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diff --git a/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/cache/WeakCachedMapProvider.java b/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/cache/WeakCachedMapProvider.java
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index 000000000..2aab35c7f
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+++ b/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/cache/WeakCachedMapProvider.java
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+/*******************************************************************************
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management
+ * in Industry THTH ry.
+ * 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:
+ *     VTT Technical Research Centre of Finland - initial API and implementation
+ *******************************************************************************/
+/*
+ *
+ * @author Toni Kalajainen
+ */
+package org.simantics.utils.datastructures.cache;
+
+import java.lang.ref.WeakReference;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * WeakCachedProvider provides values and stores the results in a cache.
+ * Cached values are held with weak references. Values are removed
+ * automatically as they are disposed.
+ *
+ * Keys are referenced with strong references.
+ *
+ * @param <K> key type
+ * @param <V> value type
+ */
+public class WeakCachedMapProvider<K, V> implements IMapProvider<K, V> {
+
+	private Map<K, WeakReference<V>> cache = 
+		new HashMap<K, WeakReference<V>>();
+	
+	private final IMapProvider<K, V> provider;
+	
+	/**
+	 * Constructs new weak cache.
+	 * 
+	 * @param provider provider of values 
+	 */
+	public WeakCachedMapProvider(IMapProvider<K, V> provider)
+	{
+		assert(provider!=null);
+		this.provider = provider;
+	}	
+	
+	@Override
+	public synchronized V get(K key) 
+	{
+		WeakReference<V> ref = cache.get(key);
+		if (ref!=null) {
+			V result = ref.get();
+			if (result!=null) return result;
+			cache.remove(ref);
+		}
+		
+		V value = provider.get(key);
+		assert(value!=null);
+		
+		ref = new WeakReference<V>(value);
+		cache.put(key, ref);
+		return value;		
+	}
+	
+	/**
+	 * Release all weak references
+	 */
+	public synchronized void clear()
+	{
+		cache.clear();
+	}	
+
+}