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3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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13  * accompanied this code).
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24 
25 package sun.jvm.hotspot.oops;
26 
27 import java.util.Observable;
28 import java.util.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 {
VM.registerVMInitializedObserver(new Observer() { public void update(Observable o, Object data) { initialize(VM.getVM().getTypeDataBase()); } })42     VM.registerVMInitializedObserver(new Observer() {
43         public void update(Observable o, Object data) {
44           initialize(VM.getVM().getTypeDataBase());
45         }
46       });
47   }
48 
typeExists(TypeDataBase db, String type)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 
initialize(TypeDataBase db)58   private static synchronized void initialize(TypeDataBase db) {
59     Type type = db.lookupType("CompressedKlassPointers");
60 
61     baseField = type.getAddressField("_narrow_klass._base");
62     shiftField = type.getCIntegerField("_narrow_klass._shift");
63   }
64 
CompressedKlassPointers()65   public CompressedKlassPointers() {
66   }
67 
getBase()68   public static long getBase() {
69     if (baseField.getValue() == null) {
70       return 0;
71     } else {
72       return baseField.getValue().minus(null);
73     }
74   }
75 
getShift()76   public static int getShift() {
77     return (int)shiftField.getValue();
78   }
79 }
80