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1 : // Implementation of INVOKE -*- C++ -*-
2 :
3 : // Copyright (C) 2016-2023 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 : #include <bits/move.h> // forward
41 :
42 : namespace std _GLIBCXX_VISIBILITY(default)
43 : {
44 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
45 :
46 : /**
47 : * @addtogroup utilities
48 : * @{
49 : */
50 :
51 : // Used by __invoke_impl instead of std::forward<_Tp> so that a
52 : // reference_wrapper is converted to an lvalue-reference.
53 : template<typename _Tp, typename _Up = typename __inv_unwrap<_Tp>::type>
54 : constexpr _Up&&
55 : __invfwd(typename remove_reference<_Tp>::type& __t) noexcept
56 : { return static_cast<_Up&&>(__t); }
57 :
58 : template<typename _Res, typename _Fn, typename... _Args>
59 : constexpr _Res
60 1605734 : __invoke_impl(__invoke_other, _Fn&& __f, _Args&&... __args)
61 1605734 : { return std::forward<_Fn>(__f)(std::forward<_Args>(__args)...); }
62 :
63 : template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
64 : constexpr _Res
65 : __invoke_impl(__invoke_memfun_ref, _MemFun&& __f, _Tp&& __t,
66 : _Args&&... __args)
67 : { return (__invfwd<_Tp>(__t).*__f)(std::forward<_Args>(__args)...); }
68 :
69 : template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
70 : constexpr _Res
71 : __invoke_impl(__invoke_memfun_deref, _MemFun&& __f, _Tp&& __t,
72 : _Args&&... __args)
73 : {
74 : return ((*std::forward<_Tp>(__t)).*__f)(std::forward<_Args>(__args)...);
75 : }
76 :
77 : template<typename _Res, typename _MemPtr, typename _Tp>
78 : constexpr _Res
79 : __invoke_impl(__invoke_memobj_ref, _MemPtr&& __f, _Tp&& __t)
80 : { return __invfwd<_Tp>(__t).*__f; }
81 :
82 : template<typename _Res, typename _MemPtr, typename _Tp>
83 : constexpr _Res
84 : __invoke_impl(__invoke_memobj_deref, _MemPtr&& __f, _Tp&& __t)
85 : { return (*std::forward<_Tp>(__t)).*__f; }
86 :
87 : /// Invoke a callable object.
88 : template<typename _Callable, typename... _Args>
89 : constexpr typename __invoke_result<_Callable, _Args...>::type
90 1605734 : __invoke(_Callable&& __fn, _Args&&... __args)
91 : noexcept(__is_nothrow_invocable<_Callable, _Args...>::value)
92 : {
93 : using __result = __invoke_result<_Callable, _Args...>;
94 : using __type = typename __result::type;
95 : using __tag = typename __result::__invoke_type;
96 1605734 : return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
97 1605734 : std::forward<_Args>(__args)...);
98 : }
99 :
100 : #if __cplusplus >= 201703L
101 : // INVOKE<R>: Invoke a callable object and convert the result to R.
102 : template<typename _Res, typename _Callable, typename... _Args>
103 : constexpr enable_if_t<is_invocable_r_v<_Res, _Callable, _Args...>, _Res>
104 0 : __invoke_r(_Callable&& __fn, _Args&&... __args)
105 : noexcept(is_nothrow_invocable_r_v<_Res, _Callable, _Args...>)
106 : {
107 : using __result = __invoke_result<_Callable, _Args...>;
108 : using __type = typename __result::type;
109 : using __tag = typename __result::__invoke_type;
110 : if constexpr (is_void_v<_Res>)
111 : std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
112 : std::forward<_Args>(__args)...);
113 : else
114 0 : return std::__invoke_impl<__type>(__tag{},
115 : std::forward<_Callable>(__fn),
116 0 : std::forward<_Args>(__args)...);
117 : }
118 : #else // C++11 or C++14
119 : // This is a non-SFINAE-friendly std::invoke_r<R>(fn, args...) for C++11/14.
120 : // It's used in std::function, std::bind, and std::packaged_task. Only
121 : // std::function is constrained on is_invocable_r, but that is checked on
122 : // construction so doesn't need to be checked again when calling __invoke_r.
123 : // Consequently, these __invoke_r overloads do not check for invocable
124 : // arguments, nor check that the invoke result is convertible to R.
125 :
126 : // INVOKE<R>: Invoke a callable object and convert the result to R.
127 : template<typename _Res, typename _Callable, typename... _Args>
128 : constexpr __enable_if_t<!is_void<_Res>::value, _Res>
129 : __invoke_r(_Callable&& __fn, _Args&&... __args)
130 : {
131 : using __result = __invoke_result<_Callable, _Args...>;
132 : using __type = typename __result::type;
133 : #if __has_builtin(__reference_converts_from_temporary)
134 : static_assert(!__reference_converts_from_temporary(_Res, __type),
135 : "INVOKE<R> must not create a dangling reference");
136 : #endif
137 : using __tag = typename __result::__invoke_type;
138 : return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
139 : std::forward<_Args>(__args)...);
140 : }
141 :
142 : // INVOKE<R> when R is cv void
143 : template<typename _Res, typename _Callable, typename... _Args>
144 : _GLIBCXX14_CONSTEXPR __enable_if_t<is_void<_Res>::value, _Res>
145 : __invoke_r(_Callable&& __fn, _Args&&... __args)
146 : {
147 : using __result = __invoke_result<_Callable, _Args...>;
148 : using __type = typename __result::type;
149 : using __tag = typename __result::__invoke_type;
150 : std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
151 : std::forward<_Args>(__args)...);
152 : }
153 : #endif // C++11 or C++14
154 :
155 : _GLIBCXX_END_NAMESPACE_VERSION
156 : } // namespace std
157 :
158 : #endif // C++11
159 :
160 : #endif // _GLIBCXX_INVOKE_H
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