1 package org.opentrafficsim.core.perception;
2
3 import java.util.Collections;
4 import java.util.Set;
5 import java.util.WeakHashMap;
6
7 import org.djunits.value.vdouble.scalar.Duration;
8 import org.djunits.value.vdouble.scalar.Time;
9
10 /**
11 * History manager with automatic garbage collection by the java garbage collector using weak references to the
12 * {@code Historical}s.
13 * <p>
14 * Copyright (c) 2013-2019 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
15 * BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
16 * <p>
17 * @version $Revision$, $LastChangedDate$, by $Author$, initial version 18 jan. 2018 <br>
18 * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
19 * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
20 * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
21 */
22 public abstract class HistoryManager
23 {
24
25 /** Set of all {@code Historical}s. */
26 // There's no WeakSet, but this is effectively the same. Iterating over this is safe, only alive objects are returned.
27 private final Set<HistoricalElement> historicals = Collections.newSetFromMap(new WeakHashMap<HistoricalElement, Boolean>());
28
29 /**
30 * Registers a historical.
31 * @param historical HistoricalElement; historical to register.
32 */
33 public void registerHistorical(final HistoricalElement historical)
34 {
35 if (historical != null)
36 {
37 this.historicals.add(historical);
38 }
39 }
40
41 /**
42 * Returns the historicals.
43 * @return the historicals
44 */
45 protected final Set<HistoricalElement> getHistoricals()
46 {
47 return this.historicals;
48 }
49
50 /**
51 * Returns the current simulation time. This is used by historicals to time-stamp state changes.
52 * @return Time; current simulation time.
53 */
54 abstract Time now();
55
56 /**
57 * Historical view for the history manager.
58 * <p>
59 * Copyright (c) 2013-2019 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved.
60 * <br>
61 * BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
62 * <p>
63 * @version $Revision$, $LastChangedDate$, by $Author$, initial version 1 feb. 2018 <br>
64 * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
65 * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
66 * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
67 */
68 public interface HistoricalElement
69 {
70 /**
71 * Removes events that are no longer needed to guarantee the history time. This is invoked by the history manager.
72 * @param history Duration; history time to keep
73 */
74 void cleanUpHistory(Duration history);
75 }
76
77 /**
78 * Method that clears the entire memory at simulation end.
79 */
80 protected final void endOfSimulation()
81 {
82 for (HistoricalElement historical : this.historicals)
83 {
84 historical.cleanUpHistory(Duration.ZERO);
85 }
86 this.historicals.clear();
87 }
88
89 }