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1   /*
2    * Copyright (c) 2002, 2006, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.
8    *
9    * This code is distributed in the hope that it will be useful, but WITHOUT
10   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12   * version 2 for more details (a copy is included in the LICENSE file that
13   * accompanied this code).
14   *
15   * You should have received a copy of the GNU General Public License version
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17   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24  
25  package sun.jvm.hotspot.utilities;
26  
27  import java.util.*;
28  import sun.jvm.hotspot.oops.*;
29  
30  /** ReversePtrs hashtable. */
31  
32  public class ReversePtrs  {
33    private HashMap rp;
34  
35    public ReversePtrs() {
36      rp = new HashMap();
37    }
38  
39    public void put(LivenessPathElement from, Oop to) {
40      if (to == null) return;
41      ArrayList al = (ArrayList) rp.get((Object) to);
42      if (al == null) al = new ArrayList();
43      // Inserting at the beginning is a hack to change the reported
44      // paths from LivenessAnalysis to look more like they used to;
45      // otherwise paths through the Finalizer queue to popular objects
46      // seem to be preferred
47      al.add(0, (Object) from);
48      rp.put((Object) to, (Object) al);
49    }
50  
51    /** Returns an ArrayList of the incoming references to this Oop if
52        it is alive, and null if it is dead according to the
53        ReversePtrsAnalysis. Currently not all roots are scanned so this
54        result is frequently inaccurate for JVM-internal objects, but is
55        usually correct for Java-level objects. */
56    public ArrayList/*<LivenessPathElement>*/ get(Oop obj) {
57      return (ArrayList) rp.get((Object)obj);
58    }
59  }