docs: private static byte[] readFile(final HttpQuery query,
                                   final File file,
                                   final int max_length) {
      final int length = (int) file.length();
      if (length <= 0) {
        return null;
      }
      FileInputStream in;
      try {
        in = new FileInputStream(file.getPath());
      } catch (FileNotFoundException e) {
        return null;
      }
      try {
        final byte[] buf = new byte[Math.min(length, max_length)];
        final int read = in.read(buf);
        if (read != buf.length) {
          logError(query, "When reading " + file + ": read only "
                   + read + " bytes instead of " + buf.length);
          return null;
        }
        return buf;
      } catch (IOException e) {
        logError(query, "Error while reading " + file, e);
        return null;
      } finally {
        try {
          in.close();
        } catch (IOException e) {
          logError(query, "Error while closing " + file, e);
        }
      }
    }