PropertyListenerList.java

/*******************************************************************************
 * Copyright (c) 2004, 2006 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.ui.internal.preferences;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * @since 3.1
 */
public final class PropertyListenerList {
    private Map listeners;
    private List globalListeners;
    private static String[] singlePropertyDelta;
    private static Object mutex = new Object();
    
    public PropertyListenerList() {
    }
    
    public void firePropertyChange(String prefId) {        
        String[] delta;
        
        // Optimization: as long as we're not being called recursively,
        // we can reuse the same delta object to avoid repeated memory
        // allocation.
        synchronized(mutex) {        
	        if (singlePropertyDelta != null) {
	            delta = singlePropertyDelta;
	            singlePropertyDelta = null;                
	        } else {
	            delta = new String[] {prefId};
	        }
        }
        
        delta[0] = prefId;
        
        firePropertyChange(delta);
        
        // Optimization: allow this same delta object to be reused at a later
        // time
        if (singlePropertyDelta == null) {
	        synchronized(mutex) {
	            singlePropertyDelta = delta;
	        }
        }
    }
    
    public void firePropertyChange(String[] propertyIds) {
        if (globalListeners != null) {
            for (Iterator iter = globalListeners.iterator(); iter.hasNext();) {
                IPropertyMapListener next = (IPropertyMapListener) iter.next();
                
                next.propertyChanged(propertyIds);
            }
        }
        
        if (listeners != null) {
            
            // To avoid temporary memory allocation, we try to simply move the
            // result pointer around if possible. We only allocate a HashSet
            // to compute which listeners we care about
            Collection result = Collections.EMPTY_SET;
            HashSet union = null;
            
            for (int i = 0; i < propertyIds.length; i++) {
                String property = propertyIds[i];
                
    	        List existingListeners = (List)listeners.get(property);
    	        
    	        if (existingListeners != null) {
    	            if (result == Collections.EMPTY_SET) {
    	                result = existingListeners;
    	            } else { 
    	                if (union == null) {
    	                    union = new HashSet();
    	                    union.addAll(result);
    	                    result = union;
    	                }
    	                
    	                union.addAll(existingListeners);
    	            }    	            
    	        }
            }
            
            for (Iterator iter = result.iterator(); iter.hasNext();) {
                IPropertyMapListener next = (IPropertyMapListener) iter.next();
                
                next.propertyChanged(propertyIds);
            }
        }
    }

    public void add(IPropertyMapListener newListener) {
        if (globalListeners == null) {
            globalListeners = new ArrayList();
        }
        
        globalListeners.add(newListener);
        newListener.listenerAttached();
    }
    
    /**
     * Adds a listener which will be notified when the given property changes
     * 
     * @param propertyId
     * @param newListener
     * @since 3.1
     */
    private void addInternal(String propertyId, IPropertyMapListener newListener) {
        if (listeners == null) {
            listeners = new HashMap();
        }
        
        List listenerList = (List)listeners.get(propertyId);
        
        if (listenerList == null) {
            listenerList = new ArrayList(1);
            listeners.put(propertyId, listenerList);
        }
        
        if (!listenerList.contains(newListener)) {
            listenerList.add(newListener);
        }
    }
    
    public void add(String[] propertyIds, IPropertyMapListener newListener) {        
        for (int i = 0; i < propertyIds.length; i++) {
            String id = propertyIds[i];
            
            addInternal(id, newListener);
        }
        newListener.listenerAttached();
    }
    
    public void remove(String propertyId, IPropertyMapListener toRemove) {
        if (listeners == null) {
            return;
        }
        List listenerList = (List)listeners.get(propertyId);
        
        if (listenerList != null) {
            listenerList.remove(toRemove);
            
            if (listenerList.isEmpty()) {
                listeners.remove(propertyId);
                
                if (listeners.isEmpty()) {
                    listeners = null;
                }
            }
        }        
    }
    
    public void removeAll() {
        globalListeners = null;
        listeners = null;
    }
    
    public void remove(IPropertyMapListener toRemove) {
        if (globalListeners != null) {
            globalListeners.remove(toRemove);
            if (globalListeners.isEmpty()) {
                globalListeners = null;
            }
        }
        
        if (listeners != null) {
            for (Iterator iter = listeners.keySet().iterator(); iter.hasNext();) {
                String key = (String) iter.next();
                
                remove(key, toRemove);
            }
        }
    }
    
    public boolean isEmpty() {
        return globalListeners == null && listeners == null;
    }
}