1 #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED 2 #define BOOST_MEMORY_ORDER_HPP_INCLUDED 3 4 // MS compatible compilers support #pragma once 5 6 #if defined(_MSC_VER) && (_MSC_VER >= 1020) 7 # pragma once 8 #endif 9 10 // boost/memory_order.hpp 11 // 12 // Defines enum boost::memory_order per the C++0x working draft 13 // 14 // Copyright (c) 2008, 2009 Peter Dimov 15 // 16 // Distributed under the Boost Software License, Version 1.0. 17 // See accompanying file LICENSE_1_0.txt or copy at 18 // http://www.boost.org/LICENSE_1_0.txt) 19 20 21 namespace boost 22 { 23 24 // 25 // Enum values are chosen so that code that needs to insert 26 // a trailing fence for acquire semantics can use a single 27 // test such as: 28 // 29 // if( mo & memory_order_acquire ) { ...fence... } 30 // 31 // For leading fences one can use: 32 // 33 // if( mo & memory_order_release ) { ...fence... } 34 // 35 // Architectures such as Alpha that need a fence on consume 36 // can use: 37 // 38 // if( mo & ( memory_order_acquire | memory_order_consume ) ) { ...fence... } 39 // 40 // The values are also in the order of increasing "strength" 41 // of the fences so that success/failure orders can be checked 42 // efficiently in compare_exchange methods. 43 // 44 45 enum memory_order 46 { 47 memory_order_relaxed = 0, 48 memory_order_consume = 1, 49 memory_order_acquire = 2, 50 memory_order_release = 4, 51 memory_order_acq_rel = 6, // acquire | release 52 memory_order_seq_cst = 14 // acq_rel | 8 53 }; 54 55 } // namespace boost 56 57 #endif // #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED 58