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/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 2008-2013 jOpenDocument, by ILM Informatique. All rights reserved.
*
* The contents of this file are subject to the terms of the GNU
* General Public License Version 3 only ("GPL").
* You may not use this file except in compliance with the License.
* You can obtain a copy of the License at http://www.gnu.org/licenses/gpl-3.0.html
* See the License for the specific language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each file.
*
*/
package org.jopendocument.util.cache;
import org.jopendocument.util.RTInterruptedException;
import org.jopendocument.util.cc.ITransformerExn;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import net.jcip.annotations.ThreadSafe;
// from "Java Concurrency in Practice"
@ThreadSafe
public class Memoizer implements ITransformerExn {
private final ConcurrentMap> cache;
private final ITransformerExn c;
public Memoizer(ITransformerExn c) {
this(c, new ConcurrentHashMap>());
}
public Memoizer(final ITransformerExn c, final ConcurrentMap> cache) {
this.c = c;
this.cache = cache;
}
public final Set getCachedItems() {
return this.cache.keySet();
}
@Override
public final V transformChecked(final A arg) throws X {
while (true) {
Future res = this.cache.get(arg);
if (res == null) {
final FutureTask ft = new FutureTask(new Callable() {
public V call() throws X {
return Memoizer.this.c.transformChecked(arg);
}
});
res = this.cache.putIfAbsent(arg, ft);
if (res == null) {
res = ft;
ft.run();
}
}
try {
return res.get();
} catch (InterruptedException e) {
throw new RTInterruptedException(e);
} catch (CancellationException e) {
this.cache.remove(arg, res);
} catch (ExecutionException e) {
@SuppressWarnings("unchecked")
final X cause = (X) e.getCause();
throw cause;
}
}
}
}