ceph/src/boost/boost/beast/core/detail/type_traits.hpp

   1 //
   2 // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // Official repository: https://github.com/boostorg/beast
   8 //
   9
  10 #ifndef BOOST_BEAST_DETAIL_TYPE_TRAITS_HPP
  11 #define BOOST_BEAST_DETAIL_TYPE_TRAITS_HPP
  12
  13 #include <boost/type_traits/make_void.hpp>
  14 #include <type_traits>
  15 #include <new>
  16
  17 namespace boost {
  18 namespace beast {
  19 namespace detail {
  20
  21 template<class U>
  22 std::size_t constexpr
  23 max_sizeof()
  24 {
  25     return sizeof(U);
  26 }
  27
  28 template<class U0, class U1, class... Us>
  29 std::size_t constexpr
  30 max_sizeof()
  31 {
  32     return
  33         max_sizeof<U0>() > max_sizeof<U1, Us...>() ?
  34         max_sizeof<U0>() : max_sizeof<U1, Us...>();
  35 }
  36
  37 template<class U>
  38 std::size_t constexpr
  39 max_alignof()
  40 {
  41     return alignof(U);
  42 }
  43
  44 template<class U0, class U1, class... Us>
  45 std::size_t constexpr
  46 max_alignof()
  47 {
  48     return
  49         max_alignof<U0>() > max_alignof<U1, Us...>() ?
  50         max_alignof<U0>() : max_alignof<U1, Us...>();
  51 }
  52
  53 // (since C++17)
  54 template<class... Ts>
  55 using make_void = boost::make_void<Ts...>;
  56 template<class... Ts>
  57 using void_t = boost::void_t<Ts...>;
  58
  59 // (since C++11) missing from g++4.8
  60 template<std::size_t Len, class... Ts>
  61 struct aligned_union
  62 {
  63     static
  64     std::size_t constexpr alignment_value =
  65         max_alignof<Ts...>();
  66
  67     using type = typename std::aligned_storage<
  68         (Len > max_sizeof<Ts...>()) ? Len : (max_sizeof<Ts...>()),
  69             alignment_value>::type;
  70 };
  71
  72 template<std::size_t Len, class... Ts>
  73 using aligned_union_t =
  74     typename aligned_union<Len, Ts...>::type;
  75
  76 //------------------------------------------------------------------------------
  77
  78 // for span
  79 template<class T, class E, class = void>
  80 struct is_contiguous_container: std::false_type {};
  81
  82 template<class T, class E>
  83 struct is_contiguous_container<T, E, void_t<
  84     decltype(
  85         std::declval<std::size_t&>() = std::declval<T const&>().size(),
  86         std::declval<E*&>() = std::declval<T&>().data()),
  87     typename std::enable_if<
  88         std::is_same<
  89             typename std::remove_cv<E>::type,
  90             typename std::remove_cv<
  91                 typename std::remove_pointer<
  92                     decltype(std::declval<T&>().data())
  93                 >::type
  94             >::type
  95         >::value
  96     >::type>>: std::true_type
  97 {};
  98
  99 template <class T, class U>
 100 T launder_cast(U* u)
 101 {
 102 #if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
 103     return std::launder(reinterpret_cast<T>(u));
 104 #elif defined(BOOST_GCC) && BOOST_GCC_VERSION > 80000
 105     return __builtin_launder(reinterpret_cast<T>(u));
 106 #else
 107     return reinterpret_cast<T>(u);
 108 #endif
 109 }
 110
 111 } // detail
 112 } // beast
 113 } // boost
 114
 115 #endif