------------------------------------------------------------------------------ -- -- -- 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) 2011-2019, 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 implements Atomic_Counter and Atomic_Unsigned operations -- 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 Atomic_Unsigned; Value : Atomic_Unsigned); pragma Import (Intrinsic, Sync_Add_And_Fetch, "__sync_add_and_fetch_4"); function Sync_Sub_And_Fetch (Ptr : access Atomic_Unsigned; Value : Atomic_Unsigned) return Atomic_Unsigned; pragma Import (Intrinsic, Sync_Sub_And_Fetch, "__sync_sub_and_fetch_4"); --------------- -- Decrement -- --------------- procedure Decrement (Item : aliased in out Atomic_Unsigned) is begin if Sync_Sub_And_Fetch (Item'Unrestricted_Access, 1) = 0 then null; end if; end Decrement; function Decrement (Item : aliased in out Atomic_Unsigned) return Boolean is begin return Sync_Sub_And_Fetch (Item'Unrestricted_Access, 1) = 0; end 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 : aliased in out Atomic_Unsigned) is begin Sync_Add_And_Fetch (Item'Unrestricted_Access, 1); end 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;