GPSDate.java
/* Copyright 2002-2019 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.time;
import java.io.Serializable;
import org.hipparchus.util.FastMath;
import org.orekit.utils.Constants;
/** Container for date in GPS form.
* @author Luc Maisonobe
* @see AbsoluteDate
* @since 9.3
*/
public class GPSDate implements Serializable, TimeStamped {
/** Serializable UID. */
private static final long serialVersionUID = 20180633L;
/** Duration of a week in seconds. */
private static final double WEEK = 7 * Constants.JULIAN_DAY;
/** conversion factor from seconds to milliseconds. */
private static final double S_TO_MS = 1000.0;
/** Week number since {@link AbsoluteDate#GPS_EPOCH GPS epoch}. */
private final int weekNumber;
/** Number of milliseconds since week start. */
private final double milliInWeek;
/** Corresponding date. */
private final transient AbsoluteDate date;
/** Build an instance corresponding to a GPS date.
* <p>GPS dates are provided as a week number starting at
* {@link AbsoluteDate#GPS_EPOCH GPS epoch} and as a number of milliseconds
* since week start.</p>
* @param weekNumber week number since {@link AbsoluteDate#GPS_EPOCH GPS epoch}
* @param milliInWeek number of milliseconds since week start
*/
public GPSDate(final int weekNumber, final double milliInWeek) {
this.weekNumber = weekNumber;
this.milliInWeek = milliInWeek;
final int day = (int) FastMath.floor(milliInWeek / (Constants.JULIAN_DAY * S_TO_MS));
final double secondsInDay = milliInWeek / S_TO_MS - day * Constants.JULIAN_DAY;
date = new AbsoluteDate(new DateComponents(DateComponents.GPS_EPOCH, weekNumber * 7 + day),
new TimeComponents(secondsInDay),
TimeScalesFactory.getGPS());
}
/** Build an instance from an absolute date.
* @param date absolute date to consider
*/
public GPSDate(final AbsoluteDate date) {
this.weekNumber = (int) FastMath.floor(date.durationFrom(AbsoluteDate.GPS_EPOCH) / WEEK);
final AbsoluteDate weekStart = new AbsoluteDate(AbsoluteDate.GPS_EPOCH, WEEK * weekNumber);
this.milliInWeek = date.durationFrom(weekStart) * S_TO_MS;
this.date = date;
}
/** Get the week number since {@link AbsoluteDate#GPS_EPOCH GPS epoch}.
* @return week number since {@link AbsoluteDate#GPS_EPOCH GPS epoch}
*/
public int getWeekNumber() {
return weekNumber;
}
/** Get the number of milliseconds since week start.
* @return number of milliseconds since week start
*/
public double getMilliInWeek() {
return milliInWeek;
}
/** {@inheritDoc} */
@Override
public AbsoluteDate getDate() {
return date;
}
/** Replace the instance with a data transfer object for serialization.
* @return data transfer object that will be serialized
*/
private Object writeReplace() {
return new DataTransferObject(weekNumber, milliInWeek);
}
/** Internal class used only for serialization. */
private static class DataTransferObject implements Serializable {
/** Serializable UID. */
private static final long serialVersionUID = 20180633L;
/** Week number since {@link AbsoluteDate#GPS_EPOCH GPS epoch}. */
private final int weekNumber;
/** Number of milliseconds since week start. */
private final double milliInWeek;
/** Simple constructor.
* @param weekNumber week number since {@link AbsoluteDate#GPS_EPOCH GPS epoch}
* @param milliInWeek number of milliseconds since week start
*/
DataTransferObject(final int weekNumber, final double milliInWeek) {
this.weekNumber = weekNumber;
this.milliInWeek = milliInWeek;
}
/** Replace the deserialized data transfer object with a {@link GPSDate}.
* @return replacement {@link GPSDate}
*/
private Object readResolve() {
return new GPSDate(weekNumber, milliInWeek);
}
}
}