org.antlr.v4.runtime.atn.PredictionContextCache.java Source code

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Here is the source code for org.antlr.v4.runtime.atn.PredictionContextCache.java

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/*
 * 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<PredictionContext, PredictionContext> cache = new HashMap<PredictionContext, PredictionContext>();

    /** 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 == PredictionContext.EMPTY)
            return PredictionContext.EMPTY;
        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();
    }
}