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- #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED
- #define BOOST_MEMORY_ORDER_HPP_INCLUDED
- // MS compatible compilers support #pragma once
- #if defined(_MSC_VER) && (_MSC_VER >= 1020)
- # pragma once
- #endif
- // boost/memory_order.hpp
- //
- // Defines enum boost::memory_order per the C++0x working draft
- //
- // Copyright (c) 2008, 2009 Peter Dimov
- //
- // Distributed under the Boost Software License, Version 1.0.
- // See accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- namespace boost
- {
- //
- // Enum values are chosen so that code that needs to insert
- // a trailing fence for acquire semantics can use a single
- // test such as:
- //
- // if( mo & memory_order_acquire ) { ...fence... }
- //
- // For leading fences one can use:
- //
- // if( mo & memory_order_release ) { ...fence... }
- //
- // Architectures such as Alpha that need a fence on consume
- // can use:
- //
- // if( mo & ( memory_order_acquire | memory_order_consume ) ) { ...fence... }
- //
- // The values are also in the order of increasing "strength"
- // of the fences so that success/failure orders can be checked
- // efficiently in compare_exchange methods.
- //
- enum memory_order
- {
- memory_order_relaxed = 0,
- memory_order_consume = 1,
- memory_order_acquire = 2,
- memory_order_release = 4,
- memory_order_acq_rel = 6, // acquire | release
- memory_order_seq_cst = 14 // acq_rel | 8
- };
- } // namespace boost
- #endif // #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED
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