Revision e9e27cce8a171ce033cd42abad598c27b07df555 authored by Valentin Chaboche on 13 September 2023, 10:43:35 UTC, committed by Marge Bot on 22 September 2023, 07:41:44 UTC
1 parent 262d346
stored_data.mli
(*****************************************************************************)
(* *)
(* Open Source License *)
(* Copyright (c) 2023 Nomadic Labs, <contact@nomadic-labs.com> *)
(* *)
(* Permission is hereby granted, free of charge, to any person obtaining a *)
(* copy of this software and associated documentation files (the "Software"),*)
(* to deal in the Software without restriction, including without limitation *)
(* the rights to use, copy, modify, merge, publish, distribute, sublicense, *)
(* and/or sell copies of the Software, and to permit persons to whom the *)
(* Software is furnished to do so, subject to the following conditions: *)
(* *)
(* The above copyright notice and this permission notice shall be included *)
(* in all copies or substantial portions of the Software. *)
(* *)
(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *)
(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL *)
(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING *)
(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER *)
(* DEALINGS IN THE SOFTWARE. *)
(* *)
(*****************************************************************************)
open Error_monad
(** Persistent data manager.
Every data read/write operation is protected by a mutex preventing
concurrent data-races. *)
(** A data structure that represents files via their paths and encodings. *)
type 'a file = private {
encoding : 'a Data_encoding.t;
eq : 'a -> 'a -> bool;
path : string;
json : bool;
}
type 'a eq := 'a -> 'a -> bool
(** The type for the (persistent) data of a file. *)
type 'a t
(** This error is returned when the requested data is not found. *)
type error += Missing_stored_data of string
(** [make_file ?(json=false) ~filepath encoding] represents a file
located at [filepath]. The content of this value is encoded using
[encoding]. By default, the content is encoded in binary content
except if [json=true].
[eq] is used internally to test whether the
contents of the file should be updated when calling {!write}
or {!update_with}.
{b Warning} It is the caller responsability to ensure that the
base directory of the [filepath] exists; otherwise, reading and
writing will fail. *)
val make_file :
?json:bool -> filepath:string -> 'a Data_encoding.t -> 'a eq -> 'a file
(** [get data] accesses the data (cached). *)
val get : 'a t -> 'a Lwt.t
(** [write data value] overwrites the previous [data] with the new
[value]. The cache is only updated if the write succeeds. If
the write fails, it is up to the user to retry. *)
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 avoiding data
races. Favour the usage of [write]. *)
val write_file : 'a 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.
The cache is only updated if the write succeeds. If
the write fails, it is up to the user to retry.
{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 : 'a file -> 'a t tzresult Lwt.t
(** [init encoded_file eq ~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 : 'a file -> initial_data:'a -> 'a t tzresult Lwt.t
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...