X-Git-Url: https://gitweb.fperrin.net/?p=GpsPrune.git;a=blobdiff_plain;f=src%2Ftim%2Fprune%2Ffunction%2Fsrtm%2FTileFinder.java;fp=src%2Ftim%2Fprune%2Ffunction%2Fsrtm%2FTileFinder.java;h=60a9479d1289faae0523e0fd7d025b56e816d37e;hp=0000000000000000000000000000000000000000;hb=ce6f2161b8596f7018d6a76bff79bc9e571f35fd;hpb=2d8cb72e84d5cc1089ce77baf1e34ea3ea2f8465

diff --git a/src/tim/prune/function/srtm/TileFinder.java b/src/tim/prune/function/srtm/TileFinder.java
new file mode 100644
index 0000000..60a9479
--- /dev/null
+++ b/src/tim/prune/function/srtm/TileFinder.java
@@ -0,0 +1,82 @@
+package tim.prune.function.srtm;
+
+import java.io.InputStream;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.ArrayList;
+
+
+/**
+ * Class to get the URLs of the SRTM tiles
+ * using the srtmtiles.dat file
+ */
+public abstract class TileFinder
+{
+	/** URL prefix for all tiles */
+	private static final String URL_PREFIX = "https://dds.cr.usgs.gov/srtm/version2_1/SRTM3/";
+	/** Directory names for each continent */
+	private static final String[] CONTINENTS = {"", "Eurasia", "North_America", "Australia",
+		"Islands", "South_America", "Africa"};
+
+
+	/**
+	 * Get the Urls for the given list of tiles
+	 * @param inTiles list of Tiles to get
+	 * @return array of URLs
+	 */
+	public static URL[] getUrls(ArrayList<SrtmTile> inTiles)
+	{
+		if (inTiles == null || inTiles.size() < 1) {return null;}
+		URL[] urls = new URL[inTiles.size()];
+		// Read dat file into array
+		byte[] lookup = readDatFile();
+		for (int t=0; t<inTiles.size(); t++)
+		{
+			SrtmTile tile = inTiles.get(t);
+			// Get byte from lookup array
+			int idx = (tile.getLatitude() + 59)*360 + (tile.getLongitude() + 180);
+			try
+			{
+				int dir = lookup[idx];
+				if (dir > 0) {
+					try {
+						urls[t] = new URL(URL_PREFIX + CONTINENTS[dir] + "/" + tile.getTileName());
+					} catch (MalformedURLException e) {} // ignore error, url stays null
+				}
+			} catch (ArrayIndexOutOfBoundsException e) {} // ignore error, url stays null
+		}
+		return urls;
+	}
+
+	/**
+	 * Read the dat file and get the contents
+	 * @return byte array containing file contents
+	 */
+	private static byte[] readDatFile()
+	{
+		InputStream in = null;
+		try
+		{
+			// Need absolute path to dat file
+			in = TileFinder.class.getResourceAsStream("/tim/prune/function/srtm/srtmtiles.dat");
+			if (in != null)
+			{
+				byte[] buffer = new byte[in.available()];
+				in.read(buffer);
+				in.close();
+				return buffer;
+			}
+		}
+		catch (java.io.IOException e) {
+			System.err.println("Exception trying to read srtmtiles.dat : " + e.getMessage());
+		}
+		finally
+		{
+			try {
+				in.close();
+			}
+			catch (Exception e) {} // ignore
+		}
+		return null;
+	}
+}