1 /*
 2  * Copyright (c) 2000, 2020, 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.oops;
26 
27 import sun.jvm.hotspot.utilities.Observable;
28 import sun.jvm.hotspot.utilities.Observer;
29 
30 import sun.jvm.hotspot.debugger.Address;
31 import sun.jvm.hotspot.runtime.VM;
32 import sun.jvm.hotspot.types.AddressField;
33 import sun.jvm.hotspot.types.CIntegerField;
34 import sun.jvm.hotspot.types.Type;
35 import sun.jvm.hotspot.types.TypeDataBase;
36 
37 public class CompressedKlassPointers {
38   private static AddressField baseField;
39   private static CIntegerField shiftField;
40 
41   static {
42     VM.registerVMInitializedObserver(new Observer() {
43         public void update(Observable o, Object data) {
44           initialize(VM.getVM().getTypeDataBase());
45         }
46       });
47   }
48 
49   private static boolean typeExists(TypeDataBase db, String type) {
50       try {
51           db.lookupType(type);
52       } catch (RuntimeException e) {
53           return false;
54       }
55       return true;
56   }
57 
58   private static synchronized void initialize(TypeDataBase db) {
59     Type type = db.lookupType("CompressedKlassPointers");
60 
61     baseField = type.getAddressField("_base");
62     shiftField = type.getCIntegerField("_shift_copy");
63   }
64 
65   public CompressedKlassPointers() {
66   }
67 
68   public static long getBase() {
69     if (baseField.getValue() == null) {
70       return 0;
71     } else {
72         System.out.println("base: " + baseField.getValue().minus(null));
73       return baseField.getValue().minus(null);
74     }
75   }
76 
77   public static int getShift() {
78 
79       System.out.println("shift: " + (int)shiftField.getValue());
80       return (int)shiftField.getValue();
81   }
82 }