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 _GLIBCXX_NOEXCEPT_PARM> 00068 struct _Weak_result_type_impl<_Res(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL> 00069 { typedef _Res result_type; }; 00070 00071 template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM> 00072 struct _Weak_result_type_impl<_Res(_ArgTypes......) _GLIBCXX_NOEXCEPT_QUAL> 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 _GLIBCXX_NOEXCEPT_PARM> 00110 struct _Weak_result_type_impl<_Res(*)(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL> 00111 { typedef _Res result_type; }; 00112 00113 template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM> 00114 struct _Weak_result_type_impl<_Res(*)(_ArgTypes......) 00115 _GLIBCXX_NOEXCEPT_QUAL> 00116 { typedef _Res result_type; }; 00117 00118 /// Retrieve result type for a member function pointer. 00119 template<typename _Res, typename _Class, typename... _ArgTypes 00120 _GLIBCXX_NOEXCEPT_PARM> 00121 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) 00122 _GLIBCXX_NOEXCEPT_QUAL> 00123 { typedef _Res result_type; }; 00124 00125 template<typename _Res, typename _Class, typename... _ArgTypes 00126 _GLIBCXX_NOEXCEPT_PARM> 00127 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) 00128 _GLIBCXX_NOEXCEPT_QUAL> 00129 { typedef _Res result_type; }; 00130 00131 /// Retrieve result type for a const member function pointer. 00132 template<typename _Res, typename _Class, typename... _ArgTypes 00133 _GLIBCXX_NOEXCEPT_PARM> 00134 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) const 00135 _GLIBCXX_NOEXCEPT_QUAL> 00136 { typedef _Res result_type; }; 00137 00138 template<typename _Res, typename _Class, typename... _ArgTypes 00139 _GLIBCXX_NOEXCEPT_PARM> 00140 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) const 00141 _GLIBCXX_NOEXCEPT_QUAL> 00142 { typedef _Res result_type; }; 00143 00144 /// Retrieve result type for a volatile member function pointer. 00145 template<typename _Res, typename _Class, typename... _ArgTypes 00146 _GLIBCXX_NOEXCEPT_PARM> 00147 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) volatile 00148 _GLIBCXX_NOEXCEPT_QUAL> 00149 { typedef _Res result_type; }; 00150 00151 template<typename _Res, typename _Class, typename... _ArgTypes 00152 _GLIBCXX_NOEXCEPT_PARM> 00153 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) volatile 00154 _GLIBCXX_NOEXCEPT_QUAL> 00155 { typedef _Res result_type; }; 00156 00157 /// Retrieve result type for a const volatile member function pointer. 00158 template<typename _Res, typename _Class, typename... _ArgTypes 00159 _GLIBCXX_NOEXCEPT_PARM> 00160 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes...) 00161 const volatile _GLIBCXX_NOEXCEPT_QUAL> 00162 { typedef _Res result_type; }; 00163 00164 template<typename _Res, typename _Class, typename... _ArgTypes 00165 _GLIBCXX_NOEXCEPT_PARM> 00166 struct _Weak_result_type_impl<_Res (_Class::*)(_ArgTypes......) 00167 const volatile _GLIBCXX_NOEXCEPT_QUAL> 00168 { typedef _Res result_type; }; 00169 00170 /** 00171 * Strip top-level cv-qualifiers from the function object and let 00172 * _Weak_result_type_impl perform the real work. 00173 */ 00174 template<typename _Functor> 00175 struct _Weak_result_type 00176 : _Weak_result_type_impl<typename remove_cv<_Functor>::type> 00177 { }; 00178 00179 // Detect nested argument_type. 00180 template<typename _Tp, typename = __void_t<>> 00181 struct _Refwrap_base_arg1 00182 { }; 00183 00184 // Nested argument_type. 00185 template<typename _Tp> 00186 struct _Refwrap_base_arg1<_Tp, 00187 __void_t<typename _Tp::argument_type>> 00188 { 00189 typedef typename _Tp::argument_type argument_type; 00190 }; 00191 00192 // Detect nested first_argument_type and second_argument_type. 00193 template<typename _Tp, typename = __void_t<>> 00194 struct _Refwrap_base_arg2 00195 { }; 00196 00197 // Nested first_argument_type and second_argument_type. 00198 template<typename _Tp> 00199 struct _Refwrap_base_arg2<_Tp, 00200 __void_t<typename _Tp::first_argument_type, 00201 typename _Tp::second_argument_type>> 00202 { 00203 typedef typename _Tp::first_argument_type first_argument_type; 00204 typedef typename _Tp::second_argument_type second_argument_type; 00205 }; 00206 00207 /** 00208 * Derives from unary_function or binary_function when it 00209 * can. Specializations handle all of the easy cases. The primary 00210 * template determines what to do with a class type, which may 00211 * derive from both unary_function and binary_function. 00212 */ 00213 template<typename _Tp> 00214 struct _Reference_wrapper_base 00215 : _Weak_result_type<_Tp>, _Refwrap_base_arg1<_Tp>, _Refwrap_base_arg2<_Tp> 00216 { }; 00217 00218 // - a function type (unary) 00219 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM> 00220 struct _Reference_wrapper_base<_Res(_T1) _GLIBCXX_NOEXCEPT_QUAL> 00221 : unary_function<_T1, _Res> 00222 { }; 00223 00224 template<typename _Res, typename _T1> 00225 struct _Reference_wrapper_base<_Res(_T1) const> 00226 : unary_function<_T1, _Res> 00227 { }; 00228 00229 template<typename _Res, typename _T1> 00230 struct _Reference_wrapper_base<_Res(_T1) volatile> 00231 : unary_function<_T1, _Res> 00232 { }; 00233 00234 template<typename _Res, typename _T1> 00235 struct _Reference_wrapper_base<_Res(_T1) const volatile> 00236 : unary_function<_T1, _Res> 00237 { }; 00238 00239 // - a function type (binary) 00240 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM> 00241 struct _Reference_wrapper_base<_Res(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL> 00242 : binary_function<_T1, _T2, _Res> 00243 { }; 00244 00245 template<typename _Res, typename _T1, typename _T2> 00246 struct _Reference_wrapper_base<_Res(_T1, _T2) const> 00247 : binary_function<_T1, _T2, _Res> 00248 { }; 00249 00250 template<typename _Res, typename _T1, typename _T2> 00251 struct _Reference_wrapper_base<_Res(_T1, _T2) volatile> 00252 : binary_function<_T1, _T2, _Res> 00253 { }; 00254 00255 template<typename _Res, typename _T1, typename _T2> 00256 struct _Reference_wrapper_base<_Res(_T1, _T2) const volatile> 00257 : binary_function<_T1, _T2, _Res> 00258 { }; 00259 00260 // - a function pointer type (unary) 00261 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM> 00262 struct _Reference_wrapper_base<_Res(*)(_T1) _GLIBCXX_NOEXCEPT_QUAL> 00263 : unary_function<_T1, _Res> 00264 { }; 00265 00266 // - a function pointer type (binary) 00267 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM> 00268 struct _Reference_wrapper_base<_Res(*)(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL> 00269 : binary_function<_T1, _T2, _Res> 00270 { }; 00271 00272 // - a pointer to member function type (unary, no qualifiers) 00273 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM> 00274 struct _Reference_wrapper_base<_Res (_T1::*)() _GLIBCXX_NOEXCEPT_QUAL> 00275 : unary_function<_T1*, _Res> 00276 { }; 00277 00278 // - a pointer to member function type (binary, no qualifiers) 00279 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM> 00280 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) _GLIBCXX_NOEXCEPT_QUAL> 00281 : binary_function<_T1*, _T2, _Res> 00282 { }; 00283 00284 // - a pointer to member function type (unary, const) 00285 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM> 00286 struct _Reference_wrapper_base<_Res (_T1::*)() const _GLIBCXX_NOEXCEPT_QUAL> 00287 : unary_function<const _T1*, _Res> 00288 { }; 00289 00290 // - a pointer to member function type (binary, const) 00291 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM> 00292 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const _GLIBCXX_NOEXCEPT_QUAL> 00293 : binary_function<const _T1*, _T2, _Res> 00294 { }; 00295 00296 // - a pointer to member function type (unary, volatile) 00297 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM> 00298 struct _Reference_wrapper_base<_Res (_T1::*)() volatile _GLIBCXX_NOEXCEPT_QUAL> 00299 : unary_function<volatile _T1*, _Res> 00300 { }; 00301 00302 // - a pointer to member function type (binary, volatile) 00303 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM> 00304 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) volatile _GLIBCXX_NOEXCEPT_QUAL> 00305 : binary_function<volatile _T1*, _T2, _Res> 00306 { }; 00307 00308 // - a pointer to member function type (unary, const volatile) 00309 template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM> 00310 struct _Reference_wrapper_base<_Res (_T1::*)() const volatile _GLIBCXX_NOEXCEPT_QUAL> 00311 : unary_function<const volatile _T1*, _Res> 00312 { }; 00313 00314 // - a pointer to member function type (binary, const volatile) 00315 template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM> 00316 struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const volatile _GLIBCXX_NOEXCEPT_QUAL> 00317 : binary_function<const volatile _T1*, _T2, _Res> 00318 { }; 00319 00320 /** 00321 * @brief Primary class template for reference_wrapper. 00322 * @ingroup functors 00323 * @{ 00324 */ 00325 template<typename _Tp> 00326 class reference_wrapper 00327 : public _Reference_wrapper_base<typename remove_cv<_Tp>::type> 00328 { 00329 _Tp* _M_data; 00330 00331 public: 00332 typedef _Tp type; 00333 00334 reference_wrapper(_Tp& __indata) noexcept 00335 : _M_data(std::__addressof(__indata)) 00336 { } 00337 00338 reference_wrapper(_Tp&&) = delete; 00339 00340 reference_wrapper(const reference_wrapper&) = default; 00341 00342 reference_wrapper& 00343 operator=(const reference_wrapper&) = default; 00344 00345 operator _Tp&() const noexcept 00346 { return this->get(); } 00347 00348 _Tp& 00349 get() const noexcept 00350 { return *_M_data; } 00351 00352 template<typename... _Args> 00353 typename result_of<_Tp&(_Args&&...)>::type 00354 operator()(_Args&&... __args) const 00355 { 00356 return std::__invoke(get(), std::forward<_Args>(__args)...); 00357 } 00358 }; 00359 00360 00361 /// Denotes a reference should be taken to a variable. 00362 template<typename _Tp> 00363 inline reference_wrapper<_Tp> 00364 ref(_Tp& __t) noexcept 00365 { return reference_wrapper<_Tp>(__t); } 00366 00367 /// Denotes a const reference should be taken to a variable. 00368 template<typename _Tp> 00369 inline reference_wrapper<const _Tp> 00370 cref(const _Tp& __t) noexcept 00371 { return reference_wrapper<const _Tp>(__t); } 00372 00373 template<typename _Tp> 00374 void ref(const _Tp&&) = delete; 00375 00376 template<typename _Tp> 00377 void cref(const _Tp&&) = delete; 00378 00379 /// Partial specialization. 00380 template<typename _Tp> 00381 inline reference_wrapper<_Tp> 00382 ref(reference_wrapper<_Tp> __t) noexcept 00383 { return ref(__t.get()); } 00384 00385 /// Partial specialization. 00386 template<typename _Tp> 00387 inline reference_wrapper<const _Tp> 00388 cref(reference_wrapper<_Tp> __t) noexcept 00389 { return cref(__t.get()); } 00390 00391 // @} group functors 00392 00393 _GLIBCXX_END_NAMESPACE_VERSION 00394 } // namespace std 00395 00396 #endif // C++11 00397 00398 #endif // _GLIBCXX_REFWRAP_H