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+// 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.
+//
+// -----------------------------------------------------------------------------
+// File: btree_map.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines B-tree maps: sorted associative containers mapping
+// keys to values.
+//
+// * `absl::btree_map<>`
+// * `absl::btree_multimap<>`
+//
+// These B-tree types are similar to the corresponding types in the STL
+// (`std::map` and `std::multimap`) and generally conform to the STL interfaces
+// of those types. However, because they are implemented using B-trees, they
+// are more efficient in most situations.
+//
+// Unlike `std::map` and `std::multimap`, which are commonly implemented using
+// red-black tree nodes, B-tree maps use more generic B-tree nodes able to hold
+// multiple values per node. Holding multiple values per node often makes
+// B-tree maps perform better than their `std::map` counterparts, because
+// multiple entries can be checked within the same cache hit.
+//
+// However, these types should not be considered drop-in replacements for
+// `std::map` and `std::multimap` as there are some API differences, which are
+// noted in this header file.
+//
+// Importantly, insertions and deletions may invalidate outstanding iterators,
+// pointers, and references to elements. Such invalidations are typically only
+// an issue if insertion and deletion operations are interleaved with the use of
+// more than one iterator, pointer, or reference simultaneously. For this
+// reason, `insert()` and `erase()` return a valid iterator at the current
+// position.
+
+#ifndef ABSL_CONTAINER_BTREE_MAP_H_
+#define ABSL_CONTAINER_BTREE_MAP_H_
+
+#include "absl/container/internal/btree.h" // IWYU pragma: export
+#include "absl/container/internal/btree_container.h" // IWYU pragma: export
+
+namespace absl {
+
+// absl::btree_map<>
+//
+// An `absl::btree_map<K, V>` is an ordered associative container of
+// unique keys and associated values designed to be a more efficient replacement
+// for `std::map` (in most cases).
+//
+// Keys are sorted using an (optional) comparison function, which defaults to
+// `std::less<K>`.
+//
+// An `absl::btree_map<K, V>` uses a default allocator of
+// `std::allocator<std::pair<const K, V>>` to allocate (and deallocate)
+// nodes, and construct and destruct values within those nodes. You may
+// instead specify a custom allocator `A` (which in turn requires specifying a
+// custom comparator `C`) as in `absl::btree_map<K, V, C, A>`.
+//
+template <typename Key, typename Value, typename Compare = std::less<Key>,
+ typename Alloc = std::allocator<std::pair<const Key, Value>>>
+class btree_map
+ : public container_internal::btree_map_container<
+ container_internal::btree<container_internal::map_params<
+ Key, Value, Compare, Alloc, /*TargetNodeSize=*/256,
+ /*Multi=*/false>>> {
+ using Base = typename btree_map::btree_map_container;
+
+ public:
+ // Constructors and Assignment Operators
+ //
+ // A `btree_map` supports the same overload set as `std::map`
+ // for construction and assignment:
+ //
+ // * Default constructor
+ //
+ // absl::btree_map<int, std::string> map1;
+ //
+ // * Initializer List constructor
+ //
+ // absl::btree_map<int, std::string> map2 =
+ // {{1, "huey"}, {2, "dewey"}, {3, "louie"},};
+ //
+ // * Copy constructor
+ //
+ // absl::btree_map<int, std::string> map3(map2);
+ //
+ // * Copy assignment operator
+ //
+ // absl::btree_map<int, std::string> map4;
+ // map4 = map3;
+ //
+ // * Move constructor
+ //
+ // // Move is guaranteed efficient
+ // absl::btree_map<int, std::string> map5(std::move(map4));
+ //
+ // * Move assignment operator
+ //
+ // // May be efficient if allocators are compatible
+ // absl::btree_map<int, std::string> map6;
+ // map6 = std::move(map5);
+ //
+ // * Range constructor
+ //
+ // std::vector<std::pair<int, std::string>> v = {{1, "a"}, {2, "b"}};
+ // absl::btree_map<int, std::string> map7(v.begin(), v.end());
+ btree_map() {}
+ using Base::Base;
+
+ // btree_map::begin()
+ //
+ // Returns an iterator to the beginning of the `btree_map`.
+ using Base::begin;
+
+ // btree_map::cbegin()
+ //
+ // Returns a const iterator to the beginning of the `btree_map`.
+ using Base::cbegin;
+
+ // btree_map::end()
+ //
+ // Returns an iterator to the end of the `btree_map`.
+ using Base::end;
+
+ // btree_map::cend()
+ //
+ // Returns a const iterator to the end of the `btree_map`.
+ using Base::cend;
+
+ // btree_map::empty()
+ //
+ // Returns whether or not the `btree_map` is empty.
+ using Base::empty;
+
+ // btree_map::max_size()
+ //
+ // Returns the largest theoretical possible number of elements within a
+ // `btree_map` under current memory constraints. This value can be thought
+ // of as the largest value of `std::distance(begin(), end())` for a
+ // `btree_map<Key, T>`.
+ using Base::max_size;
+
+ // btree_map::size()
+ //
+ // Returns the number of elements currently within the `btree_map`.
+ using Base::size;
+
+ // btree_map::clear()
+ //
+ // Removes all elements from the `btree_map`. Invalidates any references,
+ // pointers, or iterators referring to contained elements.
+ using Base::clear;
+
+ // btree_map::erase()
+ //
+ // Erases elements within the `btree_map`. If an erase occurs, any references,
+ // pointers, or iterators are invalidated.
+ // Overloads are listed below.
+ //
+ // iterator erase(iterator position):
+ // iterator erase(const_iterator position):
+ //
+ // Erases the element at `position` of the `btree_map`, returning
+ // the iterator pointing to the element after the one that was erased
+ // (or end() if none exists).
+ //
+ // iterator erase(const_iterator first, const_iterator last):
+ //
+ // Erases the elements in the open interval [`first`, `last`), returning
+ // the iterator pointing to the element after the interval that was erased
+ // (or end() if none exists).
+ //
+ // template <typename K> size_type erase(const K& key):
+ //
+ // Erases the element with the matching key, if it exists, returning the
+ // number of elements erased.
+ using Base::erase;
+
+ // btree_map::insert()
+ //
+ // Inserts an element of the specified value into the `btree_map`,
+ // returning an iterator pointing to the newly inserted element, provided that
+ // an element with the given key does not already exist. If an insertion
+ // occurs, any references, pointers, or iterators are invalidated.
+ // Overloads are listed below.
+ //
+ // std::pair<iterator,bool> insert(const value_type& value):
+ //
+ // Inserts a value into the `btree_map`. Returns a pair consisting of an
+ // iterator to the inserted element (or to the element that prevented the
+ // insertion) and a bool denoting whether the insertion took place.
+ //
+ // std::pair<iterator,bool> insert(value_type&& value):
+ //
+ // Inserts a moveable value into the `btree_map`. Returns a pair
+ // consisting of an iterator to the inserted element (or to the element that
+ // prevented the insertion) and a bool denoting whether the insertion took
+ // place.
+ //
+ // iterator insert(const_iterator hint, const value_type& value):
+ // iterator insert(const_iterator hint, value_type&& value):
+ //
+ // Inserts a value, using the position of `hint` as a non-binding suggestion
+ // for where to begin the insertion search. Returns an iterator to the
+ // inserted element, or to the existing element that prevented the
+ // insertion.
+ //
+ // void insert(InputIterator first, InputIterator last):
+ //
+ // Inserts a range of values [`first`, `last`).
+ //
+ // void insert(std::initializer_list<init_type> ilist):
+ //
+ // Inserts the elements within the initializer list `ilist`.
+ using Base::insert;
+
+ // btree_map::emplace()
+ //
+ // Inserts an element of the specified value by constructing it in-place
+ // within the `btree_map`, provided that no element with the given key
+ // already exists.
+ //
+ // The element may be constructed even if there already is an element with the
+ // key in the container, in which case the newly constructed element will be
+ // destroyed immediately. Prefer `try_emplace()` unless your key is not
+ // copyable or moveable.
+ //
+ // If an insertion occurs, any references, pointers, or iterators are
+ // invalidated.
+ using Base::emplace;
+
+ // btree_map::emplace_hint()
+ //
+ // Inserts an element of the specified value by constructing it in-place
+ // within the `btree_map`, using the position of `hint` as a non-binding
+ // suggestion for where to begin the insertion search, and only inserts
+ // provided that no element with the given key already exists.
+ //
+ // The element may be constructed even if there already is an element with the
+ // key in the container, in which case the newly constructed element will be
+ // destroyed immediately. Prefer `try_emplace()` unless your key is not
+ // copyable or moveable.
+ //
+ // If an insertion occurs, any references, pointers, or iterators are
+ // invalidated.
+ using Base::emplace_hint;
+
+ // btree_map::try_emplace()
+ //
+ // Inserts an element of the specified value by constructing it in-place
+ // within the `btree_map`, provided that no element with the given key
+ // already exists. Unlike `emplace()`, if an element with the given key
+ // already exists, we guarantee that no element is constructed.
+ //
+ // If an insertion occurs, any references, pointers, or iterators are
+ // invalidated.
+ //
+ // Overloads are listed below.
+ //
+ // std::pair<iterator, bool> try_emplace(const key_type& k, Args&&... args):
+ // std::pair<iterator, bool> try_emplace(key_type&& k, Args&&... args):
+ //
+ // Inserts (via copy or move) the element of the specified key into the
+ // `btree_map`.
+ //
+ // iterator try_emplace(const_iterator hint,
+ // const key_type& k, Args&&... args):
+ // iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args):
+ //
+ // Inserts (via copy or move) the element of the specified key into the
+ // `btree_map` using the position of `hint` as a non-binding suggestion
+ // for where to begin the insertion search.
+ using Base::try_emplace;
+
+ // btree_map::extract()
+ //
+ // Extracts the indicated element, erasing it in the process, and returns it
+ // as a C++17-compatible node handle. Overloads are listed below.
+ //
+ // node_type extract(const_iterator position):
+ //
+ // Extracts the element at the indicated position and returns a node handle
+ // owning that extracted data.
+ //
+ // template <typename K> node_type extract(const K& x):
+ //
+ // Extracts the element with the key matching the passed key value and
+ // returns a node handle owning that extracted data. If the `btree_map`
+ // does not contain an element with a matching key, this function returns an
+ // empty node handle.
+ //
+ // NOTE: In this context, `node_type` refers to the C++17 concept of a
+ // move-only type that owns and provides access to the elements in associative
+ // containers (https://en.cppreference.com/w/cpp/container/node_handle).
+ // It does NOT refer to the data layout of the underlying btree.
+ using Base::extract;
+
+ // btree_map::merge()
+ //
+ // Extracts elements from a given `source` btree_map into this
+ // `btree_map`. If the destination `btree_map` already contains an
+ // element with an equivalent key, that element is not extracted.
+ using Base::merge;
+
+ // btree_map::swap(btree_map& other)
+ //
+ // Exchanges the contents of this `btree_map` with those of the `other`
+ // btree_map, avoiding invocation of any move, copy, or swap operations on
+ // individual elements.
+ //
+ // All iterators and references on the `btree_map` remain valid, excepting
+ // for the past-the-end iterator, which is invalidated.
+ using Base::swap;
+
+ // btree_map::at()
+ //
+ // Returns a reference to the mapped value of the element with key equivalent
+ // to the passed key.
+ using Base::at;
+
+ // btree_map::contains()
+ //
+ // template <typename K> bool contains(const K& key) const:
+ //
+ // Determines whether an element comparing equal to the given `key` exists
+ // within the `btree_map`, returning `true` if so or `false` otherwise.
+ //
+ // Supports heterogeneous lookup, provided that the map is provided a
+ // compatible heterogeneous comparator.
+ using Base::contains;
+
+ // btree_map::count()
+ //
+ // template <typename K> size_type count(const K& key) const:
+ //
+ // Returns the number of elements comparing equal to the given `key` within
+ // the `btree_map`. Note that this function will return either `1` or `0`
+ // since duplicate elements are not allowed within a `btree_map`.
+ //
+ // Supports heterogeneous lookup, provided that the map is provided a
+ // compatible heterogeneous comparator.
+ using Base::count;
+
+ // btree_map::equal_range()
+ //
+ // Returns a closed range [first, last], defined by a `std::pair` of two
+ // iterators, containing all elements with the passed key in the
+ // `btree_map`.
+ using Base::equal_range;
+
+ // btree_map::find()
+ //
+ // template <typename K> iterator find(const K& key):
+ // template <typename K> const_iterator find(const K& key) const:
+ //
+ // Finds an element with the passed `key` within the `btree_map`.
+ //
+ // Supports heterogeneous lookup, provided that the map is provided a
+ // compatible heterogeneous comparator.
+ using Base::find;
+
+ // btree_map::operator[]()
+ //
+ // Returns a reference to the value mapped to the passed key within the
+ // `btree_map`, performing an `insert()` if the key does not already
+ // exist.
+ //
+ // If an insertion occurs, any references, pointers, or iterators are
+ // invalidated. Otherwise iterators are not affected and references are not
+ // invalidated. Overloads are listed below.
+ //
+ // T& operator[](key_type&& key):
+ // T& operator[](const key_type& key):
+ //
+ // Inserts a value_type object constructed in-place if the element with the
+ // given key does not exist.
+ using Base::operator[];
+
+ // btree_map::get_allocator()
+ //
+ // Returns the allocator function associated with this `btree_map`.
+ using Base::get_allocator;
+
+ // btree_map::key_comp();
+ //
+ // Returns the key comparator associated with this `btree_map`.
+ using Base::key_comp;
+
+ // btree_map::value_comp();
+ //
+ // Returns the value comparator associated with this `btree_map`.
+ using Base::value_comp;
+};
+
+// absl::swap(absl::btree_map<>, absl::btree_map<>)
+//
+// Swaps the contents of two `absl::btree_map` containers.
+template <typename K, typename V, typename C, typename A>
+void swap(btree_map<K, V, C, A> &x, btree_map<K, V, C, A> &y) {
+ return x.swap(y);
+}
+
+// absl::btree_multimap
+//
+// An `absl::btree_multimap<K, V>` is an ordered associative container of
+// keys and associated values designed to be a more efficient replacement for
+// `std::multimap` (in most cases). Unlike `absl::btree_map`, a B-tree multimap
+// allows multiple elements with equivalent keys.
+//
+// Keys are sorted using an (optional) comparison function, which defaults to
+// `std::less<K>`.
+//
+// An `absl::btree_multimap<K, V>` uses a default allocator of
+// `std::allocator<std::pair<const K, V>>` to allocate (and deallocate)
+// nodes, and construct and destruct values within those nodes. You may
+// instead specify a custom allocator `A` (which in turn requires specifying a
+// custom comparator `C`) as in `absl::btree_multimap<K, V, C, A>`.
+//
+template <typename Key, typename Value, typename Compare = std::less<Key>,
+ typename Alloc = std::allocator<std::pair<const Key, Value>>>
+class btree_multimap
+ : public container_internal::btree_multimap_container<
+ container_internal::btree<container_internal::map_params<
+ Key, Value, Compare, Alloc, /*TargetNodeSize=*/256,
+ /*Multi=*/true>>> {
+ using Base = typename btree_multimap::btree_multimap_container;
+
+ public:
+ // Constructors and Assignment Operators
+ //
+ // A `btree_multimap` supports the same overload set as `std::multimap`
+ // for construction and assignment:
+ //
+ // * Default constructor
+ //
+ // absl::btree_multimap<int, std::string> map1;
+ //
+ // * Initializer List constructor
+ //
+ // absl::btree_multimap<int, std::string> map2 =
+ // {{1, "huey"}, {2, "dewey"}, {3, "louie"},};
+ //
+ // * Copy constructor
+ //
+ // absl::btree_multimap<int, std::string> map3(map2);
+ //
+ // * Copy assignment operator
+ //
+ // absl::btree_multimap<int, std::string> map4;
+ // map4 = map3;
+ //
+ // * Move constructor
+ //
+ // // Move is guaranteed efficient
+ // absl::btree_multimap<int, std::string> map5(std::move(map4));
+ //
+ // * Move assignment operator
+ //
+ // // May be efficient if allocators are compatible
+ // absl::btree_multimap<int, std::string> map6;
+ // map6 = std::move(map5);
+ //
+ // * Range constructor
+ //
+ // std::vector<std::pair<int, std::string>> v = {{1, "a"}, {2, "b"}};
+ // absl::btree_multimap<int, std::string> map7(v.begin(), v.end());
+ btree_multimap() {}
+ using Base::Base;
+
+ // btree_multimap::begin()
+ //
+ // Returns an iterator to the beginning of the `btree_multimap`.
+ using Base::begin;
+
+ // btree_multimap::cbegin()
+ //
+ // Returns a const iterator to the beginning of the `btree_multimap`.
+ using Base::cbegin;
+
+ // btree_multimap::end()
+ //
+ // Returns an iterator to the end of the `btree_multimap`.
+ using Base::end;
+
+ // btree_multimap::cend()
+ //
+ // Returns a const iterator to the end of the `btree_multimap`.
+ using Base::cend;
+
+ // btree_multimap::empty()
+ //
+ // Returns whether or not the `btree_multimap` is empty.
+ using Base::empty;
+
+ // btree_multimap::max_size()
+ //
+ // Returns the largest theoretical possible number of elements within a
+ // `btree_multimap` under current memory constraints. This value can be
+ // thought of as the largest value of `std::distance(begin(), end())` for a
+ // `btree_multimap<Key, T>`.
+ using Base::max_size;
+
+ // btree_multimap::size()
+ //
+ // Returns the number of elements currently within the `btree_multimap`.
+ using Base::size;
+
+ // btree_multimap::clear()
+ //
+ // Removes all elements from the `btree_multimap`. Invalidates any references,
+ // pointers, or iterators referring to contained elements.
+ using Base::clear;
+
+ // btree_multimap::erase()
+ //
+ // Erases elements within the `btree_multimap`. If an erase occurs, any
+ // references, pointers, or iterators are invalidated.
+ // Overloads are listed below.
+ //
+ // iterator erase(iterator position):
+ // iterator erase(const_iterator position):
+ //
+ // Erases the element at `position` of the `btree_multimap`, returning
+ // the iterator pointing to the element after the one that was erased
+ // (or end() if none exists).
+ //
+ // iterator erase(const_iterator first, const_iterator last):
+ //
+ // Erases the elements in the open interval [`first`, `last`), returning
+ // the iterator pointing to the element after the interval that was erased
+ // (or end() if none exists).
+ //
+ // template <typename K> size_type erase(const K& key):
+ //
+ // Erases the elements matching the key, if any exist, returning the
+ // number of elements erased.
+ using Base::erase;
+
+ // btree_multimap::insert()
+ //
+ // Inserts an element of the specified value into the `btree_multimap`,
+ // returning an iterator pointing to the newly inserted element.
+ // Any references, pointers, or iterators are invalidated. Overloads are
+ // listed below.
+ //
+ // iterator insert(const value_type& value):
+ //
+ // Inserts a value into the `btree_multimap`, returning an iterator to the
+ // inserted element.
+ //
+ // iterator insert(value_type&& value):
+ //
+ // Inserts a moveable value into the `btree_multimap`, returning an iterator
+ // to the inserted element.
+ //
+ // iterator insert(const_iterator hint, const value_type& value):
+ // iterator insert(const_iterator hint, value_type&& value):
+ //
+ // Inserts a value, using the position of `hint` as a non-binding suggestion
+ // for where to begin the insertion search. Returns an iterator to the
+ // inserted element.
+ //
+ // void insert(InputIterator first, InputIterator last):
+ //
+ // Inserts a range of values [`first`, `last`).
+ //
+ // void insert(std::initializer_list<init_type> ilist):
+ //
+ // Inserts the elements within the initializer list `ilist`.
+ using Base::insert;
+
+ // btree_multimap::emplace()
+ //
+ // Inserts an element of the specified value by constructing it in-place
+ // within the `btree_multimap`. Any references, pointers, or iterators are
+ // invalidated.
+ using Base::emplace;
+
+ // btree_multimap::emplace_hint()
+ //
+ // Inserts an element of the specified value by constructing it in-place
+ // within the `btree_multimap`, using the position of `hint` as a non-binding
+ // suggestion for where to begin the insertion search.
+ //
+ // Any references, pointers, or iterators are invalidated.
+ using Base::emplace_hint;
+
+ // btree_multimap::extract()
+ //
+ // Extracts the indicated element, erasing it in the process, and returns it
+ // as a C++17-compatible node handle. Overloads are listed below.
+ //
+ // node_type extract(const_iterator position):
+ //
+ // Extracts the element at the indicated position and returns a node handle
+ // owning that extracted data.
+ //
+ // template <typename K> node_type extract(const K& x):
+ //
+ // Extracts the element with the key matching the passed key value and
+ // returns a node handle owning that extracted data. If the `btree_multimap`
+ // does not contain an element with a matching key, this function returns an
+ // empty node handle.
+ //
+ // NOTE: In this context, `node_type` refers to the C++17 concept of a
+ // move-only type that owns and provides access to the elements in associative
+ // containers (https://en.cppreference.com/w/cpp/container/node_handle).
+ // It does NOT refer to the data layout of the underlying btree.
+ using Base::extract;
+
+ // btree_multimap::merge()
+ //
+ // Extracts elements from a given `source` btree_multimap into this
+ // `btree_multimap`. If the destination `btree_multimap` already contains an
+ // element with an equivalent key, that element is not extracted.
+ using Base::merge;
+
+ // btree_multimap::swap(btree_multimap& other)
+ //
+ // Exchanges the contents of this `btree_multimap` with those of the `other`
+ // btree_multimap, avoiding invocation of any move, copy, or swap operations
+ // on individual elements.
+ //
+ // All iterators and references on the `btree_multimap` remain valid,
+ // excepting for the past-the-end iterator, which is invalidated.
+ using Base::swap;
+
+ // btree_multimap::contains()
+ //
+ // template <typename K> bool contains(const K& key) const:
+ //
+ // Determines whether an element comparing equal to the given `key` exists
+ // within the `btree_multimap`, returning `true` if so or `false` otherwise.
+ //
+ // Supports heterogeneous lookup, provided that the map is provided a
+ // compatible heterogeneous comparator.
+ using Base::contains;
+
+ // btree_multimap::count()
+ //
+ // template <typename K> size_type count(const K& key) const:
+ //
+ // Returns the number of elements comparing equal to the given `key` within
+ // the `btree_multimap`.
+ //
+ // Supports heterogeneous lookup, provided that the map is provided a
+ // compatible heterogeneous comparator.
+ using Base::count;
+
+ // btree_multimap::equal_range()
+ //
+ // Returns a closed range [first, last], defined by a `std::pair` of two
+ // iterators, containing all elements with the passed key in the
+ // `btree_multimap`.
+ using Base::equal_range;
+
+ // btree_multimap::find()
+ //
+ // template <typename K> iterator find(const K& key):
+ // template <typename K> const_iterator find(const K& key) const:
+ //
+ // Finds an element with the passed `key` within the `btree_multimap`.
+ //
+ // Supports heterogeneous lookup, provided that the map is provided a
+ // compatible heterogeneous comparator.
+ using Base::find;
+
+ // btree_multimap::get_allocator()
+ //
+ // Returns the allocator function associated with this `btree_multimap`.
+ using Base::get_allocator;
+
+ // btree_multimap::key_comp();
+ //
+ // Returns the key comparator associated with this `btree_multimap`.
+ using Base::key_comp;
+
+ // btree_multimap::value_comp();
+ //
+ // Returns the value comparator associated with this `btree_multimap`.
+ using Base::value_comp;
+};
+
+// absl::swap(absl::btree_multimap<>, absl::btree_multimap<>)
+//
+// Swaps the contents of two `absl::btree_multimap` containers.
+template <typename K, typename V, typename C, typename A>
+void swap(btree_multimap<K, V, C, A> &x, btree_multimap<K, V, C, A> &y) {
+ return x.swap(y);
+}
+
+} // namespace absl
+
+#endif // ABSL_CONTAINER_BTREE_MAP_H_