From 205d47e81d70adb1707136eda6630d15b55ef86f Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Tue, 19 Mar 2013 14:35:19 +0100
Subject: [PATCH] interface for preemptive threading Futures

---
 futures.mli | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 futures.mli

diff --git a/futures.mli b/futures.mli
new file mode 100644
index 00000000..80d66659
--- /dev/null
+++ b/futures.mli
@@ -0,0 +1,90 @@
+(*
+Copyright (c) 2013, Simon Cruanes
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  Redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+(** {1 Futures for concurrency} *)
+
+type 'a t
+  (** A future value of type 'a *)
+
+exception SendTwice
+  (** Exception raised when a future is evaluated several time *)
+
+(** {2 Thread pool} *)
+module Pool : sig
+  type t
+    (** A pool of threads *)
+
+  val create : size:int -> t
+    (** Create a pool with the given number of threads. *)
+
+  val schedule : t -> (unit -> unit) -> unit
+    (** Schedule a function to run in the pool *)
+
+  val finish : t -> unit
+    (** Kill threads in the pool *)
+end
+
+val default_pool : Pool.t
+  (** Pool of threads that is used by default *)
+
+(** {2 Basic Future functions} *)
+
+val make : ?pool:Pool.t -> unit -> 'a t
+  (** Create a future, representing a value that is not known yet.
+      A thread pool to run the future in can be provided, otherwise
+      a thread is spawned. *)
+
+val get : 'a t -> 'a
+  (** Blocking get: wait for the future to be evaluated, and get the value,
+      or the exception that failed the future is returned *)
+
+val send : 'a t -> 'a -> unit
+  (** Send a result to the future. Will raise SendTwice if [send] has
+      already been called on this future before *)
+
+val fail : 'a t -> exn -> unit
+  (** Fail the future by raising an exception inside it *)
+
+(** {2 Combinators *)
+
+val flatMap : ?pool:Pool.t -> ('a -> 'b t) -> 'a t -> 'b t
+  (** Monadic combination of futures *)
+
+(** {2 Useful futures} *)
+
+val return : 'a -> 'a t
+  (** Future that is already computed *)
+
+val spawn : ?pool:Pool.t -> (unit -> 'a) -> 'a t
+  (** Spawn a thread that wraps the given computation *)
+
+val spawn_process : ?pool:Pool.t -> ?stdin:string -> cmd:string ->
+                    (int * string * string) t
+  (** Spawn a sub-process with the given command [cmd] (and possibly input);
+      returns a future containing (returncode, stdout, stderr) *)
+
+module Infix : sig
+  val (>>=) : 'a t -> ('a -> 'b t) -> 'b t
+end