--- /dev/null
+/*******************************************************************************\r
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
+ * in Industry THTH ry.\r
+ * All rights reserved. This program and the accompanying materials\r
+ * are made available under the terms of the Eclipse Public License v1.0\r
+ * which accompanies this distribution, and is available at\r
+ * http://www.eclipse.org/legal/epl-v10.html\r
+ *\r
+ * Contributors:\r
+ * VTT Technical Research Centre of Finland - initial API and implementation\r
+ *******************************************************************************/\r
+package org.simantics.utils.datastructures.cache;\r
+\r
+import java.lang.ref.SoftReference;\r
+import java.util.ArrayList;\r
+import java.util.Collection;\r
+import java.util.Collections;\r
+import java.util.HashMap;\r
+import java.util.Map;\r
+import java.util.Timer;\r
+import java.util.concurrent.ScheduledFuture;\r
+import java.util.concurrent.TimeUnit;\r
+\r
+import org.simantics.utils.threads.ThreadUtils;\r
+\r
+/**\r
+ * A timed (Key, Value) cache which disposes the cached entry after the\r
+ * specified amount of time if it is not removed from the cache. The hold time\r
+ * is given to the {@link #put(Object, Object, long)} method, separately for\r
+ * each value.\r
+ * \r
+ * <p>\r
+ * The cached values are held as soft references, which makes them collectible\r
+ * under memory pressure, even before their hold time has ran out.\r
+ * \r
+ * @author Tuukka Lehtonen\r
+ * \r
+ * @param <K> key type, held by strong references\r
+ * @param <V> value type, held by soft references to allow collection of the\r
+ * cached elements when under memory pressure\r
+ */\r
+public class SoftTimedCache<K, V> implements ITimedCache<K, V> {\r
+\r
+ protected class Entry {\r
+ final K key;\r
+ final SoftReference<V> ref;\r
+ long holdTime;\r
+ TimeUnit unit;\r
+\r
+ ScheduledFuture<?> future;\r
+\r
+ Entry(K k, V v, long holdTime, TimeUnit unit) {\r
+ assert k != null;\r
+ assert v != null;\r
+\r
+ this.key = k;\r
+ this.ref = new SoftReference<V>(v);\r
+ this.holdTime = holdTime;\r
+ this.unit = unit;\r
+ }\r
+ }\r
+\r
+ private final Map<K, Entry> cache = Collections.synchronizedMap(new HashMap<K, Entry>());\r
+\r
+ @SuppressWarnings("unused")\r
+ private String name;\r
+\r
+ private Timer timer;\r
+\r
+ public SoftTimedCache() {\r
+ this("Cache Timer");\r
+ }\r
+\r
+ public SoftTimedCache(String name) {\r
+ this.name = name;\r
+ }\r
+\r
+ public int size() {\r
+ return cache.size();\r
+ }\r
+\r
+ @Override\r
+ protected void finalize() throws Throwable {\r
+ if (timer != null) {\r
+ timer.cancel();\r
+ }\r
+ clear();\r
+ super.finalize();\r
+ }\r
+\r
+ public synchronized void clear() {\r
+ Object[] entries;\r
+ synchronized (this) {\r
+ entries = cache.values().toArray();\r
+ cache.clear();\r
+ }\r
+ for (Object o : entries) {\r
+ @SuppressWarnings("unchecked")\r
+ Entry e = (Entry) o;\r
+ V v = e.ref.get();\r
+ e.ref.clear();\r
+ cleanup(e);\r
+ disposeValue(v);\r
+ }\r
+ }\r
+\r
+ @Override\r
+ public void put(final K k, V v, long holdTime, TimeUnit unit) {\r
+ Entry e = new Entry(k, v, holdTime, unit);\r
+ synchronized (this) {\r
+ // First dispose of a previous entry.\r
+ dispose(k);\r
+ // Then cache the new one.\r
+ cache.put(k, e);\r
+\r
+ if (unit != null && holdTime > 0) {\r
+ schedule(e);\r
+ }\r
+ }\r
+ }\r
+\r
+ @Override\r
+ public V release(K k) {\r
+ Entry e;\r
+ synchronized (this) {\r
+ e = cache.remove(k);\r
+ }\r
+ if (e == null)\r
+ return null;\r
+ return cleanup(e);\r
+ }\r
+\r
+ private V cleanup(Entry e) {\r
+ if (e.future != null) {\r
+ if (!e.future.isCancelled()) {\r
+ boolean ret = e.future.cancel(false);\r
+ if (ret == false)\r
+ // Already disposing of this cached entry, let it be.\r
+ return null;\r
+ }\r
+ }\r
+ return e.ref.get();\r
+ }\r
+\r
+ private void dispose(K k) {\r
+ Entry e;\r
+ synchronized (this) {\r
+ e = cache.remove(k);\r
+ }\r
+ if (e == null)\r
+ // Has been released.\r
+ return;\r
+\r
+ V v = e.ref.get();\r
+ if (v != null) {\r
+ if (e.future != null)\r
+ e.future.cancel(false);\r
+ e.ref.clear();\r
+ disposeValue(v);\r
+ }\r
+ }\r
+\r
+ void schedule(final Entry e) {\r
+ e.future = ThreadUtils.getNonBlockingWorkExecutor().schedule(new Runnable() {\r
+ @Override\r
+ public void run() {\r
+ // Disposal may block, must transfer to blocking work executor.\r
+ ThreadUtils.getBlockingWorkExecutor().execute(new Runnable() {\r
+ @Override\r
+ public void run() {\r
+ dispose(e.key);\r
+ }\r
+ });\r
+ }\r
+ }, e.holdTime, e.unit);\r
+ }\r
+\r
+\r
+ /**\r
+ * Override to customize disposal of values when their timer elapses.\r
+ * \r
+ * @param v the value to dispose of\r
+ */\r
+ protected void disposeValue(V v) {\r
+ // Do nothing by default.\r
+ }\r
+\r
+ public class CacheEntry {\r
+ private final Entry e;\r
+ private final V value;\r
+ public CacheEntry(Entry e) {\r
+ this.e = e;\r
+ this.value = e.ref.get();\r
+ }\r
+ public K getKey() {\r
+ return e.key;\r
+ }\r
+ public V getValue() {\r
+ return value;\r
+ }\r
+ public boolean disposeScheduled() {\r
+ return e.future != null;\r
+ }\r
+ public void schedule(long holdTime, TimeUnit unit) {\r
+ if (e.future == null) {\r
+ e.holdTime = holdTime;\r
+ e.unit = unit;\r
+ SoftTimedCache.this.schedule(e);\r
+ }\r
+ }\r
+ }\r
+\r
+ public Collection<CacheEntry> getEntries() {\r
+ ArrayList<CacheEntry> result = new ArrayList<CacheEntry>();\r
+ synchronized (this) {\r
+ for (Entry e : cache.values()) {\r
+ result.add(new CacheEntry(e));\r
+ }\r
+ }\r
+ return result;\r
+ }\r
+\r
+}\r
Code Review / simantics / platform.git / blobdiff