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using Implab;
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using Implab.Parsing;
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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace Implab.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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public class JSONParser : DFAutomaton<JSONParserContext> {
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enum MemberContext {
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MemberName,
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MemberValue
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}
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static readonly EnumAlphabet<JsonTokenType> _alphabet = EnumAlphabet<JsonTokenType>.FullAlphabet;
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static readonly DFAStateDescriptior[] _jsonDFA;
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static readonly DFAStateDescriptior[] _objectDFA;
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static readonly DFAStateDescriptior[] _arrayDFA;
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static JSONParser() {
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var jsonExpression = Token.New(JsonTokenType.BeginObject, JsonTokenType.BeginArray).Tag(0);
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var valueExpression = Token.New(JsonTokenType.BeginArray, JsonTokenType.BeginObject, JsonTokenType.Literal, JsonTokenType.Number, JsonTokenType.String);
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var memberExpression = Token.New(JsonTokenType.String).Cat(Token.New(JsonTokenType.NameSeparator)).Cat(valueExpression);
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var objectExpression = memberExpression
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.Cat(
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Token.New(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.New(JsonTokenType.EndObject))
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.Tag(0);
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var arrayExpression = valueExpression
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.Cat(
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Token.New(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.New(JsonTokenType.EndArray))
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.Tag(0);
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_jsonDFA = BuildDFA(jsonExpression).States;
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_objectDFA = BuildDFA(objectExpression).States;
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_arrayDFA = BuildDFA(arrayExpression).States;
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}
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static EDFADefinition<JsonTokenType> BuildDFA(Token expr) {
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var builder = new DFABuilder();
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var dfa = new EDFADefinition<JsonTokenType>(_alphabet);
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expr.Accept(builder);
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builder.BuildDFA(dfa);
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return dfa;
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}
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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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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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public JSONElementType ElementType {
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get { return m_elementType; }
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}
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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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public object ElementValue {
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get { return m_elementValue; }
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}
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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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} else {
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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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}
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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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}
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}
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