com.savoycraft.util.TimeUtil.java Source code

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Here is the source code for com.savoycraft.util.TimeUtil.java

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/**
 * Copyright (c) 2013 William Karnavas 
 * All Rights Reserved
 * 
 * This file is part of SavoyCraft.
 * 
 * SavoyCraft is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 * 
 * SavoyCraft is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with SavoyCraft. If not, see <http://www.gnu.org/licenses/>.
 * 
 */
package com.savoycraft.util;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Date;

import javax.sound.midi.SysexMessage;

import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.TimeInfo;

/**
 * 
 */
public class TimeUtil {

    private static boolean calibrated = false;

    private static long calibration = 0;

    private static long lastTimeRequest = 0;

    // List of time servers: http://tf.nist.gov/service/time-servers.html
    // Do not query time server more than once every 4 seconds
    public static final String TIME_SERVER = "time.nist.gov";

    /**
     * Queries a NIST time server to get a difference between its time and the
     * local system time.
     */
    public static void calibrate() {
        if (System.currentTimeMillis() < lastTimeRequest + 5000 || calibrated) {
            return;
        }

        NTPUDPClient timeClient = new NTPUDPClient();
        InetAddress inetAddress = null;
        try {
            inetAddress = InetAddress.getByName(TIME_SERVER);
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return;
        }
        TimeInfo timeInfo = null;
        try {
            timeInfo = timeClient.getTime(inetAddress);
        } catch (IOException e) {
            System.err.println("SavoyCraft could not contact time.nist.gov.");
            e.printStackTrace();
            return;
        }
        long returnTime = timeInfo.getReturnTime();
        calibration = System.currentTimeMillis() - returnTime;
        System.out.println(calibration);
        // Date time = new Date(returnTime);
        // System.out.println("Time from " + TIME_SERVER + ": " + time);

        lastTimeRequest = System.currentTimeMillis();

        calibrated = true;
    }

    public static long get() {
        if (!calibrated) {
            calibrate();
        }

        return System.currentTimeMillis() - calibration;
    }

    /**
     * Just returns the system time in millis, formatted in hex
     * 
     * @return
     */
    public static String getHexTime() {
        return Long.toHexString(System.currentTimeMillis());
    }
}