deadref.ml

type 'a t = {
  count : int Atomic.t;
  data : 'a;
}

let make a =
  { count = Atomic.make 1; data = a }

let rec acquire t =
  match Atomic.get t.count with
  | 0 -> None
  | old ->
    if Atomic.compare_and_set t.count old (succ old) then
      Some (t.data)
    else
      (Domain.cpu_relax (); acquire t)

let release t =
  match Atomic.fetch_and_add t.count (-1) with
  | 0 -> invalid_arg "double release"
  | 1 -> true
  | _v -> false

let maybe_with t f =
  let () = match acquire t with
    | Some data -> f data
    | None -> ()
  in
  release t