| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUN-TIME COMPONENTS -- |
| -- -- |
| -- S Y S T E M . A T O M I C _ C O U N T E R S -- |
| -- -- |
| -- B o d y -- |
| -- -- |
| -- 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 -- |
| -- <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 implements Atomic_Counter operatiobns for platforms where |
| -- GCC supports __sync_add_and_fetch_4 and __sync_sub_and_fetch_4 builtins. |
| |
| package body System.Atomic_Counters is |
| |
| procedure Sync_Add_And_Fetch |
| (Ptr : access Unsigned_32; |
| Value : Unsigned_32); |
| pragma Import (Intrinsic, Sync_Add_And_Fetch, "__sync_add_and_fetch_4"); |
| |
| function Sync_Sub_And_Fetch |
| (Ptr : access Unsigned_32; |
| Value : Unsigned_32) return Unsigned_32; |
| pragma Import (Intrinsic, Sync_Sub_And_Fetch, "__sync_sub_and_fetch_4"); |
| |
| --------------- |
| -- Decrement -- |
| --------------- |
| |
| function Decrement (Item : in out Atomic_Counter) return Boolean is |
| begin |
| -- Note: the use of Unrestricted_Access here is required because we |
| -- are obtaining an access-to-volatile pointer to a non-volatile object. |
| -- This is not allowed for [Unchecked_]Access, but is safe in this case |
| -- because we know that no aliases are being created. |
| |
| return Sync_Sub_And_Fetch (Item.Value'Unrestricted_Access, 1) = 0; |
| end Decrement; |
| |
| --------------- |
| -- Increment -- |
| --------------- |
| |
| procedure Increment (Item : in out Atomic_Counter) is |
| begin |
| -- Note: the use of Unrestricted_Access here is required because we are |
| -- obtaining an access-to-volatile pointer to a non-volatile object. |
| -- This is not allowed for [Unchecked_]Access, but is safe in this case |
| -- because we know that no aliases are being created. |
| |
| Sync_Add_And_Fetch (Item.Value'Unrestricted_Access, 1); |
| end Increment; |
| |
| ---------------- |
| -- Initialize -- |
| ---------------- |
| |
| procedure Initialize (Item : out Atomic_Counter) is |
| begin |
| Item.Value := 1; |
| end Initialize; |
| |
| ------------ |
| -- Is_One -- |
| ------------ |
| |
| function Is_One (Item : Atomic_Counter) return Boolean is |
| begin |
| return Item.Value = 1; |
| end Is_One; |
| |
| end System.Atomic_Counters; |
