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|
(**************************************************************************)
(* *)
(* OCaml *)
(* *)
(* Xavier Leroy, Collège de France and INRIA Paris *)
(* *)
(* Copyright 2020 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. *)
(* *)
(**************************************************************************)
(** Semaphores *)
type sem = {
mut: Mutex.t; (* protects [v] *)
mutable v: int; (* the current value *)
nonzero: Condition.t (* signaled when [v > 0] *)
}
module Counting = struct
type t = sem
let make v =
if v < 0 then invalid_arg "Semaphore.Counting.init: wrong initial value";
{ mut = Mutex.create(); v; nonzero = Condition.create() }
let release s =
Mutex.lock s.mut;
if s.v < max_int then begin
s.v <- s.v + 1;
Condition.signal s.nonzero;
Mutex.unlock s.mut
end else begin
Mutex.unlock s.mut;
raise (Sys_error "Semaphore.Counting.release: overflow")
end
let acquire s =
Mutex.lock s.mut;
while s.v = 0 do Condition.wait s.nonzero s.mut done;
s.v <- s.v - 1;
Mutex.unlock s.mut
let try_acquire s =
Mutex.lock s.mut;
let ret = if s.v = 0 then false else (s.v <- s.v - 1; true) in
Mutex.unlock s.mut;
ret
let get_value s = s.v
end
module Binary = struct
type t = sem
let make b =
{ mut = Mutex.create();
v = if b then 1 else 0;
nonzero = Condition.create() }
let release s =
Mutex.lock s.mut;
s.v <- 1;
Condition.signal s.nonzero;
Mutex.unlock s.mut
let acquire s =
Mutex.lock s.mut;
while s.v = 0 do Condition.wait s.nonzero s.mut done;
s.v <- 0;
Mutex.unlock s.mut
let try_acquire s =
Mutex.lock s.mut;
let ret = if s.v = 0 then false else (s.v <- 0; true) in
Mutex.unlock s.mut;
ret
end
|
