1// Internal policy header for unordered_set and unordered_map -*- C++ -*-
2
3// Copyright (C) 2010-2025 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_policy.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly.
28 * @headername{unordered_map,unordered_set}
29 */
30
31#ifndef _HASHTABLE_POLICY_H
32#define _HASHTABLE_POLICY_H 1
33
34#include <tuple> // for std::tuple, std::forward_as_tuple
35#include <bits/functional_hash.h> // for __is_fast_hash
36#include <bits/stl_algobase.h> // for std::min
37#include <bits/stl_pair.h> // for std::pair
38#include <ext/aligned_buffer.h> // for __gnu_cxx::__aligned_buffer
39#include <ext/alloc_traits.h> // for std::__alloc_rebind
40#include <ext/numeric_traits.h> // for __gnu_cxx::__int_traits
41
42namespace std _GLIBCXX_VISIBILITY(default)
43{
44_GLIBCXX_BEGIN_NAMESPACE_VERSION
45/// @cond undocumented
46
47 template<typename _Key, typename _Value, typename _Alloc,
48 typename _ExtractKey, typename _Equal,
49 typename _Hash, typename _RangeHash, typename _Unused,
50 typename _RehashPolicy, typename _Traits>
51 class _Hashtable;
52
53namespace __detail
54{
55 /**
56 * @defgroup hashtable-detail Base and Implementation Classes
57 * @ingroup unordered_associative_containers
58 * @{
59 */
60 template<typename _Key, typename _Value, typename _ExtractKey,
61 typename _Equal, typename _Hash, typename _RangeHash,
62 typename _Unused, typename _Traits>
63 struct _Hashtable_base;
64
65#pragma GCC diagnostic push
66#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
67 // Helper function: return distance(first, last) for forward
68 // iterators, or 0/1 for input iterators.
69 template<typename _Iterator>
70 inline typename std::iterator_traits<_Iterator>::difference_type
71 __distance_fw(_Iterator __first, _Iterator __last)
72 {
73 using _Cat = typename std::iterator_traits<_Iterator>::iterator_category;
74 if constexpr (is_convertible<_Cat, forward_iterator_tag>::value)
75 return std::distance(__first, __last);
76 else
77 return __first != __last ? 1 : 0;
78 }
79#pragma GCC diagnostic pop
80
81 struct _Identity
82 {
83 template<typename _Tp>
84 _Tp&&
85 operator()(_Tp&& __x) const noexcept
86 { return std::forward<_Tp>(__x); }
87 };
88
89 struct _Select1st
90 {
91 template<typename _Pair>
92 struct __1st_type;
93
94 template<typename _Tp, typename _Up>
95 struct __1st_type<pair<_Tp, _Up>>
96 { using type = _Tp; };
97
98 template<typename _Tp, typename _Up>
99 struct __1st_type<const pair<_Tp, _Up>>
100 { using type = const _Tp; };
101
102 template<typename _Pair>
103 struct __1st_type<_Pair&>
104 { using type = typename __1st_type<_Pair>::type&; };
105
106 template<typename _Tp>
107 typename __1st_type<_Tp>::type&&
108 operator()(_Tp&& __x) const noexcept
109 { return std::forward<_Tp>(__x).first; }
110 };
111
112 template<typename _ExKey>
113 struct _NodeBuilder;
114
115 template<>
116 struct _NodeBuilder<_Select1st>
117 {
118 template<typename _Kt, typename _Arg, typename _NodeGenerator>
119 static auto
120 _S_build(_Kt&& __k, _Arg&& __arg, _NodeGenerator& __node_gen)
121 -> typename _NodeGenerator::__node_ptr
122 {
123 return __node_gen(std::forward<_Kt>(__k),
124 std::forward<_Arg>(__arg).second);
125 }
126 };
127
128 template<>
129 struct _NodeBuilder<_Identity>
130 {
131 template<typename _Kt, typename _Arg, typename _NodeGenerator>
132 static auto
133 _S_build(_Kt&& __k, _Arg&&, _NodeGenerator& __node_gen)
134 -> typename _NodeGenerator::__node_ptr
135 { return __node_gen(std::forward<_Kt>(__k)); }
136 };
137
138 template<typename _HashtableAlloc, typename _NodePtr>
139 struct _NodePtrGuard
140 {
141 _HashtableAlloc& _M_h;
142 _NodePtr _M_ptr;
143
144 ~_NodePtrGuard()
145 {
146 if (_M_ptr)
147 _M_h._M_deallocate_node_ptr(_M_ptr);
148 }
149 };
150
151 template<typename _NodeAlloc>
152 struct _Hashtable_alloc;
153
154 // Functor recycling a pool of nodes and using allocation once the pool is
155 // empty.
156 template<typename _NodeAlloc>
157 struct _ReuseOrAllocNode
158 {
159 private:
160 using __node_alloc_type = _NodeAlloc;
161 using __hashtable_alloc = _Hashtable_alloc<__node_alloc_type>;
162 using __node_alloc_traits =
163 typename __hashtable_alloc::__node_alloc_traits;
164
165 public:
166 using __node_ptr = typename __hashtable_alloc::__node_ptr;
167
168 _ReuseOrAllocNode(__node_ptr __nodes, __hashtable_alloc& __h)
169 : _M_nodes(__nodes), _M_h(__h) { }
170 _ReuseOrAllocNode(const _ReuseOrAllocNode&) = delete;
171
172 ~_ReuseOrAllocNode()
173 { _M_h._M_deallocate_nodes(_M_nodes); }
174
175#pragma GCC diagnostic push
176#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
177 template<typename _Arg>
178 __node_ptr
179 operator()(_Arg&& __arg)
180 {
181 if (!_M_nodes)
182 return _M_h._M_allocate_node(std::forward<_Arg>(__arg));
183
184 using value_type = typename _NodeAlloc::value_type::value_type;
185
186 __node_ptr __node = _M_nodes;
187 if constexpr (is_assignable<value_type&, _Arg>::value)
188 {
189 __node->_M_v() = std::forward<_Arg>(__arg);
190 _M_nodes = _M_nodes->_M_next();
191 __node->_M_nxt = nullptr;
192 }
193 else
194 {
195 _M_nodes = _M_nodes->_M_next();
196 __node->_M_nxt = nullptr;
197 auto& __a = _M_h._M_node_allocator();
198 __node_alloc_traits::destroy(__a, __node->_M_valptr());
199 _NodePtrGuard<__hashtable_alloc, __node_ptr>
200 __guard{ _M_h, __node };
201 __node_alloc_traits::construct(__a, __node->_M_valptr(),
202 std::forward<_Arg>(__arg));
203 __guard._M_ptr = nullptr;
204 }
205 return __node;
206 }
207#pragma GCC diagnostic pop
208
209 private:
210 __node_ptr _M_nodes;
211 __hashtable_alloc& _M_h;
212 };
213
214 // Functor similar to the previous one but without any pool of nodes to
215 // recycle.
216 template<typename _NodeAlloc>
217 struct _AllocNode
218 {
219 private:
220 using __hashtable_alloc = _Hashtable_alloc<_NodeAlloc>;
221
222 public:
223 using __node_ptr = typename __hashtable_alloc::__node_ptr;
224
225 _AllocNode(__hashtable_alloc& __h)
226 : _M_h(__h) { }
227
228 template<typename... _Args>
229 __node_ptr
230 operator()(_Args&&... __args) const
231 { return _M_h._M_allocate_node(std::forward<_Args>(__args)...); }
232
233 private:
234 __hashtable_alloc& _M_h;
235 };
236
237 // Auxiliary types used for all instantiations of _Hashtable nodes
238 // and iterators.
239
240 /**
241 * struct _Hashtable_traits
242 *
243 * Important traits for hash tables.
244 *
245 * @tparam _Cache_hash_code Boolean value. True if the value of
246 * the hash function is stored along with the value. This is a
247 * time-space tradeoff. Storing it may improve lookup speed by
248 * reducing the number of times we need to call the _Hash or _Equal
249 * functors.
250 *
251 * @tparam _Constant_iterators Boolean value. True if iterator and
252 * const_iterator are both constant iterator types. This is true
253 * for unordered_set and unordered_multiset, false for
254 * unordered_map and unordered_multimap.
255 *
256 * @tparam _Unique_keys Boolean value. True if the return value
257 * of _Hashtable::count(k) is always at most one, false if it may
258 * be an arbitrary number. This is true for unordered_set and
259 * unordered_map, false for unordered_multiset and
260 * unordered_multimap.
261 */
262 template<bool _Cache_hash_code, bool _Constant_iterators, bool _Unique_keys>
263 struct _Hashtable_traits
264 {
265 using __hash_cached = __bool_constant<_Cache_hash_code>;
266 using __constant_iterators = __bool_constant<_Constant_iterators>;
267 using __unique_keys = __bool_constant<_Unique_keys>;
268 };
269
270 /**
271 * struct _Hashtable_hash_traits
272 *
273 * Important traits for hash tables depending on associated hasher.
274 *
275 */
276 template<typename _Hash>
277 struct _Hashtable_hash_traits
278 {
279 static constexpr size_t
280 __small_size_threshold() noexcept
281 { return std::__is_fast_hash<_Hash>::value ? 0 : 20; }
282 };
283
284 /**
285 * struct _Hash_node_base
286 *
287 * Nodes, used to wrap elements stored in the hash table. A policy
288 * template parameter of class template _Hashtable controls whether
289 * nodes also store a hash code. In some cases (e.g. strings) this
290 * may be a performance win.
291 */
292 struct _Hash_node_base
293 {
294 _Hash_node_base* _M_nxt;
295
296 _Hash_node_base() noexcept : _M_nxt() { }
297
298 _Hash_node_base(_Hash_node_base* __next) noexcept : _M_nxt(__next) { }
299 };
300
301 /**
302 * struct _Hash_node_value_base
303 *
304 * Node type with the value to store.
305 */
306 template<typename _Value>
307 struct _Hash_node_value_base
308 {
309 using value_type = _Value;
310
311 __gnu_cxx::__aligned_buffer<_Value> _M_storage;
312
313 // These member functions must be always_inline, see PR 111050
314
315 [[__gnu__::__always_inline__]]
316 _Value*
317 _M_valptr() noexcept
318 { return _M_storage._M_ptr(); }
319
320 [[__gnu__::__always_inline__]]
321 const _Value*
322 _M_valptr() const noexcept
323 { return _M_storage._M_ptr(); }
324
325 [[__gnu__::__always_inline__]]
326 _Value&
327 _M_v() noexcept
328 { return *_M_valptr(); }
329
330 [[__gnu__::__always_inline__]]
331 const _Value&
332 _M_v() const noexcept
333 { return *_M_valptr(); }
334 };
335
336 /**
337 * Primary template struct _Hash_node_code_cache.
338 */
339 template<bool _Cache_hash_code>
340 struct _Hash_node_code_cache
341 { };
342
343 /**
344 * Specialization for node with cache, struct _Hash_node_code_cache.
345 */
346 template<>
347 struct _Hash_node_code_cache<true>
348 { size_t _M_hash_code; };
349
350 template<typename _Value, bool _Cache_hash_code>
351 struct _Hash_node_value
352 : _Hash_node_value_base<_Value>
353 , _Hash_node_code_cache<_Cache_hash_code>
354 { };
355
356 /**
357 * Primary template struct _Hash_node.
358 */
359 template<typename _Value, bool _Cache_hash_code>
360 struct _Hash_node
361 : _Hash_node_base
362 , _Hash_node_value<_Value, _Cache_hash_code>
363 {
364 _Hash_node*
365 _M_next() const noexcept
366 { return static_cast<_Hash_node*>(this->_M_nxt); }
367 };
368
369 /// Base class for node iterators.
370 template<typename _Value, bool _Cache_hash_code>
371 struct _Node_iterator_base
372 {
373 using __node_type = _Hash_node<_Value, _Cache_hash_code>;
374
375 __node_type* _M_cur;
376
377 _Node_iterator_base() : _M_cur(nullptr) { }
378 _Node_iterator_base(__node_type* __p) noexcept
379 : _M_cur(__p) { }
380
381 void
382 _M_incr() noexcept
383 { _M_cur = _M_cur->_M_next(); }
384
385 friend bool
386 operator==(const _Node_iterator_base& __x, const _Node_iterator_base& __y)
387 noexcept
388 { return __x._M_cur == __y._M_cur; }
389
390#if __cpp_impl_three_way_comparison < 201907L
391 friend bool
392 operator!=(const _Node_iterator_base& __x, const _Node_iterator_base& __y)
393 noexcept
394 { return __x._M_cur != __y._M_cur; }
395#endif
396 };
397
398 /// Node iterators, used to iterate through all the hashtable.
399 template<typename _Value, bool __constant_iterators, bool __cache>
400 struct _Node_iterator
401 : public _Node_iterator_base<_Value, __cache>
402 {
403 private:
404 using __base_type = _Node_iterator_base<_Value, __cache>;
405 using __node_type = typename __base_type::__node_type;
406
407 public:
408 using value_type = _Value;
409 using difference_type = ptrdiff_t;
410 using iterator_category = forward_iterator_tag;
411
412 using pointer = __conditional_t<__constant_iterators,
413 const value_type*, value_type*>;
414
415 using reference = __conditional_t<__constant_iterators,
416 const value_type&, value_type&>;
417
418 _Node_iterator() = default;
419
420 explicit
421 _Node_iterator(__node_type* __p) noexcept
422 : __base_type(__p) { }
423
424 reference
425 operator*() const noexcept
426 { return this->_M_cur->_M_v(); }
427
428 pointer
429 operator->() const noexcept
430 { return this->_M_cur->_M_valptr(); }
431
432 _Node_iterator&
433 operator++() noexcept
434 {
435 this->_M_incr();
436 return *this;
437 }
438
439 _Node_iterator
440 operator++(int) noexcept
441 {
442 _Node_iterator __tmp(*this);
443 this->_M_incr();
444 return __tmp;
445 }
446
447#if __cpp_impl_three_way_comparison >= 201907L
448 friend bool
449 operator==(const _Node_iterator&, const _Node_iterator&) = default;
450#else
451 friend bool
452 operator==(const _Node_iterator& __x, const _Node_iterator& __y) noexcept
453 {
454 const __base_type& __bx = __x;
455 const __base_type& __by = __y;
456 return __bx == __by;
457 }
458
459 friend bool
460 operator!=(const _Node_iterator& __x, const _Node_iterator& __y) noexcept
461 { return !(__x == __y); }
462#endif
463 };
464
465 /// Node const_iterators, used to iterate through all the hashtable.
466 template<typename _Value, bool __constant_iterators, bool __cache>
467 struct _Node_const_iterator
468 : public _Node_iterator_base<_Value, __cache>
469 {
470 private:
471 using __base_type = _Node_iterator_base<_Value, __cache>;
472 using __node_type = typename __base_type::__node_type;
473
474 // The corresponding non-const iterator.
475 using __iterator
476 = _Node_iterator<_Value, __constant_iterators, __cache>;
477
478 public:
479 using value_type = _Value;
480 using difference_type = ptrdiff_t;
481 using iterator_category = forward_iterator_tag;
482
483 using pointer = const value_type*;
484 using reference = const value_type&;
485
486 _Node_const_iterator() = default;
487
488 explicit
489 _Node_const_iterator(__node_type* __p) noexcept
490 : __base_type(__p) { }
491
492 _Node_const_iterator(const __iterator& __x) noexcept
493 : __base_type(__x._M_cur) { }
494
495 reference
496 operator*() const noexcept
497 { return this->_M_cur->_M_v(); }
498
499 pointer
500 operator->() const noexcept
501 { return this->_M_cur->_M_valptr(); }
502
503 _Node_const_iterator&
504 operator++() noexcept
505 {
506 this->_M_incr();
507 return *this;
508 }
509
510 _Node_const_iterator
511 operator++(int) noexcept
512 {
513 _Node_const_iterator __tmp(*this);
514 this->_M_incr();
515 return __tmp;
516 }
517
518#if __cpp_impl_three_way_comparison >= 201907L
519 friend bool
520 operator==(const _Node_const_iterator&,
521 const _Node_const_iterator&) = default;
522
523 friend bool
524 operator==(const _Node_const_iterator& __x, const __iterator& __y)
525 {
526 const __base_type& __bx = __x;
527 const __base_type& __by = __y;
528 return __bx == __by;
529 }
530#else
531 friend bool
532 operator==(const _Node_const_iterator& __x,
533 const _Node_const_iterator& __y) noexcept
534 {
535 const __base_type& __bx = __x;
536 const __base_type& __by = __y;
537 return __bx == __by;
538 }
539
540 friend bool
541 operator!=(const _Node_const_iterator& __x,
542 const _Node_const_iterator& __y) noexcept
543 { return !(__x == __y); }
544
545 friend bool
546 operator==(const _Node_const_iterator& __x,
547 const __iterator& __y) noexcept
548 {
549 const __base_type& __bx = __x;
550 const __base_type& __by = __y;
551 return __bx == __by;
552 }
553
554 friend bool
555 operator!=(const _Node_const_iterator& __x,
556 const __iterator& __y) noexcept
557 { return !(__x == __y); }
558
559 friend bool
560 operator==(const __iterator& __x,
561 const _Node_const_iterator& __y) noexcept
562 {
563 const __base_type& __bx = __x;
564 const __base_type& __by = __y;
565 return __bx == __by;
566 }
567
568 friend bool
569 operator!=(const __iterator& __x,
570 const _Node_const_iterator& __y) noexcept
571 { return !(__x == __y); }
572#endif
573 };
574
575 // Many of class template _Hashtable's template parameters are policy
576 // classes. These are defaults for the policies.
577
578 /// Default range hashing function: use division to fold a large number
579 /// into the range [0, N).
580 struct _Mod_range_hashing
581 {
582 size_t
583 operator()(size_t __num, size_t __den) const noexcept
584 { return __num % __den; }
585 };
586
587 /// Default ranged hash function H. In principle it should be a
588 /// function object composed from objects of type H1 and H2 such that
589 /// h(k, N) = h2(h1(k), N), but that would mean making extra copies of
590 /// h1 and h2. So instead we'll just use a tag to tell class template
591 /// hashtable to do that composition.
592 struct _Default_ranged_hash { };
593
594 /// Default value for rehash policy. Bucket size is (usually) the
595 /// smallest prime that keeps the load factor small enough.
596 struct _Prime_rehash_policy
597 {
598 using __has_load_factor = true_type;
599
600 _Prime_rehash_policy(float __z = 1.0) noexcept
601 : _M_max_load_factor(__z), _M_next_resize(0) { }
602
603 float
604 max_load_factor() const noexcept
605 { return _M_max_load_factor; }
606
607 // Return a bucket size no smaller than n.
608 // TODO: 'const' qualifier is kept for abi compatibility reason.
609 size_t
610 _M_next_bkt(size_t __n) const;
611
612 // Return a bucket count appropriate for n elements
613 size_t
614 _M_bkt_for_elements(size_t __n) const
615 { return __builtin_ceil(__n / (double)_M_max_load_factor); }
616
617 // __n_bkt is current bucket count, __n_elt is current element count,
618 // and __n_ins is number of elements to be inserted. Do we need to
619 // increase bucket count? If so, return make_pair(true, n), where n
620 // is the new bucket count. If not, return make_pair(false, 0).
621 // TODO: 'const' qualifier is kept for abi compatibility reason.
622 std::pair<bool, size_t>
623 _M_need_rehash(size_t __n_bkt, size_t __n_elt,
624 size_t __n_ins) const;
625
626 using _State = size_t;
627
628 _State
629 _M_state() const
630 { return _M_next_resize; }
631
632 void
633 _M_reset() noexcept
634 { _M_next_resize = 0; }
635
636 void
637 _M_reset(_State __state)
638 { _M_next_resize = __state; }
639
640 static const size_t _S_growth_factor = 2;
641
642 float _M_max_load_factor;
643
644 // TODO: 'mutable' kept for abi compatibility reason.
645 mutable size_t _M_next_resize;
646 };
647
648 /// Range hashing function assuming that second arg is a power of 2.
649 struct _Mask_range_hashing
650 {
651 size_t
652 operator()(size_t __num, size_t __den) const noexcept
653 { return __num & (__den - 1); }
654 };
655
656 /// Compute closest power of 2 not less than __n
657 inline size_t
658 __clp2(size_t __n) noexcept
659 {
660 using __gnu_cxx::__int_traits;
661 // Equivalent to return __n ? std::bit_ceil(__n) : 0;
662 if (__n < 2)
663 return __n;
664 const unsigned __lz = sizeof(size_t) > sizeof(long)
665 ? __builtin_clzll(__n - 1ull)
666 : __builtin_clzl(__n - 1ul);
667 // Doing two shifts avoids undefined behaviour when __lz == 0.
668 return (size_t(1) << (__int_traits<size_t>::__digits - __lz - 1)) << 1;
669 }
670
671 /// Rehash policy providing power of 2 bucket numbers. Avoids modulo
672 /// operations.
673 struct _Power2_rehash_policy
674 {
675 using __has_load_factor = true_type;
676
677 _Power2_rehash_policy(float __z = 1.0) noexcept
678 : _M_max_load_factor(__z), _M_next_resize(0) { }
679
680 float
681 max_load_factor() const noexcept
682 { return _M_max_load_factor; }
683
684 // Return a bucket size no smaller than n (as long as n is not above the
685 // highest power of 2).
686 size_t
687 _M_next_bkt(size_t __n) noexcept
688 {
689 if (__n == 0)
690 // Special case on container 1st initialization with 0 bucket count
691 // hint. We keep _M_next_resize to 0 to make sure that next time we
692 // want to add an element allocation will take place.
693 return 1;
694
695 const auto __max_width = std::min<size_t>(a: sizeof(size_t), b: 8);
696 const auto __max_bkt = size_t(1) << (__max_width * __CHAR_BIT__ - 1);
697 size_t __res = __clp2(__n);
698
699 if (__res == 0)
700 __res = __max_bkt;
701 else if (__res == 1)
702 // If __res is 1 we force it to 2 to make sure there will be an
703 // allocation so that nothing need to be stored in the initial
704 // single bucket
705 __res = 2;
706
707 if (__res == __max_bkt)
708 // Set next resize to the max value so that we never try to rehash again
709 // as we already reach the biggest possible bucket number.
710 // Note that it might result in max_load_factor not being respected.
711 _M_next_resize = size_t(-1);
712 else
713 _M_next_resize
714 = __builtin_floor(__res * (double)_M_max_load_factor);
715
716 return __res;
717 }
718
719 // Return a bucket count appropriate for n elements
720 size_t
721 _M_bkt_for_elements(size_t __n) const noexcept
722 { return __builtin_ceil(__n / (double)_M_max_load_factor); }
723
724 // __n_bkt is current bucket count, __n_elt is current element count,
725 // and __n_ins is number of elements to be inserted. Do we need to
726 // increase bucket count? If so, return make_pair(true, n), where n
727 // is the new bucket count. If not, return make_pair(false, 0).
728 std::pair<bool, size_t>
729 _M_need_rehash(size_t __n_bkt, size_t __n_elt, size_t __n_ins) noexcept
730 {
731 if (__n_elt + __n_ins > _M_next_resize)
732 {
733 // If _M_next_resize is 0 it means that we have nothing allocated so
734 // far and that we start inserting elements. In this case we start
735 // with an initial bucket size of 11.
736 double __min_bkts
737 = std::max<size_t>(a: __n_elt + __n_ins, b: _M_next_resize ? 0 : 11)
738 / (double)_M_max_load_factor;
739 if (__min_bkts >= __n_bkt)
740 return { true,
741 _M_next_bkt(n: std::max<size_t>(a: __builtin_floor(__min_bkts) + 1,
742 b: __n_bkt * _S_growth_factor)) };
743
744 _M_next_resize
745 = __builtin_floor(__n_bkt * (double)_M_max_load_factor);
746 return { false, 0 };
747 }
748 else
749 return { false, 0 };
750 }
751
752 using _State = size_t;
753
754 _State
755 _M_state() const noexcept
756 { return _M_next_resize; }
757
758 void
759 _M_reset() noexcept
760 { _M_next_resize = 0; }
761
762 void
763 _M_reset(_State __state) noexcept
764 { _M_next_resize = __state; }
765
766 static const size_t _S_growth_factor = 2;
767
768 float _M_max_load_factor;
769 size_t _M_next_resize;
770 };
771
772 template<typename _RehashPolicy>
773 struct _RehashStateGuard
774 {
775 _RehashPolicy* _M_guarded_obj;
776 typename _RehashPolicy::_State _M_prev_state;
777
778 _RehashStateGuard(_RehashPolicy& __policy)
779 : _M_guarded_obj(std::__addressof(__policy))
780 , _M_prev_state(__policy._M_state())
781 { }
782 _RehashStateGuard(const _RehashStateGuard&) = delete;
783
784 ~_RehashStateGuard()
785 {
786 if (_M_guarded_obj)
787 _M_guarded_obj->_M_reset(_M_prev_state);
788 }
789 };
790
791 // Base classes for std::_Hashtable. We define these base classes
792 // because in some cases we want to do different things depending on
793 // the value of a policy class. In some cases the policy class
794 // affects which member functions and nested typedefs are defined;
795 // we handle that by specializing base class templates. Several of
796 // the base class templates need to access other members of class
797 // template _Hashtable, so we use a variant of the "Curiously
798 // Recurring Template Pattern" (CRTP) technique.
799
800 /**
801 * Primary class template _Map_base.
802 *
803 * If the hashtable has a value type of the form pair<const T1, T2> and
804 * a key extraction policy (_ExtractKey) that returns the first part
805 * of the pair, the hashtable gets a mapped_type typedef. If it
806 * satisfies those criteria and also has unique keys, then it also
807 * gets an operator[].
808 */
809 template<typename _Key, typename _Value, typename _Alloc,
810 typename _ExtractKey, typename _Equal,
811 typename _Hash, typename _RangeHash, typename _Unused,
812 typename _RehashPolicy, typename _Traits,
813 bool _Unique_keys = _Traits::__unique_keys::value>
814 struct _Map_base { };
815
816 /// Partial specialization, __unique_keys set to false, std::pair value type.
817 template<typename _Key, typename _Val, typename _Alloc, typename _Equal,
818 typename _Hash, typename _RangeHash, typename _Unused,
819 typename _RehashPolicy, typename _Traits>
820 struct _Map_base<_Key, pair<const _Key, _Val>, _Alloc, _Select1st, _Equal,
821 _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits, false>
822 {
823 using mapped_type = _Val;
824 };
825
826 /// Partial specialization, __unique_keys set to true.
827 template<typename _Key, typename _Val, typename _Alloc, typename _Equal,
828 typename _Hash, typename _RangeHash, typename _Unused,
829 typename _RehashPolicy, typename _Traits>
830 struct _Map_base<_Key, pair<const _Key, _Val>, _Alloc, _Select1st, _Equal,
831 _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits, true>
832 {
833 private:
834 using __hashtable_base = _Hashtable_base<_Key, pair<const _Key, _Val>,
835 _Select1st, _Equal, _Hash,
836 _RangeHash, _Unused,
837 _Traits>;
838
839 using __hashtable = _Hashtable<_Key, pair<const _Key, _Val>, _Alloc,
840 _Select1st, _Equal, _Hash, _RangeHash,
841 _Unused, _RehashPolicy, _Traits>;
842
843 using __hash_code = typename __hashtable_base::__hash_code;
844
845 public:
846 using key_type = typename __hashtable_base::key_type;
847 using mapped_type = _Val;
848
849 mapped_type&
850 operator[](const key_type& __k);
851
852 mapped_type&
853 operator[](key_type&& __k);
854
855 // _GLIBCXX_RESOLVE_LIB_DEFECTS
856 // DR 761. unordered_map needs an at() member function.
857 mapped_type&
858 at(const key_type& __k)
859 {
860 auto __ite = static_cast<__hashtable*>(this)->find(__k);
861 if (!__ite._M_cur)
862 __throw_out_of_range(__N("unordered_map::at"));
863 return __ite->second;
864 }
865
866 const mapped_type&
867 at(const key_type& __k) const
868 {
869 auto __ite = static_cast<const __hashtable*>(this)->find(__k);
870 if (!__ite._M_cur)
871 __throw_out_of_range(__N("unordered_map::at"));
872 return __ite->second;
873 }
874 };
875
876 template<typename _Key, typename _Val, typename _Alloc, typename _Equal,
877 typename _Hash, typename _RangeHash, typename _Unused,
878 typename _RehashPolicy, typename _Traits>
879 auto
880 _Map_base<_Key, pair<const _Key, _Val>, _Alloc, _Select1st, _Equal,
881 _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits, true>::
882 operator[](const key_type& __k)
883 -> mapped_type&
884 {
885 __hashtable* __h = static_cast<__hashtable*>(this);
886 __hash_code __code = __h->_M_hash_code(__k);
887 size_t __bkt = __h->_M_bucket_index(__code);
888 if (auto __node = __h->_M_find_node(__bkt, __k, __code))
889 return __node->_M_v().second;
890
891 typename __hashtable::_Scoped_node __node {
892 __h,
893 std::piecewise_construct,
894 std::tuple<const key_type&>(__k),
895 std::tuple<>()
896 };
897 auto __pos
898 = __h->_M_insert_unique_node(__bkt, __code, __node._M_node);
899 __node._M_node = nullptr;
900 return __pos->second;
901 }
902
903 template<typename _Key, typename _Val, typename _Alloc, typename _Equal,
904 typename _Hash, typename _RangeHash, typename _Unused,
905 typename _RehashPolicy, typename _Traits>
906 auto
907 _Map_base<_Key, pair<const _Key, _Val>, _Alloc, _Select1st, _Equal,
908 _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits, true>::
909 operator[](key_type&& __k)
910 -> mapped_type&
911 {
912 __hashtable* __h = static_cast<__hashtable*>(this);
913 __hash_code __code = __h->_M_hash_code(__k);
914 size_t __bkt = __h->_M_bucket_index(__code);
915 if (auto __node = __h->_M_find_node(__bkt, __k, __code))
916 return __node->_M_v().second;
917
918 typename __hashtable::_Scoped_node __node {
919 __h,
920 std::piecewise_construct,
921 std::forward_as_tuple(std::move(__k)),
922 std::tuple<>()
923 };
924 auto __pos
925 = __h->_M_insert_unique_node(__bkt, __code, __node._M_node);
926 __node._M_node = nullptr;
927 return __pos->second;
928 }
929
930 // Partial specialization for unordered_map<const T, U>, see PR 104174.
931 template<typename _Key, typename _Val, typename _Alloc, typename _Equal,
932 typename _Hash, typename _RangeHash, typename _Unused,
933 typename _RehashPolicy, typename _Traits, bool __uniq>
934 struct _Map_base<const _Key, pair<const _Key, _Val>,
935 _Alloc, _Select1st, _Equal, _Hash,
936 _RangeHash, _Unused, _RehashPolicy, _Traits, __uniq>
937 : _Map_base<_Key, pair<const _Key, _Val>, _Alloc, _Select1st, _Equal, _Hash,
938 _RangeHash, _Unused, _RehashPolicy, _Traits, __uniq>
939 { };
940
941 template<typename _Policy>
942 using __has_load_factor = typename _Policy::__has_load_factor;
943
944 /**
945 * Primary class template _Rehash_base.
946 *
947 * Give hashtable the max_load_factor functions and reserve iff the
948 * rehash policy supports it.
949 */
950 template<typename _Key, typename _Value, typename _Alloc,
951 typename _ExtractKey, typename _Equal,
952 typename _Hash, typename _RangeHash, typename _Unused,
953 typename _RehashPolicy, typename _Traits,
954 typename =
955 __detected_or_t<false_type, __has_load_factor, _RehashPolicy>>
956 struct _Rehash_base;
957
958 /// Specialization when rehash policy doesn't provide load factor management.
959 template<typename _Key, typename _Value, typename _Alloc,
960 typename _ExtractKey, typename _Equal,
961 typename _Hash, typename _RangeHash, typename _Unused,
962 typename _RehashPolicy, typename _Traits>
963 struct _Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
964 _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits,
965 false_type /* Has load factor */>
966 {
967 };
968
969 /// Specialization when rehash policy provide load factor management.
970 template<typename _Key, typename _Value, typename _Alloc,
971 typename _ExtractKey, typename _Equal,
972 typename _Hash, typename _RangeHash, typename _Unused,
973 typename _RehashPolicy, typename _Traits>
974 struct _Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
975 _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits,
976 true_type /* Has load factor */>
977 {
978 private:
979 using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
980 _Equal, _Hash, _RangeHash, _Unused,
981 _RehashPolicy, _Traits>;
982
983 public:
984 float
985 max_load_factor() const noexcept
986 {
987 const __hashtable* __this = static_cast<const __hashtable*>(this);
988 return __this->__rehash_policy().max_load_factor();
989 }
990
991 void
992 max_load_factor(float __z)
993 {
994 __hashtable* __this = static_cast<__hashtable*>(this);
995 __this->__rehash_policy(_RehashPolicy(__z));
996 }
997
998 void
999 reserve(size_t __n)
1000 {
1001 __hashtable* __this = static_cast<__hashtable*>(this);
1002 __this->rehash(__this->__rehash_policy()._M_bkt_for_elements(__n));
1003 }
1004 };
1005
1006 /**
1007 * Primary class template _Hashtable_ebo_helper.
1008 *
1009 * Helper class using [[no_unique_address]] to reduce object size.
1010 */
1011 template<typename _Tp,
1012 bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
1013 struct _Hashtable_ebo_helper
1014 {
1015 [[__no_unique_address__]] _Tp _M_obj;
1016 };
1017
1018#if ! _GLIBCXX_INLINE_VERSION
1019 // For ABI compatibility reasons, [[no_unique_address]] is only used
1020 // for empty non-final types.
1021 template<typename _Tp>
1022 struct _Hashtable_ebo_helper<_Tp, false>
1023 {
1024 _Tp _M_obj;
1025 };
1026#endif
1027
1028 /**
1029 * Primary class template _Local_iterator_base.
1030 *
1031 * Base class for local iterators, used to iterate within a bucket
1032 * but not between buckets.
1033 */
1034 template<typename _Key, typename _Value, typename _ExtractKey,
1035 typename _Hash, typename _RangeHash, typename _Unused,
1036 bool __cache_hash_code>
1037 struct _Local_iterator_base;
1038
1039 // Wraps the _Hash object and provides some utility functions for using it.
1040 template<typename _Key, typename _Value, typename _ExtractKey,
1041 typename _Hash, typename _RangeHash, typename _Unused,
1042 bool /* __cache_hash_code */>
1043 struct _Hash_code_base
1044 {
1045 // Gives the local iterator implementation access to _M_bucket_index().
1046 friend struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1047 _Hash, _RangeHash, _Unused, false>;
1048 public:
1049 using hasher = _Hash;
1050
1051 hasher
1052 hash_function() const
1053 { return _M_hash._M_obj; }
1054
1055 protected:
1056 [[__no_unique_address__]] _Hashtable_ebo_helper<_Hash> _M_hash{};
1057
1058 using __hash_code = size_t;
1059
1060 // We need the default constructor for the local iterators and _Hashtable
1061 // default constructor.
1062 _Hash_code_base() = default;
1063
1064 _Hash_code_base(const _Hash& __hash) : _M_hash{__hash} { }
1065
1066 __hash_code
1067 _M_hash_code(const _Key& __k) const
1068 {
1069 static_assert(__is_invocable<const _Hash&, const _Key&>{},
1070 "hash function must be invocable with an argument of key type");
1071 return _M_hash._M_obj(__k);
1072 }
1073
1074 template<typename _Kt>
1075 __hash_code
1076 _M_hash_code_tr(const _Kt& __k) const
1077 {
1078 static_assert(__is_invocable<const _Hash&, const _Kt&>{},
1079 "hash function must be invocable with an argument of key type");
1080 return _M_hash._M_obj(__k);
1081 }
1082
1083 __hash_code
1084 _M_hash_code(const _Hash_node_value<_Value, false>& __n) const
1085 { return _M_hash_code(_ExtractKey{}(__n._M_v())); }
1086
1087 __hash_code
1088 _M_hash_code(const _Hash_node_value<_Value, true>& __n) const
1089 { return __n._M_hash_code; }
1090
1091 size_t
1092 _M_bucket_index(__hash_code __c, size_t __bkt_count) const
1093 { return _RangeHash{}(__c, __bkt_count); }
1094
1095 size_t
1096 _M_bucket_index(const _Hash_node_value<_Value, false>& __n,
1097 size_t __bkt_count) const
1098 noexcept( noexcept(declval<const _Hash&>()(declval<const _Key&>())) )
1099 {
1100 return _RangeHash{}(_M_hash_code(_ExtractKey{}(__n._M_v())),
1101 __bkt_count);
1102 }
1103
1104 size_t
1105 _M_bucket_index(const _Hash_node_value<_Value, true>& __n,
1106 size_t __bkt_count) const noexcept
1107 { return _RangeHash{}(__n._M_hash_code, __bkt_count); }
1108 };
1109
1110 /// Partial specialization used when nodes contain a cached hash code.
1111 template<typename _Key, typename _Value, typename _ExtractKey,
1112 typename _Hash, typename _RangeHash, typename _Unused>
1113 struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1114 _Hash, _RangeHash, _Unused, true>
1115 : public _Node_iterator_base<_Value, true>
1116 {
1117 protected:
1118 using __base_node_iter = _Node_iterator_base<_Value, true>;
1119 using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1120 _Hash, _RangeHash, _Unused, true>;
1121
1122 _Local_iterator_base() = default;
1123
1124 _Local_iterator_base(const __hash_code_base&,
1125 _Hash_node<_Value, true>* __p,
1126 size_t __bkt, size_t __bkt_count)
1127 : __base_node_iter(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count)
1128 { }
1129
1130 void
1131 _M_incr()
1132 {
1133 __base_node_iter::_M_incr();
1134 if (this->_M_cur)
1135 {
1136 size_t __bkt
1137 = _RangeHash{}(this->_M_cur->_M_hash_code, _M_bucket_count);
1138 if (__bkt != _M_bucket)
1139 this->_M_cur = nullptr;
1140 }
1141 }
1142
1143 size_t _M_bucket = 0;
1144 size_t _M_bucket_count = 0;
1145
1146 public:
1147 size_t
1148 _M_get_bucket() const { return _M_bucket; } // for debug mode
1149 };
1150
1151 // Uninitialized storage for a _Hash object in a local iterator.
1152 // This type is DefaultConstructible even if the _Hash type isn't,
1153 // so that _Local_iterator_base<..., false> can be DefaultConstructible.
1154 template<typename _Hash>
1155 struct _Hash_obj_storage
1156 {
1157 union _Uninit_storage
1158 {
1159 _Uninit_storage() noexcept { }
1160 ~_Uninit_storage() { }
1161
1162 [[__no_unique_address__]] _Hash _M_h;
1163 };
1164
1165 [[__no_unique_address__]] _Uninit_storage _M_u;
1166 };
1167
1168 // Partial specialization used when hash codes are not cached
1169 template<typename _Key, typename _Value, typename _ExtractKey,
1170 typename _Hash, typename _RangeHash, typename _Unused>
1171 struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1172 _Hash, _RangeHash, _Unused, false>
1173 : _Hash_obj_storage<_Hash>, _Node_iterator_base<_Value, false>
1174 {
1175 protected:
1176 using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1177 _Hash, _RangeHash, _Unused, false>;
1178 using __hash_obj_storage = _Hash_obj_storage<_Hash>;
1179 using __node_iter_base = _Node_iterator_base<_Value, false>;
1180
1181 _Local_iterator_base() = default;
1182
1183 _Local_iterator_base(const __hash_code_base& __base,
1184 _Hash_node<_Value, false>* __p,
1185 size_t __bkt, size_t __bkt_count)
1186 : __node_iter_base(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count)
1187 { _M_init(h: __base._M_hash._M_obj); }
1188
1189 ~_Local_iterator_base()
1190 {
1191 if (_M_bucket_count != size_t(-1))
1192 _M_destroy();
1193 }
1194
1195 _Local_iterator_base(const _Local_iterator_base& __iter)
1196 : __node_iter_base(__iter._M_cur), _M_bucket(__iter._M_bucket)
1197 , _M_bucket_count(__iter._M_bucket_count)
1198 {
1199 if (_M_bucket_count != size_t(-1))
1200 _M_init(h: __iter._M_h());
1201 }
1202
1203 _Local_iterator_base&
1204 operator=(const _Local_iterator_base& __iter)
1205 {
1206 if (_M_bucket_count != size_t(-1))
1207 _M_destroy();
1208 this->_M_cur = __iter._M_cur;
1209 _M_bucket = __iter._M_bucket;
1210 _M_bucket_count = __iter._M_bucket_count;
1211 if (_M_bucket_count != size_t(-1))
1212 _M_init(h: __iter._M_h());
1213 return *this;
1214 }
1215
1216 void
1217 _M_incr()
1218 {
1219 __node_iter_base::_M_incr();
1220 if (this->_M_cur)
1221 {
1222 const auto __code = _M_h()(_ExtractKey{}(this->_M_cur->_M_v()));
1223 size_t __bkt = _RangeHash{}(__code, _M_bucket_count);
1224 if (__bkt != _M_bucket)
1225 this->_M_cur = nullptr;
1226 }
1227 }
1228
1229 size_t _M_bucket = 0;
1230 size_t _M_bucket_count = -1;
1231
1232 void
1233 _M_init(const _Hash& __h)
1234 { std::_Construct(std::__addressof(__hash_obj_storage::_M_u._M_h), __h); }
1235
1236 void
1237 _M_destroy() { __hash_obj_storage::_M_u._M_h.~_Hash(); }
1238
1239 const _Hash&
1240 _M_h() const { return __hash_obj_storage::_M_u._M_h; }
1241
1242 public:
1243 size_t
1244 _M_get_bucket() const { return _M_bucket; } // for debug mode
1245 };
1246
1247 /// local iterators
1248 template<typename _Key, typename _Value, typename _ExtractKey,
1249 typename _Hash, typename _RangeHash, typename _Unused,
1250 bool __constant_iterators, bool __cache>
1251 struct _Local_iterator
1252 : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1253 _Hash, _RangeHash, _Unused, __cache>
1254 {
1255 private:
1256 using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1257 _Hash, _RangeHash, _Unused, __cache>;
1258 using __hash_code_base = typename __base_type::__hash_code_base;
1259
1260 public:
1261 using value_type = _Value;
1262 using pointer = __conditional_t<__constant_iterators,
1263 const value_type*, value_type*>;
1264 using reference = __conditional_t<__constant_iterators,
1265 const value_type&, value_type&>;
1266 using difference_type = ptrdiff_t;
1267 using iterator_category = forward_iterator_tag;
1268
1269 _Local_iterator() = default;
1270
1271 _Local_iterator(const __hash_code_base& __base,
1272 _Hash_node<_Value, __cache>* __n,
1273 size_t __bkt, size_t __bkt_count)
1274 : __base_type(__base, __n, __bkt, __bkt_count)
1275 { }
1276
1277 reference
1278 operator*() const
1279 { return this->_M_cur->_M_v(); }
1280
1281 pointer
1282 operator->() const
1283 { return this->_M_cur->_M_valptr(); }
1284
1285 _Local_iterator&
1286 operator++()
1287 {
1288 this->_M_incr();
1289 return *this;
1290 }
1291
1292 _Local_iterator
1293 operator++(int)
1294 {
1295 _Local_iterator __tmp(*this);
1296 this->_M_incr();
1297 return __tmp;
1298 }
1299 };
1300
1301 /// local const_iterators
1302 template<typename _Key, typename _Value, typename _ExtractKey,
1303 typename _Hash, typename _RangeHash, typename _Unused,
1304 bool __constant_iterators, bool __cache>
1305 struct _Local_const_iterator
1306 : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1307 _Hash, _RangeHash, _Unused, __cache>
1308 {
1309 private:
1310 using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1311 _Hash, _RangeHash, _Unused, __cache>;
1312 using __hash_code_base = typename __base_type::__hash_code_base;
1313
1314 public:
1315 using value_type = _Value;
1316 using pointer = const value_type*;
1317 using reference = const value_type&;
1318 using difference_type = ptrdiff_t;
1319 using iterator_category = forward_iterator_tag;
1320
1321 _Local_const_iterator() = default;
1322
1323 _Local_const_iterator(const __hash_code_base& __base,
1324 _Hash_node<_Value, __cache>* __n,
1325 size_t __bkt, size_t __bkt_count)
1326 : __base_type(__base, __n, __bkt, __bkt_count)
1327 { }
1328
1329 _Local_const_iterator(const _Local_iterator<_Key, _Value, _ExtractKey,
1330 _Hash, _RangeHash, _Unused,
1331 __constant_iterators,
1332 __cache>& __x)
1333 : __base_type(__x)
1334 { }
1335
1336 reference
1337 operator*() const
1338 { return this->_M_cur->_M_v(); }
1339
1340 pointer
1341 operator->() const
1342 { return this->_M_cur->_M_valptr(); }
1343
1344 _Local_const_iterator&
1345 operator++()
1346 {
1347 this->_M_incr();
1348 return *this;
1349 }
1350
1351 _Local_const_iterator
1352 operator++(int)
1353 {
1354 _Local_const_iterator __tmp(*this);
1355 this->_M_incr();
1356 return __tmp;
1357 }
1358 };
1359
1360 /**
1361 * Primary class template _Hashtable_base.
1362 *
1363 * Helper class adding management of _Equal functor to
1364 * _Hash_code_base type.
1365 *
1366 * Base class templates are:
1367 * - __detail::_Hash_code_base
1368 */
1369 template<typename _Key, typename _Value, typename _ExtractKey,
1370 typename _Equal, typename _Hash, typename _RangeHash,
1371 typename _Unused, typename _Traits>
1372 struct _Hashtable_base
1373 : public _Hash_code_base<_Key, _Value, _ExtractKey, _Hash, _RangeHash,
1374 _Unused, _Traits::__hash_cached::value>
1375 {
1376 public:
1377 using key_type = _Key;
1378 using value_type = _Value;
1379 using key_equal = _Equal;
1380 using size_type = size_t;
1381 using difference_type = ptrdiff_t;
1382
1383 using __traits_type = _Traits;
1384 using __hash_cached = typename __traits_type::__hash_cached;
1385
1386 using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1387 _Hash, _RangeHash, _Unused,
1388 __hash_cached::value>;
1389
1390 using __hash_code = typename __hash_code_base::__hash_code;
1391
1392 protected:
1393 [[__no_unique_address__]] _Hashtable_ebo_helper<_Equal> _M_equal{};
1394
1395 _Hashtable_base() = default;
1396
1397 _Hashtable_base(const _Hash& __hash, const _Equal& __eq)
1398 : __hash_code_base(__hash), _M_equal{__eq}
1399 { }
1400
1401 bool
1402 _M_key_equals(const _Key& __k,
1403 const _Hash_node_value<_Value,
1404 __hash_cached::value>& __n) const
1405 {
1406 static_assert(__is_invocable<const _Equal&, const _Key&, const _Key&>{},
1407 "key equality predicate must be invocable with two arguments of "
1408 "key type");
1409 return _M_eq()(__k, _ExtractKey{}(__n._M_v()));
1410 }
1411
1412 template<typename _Kt>
1413 bool
1414 _M_key_equals_tr(const _Kt& __k,
1415 const _Hash_node_value<_Value,
1416 __hash_cached::value>& __n) const
1417 {
1418 static_assert(
1419 __is_invocable<const _Equal&, const _Kt&, const _Key&>{},
1420 "key equality predicate must be invocable with the argument type "
1421 "and the key type");
1422 return _M_eq()(__k, _ExtractKey{}(__n._M_v()));
1423 }
1424
1425#pragma GCC diagnostic push
1426#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
1427 bool
1428 _M_equals(const _Key& __k, __hash_code __c,
1429 const _Hash_node_value<_Value, __hash_cached::value>& __n) const
1430 {
1431 if constexpr (__hash_cached::value)
1432 if (__c != __n._M_hash_code)
1433 return false;
1434
1435 return _M_key_equals(__k, __n);
1436 }
1437
1438 template<typename _Kt>
1439 bool
1440 _M_equals_tr(const _Kt& __k, __hash_code __c,
1441 const _Hash_node_value<_Value,
1442 __hash_cached::value>& __n) const
1443 {
1444 if constexpr (__hash_cached::value)
1445 if (__c != __n._M_hash_code)
1446 return false;
1447
1448 return _M_key_equals_tr(__k, __n);
1449 }
1450
1451 bool
1452 _M_node_equals(
1453 const _Hash_node_value<_Value, __hash_cached::value>& __lhn,
1454 const _Hash_node_value<_Value, __hash_cached::value>& __rhn) const
1455 {
1456 if constexpr (__hash_cached::value)
1457 if (__lhn._M_hash_code != __rhn._M_hash_code)
1458 return false;
1459
1460 return _M_key_equals(k: _ExtractKey{}(__lhn._M_v()), n: __rhn);
1461 }
1462#pragma GCC diagnostic pop
1463
1464 const _Equal&
1465 _M_eq() const noexcept { return _M_equal._M_obj; }
1466 };
1467
1468 /**
1469 * This type deals with all allocation and keeps an allocator instance.
1470 */
1471 template<typename _NodeAlloc>
1472 struct _Hashtable_alloc
1473 {
1474 private:
1475 [[__no_unique_address__]] _Hashtable_ebo_helper<_NodeAlloc> _M_alloc{};
1476
1477 template<typename>
1478 struct __get_value_type;
1479 template<typename _Val, bool _Cache_hash_code>
1480 struct __get_value_type<_Hash_node<_Val, _Cache_hash_code>>
1481 { using type = _Val; };
1482
1483 public:
1484 using __node_type = typename _NodeAlloc::value_type;
1485 using __node_alloc_type = _NodeAlloc;
1486 // Use __gnu_cxx to benefit from _S_always_equal and al.
1487 using __node_alloc_traits = __gnu_cxx::__alloc_traits<__node_alloc_type>;
1488
1489 using __value_alloc_traits = typename __node_alloc_traits::template
1490 rebind_traits<typename __get_value_type<__node_type>::type>;
1491
1492 using __node_ptr = __node_type*;
1493 using __node_base = _Hash_node_base;
1494 using __node_base_ptr = __node_base*;
1495 using __buckets_alloc_type =
1496 __alloc_rebind<__node_alloc_type, __node_base_ptr>;
1497 using __buckets_alloc_traits = std::allocator_traits<__buckets_alloc_type>;
1498 using __buckets_ptr = __node_base_ptr*;
1499
1500 _Hashtable_alloc() = default;
1501 _Hashtable_alloc(const _Hashtable_alloc&) = default;
1502 _Hashtable_alloc(_Hashtable_alloc&&) = default;
1503
1504 template<typename _Alloc>
1505 _Hashtable_alloc(_Alloc&& __a)
1506 : _M_alloc{std::forward<_Alloc>(__a)}
1507 { }
1508
1509 __node_alloc_type&
1510 _M_node_allocator()
1511 { return _M_alloc._M_obj; }
1512
1513 const __node_alloc_type&
1514 _M_node_allocator() const
1515 { return _M_alloc._M_obj; }
1516
1517 // Allocate a node and construct an element within it.
1518 template<typename... _Args>
1519 __node_ptr
1520 _M_allocate_node(_Args&&... __args);
1521
1522 // Destroy the element within a node and deallocate the node.
1523 void
1524 _M_deallocate_node(__node_ptr __n);
1525
1526 // Deallocate a node.
1527 void
1528 _M_deallocate_node_ptr(__node_ptr __n);
1529
1530 // Deallocate the linked list of nodes pointed to by __n.
1531 // The elements within the nodes are destroyed.
1532 void
1533 _M_deallocate_nodes(__node_ptr __n);
1534
1535 __buckets_ptr
1536 _M_allocate_buckets(size_t __bkt_count);
1537
1538 void
1539 _M_deallocate_buckets(__buckets_ptr, size_t __bkt_count);
1540 };
1541
1542 // Definitions of class template _Hashtable_alloc's out-of-line member
1543 // functions.
1544 template<typename _NodeAlloc>
1545 template<typename... _Args>
1546 auto
1547 _Hashtable_alloc<_NodeAlloc>::_M_allocate_node(_Args&&... __args)
1548 -> __node_ptr
1549 {
1550 auto& __alloc = _M_node_allocator();
1551 auto __nptr = __node_alloc_traits::allocate(__alloc, 1);
1552 __node_ptr __n = std::__to_address(__nptr);
1553 __try
1554 {
1555 ::new ((void*)__n) __node_type;
1556 __node_alloc_traits::construct(__alloc, __n->_M_valptr(),
1557 std::forward<_Args>(__args)...);
1558 return __n;
1559 }
1560 __catch(...)
1561 {
1562 __n->~__node_type();
1563 __node_alloc_traits::deallocate(__alloc, __nptr, 1);
1564 __throw_exception_again;
1565 }
1566 }
1567
1568 template<typename _NodeAlloc>
1569 void
1570 _Hashtable_alloc<_NodeAlloc>::_M_deallocate_node(__node_ptr __n)
1571 {
1572 __node_alloc_traits::destroy(_M_node_allocator(), __n->_M_valptr());
1573 _M_deallocate_node_ptr(__n);
1574 }
1575
1576 template<typename _NodeAlloc>
1577 void
1578 _Hashtable_alloc<_NodeAlloc>::_M_deallocate_node_ptr(__node_ptr __n)
1579 {
1580 using _Ptr = typename __node_alloc_traits::pointer;
1581 auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__n);
1582 __n->~__node_type();
1583 __node_alloc_traits::deallocate(_M_node_allocator(), __ptr, 1);
1584 }
1585
1586 template<typename _NodeAlloc>
1587 void
1588 _Hashtable_alloc<_NodeAlloc>::_M_deallocate_nodes(__node_ptr __n)
1589 {
1590 while (__n)
1591 {
1592 __node_ptr __tmp = __n;
1593 __n = __n->_M_next();
1594 _M_deallocate_node(n: __tmp);
1595 }
1596 }
1597
1598 template<typename _NodeAlloc>
1599 auto
1600 _Hashtable_alloc<_NodeAlloc>::_M_allocate_buckets(size_t __bkt_count)
1601 -> __buckets_ptr
1602 {
1603 __buckets_alloc_type __alloc(_M_node_allocator());
1604
1605 auto __ptr = __buckets_alloc_traits::allocate(__alloc, __bkt_count);
1606 __buckets_ptr __p = std::__to_address(__ptr);
1607 __builtin_memset(__p, 0, __bkt_count * sizeof(__node_base_ptr));
1608 return __p;
1609 }
1610
1611 template<typename _NodeAlloc>
1612 void
1613 _Hashtable_alloc<_NodeAlloc>::
1614 _M_deallocate_buckets(__buckets_ptr __bkts, size_t __bkt_count)
1615 {
1616 using _Ptr = typename __buckets_alloc_traits::pointer;
1617 auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__bkts);
1618 __buckets_alloc_type __alloc(_M_node_allocator());
1619 __buckets_alloc_traits::deallocate(__alloc, __ptr, __bkt_count);
1620 }
1621
1622 ///@} hashtable-detail
1623} // namespace __detail
1624/// @endcond
1625_GLIBCXX_END_NAMESPACE_VERSION
1626} // namespace std
1627
1628#endif // _HASHTABLE_POLICY_H
1629