1/* Ppmd7Dec.c -- PPMdH Decoder
22010-03-12 : Igor Pavlov : Public domain
3This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
4
5#include "Ppmd7.h"
6
7#define kTopValue (1 << 24)
8
9Bool Ppmd7z_RangeDec_Init(CPpmd7z_RangeDec *p)
10{
11 unsigned i;
12 p->Code = 0;
13 p->Range = 0xFFFFFFFF;
14 if (p->Stream->Read((void *)p->Stream) != 0)
15 return False;
16 for (i = 0; i < 4; i++)
17 p->Code = (p->Code << 8) | p->Stream->Read((void *)p->Stream);
18 return (p->Code < 0xFFFFFFFF);
19}
20
21static UInt32 Range_GetThreshold(void *pp, UInt32 total)
22{
23 CPpmd7z_RangeDec *p = (CPpmd7z_RangeDec *)pp;
24 return (p->Code) / (p->Range /= total);
25}
26
27static void Range_Normalize(CPpmd7z_RangeDec *p)
28{
29 if (p->Range < kTopValue)
30 {
31 p->Code = (p->Code << 8) | p->Stream->Read((void *)p->Stream);
32 p->Range <<= 8;
33 if (p->Range < kTopValue)
34 {
35 p->Code = (p->Code << 8) | p->Stream->Read((void *)p->Stream);
36 p->Range <<= 8;
37 }
38 }
39}
40
41static void Range_Decode(void *pp, UInt32 start, UInt32 size)
42{
43 CPpmd7z_RangeDec *p = (CPpmd7z_RangeDec *)pp;
44 p->Code -= start * p->Range;
45 p->Range *= size;
46 Range_Normalize(p);
47}
48
49static UInt32 Range_DecodeBit(void *pp, UInt32 size0)
50{
51 CPpmd7z_RangeDec *p = (CPpmd7z_RangeDec *)pp;
52 UInt32 newBound = (p->Range >> 14) * size0;
53 UInt32 symbol;
54 if (p->Code < newBound)
55 {
56 symbol = 0;
57 p->Range = newBound;
58 }
59 else
60 {
61 symbol = 1;
62 p->Code -= newBound;
63 p->Range -= newBound;
64 }
65 Range_Normalize(p);
66 return symbol;
67}
68
69void Ppmd7z_RangeDec_CreateVTable(CPpmd7z_RangeDec *p)
70{
71 p->p.GetThreshold = Range_GetThreshold;
72 p->p.Decode = Range_Decode;
73 p->p.DecodeBit = Range_DecodeBit;
74}
75
76
77#define MASK(sym) ((signed char *)charMask)[sym]
78
79int Ppmd7_DecodeSymbol(CPpmd7 *p, IPpmd7_RangeDec *rc)
80{
81 size_t charMask[256 / sizeof(size_t)];
82 if (p->MinContext->NumStats != 1)
83 {
84 CPpmd_State *s = Ppmd7_GetStats(p, p->MinContext);
85 unsigned i;
86 UInt32 count, hiCnt;
87 if ((count = rc->GetThreshold(rc, p->MinContext->SummFreq)) < (hiCnt = s->Freq))
88 {
89 Byte symbol;
90 rc->Decode(rc, 0, s->Freq);
91 p->FoundState = s;
92 symbol = s->Symbol;
93 Ppmd7_Update1_0(p);
94 return symbol;
95 }
96 p->PrevSuccess = 0;
97 i = p->MinContext->NumStats - 1;
98 do
99 {
100 if ((hiCnt += (++s)->Freq) > count)
101 {
102 Byte symbol;
103 rc->Decode(rc, hiCnt - s->Freq, s->Freq);
104 p->FoundState = s;
105 symbol = s->Symbol;
106 Ppmd7_Update1(p);
107 return symbol;
108 }
109 }
110 while (--i);
111 if (count >= p->MinContext->SummFreq)
112 return -2;
113 p->HiBitsFlag = p->HB2Flag[p->FoundState->Symbol];
114 rc->Decode(rc, hiCnt, p->MinContext->SummFreq - hiCnt);
115 PPMD_SetAllBitsIn256Bytes(charMask);
116 MASK(s->Symbol) = 0;
117 i = p->MinContext->NumStats - 1;
118 do { MASK((--s)->Symbol) = 0; } while (--i);
119 }
120 else
121 {
122 UInt16 *prob = Ppmd7_GetBinSumm(p);
123 if (rc->DecodeBit(rc, *prob) == 0)
124 {
125 Byte symbol;
126 *prob = (UInt16)PPMD_UPDATE_PROB_0(*prob);
127 symbol = (p->FoundState = Ppmd7Context_OneState(p->MinContext))->Symbol;
128 Ppmd7_UpdateBin(p);
129 return symbol;
130 }
131 *prob = (UInt16)PPMD_UPDATE_PROB_1(*prob);
132 p->InitEsc = PPMD7_kExpEscape[*prob >> 10];
133 PPMD_SetAllBitsIn256Bytes(charMask);
134 MASK(Ppmd7Context_OneState(p->MinContext)->Symbol) = 0;
135 p->PrevSuccess = 0;
136 }
137 for (;;)
138 {
139 CPpmd_State *ps[256], *s;
140 UInt32 freqSum, count, hiCnt;
141 CPpmd_See *see;
142 unsigned i, num, numMasked = p->MinContext->NumStats;
143 do
144 {
145 p->OrderFall++;
146 if (!p->MinContext->Suffix)
147 return -1;
148 p->MinContext = Ppmd7_GetContext(p, p->MinContext->Suffix);
149 }
150 while (p->MinContext->NumStats == numMasked);
151 hiCnt = 0;
152 s = Ppmd7_GetStats(p, p->MinContext);
153 i = 0;
154 num = p->MinContext->NumStats - numMasked;
155 do
156 {
157 int k = (int)(MASK(s->Symbol));
158 hiCnt += (s->Freq & k);
159 ps[i] = s++;
160 i -= k;
161 }
162 while (i != num);
163
164 see = Ppmd7_MakeEscFreq(p, numMasked, &freqSum);
165 freqSum += hiCnt;
166 count = rc->GetThreshold(rc, freqSum);
167
168 if (count < hiCnt)
169 {
170 Byte symbol;
171 CPpmd_State **pps = ps;
172 for (hiCnt = 0; (hiCnt += (*pps)->Freq) <= count; pps++);
173 s = *pps;
174 rc->Decode(rc, hiCnt - s->Freq, s->Freq);
175 Ppmd_See_Update(see);
176 p->FoundState = s;
177 symbol = s->Symbol;
178 Ppmd7_Update2(p);
179 return symbol;
180 }
181 if (count >= freqSum)
182 return -2;
183 rc->Decode(rc, hiCnt, freqSum - hiCnt);
184 see->Summ = (UInt16)(see->Summ + freqSum);
185 do { MASK(ps[--i]->Symbol) = 0; } while (i != 0);
186 }
187}
188