sbool fileContentsIs(File f, byte[] data) ctex {
  if (isFile(f) != (data != null)) false;
  int l = l(data);
  if (fileSize(f) != l) false;
  temp BufferedInputStream in = bufferedFileInputStream(f);
  for ofs to l:
    if (data[ofs] != (byte) in.read())
      false;
  true;
}