1 files changed, 47 insertions, 0 deletions
diff --git a/bundles/org.eclipse.equinox.p2.core/src/org/eclipse/equinox/p2/core/WeakPool.java b/bundles/org.eclipse.equinox.p2.core/src/org/eclipse/equinox/p2/core/WeakPool.java
new file mode 100644
index 000000000..3f389fc75
--- /dev/null
+++ b/bundles/org.eclipse.equinox.p2.core/src/org/eclipse/equinox/p2/core/WeakPool.java
@@ -0,0 +1,47 @@
+/*******************************************************************************
+ * Copyright (c) 2011 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.equinox.p2.core;
+
+import java.lang.ref.WeakReference;
+import java.util.Map;
+import java.util.WeakHashMap;
+
+/**
+ * An object pool backed by weak references.  Objects stored in this pool
+ * will be garbage collected once all strong references to the objects are broken.
+ * <p>
+ * Since {@link WeakReference} are not particularly light-weight, a client could use a {@link StrongPool}
+ * if the pool will be short lived and explicitly nulled by the client.
+ * </p>
+ * @since 2.1
+ */
+public class WeakPool<T> implements IPool<T> {
+	private Map<T, WeakReference<T>> pool = new WeakHashMap<T, WeakReference<T>>();
+
+	/* (non-Javadoc)
+	 * @see org.eclipse.equinox.p2.core.IPool#add(T)
+	 */
+	public T add(T newObject) {
+		if (newObject == null) {
+			return null;
+		}
+
+		WeakReference<T> weakReference = pool.get(newObject);
+		if (weakReference != null) {
+			T reference = weakReference.get();
+			if (reference != null) {
+				return reference;
+			}
+		}
+		pool.put(newObject, new WeakReference<T>(newObject));
+		return newObject;
+	}
+}