org.antlr.v4.runtime.atn.LexerAction Maven / Gradle / Ivy
/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.runtime.atn;
import org.antlr.v4.runtime.CharStream;
import org.antlr.v4.runtime.Lexer;
/**
* Represents a single action which can be executed following the successful
* match of a lexer rule. Lexer actions are used for both embedded action syntax
* and ANTLR 4's new lexer command syntax.
*
* @author Sam Harwell
* @since 4.2
*/
public interface LexerAction {
/**
* Gets the serialization type of the lexer action.
*
* @return The serialization type of the lexer action.
*/
LexerActionType getActionType();
/**
* Gets whether the lexer action is position-dependent. Position-dependent
* actions may have different semantics depending on the {@link CharStream}
* index at the time the action is executed.
*
* Many lexer commands, including {@code type}, {@code skip}, and
* {@code more}, do not check the input index during their execution.
* Actions like this are position-independent, and may be stored more
* efficiently as part of the {@link LexerATNConfig#lexerActionExecutor}.
*
* @return {@code true} if the lexer action semantics can be affected by the
* position of the input {@link CharStream} at the time it is executed;
* otherwise, {@code false}.
*/
boolean isPositionDependent();
/**
* Execute the lexer action in the context of the specified {@link Lexer}.
*
* For position-dependent actions, the input stream must already be
* positioned correctly prior to calling this method.
*
* @param lexer The lexer instance.
*/
void execute(Lexer lexer);
}