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/*
* All content copyright Terracotta, Inc., unless otherwise indicated.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.terracotta.context;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.concurrent.ConcurrentHashMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class WeakIdentityHashMap {
private static final Logger LOGGER = LoggerFactory.getLogger(WeakIdentityHashMap.class);
private final ReferenceQueue referenceQueue = new ReferenceQueue();
private final ConcurrentHashMap, V> backing = new ConcurrentHashMap, V>();
public V get(K key) {
clean();
return backing.get(createReference(key, null));
}
public V putIfAbsent(K key, V value) {
clean();
return backing.putIfAbsent(createReference(key, referenceQueue), value);
}
private void clean() {
Reference ref;
while ((ref = referenceQueue.poll()) != null) {
V dead = backing.remove(ref);
if (dead instanceof Cleanable) {
try {
((Cleanable) dead).clean();
} catch (Throwable t) {
LOGGER.warn("Cleaning failed with : {}", t);
}
}
}
}
protected Reference createReference(K key, ReferenceQueue queue) {
return new IdentityWeakReference(key, queue);
}
static class IdentityWeakReference extends WeakReference {
private final int hashCode;
public IdentityWeakReference(T t) {
this(t, null);
}
public IdentityWeakReference(T t, ReferenceQueue rq) {
super(t, rq);
this.hashCode = System.identityHashCode(t);
}
@Override
public int hashCode() {
return hashCode;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
} else if (o instanceof IdentityWeakReference) {
T ourReferent = get();
return ourReferent != null && ourReferent == ((IdentityWeakReference) o).get();
} else {
return false;
}
}
}
public interface Cleanable {
void clean();
}
}