ceph/src/boost/boost/multiprecision/detail/empty_value.hpp

   1 /////////////////////////////////////////////////////////////////////
   2 //  Copyright 2018 Glen Joseph Fernandes.
   3 //  Copyright 2021 Matt Borland. Distributed under the Boost
   4 //  Software License, Version 1.0. (See accompanying file
   5 //  LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
   6
   7 #ifndef BOOST_MP_DETAIL_EMPTY_VALUE_HPP
   8 #define BOOST_MP_DETAIL_EMPTY_VALUE_HPP
   9
  10 #include <utility>
  11 #include <boost/multiprecision/detail/standalone_config.hpp>
  12
  13 #if defined(BOOST_GCC_VERSION) && (BOOST_GCC_VERSION >= 40700)
  14 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  15 #elif defined(BOOST_INTEL) && defined(_MSC_VER) && (_MSC_VER >= 1800)
  16 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  17 #elif defined(BOOST_MSVC) && (BOOST_MSVC >= 1800)
  18 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  19 #elif defined(BOOST_CLANG) && !defined(__CUDACC__)
  20 #if __has_feature(is_empty) && __has_feature(is_final)
  21 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  22 #endif
  23 #endif
  24
  25 namespace boost { namespace multiprecision { namespace detail {
  26
  27 template <typename T>
  28 struct use_empty_value_base
  29 {
  30 #if defined(BOOST_DETAIL_EMPTY_VALUE_BASE)
  31         static constexpr bool value = __is_empty(T) && !__is_final(T);
  32 #else
  33         static constexpr bool value = false;
  34 #endif
  35 };
  36
  37 struct empty_init_t {};
  38
  39 namespace empty_impl {
  40
  41 template <typename T, unsigned N = 0,
  42           bool E = boost::multiprecision::detail::use_empty_value_base<T>::value>
  43 class empty_value
  44 {
  45 private:
  46     T value_;
  47
  48 public:
  49     using type = T;
  50
  51     empty_value() = default;
  52     explicit empty_value(boost::multiprecision::detail::empty_init_t) : value_ {} {}
  53
  54     template <typename U, typename... Args>
  55     empty_value(boost::multiprecision::detail::empty_init_t, U&& value, Args&&... args) :
  56         value_ {std::forward<U>(value), std::forward<Args>(args)...} {}
  57
  58     const T& get() const noexcept { return value_; }
  59     T& get() noexcept { return value_; }
  60 };
  61
  62 template <typename T, unsigned N>
  63 class empty_value<T, N, true> : T
  64 {
  65 public:
  66     using type = T;
  67
  68     empty_value() = default;
  69     explicit empty_value(boost::multiprecision::detail::empty_init_t) : T{} {}
  70
  71     template <typename U, typename... Args>
  72     empty_value(boost::multiprecision::detail::empty_init_t, U&& value, Args&&... args) :
  73         T{std::forward<U>(value), std::forward<Args>(args)...} {}
  74
  75     const T& get() const noexcept { return *this; }
  76     T& get() noexcept { return *this; }
  77 };
  78
  79 } // Namespace empty impl
  80
  81 using empty_impl::empty_value;
  82
  83 BOOST_INLINE_CONSTEXPR empty_init_t empty_init = empty_init_t();
  84
  85 }}} // Namespaces
  86
  87 #endif // BOOST_MP_DETAIL_EMPTY_VALUE_HPP