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 - 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
  34 namespace boost {
  35 namespace atomics {
  36 namespace detail {
  37
  38 template< typename T >
  39 BOOST_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
  49 template< typename To, typename From >
  50 BOOST_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_