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1 // PpmdDecode.h
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2 // This code is based on Dmitry Shkarin's PPMdH code
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3
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4 #ifndef __COMPRESS_PPMD_DECODE_H
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5 #define __COMPRESS_PPMD_DECODE_H
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6
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7 #include "PpmdContext.h"
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8
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9 namespace NCompress {
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10 namespace NPpmd {
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11
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12 class CRangeDecoderVirt
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13 {
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14 public:
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15 virtual UInt32 GetThreshold(UInt32 total) = 0;
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16 virtual void Decode(UInt32 start, UInt32 size) = 0;
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17 virtual UInt32 DecodeBit(UInt32 size0, UInt32 numTotalBits) = 0;
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18 };
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19
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20 typedef NRangeCoder::CDecoder CRangeDecoderMy;
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21
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22 class CRangeDecoder:public CRangeDecoderVirt, public CRangeDecoderMy
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23 {
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24 UInt32 GetThreshold(UInt32 total) { return CRangeDecoderMy::GetThreshold(total); }
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25 void Decode(UInt32 start, UInt32 size) { CRangeDecoderMy::Decode(start, size); }
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26 UInt32 DecodeBit(UInt32 size0, UInt32 numTotalBits) { return CRangeDecoderMy::DecodeBit(size0, numTotalBits); }
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27 };
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28
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29 struct CDecodeInfo: public CInfo
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30 {
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31 void DecodeBinSymbol(CRangeDecoderVirt *rangeDecoder)
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32 {
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33 PPM_CONTEXT::STATE& rs = MinContext->oneState();
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34 UInt16& bs = GetBinSumm(rs, GetContextNoCheck(MinContext->Suffix)->NumStats);
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35 if (rangeDecoder->DecodeBit(bs, TOT_BITS) == 0)
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36 {
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37 FoundState = &rs;
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38 rs.Freq = (Byte)(rs.Freq + (rs.Freq < 128 ? 1: 0));
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39 bs = (UInt16)(bs + INTERVAL - GET_MEAN(bs, PERIOD_BITS, 2));
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40 PrevSuccess = 1;
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41 RunLength++;
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42 }
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43 else
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44 {
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45 bs = (UInt16)(bs - GET_MEAN(bs, PERIOD_BITS, 2));
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46 InitEsc = ExpEscape[bs >> 10];
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47 NumMasked = 1;
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48 CharMask[rs.Symbol] = EscCount;
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49 PrevSuccess = 0;
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50 FoundState = NULL;
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51 }
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52 }
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53
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54 void DecodeSymbol1(CRangeDecoderVirt *rangeDecoder)
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55 {
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56 PPM_CONTEXT::STATE* p = GetStateNoCheck(MinContext->Stats);
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57 int i, count, hiCnt;
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58 if ((count = rangeDecoder->GetThreshold(MinContext->SummFreq)) < (hiCnt = p->Freq))
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59 {
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60 PrevSuccess = (2 * hiCnt > MinContext->SummFreq);
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61 RunLength += PrevSuccess;
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62 rangeDecoder->Decode(0, p->Freq); // MinContext->SummFreq);
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63 (FoundState = p)->Freq = (Byte)(hiCnt += 4);
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64 MinContext->SummFreq += 4;
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65 if (hiCnt > MAX_FREQ)
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66 rescale();
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67 return;
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68 }
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69 PrevSuccess = 0;
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70 i = MinContext->NumStats - 1;
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71 while ((hiCnt += (++p)->Freq) <= count)
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72 if (--i == 0)
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73 {
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74 HiBitsFlag = HB2Flag[FoundState->Symbol];
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75 rangeDecoder->Decode(hiCnt, MinContext->SummFreq - hiCnt); // , MinContext->SummFreq);
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76 CharMask[p->Symbol] = EscCount;
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77 i = (NumMasked = MinContext->NumStats)-1;
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78 FoundState = NULL;
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79 do { CharMask[(--p)->Symbol] = EscCount; } while ( --i );
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80 return;
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81 }
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82 rangeDecoder->Decode(hiCnt - p->Freq, p->Freq); // , MinContext->SummFreq);
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83 update1(p);
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84 }
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85
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86
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87 void DecodeSymbol2(CRangeDecoderVirt *rangeDecoder)
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88 {
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89 int count, hiCnt, i = MinContext->NumStats - NumMasked;
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90 UInt32 freqSum;
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91 SEE2_CONTEXT* psee2c = makeEscFreq2(i, freqSum);
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92 PPM_CONTEXT::STATE* ps[256], ** pps = ps, * p = GetStateNoCheck(MinContext->Stats)-1;
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93 hiCnt = 0;
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94 do
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95 {
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96 do { p++; } while (CharMask[p->Symbol] == EscCount);
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97 hiCnt += p->Freq;
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98 *pps++ = p;
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99 }
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100 while ( --i );
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101
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102 freqSum += hiCnt;
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103 count = rangeDecoder->GetThreshold(freqSum);
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104
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105 p = *(pps = ps);
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106 if (count < hiCnt)
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107 {
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108 hiCnt = 0;
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109 while ((hiCnt += p->Freq) <= count)
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110 p=*++pps;
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111 rangeDecoder->Decode(hiCnt - p->Freq, p->Freq); // , freqSum);
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112
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113 psee2c->update();
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114 update2(p);
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115 }
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116 else
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117 {
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118 rangeDecoder->Decode(hiCnt, freqSum - hiCnt); // , freqSum);
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119
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120 i = MinContext->NumStats - NumMasked;
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121 pps--;
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122 do { CharMask[(*++pps)->Symbol] = EscCount; } while ( --i );
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123 psee2c->Summ = (UInt16)(psee2c->Summ + freqSum);
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124 NumMasked = MinContext->NumStats;
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125 }
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126 }
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127
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128 int DecodeSymbol(CRangeDecoderVirt *rangeDecoder)
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129 {
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130 if (MinContext->NumStats != 1)
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131 DecodeSymbol1(rangeDecoder);
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132 else
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133 DecodeBinSymbol(rangeDecoder);
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134 while ( !FoundState )
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135 {
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136 do
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137 {
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138 OrderFall++;
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139 MinContext = GetContext(MinContext->Suffix);
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140 if (MinContext == 0)
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141 return -1;
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142 }
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143 while (MinContext->NumStats == NumMasked);
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144 DecodeSymbol2(rangeDecoder);
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145 }
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146 Byte symbol = FoundState->Symbol;
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147 NextContext();
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148 return symbol;
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149 }
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150 };
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151
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152 }}
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153
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154 #endif
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