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163
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1 using Implab;
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2 using System;
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3 using System.Collections.Generic;
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4 using System.Diagnostics;
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5 using System.Linq;
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6
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7 namespace Implab.Automaton.RegularExpressions {
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8 /// <summary>
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9 /// Используется для построения ДКА по регулярному выражению, сначала обходит
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10 /// регулярное выражение и вычисляет followpos, затем используется метод
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11 /// <see cref="BuildDFA(IDFADefinition)"/> для построения автомата.
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12 /// </summary>
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13 public class RegularDFABuilder<TTag> : IVisitor<TTag> {
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14 int m_idx = 0;
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15 Token<TTag> m_root;
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16 HashSet<int> m_firstpos;
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17 HashSet<int> m_lastpos;
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18
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19 readonly Dictionary<int, HashSet<int>> m_followpos = new Dictionary<int, HashSet<int>>();
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20 readonly Dictionary<int, int> m_indexes = new Dictionary<int, int>();
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21 readonly Dictionary<int, TTag> m_ends = new Dictionary<int, TTag>();
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22
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23 public Dictionary<int, HashSet<int>> FollowposMap {
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24 get { return m_followpos; }
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25 }
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26
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27 public HashSet<int> Followpos(int pos) {
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28 HashSet<int> set;
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29 if (m_followpos.TryGetValue(pos, out set))
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30 return set;
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31 return m_followpos[pos] = new HashSet<int>();
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32 }
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33
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34 bool Nullable(object n) {
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35 if (n is EmptyToken<TTag> || n is StarToken<TTag>)
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36 return true;
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37 if (n is AltToken<TTag>)
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38 return Nullable(((AltToken<TTag>)n).Left) || Nullable(((AltToken<TTag>)n).Right);
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39 if (n is CatToken<TTag>)
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40 return Nullable(((CatToken<TTag>)n).Left) && Nullable(((CatToken<TTag>)n).Right);
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41 return false;
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42 }
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43
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44
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45 public void Visit(AltToken<TTag> token) {
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46 if (m_root == null)
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47 m_root = token;
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48 var firtspos = new HashSet<int>();
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49 var lastpos = new HashSet<int>();
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50
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51 token.Left.Accept(this);
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52 firtspos.UnionWith(m_firstpos);
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53 lastpos.UnionWith(m_lastpos);
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54
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55 token.Right.Accept(this);
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56 firtspos.UnionWith(m_firstpos);
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57 lastpos.UnionWith(m_lastpos);
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58
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59 m_firstpos = firtspos;
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60 m_lastpos = lastpos;
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61 }
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62
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63 public void Visit(StarToken<TTag> token) {
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64 if (m_root == null)
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65 m_root = token;
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66 token.Token.Accept(this);
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67
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68 foreach (var i in m_lastpos)
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69 Followpos(i).UnionWith(m_firstpos);
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70 }
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71
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72 public void Visit(CatToken<TTag> token) {
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73 if (m_root == null)
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74 m_root = token;
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75
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76 var firtspos = new HashSet<int>();
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77 var lastpos = new HashSet<int>();
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78 token.Left.Accept(this);
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79 firtspos.UnionWith(m_firstpos);
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80 var leftLastpos = m_lastpos;
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81
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82 token.Right.Accept(this);
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83 lastpos.UnionWith(m_lastpos);
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84 var rightFirstpos = m_firstpos;
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85
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86 if (Nullable(token.Left))
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87 firtspos.UnionWith(rightFirstpos);
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88
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89 if (Nullable(token.Right))
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90 lastpos.UnionWith(leftLastpos);
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91
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92 m_firstpos = firtspos;
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93 m_lastpos = lastpos;
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94
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95 foreach (var i in leftLastpos)
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96 Followpos(i).UnionWith(rightFirstpos);
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97
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98 }
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99
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100 public void Visit(EmptyToken<TTag> token) {
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101 if (m_root == null)
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102 m_root = token;
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103 }
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104
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105 public void Visit(SymbolToken<TTag> token) {
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106 if (m_root == null)
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107 m_root = token;
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108 m_idx++;
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109 m_indexes[m_idx] = token.Value;
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110 m_firstpos = new HashSet<int>(new[] { m_idx });
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111 m_lastpos = new HashSet<int>(new[] { m_idx });
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112 }
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113
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114 public void Visit(EndToken<TTag> token) {
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115 if (m_root == null)
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116 m_root = token;
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117 m_idx++;
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118 m_indexes[m_idx] = DFAConst.UNCLASSIFIED_INPUT;
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119 m_firstpos = new HashSet<int>(new[] { m_idx });
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120 m_lastpos = new HashSet<int>(new[] { m_idx });
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121 Followpos(m_idx);
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122 m_ends.Add(m_idx, token.Tag);
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123 }
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124
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125 public void BuildDFA(IDFADefinitionBuilder<TTag> dfa) {
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126 Safe.ArgumentNotNull(dfa,"dfa");
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127
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128 var states = new MapAlphabet<HashSet<int>>(new CustomEqualityComparer<HashSet<int>>(
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129 (x, y) => x.SetEquals(y),
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130 x => x.Sum(n => n.GetHashCode())
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131 ));
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132
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133 var initialState = states.DefineSymbol(m_firstpos);
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134
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135 var tags = GetStateTags(m_firstpos);
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136 if (tags != null && tags.Length > 0)
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137 dfa.MarkFinalState(initialState, tags);
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138
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139 var inputMax = m_indexes.Values.Max();
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140 var queue = new Queue<HashSet<int>>();
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141
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142 queue.Enqueue(m_firstpos);
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143
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144 while (queue.Count > 0) {
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145 var state = queue.Dequeue();
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146 var s1 = states.Translate(state);
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147 Debug.Assert(s1 != DFAConst.UNCLASSIFIED_INPUT);
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148
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149 for (int a = 0; a <= inputMax; a++) {
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150 var next = new HashSet<int>();
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151 foreach (var p in state) {
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152 if (m_indexes[p] == a) {
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153 next.UnionWith(Followpos(p));
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154 }
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155 }
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156 if (next.Count > 0) {
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157 int s2 = states.Translate(next);
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158 if (s2 == DFAConst.UNCLASSIFIED_INPUT) {
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159 s2 = states.DefineSymbol(next);
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160
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161 tags = GetStateTags(next);
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162 if (tags != null && tags.Length > 0)
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163 dfa.MarkFinalState(s2, tags);
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164
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165 queue.Enqueue(next);
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166 }
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167 dfa.DefineTransition(s1, s2, a);
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168 }
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169 }
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170 }
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171 }
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172
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173 TTag[] GetStateTags(IEnumerable<int> state) {
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174 Debug.Assert(state != null);
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175 return state.Where(m_ends.ContainsKey).Select(pos => m_ends[pos]).ToArray();
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176 }
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177
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178 }
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179 }
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