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(* *)
(* OCaml *)
(* *)
(* David Nowak and Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
(* *)
(* Copyright 1996 Institut National de Recherche en Informatique et *)
(* en Automatique. *)
(* *)
(* All rights reserved. This file is distributed under the terms of *)
(* the GNU Lesser General Public License version 2.1, with the *)
(* special exception on linking described in the file LICENSE. *)
(* *)
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(** First-class synchronous communication.
This module implements synchronous inter-thread communications over
channels. As in John Reppy's Concurrent ML system, the communication
events are first-class values: they can be built and combined
independently before being offered for communication.
*)
type 'a channel
(** The type of communication channels carrying values of type ['a]. *)
val new_channel : unit -> 'a channel
(** Return a new channel. *)
type +'a event
(** The type of communication events returning a result of type ['a]. *)
(** [send ch v] returns the event consisting in sending the value [v]
over the channel [ch]. The result value of this event is [()]. *)
val send : 'a channel -> 'a -> unit event
(** [receive ch] returns the event consisting in receiving a value
from the channel [ch]. The result value of this event is the
value received. *)
val receive : 'a channel -> 'a event
val always : 'a -> 'a event
(** [always v] returns an event that is always ready for
synchronization. The result value of this event is [v]. *)
val choose : 'a event list -> 'a event
(** [choose evl] returns the event that is the alternative of
all the events in the list [evl]. *)
val wrap : 'a event -> ('a -> 'b) -> 'b event
(** [wrap ev fn] returns the event that performs the same communications
as [ev], then applies the post-processing function [fn]
on the return value. *)
val wrap_abort : 'a event -> (unit -> unit) -> 'a event
(** [wrap_abort ev fn] returns the event that performs
the same communications as [ev], but if it is not selected
the function [fn] is called after the synchronization. *)
val guard : (unit -> 'a event) -> 'a event
(** [guard fn] returns the event that, when synchronized, computes
[fn()] and behaves as the resulting event. This allows to
compute events with side-effects at the time of the synchronization
operation. *)
val sync : 'a event -> 'a
(** 'Synchronize' on an event: offer all the communication
possibilities specified in the event to the outside world,
and block until one of the communications succeed. The result
value of that communication is returned. *)
val select : 'a event list -> 'a
(** 'Synchronize' on an alternative of events.
[select evl] is shorthand for [sync(choose evl)]. *)
val poll : 'a event -> 'a option
(** Non-blocking version of {!Event.sync}: offer all the communication
possibilities specified in the event to the outside world,
and if one can take place immediately, perform it and return
[Some r] where [r] is the result value of that communication.
Otherwise, return [None] without blocking. *)
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