source: josm/src/org/openstreetmap/josm/io/RawGpsReader.java@ 189

package org.openstreetmap.josm.io;

import static org.openstreetmap.josm.tools.I18n.tr;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedList;
import java.util.Stack;

import org.openstreetmap.josm.data.coor.LatLon;
import org.openstreetmap.josm.gui.layer.MarkerLayer.Marker;
import org.openstreetmap.josm.gui.layer.RawGpsLayer.GpsPoint;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;

import uk.co.wilson.xml.MinML2;

/**
 * Read raw gps data from a gpx file. Only way points with their ways segments
 * and waypoints are imported.
 * @author imi
 */
public class RawGpsReader {

        /**
         * Hold the resulting gps data (tracks and their track points)
         */
        public Collection<Collection<GpsPoint>> trackData = new LinkedList<Collection<GpsPoint>>();

        /**
         * Hold the waypoints of the gps data.
         */
        public Collection<Marker> markerData = new ArrayList<Marker>();

        private class Parser extends MinML2 {
                /**
                 * Current track to be read. The last entry is the current trkpt.
                 * If in wpt-mode, it contain only one GpsPoint.
                 */
                private Collection<GpsPoint> current = new LinkedList<GpsPoint>();
                private LatLon currentLatLon;
                private String currentTime = "";
                private String currentName = "";
                private Stack<String> tags = new Stack<String>();

                @Override public void startElement(String namespaceURI, String localName, String qName, Attributes atts) throws SAXException {
                        if (qName.equals("wpt") || qName.equals("trkpt")) {
                                try {
                        double lat = Double.parseDouble(atts.getValue("lat"));
                        double lon = Double.parseDouble(atts.getValue("lon"));
                                if (Math.abs(lat) > 90)
                                        throw new SAXException(tr("Data error: lat value \"{0}\" is out of bound.", lat));
                                if (Math.abs(lon) > 180)
                                        throw new SAXException(tr("Data error: lon value \"{0}\" is out of bound.", lon));
                        currentLatLon = new LatLon(lat, lon);
                } catch (NumberFormatException e) {
                        e.printStackTrace();
                        throw new SAXException(e);
                }
                currentTime = "";
                currentName = "";
                        }
                        tags.push(qName);
                }

                @Override public void characters(char[] ch, int start, int length) {
                        String peek = tags.peek();
                        if (peek.equals("time") || peek.equals("name")) {
                                String tag = tags.pop();
                                if (tags.empty() || (!tags.peek().equals("wpt") && !tags.peek().equals("trkpt"))) {
                                        tags.push(tag);
                                        return;
                                }
                                String contents = new String(ch, start, length);
                                if (peek.equals("time")) currentTime += contents; else currentName += contents;
                                tags.push(tag);
                        }
                }

                @Override public void endElement(String namespaceURI, String localName, String qName) {
                        if (qName.equals("trkpt")) {
                                current.add(new GpsPoint(currentLatLon, currentTime));
                                currentTime = "";
                                currentName = "";
                        } else if (qName.equals("wpt")) {
                                markerData.add(new Marker(currentLatLon, currentName, null));
                                currentTime = "";
                                currentName = "";
                        } else if (qName.equals("trkseg") || qName.equals("trk") || qName.equals("gpx")) {
                                newTrack();
                                currentTime = "";
                                currentName = "";
                        }
                        tags.pop();
        }

                private void newTrack() {
                        if (!current.isEmpty()) {
                                trackData.add(current);
                                current = new LinkedList<GpsPoint>();
                        }
                }
        }


        /**
         * Parse the input stream and store the result in trackData and markerData 
         */
        public RawGpsReader(InputStream source) throws SAXException, IOException {
                Parser parser = new Parser();
                parser.parse(new InputStreamReader(source, "UTF-8"));
        }
}