KmlParser.java

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed 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 com.android.ddmuilib.location;

import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;

import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

/**
 * A very basic KML parser to meet the need of the emulator control panel.
 * <p/>
 * It parses basic Placemark information.
 */
public class KmlParser {
    
    private final static String NS_KML_2 = "http://earth.google.com/kml/2.";  //$NON-NLS-1$
        
    private final static String NODE_PLACEMARK = "Placemark"; //$NON-NLS-1$
    private final static String NODE_NAME = "name"; //$NON-NLS-1$
    private final static String NODE_COORDINATES = "coordinates"; //$NON-NLS-1$
    
    private final static Pattern sLocationPattern = Pattern.compile("([^,]+),([^,]+)(?:,([^,]+))?");
    
    private static SAXParserFactory sParserFactory;
    
    static {
        sParserFactory = SAXParserFactory.newInstance();
        sParserFactory.setNamespaceAware(true);
    }

    private String mFileName;

    private KmlHandler mHandler;
    
    /**
     * Handler for the SAX parser.
     */
    private static class KmlHandler extends DefaultHandler {
        // --------- parsed data --------- 
        List<WayPoint> mWayPoints;
        
        // --------- state for parsing --------- 
        WayPoint mCurrentWayPoint;
        final StringBuilder mStringAccumulator = new StringBuilder();

        boolean mSuccess = true;

        @Override
        public void startElement(String uri, String localName, String name, Attributes attributes)
                throws SAXException {
            // we only care about the standard GPX nodes.
            try {
                if (uri.startsWith(NS_KML_2)) {
                    if (NODE_PLACEMARK.equals(localName)) {
                        if (mWayPoints == null) {
                            mWayPoints = new ArrayList<WayPoint>();
                        }
                        
                        mWayPoints.add(mCurrentWayPoint = new WayPoint());
                    }
                }
            } finally {
                // no matter the node, we empty the StringBuilder accumulator when we start
                // a new node.
                mStringAccumulator.setLength(0);
            }
        }

        /**
         * Processes new characters for the node content. The characters are simply stored,
         * and will be processed when {@link #endElement(String, String, String)} is called.
         */
        @Override
        public void characters(char[] ch, int start, int length) throws SAXException {
            mStringAccumulator.append(ch, start, length);
        }
        
        @Override
        public void endElement(String uri, String localName, String name) throws SAXException {
            if (uri.startsWith(NS_KML_2)) {
                if (NODE_PLACEMARK.equals(localName)) {
                    mCurrentWayPoint = null;
                } else if (NODE_NAME.equals(localName)) {
                    if (mCurrentWayPoint != null) {
                        mCurrentWayPoint.setName(mStringAccumulator.toString());
                    }
                } else if (NODE_COORDINATES.equals(localName)) {
                    if (mCurrentWayPoint != null) {
                        parseLocation(mCurrentWayPoint, mStringAccumulator.toString());
                    }
                }
            }
        }

        @Override
        public void error(SAXParseException e) throws SAXException {
            mSuccess = false;
        }

        @Override
        public void fatalError(SAXParseException e) throws SAXException {
            mSuccess = false;
        }
        
        /**
         * Parses the location string and store the information into a {@link LocationPoint}.
         * @param locationNode the {@link LocationPoint} to receive the location data.
         * @param location The string containing the location info.
         */
        private void parseLocation(LocationPoint locationNode, String location) {
            Matcher m = sLocationPattern.matcher(location);
            if (m.matches()) {
                try {
                    double longitude = Double.parseDouble(m.group(1));
                    double latitude = Double.parseDouble(m.group(2));
                    
                    locationNode.setLocation(longitude, latitude);
                    
                    if (m.groupCount() == 3) {
                        // looks like we have elevation data.
                        locationNode.setElevation(Double.parseDouble(m.group(3)));
                    }
                } catch (NumberFormatException e) {
                    // wrong data, do nothing.
                }
            }
        }
        
        WayPoint[] getWayPoints() {
            if (mWayPoints != null) {
                return mWayPoints.toArray(new WayPoint[mWayPoints.size()]);
            }

            return null;
        }

        boolean getSuccess() {
            return mSuccess;
        }
    }

    /**
     * Creates a new GPX parser for a file specified by its full path.
     * @param fileName The full path of the GPX file to parse.
     */
    public KmlParser(String fileName) {
        mFileName = fileName;
    }

    /**
     * Parses the GPX file.
     * @return <code>true</code> if success.
     */
    public boolean parse() {
        try {
            SAXParser parser = sParserFactory.newSAXParser();

            mHandler = new KmlHandler();

            parser.parse(new InputSource(new FileReader(mFileName)), mHandler);
            
            return mHandler.getSuccess();
        } catch (ParserConfigurationException e) {
        } catch (SAXException e) {
        } catch (IOException e) {
        } finally {
        }

        return false;
    }
    
    /**
     * Returns the parsed {@link WayPoint} objects, or <code>null</code> if none were found (or
     * if the parsing failed.
     */
    public WayPoint[] getWayPoints() {
        if (mHandler != null) {
            return mHandler.getWayPoints();
        }
        
        return null;
    }
}