1 /* Ppmd7Dec.c -- PPMdH Decoder
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2 2010-03-12 : Igor Pavlov : Public domain
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3 This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
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7 #define kTopValue (1 << 24)
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9 Bool Ppmd7z_RangeDec_Init(CPpmd7z_RangeDec *p)
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13 p->Range = 0xFFFFFFFF;
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14 if (p->Stream->Read((void *)p->Stream) != 0)
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16 for (i = 0; i < 4; i++)
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17 p->Code = (p->Code << 8) | p->Stream->Read((void *)p->Stream);
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18 return (p->Code < 0xFFFFFFFF);
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21 static UInt32 Range_GetThreshold(void *pp, UInt32 total)
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23 CPpmd7z_RangeDec *p = (CPpmd7z_RangeDec *)pp;
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24 return (p->Code) / (p->Range /= total);
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27 static void Range_Normalize(CPpmd7z_RangeDec *p)
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29 if (p->Range < kTopValue)
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31 p->Code = (p->Code << 8) | p->Stream->Read((void *)p->Stream);
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33 if (p->Range < kTopValue)
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35 p->Code = (p->Code << 8) | p->Stream->Read((void *)p->Stream);
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41 static void Range_Decode(void *pp, UInt32 start, UInt32 size)
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43 CPpmd7z_RangeDec *p = (CPpmd7z_RangeDec *)pp;
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44 p->Code -= start * p->Range;
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49 static UInt32 Range_DecodeBit(void *pp, UInt32 size0)
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51 CPpmd7z_RangeDec *p = (CPpmd7z_RangeDec *)pp;
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52 UInt32 newBound = (p->Range >> 14) * size0;
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54 if (p->Code < newBound)
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57 p->Range = newBound;
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62 p->Code -= newBound;
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63 p->Range -= newBound;
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69 void Ppmd7z_RangeDec_CreateVTable(CPpmd7z_RangeDec *p)
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71 p->p.GetThreshold = Range_GetThreshold;
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72 p->p.Decode = Range_Decode;
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73 p->p.DecodeBit = Range_DecodeBit;
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77 #define MASK(sym) ((signed char *)charMask)[sym]
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79 int Ppmd7_DecodeSymbol(CPpmd7 *p, IPpmd7_RangeDec *rc)
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81 size_t charMask[256 / sizeof(size_t)];
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82 if (p->MinContext->NumStats != 1)
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84 CPpmd_State *s = Ppmd7_GetStats(p, p->MinContext);
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86 UInt32 count, hiCnt;
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87 if ((count = rc->GetThreshold(rc, p->MinContext->SummFreq)) < (hiCnt = s->Freq))
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90 rc->Decode(rc, 0, s->Freq);
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97 i = p->MinContext->NumStats - 1;
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100 if ((hiCnt += (++s)->Freq) > count)
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103 rc->Decode(rc, hiCnt - s->Freq, s->Freq);
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105 symbol = s->Symbol;
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111 if (count >= p->MinContext->SummFreq)
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113 p->HiBitsFlag = p->HB2Flag[p->FoundState->Symbol];
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114 rc->Decode(rc, hiCnt, p->MinContext->SummFreq - hiCnt);
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115 PPMD_SetAllBitsIn256Bytes(charMask);
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116 MASK(s->Symbol) = 0;
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117 i = p->MinContext->NumStats - 1;
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118 do { MASK((--s)->Symbol) = 0; } while (--i);
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122 UInt16 *prob = Ppmd7_GetBinSumm(p);
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123 if (rc->DecodeBit(rc, *prob) == 0)
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126 *prob = (UInt16)PPMD_UPDATE_PROB_0(*prob);
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127 symbol = (p->FoundState = Ppmd7Context_OneState(p->MinContext))->Symbol;
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128 Ppmd7_UpdateBin(p);
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131 *prob = (UInt16)PPMD_UPDATE_PROB_1(*prob);
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132 p->InitEsc = PPMD7_kExpEscape[*prob >> 10];
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133 PPMD_SetAllBitsIn256Bytes(charMask);
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134 MASK(Ppmd7Context_OneState(p->MinContext)->Symbol) = 0;
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135 p->PrevSuccess = 0;
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139 CPpmd_State *ps[256], *s;
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140 UInt32 freqSum, count, hiCnt;
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142 unsigned i, num, numMasked = p->MinContext->NumStats;
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146 if (!p->MinContext->Suffix)
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148 p->MinContext = Ppmd7_GetContext(p, p->MinContext->Suffix);
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150 while (p->MinContext->NumStats == numMasked);
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152 s = Ppmd7_GetStats(p, p->MinContext);
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154 num = p->MinContext->NumStats - numMasked;
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157 int k = (int)(MASK(s->Symbol));
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158 hiCnt += (s->Freq & k);
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164 see = Ppmd7_MakeEscFreq(p, numMasked, &freqSum);
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166 count = rc->GetThreshold(rc, freqSum);
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171 CPpmd_State **pps = ps;
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172 for (hiCnt = 0; (hiCnt += (*pps)->Freq) <= count; pps++);
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174 rc->Decode(rc, hiCnt - s->Freq, s->Freq);
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175 Ppmd_See_Update(see);
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177 symbol = s->Symbol;
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181 if (count >= freqSum)
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183 rc->Decode(rc, hiCnt, freqSum - hiCnt);
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184 see->Summ = (UInt16)(see->Summ + freqSum);
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185 do { MASK(ps[--i]->Symbol) = 0; } while (i != 0);
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