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165
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1 using System;
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163
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2 using System.Globalization;
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165
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3 using Implab.Automaton;
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176
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4 using System.Text;
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5 using Implab.Components;
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6 using System.IO;
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163
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7
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228
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8 namespace Implab.Formats.Json {
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163
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9 /// <summary>
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10 /// Сканнер (лексер), разбивающий поток символов на токены JSON.
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11 /// </summary>
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228
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12 public abstract class JsonScanner : Disposable {
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13 readonly InputScanner<JsonGrammar.TokenType> m_jsonContext = JsonGrammar.CreateJsonExpressionScanner();
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14 readonly InputScanner<JsonGrammar.TokenType> m_stringContext = JsonGrammar.CreateStringExpressionScanner();
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176
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15
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16 readonly char[] m_unescapeBuf = new char[4];
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17 readonly char[] m_buffer;
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18 int m_length;
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19 int m_pos;
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20 readonly StringBuilder m_tokenBuilder = new StringBuilder();
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21
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228
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22 protected JsonScanner(char[] buffer, int pos, int length) {
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23 m_buffer = buffer;
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24 m_pos = pos;
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25 m_length = length;
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176
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26 }
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27
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28 bool ReadChunk(InputScanner<JsonGrammar.TokenType> scanner, out JsonGrammar.TokenType tokenType) {
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29 scanner.ResetState();
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30
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31 while(scanner.Scan(m_buffer, m_pos, m_length)) {
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32 // scanner requests new data
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33
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34 if (m_pos != m_length) // capture results for the future
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35 m_tokenBuilder.Append(m_buffer, m_pos, m_length - m_pos);
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36
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37 // read next data
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38 m_length = Read(m_buffer, 0, m_buffer.Length);
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39
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40 if (m_length == 0) {
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41 // no data is read
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42 if (scanner.Position == m_pos) {
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43 // scanned hasn't moved, that's the end
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44 m_pos = 0;
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45 tokenType = JsonGrammar.TokenType.None;
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46 return false;
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47 }
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48
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49 if (scanner.IsFinal) {
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50 m_pos = 0;
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51 tokenType = scanner.Tag;
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52 return true;
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53 } else {
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54 throw new ParserException("Unexpected EOF");
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55 }
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228
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56 }
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229
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57
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58 m_pos = 0;
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59 }
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60 var scannerPos = scanner.Position;
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229
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61
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62 // scanner stops as scannerPos
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63 if (!scanner.IsFinal)
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64 throw new ParserException($"Unexpected character '{m_buffer[scannerPos + 1]}'");
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65
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66 tokenType = scanner.Tag;
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67 if (scannerPos != m_pos && tokenType == JsonGrammar.TokenType.Number || tokenType == JsonGrammar.TokenType.Literal)
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68 m_tokenBuilder.Append(m_buffer, m_pos, scannerPos - m_pos);
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69
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70 m_pos = scannerPos;
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71 return true;
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72 }
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73
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74 bool ReadStringChunk(InputScanner<JsonGrammar.TokenType> scanner, out JsonGrammar.TokenType tokenType) {
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75 scanner.ResetState();
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76
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77 while (scanner.Scan(m_buffer, m_pos, m_length)) {
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78 // scanner requests new data
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79
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80 if (m_pos != m_length) // capture results for the future
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81 m_tokenBuilder.Append(m_buffer, m_pos, m_length - m_pos);
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82
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83 // read next data
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84 m_length = Read(m_buffer, 0, m_buffer.Length);
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85
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86 if (m_length == 0) {
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87 // no data is read
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88 if (scanner.Position == m_pos) {
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89 // scanned hasn't moved, that's the end
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90 m_pos = 0;
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91 tokenType = JsonGrammar.TokenType.None;
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92 return false;
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93 }
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94
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95 if (scanner.IsFinal) {
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96 m_pos = 0;
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97 tokenType = scanner.Tag;
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98 return true;
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99 } else {
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100 throw new ParserException("Unexpected EOF");
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101 }
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102 }
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103
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104 m_pos = 0;
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105 }
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106 var scannerPos = scanner.Position;
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107
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108 // scanner stops as scannerPos
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109 if (!scanner.IsFinal)
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110 throw new ParserException($"Unexpected character '{m_buffer[scannerPos + 1]}'");
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111
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228
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112 if (scannerPos != m_pos) {
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113 m_tokenBuilder.Append(m_buffer, m_pos, scannerPos - m_pos);
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114 m_pos = scannerPos;
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115 }
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116 tokenType = scanner.Tag;
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117 return true;
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163
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118 }
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119
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228
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120 protected abstract int Read(char[] buffer, int offset, int size);
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121
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180
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122
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163
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123 /// <summary>
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124 /// Читает следующий лексический элемент из входных данных.
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125 /// </summary>
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126 /// <param name="tokenValue">Возвращает значение прочитанного токена.</param>
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127 /// <param name="tokenType">Возвращает тип прочитанного токена.</param>
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128 /// <returns><c>true</c> - чтение произведено успешно. <c>false</c> - достигнут конец входных данных</returns>
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129 /// <remarks>В случе если токен не распознается, возникает исключение. Значения токенов обрабатываются, т.е.
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130 /// в строках обрабатываются экранированные символы, числа становтся типа double.</remarks>
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229
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131 public bool ReadToken(out string tokenValue, out JsonTokenType tokenType) {
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228
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132 JsonGrammar.TokenType tag;
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133 m_tokenBuilder.Clear();
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229
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134 while (ReadChunk(m_jsonContext, out tag)) {
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228
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135 switch (tag) {
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136 case JsonGrammar.TokenType.StringBound:
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163
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137 tokenValue = ReadString();
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138 tokenType = JsonTokenType.String;
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139 break;
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228
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140 case JsonGrammar.TokenType.Number:
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141 tokenValue = m_tokenBuilder.ToString();
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142 tokenType = JsonTokenType.Number;
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143 break;
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228
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144 case JsonGrammar.TokenType.Literal:
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145 tokenType = JsonTokenType.Literal;
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146 tokenValue = m_tokenBuilder.ToString();
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147 break;
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148 case JsonGrammar.TokenType.Whitespace:
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149 m_tokenBuilder.Clear();
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183
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150 continue;
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163
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151 default:
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152 tokenType = (JsonTokenType)tag;
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153 tokenValue = null;
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163
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154 break;
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155 }
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156 return true;
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157 }
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158 tokenValue = null;
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159 tokenType = JsonTokenType.None;
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160 return false;
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161 }
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162
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163 string ReadString() {
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228
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164 JsonGrammar.TokenType tag;
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165 m_tokenBuilder.Clear();
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176
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166
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229
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167 while (ReadStringChunk(m_stringContext, out tag)) {
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228
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168 switch (tag) {
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169 case JsonGrammar.TokenType.StringBound:
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170 m_tokenBuilder.Length--;
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171 return m_tokenBuilder.ToString();
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172 case JsonGrammar.TokenType.UnescapedChar:
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163
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173 break;
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228
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174 case JsonGrammar.TokenType.EscapedUnicode: // \xXXXX - unicode escape sequence
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175 m_tokenBuilder.CopyTo(m_tokenBuilder.Length - 4, m_unescapeBuf, 0, 4);
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176 m_tokenBuilder.Length -= 6;
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177 m_tokenBuilder.Append(StringTranslator.TranslateHexUnicode(m_unescapeBuf, 0));
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163
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178 break;
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228
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179 case JsonGrammar.TokenType.EscapedChar: // \t - escape sequence
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180 var ch = m_tokenBuilder[m_tokenBuilder.Length-1];
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181 m_tokenBuilder.Length -= 2;
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182 m_tokenBuilder.Append(StringTranslator.TranslateEscapedChar(ch));
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163
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183 break;
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184 }
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185 }
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186
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187 throw new ParserException("Unexpected end of data");
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188 }
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189 }
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190 }
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