timeoutmanager.java

High performance DB query

/*
 * @(#)$Id: TimeoutManager.java,v 1.5 2004/07/02 23:59:23 huebsch Exp $
 *
 * Copyright (c) 2001-2004 Regents of the University of California.
 * All rights reserved.
 *
 * This file is distributed under the terms in the attached BERKELEY-LICENSE
 * file. If you do not find these files, copies can be found by writing to:
 * Computer Science Division, Database Group, Universite of California,
 * 617 Soda Hall #1776, Berkeley, CA 94720-1776. Attention: Berkeley License
 *
 * Copyright (c) 2003-2004 Intel Corporation. All rights reserved.
 *
 * This file is distributed under the terms in the attached INTEL-LICENSE file.
 * If you do not find these files, copies can be found by writing to:
 * Intel Research Berkeley, 2150 Shattuck Avenue, Suite 1300,
 * Berkeley, CA, 94704.  Attention:  Intel License Inquiry.
 */


package util.timer.timeouts;

import java.util.HashMap;
import java.util.TreeMap;
import services.LocalNode;
import services.timer.TimerClient;

/**
 * Class TimeoutManager
 *
 */
public class TimeoutManager implements TimerClient {

    private HashMap itemLookup;
    private TreeMap items;
    private double nextAlarm;

    /**
     * Constructor TimeoutManager
     */
    public TimeoutManager() {
        itemLookup = new HashMap();
        items = new TreeMap();
        this.nextAlarm = Double.MAX_VALUE;
    }

    /**
     * Method addTimeout
     *
     * @param item
     * @param delay
     * @param client
     */
    public void addTimeout(Object item, double delay,
                           TimeoutManagerClient client) {
        addTimeout(item, item, delay, client);
    }

    /**
     * Method addTimeout
     *
     * @param item
     * @param key
     * @param delay
     * @param client
     */
    public void addTimeout(Object item, Object key, double delay,
                           TimeoutManagerClient client) {
        double currentTime = LocalNode.myTimer.getCurrentTime();

        addAbsoluteTimeout(item, key, currentTime + delay, client);
    }

    /**
     * Method addAbsoluteTimeout
     *
     * @param item
     * @param timeout
     * @param client
     */
    public void addAbsoluteTimeout(Object item, double timeout,
                                   TimeoutManagerClient client) {
        addAbsoluteTimeout(item, item, timeout, client);
    }

    /**
     * Method addAbsoluteTimeout
     *
     * @param item
     * @param key
     * @param timeout
     * @param client
     */
    public void addAbsoluteTimeout(Object item, Object key, double timeout,
                                   TimeoutManagerClient client) {
        TimeoutManagerEntry entry = TimeoutManagerEntry.allocate(item, key,
                                        timeout, client);

        items.put(entry, entry);
        itemLookup.put(key, entry);
        determineNextTimer();
    }

    /**
     * Remove a timeout, to prevent a callback
     * @param key the key provided when registering (adding) the timeout
     * @return the item (not the key) obtained from registering the timeout
     */
    public Object removeTimeout(Object key) {
        Object entry = itemLookup.remove(key);

        if (entry != null) {
            TimeoutManagerEntry result =
                (TimeoutManagerEntry) items.remove(entry);

            return result.getItem();
        }

        return null;
    }

    private void setNextTimer(double nextUpdate) {
        if (nextUpdate < nextAlarm) {
            LocalNode.myTimer.schedule(
                nextUpdate - LocalNode.myTimer.getCurrentTime(), null, this);

            nextAlarm = nextUpdate;
        }
    }

    private void determineNextTimer() {
        if (items.size() != 0) {
            TimeoutManagerEntry firstItem =
                (TimeoutManagerEntry) items.firstKey();

            setNextTimer(firstItem.getTimeout());
        }
    }

    /**
     * Method handleClock
     *
     * @param data
     */
    public void handleClock(Object data) {
        double currentTime = LocalNode.myTimer.getCurrentTime();

        nextAlarm = Double.MAX_VALUE;

        while (items.size() != 0) {
            TimeoutManagerEntry headItem =
                (TimeoutManagerEntry) items.firstKey();

            if (headItem.getTimeout() > currentTime) {
                determineNextTimer();

                return;
            } else {
                items.remove(headItem);
                itemLookup.remove(headItem.getKey());
                headItem.getClient().handleTimeout(headItem.getItem(),
                                                   currentTime);
            }
        }
    }
}