/*
* Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package sun.jvm.hotspot.oops;
import sun.jvm.hotspot.utilities.Observable;
import sun.jvm.hotspot.utilities.Observer;
import sun.jvm.hotspot.debugger.Address;
import sun.jvm.hotspot.runtime.VM;
import sun.jvm.hotspot.types.AddressField;
import sun.jvm.hotspot.types.CIntegerField;
import sun.jvm.hotspot.types.Type;
import sun.jvm.hotspot.types.TypeDataBase;
public class CompressedKlassPointers {
private static AddressField baseField;
private static CIntegerField shiftField;
static {
VM.registerVMInitializedObserver(new Observer() {
public void update(Observable o, Object data) {
initialize(VM.getVM().getTypeDataBase());
}
});
}
private static boolean typeExists(TypeDataBase db, String type) {
try {
db.lookupType(type);
} catch (RuntimeException e) {
return false;
}
return true;
}
private static synchronized void initialize(TypeDataBase db) {
Type type = db.lookupType("CompressedKlassPointers");
baseField = type.getAddressField("_narrow_klass._base");
shiftField = type.getCIntegerField("_narrow_klass._shift");
}
public CompressedKlassPointers() {
}
public static long getBase() {
if (baseField.getValue() == null) {
return 0;
} else {
return baseField.getValue().minus(null);
}
}
public static int getShift() {
return (int)shiftField.getValue();
}
}