ceph/src/boost/boost/atomic/detail/cas_based_exchange.hpp

   1 /*
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * Copyright (c) 2014 Andrey Semashev
   7  */
   8 /*!
   9  * \file   atomic/detail/cas_based_exchange.hpp
  10  *
  11  * This header contains CAS-based implementation of exchange operation.
  12  */
  13
  14 #ifndef BOOST_ATOMIC_DETAIL_CAS_BASED_EXCHANGE_HPP_INCLUDED_
  15 #define BOOST_ATOMIC_DETAIL_CAS_BASED_EXCHANGE_HPP_INCLUDED_
  16
  17 #include <boost/memory_order.hpp>
  18 #include <boost/atomic/detail/config.hpp>
  19 #include <boost/atomic/detail/header.hpp>
  20
  21 #ifdef BOOST_HAS_PRAGMA_ONCE
  22 #pragma once
  23 #endif
  24
  25 namespace boost {
  26 namespace atomics {
  27 namespace detail {
  28
  29 template< typename Base >
  30 struct cas_based_exchange :
  31     public Base
  32 {
  33     typedef typename Base::storage_type storage_type;
  34
  35     static BOOST_FORCEINLINE storage_type exchange(storage_type volatile& storage, storage_type v, memory_order order) BOOST_NOEXCEPT
  36     {
  37         storage_type old_val;
  38         atomics::detail::non_atomic_load(storage, old_val);
  39         while (!Base::compare_exchange_weak(storage, old_val, v, order, memory_order_relaxed)) {}
  40         return old_val;
  41     }
  42 };
  43
  44 } // namespace detail
  45 } // namespace atomics
  46 } // namespace boost
  47
  48 #include <boost/atomic/detail/footer.hpp>
  49
  50 #endif // BOOST_ATOMIC_DETAIL_CAS_BASED_EXCHANGE_HPP_INCLUDED_