/*******************************************************************************
* Copyright (c) 2006, 2015 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
* Matthew Hall - bugs 208332, 265727
* Stefan Xenos <sxenos@gmail.com> - Bug 335792
*******************************************************************************/
package org.eclipse.core.databinding.observable.set;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;
import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.IObservable;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.internal.databinding.observable.IStalenessConsumer;
import org.eclipse.core.internal.databinding.observable.StalenessTracker;
/**
* Represents a set consisting of the union of elements from one or more other
* sets. This object does not need to be explicitly disposed. If nobody is
* listening to the UnionSet, the set will remove its listeners.
*
* <p>
* This class is thread safe. All state accessing methods must be invoked from
* the {@link Realm#isCurrent() current realm}. Methods for adding and removing
* listeners may be invoked from any thread.
* </p>
*
* @param <E>
* type of the elements in the union set
* @since 1.0
*/
public final class UnionSet<E> extends ObservableSet<E> {
/**
* child sets
*/
private Set<IObservableSet<? extends E>> childSets;
private boolean stale = false;
/**
* Map of elements onto Integer reference counts. This map is constructed
* when the first listener is added to the union set. Null if nobody is
* listening to the UnionSet.
*/
private HashMap<E, Integer> refCounts = null;
private StalenessTracker stalenessTracker;
/**
* @param childSets
*/
public UnionSet(IObservableSet<? extends E>[] childSets) {
this(new HashSet<IObservableSet<? extends E>>(Arrays.asList(childSets)));
}
/**
* @param childSets
* @since 1.6
*/
public UnionSet(Set<IObservableSet<? extends E>> childSets) {
this(childSets, childSets.iterator().next().getElementType());
}
/**
* @param childSets
* @param elementType
* @since 1.2
*/
public UnionSet(IObservableSet<? extends E>[] childSets, Object elementType) {
this(new HashSet<IObservableSet<? extends E>>(Arrays.asList(childSets)), elementType);
}
/**
* @param childSets
* @param elementType
* @since 1.6
*/
public UnionSet(Set<IObservableSet<? extends E>> childSets, Object elementType) {
super(childSets.iterator().next().getRealm(), null, elementType);
this.childSets = childSets;
this.stalenessTracker = new StalenessTracker(childSets.toArray(new IObservableSet[0]), stalenessConsumer);
}
private ISetChangeListener<E> childSetChangeListener = new ISetChangeListener<E>() {
@Override
public void handleSetChange(SetChangeEvent<? extends E> event) {
processAddsAndRemoves(event.diff.getAdditions(), event.diff.getRemovals());
}
};
private IStalenessConsumer stalenessConsumer = new IStalenessConsumer() {
@Override
public void setStale(boolean stale) {
boolean oldStale = UnionSet.this.stale;
UnionSet.this.stale = stale;
if (stale && !oldStale) {
fireStale();
}
}
};
@Override
public boolean isStale() {
getterCalled();
if (refCounts != null) {
return stale;
}
for (IObservableSet<? extends E> childSet : childSets) {
if (childSet.isStale()) {
return true;
}
}
return false;
}
private void processAddsAndRemoves(Set<? extends E> adds, Set<? extends E> removes) {
Set<E> addsToFire = new HashSet<>();
Set<E> removesToFire = new HashSet<>();
for (E added : adds) {
Integer refCount = refCounts.get(added);
if (refCount == null) {
refCounts.put(added, Integer.valueOf(1));
addsToFire.add(added);
} else {
int refs = refCount.intValue();
refCount = Integer.valueOf(refs + 1);
refCounts.put(added, refCount);
}
}
for (E removed : removes) {
Integer refCount = refCounts.get(removed);
if (refCount != null) {
int refs = refCount.intValue();
if (refs <= 1) {
removesToFire.add(removed);
refCounts.remove(removed);
} else {
refCount = Integer.valueOf(refCount.intValue() - 1);
refCounts.put(removed, refCount);
}
}
}
// just in case the removes overlapped with the adds
addsToFire.removeAll(removesToFire);
if (addsToFire.size() > 0 || removesToFire.size() > 0) {
fireSetChange(Diffs.createSetDiff(addsToFire, removesToFire));
}
}
@Override
protected void firstListenerAdded() {
super.firstListenerAdded();
refCounts = new HashMap<>();
for (IObservableSet<? extends E> childSet : childSets) {
childSet.addSetChangeListener(childSetChangeListener);
incrementRefCounts(childSet);
}
stalenessTracker = new StalenessTracker(
childSets.toArray(new IObservable[0]), stalenessConsumer);
setWrappedSet(refCounts.keySet());
}
@Override
protected void lastListenerRemoved() {
super.lastListenerRemoved();
for (IObservableSet<? extends E> childSet : childSets) {
childSet.removeSetChangeListener(childSetChangeListener);
stalenessTracker.removeObservable(childSet);
}
refCounts = null;
stalenessTracker = null;
setWrappedSet(null);
}
private ArrayList<E> incrementRefCounts(Collection<? extends E> added) {
ArrayList<E> adds = new ArrayList<>();
for (E next : added) {
Integer refCount = refCounts.get(next);
if (refCount == null) {
adds.add(next);
refCount = Integer.valueOf(1);
refCounts.put(next, refCount);
} else {
refCount = Integer.valueOf(refCount.intValue() + 1);
refCounts.put(next, refCount);
}
}
return adds;
}
@Override
protected void getterCalled() {
super.getterCalled();
if (refCounts == null) {
// no listeners, recompute
setWrappedSet(computeElements());
}
}
private Set<E> computeElements() {
// If there is no cached value, compute the union from scratch
if (refCounts == null) {
Set<E> result = new HashSet<>();
for (IObservableSet<? extends E> childSet : childSets) {
result.addAll(childSet);
}
return result;
}
// Else there is a cached value. Return it.
return refCounts.keySet();
}
}