ceph/src/boost/boost/atomic/detail/bitwise_cast.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) 2009 Helge Bahmann
   7  * Copyright (c) 2012 Tim Blechmann
   8  * Copyright (c) 2013 - 2018, 2020 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 #include <boost/atomic/detail/header.hpp>
  25
  26 #ifdef BOOST_HAS_PRAGMA_ONCE
  27 #pragma once
  28 #endif
  29
  30 #if defined(BOOST_GCC) && BOOST_GCC >= 80000
  31 #pragma GCC diagnostic push
  32 // copying an object of non-trivial type X from an array of Y. This is benign because we use memcpy to copy trivially copyable objects.
  33 #pragma GCC diagnostic ignored "-Wclass-memaccess"
  34 #endif
  35
  36 namespace boost {
  37 namespace atomics {
  38 namespace detail {
  39
  40 template< std::size_t FromSize, typename To >
  41 BOOST_FORCEINLINE void clear_tail_padding_bits(To& to, atomics::detail::true_type) BOOST_NOEXCEPT
  42 {
  43     BOOST_ATOMIC_DETAIL_MEMSET(reinterpret_cast< unsigned char* >(atomics::detail::addressof(to)) + FromSize, 0, sizeof(To) - FromSize);
  44 }
  45
  46 template< std::size_t FromSize, typename To >
  47 BOOST_FORCEINLINE void clear_tail_padding_bits(To&, atomics::detail::false_type) BOOST_NOEXCEPT
  48 {
  49 }
  50
  51 template< std::size_t FromSize, typename To >
  52 BOOST_FORCEINLINE void clear_tail_padding_bits(To& to) BOOST_NOEXCEPT
  53 {
  54     atomics::detail::clear_tail_padding_bits< FromSize >(to, atomics::detail::integral_constant< bool, FromSize < sizeof(To) >());
  55 }
  56
  57 template< typename To, std::size_t FromSize, typename From >
  58 BOOST_FORCEINLINE To bitwise_cast(From const& from) BOOST_NOEXCEPT
  59 {
  60     To to;
  61     BOOST_ATOMIC_DETAIL_MEMCPY
  62     (
  63         atomics::detail::addressof(to),
  64         atomics::detail::addressof(from),
  65         (FromSize < sizeof(To) ? FromSize : sizeof(To))
  66     );
  67     atomics::detail::clear_tail_padding_bits< FromSize >(to);
  68     return to;
  69 }
  70
  71 template< typename To, typename From >
  72 BOOST_FORCEINLINE To bitwise_cast(From const& from) BOOST_NOEXCEPT
  73 {
  74     return atomics::detail::bitwise_cast< To, sizeof(From) >(from);
  75 }
  76
  77 } // namespace detail
  78 } // namespace atomics
  79 } // namespace boost
  80
  81 #if defined(BOOST_GCC) && BOOST_GCC >= 80000
  82 #pragma GCC diagnostic pop
  83 #endif
  84
  85 #include <boost/atomic/detail/footer.hpp>
  86
  87 #endif // BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_