org.opendaylight.yangtools.concepts.AbstractRegistration Maven / Gradle / Ivy
/*
* Copyright (c) 2013 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.yangtools.concepts;
import com.google.common.base.MoreObjects;
import com.google.common.base.MoreObjects.ToStringHelper;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
/**
* Utility registration handle. It is a convenience for register-style method which can return an AutoCloseable realized
* by a subclass of this class. Invoking the close() method triggers unregistration of the state the method installed.
*/
public abstract class AbstractRegistration implements Registration {
private static final VarHandle CLOSED;
// All access needs to go through this handle
@SuppressWarnings("unused")
private volatile byte closed;
static {
try {
CLOSED = MethodHandles.lookup().findVarHandle(AbstractRegistration.class, "closed", byte.class);
} catch (ReflectiveOperationException e) {
throw new ExceptionInInitializerError(e);
}
}
/**
* Remove the state referenced by this registration. This method is guaranteed to be called at most once.
* Referenced state must be retained until this method is invoked.
*/
protected abstract void removeRegistration();
/**
* Query the state of this registration. Returns true if it was closed. Equivalent of {@code !notClosed()}.
*
* @return true if the registration was closed, false otherwise.
*/
public final boolean isClosed() {
return (byte) CLOSED.getAcquire(this) != 0;
}
/**
* Query the state of this registration. Returns false if it was closed. Equivalent of {@code !isClosed()}.
*
* @return false if the registration was closed, true otherwise.
*/
public final boolean notClosed() {
return (byte) CLOSED.getAcquire(this) == 0;
}
@Override
public final void close() {
// We want full setVolatile() memory semantics here, as all state before calling this method
// needs to be visible
if (CLOSED.compareAndSet(this, (byte) 0, (byte) 1)) {
removeRegistration();
}
}
@Override
public final String toString() {
return addToStringAttributes(MoreObjects.toStringHelper(this).omitNullValues()).toString();
}
protected ToStringHelper addToStringAttributes(final ToStringHelper toStringHelper) {
return toStringHelper.add("closed", isClosed());
}
}