ceph/src/boost/boost/core/empty_value.hpp

   1 /*
   2 Copyright 2018 Glen Joseph Fernandes
   3 (glenjofe@gmail.com)
   4
   5 Distributed under the Boost Software License, Version 1.0.
   6 (http://www.boost.org/LICENSE_1_0.txt)
   7 */
   8 #ifndef BOOST_CORE_EMPTY_VALUE_HPP
   9 #define BOOST_CORE_EMPTY_VALUE_HPP
  10
  11 #include <boost/config.hpp>
  12 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
  13 #include <utility>
  14 #endif
  15
  16 #if defined(BOOST_GCC_VERSION) && (BOOST_GCC_VERSION >= 40700)
  17 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  18 #elif defined(BOOST_INTEL) && defined(_MSC_VER) && (_MSC_VER >= 1800)
  19 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  20 #elif defined(BOOST_MSVC) && (BOOST_MSVC >= 1800)
  21 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  22 #elif defined(BOOST_CLANG) && !defined(__CUDACC__)
  23 #if __has_feature(is_empty) && __has_feature(is_final)
  24 #define BOOST_DETAIL_EMPTY_VALUE_BASE
  25 #endif
  26 #endif
  27
  28 #if defined(_MSC_VER)
  29 #pragma warning(push)
  30 #pragma warning(disable:4510)
  31 #endif
  32
  33 namespace boost {
  34
  35 template<class T>
  36 struct use_empty_value_base {
  37     enum {
  38 #if defined(BOOST_DETAIL_EMPTY_VALUE_BASE)
  39         value = __is_empty(T) && !__is_final(T)
  40 #else
  41         value = false
  42 #endif
  43     };
  44 };
  45
  46 struct empty_init_t { };
  47
  48 namespace empty_ {
  49
  50 template<class T, unsigned N = 0,
  51     bool E = boost::use_empty_value_base<T>::value>
  52 class empty_value {
  53 public:
  54     typedef T type;
  55
  56 #if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS)
  57     empty_value() = default;
  58 #else
  59     empty_value() { }
  60 #endif
  61
  62     empty_value(boost::empty_init_t)
  63         : value_() { }
  64
  65 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
  66 #if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
  67     template<class U, class... Args>
  68     empty_value(boost::empty_init_t, U&& value, Args&&... args)
  69         : value_(std::forward<U>(value), std::forward<Args>(args)...) { }
  70 #else
  71     template<class U>
  72     empty_value(boost::empty_init_t, U&& value)
  73         : value_(std::forward<U>(value)) { }
  74 #endif
  75 #else
  76     template<class U>
  77     empty_value(boost::empty_init_t, const U& value)
  78         : value_(value) { }
  79
  80     template<class U>
  81     empty_value(boost::empty_init_t, U& value)
  82         : value_(value) { }
  83 #endif
  84
  85     const T& get() const BOOST_NOEXCEPT {
  86         return value_;
  87     }
  88
  89     T& get() BOOST_NOEXCEPT {
  90         return value_;
  91     }
  92
  93 private:
  94     T value_;
  95 };
  96
  97 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
  98 template<class T, unsigned N>
  99 class empty_value<T, N, true>
 100     : T {
 101 public:
 102     typedef T type;
 103
 104 #if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS)
 105     empty_value() = default;
 106 #else
 107     empty_value() { }
 108 #endif
 109
 110     empty_value(boost::empty_init_t)
 111         : T() { }
 112
 113 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
 114 #if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
 115     template<class U, class... Args>
 116     empty_value(boost::empty_init_t, U&& value, Args&&... args)
 117         : T(std::forward<U>(value), std::forward<Args>(args)...) { }
 118 #else
 119     template<class U>
 120     empty_value(boost::empty_init_t, U&& value)
 121         : T(std::forward<U>(value)) { }
 122 #endif
 123 #else
 124     template<class U>
 125     empty_value(boost::empty_init_t, const U& value)
 126         : T(value) { }
 127
 128     template<class U>
 129     empty_value(boost::empty_init_t, U& value)
 130         : T(value) { }
 131 #endif
 132
 133     const T& get() const BOOST_NOEXCEPT {
 134         return *this;
 135     }
 136
 137     T& get() BOOST_NOEXCEPT {
 138         return *this;
 139     }
 140 };
 141 #endif
 142
 143 } /* empty_ */
 144
 145 using empty_::empty_value;
 146
 147 BOOST_INLINE_CONSTEXPR empty_init_t empty_init = empty_init_t();
 148
 149 } /* boost */
 150
 151 #if defined(_MSC_VER)
 152 #pragma warning(pop)
 153 #endif
 154
 155 #endif