1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME COMPONENTS -- 4-- -- 5-- S Y S T E M . A T O M I C _ C O U N T E R S -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 2011, AdaCore -- 10-- -- 11-- GNAT is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 3, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. -- 17-- -- 18-- As a special exception under Section 7 of GPL version 3, you are granted -- 19-- additional permissions described in the GCC Runtime Library Exception, -- 20-- version 3.1, as published by the Free Software Foundation. -- 21-- -- 22-- You should have received a copy of the GNU General Public License and -- 23-- a copy of the GCC Runtime Library Exception along with this program; -- 24-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- 25-- <http://www.gnu.org/licenses/>. -- 26-- -- 27-- GNAT was originally developed by the GNAT team at New York University. -- 28-- Extensive contributions were provided by Ada Core Technologies Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This package provides atomic counter on platforms where it is supported: 33-- - all Alpha platforms 34-- - all ia64 platforms 35-- - all PowerPC platforms 36-- - all SPARC V9 platforms 37-- - all x86 platforms 38-- - all x86_64 platforms 39 40-- Why isn't this package available to application programs??? 41 42package System.Atomic_Counters is 43 44 pragma Preelaborate; 45 46 type Atomic_Counter is limited private; 47 -- Type for atomic counter objects. Note, initial value of the counter is 48 -- one. This allows using an atomic counter as member of record types when 49 -- object of these types are created at library level in preelaborable 50 -- compilation units. 51 -- 52 -- Atomic_Counter is declared as private limited type to provide highest 53 -- level of protection from unexpected use. All available operations are 54 -- declared below, and this set should be as small as possible. 55 56 procedure Increment (Item : in out Atomic_Counter); 57 pragma Inline_Always (Increment); 58 -- Increments value of atomic counter. 59 60 function Decrement (Item : in out Atomic_Counter) return Boolean; 61 pragma Inline_Always (Decrement); 62 -- Decrements value of atomic counter, returns True when value reach zero. 63 64 function Is_One (Item : Atomic_Counter) return Boolean; 65 pragma Inline_Always (Is_One); 66 -- Returns True when value of the atomic counter is one. 67 68private 69 70 type Unsigned_32 is mod 2 ** 32; 71 72 type Atomic_Counter is limited record 73 Value : aliased Unsigned_32 := 1; 74 pragma Atomic (Value); 75 end record; 76 77end System.Atomic_Counters; 78