1 // Implementation of std::reference_wrapper -*- C++ -*-
2
3 // Copyright (C) 2004-2017 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/bind.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_REFWRAP_H
31 #define _GLIBCXX_REFWRAP_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 <bits/move.h>
40 #include <bits/invoke.h>
41 #include <bits/stl_function.h> // for unary_function and binary_function
42
_GLIBCXX_VISIBILITY(default)43 namespace std _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46
47 /// If we have found a result_type, extract it.
48 template<typename _Functor, typename = __void_t<>>
49 struct _Maybe_get_result_type
50 { };
51
52 template<typename _Functor>
53 struct _Maybe_get_result_type<_Functor,
54 __void_t<typename _Functor::result_type>>
55 { typedef typename _Functor::result_type result_type; };
56
57 /**
58 * Base class for any function object that has a weak result type, as
59 * defined in 20.8.2 [func.require] of C++11.
60 */
61 template<typename _Functor>
62 struct _Weak_result_type_impl
63 : _Maybe_get_result_type<_Functor>
64 { };
65
66 /// Retrieve the result type for a function type.
67 template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
68 struct _Weak_result_type_impl<_Res(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL>
69 { typedef _Res result_type; };
70
71 template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
72 struct _Weak_result_type_impl<_Res(_ArgTypes......) _GLIBCXX_NOEXCEPT_QUAL>
73 { typedef _Res result_type; };
74
75 template<typename _Res, typename... _ArgTypes>
76 struct _Weak_result_type_impl<_Res(_ArgTypes...) const>
77 { typedef _Res result_type; };
78
79 template<typename _Res, typename... _ArgTypes>
80 struct _Weak_result_type_impl<_Res(_ArgTypes......) const>
81 { typedef _Res result_type; };
82
83 template<typename _Res, typename... _ArgTypes>
84 struct _Weak_result_type_impl<_Res(_ArgTypes...) volatile>
85 { typedef _Res result_type; };
86
87 template<typename _Res, typename... _ArgTypes>
88 struct _Weak_result_type_impl<_Res(_ArgTypes......) volatile>
89 { typedef _Res result_type; };
90
91 template<typename _Res, typename... _ArgTypes>
92 struct _Weak_result_type_impl<_Res(_ArgTypes...) const volatile>
93 { typedef _Res result_type; };
94
95 template<typename _Res, typename... _ArgTypes>
96 struct _Weak_result_type_impl<_Res(_ArgTypes......) const volatile>
97 { typedef _Res result_type; };
98
99 /// Retrieve the result type for a function reference.
100 template<typename _Res, typename... _ArgTypes>
101 struct _Weak_result_type_impl<_Res(&)(_ArgTypes...)>
102 { typedef _Res result_type; };
103
104 template<typename _Res, typename... _ArgTypes>
105 struct _Weak_result_type_impl<_Res(&)(_ArgTypes......)>
106 { typedef _Res result_type; };
107
108 /// Retrieve the result type for a function pointer.
109 template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
110 struct _Weak_result_type_impl<_Res(*)(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL>
111 { typedef _Res result_type; };
112
113 template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
114 struct _Weak_result_type_impl<_Res(*)(_ArgTypes......)
115 _GLIBCXX_NOEXCEPT_QUAL>
116 { typedef _Res result_type; };
117
118 /// Retrieve result type for a member function pointer.
119 template<typename _Res, typename _Class, typename... _ArgTypes
120 _GLIBCXX_NOEXCEPT_PARM>
121 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...)
122 _GLIBCXX_NOEXCEPT_QUAL>
123 { typedef _Res result_type; };
124
125 template<typename _Res, typename _Class, typename... _ArgTypes
126 _GLIBCXX_NOEXCEPT_PARM>
127 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......)
128 _GLIBCXX_NOEXCEPT_QUAL>
129 { typedef _Res result_type; };
130
131 /// Retrieve result type for a const member function pointer.
132 template<typename _Res, typename _Class, typename... _ArgTypes
133 _GLIBCXX_NOEXCEPT_PARM>
134 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) const
135 _GLIBCXX_NOEXCEPT_QUAL>
136 { typedef _Res result_type; };
137
138 template<typename _Res, typename _Class, typename... _ArgTypes
139 _GLIBCXX_NOEXCEPT_PARM>
140 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) const
141 _GLIBCXX_NOEXCEPT_QUAL>
142 { typedef _Res result_type; };
143
144 /// Retrieve result type for a volatile member function pointer.
145 template<typename _Res, typename _Class, typename... _ArgTypes
146 _GLIBCXX_NOEXCEPT_PARM>
147 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) volatile
148 _GLIBCXX_NOEXCEPT_QUAL>
149 { typedef _Res result_type; };
150
151 template<typename _Res, typename _Class, typename... _ArgTypes
152 _GLIBCXX_NOEXCEPT_PARM>
153 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) volatile
154 _GLIBCXX_NOEXCEPT_QUAL>
155 { typedef _Res result_type; };
156
157 /// Retrieve result type for a const volatile member function pointer.
158 template<typename _Res, typename _Class, typename... _ArgTypes
159 _GLIBCXX_NOEXCEPT_PARM>
160 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...)
161 const volatile _GLIBCXX_NOEXCEPT_QUAL>
162 { typedef _Res result_type; };
163
164 template<typename _Res, typename _Class, typename... _ArgTypes
165 _GLIBCXX_NOEXCEPT_PARM>
166 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......)
167 const volatile _GLIBCXX_NOEXCEPT_QUAL>
168 { typedef _Res result_type; };
169
170 /**
171 * Strip top-level cv-qualifiers from the function object and let
172 * _Weak_result_type_impl perform the real work.
173 */
174 template<typename _Functor>
175 struct _Weak_result_type
176 : _Weak_result_type_impl<typename remove_cv<_Functor>::type>
177 { };
178
179 // Detect nested argument_type.
180 template<typename _Tp, typename = __void_t<>>
181 struct _Refwrap_base_arg1
182 { };
183
184 // Nested argument_type.
185 template<typename _Tp>
186 struct _Refwrap_base_arg1<_Tp,
187 __void_t<typename _Tp::argument_type>>
188 {
189 typedef typename _Tp::argument_type argument_type;
190 };
191
192 // Detect nested first_argument_type and second_argument_type.
193 template<typename _Tp, typename = __void_t<>>
194 struct _Refwrap_base_arg2
195 { };
196
197 // Nested first_argument_type and second_argument_type.
198 template<typename _Tp>
199 struct _Refwrap_base_arg2<_Tp,
200 __void_t<typename _Tp::first_argument_type,
201 typename _Tp::second_argument_type>>
202 {
203 typedef typename _Tp::first_argument_type first_argument_type;
204 typedef typename _Tp::second_argument_type second_argument_type;
205 };
206
207 /**
208 * Derives from unary_function or binary_function when it
209 * can. Specializations handle all of the easy cases. The primary
210 * template determines what to do with a class type, which may
211 * derive from both unary_function and binary_function.
212 */
213 template<typename _Tp>
214 struct _Reference_wrapper_base
215 : _Weak_result_type<_Tp>, _Refwrap_base_arg1<_Tp>, _Refwrap_base_arg2<_Tp>
216 { };
217
218 // - a function type (unary)
219 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
220 struct _Reference_wrapper_base<_Res(_T1) _GLIBCXX_NOEXCEPT_QUAL>
221 : unary_function<_T1, _Res>
222 { };
223
224 template<typename _Res, typename _T1>
225 struct _Reference_wrapper_base<_Res(_T1) const>
226 : unary_function<_T1, _Res>
227 { };
228
229 template<typename _Res, typename _T1>
230 struct _Reference_wrapper_base<_Res(_T1) volatile>
231 : unary_function<_T1, _Res>
232 { };
233
234 template<typename _Res, typename _T1>
235 struct _Reference_wrapper_base<_Res(_T1) const volatile>
236 : unary_function<_T1, _Res>
237 { };
238
239 // - a function type (binary)
240 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
241 struct _Reference_wrapper_base<_Res(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL>
242 : binary_function<_T1, _T2, _Res>
243 { };
244
245 template<typename _Res, typename _T1, typename _T2>
246 struct _Reference_wrapper_base<_Res(_T1, _T2) const>
247 : binary_function<_T1, _T2, _Res>
248 { };
249
250 template<typename _Res, typename _T1, typename _T2>
251 struct _Reference_wrapper_base<_Res(_T1, _T2) volatile>
252 : binary_function<_T1, _T2, _Res>
253 { };
254
255 template<typename _Res, typename _T1, typename _T2>
256 struct _Reference_wrapper_base<_Res(_T1, _T2) const volatile>
257 : binary_function<_T1, _T2, _Res>
258 { };
259
260 // - a function pointer type (unary)
261 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
262 struct _Reference_wrapper_base<_Res(*)(_T1) _GLIBCXX_NOEXCEPT_QUAL>
263 : unary_function<_T1, _Res>
264 { };
265
266 // - a function pointer type (binary)
267 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
268 struct _Reference_wrapper_base<_Res(*)(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL>
269 : binary_function<_T1, _T2, _Res>
270 { };
271
272 // - a pointer to member function type (unary, no qualifiers)
273 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
274 struct _Reference_wrapper_base<_Res (_T1::*)() _GLIBCXX_NOEXCEPT_QUAL>
275 : unary_function<_T1*, _Res>
276 { };
277
278 // - a pointer to member function type (binary, no qualifiers)
279 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
280 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) _GLIBCXX_NOEXCEPT_QUAL>
281 : binary_function<_T1*, _T2, _Res>
282 { };
283
284 // - a pointer to member function type (unary, const)
285 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
286 struct _Reference_wrapper_base<_Res (_T1::*)() const _GLIBCXX_NOEXCEPT_QUAL>
287 : unary_function<const _T1*, _Res>
288 { };
289
290 // - a pointer to member function type (binary, const)
291 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
292 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const _GLIBCXX_NOEXCEPT_QUAL>
293 : binary_function<const _T1*, _T2, _Res>
294 { };
295
296 // - a pointer to member function type (unary, volatile)
297 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
298 struct _Reference_wrapper_base<_Res (_T1::*)() volatile _GLIBCXX_NOEXCEPT_QUAL>
299 : unary_function<volatile _T1*, _Res>
300 { };
301
302 // - a pointer to member function type (binary, volatile)
303 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
304 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) volatile _GLIBCXX_NOEXCEPT_QUAL>
305 : binary_function<volatile _T1*, _T2, _Res>
306 { };
307
308 // - a pointer to member function type (unary, const volatile)
309 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
310 struct _Reference_wrapper_base<_Res (_T1::*)() const volatile _GLIBCXX_NOEXCEPT_QUAL>
311 : unary_function<const volatile _T1*, _Res>
312 { };
313
314 // - a pointer to member function type (binary, const volatile)
315 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
316 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const volatile _GLIBCXX_NOEXCEPT_QUAL>
317 : binary_function<const volatile _T1*, _T2, _Res>
318 { };
319
320 /**
321 * @brief Primary class template for reference_wrapper.
322 * @ingroup functors
323 * @{
324 */
325 template<typename _Tp>
326 class reference_wrapper
327 : public _Reference_wrapper_base<typename remove_cv<_Tp>::type>
328 {
329 _Tp* _M_data;
330
331 public:
332 typedef _Tp type;
333
334 reference_wrapper(_Tp& __indata) noexcept
335 : _M_data(std::__addressof(__indata))
336 { }
337
338 reference_wrapper(_Tp&&) = delete;
339
340 reference_wrapper(const reference_wrapper&) = default;
341
342 reference_wrapper&
343 operator=(const reference_wrapper&) = default;
344
345 operator _Tp&() const noexcept
346 { return this->get(); }
347
348 _Tp&
349 get() const noexcept
350 { return *_M_data; }
351
352 template<typename... _Args>
353 typename result_of<_Tp&(_Args&&...)>::type
354 operator()(_Args&&... __args) const
355 {
356 return std::__invoke(get(), std::forward<_Args>(__args)...);
357 }
358 };
359
360
361 /// Denotes a reference should be taken to a variable.
362 template<typename _Tp>
363 inline reference_wrapper<_Tp>
364 ref(_Tp& __t) noexcept
365 { return reference_wrapper<_Tp>(__t); }
366
367 /// Denotes a const reference should be taken to a variable.
368 template<typename _Tp>
369 inline reference_wrapper<const _Tp>
370 cref(const _Tp& __t) noexcept
371 { return reference_wrapper<const _Tp>(__t); }
372
373 template<typename _Tp>
374 void ref(const _Tp&&) = delete;
375
376 template<typename _Tp>
377 void cref(const _Tp&&) = delete;
378
379 /// Partial specialization.
380 template<typename _Tp>
381 inline reference_wrapper<_Tp>
382 ref(reference_wrapper<_Tp> __t) noexcept
383 { return ref(__t.get()); }
384
385 /// Partial specialization.
386 template<typename _Tp>
387 inline reference_wrapper<const _Tp>
388 cref(reference_wrapper<_Tp> __t) noexcept
389 { return cref(__t.get()); }
390
391 // @} group functors
392
393 _GLIBCXX_END_NAMESPACE_VERSION
394 } // namespace std
395
396 #endif // C++11
397
398 #endif // _GLIBCXX_REFWRAP_H
399