module type SA =
  sig
    type data
    type t
    val make : data -> t
    val node : t -> data
    val hash : t -> int
    val uid : t -> Uid.t
    val equal : t -> t -> bool
    val stats : unit -> unit
    val init : unit -> unit
  end

module type S = sig
    type data
    type t = private { id   : Uid.t;
                       key  : int;
                       node : data }
    val make : data -> t
    val node : t -> data
    val hash : t -> int
    val uid : t -> Uid.t
    val equal : t -> t -> bool
    val stats : unit -> unit
    val init : unit -> unit

end

module Make (H : Hashtbl.HashedType) : S with type data = H.t