libstdc++
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00001 // Implementation of std::reference_wrapper -*- C++ -*- 00002 00003 // Copyright (C) 2004-2017 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file include/bits/bind.h 00026 * This is an internal header file, included by other library headers. 00027 * Do not attempt to use it directly. @headername{functional} 00028 */ 00029 00030 #ifndef _GLIBCXX_REFWRAP_H 00031 #define _GLIBCXX_REFWRAP_H 1 00032 00033 #pragma GCC system_header 00034 00035 #if __cplusplus < 201103L 00036 # include <bits/c++0x_warning.h> 00037 #else 00038 00039 #include <bits/move.h> 00040 #include <bits/invoke.h> 00041 #include <bits/stl_function.h> // for unary_function and binary_function 00042 00043 namespace std _GLIBCXX_VISIBILITY(default) 00044 { 00045 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00046 00047 /// If we have found a result_type, extract it. 00048 template<typename _Functor, typename = __void_t<>> 00049 struct _Maybe_get_result_type 00050 { }; 00051 00052 template<typename _Functor> 00053 struct _Maybe_get_result_type<_Functor, 00054 __void_t<typename _Functor::result_type>> 00055 { typedef typename _Functor::result_type result_type; }; 00056 00057 /** 00058 * Base class for any function object that has a weak result type, as 00059 * defined in 20.8.2 [func.require] of C++11. 00060 */ 00061 template<typename _Functor> 00062 struct _Weak_result_type_impl 00063 : _Maybe_get_result_type<_Functor> 00064 { }; 00065 00066 /// Retrieve the result type for a function type. 00067 template<typename _Res, typename... _ArgTypes> 00068 struct _Weak_result_type_impl<_Res(_ArgTypes...)> 00069 { typedef _Res result_type; }; 00070 00071 template<typename _Res, typename... _ArgTypes> 00072 struct _Weak_result_type_impl<_Res(_ArgTypes......)> 00073 { typedef _Res result_type; }; 00074 00075 template<typename _Res, typename... _ArgTypes> 00076 struct _Weak_result_type_impl<_Res(_ArgTypes...) const> 00077 { typedef _Res result_type; }; 00078 00079 template<typename _Res, typename... _ArgTypes> 00080 struct _Weak_result_type_impl<_Res(_ArgTypes......) const> 00081 { typedef _Res result_type; }; 00082 00083 template<typename _Res, typename... _ArgTypes> 00084 struct _Weak_result_type_impl<_Res(_ArgTypes...) volatile> 00085 { typedef _Res result_type; }; 00086 00087 template<typename _Res, typename... _ArgTypes> 00088 struct _Weak_result_type_impl<_Res(_ArgTypes......) volatile> 00089 { typedef _Res result_type; }; 00090 00091 template<typename _Res, typename... _ArgTypes> 00092 struct _Weak_result_type_impl<_Res(_ArgTypes...) const volatile> 00093 { typedef _Res result_type; }; 00094 00095 template<typename _Res, typename... _ArgTypes> 00096 struct _Weak_result_type_impl<_Res(_ArgTypes......) const volatile> 00097 { typedef _Res result_type; }; 00098 00099 /// Retrieve the result type for a function reference. 00100 template<typename _Res, typename... _ArgTypes> 00101 struct _Weak_result_type_impl<_Res(&)(_ArgTypes...)> 00102 { typedef _Res result_type; }; 00103 00104 template<typename _Res, typename... _ArgTypes> 00105 struct _Weak_result_type_impl<_Res(&)(_ArgTypes......)> 00106 { typedef _Res result_type; }; 00107 00108 /// Retrieve the result type for a function pointer. 00109 template<typename _Res, typename... _ArgTypes> 00110 struct _Weak_result_type_impl<_Res(*)(_ArgTypes...)> 00111 { typedef _Res result_type; }; 00112 00113 template<typename _Res, typename... _ArgTypes> 00114 struct _Weak_result_type_impl<_Res(*)(_ArgTypes......)> 00115 { typedef _Res result_type; }; 00116 00117 /// Retrieve result type for a member function pointer. 00118 template<typename _Res, typename _Class, typename... _ArgTypes> 00119 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...)> 00120 { typedef _Res result_type; }; 00121 00122 template<typename _Res, typename _Class, typename... _ArgTypes> 00123 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......)> 00124 { typedef _Res result_type; }; 00125 00126 /// Retrieve result type for a const member function pointer. 00127 template<typename _Res, typename _Class, typename... _ArgTypes> 00128 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) const> 00129 { typedef _Res result_type; }; 00130 00131 template<typename _Res, typename _Class, typename... _ArgTypes> 00132 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) const> 00133 { typedef _Res result_type; }; 00134 00135 /// Retrieve result type for a volatile member function pointer. 00136 template<typename _Res, typename _Class, typename... _ArgTypes> 00137 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) volatile> 00138 { typedef _Res result_type; }; 00139 00140 template<typename _Res, typename _Class, typename... _ArgTypes> 00141 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) volatile> 00142 { typedef _Res result_type; }; 00143 00144 /// Retrieve result type for a const volatile member function pointer. 00145 template<typename _Res, typename _Class, typename... _ArgTypes> 00146 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) 00147 const volatile> 00148 { typedef _Res result_type; }; 00149 00150 template<typename _Res, typename _Class, typename... _ArgTypes> 00151 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) 00152 const volatile> 00153 { typedef _Res result_type; }; 00154 00155 /** 00156 * Strip top-level cv-qualifiers from the function object and let 00157 * _Weak_result_type_impl perform the real work. 00158 */ 00159 template<typename _Functor> 00160 struct _Weak_result_type 00161 : _Weak_result_type_impl<typename remove_cv<_Functor>::type> 00162 { }; 00163 00164 // Detect nested argument_type. 00165 template<typename _Tp, typename = __void_t<>> 00166 struct _Refwrap_base_arg1 00167 { }; 00168 00169 // Nested argument_type. 00170 template<typename _Tp> 00171 struct _Refwrap_base_arg1<_Tp, 00172 __void_t<typename _Tp::argument_type>> 00173 { 00174 typedef typename _Tp::argument_type argument_type; 00175 }; 00176 00177 // Detect nested first_argument_type and second_argument_type. 00178 template<typename _Tp, typename = __void_t<>> 00179 struct _Refwrap_base_arg2 00180 { }; 00181 00182 // Nested first_argument_type and second_argument_type. 00183 template<typename _Tp> 00184 struct _Refwrap_base_arg2<_Tp, 00185 __void_t<typename _Tp::first_argument_type, 00186 typename _Tp::second_argument_type>> 00187 { 00188 typedef typename _Tp::first_argument_type first_argument_type; 00189 typedef typename _Tp::second_argument_type second_argument_type; 00190 }; 00191 00192 /** 00193 * Derives from unary_function or binary_function when it 00194 * can. Specializations handle all of the easy cases. The primary 00195 * template determines what to do with a class type, which may 00196 * derive from both unary_function and binary_function. 00197 */ 00198 template<typename _Tp> 00199 struct _Reference_wrapper_base 00200 : _Weak_result_type<_Tp>, _Refwrap_base_arg1<_Tp>, _Refwrap_base_arg2<_Tp> 00201 { }; 00202 00203 // - a function type (unary) 00204 template<typename _Res, typename _T1> 00205 struct _Reference_wrapper_base<_Res(_T1)> 00206 : unary_function<_T1, _Res> 00207 { }; 00208 00209 template<typename _Res, typename _T1> 00210 struct _Reference_wrapper_base<_Res(_T1) const> 00211 : unary_function<_T1, _Res> 00212 { }; 00213 00214 template<typename _Res, typename _T1> 00215 struct _Reference_wrapper_base<_Res(_T1) volatile> 00216 : unary_function<_T1, _Res> 00217 { }; 00218 00219 template<typename _Res, typename _T1> 00220 struct _Reference_wrapper_base<_Res(_T1) const volatile> 00221 : unary_function<_T1, _Res> 00222 { }; 00223 00224 // - a function type (binary) 00225 template<typename _Res, typename _T1, typename _T2> 00226 struct _Reference_wrapper_base<_Res(_T1, _T2)> 00227 : binary_function<_T1, _T2, _Res> 00228 { }; 00229 00230 template<typename _Res, typename _T1, typename _T2> 00231 struct _Reference_wrapper_base<_Res(_T1, _T2) const> 00232 : binary_function<_T1, _T2, _Res> 00233 { }; 00234 00235 template<typename _Res, typename _T1, typename _T2> 00236 struct _Reference_wrapper_base<_Res(_T1, _T2) volatile> 00237 : binary_function<_T1, _T2, _Res> 00238 { }; 00239 00240 template<typename _Res, typename _T1, typename _T2> 00241 struct _Reference_wrapper_base<_Res(_T1, _T2) const volatile> 00242 : binary_function<_T1, _T2, _Res> 00243 { }; 00244 00245 // - a function pointer type (unary) 00246 template<typename _Res, typename _T1> 00247 struct _Reference_wrapper_base<_Res(*)(_T1)> 00248 : unary_function<_T1, _Res> 00249 { }; 00250 00251 // - a function pointer type (binary) 00252 template<typename _Res, typename _T1, typename _T2> 00253 struct _Reference_wrapper_base<_Res(*)(_T1, _T2)> 00254 : binary_function<_T1, _T2, _Res> 00255 { }; 00256 00257 // - a pointer to member function type (unary, no qualifiers) 00258 template<typename _Res, typename _T1> 00259 struct _Reference_wrapper_base<_Res (_T1::*)()> 00260 : unary_function<_T1*, _Res> 00261 { }; 00262 00263 // - a pointer to member function type (binary, no qualifiers) 00264 template<typename _Res, typename _T1, typename _T2> 00265 struct _Reference_wrapper_base<_Res (_T1::*)(_T2)> 00266 : binary_function<_T1*, _T2, _Res> 00267 { }; 00268 00269 // - a pointer to member function type (unary, const) 00270 template<typename _Res, typename _T1> 00271 struct _Reference_wrapper_base<_Res (_T1::*)() const> 00272 : unary_function<const _T1*, _Res> 00273 { }; 00274 00275 // - a pointer to member function type (binary, const) 00276 template<typename _Res, typename _T1, typename _T2> 00277 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const> 00278 : binary_function<const _T1*, _T2, _Res> 00279 { }; 00280 00281 // - a pointer to member function type (unary, volatile) 00282 template<typename _Res, typename _T1> 00283 struct _Reference_wrapper_base<_Res (_T1::*)() volatile> 00284 : unary_function<volatile _T1*, _Res> 00285 { }; 00286 00287 // - a pointer to member function type (binary, volatile) 00288 template<typename _Res, typename _T1, typename _T2> 00289 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) volatile> 00290 : binary_function<volatile _T1*, _T2, _Res> 00291 { }; 00292 00293 // - a pointer to member function type (unary, const volatile) 00294 template<typename _Res, typename _T1> 00295 struct _Reference_wrapper_base<_Res (_T1::*)() const volatile> 00296 : unary_function<const volatile _T1*, _Res> 00297 { }; 00298 00299 // - a pointer to member function type (binary, const volatile) 00300 template<typename _Res, typename _T1, typename _T2> 00301 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const volatile> 00302 : binary_function<const volatile _T1*, _T2, _Res> 00303 { }; 00304 00305 /** 00306 * @brief Primary class template for reference_wrapper. 00307 * @ingroup functors 00308 * @{ 00309 */ 00310 template<typename _Tp> 00311 class reference_wrapper 00312 : public _Reference_wrapper_base<typename remove_cv<_Tp>::type> 00313 { 00314 _Tp* _M_data; 00315 00316 public: 00317 typedef _Tp type; 00318 00319 reference_wrapper(_Tp& __indata) noexcept 00320 : _M_data(std::__addressof(__indata)) 00321 { } 00322 00323 reference_wrapper(_Tp&&) = delete; 00324 00325 reference_wrapper(const reference_wrapper&) = default; 00326 00327 reference_wrapper& 00328 operator=(const reference_wrapper&) = default; 00329 00330 operator _Tp&() const noexcept 00331 { return this->get(); } 00332 00333 _Tp& 00334 get() const noexcept 00335 { return *_M_data; } 00336 00337 template<typename... _Args> 00338 typename result_of<_Tp&(_Args&&...)>::type 00339 operator()(_Args&&... __args) const 00340 { 00341 return std::__invoke(get(), std::forward<_Args>(__args)...); 00342 } 00343 }; 00344 00345 00346 /// Denotes a reference should be taken to a variable. 00347 template<typename _Tp> 00348 inline reference_wrapper<_Tp> 00349 ref(_Tp& __t) noexcept 00350 { return reference_wrapper<_Tp>(__t); } 00351 00352 /// Denotes a const reference should be taken to a variable. 00353 template<typename _Tp> 00354 inline reference_wrapper<const _Tp> 00355 cref(const _Tp& __t) noexcept 00356 { return reference_wrapper<const _Tp>(__t); } 00357 00358 template<typename _Tp> 00359 void ref(const _Tp&&) = delete; 00360 00361 template<typename _Tp> 00362 void cref(const _Tp&&) = delete; 00363 00364 /// Partial specialization. 00365 template<typename _Tp> 00366 inline reference_wrapper<_Tp> 00367 ref(reference_wrapper<_Tp> __t) noexcept 00368 { return ref(__t.get()); } 00369 00370 /// Partial specialization. 00371 template<typename _Tp> 00372 inline reference_wrapper<const _Tp> 00373 cref(reference_wrapper<_Tp> __t) noexcept 00374 { return cref(__t.get()); } 00375 00376 // @} group functors 00377 00378 _GLIBCXX_END_NAMESPACE_VERSION 00379 } // namespace std 00380 00381 #endif // C++11 00382 00383 #endif // _GLIBCXX_REFWRAP_H