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 <__config>
14 #include <__functional/invoke.h>
15 #include <__functional/weak_result_type.h>
16 #include <__memory/addressof.h>
17 #include <__type_traits/enable_if.h>
18 #include <__type_traits/remove_cvref.h>
19 #include <__utility/declval.h>
20 #include <__utility/forward.h>
21 
22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23 #  pragma GCC system_header
24 #endif
25 
26 _LIBCPP_BEGIN_NAMESPACE_STD
27 
28 template <class _Tp>
29 class _LIBCPP_TEMPLATE_VIS reference_wrapper : public __weak_result_type<_Tp>
30 {
31 public:
32     // types
33     typedef _Tp type;
34 private:
35     type* __f_;
36 
37     static void __fun(_Tp&) _NOEXCEPT;
38     static void __fun(_Tp&&) = delete;
39 
40 public:
41     template <class _Up, class = __enable_if_t<!__is_same_uncvref<_Up, reference_wrapper>::value, decltype(__fun(std::declval<_Up>())) > >
42     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
43     reference_wrapper(_Up&& __u) _NOEXCEPT_(noexcept(__fun(std::declval<_Up>()))) {
44         type& __f = static_cast<_Up&&>(__u);
45         __f_ = _VSTD::addressof(__f);
46     }
47 
48     // access
49     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
50     operator type&() const _NOEXCEPT {return *__f_;}
51     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
52     type& get() const _NOEXCEPT {return *__f_;}
53 
54     // invoke
55     template <class... _ArgTypes>
56     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
57     typename __invoke_of<type&, _ArgTypes...>::type
58     operator() (_ArgTypes&&... __args) const {
59         return std::__invoke(get(), std::forward<_ArgTypes>(__args)...);
60     }
61 };
62 
63 #if _LIBCPP_STD_VER > 14
64 template <class _Tp>
65 reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
66 #endif
67 
68 template <class _Tp>
69 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
70 reference_wrapper<_Tp>
71 ref(_Tp& __t) _NOEXCEPT
72 {
73     return reference_wrapper<_Tp>(__t);
74 }
75 
76 template <class _Tp>
77 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
78 reference_wrapper<_Tp>
79 ref(reference_wrapper<_Tp> __t) _NOEXCEPT
80 {
81     return __t;
82 }
83 
84 template <class _Tp>
85 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
86 reference_wrapper<const _Tp>
87 cref(const _Tp& __t) _NOEXCEPT
88 {
89     return reference_wrapper<const _Tp>(__t);
90 }
91 
92 template <class _Tp>
93 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
94 reference_wrapper<const _Tp>
95 cref(reference_wrapper<_Tp> __t) _NOEXCEPT
96 {
97     return __t;
98 }
99 
100 template <class _Tp> void ref(const _Tp&&) = delete;
101 template <class _Tp> void cref(const _Tp&&) = delete;
102 
103 _LIBCPP_END_NAMESPACE_STD
104 
105 #endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H
106