java_lang_Class.java revision 11748:2e21095f80c6 
1/*
2 * Copyright (c) 2011, 2016, 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
25package sun.jvm.hotspot.oops;
26
27import java.util.*;
28
29import sun.jvm.hotspot.debugger.*;
30import sun.jvm.hotspot.memory.*;
31import sun.jvm.hotspot.runtime.*;
32import sun.jvm.hotspot.types.AddressField;
33import sun.jvm.hotspot.types.Type;
34import sun.jvm.hotspot.types.TypeDataBase;
35import sun.jvm.hotspot.utilities.*;
36
37/** A utility class encapsulating useful oop operations */
38
39// initialize fields for java.lang.Class
40public class java_lang_Class {
41
42  // java.lang.Class fields
43  static int klassOffset;
44  static IntField oopSizeField;
45
46  static {
47    VM.registerVMInitializedObserver(new Observer() {
48        public void update(Observable o, Object data) {
49          initialize(VM.getVM().getTypeDataBase());
50        }
51      });
52  }
53
54  private static synchronized void initialize(TypeDataBase db) {
55    // klass and oop_size are HotSpot magic fields and hence we can't
56    // find them from InstanceKlass for java.lang.Class.
57    Type jlc = db.lookupType("java_lang_Class");
58    klassOffset = (int) jlc.getCIntegerField("_klass_offset").getValue();
59    int oopSizeOffset = (int) jlc.getCIntegerField("_oop_size_offset").getValue();
60    oopSizeField = new IntField(new NamedFieldIdentifier("oop_size"), oopSizeOffset, true);
61  }
62
63  /** get Klass* field at offset hc_klass_offset from a java.lang.Class object */
64  public static Klass asKlass(Oop aClass) {
65    return (Klass)Metadata.instantiateWrapperFor(aClass.getHandle().getAddressAt(klassOffset));
66  }
67
68  /** get oop_size field at offset oop_size_offset from a java.lang.Class object */
69  public static long getOopSize(Oop aClass) {
70    return java_lang_Class.oopSizeField.getValue(aClass);
71  }
72}
73