1 // Node handles for containers -*- C++ -*- 2 3 // Copyright (C) 2016-2022 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 bits/node_handle.h 26 * This is an internal header file, included by other library headers. 27 * Do not attempt to use it directly. 28 * @headername{map,set,unordered_map,unordered_set} 29 */ 30 31 #ifndef _NODE_HANDLE 32 #define _NODE_HANDLE 1 33 34 #pragma GCC system_header 35 36 #if __cplusplus >= 201703L 37 # define __cpp_lib_node_extract 201606L 38 39 #include <new> 40 #include <bits/alloc_traits.h> 41 #include <bits/ptr_traits.h> 42 43 namespace std _GLIBCXX_VISIBILITY(default) 44 { 45 _GLIBCXX_BEGIN_NAMESPACE_VERSION 46 47 /** 48 * @defgroup node_handles Node handles 49 * @ingroup associative_containers 50 * @since C++17 51 * 52 * The associative containers (`map`, `set`, `multimap` and `multiset`) 53 * support extracting and re-inserting nodes from the container. Those 54 * operations use the container's `node_handle` type, which is an alias 55 * for a `_Node_handle<...>` type. You should always use the container's 56 * `node_handle` type (e.g. `std::set<int>::node_handle`) to refer to 57 * these types, not the non-standard internal `_Node_handle` names. 58 * 59 * @{ 60 */ 61 62 /// Base class for node handle types of maps and sets. 63 template<typename _Val, typename _NodeAlloc> 64 class _Node_handle_common 65 { 66 using _AllocTraits = allocator_traits<_NodeAlloc>; 67 68 public: 69 using allocator_type = __alloc_rebind<_NodeAlloc, _Val>; 70 71 allocator_type 72 get_allocator() const noexcept 73 { 74 __glibcxx_assert(!this->empty()); 75 return allocator_type(_M_alloc._M_alloc); 76 } 77 78 explicit operator bool() const noexcept { return _M_ptr != nullptr; } 79 80 [[nodiscard]] bool empty() const noexcept { return _M_ptr == nullptr; } 81 82 /// @cond undocumented 83 protected: 84 constexpr _Node_handle_common() noexcept : _M_ptr() { } 85 86 ~_Node_handle_common() 87 { 88 if (!empty()) 89 _M_reset(); 90 } 91 92 _Node_handle_common(_Node_handle_common&& __nh) noexcept 93 : _M_ptr(__nh._M_ptr) 94 { 95 if (_M_ptr) 96 _M_move(std::move(__nh)); 97 } 98 99 _Node_handle_common& 100 operator=(_Node_handle_common&& __nh) noexcept 101 { 102 if (empty()) 103 { 104 if (!__nh.empty()) 105 _M_move(std::move(__nh)); 106 } 107 else if (__nh.empty()) 108 _M_reset(); 109 else 110 { 111 // Free the current node before replacing the allocator. 112 _AllocTraits::destroy(*_M_alloc, _M_ptr->_M_valptr()); 113 _AllocTraits::deallocate(*_M_alloc, _M_ptr, 1); 114 115 _M_alloc = __nh._M_alloc.release(); // assigns if POCMA 116 _M_ptr = __nh._M_ptr; 117 __nh._M_ptr = nullptr; 118 } 119 return *this; 120 } 121 122 _Node_handle_common(typename _AllocTraits::pointer __ptr, 123 const _NodeAlloc& __alloc) 124 : _M_ptr(__ptr), _M_alloc(__alloc) 125 { 126 __glibcxx_assert(__ptr != nullptr); 127 } 128 129 void 130 _M_swap(_Node_handle_common& __nh) noexcept 131 { 132 if (empty()) 133 { 134 if (!__nh.empty()) 135 _M_move(std::move(__nh)); 136 } 137 else if (__nh.empty()) 138 __nh._M_move(std::move(*this)); 139 else 140 { 141 using std::swap; 142 swap(_M_ptr, __nh._M_ptr); 143 _M_alloc.swap(__nh._M_alloc); // swaps if POCS 144 } 145 } 146 147 private: 148 // Moves the pointer and allocator from __nh to *this. 149 // Precondition: empty() && !__nh.empty() 150 // Postcondition: !empty() && __nh.empty() 151 void 152 _M_move(_Node_handle_common&& __nh) noexcept 153 { 154 ::new (std::__addressof(_M_alloc)) _NodeAlloc(__nh._M_alloc.release()); 155 _M_ptr = __nh._M_ptr; 156 __nh._M_ptr = nullptr; 157 } 158 159 // Deallocates the node, destroys the allocator. 160 // Precondition: !empty() 161 // Postcondition: empty() 162 void 163 _M_reset() noexcept 164 { 165 _NodeAlloc __alloc = _M_alloc.release(); 166 _AllocTraits::destroy(__alloc, _M_ptr->_M_valptr()); 167 _AllocTraits::deallocate(__alloc, _M_ptr, 1); 168 _M_ptr = nullptr; 169 } 170 171 protected: 172 typename _AllocTraits::pointer _M_ptr; 173 174 private: 175 // A simplified, non-copyable std::optional<_NodeAlloc>. 176 // Call release() before destruction iff the allocator member is active. 177 union _Optional_alloc 178 { 179 _Optional_alloc() { } 180 ~_Optional_alloc() { } 181 182 _Optional_alloc(_Optional_alloc&&) = delete; 183 _Optional_alloc& operator=(_Optional_alloc&&) = delete; 184 185 _Optional_alloc(const _NodeAlloc& __alloc) noexcept 186 : _M_alloc(__alloc) 187 { } 188 189 // Precondition: _M_alloc is the active member of the union. 190 void 191 operator=(_NodeAlloc&& __alloc) noexcept 192 { 193 using _ATr = _AllocTraits; 194 if constexpr (_ATr::propagate_on_container_move_assignment::value) 195 _M_alloc = std::move(__alloc); 196 else if constexpr (!_AllocTraits::is_always_equal::value) 197 __glibcxx_assert(_M_alloc == __alloc); 198 } 199 200 // Precondition: _M_alloc is the active member of both unions. 201 void 202 swap(_Optional_alloc& __other) noexcept 203 { 204 using std::swap; 205 if constexpr (_AllocTraits::propagate_on_container_swap::value) 206 swap(_M_alloc, __other._M_alloc); 207 else if constexpr (!_AllocTraits::is_always_equal::value) 208 __glibcxx_assert(_M_alloc == __other._M_alloc); 209 } 210 211 // Precondition: _M_alloc is the active member of the union. 212 _NodeAlloc& operator*() noexcept { return _M_alloc; } 213 214 // Precondition: _M_alloc is the active member of the union. 215 _NodeAlloc release() noexcept 216 { 217 _NodeAlloc __tmp = std::move(_M_alloc); 218 _M_alloc.~_NodeAlloc(); 219 return __tmp; 220 } 221 222 struct _Empty { }; 223 224 [[__no_unique_address__]] _Empty _M_empty; 225 [[__no_unique_address__]] _NodeAlloc _M_alloc; 226 }; 227 228 [[__no_unique_address__]] _Optional_alloc _M_alloc; 229 230 template<typename _Key2, typename _Value2, typename _KeyOfValue, 231 typename _Compare, typename _ValueAlloc> 232 friend class _Rb_tree; 233 234 /// @endcond 235 }; 236 237 /// Node handle type for maps. 238 template<typename _Key, typename _Value, typename _NodeAlloc> 239 class _Node_handle : public _Node_handle_common<_Value, _NodeAlloc> 240 { 241 public: 242 constexpr _Node_handle() noexcept = default; 243 ~_Node_handle() = default; 244 _Node_handle(_Node_handle&&) noexcept = default; 245 246 _Node_handle& 247 operator=(_Node_handle&&) noexcept = default; 248 249 using key_type = _Key; 250 using mapped_type = typename _Value::second_type; 251 252 key_type& 253 key() const noexcept 254 { 255 __glibcxx_assert(!this->empty()); 256 return *_M_pkey; 257 } 258 259 mapped_type& 260 mapped() const noexcept 261 { 262 __glibcxx_assert(!this->empty()); 263 return *_M_pmapped; 264 } 265 266 void 267 swap(_Node_handle& __nh) noexcept 268 { 269 this->_M_swap(__nh); 270 using std::swap; 271 swap(_M_pkey, __nh._M_pkey); 272 swap(_M_pmapped, __nh._M_pmapped); 273 } 274 275 friend void 276 swap(_Node_handle& __x, _Node_handle& __y) 277 noexcept(noexcept(__x.swap(__y))) 278 { __x.swap(__y); } 279 280 private: 281 using _AllocTraits = allocator_traits<_NodeAlloc>; 282 283 _Node_handle(typename _AllocTraits::pointer __ptr, 284 const _NodeAlloc& __alloc) 285 : _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc) 286 { 287 if (__ptr) 288 { 289 auto& __key = const_cast<_Key&>(__ptr->_M_valptr()->first); 290 _M_pkey = _S_pointer_to(__key); 291 _M_pmapped = _S_pointer_to(__ptr->_M_valptr()->second); 292 } 293 else 294 { 295 _M_pkey = nullptr; 296 _M_pmapped = nullptr; 297 } 298 } 299 300 template<typename _Tp> 301 using __pointer 302 = __ptr_rebind<typename _AllocTraits::pointer, 303 remove_reference_t<_Tp>>; 304 305 __pointer<_Key> _M_pkey = nullptr; 306 __pointer<typename _Value::second_type> _M_pmapped = nullptr; 307 308 template<typename _Tp> 309 __pointer<_Tp> 310 _S_pointer_to(_Tp& __obj) 311 { return pointer_traits<__pointer<_Tp>>::pointer_to(__obj); } 312 313 const key_type& 314 _M_key() const noexcept { return key(); } 315 316 template<typename _Key2, typename _Value2, typename _KeyOfValue, 317 typename _Compare, typename _ValueAlloc> 318 friend class _Rb_tree; 319 320 template<typename _Key2, typename _Value2, typename _ValueAlloc, 321 typename _ExtractKey, typename _Equal, 322 typename _Hash, typename _RangeHash, typename _Unused, 323 typename _RehashPolicy, typename _Traits> 324 friend class _Hashtable; 325 }; 326 327 /// Node handle type for sets. 328 template<typename _Value, typename _NodeAlloc> 329 class _Node_handle<_Value, _Value, _NodeAlloc> 330 : public _Node_handle_common<_Value, _NodeAlloc> 331 { 332 public: 333 constexpr _Node_handle() noexcept = default; 334 ~_Node_handle() = default; 335 _Node_handle(_Node_handle&&) noexcept = default; 336 337 _Node_handle& 338 operator=(_Node_handle&&) noexcept = default; 339 340 using value_type = _Value; 341 342 value_type& 343 value() const noexcept 344 { 345 __glibcxx_assert(!this->empty()); 346 return *this->_M_ptr->_M_valptr(); 347 } 348 349 void 350 swap(_Node_handle& __nh) noexcept 351 { this->_M_swap(__nh); } 352 353 friend void 354 swap(_Node_handle& __x, _Node_handle& __y) 355 noexcept(noexcept(__x.swap(__y))) 356 { __x.swap(__y); } 357 358 private: 359 using _AllocTraits = allocator_traits<_NodeAlloc>; 360 361 _Node_handle(typename _AllocTraits::pointer __ptr, 362 const _NodeAlloc& __alloc) 363 : _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc) { } 364 365 const value_type& 366 _M_key() const noexcept { return value(); } 367 368 template<typename _Key, typename _Val, typename _KeyOfValue, 369 typename _Compare, typename _Alloc> 370 friend class _Rb_tree; 371 372 template<typename _Key2, typename _Value2, typename _ValueAlloc, 373 typename _ExtractKey, typename _Equal, 374 typename _Hash, typename _RangeHash, typename _Unused, 375 typename _RehashPolicy, typename _Traits> 376 friend class _Hashtable; 377 }; 378 379 /// Return type of insert(node_handle&&) on unique maps/sets. 380 template<typename _Iterator, typename _NodeHandle> 381 struct _Node_insert_return 382 { 383 _Iterator position = _Iterator(); 384 bool inserted = false; 385 _NodeHandle node; 386 }; 387 388 /// @} 389 390 _GLIBCXX_END_NAMESPACE_VERSION 391 } // namespace std 392 393 #endif // C++17 394 #endif 395