------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- S Y S T E M . A T O M I C _ C O U N T E R S -- -- -- -- S p e c -- -- -- -- Copyright (C) 2011-2013, 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 3, 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. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This package provides atomic counter on platforms where it is supported: -- - all Alpha platforms -- - all ia64 platforms -- - all PowerPC platforms -- - all SPARC V9 platforms -- - all x86 platforms -- - all x86_64 platforms -- Why isn't this package available to application programs??? package System.Atomic_Counters is pragma Preelaborate; type Atomic_Counter is limited private; -- Type for atomic counter objects. Note, initial value of the counter is -- one. This allows using an atomic counter as member of record types when -- object of these types are created at library level in preelaborable -- compilation units. -- -- Atomic_Counter is declared as private limited type to provide highest -- level of protection from unexpected use. All available operations are -- declared below, and this set should be as small as possible. procedure Increment (Item : in out Atomic_Counter); pragma Inline_Always (Increment); -- Increments value of atomic counter. function Decrement (Item : in out Atomic_Counter) return Boolean; pragma Inline_Always (Decrement); -- Decrements value of atomic counter, returns True when value reach zero. function Is_One (Item : Atomic_Counter) return Boolean; pragma Inline_Always (Is_One); -- Returns True when value of the atomic counter is one. procedure Initialize (Item : out Atomic_Counter); pragma Inline_Always (Initialize); -- Initialize counter by setting its value to one. This subprogram is -- intended to be used in special cases when counter object can't be -- initialized in standard way. private type Unsigned_32 is mod 2 ** 32; type Atomic_Counter is limited record Value : aliased Unsigned_32 := 1; pragma Atomic (Value); end record; end System.Atomic_Counters;