org.eclipse.jface.viewers.deferred.ChangeQueue Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2004, 2010 IBM Corporation 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:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jface.viewers.deferred;
import java.io.Serializable;
import java.util.Iterator;
import java.util.LinkedList;
/**
* Holds a queue of additions, removals, updates, and SET calls for a
* BackgroundContentProvider
*/
final class ChangeQueue implements Serializable {
/**
* Represents the addition of an item
* @since 1.0
*/
public static final int ADD = 0;
/**
* Represents the removal of an item
* @since 1.0
*/
public static final int REMOVE = 1;
/**
* Represents a reset of all the items
* @since 1.0
*/
public static final int SET = 2;
/**
* Represents an update of an item
* @since 1.0
*/
public static final int UPDATE = 3;
/**
*
* @since 1.0
*/
public static final class Change {
private int type;
private Object[] elements;
/**
* Create a change of the specified type that affects the given elements.
*
* @param type one of ADD, REMOVE, SET, or UPDATE.
* @param elements the elements affected by the change.
*
* @since 1.0
*/
public Change(int type, Object[] elements) {
this.type = type;
this.elements = elements;
}
/**
* Get the type of change.
* @return one of ADD, REMOVE, SET, or UPDATE.
*
* @since 1.0
*/
public int getType() {
return type;
}
/**
* Return the elements associated with the change.
* @return the elements affected by the change.
*
* @since 1.0
*/
public Object[] getElements() {
return elements;
}
}
private LinkedList queue = new LinkedList();
/**
* Create a change of the given type and elements and enqueue it.
*
* @param type the type of change to be created
* @param elements the elements affected by the change
*/
public synchronized void enqueue(int type, Object[] elements) {
enqueue(new Change(type, elements));
}
/**
* Add the specified change to the queue
* @param toQueue the change to be added
*/
public synchronized void enqueue(Change toQueue) {
// A SET event makes all previous adds, removes, and sets redundant... so remove
// them from the queue
if (toQueue.type == SET) {
LinkedList newQueue = new LinkedList();
for (Iterator iter = queue.iterator(); iter.hasNext();) {
Change next = (Change) iter.next();
if (next.getType() == ADD || next.getType() == REMOVE || next.getType() == SET) {
continue;
}
newQueue.add(next);
}
queue = newQueue;
}
queue.add(toQueue);
}
/**
* Remove the first change from the queue.
* @return the first change
*/
public synchronized Change dequeue() {
Change result = (Change)queue.removeFirst();
return result;
}
/**
* Return whether the queue is empty
* @return true if empty, false otherwise
*/
public synchronized boolean isEmpty() {
return queue.isEmpty();
}
}