Unicode defines a name and a number of all of the glyphs it
encompasses: the numbers are called code points: they run from
0 to 0x10FFFF.
utf8ToInt converts a length-one character string encoded in
UTF-8 to an integer vector of Unicode code points. It checks validity
of the input and returns NA if it is invalid.
intToUtf8 converts a numeric vector of Unicode code points
either to a single character string or a character vector of single
characters. (For a single character string 0 is silently
omitted: otherwise 0 is mapped to "". Non-integral
numeric values are truncated to integers.) The Encoding
is declared as "UTF-8".
NA inputs are mapped to NA output.