BSTHashMap.h

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#pragma once
 
#include "RE/B/BSTTuple.h"
#include "RE/C/CRC.h"
#include "RE/M/MemoryManager.h"
 
namespace RE
{
    namespace detail
    {
        static constexpr std::uint8_t BSTScatterTableSentinel[] = { 0xDEu, 0xADu, 0xBEu, 0xEFu };
    }
 
    // scatter table with chaining
    template <
        class Hash,
        class KeyEqual,
        class Traits,
        template <std::size_t, std::size_t> class Allocator>
    class BSTScatterTable
    {
    public:
        using traits_type = Traits;
        using key_type = typename Traits::key_type;
        using mapped_type = typename Traits::mapped_type;
        using value_type = typename Traits::value_type;
        using size_type = std::uint32_t;
        using difference_type = std::int32_t;
        using hasher = Hash;
        using key_equal = KeyEqual;
        using reference = value_type&;
        using const_reference = const value_type&;
        using pointer = value_type*;
        using const_pointer = const value_type*;
 
        static_assert(std::is_invocable_r_v<size_type, const hasher&, const key_type&>);
        static_assert(std::is_invocable_r_v<bool, const key_equal&, const key_type&, const key_type&>);
 
    private:
        struct entry_type
        {
            entry_type() = default;
            entry_type(const entry_type&) = delete;
 
            entry_type(entry_type&& a_rhs)  //
                noexcept(std::is_nothrow_move_constructible_v<value_type>&&
                        std::is_nothrow_destructible_v<value_type>)
            {
                if (a_rhs.has_value()) {
                    const auto rnext = a_rhs.next;
                    emplace(std::move(a_rhs).steal(), rnext);
                }
            }
 
            ~entry_type() noexcept { destroy(); };
 
            entry_type& operator=(const entry_type&) = delete;
 
            entry_type& operator=(entry_type&& a_rhs)  //
                noexcept(std::is_nothrow_move_constructible_v<value_type>&&
                        std::is_nothrow_destructible_v<value_type>)
            {
                if (this != std::addressof(a_rhs)) {
                    destroy();
                    if (a_rhs.has_value()) {
                        const auto rnext = a_rhs.next;
                        emplace(std::move(a_rhs).steal(), rnext);
                    }
                }
                return *this;
            }
 
            [[nodiscard]] bool has_value() const noexcept { return next != nullptr; }
 
            void destroy()  //
                noexcept(std::is_nothrow_destructible_v<value_type>)
            {
                if (has_value()) {
                    std::destroy_at(std::addressof(value));
                    next = nullptr;
                }
                assert(!has_value());
            }
 
            template <class Arg>
            void emplace(Arg&& a_value, const entry_type* a_next)  //
                noexcept(std::is_nothrow_constructible_v<value_type, Arg>)
            {
                static_assert(std::same_as<std::decay_t<Arg>, value_type>);
                destroy();
                std::construct_at(std::addressof(value), std::forward<Arg>(a_value));
                next = const_cast<entry_type*>(a_next);
                assert(has_value());
            }
 
            [[nodiscard]] value_type steal() &&  //
                noexcept(std::is_nothrow_move_constructible_v<value_type>&&
                        std::is_nothrow_destructible_v<value_type>)
            {
                assert(has_value());
                value_type val = std::move(value);
                destroy();
                assert(!has_value());
                return val;
            }
 
            union
            {
                value_type value;
                std::byte  buffer[sizeof(value_type)]{ static_cast<std::byte>(0) };
            };
            entry_type* next{ nullptr };
        };
 
        template <class U>
        class iterator_base
        {
        public:
            using difference_type = std::ptrdiff_t;
            using value_type = std::remove_const_t<U>;
            using pointer = value_type*;
            using reference = value_type&;
            using iterator_category = std::forward_iterator_tag;
 
            iterator_base() = default;
            ~iterator_base() = default;
 
            iterator_base(const volatile iterator_base&) = delete;
            iterator_base& operator=(const volatile iterator_base&) = delete;
 
            template <class V>
            iterator_base(const iterator_base<V>& a_rhs) noexcept  //
                requires(std::convertible_to<typename iterator_base<V>::reference, reference>) :
                _first(a_rhs._first),
                _last(a_rhs._last)
            {}
 
            template <class V>
            iterator_base& operator=(const iterator_base<V>& a_rhs) noexcept  //
                requires(std::convertible_to<typename iterator_base<V>::reference, reference>)
            {
                assert(_last == a_rhs._last);
                _first = a_rhs._first;
                _last = a_rhs._last;
                return *this;
            }
 
            [[nodiscard]] reference operator*() const noexcept
            {
                assert(iterable());
                assert(_first->has_value());
                return _first->value;
            }
 
            template <class V>
            [[nodiscard]] bool operator==(const iterator_base<V>& a_rhs) const noexcept
            {
                assert(_last == a_rhs._last);
                return _first == a_rhs._first;
            }
 
            iterator_base& operator++() noexcept
            {
                seek();
                return *this;
            }
 
            iterator_base operator++(int) noexcept
            {
                iterator_base result = *this;
                ++result;
                return result;
            }
 
            [[nodiscard]] pointer operator->() const noexcept
            {
                return &**this;
            }
 
        protected:
            friend class BSTScatterTable;
 
            iterator_base(entry_type* a_first, entry_type* a_last) noexcept :
                _first(a_first),
                _last(a_last)
            {
                assert(!!_first == !!_last);  // both or neither have values
                assert(_first <= _last);
                if (iterable() && !_first->has_value()) {
                    seek();
                }
            }
 
            [[nodiscard]] entry_type* get_entry() const noexcept { return _first; }
 
        private:
            template <class>
            friend class iterator_base;
 
            [[nodiscard]] bool iterable() const noexcept { return _first && _last && _first != _last; }
 
            void seek() noexcept
            {
                assert(iterable());
                do {
                    ++_first;
                } while (_first != _last && !_first->has_value());
            }
 
            entry_type* _first{ nullptr };
            entry_type* _last{ nullptr };
        };
 
    public:
        using allocator_type = Allocator<sizeof(entry_type), alignof(entry_type)>;
        using iterator = iterator_base<value_type>;
        using const_iterator = iterator_base<const value_type>;
 
        BSTScatterTable() = default;
 
        BSTScatterTable(const BSTScatterTable& a_rhs) { insert(a_rhs.begin(), a_rhs.end()); }
 
        BSTScatterTable(BSTScatterTable&& a_rhs) noexcept  //
            requires(std::same_as<typename allocator_type::propagate_on_container_move_assignment, std::true_type>) :
            _capacity(std::exchange(a_rhs._capacity, 0)),
            _free(std::exchange(a_rhs._free, 0)),
            _good(std::exchange(a_rhs._good, 0)),
            _sentinel(a_rhs._sentinel),
            _allocator(std::move(a_rhs._allocator))
        {
            assert(a_rhs.empty());
        }
 
        ~BSTScatterTable() { free_resources(); }
 
        BSTScatterTable& operator=(const BSTScatterTable& a_rhs)
        {
            if (this != std::addressof(a_rhs)) {
                clear();
                insert(a_rhs.begin(), a_rhs.end());
            }
            return *this;
        }
 
        BSTScatterTable& operator=(BSTScatterTable&& a_rhs)  //
            requires(std::same_as<typename allocator_type::propagate_on_container_move_assignment, std::true_type>)
        {
            if (this != std::addressof(a_rhs)) {
                free_resources();
 
                _capacity = std::exchange(a_rhs._capacity, 0);
                _free = std::exchange(a_rhs._free, 0);
                _good = std::exchange(a_rhs._good, 0);
                _sentinel = a_rhs._sentinel;
                _allocator = std::move(a_rhs._allocator);
 
                assert(a_rhs.empty());
            }
            return *this;
        }
 
        [[nodiscard]] iterator       begin() noexcept { return make_iterator<iterator>(get_entries()); }
        [[nodiscard]] const_iterator begin() const noexcept { return make_iterator<const_iterator>(get_entries()); }
        [[nodiscard]] const_iterator cbegin() const noexcept { return make_iterator<const_iterator>(get_entries()); }
 
        [[nodiscard]] iterator       end() noexcept { return make_iterator<iterator>(); }
        [[nodiscard]] const_iterator end() const noexcept { return make_iterator<const_iterator>(); }
        [[nodiscard]] const_iterator cend() const noexcept { return make_iterator<const_iterator>(); }
 
        [[nodiscard]] bool      empty() const noexcept { return size() == 0; }
        [[nodiscard]] size_type size() const noexcept { return _capacity - _free; }
 
        void clear()
        {
            if (size() > 0) {
                const auto entries = get_entries();
                assert(entries != nullptr);
                for (size_type i = 0; i < _capacity; ++i) {
                    entries[i].destroy();
                }
                _free = _capacity;
                _good = 0;
            }
 
            assert(empty());
        }
 
        std::pair<iterator, bool> insert(const value_type& a_value) { return do_insert(a_value); }
        std::pair<iterator, bool> insert(value_type&& a_value) { return do_insert(std::move(a_value)); }
 
        template <std::input_iterator InputIt>
        void insert(InputIt a_first, InputIt a_last)  //
            requires(std::convertible_to<std::iter_reference_t<InputIt>, const_reference>)
        {
            reserve(size() + static_cast<size_type>(std::distance(a_first, a_last)));
            for (; a_first != a_last; ++a_first) {
                insert(*std::move(a_first));
            }
        }
 
        template <class... Args>
        std::pair<iterator, bool> emplace(Args&&... a_args)  //
            requires(std::constructible_from<value_type, Args...>)
        {
            return insert(value_type(std::forward<Args>(a_args)...));
        }
 
        iterator erase(const_iterator a_pos) { return do_erase(a_pos); }
        iterator erase(iterator a_pos) { return do_erase(a_pos); }
 
        size_type erase(const key_type& a_key)
        {
            const auto pos = find(a_key);
            const auto result = pos != end() ? erase(pos) : pos;
            return result != end() ? 1 : 0;
        }
 
        [[nodiscard]] iterator       find(const key_type& a_key) { return do_find<iterator>(a_key); }
        [[nodiscard]] const_iterator find(const key_type& a_key) const { return do_find<const_iterator>(a_key); }
 
        [[nodiscard]] bool contains(const key_type& a_key) const { return find(a_key) != end(); }
 
        void reserve(size_type a_count)
        {
            if (a_count <= _capacity) {
                return;
            }
 
            const auto oldCap = _capacity;
            const auto oldEntries = get_entries();
 
            const auto [newCap, newEntries] = [&]() {
                constexpr std::uint64_t min = allocator_type::min_size();
                static_assert(min > 0 && std::has_single_bit(min));
                const auto cap = std::max(std::bit_ceil<std::uint64_t>(a_count), min);
                assert(cap >= min);
                if (cap > 1u << 31) {
                    stl::report_and_fail("a buffer grew too large"sv);
                }
 
                const auto entries = allocate(static_cast<size_type>(cap));
                if (!entries) {
                    stl::report_and_fail("failed to handle an allocation"sv);
                }
 
                return std::make_pair(static_cast<size_type>(cap), entries);
            }();
 
            const auto setCap = [&](size_type a_newCap) {
                _capacity = a_newCap;
                _free = _capacity;
                _good = 0;
            };
 
            if (newEntries == oldEntries) {
                std::uninitialized_default_construct_n(oldEntries + oldCap, newCap - oldCap);
                std::vector<value_type> todo;
                todo.reserve(size());
                for (size_type i = 0; i < oldCap; ++i) {
                    auto& entry = oldEntries[i];
                    if (entry.has_value()) {
                        todo.emplace_back(std::move(entry).steal());
                    }
                }
                setCap(newCap);
                insert(
                    std::make_move_iterator(todo.begin()),
                    std::make_move_iterator(todo.end()));
            } else {
                // in with the new
                std::uninitialized_default_construct_n(newEntries, newCap);
                setCap(newCap);
                set_entries(newEntries);
 
                if (oldEntries) {  // out with the old
                    for (size_type i = 0; i < oldCap; ++i) {
                        auto& entry = oldEntries[i];
                        if (entry.has_value()) {
                            insert(std::move(entry).steal());
                        }
                    }
                    std::destroy_n(oldEntries, oldCap);
                    deallocate(oldEntries);
                }
            }
        }
 
    private:
        [[nodiscard]] static const key_type& unwrap_key(const value_type& a_value) noexcept
        {
            return traits_type::unwrap_key(a_value);
        }
 
        [[nodiscard]] entry_type* allocate(size_type a_count)
        {
            return static_cast<entry_type*>(_allocator.allocate_bytes(sizeof(entry_type) * a_count));
        }
 
        void deallocate(entry_type* a_entry) { _allocator.deallocate_bytes(a_entry); }
 
        [[nodiscard]] iterator do_erase(const_iterator a_pos)
        {
            assert(a_pos != end());
            const auto entry = a_pos.get_entry();
            assert(entry != nullptr);
            assert(entry->has_value());
 
            if (entry->next == _sentinel) {  // end of chain
                if (auto prev = &get_entry_for(unwrap_key(entry->value)); prev != entry) {
                    while (prev->next != entry) {
                        prev = prev->next;
                    }
                    prev->next = const_cast<entry_type*>(_sentinel);  // detach from chain
                }
 
                entry->destroy();
            } else {  // move next into current
                *entry = std::move(*entry->next);
            }
 
            ++_free;
            return make_iterator<iterator>(entry + 1);
        }
 
        template <class Iter>
        [[nodiscard]] Iter do_find(const key_type& a_key) const  //
            noexcept(noexcept(hash_function(a_key)) && noexcept(key_eq(a_key, a_key)))
        {
            if (empty()) {
                return make_iterator<Iter>();
            }
 
            auto entry = &get_entry_for(a_key);
            if (entry->has_value()) {
                do {  // follow chain
                    if (key_eq(unwrap_key(entry->value), a_key)) {
                        return make_iterator<Iter>(entry);
                    } else {
                        entry = entry->next;
                    }
                } while (entry != _sentinel);
            }
 
            return make_iterator<Iter>();
        }
 
        template <class P>
        [[nodiscard]] std::pair<iterator, bool> do_insert(P&& a_value)  //
            requires(std::same_as<std::decay_t<P>, value_type>)
        {
            if (const auto it = find(unwrap_key(a_value)); it != end()) {  // already exists
                return std::make_pair(it, false);
            }
 
            if (_free == 0) {  // no free entries
                reserve(_capacity + 1);
                assert(_free > 0);
            }
 
            const stl::scope_exit decrement{ [&]() noexcept { --_free; } };
            const auto            entry = &get_entry_for(unwrap_key(a_value));
            if (entry->has_value()) {  // slot is taken, resolve conflict
                const auto free = &get_free_entry();
                const auto wouldve = &get_entry_for(unwrap_key(entry->value));
                if (wouldve == entry) {  // hash collision
                    free->emplace(std::forward<P>(a_value), std::exchange(entry->next, free));
                    return std::make_pair(make_iterator<iterator>(free), true);
                } else {  // how did we get here?
                    auto prev = wouldve;
                    while (prev->next != entry) {
                        prev = prev->next;
                    }
 
                    // evict current value and detach from chain
                    *free = std::move(*entry);
                    prev->next = free;
                    entry->emplace(std::forward<P>(a_value), _sentinel);
 
                    return std::make_pair(make_iterator<iterator>(entry), true);
                }
            } else {  // its free realestate
                entry->emplace(std::forward<P>(a_value), _sentinel);
                return std::make_pair(make_iterator<iterator>(entry), true);
            }
        }
 
        void free_resources()
        {
            if (_capacity > 0) {
                assert(get_entries() != nullptr);
                std::destroy_n(get_entries(), _capacity);
                deallocate(get_entries());
                set_entries(nullptr);
                _capacity = 0;
                _free = 0;
                _good = 0;
            }
 
            assert(get_entries() == nullptr);
            assert(_capacity == 0);
            assert(_free == 0);
        }
 
        [[nodiscard]] entry_type& get_entry_for(const key_type& a_key) const  //
            noexcept(noexcept(hash_function(a_key)))
        {
            assert(get_entries() != nullptr);
            assert(std::has_single_bit(_capacity));
 
            const auto hash = hash_function(a_key);
            const auto idx = hash & (_capacity - 1);  // quick modulo
            return get_entries()[idx];
        }
 
        [[nodiscard]] entry_type* get_entries() const noexcept { return static_cast<entry_type*>(_allocator.get_entries()); }
 
        [[nodiscard]] entry_type& get_free_entry() noexcept
        {
            assert(_free > 0);
            assert(get_entries() != nullptr);
            assert(std::has_single_bit(_capacity));
            assert([&]() noexcept {
                const auto begin = get_entries();
                const auto end = get_entries() + _capacity;
                return std::find_if(
                           begin,
                           end,
                           [](const auto& a_entry) noexcept {
                               return !a_entry.has_value();
                           }) != end;
            }());
 
            const auto entries = get_entries();
            while (entries[_good].has_value()) {
                _good = (_good + 1) & (_capacity - 1);  // wrap around w/ quick modulo
            }
            return entries[_good];
        }
 
        [[nodiscard]] size_type hash_function(const key_type& a_key) const  //
            noexcept(std::is_nothrow_constructible_v<hasher>&&
                    std::is_nothrow_invocable_v<const hasher&, const key_type&>)
        {
            return static_cast<size_type>(hasher()(a_key));
        }
 
        [[nodiscard]] bool key_eq(const key_type& a_lhs, const key_type& a_rhs) const  //
            noexcept(std::is_nothrow_constructible_v<key_equal>&&
                    std::is_nothrow_invocable_v<const key_equal&, const key_type&, const key_type&>)
        {
            return static_cast<bool>(key_equal()(a_lhs, a_rhs));
        }
 
        template <class Iter>
        [[nodiscard]] Iter make_iterator() const noexcept
        {
            return Iter(get_entries() + _capacity, get_entries() + _capacity);
        }
 
        template <class Iter>
        [[nodiscard]] Iter make_iterator(entry_type* a_first) const noexcept
        {
            return Iter(a_first, get_entries() + _capacity);
        }
 
        void set_entries(entry_type* a_entries) noexcept { _allocator.set_entries(a_entries); }
 
        // members
        std::uint64_t     _pad00{ 0 };                                                                        // 00
        std::uint32_t     _pad08{ 0 };                                                                        // 08
        size_type         _capacity{ 0 };                                                                     // 0C - total # of slots, always a power of 2
        size_type         _free{ 0 };                                                                         // 10 - # of free slots
        size_type         _good{ 0 };                                                                         // 14 - last free index
        const entry_type* _sentinel{ reinterpret_cast<const entry_type*>(detail::BSTScatterTableSentinel) };  // 18 - signals end of chain
        allocator_type    _allocator;                                                                         // 20
    };
 
    template <class Key, class T>
    class BSTScatterTableTraits
    {
    public:
        using key_type = Key;
        using mapped_type = T;
        using value_type = RE::BSTTuple<const key_type, mapped_type>;
 
        [[nodiscard]] static const key_type& unwrap_key(const value_type& a_value) noexcept { return a_value.first; }
    };
 
    template <class Key>
    class BSTSetTraits
    {
    public:
        using key_type = Key;
        using mapped_type = void;
        using value_type = key_type;
 
        [[nodiscard]] static const key_type& unwrap_key(const value_type& a_value) noexcept { return a_value; }
    };
 
    template <std::size_t S, std::size_t A>
    struct BSTScatterTableHeapAllocator
    {
    public:
        using size_type = std::uint32_t;
        using propagate_on_container_move_assignment = std::true_type;
 
        BSTScatterTableHeapAllocator() = default;
        BSTScatterTableHeapAllocator(const BSTScatterTableHeapAllocator&) = delete;
 
        BSTScatterTableHeapAllocator(BSTScatterTableHeapAllocator&& a_rhs) noexcept :
            _entries(std::exchange(a_rhs._entries, nullptr))
        {}
 
        ~BSTScatterTableHeapAllocator() = default;
        BSTScatterTableHeapAllocator& operator=(const BSTScatterTableHeapAllocator&) = delete;
 
        BSTScatterTableHeapAllocator& operator=(BSTScatterTableHeapAllocator&& a_rhs) noexcept
        {
            if (this != std::addressof(a_rhs)) {
                assert(_entries == nullptr);
                _entries = std::exchange(a_rhs._entries, nullptr);
            }
            return *this;
        }
 
        [[nodiscard]] static constexpr size_type min_size() noexcept { return 1u << 3; }
 
        [[nodiscard]] void* allocate_bytes(std::size_t a_bytes)
        {
            assert(a_bytes % S == 0);
            return malloc(a_bytes);
        }
 
        void deallocate_bytes(void* a_ptr) { free(a_ptr); }
 
        [[nodiscard]] void* get_entries() const noexcept { return _entries; }
        void                set_entries(void* a_entries) noexcept { _entries = static_cast<std::byte*>(a_entries); }
 
    private:
        // members
        std::uint64_t _pad00{ 0 };          // 00 (20)
        std::byte*    _entries{ nullptr };  // 08 (28)
    };
 
    template <std::uint32_t N>
    struct BSTStaticHashMapBase
    {
    public:
        static_assert(N > 0 && std::has_single_bit(N));
 
        template <std::size_t S, std::size_t A>
        struct Allocator
        {
        public:
            using size_type = std::uint32_t;
            using propagate_on_container_move_assignment = std::false_type;
 
            Allocator() = default;
            Allocator(const Allocator&) = delete;
            Allocator(Allocator&&) = delete;
            ~Allocator() = default;
            Allocator& operator=(const Allocator&) = delete;
            Allocator& operator=(Allocator&&) = delete;
 
            [[nodiscard]] static constexpr size_type min_size() noexcept { return N; }
 
            [[nodiscard]] void* allocate_bytes(std::size_t a_bytes)
            {
                assert(a_bytes % S == 0);
                return a_bytes <= N * S ? _buffer : nullptr;
            }
 
            void deallocate_bytes([[maybe_unused]] void* a_ptr) { assert(a_ptr == _buffer); }
 
            [[nodiscard]] void* get_entries() const noexcept { return _entries; }
 
            void set_entries(void* a_entries) noexcept
            {
                assert(a_entries == _buffer || a_entries == nullptr);
                _entries = static_cast<std::byte*>(a_entries);
            }
 
        private:
            alignas(A) std::byte _buffer[N * S]{ static_cast<std::byte>(0) };  // 00 (20)
            std::byte* _entries{ nullptr };                                    // ??
        };
    };
 
    template <std::size_t S, std::size_t A>
    class BSTScatterTableScrapAllocator
    {
    public:
        using size_type = std::uint32_t;
        using propagate_on_container_move_assignment = std::false_type;
 
        BSTScatterTableScrapAllocator() = default;
        BSTScatterTableScrapAllocator(const BSTScatterTableScrapAllocator&) = delete;
        BSTScatterTableScrapAllocator(BSTScatterTableScrapAllocator&&) = delete;
        ~BSTScatterTableScrapAllocator() = default;
        BSTScatterTableScrapAllocator& operator=(const BSTScatterTableScrapAllocator&) = delete;
        BSTScatterTableScrapAllocator& operator=(BSTScatterTableScrapAllocator&&) = delete;
 
        [[nodiscard]] static constexpr size_type min_size() noexcept { return 1u << 3; }
 
        [[nodiscard]] void* allocate_bytes(std::size_t a_bytes)
        {
            assert(_allocator != nullptr);
            assert(a_bytes % S == 0);
            return _allocator->Allocate(a_bytes, 0x10);
        }
 
        void deallocate_bytes(void* a_ptr)
        {
            assert(_allocator != nullptr);
            _allocator->Deallocate(a_ptr);
        }
 
        [[nodiscard]] void* get_entries() const noexcept { return _entries; }
        void                set_entries(void* a_entries) noexcept { _entries = static_cast<std::byte*>(a_entries); }
 
    private:
        // members
        ScrapHeap* _allocator{ MemoryManager::GetSingleton()->GetThreadScrapHeap() };  // 00 (20)
        std::byte* _entries{ nullptr };                                                // 08 (28)
    };
 
    template <
        class Key,
        class T,
        class Hash = BSCRC32<Key>,
        class KeyEq = std::equal_to<Key>>
    using BSTHashMap =
        BSTScatterTable<
            Hash,
            KeyEq,
            BSTScatterTableTraits<Key, T>,
            BSTScatterTableHeapAllocator>;
 
    namespace detail
    {
        using _dummy_bsthashmap = BSTHashMap<int, int>;
        static_assert(std::forward_iterator<_dummy_bsthashmap::iterator>);
    }
 
    template <
        class Key,
        class Hash = BSCRC32<Key>,
        class KeyEq = std::equal_to<Key>>
    using BSTSet =
        BSTScatterTable<
            Hash,
            KeyEq,
            BSTSetTraits<Key>,
            BSTScatterTableHeapAllocator>;
 
    template <
        class Key,
        class T,
        std::uint32_t N,
        class Hash = BSCRC32<Key>,
        class KeyEq = std::equal_to<Key>>
    using BSTStaticHashMap =
        BSTScatterTable<
            Hash,
            KeyEq,
            BSTScatterTableTraits<Key, T>,
            BSTStaticHashMapBase<N>::template Allocator>;
 
    template <
        class Key,
        class T,
        class Hash = BSCRC32<Key>,
        class KeyEq = std::equal_to<Key>>
    using BSTScrapHashMap =
        BSTScatterTable<
            Hash,
            KeyEq,
            BSTScatterTableTraits<Key, T>,
            BSTScatterTableScrapAllocator>;
 
    using UnkKey = std::uintptr_t;
    using UnkValue = std::uintptr_t;
}