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/*
* Copyright (C) 2014 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 com.android.camera.async;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* Enables handling the shut-down of components in a structured way.
* <p>
* Lifetimes are nestable sets of {@link SafeCloseable}s useful for guaranteeing
* that resources, such as threads, files, hardware devices, etc., are properly
* closed when necessary.
* <p>
* Child lifetimes are closed when their parent is closed, or when they are
* closed directly, whichever comes first. Objects added to a particular
* lifetime will only ever be closed once by that lifetime.
* </p>
*/
public class Lifetime implements SafeCloseable {
/**
* The parent, or null if there is no parent lifetime.
*/
private final Lifetime mParent;
private final Object mLock;
private final Set<SafeCloseable> mCloseables;
private boolean mClosed;
public Lifetime() {
mLock = new Object();
mCloseables = new HashSet<SafeCloseable>();
mParent = null;
mClosed = false;
}
public Lifetime(Lifetime parent) {
mLock = new Object();
mCloseables = new HashSet<SafeCloseable>();
mParent = parent;
mClosed = false;
parent.mCloseables.add(this);
}
/**
* Adds the given object to this lifetime and returns it.
*/
public <T extends SafeCloseable> T add(T closeable) {
boolean needToClose = false;
synchronized (mLock) {
if (mClosed) {
needToClose = true;
} else {
mCloseables.add(closeable);
}
}
if (needToClose) {
closeable.close();
}
return closeable;
}
@Override
public void close() {
List<SafeCloseable> toClose = new ArrayList<SafeCloseable>();
synchronized (mLock) {
if (mClosed) {
return;
}
mClosed = true;
// Remove from parent to avoid leaking memory if a long-lasting
// lifetime has lots of shorter-lived lifetimes created and
// destroyed repeatedly.
if (mParent != null) {
mParent.mCloseables.remove(this);
}
toClose.addAll(mCloseables);
mCloseables.clear();
}
// Invoke close() outside the critical section
for (SafeCloseable closeable : toClose) {
closeable.close();
}
}
}
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