Version 20.1, December 2020

[GpsPrune.git] / src / tim / prune / function / srtm / TileDownloader.java

diff --git a/src/tim/prune/function/srtm/TileDownloader.java b/src/tim/prune/function/srtm/TileDownloader.java
new file mode 100644 (file)
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+++ b/src/tim/prune/function/srtm/TileDownloader.java
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+package tim.prune.function.srtm;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.net.URLConnection;
+
+import tim.prune.GpsPrune;
+import tim.prune.config.Config;
+
+/**
+ * Class to provide a download function for the Space Shuttle's SRTM data files.
+ * HGT files are downloaded into memory via HTTP and stored in the map cache.
+ */
+public class TileDownloader
+{
+       /** Possible results of the download */
+       public enum Result {DOWNLOADED, NOTHING_TO_DO, DOWNLOAD_FAILED, CACHE_FAILED};
+
+       /**
+        * Download a single tile of SRTM data
+        * @param inUrl remote URL to get
+        */
+       public Result downloadTile(URL inUrl)
+       {
+               if (inUrl == null) {
+                       return Result.NOTHING_TO_DO;
+               }
+
+               // Check the cache is ok
+               final String diskCachePath = Config.getConfigString(Config.KEY_DISK_CACHE);
+               if (diskCachePath != null)
+               {
+                       File srtmDir = new File(diskCachePath, "srtm");
+                       if (srtmDir.exists() && !srtmDir.isDirectory()) {
+                               // exists but isn't a directory - can't be used
+                               return Result.CACHE_FAILED;
+                       }
+                       if (!srtmDir.exists() && !srtmDir.mkdir()) {
+                               // can't create the srtm directory
+                               return Result.CACHE_FAILED;
+                       }
+               }
+               else {
+                       // no cache set up
+                       return Result.CACHE_FAILED;
+               }
+
+               // Define streams
+               FileOutputStream outStream = null;
+               InputStream inStream = null;
+               Result result = Result.NOTHING_TO_DO;
+               try
+               {
+                       // See if we've already got this tile or not
+                       File outputFile = getFileToWrite(inUrl);
+                       if (outputFile != null)
+                       {
+                               System.out.println("Download: Need to download: " + inUrl);
+                               outStream = new FileOutputStream(outputFile);
+                               URLConnection conn = inUrl.openConnection();
+                               conn.setRequestProperty("User-Agent", "GpsPrune v" + GpsPrune.VERSION_NUMBER);
+                               inStream = conn.getInputStream();
+                               // Copy all the bytes to the file
+                               int c;
+                               while ((c = inStream.read()) != -1)
+                               {
+                                       outStream.write(c);
+                               }
+                               result = Result.DOWNLOADED;
+                       }
+               }
+               catch (IOException ioe) {
+                       System.err.println(ioe.getClass().getName() + " - " + ioe.getMessage());
+                       result = Result.DOWNLOAD_FAILED;
+               }
+               // Make sure streams are closed
+               try {inStream.close();} catch (Exception e) {}
+               try {outStream.close();} catch (Exception e) {}
+
+               return result;
+       }
+
+       /**
+        * See whether the SRTM file is already available locally
+        * @param inUrl URL for online resource
+        * @return file object to write to, or null if already there
+        */
+       private static File getFileToWrite(URL inUrl)
+       {
+               String diskCachePath = Config.getConfigString(Config.KEY_DISK_CACHE);
+               if (diskCachePath != null)
+               {
+                       File srtmDir = new File(diskCachePath, "srtm");
+                       if (srtmDir.exists() && srtmDir.isDirectory() && srtmDir.canRead())
+                       {
+                               File srtmFile = new File(srtmDir, new File(inUrl.getFile()).getName());
+                               if (!srtmFile.exists() || !srtmFile.canRead() || srtmFile.length() <= 400) {
+                                       return srtmFile;
+                               }
+                       }
+               }
+               return null;
+       }
+}