1 /* Ppmd7Dec.c -- PPMdH Decoder
2 2018-07-04 : Igor Pavlov : Public domain
3 This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
4
5 #include "Precomp.h"
6
7 #include "Ppmd7.h"
8
9 #define kTopValue (1 << 24)
10
Ppmd7z_RangeDec_Init(CPpmd7z_RangeDec * p)11 BoolInt Ppmd7z_RangeDec_Init(CPpmd7z_RangeDec *p)
12 {
13 unsigned i;
14 p->Code = 0;
15 p->Range = 0xFFFFFFFF;
16 if (IByteIn_Read(p->Stream) != 0)
17 return False;
18 for (i = 0; i < 4; i++)
19 p->Code = (p->Code << 8) | IByteIn_Read(p->Stream);
20 return (p->Code < 0xFFFFFFFF);
21 }
22
23 #define GET_Ppmd7z_RangeDec CPpmd7z_RangeDec *p = CONTAINER_FROM_VTBL(pp, CPpmd7z_RangeDec, vt);
24
Range_GetThreshold(const IPpmd7_RangeDec * pp,UInt32 total)25 static UInt32 Range_GetThreshold(const IPpmd7_RangeDec *pp, UInt32 total)
26 {
27 GET_Ppmd7z_RangeDec
28 return p->Code / (p->Range /= total);
29 }
30
Range_Normalize(CPpmd7z_RangeDec * p)31 static void Range_Normalize(CPpmd7z_RangeDec *p)
32 {
33 if (p->Range < kTopValue)
34 {
35 p->Code = (p->Code << 8) | IByteIn_Read(p->Stream);
36 p->Range <<= 8;
37 if (p->Range < kTopValue)
38 {
39 p->Code = (p->Code << 8) | IByteIn_Read(p->Stream);
40 p->Range <<= 8;
41 }
42 }
43 }
44
Range_Decode(const IPpmd7_RangeDec * pp,UInt32 start,UInt32 size)45 static void Range_Decode(const IPpmd7_RangeDec *pp, UInt32 start, UInt32 size)
46 {
47 GET_Ppmd7z_RangeDec
48 p->Code -= start * p->Range;
49 p->Range *= size;
50 Range_Normalize(p);
51 }
52
Range_DecodeBit(const IPpmd7_RangeDec * pp,UInt32 size0)53 static UInt32 Range_DecodeBit(const IPpmd7_RangeDec *pp, UInt32 size0)
54 {
55 GET_Ppmd7z_RangeDec
56 UInt32 newBound = (p->Range >> 14) * size0;
57 UInt32 symbol;
58 if (p->Code < newBound)
59 {
60 symbol = 0;
61 p->Range = newBound;
62 }
63 else
64 {
65 symbol = 1;
66 p->Code -= newBound;
67 p->Range -= newBound;
68 }
69 Range_Normalize(p);
70 return symbol;
71 }
72
Ppmd7z_RangeDec_CreateVTable(CPpmd7z_RangeDec * p)73 void Ppmd7z_RangeDec_CreateVTable(CPpmd7z_RangeDec *p)
74 {
75 p->vt.GetThreshold = Range_GetThreshold;
76 p->vt.Decode = Range_Decode;
77 p->vt.DecodeBit = Range_DecodeBit;
78 }
79
80
81 #define MASK(sym) ((signed char *)charMask)[sym]
82
Ppmd7_DecodeSymbol(CPpmd7 * p,const IPpmd7_RangeDec * rc)83 int Ppmd7_DecodeSymbol(CPpmd7 *p, const IPpmd7_RangeDec *rc)
84 {
85 size_t charMask[256 / sizeof(size_t)];
86 if (p->MinContext->NumStats != 1)
87 {
88 CPpmd_State *s = Ppmd7_GetStats(p, p->MinContext);
89 unsigned i;
90 UInt32 count, hiCnt;
91 if ((count = rc->GetThreshold(rc, p->MinContext->SummFreq)) < (hiCnt = s->Freq))
92 {
93 Byte symbol;
94 rc->Decode(rc, 0, s->Freq);
95 p->FoundState = s;
96 symbol = s->Symbol;
97 Ppmd7_Update1_0(p);
98 return symbol;
99 }
100 p->PrevSuccess = 0;
101 i = p->MinContext->NumStats - 1;
102 do
103 {
104 if ((hiCnt += (++s)->Freq) > count)
105 {
106 Byte symbol;
107 rc->Decode(rc, hiCnt - s->Freq, s->Freq);
108 p->FoundState = s;
109 symbol = s->Symbol;
110 Ppmd7_Update1(p);
111 return symbol;
112 }
113 }
114 while (--i);
115 if (count >= p->MinContext->SummFreq)
116 return -2;
117 p->HiBitsFlag = p->HB2Flag[p->FoundState->Symbol];
118 rc->Decode(rc, hiCnt, p->MinContext->SummFreq - hiCnt);
119 PPMD_SetAllBitsIn256Bytes(charMask);
120 MASK(s->Symbol) = 0;
121 i = p->MinContext->NumStats - 1;
122 do { MASK((--s)->Symbol) = 0; } while (--i);
123 }
124 else
125 {
126 UInt16 *prob = Ppmd7_GetBinSumm(p);
127 if (rc->DecodeBit(rc, *prob) == 0)
128 {
129 Byte symbol;
130 *prob = (UInt16)PPMD_UPDATE_PROB_0(*prob);
131 symbol = (p->FoundState = Ppmd7Context_OneState(p->MinContext))->Symbol;
132 Ppmd7_UpdateBin(p);
133 return symbol;
134 }
135 *prob = (UInt16)PPMD_UPDATE_PROB_1(*prob);
136 p->InitEsc = PPMD7_kExpEscape[*prob >> 10];
137 PPMD_SetAllBitsIn256Bytes(charMask);
138 MASK(Ppmd7Context_OneState(p->MinContext)->Symbol) = 0;
139 p->PrevSuccess = 0;
140 }
141 for (;;)
142 {
143 CPpmd_State *ps[256], *s;
144 UInt32 freqSum, count, hiCnt;
145 CPpmd_See *see;
146 unsigned i, num, numMasked = p->MinContext->NumStats;
147 do
148 {
149 p->OrderFall++;
150 if (!p->MinContext->Suffix)
151 return -1;
152 p->MinContext = Ppmd7_GetContext(p, p->MinContext->Suffix);
153 }
154 while (p->MinContext->NumStats == numMasked);
155 hiCnt = 0;
156 s = Ppmd7_GetStats(p, p->MinContext);
157 i = 0;
158 num = p->MinContext->NumStats - numMasked;
159 do
160 {
161 int k = (int)(MASK(s->Symbol));
162 hiCnt += (s->Freq & k);
163 ps[i] = s++;
164 i -= k;
165 }
166 while (i != num);
167
168 see = Ppmd7_MakeEscFreq(p, numMasked, &freqSum);
169 freqSum += hiCnt;
170 count = rc->GetThreshold(rc, freqSum);
171
172 if (count < hiCnt)
173 {
174 Byte symbol;
175 CPpmd_State **pps = ps;
176 for (hiCnt = 0; (hiCnt += (*pps)->Freq) <= count; pps++);
177 s = *pps;
178 rc->Decode(rc, hiCnt - s->Freq, s->Freq);
179 Ppmd_See_Update(see);
180 p->FoundState = s;
181 symbol = s->Symbol;
182 Ppmd7_Update2(p);
183 return symbol;
184 }
185 if (count >= freqSum)
186 return -2;
187 rc->Decode(rc, hiCnt, freqSum - hiCnt);
188 see->Summ = (UInt16)(see->Summ + freqSum);
189 do { MASK(ps[--i]->Symbol) = 0; } while (i != 0);
190 }
191 }
192