1 // Implementation of INVOKE -*- C++ -*-
2
3 // Copyright (C) 2016-2020 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /** @file include/bits/invoke.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{functional}
28 */
29
30 #ifndef _GLIBCXX_INVOKE_H
31 #define _GLIBCXX_INVOKE_H 1
32
33 #pragma GCC system_header
34
35 #if __cplusplus < 201103L
36 # include <bits/c++0x_warning.h>
37 #else
38
39 #include <type_traits>
40
_GLIBCXX_VISIBILITY(default)41 namespace std _GLIBCXX_VISIBILITY(default)
42 {
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45 /**
46 * @addtogroup utilities
47 * @{
48 */
49
50 // Used by __invoke_impl instead of std::forward<_Tp> so that a
51 // reference_wrapper is converted to an lvalue-reference.
52 template<typename _Tp, typename _Up = typename __inv_unwrap<_Tp>::type>
53 constexpr _Up&&
54 __invfwd(typename remove_reference<_Tp>::type& __t) noexcept
55 { return static_cast<_Up&&>(__t); }
56
57 template<typename _Res, typename _Fn, typename... _Args>
58 constexpr _Res
59 __invoke_impl(__invoke_other, _Fn&& __f, _Args&&... __args)
60 { return std::forward<_Fn>(__f)(std::forward<_Args>(__args)...); }
61
62 template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
63 constexpr _Res
64 __invoke_impl(__invoke_memfun_ref, _MemFun&& __f, _Tp&& __t,
65 _Args&&... __args)
66 { return (__invfwd<_Tp>(__t).*__f)(std::forward<_Args>(__args)...); }
67
68 template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
69 constexpr _Res
70 __invoke_impl(__invoke_memfun_deref, _MemFun&& __f, _Tp&& __t,
71 _Args&&... __args)
72 {
73 return ((*std::forward<_Tp>(__t)).*__f)(std::forward<_Args>(__args)...);
74 }
75
76 template<typename _Res, typename _MemPtr, typename _Tp>
77 constexpr _Res
78 __invoke_impl(__invoke_memobj_ref, _MemPtr&& __f, _Tp&& __t)
79 { return __invfwd<_Tp>(__t).*__f; }
80
81 template<typename _Res, typename _MemPtr, typename _Tp>
82 constexpr _Res
83 __invoke_impl(__invoke_memobj_deref, _MemPtr&& __f, _Tp&& __t)
84 { return (*std::forward<_Tp>(__t)).*__f; }
85
86 /// Invoke a callable object.
87 template<typename _Callable, typename... _Args>
88 constexpr typename __invoke_result<_Callable, _Args...>::type
89 __invoke(_Callable&& __fn, _Args&&... __args)
90 noexcept(__is_nothrow_invocable<_Callable, _Args...>::value)
91 {
92 using __result = __invoke_result<_Callable, _Args...>;
93 using __type = typename __result::type;
94 using __tag = typename __result::__invoke_type;
95 return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
96 std::forward<_Args>(__args)...);
97 }
98
99 #if __cplusplus >= 201703L
100 // INVOKE<R>: Invoke a callable object and convert the result to R.
101 template<typename _Res, typename _Callable, typename... _Args>
102 constexpr enable_if_t<is_invocable_r_v<_Res, _Callable, _Args...>, _Res>
103 __invoke_r(_Callable&& __fn, _Args&&... __args)
104 noexcept(is_nothrow_invocable_r_v<_Res, _Callable, _Args...>)
105 {
106 using __result = __invoke_result<_Callable, _Args...>;
107 using __type = typename __result::type;
108 using __tag = typename __result::__invoke_type;
109 if constexpr (is_void_v<_Res>)
110 std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
111 std::forward<_Args>(__args)...);
112 else
113 return std::__invoke_impl<__type>(__tag{},
114 std::forward<_Callable>(__fn),
115 std::forward<_Args>(__args)...);
116 }
117 #else // C++11
118 template<typename _Res, typename _Callable, typename... _Args>
119 using __can_invoke_as_void = __enable_if_t<
120 __and_<is_void<_Res>, __is_invocable<_Callable, _Args...>>::value,
121 _Res
122 >;
123
124 template<typename _Res, typename _Callable, typename... _Args>
125 using __can_invoke_as_nonvoid = __enable_if_t<
126 __and_<__not_<is_void<_Res>>,
127 is_convertible<typename __invoke_result<_Callable, _Args...>::type,
128 _Res>
129 >::value,
130 _Res
131 >;
132
133 // INVOKE<R>: Invoke a callable object and convert the result to R.
134 template<typename _Res, typename _Callable, typename... _Args>
135 constexpr __can_invoke_as_nonvoid<_Res, _Callable, _Args...>
136 __invoke_r(_Callable&& __fn, _Args&&... __args)
137 {
138 using __result = __invoke_result<_Callable, _Args...>;
139 using __type = typename __result::type;
140 using __tag = typename __result::__invoke_type;
141 return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
142 std::forward<_Args>(__args)...);
143 }
144
145 // INVOKE<R> when R is cv void
146 template<typename _Res, typename _Callable, typename... _Args>
147 _GLIBCXX14_CONSTEXPR __can_invoke_as_void<_Res, _Callable, _Args...>
148 __invoke_r(_Callable&& __fn, _Args&&... __args)
149 {
150 using __result = __invoke_result<_Callable, _Args...>;
151 using __type = typename __result::type;
152 using __tag = typename __result::__invoke_type;
153 std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
154 std::forward<_Args>(__args)...);
155 }
156 #endif // C++11
157
158 _GLIBCXX_END_NAMESPACE_VERSION
159 } // namespace std
160
161 #endif // C++11
162
163 #endif // _GLIBCXX_INVOKE_H
164