annotate Implab/Formats/JSON/JSONScanner.cs @ 178:d5c5db0335ee ref20160224

working on JSON parser
author cin
date Wed, 23 Mar 2016 19:51:45 +0300
parents a0ff6a0e9c44
children 478ef706906a
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1 using System;
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2 using System.Globalization;
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3 using Implab.Automaton;
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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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7
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8 namespace Implab.Formats.JSON {
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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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12 public class JSONScanner : Disposable {
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13 readonly StringBuilder m_builder = new StringBuilder();
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14
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15 readonly ScannerContext<JSONGrammar.TokenType> m_jsonContext = JSONGrammar.Instance.JsonDFA;
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16 readonly ScannerContext<JSONGrammar.TokenType> m_stringContext = JSONGrammar.Instance.JsonStringDFA;
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18
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19 readonly TextScanner m_scanner;
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20
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21 /// <summary>
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22 /// Создает новый экземпляр сканнера
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23 /// </summary>
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24 public JSONScanner(string text) {
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25 Safe.ArgumentNotEmpty(text, "text");
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26
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27 m_scanner = new StringScanner(text);
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28 }
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29
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30 public JSONScanner(TextReader reader, int bufferMax, int chunkSize) {
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31 Safe.ArgumentNotNull(reader, "reader");
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32
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33 m_scanner = new ReaderScanner(reader, bufferMax, chunkSize);
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34 }
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35
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36 /// <summary>
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37 /// Читает следующий лексический элемент из входных данных.
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38 /// </summary>
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39 /// <param name="tokenValue">Возвращает значение прочитанного токена.</param>
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40 /// <param name="tokenType">Возвращает тип прочитанного токена.</param>
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41 /// <returns><c>true</c> - чтение произведено успешно. <c>false</c> - достигнут конец входных данных</returns>
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42 /// <remarks>В случе если токен не распознается, возникает исключение. Значения токенов обрабатываются, т.е.
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43 /// в строках обрабатываются экранированные символы, числа становтся типа double.</remarks>
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44 public bool ReadToken(out object tokenValue, out JsonTokenType tokenType) {
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45 JSONGrammar.TokenType[] tag;
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46 if (m_jsonContext.Execute(m_scanner, out tag)) {
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47 switch (tag[0]) {
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48 case JSONGrammar.TokenType.StringBound:
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49 tokenValue = ReadString();
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50 tokenType = JsonTokenType.String;
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51 break;
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52 case JSONGrammar.TokenType.Number:
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53 tokenValue = Double.Parse(m_scanner.GetTokenValue(), CultureInfo.InvariantCulture);
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54 tokenType = JsonTokenType.Number;
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55 break;
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56 default:
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57 tokenType = (JsonTokenType)tag[0];
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58 tokenValue = m_scanner.GetTokenValue();
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59 break;
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60 }
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61 return true;
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62 }
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63 tokenValue = null;
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64 tokenType = JsonTokenType.None;
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65 return false;
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66 }
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68 string ReadString() {
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69 int pos = 0;
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70 var buf = new char[6]; // the buffer for unescaping chars
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72 JSONGrammar.TokenType[] tag;
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73 m_builder.Clear();
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74
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75 while (m_stringContext.Execute(m_scanner, out tag)) {
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76 switch (tag[0]) {
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77 case JSONGrammar.TokenType.StringBound:
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78 return m_builder.ToString();
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79 case JSONGrammar.TokenType.UnescapedChar:
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80 m_scanner.CopyTokenTo(m_builder);
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81 break;
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82 case JSONGrammar.TokenType.EscapedUnicode: // \xXXXX - unicode escape sequence
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83 m_scanner.CopyTokenTo(buf, 0);
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84 m_builder.Append(StringTranslator.TranslateHexUnicode(buf, 2));
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85 pos++;
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86 break;
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87 case JSONGrammar.TokenType.EscapedChar: // \t - escape sequence
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88 m_scanner.CopyTokenTo(buf, 0);
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89 m_builder.Append(StringTranslator.TranslateEscapedChar(buf[1]));
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90 break;
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91 }
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93 }
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95 throw new ParserException("Unexpected end of data");
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96 }
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97
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98 protected override void Dispose(bool disposing) {
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99 if (disposing)
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100 Safe.Dispose(m_scanner);
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101 base.Dispose(disposing);
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102 }
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103 }
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104 }