compose_codepoints

# File activesupport/lib/active_support/multibyte/handlers/utf8_handler.rb, line 503
      def compose_codepoints(codepoints)
        pos = 0
        eoa = codepoints.length - 1
        starter_pos = 0
        starter_char = codepoints[0]
        previous_combining_class = -1
        while pos < eoa
          pos += 1
          lindex = starter_char - HANGUL_LBASE
          # -- Hangul
          if 0 <= lindex and lindex < HANGUL_LCOUNT
            vindex = codepoints[starter_pos+1] - HANGUL_VBASE rescue vindex = -1
            if 0 <= vindex and vindex < HANGUL_VCOUNT
              tindex = codepoints[starter_pos+2] - HANGUL_TBASE rescue tindex = -1
              if 0 <= tindex and tindex < HANGUL_TCOUNT
                j = starter_pos + 2
                eoa -= 2
              else
                tindex = 0
                j = starter_pos + 1
                eoa -= 1
              end
              codepoints[starter_pos..j] = (lindex * HANGUL_VCOUNT + vindex) * HANGUL_TCOUNT + tindex + HANGUL_SBASE
            end
            starter_pos += 1
            starter_char = codepoints[starter_pos]
          # -- Other characters
          else
            current_char = codepoints[pos]
            current = UCD[current_char]
            if current.combining_class > previous_combining_class
              if ref = UCD.composition_map[starter_char]
                composition = ref[current_char]
              else
                composition = nil
              end
              unless composition.nil?
                codepoints[starter_pos] = composition
                starter_char = composition
                codepoints.delete_at pos
                eoa -= 1
                pos -= 1
                previous_combining_class = -1
              else
                previous_combining_class = current.combining_class
              end
            else
              previous_combining_class = current.combining_class
            end
            if current.combining_class == 0
              starter_pos = pos
              starter_char = codepoints[pos]
            end
          end
        end
        codepoints
      end