public ByteBuffer run(Retriever retriever) {
      if (!retriever.getState().equals(Retriever.RETRIEVER_STATE_SUCCESSFUL)) return null;

      HTTPRetriever htr = (HTTPRetriever) retriever;
      if (htr.getResponseCode() == HttpURLConnection.HTTP_NO_CONTENT) {
        // Mark tile as missing to avoid excessive attempts
        MercatorTiledImageLayer.this.levels.markResourceAbsent(tile);
        return null;
      }

      if (htr.getResponseCode() != HttpURLConnection.HTTP_OK) return null;

      URLRetriever r = (URLRetriever) retriever;
      ByteBuffer buffer = r.getBuffer();

      String suffix = WWIO.makeSuffixForMimeType(htr.getContentType());
      if (suffix == null) {
        return null; // TODO: log error
      }

      String path = tile.getPath().substring(0, tile.getPath().lastIndexOf("."));
      path += suffix;

      final File outFile = WorldWind.getDataFileStore().newFile(path);
      if (outFile == null) return null;

      try {
        WWIO.saveBuffer(buffer, outFile);
        return buffer;
      } catch (IOException e) {
        e.printStackTrace(); // TODO: log error
        return null;
      }
    }
 protected void saveBuffer(java.nio.ByteBuffer buffer, java.io.File outFile)
     throws java.io.IOException {
   synchronized (this.fileLock) // sychronized with read of file in RequestTask.run()
   {
     WWIO.saveBuffer(buffer, outFile);
   }
 }