code: private void writeClass(File directory, String name, ByteBuffer def) {
      writeClass(directory, name, def, computeClassDigest(def));
    }
docs: Writes a class definition.
  @param directory The directory under which to write the class
  definition.
  @param name The fully qualified name of the class.
  @param def A <code>ByteBuffer</code> containing the class definition.