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Diffstat (limited to 'deps/include/entt/container/dense_set.hpp')
| -rw-r--r-- | deps/include/entt/container/dense_set.hpp | 927 |
1 files changed, 927 insertions, 0 deletions
diff --git a/deps/include/entt/container/dense_set.hpp b/deps/include/entt/container/dense_set.hpp new file mode 100644 index 0000000..d996dfd --- /dev/null +++ b/deps/include/entt/container/dense_set.hpp @@ -0,0 +1,927 @@ +#ifndef ENTT_CONTAINER_DENSE_SET_HPP
+#define ENTT_CONTAINER_DENSE_SET_HPP
+
+#include <cmath>
+#include <cstddef>
+#include <functional>
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <vector>
+#include "../config/config.h"
+#include "../core/bit.hpp"
+#include "../core/compressed_pair.hpp"
+#include "../core/type_traits.hpp"
+#include "fwd.hpp"
+
+namespace entt {
+
+/*! @cond TURN_OFF_DOXYGEN */
+namespace internal {
+
+template<typename It>
+class dense_set_iterator final {
+ template<typename>
+ friend class dense_set_iterator;
+
+public:
+ using value_type = typename It::value_type::second_type;
+ using pointer = const value_type *;
+ using reference = const value_type &;
+ using difference_type = std::ptrdiff_t;
+ using iterator_category = std::random_access_iterator_tag;
+
+ constexpr dense_set_iterator() noexcept
+ : it{} {}
+
+ constexpr dense_set_iterator(const It iter) noexcept
+ : it{iter} {}
+
+ template<typename Other, typename = std::enable_if_t<!std::is_same_v<It, Other> && std::is_constructible_v<It, Other>>>
+ constexpr dense_set_iterator(const dense_set_iterator<Other> &other) noexcept
+ : it{other.it} {}
+
+ constexpr dense_set_iterator &operator++() noexcept {
+ return ++it, *this;
+ }
+
+ constexpr dense_set_iterator operator++(int) noexcept {
+ dense_set_iterator orig = *this;
+ return ++(*this), orig;
+ }
+
+ constexpr dense_set_iterator &operator--() noexcept {
+ return --it, *this;
+ }
+
+ constexpr dense_set_iterator operator--(int) noexcept {
+ dense_set_iterator orig = *this;
+ return operator--(), orig;
+ }
+
+ constexpr dense_set_iterator &operator+=(const difference_type value) noexcept {
+ it += value;
+ return *this;
+ }
+
+ constexpr dense_set_iterator operator+(const difference_type value) const noexcept {
+ dense_set_iterator copy = *this;
+ return (copy += value);
+ }
+
+ constexpr dense_set_iterator &operator-=(const difference_type value) noexcept {
+ return (*this += -value);
+ }
+
+ constexpr dense_set_iterator operator-(const difference_type value) const noexcept {
+ return (*this + -value);
+ }
+
+ [[nodiscard]] constexpr reference operator[](const difference_type value) const noexcept {
+ return it[value].second;
+ }
+
+ [[nodiscard]] constexpr pointer operator->() const noexcept {
+ return std::addressof(operator[](0));
+ }
+
+ [[nodiscard]] constexpr reference operator*() const noexcept {
+ return operator[](0);
+ }
+
+ template<typename Lhs, typename Rhs>
+ friend constexpr std::ptrdiff_t operator-(const dense_set_iterator<Lhs> &, const dense_set_iterator<Rhs> &) noexcept;
+
+ template<typename Lhs, typename Rhs>
+ friend constexpr bool operator==(const dense_set_iterator<Lhs> &, const dense_set_iterator<Rhs> &) noexcept;
+
+ template<typename Lhs, typename Rhs>
+ friend constexpr bool operator<(const dense_set_iterator<Lhs> &, const dense_set_iterator<Rhs> &) noexcept;
+
+private:
+ It it;
+};
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr std::ptrdiff_t operator-(const dense_set_iterator<Lhs> &lhs, const dense_set_iterator<Rhs> &rhs) noexcept {
+ return lhs.it - rhs.it;
+}
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator==(const dense_set_iterator<Lhs> &lhs, const dense_set_iterator<Rhs> &rhs) noexcept {
+ return lhs.it == rhs.it;
+}
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator!=(const dense_set_iterator<Lhs> &lhs, const dense_set_iterator<Rhs> &rhs) noexcept {
+ return !(lhs == rhs);
+}
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator<(const dense_set_iterator<Lhs> &lhs, const dense_set_iterator<Rhs> &rhs) noexcept {
+ return lhs.it < rhs.it;
+}
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator>(const dense_set_iterator<Lhs> &lhs, const dense_set_iterator<Rhs> &rhs) noexcept {
+ return rhs < lhs;
+}
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator<=(const dense_set_iterator<Lhs> &lhs, const dense_set_iterator<Rhs> &rhs) noexcept {
+ return !(lhs > rhs);
+}
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator>=(const dense_set_iterator<Lhs> &lhs, const dense_set_iterator<Rhs> &rhs) noexcept {
+ return !(lhs < rhs);
+}
+
+template<typename It>
+class dense_set_local_iterator final {
+ template<typename>
+ friend class dense_set_local_iterator;
+
+public:
+ using value_type = typename It::value_type::second_type;
+ using pointer = const value_type *;
+ using reference = const value_type &;
+ using difference_type = std::ptrdiff_t;
+ using iterator_category = std::forward_iterator_tag;
+
+ constexpr dense_set_local_iterator() noexcept
+ : it{},
+ offset{} {}
+
+ constexpr dense_set_local_iterator(It iter, const std::size_t pos) noexcept
+ : it{iter},
+ offset{pos} {}
+
+ template<typename Other, typename = std::enable_if_t<!std::is_same_v<It, Other> && std::is_constructible_v<It, Other>>>
+ constexpr dense_set_local_iterator(const dense_set_local_iterator<Other> &other) noexcept
+ : it{other.it},
+ offset{other.offset} {}
+
+ constexpr dense_set_local_iterator &operator++() noexcept {
+ return offset = it[offset].first, *this;
+ }
+
+ constexpr dense_set_local_iterator operator++(int) noexcept {
+ dense_set_local_iterator orig = *this;
+ return ++(*this), orig;
+ }
+
+ [[nodiscard]] constexpr pointer operator->() const noexcept {
+ return std::addressof(it[offset].second);
+ }
+
+ [[nodiscard]] constexpr reference operator*() const noexcept {
+ return *operator->();
+ }
+
+ [[nodiscard]] constexpr std::size_t index() const noexcept {
+ return offset;
+ }
+
+private:
+ It it;
+ std::size_t offset;
+};
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator==(const dense_set_local_iterator<Lhs> &lhs, const dense_set_local_iterator<Rhs> &rhs) noexcept {
+ return lhs.index() == rhs.index();
+}
+
+template<typename Lhs, typename Rhs>
+[[nodiscard]] constexpr bool operator!=(const dense_set_local_iterator<Lhs> &lhs, const dense_set_local_iterator<Rhs> &rhs) noexcept {
+ return !(lhs == rhs);
+}
+
+} // namespace internal
+/*! @endcond */
+
+/**
+ * @brief Associative container for unique objects of a given type.
+ *
+ * Internally, elements are organized into buckets. Which bucket an element is
+ * placed into depends entirely on its hash. Elements with the same hash code
+ * appear in the same bucket.
+ *
+ * @tparam Type Value type of the associative container.
+ * @tparam Hash Type of function to use to hash the values.
+ * @tparam KeyEqual Type of function to use to compare the values for equality.
+ * @tparam Allocator Type of allocator used to manage memory and elements.
+ */
+template<typename Type, typename Hash, typename KeyEqual, typename Allocator>
+class dense_set {
+ static constexpr float default_threshold = 0.875f;
+ static constexpr std::size_t minimum_capacity = 8u;
+
+ using node_type = std::pair<std::size_t, Type>;
+ using alloc_traits = std::allocator_traits<Allocator>;
+ static_assert(std::is_same_v<typename alloc_traits::value_type, Type>, "Invalid value type");
+ using sparse_container_type = std::vector<std::size_t, typename alloc_traits::template rebind_alloc<std::size_t>>;
+ using packed_container_type = std::vector<node_type, typename alloc_traits::template rebind_alloc<node_type>>;
+
+ template<typename Other>
+ [[nodiscard]] std::size_t value_to_bucket(const Other &value) const noexcept {
+ return fast_mod(static_cast<size_type>(sparse.second()(value)), bucket_count());
+ }
+
+ template<typename Other>
+ [[nodiscard]] auto constrained_find(const Other &value, std::size_t bucket) {
+ for(auto it = begin(bucket), last = end(bucket); it != last; ++it) {
+ if(packed.second()(*it, value)) {
+ return begin() + static_cast<typename iterator::difference_type>(it.index());
+ }
+ }
+
+ return end();
+ }
+
+ template<typename Other>
+ [[nodiscard]] auto constrained_find(const Other &value, std::size_t bucket) const {
+ for(auto it = cbegin(bucket), last = cend(bucket); it != last; ++it) {
+ if(packed.second()(*it, value)) {
+ return cbegin() + static_cast<typename iterator::difference_type>(it.index());
+ }
+ }
+
+ return cend();
+ }
+
+ template<typename Other>
+ [[nodiscard]] auto insert_or_do_nothing(Other &&value) {
+ const auto index = value_to_bucket(value);
+
+ if(auto it = constrained_find(value, index); it != end()) {
+ return std::make_pair(it, false);
+ }
+
+ packed.first().emplace_back(sparse.first()[index], std::forward<Other>(value));
+ sparse.first()[index] = packed.first().size() - 1u;
+ rehash_if_required();
+
+ return std::make_pair(--end(), true);
+ }
+
+ void move_and_pop(const std::size_t pos) {
+ if(const auto last = size() - 1u; pos != last) {
+ size_type *curr = &sparse.first()[value_to_bucket(packed.first().back().second)];
+ packed.first()[pos] = std::move(packed.first().back());
+ for(; *curr != last; curr = &packed.first()[*curr].first) {}
+ *curr = pos;
+ }
+
+ packed.first().pop_back();
+ }
+
+ void rehash_if_required() {
+ if(size() > (bucket_count() * max_load_factor())) {
+ rehash(bucket_count() * 2u);
+ }
+ }
+
+public:
+ /*! @brief Allocator type. */
+ using allocator_type = Allocator;
+ /*! @brief Key type of the container. */
+ using key_type = Type;
+ /*! @brief Value type of the container. */
+ using value_type = Type;
+ /*! @brief Unsigned integer type. */
+ using size_type = std::size_t;
+ /*! @brief Type of function to use to hash the elements. */
+ using hasher = Hash;
+ /*! @brief Type of function to use to compare the elements for equality. */
+ using key_equal = KeyEqual;
+ /*! @brief Random access iterator type. */
+ using iterator = internal::dense_set_iterator<typename packed_container_type::iterator>;
+ /*! @brief Constant random access iterator type. */
+ using const_iterator = internal::dense_set_iterator<typename packed_container_type::const_iterator>;
+ /*! @brief Reverse iterator type. */
+ using reverse_iterator = std::reverse_iterator<iterator>;
+ /*! @brief Constant reverse iterator type. */
+ using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+ /*! @brief Forward iterator type. */
+ using local_iterator = internal::dense_set_local_iterator<typename packed_container_type::iterator>;
+ /*! @brief Constant forward iterator type. */
+ using const_local_iterator = internal::dense_set_local_iterator<typename packed_container_type::const_iterator>;
+
+ /*! @brief Default constructor. */
+ dense_set()
+ : dense_set{minimum_capacity} {}
+
+ /**
+ * @brief Constructs an empty container with a given allocator.
+ * @param allocator The allocator to use.
+ */
+ explicit dense_set(const allocator_type &allocator)
+ : dense_set{minimum_capacity, hasher{}, key_equal{}, allocator} {}
+
+ /**
+ * @brief Constructs an empty container with a given allocator and user
+ * supplied minimal number of buckets.
+ * @param cnt Minimal number of buckets.
+ * @param allocator The allocator to use.
+ */
+ dense_set(const size_type cnt, const allocator_type &allocator)
+ : dense_set{cnt, hasher{}, key_equal{}, allocator} {}
+
+ /**
+ * @brief Constructs an empty container with a given allocator, hash
+ * function and user supplied minimal number of buckets.
+ * @param cnt Minimal number of buckets.
+ * @param hash Hash function to use.
+ * @param allocator The allocator to use.
+ */
+ dense_set(const size_type cnt, const hasher &hash, const allocator_type &allocator)
+ : dense_set{cnt, hash, key_equal{}, allocator} {}
+
+ /**
+ * @brief Constructs an empty container with a given allocator, hash
+ * function, compare function and user supplied minimal number of buckets.
+ * @param cnt Minimal number of buckets.
+ * @param hash Hash function to use.
+ * @param equal Compare function to use.
+ * @param allocator The allocator to use.
+ */
+ explicit dense_set(const size_type cnt, const hasher &hash = hasher{}, const key_equal &equal = key_equal{}, const allocator_type &allocator = allocator_type{})
+ : sparse{allocator, hash},
+ packed{allocator, equal} {
+ rehash(cnt);
+ }
+
+ /*! @brief Default copy constructor. */
+ dense_set(const dense_set &) = default;
+
+ /**
+ * @brief Allocator-extended copy constructor.
+ * @param other The instance to copy from.
+ * @param allocator The allocator to use.
+ */
+ dense_set(const dense_set &other, const allocator_type &allocator)
+ : sparse{std::piecewise_construct, std::forward_as_tuple(other.sparse.first(), allocator), std::forward_as_tuple(other.sparse.second())},
+ packed{std::piecewise_construct, std::forward_as_tuple(other.packed.first(), allocator), std::forward_as_tuple(other.packed.second())},
+ threshold{other.threshold} {}
+
+ /*! @brief Default move constructor. */
+ dense_set(dense_set &&) noexcept(std::is_nothrow_move_constructible_v<compressed_pair<sparse_container_type, hasher>> && std::is_nothrow_move_constructible_v<compressed_pair<packed_container_type, key_equal>>) = default;
+
+ /**
+ * @brief Allocator-extended move constructor.
+ * @param other The instance to move from.
+ * @param allocator The allocator to use.
+ */
+ dense_set(dense_set &&other, const allocator_type &allocator)
+ : sparse{std::piecewise_construct, std::forward_as_tuple(std::move(other.sparse.first()), allocator), std::forward_as_tuple(std::move(other.sparse.second()))},
+ packed{std::piecewise_construct, std::forward_as_tuple(std::move(other.packed.first()), allocator), std::forward_as_tuple(std::move(other.packed.second()))},
+ threshold{other.threshold} {}
+
+ /*! @brief Default destructor. */
+ ~dense_set() noexcept = default;
+
+ /**
+ * @brief Default copy assignment operator.
+ * @return This container.
+ */
+ dense_set &operator=(const dense_set &) = default;
+
+ /**
+ * @brief Default move assignment operator.
+ * @return This container.
+ */
+ dense_set &operator=(dense_set &&) noexcept(std::is_nothrow_move_assignable_v<compressed_pair<sparse_container_type, hasher>> && std::is_nothrow_move_assignable_v<compressed_pair<packed_container_type, key_equal>>) = default;
+
+ /**
+ * @brief Returns the associated allocator.
+ * @return The associated allocator.
+ */
+ [[nodiscard]] constexpr allocator_type get_allocator() const noexcept {
+ return sparse.first().get_allocator();
+ }
+
+ /**
+ * @brief Returns an iterator to the beginning.
+ *
+ * If the array is empty, the returned iterator will be equal to `end()`.
+ *
+ * @return An iterator to the first instance of the internal array.
+ */
+ [[nodiscard]] const_iterator cbegin() const noexcept {
+ return packed.first().begin();
+ }
+
+ /*! @copydoc cbegin */
+ [[nodiscard]] const_iterator begin() const noexcept {
+ return cbegin();
+ }
+
+ /*! @copydoc begin */
+ [[nodiscard]] iterator begin() noexcept {
+ return packed.first().begin();
+ }
+
+ /**
+ * @brief Returns an iterator to the end.
+ * @return An iterator to the element following the last instance of the
+ * internal array.
+ */
+ [[nodiscard]] const_iterator cend() const noexcept {
+ return packed.first().end();
+ }
+
+ /*! @copydoc cend */
+ [[nodiscard]] const_iterator end() const noexcept {
+ return cend();
+ }
+
+ /*! @copydoc end */
+ [[nodiscard]] iterator end() noexcept {
+ return packed.first().end();
+ }
+
+ /**
+ * @brief Returns a reverse iterator to the beginning.
+ *
+ * If the array is empty, the returned iterator will be equal to `rend()`.
+ *
+ * @return An iterator to the first instance of the reversed internal array.
+ */
+ [[nodiscard]] const_reverse_iterator crbegin() const noexcept {
+ return std::make_reverse_iterator(cend());
+ }
+
+ /*! @copydoc crbegin */
+ [[nodiscard]] const_reverse_iterator rbegin() const noexcept {
+ return crbegin();
+ }
+
+ /*! @copydoc rbegin */
+ [[nodiscard]] reverse_iterator rbegin() noexcept {
+ return std::make_reverse_iterator(end());
+ }
+
+ /**
+ * @brief Returns a reverse iterator to the end.
+ * @return An iterator to the element following the last instance of the
+ * reversed internal array.
+ */
+ [[nodiscard]] const_reverse_iterator crend() const noexcept {
+ return std::make_reverse_iterator(cbegin());
+ }
+
+ /*! @copydoc crend */
+ [[nodiscard]] const_reverse_iterator rend() const noexcept {
+ return crend();
+ }
+
+ /*! @copydoc rend */
+ [[nodiscard]] reverse_iterator rend() noexcept {
+ return std::make_reverse_iterator(begin());
+ }
+
+ /**
+ * @brief Checks whether a container is empty.
+ * @return True if the container is empty, false otherwise.
+ */
+ [[nodiscard]] bool empty() const noexcept {
+ return packed.first().empty();
+ }
+
+ /**
+ * @brief Returns the number of elements in a container.
+ * @return Number of elements in a container.
+ */
+ [[nodiscard]] size_type size() const noexcept {
+ return packed.first().size();
+ }
+
+ /**
+ * @brief Returns the maximum possible number of elements.
+ * @return Maximum possible number of elements.
+ */
+ [[nodiscard]] size_type max_size() const noexcept {
+ return packed.first().max_size();
+ }
+
+ /*! @brief Clears the container. */
+ void clear() noexcept {
+ sparse.first().clear();
+ packed.first().clear();
+ rehash(0u);
+ }
+
+ /**
+ * @brief Inserts an element into the container, if it does not exist.
+ * @param value An element to insert into the container.
+ * @return 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(const value_type &value) {
+ return insert_or_do_nothing(value);
+ }
+
+ /*! @copydoc insert */
+ std::pair<iterator, bool> insert(value_type &&value) {
+ return insert_or_do_nothing(std::move(value));
+ }
+
+ /**
+ * @brief Inserts elements into the container, if they do not exist.
+ * @tparam It Type of input iterator.
+ * @param first An iterator to the first element of the range of elements.
+ * @param last An iterator past the last element of the range of elements.
+ */
+ template<typename It>
+ void insert(It first, It last) {
+ for(; first != last; ++first) {
+ insert(*first);
+ }
+ }
+
+ /**
+ * @brief Constructs an element in-place, if it does not exist.
+ *
+ * The element is also constructed when the container already has the key,
+ * in which case the newly constructed object is destroyed immediately.
+ *
+ * @tparam Args Types of arguments to forward to the constructor of the
+ * element.
+ * @param args Arguments to forward to the constructor of the element.
+ * @return 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.
+ */
+ template<typename... Args>
+ std::pair<iterator, bool> emplace(Args &&...args) {
+ if constexpr(((sizeof...(Args) == 1u) && ... && std::is_same_v<std::decay_t<Args>, value_type>)) {
+ return insert_or_do_nothing(std::forward<Args>(args)...);
+ } else {
+ auto &node = packed.first().emplace_back(std::piecewise_construct, std::make_tuple(packed.first().size()), std::forward_as_tuple(std::forward<Args>(args)...));
+ const auto index = value_to_bucket(node.second);
+
+ if(auto it = constrained_find(node.second, index); it != end()) {
+ packed.first().pop_back();
+ return std::make_pair(it, false);
+ }
+
+ std::swap(node.first, sparse.first()[index]);
+ rehash_if_required();
+
+ return std::make_pair(--end(), true);
+ }
+ }
+
+ /**
+ * @brief Removes an element from a given position.
+ * @param pos An iterator to the element to remove.
+ * @return An iterator following the removed element.
+ */
+ iterator erase(const_iterator pos) {
+ const auto diff = pos - cbegin();
+ erase(*pos);
+ return begin() + diff;
+ }
+
+ /**
+ * @brief Removes the given elements from a container.
+ * @param first An iterator to the first element of the range of elements.
+ * @param last An iterator past the last element of the range of elements.
+ * @return An iterator following the last removed element.
+ */
+ iterator erase(const_iterator first, const_iterator last) {
+ const auto dist = first - cbegin();
+
+ for(auto from = last - cbegin(); from != dist; --from) {
+ erase(packed.first()[from - 1u].second);
+ }
+
+ return (begin() + dist);
+ }
+
+ /**
+ * @brief Removes the element associated with a given value.
+ * @param value Value of an element to remove.
+ * @return Number of elements removed (either 0 or 1).
+ */
+ size_type erase(const value_type &value) {
+ for(size_type *curr = &sparse.first()[value_to_bucket(value)]; *curr != (std::numeric_limits<size_type>::max)(); curr = &packed.first()[*curr].first) {
+ if(packed.second()(packed.first()[*curr].second, value)) {
+ const auto index = *curr;
+ *curr = packed.first()[*curr].first;
+ move_and_pop(index);
+ return 1u;
+ }
+ }
+
+ return 0u;
+ }
+
+ /**
+ * @brief Exchanges the contents with those of a given container.
+ * @param other Container to exchange the content with.
+ */
+ void swap(dense_set &other) {
+ using std::swap;
+ swap(sparse, other.sparse);
+ swap(packed, other.packed);
+ swap(threshold, other.threshold);
+ }
+
+ /**
+ * @brief Returns the number of elements matching a value (either 1 or 0).
+ * @param key Key value of an element to search for.
+ * @return Number of elements matching the key (either 1 or 0).
+ */
+ [[nodiscard]] size_type count(const value_type &key) const {
+ return find(key) != end();
+ }
+
+ /**
+ * @brief Returns the number of elements matching a key (either 1 or 0).
+ * @tparam Other Type of the key value of an element to search for.
+ * @param key Key value of an element to search for.
+ * @return Number of elements matching the key (either 1 or 0).
+ */
+ template<typename Other>
+ [[nodiscard]] std::enable_if_t<is_transparent_v<hasher> && is_transparent_v<key_equal>, std::conditional_t<false, Other, size_type>>
+ count(const Other &key) const {
+ return find(key) != end();
+ }
+
+ /**
+ * @brief Finds an element with a given value.
+ * @param value Value of an element to search for.
+ * @return An iterator to an element with the given value. If no such
+ * element is found, a past-the-end iterator is returned.
+ */
+ [[nodiscard]] iterator find(const value_type &value) {
+ return constrained_find(value, value_to_bucket(value));
+ }
+
+ /*! @copydoc find */
+ [[nodiscard]] const_iterator find(const value_type &value) const {
+ return constrained_find(value, value_to_bucket(value));
+ }
+
+ /**
+ * @brief Finds an element that compares _equivalent_ to a given value.
+ * @tparam Other Type of an element to search for.
+ * @param value Value of an element to search for.
+ * @return An iterator to an element with the given value. If no such
+ * element is found, a past-the-end iterator is returned.
+ */
+ template<typename Other>
+ [[nodiscard]] std::enable_if_t<is_transparent_v<hasher> && is_transparent_v<key_equal>, std::conditional_t<false, Other, iterator>>
+ find(const Other &value) {
+ return constrained_find(value, value_to_bucket(value));
+ }
+
+ /*! @copydoc find */
+ template<typename Other>
+ [[nodiscard]] std::enable_if_t<is_transparent_v<hasher> && is_transparent_v<key_equal>, std::conditional_t<false, Other, const_iterator>>
+ find(const Other &value) const {
+ return constrained_find(value, value_to_bucket(value));
+ }
+
+ /**
+ * @brief Returns a range containing all elements with a given value.
+ * @param value Value of an element to search for.
+ * @return A pair of iterators pointing to the first element and past the
+ * last element of the range.
+ */
+ [[nodiscard]] std::pair<iterator, iterator> equal_range(const value_type &value) {
+ const auto it = find(value);
+ return {it, it + !(it == end())};
+ }
+
+ /*! @copydoc equal_range */
+ [[nodiscard]] std::pair<const_iterator, const_iterator> equal_range(const value_type &value) const {
+ const auto it = find(value);
+ return {it, it + !(it == cend())};
+ }
+
+ /**
+ * @brief Returns a range containing all elements that compare _equivalent_
+ * to a given value.
+ * @tparam Other Type of an element to search for.
+ * @param value Value of an element to search for.
+ * @return A pair of iterators pointing to the first element and past the
+ * last element of the range.
+ */
+ template<typename Other>
+ [[nodiscard]] std::enable_if_t<is_transparent_v<hasher> && is_transparent_v<key_equal>, std::conditional_t<false, Other, std::pair<iterator, iterator>>>
+ equal_range(const Other &value) {
+ const auto it = find(value);
+ return {it, it + !(it == end())};
+ }
+
+ /*! @copydoc equal_range */
+ template<typename Other>
+ [[nodiscard]] std::enable_if_t<is_transparent_v<hasher> && is_transparent_v<key_equal>, std::conditional_t<false, Other, std::pair<const_iterator, const_iterator>>>
+ equal_range(const Other &value) const {
+ const auto it = find(value);
+ return {it, it + !(it == cend())};
+ }
+
+ /**
+ * @brief Checks if the container contains an element with a given value.
+ * @param value Value of an element to search for.
+ * @return True if there is such an element, false otherwise.
+ */
+ [[nodiscard]] bool contains(const value_type &value) const {
+ return (find(value) != cend());
+ }
+
+ /**
+ * @brief Checks if the container contains an element that compares
+ * _equivalent_ to a given value.
+ * @tparam Other Type of an element to search for.
+ * @param value Value of an element to search for.
+ * @return True if there is such an element, false otherwise.
+ */
+ template<typename Other>
+ [[nodiscard]] std::enable_if_t<is_transparent_v<hasher> && is_transparent_v<key_equal>, std::conditional_t<false, Other, bool>>
+ contains(const Other &value) const {
+ return (find(value) != cend());
+ }
+
+ /**
+ * @brief Returns an iterator to the beginning of a given bucket.
+ * @param index An index of a bucket to access.
+ * @return An iterator to the beginning of the given bucket.
+ */
+ [[nodiscard]] const_local_iterator cbegin(const size_type index) const {
+ return {packed.first().begin(), sparse.first()[index]};
+ }
+
+ /**
+ * @brief Returns an iterator to the beginning of a given bucket.
+ * @param index An index of a bucket to access.
+ * @return An iterator to the beginning of the given bucket.
+ */
+ [[nodiscard]] const_local_iterator begin(const size_type index) const {
+ return cbegin(index);
+ }
+
+ /**
+ * @brief Returns an iterator to the beginning of a given bucket.
+ * @param index An index of a bucket to access.
+ * @return An iterator to the beginning of the given bucket.
+ */
+ [[nodiscard]] local_iterator begin(const size_type index) {
+ return {packed.first().begin(), sparse.first()[index]};
+ }
+
+ /**
+ * @brief Returns an iterator to the end of a given bucket.
+ * @param index An index of a bucket to access.
+ * @return An iterator to the end of the given bucket.
+ */
+ [[nodiscard]] const_local_iterator cend([[maybe_unused]] const size_type index) const {
+ return {packed.first().begin(), (std::numeric_limits<size_type>::max)()};
+ }
+
+ /**
+ * @brief Returns an iterator to the end of a given bucket.
+ * @param index An index of a bucket to access.
+ * @return An iterator to the end of the given bucket.
+ */
+ [[nodiscard]] const_local_iterator end(const size_type index) const {
+ return cend(index);
+ }
+
+ /**
+ * @brief Returns an iterator to the end of a given bucket.
+ * @param index An index of a bucket to access.
+ * @return An iterator to the end of the given bucket.
+ */
+ [[nodiscard]] local_iterator end([[maybe_unused]] const size_type index) {
+ return {packed.first().begin(), (std::numeric_limits<size_type>::max)()};
+ }
+
+ /**
+ * @brief Returns the number of buckets.
+ * @return The number of buckets.
+ */
+ [[nodiscard]] size_type bucket_count() const {
+ return sparse.first().size();
+ }
+
+ /**
+ * @brief Returns the maximum number of buckets.
+ * @return The maximum number of buckets.
+ */
+ [[nodiscard]] size_type max_bucket_count() const {
+ return sparse.first().max_size();
+ }
+
+ /**
+ * @brief Returns the number of elements in a given bucket.
+ * @param index The index of the bucket to examine.
+ * @return The number of elements in the given bucket.
+ */
+ [[nodiscard]] size_type bucket_size(const size_type index) const {
+ return static_cast<size_type>(std::distance(begin(index), end(index)));
+ }
+
+ /**
+ * @brief Returns the bucket for a given element.
+ * @param value The value of the element to examine.
+ * @return The bucket for the given element.
+ */
+ [[nodiscard]] size_type bucket(const value_type &value) const {
+ return value_to_bucket(value);
+ }
+
+ /**
+ * @brief Returns the average number of elements per bucket.
+ * @return The average number of elements per bucket.
+ */
+ [[nodiscard]] float load_factor() const {
+ return size() / static_cast<float>(bucket_count());
+ }
+
+ /**
+ * @brief Returns the maximum average number of elements per bucket.
+ * @return The maximum average number of elements per bucket.
+ */
+ [[nodiscard]] float max_load_factor() const {
+ return threshold;
+ }
+
+ /**
+ * @brief Sets the desired maximum average number of elements per bucket.
+ * @param value A desired maximum average number of elements per bucket.
+ */
+ void max_load_factor(const float value) {
+ ENTT_ASSERT(value > 0.f, "Invalid load factor");
+ threshold = value;
+ rehash(0u);
+ }
+
+ /**
+ * @brief Reserves at least the specified number of buckets and regenerates
+ * the hash table.
+ * @param cnt New number of buckets.
+ */
+ void rehash(const size_type cnt) {
+ auto value = cnt > minimum_capacity ? cnt : minimum_capacity;
+ const auto cap = static_cast<size_type>(size() / max_load_factor());
+ value = value > cap ? value : cap;
+
+ if(const auto sz = next_power_of_two(value); sz != bucket_count()) {
+ sparse.first().resize(sz);
+
+ for(auto &&elem: sparse.first()) {
+ elem = (std::numeric_limits<size_type>::max)();
+ }
+
+ for(size_type pos{}, last = size(); pos < last; ++pos) {
+ const auto index = value_to_bucket(packed.first()[pos].second);
+ packed.first()[pos].first = std::exchange(sparse.first()[index], pos);
+ }
+ }
+ }
+
+ /**
+ * @brief Reserves space for at least the specified number of elements and
+ * regenerates the hash table.
+ * @param cnt New number of elements.
+ */
+ void reserve(const size_type cnt) {
+ packed.first().reserve(cnt);
+ rehash(static_cast<size_type>(std::ceil(cnt / max_load_factor())));
+ }
+
+ /**
+ * @brief Returns the function used to hash the elements.
+ * @return The function used to hash the elements.
+ */
+ [[nodiscard]] hasher hash_function() const {
+ return sparse.second();
+ }
+
+ /**
+ * @brief Returns the function used to compare elements for equality.
+ * @return The function used to compare elements for equality.
+ */
+ [[nodiscard]] key_equal key_eq() const {
+ return packed.second();
+ }
+
+private:
+ compressed_pair<sparse_container_type, hasher> sparse;
+ compressed_pair<packed_container_type, key_equal> packed;
+ float threshold{default_threshold};
+};
+
+} // namespace entt
+
+#endif
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