org.antlr.v4.runtime.atn.PredictionContextCache Maven / Gradle / Ivy
/*
* [The "BSD license"]
* Copyright (c) 2012 Terence Parr
* Copyright (c) 2012 Sam Harwell
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
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 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==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();
}
}