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1   /*
2    * Copyright (c) 2000, 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
16   * 2 along with this work; if not, write to the Free Software Foundation,
17   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18   *
19   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20   * or visit www.oracle.com if you need additional information or have any
21   * questions.
22   *
23   */
24  
25  package sun.jvm.hotspot.runtime;
26  
27  import java.util.*;
28  import sun.jvm.hotspot.debugger.*;
29  import sun.jvm.hotspot.types.*;
30  
31  public class JNIHandles {
32    private static AddressField      globalHandlesField;
33    private static AddressField      weakGlobalHandlesField;
34    private static OopField          deletedHandleField;
35  
36    static {
37      VM.registerVMInitializedObserver(new Observer() {
38          public void update(Observable o, Object data) {
39            initialize(VM.getVM().getTypeDataBase());
40          }
41        });
42    }
43  
44    private static synchronized void initialize(TypeDataBase db) {
45      Type type = db.lookupType("JNIHandles");
46  
47      globalHandlesField = type.getAddressField("_global_handles");
48      weakGlobalHandlesField = type.getAddressField("_weak_global_handles");
49      deletedHandleField = type.getOopField("_deleted_handle");
50  
51    }
52  
53    public JNIHandles() {
54    }
55  
56    public JNIHandleBlock globalHandles() {
57      Address handleAddr  = globalHandlesField.getValue();
58      if (handleAddr == null) {
59        return null;
60      }
61      return new JNIHandleBlock(handleAddr);
62    }
63  
64    public JNIHandleBlock weakGlobalHandles() {
65      Address handleAddr  = weakGlobalHandlesField.getValue();
66      if (handleAddr == null) {
67        return null;
68      }
69      return new JNIHandleBlock(handleAddr);
70    }
71  
72    public OopHandle deletedHandle() {
73      return deletedHandleField.getValue();
74    }
75  
76    public boolean isDeletedHandle(OopHandle handle) {
77      return (handle != null && handle.equals(deletedHandle()));
78    }
79  
80  }