# File lib/multi_json/vendor/ok_json.rb, line 363
    def unsubst(u)
      if u < Usurrself || u > Umax || surrogate?(u)
        return Ucharerr, Ucharerr
      end
      u -= Usurrself
      [Usurr1 + ((u>>10)&0x3ff), Usurr2 + (u&0x3ff)]
    end