actualtimerthread.java

High performance DB query

/*
 * @(#)$Id: ActualTimerThread.java,v 1.3 2004/07/02 23:59:22 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 runtime.services.timer;

import java.util.TreeMap;

/**
 * Class ActualTimerThread
 *
 */
public class ActualTimerThread extends Thread implements Runnable {

    private TreeMap events;
    private ActualTimer eventProcessor;
    private long defaultSleepTime;
    private boolean run;

    /**
     * Constructor ActualTimerThread
     *
     * @param events
     * @param eventProcessor
     * @param defaultSleepTime
     */
    public ActualTimerThread(TreeMap events, ActualTimer eventProcessor,
                             long defaultSleepTime) {
        this.events = events;
        this.eventProcessor = eventProcessor;
        this.defaultSleepTime = defaultSleepTime;
        this.run = true;
    }

    private ActualTimerEvent getFirstEvent() {
        synchronized (events) {
            if (events.size() > 0) {
                return (ActualTimerEvent) events.firstKey();
            } else {
                return null;
            }
        }
    }

    private void removeEvent(ActualTimerEvent event) {
        synchronized (events) {
            events.remove(event);
        }
    }

    private void processQueue() {
        ActualTimerEvent firstEvent = getFirstEvent();

        while (firstEvent != null) {
            double currentTime = eventProcessor.getCurrentTime();
            double eventTime = firstEvent.getExecutionTime();

            if (eventTime <= currentTime) {
                removeEvent(firstEvent);
                eventProcessor.runEvent(firstEvent);
            } else {
                break;
            }

            // Get the next event
            firstEvent = getFirstEvent();
        }
    }

    private long determineSleepTime() {
        ActualTimerEvent firstEvent = getFirstEvent();

        if (firstEvent != null) {
            double currentTime = eventProcessor.getCurrentTime();
            double eventTime = firstEvent.getExecutionTime();
            double delay = eventTime - currentTime;

            if (delay < 0) {
                delay = 0;
            }

            return (long) ((delay) * 1000);
        } else {
            return defaultSleepTime;
        }
    }

    /**
     * Method run
     */
    public void run() {
        while (run) {
            processQueue();

            try {
                Thread.sleep(determineSleepTime());
            } catch (InterruptedException e) {}
        }
    }

    /**
     * Method end
     */
    public void end() {
        run = false;
    }
}