The decoding phase will do that, if needed. Also note that in many cases you must process it as opaque binary, even though it should be valid UTF-8. This is in

The decoding phase will do that, if needed. Also note that in many cases you must process it as opaque binary, even though it should be valid UTF-8. This is in particular with filenames on POSIX systems because otherwise you could not access any files that happen to have invalid UTF-8 in their names.