ceph/src/boost/libs/optional/include/boost/optional/detail/optional_reference_spec.hpp

   1 // Copyright (C) 2015-2016 Andrzej Krzemienski.
   2 //
   3 // Use, modification, and distribution is subject to the Boost Software
   4 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // See http://www.boost.org/libs/optional for documentation.
   8 //
   9 // You are welcome to contact the author at:
  10 //  akrzemi1@gmail.com
  11
  12 #ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_REFERENCE_SPEC_AJK_03OCT2015_HPP
  13 #define BOOST_OPTIONAL_DETAIL_OPTIONAL_REFERENCE_SPEC_AJK_03OCT2015_HPP
  14
  15 #ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
  16 #include <boost/type_traits/is_integral.hpp>
  17 #include <boost/type_traits/is_const.hpp>
  18 #endif
  19
  20 # if 1
  21
  22 namespace boost {
  23
  24 namespace detail {
  25
  26 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
  27
  28 template <class From>
  29 void prevent_binding_rvalue()
  30 {
  31 #ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
  32     BOOST_STATIC_ASSERT_MSG(boost::is_lvalue_reference<From>::value,
  33                             "binding rvalue references to optional lvalue references is disallowed");
  34 #endif
  35 }
  36
  37 template <class T>
  38 BOOST_DEDUCED_TYPENAME boost::remove_reference<T>::type& forward_reference(T&& r)
  39 {
  40     BOOST_STATIC_ASSERT_MSG(boost::is_lvalue_reference<T>::value,
  41                             "binding rvalue references to optional lvalue references is disallowed");
  42     return boost::forward<T>(r);
  43 }
  44
  45 #endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
  46
  47
  48 template <class T>
  49 struct is_const_integral
  50 {
  51   static const bool value = boost::is_const<T>::value && boost::is_integral<T>::value;
  52 };
  53
  54 template <class T>
  55 struct is_const_integral_bad_for_conversion
  56 {
  57 #if (!defined BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES) && (defined BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT)
  58   static const bool value = boost::is_const<T>::value && boost::is_integral<T>::value;
  59 #else
  60   static const bool value = false;
  61 #endif
  62 };
  63
  64 template <class From>
  65 void prevent_assignment_from_false_const_integral()
  66 {
  67 #ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
  68 #ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
  69     // MSVC compiler without rvalue refernces: we need to disable the asignment from
  70     // const integral lvalue reference, as it may be an invalid temporary
  71     BOOST_STATIC_ASSERT_MSG(!is_const_integral<From>::value,
  72                             "binding const lvalue references to integral types is disabled in this compiler");
  73 #endif
  74 #endif
  75 }
  76
  77
  78 template <class T>
  79 struct is_optional_
  80 {
  81   static const bool value = false;
  82 };
  83
  84 template <class U>
  85 struct is_optional_< ::boost::optional<U> >
  86 {
  87   static const bool value = true;
  88 };
  89
  90 template <class T>
  91 struct is_no_optional
  92 {
  93   static const bool value = !is_optional_<BOOST_DEDUCED_TYPENAME boost::decay<T>::type>::value;
  94 };
  95
  96
  97 template <class T, class U>
  98   struct is_same_decayed
  99   {
 100     static const bool value = ::boost::is_same<T, BOOST_DEDUCED_TYPENAME ::boost::remove_reference<U>::type>::value
 101                            || ::boost::is_same<T, const BOOST_DEDUCED_TYPENAME ::boost::remove_reference<U>::type>::value;
 102   };
 103
 104 template <class T, class U>
 105 struct no_unboxing_cond
 106 {
 107   static const bool value = is_no_optional<U>::value && !is_same_decayed<T, U>::value;
 108 };
 109
 110
 111 } // namespace detail
 112
 113 template <class T>
 114 class optional<T&> : public optional_detail::optional_tag
 115 {
 116     T* ptr_;
 117
 118 public:
 119     typedef T& value_type;
 120     typedef T& reference_type;
 121     typedef T& reference_const_type;
 122     typedef T& rval_reference_type;
 123     typedef T* pointer_type;
 124     typedef T* pointer_const_type;
 125
 126     optional() BOOST_NOEXCEPT : ptr_() {}
 127     optional(none_t) BOOST_NOEXCEPT : ptr_() {}
 128
 129     template <class U>
 130         explicit optional(const optional<U&>& rhs) BOOST_NOEXCEPT : ptr_(rhs.get_ptr()) {}
 131     optional(const optional& rhs) BOOST_NOEXCEPT : ptr_(rhs.get_ptr()) {}
 132
 133     // the following two implement a 'conditionally explicit' constructor: condition is a hack for buggy compilers with srewed conversion construction from const int
 134     template <class U>
 135       explicit optional(U& rhs, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::is_same_decayed<T, U>::value && detail::is_const_integral_bad_for_conversion<U>::value>::type* = 0) BOOST_NOEXCEPT
 136       : ptr_(boost::addressof(rhs)) {}
 137
 138     template <class U>
 139       optional(U& rhs, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::is_same_decayed<T, U>::value && !detail::is_const_integral_bad_for_conversion<U>::value>::type* = 0) BOOST_NOEXCEPT
 140       : ptr_(boost::addressof(rhs)) {}
 141
 142     optional& operator=(const optional& rhs) BOOST_NOEXCEPT { ptr_ = rhs.get_ptr(); return *this; }
 143     template <class U>
 144         optional& operator=(const optional<U&>& rhs) BOOST_NOEXCEPT { ptr_ = rhs.get_ptr(); return *this; }
 145     optional& operator=(none_t) BOOST_NOEXCEPT { ptr_ = 0; return *this; }
 146
 147
 148     void swap(optional& rhs) BOOST_NOEXCEPT { std::swap(ptr_, rhs.ptr_); }
 149     T& get() const { BOOST_ASSERT(ptr_); return   *ptr_; }
 150
 151     T* get_ptr() const BOOST_NOEXCEPT { return ptr_; }
 152     T* operator->() const { BOOST_ASSERT(ptr_); return ptr_; }
 153     T& operator*() const { BOOST_ASSERT(ptr_); return *ptr_; }
 154     T& value() const { return ptr_ ? *ptr_ : (throw_exception(bad_optional_access()), *ptr_); }
 155
 156     bool operator!() const BOOST_NOEXCEPT { return ptr_ == 0; }
 157     BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
 158
 159     void reset() BOOST_NOEXCEPT { ptr_ = 0; }
 160
 161     bool is_initialized() const BOOST_NOEXCEPT { return ptr_ != 0; }
 162
 163 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 164
 165     optional(T&& /* rhs */) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<T&&>(); }
 166
 167     template <class R>
 168         optional(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::no_unboxing_cond<T, R> >::type* = 0) BOOST_NOEXCEPT
 169         : ptr_(boost::addressof(r)) { detail::prevent_binding_rvalue<R>(); }
 170
 171     template <class R>
 172         optional(bool cond, R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
 173         : ptr_(cond ? boost::addressof(r) : 0) { detail::prevent_binding_rvalue<R>(); }
 174
 175     template <class R>
 176         BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, optional<T&>&>::type
 177         operator=(R&& r) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); return *this; }
 178
 179     template <class R>
 180         void emplace(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
 181         { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); }
 182
 183     template <class R>
 184       T& get_value_or(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) const BOOST_NOEXCEPT
 185       { detail::prevent_binding_rvalue<R>(); return ptr_ ? *ptr_ : r; }
 186
 187     template <class R>
 188         T& value_or(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) const BOOST_NOEXCEPT
 189         { detail::prevent_binding_rvalue<R>(); return ptr_ ? *ptr_ : r; }
 190
 191     template <class R>
 192       void reset(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
 193       { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); }
 194
 195     template <class F>
 196         T& value_or_eval(F f) const { return ptr_ ? *ptr_ : detail::forward_reference(f()); }
 197
 198 #else  // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 199
 200
 201     // the following two implement a 'conditionally explicit' constructor
 202     template <class U>
 203       explicit optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::no_unboxing_cond<T, U>::value && detail::is_const_integral_bad_for_conversion<U>::value >::type* = 0) BOOST_NOEXCEPT
 204       : ptr_(boost::addressof(v)) { }
 205
 206     template <class U>
 207       optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::no_unboxing_cond<T, U>::value && !detail::is_const_integral_bad_for_conversion<U>::value >::type* = 0) BOOST_NOEXCEPT
 208       : ptr_(boost::addressof(v)) { }
 209
 210     template <class U>
 211       optional(bool cond, U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT : ptr_(cond ? boost::addressof(v) : 0) {}
 212
 213     template <class U>
 214       BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, optional<T&>&>::type
 215       operator=(U& v) BOOST_NOEXCEPT
 216       {
 217         detail::prevent_assignment_from_false_const_integral<U>();
 218         ptr_ = boost::addressof(v); return *this;
 219       }
 220
 221     template <class U>
 222         void emplace(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT
 223         { ptr_ = boost::addressof(v); }
 224
 225     template <class U>
 226       T& get_value_or(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) const BOOST_NOEXCEPT
 227       { return ptr_ ? *ptr_ : v; }
 228
 229     template <class U>
 230         T& value_or(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) const BOOST_NOEXCEPT
 231         { return ptr_ ? *ptr_ : v; }
 232
 233     template <class U>
 234       void reset(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT
 235       { ptr_ = boost::addressof(v); }
 236
 237     template <class F>
 238       T& value_or_eval(F f) const { return ptr_ ? *ptr_ : f(); }
 239
 240 #endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 241 };
 242
 243 template <class T>
 244   void swap ( optional<T&>& x, optional<T&>& y) BOOST_NOEXCEPT
 245 {
 246   x.swap(y);
 247 }
 248
 249 } // namespace boost
 250
 251 #endif // 1/0
 252
 253 #endif // header guard