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