// 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 <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"

#include "absl/meta/type_traits.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>;

  template <typename TheA>

  using AllocatorTraits = inlined_vector_internal::AllocatorTraits<TheA>;

  template <typename TheA>

  using MoveIterator = inlined_vector_internal::MoveIterator<TheA>;

  template <typename TheA>

  using IsMoveAssignOk = inlined_vector_internal::IsMoveAssignOk<TheA>;

  template <typename TheA, typename Iterator>

  using IteratorValueAdapter =

      inlined_vector_internal::IteratorValueAdapter<TheA, Iterator>;

  template <typename TheA>

  using CopyValueAdapter = inlined_vector_internal::CopyValueAdapter<TheA>;

  template <typename TheA>

  using DefaultValueAdapter =

      inlined_vector_internal::DefaultValueAdapter<TheA>;

  template <typename Iterator>

  using EnableIfAtLeastForwardIterator = absl::enable_if_t<

      inlined_vector_internal::IsAtLeastForwardIterator<Iterator>::value, int>;

  template <typename Iterator>

  using DisableIfAtLeastForwardIterator = absl::enable_if_t<

      !inlined_vector_internal::IsAtLeastForwardIterator<Iterator>::value, int>;

  using MemcpyPolicy = typename Storage::MemcpyPolicy;

  using ElementwiseAssignPolicy = typename Storage::ElementwiseAssignPolicy;

  using ElementwiseConstructPolicy =

      typename Storage::ElementwiseConstructPolicy;

  using MoveAssignmentPolicy = typename Storage::MoveAssignmentPolicy;

 public:

  using allocator_type = A;

  using value_type = inlined_vector_internal::ValueType<A>;

  using pointer = inlined_vector_internal::Pointer<A>;

  using const_pointer = inlined_vector_internal::ConstPointer<A>;

  using size_type = inlined_vector_internal::SizeType<A>;

  using difference_type = inlined_vector_internal::DifferenceType<A>;

  using reference = inlined_vector_internal::Reference<A>;

  using const_reference = inlined_vector_internal::ConstReference<A>;

  using iterator = inlined_vector_internal::Iterator<A>;

  using const_iterator = inlined_vector_internal::ConstIterator<A>;

  using reverse_iterator = inlined_vector_internal::ReverseIterator<A>;

  using const_reverse_iterator =

      inlined_vector_internal::ConstReverseIterator<A>;

  // ---------------------------------------------------------------------------

  // 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 `allocator`.

  explicit InlinedVector(const allocator_type& allocator) noexcept

      : storage_(allocator) {}

  // Creates an inlined vector with `n` copies of `value_type()`.

  explicit InlinedVector(size_type n,

                         const allocator_type& allocator = allocator_type())

      : storage_(allocator) {

    storage_.Initialize(DefaultValueAdapter<A>(), n);

  }

  // Creates an inlined vector with `n` copies of `v`.

  InlinedVector(size_type n, const_reference v,

                const allocator_type& allocator = allocator_type())

      : storage_(allocator) {

    storage_.Initialize(CopyValueAdapter<A>(std::addressof(v)), n);

  }

  // Creates an inlined vector with copies of the elements of `list`.

  InlinedVector(std::initializer_list<value_type> list,

                const allocator_type& allocator = allocator_type())

      : InlinedVector(list.begin(), list.end(), allocator) {}

  // 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> = 0>

  InlinedVector(ForwardIterator first, ForwardIterator last,

                const allocator_type& allocator = allocator_type())

      : storage_(allocator) {

    storage_.Initialize(IteratorValueAdapter<A, ForwardIterator>(first),

                        static_cast<size_t>(std::distance(first, last)));

  }

  // Creates an inlined vector with elements constructed from the provided input

  // iterator range [`first`, `last`).

  template <typename InputIterator,

            DisableIfAtLeastForwardIterator<InputIterator> = 0>

  InlinedVector(InputIterator first, InputIterator last,

                const allocator_type& allocator = allocator_type())

      : storage_(allocator) {

    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_.GetAllocator()) {}

  // Creates an inlined vector by copying the contents of `other` using the

  // provided `allocator`.

  InlinedVector(const InlinedVector& other, const allocator_type& allocator)

      : storage_(allocator) {

    // Fast path: if the other vector is empty, there's nothing for us to do.

    if (other.empty()) {

      return;

    }

    // Fast path: if the value type is trivially copy constructible, we know the

    // allocator doesn't do anything fancy, and there is nothing on the heap

    // then we know it is legal for us to simply memcpy the other vector's

    // inlined bytes to form our copy of its elements.

    if (absl::is_trivially_copy_constructible<value_type>::value &&

        std::is_same<A, std::allocator<value_type>>::value &&

        !other.storage_.GetIsAllocated()) {

      storage_.MemcpyFrom(other.storage_);

      return;

    }

    storage_.InitFrom(other.storage_);

  }

  // 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_.GetAllocator()) {

    // Fast path: if the value type can be trivially relocated (i.e. moved from

    // and destroyed), and we know the allocator doesn't do anything fancy, then

    // it's safe for us to simply adopt the contents of the storage for `other`

    // and remove its own reference to them. It's as if we had individually

    // move-constructed each value and then destroyed the original.

    if (absl::is_trivially_relocatable<value_type>::value &&

        std::is_same<A, std::allocator<value_type>>::value) {

      storage_.MemcpyFrom(other.storage_);

      other.storage_.SetInlinedSize(0);

      return;

    }

    // Fast path: if the other vector is on the heap, we can simply take over

    // its allocation.

    if (other.storage_.GetIsAllocated()) {

      storage_.SetAllocation({other.storage_.GetAllocatedData(),

                              other.storage_.GetAllocatedCapacity()});

      storage_.SetAllocatedSize(other.storage_.GetSize());

      other.storage_.SetInlinedSize(0);

      return;

    }

    // Otherwise we must move each element individually.

    IteratorValueAdapter<A, MoveIterator<A>> other_values(

        MoveIterator<A>(other.storage_.GetInlinedData()));

    inlined_vector_internal::ConstructElements<A>(

        storage_.GetAllocator(), 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 `allocator`.

  //

  // NOTE: if `other`'s allocator is not equal to `allocator`, 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&

          allocator) noexcept(absl::allocator_is_nothrow<allocator_type>::value)

      : storage_(allocator) {

    // Fast path: if the value type can be trivially relocated (i.e. moved from

    // and destroyed), and we know the allocator doesn't do anything fancy, then

    // it's safe for us to simply adopt the contents of the storage for `other`

    // and remove its own reference to them. It's as if we had individually

    // move-constructed each value and then destroyed the original.

    if (absl::is_trivially_relocatable<value_type>::value &&

        std::is_same<A, std::allocator<value_type>>::value) {

      storage_.MemcpyFrom(other.storage_);

      other.storage_.SetInlinedSize(0);

      return;

    }

    // Fast path: if the other vector is on the heap and shared the same

    // allocator, we can simply take over its allocation.

    if ((storage_.GetAllocator() == other.storage_.GetAllocator()) &&

        other.storage_.GetIsAllocated()) {

      storage_.SetAllocation({other.storage_.GetAllocatedData(),

                              other.storage_.GetAllocatedCapacity()});

      storage_.SetAllocatedSize(other.storage_.GetSize());

      other.storage_.SetInlinedSize(0);

      return;

    }

    // Otherwise we must move each element individually.

    storage_.Initialize(

        IteratorValueAdapter<A, MoveIterator<A>>(MoveIterator<A>(other.data())),

        other.size());

  }

  ~InlinedVector() {}

absl::InlinedVector<absl::LogSink*, 16ul, std::__1::allocator<absl::LogSink*> >::~InlinedVector()

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  ~InlinedVector() {}

Unexecuted instantiation: absl::InlinedVector<absl::str_format_internal::FormatArgImpl, 4ul, std::__1::allocator<absl::str_format_internal::FormatArgImpl> >::~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(); }

absl::InlinedVector<absl::LogSink*, 16ul, std::__1::allocator<absl::LogSink*> >::size() const

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  size_type size() const noexcept { return storage_.GetSize(); }

Unexecuted instantiation: absl::InlinedVector<absl::str_format_internal::FormatArgImpl, 4ul, std::__1::allocator<absl::str_format_internal::FormatArgImpl> >::size() const

  // `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 the minimum of the limit of how many

    // objects we can allocate and std::numeric_limits<size_type>::max() / 2.

    return (std::min)(AllocatorTraits<A>::max_size(storage_.GetAllocator()),

                      (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 ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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 ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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_ATTRIBUTE_LIFETIME_BOUND {

    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_ATTRIBUTE_LIFETIME_BOUND {

    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) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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 ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(!empty());

    return data()[0];

  }

  // Overload of `InlinedVector::front()` that returns a `const_reference` to

  // the first element of the inlined vector.

  const_reference front() const ABSL_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(!empty());

    return data()[0];

  }

  // `InlinedVector::back()`

  //

  // Returns a `reference` to the last element of the inlined vector.

  reference back() ABSL_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(!empty());

    return data()[size() - 1];

  }

  // Overload of `InlinedVector::back()` that returns a `const_reference` to the

  // last element of the inlined vector.

  const_reference back() const ABSL_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(!empty());

    return data()[size() - 1];

  }

  // `InlinedVector::begin()`

  //

  // Returns an `iterator` to the beginning of the inlined vector.

  iterator begin() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND { return data(); }

  // Overload of `InlinedVector::begin()` that returns a `const_iterator` to

  // the beginning of the inlined vector.

  const_iterator begin() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return data();

  }

  // `InlinedVector::end()`

  //

  // Returns an `iterator` to the end of the inlined vector.

  iterator end() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return data() + size();

  }

  // Overload of `InlinedVector::end()` that returns a `const_iterator` to the

  // end of the inlined vector.

  const_iterator end() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return data() + size();

  }

  // `InlinedVector::cbegin()`

  //

  // Returns a `const_iterator` to the beginning of the inlined vector.

  const_iterator cbegin() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return begin();

  }

  // `InlinedVector::cend()`

  //

  // Returns a `const_iterator` to the end of the inlined vector.

  const_iterator cend() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return end();

  }

  // `InlinedVector::rbegin()`

  //

  // Returns a `reverse_iterator` from the end of the inlined vector.

  reverse_iterator rbegin() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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 ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return const_reverse_iterator(end());

  }

  // `InlinedVector::rend()`

  //

  // Returns a `reverse_iterator` from the beginning of the inlined vector.

  reverse_iterator rend() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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 ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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

      ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return rbegin();

  }

  // `InlinedVector::crend()`

  //

  // Returns a `const_reverse_iterator` from the beginning of the inlined

  // vector.

  const_reverse_iterator crend() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {

    return rend();

  }

  // `InlinedVector::get_allocator()`

  //

  // Returns a copy of the inlined vector's allocator.

  allocator_type get_allocator() const { return storage_.GetAllocator(); }

  // ---------------------------------------------------------------------------

  // 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))) {

      MoveAssignment(MoveAssignmentPolicy{}, std::move(other));

    }

    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<A>(std::addressof(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> = 0>

  void assign(ForwardIterator first, ForwardIterator last) {

    storage_.Assign(IteratorValueAdapter<A, ForwardIterator>(first),

                    static_cast<size_t>(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> = 0>

  void assign(InputIterator first, InputIterator last) {

    size_type i = 0;

    for (; i < size() && first != last; ++i, static_cast<void>(++first)) {

      data()[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) {

    ABSL_HARDENING_ASSERT(n <= max_size());

    storage_.Resize(DefaultValueAdapter<A>(), 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) {

    ABSL_HARDENING_ASSERT(n <= max_size());

    storage_.Resize(CopyValueAdapter<A>(std::addressof(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) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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,

                  value_type&& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(pos >= begin());

    ABSL_HARDENING_ASSERT(pos <= end());

    if (ABSL_PREDICT_TRUE(n != 0)) {

      value_type dealias = v;

      // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102329#c2

      // It appears that GCC thinks that since `pos` is a const pointer and may

      // point to uninitialized memory at this point, a warning should be

      // issued. But `pos` is actually only used to compute an array index to

      // write to.

#if !defined(__clang__) && defined(__GNUC__)

#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

#endif

      return storage_.Insert(pos, CopyValueAdapter<A>(std::addressof(dealias)),

                             n);

#if !defined(__clang__) && defined(__GNUC__)

#pragma GCC diagnostic pop

#endif

    } 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)

      ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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> = 0>

  iterator insert(const_iterator pos, ForwardIterator first,

                  ForwardIterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(pos >= begin());

    ABSL_HARDENING_ASSERT(pos <= end());

    if (ABSL_PREDICT_TRUE(first != last)) {

      return storage_.Insert(

          pos, IteratorValueAdapter<A, ForwardIterator>(first),

          static_cast<size_type>(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> = 0>

  iterator insert(const_iterator pos, InputIterator first,

                  InputIterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(pos >= begin());

    ABSL_HARDENING_ASSERT(pos <= end());

    size_type index = static_cast<size_type>(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_ATTRIBUTE_LIFETIME_BOUND {

    ABSL_HARDENING_ASSERT(pos >= begin());

    ABSL_HARDENING_ASSERT(pos <= end());

    value_type dealias(std::forward<Args>(args)...);

    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102329#c2

    // It appears that GCC thinks that since `pos` is a const pointer and may

    // point to uninitialized memory at this point, a warning should be

    // issued. But `pos` is actually only used to compute an array index to

    // write to.

#if !defined(__clang__) && defined(__GNUC__)

#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

#endif

    return storage_.Insert(pos,

                           IteratorValueAdapter<A, MoveIterator<A>>(

                               MoveIterator<A>(std::addressof(dealias))),

                           1);

#if !defined(__clang__) && defined(__GNUC__)

#pragma GCC diagnostic pop

#endif

  }

  // `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) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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(value_type&& 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<A>::destroy(storage_.GetAllocator(), 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 dereferenceable.

  iterator erase(const_iterator pos) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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 dereferenceable.

  iterator erase(const_iterator from,

                 const_iterator to) ABSL_ATTRIBUTE_LIFETIME_BOUND {

    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::DestroyAdapter<A>::DestroyElements(

        storage_.GetAllocator(), 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()`

  //

  // Attempts to reduce memory usage by moving elements to (or keeping elements

  // in) the smallest available buffer sufficient for containing `size()`

  // elements.

  //

  // If `size()` is sufficiently small, the elements will be moved into (or kept

  // in) the inlined space.

  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);

  void MoveAssignment(MemcpyPolicy, InlinedVector&& other) {

    // Assumption check: we shouldn't be told to use memcpy to implement move

    // assignment unless we have trivially destructible elements and an

    // allocator that does nothing fancy.

    static_assert(absl::is_trivially_destructible<value_type>::value, "");

    static_assert(std::is_same<A, std::allocator<value_type>>::value, "");

    // Throw away our existing heap allocation, if any. There is no need to

    // destroy the existing elements one by one because we know they are

    // trivially destructible.

    storage_.DeallocateIfAllocated();

    // Adopt the other vector's inline elements or heap allocation.

    storage_.MemcpyFrom(other.storage_);

    other.storage_.SetInlinedSize(0);

  }

  // Destroy our existing elements, if any, and adopt the heap-allocated

  // elements of the other vector.

  //

  // REQUIRES: other.storage_.GetIsAllocated()

  void DestroyExistingAndAdopt(InlinedVector&& other) {

    ABSL_HARDENING_ASSERT(other.storage_.GetIsAllocated());

    inlined_vector_internal::DestroyAdapter<A>::DestroyElements(

        storage_.GetAllocator(), data(), size());

    storage_.DeallocateIfAllocated();

    storage_.MemcpyFrom(other.storage_);

    other.storage_.SetInlinedSize(0);

  }

  void MoveAssignment(ElementwiseAssignPolicy, InlinedVector&& other) {

    // Fast path: if the other vector is on the heap then we don't worry about

    // actually move-assigning each element. Instead we only throw away our own

    // existing elements and adopt the heap allocation of the other vector.

    if (other.storage_.GetIsAllocated()) {

      DestroyExistingAndAdopt(std::move(other));

      return;

    }

    storage_.Assign(IteratorValueAdapter<A, MoveIterator<A>>(

                        MoveIterator<A>(other.storage_.GetInlinedData())),

                    other.size());

  }

  void MoveAssignment(ElementwiseConstructPolicy, InlinedVector&& other) {

    // Fast path: if the other vector is on the heap then we don't worry about

    // actually move-assigning each element. Instead we only throw away our own

    // existing elements and adopt the heap allocation of the other vector.

    if (other.storage_.GetIsAllocated()) {

      DestroyExistingAndAdopt(std::move(other));

      return;

    }

    inlined_vector_internal::DestroyAdapter<A>::DestroyElements(

        storage_.GetAllocator(), data(), size());

    storage_.DeallocateIfAllocated();

    IteratorValueAdapter<A, MoveIterator<A>> other_values(

        MoveIterator<A>(other.storage_.GetInlinedData()));

    inlined_vector_internal::ConstructElements<A>(

        storage_.GetAllocator(), storage_.GetInlinedData(), other_values,

        other.storage_.GetSize());

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

  }

  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 std::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_