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<>>
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