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-- B o d y -- 8-- -- 9-- Copyright (C) 2011-2013, Free Software Foundation, Inc. -- 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 implements Atomic_Counter operatiobns for platforms where 33-- GCC supports __sync_add_and_fetch_4 and __sync_sub_and_fetch_4 builtins. 34 35package body System.Atomic_Counters is 36 37 procedure Sync_Add_And_Fetch 38 (Ptr : access Unsigned_32; 39 Value : Unsigned_32); 40 pragma Import (Intrinsic, Sync_Add_And_Fetch, "__sync_add_and_fetch_4"); 41 42 function Sync_Sub_And_Fetch 43 (Ptr : access Unsigned_32; 44 Value : Unsigned_32) return Unsigned_32; 45 pragma Import (Intrinsic, Sync_Sub_And_Fetch, "__sync_sub_and_fetch_4"); 46 47 --------------- 48 -- Decrement -- 49 --------------- 50 51 function Decrement (Item : in out Atomic_Counter) return Boolean is 52 begin 53 -- Note: the use of Unrestricted_Access here is required because we 54 -- are obtaining an access-to-volatile pointer to a non-volatile object. 55 -- This is not allowed for [Unchecked_]Access, but is safe in this case 56 -- because we know that no aliases are being created. 57 58 return Sync_Sub_And_Fetch (Item.Value'Unrestricted_Access, 1) = 0; 59 end Decrement; 60 61 --------------- 62 -- Increment -- 63 --------------- 64 65 procedure Increment (Item : in out Atomic_Counter) is 66 begin 67 -- Note: the use of Unrestricted_Access here is required because we are 68 -- obtaining an access-to-volatile pointer to a non-volatile object. 69 -- This is not allowed for [Unchecked_]Access, but is safe in this case 70 -- because we know that no aliases are being created. 71 72 Sync_Add_And_Fetch (Item.Value'Unrestricted_Access, 1); 73 end Increment; 74 75 ---------------- 76 -- Initialize -- 77 ---------------- 78 79 procedure Initialize (Item : out Atomic_Counter) is 80 begin 81 Item.Value := 1; 82 end Initialize; 83 84 ------------ 85 -- Is_One -- 86 ------------ 87 88 function Is_One (Item : Atomic_Counter) return Boolean is 89 begin 90 return Item.Value = 1; 91 end Is_One; 92 93end System.Atomic_Counters; 94