annotate Implab/JSON/JSONScanner.cs @ 62:62b440d46313

Added Skip method to JSON parser to skip contents of the current node
author cin
date Sun, 22 Jun 2014 04:14:02 +0400
parents 10c7337d29e7
children 130781364799
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1 using Implab.Parsing;
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2 using System;
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3 using System.Collections.Generic;
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4 using System.Globalization;
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5 using System.Linq;
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6 using System.Text;
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7 using System.Threading.Tasks;
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8
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9 namespace Implab.JSON {
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10 /// <summary>
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11 /// Сканнер (лексер), разбивающий поток символов на токены JSON.
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12 /// </summary>
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13 public class JSONScanner : Scanner {
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14 char[] m_stringBuffer;
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15 DFAStateDescriptior[] m_stringDFA;
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16 int[] m_stringAlphabet;
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17
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18 /// <summary>
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19 /// Создает новый экземпляр сканнера
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20 /// </summary>
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21 public JSONScanner()
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22 : base(JSONGrammar.Instance.JsonDFA) {
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23 m_stringBuffer = new char[1024];
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24 var dfa = JSONGrammar.Instance.JsonStringDFA;
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25 m_stringAlphabet = dfa.Alphabet.GetTranslationMap();
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26 m_stringDFA = dfa.States;
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27 }
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28
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29 /// <summary>
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30 /// Читает следующий лексический элемент из входных данных.
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31 /// </summary>
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32 /// <param name="tokenValue">Возвращает значение прочитанного токена.</param>
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33 /// <param name="tokenType">Возвращает тип прочитанного токена.</param>
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34 /// <returns><c>true</c> - чтение произведено успешно. <c>false</c> - достигнут конец входных данных</returns>
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35 /// <remarks>В случе если токен не распознается, возникает исключение. Значения токенов обрабатываются, т.е.
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36 /// в строках обрабатываются экранированные символы, числа становтся типа double.</remarks>
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37 public bool ReadToken(out object tokenValue, out JsonTokenType tokenType) {
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38 if (ReadTokenInternal()) {
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39 switch ((JSONGrammar.TokenType)m_currentState.tag[0]) {
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40 case JSONGrammar.TokenType.StringBound:
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41 tokenValue = ReadString();
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42 tokenType = JsonTokenType.String;
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43 break;
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44 case JSONGrammar.TokenType.Number:
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45 tokenValue = Double.Parse(new String(m_buffer, m_tokenOffset, m_tokenLen), CultureInfo.InvariantCulture);
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46 tokenType = JsonTokenType.Number;
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47 break;
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48 default:
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49 tokenType = (JsonTokenType)m_currentState.tag[0];
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50 tokenValue = new String(m_buffer, m_tokenOffset, m_tokenLen);
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51 break;
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52 }
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53 return true;
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54 }
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55 tokenValue = null;
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56 tokenType = JsonTokenType.None;
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57 return false;
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58 }
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59
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60 string ReadString() {
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61 int pos = 0;
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62 Switch(m_stringDFA, m_stringAlphabet);
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63 while (ReadTokenInternal()) {
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64 switch ((JSONGrammar.TokenType)m_currentState.tag[0]) {
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65 case JSONGrammar.TokenType.StringBound:
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66 Restore();
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67 return new String(m_stringBuffer, 0, pos);
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68 case JSONGrammar.TokenType.UnescapedChar:
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69 EnsureStringBufferSize(pos + m_tokenLen);
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70 Array.Copy(m_buffer, m_tokenOffset, m_stringBuffer, pos, m_tokenLen);
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71 pos += m_tokenLen;
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72 break;
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73 case JSONGrammar.TokenType.EscapedUnicode:
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74 EnsureStringBufferSize(pos + 1);
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75 m_stringBuffer[pos] = StringTranslator.TranslateHexUnicode(m_buffer, m_tokenOffset + 2);
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76 pos++;
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77 break;
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78 case JSONGrammar.TokenType.EscapedChar:
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79 EnsureStringBufferSize(pos + 1);
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80 m_stringBuffer[pos] = StringTranslator.TranslateEscapedChar(m_buffer[m_tokenOffset + 1]);
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81 pos++;
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82 break;
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83 default:
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84 break;
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85 }
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86
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87 }
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88
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89 throw new ParserException("Unexpected end of data");
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90 }
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91
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92 void EnsureStringBufferSize(int size) {
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93 if (size > m_stringBuffer.Length) {
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94 var newBuffer = new char[size];
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95 m_stringBuffer.CopyTo(newBuffer, 0);
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96 m_stringBuffer = newBuffer;
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97 }
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98 }
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99 }
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100 }