source: josm/src/org/openstreetmap/josm/io/OsmWriter.java@ 90

package org.openstreetmap.josm.io;

import java.io.PrintWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map.Entry;

import org.openstreetmap.josm.data.osm.DataSet;
import org.openstreetmap.josm.data.osm.Node;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.Segment;
import org.openstreetmap.josm.data.osm.Way;
import org.openstreetmap.josm.data.osm.visitor.Visitor;
import org.openstreetmap.josm.tools.XmlWriter;

/**
 * Save the dataset into a stream as osm intern xml format. This is not using any
 * xml library for storing.
 * @author imi
 */
public class OsmWriter implements Visitor {

        /**
         * The output writer to save the values to.
         */
        private PrintWriter out;

        /**
         * The counter for new created objects. Starting at -1 and goes down.
         */
        private long newIdCounter = -1;
        /**
         * All newly created ids and their primitive that uses it. This is a back reference
         * map to allow references to use the correnct primitives.
         */
        private HashMap<OsmPrimitive, Long> usedNewIds = new HashMap<OsmPrimitive, Long>();

        private final boolean osmConform;

        /**
         * Output the data to the stream
         * @param osmConform <code>true</code>, if the xml should be 100% osm conform. In this
         *              case, not all information can be retrieved later (as example, modified state
         *              is lost and id's remain 0 instead of decrementing from -1)
         */
        public static void output(Writer out, DataSet ds, boolean osmConform) {
                OsmWriter writer = new OsmWriter(out, osmConform);
                writer.out.println("<?xml version='1.0' encoding='UTF-8'?>");
                writer.out.println("<osm version='0.3' generator='JOSM'>");
                for (Node n : ds.nodes)
                        writer.visit(n);
                for (Segment ls : ds.segments)
                        writer.visit(ls);
                for (Way w : ds.ways)
                        writer.visit(w);
                writer.out.println("</osm>");
        }

        public static void outputSingle(Writer out, OsmPrimitive osm, boolean osmConform) {
                OsmWriter writer = new OsmWriter(out, osmConform);
                writer.out.println(XmlWriter.header());
                writer.out.println("<osm version='0.3' generator='JOSM'>");
                osm.visit(writer);
                writer.out.println("</osm>");
        }

        private OsmWriter(Writer out, boolean osmConform) {
                if (out instanceof PrintWriter)
                        this.out = (PrintWriter)out;
                else
                        this.out = new PrintWriter(out);
                this.osmConform = osmConform;
        }

        public void visit(Node n) {
                addCommon(n, "node");
                out.print(" lat='"+n.coor.lat()+"' lon='"+n.coor.lon()+"'");
                addTags(n, "node", true);
        }

        public void visit(Segment ls) {
                if (ls.incomplete)
                        return; // Do not write an incomplete segment
                addCommon(ls, "segment");
                out.print(" from='"+getUsedId(ls.from)+"' to='"+getUsedId(ls.to)+"'");
                addTags(ls, "segment", true);
        }

        public void visit(Way w) {
                addCommon(w, "way");
                out.println(">");
                for (Segment ls : w.segments)
                        out.println("    <seg id='"+getUsedId(ls)+"' />");
                addTags(w, "way", false);
        }

        /**
         * Return the id for the given osm primitive (may access the usedId map)
         */
        private long getUsedId(OsmPrimitive osm) {
                if (osm.id != 0)
                        return osm.id;
                if (usedNewIds.containsKey(osm))
                        return usedNewIds.get(osm);
                usedNewIds.put(osm, newIdCounter);
                return osmConform ? 0 : newIdCounter--;
        }


        private void addTags(OsmPrimitive osm, String tagname, boolean tagOpen) {
                if (osm.keys != null) {
                        if (tagOpen)
                                out.println(">");
                        for (Entry<String, String> e : osm.keys.entrySet())
                                out.println("    <tag k='"+ XmlWriter.encode(e.getKey()) +
                                                "' v='"+XmlWriter.encode(e.getValue())+ "' />");
                        out.println("  </" + tagname + ">");
                } else if (tagOpen)
                        out.println(" />");
                else
                        out.println("  </" + tagname + ">");
        }

        /**
         * Add the common part as the from of the tag as well as the id or the action tag.
         */
        private void addCommon(OsmPrimitive osm, String tagname) {
                out.print("  <"+tagname+" id='"+getUsedId(osm)+"'");
                if (!osmConform) {
                        String action = null;
                        if (osm.deleted)
                                action = "delete";
                        else if (osm.modified)
                                action = "modify";
                        if (action != null)
                                out.print(" action='"+action+"'");
                }
                if (osm.timestamp != null) {
                        String time = osm.getTimeStr();
                        out.print(" timestamp='"+time+"'");
                }
        }
}