Source file lwt_switch.ml
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exception Off
type on_switch = {
mutable hooks : (unit -> unit Lwt.t) list;
}
type state =
| St_on of on_switch
| St_off
type t = { mutable state : state }
let create () = { state = St_on { hooks = [] } }
let is_on switch =
match switch.state with
| St_on _ -> true
| St_off -> false
let check = function
| Some{ state = St_off } -> raise Off
| Some {state = St_on _} | None -> ()
let add_hook switch hook =
match switch with
| Some { state = St_on os } ->
os.hooks <- hook :: os.hooks
| Some { state = St_off } ->
raise Off
| None ->
()
let add_hook_or_exec switch hook =
match switch with
| Some { state = St_on os } ->
os.hooks <- hook :: os.hooks;
Lwt.return_unit
| Some { state = St_off } ->
hook ()
| None ->
Lwt.return_unit
let turn_off switch =
match switch.state with
| St_on { hooks = hooks } ->
switch.state <- St_off;
Lwt.join (List.map (fun hook -> Lwt.apply hook ()) hooks)
| St_off ->
Lwt.return_unit
let with_switch fn =
let switch = create () in
Lwt.finalize
(fun () -> fn switch)
(fun () -> turn_off switch)