summaryrefslogtreecommitdiff
path: root/absl/container/inlined_vector.h
blob: 5f6f6154bf6443792b897df0f9333655e10544a7 (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
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
// Copyright 2019 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.
//
// -----------------------------------------------------------------------------
// File: inlined_vector.h
// -----------------------------------------------------------------------------
//
// This header file contains the declaration and definition of an "inlined
// vector" which behaves in an equivalent fashion to a `std::vector`, except
// that storage for small sequences of the vector are provided inline without
// requiring any heap allocation.
//
// An `absl::InlinedVector<T, N>` specifies the default capacity `N` as one of
// its template parameters. Instances where `size() <= N` hold contained
// elements in inline space. Typically `N` is very small so that sequences that
// are expected to be short do not require allocations.
//
// An `absl::InlinedVector` does not usually require a specific allocator. If
// the inlined vector grows beyond its initial constraints, it will need to
// allocate (as any normal `std::vector` would). This is usually performed with
// the default allocator (defined as `std::allocator<T>`). Optionally, a custom
// allocator type may be specified as `A` in `absl::InlinedVector<T, N, A>`.

#ifndef ABSL_CONTAINER_INLINED_VECTOR_H_
#define ABSL_CONTAINER_INLINED_VECTOR_H_

#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <initializer_list>
#include <iterator>
#include <memory>
#include <type_traits>
#include <utility>

#include "absl/algorithm/algorithm.h"
#include "absl/base/internal/throw_delegate.h"
#include "absl/base/macros.h"
#include "absl/base/optimization.h"
#include "absl/base/port.h"
#include "absl/container/internal/inlined_vector.h"
#include "absl/memory/memory.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
// -----------------------------------------------------------------------------
// InlinedVector
// -----------------------------------------------------------------------------
//
// An `absl::InlinedVector` is designed to be a drop-in replacement for
// `std::vector` for use cases where the vector's size is sufficiently small
// that it can be inlined. If the inlined vector does grow beyond its estimated
// capacity, it will trigger an initial allocation on the heap, and will behave
// as a `std:vector`. The API of the `absl::InlinedVector` within this file is
// designed to cover the same API footprint as covered by `std::vector`.
template <typename T, size_t N, typename A = std::allocator<T>>
class InlinedVector {
  static_assert(N > 0, "`absl::InlinedVector` requires an inlined capacity.");

  using Storage = inlined_vector_internal::Storage<T, N, A>;

  using AllocatorTraits = typename Storage::AllocatorTraits;
  using RValueReference = typename Storage::RValueReference;
  using MoveIterator = typename Storage::MoveIterator;
  using IsMemcpyOk = typename Storage::IsMemcpyOk;

  template <typename Iterator>
  using IteratorValueAdapter =
      typename Storage::template IteratorValueAdapter<Iterator>;
  using CopyValueAdapter = typename Storage::CopyValueAdapter;
  using DefaultValueAdapter = typename Storage::DefaultValueAdapter;

  template <typename Iterator>
  using EnableIfAtLeastForwardIterator = absl::enable_if_t<
      inlined_vector_internal::IsAtLeastForwardIterator<Iterator>::value>;
  template <typename Iterator>
  using DisableIfAtLeastForwardIterator = absl::enable_if_t<
      !inlined_vector_internal::IsAtLeastForwardIterator<Iterator>::value>;

 public:
  using allocator_type = typename Storage::allocator_type;
  using value_type = typename Storage::value_type;
  using pointer = typename Storage::pointer;
  using const_pointer = typename Storage::const_pointer;
  using size_type = typename Storage::size_type;
  using difference_type = typename Storage::difference_type;
  using reference = typename Storage::reference;
  using const_reference = typename Storage::const_reference;
  using iterator = typename Storage::iterator;
  using const_iterator = typename Storage::const_iterator;
  using reverse_iterator = typename Storage::reverse_iterator;
  using const_reverse_iterator = typename Storage::const_reverse_iterator;

  // ---------------------------------------------------------------------------
  // InlinedVector Constructors and Destructor
  // ---------------------------------------------------------------------------

  // Creates an empty inlined vector with a value-initialized allocator.
  InlinedVector() noexcept(noexcept(allocator_type())) : storage_() {}

  // Creates an empty inlined vector with a copy of `alloc`.
  explicit InlinedVector(const allocator_type& alloc) noexcept
      : storage_(alloc) {}

  // Creates an inlined vector with `n` copies of `value_type()`.
  explicit InlinedVector(size_type n,
                         const allocator_type& alloc = allocator_type())
      : storage_(alloc) {
    storage_.Initialize(DefaultValueAdapter(), n);
  }

  // Creates an inlined vector with `n` copies of `v`.
  InlinedVector(size_type n, const_reference v,
                const allocator_type& alloc = allocator_type())
      : storage_(alloc) {
    storage_.Initialize(CopyValueAdapter(v), n);
  }

  // Creates an inlined vector with copies of the elements of `list`.
  InlinedVector(std::initializer_list<value_type> list,
                const allocator_type& alloc = allocator_type())
      : InlinedVector(list.begin(), list.end(), alloc) {}

  // Creates an inlined vector with elements constructed from the provided
  // forward iterator range [`first`, `last`).
  //
  // NOTE: the `enable_if` prevents ambiguous interpretation between a call to
  // this constructor with two integral arguments and a call to the above
  // `InlinedVector(size_type, const_reference)` constructor.
  template <typename ForwardIterator,
            EnableIfAtLeastForwardIterator<ForwardIterator>* = nullptr>
  InlinedVector(ForwardIterator first, ForwardIterator last,
                const allocator_type& alloc = allocator_type())
      : storage_(alloc) {
    storage_.Initialize(IteratorValueAdapter<ForwardIterator>(first),
                        std::distance(first, last));
  }

  // Creates an inlined vector with elements constructed from the provided input
  // iterator range [`first`, `last`).
  template <typename InputIterator,
            DisableIfAtLeastForwardIterator<InputIterator>* = nullptr>
  InlinedVector(InputIterator first, InputIterator last,
                const allocator_type& alloc = allocator_type())
      : storage_(alloc) {
    std::copy(first, last, std::back_inserter(*this));
  }

  // Creates an inlined vector by copying the contents of `other` using
  // `other`'s allocator.
  InlinedVector(const InlinedVector& other)
      : InlinedVector(other, *other.storage_.GetAllocPtr()) {}

  // Creates an inlined vector by copying the contents of `other` using `alloc`.
  InlinedVector(const InlinedVector& other, const allocator_type& alloc)
      : storage_(alloc) {
    if (IsMemcpyOk::value && !other.storage_.GetIsAllocated()) {
      storage_.MemcpyFrom(other.storage_);
    } else {
      storage_.Initialize(IteratorValueAdapter<const_pointer>(other.data()),
                          other.size());
    }
  }

  // Creates an inlined vector by moving in the contents of `other` without
  // allocating. If `other` contains allocated memory, the newly-created inlined
  // vector will take ownership of that memory. However, if `other` does not
  // contain allocated memory, the newly-created inlined vector will perform
  // element-wise move construction of the contents of `other`.
  //
  // NOTE: since no allocation is performed for the inlined vector in either
  // case, the `noexcept(...)` specification depends on whether moving the
  // underlying objects can throw. It is assumed assumed that...
  //  a) move constructors should only throw due to allocation failure.
  //  b) if `value_type`'s move constructor allocates, it uses the same
  //     allocation function as the inlined vector's allocator.
  // Thus, the move constructor is non-throwing if the allocator is non-throwing
  // or `value_type`'s move constructor is specified as `noexcept`.
  InlinedVector(InlinedVector&& other) noexcept(
      absl::allocator_is_nothrow<allocator_type>::value ||
      std::is_nothrow_move_constructible<value_type>::value)
      : storage_(*other.storage_.GetAllocPtr()) {
    if (IsMemcpyOk::value) {
      storage_.MemcpyFrom(other.storage_);

      other.storage_.SetInlinedSize(0);
    } else if (other.storage_.GetIsAllocated()) {
      storage_.SetAllocatedData(other.storage_.GetAllocatedData(),
                                other.storage_.GetAllocatedCapacity());
      storage_.SetAllocatedSize(other.storage_.GetSize());

      other.storage_.SetInlinedSize(0);
    } else {
      IteratorValueAdapter<MoveIterator> other_values(
          MoveIterator(other.storage_.GetInlinedData()));

      inlined_vector_internal::ConstructElements(
          storage_.GetAllocPtr(), storage_.GetInlinedData(), &other_values,
          other.storage_.GetSize());

      storage_.SetInlinedSize(other.storage_.GetSize());
    }
  }

  // Creates an inlined vector by moving in the contents of `other` with a copy
  // of `alloc`.
  //
  // NOTE: if `other`'s allocator is not equal to `alloc`, even if `other`
  // contains allocated memory, this move constructor will still allocate. Since
  // allocation is performed, this constructor can only be `noexcept` if the
  // specified allocator is also `noexcept`.
  InlinedVector(InlinedVector&& other, const allocator_type& alloc) noexcept(
      absl::allocator_is_nothrow<allocator_type>::value)
      : storage_(alloc) {
    if (IsMemcpyOk::value) {
      storage_.MemcpyFrom(other.storage_);

      other.storage_.SetInlinedSize(0);
    } else if ((*storage_.GetAllocPtr() == *other.storage_.GetAllocPtr()) &&
               other.storage_.GetIsAllocated()) {
      storage_.SetAllocatedData(other.storage_.GetAllocatedData(),
                                other.storage_.GetAllocatedCapacity());
      storage_.SetAllocatedSize(other.storage_.GetSize());

      other.storage_.SetInlinedSize(0);
    } else {
      storage_.Initialize(
          IteratorValueAdapter<MoveIterator>(MoveIterator(other.data())),
          other.size());
    }
  }

  ~InlinedVector() {}

  // ---------------------------------------------------------------------------
  // InlinedVector Member Accessors
  // ---------------------------------------------------------------------------

  // `InlinedVector::empty()`
  //
  // Returns whether the inlined vector contains no elements.
  bool empty() const noexcept { return !size(); }

  // `InlinedVector::size()`
  //
  // Returns the number of elements in the inlined vector.
  size_type size() const noexcept { return storage_.GetSize(); }

  // `InlinedVector::max_size()`
  //
  // Returns the maximum number of elements the inlined vector can hold.
  size_type max_size() const noexcept {
    // One bit of the size storage is used to indicate whether the inlined
    // vector contains allocated memory. As a result, the maximum size that the
    // inlined vector can express is half of the max for `size_type`.
    return (std::numeric_limits<size_type>::max)() / 2;
  }

  // `InlinedVector::capacity()`
  //
  // Returns the number of elements that could be stored in the inlined vector
  // without requiring a reallocation.
  //
  // NOTE: for most inlined vectors, `capacity()` should be equal to the
  // template parameter `N`. For inlined vectors which exceed this capacity,
  // they will no longer be inlined and `capacity()` will equal the capactity of
  // the allocated memory.
  size_type capacity() const noexcept {
    return storage_.GetIsAllocated() ? storage_.GetAllocatedCapacity()
                                     : storage_.GetInlinedCapacity();
  }

  // `InlinedVector::data()`
  //
  // Returns a `pointer` to the elements of the inlined vector. This pointer
  // can be used to access and modify the contained elements.
  //
  // NOTE: only elements within [`data()`, `data() + size()`) are valid.
  pointer data() noexcept {
    return storage_.GetIsAllocated() ? storage_.GetAllocatedData()
                                     : storage_.GetInlinedData();
  }

  // Overload of `InlinedVector::data()` that returns a `const_pointer` to the
  // elements of the inlined vector. This pointer can be used to access but not
  // modify the contained elements.
  //
  // NOTE: only elements within [`data()`, `data() + size()`) are valid.
  const_pointer data() const noexcept {
    return storage_.GetIsAllocated() ? storage_.GetAllocatedData()
                                     : storage_.GetInlinedData();
  }

  // `InlinedVector::operator[](...)`
  //
  // Returns a `reference` to the `i`th element of the inlined vector.
  reference operator[](size_type i) {
    ABSL_HARDENING_ASSERT(i < size());
    return data()[i];
  }

  // Overload of `InlinedVector::operator[](...)` that returns a
  // `const_reference` to the `i`th element of the inlined vector.
  const_reference operator[](size_type i) const {
    ABSL_HARDENING_ASSERT(i < size());
    return data()[i];
  }

  // `InlinedVector::at(...)`
  //
  // Returns a `reference` to the `i`th element of the inlined vector.
  //
  // NOTE: if `i` is not within the required range of `InlinedVector::at(...)`,
  // in both debug and non-debug builds, `std::out_of_range` will be thrown.
  reference at(size_type i) {
    if (ABSL_PREDICT_FALSE(i >= size())) {
      base_internal::ThrowStdOutOfRange(
          "`InlinedVector::at(size_type)` failed bounds check");
    }
    return data()[i];
  }

  // Overload of `InlinedVector::at(...)` that returns a `const_reference` to
  // the `i`th element of the inlined vector.
  //
  // NOTE: if `i` is not within the required range of `InlinedVector::at(...)`,
  // in both debug and non-debug builds, `std::out_of_range` will be thrown.
  const_reference at(size_type i) const {
    if (ABSL_PREDICT_FALSE(i >= size())) {
      base_internal::ThrowStdOutOfRange(
          "`InlinedVector::at(size_type) const` failed bounds check");
    }
    return data()[i];
  }

  // `InlinedVector::front()`
  //
  // Returns a `reference` to the first element of the inlined vector.
  reference front() {
    ABSL_HARDENING_ASSERT(!empty());
    return at(0);
  }

  // Overload of `InlinedVector::front()` that returns a `const_reference` to
  // the first element of the inlined vector.
  const_reference front() const {
    ABSL_HARDENING_ASSERT(!empty());
    return at(0);
  }

  // `InlinedVector::back()`
  //
  // Returns a `reference` to the last element of the inlined vector.
  reference back() {
    ABSL_HARDENING_ASSERT(!empty());
    return at(size() - 1);
  }

  // Overload of `InlinedVector::back()` that returns a `const_reference` to the
  // last element of the inlined vector.
  const_reference back() const {
    ABSL_HARDENING_ASSERT(!empty());
    return at(size() - 1);
  }

  // `InlinedVector::begin()`
  //
  // Returns an `iterator` to the beginning of the inlined vector.
  iterator begin() noexcept { return data(); }

  // Overload of `InlinedVector::begin()` that returns a `const_iterator` to
  // the beginning of the inlined vector.
  const_iterator begin() const noexcept { return data(); }

  // `InlinedVector::end()`
  //
  // Returns an `iterator` to the end of the inlined vector.
  iterator end() noexcept { return data() + size(); }

  // Overload of `InlinedVector::end()` that returns a `const_iterator` to the
  // end of the inlined vector.
  const_iterator end() const noexcept { return data() + size(); }

  // `InlinedVector::cbegin()`
  //
  // Returns a `const_iterator` to the beginning of the inlined vector.
  const_iterator cbegin() const noexcept { return begin(); }

  // `InlinedVector::cend()`
  //
  // Returns a `const_iterator` to the end of the inlined vector.
  const_iterator cend() const noexcept { return end(); }

  // `InlinedVector::rbegin()`
  //
  // Returns a `reverse_iterator` from the end of the inlined vector.
  reverse_iterator rbegin() noexcept { return reverse_iterator(end()); }

  // Overload of `InlinedVector::rbegin()` that returns a
  // `const_reverse_iterator` from the end of the inlined vector.
  const_reverse_iterator rbegin() const noexcept {
    return const_reverse_iterator(end());
  }

  // `InlinedVector::rend()`
  //
  // Returns a `reverse_iterator` from the beginning of the inlined vector.
  reverse_iterator rend() noexcept { return reverse_iterator(begin()); }

  // Overload of `InlinedVector::rend()` that returns a `const_reverse_iterator`
  // from the beginning of the inlined vector.
  const_reverse_iterator rend() const noexcept {
    return const_reverse_iterator(begin());
  }

  // `InlinedVector::crbegin()`
  //
  // Returns a `const_reverse_iterator` from the end of the inlined vector.
  const_reverse_iterator crbegin() const noexcept { return rbegin(); }

  // `InlinedVector::crend()`
  //
  // Returns a `const_reverse_iterator` from the beginning of the inlined
  // vector.
  const_reverse_iterator crend() const noexcept { return rend(); }

  // `InlinedVector::get_allocator()`
  //
  // Returns a copy of the inlined vector's allocator.
  allocator_type get_allocator() const { return *storage_.GetAllocPtr(); }

  // ---------------------------------------------------------------------------
  // InlinedVector Member Mutators
  // ---------------------------------------------------------------------------

  // `InlinedVector::operator=(...)`
  //
  // Replaces the elements of the inlined vector with copies of the elements of
  // `list`.
  InlinedVector& operator=(std::initializer_list<value_type> list) {
    assign(list.begin(), list.end());

    return *this;
  }

  // Overload of `InlinedVector::operator=(...)` that replaces the elements of
  // the inlined vector with copies of the elements of `other`.
  InlinedVector& operator=(const InlinedVector& other) {
    if (ABSL_PREDICT_TRUE(this != std::addressof(other))) {
      const_pointer other_data = other.data();
      assign(other_data, other_data + other.size());
    }

    return *this;
  }

  // Overload of `InlinedVector::operator=(...)` that moves the elements of
  // `other` into the inlined vector.
  //
  // NOTE: as a result of calling this overload, `other` is left in a valid but
  // unspecified state.
  InlinedVector& operator=(InlinedVector&& other) {
    if (ABSL_PREDICT_TRUE(this != std::addressof(other))) {
      if (IsMemcpyOk::value || other.storage_.GetIsAllocated()) {
        inlined_vector_internal::DestroyElements(storage_.GetAllocPtr(), data(),
                                                 size());
        storage_.DeallocateIfAllocated();
        storage_.MemcpyFrom(other.storage_);

        other.storage_.SetInlinedSize(0);
      } else {
        storage_.Assign(IteratorValueAdapter<MoveIterator>(
                            MoveIterator(other.storage_.GetInlinedData())),
                        other.size());
      }
    }

    return *this;
  }

  // `InlinedVector::assign(...)`
  //
  // Replaces the contents of the inlined vector with `n` copies of `v`.
  void assign(size_type n, const_reference v) {
    storage_.Assign(CopyValueAdapter(v), n);
  }

  // Overload of `InlinedVector::assign(...)` that replaces the contents of the
  // inlined vector with copies of the elements of `list`.
  void assign(std::initializer_list<value_type> list) {
    assign(list.begin(), list.end());
  }

  // Overload of `InlinedVector::assign(...)` to replace the contents of the
  // inlined vector with the range [`first`, `last`).
  //
  // NOTE: this overload is for iterators that are "forward" category or better.
  template <typename ForwardIterator,
            EnableIfAtLeastForwardIterator<ForwardIterator>* = nullptr>
  void assign(ForwardIterator first, ForwardIterator last) {
    storage_.Assign(IteratorValueAdapter<ForwardIterator>(first),
                    std::distance(first, last));
  }

  // Overload of `InlinedVector::assign(...)` to replace the contents of the
  // inlined vector with the range [`first`, `last`).
  //
  // NOTE: this overload is for iterators that are "input" category.
  template <typename InputIterator,
            DisableIfAtLeastForwardIterator<InputIterator>* = nullptr>
  void assign(InputIterator first, InputIterator last) {
    size_type i = 0;
    for (; i < size() && first != last; ++i, static_cast<void>(++first)) {
      at(i) = *first;
    }

    erase(data() + i, data() + size());
    std::copy(first, last, std::back_inserter(*this));
  }

  // `InlinedVector::resize(...)`
  //
  // Resizes the inlined vector to contain `n` elements.
  //
  // NOTE: if `n` is smaller than `size()`, extra elements are destroyed. If `n`
  // is larger than `size()`, new elements are value-initialized.
  void resize(size_type n) { storage_.Resize(DefaultValueAdapter(), n); }

  // Overload of `InlinedVector::resize(...)` that resizes the inlined vector to
  // contain `n` elements.
  //
  // NOTE: if `n` is smaller than `size()`, extra elements are destroyed. If `n`
  // is larger than `size()`, new elements are copied-constructed from `v`.
  void resize(size_type n, const_reference v) {
    storage_.Resize(CopyValueAdapter(v), n);
  }

  // `InlinedVector::insert(...)`
  //
  // Inserts a copy of `v` at `pos`, returning an `iterator` to the newly
  // inserted element.
  iterator insert(const_iterator pos, const_reference v) {
    return emplace(pos, v);
  }

  // Overload of `InlinedVector::insert(...)` that inserts `v` at `pos` using
  // move semantics, returning an `iterator` to the newly inserted element.
  iterator insert(const_iterator pos, RValueReference v) {
    return emplace(pos, std::move(v));
  }

  // Overload of `InlinedVector::insert(...)` that inserts `n` contiguous copies
  // of `v` starting at `pos`, returning an `iterator` pointing to the first of
  // the newly inserted elements.
  iterator insert(const_iterator pos, size_type n, const_reference v) {
    ABSL_HARDENING_ASSERT(pos >= begin());
    ABSL_HARDENING_ASSERT(pos <= end());

    if (ABSL_PREDICT_TRUE(n != 0)) {
      value_type dealias = v;
      return storage_.Insert(pos, CopyValueAdapter(dealias), n);
    } else {
      return const_cast<iterator>(pos);
    }
  }

  // Overload of `InlinedVector::insert(...)` that inserts copies of the
  // elements of `list` starting at `pos`, returning an `iterator` pointing to
  // the first of the newly inserted elements.
  iterator insert(const_iterator pos, std::initializer_list<value_type> list) {
    return insert(pos, list.begin(), list.end());
  }

  // Overload of `InlinedVector::insert(...)` that inserts the range [`first`,
  // `last`) starting at `pos`, returning an `iterator` pointing to the first
  // of the newly inserted elements.
  //
  // NOTE: this overload is for iterators that are "forward" category or better.
  template <typename ForwardIterator,
            EnableIfAtLeastForwardIterator<ForwardIterator>* = nullptr>
  iterator insert(const_iterator pos, ForwardIterator first,
                  ForwardIterator last) {
    ABSL_HARDENING_ASSERT(pos >= begin());
    ABSL_HARDENING_ASSERT(pos <= end());

    if (ABSL_PREDICT_TRUE(first != last)) {
      return storage_.Insert(pos, IteratorValueAdapter<ForwardIterator>(first),
                             std::distance(first, last));
    } else {
      return const_cast<iterator>(pos);
    }
  }

  // Overload of `InlinedVector::insert(...)` that inserts the range [`first`,
  // `last`) starting at `pos`, returning an `iterator` pointing to the first
  // of the newly inserted elements.
  //
  // NOTE: this overload is for iterators that are "input" category.
  template <typename InputIterator,
            DisableIfAtLeastForwardIterator<InputIterator>* = nullptr>
  iterator insert(const_iterator pos, InputIterator first, InputIterator last) {
    ABSL_HARDENING_ASSERT(pos >= begin());
    ABSL_HARDENING_ASSERT(pos <= end());

    size_type index = std::distance(cbegin(), pos);
    for (size_type i = index; first != last; ++i, static_cast<void>(++first)) {
      insert(data() + i, *first);
    }

    return iterator(data() + index);
  }

  // `InlinedVector::emplace(...)`
  //
  // Constructs and inserts an element using `args...` in the inlined vector at
  // `pos`, returning an `iterator` pointing to the newly emplaced element.
  template <typename... Args>
  iterator emplace(const_iterator pos, Args&&... args) {
    ABSL_HARDENING_ASSERT(pos >= begin());
    ABSL_HARDENING_ASSERT(pos <= end());

    value_type dealias(std::forward<Args>(args)...);
    return storage_.Insert(pos,
                           IteratorValueAdapter<MoveIterator>(
                               MoveIterator(std::addressof(dealias))),
                           1);
  }

  // `InlinedVector::emplace_back(...)`
  //
  // Constructs and inserts an element using `args...` in the inlined vector at
  // `end()`, returning a `reference` to the newly emplaced element.
  template <typename... Args>
  reference emplace_back(Args&&... args) {
    return storage_.EmplaceBack(std::forward<Args>(args)...);
  }

  // `InlinedVector::push_back(...)`
  //
  // Inserts a copy of `v` in the inlined vector at `end()`.
  void push_back(const_reference v) { static_cast<void>(emplace_back(v)); }

  // Overload of `InlinedVector::push_back(...)` for inserting `v` at `end()`
  // using move semantics.
  void push_back(RValueReference v) {
    static_cast<void>(emplace_back(std::move(v)));
  }

  // `InlinedVector::pop_back()`
  //
  // Destroys the element at `back()`, reducing the size by `1`.
  void pop_back() noexcept {
    ABSL_HARDENING_ASSERT(!empty());

    AllocatorTraits::destroy(*storage_.GetAllocPtr(), data() + (size() - 1));
    storage_.SubtractSize(1);
  }

  // `InlinedVector::erase(...)`
  //
  // Erases the element at `pos`, returning an `iterator` pointing to where the
  // erased element was located.
  //
  // NOTE: may return `end()`, which is not dereferencable.
  iterator erase(const_iterator pos) {
    ABSL_HARDENING_ASSERT(pos >= begin());
    ABSL_HARDENING_ASSERT(pos < end());

    return storage_.Erase(pos, pos + 1);
  }

  // Overload of `InlinedVector::erase(...)` that erases every element in the
  // range [`from`, `to`), returning an `iterator` pointing to where the first
  // erased element was located.
  //
  // NOTE: may return `end()`, which is not dereferencable.
  iterator erase(const_iterator from, const_iterator to) {
    ABSL_HARDENING_ASSERT(from >= begin());
    ABSL_HARDENING_ASSERT(from <= to);
    ABSL_HARDENING_ASSERT(to <= end());

    if (ABSL_PREDICT_TRUE(from != to)) {
      return storage_.Erase(from, to);
    } else {
      return const_cast<iterator>(from);
    }
  }

  // `InlinedVector::clear()`
  //
  // Destroys all elements in the inlined vector, setting the size to `0` and
  // deallocating any held memory.
  void clear() noexcept {
    inlined_vector_internal::DestroyElements(storage_.GetAllocPtr(), data(),
                                             size());
    storage_.DeallocateIfAllocated();

    storage_.SetInlinedSize(0);
  }

  // `InlinedVector::reserve(...)`
  //
  // Ensures that there is enough room for at least `n` elements.
  void reserve(size_type n) { storage_.Reserve(n); }

  // `InlinedVector::shrink_to_fit()`
  //
  // Reduces memory usage by freeing unused memory. After being called, calls to
  // `capacity()` will be equal to `max(N, size())`.
  //
  // If `size() <= N` and the inlined vector contains allocated memory, the
  // elements will all be moved to the inlined space and the allocated memory
  // will be deallocated.
  //
  // If `size() > N` and `size() < capacity()`, the elements will be moved to a
  // smaller allocation.
  void shrink_to_fit() {
    if (storage_.GetIsAllocated()) {
      storage_.ShrinkToFit();
    }
  }

  // `InlinedVector::swap(...)`
  //
  // Swaps the contents of the inlined vector with `other`.
  void swap(InlinedVector& other) {
    if (ABSL_PREDICT_TRUE(this != std::addressof(other))) {
      storage_.Swap(std::addressof(other.storage_));
    }
  }

 private:
  template <typename H, typename TheT, size_t TheN, typename TheA>
  friend H AbslHashValue(H h, const absl::InlinedVector<TheT, TheN, TheA>& a);

  Storage storage_;
};

// -----------------------------------------------------------------------------
// InlinedVector Non-Member Functions
// -----------------------------------------------------------------------------

// `swap(...)`
//
// Swaps the contents of two inlined vectors.
template <typename T, size_t N, typename A>
void swap(absl::InlinedVector<T, N, A>& a,
          absl::InlinedVector<T, N, A>& b) noexcept(noexcept(a.swap(b))) {
  a.swap(b);
}

// `operator==(...)`
//
// Tests for value-equality of two inlined vectors.
template <typename T, size_t N, typename A>
bool operator==(const absl::InlinedVector<T, N, A>& a,
                const absl::InlinedVector<T, N, A>& b) {
  auto a_data = a.data();
  auto b_data = b.data();
  return absl::equal(a_data, a_data + a.size(), b_data, b_data + b.size());
}

// `operator!=(...)`
//
// Tests for value-inequality of two inlined vectors.
template <typename T, size_t N, typename A>
bool operator!=(const absl::InlinedVector<T, N, A>& a,
                const absl::InlinedVector<T, N, A>& b) {
  return !(a == b);
}

// `operator<(...)`
//
// Tests whether the value of an inlined vector is less than the value of
// another inlined vector using a lexicographical comparison algorithm.
template <typename T, size_t N, typename A>
bool operator<(const absl::InlinedVector<T, N, A>& a,
               const absl::InlinedVector<T, N, A>& b) {
  auto a_data = a.data();
  auto b_data = b.data();
  return std::lexicographical_compare(a_data, a_data + a.size(), b_data,
                                      b_data + b.size());
}

// `operator>(...)`
//
// Tests whether the value of an inlined vector is greater than the value of
// another inlined vector using a lexicographical comparison algorithm.
template <typename T, size_t N, typename A>
bool operator>(const absl::InlinedVector<T, N, A>& a,
               const absl::InlinedVector<T, N, A>& b) {
  return b < a;
}

// `operator<=(...)`
//
// Tests whether the value of an inlined vector is less than or equal to the
// value of another inlined vector using a lexicographical comparison algorithm.
template <typename T, size_t N, typename A>
bool operator<=(const absl::InlinedVector<T, N, A>& a,
                const absl::InlinedVector<T, N, A>& b) {
  return !(b < a);
}

// `operator>=(...)`
//
// Tests whether the value of an inlined vector is greater than or equal to the
// value of another inlined vector using a lexicographical comparison algorithm.
template <typename T, size_t N, typename A>
bool operator>=(const absl::InlinedVector<T, N, A>& a,
                const absl::InlinedVector<T, N, A>& b) {
  return !(a < b);
}

// `AbslHashValue(...)`
//
// Provides `absl::Hash` support for `absl::InlinedVector`. It is uncommon to
// call this directly.
template <typename H, typename T, size_t N, typename A>
H AbslHashValue(H h, const absl::InlinedVector<T, N, A>& a) {
  auto size = a.size();
  return H::combine(H::combine_contiguous(std::move(h), a.data(), size), size);
}

ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_CONTAINER_INLINED_VECTOR_H_