Antlr4.Runtime.Atn.LexerActionExecutor.FixOffsetBeforeMatch C# (CSharp) Method

LexerActionExecutor Class Documentation Usage Examples Of Antlr4.Runtime.Atn.LexerActionExecutor::FixOffsetBeforeMatch Mostra file Open project: sharwell/antlr4cs

FixOffsetBeforeMatch() public method

Creates a LexerActionExecutor which encodes the current offset for position-dependent lexer actions.

Normally, when the executor encounters lexer actions where ILexerAction.IsPositionDependent() returns , it calls Antlr4.Runtime.IIntStream.Seek(int) on the input Antlr4.Runtime.ICharStream to set the input position to the end of the current token. This behavior provides for efficient DFA representation of lexer actions which appear at the end of a lexer rule, even when the lexer rule matches a variable number of characters.

Prior to traversing a match transition in the ATN, the current offset from the token start index is assigned to all position-dependent lexer actions which have not already been assigned a fixed offset. By storing the offsets relative to the token start index, the DFA representation of lexer actions which appear in the middle of tokens remains efficient due to sharing among tokens of the same length, regardless of their absolute position in the input stream.

If the current executor already has offsets assigned to all position-dependent lexer actions, the method returns this .

public FixOffsetBeforeMatch ( int offset ) : Antlr4.Runtime.Atn.LexerActionExecutor
offset	int	/// The current offset to assign to all position-dependent /// lexer actions which do not already have offsets assigned. ///
return	Antlr4.Runtime.Atn.LexerActionExecutor

        public virtual Antlr4.Runtime.Atn.LexerActionExecutor FixOffsetBeforeMatch(int offset)
        {
            ILexerAction[] updatedLexerActions = null;
            for (int i = 0; i < lexerActions.Length; i++)
            {
                if (lexerActions[i].IsPositionDependent && !(lexerActions[i] is LexerIndexedCustomAction))
                {
                    if (updatedLexerActions == null)
                    {
                        updatedLexerActions = (ILexerAction[])lexerActions.Clone();
                    }
                    updatedLexerActions[i] = new LexerIndexedCustomAction(offset, lexerActions[i]);
                }
            }
            if (updatedLexerActions == null)
            {
                return this;
            }
            return new Antlr4.Runtime.Atn.LexerActionExecutor(updatedLexerActions);
        }

Usage Example

Esempio n. 1

Mostra file

        /** Given a starting configuration set, figure out all ATN configurations
         *  we can reach upon input {@code t}. Parameter {@code reach} is a return
         *  parameter.
         */
        protected void GetReachableConfigSet(ICharStream input, ATNConfigSet closure, ATNConfigSet reach, int t)
        {
            // this is used to skip processing for configs which have a lower priority
            // than a config that already reached an accept state for the same rule
            int skipAlt = ATN.INVALID_ALT_NUMBER;

            foreach (ATNConfig c in closure.configs)
            {
                bool currentAltReachedAcceptState = c.alt == skipAlt;
                if (currentAltReachedAcceptState && ((LexerATNConfig)c).hasPassedThroughNonGreedyDecision())
                {
                    continue;
                }

                if (debug)
                {
                    ConsoleWriteLine("testing " + GetTokenName(t) + " at " + c.ToString(recog, true));
                }

                int n = c.state.NumberOfTransitions;
                for (int ti = 0; ti < n; ti++)
                {                               // for each transition
                    Transition trans  = c.state.Transition(ti);
                    ATNState   target = GetReachableTarget(trans, t);
                    if (target != null)
                    {
                        LexerActionExecutor lexerActionExecutor = ((LexerATNConfig)c).getLexerActionExecutor();
                        if (lexerActionExecutor != null)
                        {
                            lexerActionExecutor = lexerActionExecutor.FixOffsetBeforeMatch(input.Index - startIndex);
                        }

                        bool treatEofAsEpsilon = t == IntStreamConstants.EOF;
                        if (Closure(input, new LexerATNConfig((LexerATNConfig)c, target, lexerActionExecutor), reach, currentAltReachedAcceptState, true, treatEofAsEpsilon))
                        {
                            // any remaining configs for this alt have a lower priority than
                            // the one that just reached an accept state.
                            skipAlt = c.alt;
                            break;
                        }
                    }
                }
            }
        }

All Usage Examples Of Antlr4.Runtime.Atn.LexerActionExecutor::FixOffsetBeforeMatch

LexerActionExecutor

Append

Equals

Execute

FixOffsetBeforeMatch

GetHashCode

LexerActionExecutor