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------------------------------------------------------------------------------
-- --
-- GNAT RUNTIME COMPONENTS --
-- --
-- A D A . S Y N C H R O N O U S _ T A S K _ C O N T R O L --
-- --
-- B o d y --
-- --
-- --
-- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Interfaces.C;
package body Ada.Synchronous_Task_Control is
use System.OS_Interface;
use type Interfaces.C.int;
-------------------
-- Current_State --
-------------------
function Current_State (S : Suspension_Object) return Boolean is
St : STATUS;
Result : Boolean := False;
begin
-- Determine state by attempting to take the semaphore with
-- a 0 timeout value. Status = OK indicates the semaphore was
-- full, so reset it to the full state.
St := semTake (S.Sema, NO_WAIT);
if St = OK then
-- Took the semaphore. Reset semaphore state to FULL
Result := True;
St := semGive (S.Sema);
end if;
return Result;
end Current_State;
---------------
-- Set_False --
---------------
procedure Set_False (S : in out Suspension_Object) is
St : STATUS;
begin
-- Need to get the semaphore into the "empty" state.
-- On return, this task will have made the semaphore
-- empty (St = OK) or have left it empty.
St := semTake (S.Sema, NO_WAIT);
end Set_False;
--------------
-- Set_True --
--------------
procedure Set_True (S : in out Suspension_Object) is
St : STATUS;
begin
St := semGive (S.Sema);
end Set_True;
------------------------
-- Suspend_Until_True --
------------------------
procedure Suspend_Until_True (S : in out Suspension_Object) is
St : STATUS;
-- Declare local exception so the mutex can still be reset
-- to full if Program_Error is raised
Task_Already_Pending : exception;
begin
-- Determine whether another task is pending on the suspension
-- object. Should never be called from an ISR. Therefore semTake can
-- be called on the mutex
St := semTake (S.Mutex, NO_WAIT);
if St = OK then
-- Wait for suspension object
St := semTake (S.Sema, WAIT_FOREVER);
St := semGive (S.Mutex);
else
-- Another task is pending on the suspension object
raise Task_Already_Pending;
end if;
exception
when Task_Already_Pending =>
raise Program_Error;
when others =>
St := semGive (S.Mutex);
raise;
end Suspend_Until_True;
procedure Initialize (S : in out Suspension_Object) is
begin
S.Sema := semBCreate (SEM_Q_FIFO, SEM_EMPTY);
-- Use simpler binary semaphore instead of VxWorks
-- mutual exclusion semaphore, because we don't need
-- the fancier semantics and their overhead.
S.Mutex := semBCreate (SEM_Q_FIFO, SEM_FULL);
end Initialize;
procedure Finalize (S : in out Suspension_Object) is
St : STATUS;
begin
St := semDelete (S.Sema);
St := semDelete (S.Mutex);
end Finalize;
end Ada.Synchronous_Task_Control;
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