| // 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: node_hash_map.h |
| // ----------------------------------------------------------------------------- |
| // |
| // An `absl::node_hash_map<K, V>` is an unordered associative container of |
| // unique keys and associated values designed to be a more efficient replacement |
| // for `std::unordered_map`. Like `unordered_map`, search, insertion, and |
| // deletion of map elements can be done as an `O(1)` operation. However, |
| // `node_hash_map` (and other unordered associative containers known as the |
| // collection of Abseil "Swiss tables") contain other optimizations that result |
| // in both memory and computation advantages. |
| // |
| // In most cases, your default choice for a hash map should be a map of type |
| // `flat_hash_map`. However, if you need pointer stability and cannot store |
| // a `flat_hash_map` with `unique_ptr` elements, a `node_hash_map` may be a |
| // valid alternative. As well, if you are migrating your code from using |
| // `std::unordered_map`, a `node_hash_map` provides a more straightforward |
| // migration, because it guarantees pointer stability. Consider migrating to |
| // `node_hash_map` and perhaps converting to a more efficient `flat_hash_map` |
| // upon further review. |
| |
| #ifndef ABSL_CONTAINER_NODE_HASH_MAP_H_ |
| #define ABSL_CONTAINER_NODE_HASH_MAP_H_ |
| |
| #include <tuple> |
| #include <type_traits> |
| #include <utility> |
| |
| #include "absl/algorithm/container.h" |
| #include "absl/base/macros.h" |
| #include "absl/container/internal/container_memory.h" |
| #include "absl/container/internal/hash_function_defaults.h" // IWYU pragma: export |
| #include "absl/container/internal/node_slot_policy.h" |
| #include "absl/container/internal/raw_hash_map.h" // IWYU pragma: export |
| #include "absl/memory/memory.h" |
| |
| namespace absl { |
| ABSL_NAMESPACE_BEGIN |
| namespace container_internal { |
| template <class Key, class Value> |
| class NodeHashMapPolicy; |
| } // namespace container_internal |
| |
| // ----------------------------------------------------------------------------- |
| // absl::node_hash_map |
| // ----------------------------------------------------------------------------- |
| // |
| // An `absl::node_hash_map<K, V>` is an unordered associative container which |
| // has been optimized for both speed and memory footprint in most common use |
| // cases. Its interface is similar to that of `std::unordered_map<K, V>` with |
| // the following notable differences: |
| // |
| // * Supports heterogeneous lookup, through `find()`, `operator[]()` and |
| // `insert()`, provided that the map is provided a compatible heterogeneous |
| // hashing function and equality operator. |
| // * Contains a `capacity()` member function indicating the number of element |
| // slots (open, deleted, and empty) within the hash map. |
| // * Returns `void` from the `erase(iterator)` overload. |
| // |
| // By default, `node_hash_map` uses the `absl::Hash` hashing framework. |
| // All fundamental and Abseil types that support the `absl::Hash` framework have |
| // a compatible equality operator for comparing insertions into `node_hash_map`. |
| // If your type is not yet supported by the `absl::Hash` framework, see |
| // absl/hash/hash.h for information on extending Abseil hashing to user-defined |
| // types. |
| // |
| // Using `absl::node_hash_map` at interface boundaries in dynamically loaded |
| // libraries (e.g. .dll, .so) is unsupported due to way `absl::Hash` values may |
| // be randomized across dynamically loaded libraries. |
| // |
| // Example: |
| // |
| // // Create a node hash map of three strings (that map to strings) |
| // absl::node_hash_map<std::string, std::string> ducks = |
| // {{"a", "huey"}, {"b", "dewey"}, {"c", "louie"}}; |
| // |
| // // Insert a new element into the node hash map |
| // ducks.insert({"d", "donald"}}; |
| // |
| // // Force a rehash of the node hash map |
| // ducks.rehash(0); |
| // |
| // // Find the element with the key "b" |
| // std::string search_key = "b"; |
| // auto result = ducks.find(search_key); |
| // if (result != ducks.end()) { |
| // std::cout << "Result: " << result->second << std::endl; |
| // } |
| template <class Key, class Value, |
| class Hash = absl::container_internal::hash_default_hash<Key>, |
| class Eq = absl::container_internal::hash_default_eq<Key>, |
| class Alloc = std::allocator<std::pair<const Key, Value>>> |
| class node_hash_map |
| : public absl::container_internal::raw_hash_map< |
| absl::container_internal::NodeHashMapPolicy<Key, Value>, Hash, Eq, |
| Alloc> { |
| using Base = typename node_hash_map::raw_hash_map; |
| |
| public: |
| // Constructors and Assignment Operators |
| // |
| // A node_hash_map supports the same overload set as `std::unordered_map` |
| // for construction and assignment: |
| // |
| // * Default constructor |
| // |
| // // No allocation for the table's elements is made. |
| // absl::node_hash_map<int, std::string> map1; |
| // |
| // * Initializer List constructor |
| // |
| // absl::node_hash_map<int, std::string> map2 = |
| // {{1, "huey"}, {2, "dewey"}, {3, "louie"},}; |
| // |
| // * Copy constructor |
| // |
| // absl::node_hash_map<int, std::string> map3(map2); |
| // |
| // * Copy assignment operator |
| // |
| // // Hash functor and Comparator are copied as well |
| // absl::node_hash_map<int, std::string> map4; |
| // map4 = map3; |
| // |
| // * Move constructor |
| // |
| // // Move is guaranteed efficient |
| // absl::node_hash_map<int, std::string> map5(std::move(map4)); |
| // |
| // * Move assignment operator |
| // |
| // // May be efficient if allocators are compatible |
| // absl::node_hash_map<int, std::string> map6; |
| // map6 = std::move(map5); |
| // |
| // * Range constructor |
| // |
| // std::vector<std::pair<int, std::string>> v = {{1, "a"}, {2, "b"}}; |
| // absl::node_hash_map<int, std::string> map7(v.begin(), v.end()); |
| node_hash_map() {} |
| using Base::Base; |
| |
| // node_hash_map::begin() |
| // |
| // Returns an iterator to the beginning of the `node_hash_map`. |
| using Base::begin; |
| |
| // node_hash_map::cbegin() |
| // |
| // Returns a const iterator to the beginning of the `node_hash_map`. |
| using Base::cbegin; |
| |
| // node_hash_map::cend() |
| // |
| // Returns a const iterator to the end of the `node_hash_map`. |
| using Base::cend; |
| |
| // node_hash_map::end() |
| // |
| // Returns an iterator to the end of the `node_hash_map`. |
| using Base::end; |
| |
| // node_hash_map::capacity() |
| // |
| // Returns the number of element slots (assigned, deleted, and empty) |
| // available within the `node_hash_map`. |
| // |
| // NOTE: this member function is particular to `absl::node_hash_map` and is |
| // not provided in the `std::unordered_map` API. |
| using Base::capacity; |
| |
| // node_hash_map::empty() |
| // |
| // Returns whether or not the `node_hash_map` is empty. |
| using Base::empty; |
| |
| // node_hash_map::max_size() |
| // |
| // Returns the largest theoretical possible number of elements within a |
| // `node_hash_map` under current memory constraints. This value can be thought |
| // of as the largest value of `std::distance(begin(), end())` for a |
| // `node_hash_map<K, V>`. |
| using Base::max_size; |
| |
| // node_hash_map::size() |
| // |
| // Returns the number of elements currently within the `node_hash_map`. |
| using Base::size; |
| |
| // node_hash_map::clear() |
| // |
| // Removes all elements from the `node_hash_map`. Invalidates any references, |
| // pointers, or iterators referring to contained elements. |
| // |
| // NOTE: this operation may shrink the underlying buffer. To avoid shrinking |
| // the underlying buffer call `erase(begin(), end())`. |
| using Base::clear; |
| |
| // node_hash_map::erase() |
| // |
| // Erases elements within the `node_hash_map`. Erasing does not trigger a |
| // rehash. Overloads are listed below. |
| // |
| // void erase(const_iterator pos): |
| // |
| // Erases the element at `position` of the `node_hash_map`, returning |
| // `void`. |
| // |
| // NOTE: this return behavior is different than that of STL containers in |
| // general and `std::unordered_map` in particular. |
| // |
| // iterator erase(const_iterator first, const_iterator last): |
| // |
| // Erases the elements in the open interval [`first`, `last`), returning an |
| // iterator pointing to `last`. |
| // |
| // size_type erase(const key_type& key): |
| // |
| // Erases the element with the matching key, if it exists, returning the |
| // number of elements erased (0 or 1). |
| using Base::erase; |
| |
| // node_hash_map::insert() |
| // |
| // Inserts an element of the specified value into the `node_hash_map`, |
| // returning an iterator pointing to the newly inserted element, provided that |
| // an element with the given key does not already exist. If rehashing occurs |
| // due to the insertion, all iterators are invalidated. Overloads are listed |
| // below. |
| // |
| // std::pair<iterator,bool> insert(const init_type& value): |
| // |
| // Inserts a value into the `node_hash_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(T&& value): |
| // std::pair<iterator,bool> insert(init_type&& value): |
| // |
| // Inserts a moveable value into the `node_hash_map`. Returns a `std::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 init_type& value): |
| // iterator insert(const_iterator hint, T&& value): |
| // iterator insert(const_iterator hint, init_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`). |
| // |
| // NOTE: Although the STL does not specify which element may be inserted if |
| // multiple keys compare equivalently, for `node_hash_map` we guarantee the |
| // first match is inserted. |
| // |
| // void insert(std::initializer_list<init_type> ilist): |
| // |
| // Inserts the elements within the initializer list `ilist`. |
| // |
| // NOTE: Although the STL does not specify which element may be inserted if |
| // multiple keys compare equivalently within the initializer list, for |
| // `node_hash_map` we guarantee the first match is inserted. |
| using Base::insert; |
| |
| // node_hash_map::insert_or_assign() |
| // |
| // Inserts an element of the specified value into the `node_hash_map` provided |
| // that a value with the given key does not already exist, or replaces it with |
| // the element value if a key for that value already exists, returning an |
| // iterator pointing to the newly inserted element. If rehashing occurs due to |
| // the insertion, all iterators are invalidated. Overloads are listed |
| // below. |
| // |
| // std::pair<iterator, bool> insert_or_assign(const init_type& k, T&& obj): |
| // std::pair<iterator, bool> insert_or_assign(init_type&& k, T&& obj): |
| // |
| // Inserts/Assigns (or moves) the element of the specified key into the |
| // `node_hash_map`. |
| // |
| // iterator insert_or_assign(const_iterator hint, |
| // const init_type& k, T&& obj): |
| // iterator insert_or_assign(const_iterator hint, init_type&& k, T&& obj): |
| // |
| // Inserts/Assigns (or moves) the element of the specified key into the |
| // `node_hash_map` using the position of `hint` as a non-binding suggestion |
| // for where to begin the insertion search. |
| using Base::insert_or_assign; |
| |
| // node_hash_map::emplace() |
| // |
| // Inserts an element of the specified value by constructing it in-place |
| // within the `node_hash_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 rehashing occurs due to the insertion, all iterators are invalidated. |
| using Base::emplace; |
| |
| // node_hash_map::emplace_hint() |
| // |
| // Inserts an element of the specified value by constructing it in-place |
| // within the `node_hash_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 rehashing occurs due to the insertion, all iterators are invalidated. |
| using Base::emplace_hint; |
| |
| // node_hash_map::try_emplace() |
| // |
| // Inserts an element of the specified value by constructing it in-place |
| // within the `node_hash_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 rehashing occurs due to the insertion, all 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 |
| // `node_hash_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 |
| // `node_hash_map` using the position of `hint` as a non-binding suggestion |
| // for where to begin the insertion search. |
| // |
| // All `try_emplace()` overloads make the same guarantees regarding rvalue |
| // arguments as `std::unordered_map::try_emplace()`, namely that these |
| // functions will not move from rvalue arguments if insertions do not happen. |
| using Base::try_emplace; |
| |
| // node_hash_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 key,value pair of the element at the indicated position and |
| // returns a node handle owning that extracted data. |
| // |
| // node_type extract(const key_type& x): |
| // |
| // Extracts the key,value pair of the element with a key matching the passed |
| // key value and returns a node handle owning that extracted data. If the |
| // `node_hash_map` does not contain an element with a matching key, this |
| // function returns an empty node handle. |
| // |
| // NOTE: when compiled in an earlier version of C++ than C++17, |
| // `node_type::key()` returns a const reference to the key instead of a |
| // mutable reference. We cannot safely return a mutable reference without |
| // std::launder (which is not available before C++17). |
| using Base::extract; |
| |
| // node_hash_map::merge() |
| // |
| // Extracts elements from a given `source` node hash map into this |
| // `node_hash_map`. If the destination `node_hash_map` already contains an |
| // element with an equivalent key, that element is not extracted. |
| using Base::merge; |
| |
| // node_hash_map::swap(node_hash_map& other) |
| // |
| // Exchanges the contents of this `node_hash_map` with those of the `other` |
| // node hash map, avoiding invocation of any move, copy, or swap operations on |
| // individual elements. |
| // |
| // All iterators and references on the `node_hash_map` remain valid, excepting |
| // for the past-the-end iterator, which is invalidated. |
| // |
| // `swap()` requires that the node hash map's hashing and key equivalence |
| // functions be Swappable, and are exchaged using unqualified calls to |
| // non-member `swap()`. If the map's allocator has |
| // `std::allocator_traits<allocator_type>::propagate_on_container_swap::value` |
| // set to `true`, the allocators are also exchanged using an unqualified call |
| // to non-member `swap()`; otherwise, the allocators are not swapped. |
| using Base::swap; |
| |
| // node_hash_map::rehash(count) |
| // |
| // Rehashes the `node_hash_map`, setting the number of slots to be at least |
| // the passed value. If the new number of slots increases the load factor more |
| // than the current maximum load factor |
| // (`count` < `size()` / `max_load_factor()`), then the new number of slots |
| // will be at least `size()` / `max_load_factor()`. |
| // |
| // To force a rehash, pass rehash(0). |
| using Base::rehash; |
| |
| // node_hash_map::reserve(count) |
| // |
| // Sets the number of slots in the `node_hash_map` to the number needed to |
| // accommodate at least `count` total elements without exceeding the current |
| // maximum load factor, and may rehash the container if needed. |
| using Base::reserve; |
| |
| // node_hash_map::at() |
| // |
| // Returns a reference to the mapped value of the element with key equivalent |
| // to the passed key. |
| using Base::at; |
| |
| // node_hash_map::contains() |
| // |
| // Determines whether an element with a key comparing equal to the given `key` |
| // exists within the `node_hash_map`, returning `true` if so or `false` |
| // otherwise. |
| using Base::contains; |
| |
| // node_hash_map::count(const Key& key) const |
| // |
| // Returns the number of elements with a key comparing equal to the given |
| // `key` within the `node_hash_map`. note that this function will return |
| // either `1` or `0` since duplicate keys are not allowed within a |
| // `node_hash_map`. |
| using Base::count; |
| |
| // node_hash_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 |
| // `node_hash_map`. |
| using Base::equal_range; |
| |
| // node_hash_map::find() |
| // |
| // Finds an element with the passed `key` within the `node_hash_map`. |
| using Base::find; |
| |
| // node_hash_map::operator[]() |
| // |
| // Returns a reference to the value mapped to the passed key within the |
| // `node_hash_map`, performing an `insert()` if the key does not already |
| // exist. If an insertion occurs and results in a rehashing of the container, |
| // all iterators are invalidated. Otherwise iterators are not affected and |
| // references are not invalidated. Overloads are listed below. |
| // |
| // T& operator[](const Key& key): |
| // |
| // Inserts an init_type object constructed in-place if the element with the |
| // given key does not exist. |
| // |
| // T& operator[](Key&& key): |
| // |
| // Inserts an init_type object constructed in-place provided that an element |
| // with the given key does not exist. |
| using Base::operator[]; |
| |
| // node_hash_map::bucket_count() |
| // |
| // Returns the number of "buckets" within the `node_hash_map`. |
| using Base::bucket_count; |
| |
| // node_hash_map::load_factor() |
| // |
| // Returns the current load factor of the `node_hash_map` (the average number |
| // of slots occupied with a value within the hash map). |
| using Base::load_factor; |
| |
| // node_hash_map::max_load_factor() |
| // |
| // Manages the maximum load factor of the `node_hash_map`. Overloads are |
| // listed below. |
| // |
| // float node_hash_map::max_load_factor() |
| // |
| // Returns the current maximum load factor of the `node_hash_map`. |
| // |
| // void node_hash_map::max_load_factor(float ml) |
| // |
| // Sets the maximum load factor of the `node_hash_map` to the passed value. |
| // |
| // NOTE: This overload is provided only for API compatibility with the STL; |
| // `node_hash_map` will ignore any set load factor and manage its rehashing |
| // internally as an implementation detail. |
| using Base::max_load_factor; |
| |
| // node_hash_map::get_allocator() |
| // |
| // Returns the allocator function associated with this `node_hash_map`. |
| using Base::get_allocator; |
| |
| // node_hash_map::hash_function() |
| // |
| // Returns the hashing function used to hash the keys within this |
| // `node_hash_map`. |
| using Base::hash_function; |
| |
| // node_hash_map::key_eq() |
| // |
| // Returns the function used for comparing keys equality. |
| using Base::key_eq; |
| }; |
| |
| // erase_if(node_hash_map<>, Pred) |
| // |
| // Erases all elements that satisfy the predicate `pred` from the container `c`. |
| // Returns the number of erased elements. |
| template <typename K, typename V, typename H, typename E, typename A, |
| typename Predicate> |
| typename node_hash_map<K, V, H, E, A>::size_type erase_if( |
| node_hash_map<K, V, H, E, A>& c, Predicate pred) { |
| return container_internal::EraseIf(pred, &c); |
| } |
| |
| namespace container_internal { |
| |
| template <class Key, class Value> |
| class NodeHashMapPolicy |
| : public absl::container_internal::node_slot_policy< |
| std::pair<const Key, Value>&, NodeHashMapPolicy<Key, Value>> { |
| using value_type = std::pair<const Key, Value>; |
| |
| public: |
| using key_type = Key; |
| using mapped_type = Value; |
| using init_type = std::pair</*non const*/ key_type, mapped_type>; |
| |
| template <class Allocator, class... Args> |
| static value_type* new_element(Allocator* alloc, Args&&... args) { |
| using PairAlloc = typename absl::allocator_traits< |
| Allocator>::template rebind_alloc<value_type>; |
| PairAlloc pair_alloc(*alloc); |
| value_type* res = |
| absl::allocator_traits<PairAlloc>::allocate(pair_alloc, 1); |
| absl::allocator_traits<PairAlloc>::construct(pair_alloc, res, |
| std::forward<Args>(args)...); |
| return res; |
| } |
| |
| template <class Allocator> |
| static void delete_element(Allocator* alloc, value_type* pair) { |
| using PairAlloc = typename absl::allocator_traits< |
| Allocator>::template rebind_alloc<value_type>; |
| PairAlloc pair_alloc(*alloc); |
| absl::allocator_traits<PairAlloc>::destroy(pair_alloc, pair); |
| absl::allocator_traits<PairAlloc>::deallocate(pair_alloc, pair, 1); |
| } |
| |
| template <class F, class... Args> |
| static decltype(absl::container_internal::DecomposePair( |
| std::declval<F>(), std::declval<Args>()...)) |
| apply(F&& f, Args&&... args) { |
| return absl::container_internal::DecomposePair(std::forward<F>(f), |
| std::forward<Args>(args)...); |
| } |
| |
| static size_t element_space_used(const value_type*) { |
| return sizeof(value_type); |
| } |
| |
| static Value& value(value_type* elem) { return elem->second; } |
| static const Value& value(const value_type* elem) { return elem->second; } |
| }; |
| } // namespace container_internal |
| |
| namespace container_algorithm_internal { |
| |
| // Specialization of trait in absl/algorithm/container.h |
| template <class Key, class T, class Hash, class KeyEqual, class Allocator> |
| struct IsUnorderedContainer< |
| absl::node_hash_map<Key, T, Hash, KeyEqual, Allocator>> : std::true_type {}; |
| |
| } // namespace container_algorithm_internal |
| |
| ABSL_NAMESPACE_END |
| } // namespace absl |
| |
| #endif // ABSL_CONTAINER_NODE_HASH_MAP_H_ |