/*
* Copyright (C) 2011 The Android Open Source Project
*
* 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 java.lang.ref;
/**
* @hide
*/
public final class FinalizerReference<T> extends Reference<T> {
public static final ReferenceQueue<Object> queue = new ReferenceQueue<Object>();
private static FinalizerReference head = null;
private T zombie;
private FinalizerReference prev;
private FinalizerReference next;
public FinalizerReference(T r, ReferenceQueue<? super T> q) {
super(r, q);
}
@Override
public T get() {
return zombie;
}
@Override
public void clear() {
zombie = null;
}
static void add(Object referent) {
FinalizerReference<?> reference = new FinalizerReference<Object>(referent, queue);
synchronized (FinalizerReference.class) {
reference.prev = null;
reference.next = head;
if (head != null) {
head.prev = reference;
}
head = reference;
}
}
public static void remove(FinalizerReference reference) {
synchronized (FinalizerReference.class) {
FinalizerReference next = reference.next;
FinalizerReference prev = reference.prev;
reference.next = null;
reference.prev = null;
if (prev != null) {
prev.next = next;
} else {
head = next;
}
if (next != null) {
next.prev = prev;
}
}
}
/**
* Returns once all currently-enqueued references have been finalized.
*/
public static void finalizeAllEnqueued() throws InterruptedException {
Sentinel sentinel = new Sentinel();
FinalizerReference<Object> reference = new FinalizerReference<Object>(null, queue);
reference.zombie = sentinel;
reference.enqueueInternal();
sentinel.awaitFinalization();
}
/**
* A marker object that we can immediately enqueue. When this object's
* finalize() method is called, we know all previously-enqueued finalizable
* references have been finalized.
*
* <p>Each instance of this class will be finalized twice as it is enqueued
* directly and by the garbage collector.
*/
private static class Sentinel {
boolean finalized = false;
@Override protected synchronized void finalize() throws Throwable {
finalized = true;
notifyAll();
}
synchronized void awaitFinalization() throws InterruptedException {
while (!finalized) {
wait();
}
}
}
}