deleter.java

Java的面向对象数据库系统的源代码

// You can redistribute this software and/or modify it under the terms of
// the Ozone Core License version 1 published by ozone-db.org.
//
// Copyright (C) 2003-@year@, Leo Mekenkamp. All rights reserved.
//
// $Id: Deleter.java,v 1.1.2.1 2004/03/28 16:40:03 per_nyfelt Exp $

package org.ozoneDB.core.storage.gammaStore;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.ozoneDB.OzoneInternalException;

/**
 * <p>Takes care of <code>Storable</code> implemeting instances, in that it
 * has different threads for serializing and writing to <code>Storage</code>.
 * <code>Remove()</code> ensures that if a null is
 * returned that the <code>Storable</code> for the given key has been
 * completely written to <code>Storage</code>.</p>
 *
 * <p>For every instance of this class 2 threads are created, so keep this in
 * mind when creating instances; this might be a resource hog...</p>
 *
 * @author  leo
 */
public class Deleter {
    
    private class DeleteTask implements Runnable {
    
        private Storable storable;
        private StorageFactory storageFactory;
        
        DeleteTask(Storable storable, StorageFactory storageFactory) {
            this.storable = storable;
            this.storageFactory = storageFactory;
        }
        
        public void run() {
            try {
                storageFactory.delete(storable.getStorageName());
            } catch (IOException e) {
                throw new OzoneInternalException(e);
            }
        }
        
        public boolean equals(Object obj) {
            return false;
        }
        
    }
    
    private static final Logger log = Logger.getLogger(Deleter.class.getName());
    
    private AsyncExec asyncExec;

    public Deleter(String name) {
        asyncExec = new AsyncExec(name, Thread.MIN_PRIORITY, true);
    }
    
    /**
     * Places a storable into a delete queue. Works like 'Fire and forget'.
     */
    public void delete(Storable storable, StorageFactory storageFactory) {
        if (log.isLoggable(Level.FINER)) log.finer("enqueueing " + storable + " for deletion");
        DeleteTask deleteTask = new DeleteTask(storable, storageFactory);
        asyncExec.put(deleteTask, deleteTask);
    }
    
    public int size() {
        return asyncExec.size();
    }
    
    public void stopWhenReady() {
        asyncExec.stopWhenReady();
    }
    
}