------------------------------------------------------------------------------ -- -- -- GNAT LIBRARY COMPONENTS -- -- -- -- G N A T . S E M A P H O R E S -- -- -- -- S p e c -- -- -- -- Copyright (C) 2003-2005, AdaCore -- -- -- -- 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, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, 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. -- -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- -- -- ------------------------------------------------------------------------------ -- This package provides classic counting semaphores and binary semaphores. -- Both types are visibly defined as protected types so that users can make -- conditional and timed calls when appropriate. with System; package GNAT.Semaphores is Default_Ceiling : constant System.Priority := System.Default_Priority; -- A convenient value for the priority discriminants that follow ------------------------ -- Counting_Semaphore -- ------------------------ protected type Counting_Semaphore (Initial_Value : Natural; -- A counting semaphore contains an internal counter. The initial -- value of this counter is set by clients via the discriminant. Ceiling : System.Priority) -- Users must specify the ceiling priority for the object. If the -- Real-Time Systems Annex is not in use this value is not important. is pragma Priority (Ceiling); entry Seize; -- Blocks caller until/unless the semaphore's internal counter is -- greater than zero. Decrements the semaphore's internal counter when -- executed. procedure Release; -- Increments the semaphore's internal counter private Count : Natural := Initial_Value; end Counting_Semaphore; ---------------------- -- Binary_Semaphore -- ---------------------- protected type Binary_Semaphore (Initially_Available : Boolean; -- Binary semaphores are either available or not; there is no internal -- count involved. The discriminant value determines whether the -- individual object is initially available. Ceiling : System.Priority) -- Users must specify the ceiling priority for the object. If the -- Real-Time Systems Annex is not in use this value is not important. is pragma Priority (Ceiling); entry Seize; -- Blocks the caller unless/until semaphore is available. After -- execution the semaphore is no longer available. procedure Release; -- Makes the semaphore available private Available : Boolean := Initially_Available; end Binary_Semaphore; end GNAT.Semaphores;