1 /* Ppmd7Dec.c -- PPMdH Decoder
2 2017-04-03 : 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 Bool 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