------------------------------------------------------------------------------
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------------------------------------------------------------------------------

--  This is the body of this package using POSIX barriers

with Interfaces.C; use Interfaces.C;

package body Ada.Synchronous_Barriers is

   --------------------
   -- POSIX barriers --
   --------------------

   function pthread_barrier_init
     (barrier : not null access pthread_barrier_t;
      attr    : System.Address := System.Null_Address;
      count   : unsigned) return int;
   pragma Import (C, pthread_barrier_init, "pthread_barrier_init");
   --  Initialize barrier with the attributes in attr. The barrier is opened
   --  when count waiters arrived. If attr is null the default barrier
   --  attributes shall be used.

   function pthread_barrier_destroy
     (barrier : not null access pthread_barrier_t) return int;
   pragma Import (C, pthread_barrier_destroy, "pthread_barrier_destroy");
   --  Destroy a previously dynamically initialized barrier

   function pthread_barrier_wait
     (barrier : not null access pthread_barrier_t) return int;
   pragma Import (C, pthread_barrier_wait, "pthread_barrier_wait");
   --  Wait on barrier

   --------------
   -- Finalize --
   --------------

   overriding procedure Finalize (Barrier : in out Synchronous_Barrier) is
      Result : int;
   begin
      Result := pthread_barrier_destroy (Barrier.POSIX_Barrier'Access);
      pragma Assert (Result = 0);
   end Finalize;

   overriding procedure Initialize (Barrier : in out Synchronous_Barrier) is
      Result : int;
   begin
      Result := pthread_barrier_init
        (barrier => Barrier.POSIX_Barrier'Access,
         attr    => System.Null_Address,
         count   => unsigned (Barrier.Release_Threshold));
      pragma Assert (Result = 0);
   end Initialize;

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

   procedure Wait_For_Release
     (The_Barrier : in out Synchronous_Barrier;
      Notified    : out Boolean)
   is
      Result : int;

      PTHREAD_BARRIER_SERIAL_THREAD : constant := -1;
      --  Value used to indicate the task which receives the notification for
      --  the barrier open.

   begin
      Result := pthread_barrier_wait
        (barrier => The_Barrier.POSIX_Barrier'Access);
      pragma Assert
        (Result = 0 or else Result = PTHREAD_BARRIER_SERIAL_THREAD);

      Notified := (Result = PTHREAD_BARRIER_SERIAL_THREAD);
   end Wait_For_Release;

end Ada.Synchronous_Barriers;
