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165
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1 using System;
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163
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2 using System.Diagnostics;
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3 using System.IO;
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165
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4 using Implab.Automaton;
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5 using Implab.Automaton.RegularExpressions;
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6 using System.Linq;
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7 using Implab.Components;
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180
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8 using System.Collections.Generic;
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163
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9
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165
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10 namespace Implab.Formats.JSON {
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163
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11 /// <summary>
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12 /// Pull парсер JSON данных.
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13 /// </summary>
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14 /// <remarks>
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15 /// Следует отметить отдельную интерпретацию свойства <see cref="Level"/>,
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16 /// оно означает текущий уровень вложенности объектов, однако закрывающий
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17 /// элемент объекта и массива имеет уровень меньше, чем сам объект.
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18 /// <code>
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19 /// { // Level = 1
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20 /// "name" : "Peter", // Level = 1
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21 /// "address" : { // Level = 2
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22 /// city : "Stern" // Level = 2
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23 /// } // Level = 1
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24 /// } // Level = 0
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25 /// </code>
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26 /// </remarks>
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27 public class JSONParser : Disposable {
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28
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29 enum MemberContext {
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30 MemberName,
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31 MemberValue
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32 }
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33
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178
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34 #region Parser rules
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35 struct ParserContext {
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36 readonly int[,] m_dfa;
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37 int m_state;
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38
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39 readonly JSONElementContext m_elementContext;
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40
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41 public ParserContext(int[,] dfa, int state, JSONElementContext context) {
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42 m_dfa = dfa;
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43 m_state = state;
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44 m_elementContext = context;
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45 }
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46
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47 public bool Move(JsonTokenType token) {
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48 var next = m_dfa[m_state, (int)token];
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49 if (next == AutomatonConst.UNREACHABLE_STATE)
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50 return false;
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51 m_state = next;
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52 return true;
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178
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53 }
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54
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55 public JSONElementContext ElementContext {
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56 get { return m_elementContext; }
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57 }
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58 }
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59
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60 static readonly ParserContext _jsonContext;
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61 static readonly ParserContext _objectContext;
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62 static readonly ParserContext _arrayContext;
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63
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64 static JSONParser() {
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65
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66 var valueExpression = MakeToken(JsonTokenType.BeginArray, JsonTokenType.BeginObject, JsonTokenType.Literal, JsonTokenType.Number, JsonTokenType.String);
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67 var memberExpression = MakeToken(JsonTokenType.String).Cat(MakeToken(JsonTokenType.NameSeparator)).Cat(valueExpression);
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68
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69 var objectExpression = memberExpression
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70 .Cat(
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71 MakeToken(JsonTokenType.ValueSeparator)
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72 .Cat(memberExpression)
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73 .EClosure()
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74 )
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75 .Optional()
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76 .Cat(MakeToken(JsonTokenType.EndObject))
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77 .End();
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78
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79 var arrayExpression = valueExpression
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80 .Cat(
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81 MakeToken(JsonTokenType.ValueSeparator)
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82 .Cat(valueExpression)
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83 .EClosure()
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84 )
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85 .Optional()
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86 .Cat(MakeToken(JsonTokenType.EndArray))
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87 .End();
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88
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89 var jsonExpression = valueExpression.End();
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90
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91 _jsonContext = CreateParserContext(jsonExpression, JSONElementContext.None);
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92 _objectContext = CreateParserContext(objectExpression, JSONElementContext.Object);
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93 _arrayContext = CreateParserContext(arrayExpression, JSONElementContext.Array);
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94 }
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95
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96 static Token MakeToken(params JsonTokenType[] input) {
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97 return Token.New( input.Select(t => (int)t).ToArray() );
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98 }
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99
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100 static ParserContext CreateParserContext(Token expr, JSONElementContext context) {
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101
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102 var dfa = new DFATable();
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103 var builder = new RegularExpressionVisitor(dfa);
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104 expr.Accept(builder);
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105 builder.BuildDFA();
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106
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107 return new ParserContext(dfa.CreateTransitionTable(), dfa.InitialState, context);
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108 }
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109
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178
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110 #endregion
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111
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112 readonly JSONScanner m_scanner;
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113 MemberContext m_memberContext;
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114
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115 JSONElementType m_elementType;
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116 object m_elementValue;
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180
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117 string m_memberName = String.Empty;
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118
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119 Stack<ParserContext> m_stack = new Stack<ParserContext>();
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120 ParserContext m_context = _jsonContext;
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121
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122 /// <summary>
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123 /// Создает новый парсер на основе строки, содержащей JSON
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124 /// </summary>
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125 /// <param name="text"></param>
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126 public JSONParser(string text) {
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127 Safe.ArgumentNotEmpty(text, "text");
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128 m_scanner = new JSONScanner(text);
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129 }
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130
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131 /// <summary>
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132 /// Создает новый экземпляр парсера, на основе текстового потока.
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133 /// </summary>
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134 /// <param name="reader">Текстовый поток.</param>
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135 public JSONParser(TextReader reader) {
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136 Safe.ArgumentNotNull(reader, "reader");
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137 m_scanner = new JSONScanner(reader);
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138 }
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139
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140 public int Level {
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141 get { return m_stack.Count; }
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163
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142 }
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143
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144 /// <summary>
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145 /// Тип текущего элемента на котором стоит парсер.
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146 /// </summary>
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147 public JSONElementType ElementType {
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148 get { return m_elementType; }
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149 }
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150
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151 /// <summary>
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152 /// Имя элемента - имя свойства родительского контейнера. Для элементов массивов и корневого всегда
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153 /// пустая строка.
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154 /// </summary>
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155 public string ElementName {
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156 get { return m_memberName; }
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163
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157 }
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158
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159 /// <summary>
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160 /// Значение элемента. Только для элементов типа <see cref="JSONElementType.Value"/>, для остальных <c>null</c>
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161 /// </summary>
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162 public object ElementValue {
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163 get { return m_elementValue; }
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164 }
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165
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166 /// <summary>
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167 /// Читает слеюудущий объект из потока
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168 /// </summary>
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169 /// <returns><c>true</c> - операция чтения прошла успешно, <c>false</c> - конец данных</returns>
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170 public bool Read() {
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171 object tokenValue;
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172 JsonTokenType tokenType;
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180
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173
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174 m_memberName = String.Empty;
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175
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163
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176 while (m_scanner.ReadToken(out tokenValue, out tokenType)) {
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180
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177 if(!m_context.Move(tokenType))
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178 UnexpectedToken(tokenValue, tokenType);
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180
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179
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180 switch (tokenType) {
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181 case JsonTokenType.BeginObject:
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180
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182 m_stack.Push(m_context);
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183 m_context = _objectContext;
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184
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185 m_elementValue = null;
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186 m_memberContext = MemberContext.MemberName;
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187 m_elementType = JSONElementType.BeginObject;
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188 return true;
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189 case JsonTokenType.EndObject:
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180
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190 if (m_stack.Count == 0)
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191 UnexpectedToken(tokenValue, tokenType);
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192 m_context = m_stack.Pop();
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193
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194 m_elementValue = null;
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195 m_elementType = JSONElementType.EndObject;
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196 return true;
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197 case JsonTokenType.BeginArray:
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198 m_stack.Push(m_context);
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199 m_context = _arrayContext;
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200
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201 m_elementValue = null;
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202 m_memberContext = MemberContext.MemberValue;
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203 m_elementType = JSONElementType.BeginArray;
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204 return true;
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205 case JsonTokenType.EndArray:
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180
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206 if (m_stack.Count == 0)
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207 UnexpectedToken(tokenValue, tokenType);
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208 m_context = m_stack.Pop();
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209
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210 m_elementValue = null;
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211 m_elementType = JSONElementType.EndArray;
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212 return true;
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213 case JsonTokenType.String:
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214 if (m_memberContext == MemberContext.MemberName) {
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215 m_memberName = (string)tokenValue;
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216 break;
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217 }
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218 m_elementType = JSONElementType.Value;
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219 m_elementValue = tokenValue;
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220 return true;
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221 case JsonTokenType.Number:
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222 m_elementType = JSONElementType.Value;
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223 m_elementValue = tokenValue;
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224 return true;
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225 case JsonTokenType.Literal:
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226 m_elementType = JSONElementType.Value;
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227 m_elementValue = ParseLiteral((string)tokenValue);
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228 return true;
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229 case JsonTokenType.NameSeparator:
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230 m_memberContext = MemberContext.MemberValue;
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231 break;
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232 case JsonTokenType.ValueSeparator:
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233 m_memberContext = m_context.ElementContext == JSONElementContext.Object ? MemberContext.MemberName : MemberContext.MemberValue;
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234 break;
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235 default:
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236 UnexpectedToken(tokenValue, tokenType);
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237 break;
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238 }
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239 }
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180
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240 if (m_context.ElementContext != JSONElementContext.None)
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241 throw new ParserException("Unexpedted end of data");
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242
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243 EOF = true;
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244
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245 return false;
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246 }
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247
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248 object ParseLiteral(string literal) {
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249 switch (literal) {
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250 case "null":
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251 return null;
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252 case "false":
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253 return false;
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254 case "true":
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255 return true;
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256 default:
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257 UnexpectedToken(literal, JsonTokenType.Literal);
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258 return null; // avoid compliler error
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259 }
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260 }
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261
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262 void UnexpectedToken(object value, JsonTokenType tokenType) {
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263 throw new ParserException(String.Format("Unexpected token {0}: '{1}'", tokenType, value));
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264 }
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265
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266
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267 /// <summary>
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268 /// Признак конца потока
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269 /// </summary>
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270 public bool EOF {
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180
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271 get;
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272 private set;
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163
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273 }
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274
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275 protected override void Dispose(bool disposing) {
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180
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276 if (disposing)
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277 Safe.Dispose(m_scanner);
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163
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278 }
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279
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280 /// <summary>
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281 /// Переходит в конец текущего объекта.
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282 /// </summary>
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283 public void SeekElementEnd() {
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284 var level = Level - 1;
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285
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286 Debug.Assert(level >= 0);
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287
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288 while (Level != level)
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289 Read();
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290 }
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291 }
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292
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293 }
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