Function std::str::from_utf8
pub fn from_utf8<'a>(v: &'a [u8]) -> Option<&'a str>
Converts a vector to a string slice without performing any allocations.
Once the slice has been validated as utf-8, it is transmuted in-place and returned as a '&str' instead of a '&[u8]'
Returns None if the slice is not utf-8.