wrap

# File lib/rdoc/markup/simple_markup/to_html.rb, line 115
    def wrap(txt, line_len = 76)
      res = ""
      sp = 0
      ep = txt.length
      while sp < ep
        # scan back for a space
        p = sp + line_len - 1
        if p >= ep
          p = ep
        else
          while p > sp and txt[p] != ?\s
            p -= 1
          end
          if p <= sp
            p = sp + line_len
            while p < ep and txt[p] != ?\s
              p += 1
            end
          end
        end
        res << txt[sp...p] << "\n"
        sp = p
        sp += 1 while sp < ep and txt[sp] == ?\s
      end
      res
    end