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package org.eclipse.cdt.dsf.concurrent;
/*******************************************************************************
* Copyright (c) 2008 Wind River 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
*
* Contributors:
* Wind River Systems - initial API and implementation
*******************************************************************************/
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
/**
* A general purpose cache, which caches the result of a single request.
* Sub classes need to implement {@link #retrieve(DataRequestMonitor)} to fetch
* data from the data source. Clients are responsible for calling
* {@link #disable()} and {@link #reset()} to manage the state of the cache in
* response to events from the data source.
* <p>
* This cache requires an executor to use. The executor is used to synchronize
* access to the cache state and data.
* </p>
* @since 2.2
*/
@ConfinedToDsfExecutor("fExecutor")
public abstract class RequestCache<V> extends AbstractCache<V> {
protected DataRequestMonitor<V> fRm;
public RequestCache(ImmediateInDsfExecutor executor) {
super(executor);
}
@Override
protected final void retrieve() {
// Make sure to cancel the previous rm. This may lead to the rm being
// canceled twice, but that's not harmful.
if (fRm != null) {
fRm.cancel();
}
fRm = new DataRequestMonitor<V>(getImmediateInDsfExecutor(), null) {
private IStatus fRawStatus = Status.OK_STATUS;
@Override
protected void handleCompleted() {
if (this == fRm) {
fRm = null;
IStatus status;
synchronized (this) {
status = fRawStatus;
}
set(getData(), status);
}
}
@Override
public synchronized void setStatus(IStatus status) {
fRawStatus = status;
};
@Override
public boolean isCanceled() {
return super.isCanceled() || RequestCache.this.isCanceled();
};
};
retrieve(fRm);
}
/**
* Sub-classes should override this method to retrieve the cache data
* from its source.
*
* @param rm Request monitor for completion of data retrieval.
*/
protected abstract void retrieve(DataRequestMonitor<V> rm);
@Override
protected synchronized void canceled() {
if (fRm != null) {
fRm.cancel();
}
}
@Override
protected void set(V data, IStatus status) {
if (fRm != null) {
fRm.cancel();
fRm = null;
}
super.set(data, status);
}
}
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