1 // Node handles for containers -*- C++ -*-
2
3 // Copyright (C) 2016-2021 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 201606
38
39 #include <new>
40 #include <bits/alloc_traits.h>
41 #include <bits/ptr_traits.h>
42
_GLIBCXX_VISIBILITY(default)43 namespace std _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46
47 /// Base class for node handle types of maps and sets.
48 template<typename _Val, typename _NodeAlloc>
49 class _Node_handle_common
50 {
51 using _AllocTraits = allocator_traits<_NodeAlloc>;
52
53 public:
54 using allocator_type = __alloc_rebind<_NodeAlloc, _Val>;
55
56 allocator_type
57 get_allocator() const noexcept
58 {
59 __glibcxx_assert(!this->empty());
60 return allocator_type(_M_alloc._M_alloc);
61 }
62
63 explicit operator bool() const noexcept { return _M_ptr != nullptr; }
64
65 [[nodiscard]] bool empty() const noexcept { return _M_ptr == nullptr; }
66
67 protected:
68 constexpr _Node_handle_common() noexcept : _M_ptr() { }
69
70 ~_Node_handle_common()
71 {
72 if (!empty())
73 _M_reset();
74 }
75
76 _Node_handle_common(_Node_handle_common&& __nh) noexcept
77 : _M_ptr(__nh._M_ptr)
78 {
79 if (_M_ptr)
80 _M_move(std::move(__nh));
81 }
82
83 _Node_handle_common&
84 operator=(_Node_handle_common&& __nh) noexcept
85 {
86 if (empty())
87 {
88 if (!__nh.empty())
89 _M_move(std::move(__nh));
90 }
91 else if (__nh.empty())
92 _M_reset();
93 else
94 {
95 // Free the current node before replacing the allocator.
96 _AllocTraits::destroy(*_M_alloc, _M_ptr->_M_valptr());
97 _AllocTraits::deallocate(*_M_alloc, _M_ptr, 1);
98
99 _M_alloc = __nh._M_alloc.release(); // assigns if POCMA
100 _M_ptr = __nh._M_ptr;
101 __nh._M_ptr = nullptr;
102 }
103 return *this;
104 }
105
106 _Node_handle_common(typename _AllocTraits::pointer __ptr,
107 const _NodeAlloc& __alloc)
108 : _M_ptr(__ptr), _M_alloc(__alloc)
109 {
110 __glibcxx_assert(__ptr != nullptr);
111 }
112
113 void
114 _M_swap(_Node_handle_common& __nh) noexcept
115 {
116 if (empty())
117 {
118 if (!__nh.empty())
119 _M_move(std::move(__nh));
120 }
121 else if (__nh.empty())
122 __nh._M_move(std::move(*this));
123 else
124 {
125 using std::swap;
126 swap(_M_ptr, __nh._M_ptr);
127 _M_alloc.swap(__nh._M_alloc); // swaps if POCS
128 }
129 }
130
131 private:
132 // Moves the pointer and allocator from __nh to *this.
133 // Precondition: empty() && !__nh.empty()
134 // Postcondition: !empty() && __nh.empty()
135 void
136 _M_move(_Node_handle_common&& __nh) noexcept
137 {
138 ::new (std::__addressof(_M_alloc)) _NodeAlloc(__nh._M_alloc.release());
139 _M_ptr = __nh._M_ptr;
140 __nh._M_ptr = nullptr;
141 }
142
143 // Deallocates the node, destroys the allocator.
144 // Precondition: !empty()
145 // Postcondition: empty()
146 void
147 _M_reset() noexcept
148 {
149 _NodeAlloc __alloc = _M_alloc.release();
150 _AllocTraits::destroy(__alloc, _M_ptr->_M_valptr());
151 _AllocTraits::deallocate(__alloc, _M_ptr, 1);
152 _M_ptr = nullptr;
153 }
154
155 protected:
156 typename _AllocTraits::pointer _M_ptr;
157
158 private:
159 // A simplified, non-copyable std::optional<_NodeAlloc>.
160 // Call release() before destruction iff the allocator member is active.
161 union _Optional_alloc
162 {
163 _Optional_alloc() { }
164 ~_Optional_alloc() { }
165
166 _Optional_alloc(_Optional_alloc&&) = delete;
167 _Optional_alloc& operator=(_Optional_alloc&&) = delete;
168
169 _Optional_alloc(const _NodeAlloc& __alloc) noexcept
170 : _M_alloc(__alloc)
171 { }
172
173 // Precondition: _M_alloc is the active member of the union.
174 void
175 operator=(_NodeAlloc&& __alloc) noexcept
176 {
177 using _ATr = _AllocTraits;
178 if constexpr (_ATr::propagate_on_container_move_assignment::value)
179 _M_alloc = std::move(__alloc);
180 else if constexpr (!_AllocTraits::is_always_equal::value)
181 __glibcxx_assert(_M_alloc == __alloc);
182 }
183
184 // Precondition: _M_alloc is the active member of both unions.
185 void
186 swap(_Optional_alloc& __other) noexcept
187 {
188 using std::swap;
189 if constexpr (_AllocTraits::propagate_on_container_swap::value)
190 swap(_M_alloc, __other._M_alloc);
191 else if constexpr (!_AllocTraits::is_always_equal::value)
192 __glibcxx_assert(_M_alloc == __other._M_alloc);
193 }
194
195 // Precondition: _M_alloc is the active member of the union.
196 _NodeAlloc& operator*() noexcept { return _M_alloc; }
197
198 // Precondition: _M_alloc is the active member of the union.
199 _NodeAlloc release() noexcept
200 {
201 _NodeAlloc __tmp = std::move(_M_alloc);
202 _M_alloc.~_NodeAlloc();
203 return __tmp;
204 }
205
206 struct _Empty { };
207
208 [[__no_unique_address__]] _Empty _M_empty;
209 [[__no_unique_address__]] _NodeAlloc _M_alloc;
210 };
211
212 [[__no_unique_address__]] _Optional_alloc _M_alloc;
213
214 template<typename _Key2, typename _Value2, typename _KeyOfValue,
215 typename _Compare, typename _ValueAlloc>
216 friend class _Rb_tree;
217 };
218
219 /// Node handle type for maps.
220 template<typename _Key, typename _Value, typename _NodeAlloc>
221 class _Node_handle : public _Node_handle_common<_Value, _NodeAlloc>
222 {
223 public:
224 constexpr _Node_handle() noexcept = default;
225 ~_Node_handle() = default;
226 _Node_handle(_Node_handle&&) noexcept = default;
227
228 _Node_handle&
229 operator=(_Node_handle&&) noexcept = default;
230
231 using key_type = _Key;
232 using mapped_type = typename _Value::second_type;
233
234 key_type&
235 key() const noexcept
236 {
237 __glibcxx_assert(!this->empty());
238 return *_M_pkey;
239 }
240
241 mapped_type&
242 mapped() const noexcept
243 {
244 __glibcxx_assert(!this->empty());
245 return *_M_pmapped;
246 }
247
248 void
249 swap(_Node_handle& __nh) noexcept
250 {
251 this->_M_swap(__nh);
252 using std::swap;
253 swap(_M_pkey, __nh._M_pkey);
254 swap(_M_pmapped, __nh._M_pmapped);
255 }
256
257 friend void
258 swap(_Node_handle& __x, _Node_handle& __y)
259 noexcept(noexcept(__x.swap(__y)))
260 { __x.swap(__y); }
261
262 private:
263 using _AllocTraits = allocator_traits<_NodeAlloc>;
264
265 _Node_handle(typename _AllocTraits::pointer __ptr,
266 const _NodeAlloc& __alloc)
267 : _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc)
268 {
269 if (__ptr)
270 {
271 auto& __key = const_cast<_Key&>(__ptr->_M_valptr()->first);
272 _M_pkey = _S_pointer_to(__key);
273 _M_pmapped = _S_pointer_to(__ptr->_M_valptr()->second);
274 }
275 else
276 {
277 _M_pkey = nullptr;
278 _M_pmapped = nullptr;
279 }
280 }
281
282 template<typename _Tp>
283 using __pointer
284 = __ptr_rebind<typename _AllocTraits::pointer,
285 remove_reference_t<_Tp>>;
286
287 __pointer<_Key> _M_pkey = nullptr;
288 __pointer<typename _Value::second_type> _M_pmapped = nullptr;
289
290 template<typename _Tp>
291 __pointer<_Tp>
292 _S_pointer_to(_Tp& __obj)
293 { return pointer_traits<__pointer<_Tp>>::pointer_to(__obj); }
294
295 const key_type&
296 _M_key() const noexcept { return key(); }
297
298 template<typename _Key2, typename _Value2, typename _KeyOfValue,
299 typename _Compare, typename _ValueAlloc>
300 friend class _Rb_tree;
301
302 template<typename _Key2, typename _Value2, typename _ValueAlloc,
303 typename _ExtractKey, typename _Equal,
304 typename _Hash, typename _RangeHash, typename _Unused,
305 typename _RehashPolicy, typename _Traits>
306 friend class _Hashtable;
307 };
308
309 /// Node handle type for sets.
310 template<typename _Value, typename _NodeAlloc>
311 class _Node_handle<_Value, _Value, _NodeAlloc>
312 : public _Node_handle_common<_Value, _NodeAlloc>
313 {
314 public:
315 constexpr _Node_handle() noexcept = default;
316 ~_Node_handle() = default;
317 _Node_handle(_Node_handle&&) noexcept = default;
318
319 _Node_handle&
320 operator=(_Node_handle&&) noexcept = default;
321
322 using value_type = _Value;
323
324 value_type&
325 value() const noexcept
326 {
327 __glibcxx_assert(!this->empty());
328 return *this->_M_ptr->_M_valptr();
329 }
330
331 void
332 swap(_Node_handle& __nh) noexcept
333 { this->_M_swap(__nh); }
334
335 friend void
336 swap(_Node_handle& __x, _Node_handle& __y)
337 noexcept(noexcept(__x.swap(__y)))
338 { __x.swap(__y); }
339
340 private:
341 using _AllocTraits = allocator_traits<_NodeAlloc>;
342
343 _Node_handle(typename _AllocTraits::pointer __ptr,
344 const _NodeAlloc& __alloc)
345 : _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc) { }
346
347 const value_type&
348 _M_key() const noexcept { return value(); }
349
350 template<typename _Key, typename _Val, typename _KeyOfValue,
351 typename _Compare, typename _Alloc>
352 friend class _Rb_tree;
353
354 template<typename _Key2, typename _Value2, typename _ValueAlloc,
355 typename _ExtractKey, typename _Equal,
356 typename _Hash, typename _RangeHash, typename _Unused,
357 typename _RehashPolicy, typename _Traits>
358 friend class _Hashtable;
359 };
360
361 /// Return type of insert(node_handle&&) on unique maps/sets.
362 template<typename _Iterator, typename _NodeHandle>
363 struct _Node_insert_return
364 {
365 _Iterator position = _Iterator();
366 bool inserted = false;
367 _NodeHandle node;
368 };
369
370 _GLIBCXX_END_NAMESPACE_VERSION
371 } // namespace std
372
373 #endif // C++17
374 #endif
375