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using System;
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using System.Diagnostics;
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using System.IO;
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using Implab.Automaton;
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using Implab.Automaton.RegularExpressions;
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using System.Linq;
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using Implab.Components;
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namespace Implab.Formats.JSON {
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/// <summary>
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/// internal
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/// </summary>
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public struct JSONParserContext {
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public string memberName;
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public JSONElementContext elementContext;
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}
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/// <summary>
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/// Pull парсер JSON данных.
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/// </summary>
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/// <remarks>
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/// Следует отметить отдельную интерпретацию свойства <see cref="Level"/>,
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/// оно означает текущий уровень вложенности объектов, однако закрывающий
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/// элемент объекта и массива имеет уровень меньше, чем сам объект.
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/// <code>
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/// { // Level = 1
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/// "name" : "Peter", // Level = 1
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/// "address" : { // Level = 2
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/// city : "Stern" // Level = 2
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/// } // Level = 1
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/// } // Level = 0
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/// </code>
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/// </remarks>
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public class JSONParser : Disposable {
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enum MemberContext {
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MemberName,
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MemberValue
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}
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#region Parser rules
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struct ParserContext {
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readonly int[,] m_dfa;
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int m_state;
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readonly JSONElementContext m_elementContext;
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public ParserContext(int[,] dfa, int state, JSONElementContext context) {
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m_dfa = dfa;
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m_state = state;
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m_elementContext = context;
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}
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public bool Move(JsonTokenType token) {
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var next = m_dfa[m_state, token];
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if (next == AutomatonConst.UNREACHABLE_STATE)
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return false;
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m_state = next;
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}
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public JSONElementContext ElementContext {
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get { return m_elementContext; }
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}
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}
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static JSONParser() {
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var valueExpression = Token(JsonTokenType.BeginArray, JsonTokenType.BeginObject, JsonTokenType.Literal, JsonTokenType.Number, JsonTokenType.String);
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var memberExpression = Token(JsonTokenType.String).Cat(Token(JsonTokenType.NameSeparator)).Cat(valueExpression);
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var objectExpression = memberExpression
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.Cat(
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Token(JsonTokenType.ValueSeparator)
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.Cat(memberExpression)
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.EClosure()
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)
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.Optional()
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.Cat(Token(JsonTokenType.EndObject))
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.End();
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var arrayExpression = valueExpression
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.Cat(
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Token(JsonTokenType.ValueSeparator)
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.Cat(valueExpression)
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.EClosure()
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)
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.Optional()
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.Cat(Token(JsonTokenType.EndArray))
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.End();
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var jsonExpression = valueExpression.End();
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_jsonDFA = CreateParserContext(jsonExpression, JSONElementContext.None);
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_objectDFA = CreateParserContext(objectExpression, JSONElementContext.Object);
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_arrayDFA = CreateParserContext(arrayExpression, JSONElementContext.Array);
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}
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static Token Token(params JsonTokenType[] input) {
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return Token.New( input.Select(t => (int)t).ToArray() );
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}
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static ParserContext CreateParserContext(Token expr, JSONElementContext context) {
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var dfa = new DFATable();
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var builder = new RegularExpressionVisitor(dfa);
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expr.Accept(builder);
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builder.BuildDFA();
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return new ParserContext(dfa.CreateTransitionTable(), dfa.InitialState, context);
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}
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#endregion
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JSONScanner m_scanner;
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MemberContext m_memberContext;
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JSONElementType m_elementType;
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object m_elementValue;
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/// <summary>
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/// Создает новый парсер на основе строки, содержащей JSON
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/// </summary>
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/// <param name="text"></param>
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public JSONParser(string text)
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: base(_jsonDFA, INITIAL_STATE, new JSONParserContext { elementContext = JSONElementContext.None, memberName = String.Empty }) {
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Safe.ArgumentNotEmpty(text, "text");
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m_scanner = new JSONScanner();
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m_scanner.Feed(text.ToCharArray());
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}
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/// <summary>
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/// Создает новый экземпляр парсера, на основе текстового потока.
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/// </summary>
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/// <param name="reader">Текстовый поток.</param>
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public JSONParser(TextReader reader)
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: base(_jsonDFA, INITIAL_STATE, new JSONParserContext { elementContext = JSONElementContext.None, memberName = String.Empty }) {
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Safe.ArgumentNotNull(reader, "reader");
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m_scanner = new JSONScanner();
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m_scanner.Feed(reader, dispose);
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}
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/// <summary>
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/// Тип текущего элемента на котором стоит парсер.
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/// </summary>
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public JSONElementType ElementType {
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get { return m_elementType; }
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}
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/// <summary>
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/// Имя элемента - имя свойства родительского контейнера. Для элементов массивов и корневого всегда
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/// пустая строка.
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/// </summary>
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public string ElementName {
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get { return m_context.info.memberName; }
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}
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/// <summary>
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/// Значение элемента. Только для элементов типа <see cref="JSONElementType.Value"/>, для остальных <c>null</c>
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/// </summary>
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public object ElementValue {
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get { return m_elementValue; }
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}
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/// <summary>
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/// Читает слеюудущий объект из потока
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/// </summary>
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/// <returns><c>true</c> - операция чтения прошла успешно, <c>false</c> - конец данных</returns>
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public bool Read() {
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if (m_context.current == UNREACHEBLE_STATE)
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throw new InvalidOperationException("The parser is in invalid state");
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object tokenValue;
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JsonTokenType tokenType;
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m_context.info.memberName = String.Empty;
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while (m_scanner.ReadToken(out tokenValue, out tokenType)) {
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Move((int)tokenType);
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if (m_context.current == UNREACHEBLE_STATE)
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UnexpectedToken(tokenValue, tokenType);
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switch (tokenType) {
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case JsonTokenType.BeginObject:
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Switch(
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_objectDFA,
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INITIAL_STATE,
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new JSONParserContext {
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memberName = m_context.info.memberName,
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elementContext = JSONElementContext.Object
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}
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);
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m_elementValue = null;
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m_memberContext = MemberContext.MemberName;
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m_elementType = JSONElementType.BeginObject;
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return true;
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case JsonTokenType.EndObject:
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Restore();
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m_elementValue = null;
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m_elementType = JSONElementType.EndObject;
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return true;
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case JsonTokenType.BeginArray:
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Switch(
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_arrayDFA,
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INITIAL_STATE,
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new JSONParserContext {
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memberName = m_context.info.memberName,
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elementContext = JSONElementContext.Array
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}
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);
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m_elementValue = null;
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m_memberContext = MemberContext.MemberValue;
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m_elementType = JSONElementType.BeginArray;
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return true;
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case JsonTokenType.EndArray:
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Restore();
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m_elementValue = null;
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m_elementType = JSONElementType.EndArray;
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return true;
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case JsonTokenType.String:
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if (m_memberContext == MemberContext.MemberName) {
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m_context.info.memberName = (string)tokenValue;
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break;
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}
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m_elementType = JSONElementType.Value;
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m_elementValue = tokenValue;
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return true;
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case JsonTokenType.Number:
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m_elementType = JSONElementType.Value;
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m_elementValue = tokenValue;
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return true;
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case JsonTokenType.Literal:
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m_elementType = JSONElementType.Value;
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m_elementValue = ParseLiteral((string)tokenValue);
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return true;
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case JsonTokenType.NameSeparator:
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m_memberContext = MemberContext.MemberValue;
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break;
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case JsonTokenType.ValueSeparator:
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m_memberContext = m_context.info.elementContext == JSONElementContext.Object ? MemberContext.MemberName : MemberContext.MemberValue;
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break;
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default:
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UnexpectedToken(tokenValue, tokenType);
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break;
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}
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}
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if (m_context.info.elementContext != JSONElementContext.None)
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throw new ParserException("Unexpedted end of data");
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return false;
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}
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object ParseLiteral(string literal) {
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switch (literal) {
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case "null":
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return null;
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case "false":
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return false;
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case "true":
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return true;
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default:
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UnexpectedToken(literal, JsonTokenType.Literal);
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return null; // avoid compliler error
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}
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}
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void UnexpectedToken(object value, JsonTokenType tokenType) {
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throw new ParserException(String.Format("Unexpected token {0}: '{1}'", tokenType, value));
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}
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/// <summary>
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/// Признак конца потока
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/// </summary>
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public bool EOF {
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get {
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return m_scanner.EOF;
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}
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}
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protected override void Dispose(bool disposing) {
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if (disposing) {
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m_scanner.Dispose();
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}
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}
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/// <summary>
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/// Переходит в конец текущего объекта.
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/// </summary>
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public void SeekElementEnd() {
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var level = Level - 1;
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Debug.Assert(level >= 0);
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while (Level != level)
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Read();
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}
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}
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}
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