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/weak_result_type.h>
15 #include <__memory/addressof.h>
16 #include <__utility/forward.h>
17 #include <type_traits>
18 
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #  pragma GCC system_header
21 #endif
22 
23 _LIBCPP_BEGIN_NAMESPACE_STD
24 
25 template <class _Tp>
26 class _LIBCPP_TEMPLATE_VIS reference_wrapper : public __weak_result_type<_Tp>
27 {
28 public:
29     // types
30     typedef _Tp type;
31 private:
32     type* __f_;
33 
34     static void __fun(_Tp&) _NOEXCEPT;
35     static void __fun(_Tp&&) = delete;
36 
37 public:
38     template <class _Up, class = __enable_if_t<!__is_same_uncvref<_Up, reference_wrapper>::value, decltype(__fun(declval<_Up>())) > >
39     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
40     reference_wrapper(_Up&& __u) _NOEXCEPT_(noexcept(__fun(declval<_Up>()))) {
41         type& __f = static_cast<_Up&&>(__u);
42         __f_ = _VSTD::addressof(__f);
43     }
44 
45     // access
46     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
47     operator type&() const _NOEXCEPT {return *__f_;}
48     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
49     type& get() const _NOEXCEPT {return *__f_;}
50 
51     // invoke
52     template <class... _ArgTypes>
53     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
54     typename __invoke_of<type&, _ArgTypes...>::type
55     operator() (_ArgTypes&&... __args) const {
56         return std::__invoke(get(), std::forward<_ArgTypes>(__args)...);
57     }
58 };
59 
60 #if _LIBCPP_STD_VER > 14
61 template <class _Tp>
62 reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
63 #endif
64 
65 template <class _Tp>
66 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
67 reference_wrapper<_Tp>
68 ref(_Tp& __t) _NOEXCEPT
69 {
70     return reference_wrapper<_Tp>(__t);
71 }
72 
73 template <class _Tp>
74 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
75 reference_wrapper<_Tp>
76 ref(reference_wrapper<_Tp> __t) _NOEXCEPT
77 {
78     return __t;
79 }
80 
81 template <class _Tp>
82 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
83 reference_wrapper<const _Tp>
84 cref(const _Tp& __t) _NOEXCEPT
85 {
86     return reference_wrapper<const _Tp>(__t);
87 }
88 
89 template <class _Tp>
90 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
91 reference_wrapper<const _Tp>
92 cref(reference_wrapper<_Tp> __t) _NOEXCEPT
93 {
94     return __t;
95 }
96 
97 template <class _Tp> void ref(const _Tp&&) = delete;
98 template <class _Tp> void cref(const _Tp&&) = delete;
99 
100 _LIBCPP_END_NAMESPACE_STD
101 
102 #endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H
103