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
32template <class _Tp>
33class _LIBCPP_TEMPLATE_VIS reference_wrapper : public __weak_result_type<_Tp> {
34public:
35 // types
36 typedef _Tp type;
37
38private:
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
44public:
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
121template <class _Tp>
122reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
123#endif
124
125template <class _Tp>
126inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> ref(_Tp& __t) _NOEXCEPT {
127 return reference_wrapper<_Tp>(__t);
128}
129
130template <class _Tp>
131inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp>
132ref(reference_wrapper<_Tp> __t) _NOEXCEPT {
133 return __t;
134}
135
136template <class _Tp>
137inline _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
141template <class _Tp>
142inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp>
143cref(reference_wrapper<_Tp> __t) _NOEXCEPT {
144 return __t;
145}
146
147template <class _Tp>
148void ref(const _Tp&&) = delete;
149template <class _Tp>
150void cref(const _Tp&&) = delete;
151
152_LIBCPP_END_NAMESPACE_STD
153
154#endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H
155