1 // -*- C++ -*- 2 //===----------------------------------------------------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 11 #define _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 12 13 #include <__compare/synth_three_way.h> 14 #include <__concepts/boolean_testable.h> 15 #include <__config> 16 #include <__functional/invoke.h> 17 #include <__functional/weak_result_type.h> 18 #include <__memory/addressof.h> 19 #include <__type_traits/enable_if.h> 20 #include <__type_traits/is_const.h> 21 #include <__type_traits/remove_cvref.h> 22 #include <__type_traits/void_t.h> 23 #include <__utility/declval.h> 24 #include <__utility/forward.h> 25 26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 27 # pragma GCC system_header 28 #endif 29 30 _LIBCPP_BEGIN_NAMESPACE_STD 31 32 template <class _Tp> 33 class _LIBCPP_TEMPLATE_VIS reference_wrapper : public __weak_result_type<_Tp> { 34 public: 35 // types 36 typedef _Tp type; 37 38 private: 39 type* __f_; 40 41 static void __fun(_Tp&) _NOEXCEPT; 42 static void __fun(_Tp&&) = delete; // NOLINT(modernize-use-equals-delete) ; This is llvm.org/PR54276 43 44 public: 45 template <class _Up, 46 class = __void_t<decltype(__fun(std::declval<_Up>()))>, 47 __enable_if_t<!__is_same_uncvref<_Up, reference_wrapper>::value, int> = 0> 48 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper(_Up&& __u) 49 _NOEXCEPT_(noexcept(__fun(std::declval<_Up>()))) { 50 type& __f = static_cast<_Up&&>(__u); 51 __f_ = std::addressof(__f); 52 } 53 54 // access 55 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 operator type&() const _NOEXCEPT { return *__f_; } 56 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 type& get() const _NOEXCEPT { return *__f_; } 57 58 // invoke 59 template <class... _ArgTypes> 60 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __invoke_of<type&, _ArgTypes...>::type 61 operator()(_ArgTypes&&... __args) const 62 #if _LIBCPP_STD_VER >= 17 63 // Since is_nothrow_invocable requires C++17 LWG3764 is not backported 64 // to earlier versions. 65 noexcept(is_nothrow_invocable_v<_Tp&, _ArgTypes...>) 66 #endif 67 { 68 return std::__invoke(get(), std::forward<_ArgTypes>(__args)...); 69 } 70 71 #if _LIBCPP_STD_VER >= 26 72 73 // [refwrap.comparisons], comparisons 74 75 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, reference_wrapper __y) 76 requires requires { 77 { __x.get() == __y.get() } -> __boolean_testable; 78 } 79 { 80 return __x.get() == __y.get(); 81 } 82 83 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, const _Tp& __y) 84 requires requires { 85 { __x.get() == __y } -> __boolean_testable; 86 } 87 { 88 return __x.get() == __y; 89 } 90 91 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, reference_wrapper<const _Tp> __y) 92 requires(!is_const_v<_Tp>) && requires { 93 { __x.get() == __y.get() } -> __boolean_testable; 94 } 95 { 96 return __x.get() == __y.get(); 97 } 98 99 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, reference_wrapper __y) 100 requires requires { std::__synth_three_way(__x.get(), __y.get()); } 101 { 102 return std::__synth_three_way(__x.get(), __y.get()); 103 } 104 105 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, const _Tp& __y) 106 requires requires { std::__synth_three_way(__x.get(), __y); } 107 { 108 return std::__synth_three_way(__x.get(), __y); 109 } 110 111 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, reference_wrapper<const _Tp> __y) 112 requires(!is_const_v<_Tp>) && requires { std::__synth_three_way(__x.get(), __y.get()); } 113 { 114 return std::__synth_three_way(__x.get(), __y.get()); 115 } 116 117 #endif // _LIBCPP_STD_VER >= 26 118 }; 119 120 #if _LIBCPP_STD_VER >= 17 121 template <class _Tp> 122 reference_wrapper(_Tp&) -> reference_wrapper<_Tp>; 123 #endif 124 125 template <class _Tp> 126 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> ref(_Tp& __t) _NOEXCEPT { 127 return reference_wrapper<_Tp>(__t); 128 } 129 130 template <class _Tp> 131 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> 132 ref(reference_wrapper<_Tp> __t) _NOEXCEPT { 133 return __t; 134 } 135 136 template <class _Tp> 137 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp> cref(const _Tp& __t) _NOEXCEPT { 138 return reference_wrapper<const _Tp>(__t); 139 } 140 141 template <class _Tp> 142 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp> 143 cref(reference_wrapper<_Tp> __t) _NOEXCEPT { 144 return __t; 145 } 146 147 template <class _Tp> 148 void ref(const _Tp&&) = delete; 149 template <class _Tp> 150 void cref(const _Tp&&) = delete; 151 152 _LIBCPP_END_NAMESPACE_STD 153 154 #endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 155