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(** Persistent data manager.

    Every data read/write operation is protected by a mutex preventing
    concurrent data-races. *)

(** The type for the persistent data. *)
type 'a t

(** [get data] accesses the data (cached). *)
val get : 'a t -> 'a Lwt.t

(** [write data value] overwrites the previous [data] with the new
    [value]. *)
val write : 'a t -> 'a -> unit tzresult Lwt.t

(** [write_file encoded_file value] raw writes the [encoded_file] with
   the [value].

    {b Warning} this function should not be used in a normal context
   as it aims to overwrite the target without preserving data
   races. Favour the usage of [write]. *)
val write_file : ('kind, 'a) Naming.encoded_file -> 'a -> unit tzresult Lwt.t

(** [update_with data f] {b atomically} updates [data] with the result
    of the application of [f]. Concurrent accesses to the data will
    block until the value is updated.

    {b Warning} Calling read/write in [f] will result in a deadlock. *)
val update_with : 'a t -> ('a -> 'a Lwt.t) -> unit tzresult Lwt.t

(** [load encoded_file] loads and decode a data from an
    [encoded_file]. *)
val load : ('kind, 'a) Naming.encoded_file -> 'a t tzresult Lwt.t

(** [init encoded_file ~initial_data] creates or load an on-disk
    data. If the file already exists, then the data is read from the
    file. Otherwise, [initial_data] is used. *)
val init :
  ('kind, 'a) Naming.encoded_file -> initial_data:'a -> 'a t tzresult Lwt.t