spork/utf8/decode-rune

    cfunction
    src/utf8.c on line 29, column 1

    (utf8/decode-rune buf &opt start)

    Read a UTF-8 encoded Unicode codepoint from the buffer which starts 
    at the given index. Returns a tuple [value width], where width $=$ 
    number of bytes consumed. If at the end of buffer or the buffer 
    contains malformed UTF-8, returns [nil 0].