GeneralTaskRunnable.java revision cc7c18212481f5e9ee508afe2ffcaecb6b9330f5
/**
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2007 Sun Microsystems Inc. All Rights Reserved
*
* The contents of this file are subject to the terms
* of the Common Development and Distribution License
* (the License). You may not use this file except in
* compliance with the License.
*
* You can obtain a copy of the License at
* See the License for the specific language governing
* permission and limitations under the License.
*
* When distributing Covered Code, include this CDDL
* Header Notice in each file and include the License file
* at opensso/legal/CDDLv1.0.txt.
* If applicable, add the following below the CDDL Header,
* with the fields enclosed by brackets [] replaced by
* your own identifying information:
* "Portions Copyrighted [year] [name of copyright owner]"
*
* $Id: GeneralTaskRunnable.java,v 1.4 2008/06/25 05:52:51 qcheng Exp $
*
*/
/**
* An abstract class which works as a base class of scheduleable unit with the
* implementations of some functions of TaskRunnable interface.
*
*/
public abstract class GeneralTaskRunnable implements TaskRunnable {
protected volatile TaskRunnable nextTask;
protected volatile TaskRunnable previousTask;
protected volatile HeadTaskRunnable headTask;
/**
* Sets the head task for this linkable TaskRunnable
*
* The head task of this TaskRunnable will be set. HeadTask works as a lock
* when the elements of the linked task is going to be changed.
*
* @param headTask The HeadTaskRunnable
*/
}
/**
* Returns the head task of this linkable TaskRunnable.
*
* @return The head task of this linkable TaskRunnable
*/
public HeadTaskRunnable getHeadTask() {
// no need to synchronize for single operation
return headTask;
}
/**
* Returns the TaskRunnable previous to this TaskRunnable in the
* linked-list.
*
* The correct HeadTaskRunnable must be locked before calling this function.
*
* @return previous TaskRunnable object or null if it is not set
*/
public TaskRunnable previous() {
return previousTask;
}
/**
* Returns the TaskRunnable next to this TaskRunnable in the linked-list.
*
* The correct HeadTaskRunnable must be locked before calling this function.
*
* @return next TaskRunnable object or null if it is not set
*/
public TaskRunnable next() {
return nextTask;
}
/**
* Sets the TaskRunnable previous to this TaskRunnable in the linked-list.
*
* The correct HeadTaskRunnable must be locked before calling this function.
*
* @param task The previous TaskRunnable
*/
previousTask = task;
}
/**
* Sets the TaskRunnable next to this TaskRunnable in the linked-list.
*
* The correct HeadTaskRunnable must be locked before calling this function.
*
* @param task The next TaskRunnable
*/
}
/**
* Returns the scheduled time of this TaskRunnable.
*
* @return A long value indicate the time this TaskRunnable is scheduled,
* or -1 if it is not scheduled yet
*/
public long scheduledExecutionTime() {
// synchronize for more than 1 operation
synchronized (this) {
return headTask.scheduledExecutionTime();
}
}
return -1;
}
/**
* Returns true if this TaskRunnable is scheduled to run; otherwise returns false.
*
* @return A boolean value indicating whether or not this TaskRunnable is scheduled.
*/
public boolean isScheduled() {
return scheduledExecutionTime() != -1;
}
/**
* Implements for TaskRunnable interface.
*
* Cancels the task from the associated Timer.
*/
public void cancel() {
do {
if (oldHeadTask != null) {
if (oldHeadTask.acquireValidLock()) {
try {
if (oldHeadTask == headTask) {
if (!oldHeadTask.isTimedOut()) {
} else {
}
}
break;
}
} finally {
}
}
}
} while (oldHeadTask != headTask);
}
}