summaryrefslogtreecommitdiff
path: root/absl/container/internal/btree_container.h
blob: a68ce445542226420d76e7b9eac92e2b37902bb8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
// Copyright 2018 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef ABSL_CONTAINER_INTERNAL_BTREE_CONTAINER_H_
#define ABSL_CONTAINER_INTERNAL_BTREE_CONTAINER_H_

#include <algorithm>
#include <initializer_list>
#include <iterator>
#include <utility>

#include "absl/base/attributes.h"
#include "absl/base/internal/throw_delegate.h"
#include "absl/container/internal/btree.h"  // IWYU pragma: export
#include "absl/container/internal/common.h"
#include "absl/memory/memory.h"
#include "absl/meta/type_traits.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace container_internal {

// A common base class for btree_set, btree_map, btree_multiset, and
// btree_multimap.
template <typename Tree>
class btree_container {
  using params_type = typename Tree::params_type;

 protected:
  // Alias used for heterogeneous lookup functions.
  // `key_arg<K>` evaluates to `K` when the functors are transparent and to
  // `key_type` otherwise. It permits template argument deduction on `K` for the
  // transparent case.
  template <class K>
  using key_arg =
      typename KeyArg<params_type::kIsKeyCompareTransparent>::template type<
          K, typename Tree::key_type>;

 public:
  using key_type = typename Tree::key_type;
  using value_type = typename Tree::value_type;
  using size_type = typename Tree::size_type;
  using difference_type = typename Tree::difference_type;
  using key_compare = typename Tree::original_key_compare;
  using value_compare = typename Tree::value_compare;
  using allocator_type = typename Tree::allocator_type;
  using reference = typename Tree::reference;
  using const_reference = typename Tree::const_reference;
  using pointer = typename Tree::pointer;
  using const_pointer = typename Tree::const_pointer;
  using iterator = typename Tree::iterator;
  using const_iterator = typename Tree::const_iterator;
  using reverse_iterator = typename Tree::reverse_iterator;
  using const_reverse_iterator = typename Tree::const_reverse_iterator;
  using node_type = typename Tree::node_handle_type;

  struct extract_and_get_next_return_type {
    node_type node;
    iterator next;
  };

  // Constructors/assignments.
  btree_container() : tree_(key_compare(), allocator_type()) {}
  explicit btree_container(const key_compare &comp,
                           const allocator_type &alloc = allocator_type())
      : tree_(comp, alloc) {}
  explicit btree_container(const allocator_type &alloc)
      : tree_(key_compare(), alloc) {}

  btree_container(const btree_container &other)
      : btree_container(other, absl::allocator_traits<allocator_type>::
                                   select_on_container_copy_construction(
                                       other.get_allocator())) {}
  btree_container(const btree_container &other, const allocator_type &alloc)
      : tree_(other.tree_, alloc) {}

  btree_container(btree_container &&other) noexcept(
      std::is_nothrow_move_constructible<Tree>::value) = default;
  btree_container(btree_container &&other, const allocator_type &alloc)
      : tree_(std::move(other.tree_), alloc) {}

  btree_container &operator=(const btree_container &other) = default;
  btree_container &operator=(btree_container &&other) noexcept(
      std::is_nothrow_move_assignable<Tree>::value) = default;

  // Iterator routines.
  iterator begin() ABSL_ATTRIBUTE_LIFETIME_BOUND { return tree_.begin(); }
  const_iterator begin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.begin();
  }
  const_iterator cbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.begin();
  }
  iterator end() ABSL_ATTRIBUTE_LIFETIME_BOUND { return tree_.end(); }
  const_iterator end() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.end();
  }
  const_iterator cend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.end();
  }
  reverse_iterator rbegin() ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.rbegin();
  }
  const_reverse_iterator rbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.rbegin();
  }
  const_reverse_iterator crbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.rbegin();
  }
  reverse_iterator rend() ABSL_ATTRIBUTE_LIFETIME_BOUND { return tree_.rend(); }
  const_reverse_iterator rend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.rend();
  }
  const_reverse_iterator crend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.rend();
  }

  // Lookup routines.
  template <typename K = key_type>
  size_type count(const key_arg<K> &key) const {
    auto equal_range = this->equal_range(key);
    return equal_range.second - equal_range.first;
  }
  template <typename K = key_type>
  iterator find(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.find(key);
  }
  template <typename K = key_type>
  const_iterator find(const key_arg<K> &key) const
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.find(key);
  }
  template <typename K = key_type>
  bool contains(const key_arg<K> &key) const {
    return find(key) != end();
  }
  template <typename K = key_type>
  iterator lower_bound(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.lower_bound(key);
  }
  template <typename K = key_type>
  const_iterator lower_bound(const key_arg<K> &key) const
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.lower_bound(key);
  }
  template <typename K = key_type>
  iterator upper_bound(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.upper_bound(key);
  }
  template <typename K = key_type>
  const_iterator upper_bound(const key_arg<K> &key) const
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.upper_bound(key);
  }
  template <typename K = key_type>
  std::pair<iterator, iterator> equal_range(const key_arg<K> &key)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.equal_range(key);
  }
  template <typename K = key_type>
  std::pair<const_iterator, const_iterator> equal_range(
      const key_arg<K> &key) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.equal_range(key);
  }

  // Deletion routines. Note that there is also a deletion routine that is
  // specific to btree_set_container/btree_multiset_container.

  // Erase the specified iterator from the btree. The iterator must be valid
  // (i.e. not equal to end()).  Return an iterator pointing to the node after
  // the one that was erased (or end() if none exists).
  iterator erase(const_iterator iter) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.erase(iterator(iter));
  }
  iterator erase(iterator iter) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.erase(iter);
  }
  iterator erase(const_iterator first,
                 const_iterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return tree_.erase_range(iterator(first), iterator(last)).second;
  }
  template <typename K = key_type>
  size_type erase(const key_arg<K> &key) {
    auto equal_range = this->equal_range(key);
    return tree_.erase_range(equal_range.first, equal_range.second).first;
  }

  // Extract routines.
  extract_and_get_next_return_type extract_and_get_next(const_iterator position)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    // Use Construct instead of Transfer because the rebalancing code will
    // destroy the slot later.
    // Note: we rely on erase() taking place after Construct().
    return {CommonAccess::Construct<node_type>(get_allocator(),
                                               iterator(position).slot()),
            erase(position)};
  }
  node_type extract(iterator position) {
    // Use Construct instead of Transfer because the rebalancing code will
    // destroy the slot later.
    auto node =
        CommonAccess::Construct<node_type>(get_allocator(), position.slot());
    erase(position);
    return node;
  }
  node_type extract(const_iterator position) {
    return extract(iterator(position));
  }

  // Utility routines.
  ABSL_ATTRIBUTE_REINITIALIZES void clear() { tree_.clear(); }
  void swap(btree_container &other) { tree_.swap(other.tree_); }
  void verify() const { tree_.verify(); }

  // Size routines.
  size_type size() const { return tree_.size(); }
  size_type max_size() const { return tree_.max_size(); }
  bool empty() const { return tree_.empty(); }

  friend bool operator==(const btree_container &x, const btree_container &y) {
    if (x.size() != y.size()) return false;
    return std::equal(x.begin(), x.end(), y.begin());
  }

  friend bool operator!=(const btree_container &x, const btree_container &y) {
    return !(x == y);
  }

  friend bool operator<(const btree_container &x, const btree_container &y) {
    return std::lexicographical_compare(x.begin(), x.end(), y.begin(), y.end());
  }

  friend bool operator>(const btree_container &x, const btree_container &y) {
    return y < x;
  }

  friend bool operator<=(const btree_container &x, const btree_container &y) {
    return !(y < x);
  }

  friend bool operator>=(const btree_container &x, const btree_container &y) {
    return !(x < y);
  }

  // The allocator used by the btree.
  allocator_type get_allocator() const { return tree_.get_allocator(); }

  // The key comparator used by the btree.
  key_compare key_comp() const { return key_compare(tree_.key_comp()); }
  value_compare value_comp() const { return tree_.value_comp(); }

  // Support absl::Hash.
  template <typename State>
  friend State AbslHashValue(State h, const btree_container &b) {
    for (const auto &v : b) {
      h = State::combine(std::move(h), v);
    }
    return State::combine(std::move(h), b.size());
  }

 protected:
  friend struct btree_access;
  Tree tree_;
};

// A common base class for btree_set and btree_map.
template <typename Tree>
class btree_set_container : public btree_container<Tree> {
  using super_type = btree_container<Tree>;
  using params_type = typename Tree::params_type;
  using init_type = typename params_type::init_type;
  using is_key_compare_to = typename params_type::is_key_compare_to;
  friend class BtreeNodePeer;

 protected:
  template <class K>
  using key_arg = typename super_type::template key_arg<K>;

 public:
  using key_type = typename Tree::key_type;
  using value_type = typename Tree::value_type;
  using size_type = typename Tree::size_type;
  using key_compare = typename Tree::original_key_compare;
  using allocator_type = typename Tree::allocator_type;
  using iterator = typename Tree::iterator;
  using const_iterator = typename Tree::const_iterator;
  using node_type = typename super_type::node_type;
  using insert_return_type = InsertReturnType<iterator, node_type>;

  // Inherit constructors.
  using super_type::super_type;
  btree_set_container() {}

  // Range constructors.
  template <class InputIterator>
  btree_set_container(InputIterator b, InputIterator e,
                      const key_compare &comp = key_compare(),
                      const allocator_type &alloc = allocator_type())
      : super_type(comp, alloc) {
    insert(b, e);
  }
  template <class InputIterator>
  btree_set_container(InputIterator b, InputIterator e,
                      const allocator_type &alloc)
      : btree_set_container(b, e, key_compare(), alloc) {}

  // Initializer list constructors.
  btree_set_container(std::initializer_list<init_type> init,
                      const key_compare &comp = key_compare(),
                      const allocator_type &alloc = allocator_type())
      : btree_set_container(init.begin(), init.end(), comp, alloc) {}
  btree_set_container(std::initializer_list<init_type> init,
                      const allocator_type &alloc)
      : btree_set_container(init.begin(), init.end(), alloc) {}

  // Insertion routines.
  std::pair<iterator, bool> insert(const value_type &v)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_.insert_unique(params_type::key(v), v);
  }
  std::pair<iterator, bool> insert(value_type &&v)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_.insert_unique(params_type::key(v), std::move(v));
  }
  template <typename... Args>
  std::pair<iterator, bool> emplace(Args &&...args)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    // Use a node handle to manage a temp slot.
    auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                   std::forward<Args>(args)...);
    auto *slot = CommonAccess::GetSlot(node);
    return this->tree_.insert_unique(params_type::key(slot), slot);
  }
  iterator insert(const_iterator hint,
                  const value_type &v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_
        .insert_hint_unique(iterator(hint), params_type::key(v), v)
        .first;
  }
  iterator insert(const_iterator hint,
                  value_type &&v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_
        .insert_hint_unique(iterator(hint), params_type::key(v), std::move(v))
        .first;
  }
  template <typename... Args>
  iterator emplace_hint(const_iterator hint,
                        Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    // Use a node handle to manage a temp slot.
    auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                   std::forward<Args>(args)...);
    auto *slot = CommonAccess::GetSlot(node);
    return this->tree_
        .insert_hint_unique(iterator(hint), params_type::key(slot), slot)
        .first;
  }
  template <typename InputIterator>
  void insert(InputIterator b, InputIterator e) {
    this->tree_.insert_iterator_unique(b, e, 0);
  }
  void insert(std::initializer_list<init_type> init) {
    this->tree_.insert_iterator_unique(init.begin(), init.end(), 0);
  }
  insert_return_type insert(node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    if (!node) return {this->end(), false, node_type()};
    std::pair<iterator, bool> res =
        this->tree_.insert_unique(params_type::key(CommonAccess::GetSlot(node)),
                                  CommonAccess::GetSlot(node));
    if (res.second) {
      CommonAccess::Destroy(&node);
      return {res.first, true, node_type()};
    } else {
      return {res.first, false, std::move(node)};
    }
  }
  iterator insert(const_iterator hint,
                  node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    if (!node) return this->end();
    std::pair<iterator, bool> res = this->tree_.insert_hint_unique(
        iterator(hint), params_type::key(CommonAccess::GetSlot(node)),
        CommonAccess::GetSlot(node));
    if (res.second) CommonAccess::Destroy(&node);
    return res.first;
  }

  // Node extraction routines.
  template <typename K = key_type>
  node_type extract(const key_arg<K> &key) {
    const std::pair<iterator, bool> lower_and_equal =
        this->tree_.lower_bound_equal(key);
    return lower_and_equal.second ? extract(lower_and_equal.first)
                                  : node_type();
  }
  using super_type::extract;

  // Merge routines.
  // Moves elements from `src` into `this`. If the element already exists in
  // `this`, it is left unmodified in `src`.
  template <
      typename T,
      typename absl::enable_if_t<
          absl::conjunction<
              std::is_same<value_type, typename T::value_type>,
              std::is_same<allocator_type, typename T::allocator_type>,
              std::is_same<typename params_type::is_map_container,
                           typename T::params_type::is_map_container>>::value,
          int> = 0>
  void merge(btree_container<T> &src) {  // NOLINT
    for (auto src_it = src.begin(); src_it != src.end();) {
      if (insert(std::move(params_type::element(src_it.slot()))).second) {
        src_it = src.erase(src_it);
      } else {
        ++src_it;
      }
    }
  }

  template <
      typename T,
      typename absl::enable_if_t<
          absl::conjunction<
              std::is_same<value_type, typename T::value_type>,
              std::is_same<allocator_type, typename T::allocator_type>,
              std::is_same<typename params_type::is_map_container,
                           typename T::params_type::is_map_container>>::value,
          int> = 0>
  void merge(btree_container<T> &&src) {
    merge(src);
  }
};

// Base class for btree_map.
template <typename Tree>
class btree_map_container : public btree_set_container<Tree> {
  using super_type = btree_set_container<Tree>;
  using params_type = typename Tree::params_type;
  friend class BtreeNodePeer;

 private:
  template <class K>
  using key_arg = typename super_type::template key_arg<K>;

 public:
  using key_type = typename Tree::key_type;
  using mapped_type = typename params_type::mapped_type;
  using value_type = typename Tree::value_type;
  using key_compare = typename Tree::original_key_compare;
  using allocator_type = typename Tree::allocator_type;
  using iterator = typename Tree::iterator;
  using const_iterator = typename Tree::const_iterator;

  // Inherit constructors.
  using super_type::super_type;
  btree_map_container() {}

  // Insertion routines.
  // Note: the nullptr template arguments and extra `const M&` overloads allow
  // for supporting bitfield arguments.
  template <typename K = key_type, class M>
  std::pair<iterator, bool> insert_or_assign(const key_arg<K> &k, const M &obj)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_impl(k, obj);
  }
  template <typename K = key_type, class M, K * = nullptr>
  std::pair<iterator, bool> insert_or_assign(key_arg<K> &&k, const M &obj)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_impl(std::forward<K>(k), obj);
  }
  template <typename K = key_type, class M, M * = nullptr>
  std::pair<iterator, bool> insert_or_assign(const key_arg<K> &k, M &&obj)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_impl(k, std::forward<M>(obj));
  }
  template <typename K = key_type, class M, K * = nullptr, M * = nullptr>
  std::pair<iterator, bool> insert_or_assign(key_arg<K> &&k, M &&obj)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_impl(std::forward<K>(k), std::forward<M>(obj));
  }
  template <typename K = key_type, class M>
  iterator insert_or_assign(const_iterator hint, const key_arg<K> &k,
                            const M &obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_hint_impl(hint, k, obj);
  }
  template <typename K = key_type, class M, K * = nullptr>
  iterator insert_or_assign(const_iterator hint, key_arg<K> &&k,
                            const M &obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_hint_impl(hint, std::forward<K>(k), obj);
  }
  template <typename K = key_type, class M, M * = nullptr>
  iterator insert_or_assign(const_iterator hint, const key_arg<K> &k,
                            M &&obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_hint_impl(hint, k, std::forward<M>(obj));
  }
  template <typename K = key_type, class M, K * = nullptr, M * = nullptr>
  iterator insert_or_assign(const_iterator hint, key_arg<K> &&k,
                            M &&obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return insert_or_assign_hint_impl(hint, std::forward<K>(k),
                                      std::forward<M>(obj));
  }

  template <typename K = key_type, typename... Args,
            typename absl::enable_if_t<
                !std::is_convertible<K, const_iterator>::value, int> = 0>
  std::pair<iterator, bool> try_emplace(const key_arg<K> &k, Args &&...args)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return try_emplace_impl(k, std::forward<Args>(args)...);
  }
  template <typename K = key_type, typename... Args,
            typename absl::enable_if_t<
                !std::is_convertible<K, const_iterator>::value, int> = 0>
  std::pair<iterator, bool> try_emplace(key_arg<K> &&k, Args &&...args)
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return try_emplace_impl(std::forward<K>(k), std::forward<Args>(args)...);
  }
  template <typename K = key_type, typename... Args>
  iterator try_emplace(const_iterator hint, const key_arg<K> &k,
                       Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return try_emplace_hint_impl(hint, k, std::forward<Args>(args)...);
  }
  template <typename K = key_type, typename... Args>
  iterator try_emplace(const_iterator hint, key_arg<K> &&k,
                       Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return try_emplace_hint_impl(hint, std::forward<K>(k),
                                 std::forward<Args>(args)...);
  }

  template <typename K = key_type>
  mapped_type &operator[](const key_arg<K> &k) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return try_emplace(k).first->second;
  }
  template <typename K = key_type>
  mapped_type &operator[](key_arg<K> &&k) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return try_emplace(std::forward<K>(k)).first->second;
  }

  template <typename K = key_type>
  mapped_type &at(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    auto it = this->find(key);
    if (it == this->end())
      base_internal::ThrowStdOutOfRange("absl::btree_map::at");
    return it->second;
  }
  template <typename K = key_type>
  const mapped_type &at(const key_arg<K> &key) const
      ABSL_ATTRIBUTE_LIFETIME_BOUND {
    auto it = this->find(key);
    if (it == this->end())
      base_internal::ThrowStdOutOfRange("absl::btree_map::at");
    return it->second;
  }

 private:
  // Note: when we call `std::forward<M>(obj)` twice, it's safe because
  // insert_unique/insert_hint_unique are guaranteed to not consume `obj` when
  // `ret.second` is false.
  template <class K, class M>
  std::pair<iterator, bool> insert_or_assign_impl(K &&k, M &&obj) {
    const std::pair<iterator, bool> ret =
        this->tree_.insert_unique(k, std::forward<K>(k), std::forward<M>(obj));
    if (!ret.second) ret.first->second = std::forward<M>(obj);
    return ret;
  }
  template <class K, class M>
  iterator insert_or_assign_hint_impl(const_iterator hint, K &&k, M &&obj) {
    const std::pair<iterator, bool> ret = this->tree_.insert_hint_unique(
        iterator(hint), k, std::forward<K>(k), std::forward<M>(obj));
    if (!ret.second) ret.first->second = std::forward<M>(obj);
    return ret.first;
  }

  template <class K, class... Args>
  std::pair<iterator, bool> try_emplace_impl(K &&k, Args &&... args) {
    return this->tree_.insert_unique(
        k, std::piecewise_construct, std::forward_as_tuple(std::forward<K>(k)),
        std::forward_as_tuple(std::forward<Args>(args)...));
  }
  template <class K, class... Args>
  iterator try_emplace_hint_impl(const_iterator hint, K &&k, Args &&... args) {
    return this->tree_
        .insert_hint_unique(iterator(hint), k, std::piecewise_construct,
                            std::forward_as_tuple(std::forward<K>(k)),
                            std::forward_as_tuple(std::forward<Args>(args)...))
        .first;
  }
};

// A common base class for btree_multiset and btree_multimap.
template <typename Tree>
class btree_multiset_container : public btree_container<Tree> {
  using super_type = btree_container<Tree>;
  using params_type = typename Tree::params_type;
  using init_type = typename params_type::init_type;
  using is_key_compare_to = typename params_type::is_key_compare_to;
  friend class BtreeNodePeer;

  template <class K>
  using key_arg = typename super_type::template key_arg<K>;

 public:
  using key_type = typename Tree::key_type;
  using value_type = typename Tree::value_type;
  using size_type = typename Tree::size_type;
  using key_compare = typename Tree::original_key_compare;
  using allocator_type = typename Tree::allocator_type;
  using iterator = typename Tree::iterator;
  using const_iterator = typename Tree::const_iterator;
  using node_type = typename super_type::node_type;

  // Inherit constructors.
  using super_type::super_type;
  btree_multiset_container() {}

  // Range constructors.
  template <class InputIterator>
  btree_multiset_container(InputIterator b, InputIterator e,
                           const key_compare &comp = key_compare(),
                           const allocator_type &alloc = allocator_type())
      : super_type(comp, alloc) {
    insert(b, e);
  }
  template <class InputIterator>
  btree_multiset_container(InputIterator b, InputIterator e,
                           const allocator_type &alloc)
      : btree_multiset_container(b, e, key_compare(), alloc) {}

  // Initializer list constructors.
  btree_multiset_container(std::initializer_list<init_type> init,
                           const key_compare &comp = key_compare(),
                           const allocator_type &alloc = allocator_type())
      : btree_multiset_container(init.begin(), init.end(), comp, alloc) {}
  btree_multiset_container(std::initializer_list<init_type> init,
                           const allocator_type &alloc)
      : btree_multiset_container(init.begin(), init.end(), alloc) {}

  // Insertion routines.
  iterator insert(const value_type &v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_.insert_multi(v);
  }
  iterator insert(value_type &&v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_.insert_multi(std::move(v));
  }
  iterator insert(const_iterator hint,
                  const value_type &v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_.insert_hint_multi(iterator(hint), v);
  }
  iterator insert(const_iterator hint,
                  value_type &&v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    return this->tree_.insert_hint_multi(iterator(hint), std::move(v));
  }
  template <typename InputIterator>
  void insert(InputIterator b, InputIterator e) {
    this->tree_.insert_iterator_multi(b, e);
  }
  void insert(std::initializer_list<init_type> init) {
    this->tree_.insert_iterator_multi(init.begin(), init.end());
  }
  template <typename... Args>
  iterator emplace(Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    // Use a node handle to manage a temp slot.
    auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                   std::forward<Args>(args)...);
    return this->tree_.insert_multi(CommonAccess::GetSlot(node));
  }
  template <typename... Args>
  iterator emplace_hint(const_iterator hint,
                        Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    // Use a node handle to manage a temp slot.
    auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                   std::forward<Args>(args)...);
    return this->tree_.insert_hint_multi(iterator(hint),
                                         CommonAccess::GetSlot(node));
  }
  iterator insert(node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    if (!node) return this->end();
    iterator res =
        this->tree_.insert_multi(params_type::key(CommonAccess::GetSlot(node)),
                                 CommonAccess::GetSlot(node));
    CommonAccess::Destroy(&node);
    return res;
  }
  iterator insert(const_iterator hint,
                  node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
    if (!node) return this->end();
    iterator res = this->tree_.insert_hint_multi(
        iterator(hint),
        std::move(params_type::element(CommonAccess::GetSlot(node))));
    CommonAccess::Destroy(&node);
    return res;
  }

  // Node extraction routines.
  template <typename K = key_type>
  node_type extract(const key_arg<K> &key) {
    const std::pair<iterator, bool> lower_and_equal =
        this->tree_.lower_bound_equal(key);
    return lower_and_equal.second ? extract(lower_and_equal.first)
                                  : node_type();
  }
  using super_type::extract;

  // Merge routines.
  // Moves all elements from `src` into `this`.
  template <
      typename T,
      typename absl::enable_if_t<
          absl::conjunction<
              std::is_same<value_type, typename T::value_type>,
              std::is_same<allocator_type, typename T::allocator_type>,
              std::is_same<typename params_type::is_map_container,
                           typename T::params_type::is_map_container>>::value,
          int> = 0>
  void merge(btree_container<T> &src) {  // NOLINT
    for (auto src_it = src.begin(), end = src.end(); src_it != end; ++src_it) {
      insert(std::move(params_type::element(src_it.slot())));
    }
    src.clear();
  }

  template <
      typename T,
      typename absl::enable_if_t<
          absl::conjunction<
              std::is_same<value_type, typename T::value_type>,
              std::is_same<allocator_type, typename T::allocator_type>,
              std::is_same<typename params_type::is_map_container,
                           typename T::params_type::is_map_container>>::value,
          int> = 0>
  void merge(btree_container<T> &&src) {
    merge(src);
  }
};

// A base class for btree_multimap.
template <typename Tree>
class btree_multimap_container : public btree_multiset_container<Tree> {
  using super_type = btree_multiset_container<Tree>;
  using params_type = typename Tree::params_type;
  friend class BtreeNodePeer;

 public:
  using mapped_type = typename params_type::mapped_type;

  // Inherit constructors.
  using super_type::super_type;
  btree_multimap_container() {}
};

}  // namespace container_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_CONTAINER_INTERNAL_BTREE_CONTAINER_H_