samer@0: /*
samer@0:  *	Copyright (c) 2000, Samer Abdallah, King's College London.
samer@0:  *	All rights reserved.
samer@0:  *
samer@0:  *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
samer@0:  *	without even the implied warranty of MERCHANTABILITY or 
samer@0:  *	FITNESS FOR A PARTICULAR PURPOSE.
samer@0:  */
samer@0: 
samer@0: package samer.tools;
samer@0: 
samer@0: /**
samer@0:   *		This is a task that consists of a list of
samer@0:   *		sub tasks. The task is no more than the sum
samer@0:   *		of its subtasks -- ie there can be no extra
samer@0:   *		processing other than that done by the tasks
samer@0:   *		in the list. This is why the Task methods
samer@0:   *		are decalared <code>final</code>.
samer@0:   */
samer@0: 
samer@0: public class CompoundTask implements Task
samer@0: {
samer@0: 	private TaskLink head=null, tail=null;
samer@0: 
samer@0: 	public CompoundTask() {}
samer@0: 	public CompoundTask(Task t) { addTask(t); }
samer@0: 
samer@0: 	public String toString() { return "CompoundTask"; }
samer@0: 	
samer@0: 	// task list implementation
samer@0: 
samer@0: 	public void addTask(Task t)
samer@0: 	{
samer@0: 		if (head==null) {
samer@0: 			head=new TaskLink(t,null);
samer@0: 			tail=head;
samer@0: 		} else {
samer@0: 			tail.next=new TaskLink(t,null);
samer@0: 			tail=tail.next;
samer@0: 		}
samer@0: 	}
samer@0: 
samer@0: 	public void addTaskAfter(Task t, Task b)
samer@0: 	{
samer@0: 		if (head==null) addTask(t);
samer@0: 		else if (b==null) head=new TaskLink(t,head);
samer@0: 		else {
samer@0: 			TaskLink q=head;
samer@0: 			while (q!=null && q.task!=b) q=q.next;
samer@0: 			if (q!=null) q.next=new TaskLink(t,q.next);
samer@0: 			else addTask(t);
samer@0: 		}
samer@0: 	}
samer@0: 
samer@0: 	public void removeTask(Task t)
samer@0: 	{
samer@0: 		TaskLink prev=null;
samer@0: 
samer@0: 		for (TaskLink l=head; l!=null; prev=l, l=l.next) {
samer@0: 			if (l.task==t) {
samer@0: 				if (prev!=null) prev.next=l.next;
samer@0: 				else head=l.next;
samer@0: 				if (tail==l) tail=prev;
samer@0: 			}
samer@0: 		}
samer@0: 	}
samer@0: 
samer@0: 	public Iterator iterator() { return new Iterator(); }
samer@0: 
samer@0: 	// Task implementation
samer@0: 
samer@0: 	public final void starting() {
samer@0: 		for (TaskLink l=head; l!=null; l=l.next) l.task.starting();
samer@0: 	}
samer@0: 	public final void stopping() {
samer@0: 		for (TaskLink l=head; l!=null; l=l.next) l.task.stopping();
samer@0: 	}
samer@0: 	public final void run() throws Exception {
samer@0: 		for (TaskLink l=head; l!=null; l=l.next) l.task.run();
samer@0: 	}
samer@0: 	public void dispose() {
samer@0: 		for (TaskLink l=head; l!=null; l=l.next) l.task.dispose();
samer@0: 	}
samer@0: 
samer@0: 	// using a linked list for speed
samer@0: 	private static class TaskLink {
samer@0: 		Task		task;
samer@0: 		TaskLink next;
samer@0: 
samer@0: 		TaskLink(Task t, TaskLink n) { task=t; next=n; }
samer@0: 	}
samer@0: 
samer@0: 	// list iterator
samer@0: 	public class Iterator implements java.util.Iterator {
samer@0: 		TaskLink	l=head;
samer@0: 		public final boolean more() { return l!=null; }
samer@0: 		public final boolean hasNext() { return l!=null; }
samer@0: 		public final Task		next() { Task t=l.task; l=l.next; return t; }
samer@0: 		public final void    remove() { l.task=l.next.task; l.next=l.next.next; }
samer@0: 	}
samer@0: }