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//
// Copyright 2001 iPlanet/ Sun Microsystems, Inc. All Rights Reserved.
//
// Author : darpan
// Module : Utils
//
package com.sun.enterprise.util.scheduler;
import com.sun.enterprise.util.collection.DListNode;
/**
* Maintains a list of elements in an increasing order. Each element is a
* TaskData object encapsulating an absolute execute time and the servicable
* task object.
* <BR> <I>$Source: /cvs/glassfish/appserv-commons/src/java/com/sun/enterprise/util/scheduler/TimedTaskList.java,v $</I>
* @author $Author: tcfujii $
* @version 1.0 $Revision: 1.4 $ $Date: 2007/05/05 05:32:17 $
* @see PeriodicallyServicable
*/
public class TimedTaskList
{
/** First dummy node. */
private DListNode first;
/** Last dummy node. */
private DListNode last;
/** Maintains the current size of the list. */
private int size = 0;
/**
* Constructor for TimedTaskList, created a new DList object.
*/
protected TimedTaskList()
{
first = new DListNode(null);
last = new DListNode(null);
first.next = last;
last.prev = first;
first.prev = last.next = null;
}
/**
* Return the size of the task list.
* @return 0 if empty, otherwise a number indicating the number of elements.
*/
protected int size()
{
return size;
}
/**
* Remove first task from the ordered list, and return it.
* @return first task on the queue.
*/
protected TaskData getFirstTask()
{
DListNode node = first;
node = node.next;
if(null!=node.next) // not the end
{
node.delink();
--size;
return (TaskData) node.object;
}
return null;
}
/**
* Add a new servicable task into the task list (ordered in increasing order).
* @param taskObj servicable object to add.
* @param startingTime wait for how long to start considering this task.
* @param currentTime current time when executing other tasks.
* @return boolean true on success, false otherwise.
*/
protected boolean addTask(PeriodicallyServicable taskObj, int startingTime, long currentTime)
{
TaskData task = new TaskData();
task.obj = taskObj;
// decrement frequency time as it will be added on insertTask( ) anyway
task.abs_execute_time = currentTime + startingTime - taskObj.getFrequency();
return insertTask(task);
}
/**
* Insert task back into the task list (ordered in increasing order).
* @param task object to execute in an order.
* @return boolean true on success, false otherwise.
*/
protected boolean insertTask(TaskData task)
{
task.abs_execute_time += ((PeriodicallyServicable)task.obj).getFrequency();
DListNode addingNode = new DListNode(task);
DListNode node = first;
++size;
for(int i=0; i<size-1; i++)
{
node = node.next;
long nodeTime = ((TaskData)node.object).abs_execute_time;
if(nodeTime > task.abs_execute_time)
{
node.insertBefore(addingNode);
return true;
}
}
node.insertAfter(addingNode);
return true;
}
/**
* Removes the Servicable object from the task list permanently.
* @param obj servicable object to remove.
* @return boolean true on success, false otherwise.
*/
protected boolean removeTask(PeriodicallyServicable obj)
{
DListNode node = first;
for(int i=0; i<size; i++)
{
node = node.next;
PeriodicallyServicable nodeObj = ((TaskData)node.object).obj;
if(nodeObj.equals(obj))
{
node.delink();
--size;
return true;
}
}
return false;
}
/**
* Prints information about the list and its contents.
* @return String
*/
public String toString()
{
StringBuffer sb = new StringBuffer(100);
sb.append(" [TimedTaskList: ");
sb.append( size + " elements: ");
DListNode node = first;
while(null!=node.next && null!=node.next.object)
{
node = node.next;
sb.append((int) ( ((TaskData)node.object).abs_execute_time / 1000) );
sb.append(",");
}
sb.append("] ");
return sb.toString();
}
}