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) 2009 Helge Bahmann
7 * Copyright (c) 2012 Tim Blechmann
8 * Copyright (c) 2013 - 2018 Andrey Semashev
9 */
10 /*!
11 * \file atomic/detail/bitwise_cast.hpp
12 *
13 * This header defines \c bitwise_cast used to convert between storage and value types
14 */
15
16 #ifndef BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_
17 #define BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_
18
19 #include <cstddef>
20 #include <boost/atomic/detail/config.hpp>
21 #include <boost/atomic/detail/addressof.hpp>
22 #include <boost/atomic/detail/string_ops.hpp>
23 #include <boost/atomic/detail/type_traits/integral_constant.hpp>
24
25 #ifdef BOOST_HAS_PRAGMA_ONCE
26 #pragma once
27 #endif
28
29 namespace boost {
30 namespace atomics {
31 namespace detail {
32
33 template< std::size_t FromSize, typename To >
clear_padding(To & to,atomics::detail::true_type)34 BOOST_FORCEINLINE void clear_padding(To& to, atomics::detail::true_type) BOOST_NOEXCEPT
35 {
36 BOOST_ATOMIC_DETAIL_MEMSET(reinterpret_cast< unsigned char* >(atomics::detail::addressof(to)) + FromSize, 0, sizeof(To) - FromSize);
37 }
38
39 template< std::size_t FromSize, typename To >
clear_padding(To &,atomics::detail::false_type)40 BOOST_FORCEINLINE void clear_padding(To&, atomics::detail::false_type) BOOST_NOEXCEPT
41 {
42 }
43
44 template< typename To, std::size_t FromSize, typename From >
bitwise_cast(From const & from)45 BOOST_FORCEINLINE To bitwise_cast(From const& from) BOOST_NOEXCEPT
46 {
47 To to;
48 BOOST_ATOMIC_DETAIL_MEMCPY
49 (
50 atomics::detail::addressof(to),
51 atomics::detail::addressof(from),
52 (FromSize < sizeof(To) ? FromSize : sizeof(To))
53 );
54 atomics::detail::clear_padding< FromSize >(to, atomics::detail::integral_constant< bool, FromSize < sizeof(To) >());
55 return to;
56 }
57
58 template< typename To, typename From >
bitwise_cast(From const & from)59 BOOST_FORCEINLINE To bitwise_cast(From const& from) BOOST_NOEXCEPT
60 {
61 return atomics::detail::bitwise_cast< To, sizeof(From) >(from);
62 }
63
64 } // namespace detail
65 } // namespace atomics
66 } // namespace boost
67
68 #endif // BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_
69