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diff --git a/absl/container/btree_set.h b/absl/container/btree_set.h new file mode 100644 index 000000000000..6e47b4aae652 --- /dev/null +++ b/absl/container/btree_set.h @@ -0,0 +1,653 @@ +// 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_set.h +// ----------------------------------------------------------------------------- +// +// This header file defines B-tree sets: sorted associative containers of +// values. +// +// * `absl::btree_set<>` +// * `absl::btree_multiset<>` +// +// These B-tree types are similar to the corresponding types in the STL +// (`std::set` and `std::multiset`) 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::set` and `std::multiset`, which are commonly implemented using +// red-black tree nodes, B-tree sets use more generic B-tree nodes able to hold +// multiple values per node. Holding multiple values per node often makes +// B-tree sets perform better than their `std::set` counterparts, because +// multiple entries can be checked within the same cache hit. +// +// However, these types should not be considered drop-in replacements for +// `std::set` and `std::multiset` 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_SET_H_ +#define ABSL_CONTAINER_BTREE_SET_H_ + +#include "absl/container/internal/btree.h" // IWYU pragma: export +#include "absl/container/internal/btree_container.h" // IWYU pragma: export + +namespace absl { + +// absl::btree_set<> +// +// An `absl::btree_set<K>` is an ordered associative container of unique key +// values designed to be a more efficient replacement for `std::set` (in most +// cases). +// +// Keys are sorted using an (optional) comparison function, which defaults to +// `std::less<K>`. +// +// An `absl::btree_set<K>` uses a default allocator of `std::allocator<K>` 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_set<K, C, A>`. +// +template <typename Key, typename Compare = std::less<Key>, + typename Alloc = std::allocator<Key>> +class btree_set + : public container_internal::btree_set_container< + container_internal::btree<container_internal::set_params< + Key, Compare, Alloc, /*TargetNodeSize=*/256, + /*Multi=*/false>>> { + using Base = typename btree_set::btree_set_container; + + public: + // Constructors and Assignment Operators + // + // A `btree_set` supports the same overload set as `std::set` + // for construction and assignment: + // + // * Default constructor + // + // absl::btree_set<std::string> set1; + // + // * Initializer List constructor + // + // absl::btree_set<std::string> set2 = + // {{"huey"}, {"dewey"}, {"louie"},}; + // + // * Copy constructor + // + // absl::btree_set<std::string> set3(set2); + // + // * Copy assignment operator + // + // absl::btree_set<std::string> set4; + // set4 = set3; + // + // * Move constructor + // + // // Move is guaranteed efficient + // absl::btree_set<std::string> set5(std::move(set4)); + // + // * Move assignment operator + // + // // May be efficient if allocators are compatible + // absl::btree_set<std::string> set6; + // set6 = std::move(set5); + // + // * Range constructor + // + // std::vector<std::string> v = {"a", "b"}; + // absl::btree_set<std::string> set7(v.begin(), v.end()); + btree_set() {} + using Base::Base; + + // btree_set::begin() + // + // Returns an iterator to the beginning of the `btree_set`. + using Base::begin; + + // btree_set::cbegin() + // + // Returns a const iterator to the beginning of the `btree_set`. + using Base::cbegin; + + // btree_set::end() + // + // Returns an iterator to the end of the `btree_set`. + using Base::end; + + // btree_set::cend() + // + // Returns a const iterator to the end of the `btree_set`. + using Base::cend; + + // btree_set::empty() + // + // Returns whether or not the `btree_set` is empty. + using Base::empty; + + // btree_set::max_size() + // + // Returns the largest theoretical possible number of elements within a + // `btree_set` under current memory constraints. This value can be thought + // of as the largest value of `std::distance(begin(), end())` for a + // `btree_set<Key>`. + using Base::max_size; + + // btree_set::size() + // + // Returns the number of elements currently within the `btree_set`. + using Base::size; + + // btree_set::clear() + // + // Removes all elements from the `btree_set`. Invalidates any references, + // pointers, or iterators referring to contained elements. + using Base::clear; + + // btree_set::erase() + // + // Erases elements within the `btree_set`. Overloads are listed below. + // + // iterator erase(iterator position): + // iterator erase(const_iterator position): + // + // Erases the element at `position` of the `btree_set`, 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_set::insert() + // + // Inserts an element of the specified value into the `btree_set`, + // 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_set`. 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_set`. 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_set::emplace() + // + // Inserts an element of the specified value by constructing it in-place + // within the `btree_set`, 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. + // + // If an insertion occurs, any references, pointers, or iterators are + // invalidated. + using Base::emplace; + + // btree_set::emplace_hint() + // + // Inserts an element of the specified value by constructing it in-place + // within the `btree_set`, 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. + // + // If an insertion occurs, any references, pointers, or iterators are + // invalidated. + using Base::emplace_hint; + + // btree_set::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_set` + // 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_set::merge() + // + // Extracts elements from a given `source` btree_set into this + // `btree_set`. If the destination `btree_set` already contains an + // element with an equivalent key, that element is not extracted. + using Base::merge; + + // btree_set::swap(btree_set& other) + // + // Exchanges the contents of this `btree_set` with those of the `other` + // btree_set, avoiding invocation of any move, copy, or swap operations on + // individual elements. + // + // All iterators and references on the `btree_set` remain valid, excepting + // for the past-the-end iterator, which is invalidated. + using Base::swap; + + // btree_set::contains() + // + // template <typename K> bool contains(const K& key) const: + // + // Determines whether an element comparing equal to the given `key` exists + // within the `btree_set`, returning `true` if so or `false` otherwise. + // + // Supports heterogeneous lookup, provided that the set is provided a + // compatible heterogeneous comparator. + using Base::contains; + + // btree_set::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_set`. Note that this function will return either `1` or `0` + // since duplicate elements are not allowed within a `btree_set`. + // + // Supports heterogeneous lookup, provided that the set is provided a + // compatible heterogeneous comparator. + using Base::count; + + // btree_set::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_set`. + using Base::equal_range; + + // btree_set::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_set`. + // + // Supports heterogeneous lookup, provided that the set is provided a + // compatible heterogeneous comparator. + using Base::find; + + // btree_set::get_allocator() + // + // Returns the allocator function associated with this `btree_set`. + using Base::get_allocator; + + // btree_set::key_comp(); + // + // Returns the key comparator associated with this `btree_set`. + using Base::key_comp; + + // btree_set::value_comp(); + // + // Returns the value comparator associated with this `btree_set`. The keys to + // sort the elements are the values themselves, therefore `value_comp` and its + // sibling member function `key_comp` are equivalent. + using Base::value_comp; +}; + +// absl::swap(absl::btree_set<>, absl::btree_set<>) +// +// Swaps the contents of two `absl::btree_set` containers. +template <typename K, typename C, typename A> +void swap(btree_set<K, C, A> &x, btree_set<K, C, A> &y) { + return x.swap(y); +} + +// absl::btree_multiset<> +// +// An `absl::btree_multiset<K>` is an ordered associative container of +// keys and associated values designed to be a more efficient replacement +// for `std::multiset` (in most cases). Unlike `absl::btree_set`, a B-tree +// multiset allows equivalent elements. +// +// Keys are sorted using an (optional) comparison function, which defaults to +// `std::less<K>`. +// +// An `absl::btree_multiset<K>` uses a default allocator of `std::allocator<K>` +// 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_multiset<K, C, A>`. +// +template <typename Key, typename Compare = std::less<Key>, + typename Alloc = std::allocator<Key>> +class btree_multiset + : public container_internal::btree_multiset_container< + container_internal::btree<container_internal::set_params< + Key, Compare, Alloc, /*TargetNodeSize=*/256, + /*Multi=*/true>>> { + using Base = typename btree_multiset::btree_multiset_container; + + public: + // Constructors and Assignment Operators + // + // A `btree_multiset` supports the same overload set as `std::set` + // for construction and assignment: + // + // * Default constructor + // + // absl::btree_multiset<std::string> set1; + // + // * Initializer List constructor + // + // absl::btree_multiset<std::string> set2 = + // {{"huey"}, {"dewey"}, {"louie"},}; + // + // * Copy constructor + // + // absl::btree_multiset<std::string> set3(set2); + // + // * Copy assignment operator + // + // absl::btree_multiset<std::string> set4; + // set4 = set3; + // + // * Move constructor + // + // // Move is guaranteed efficient + // absl::btree_multiset<std::string> set5(std::move(set4)); + // + // * Move assignment operator + // + // // May be efficient if allocators are compatible + // absl::btree_multiset<std::string> set6; + // set6 = std::move(set5); + // + // * Range constructor + // + // std::vector<std::string> v = {"a", "b"}; + // absl::btree_multiset<std::string> set7(v.begin(), v.end()); + btree_multiset() {} + using Base::Base; + + // btree_multiset::begin() + // + // Returns an iterator to the beginning of the `btree_multiset`. + using Base::begin; + + // btree_multiset::cbegin() + // + // Returns a const iterator to the beginning of the `btree_multiset`. + using Base::cbegin; + + // btree_multiset::end() + // + // Returns an iterator to the end of the `btree_multiset`. + using Base::end; + + // btree_multiset::cend() + // + // Returns a const iterator to the end of the `btree_multiset`. + using Base::cend; + + // btree_multiset::empty() + // + // Returns whether or not the `btree_multiset` is empty. + using Base::empty; + + // btree_multiset::max_size() + // + // Returns the largest theoretical possible number of elements within a + // `btree_multiset` under current memory constraints. This value can be + // thought of as the largest value of `std::distance(begin(), end())` for a + // `btree_multiset<Key>`. + using Base::max_size; + + // btree_multiset::size() + // + // Returns the number of elements currently within the `btree_multiset`. + using Base::size; + + // btree_multiset::clear() + // + // Removes all elements from the `btree_multiset`. Invalidates any references, + // pointers, or iterators referring to contained elements. + using Base::clear; + + // btree_multiset::erase() + // + // Erases elements within the `btree_multiset`. Overloads are listed below. + // + // iterator erase(iterator position): + // iterator erase(const_iterator position): + // + // Erases the element at `position` of the `btree_multiset`, 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_multiset::insert() + // + // Inserts an element of the specified value into the `btree_multiset`, + // 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_multiset`, returning an iterator to the + // inserted element. + // + // iterator insert(value_type&& value): + // + // Inserts a moveable value into the `btree_multiset`, 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_multiset::emplace() + // + // Inserts an element of the specified value by constructing it in-place + // within the `btree_multiset`. Any references, pointers, or iterators are + // invalidated. + using Base::emplace; + + // btree_multiset::emplace_hint() + // + // Inserts an element of the specified value by constructing it in-place + // within the `btree_multiset`, 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_multiset::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_multiset` + // 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_multiset::merge() + // + // Extracts elements from a given `source` btree_multiset into this + // `btree_multiset`. If the destination `btree_multiset` already contains an + // element with an equivalent key, that element is not extracted. + using Base::merge; + + // btree_multiset::swap(btree_multiset& other) + // + // Exchanges the contents of this `btree_multiset` with those of the `other` + // btree_multiset, avoiding invocation of any move, copy, or swap operations + // on individual elements. + // + // All iterators and references on the `btree_multiset` remain valid, + // excepting for the past-the-end iterator, which is invalidated. + using Base::swap; + + // btree_multiset::contains() + // + // template <typename K> bool contains(const K& key) const: + // + // Determines whether an element comparing equal to the given `key` exists + // within the `btree_multiset`, returning `true` if so or `false` otherwise. + // + // Supports heterogeneous lookup, provided that the set is provided a + // compatible heterogeneous comparator. + using Base::contains; + + // btree_multiset::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_multiset`. + // + // Supports heterogeneous lookup, provided that the set is provided a + // compatible heterogeneous comparator. + using Base::count; + + // btree_multiset::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_multiset`. + using Base::equal_range; + + // btree_multiset::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_multiset`. + // + // Supports heterogeneous lookup, provided that the set is provided a + // compatible heterogeneous comparator. + using Base::find; + + // btree_multiset::get_allocator() + // + // Returns the allocator function associated with this `btree_multiset`. + using Base::get_allocator; + + // btree_multiset::key_comp(); + // + // Returns the key comparator associated with this `btree_multiset`. + using Base::key_comp; + + // btree_multiset::value_comp(); + // + // Returns the value comparator associated with this `btree_multiset`. The + // keys to sort the elements are the values themselves, therefore `value_comp` + // and its sibling member function `key_comp` are equivalent. + using Base::value_comp; +}; + +// absl::swap(absl::btree_multiset<>, absl::btree_multiset<>) +// +// Swaps the contents of two `absl::btree_multiset` containers. +template <typename K, typename C, typename A> +void swap(btree_multiset<K, C, A> &x, btree_multiset<K, C, A> &y) { + return x.swap(y); +} + +} // namespace absl + +#endif // ABSL_CONTAINER_BTREE_SET_H_ |