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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
//
//
// 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. The most consequential differences with respect to
// migrating to b-tree from the STL types are listed in the next paragraph.
// Other API differences are minor.
//
// 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()`, `erase()`, and `extract_and_get_next()` return a valid
// iterator at the current position.
//
// Another API difference is that btree iterators can be subtracted, and this
// is faster than using std::distance.
#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_NAMESPACE_BEGIN
namespace container_internal {
template <typename Key>
struct set_slot_policy;
template <typename Key, typename Compare, typename Alloc, int TargetNodeSize,
bool IsMulti>
struct set_params;
} // namespace container_internal
// 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,
/*IsMulti=*/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 (0 or 1).
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. Any references, pointers, or iterators
// are invalidated. 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& k):
//
// 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
// It does NOT refer to the data layout of the underlying btree.
using Base::extract;
// btree_set::extract_and_get_next()
//
// Extracts the indicated element, erasing it in the process, and returns it
// as a C++17-compatible node handle along with an iterator to the next
// element.
//
// extract_and_get_next_return_type extract_and_get_next(
// const_iterator position):
//
// Extracts the element at the indicated position, returns a struct
// containing a member named `node`: a node handle owning that extracted
// data and a member named `next`: an iterator pointing to the next element
// in the btree.
using Base::extract_and_get_next;
// 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 has 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 has 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 has a compatible
// heterogeneous comparator.
using Base::find;
// btree_set::lower_bound()
//
// template <typename K> iterator lower_bound(const K& key):
// template <typename K> const_iterator lower_bound(const K& key) const:
//
// Finds the first element that is not less than `key` within the `btree_set`.
//
// Supports heterogeneous lookup, provided that the set has a compatible
// heterogeneous comparator.
using Base::lower_bound;
// btree_set::upper_bound()
//
// template <typename K> iterator upper_bound(const K& key):
// template <typename K> const_iterator upper_bound(const K& key) const:
//
// Finds the first element that is greater than `key` within the `btree_set`.
//
// Supports heterogeneous lookup, provided that the set has a compatible
// heterogeneous comparator.
using Base::upper_bound;
// 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::erase_if(absl::btree_set<>, Pred)
//
// Erases all elements that satisfy the predicate pred from the container.
// Returns the number of erased elements.
template <typename K, typename C, typename A, typename Pred>
typename btree_set<K, C, A>::size_type erase_if(btree_set<K, C, A> &set,
Pred pred) {
return container_internal::btree_access::erase_if(set, std::move(pred));
}
// 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,
/*IsMulti=*/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& k):
//
// 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
// It does NOT refer to the data layout of the underlying btree.
using Base::extract;
// btree_multiset::extract_and_get_next()
//
// Extracts the indicated element, erasing it in the process, and returns it
// as a C++17-compatible node handle along with an iterator to the next
// element.
//
// extract_and_get_next_return_type extract_and_get_next(
// const_iterator position):
//
// Extracts the element at the indicated position, returns a struct
// containing a member named `node`: a node handle owning that extracted
// data and a member named `next`: an iterator pointing to the next element
// in the btree.
using Base::extract_and_get_next;
// btree_multiset::merge()
//
// Extracts all elements from a given `source` btree_multiset into this
// `btree_multiset`.
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 has 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 has 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 has a compatible
// heterogeneous comparator.
using Base::find;
// btree_multiset::lower_bound()
//
// template <typename K> iterator lower_bound(const K& key):
// template <typename K> const_iterator lower_bound(const K& key) const:
//
// Finds the first element that is not less than `key` within the
// `btree_multiset`.
//
// Supports heterogeneous lookup, provided that the set has a compatible
// heterogeneous comparator.
using Base::lower_bound;
// btree_multiset::upper_bound()
//
// template <typename K> iterator upper_bound(const K& key):
// template <typename K> const_iterator upper_bound(const K& key) const:
//
// Finds the first element that is greater than `key` within the
// `btree_multiset`.
//
// Supports heterogeneous lookup, provided that the set has a compatible
// heterogeneous comparator.
using Base::upper_bound;
// 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);
}
// absl::erase_if(absl::btree_multiset<>, Pred)
//
// Erases all elements that satisfy the predicate pred from the container.
// Returns the number of erased elements.
template <typename K, typename C, typename A, typename Pred>
typename btree_multiset<K, C, A>::size_type erase_if(
btree_multiset<K, C, A> & set, Pred pred) {
return container_internal::btree_access::erase_if(set, std::move(pred));
}
namespace container_internal {
// This type implements the necessary functions from the
// absl::container_internal::slot_type interface for btree_(multi)set.
template <typename Key>
struct set_slot_policy {
using slot_type = Key;
using value_type = Key;
using mutable_value_type = Key;
static value_type &element(slot_type *slot) { return *slot; }
static const value_type &element(const slot_type *slot) { return *slot; }
template <typename Alloc, class... Args>
static void construct(Alloc *alloc, slot_type *slot, Args &&...args) {
absl::allocator_traits<Alloc>::construct(*alloc, slot,
std::forward<Args>(args)...);
}
template <typename Alloc>
static void construct(Alloc *alloc, slot_type *slot, slot_type *other) {
absl::allocator_traits<Alloc>::construct(*alloc, slot, std::move(*other));
}
template <typename Alloc>
static void construct(Alloc *alloc, slot_type *slot, const slot_type *other) {
absl::allocator_traits<Alloc>::construct(*alloc, slot, *other);
}
template <typename Alloc>
static void destroy(Alloc *alloc, slot_type *slot) {
absl::allocator_traits<Alloc>::destroy(*alloc, slot);
}
};
// A parameters structure for holding the type parameters for a btree_set.
// Compare and Alloc should be nothrow copy-constructible.
template <typename Key, typename Compare, typename Alloc, int TargetNodeSize,
bool IsMulti>
struct set_params : common_params<Key, Compare, Alloc, TargetNodeSize, IsMulti,
/*IsMap=*/false, set_slot_policy<Key>> {
using value_type = Key;
using slot_type = typename set_params::common_params::slot_type;
template <typename V>
static const V &key(const V &value) {
return value;
}
static const Key &key(const slot_type *slot) { return *slot; }
static const Key &key(slot_type *slot) { return *slot; }
};
} // namespace container_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_CONTAINER_BTREE_SET_H_