org.antlr.v4.runtime.atn.PredictionContextCache 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 java.util.HashMap;
import java.util.Map;
/** Used to cache {@link PredictionContext} objects. Its used for the shared
* context cash associated with contexts in DFA states. This cache
* can be used for both lexers and parsers.
*/
public class PredictionContextCache {
protected final Map cache =
new HashMap();
/** Add a context to the cache and return it. If the context already exists,
* return that one instead and do not add a new context to the cache.
* Protect shared cache from unsafe thread access.
*/
public PredictionContext add(PredictionContext ctx) {
if ( ctx==EmptyPredictionContext.Instance ) return EmptyPredictionContext.Instance;
PredictionContext existing = cache.get(ctx);
if ( existing!=null ) {
// System.out.println(name+" reuses "+existing);
return existing;
}
cache.put(ctx, ctx);
return ctx;
}
public PredictionContext get(PredictionContext ctx) {
return cache.get(ctx);
}
public int size() {
return cache.size();
}
}