FALSE
means that a string is certainly not valid UTF-8.
However, false positives are possible. For instance,
(c4,85)
represents ('a with ogonek') in UTF-8
as well as ('A umlaut', 'Ellipsis') in WINDOWS-1250.
Also note that UTF-8, as well as most 8-bit encodings, extend ASCII
(note that stri_enc_isascii
implies that
stri_enc_isutf8
).
However, the longer the sequence,
the greater the possibility that the result
is indeed in UTF-8 -- this is because not all sequences of bytes
are valid UTF-8.
This function is independent of the way R marks encodings in
character strings (see Encoding and stringi-encoding).