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 

    25 package sun.jvm.hotspot.oops;

    26 

    27 import java.util.*;

    28 

    29 import sun.jvm.hotspot.debugger.*;

    30 import sun.jvm.hotspot.memory.*;

    31 import sun.jvm.hotspot.runtime.*;

    32 import sun.jvm.hotspot.types.AddressField;

    33 import sun.jvm.hotspot.types.Type;

    34 import sun.jvm.hotspot.types.TypeDataBase;

    35 import sun.jvm.hotspot.utilities.*;

    36 

    37 /** A utility class encapsulating useful oop operations */

    38 

    39 // initialize fields for java.lang.Class

    40 public 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 }