Application: gvSIG desktop

/* gvSIG. Sistema de Informaci?n Geogr?fica de la Generalitat Valenciana

 *

 * Copyright (C) 2005 IVER T.I. and Generalitat Valenciana.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2

 * of the License, or (at your option) any later version.

 *

 * This program 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 General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,USA.

 *

 * For more information, contact:

 *

 *  Generalitat Valenciana

 *   Conselleria d'Infraestructures i Transport

 *   Av. Blasco Ib??ez, 50

 *   46010 VALENCIA

 *   SPAIN

 *

 *      +34 963862235

 *   gvsig@gva.es

 *      www.gvsig.gva.es

 *

 *    or

 *

 *   IVER T.I. S.A

 *   Salamanca 50

 *   46005 Valencia

 *   Spain

 *

 *   +34 963163400

 *   dac@iver.es

 */

/* CVS MESSAGES:

*

* $Id: NMEASentence.java 5085 2006-05-08 11:54:50Z jaume $

* $Log$

* Revision 1.2  2006-05-08 11:54:50  jaume

* small architecture aspects

*

* Revision 1.1  2006/04/03 16:10:27  jaume

* *** empty log message ***

*

* Revision 1.1  2006/03/31 09:55:34  jaume

* *** empty log message ***

*

*

*/

package org.gvsig.gps.parser.NMEA;

/**

 * <p>

 * NMEA messages have a common structure, consisting of a message header, 

 * data fields.

 * </p>

 * <p>

 * <li><b>Example: $GPYYY,xxx,xxx,xxx?</b></li>

 * </p><br>

 * <p>This class implements an abstraction of these messages, it keeps track

 * of the time the message is created, so you can treat it as a valid or 

 * otherwise as an old message.<br>

 * </p>

 * <p>

 * Any specific class implementing a concrete NMEA message must extend NMEASentence

 * and implement its abstract methods.

 * </p>

 * @author jaume dominguez faus - jaume.dominguez@iver.es

 *

 */

public abstract class NMEASentence {

        private String[] data;

        private byte checksum;

        protected long time;

        public final void setData(String sentence) throws IllegalSentenceException {

                int ind = sentence.indexOf('*');

                checksum = Byte.decode("0x"+sentence.substring(ind+1, ind+3)).byteValue();

                this.data = sentence.substring(0, ind).split(",");

                // TODO: checksum? maybe one day...

                parse();

        }

        /**

         * The amount of fields that this sentence contains.<br>

         * The first field (index=0) is the sentence name.

         * @return The amount of fields

         */

        public final int getFieldCount() {

                return data.length;

        }

        /**

         * The name of the NMEA sentence.

         * @return A string containing the name.

         */

        public final String getName() {

                return data[0];

        }

        /**

         * The time when this class was created. Typically, the GPS receivers are

         * always sending data. Using this timestamp you can filter this messages

         * by age.

         * @return the difference, measured in milliseconds, between the time when it

         * was set and midnight, January 1, 1970 UTC.

         */

        public final long getTime() {

                return time;

        }

        /**

         * From the list of fields, extracts the field definded by the index.

         * @param iField

         * @return String containing the iField-th field data

         */

        public final String getFieldValue(int iField) {

                return data[iField];

        }

        /**

         * Sets the timestamp. Usually, the value used for time is a typical 

         * System.currentTimeMillis() call.

         * @param time, a long containing the amount of milliseconds.

         */

        public final void setTime(long time) {

                this.time = time;

        }

        /**

         * Parses the message and initializes the fields.

         * @throws IllegalSentenceException

         */

        public abstract void parse() throws IllegalSentenceException;

        /**

         * Returns true, if this instance of NMEA is equivalent to other passed

         * as argument regardless the time they both were created and -potentially-

         * regardless other values in fields, too. Otherwise, it returns false.

         * @param NMEASentenceTest otherSentence

         * @return True, if they are equivalent. False, otherwise.

         */

        public abstract boolean isEquivalentTo(NMEASentence otherSentence);

        public String toString() {

                String s = data[0];

                for (int i = 1; i < data.length; i++) {

                        s += ","+data[i];

                }                

                return s + "\n";

        }

}