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 - 2014 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 <boost/atomic/detail/config.hpp>
20#if !defined(BOOST_ATOMIC_DETAIL_HAS_BUILTIN_MEMCPY)
21#include <cstring>
22#endif
23
24#ifdef BOOST_HAS_PRAGMA_ONCE
25#pragma once
26#endif
27
28#if defined(BOOST_GCC) && (BOOST_GCC+0) >= 40600
29#pragma GCC diagnostic push
30// missing initializer for member var
31#pragma GCC diagnostic ignored "-Wmissing-field-initializers"
32#endif
33
34namespace boost {
35namespace atomics {
36namespace detail {
37
38template< typename T >
39BOOST_FORCEINLINE T* addressof(T& value) BOOST_NOEXCEPT
40{
41 // Note: The point of using a local struct as the intermediate type instead of char is to avoid gcc warnings
42 // if T is a const volatile char*:
43 // warning: casting 'const volatile char* const' to 'const volatile char&' does not dereference pointer
44 // The local struct makes sure T is not related to the cast target type.
45 struct opaque_type;
46 return reinterpret_cast< T* >(&const_cast< opaque_type& >(reinterpret_cast< const volatile opaque_type& >(value)));
47}
48
49template< typename To, typename From >
50BOOST_FORCEINLINE To bitwise_cast(From const& from) BOOST_NOEXCEPT
51{
52 struct
53 {
54 To to;
55 }
56 value = {};
57 BOOST_ATOMIC_DETAIL_MEMCPY
58 (
59 atomics::detail::addressof(value.to),
60 atomics::detail::addressof(from),
61 (sizeof(From) < sizeof(To) ? sizeof(From) : sizeof(To))
62 );
63 return value.to;
64}
65
66} // namespace detail
67} // namespace atomics
68} // namespace boost
69
70#if defined(BOOST_GCC) && (BOOST_GCC+0) >= 40600
71#pragma GCC diagnostic pop
72#endif
73
74#endif // BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_
75