1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--             A D A . S Y N C H R O N O U S _ B A R R I E R S              --
6--                                                                          --
7--                                  B o d y                                 --
8--                                                                          --
9--          Copyright (C) 1992-2011, Free Software Foundation, Inc.         --
10--                                                                          --
11-- This specification is derived from the Ada Reference Manual for use with --
12-- GNAT. The copyright notice above, and the license provisions that follow --
13-- apply solely to the  contents of the part following the private keyword. --
14--                                                                          --
15-- GNAT is free software;  you can  redistribute it  and/or modify it under --
16-- terms of the  GNU General Public License as published  by the Free Soft- --
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20-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
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22-- As a special exception under Section 7 of GPL version 3, you are granted --
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29-- <http://www.gnu.org/licenses/>.                                          --
30--                                                                          --
31-- GNAT was originally developed  by the GNAT team at  New York University. --
32-- Extensive contributions were provided by Ada Core Technologies Inc.      --
33--                                                                          --
34------------------------------------------------------------------------------
35
36package body Ada.Synchronous_Barriers is
37
38   protected body Synchronous_Barrier is
39
40      --  The condition "Wait'Count = Release_Threshold" opens the barrier when
41      --  the required number of tasks is reached. The condition "Keep_Open"
42      --  leaves the barrier open while there are queued tasks. While there are
43      --  tasks in the queue no new task will be queued (no new protected
44      --  action can be started on a protected object while another protected
45      --  action on the same protected object is underway, RM 9.5.1 (4)),
46      --  guaranteeing that the barrier will remain open only for those tasks
47      --  already inside the queue when the barrier was open.
48
49      entry Wait (Notified : out Boolean)
50        when Keep_Open or else Wait'Count = Release_Threshold
51      is
52      begin
53         --  If we are executing the entry it means that the required number of
54         --  tasks have been queued in the entry. Keep_Open barrier will remain
55         --  true until all queued tasks are out.
56
57         Keep_Open := Wait'Count > 0;
58
59         --  The last released task will close the barrier and get the Notified
60         --  token.
61
62         Notified := Wait'Count = 0;
63      end Wait;
64   end Synchronous_Barrier;
65
66   ----------------------
67   -- Wait_For_Release --
68   ----------------------
69
70   procedure Wait_For_Release
71     (The_Barrier : in out Synchronous_Barrier;
72      Notified    : out Boolean)
73   is
74   begin
75      The_Barrier.Wait (Notified);
76   end Wait_For_Release;
77
78end Ada.Synchronous_Barriers;
79