| ------------------------------------------------------------------------------ |
| -- -- |
| -- 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) 2011-2022, 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 -- |
| -- <http://www.gnu.org/licenses/>. -- |
| -- -- |
| -- 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 AARCH64 platforms |
| -- - all ARM platforms |
| -- - all ia64 platforms |
| -- - all PowerPC platforms |
| -- - all SPARC V9 platforms |
| -- - all x86 platforms |
| -- - all x86_64 platforms |
| |
| package System.Atomic_Counters is |
| |
| pragma Pure; |
| 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. |
| -- Increment/Decrement operations for this type raise Program_Error on |
| -- platforms not supporting the atomic primitives. |
| |
| 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 the counter object cannot be |
| -- initialized in standard way. |
| |
| type Atomic_Unsigned is mod 2 ** 32 with Default_Value => 0, Atomic; |
| -- Modular compatible atomic unsigned type. |
| -- Increment/Decrement operations for this type are atomic only on |
| -- supported platforms. See top of the file. |
| |
| procedure Increment |
| (Item : aliased in out Atomic_Unsigned) with Inline_Always; |
| -- Increments value of atomic counter |
| |
| function Decrement |
| (Item : aliased in out Atomic_Unsigned) return Boolean with Inline_Always; |
| |
| procedure Decrement |
| (Item : aliased in out Atomic_Unsigned) with Inline_Always; |
| -- Decrements value of atomic counter |
| |
| -- The "+" and "-" abstract routine provided below to disable BT := BT + 1 |
| -- constructions. |
| |
| function "+" |
| (Left, Right : Atomic_Unsigned) return Atomic_Unsigned is abstract; |
| |
| function "-" |
| (Left, Right : Atomic_Unsigned) return Atomic_Unsigned is abstract; |
| |
| private |
| |
| type Atomic_Counter is record |
| Value : aliased Atomic_Unsigned := 1; |
| end record; |
| |
| end System.Atomic_Counters; |
