org.antlr.v4.runtime.atn.Transition 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.misc.IntervalSet;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/** An ATN transition between any two ATN states. Subclasses define
* atom, set, epsilon, action, predicate, rule transitions.
*
* This is a one way link. It emanates from a state (usually via a list of
* transitions) and has a target state.
*
* Since we never have to change the ATN transitions once we construct it,
* we can fix these transitions as specific classes. The DFA transitions
* on the other hand need to update the labels as it adds transitions to
* the states. We'll use the term Edge for the DFA to distinguish them from
* ATN transitions.
*/
public abstract class Transition {
// constants for serialization
public static final int EPSILON = 1;
public static final int RANGE = 2;
public static final int RULE = 3;
public static final int PREDICATE = 4; // e.g., {isType(input.LT(1))}?
public static final int ATOM = 5;
public static final int ACTION = 6;
public static final int SET = 7; // ~(A|B) or ~atom, wildcard, which convert to next 2
public static final int NOT_SET = 8;
public static final int WILDCARD = 9;
public static final int PRECEDENCE = 10;
public static final List serializationNames =
Collections.unmodifiableList(Arrays.asList(
"INVALID",
"EPSILON",
"RANGE",
"RULE",
"PREDICATE",
"ATOM",
"ACTION",
"SET",
"NOT_SET",
"WILDCARD",
"PRECEDENCE"
));
public static final Map, Integer> serializationTypes =
Collections.unmodifiableMap(new HashMap, Integer>() {{
put(EpsilonTransition.class, EPSILON);
put(RangeTransition.class, RANGE);
put(RuleTransition.class, RULE);
put(PredicateTransition.class, PREDICATE);
put(AtomTransition.class, ATOM);
put(ActionTransition.class, ACTION);
put(SetTransition.class, SET);
put(NotSetTransition.class, NOT_SET);
put(WildcardTransition.class, WILDCARD);
put(PrecedencePredicateTransition.class, PRECEDENCE);
}});
/** The target of this transition. */
public ATNState target;
protected Transition(ATNState target) {
if (target == null) {
throw new NullPointerException("target cannot be null.");
}
this.target = target;
}
public abstract int getSerializationType();
/**
* Determines if the transition is an "epsilon" transition.
*
* The default implementation returns {@code false}.
*
* @return {@code true} if traversing this transition in the ATN does not
* consume an input symbol; otherwise, {@code false} if traversing this
* transition consumes (matches) an input symbol.
*/
public boolean isEpsilon() {
return false;
}
public IntervalSet label() { return null; }
public abstract boolean matches(int symbol, int minVocabSymbol, int maxVocabSymbol);
}