001// License: GPL. For details, see LICENSE file.
002package org.openstreetmap.josm.data.projection.datum;
003
004import java.io.IOException;
005import java.io.InputStream;
006
007import org.openstreetmap.josm.io.CachedFile;
008
009/**
010 * Wrapper for {@link NTV2GridShiftFile}.
011 *
012 * Loads the shift file from disk, when it is first accessed.
013 * @since 5226
014 */
015public class NTV2GridShiftFileWrapper {
016
017    // CHECKSTYLE.OFF: LineLength
018
019    /**
020     * Used in Germany to convert coordinates between the DHDN (<i>Deutsches Hauptdreiecksnetz</i>)
021     * and ETRS89 (<i>European Terrestrial Reference System 1989</i>) datums.
022     * @see <a href="http://crs.bkg.bund.de/crseu/crs/descrtrans/eu-descrtrans.php?crs_id=REVfREhETiAvIEdLXzM=&op_id=REVfREhETiAoQmVUQSwgMjAwNykgdG8gRVRSUzg5">
023     * Description of Transformation - DE_DHDN (BeTA, 2007) to ETRS89</a>
024     */
025    public static final NTV2GridShiftFileWrapper BETA2007 = new NTV2GridShiftFileWrapper("resource://data/projection/BETA2007.gsb");
026
027    /**
028     * Used in France to convert coordinates between the NTF (<i>Nouvelle triangulation de la France</i>)
029     * and RGF93 (<i>Réseau géodésique français 1993</i>) datums.
030     * @see <a href="http://geodesie.ign.fr/contenu/fichiers/documentation/algorithmes/notice/NT111_V1_HARMEL_TransfoNTF-RGF93_FormatGrilleNTV2.pdf">
031     * [French] Transformation de coordonnées NTF – RGF93 / Format de grille NTv2</a>
032     */
033    public static final NTV2GridShiftFileWrapper ntf_rgf93 = new NTV2GridShiftFileWrapper("resource://data/projection/ntf_r93_b.gsb");
034
035    // CHECKSTYLE.ON: LineLength
036
037    private NTV2GridShiftFile instance;
038    private final String gridFileName;
039
040    /**
041     * Constructs a new {@code NTV2GridShiftFileWrapper}.
042     * @param filename Path to the grid file (GSB format)
043     */
044    public NTV2GridShiftFileWrapper(String filename) {
045        this.gridFileName = filename;
046    }
047
048    /**
049     * Returns the actual {@link NTV2GridShiftFile} behind this wrapper.
050     * The grid file is only loaded once, when first accessed.
051     * @return The NTv2 grid file
052     */
053    public NTV2GridShiftFile getShiftFile() {
054        if (instance == null) {
055            try (CachedFile cf = new CachedFile(gridFileName); InputStream is = cf.getInputStream()) {
056                instance = new NTV2GridShiftFile();
057                instance.loadGridShiftFile(is, false);
058            } catch (IOException e) {
059                throw new RuntimeException(e);
060            }
061        }
062        return instance;
063    }
064}