70 lines
3.0 KiB
OCaml
70 lines
3.0 KiB
OCaml
(*****************************************************************************)
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(* *)
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(* Open Source License *)
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(* Copyright (c) 2018 Dynamic Ledger Solutions, Inc. <contact@tezos.com> *)
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(* *)
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(* Permission is hereby granted, free of charge, to any person obtaining a *)
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(* copy of this software and associated documentation files (the "Software"),*)
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(* to deal in the Software without restriction, including without limitation *)
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(* the rights to use, copy, modify, merge, publish, distribute, sublicense, *)
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(* and/or sell copies of the Software, and to permit persons to whom the *)
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(* Software is furnished to do so, subject to the following conditions: *)
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(* *)
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(* The above copyright notice and this permission notice shall be included *)
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(* in all copies or substantial portions of the Software. *)
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(* *)
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(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
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(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *)
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(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL *)
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(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
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(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING *)
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(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER *)
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(* DEALINGS IN THE SOFTWARE. *)
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(* *)
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(*****************************************************************************)
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open Lwt.Infix
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type t = {
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cancelation: unit Lwt_condition.t ;
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cancelation_complete: unit Lwt_condition.t ;
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mutable cancel_hook: unit -> unit Lwt.t ;
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mutable canceling: bool ;
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mutable canceled: bool ;
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}
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let create () =
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let cancelation = Lwt_condition.create () in
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let cancelation_complete = Lwt_condition.create () in
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{ cancelation ; cancelation_complete ;
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cancel_hook = (fun () -> Lwt.return_unit) ;
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canceling = false ;
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canceled = false ;
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}
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let cancel st =
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if st.canceled then
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Lwt.return_unit
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else if st.canceling then
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Lwt_condition.wait st.cancelation_complete
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else begin
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st.canceling <- true ;
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Lwt_condition.broadcast st.cancelation () ;
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Lwt.finalize
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st.cancel_hook
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(fun () ->
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st.canceled <- true ;
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Lwt_condition.broadcast st.cancelation_complete () ;
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Lwt.return_unit)
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end
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let on_cancel st cb =
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let hook = st.cancel_hook in
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st.cancel_hook <- (fun () -> hook () >>= cb)
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let cancelation st =
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if st.canceling then Lwt.return_unit
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else Lwt_condition.wait st.cancelation
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let canceled st = st.canceling
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