1	// hashtable.h header -*- C++ -*-
2
3	// Copyright (C) 2007-2021 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/hashtable.h
26	* This is an internal header file, included by other library headers.
27	* Do not attempt to use it directly. @headername{unordered_map, unordered_set}
28	*/
29
30	#ifndef _HASHTABLE_H
31	#define _HASHTABLE_H 1
32
33	#pragma GCC system_header
34
35	#include <bits/hashtable_policy.h>
36	#include <bits/enable_special_members.h>
37	#if __cplusplus > 201402L
38	# include <bits/node_handle.h>
39	#endif
40
41	namespace std _GLIBCXX_VISIBILITY(default)
42	{
43	_GLIBCXX_BEGIN_NAMESPACE_VERSION
44	/// @cond undocumented
45
46	template<typename _Tp, typename _Hash>
47	using __cache_default
48	= __not_<__and_<// Do not cache for fast hasher.
49	__is_fast_hash<_Hash>,
50	// Mandatory to have erase not throwing.
51	__is_nothrow_invocable<const _Hash&, const _Tp&>>>;
52
53	// Helper to conditionally delete the default constructor.
54	// The _Hash_node_base type is used to distinguish this specialization
55	// from any other potentially-overlapping subobjects of the hashtable.
56	template<typename _Equal, typename _Hash, typename _Allocator>
57	using _Hashtable_enable_default_ctor
58	= _Enable_default_constructor<__and_<is_default_constructible<_Equal>,
59	is_default_constructible<_Hash>,
60	is_default_constructible<_Allocator>>{},
61	__detail::_Hash_node_base>;
62
63	/**
64	* Primary class template _Hashtable.
65	*
66	* @ingroup hashtable-detail
67	*
68	* @tparam _Value CopyConstructible type.
69	*
70	* @tparam _Key CopyConstructible type.
71	*
72	* @tparam _Alloc An allocator type
73	* ([lib.allocator.requirements]) whose _Alloc::value_type is
74	* _Value. As a conforming extension, we allow for
75	* _Alloc::value_type != _Value.
76	*
77	* @tparam _ExtractKey Function object that takes an object of type
78	* _Value and returns a value of type _Key.
79	*
80	* @tparam _Equal Function object that takes two objects of type k
81	* and returns a bool-like value that is true if the two objects
82	* are considered equal.
83	*
84	* @tparam _Hash The hash function. A unary function object with
85	* argument type _Key and result type size_t. Return values should
86	* be distributed over the entire range [0, numeric_limits<size_t>:::max()].
87	*
88	* @tparam _RangeHash The range-hashing function (in the terminology of
89	* Tavori and Dreizin). A binary function object whose argument
90	* types and result type are all size_t. Given arguments r and N,
91	* the return value is in the range [0, N).
92	*
93	* @tparam _Unused Not used.
94	*
95	* @tparam _RehashPolicy Policy class with three members, all of
96	* which govern the bucket count. _M_next_bkt(n) returns a bucket
97	* count no smaller than n. _M_bkt_for_elements(n) returns a
98	* bucket count appropriate for an element count of n.
99	* _M_need_rehash(n_bkt, n_elt, n_ins) determines whether, if the
100	* current bucket count is n_bkt and the current element count is
101	* n_elt, we need to increase the bucket count for n_ins insertions.
102	* If so, returns make_pair(true, n), where n is the new bucket count. If
103	* not, returns make_pair(false, <anything>)
104	*
105	* @tparam _Traits Compile-time class with three boolean
106	* std::integral_constant members: __cache_hash_code, __constant_iterators,
107	* __unique_keys.
108	*
109	* Each _Hashtable data structure has:
110	*
111	* - _Bucket[] _M_buckets
112	* - _Hash_node_base _M_before_begin
113	* - size_type _M_bucket_count
114	* - size_type _M_element_count
115	*
116	* with _Bucket being _Hash_node_base* and _Hash_node containing:
117	*
118	* - _Hash_node* _M_next
119	* - Tp _M_value
120	* - size_t _M_hash_code if cache_hash_code is true
121	*
122	* In terms of Standard containers the hashtable is like the aggregation of:
123	*
124	* - std::forward_list<_Node> containing the elements
125	* - std::vector<std::forward_list<_Node>::iterator> representing the buckets
126	*
127	* The non-empty buckets contain the node before the first node in the
128	* bucket. This design makes it possible to implement something like a
129	* std::forward_list::insert_after on container insertion and
130	* std::forward_list::erase_after on container erase
131	* calls. _M_before_begin is equivalent to
132	* std::forward_list::before_begin. Empty buckets contain
133	* nullptr. Note that one of the non-empty buckets contains
134	* &_M_before_begin which is not a dereferenceable node so the
135	* node pointer in a bucket shall never be dereferenced, only its
136	* next node can be.
137	*
138	* Walking through a bucket's nodes requires a check on the hash code to
139	* see if each node is still in the bucket. Such a design assumes a
140	* quite efficient hash functor and is one of the reasons it is
141	* highly advisable to set __cache_hash_code to true.
142	*
143	* The container iterators are simply built from nodes. This way
144	* incrementing the iterator is perfectly efficient independent of
145	* how many empty buckets there are in the container.
146	*
147	* On insert we compute the element's hash code and use it to find the
148	* bucket index. If the element must be inserted in an empty bucket
149	* we add it at the beginning of the singly linked list and make the
150	* bucket point to _M_before_begin. The bucket that used to point to
151	* _M_before_begin, if any, is updated to point to its new before
152	* begin node.
153	*
154	* On erase, the simple iterator design requires using the hash
155	* functor to get the index of the bucket to update. For this
156	* reason, when __cache_hash_code is set to false the hash functor must
157	* not throw and this is enforced by a static assertion.
158	*
159	* Functionality is implemented by decomposition into base classes,
160	* where the derived _Hashtable class is used in _Map_base,
161	* _Insert, _Rehash_base, and _Equality base classes to access the
162	* "this" pointer. _Hashtable_base is used in the base classes as a
163	* non-recursive, fully-completed-type so that detailed nested type
164	* information, such as iterator type and node type, can be
165	* used. This is similar to the "Curiously Recurring Template
166	* Pattern" (CRTP) technique, but uses a reconstructed, not
167	* explicitly passed, template pattern.
168	*
169	* Base class templates are:
170	* - __detail::_Hashtable_base
171	* - __detail::_Map_base
172	* - __detail::_Insert
173	* - __detail::_Rehash_base
174	* - __detail::_Equality
175	*/
176	template<typename _Key, typename _Value, typename _Alloc,
177	typename _ExtractKey, typename _Equal,
178	typename _Hash, typename _RangeHash, typename _Unused,
179	typename _RehashPolicy, typename _Traits>
180	class _Hashtable
181	: public __detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal,
182	_Hash, _RangeHash, _Unused, _Traits>,
183	public __detail::_Map_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
184	_Hash, _RangeHash, _Unused,
185	_RehashPolicy, _Traits>,
186	public __detail::_Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal,
187	_Hash, _RangeHash, _Unused,
188	_RehashPolicy, _Traits>,
189	public __detail::_Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
190	_Hash, _RangeHash, _Unused,
191	_RehashPolicy, _Traits>,
192	public __detail::_Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
193	_Hash, _RangeHash, _Unused,
194	_RehashPolicy, _Traits>,
195	private __detail::_Hashtable_alloc<
196	__alloc_rebind<_Alloc,
197	__detail::_Hash_node<_Value,
198	_Traits::__hash_cached::value>>>,
199	private _Hashtable_enable_default_ctor<_Equal, _Hash, _Alloc>
200	{
201	static_assert(is_same<typename remove_cv<_Value>::type, _Value>::value,
202	"unordered container must have a non-const, non-volatile value_type");
203	#if __cplusplus > 201703L || defined __STRICT_ANSI__
204	static_assert(is_same<typename _Alloc::value_type, _Value>{},
205	"unordered container must have the same value_type as its allocator");
206	#endif
207
208	using __traits_type = _Traits;
209	using __hash_cached = typename __traits_type::__hash_cached;
210	using __constant_iterators = typename __traits_type::__constant_iterators;
211	using __node_type = __detail::_Hash_node<_Value, __hash_cached::value>;
212	using __node_alloc_type = __alloc_rebind<_Alloc, __node_type>;
213
214	using __hashtable_alloc = __detail::_Hashtable_alloc<__node_alloc_type>;
215
216	using __node_value_type =
217	__detail::_Hash_node_value<_Value, __hash_cached::value>;
218	using __node_ptr = typename __hashtable_alloc::__node_ptr;
219	using __value_alloc_traits =
220	typename __hashtable_alloc::__value_alloc_traits;
221	using __node_alloc_traits =
222	typename __hashtable_alloc::__node_alloc_traits;
223	using __node_base = typename __hashtable_alloc::__node_base;
224	using __node_base_ptr = typename __hashtable_alloc::__node_base_ptr;
225	using __buckets_ptr = typename __hashtable_alloc::__buckets_ptr;
226
227	using __insert_base = __detail::_Insert<_Key, _Value, _Alloc, _ExtractKey,
228	_Equal, _Hash,
229	_RangeHash, _Unused,
230	_RehashPolicy, _Traits>;
231	using __enable_default_ctor
232	= _Hashtable_enable_default_ctor<_Equal, _Hash, _Alloc>;
233
234	public:
235	typedef _Key key_type;
236	typedef _Value value_type;
237	typedef _Alloc allocator_type;
238	typedef _Equal key_equal;
239
240	// mapped_type, if present, comes from _Map_base.
241	// hasher, if present, comes from _Hash_code_base/_Hashtable_base.
242	typedef typename __value_alloc_traits::pointer pointer;
243	typedef typename __value_alloc_traits::const_pointer const_pointer;
244	typedef value_type& reference;
245	typedef const value_type& const_reference;
246
247	using iterator = typename __insert_base::iterator;
248
249	using const_iterator = typename __insert_base::const_iterator;
250
251	using local_iterator = __detail::_Local_iterator<key_type, _Value,
252	_ExtractKey, _Hash, _RangeHash, _Unused,
253	__constant_iterators::value,
254	__hash_cached::value>;
255
256	using const_local_iterator = __detail::_Local_const_iterator<
257	key_type, _Value,
258	_ExtractKey, _Hash, _RangeHash, _Unused,
259	__constant_iterators::value, __hash_cached::value>;
260
261	private:
262	using __rehash_type = _RehashPolicy;
263	using __rehash_state = typename __rehash_type::_State;
264
265	using __unique_keys = typename __traits_type::__unique_keys;
266
267	using __hashtable_base = __detail::
268	_Hashtable_base<_Key, _Value, _ExtractKey,
269	_Equal, _Hash, _RangeHash, _Unused, _Traits>;
270
271	using __hash_code_base = typename __hashtable_base::__hash_code_base;
272	using __hash_code = typename __hashtable_base::__hash_code;
273	using __ireturn_type = typename __insert_base::__ireturn_type;
274
275	using __map_base = __detail::_Map_base<_Key, _Value, _Alloc, _ExtractKey,
276	_Equal, _Hash, _RangeHash, _Unused,
277	_RehashPolicy, _Traits>;
278
279	using __rehash_base = __detail::_Rehash_base<_Key, _Value, _Alloc,
280	_ExtractKey, _Equal,
281	_Hash, _RangeHash, _Unused,
282	_RehashPolicy, _Traits>;
283
284	using __eq_base = __detail::_Equality<_Key, _Value, _Alloc, _ExtractKey,
285	_Equal, _Hash, _RangeHash, _Unused,
286	_RehashPolicy, _Traits>;
287
288	using __reuse_or_alloc_node_gen_t =
289	__detail::_ReuseOrAllocNode<__node_alloc_type>;
290	using __alloc_node_gen_t =
291	__detail::_AllocNode<__node_alloc_type>;
292
293	// Simple RAII type for managing a node containing an element
294	struct _Scoped_node
295	{
296	// Take ownership of a node with a constructed element.
297	_Scoped_node(__node_ptr __n, __hashtable_alloc* __h)
298	: _M_h(__h), _M_node(__n) { }
299
300	// Allocate a node and construct an element within it.
301	template<typename... _Args>
302	_Scoped_node(__hashtable_alloc* __h, _Args&&... __args)
303	: _M_h(__h),
304	_M_node(__h->_M_allocate_node(std::forward<_Args>(__args)...))
305	{ }
306
307	// Destroy element and deallocate node.
308	~_Scoped_node() { if (_M_node) _M_h->_M_deallocate_node(_M_node); };
309
310	_Scoped_node(const _Scoped_node&) = delete;
311	_Scoped_node& operator=(const _Scoped_node&) = delete;
312
313	__hashtable_alloc* _M_h;
314	__node_ptr _M_node;
315	};
316
317	template<typename _Ht>
318	static constexpr
319	typename conditional<std::is_lvalue_reference<_Ht>::value,
320	const value_type&, value_type&&>::type
321	__fwd_value_for(value_type& __val) noexcept
322	{ return std::move(__val); }
323
324	// Compile-time diagnostics.
325
326	// _Hash_code_base has everything protected, so use this derived type to
327	// access it.
328	struct __hash_code_base_access : __hash_code_base
329	{ using __hash_code_base::_M_bucket_index; };
330
331	// Getting a bucket index from a node shall not throw because it is used
332	// in methods (erase, swap...) that shall not throw.
333	static_assert(noexcept(declval<const __hash_code_base_access&>()
334	._M_bucket_index(declval<const __node_value_type&>(),
335	(std::size_t)0)),
336	"Cache the hash code or qualify your functors involved"
337	" in hash code and bucket index computation with noexcept");
338
339	// To get bucket index we need _RangeHash not to throw.
340	static_assert(is_nothrow_default_constructible<_RangeHash>::value,
341	"Functor used to map hash code to bucket index"
342	" must be nothrow default constructible");
343	static_assert(noexcept(
344	std::declval<const _RangeHash&>()((std::size_t)0, (std::size_t)0)),
345	"Functor used to map hash code to bucket index must be"
346	" noexcept");
347
348	// To compute bucket index we also need _ExtratKey not to throw.
349	static_assert(is_nothrow_default_constructible<_ExtractKey>::value,
350	"_ExtractKey must be nothrow default constructible");
351	static_assert(noexcept(
352	std::declval<const _ExtractKey&>()(std::declval<_Value>())),
353	"_ExtractKey functor must be noexcept invocable");
354
355	template<typename _Keya, typename _Valuea, typename _Alloca,
356	typename _ExtractKeya, typename _Equala,
357	typename _Hasha, typename _RangeHasha, typename _Unuseda,
358	typename _RehashPolicya, typename _Traitsa,
359	bool _Unique_keysa>
360	friend struct __detail::_Map_base;
361
362	template<typename _Keya, typename _Valuea, typename _Alloca,
363	typename _ExtractKeya, typename _Equala,
364	typename _Hasha, typename _RangeHasha, typename _Unuseda,
365	typename _RehashPolicya, typename _Traitsa>
366	friend struct __detail::_Insert_base;
367
368	template<typename _Keya, typename _Valuea, typename _Alloca,
369	typename _ExtractKeya, typename _Equala,
370	typename _Hasha, typename _RangeHasha, typename _Unuseda,
371	typename _RehashPolicya, typename _Traitsa,
372	bool _Constant_iteratorsa>
373	friend struct __detail::_Insert;
374
375	template<typename _Keya, typename _Valuea, typename _Alloca,
376	typename _ExtractKeya, typename _Equala,
377	typename _Hasha, typename _RangeHasha, typename _Unuseda,
378	typename _RehashPolicya, typename _Traitsa,
379	bool _Unique_keysa>
380	friend struct __detail::_Equality;
381
382	public:
383	using size_type = typename __hashtable_base::size_type;
384	using difference_type = typename __hashtable_base::difference_type;
385
386	#if __cplusplus > 201402L
387	using node_type = _Node_handle<_Key, _Value, __node_alloc_type>;
388	using insert_return_type = _Node_insert_return<iterator, node_type>;
389	#endif
390
391	private:
392	__buckets_ptr _M_buckets = &_M_single_bucket;
393	size_type _M_bucket_count = 1;
394	__node_base _M_before_begin;
395	size_type _M_element_count = 0;
396	_RehashPolicy _M_rehash_policy;
397
398	// A single bucket used when only need for 1 bucket. Especially
399	// interesting in move semantic to leave hashtable with only 1 bucket
400	// which is not allocated so that we can have those operations noexcept
401	// qualified.
402	// Note that we can't leave hashtable with 0 bucket without adding
403	// numerous checks in the code to avoid 0 modulus.
404	__node_base_ptr _M_single_bucket = nullptr;
405
406	void
407	_M_update_bbegin()
408	{
409	if (_M_begin())
410	_M_buckets[_M_bucket_index(*_M_begin())] = &_M_before_begin;
411	}
412
413	void
414	_M_update_bbegin(__node_ptr __n)
415	{
416	_M_before_begin._M_nxt = __n;
417	_M_update_bbegin();
418	}
419
420	bool
421	_M_uses_single_bucket(__buckets_ptr __bkts) const
422	{ return __builtin_expect(__bkts == &_M_single_bucket, false); }
423
424	bool
425	_M_uses_single_bucket() const
426	{ return _M_uses_single_bucket(_M_buckets); }
427
428	__hashtable_alloc&
429	_M_base_alloc() { return *this; }
430
431	__buckets_ptr
432	_M_allocate_buckets(size_type __bkt_count)
433	{
434	if (__builtin_expect(__bkt_count == 1, false))
435	{
436	_M_single_bucket = nullptr;
437	return &_M_single_bucket;
438	}
439
440	return __hashtable_alloc::_M_allocate_buckets(__bkt_count);
441	}
442
443	void
444	_M_deallocate_buckets(__buckets_ptr __bkts, size_type __bkt_count)
445	{
446	if (_M_uses_single_bucket(__bkts))
447	return;
448
449	__hashtable_alloc::_M_deallocate_buckets(__bkts, __bkt_count);
450	}
451
452	void
453	_M_deallocate_buckets()
454	{ _M_deallocate_buckets(_M_buckets, _M_bucket_count); }
455
456	// Gets bucket begin, deals with the fact that non-empty buckets contain
457	// their before begin node.
458	__node_ptr
459	_M_bucket_begin(size_type __bkt) const;
460
461	__node_ptr
462	_M_begin() const
463	{ return static_cast<__node_ptr>(_M_before_begin._M_nxt); }
464
465	// Assign *this using another _Hashtable instance. Whether elements
466	// are copied or moved depends on the _Ht reference.
467	template<typename _Ht>
468	void
469	_M_assign_elements(_Ht&&);
470
471	template<typename _Ht, typename _NodeGenerator>
472	void
473	_M_assign(_Ht&&, const _NodeGenerator&);
474
475	void
476	_M_move_assign(_Hashtable&&, true_type);
477
478	void
479	_M_move_assign(_Hashtable&&, false_type);
480
481	void
482	_M_reset() noexcept;
483
484	_Hashtable(const _Hash& __h, const _Equal& __eq,
485	const allocator_type& __a)
486	: __hashtable_base(__h, __eq),
487	__hashtable_alloc(__node_alloc_type(__a)),
488	__enable_default_ctor(_Enable_default_constructor_tag{})
489	{ }
490
491	template<bool _No_realloc = true>
492	static constexpr bool
493	_S_nothrow_move()
494	{
495	#if __cplusplus <= 201402L
496	return __and_<__bool_constant<_No_realloc>,
497	is_nothrow_copy_constructible<_Hash>,
498	is_nothrow_copy_constructible<_Equal>>::value;
499	#else
500	if constexpr (_No_realloc)
501	if constexpr (is_nothrow_copy_constructible<_Hash>())
502	return is_nothrow_copy_constructible<_Equal>();
503	return false;
504	#endif
505	}
506
507	_Hashtable(_Hashtable&& __ht, __node_alloc_type&& __a,
508	true_type /* alloc always equal */)
509	noexcept(_S_nothrow_move());
510
511	_Hashtable(_Hashtable&&, __node_alloc_type&&,
512	false_type /* alloc always equal */);
513
514	template<typename _InputIterator>
515	_Hashtable(_InputIterator __first, _InputIterator __last,
516	size_type __bkt_count_hint,
517	const _Hash&, const _Equal&, const allocator_type&,
518	true_type __uks);
519
520	template<typename _InputIterator>
521	_Hashtable(_InputIterator __first, _InputIterator __last,
522	size_type __bkt_count_hint,
523	const _Hash&, const _Equal&, const allocator_type&,
524	false_type __uks);
525
526	public:
527	// Constructor, destructor, assignment, swap
528	_Hashtable() = default;
529
530	_Hashtable(const _Hashtable&);
531
532	_Hashtable(const _Hashtable&, const allocator_type&);
533
534	explicit
535	_Hashtable(size_type __bkt_count_hint,
536	const _Hash& __hf = _Hash(),
537	const key_equal& __eql = key_equal(),
538	const allocator_type& __a = allocator_type());
539
540	// Use delegating constructors.
541	_Hashtable(_Hashtable&& __ht)
542	noexcept(_S_nothrow_move())
543	: _Hashtable(std::move(__ht), std::move(__ht._M_node_allocator()),
544	true_type{})
545	{ }
546
547	_Hashtable(_Hashtable&& __ht, const allocator_type& __a)
548	noexcept(_S_nothrow_move<__node_alloc_traits::_S_always_equal()>())
549	: _Hashtable(std::move(__ht), __node_alloc_type(__a),
550	typename __node_alloc_traits::is_always_equal{})
551	{ }
552
553	explicit
554	_Hashtable(const allocator_type& __a)
555	: __hashtable_alloc(__node_alloc_type(__a)),
556	__enable_default_ctor(_Enable_default_constructor_tag{})
557	{ }
558
559	template<typename _InputIterator>
560	_Hashtable(_InputIterator __f, _InputIterator __l,
561	size_type __bkt_count_hint = 0,
562	const _Hash& __hf = _Hash(),
563	const key_equal& __eql = key_equal(),
564	const allocator_type& __a = allocator_type())
565	: _Hashtable(__f, __l, __bkt_count_hint, __hf, __eql, __a,
566	__unique_keys{})
567	{ }
568
569	_Hashtable(initializer_list<value_type> __l,
570	size_type __bkt_count_hint = 0,
571	const _Hash& __hf = _Hash(),
572	const key_equal& __eql = key_equal(),
573	const allocator_type& __a = allocator_type())
574	: _Hashtable(__l.begin(), __l.end(), __bkt_count_hint,
575	__hf, __eql, __a, __unique_keys{})
576	{ }
577
578	_Hashtable&
579	operator=(const _Hashtable& __ht);
580
581	_Hashtable&
582	operator=(_Hashtable&& __ht)
583	noexcept(__node_alloc_traits::_S_nothrow_move()
584	&& is_nothrow_move_assignable<_Hash>::value
585	&& is_nothrow_move_assignable<_Equal>::value)
586	{
587	constexpr bool __move_storage =
588	__node_alloc_traits::_S_propagate_on_move_assign()
589	|| __node_alloc_traits::_S_always_equal();
590	_M_move_assign(std::move(__ht), __bool_constant<__move_storage>());
591	return *this;
592	}
593
594	_Hashtable&
595	operator=(initializer_list<value_type> __l)
596	{
597	__reuse_or_alloc_node_gen_t __roan(_M_begin(), *this);
598	_M_before_begin._M_nxt = nullptr;
599	clear();
600
601	// We consider that all elements of __l are going to be inserted.
602	auto __l_bkt_count = _M_rehash_policy._M_bkt_for_elements(__l.size());
603
604	// Do not shrink to keep potential user reservation.
605	if (_M_bucket_count < __l_bkt_count)
606	rehash(bkt_count: __l_bkt_count);
607
608	this->_M_insert_range(__l.begin(), __l.end(), __roan, __unique_keys{});
609	return *this;
610	}
611
612	~_Hashtable() noexcept;
613
614	void
615	swap(_Hashtable&)
616	noexcept(__and_<__is_nothrow_swappable<_Hash>,
617	__is_nothrow_swappable<_Equal>>::value);
618
619	// Basic container operations
620	iterator
621	begin() noexcept
622	{ return iterator(_M_begin()); }
623
624	const_iterator
625	begin() const noexcept
626	{ return const_iterator(_M_begin()); }
627
628	iterator
629	end() noexcept
630	{ return iterator(nullptr); }
631
632	const_iterator
633	end() const noexcept
634	{ return const_iterator(nullptr); }
635
636	const_iterator
637	cbegin() const noexcept
638	{ return const_iterator(_M_begin()); }
639
640	const_iterator
641	cend() const noexcept
642	{ return const_iterator(nullptr); }
643
644	size_type
645	size() const noexcept
646	{ return _M_element_count; }
647
648	_GLIBCXX_NODISCARD bool
649	empty() const noexcept
650	{ return size() == 0; }
651
652	allocator_type
653	get_allocator() const noexcept
654	{ return allocator_type(this->_M_node_allocator()); }
655
656	size_type
657	max_size() const noexcept
658	{ return __node_alloc_traits::max_size(this->_M_node_allocator()); }
659
660	// Observers
661	key_equal
662	key_eq() const
663	{ return this->_M_eq(); }
664
665	// hash_function, if present, comes from _Hash_code_base.
666
667	// Bucket operations
668	size_type
669	bucket_count() const noexcept
670	{ return _M_bucket_count; }
671
672	size_type
673	max_bucket_count() const noexcept
674	{ return max_size(); }
675
676	size_type
677	bucket_size(size_type __bkt) const
678	{ return std::distance(begin(__bkt), end(__bkt)); }
679
680	size_type
681	bucket(const key_type& __k) const
682	{ return _M_bucket_index(this->_M_hash_code(__k)); }
683
684	local_iterator
685	begin(size_type __bkt)
686	{
687	return local_iterator(*this, _M_bucket_begin(__bkt),
688	__bkt, _M_bucket_count);
689	}
690
691	local_iterator
692	end(size_type __bkt)
693	{ return local_iterator(*this, nullptr, __bkt, _M_bucket_count); }
694
695	const_local_iterator
696	begin(size_type __bkt) const
697	{
698	return const_local_iterator(*this, _M_bucket_begin(__bkt),
699	__bkt, _M_bucket_count);
700	}
701
702	const_local_iterator
703	end(size_type __bkt) const
704	{ return const_local_iterator(*this, nullptr, __bkt, _M_bucket_count); }
705
706	// DR 691.
707	const_local_iterator
708	cbegin(size_type __bkt) const
709	{
710	return const_local_iterator(*this, _M_bucket_begin(__bkt),
711	__bkt, _M_bucket_count);
712	}
713
714	const_local_iterator
715	cend(size_type __bkt) const
716	{ return const_local_iterator(*this, nullptr, __bkt, _M_bucket_count); }
717
718	float
719	load_factor() const noexcept
720	{
721	return static_cast<float>(size()) / static_cast<float>(bucket_count());
722	}
723
724	// max_load_factor, if present, comes from _Rehash_base.
725
726	// Generalization of max_load_factor. Extension, not found in
727	// TR1. Only useful if _RehashPolicy is something other than
728	// the default.
729	const _RehashPolicy&
730	__rehash_policy() const
731	{ return _M_rehash_policy; }
732
733	void
734	__rehash_policy(const _RehashPolicy& __pol)
735	{ _M_rehash_policy = __pol; }
736
737	// Lookup.
738	iterator
739	find(const key_type& __k);
740
741	const_iterator
742	find(const key_type& __k) const;
743
744	size_type
745	count(const key_type& __k) const;
746
747	std::pair<iterator, iterator>
748	equal_range(const key_type& __k);
749
750	std::pair<const_iterator, const_iterator>
751	equal_range(const key_type& __k) const;
752
753	#if __cplusplus >= 202002L
754	#define __cpp_lib_generic_unordered_lookup 201811L
755
756	template<typename _Kt,
757	typename = __has_is_transparent_t<_Hash, _Kt>,
758	typename = __has_is_transparent_t<_Equal, _Kt>>
759	iterator
760	_M_find_tr(const _Kt& __k);
761
762	template<typename _Kt,
763	typename = __has_is_transparent_t<_Hash, _Kt>,
764	typename = __has_is_transparent_t<_Equal, _Kt>>
765	const_iterator
766	_M_find_tr(const _Kt& __k) const;
767
768	template<typename _Kt,
769	typename = __has_is_transparent_t<_Hash, _Kt>,
770	typename = __has_is_transparent_t<_Equal, _Kt>>
771	size_type
772	_M_count_tr(const _Kt& __k) const;
773
774	template<typename _Kt,
775	typename = __has_is_transparent_t<_Hash, _Kt>,
776	typename = __has_is_transparent_t<_Equal, _Kt>>
777	pair<iterator, iterator>
778	_M_equal_range_tr(const _Kt& __k);
779
780	template<typename _Kt,
781	typename = __has_is_transparent_t<_Hash, _Kt>,
782	typename = __has_is_transparent_t<_Equal, _Kt>>
783	pair<const_iterator, const_iterator>
784	_M_equal_range_tr(const _Kt& __k) const;
785	#endif // C++20
786
787	private:
788	// Bucket index computation helpers.
789	size_type
790	_M_bucket_index(const __node_value_type& __n) const noexcept
791	{ return __hash_code_base::_M_bucket_index(__n, _M_bucket_count); }
792
793	size_type
794	_M_bucket_index(__hash_code __c) const
795	{ return __hash_code_base::_M_bucket_index(__c, _M_bucket_count); }
796
797	// Find and insert helper functions and types
798	// Find the node before the one matching the criteria.
799	__node_base_ptr
800	_M_find_before_node(size_type, const key_type&, __hash_code) const;
801
802	template<typename _Kt>
803	__node_base_ptr
804	_M_find_before_node_tr(size_type, const _Kt&, __hash_code) const;
805
806	__node_ptr
807	_M_find_node(size_type __bkt, const key_type& __key,
808	__hash_code __c) const
809	{
810	__node_base_ptr __before_n = _M_find_before_node(__bkt, __key, __c);
811	if (__before_n)
812	return static_cast<__node_ptr>(__before_n->_M_nxt);
813	return nullptr;
814	}
815
816	template<typename _Kt>
817	__node_ptr
818	_M_find_node_tr(size_type __bkt, const _Kt& __key,
819	__hash_code __c) const
820	{
821	auto __before_n = _M_find_before_node_tr(__bkt, __key, __c);
822	if (__before_n)
823	return static_cast<__node_ptr>(__before_n->_M_nxt);
824	return nullptr;
825	}
826
827	// Insert a node at the beginning of a bucket.
828	void
829	_M_insert_bucket_begin(size_type, __node_ptr);
830
831	// Remove the bucket first node
832	void
833	_M_remove_bucket_begin(size_type __bkt, __node_ptr __next_n,
834	size_type __next_bkt);
835
836	// Get the node before __n in the bucket __bkt
837	__node_base_ptr
838	_M_get_previous_node(size_type __bkt, __node_ptr __n);
839
840	// Insert node __n with hash code __code, in bucket __bkt if no
841	// rehash (assumes no element with same key already present).
842	// Takes ownership of __n if insertion succeeds, throws otherwise.
843	iterator
844	_M_insert_unique_node(size_type __bkt, __hash_code,
845	__node_ptr __n, size_type __n_elt = 1);
846
847	// Insert node __n with key __k and hash code __code.
848	// Takes ownership of __n if insertion succeeds, throws otherwise.
849	iterator
850	_M_insert_multi_node(__node_ptr __hint,
851	__hash_code __code, __node_ptr __n);
852
853	template<typename... _Args>
854	std::pair<iterator, bool>
855	_M_emplace(true_type __uks, _Args&&... __args);
856
857	template<typename... _Args>
858	iterator
859	_M_emplace(false_type __uks, _Args&&... __args)
860	{ return _M_emplace(cend(), __uks, std::forward<_Args>(__args)...); }
861
862	// Emplace with hint, useless when keys are unique.
863	template<typename... _Args>
864	iterator
865	_M_emplace(const_iterator, true_type __uks, _Args&&... __args)
866	{ return _M_emplace(__uks, std::forward<_Args>(__args)...).first; }
867
868	template<typename... _Args>
869	iterator
870	_M_emplace(const_iterator, false_type __uks, _Args&&... __args);
871
872	template<typename _Arg, typename _NodeGenerator>
873	std::pair<iterator, bool>
874	_M_insert(_Arg&&, const _NodeGenerator&, true_type __uks);
875
876	template<typename _Arg, typename _NodeGenerator>
877	iterator
878	_M_insert(_Arg&& __arg, const _NodeGenerator& __node_gen,
879	false_type __uks)
880	{
881	return _M_insert(cend(), std::forward<_Arg>(__arg), __node_gen,
882	__uks);
883	}
884
885	// Insert with hint, not used when keys are unique.
886	template<typename _Arg, typename _NodeGenerator>
887	iterator
888	_M_insert(const_iterator, _Arg&& __arg,
889	const _NodeGenerator& __node_gen, true_type __uks)
890	{
891	return
892	_M_insert(std::forward<_Arg>(__arg), __node_gen, __uks).first;
893	}
894
895	// Insert with hint when keys are not unique.
896	template<typename _Arg, typename _NodeGenerator>
897	iterator
898	_M_insert(const_iterator, _Arg&&,
899	const _NodeGenerator&, false_type __uks);
900
901	size_type
902	_M_erase(true_type __uks, const key_type&);
903
904	size_type
905	_M_erase(false_type __uks, const key_type&);
906
907	iterator
908	_M_erase(size_type __bkt, __node_base_ptr __prev_n, __node_ptr __n);
909
910	public:
911	// Emplace
912	template<typename... _Args>
913	__ireturn_type
914	emplace(_Args&&... __args)
915	{ return _M_emplace(__unique_keys{}, std::forward<_Args>(__args)...); }
916
917	template<typename... _Args>
918	iterator
919	emplace_hint(const_iterator __hint, _Args&&... __args)
920	{
921	return _M_emplace(__hint, __unique_keys{},
922	std::forward<_Args>(__args)...);
923	}
924
925	// Insert member functions via inheritance.
926
927	// Erase
928	iterator
929	erase(const_iterator);
930
931	// LWG 2059.
932	iterator
933	erase(iterator __it)
934	{ return erase(const_iterator(__it)); }
935
936	size_type
937	erase(const key_type& __k)
938	{ return _M_erase(__unique_keys{}, __k); }
939
940	iterator
941	erase(const_iterator, const_iterator);
942
943	void
944	clear() noexcept;
945
946	// Set number of buckets keeping it appropriate for container's number
947	// of elements.
948	void rehash(size_type __bkt_count);
949
950	// DR 1189.
951	// reserve, if present, comes from _Rehash_base.
952
953	#if __cplusplus > 201402L
954	/// Re-insert an extracted node into a container with unique keys.
955	insert_return_type
956	_M_reinsert_node(node_type&& __nh)
957	{
958	insert_return_type __ret;
959	if (__nh.empty())
960	__ret.position = end();
961	else
962	{
963	__glibcxx_assert(get_allocator() == __nh.get_allocator());
964
965	const key_type& __k = __nh._M_key();
966	__hash_code __code = this->_M_hash_code(__k);
967	size_type __bkt = _M_bucket_index(__code);
968	if (__node_ptr __n = _M_find_node(__bkt, __k, __code))
969	{
970	__ret.node = std::move(__nh);
971	__ret.position = iterator(__n);
972	__ret.inserted = false;
973	}
974	else
975	{
976	__ret.position
977	= _M_insert_unique_node(__bkt, __code, __nh._M_ptr);
978	__nh._M_ptr = nullptr;
979	__ret.inserted = true;
980	}
981	}
982	return __ret;
983	}
984
985	/// Re-insert an extracted node into a container with equivalent keys.
986	iterator
987	_M_reinsert_node_multi(const_iterator __hint, node_type&& __nh)
988	{
989	if (__nh.empty())
990	return end();
991
992	__glibcxx_assert(get_allocator() == __nh.get_allocator());
993
994	const key_type& __k = __nh._M_key();
995	auto __code = this->_M_hash_code(__k);
996	auto __ret
997	= _M_insert_multi_node(__hint._M_cur, __code, __nh._M_ptr);
998	__nh._M_ptr = nullptr;
999	return __ret;
1000	}
1001
1002	private:
1003	node_type
1004	_M_extract_node(size_t __bkt, __node_base_ptr __prev_n)
1005	{
1006	__node_ptr __n = static_cast<__node_ptr>(__prev_n->_M_nxt);
1007	if (__prev_n == _M_buckets[__bkt])
1008	_M_remove_bucket_begin(__bkt, __n->_M_next(),
1009	__n->_M_nxt ? _M_bucket_index(*__n->_M_next()) : 0);
1010	else if (__n->_M_nxt)
1011	{
1012	size_type __next_bkt = _M_bucket_index(*__n->_M_next());
1013	if (__next_bkt != __bkt)
1014	_M_buckets[__next_bkt] = __prev_n;
1015	}
1016
1017	__prev_n->_M_nxt = __n->_M_nxt;
1018	__n->_M_nxt = nullptr;
1019	--_M_element_count;
1020	return { __n, this->_M_node_allocator() };
1021	}
1022
1023	public:
1024	// Extract a node.
1025	node_type
1026	extract(const_iterator __pos)
1027	{
1028	size_t __bkt = _M_bucket_index(*__pos._M_cur);
1029	return _M_extract_node(__bkt,
1030	_M_get_previous_node(__bkt, __pos._M_cur));
1031	}
1032
1033	/// Extract a node.
1034	node_type
1035	extract(const _Key& __k)
1036	{
1037	node_type __nh;
1038	__hash_code __code = this->_M_hash_code(__k);
1039	std::size_t __bkt = _M_bucket_index(__code);
1040	if (__node_base_ptr __prev_node = _M_find_before_node(__bkt, __k, __code))
1041	__nh = _M_extract_node(__bkt, __prev_node);
1042	return __nh;
1043	}
1044
1045	/// Merge from a compatible container into one with unique keys.
1046	template<typename _Compatible_Hashtable>
1047	void
1048	_M_merge_unique(_Compatible_Hashtable& __src) noexcept
1049	{
1050	static_assert(is_same_v<typename _Compatible_Hashtable::node_type,
1051	node_type>, "Node types are compatible");
1052	__glibcxx_assert(get_allocator() == __src.get_allocator());
1053
1054	auto __n_elt = __src.size();
1055	for (auto __i = __src.begin(), __end = __src.end(); __i != __end;)
1056	{
1057	auto __pos = __i++;
1058	const key_type& __k = _ExtractKey{}(*__pos);
1059	__hash_code __code = this->_M_hash_code(__k);
1060	size_type __bkt = _M_bucket_index(__code);
1061	if (_M_find_node(__bkt, __k, __code) == nullptr)
1062	{
1063	auto __nh = __src.extract(__pos);
1064	_M_insert_unique_node(__bkt, __code, __nh._M_ptr, __n_elt);
1065	__nh._M_ptr = nullptr;
1066	__n_elt = 1;
1067	}
1068	else if (__n_elt != 1)
1069	--__n_elt;
1070	}
1071	}
1072
1073	/// Merge from a compatible container into one with equivalent keys.
1074	template<typename _Compatible_Hashtable>
1075	void
1076	_M_merge_multi(_Compatible_Hashtable& __src) noexcept
1077	{
1078	static_assert(is_same_v<typename _Compatible_Hashtable::node_type,
1079	node_type>, "Node types are compatible");
1080	__glibcxx_assert(get_allocator() == __src.get_allocator());
1081
1082	this->reserve(size() + __src.size());
1083	for (auto __i = __src.begin(), __end = __src.end(); __i != __end;)
1084	_M_reinsert_node_multi(cend(), __src.extract(__i++));
1085	}
1086	#endif // C++17
1087
1088	private:
1089	// Helper rehash method used when keys are unique.
1090	void _M_rehash_aux(size_type __bkt_count, true_type __uks);
1091
1092	// Helper rehash method used when keys can be non-unique.
1093	void _M_rehash_aux(size_type __bkt_count, false_type __uks);
1094
1095	// Unconditionally change size of bucket array to n, restore
1096	// hash policy state to __state on exception.
1097	void _M_rehash(size_type __bkt_count, const __rehash_state& __state);
1098	};
1099
1100
1101	// Definitions of class template _Hashtable's out-of-line member functions.
1102	template<typename _Key, typename _Value, typename _Alloc,
1103	typename _ExtractKey, typename _Equal,
1104	typename _Hash, typename _RangeHash, typename _Unused,
1105	typename _RehashPolicy, typename _Traits>
1106	auto
1107	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1108	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1109	_M_bucket_begin(size_type __bkt) const
1110	-> __node_ptr
1111	{
1112	__node_base_ptr __n = _M_buckets[__bkt];
1113	return __n ? static_cast<__node_ptr>(__n->_M_nxt) : nullptr;
1114	}
1115
1116	template<typename _Key, typename _Value, typename _Alloc,
1117	typename _ExtractKey, typename _Equal,
1118	typename _Hash, typename _RangeHash, typename _Unused,
1119	typename _RehashPolicy, typename _Traits>
1120	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1121	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1122	_Hashtable(size_type __bkt_count_hint,
1123	const _Hash& __h, const _Equal& __eq, const allocator_type& __a)
1124	: _Hashtable(__h, __eq, __a)
1125	{
1126	auto __bkt_count = _M_rehash_policy._M_next_bkt(__bkt_count_hint);
1127	if (__bkt_count > _M_bucket_count)
1128	{
1129	_M_buckets = _M_allocate_buckets(__bkt_count);
1130	_M_bucket_count = __bkt_count;
1131	}
1132	}
1133
1134	template<typename _Key, typename _Value, typename _Alloc,
1135	typename _ExtractKey, typename _Equal,
1136	typename _Hash, typename _RangeHash, typename _Unused,
1137	typename _RehashPolicy, typename _Traits>
1138	template<typename _InputIterator>
1139	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1140	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1141	_Hashtable(_InputIterator __f, _InputIterator __l,
1142	size_type __bkt_count_hint,
1143	const _Hash& __h, const _Equal& __eq,
1144	const allocator_type& __a, true_type /* __uks */)
1145	: _Hashtable(__bkt_count_hint, __h, __eq, __a)
1146	{
1147	for (; __f != __l; ++__f)
1148	this->insert(*__f);
1149	}
1150
1151	template<typename _Key, typename _Value, typename _Alloc,
1152	typename _ExtractKey, typename _Equal,
1153	typename _Hash, typename _RangeHash, typename _Unused,
1154	typename _RehashPolicy, typename _Traits>
1155	template<typename _InputIterator>
1156	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1157	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1158	_Hashtable(_InputIterator __f, _InputIterator __l,
1159	size_type __bkt_count_hint,
1160	const _Hash& __h, const _Equal& __eq,
1161	const allocator_type& __a, false_type /* __uks */)
1162	: _Hashtable(__h, __eq, __a)
1163	{
1164	auto __nb_elems = __detail::__distance_fw(__f, __l);
1165	auto __bkt_count =
1166	_M_rehash_policy._M_next_bkt(
1167	std::max(_M_rehash_policy._M_bkt_for_elements(__nb_elems),
1168	__bkt_count_hint));
1169
1170	if (__bkt_count > _M_bucket_count)
1171	{
1172	_M_buckets = _M_allocate_buckets(__bkt_count);
1173	_M_bucket_count = __bkt_count;
1174	}
1175
1176	for (; __f != __l; ++__f)
1177	this->insert(*__f);
1178	}
1179
1180	template<typename _Key, typename _Value, typename _Alloc,
1181	typename _ExtractKey, typename _Equal,
1182	typename _Hash, typename _RangeHash, typename _Unused,
1183	typename _RehashPolicy, typename _Traits>
1184	auto
1185	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1186	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1187	operator=(const _Hashtable& __ht)
1188	-> _Hashtable&
1189	{
1190	if (&__ht == this)
1191	return *this;
1192
1193	if (__node_alloc_traits::_S_propagate_on_copy_assign())
1194	{
1195	auto& __this_alloc = this->_M_node_allocator();
1196	auto& __that_alloc = __ht._M_node_allocator();
1197	if (!__node_alloc_traits::_S_always_equal()
1198	&& __this_alloc != __that_alloc)
1199	{
1200	// Replacement allocator cannot free existing storage.
1201	this->_M_deallocate_nodes(_M_begin());
1202	_M_before_begin._M_nxt = nullptr;
1203	_M_deallocate_buckets();
1204	_M_buckets = nullptr;
1205	std::__alloc_on_copy(__this_alloc, __that_alloc);
1206	__hashtable_base::operator=(__ht);
1207	_M_bucket_count = __ht._M_bucket_count;
1208	_M_element_count = __ht._M_element_count;
1209	_M_rehash_policy = __ht._M_rehash_policy;
1210	__alloc_node_gen_t __alloc_node_gen(*this);
1211	__try
1212	{
1213	_M_assign(__ht, __alloc_node_gen);
1214	}
1215	__catch(...)
1216	{
1217	// _M_assign took care of deallocating all memory. Now we
1218	// must make sure this instance remains in a usable state.
1219	_M_reset();
1220	__throw_exception_again;
1221	}
1222	return *this;
1223	}
1224	std::__alloc_on_copy(__this_alloc, __that_alloc);
1225	}
1226
1227	// Reuse allocated buckets and nodes.
1228	_M_assign_elements(__ht);
1229	return *this;
1230	}
1231
1232	template<typename _Key, typename _Value, typename _Alloc,
1233	typename _ExtractKey, typename _Equal,
1234	typename _Hash, typename _RangeHash, typename _Unused,
1235	typename _RehashPolicy, typename _Traits>
1236	template<typename _Ht>
1237	void
1238	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1239	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1240	_M_assign_elements(_Ht&& __ht)
1241	{
1242	__buckets_ptr __former_buckets = nullptr;
1243	std::size_t __former_bucket_count = _M_bucket_count;
1244	const __rehash_state& __former_state = _M_rehash_policy._M_state();
1245
1246	if (_M_bucket_count != __ht._M_bucket_count)
1247	{
1248	__former_buckets = _M_buckets;
1249	_M_buckets = _M_allocate_buckets(bkt_count: __ht._M_bucket_count);
1250	_M_bucket_count = __ht._M_bucket_count;
1251	}
1252	else
1253	__builtin_memset(_M_buckets, 0,
1254	_M_bucket_count * sizeof(__node_base_ptr));
1255
1256	__try
1257	{
1258	__hashtable_base::operator=(std::forward<_Ht>(__ht));
1259	_M_element_count = __ht._M_element_count;
1260	_M_rehash_policy = __ht._M_rehash_policy;
1261	__reuse_or_alloc_node_gen_t __roan(_M_begin(), *this);
1262	_M_before_begin._M_nxt = nullptr;
1263	_M_assign(std::forward<_Ht>(__ht), __roan);
1264	if (__former_buckets)
1265	_M_deallocate_buckets(__former_buckets, __former_bucket_count);
1266	}
1267	__catch(...)
1268	{
1269	if (__former_buckets)
1270	{
1271	// Restore previous buckets.
1272	_M_deallocate_buckets();
1273	_M_rehash_policy._M_reset(__former_state);
1274	_M_buckets = __former_buckets;
1275	_M_bucket_count = __former_bucket_count;
1276	}
1277	__builtin_memset(_M_buckets, 0,
1278	_M_bucket_count * sizeof(__node_base_ptr));
1279	__throw_exception_again;
1280	}
1281	}
1282
1283	template<typename _Key, typename _Value, typename _Alloc,
1284	typename _ExtractKey, typename _Equal,
1285	typename _Hash, typename _RangeHash, typename _Unused,
1286	typename _RehashPolicy, typename _Traits>
1287	template<typename _Ht, typename _NodeGenerator>
1288	void
1289	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1290	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1291	_M_assign(_Ht&& __ht, const _NodeGenerator& __node_gen)
1292	{
1293	__buckets_ptr __buckets = nullptr;
1294	if (!_M_buckets)
1295	_M_buckets = __buckets = _M_allocate_buckets(bkt_count: _M_bucket_count);
1296
1297	__try
1298	{
1299	if (!__ht._M_before_begin._M_nxt)
1300	return;
1301
1302	// First deal with the special first node pointed to by
1303	// _M_before_begin.
1304	__node_ptr __ht_n = __ht._M_begin();
1305	__node_ptr __this_n
1306	= __node_gen(__fwd_value_for<_Ht>(__ht_n->_M_v()));
1307	this->_M_copy_code(*__this_n, *__ht_n);
1308	_M_update_bbegin(__this_n);
1309
1310	// Then deal with other nodes.
1311	__node_ptr __prev_n = __this_n;
1312	for (__ht_n = __ht_n->_M_next(); __ht_n; __ht_n = __ht_n->_M_next())
1313	{
1314	__this_n = __node_gen(__fwd_value_for<_Ht>(__ht_n->_M_v()));
1315	__prev_n->_M_nxt = __this_n;
1316	this->_M_copy_code(*__this_n, *__ht_n);
1317	size_type __bkt = _M_bucket_index(*__this_n);
1318	if (!_M_buckets[__bkt])
1319	_M_buckets[__bkt] = __prev_n;
1320	__prev_n = __this_n;
1321	}
1322	}
1323	__catch(...)
1324	{
1325	clear();
1326	if (__buckets)
1327	_M_deallocate_buckets();
1328	__throw_exception_again;
1329	}
1330	}
1331
1332	template<typename _Key, typename _Value, typename _Alloc,
1333	typename _ExtractKey, typename _Equal,
1334	typename _Hash, typename _RangeHash, typename _Unused,
1335	typename _RehashPolicy, typename _Traits>
1336	void
1337	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1338	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1339	_M_reset() noexcept
1340	{
1341	_M_rehash_policy._M_reset();
1342	_M_bucket_count = 1;
1343	_M_single_bucket = nullptr;
1344	_M_buckets = &_M_single_bucket;
1345	_M_before_begin._M_nxt = nullptr;
1346	_M_element_count = 0;
1347	}
1348
1349	template<typename _Key, typename _Value, typename _Alloc,
1350	typename _ExtractKey, typename _Equal,
1351	typename _Hash, typename _RangeHash, typename _Unused,
1352	typename _RehashPolicy, typename _Traits>
1353	void
1354	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1355	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1356	_M_move_assign(_Hashtable&& __ht, true_type)
1357	{
1358	if (__builtin_expect(std::__addressof(__ht) == this, false))
1359	return;
1360
1361	this->_M_deallocate_nodes(_M_begin());
1362	_M_deallocate_buckets();
1363	__hashtable_base::operator=(std::move(__ht));
1364	_M_rehash_policy = __ht._M_rehash_policy;
1365	if (!__ht._M_uses_single_bucket())
1366	_M_buckets = __ht._M_buckets;
1367	else
1368	{
1369	_M_buckets = &_M_single_bucket;
1370	_M_single_bucket = __ht._M_single_bucket;
1371	}
1372
1373	_M_bucket_count = __ht._M_bucket_count;
1374	_M_before_begin._M_nxt = __ht._M_before_begin._M_nxt;
1375	_M_element_count = __ht._M_element_count;
1376	std::__alloc_on_move(this->_M_node_allocator(), __ht._M_node_allocator());
1377
1378	// Fix bucket containing the _M_before_begin pointer that can't be moved.
1379	_M_update_bbegin();
1380	__ht._M_reset();
1381	}
1382
1383	template<typename _Key, typename _Value, typename _Alloc,
1384	typename _ExtractKey, typename _Equal,
1385	typename _Hash, typename _RangeHash, typename _Unused,
1386	typename _RehashPolicy, typename _Traits>
1387	void
1388	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1389	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1390	_M_move_assign(_Hashtable&& __ht, false_type)
1391	{
1392	if (__ht._M_node_allocator() == this->_M_node_allocator())
1393	_M_move_assign(std::move(__ht), true_type{});
1394	else
1395	{
1396	// Can't move memory, move elements then.
1397	_M_assign_elements(std::move(__ht));
1398	__ht.clear();
1399	}
1400	}
1401
1402	template<typename _Key, typename _Value, typename _Alloc,
1403	typename _ExtractKey, typename _Equal,
1404	typename _Hash, typename _RangeHash, typename _Unused,
1405	typename _RehashPolicy, typename _Traits>
1406	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1407	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1408	_Hashtable(const _Hashtable& __ht)
1409	: __hashtable_base(__ht),
1410	__map_base(__ht),
1411	__rehash_base(__ht),
1412	__hashtable_alloc(
1413	__node_alloc_traits::_S_select_on_copy(__ht._M_node_allocator())),
1414	__enable_default_ctor(__ht),
1415	_M_buckets(nullptr),
1416	_M_bucket_count(__ht._M_bucket_count),
1417	_M_element_count(__ht._M_element_count),
1418	_M_rehash_policy(__ht._M_rehash_policy)
1419	{
1420	__alloc_node_gen_t __alloc_node_gen(*this);
1421	_M_assign(__ht, __alloc_node_gen);
1422	}
1423
1424	template<typename _Key, typename _Value, typename _Alloc,
1425	typename _ExtractKey, typename _Equal,
1426	typename _Hash, typename _RangeHash, typename _Unused,
1427	typename _RehashPolicy, typename _Traits>
1428	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1429	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1430	_Hashtable(_Hashtable&& __ht, __node_alloc_type&& __a,
1431	true_type /* alloc always equal */)
1432	noexcept(_S_nothrow_move())
1433	: __hashtable_base(__ht),
1434	__map_base(__ht),
1435	__rehash_base(__ht),
1436	__hashtable_alloc(std::move(__a)),
1437	__enable_default_ctor(__ht),
1438	_M_buckets(__ht._M_buckets),
1439	_M_bucket_count(__ht._M_bucket_count),
1440	_M_before_begin(__ht._M_before_begin._M_nxt),
1441	_M_element_count(__ht._M_element_count),
1442	_M_rehash_policy(__ht._M_rehash_policy)
1443	{
1444	// Update buckets if __ht is using its single bucket.
1445	if (__ht._M_uses_single_bucket())
1446	{
1447	_M_buckets = &_M_single_bucket;
1448	_M_single_bucket = __ht._M_single_bucket;
1449	}
1450
1451	// Fix bucket containing the _M_before_begin pointer that can't be moved.
1452	_M_update_bbegin();
1453
1454	__ht._M_reset();
1455	}
1456
1457	template<typename _Key, typename _Value, typename _Alloc,
1458	typename _ExtractKey, typename _Equal,
1459	typename _Hash, typename _RangeHash, typename _Unused,
1460	typename _RehashPolicy, typename _Traits>
1461	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1462	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1463	_Hashtable(const _Hashtable& __ht, const allocator_type& __a)
1464	: __hashtable_base(__ht),
1465	__map_base(__ht),
1466	__rehash_base(__ht),
1467	__hashtable_alloc(__node_alloc_type(__a)),
1468	__enable_default_ctor(__ht),
1469	_M_buckets(),
1470	_M_bucket_count(__ht._M_bucket_count),
1471	_M_element_count(__ht._M_element_count),
1472	_M_rehash_policy(__ht._M_rehash_policy)
1473	{
1474	__alloc_node_gen_t __alloc_node_gen(*this);
1475	_M_assign(__ht, __alloc_node_gen);
1476	}
1477
1478	template<typename _Key, typename _Value, typename _Alloc,
1479	typename _ExtractKey, typename _Equal,
1480	typename _Hash, typename _RangeHash, typename _Unused,
1481	typename _RehashPolicy, typename _Traits>
1482	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1483	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1484	_Hashtable(_Hashtable&& __ht, __node_alloc_type&& __a,
1485	false_type /* alloc always equal */)
1486	: __hashtable_base(__ht),
1487	__map_base(__ht),
1488	__rehash_base(__ht),
1489	__hashtable_alloc(std::move(__a)),
1490	__enable_default_ctor(__ht),
1491	_M_buckets(nullptr),
1492	_M_bucket_count(__ht._M_bucket_count),
1493	_M_element_count(__ht._M_element_count),
1494	_M_rehash_policy(__ht._M_rehash_policy)
1495	{
1496	if (__ht._M_node_allocator() == this->_M_node_allocator())
1497	{
1498	if (__ht._M_uses_single_bucket())
1499	{
1500	_M_buckets = &_M_single_bucket;
1501	_M_single_bucket = __ht._M_single_bucket;
1502	}
1503	else
1504	_M_buckets = __ht._M_buckets;
1505
1506	// Fix bucket containing the _M_before_begin pointer that can't be
1507	// moved.
1508	_M_update_bbegin(__ht._M_begin());
1509
1510	__ht._M_reset();
1511	}
1512	else
1513	{
1514	__alloc_node_gen_t __alloc_gen(*this);
1515
1516	using _Fwd_Ht = typename
1517	conditional<__move_if_noexcept_cond<value_type>::value,
1518	const _Hashtable&, _Hashtable&&>::type;
1519	_M_assign(std::forward<_Fwd_Ht>(__ht), __alloc_gen);
1520	__ht.clear();
1521	}
1522	}
1523
1524	template<typename _Key, typename _Value, typename _Alloc,
1525	typename _ExtractKey, typename _Equal,
1526	typename _Hash, typename _RangeHash, typename _Unused,
1527	typename _RehashPolicy, typename _Traits>
1528	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1529	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1530	~_Hashtable() noexcept
1531	{
1532	clear();
1533	_M_deallocate_buckets();
1534	}
1535
1536	template<typename _Key, typename _Value, typename _Alloc,
1537	typename _ExtractKey, typename _Equal,
1538	typename _Hash, typename _RangeHash, typename _Unused,
1539	typename _RehashPolicy, typename _Traits>
1540	void
1541	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1542	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1543	swap(_Hashtable& __x)
1544	noexcept(__and_<__is_nothrow_swappable<_Hash>,
1545	__is_nothrow_swappable<_Equal>>::value)
1546	{
1547	// The only base class with member variables is hash_code_base.
1548	// We define _Hash_code_base::_M_swap because different
1549	// specializations have different members.
1550	this->_M_swap(__x);
1551
1552	std::__alloc_on_swap(this->_M_node_allocator(), __x._M_node_allocator());
1553	std::swap(_M_rehash_policy, __x._M_rehash_policy);
1554
1555	// Deal properly with potentially moved instances.
1556	if (this->_M_uses_single_bucket())
1557	{
1558	if (!__x._M_uses_single_bucket())
1559	{
1560	_M_buckets = __x._M_buckets;
1561	__x._M_buckets = &__x._M_single_bucket;
1562	}
1563	}
1564	else if (__x._M_uses_single_bucket())
1565	{
1566	__x._M_buckets = _M_buckets;
1567	_M_buckets = &_M_single_bucket;
1568	}
1569	else
1570	std::swap(_M_buckets, __x._M_buckets);
1571
1572	std::swap(_M_bucket_count, __x._M_bucket_count);
1573	std::swap(_M_before_begin._M_nxt, __x._M_before_begin._M_nxt);
1574	std::swap(_M_element_count, __x._M_element_count);
1575	std::swap(_M_single_bucket, __x._M_single_bucket);
1576
1577	// Fix buckets containing the _M_before_begin pointers that can't be
1578	// swapped.
1579	_M_update_bbegin();
1580	__x._M_update_bbegin();
1581	}
1582
1583	template<typename _Key, typename _Value, typename _Alloc,
1584	typename _ExtractKey, typename _Equal,
1585	typename _Hash, typename _RangeHash, typename _Unused,
1586	typename _RehashPolicy, typename _Traits>
1587	auto
1588	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1589	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1590	find(const key_type& __k)
1591	-> iterator
1592	{
1593	__hash_code __code = this->_M_hash_code(__k);
1594	std::size_t __bkt = _M_bucket_index(__code);
1595	return iterator(_M_find_node(__bkt, key: __k, c: __code));
1596	}
1597
1598	template<typename _Key, typename _Value, typename _Alloc,
1599	typename _ExtractKey, typename _Equal,
1600	typename _Hash, typename _RangeHash, typename _Unused,
1601	typename _RehashPolicy, typename _Traits>
1602	auto
1603	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1604	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1605	find(const key_type& __k) const
1606	-> const_iterator
1607	{
1608	__hash_code __code = this->_M_hash_code(__k);
1609	std::size_t __bkt = _M_bucket_index(__code);
1610	return const_iterator(_M_find_node(__bkt, key: __k, c: __code));
1611	}
1612
1613	#if __cplusplus > 201703L
1614	template<typename _Key, typename _Value, typename _Alloc,
1615	typename _ExtractKey, typename _Equal,
1616	typename _Hash, typename _RangeHash, typename _Unused,
1617	typename _RehashPolicy, typename _Traits>
1618	template<typename _Kt, typename, typename>
1619	auto
1620	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1621	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1622	_M_find_tr(const _Kt& __k)
1623	-> iterator
1624	{
1625	__hash_code __code = this->_M_hash_code_tr(__k);
1626	std::size_t __bkt = _M_bucket_index(__code);
1627	return iterator(_M_find_node_tr(__bkt, __k, __code));
1628	}
1629
1630	template<typename _Key, typename _Value, typename _Alloc,
1631	typename _ExtractKey, typename _Equal,
1632	typename _Hash, typename _RangeHash, typename _Unused,
1633	typename _RehashPolicy, typename _Traits>
1634	template<typename _Kt, typename, typename>
1635	auto
1636	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1637	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1638	_M_find_tr(const _Kt& __k) const
1639	-> const_iterator
1640	{
1641	__hash_code __code = this->_M_hash_code_tr(__k);
1642	std::size_t __bkt = _M_bucket_index(__code);
1643	return const_iterator(_M_find_node_tr(__bkt, __k, __code));
1644	}
1645	#endif
1646
1647	template<typename _Key, typename _Value, typename _Alloc,
1648	typename _ExtractKey, typename _Equal,
1649	typename _Hash, typename _RangeHash, typename _Unused,
1650	typename _RehashPolicy, typename _Traits>
1651	auto
1652	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1653	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1654	count(const key_type& __k) const
1655	-> size_type
1656	{
1657	auto __it = find(__k);
1658	if (!__it._M_cur)
1659	return 0;
1660
1661	if (__unique_keys::value)
1662	return 1;
1663
1664	// All equivalent values are next to each other, if we find a
1665	// non-equivalent value after an equivalent one it means that we won't
1666	// find any new equivalent value.
1667	size_type __result = 1;
1668	for (auto __ref = __it++;
1669	__it._M_cur && this->_M_node_equals(*__ref._M_cur, *__it._M_cur);
1670	++__it)
1671	++__result;
1672
1673	return __result;
1674	}
1675
1676	#if __cplusplus > 201703L
1677	template<typename _Key, typename _Value, typename _Alloc,
1678	typename _ExtractKey, typename _Equal,
1679	typename _Hash, typename _RangeHash, typename _Unused,
1680	typename _RehashPolicy, typename _Traits>
1681	template<typename _Kt, typename, typename>
1682	auto
1683	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1684	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1685	_M_count_tr(const _Kt& __k) const
1686	-> size_type
1687	{
1688	__hash_code __code = this->_M_hash_code_tr(__k);
1689	std::size_t __bkt = _M_bucket_index(__code);
1690	auto __n = _M_find_node_tr(__bkt, __k, __code);
1691	if (!__n)
1692	return 0;
1693
1694	// All equivalent values are next to each other, if we find a
1695	// non-equivalent value after an equivalent one it means that we won't
1696	// find any new equivalent value.
1697	iterator __it(__n);
1698	size_type __result = 1;
1699	for (++__it;
1700	__it._M_cur && this->_M_equals_tr(__k, __code, *__it._M_cur);
1701	++__it)
1702	++__result;
1703
1704	return __result;
1705	}
1706	#endif
1707
1708	template<typename _Key, typename _Value, typename _Alloc,
1709	typename _ExtractKey, typename _Equal,
1710	typename _Hash, typename _RangeHash, typename _Unused,
1711	typename _RehashPolicy, typename _Traits>
1712	auto
1713	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1714	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1715	equal_range(const key_type& __k)
1716	-> pair<iterator, iterator>
1717	{
1718	auto __ite = find(__k);
1719	if (!__ite._M_cur)
1720	return { __ite, __ite };
1721
1722	auto __beg = __ite++;
1723	if (__unique_keys::value)
1724	return { __beg, __ite };
1725
1726	// All equivalent values are next to each other, if we find a
1727	// non-equivalent value after an equivalent one it means that we won't
1728	// find any new equivalent value.
1729	while (__ite._M_cur && this->_M_node_equals(*__beg._M_cur, *__ite._M_cur))
1730	++__ite;
1731
1732	return { __beg, __ite };
1733	}
1734
1735	template<typename _Key, typename _Value, typename _Alloc,
1736	typename _ExtractKey, typename _Equal,
1737	typename _Hash, typename _RangeHash, typename _Unused,
1738	typename _RehashPolicy, typename _Traits>
1739	auto
1740	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1741	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1742	equal_range(const key_type& __k) const
1743	-> pair<const_iterator, const_iterator>
1744	{
1745	auto __ite = find(__k);
1746	if (!__ite._M_cur)
1747	return { __ite, __ite };
1748
1749	auto __beg = __ite++;
1750	if (__unique_keys::value)
1751	return { __beg, __ite };
1752
1753	// All equivalent values are next to each other, if we find a
1754	// non-equivalent value after an equivalent one it means that we won't
1755	// find any new equivalent value.
1756	while (__ite._M_cur && this->_M_node_equals(*__beg._M_cur, *__ite._M_cur))
1757	++__ite;
1758
1759	return { __beg, __ite };
1760	}
1761
1762	#if __cplusplus > 201703L
1763	template<typename _Key, typename _Value, typename _Alloc,
1764	typename _ExtractKey, typename _Equal,
1765	typename _Hash, typename _RangeHash, typename _Unused,
1766	typename _RehashPolicy, typename _Traits>
1767	template<typename _Kt, typename, typename>
1768	auto
1769	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1770	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1771	_M_equal_range_tr(const _Kt& __k)
1772	-> pair<iterator, iterator>
1773	{
1774	__hash_code __code = this->_M_hash_code_tr(__k);
1775	std::size_t __bkt = _M_bucket_index(__code);
1776	auto __n = _M_find_node_tr(__bkt, __k, __code);
1777	iterator __ite(__n);
1778	if (!__n)
1779	return { __ite, __ite };
1780
1781	// All equivalent values are next to each other, if we find a
1782	// non-equivalent value after an equivalent one it means that we won't
1783	// find any new equivalent value.
1784	auto __beg = __ite++;
1785	while (__ite._M_cur && this->_M_equals_tr(__k, __code, *__ite._M_cur))
1786	++__ite;
1787
1788	return { __beg, __ite };
1789	}
1790
1791	template<typename _Key, typename _Value, typename _Alloc,
1792	typename _ExtractKey, typename _Equal,
1793	typename _Hash, typename _RangeHash, typename _Unused,
1794	typename _RehashPolicy, typename _Traits>
1795	template<typename _Kt, typename, typename>
1796	auto
1797	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1798	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1799	_M_equal_range_tr(const _Kt& __k) const
1800	-> pair<const_iterator, const_iterator>
1801	{
1802	__hash_code __code = this->_M_hash_code_tr(__k);
1803	std::size_t __bkt = _M_bucket_index(__code);
1804	auto __n = _M_find_node_tr(__bkt, __k, __code);
1805	const_iterator __ite(__n);
1806	if (!__n)
1807	return { __ite, __ite };
1808
1809	// All equivalent values are next to each other, if we find a
1810	// non-equivalent value after an equivalent one it means that we won't
1811	// find any new equivalent value.
1812	auto __beg = __ite++;
1813	while (__ite._M_cur && this->_M_equals_tr(__k, __code, *__ite._M_cur))
1814	++__ite;
1815
1816	return { __beg, __ite };
1817	}
1818	#endif
1819
1820	// Find the node before the one whose key compares equal to k in the bucket
1821	// bkt. Return nullptr if no node is found.
1822	template<typename _Key, typename _Value, typename _Alloc,
1823	typename _ExtractKey, typename _Equal,
1824	typename _Hash, typename _RangeHash, typename _Unused,
1825	typename _RehashPolicy, typename _Traits>
1826	auto
1827	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1828	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1829	_M_find_before_node(size_type __bkt, const key_type& __k,
1830	__hash_code __code) const
1831	-> __node_base_ptr
1832	{
1833	__node_base_ptr __prev_p = _M_buckets[__bkt];
1834	if (!__prev_p)
1835	return nullptr;
1836
1837	for (__node_ptr __p = static_cast<__node_ptr>(__prev_p->_M_nxt);;
1838	__p = __p->_M_next())
1839	{
1840	if (this->_M_equals(__k, __code, *__p))
1841	return __prev_p;
1842
1843	if (!__p->_M_nxt || _M_bucket_index(*__p->_M_next()) != __bkt)
1844	break;
1845	__prev_p = __p;
1846	}
1847
1848	return nullptr;
1849	}
1850
1851	template<typename _Key, typename _Value, typename _Alloc,
1852	typename _ExtractKey, typename _Equal,
1853	typename _Hash, typename _RangeHash, typename _Unused,
1854	typename _RehashPolicy, typename _Traits>
1855	template<typename _Kt>
1856	auto
1857	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1858	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1859	_M_find_before_node_tr(size_type __bkt, const _Kt& __k,
1860	__hash_code __code) const
1861	-> __node_base_ptr
1862	{
1863	__node_base_ptr __prev_p = _M_buckets[__bkt];
1864	if (!__prev_p)
1865	return nullptr;
1866
1867	for (__node_ptr __p = static_cast<__node_ptr>(__prev_p->_M_nxt);;
1868	__p = __p->_M_next())
1869	{
1870	if (this->_M_equals_tr(__k, __code, *__p))
1871	return __prev_p;
1872
1873	if (!__p->_M_nxt || _M_bucket_index(*__p->_M_next()) != __bkt)
1874	break;
1875	__prev_p = __p;
1876	}
1877
1878	return nullptr;
1879	}
1880
1881	template<typename _Key, typename _Value, typename _Alloc,
1882	typename _ExtractKey, typename _Equal,
1883	typename _Hash, typename _RangeHash, typename _Unused,
1884	typename _RehashPolicy, typename _Traits>
1885	void
1886	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1887	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1888	_M_insert_bucket_begin(size_type __bkt, __node_ptr __node)
1889	{
1890	if (_M_buckets[__bkt])
1891	{
1892	// Bucket is not empty, we just need to insert the new node
1893	// after the bucket before begin.
1894	__node->_M_nxt = _M_buckets[__bkt]->_M_nxt;
1895	_M_buckets[__bkt]->_M_nxt = __node;
1896	}
1897	else
1898	{
1899	// The bucket is empty, the new node is inserted at the
1900	// beginning of the singly-linked list and the bucket will
1901	// contain _M_before_begin pointer.
1902	__node->_M_nxt = _M_before_begin._M_nxt;
1903	_M_before_begin._M_nxt = __node;
1904
1905	if (__node->_M_nxt)
1906	// We must update former begin bucket that is pointing to
1907	// _M_before_begin.
1908	_M_buckets[_M_bucket_index(*__node->_M_next())] = __node;
1909
1910	_M_buckets[__bkt] = &_M_before_begin;
1911	}
1912	}
1913
1914	template<typename _Key, typename _Value, typename _Alloc,
1915	typename _ExtractKey, typename _Equal,
1916	typename _Hash, typename _RangeHash, typename _Unused,
1917	typename _RehashPolicy, typename _Traits>
1918	void
1919	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1920	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1921	_M_remove_bucket_begin(size_type __bkt, __node_ptr __next,
1922	size_type __next_bkt)
1923	{
1924	if (!__next || __next_bkt != __bkt)
1925	{
1926	// Bucket is now empty
1927	// First update next bucket if any
1928	if (__next)
1929	_M_buckets[__next_bkt] = _M_buckets[__bkt];
1930
1931	// Second update before begin node if necessary
1932	if (&_M_before_begin == _M_buckets[__bkt])
1933	_M_before_begin._M_nxt = __next;
1934	_M_buckets[__bkt] = nullptr;
1935	}
1936	}
1937
1938	template<typename _Key, typename _Value, typename _Alloc,
1939	typename _ExtractKey, typename _Equal,
1940	typename _Hash, typename _RangeHash, typename _Unused,
1941	typename _RehashPolicy, typename _Traits>
1942	auto
1943	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1944	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1945	_M_get_previous_node(size_type __bkt, __node_ptr __n)
1946	-> __node_base_ptr
1947	{
1948	__node_base_ptr __prev_n = _M_buckets[__bkt];
1949	while (__prev_n->_M_nxt != __n)
1950	__prev_n = __prev_n->_M_nxt;
1951	return __prev_n;
1952	}
1953
1954	template<typename _Key, typename _Value, typename _Alloc,
1955	typename _ExtractKey, typename _Equal,
1956	typename _Hash, typename _RangeHash, typename _Unused,
1957	typename _RehashPolicy, typename _Traits>
1958	template<typename... _Args>
1959	auto
1960	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1961	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1962	_M_emplace(true_type /* __uks */, _Args&&... __args)
1963	-> pair<iterator, bool>
1964	{
1965	// First build the node to get access to the hash code
1966	_Scoped_node __node { this, std::forward<_Args>(__args)... };
1967	const key_type& __k = _ExtractKey{}(__node._M_node->_M_v());
1968	__hash_code __code = this->_M_hash_code(__k);
1969	size_type __bkt = _M_bucket_index(__code);
1970	if (__node_ptr __p = _M_find_node(__bkt, key: __k, c: __code))
1971	// There is already an equivalent node, no insertion
1972	return std::make_pair(iterator(__p), false);
1973
1974	// Insert the node
1975	auto __pos = _M_insert_unique_node(__bkt, __code, n: __node._M_node);
1976	__node._M_node = nullptr;
1977	return { __pos, true };
1978	}
1979
1980	template<typename _Key, typename _Value, typename _Alloc,
1981	typename _ExtractKey, typename _Equal,
1982	typename _Hash, typename _RangeHash, typename _Unused,
1983	typename _RehashPolicy, typename _Traits>
1984	template<typename... _Args>
1985	auto
1986	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1987	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
1988	_M_emplace(const_iterator __hint, false_type /* __uks */,
1989	_Args&&... __args)
1990	-> iterator
1991	{
1992	// First build the node to get its hash code.
1993	_Scoped_node __node { this, std::forward<_Args>(__args)... };
1994	const key_type& __k = _ExtractKey{}(__node._M_node->_M_v());
1995
1996	__hash_code __code = this->_M_hash_code(__k);
1997	auto __pos
1998	= _M_insert_multi_node(hint: __hint._M_cur, __code, n: __node._M_node);
1999	__node._M_node = nullptr;
2000	return __pos;
2001	}
2002
2003	template<typename _Key, typename _Value, typename _Alloc,
2004	typename _ExtractKey, typename _Equal,
2005	typename _Hash, typename _RangeHash, typename _Unused,
2006	typename _RehashPolicy, typename _Traits>
2007	auto
2008	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2009	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2010	_M_insert_unique_node(size_type __bkt, __hash_code __code,
2011	__node_ptr __node, size_type __n_elt)
2012	-> iterator
2013	{
2014	const __rehash_state& __saved_state = _M_rehash_policy._M_state();
2015	std::pair<bool, std::size_t> __do_rehash
2016	= _M_rehash_policy._M_need_rehash(_M_bucket_count, _M_element_count,
2017	__n_elt);
2018
2019	if (__do_rehash.first)
2020	{
2021	_M_rehash(bkt_count: __do_rehash.second, state: __saved_state);
2022	__bkt = _M_bucket_index(__code);
2023	}
2024
2025	this->_M_store_code(*__node, __code);
2026
2027	// Always insert at the beginning of the bucket.
2028	_M_insert_bucket_begin(__bkt, __node);
2029	++_M_element_count;
2030	return iterator(__node);
2031	}
2032
2033	template<typename _Key, typename _Value, typename _Alloc,
2034	typename _ExtractKey, typename _Equal,
2035	typename _Hash, typename _RangeHash, typename _Unused,
2036	typename _RehashPolicy, typename _Traits>
2037	auto
2038	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2039	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2040	_M_insert_multi_node(__node_ptr __hint,
2041	__hash_code __code, __node_ptr __node)
2042	-> iterator
2043	{
2044	const __rehash_state& __saved_state = _M_rehash_policy._M_state();
2045	std::pair<bool, std::size_t> __do_rehash
2046	= _M_rehash_policy._M_need_rehash(_M_bucket_count, _M_element_count, 1);
2047
2048	if (__do_rehash.first)
2049	_M_rehash(bkt_count: __do_rehash.second, state: __saved_state);
2050
2051	this->_M_store_code(*__node, __code);
2052	const key_type& __k = _ExtractKey{}(__node->_M_v());
2053	size_type __bkt = _M_bucket_index(__code);
2054
2055	// Find the node before an equivalent one or use hint if it exists and
2056	// if it is equivalent.
2057	__node_base_ptr __prev
2058	= __builtin_expect(__hint != nullptr, false)
2059	&& this->_M_equals(__k, __code, *__hint)
2060	? __hint
2061	: _M_find_before_node(__bkt, __k, __code);
2062
2063	if (__prev)
2064	{
2065	// Insert after the node before the equivalent one.
2066	__node->_M_nxt = __prev->_M_nxt;
2067	__prev->_M_nxt = __node;
2068	if (__builtin_expect(__prev == __hint, false))
2069	// hint might be the last bucket node, in this case we need to
2070	// update next bucket.
2071	if (__node->_M_nxt
2072	&& !this->_M_equals(__k, __code, *__node->_M_next()))
2073	{
2074	size_type __next_bkt = _M_bucket_index(*__node->_M_next());
2075	if (__next_bkt != __bkt)
2076	_M_buckets[__next_bkt] = __node;
2077	}
2078	}
2079	else
2080	// The inserted node has no equivalent in the hashtable. We must
2081	// insert the new node at the beginning of the bucket to preserve
2082	// equivalent elements' relative positions.
2083	_M_insert_bucket_begin(__bkt, __node);
2084	++_M_element_count;
2085	return iterator(__node);
2086	}
2087
2088	// Insert v if no element with its key is already present.
2089	template<typename _Key, typename _Value, typename _Alloc,
2090	typename _ExtractKey, typename _Equal,
2091	typename _Hash, typename _RangeHash, typename _Unused,
2092	typename _RehashPolicy, typename _Traits>
2093	template<typename _Arg, typename _NodeGenerator>
2094	auto
2095	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2096	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2097	_M_insert(_Arg&& __v, const _NodeGenerator& __node_gen,
2098	true_type /* __uks */)
2099	-> pair<iterator, bool>
2100	{
2101	const key_type& __k = _ExtractKey{}(__v);
2102	__hash_code __code = this->_M_hash_code(__k);
2103	size_type __bkt = _M_bucket_index(__code);
2104
2105	if (__node_ptr __node = _M_find_node(__bkt, key: __k, c: __code))
2106	return { iterator(__node), false };
2107
2108	_Scoped_node __node{ __node_gen(std::forward<_Arg>(__v)), this };
2109	auto __pos
2110	= _M_insert_unique_node(__bkt, __code, node: __node._M_node);
2111	__node._M_node = nullptr;
2112	return { __pos, true };
2113	}
2114
2115	// Insert v unconditionally.
2116	template<typename _Key, typename _Value, typename _Alloc,
2117	typename _ExtractKey, typename _Equal,
2118	typename _Hash, typename _RangeHash, typename _Unused,
2119	typename _RehashPolicy, typename _Traits>
2120	template<typename _Arg, typename _NodeGenerator>
2121	auto
2122	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2123	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2124	_M_insert(const_iterator __hint, _Arg&& __v,
2125	const _NodeGenerator& __node_gen,
2126	false_type /* __uks */)
2127	-> iterator
2128	{
2129	// First compute the hash code so that we don't do anything if it
2130	// throws.
2131	__hash_code __code = this->_M_hash_code(_ExtractKey{}(__v));
2132
2133	// Second allocate new node so that we don't rehash if it throws.
2134	_Scoped_node __node{ __node_gen(std::forward<_Arg>(__v)), this };
2135	auto __pos
2136	= _M_insert_multi_node(hint: __hint._M_cur, __code, node: __node._M_node);
2137	__node._M_node = nullptr;
2138	return __pos;
2139	}
2140
2141	template<typename _Key, typename _Value, typename _Alloc,
2142	typename _ExtractKey, typename _Equal,
2143	typename _Hash, typename _RangeHash, typename _Unused,
2144	typename _RehashPolicy, typename _Traits>
2145	auto
2146	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2147	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2148	erase(const_iterator __it)
2149	-> iterator
2150	{
2151	__node_ptr __n = __it._M_cur;
2152	std::size_t __bkt = _M_bucket_index(*__n);
2153
2154	// Look for previous node to unlink it from the erased one, this
2155	// is why we need buckets to contain the before begin to make
2156	// this search fast.
2157	__node_base_ptr __prev_n = _M_get_previous_node(__bkt, __n);
2158	return _M_erase(__bkt, __prev_n, __n);
2159	}
2160
2161	template<typename _Key, typename _Value, typename _Alloc,
2162	typename _ExtractKey, typename _Equal,
2163	typename _Hash, typename _RangeHash, typename _Unused,
2164	typename _RehashPolicy, typename _Traits>
2165	auto
2166	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2167	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2168	_M_erase(size_type __bkt, __node_base_ptr __prev_n, __node_ptr __n)
2169	-> iterator
2170	{
2171	if (__prev_n == _M_buckets[__bkt])
2172	_M_remove_bucket_begin(__bkt, next: __n->_M_next(),
2173	next_bkt: __n->_M_nxt ? _M_bucket_index(*__n->_M_next()) : 0);
2174	else if (__n->_M_nxt)
2175	{
2176	size_type __next_bkt = _M_bucket_index(*__n->_M_next());
2177	if (__next_bkt != __bkt)
2178	_M_buckets[__next_bkt] = __prev_n;
2179	}
2180
2181	__prev_n->_M_nxt = __n->_M_nxt;
2182	iterator __result(__n->_M_next());
2183	this->_M_deallocate_node(__n);
2184	--_M_element_count;
2185
2186	return __result;
2187	}
2188
2189	template<typename _Key, typename _Value, typename _Alloc,
2190	typename _ExtractKey, typename _Equal,
2191	typename _Hash, typename _RangeHash, typename _Unused,
2192	typename _RehashPolicy, typename _Traits>
2193	auto
2194	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2195	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2196	_M_erase(true_type /* __uks */, const key_type& __k)
2197	-> size_type
2198	{
2199	__hash_code __code = this->_M_hash_code(__k);
2200	std::size_t __bkt = _M_bucket_index(__code);
2201
2202	// Look for the node before the first matching node.
2203	__node_base_ptr __prev_n = _M_find_before_node(__bkt, __k, __code);
2204	if (!__prev_n)
2205	return 0;
2206
2207	// We found a matching node, erase it.
2208	__node_ptr __n = static_cast<__node_ptr>(__prev_n->_M_nxt);
2209	_M_erase(__bkt, __prev_n, __n);
2210	return 1;
2211	}
2212
2213	template<typename _Key, typename _Value, typename _Alloc,
2214	typename _ExtractKey, typename _Equal,
2215	typename _Hash, typename _RangeHash, typename _Unused,
2216	typename _RehashPolicy, typename _Traits>
2217	auto
2218	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2219	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2220	_M_erase(false_type /* __uks */, const key_type& __k)
2221	-> size_type
2222	{
2223	__hash_code __code = this->_M_hash_code(__k);
2224	std::size_t __bkt = _M_bucket_index(__code);
2225
2226	// Look for the node before the first matching node.
2227	__node_base_ptr __prev_n = _M_find_before_node(__bkt, __k, __code);
2228	if (!__prev_n)
2229	return 0;
2230
2231	// _GLIBCXX_RESOLVE_LIB_DEFECTS
2232	// 526. Is it undefined if a function in the standard changes
2233	// in parameters?
2234	// We use one loop to find all matching nodes and another to deallocate
2235	// them so that the key stays valid during the first loop. It might be
2236	// invalidated indirectly when destroying nodes.
2237	__node_ptr __n = static_cast<__node_ptr>(__prev_n->_M_nxt);
2238	__node_ptr __n_last = __n->_M_next();
2239	while (__n_last && this->_M_node_equals(*__n, *__n_last))
2240	__n_last = __n_last->_M_next();
2241
2242	std::size_t __n_last_bkt = __n_last ? _M_bucket_index(*__n_last) : __bkt;
2243
2244	// Deallocate nodes.
2245	size_type __result = 0;
2246	do
2247	{
2248	__node_ptr __p = __n->_M_next();
2249	this->_M_deallocate_node(__n);
2250	__n = __p;
2251	++__result;
2252	}
2253	while (__n != __n_last);
2254
2255	_M_element_count -= __result;
2256	if (__prev_n == _M_buckets[__bkt])
2257	_M_remove_bucket_begin(__bkt, next: __n_last, next_bkt: __n_last_bkt);
2258	else if (__n_last_bkt != __bkt)
2259	_M_buckets[__n_last_bkt] = __prev_n;
2260	__prev_n->_M_nxt = __n_last;
2261	return __result;
2262	}
2263
2264	template<typename _Key, typename _Value, typename _Alloc,
2265	typename _ExtractKey, typename _Equal,
2266	typename _Hash, typename _RangeHash, typename _Unused,
2267	typename _RehashPolicy, typename _Traits>
2268	auto
2269	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2270	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2271	erase(const_iterator __first, const_iterator __last)
2272	-> iterator
2273	{
2274	__node_ptr __n = __first._M_cur;
2275	__node_ptr __last_n = __last._M_cur;
2276	if (__n == __last_n)
2277	return iterator(__n);
2278
2279	std::size_t __bkt = _M_bucket_index(*__n);
2280
2281	__node_base_ptr __prev_n = _M_get_previous_node(__bkt, __n);
2282	bool __is_bucket_begin = __n == _M_bucket_begin(__bkt);
2283	std::size_t __n_bkt = __bkt;
2284	for (;;)
2285	{
2286	do
2287	{
2288	__node_ptr __tmp = __n;
2289	__n = __n->_M_next();
2290	this->_M_deallocate_node(__tmp);
2291	--_M_element_count;
2292	if (!__n)
2293	break;
2294	__n_bkt = _M_bucket_index(*__n);
2295	}
2296	while (__n != __last_n && __n_bkt == __bkt);
2297	if (__is_bucket_begin)
2298	_M_remove_bucket_begin(__bkt, next: __n, next_bkt: __n_bkt);
2299	if (__n == __last_n)
2300	break;
2301	__is_bucket_begin = true;
2302	__bkt = __n_bkt;
2303	}
2304
2305	if (__n && (__n_bkt != __bkt || __is_bucket_begin))
2306	_M_buckets[__n_bkt] = __prev_n;
2307	__prev_n->_M_nxt = __n;
2308	return iterator(__n);
2309	}
2310
2311	template<typename _Key, typename _Value, typename _Alloc,
2312	typename _ExtractKey, typename _Equal,
2313	typename _Hash, typename _RangeHash, typename _Unused,
2314	typename _RehashPolicy, typename _Traits>
2315	void
2316	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2317	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2318	clear() noexcept
2319	{
2320	this->_M_deallocate_nodes(_M_begin());
2321	__builtin_memset(_M_buckets, 0,
2322	_M_bucket_count * sizeof(__node_base_ptr));
2323	_M_element_count = 0;
2324	_M_before_begin._M_nxt = nullptr;
2325	}
2326
2327	template<typename _Key, typename _Value, typename _Alloc,
2328	typename _ExtractKey, typename _Equal,
2329	typename _Hash, typename _RangeHash, typename _Unused,
2330	typename _RehashPolicy, typename _Traits>
2331	void
2332	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2333	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2334	rehash(size_type __bkt_count)
2335	{
2336	const __rehash_state& __saved_state = _M_rehash_policy._M_state();
2337	__bkt_count
2338	= std::max(_M_rehash_policy._M_bkt_for_elements(_M_element_count + 1),
2339	__bkt_count);
2340	__bkt_count = _M_rehash_policy._M_next_bkt(__bkt_count);
2341
2342	if (__bkt_count != _M_bucket_count)
2343	_M_rehash(__bkt_count, state: __saved_state);
2344	else
2345	// No rehash, restore previous state to keep it consistent with
2346	// container state.
2347	_M_rehash_policy._M_reset(__saved_state);
2348	}
2349
2350	template<typename _Key, typename _Value, typename _Alloc,
2351	typename _ExtractKey, typename _Equal,
2352	typename _Hash, typename _RangeHash, typename _Unused,
2353	typename _RehashPolicy, typename _Traits>
2354	void
2355	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2356	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2357	_M_rehash(size_type __bkt_count, const __rehash_state& __state)
2358	{
2359	__try
2360	{
2361	_M_rehash_aux(__bkt_count, __unique_keys{});
2362	}
2363	__catch(...)
2364	{
2365	// A failure here means that buckets allocation failed. We only
2366	// have to restore hash policy previous state.
2367	_M_rehash_policy._M_reset(__state);
2368	__throw_exception_again;
2369	}
2370	}
2371
2372	// Rehash when there is no equivalent elements.
2373	template<typename _Key, typename _Value, typename _Alloc,
2374	typename _ExtractKey, typename _Equal,
2375	typename _Hash, typename _RangeHash, typename _Unused,
2376	typename _RehashPolicy, typename _Traits>
2377	void
2378	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2379	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2380	_M_rehash_aux(size_type __bkt_count, true_type /* __uks */)
2381	{
2382	__buckets_ptr __new_buckets = _M_allocate_buckets(__bkt_count);
2383	__node_ptr __p = _M_begin();
2384	_M_before_begin._M_nxt = nullptr;
2385	std::size_t __bbegin_bkt = 0;
2386	while (__p)
2387	{
2388	__node_ptr __next = __p->_M_next();
2389	std::size_t __bkt
2390	= __hash_code_base::_M_bucket_index(*__p, __bkt_count);
2391	if (!__new_buckets[__bkt])
2392	{
2393	__p->_M_nxt = _M_before_begin._M_nxt;
2394	_M_before_begin._M_nxt = __p;
2395	__new_buckets[__bkt] = &_M_before_begin;
2396	if (__p->_M_nxt)
2397	__new_buckets[__bbegin_bkt] = __p;
2398	__bbegin_bkt = __bkt;
2399	}
2400	else
2401	{
2402	__p->_M_nxt = __new_buckets[__bkt]->_M_nxt;
2403	__new_buckets[__bkt]->_M_nxt = __p;
2404	}
2405
2406	__p = __next;
2407	}
2408
2409	_M_deallocate_buckets();
2410	_M_bucket_count = __bkt_count;
2411	_M_buckets = __new_buckets;
2412	}
2413
2414	// Rehash when there can be equivalent elements, preserve their relative
2415	// order.
2416	template<typename _Key, typename _Value, typename _Alloc,
2417	typename _ExtractKey, typename _Equal,
2418	typename _Hash, typename _RangeHash, typename _Unused,
2419	typename _RehashPolicy, typename _Traits>
2420	void
2421	_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
2422	_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
2423	_M_rehash_aux(size_type __bkt_count, false_type /* __uks */)
2424	{
2425	__buckets_ptr __new_buckets = _M_allocate_buckets(__bkt_count);
2426	__node_ptr __p = _M_begin();
2427	_M_before_begin._M_nxt = nullptr;
2428	std::size_t __bbegin_bkt = 0;
2429	std::size_t __prev_bkt = 0;
2430	__node_ptr __prev_p = nullptr;
2431	bool __check_bucket = false;
2432
2433	while (__p)
2434	{
2435	__node_ptr __next = __p->_M_next();
2436	std::size_t __bkt
2437	= __hash_code_base::_M_bucket_index(*__p, __bkt_count);
2438
2439	if (__prev_p && __prev_bkt == __bkt)
2440	{
2441	// Previous insert was already in this bucket, we insert after
2442	// the previously inserted one to preserve equivalent elements
2443	// relative order.
2444	__p->_M_nxt = __prev_p->_M_nxt;
2445	__prev_p->_M_nxt = __p;
2446
2447	// Inserting after a node in a bucket require to check that we
2448	// haven't change the bucket last node, in this case next
2449	// bucket containing its before begin node must be updated. We
2450	// schedule a check as soon as we move out of the sequence of
2451	// equivalent nodes to limit the number of checks.
2452	__check_bucket = true;
2453	}
2454	else
2455	{
2456	if (__check_bucket)
2457	{
2458	// Check if we shall update the next bucket because of
2459	// insertions into __prev_bkt bucket.
2460	if (__prev_p->_M_nxt)
2461	{
2462	std::size_t __next_bkt
2463	= __hash_code_base::_M_bucket_index(
2464	*__prev_p->_M_next(), __bkt_count);
2465	if (__next_bkt != __prev_bkt)
2466	__new_buckets[__next_bkt] = __prev_p;
2467	}
2468	__check_bucket = false;
2469	}
2470
2471	if (!__new_buckets[__bkt])
2472	{
2473	__p->_M_nxt = _M_before_begin._M_nxt;
2474	_M_before_begin._M_nxt = __p;
2475	__new_buckets[__bkt] = &_M_before_begin;
2476	if (__p->_M_nxt)
2477	__new_buckets[__bbegin_bkt] = __p;
2478	__bbegin_bkt = __bkt;
2479	}
2480	else
2481	{
2482	__p->_M_nxt = __new_buckets[__bkt]->_M_nxt;
2483	__new_buckets[__bkt]->_M_nxt = __p;
2484	}
2485	}
2486	__prev_p = __p;
2487	__prev_bkt = __bkt;
2488	__p = __next;
2489	}
2490
2491	if (__check_bucket && __prev_p->_M_nxt)
2492	{
2493	std::size_t __next_bkt
2494	= __hash_code_base::_M_bucket_index(*__prev_p->_M_next(),
2495	__bkt_count);
2496	if (__next_bkt != __prev_bkt)
2497	__new_buckets[__next_bkt] = __prev_p;
2498	}
2499
2500	_M_deallocate_buckets();
2501	_M_bucket_count = __bkt_count;
2502	_M_buckets = __new_buckets;
2503	}
2504
2505	#if __cplusplus > 201402L
2506	template<typename, typename, typename> class _Hash_merge_helper { };
2507	#endif // C++17
2508
2509	#if __cpp_deduction_guides >= 201606
2510	// Used to constrain deduction guides
2511	template<typename _Hash>
2512	using _RequireNotAllocatorOrIntegral
2513	= __enable_if_t<!__or_<is_integral<_Hash>, __is_allocator<_Hash>>::value>;
2514	#endif
2515
2516	/// @endcond
2517	_GLIBCXX_END_NAMESPACE_VERSION
2518	} // namespace std
2519
2520	#endif // _HASHTABLE_H
2521