S.IOval is_closed : ic -> boolval write_int64_be : oc -> int64 -> unit Lwt.tval read_int64_be : ic -> int64 Lwt.tval flush : oc -> unit Lwt.tval write : oc -> string -> unit Lwt.tval read_into_exactly : ic -> bytes -> int -> int -> unit Lwt.tval write_char : oc -> char -> unit Lwt.tval read_char : ic -> char Lwt.t