libstdc++
refwrap.h
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 
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<>>
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>
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>
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>
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>
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>
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>
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 
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>
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>
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>
383  { return ref(__t.get()); }
384 
385  /// Partial specialization.
386  template<typename _Tp>
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
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:47
ISO C++ entities toplevel namespace is std.
If we have found a result_type, extract it.
Definition: refwrap.h:49
Primary class template for reference_wrapper.
Definition: refwrap.h:326
constexpr __invoke_result< _Callable, _Args... >::type __invoke(_Callable &&__fn, _Args &&... __args) noexcept(__is_nothrow_invocable< _Callable, _Args... >::value)
Invoke a callable object.
Definition: invoke.h:89
reference_wrapper< const _Tp > cref(const _Tp &__t) noexcept
Denotes a const reference should be taken to a variable.
Definition: refwrap.h:370
reference_wrapper< _Tp > ref(_Tp &__t) noexcept
Denotes a reference should be taken to a variable.
Definition: refwrap.h:364