------------------------------------------------------------------------------ -- -- -- 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;