val low = (if (i + 1 < limit) this[i + 1] else '\u0000')
            if (c.isLowSurrogate() || !low.isLowSurrogate()) {
              '?'.code
            } else {
              i++
              0x010000 + (c.code and 0x03ff shl 10 or (low.code and 0x03ff))
            }
          }

          else -> c.code
        }
      i++
    }
    return result
  }