/*
 * Copyright 2005 NAKAMURA Minoru (nminoru@nminoru.jp)
 */

package jp.nminoru.ref;

import java.lang.ref.*;
import java.lang.reflect.Field;

public final class CleanupReference extends PhantomReference {
  private static Field          referentField ;
  private static ReferenceQueue queue = new ReferenceQueue();

  static {
    Class klass = java.lang.ref.Reference.class;
    
    try {
      referentField = klass.getDeclaredField("referent");
      referentField.setAccessible(true);
    } catch(NoSuchFieldException e){
      System.exit(1);
    } 

    Thread handler = new ReferenceHandler();
    handler.setPriority(Thread.MAX_PRIORITY);
    handler.setDaemon(true);
    handler.start();
  }

  private static class ReferenceHandler extends Thread {
    public void run() {
      try {
        for (;;) {
          Reference r;
          CleanupReference reference = (CleanupReference)queue.remove();
          Object target = reference.get();
          
          if (target != null) {
            Cleaner cleaner = reference.cleaner;
            cleaner.clean(target);
            reference.clear();
          }
        }
      } catch(InterruptedException e) {
      }
    }
  }

  Cleaner cleaner;

  public CleanupReference(Object referent, Cleaner cleaner) {
    super(referent, queue);
    this.cleaner = cleaner;
  }
  
  public Object get() {
    try {
      return referentField.get(this);
    } catch(IllegalAccessException e){
      System.err.println(e);						
    }
    return null;
  }
}