/*
 * Copyright (C) 2014, United States Government, as represented by the
 * Administrator of the National Aeronautics and Space Administration.
 * All rights reserved.
 *
 * The Java Pathfinder core (jpf-core) platform is licensed under the
 * Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 *        http://www.apache.org/licenses/LICENSE-2.0. 
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and 
 * limitations under the License.
 */
package gov.nasa.jpf;

/**
 * @author Nastaran Shafiei <nastaran.shafiei@gmail.com>
 *  
 * Represents the finalizer thread which runs finalize() methods upon
 * garbage collection of finalizable objects, i.e. the class of a finalizable 
 * object overrides the Object.finalize() method.
 * 
 * Note that, by default, we don't process finalizers. To run finalizers one
 * needs to set the property "vm.process_finalizers" to true.
 */
public class FinalizerThread extends Thread {
  
  // upon their garbage collection, finalizable objects are added into this list instead 
  // of being removed by gc().sweep()
  private Object[] finalizeQueue;
  
  private Object semaphore;
  private boolean done;
  
  
  private void runAllFinalizers() {
    while(!isEmpty()) {
      try {
        // runFinalizer processes and removes the first element in the list
        runFinalizer(finalizeQueue[0]);
      } catch (Throwable e) { 
        // FinalizerThread ignores exceptions thrown by finalizers.
      }
    }
  }
  
  boolean isEmpty() {
    return (finalizeQueue.length == 0);
  }
  
  // invoke finalize() on the give object
  private native void runFinalizer(Object o);
  
  private native void manageState();
  
  private void processFinalizers() {
    runAllFinalizers();
    manageState();
  }

  @Override
  public void run() {
    while (!done){
      processFinalizers();
    }
  }
}