;
UInt32 count, hiCnt;
if ((count = RangeDec_GetThreshold(p, p->MinContext->SummFreq)) < (hiCnt = s->Freq))
{
Byte symbol;
RangeDec_Decode(p, 0, s->Freq);
p->FoundState = s;
symbol = s->Symbol;
Ppmd8_Update1_0(p);
return symbol;
}
p->PrevSuccess = 0;
i = p->MinContext->NumStats;
do
{
if ((hiCnt += (++s)->Freq) > count)
{
Byte symbol;
RangeDec_Decode(p, hiCnt - s->Freq, s->Freq);
p->FoundState = s;
symbol = s->Symbol;
Ppmd8_Update1(p);
return symbol;
}
}
while (--i);
if (count >= p->MinContext->SummFreq)
return -2;
RangeDec_Decode(p, hiCnt, p->MinContext->SummFreq - hiCnt);
PPMD_SetAllBitsIn256Bytes(charMask);
MASK(s->Symbol) = 0;
i = p->MinContext->NumStats;
do { MASK((--s)->Symbol) = 0; } while (--i);
}
else
{
UInt16 *prob = Ppmd8_GetBinSumm(p);
if (((p->Code / (p->Range >>= 14)) < *prob))
{
Byte symbol;
RangeDec_Decode(p, 0, *prob);
*prob = (UInt16)PPMD_UPDATE_PROB_0(*prob);
symbol = (p->FoundState = Ppmd8Context_OneState(p->MinContext))->Symbol;
Ppmd8_UpdateBin(p);
return symbol;
}
RangeDec_Decode(p, *prob, (1 << 14) - *prob);
*prob = (UInt16)PPMD_UPDATE_PROB_1(*prob);
p->InitEsc = PPMD8_kExpEscape[*prob >> 10];
PPMD_SetAllBitsIn256Bytes(charMask);
MASK(Ppmd8Context_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 = Ppmd8_GetContext(p, p->MinContext->Suffix);
}
while (p->MinContext->NumStats == numMasked);
hiCnt = 0;
s = Ppmd8_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 = Ppmd8_MakeEscFreq(p, numMasked, &freqSum);
freqSum += hiCnt;
count = RangeDec_GetThreshold(p, freqSum);
if (count < hiCnt)
{
Byte symbol;
CPpmd_State **pps = ps;
for (hiCnt = 0; (hiCnt += (*pps)->Freq) <= count; pps++);
s = *pps;
RangeDec_Decode(p, hiCnt - s->Freq, s->Freq);
Ppmd_See_Update(see);
p->FoundState = s;
symbol = s->Symbol;
Ppmd8_Update2(p);
return symbol;
}
if (count >= freqSum)
return -2;
RangeDec_Decode(p, hiCnt, freqSum - hiCnt);
see->Summ = (UInt16)(see->Summ + freqSum);
do { MASK(ps[--i]->Symbol) = 0; } while (i != 0);
}
}
|
