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/extending_cas_based_arithmetic.hpp
10  *
11  * This header contains a boilerplate of core atomic operations that require sign/zero extension in arithmetic operations.
12  */
13 
14 #ifndef BOOST_ATOMIC_DETAIL_EXTENDING_CAS_BASED_ARITHMETIC_HPP_INCLUDED_
15 #define BOOST_ATOMIC_DETAIL_EXTENDING_CAS_BASED_ARITHMETIC_HPP_INCLUDED_
16 
17 #include <cstddef>
18 #include <boost/memory_order.hpp>
19 #include <boost/atomic/detail/config.hpp>
20 #include <boost/atomic/detail/storage_traits.hpp>
21 #include <boost/atomic/detail/integral_conversions.hpp>
22 #include <boost/atomic/detail/header.hpp>
23 
24 #ifdef BOOST_HAS_PRAGMA_ONCE
25 #pragma once
26 #endif
27 
28 namespace boost {
29 namespace atomics {
30 namespace detail {
31 
32 template< typename Base, std::size_t Size, bool Signed >
33 struct extending_cas_based_arithmetic :
34     public Base
35 {
36     typedef typename Base::storage_type storage_type;
37     typedef typename storage_traits< Size >::type emulated_storage_type;
38 
fetch_addboost::atomics::detail::extending_cas_based_arithmetic39     static BOOST_FORCEINLINE storage_type fetch_add(storage_type volatile& storage, storage_type v, memory_order order) BOOST_NOEXCEPT
40     {
41         storage_type old_val;
42         atomics::detail::non_atomic_load(storage, old_val);
43         storage_type new_val;
44         do
45         {
46             new_val = atomics::detail::integral_extend< Signed, storage_type >(static_cast< emulated_storage_type >(old_val + v));
47         }
48         while (!Base::compare_exchange_weak(storage, old_val, new_val, order, memory_order_relaxed));
49         return old_val;
50     }
51 
fetch_subboost::atomics::detail::extending_cas_based_arithmetic52     static BOOST_FORCEINLINE storage_type fetch_sub(storage_type volatile& storage, storage_type v, memory_order order) BOOST_NOEXCEPT
53     {
54         storage_type old_val;
55         atomics::detail::non_atomic_load(storage, old_val);
56         storage_type new_val;
57         do
58         {
59             new_val = atomics::detail::integral_extend< Signed, storage_type >(static_cast< emulated_storage_type >(old_val - v));
60         }
61         while (!Base::compare_exchange_weak(storage, old_val, new_val, order, memory_order_relaxed));
62         return old_val;
63     }
64 };
65 
66 } // namespace detail
67 } // namespace atomics
68 } // namespace boost
69 
70 #include <boost/atomic/detail/footer.hpp>
71 
72 #endif // BOOST_ATOMIC_DETAIL_EXTENDING_CAS_BASED_ARITHMETIC_HPP_INCLUDED_
73