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