| /******************************************************************************* |
| * Copyright (c) 2004, 2005 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.util.Iterator; |
| import java.util.LinkedList; |
| |
| /** |
| * Holds a queue of additions, removals, updates, and SET calls for a |
| * BackgroundContentProvider |
| */ |
| final class ChangeQueue { |
| /** |
| * Represents the addition of an item |
| * @since 3.1 |
| */ |
| public static final int ADD = 0; |
| /** |
| * Represents the removal of an item |
| * @since 3.1 |
| */ |
| public static final int REMOVE = 1; |
| /** |
| * Represents a reset of all the items |
| * @since 3.1 |
| */ |
| public static final int SET = 2; |
| /** |
| * Represents an update of an item |
| * @since 3.1 |
| */ |
| public static final int UPDATE = 3; |
| |
| /** |
| * |
| * @since 3.1 |
| */ |
| 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 <code>ADD</code>, <code>REMOVE</code>, <code>SET</code>, or <code>UPDATE</code>. |
| * @param elements the elements affected by the change. |
| * |
| * @since 3.1 |
| */ |
| public Change(int type, Object[] elements) { |
| this.type = type; |
| this.elements = elements; |
| } |
| |
| /** |
| * Get the type of change. |
| * @return one of <code>ADD</code>, <code>REMOVE</code>, <code>SET</code>, or <code>UPDATE</code>. |
| * |
| * @since 3.1 |
| */ |
| public int getType() { |
| return type; |
| } |
| |
| /** |
| * Return the elements associated with the change. |
| * @return the elements affected by the change. |
| * |
| * @since 3.1 |
| */ |
| public Object[] getElements() { |
| return elements; |
| } |
| } |
| |
| private LinkedList queue = new LinkedList(); |
| private int workload = 0; |
| |
| /** |
| * 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) { |
| workload = 0; |
| 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); |
| workload += next.elements.length; |
| } |
| queue = newQueue; |
| } |
| |
| queue.add(toQueue); |
| workload += toQueue.elements.length; |
| } |
| |
| /** |
| * Remove the first change from the queue. |
| * @return the first change |
| */ |
| public synchronized Change dequeue() { |
| Change result = (Change)queue.removeFirst(); |
| |
| workload -= result.elements.length; |
| return result; |
| } |
| |
| /** |
| * Return whether the queue is empty |
| * @return <code>true</code> if empty, <code>false</code> otherwise |
| */ |
| public synchronized boolean isEmpty() { |
| return queue.isEmpty(); |
| } |
| } |