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/convertible_to.h>
15#include <__config>
16#include <__functional/weak_result_type.h>
17#include <__memory/addressof.h>
18#include <__type_traits/common_reference.h>
19#include <__type_traits/desugars_to.h>
20#include <__type_traits/enable_if.h>
21#include <__type_traits/invoke.h>
22#include <__type_traits/is_const.h>
23#include <__type_traits/is_core_convertible.h>
24#include <__type_traits/is_same.h>
25#include <__type_traits/is_specialization.h>
26#include <__type_traits/remove_cvref.h>
27#include <__type_traits/void_t.h>
28#include <__utility/declval.h>
29#include <__utility/forward.h>
30
31#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
32# pragma GCC system_header
33#endif
34
35_LIBCPP_BEGIN_NAMESPACE_STD
36
37template <class _Tp>
38class reference_wrapper : public __weak_result_type<_Tp> {
39public:
40 // types
41 typedef _Tp type;
42
43private:
44 type* __f_;
45
46 static void __fun(_Tp&) _NOEXCEPT;
47 static void __fun(_Tp&&) = delete; // NOLINT(modernize-use-equals-delete) ; This is llvm.org/PR54276
48
49public:
50 template <class _Up,
51 class = __void_t<decltype(__fun(std::declval<_Up>()))>,
52 __enable_if_t<!is_same<__remove_cvref_t<_Up>, reference_wrapper>::value, int> = 0>
53 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper(_Up&& __u)
54 _NOEXCEPT_(noexcept(__fun(std::declval<_Up>()))) {
55 type& __f = static_cast<_Up&&>(__u);
56 __f_ = std::addressof(__f);
57 }
58
59 // access
60 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 operator type&() const _NOEXCEPT { return *__f_; }
61 [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 type& get() const _NOEXCEPT { return *__f_; }
62
63 // invoke
64 template <class... _ArgTypes>
65 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __invoke_result_t<type&, _ArgTypes...>
66 operator()(_ArgTypes&&... __args) const
67#if _LIBCPP_STD_VER >= 17
68 // Since is_nothrow_invocable requires C++17 LWG3764 is not backported
69 // to earlier versions.
70 noexcept(is_nothrow_invocable_v<_Tp&, _ArgTypes...>)
71#endif
72 {
73 return std::__invoke(get(), std::forward<_ArgTypes>(__args)...);
74 }
75
76#if _LIBCPP_STD_VER >= 26
77
78 // [refwrap.comparisons], comparisons
79
80 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, reference_wrapper __y)
81 requires requires {
82 { __x.get() == __y.get() } -> __core_convertible_to<bool>;
83 }
84 {
85 return __x.get() == __y.get();
86 }
87
88 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, const _Tp& __y)
89 requires requires {
90 { __x.get() == __y } -> __core_convertible_to<bool>;
91 }
92 {
93 return __x.get() == __y;
94 }
95
96 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, reference_wrapper<const _Tp> __y)
97 requires(!is_const_v<_Tp>) && requires {
98 { __x.get() == __y.get() } -> __core_convertible_to<bool>;
99 }
100 {
101 return __x.get() == __y.get();
102 }
103
104 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, reference_wrapper __y)
105 requires requires { std::__synth_three_way(__x.get(), __y.get()); }
106 {
107 return std::__synth_three_way(__x.get(), __y.get());
108 }
109
110 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, const _Tp& __y)
111 requires requires { std::__synth_three_way(__x.get(), __y); }
112 {
113 return std::__synth_three_way(__x.get(), __y);
114 }
115
116 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, reference_wrapper<const _Tp> __y)
117 requires(!is_const_v<_Tp>) && requires { std::__synth_three_way(__x.get(), __y.get()); }
118 {
119 return std::__synth_three_way(__x.get(), __y.get());
120 }
121
122#endif // _LIBCPP_STD_VER >= 26
123};
124
125#if _LIBCPP_STD_VER >= 17
126template <class _Tp>
127reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
128#endif
129
130template <class _Tp>
131[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI
132_LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> ref(_Tp& __t) _NOEXCEPT {
133 return reference_wrapper<_Tp>(__t);
134}
135
136template <class _Tp>
137[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp>
138ref(reference_wrapper<_Tp> __t) _NOEXCEPT {
139 return __t;
140}
141
142template <class _Tp>
143[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp>
144cref(const _Tp& __t) _NOEXCEPT {
145 return reference_wrapper<const _Tp>(__t);
146}
147
148template <class _Tp>
149[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp>
150cref(reference_wrapper<_Tp> __t) _NOEXCEPT {
151 return __t;
152}
153
154template <class _Tp>
155void ref(const _Tp&&) = delete;
156template <class _Tp>
157void cref(const _Tp&&) = delete;
158
159// Let desugars-to pass through std::reference_wrapper
160template <class _CanonicalTag, class _Operation, class... _Args>
161inline const bool __desugars_to_v<_CanonicalTag, reference_wrapper<_Operation>, _Args...> =
162 __desugars_to_v<_CanonicalTag, _Operation, _Args...>;
163
164#if _LIBCPP_STD_VER >= 20
165
166template <class _Tp>
167inline constexpr bool __is_ref_wrapper = __is_specialization_v<_Tp, reference_wrapper>;
168
169template <class _Rp, class _Tp, class _RpQual, class _TpQual>
170concept __ref_wrap_common_reference_exists_with = __is_ref_wrapper<_Rp> && requires {
171 typename common_reference_t<typename _Rp::type&, _TpQual>;
172} && convertible_to<_RpQual, common_reference_t<typename _Rp::type&, _TpQual>>;
173
174template <class _Rp, class _Tp, template <class> class _RpQual, template <class> class _TpQual>
175 requires(__ref_wrap_common_reference_exists_with<_Rp, _Tp, _RpQual<_Rp>, _TpQual<_Tp>> &&
176 !__ref_wrap_common_reference_exists_with<_Tp, _Rp, _TpQual<_Tp>, _RpQual<_Rp>>)
177struct basic_common_reference<_Rp, _Tp, _RpQual, _TpQual> {
178 using type _LIBCPP_NODEBUG = common_reference_t<typename _Rp::type&, _TpQual<_Tp>>;
179};
180
181template <class _Tp, class _Rp, template <class> class _TpQual, template <class> class _RpQual>
182 requires(__ref_wrap_common_reference_exists_with<_Rp, _Tp, _RpQual<_Rp>, _TpQual<_Tp>> &&
183 !__ref_wrap_common_reference_exists_with<_Tp, _Rp, _TpQual<_Tp>, _RpQual<_Rp>>)
184struct basic_common_reference<_Tp, _Rp, _TpQual, _RpQual> {
185 using type _LIBCPP_NODEBUG = common_reference_t<typename _Rp::type&, _TpQual<_Tp>>;
186};
187
188#endif // _LIBCPP_STD_VER >= 20
189
190_LIBCPP_END_NAMESPACE_STD
191
192#endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H
193