//
// Copyright (C) 2006 United States Government as represented by the
// Administrator of the National Aeronautics and Space Administration
// (NASA). All Rights Reserved.
//
// This software is distributed under the NASA Open Source Agreement
// (NOSA), version 1.3. The NOSA has been approved by the Open Source
// Initiative. See the file NOSA-1.3-JPF at the top of the distribution
// directory tree for the complete NOSA document.
//
// THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
// KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
// LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
// SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
// A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
// THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
// DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
//
package gov.nasa.jpf.vm;
public abstract class AbstractRestorer<Saved> implements StateRestorer<Saved>, KernelState.ChangeListener {
protected Saved cached = null;
VM vm;
protected KernelState ks = null;
public void attach(VM vm) {
this.vm = vm;
this.ks = vm.getKernelState();
}
public Saved getRestorableData() {
if (cached == null) {
cached = computeRestorableData();
ks.pushChangeListener(this);
}
return cached;
}
public void restore (Saved data) {
doRestore(data);
if (cached == null) {
ks.pushChangeListener(this);
} else {
// invariant says we're already waiting for changes
}
cached = data;
}
public void kernelStateChanged (KernelState same) {
cached = null;
}
protected abstract Saved computeRestorableData();
protected abstract void doRestore(Saved data);
}