1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME COMPONENTS -- 4-- -- 5-- S Y S T E M . A T O M I C _ P R I M I T I V E S -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 2012-2021, 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 32package body System.Atomic_Primitives is 33 34 -------------------- 35 -- Lock_Free_Read -- 36 -------------------- 37 38 function Lock_Free_Read (Ptr : Address) return Atomic_Type is 39 function My_Atomic_Load is new Atomic_Load (Atomic_Type); 40 41 begin 42 if Atomic_Type'Atomic_Always_Lock_Free then 43 return My_Atomic_Load (Ptr, Acquire); 44 else 45 raise Program_Error; 46 end if; 47 end Lock_Free_Read; 48 49 ------------------------- 50 -- Lock_Free_Try_Write -- 51 ------------------------- 52 53 function Lock_Free_Try_Write 54 (Ptr : Address; 55 Expected : in out Atomic_Type; 56 Desired : Atomic_Type) return Boolean 57 is 58 function My_Sync_Compare_And_Swap is 59 new Sync_Compare_And_Swap (Atomic_Type); 60 61 Actual : Atomic_Type; 62 63 begin 64 if Expected /= Desired then 65 if Atomic_Type'Atomic_Always_Lock_Free then 66 Actual := My_Sync_Compare_And_Swap (Ptr, Expected, Desired); 67 else 68 raise Program_Error; 69 end if; 70 71 if Actual /= Expected then 72 Expected := Actual; 73 return False; 74 end if; 75 end if; 76 77 return True; 78 end Lock_Free_Try_Write; 79 80end System.Atomic_Primitives; 81