1// unordered_map implementation -*- C++ -*-
2
3// Copyright (C) 2010-2019 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/unordered_map.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{unordered_map}
28 */
29
30#ifndef _UNORDERED_MAP_H
31#define _UNORDERED_MAP_H
32
33namespace std _GLIBCXX_VISIBILITY(default)
34{
35_GLIBCXX_BEGIN_NAMESPACE_VERSION
36_GLIBCXX_BEGIN_NAMESPACE_CONTAINER
37
38 /// Base types for unordered_map.
39 template<bool _Cache>
40 using __umap_traits = __detail::_Hashtable_traits<_Cache, false, true>;
41
42 template<typename _Key,
43 typename _Tp,
44 typename _Hash = hash<_Key>,
45 typename _Pred = std::equal_to<_Key>,
46 typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >,
47 typename _Tr = __umap_traits<__cache_default<_Key, _Hash>::value>>
48 using __umap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>,
49 _Alloc, __detail::_Select1st,
50 _Pred, _Hash,
51 __detail::_Mod_range_hashing,
52 __detail::_Default_ranged_hash,
53 __detail::_Prime_rehash_policy, _Tr>;
54
55 /// Base types for unordered_multimap.
56 template<bool _Cache>
57 using __ummap_traits = __detail::_Hashtable_traits<_Cache, false, false>;
58
59 template<typename _Key,
60 typename _Tp,
61 typename _Hash = hash<_Key>,
62 typename _Pred = std::equal_to<_Key>,
63 typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >,
64 typename _Tr = __ummap_traits<__cache_default<_Key, _Hash>::value>>
65 using __ummap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>,
66 _Alloc, __detail::_Select1st,
67 _Pred, _Hash,
68 __detail::_Mod_range_hashing,
69 __detail::_Default_ranged_hash,
70 __detail::_Prime_rehash_policy, _Tr>;
71
72 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
73 class unordered_multimap;
74
75 /**
76 * @brief A standard container composed of unique keys (containing
77 * at most one of each key value) that associates values of another type
78 * with the keys.
79 *
80 * @ingroup unordered_associative_containers
81 *
82 * @tparam _Key Type of key objects.
83 * @tparam _Tp Type of mapped objects.
84 * @tparam _Hash Hashing function object type, defaults to hash<_Value>.
85 * @tparam _Pred Predicate function object type, defaults
86 * to equal_to<_Value>.
87 * @tparam _Alloc Allocator type, defaults to
88 * std::allocator<std::pair<const _Key, _Tp>>.
89 *
90 * Meets the requirements of a <a href="tables.html#65">container</a>, and
91 * <a href="tables.html#xx">unordered associative container</a>
92 *
93 * The resulting value type of the container is std::pair<const _Key, _Tp>.
94 *
95 * Base is _Hashtable, dispatched at compile time via template
96 * alias __umap_hashtable.
97 */
98 template<typename _Key, typename _Tp,
99 typename _Hash = hash<_Key>,
100 typename _Pred = equal_to<_Key>,
101 typename _Alloc = allocator<std::pair<const _Key, _Tp>>>
102 class unordered_map
103 {
104 typedef __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc> _Hashtable;
105 _Hashtable _M_h;
106
107 public:
108 // typedefs:
109 //@{
110 /// Public typedefs.
111 typedef typename _Hashtable::key_type key_type;
112 typedef typename _Hashtable::value_type value_type;
113 typedef typename _Hashtable::mapped_type mapped_type;
114 typedef typename _Hashtable::hasher hasher;
115 typedef typename _Hashtable::key_equal key_equal;
116 typedef typename _Hashtable::allocator_type allocator_type;
117 //@}
118
119 //@{
120 /// Iterator-related typedefs.
121 typedef typename _Hashtable::pointer pointer;
122 typedef typename _Hashtable::const_pointer const_pointer;
123 typedef typename _Hashtable::reference reference;
124 typedef typename _Hashtable::const_reference const_reference;
125 typedef typename _Hashtable::iterator iterator;
126 typedef typename _Hashtable::const_iterator const_iterator;
127 typedef typename _Hashtable::local_iterator local_iterator;
128 typedef typename _Hashtable::const_local_iterator const_local_iterator;
129 typedef typename _Hashtable::size_type size_type;
130 typedef typename _Hashtable::difference_type difference_type;
131 //@}
132
133#if __cplusplus > 201402L
134 using node_type = typename _Hashtable::node_type;
135 using insert_return_type = typename _Hashtable::insert_return_type;
136#endif
137
138 //construct/destroy/copy
139
140 /// Default constructor.
141 unordered_map() = default;
142
143 /**
144 * @brief Default constructor creates no elements.
145 * @param __n Minimal initial number of buckets.
146 * @param __hf A hash functor.
147 * @param __eql A key equality functor.
148 * @param __a An allocator object.
149 */
150 explicit
151 unordered_map(size_type __n,
152 const hasher& __hf = hasher(),
153 const key_equal& __eql = key_equal(),
154 const allocator_type& __a = allocator_type())
155 : _M_h(__n, __hf, __eql, __a)
156 { }
157
158 /**
159 * @brief Builds an %unordered_map from a range.
160 * @param __first An input iterator.
161 * @param __last An input iterator.
162 * @param __n Minimal initial number of buckets.
163 * @param __hf A hash functor.
164 * @param __eql A key equality functor.
165 * @param __a An allocator object.
166 *
167 * Create an %unordered_map consisting of copies of the elements from
168 * [__first,__last). This is linear in N (where N is
169 * distance(__first,__last)).
170 */
171 template<typename _InputIterator>
172 unordered_map(_InputIterator __first, _InputIterator __last,
173 size_type __n = 0,
174 const hasher& __hf = hasher(),
175 const key_equal& __eql = key_equal(),
176 const allocator_type& __a = allocator_type())
177 : _M_h(__first, __last, __n, __hf, __eql, __a)
178 { }
179
180 /// Copy constructor.
181 unordered_map(const unordered_map&) = default;
182
183 /// Move constructor.
184 unordered_map(unordered_map&&) = default;
185
186 /**
187 * @brief Creates an %unordered_map with no elements.
188 * @param __a An allocator object.
189 */
190 explicit
191 unordered_map(const allocator_type& __a)
192 : _M_h(__a)
193 { }
194
195 /*
196 * @brief Copy constructor with allocator argument.
197 * @param __uset Input %unordered_map to copy.
198 * @param __a An allocator object.
199 */
200 unordered_map(const unordered_map& __umap,
201 const allocator_type& __a)
202 : _M_h(__umap._M_h, __a)
203 { }
204
205 /*
206 * @brief Move constructor with allocator argument.
207 * @param __uset Input %unordered_map to move.
208 * @param __a An allocator object.
209 */
210 unordered_map(unordered_map&& __umap,
211 const allocator_type& __a)
212 : _M_h(std::move(__umap._M_h), __a)
213 { }
214
215 /**
216 * @brief Builds an %unordered_map from an initializer_list.
217 * @param __l An initializer_list.
218 * @param __n Minimal initial number of buckets.
219 * @param __hf A hash functor.
220 * @param __eql A key equality functor.
221 * @param __a An allocator object.
222 *
223 * Create an %unordered_map consisting of copies of the elements in the
224 * list. This is linear in N (where N is @a __l.size()).
225 */
226 unordered_map(initializer_list<value_type> __l,
227 size_type __n = 0,
228 const hasher& __hf = hasher(),
229 const key_equal& __eql = key_equal(),
230 const allocator_type& __a = allocator_type())
231 : _M_h(__l, __n, __hf, __eql, __a)
232 { }
233
234 unordered_map(size_type __n, const allocator_type& __a)
235 : unordered_map(__n, hasher(), key_equal(), __a)
236 { }
237
238 unordered_map(size_type __n, const hasher& __hf,
239 const allocator_type& __a)
240 : unordered_map(__n, __hf, key_equal(), __a)
241 { }
242
243 template<typename _InputIterator>
244 unordered_map(_InputIterator __first, _InputIterator __last,
245 size_type __n,
246 const allocator_type& __a)
247 : unordered_map(__first, __last, __n, hasher(), key_equal(), __a)
248 { }
249
250 template<typename _InputIterator>
251 unordered_map(_InputIterator __first, _InputIterator __last,
252 size_type __n, const hasher& __hf,
253 const allocator_type& __a)
254 : unordered_map(__first, __last, __n, __hf, key_equal(), __a)
255 { }
256
257 unordered_map(initializer_list<value_type> __l,
258 size_type __n,
259 const allocator_type& __a)
260 : unordered_map(__l, __n, hasher(), key_equal(), __a)
261 { }
262
263 unordered_map(initializer_list<value_type> __l,
264 size_type __n, const hasher& __hf,
265 const allocator_type& __a)
266 : unordered_map(__l, __n, __hf, key_equal(), __a)
267 { }
268
269 /// Copy assignment operator.
270 unordered_map&
271 operator=(const unordered_map&) = default;
272
273 /// Move assignment operator.
274 unordered_map&
275 operator=(unordered_map&&) = default;
276
277 /**
278 * @brief %Unordered_map list assignment operator.
279 * @param __l An initializer_list.
280 *
281 * This function fills an %unordered_map with copies of the elements in
282 * the initializer list @a __l.
283 *
284 * Note that the assignment completely changes the %unordered_map and
285 * that the resulting %unordered_map's size is the same as the number
286 * of elements assigned.
287 */
288 unordered_map&
289 operator=(initializer_list<value_type> __l)
290 {
291 _M_h = __l;
292 return *this;
293 }
294
295 /// Returns the allocator object used by the %unordered_map.
296 allocator_type
297 get_allocator() const noexcept
298 { return _M_h.get_allocator(); }
299
300 // size and capacity:
301
302 /// Returns true if the %unordered_map is empty.
303 _GLIBCXX_NODISCARD bool
304 empty() const noexcept
305 { return _M_h.empty(); }
306
307 /// Returns the size of the %unordered_map.
308 size_type
309 size() const noexcept
310 { return _M_h.size(); }
311
312 /// Returns the maximum size of the %unordered_map.
313 size_type
314 max_size() const noexcept
315 { return _M_h.max_size(); }
316
317 // iterators.
318
319 /**
320 * Returns a read/write iterator that points to the first element in the
321 * %unordered_map.
322 */
323 iterator
324 begin() noexcept
325 { return _M_h.begin(); }
326
327 //@{
328 /**
329 * Returns a read-only (constant) iterator that points to the first
330 * element in the %unordered_map.
331 */
332 const_iterator
333 begin() const noexcept
334 { return _M_h.begin(); }
335
336 const_iterator
337 cbegin() const noexcept
338 { return _M_h.begin(); }
339 //@}
340
341 /**
342 * Returns a read/write iterator that points one past the last element in
343 * the %unordered_map.
344 */
345 iterator
346 end() noexcept
347 { return _M_h.end(); }
348
349 //@{
350 /**
351 * Returns a read-only (constant) iterator that points one past the last
352 * element in the %unordered_map.
353 */
354 const_iterator
355 end() const noexcept
356 { return _M_h.end(); }
357
358 const_iterator
359 cend() const noexcept
360 { return _M_h.end(); }
361 //@}
362
363 // modifiers.
364
365 /**
366 * @brief Attempts to build and insert a std::pair into the
367 * %unordered_map.
368 *
369 * @param __args Arguments used to generate a new pair instance (see
370 * std::piecewise_contruct for passing arguments to each
371 * part of the pair constructor).
372 *
373 * @return A pair, of which the first element is an iterator that points
374 * to the possibly inserted pair, and the second is a bool that
375 * is true if the pair was actually inserted.
376 *
377 * This function attempts to build and insert a (key, value) %pair into
378 * the %unordered_map.
379 * An %unordered_map relies on unique keys and thus a %pair is only
380 * inserted if its first element (the key) is not already present in the
381 * %unordered_map.
382 *
383 * Insertion requires amortized constant time.
384 */
385 template<typename... _Args>
386 std::pair<iterator, bool>
387 emplace(_Args&&... __args)
388 { return _M_h.emplace(std::forward<_Args>(__args)...); }
389
390 /**
391 * @brief Attempts to build and insert a std::pair into the
392 * %unordered_map.
393 *
394 * @param __pos An iterator that serves as a hint as to where the pair
395 * should be inserted.
396 * @param __args Arguments used to generate a new pair instance (see
397 * std::piecewise_contruct for passing arguments to each
398 * part of the pair constructor).
399 * @return An iterator that points to the element with key of the
400 * std::pair built from @a __args (may or may not be that
401 * std::pair).
402 *
403 * This function is not concerned about whether the insertion took place,
404 * and thus does not return a boolean like the single-argument emplace()
405 * does.
406 * Note that the first parameter is only a hint and can potentially
407 * improve the performance of the insertion process. A bad hint would
408 * cause no gains in efficiency.
409 *
410 * See
411 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
412 * for more on @a hinting.
413 *
414 * Insertion requires amortized constant time.
415 */
416 template<typename... _Args>
417 iterator
418 emplace_hint(const_iterator __pos, _Args&&... __args)
419 { return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); }
420
421#if __cplusplus > 201402L
422 /// Extract a node.
423 node_type
424 extract(const_iterator __pos)
425 {
426 __glibcxx_assert(__pos != end());
427 return _M_h.extract(__pos);
428 }
429
430 /// Extract a node.
431 node_type
432 extract(const key_type& __key)
433 { return _M_h.extract(__key); }
434
435 /// Re-insert an extracted node.
436 insert_return_type
437 insert(node_type&& __nh)
438 { return _M_h._M_reinsert_node(std::move(__nh)); }
439
440 /// Re-insert an extracted node.
441 iterator
442 insert(const_iterator, node_type&& __nh)
443 { return _M_h._M_reinsert_node(std::move(__nh)).position; }
444
445#define __cpp_lib_unordered_map_try_emplace 201411
446 /**
447 * @brief Attempts to build and insert a std::pair into the
448 * %unordered_map.
449 *
450 * @param __k Key to use for finding a possibly existing pair in
451 * the unordered_map.
452 * @param __args Arguments used to generate the .second for a
453 * new pair instance.
454 *
455 * @return A pair, of which the first element is an iterator that points
456 * to the possibly inserted pair, and the second is a bool that
457 * is true if the pair was actually inserted.
458 *
459 * This function attempts to build and insert a (key, value) %pair into
460 * the %unordered_map.
461 * An %unordered_map relies on unique keys and thus a %pair is only
462 * inserted if its first element (the key) is not already present in the
463 * %unordered_map.
464 * If a %pair is not inserted, this function has no effect.
465 *
466 * Insertion requires amortized constant time.
467 */
468 template <typename... _Args>
469 pair<iterator, bool>
470 try_emplace(const key_type& __k, _Args&&... __args)
471 {
472 iterator __i = find(__k);
473 if (__i == end())
474 {
475 __i = emplace(std::piecewise_construct,
476 std::forward_as_tuple(__k),
477 std::forward_as_tuple(
478 std::forward<_Args>(__args)...))
479 .first;
480 return {__i, true};
481 }
482 return {__i, false};
483 }
484
485 // move-capable overload
486 template <typename... _Args>
487 pair<iterator, bool>
488 try_emplace(key_type&& __k, _Args&&... __args)
489 {
490 iterator __i = find(__k);
491 if (__i == end())
492 {
493 __i = emplace(std::piecewise_construct,
494 std::forward_as_tuple(std::move(__k)),
495 std::forward_as_tuple(
496 std::forward<_Args>(__args)...))
497 .first;
498 return {__i, true};
499 }
500 return {__i, false};
501 }
502
503 /**
504 * @brief Attempts to build and insert a std::pair into the
505 * %unordered_map.
506 *
507 * @param __hint An iterator that serves as a hint as to where the pair
508 * should be inserted.
509 * @param __k Key to use for finding a possibly existing pair in
510 * the unordered_map.
511 * @param __args Arguments used to generate the .second for a
512 * new pair instance.
513 * @return An iterator that points to the element with key of the
514 * std::pair built from @a __args (may or may not be that
515 * std::pair).
516 *
517 * This function is not concerned about whether the insertion took place,
518 * and thus does not return a boolean like the single-argument emplace()
519 * does. However, if insertion did not take place,
520 * this function has no effect.
521 * Note that the first parameter is only a hint and can potentially
522 * improve the performance of the insertion process. A bad hint would
523 * cause no gains in efficiency.
524 *
525 * See
526 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
527 * for more on @a hinting.
528 *
529 * Insertion requires amortized constant time.
530 */
531 template <typename... _Args>
532 iterator
533 try_emplace(const_iterator __hint, const key_type& __k,
534 _Args&&... __args)
535 {
536 iterator __i = find(__k);
537 if (__i == end())
538 __i = emplace_hint(__hint, std::piecewise_construct,
539 std::forward_as_tuple(__k),
540 std::forward_as_tuple(
541 std::forward<_Args>(__args)...));
542 return __i;
543 }
544
545 // move-capable overload
546 template <typename... _Args>
547 iterator
548 try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args)
549 {
550 iterator __i = find(__k);
551 if (__i == end())
552 __i = emplace_hint(__hint, std::piecewise_construct,
553 std::forward_as_tuple(std::move(__k)),
554 std::forward_as_tuple(
555 std::forward<_Args>(__args)...));
556 return __i;
557 }
558#endif // C++17
559
560 //@{
561 /**
562 * @brief Attempts to insert a std::pair into the %unordered_map.
563
564 * @param __x Pair to be inserted (see std::make_pair for easy
565 * creation of pairs).
566 *
567 * @return A pair, of which the first element is an iterator that
568 * points to the possibly inserted pair, and the second is
569 * a bool that is true if the pair was actually inserted.
570 *
571 * This function attempts to insert a (key, value) %pair into the
572 * %unordered_map. An %unordered_map relies on unique keys and thus a
573 * %pair is only inserted if its first element (the key) is not already
574 * present in the %unordered_map.
575 *
576 * Insertion requires amortized constant time.
577 */
578 std::pair<iterator, bool>
579 insert(const value_type& __x)
580 { return _M_h.insert(__x); }
581
582 // _GLIBCXX_RESOLVE_LIB_DEFECTS
583 // 2354. Unnecessary copying when inserting into maps with braced-init
584 std::pair<iterator, bool>
585 insert(value_type&& __x)
586 { return _M_h.insert(std::move(__x)); }
587
588 template<typename _Pair>
589 __enable_if_t<is_constructible<value_type, _Pair&&>::value,
590 pair<iterator, bool>>
591 insert(_Pair&& __x)
592 { return _M_h.emplace(std::forward<_Pair>(__x)); }
593 //@}
594
595 //@{
596 /**
597 * @brief Attempts to insert a std::pair into the %unordered_map.
598 * @param __hint An iterator that serves as a hint as to where the
599 * pair should be inserted.
600 * @param __x Pair to be inserted (see std::make_pair for easy creation
601 * of pairs).
602 * @return An iterator that points to the element with key of
603 * @a __x (may or may not be the %pair passed in).
604 *
605 * This function is not concerned about whether the insertion took place,
606 * and thus does not return a boolean like the single-argument insert()
607 * does. Note that the first parameter is only a hint and can
608 * potentially improve the performance of the insertion process. A bad
609 * hint would cause no gains in efficiency.
610 *
611 * See
612 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
613 * for more on @a hinting.
614 *
615 * Insertion requires amortized constant time.
616 */
617 iterator
618 insert(const_iterator __hint, const value_type& __x)
619 { return _M_h.insert(__hint, __x); }
620
621 // _GLIBCXX_RESOLVE_LIB_DEFECTS
622 // 2354. Unnecessary copying when inserting into maps with braced-init
623 iterator
624 insert(const_iterator __hint, value_type&& __x)
625 { return _M_h.insert(__hint, std::move(__x)); }
626
627 template<typename _Pair>
628 __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator>
629 insert(const_iterator __hint, _Pair&& __x)
630 { return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); }
631 //@}
632
633 /**
634 * @brief A template function that attempts to insert a range of
635 * elements.
636 * @param __first Iterator pointing to the start of the range to be
637 * inserted.
638 * @param __last Iterator pointing to the end of the range.
639 *
640 * Complexity similar to that of the range constructor.
641 */
642 template<typename _InputIterator>
643 void
644 insert(_InputIterator __first, _InputIterator __last)
645 { _M_h.insert(__first, __last); }
646
647 /**
648 * @brief Attempts to insert a list of elements into the %unordered_map.
649 * @param __l A std::initializer_list<value_type> of elements
650 * to be inserted.
651 *
652 * Complexity similar to that of the range constructor.
653 */
654 void
655 insert(initializer_list<value_type> __l)
656 { _M_h.insert(__l); }
657
658
659#if __cplusplus > 201402L
660#define __cpp_lib_unordered_map_insertion 201411 // non-standard macro
661 /**
662 * @brief Attempts to insert a std::pair into the %unordered_map.
663 * @param __k Key to use for finding a possibly existing pair in
664 * the map.
665 * @param __obj Argument used to generate the .second for a pair
666 * instance.
667 *
668 * @return A pair, of which the first element is an iterator that
669 * points to the possibly inserted pair, and the second is
670 * a bool that is true if the pair was actually inserted.
671 *
672 * This function attempts to insert a (key, value) %pair into the
673 * %unordered_map. An %unordered_map relies on unique keys and thus a
674 * %pair is only inserted if its first element (the key) is not already
675 * present in the %unordered_map.
676 * If the %pair was already in the %unordered_map, the .second of
677 * the %pair is assigned from __obj.
678 *
679 * Insertion requires amortized constant time.
680 */
681 template <typename _Obj>
682 pair<iterator, bool>
683 insert_or_assign(const key_type& __k, _Obj&& __obj)
684 {
685 iterator __i = find(__k);
686 if (__i == end())
687 {
688 __i = emplace(std::piecewise_construct,
689 std::forward_as_tuple(__k),
690 std::forward_as_tuple(std::forward<_Obj>(__obj)))
691 .first;
692 return {__i, true};
693 }
694 (*__i).second = std::forward<_Obj>(__obj);
695 return {__i, false};
696 }
697
698 // move-capable overload
699 template <typename _Obj>
700 pair<iterator, bool>
701 insert_or_assign(key_type&& __k, _Obj&& __obj)
702 {
703 iterator __i = find(__k);
704 if (__i == end())
705 {
706 __i = emplace(std::piecewise_construct,
707 std::forward_as_tuple(std::move(__k)),
708 std::forward_as_tuple(std::forward<_Obj>(__obj)))
709 .first;
710 return {__i, true};
711 }
712 (*__i).second = std::forward<_Obj>(__obj);
713 return {__i, false};
714 }
715
716 /**
717 * @brief Attempts to insert a std::pair into the %unordered_map.
718 * @param __hint An iterator that serves as a hint as to where the
719 * pair should be inserted.
720 * @param __k Key to use for finding a possibly existing pair in
721 * the unordered_map.
722 * @param __obj Argument used to generate the .second for a pair
723 * instance.
724 * @return An iterator that points to the element with key of
725 * @a __x (may or may not be the %pair passed in).
726 *
727 * This function is not concerned about whether the insertion took place,
728 * and thus does not return a boolean like the single-argument insert()
729 * does.
730 * If the %pair was already in the %unordered map, the .second of
731 * the %pair is assigned from __obj.
732 * Note that the first parameter is only a hint and can
733 * potentially improve the performance of the insertion process. A bad
734 * hint would cause no gains in efficiency.
735 *
736 * See
737 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
738 * for more on @a hinting.
739 *
740 * Insertion requires amortized constant time.
741 */
742 template <typename _Obj>
743 iterator
744 insert_or_assign(const_iterator __hint, const key_type& __k,
745 _Obj&& __obj)
746 {
747 iterator __i = find(__k);
748 if (__i == end())
749 {
750 return emplace_hint(__hint, std::piecewise_construct,
751 std::forward_as_tuple(__k),
752 std::forward_as_tuple(
753 std::forward<_Obj>(__obj)));
754 }
755 (*__i).second = std::forward<_Obj>(__obj);
756 return __i;
757 }
758
759 // move-capable overload
760 template <typename _Obj>
761 iterator
762 insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj)
763 {
764 iterator __i = find(__k);
765 if (__i == end())
766 {
767 return emplace_hint(__hint, std::piecewise_construct,
768 std::forward_as_tuple(std::move(__k)),
769 std::forward_as_tuple(
770 std::forward<_Obj>(__obj)));
771 }
772 (*__i).second = std::forward<_Obj>(__obj);
773 return __i;
774 }
775#endif
776
777 //@{
778 /**
779 * @brief Erases an element from an %unordered_map.
780 * @param __position An iterator pointing to the element to be erased.
781 * @return An iterator pointing to the element immediately following
782 * @a __position prior to the element being erased. If no such
783 * element exists, end() is returned.
784 *
785 * This function erases an element, pointed to by the given iterator,
786 * from an %unordered_map.
787 * Note that this function only erases the element, and that if the
788 * element is itself a pointer, the pointed-to memory is not touched in
789 * any way. Managing the pointer is the user's responsibility.
790 */
791 iterator
792 erase(const_iterator __position)
793 { return _M_h.erase(__position); }
794
795 // LWG 2059.
796 iterator
797 erase(iterator __position)
798 { return _M_h.erase(__position); }
799 //@}
800
801 /**
802 * @brief Erases elements according to the provided key.
803 * @param __x Key of element to be erased.
804 * @return The number of elements erased.
805 *
806 * This function erases all the elements located by the given key from
807 * an %unordered_map. For an %unordered_map the result of this function
808 * can only be 0 (not present) or 1 (present).
809 * Note that this function only erases the element, and that if the
810 * element is itself a pointer, the pointed-to memory is not touched in
811 * any way. Managing the pointer is the user's responsibility.
812 */
813 size_type
814 erase(const key_type& __x)
815 { return _M_h.erase(__x); }
816
817 /**
818 * @brief Erases a [__first,__last) range of elements from an
819 * %unordered_map.
820 * @param __first Iterator pointing to the start of the range to be
821 * erased.
822 * @param __last Iterator pointing to the end of the range to
823 * be erased.
824 * @return The iterator @a __last.
825 *
826 * This function erases a sequence of elements from an %unordered_map.
827 * Note that this function only erases the elements, and that if
828 * the element is itself a pointer, the pointed-to memory is not touched
829 * in any way. Managing the pointer is the user's responsibility.
830 */
831 iterator
832 erase(const_iterator __first, const_iterator __last)
833 { return _M_h.erase(__first, __last); }
834
835 /**
836 * Erases all elements in an %unordered_map.
837 * Note that this function only erases the elements, and that if the
838 * elements themselves are pointers, the pointed-to memory is not touched
839 * in any way. Managing the pointer is the user's responsibility.
840 */
841 void
842 clear() noexcept
843 { _M_h.clear(); }
844
845 /**
846 * @brief Swaps data with another %unordered_map.
847 * @param __x An %unordered_map of the same element and allocator
848 * types.
849 *
850 * This exchanges the elements between two %unordered_map in constant
851 * time.
852 * Note that the global std::swap() function is specialized such that
853 * std::swap(m1,m2) will feed to this function.
854 */
855 void
856 swap(unordered_map& __x)
857 noexcept( noexcept(_M_h.swap(__x._M_h)) )
858 { _M_h.swap(__x._M_h); }
859
860#if __cplusplus > 201402L
861 template<typename, typename, typename>
862 friend class std::_Hash_merge_helper;
863
864 template<typename _H2, typename _P2>
865 void
866 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source)
867 {
868 using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>;
869 _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source));
870 }
871
872 template<typename _H2, typename _P2>
873 void
874 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
875 { merge(__source); }
876
877 template<typename _H2, typename _P2>
878 void
879 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source)
880 {
881 using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>;
882 _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source));
883 }
884
885 template<typename _H2, typename _P2>
886 void
887 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
888 { merge(__source); }
889#endif // C++17
890
891 // observers.
892
893 /// Returns the hash functor object with which the %unordered_map was
894 /// constructed.
895 hasher
896 hash_function() const
897 { return _M_h.hash_function(); }
898
899 /// Returns the key comparison object with which the %unordered_map was
900 /// constructed.
901 key_equal
902 key_eq() const
903 { return _M_h.key_eq(); }
904
905 // lookup.
906
907 //@{
908 /**
909 * @brief Tries to locate an element in an %unordered_map.
910 * @param __x Key to be located.
911 * @return Iterator pointing to sought-after element, or end() if not
912 * found.
913 *
914 * This function takes a key and tries to locate the element with which
915 * the key matches. If successful the function returns an iterator
916 * pointing to the sought after element. If unsuccessful it returns the
917 * past-the-end ( @c end() ) iterator.
918 */
919 iterator
920 find(const key_type& __x)
921 { return _M_h.find(__x); }
922
923 const_iterator
924 find(const key_type& __x) const
925 { return _M_h.find(__x); }
926 //@}
927
928 /**
929 * @brief Finds the number of elements.
930 * @param __x Key to count.
931 * @return Number of elements with specified key.
932 *
933 * This function only makes sense for %unordered_multimap; for
934 * %unordered_map the result will either be 0 (not present) or 1
935 * (present).
936 */
937 size_type
938 count(const key_type& __x) const
939 { return _M_h.count(__x); }
940
941#if __cplusplus > 201703L
942 /**
943 * @brief Finds whether an element with the given key exists.
944 * @param __x Key of elements to be located.
945 * @return True if there is any element with the specified key.
946 */
947 bool
948 contains(const key_type& __x) const
949 { return _M_h.find(__x) != _M_h.end(); }
950#endif
951
952 //@{
953 /**
954 * @brief Finds a subsequence matching given key.
955 * @param __x Key to be located.
956 * @return Pair of iterators that possibly points to the subsequence
957 * matching given key.
958 *
959 * This function probably only makes sense for %unordered_multimap.
960 */
961 std::pair<iterator, iterator>
962 equal_range(const key_type& __x)
963 { return _M_h.equal_range(__x); }
964
965 std::pair<const_iterator, const_iterator>
966 equal_range(const key_type& __x) const
967 { return _M_h.equal_range(__x); }
968 //@}
969
970 //@{
971 /**
972 * @brief Subscript ( @c [] ) access to %unordered_map data.
973 * @param __k The key for which data should be retrieved.
974 * @return A reference to the data of the (key,data) %pair.
975 *
976 * Allows for easy lookup with the subscript ( @c [] )operator. Returns
977 * data associated with the key specified in subscript. If the key does
978 * not exist, a pair with that key is created using default values, which
979 * is then returned.
980 *
981 * Lookup requires constant time.
982 */
983 mapped_type&
984 operator[](const key_type& __k)
985 { return _M_h[__k]; }
986
987 mapped_type&
988 operator[](key_type&& __k)
989 { return _M_h[std::move(__k)]; }
990 //@}
991
992 //@{
993 /**
994 * @brief Access to %unordered_map data.
995 * @param __k The key for which data should be retrieved.
996 * @return A reference to the data whose key is equal to @a __k, if
997 * such a data is present in the %unordered_map.
998 * @throw std::out_of_range If no such data is present.
999 */
1000 mapped_type&
1001 at(const key_type& __k)
1002 { return _M_h.at(__k); }
1003
1004 const mapped_type&
1005 at(const key_type& __k) const
1006 { return _M_h.at(__k); }
1007 //@}
1008
1009 // bucket interface.
1010
1011 /// Returns the number of buckets of the %unordered_map.
1012 size_type
1013 bucket_count() const noexcept
1014 { return _M_h.bucket_count(); }
1015
1016 /// Returns the maximum number of buckets of the %unordered_map.
1017 size_type
1018 max_bucket_count() const noexcept
1019 { return _M_h.max_bucket_count(); }
1020
1021 /*
1022 * @brief Returns the number of elements in a given bucket.
1023 * @param __n A bucket index.
1024 * @return The number of elements in the bucket.
1025 */
1026 size_type
1027 bucket_size(size_type __n) const
1028 { return _M_h.bucket_size(__n); }
1029
1030 /*
1031 * @brief Returns the bucket index of a given element.
1032 * @param __key A key instance.
1033 * @return The key bucket index.
1034 */
1035 size_type
1036 bucket(const key_type& __key) const
1037 { return _M_h.bucket(__key); }
1038
1039 /**
1040 * @brief Returns a read/write iterator pointing to the first bucket
1041 * element.
1042 * @param __n The bucket index.
1043 * @return A read/write local iterator.
1044 */
1045 local_iterator
1046 begin(size_type __n)
1047 { return _M_h.begin(__n); }
1048
1049 //@{
1050 /**
1051 * @brief Returns a read-only (constant) iterator pointing to the first
1052 * bucket element.
1053 * @param __n The bucket index.
1054 * @return A read-only local iterator.
1055 */
1056 const_local_iterator
1057 begin(size_type __n) const
1058 { return _M_h.begin(__n); }
1059
1060 const_local_iterator
1061 cbegin(size_type __n) const
1062 { return _M_h.cbegin(__n); }
1063 //@}
1064
1065 /**
1066 * @brief Returns a read/write iterator pointing to one past the last
1067 * bucket elements.
1068 * @param __n The bucket index.
1069 * @return A read/write local iterator.
1070 */
1071 local_iterator
1072 end(size_type __n)
1073 { return _M_h.end(__n); }
1074
1075 //@{
1076 /**
1077 * @brief Returns a read-only (constant) iterator pointing to one past
1078 * the last bucket elements.
1079 * @param __n The bucket index.
1080 * @return A read-only local iterator.
1081 */
1082 const_local_iterator
1083 end(size_type __n) const
1084 { return _M_h.end(__n); }
1085
1086 const_local_iterator
1087 cend(size_type __n) const
1088 { return _M_h.cend(__n); }
1089 //@}
1090
1091 // hash policy.
1092
1093 /// Returns the average number of elements per bucket.
1094 float
1095 load_factor() const noexcept
1096 { return _M_h.load_factor(); }
1097
1098 /// Returns a positive number that the %unordered_map tries to keep the
1099 /// load factor less than or equal to.
1100 float
1101 max_load_factor() const noexcept
1102 { return _M_h.max_load_factor(); }
1103
1104 /**
1105 * @brief Change the %unordered_map maximum load factor.
1106 * @param __z The new maximum load factor.
1107 */
1108 void
1109 max_load_factor(float __z)
1110 { _M_h.max_load_factor(__z); }
1111
1112 /**
1113 * @brief May rehash the %unordered_map.
1114 * @param __n The new number of buckets.
1115 *
1116 * Rehash will occur only if the new number of buckets respect the
1117 * %unordered_map maximum load factor.
1118 */
1119 void
1120 rehash(size_type __n)
1121 { _M_h.rehash(__n); }
1122
1123 /**
1124 * @brief Prepare the %unordered_map for a specified number of
1125 * elements.
1126 * @param __n Number of elements required.
1127 *
1128 * Same as rehash(ceil(n / max_load_factor())).
1129 */
1130 void
1131 reserve(size_type __n)
1132 { _M_h.reserve(__n); }
1133
1134 template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1,
1135 typename _Alloc1>
1136 friend bool
1137 operator==(const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&,
1138 const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&);
1139 };
1140
1141#if __cpp_deduction_guides >= 201606
1142
1143 template<typename _InputIterator,
1144 typename _Hash = hash<__iter_key_t<_InputIterator>>,
1145 typename _Pred = equal_to<__iter_key_t<_InputIterator>>,
1146 typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>,
1147 typename = _RequireInputIter<_InputIterator>,
1148 typename = _RequireNotAllocatorOrIntegral<_Hash>,
1149 typename = _RequireNotAllocator<_Pred>,
1150 typename = _RequireAllocator<_Allocator>>
1151 unordered_map(_InputIterator, _InputIterator,
1152 typename unordered_map<int, int>::size_type = {},
1153 _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
1154 -> unordered_map<__iter_key_t<_InputIterator>,
1155 __iter_val_t<_InputIterator>,
1156 _Hash, _Pred, _Allocator>;
1157
1158 template<typename _Key, typename _Tp, typename _Hash = hash<_Key>,
1159 typename _Pred = equal_to<_Key>,
1160 typename _Allocator = allocator<pair<const _Key, _Tp>>,
1161 typename = _RequireNotAllocatorOrIntegral<_Hash>,
1162 typename = _RequireNotAllocator<_Pred>,
1163 typename = _RequireAllocator<_Allocator>>
1164 unordered_map(initializer_list<pair<_Key, _Tp>>,
1165 typename unordered_map<int, int>::size_type = {},
1166 _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
1167 -> unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>;
1168
1169 template<typename _InputIterator, typename _Allocator,
1170 typename = _RequireInputIter<_InputIterator>,
1171 typename = _RequireAllocator<_Allocator>>
1172 unordered_map(_InputIterator, _InputIterator,
1173 typename unordered_map<int, int>::size_type, _Allocator)
1174 -> unordered_map<__iter_key_t<_InputIterator>,
1175 __iter_val_t<_InputIterator>,
1176 hash<__iter_key_t<_InputIterator>>,
1177 equal_to<__iter_key_t<_InputIterator>>,
1178 _Allocator>;
1179
1180 template<typename _InputIterator, typename _Allocator,
1181 typename = _RequireInputIter<_InputIterator>,
1182 typename = _RequireAllocator<_Allocator>>
1183 unordered_map(_InputIterator, _InputIterator, _Allocator)
1184 -> unordered_map<__iter_key_t<_InputIterator>,
1185 __iter_val_t<_InputIterator>,
1186 hash<__iter_key_t<_InputIterator>>,
1187 equal_to<__iter_key_t<_InputIterator>>,
1188 _Allocator>;
1189
1190 template<typename _InputIterator, typename _Hash, typename _Allocator,
1191 typename = _RequireInputIter<_InputIterator>,
1192 typename = _RequireNotAllocatorOrIntegral<_Hash>,
1193 typename = _RequireAllocator<_Allocator>>
1194 unordered_map(_InputIterator, _InputIterator,
1195 typename unordered_map<int, int>::size_type,
1196 _Hash, _Allocator)
1197 -> unordered_map<__iter_key_t<_InputIterator>,
1198 __iter_val_t<_InputIterator>, _Hash,
1199 equal_to<__iter_key_t<_InputIterator>>, _Allocator>;
1200
1201 template<typename _Key, typename _Tp, typename _Allocator,
1202 typename = _RequireAllocator<_Allocator>>
1203 unordered_map(initializer_list<pair<_Key, _Tp>>,
1204 typename unordered_map<int, int>::size_type,
1205 _Allocator)
1206 -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
1207
1208 template<typename _Key, typename _Tp, typename _Allocator,
1209 typename = _RequireAllocator<_Allocator>>
1210 unordered_map(initializer_list<pair<_Key, _Tp>>, _Allocator)
1211 -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
1212
1213 template<typename _Key, typename _Tp, typename _Hash, typename _Allocator,
1214 typename = _RequireNotAllocatorOrIntegral<_Hash>,
1215 typename = _RequireAllocator<_Allocator>>
1216 unordered_map(initializer_list<pair<_Key, _Tp>>,
1217 typename unordered_map<int, int>::size_type,
1218 _Hash, _Allocator)
1219 -> unordered_map<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;
1220
1221#endif
1222
1223 /**
1224 * @brief A standard container composed of equivalent keys
1225 * (possibly containing multiple of each key value) that associates
1226 * values of another type with the keys.
1227 *
1228 * @ingroup unordered_associative_containers
1229 *
1230 * @tparam _Key Type of key objects.
1231 * @tparam _Tp Type of mapped objects.
1232 * @tparam _Hash Hashing function object type, defaults to hash<_Value>.
1233 * @tparam _Pred Predicate function object type, defaults
1234 * to equal_to<_Value>.
1235 * @tparam _Alloc Allocator type, defaults to
1236 * std::allocator<std::pair<const _Key, _Tp>>.
1237 *
1238 * Meets the requirements of a <a href="tables.html#65">container</a>, and
1239 * <a href="tables.html#xx">unordered associative container</a>
1240 *
1241 * The resulting value type of the container is std::pair<const _Key, _Tp>.
1242 *
1243 * Base is _Hashtable, dispatched at compile time via template
1244 * alias __ummap_hashtable.
1245 */
1246 template<typename _Key, typename _Tp,
1247 typename _Hash = hash<_Key>,
1248 typename _Pred = equal_to<_Key>,
1249 typename _Alloc = allocator<std::pair<const _Key, _Tp>>>
1250 class unordered_multimap
1251 {
1252 typedef __ummap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc> _Hashtable;
1253 _Hashtable _M_h;
1254
1255 public:
1256 // typedefs:
1257 //@{
1258 /// Public typedefs.
1259 typedef typename _Hashtable::key_type key_type;
1260 typedef typename _Hashtable::value_type value_type;
1261 typedef typename _Hashtable::mapped_type mapped_type;
1262 typedef typename _Hashtable::hasher hasher;
1263 typedef typename _Hashtable::key_equal key_equal;
1264 typedef typename _Hashtable::allocator_type allocator_type;
1265 //@}
1266
1267 //@{
1268 /// Iterator-related typedefs.
1269 typedef typename _Hashtable::pointer pointer;
1270 typedef typename _Hashtable::const_pointer const_pointer;
1271 typedef typename _Hashtable::reference reference;
1272 typedef typename _Hashtable::const_reference const_reference;
1273 typedef typename _Hashtable::iterator iterator;
1274 typedef typename _Hashtable::const_iterator const_iterator;
1275 typedef typename _Hashtable::local_iterator local_iterator;
1276 typedef typename _Hashtable::const_local_iterator const_local_iterator;
1277 typedef typename _Hashtable::size_type size_type;
1278 typedef typename _Hashtable::difference_type difference_type;
1279 //@}
1280
1281#if __cplusplus > 201402L
1282 using node_type = typename _Hashtable::node_type;
1283#endif
1284
1285 //construct/destroy/copy
1286
1287 /// Default constructor.
1288 unordered_multimap() = default;
1289
1290 /**
1291 * @brief Default constructor creates no elements.
1292 * @param __n Mnimal initial number of buckets.
1293 * @param __hf A hash functor.
1294 * @param __eql A key equality functor.
1295 * @param __a An allocator object.
1296 */
1297 explicit
1298 unordered_multimap(size_type __n,
1299 const hasher& __hf = hasher(),
1300 const key_equal& __eql = key_equal(),
1301 const allocator_type& __a = allocator_type())
1302 : _M_h(__n, __hf, __eql, __a)
1303 { }
1304
1305 /**
1306 * @brief Builds an %unordered_multimap from a range.
1307 * @param __first An input iterator.
1308 * @param __last An input iterator.
1309 * @param __n Minimal initial number of buckets.
1310 * @param __hf A hash functor.
1311 * @param __eql A key equality functor.
1312 * @param __a An allocator object.
1313 *
1314 * Create an %unordered_multimap consisting of copies of the elements
1315 * from [__first,__last). This is linear in N (where N is
1316 * distance(__first,__last)).
1317 */
1318 template<typename _InputIterator>
1319 unordered_multimap(_InputIterator __first, _InputIterator __last,
1320 size_type __n = 0,
1321 const hasher& __hf = hasher(),
1322 const key_equal& __eql = key_equal(),
1323 const allocator_type& __a = allocator_type())
1324 : _M_h(__first, __last, __n, __hf, __eql, __a)
1325 { }
1326
1327 /// Copy constructor.
1328 unordered_multimap(const unordered_multimap&) = default;
1329
1330 /// Move constructor.
1331 unordered_multimap(unordered_multimap&&) = default;
1332
1333 /**
1334 * @brief Creates an %unordered_multimap with no elements.
1335 * @param __a An allocator object.
1336 */
1337 explicit
1338 unordered_multimap(const allocator_type& __a)
1339 : _M_h(__a)
1340 { }
1341
1342 /*
1343 * @brief Copy constructor with allocator argument.
1344 * @param __uset Input %unordered_multimap to copy.
1345 * @param __a An allocator object.
1346 */
1347 unordered_multimap(const unordered_multimap& __ummap,
1348 const allocator_type& __a)
1349 : _M_h(__ummap._M_h, __a)
1350 { }
1351
1352 /*
1353 * @brief Move constructor with allocator argument.
1354 * @param __uset Input %unordered_multimap to move.
1355 * @param __a An allocator object.
1356 */
1357 unordered_multimap(unordered_multimap&& __ummap,
1358 const allocator_type& __a)
1359 : _M_h(std::move(__ummap._M_h), __a)
1360 { }
1361
1362 /**
1363 * @brief Builds an %unordered_multimap from an initializer_list.
1364 * @param __l An initializer_list.
1365 * @param __n Minimal initial number of buckets.
1366 * @param __hf A hash functor.
1367 * @param __eql A key equality functor.
1368 * @param __a An allocator object.
1369 *
1370 * Create an %unordered_multimap consisting of copies of the elements in
1371 * the list. This is linear in N (where N is @a __l.size()).
1372 */
1373 unordered_multimap(initializer_list<value_type> __l,
1374 size_type __n = 0,
1375 const hasher& __hf = hasher(),
1376 const key_equal& __eql = key_equal(),
1377 const allocator_type& __a = allocator_type())
1378 : _M_h(__l, __n, __hf, __eql, __a)
1379 { }
1380
1381 unordered_multimap(size_type __n, const allocator_type& __a)
1382 : unordered_multimap(__n, hasher(), key_equal(), __a)
1383 { }
1384
1385 unordered_multimap(size_type __n, const hasher& __hf,
1386 const allocator_type& __a)
1387 : unordered_multimap(__n, __hf, key_equal(), __a)
1388 { }
1389
1390 template<typename _InputIterator>
1391 unordered_multimap(_InputIterator __first, _InputIterator __last,
1392 size_type __n,
1393 const allocator_type& __a)
1394 : unordered_multimap(__first, __last, __n, hasher(), key_equal(), __a)
1395 { }
1396
1397 template<typename _InputIterator>
1398 unordered_multimap(_InputIterator __first, _InputIterator __last,
1399 size_type __n, const hasher& __hf,
1400 const allocator_type& __a)
1401 : unordered_multimap(__first, __last, __n, __hf, key_equal(), __a)
1402 { }
1403
1404 unordered_multimap(initializer_list<value_type> __l,
1405 size_type __n,
1406 const allocator_type& __a)
1407 : unordered_multimap(__l, __n, hasher(), key_equal(), __a)
1408 { }
1409
1410 unordered_multimap(initializer_list<value_type> __l,
1411 size_type __n, const hasher& __hf,
1412 const allocator_type& __a)
1413 : unordered_multimap(__l, __n, __hf, key_equal(), __a)
1414 { }
1415
1416 /// Copy assignment operator.
1417 unordered_multimap&
1418 operator=(const unordered_multimap&) = default;
1419
1420 /// Move assignment operator.
1421 unordered_multimap&
1422 operator=(unordered_multimap&&) = default;
1423
1424 /**
1425 * @brief %Unordered_multimap list assignment operator.
1426 * @param __l An initializer_list.
1427 *
1428 * This function fills an %unordered_multimap with copies of the
1429 * elements in the initializer list @a __l.
1430 *
1431 * Note that the assignment completely changes the %unordered_multimap
1432 * and that the resulting %unordered_multimap's size is the same as the
1433 * number of elements assigned.
1434 */
1435 unordered_multimap&
1436 operator=(initializer_list<value_type> __l)
1437 {
1438 _M_h = __l;
1439 return *this;
1440 }
1441
1442 /// Returns the allocator object used by the %unordered_multimap.
1443 allocator_type
1444 get_allocator() const noexcept
1445 { return _M_h.get_allocator(); }
1446
1447 // size and capacity:
1448
1449 /// Returns true if the %unordered_multimap is empty.
1450 _GLIBCXX_NODISCARD bool
1451 empty() const noexcept
1452 { return _M_h.empty(); }
1453
1454 /// Returns the size of the %unordered_multimap.
1455 size_type
1456 size() const noexcept
1457 { return _M_h.size(); }
1458
1459 /// Returns the maximum size of the %unordered_multimap.
1460 size_type
1461 max_size() const noexcept
1462 { return _M_h.max_size(); }
1463
1464 // iterators.
1465
1466 /**
1467 * Returns a read/write iterator that points to the first element in the
1468 * %unordered_multimap.
1469 */
1470 iterator
1471 begin() noexcept
1472 { return _M_h.begin(); }
1473
1474 //@{
1475 /**
1476 * Returns a read-only (constant) iterator that points to the first
1477 * element in the %unordered_multimap.
1478 */
1479 const_iterator
1480 begin() const noexcept
1481 { return _M_h.begin(); }
1482
1483 const_iterator
1484 cbegin() const noexcept
1485 { return _M_h.begin(); }
1486 //@}
1487
1488 /**
1489 * Returns a read/write iterator that points one past the last element in
1490 * the %unordered_multimap.
1491 */
1492 iterator
1493 end() noexcept
1494 { return _M_h.end(); }
1495
1496 //@{
1497 /**
1498 * Returns a read-only (constant) iterator that points one past the last
1499 * element in the %unordered_multimap.
1500 */
1501 const_iterator
1502 end() const noexcept
1503 { return _M_h.end(); }
1504
1505 const_iterator
1506 cend() const noexcept
1507 { return _M_h.end(); }
1508 //@}
1509
1510 // modifiers.
1511
1512 /**
1513 * @brief Attempts to build and insert a std::pair into the
1514 * %unordered_multimap.
1515 *
1516 * @param __args Arguments used to generate a new pair instance (see
1517 * std::piecewise_contruct for passing arguments to each
1518 * part of the pair constructor).
1519 *
1520 * @return An iterator that points to the inserted pair.
1521 *
1522 * This function attempts to build and insert a (key, value) %pair into
1523 * the %unordered_multimap.
1524 *
1525 * Insertion requires amortized constant time.
1526 */
1527 template<typename... _Args>
1528 iterator
1529 emplace(_Args&&... __args)
1530 { return _M_h.emplace(std::forward<_Args>(__args)...); }
1531
1532 /**
1533 * @brief Attempts to build and insert a std::pair into the
1534 * %unordered_multimap.
1535 *
1536 * @param __pos An iterator that serves as a hint as to where the pair
1537 * should be inserted.
1538 * @param __args Arguments used to generate a new pair instance (see
1539 * std::piecewise_contruct for passing arguments to each
1540 * part of the pair constructor).
1541 * @return An iterator that points to the element with key of the
1542 * std::pair built from @a __args.
1543 *
1544 * Note that the first parameter is only a hint and can potentially
1545 * improve the performance of the insertion process. A bad hint would
1546 * cause no gains in efficiency.
1547 *
1548 * See
1549 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
1550 * for more on @a hinting.
1551 *
1552 * Insertion requires amortized constant time.
1553 */
1554 template<typename... _Args>
1555 iterator
1556 emplace_hint(const_iterator __pos, _Args&&... __args)
1557 { return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); }
1558
1559 //@{
1560 /**
1561 * @brief Inserts a std::pair into the %unordered_multimap.
1562 * @param __x Pair to be inserted (see std::make_pair for easy
1563 * creation of pairs).
1564 *
1565 * @return An iterator that points to the inserted pair.
1566 *
1567 * Insertion requires amortized constant time.
1568 */
1569 iterator
1570 insert(const value_type& __x)
1571 { return _M_h.insert(__x); }
1572
1573 iterator
1574 insert(value_type&& __x)
1575 { return _M_h.insert(std::move(__x)); }
1576
1577 template<typename _Pair>
1578 __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator>
1579 insert(_Pair&& __x)
1580 { return _M_h.emplace(std::forward<_Pair>(__x)); }
1581 //@}
1582
1583 //@{
1584 /**
1585 * @brief Inserts a std::pair into the %unordered_multimap.
1586 * @param __hint An iterator that serves as a hint as to where the
1587 * pair should be inserted.
1588 * @param __x Pair to be inserted (see std::make_pair for easy creation
1589 * of pairs).
1590 * @return An iterator that points to the element with key of
1591 * @a __x (may or may not be the %pair passed in).
1592 *
1593 * Note that the first parameter is only a hint and can potentially
1594 * improve the performance of the insertion process. A bad hint would
1595 * cause no gains in efficiency.
1596 *
1597 * See
1598 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
1599 * for more on @a hinting.
1600 *
1601 * Insertion requires amortized constant time.
1602 */
1603 iterator
1604 insert(const_iterator __hint, const value_type& __x)
1605 { return _M_h.insert(__hint, __x); }
1606
1607 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1608 // 2354. Unnecessary copying when inserting into maps with braced-init
1609 iterator
1610 insert(const_iterator __hint, value_type&& __x)
1611 { return _M_h.insert(__hint, std::move(__x)); }
1612
1613 template<typename _Pair>
1614 __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator>
1615 insert(const_iterator __hint, _Pair&& __x)
1616 { return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); }
1617 //@}
1618
1619 /**
1620 * @brief A template function that attempts to insert a range of
1621 * elements.
1622 * @param __first Iterator pointing to the start of the range to be
1623 * inserted.
1624 * @param __last Iterator pointing to the end of the range.
1625 *
1626 * Complexity similar to that of the range constructor.
1627 */
1628 template<typename _InputIterator>
1629 void
1630 insert(_InputIterator __first, _InputIterator __last)
1631 { _M_h.insert(__first, __last); }
1632
1633 /**
1634 * @brief Attempts to insert a list of elements into the
1635 * %unordered_multimap.
1636 * @param __l A std::initializer_list<value_type> of elements
1637 * to be inserted.
1638 *
1639 * Complexity similar to that of the range constructor.
1640 */
1641 void
1642 insert(initializer_list<value_type> __l)
1643 { _M_h.insert(__l); }
1644
1645#if __cplusplus > 201402L
1646 /// Extract a node.
1647 node_type
1648 extract(const_iterator __pos)
1649 {
1650 __glibcxx_assert(__pos != end());
1651 return _M_h.extract(__pos);
1652 }
1653
1654 /// Extract a node.
1655 node_type
1656 extract(const key_type& __key)
1657 { return _M_h.extract(__key); }
1658
1659 /// Re-insert an extracted node.
1660 iterator
1661 insert(node_type&& __nh)
1662 { return _M_h._M_reinsert_node_multi(cend(), std::move(__nh)); }
1663
1664 /// Re-insert an extracted node.
1665 iterator
1666 insert(const_iterator __hint, node_type&& __nh)
1667 { return _M_h._M_reinsert_node_multi(__hint, std::move(__nh)); }
1668#endif // C++17
1669
1670 //@{
1671 /**
1672 * @brief Erases an element from an %unordered_multimap.
1673 * @param __position An iterator pointing to the element to be erased.
1674 * @return An iterator pointing to the element immediately following
1675 * @a __position prior to the element being erased. If no such
1676 * element exists, end() is returned.
1677 *
1678 * This function erases an element, pointed to by the given iterator,
1679 * from an %unordered_multimap.
1680 * Note that this function only erases the element, and that if the
1681 * element is itself a pointer, the pointed-to memory is not touched in
1682 * any way. Managing the pointer is the user's responsibility.
1683 */
1684 iterator
1685 erase(const_iterator __position)
1686 { return _M_h.erase(__position); }
1687
1688 // LWG 2059.
1689 iterator
1690 erase(iterator __position)
1691 { return _M_h.erase(__position); }
1692 //@}
1693
1694 /**
1695 * @brief Erases elements according to the provided key.
1696 * @param __x Key of elements to be erased.
1697 * @return The number of elements erased.
1698 *
1699 * This function erases all the elements located by the given key from
1700 * an %unordered_multimap.
1701 * Note that this function only erases the element, and that if the
1702 * element is itself a pointer, the pointed-to memory is not touched in
1703 * any way. Managing the pointer is the user's responsibility.
1704 */
1705 size_type
1706 erase(const key_type& __x)
1707 { return _M_h.erase(__x); }
1708
1709 /**
1710 * @brief Erases a [__first,__last) range of elements from an
1711 * %unordered_multimap.
1712 * @param __first Iterator pointing to the start of the range to be
1713 * erased.
1714 * @param __last Iterator pointing to the end of the range to
1715 * be erased.
1716 * @return The iterator @a __last.
1717 *
1718 * This function erases a sequence of elements from an
1719 * %unordered_multimap.
1720 * Note that this function only erases the elements, and that if
1721 * the element is itself a pointer, the pointed-to memory is not touched
1722 * in any way. Managing the pointer is the user's responsibility.
1723 */
1724 iterator
1725 erase(const_iterator __first, const_iterator __last)
1726 { return _M_h.erase(__first, __last); }
1727
1728 /**
1729 * Erases all elements in an %unordered_multimap.
1730 * Note that this function only erases the elements, and that if the
1731 * elements themselves are pointers, the pointed-to memory is not touched
1732 * in any way. Managing the pointer is the user's responsibility.
1733 */
1734 void
1735 clear() noexcept
1736 { _M_h.clear(); }
1737
1738 /**
1739 * @brief Swaps data with another %unordered_multimap.
1740 * @param __x An %unordered_multimap of the same element and allocator
1741 * types.
1742 *
1743 * This exchanges the elements between two %unordered_multimap in
1744 * constant time.
1745 * Note that the global std::swap() function is specialized such that
1746 * std::swap(m1,m2) will feed to this function.
1747 */
1748 void
1749 swap(unordered_multimap& __x)
1750 noexcept( noexcept(_M_h.swap(__x._M_h)) )
1751 { _M_h.swap(__x._M_h); }
1752
1753#if __cplusplus > 201402L
1754 template<typename, typename, typename>
1755 friend class std::_Hash_merge_helper;
1756
1757 template<typename _H2, typename _P2>
1758 void
1759 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source)
1760 {
1761 using _Merge_helper
1762 = _Hash_merge_helper<unordered_multimap, _H2, _P2>;
1763 _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source));
1764 }
1765
1766 template<typename _H2, typename _P2>
1767 void
1768 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
1769 { merge(__source); }
1770
1771 template<typename _H2, typename _P2>
1772 void
1773 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source)
1774 {
1775 using _Merge_helper
1776 = _Hash_merge_helper<unordered_multimap, _H2, _P2>;
1777 _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source));
1778 }
1779
1780 template<typename _H2, typename _P2>
1781 void
1782 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
1783 { merge(__source); }
1784#endif // C++17
1785
1786 // observers.
1787
1788 /// Returns the hash functor object with which the %unordered_multimap
1789 /// was constructed.
1790 hasher
1791 hash_function() const
1792 { return _M_h.hash_function(); }
1793
1794 /// Returns the key comparison object with which the %unordered_multimap
1795 /// was constructed.
1796 key_equal
1797 key_eq() const
1798 { return _M_h.key_eq(); }
1799
1800 // lookup.
1801
1802 //@{
1803 /**
1804 * @brief Tries to locate an element in an %unordered_multimap.
1805 * @param __x Key to be located.
1806 * @return Iterator pointing to sought-after element, or end() if not
1807 * found.
1808 *
1809 * This function takes a key and tries to locate the element with which
1810 * the key matches. If successful the function returns an iterator
1811 * pointing to the sought after element. If unsuccessful it returns the
1812 * past-the-end ( @c end() ) iterator.
1813 */
1814 iterator
1815 find(const key_type& __x)
1816 { return _M_h.find(__x); }
1817
1818 const_iterator
1819 find(const key_type& __x) const
1820 { return _M_h.find(__x); }
1821 //@}
1822
1823 /**
1824 * @brief Finds the number of elements.
1825 * @param __x Key to count.
1826 * @return Number of elements with specified key.
1827 */
1828 size_type
1829 count(const key_type& __x) const
1830 { return _M_h.count(__x); }
1831
1832#if __cplusplus > 201703L
1833 /**
1834 * @brief Finds whether an element with the given key exists.
1835 * @param __x Key of elements to be located.
1836 * @return True if there is any element with the specified key.
1837 */
1838 bool
1839 contains(const key_type& __x) const
1840 { return _M_h.find(__x) != _M_h.end(); }
1841#endif
1842
1843 //@{
1844 /**
1845 * @brief Finds a subsequence matching given key.
1846 * @param __x Key to be located.
1847 * @return Pair of iterators that possibly points to the subsequence
1848 * matching given key.
1849 */
1850 std::pair<iterator, iterator>
1851 equal_range(const key_type& __x)
1852 { return _M_h.equal_range(__x); }
1853
1854 std::pair<const_iterator, const_iterator>
1855 equal_range(const key_type& __x) const
1856 { return _M_h.equal_range(__x); }
1857 //@}
1858
1859 // bucket interface.
1860
1861 /// Returns the number of buckets of the %unordered_multimap.
1862 size_type
1863 bucket_count() const noexcept
1864 { return _M_h.bucket_count(); }
1865
1866 /// Returns the maximum number of buckets of the %unordered_multimap.
1867 size_type
1868 max_bucket_count() const noexcept
1869 { return _M_h.max_bucket_count(); }
1870
1871 /*
1872 * @brief Returns the number of elements in a given bucket.
1873 * @param __n A bucket index.
1874 * @return The number of elements in the bucket.
1875 */
1876 size_type
1877 bucket_size(size_type __n) const
1878 { return _M_h.bucket_size(__n); }
1879
1880 /*
1881 * @brief Returns the bucket index of a given element.
1882 * @param __key A key instance.
1883 * @return The key bucket index.
1884 */
1885 size_type
1886 bucket(const key_type& __key) const
1887 { return _M_h.bucket(__key); }
1888
1889 /**
1890 * @brief Returns a read/write iterator pointing to the first bucket
1891 * element.
1892 * @param __n The bucket index.
1893 * @return A read/write local iterator.
1894 */
1895 local_iterator
1896 begin(size_type __n)
1897 { return _M_h.begin(__n); }
1898
1899 //@{
1900 /**
1901 * @brief Returns a read-only (constant) iterator pointing to the first
1902 * bucket element.
1903 * @param __n The bucket index.
1904 * @return A read-only local iterator.
1905 */
1906 const_local_iterator
1907 begin(size_type __n) const
1908 { return _M_h.begin(__n); }
1909
1910 const_local_iterator
1911 cbegin(size_type __n) const
1912 { return _M_h.cbegin(__n); }
1913 //@}
1914
1915 /**
1916 * @brief Returns a read/write iterator pointing to one past the last
1917 * bucket elements.
1918 * @param __n The bucket index.
1919 * @return A read/write local iterator.
1920 */
1921 local_iterator
1922 end(size_type __n)
1923 { return _M_h.end(__n); }
1924
1925 //@{
1926 /**
1927 * @brief Returns a read-only (constant) iterator pointing to one past
1928 * the last bucket elements.
1929 * @param __n The bucket index.
1930 * @return A read-only local iterator.
1931 */
1932 const_local_iterator
1933 end(size_type __n) const
1934 { return _M_h.end(__n); }
1935
1936 const_local_iterator
1937 cend(size_type __n) const
1938 { return _M_h.cend(__n); }
1939 //@}
1940
1941 // hash policy.
1942
1943 /// Returns the average number of elements per bucket.
1944 float
1945 load_factor() const noexcept
1946 { return _M_h.load_factor(); }
1947
1948 /// Returns a positive number that the %unordered_multimap tries to keep
1949 /// the load factor less than or equal to.
1950 float
1951 max_load_factor() const noexcept
1952 { return _M_h.max_load_factor(); }
1953
1954 /**
1955 * @brief Change the %unordered_multimap maximum load factor.
1956 * @param __z The new maximum load factor.
1957 */
1958 void
1959 max_load_factor(float __z)
1960 { _M_h.max_load_factor(__z); }
1961
1962 /**
1963 * @brief May rehash the %unordered_multimap.
1964 * @param __n The new number of buckets.
1965 *
1966 * Rehash will occur only if the new number of buckets respect the
1967 * %unordered_multimap maximum load factor.
1968 */
1969 void
1970 rehash(size_type __n)
1971 { _M_h.rehash(__n); }
1972
1973 /**
1974 * @brief Prepare the %unordered_multimap for a specified number of
1975 * elements.
1976 * @param __n Number of elements required.
1977 *
1978 * Same as rehash(ceil(n / max_load_factor())).
1979 */
1980 void
1981 reserve(size_type __n)
1982 { _M_h.reserve(__n); }
1983
1984 template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1,
1985 typename _Alloc1>
1986 friend bool
1987 operator==(const unordered_multimap<_Key1, _Tp1,
1988 _Hash1, _Pred1, _Alloc1>&,
1989 const unordered_multimap<_Key1, _Tp1,
1990 _Hash1, _Pred1, _Alloc1>&);
1991 };
1992
1993#if __cpp_deduction_guides >= 201606
1994
1995 template<typename _InputIterator,
1996 typename _Hash = hash<__iter_key_t<_InputIterator>>,
1997 typename _Pred = equal_to<__iter_key_t<_InputIterator>>,
1998 typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>,
1999 typename = _RequireInputIter<_InputIterator>,
2000 typename = _RequireNotAllocatorOrIntegral<_Hash>,
2001 typename = _RequireNotAllocator<_Pred>,
2002 typename = _RequireAllocator<_Allocator>>
2003 unordered_multimap(_InputIterator, _InputIterator,
2004 unordered_multimap<int, int>::size_type = {},
2005 _Hash = _Hash(), _Pred = _Pred(),
2006 _Allocator = _Allocator())
2007 -> unordered_multimap<__iter_key_t<_InputIterator>,
2008 __iter_val_t<_InputIterator>, _Hash, _Pred,
2009 _Allocator>;
2010
2011 template<typename _Key, typename _Tp, typename _Hash = hash<_Key>,
2012 typename _Pred = equal_to<_Key>,
2013 typename _Allocator = allocator<pair<const _Key, _Tp>>,
2014 typename = _RequireNotAllocatorOrIntegral<_Hash>,
2015 typename = _RequireNotAllocator<_Pred>,
2016 typename = _RequireAllocator<_Allocator>>
2017 unordered_multimap(initializer_list<pair<_Key, _Tp>>,
2018 unordered_multimap<int, int>::size_type = {},
2019 _Hash = _Hash(), _Pred = _Pred(),
2020 _Allocator = _Allocator())
2021 -> unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>;
2022
2023 template<typename _InputIterator, typename _Allocator,
2024 typename = _RequireInputIter<_InputIterator>,
2025 typename = _RequireAllocator<_Allocator>>
2026 unordered_multimap(_InputIterator, _InputIterator,
2027 unordered_multimap<int, int>::size_type, _Allocator)
2028 -> unordered_multimap<__iter_key_t<_InputIterator>,
2029 __iter_val_t<_InputIterator>,
2030 hash<__iter_key_t<_InputIterator>>,
2031 equal_to<__iter_key_t<_InputIterator>>, _Allocator>;
2032
2033 template<typename _InputIterator, typename _Allocator,
2034 typename = _RequireInputIter<_InputIterator>,
2035 typename = _RequireAllocator<_Allocator>>
2036 unordered_multimap(_InputIterator, _InputIterator, _Allocator)
2037 -> unordered_multimap<__iter_key_t<_InputIterator>,
2038 __iter_val_t<_InputIterator>,
2039 hash<__iter_key_t<_InputIterator>>,
2040 equal_to<__iter_key_t<_InputIterator>>, _Allocator>;
2041
2042 template<typename _InputIterator, typename _Hash, typename _Allocator,
2043 typename = _RequireInputIter<_InputIterator>,
2044 typename = _RequireNotAllocatorOrIntegral<_Hash>,
2045 typename = _RequireAllocator<_Allocator>>
2046 unordered_multimap(_InputIterator, _InputIterator,
2047 unordered_multimap<int, int>::size_type, _Hash,
2048 _Allocator)
2049 -> unordered_multimap<__iter_key_t<_InputIterator>,
2050 __iter_val_t<_InputIterator>, _Hash,
2051 equal_to<__iter_key_t<_InputIterator>>, _Allocator>;
2052
2053 template<typename _Key, typename _Tp, typename _Allocator,
2054 typename = _RequireAllocator<_Allocator>>
2055 unordered_multimap(initializer_list<pair<_Key, _Tp>>,
2056 unordered_multimap<int, int>::size_type,
2057 _Allocator)
2058 -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
2059
2060 template<typename _Key, typename _Tp, typename _Allocator,
2061 typename = _RequireAllocator<_Allocator>>
2062 unordered_multimap(initializer_list<pair<_Key, _Tp>>, _Allocator)
2063 -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
2064
2065 template<typename _Key, typename _Tp, typename _Hash, typename _Allocator,
2066 typename = _RequireNotAllocatorOrIntegral<_Hash>,
2067 typename = _RequireAllocator<_Allocator>>
2068 unordered_multimap(initializer_list<pair<_Key, _Tp>>,
2069 unordered_multimap<int, int>::size_type,
2070 _Hash, _Allocator)
2071 -> unordered_multimap<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;
2072
2073#endif
2074
2075 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
2076 inline void
2077 swap(unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
2078 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
2079 noexcept(noexcept(__x.swap(__y)))
2080 { __x.swap(__y); }
2081
2082 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
2083 inline void
2084 swap(unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
2085 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
2086 noexcept(noexcept(__x.swap(__y)))
2087 { __x.swap(__y); }
2088
2089 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
2090 inline bool
2091 operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
2092 const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
2093 { return __x._M_h._M_equal(__y._M_h); }
2094
2095 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
2096 inline bool
2097 operator!=(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
2098 const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
2099 { return !(__x == __y); }
2100
2101 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
2102 inline bool
2103 operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
2104 const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
2105 { return __x._M_h._M_equal(__y._M_h); }
2106
2107 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
2108 inline bool
2109 operator!=(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
2110 const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
2111 { return !(__x == __y); }
2112
2113_GLIBCXX_END_NAMESPACE_CONTAINER
2114
2115#if __cplusplus > 201402L
2116 // Allow std::unordered_map access to internals of compatible maps.
2117 template<typename _Key, typename _Val, typename _Hash1, typename _Eq1,
2118 typename _Alloc, typename _Hash2, typename _Eq2>
2119 struct _Hash_merge_helper<
2120 _GLIBCXX_STD_C::unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>,
2121 _Hash2, _Eq2>
2122 {
2123 private:
2124 template<typename... _Tp>
2125 using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>;
2126 template<typename... _Tp>
2127 using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>;
2128
2129 friend unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>;
2130
2131 static auto&
2132 _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
2133 { return __map._M_h; }
2134
2135 static auto&
2136 _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
2137 { return __map._M_h; }
2138 };
2139
2140 // Allow std::unordered_multimap access to internals of compatible maps.
2141 template<typename _Key, typename _Val, typename _Hash1, typename _Eq1,
2142 typename _Alloc, typename _Hash2, typename _Eq2>
2143 struct _Hash_merge_helper<
2144 _GLIBCXX_STD_C::unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>,
2145 _Hash2, _Eq2>
2146 {
2147 private:
2148 template<typename... _Tp>
2149 using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>;
2150 template<typename... _Tp>
2151 using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>;
2152
2153 friend unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>;
2154
2155 static auto&
2156 _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
2157 { return __map._M_h; }
2158
2159 static auto&
2160 _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
2161 { return __map._M_h; }
2162 };
2163#endif // C++17
2164
2165_GLIBCXX_END_NAMESPACE_VERSION
2166} // namespace std
2167
2168#endif /* _UNORDERED_MAP_H */
2169