+ # Adds the UTF-8 representation of `c` to `self`
+ #
+ # var b = new Bytes.empty
+ # b.add_char('A')
+ # b.add_char('キ')
+ # assert b.hexdigest == "41E382AD"
+ fun add_char(c: Char) do
+ if persisted then regen
+ var cln = c.u8char_len
+ var ln = length
+ enlarge(ln + cln)
+ items.set_char_at(length, c)
+ length += cln
+ end
+