------------------------------------------------------------------------------
--                                                                          --
--                         GNAT RUN-TIME COMPONENTS                         --
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--             A D A . S Y N C H R O N O U S _ B A R R I E R S              --
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--                                  B o d y                                 --
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--          Copyright (C) 1992-2019, Free Software Foundation, Inc.         --
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-- This specification is derived from the Ada Reference Manual for use with --
-- GNAT. The copyright notice above, and the license provisions that follow --
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------------------------------------------------------------------------------

package body Ada.Synchronous_Barriers is

   protected body Synchronous_Barrier is

      --  The condition "Wait'Count = Release_Threshold" opens the barrier when
      --  the required number of tasks is reached. The condition "Keep_Open"
      --  leaves the barrier open while there are queued tasks. While there are
      --  tasks in the queue no new task will be queued (no new protected
      --  action can be started on a protected object while another protected
      --  action on the same protected object is underway, RM 9.5.1 (4)),
      --  guaranteeing that the barrier will remain open only for those tasks
      --  already inside the queue when the barrier was open.

      entry Wait (Notified : out Boolean)
        when Keep_Open or else Wait'Count = Release_Threshold
      is
      begin
         --  If we are executing the entry it means that the required number of
         --  tasks have been queued in the entry. Keep_Open barrier will remain
         --  true until all queued tasks are out.

         Keep_Open := Wait'Count > 0;

         --  The last released task will close the barrier and get the Notified
         --  token.

         Notified := Wait'Count = 0;
      end Wait;
   end Synchronous_Barrier;

   ----------------------
   -- Wait_For_Release --
   ----------------------

   procedure Wait_For_Release
     (The_Barrier : in out Synchronous_Barrier;
      Notified    : out Boolean)
   is
   begin
      The_Barrier.Wait (Notified);
   end Wait_For_Release;

end Ada.Synchronous_Barriers;
