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/ops_extending_cas_based.hpp
10  *
11  * This header contains a boilerplate of the \c operations template implementation that requires sign/zero extension in arithmetic operations.
12  */
13 
14 #ifndef BOOST_ATOMIC_DETAIL_OPS_EXTENDING_CAS_BASED_HPP_INCLUDED_
15 #define BOOST_ATOMIC_DETAIL_OPS_EXTENDING_CAS_BASED_HPP_INCLUDED_
16 
17 #include <boost/memory_order.hpp>
18 #include <boost/atomic/detail/config.hpp>
19 #include <boost/atomic/detail/storage_type.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, unsigned int Size, bool Signed >
30 struct extending_cas_based_operations :
31     public Base
32 {
33     typedef typename Base::storage_type storage_type;
34     typedef typename make_storage_type< Size, Signed >::type emulated_storage_type;
35 
fetch_addboost::atomics::detail::extending_cas_based_operations36     static BOOST_FORCEINLINE storage_type fetch_add(storage_type volatile& storage, storage_type v, memory_order order) BOOST_NOEXCEPT
37     {
38         storage_type old_val = Base::load(storage, memory_order_relaxed);
39         emulated_storage_type new_val;
40         do
41         {
42             new_val = static_cast< emulated_storage_type >(old_val) + static_cast< emulated_storage_type >(v);
43         }
44         while (!Base::compare_exchange_weak(storage, old_val, static_cast< storage_type >(new_val), order, memory_order_relaxed));
45         return old_val;
46     }
47 
fetch_subboost::atomics::detail::extending_cas_based_operations48     static BOOST_FORCEINLINE storage_type fetch_sub(storage_type volatile& storage, storage_type v, memory_order order) BOOST_NOEXCEPT
49     {
50         storage_type old_val = Base::load(storage, memory_order_relaxed);
51         emulated_storage_type new_val;
52         do
53         {
54             new_val = static_cast< emulated_storage_type >(old_val) - static_cast< emulated_storage_type >(v);
55         }
56         while (!Base::compare_exchange_weak(storage, old_val, static_cast< storage_type >(new_val), order, memory_order_relaxed));
57         return old_val;
58     }
59 };
60 
61 } // namespace detail
62 } // namespace atomics
63 } // namespace boost
64 
65 #endif // BOOST_ATOMIC_DETAIL_OPS_EXTENDING_CAS_BASED_HPP_INCLUDED_
66