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;
008import org.openstreetmap.josm.tools.JosmRuntimeException;
009
010/**
011 * Wrapper for {@link NTV2GridShiftFile}.
012 *
013 * Loads the shift file from disk, when it is first accessed.
014 * @since 5226
015 */
016public class NTV2GridShiftFileWrapper {
017
018    // CHECKSTYLE.OFF: LineLength
019
020    /**
021     * Used in Germany to convert coordinates between the DHDN (<i>Deutsches Hauptdreiecksnetz</i>)
022     * and ETRS89 (<i>European Terrestrial Reference System 1989</i>) datums.
023     * @see <a href="http://crs.bkg.bund.de/crseu/crs/descrtrans/eu-descrtrans.php?crs_id=REVfREhETiAvIEdLXzM=&op_id=REVfREhETiAoQmVUQSwgMjAwNykgdG8gRVRSUzg5">
024     * Description of Transformation - DE_DHDN (BeTA, 2007) to ETRS89</a>
025     */
026    public static final NTV2GridShiftFileWrapper BETA2007 = new NTV2GridShiftFileWrapper("resource://data/projection/BETA2007.gsb");
027
028    /**
029     * Used in France to convert coordinates between the NTF (<i>Nouvelle triangulation de la France</i>)
030     * and RGF93 (<i>Réseau géodésique français 1993</i>) datums.
031     * @see <a href="http://geodesie.ign.fr/contenu/fichiers/documentation/algorithmes/notice/NT111_V1_HARMEL_TransfoNTF-RGF93_FormatGrilleNTV2.pdf">
032     * [French] Transformation de coordonnées NTF – RGF93 / Format de grille NTv2</a>
033     */
034    public static final NTV2GridShiftFileWrapper ntf_rgf93 = new NTV2GridShiftFileWrapper("resource://data/projection/ntf_r93_b.gsb");
035
036    // CHECKSTYLE.ON: LineLength
037
038    private NTV2GridShiftFile instance;
039    private final String gridFileName;
040
041    /**
042     * Constructs a new {@code NTV2GridShiftFileWrapper}.
043     * @param filename Path to the grid file (GSB format)
044     */
045    public NTV2GridShiftFileWrapper(String filename) {
046        this.gridFileName = filename;
047    }
048
049    /**
050     * Returns the actual {@link NTV2GridShiftFile} behind this wrapper.
051     * The grid file is only loaded once, when first accessed.
052     * @return The NTv2 grid file
053     */
054    public NTV2GridShiftFile getShiftFile() {
055        if (instance == null) {
056            try (CachedFile cf = new CachedFile(gridFileName); InputStream is = cf.getInputStream()) {
057                instance = new NTV2GridShiftFile();
058                instance.loadGridShiftFile(is, false);
059            } catch (IOException e) {
060                throw new JosmRuntimeException(e);
061            }
062        }
063        return instance;
064    }
065}