1 /* 2 * Copyright (c) 2000, 2019, 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.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