BSSimpleList.h

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#pragma once
 
#include "RE/M/MemoryManager.h"
 
namespace RE
{
    // forward list
    template <class T>
    class BSSimpleList
    {
    public:
        using value_type = T;
        using size_type = std::uint32_t;
        using reference = value_type&;
        using const_reference = const value_type&;
 
        struct Node
        {
        public:
            inline Node() :
                item{},
                next(nullptr)
            {}
 
            inline Node(value_type a_value, Node* a_next) :
                item(a_value),
                next(a_next)
            {}
 
            inline Node(const Node& a_rhs) :
                item(a_rhs.item),
                next(a_rhs.next)
            {}
 
            inline Node(Node&& a_rhs) :
                item(std::move(a_rhs.item)),
                next(std::move(a_rhs.next))
            {
                a_rhs.next = nullptr;
            }
 
            inline Node(const value_type& a_value) :
                item(a_value),
                next(nullptr)
            {}
 
            inline Node(value_type&& a_value) :
                item(std::move(a_value)),
                next(nullptr)
            {}
 
            ~Node() = default;
 
            inline Node& operator=(const Node& a_rhs)
            {
                if (this != std::addressof(a_rhs)) {
                    item = a_rhs.item;
                    next = a_rhs.next;
                }
                return *this;
            }
 
            inline Node& operator=(Node&& a_rhs)
            {
                if (this != std::addressof(a_rhs)) {
                    item = std::move(a_rhs.item);
 
                    next = std::move(a_rhs.next);
                    a_rhs.next = nullptr;
                }
                return *this;
            }
 
            TES_HEAP_REDEFINE_NEW();
 
            // members
            value_type           item;  // 00
            stl::observer<Node*> next;  // ??
        };
 
        template <class U>
        class iterator_base
        {
        public:
            using difference_type = std::ptrdiff_t;
            using value_type = U;
            using pointer = U*;
            using reference = U&;
            using iterator_category = std::forward_iterator_tag;
 
            constexpr iterator_base() noexcept :
                _cur(nullptr)
            {}
 
            constexpr iterator_base(const iterator_base& a_rhs) noexcept :
                _cur(a_rhs._cur)
            {}
 
            constexpr iterator_base(iterator_base&& a_rhs) noexcept :
                _cur(std::move(a_rhs._cur))
            {
                a_rhs._cur = nullptr;
            }
 
            constexpr iterator_base(Node* a_node) noexcept :
                _cur(a_node)
            {}
 
            inline ~iterator_base() noexcept { _cur = nullptr; }
 
            constexpr iterator_base& operator=(const iterator_base& a_rhs) noexcept
            {
                if (this != std::addressof(a_rhs)) {
                    _cur = a_rhs._cur;
                }
                return *this;
            }
 
            constexpr iterator_base& operator=(iterator_base&& a_rhs) noexcept
            {
                if (this != std::addressof(a_rhs)) {
                    _cur = std::move(a_rhs._cur);
                    a_rhs._cur = nullptr;
                }
                return *this;
            }
 
            [[nodiscard]] constexpr reference operator*() const noexcept { return _cur->item; }
            [[nodiscard]] constexpr pointer   operator->() const noexcept { return std::addressof(_cur->item); }
 
            [[nodiscard]] constexpr bool operator==(const iterator_base& a_rhs) const noexcept { return _cur == a_rhs._cur; }
            [[nodiscard]] constexpr bool operator!=(const iterator_base& a_rhs) const noexcept { return !(*this == a_rhs); }
 
            // prefix
            constexpr iterator_base& operator++() noexcept
            {
                assert(_cur);
                _cur = _cur->next;
                return *this;
            }
 
            // postfix
            [[nodiscard]] constexpr iterator_base operator++(int) noexcept
            {
                iterator_base tmp(*this);
                ++(*this);
                return tmp;
            }
 
        protected:
            friend class BSSimpleList<T>;
 
            [[nodiscard]] constexpr Node*       get_current() noexcept { return _cur; }
            [[nodiscard]] constexpr const Node* get_current() const noexcept { return _cur; }
 
            [[nodiscard]] constexpr bool comes_before(const iterator_base& a_rhs) const noexcept
            {
                for (auto iter = _cur; iter; iter = iter->next) {
                    if (iter == a_rhs._cur) {
                        return true;
                    }
                }
                return false;
            }
 
        private:
            stl::observer<Node*> _cur;
        };
 
        using iterator = iterator_base<value_type>;
        using const_iterator = iterator_base<const value_type>;
 
        inline BSSimpleList() :
            _listHead()
        {}
 
        inline BSSimpleList(const BSSimpleList& a_rhs) :
            _listHead()
        {
            copy_from(a_rhs);
        }
 
        inline BSSimpleList(BSSimpleList&& a_rhs) :
            _listHead(std::move(a_rhs._listHead))
        {}
 
        inline ~BSSimpleList()
        {
            clear();
        }
 
        inline BSSimpleList& operator=(const BSSimpleList& a_rhs)
        {
            if (this != std::addressof(a_rhs)) {
                clear();
                copy_from(a_rhs);
            }
            return *this;
        }
 
        inline BSSimpleList& operator=(BSSimpleList&& a_rhs)
        {
            if (this != std::addressof(a_rhs)) {
                clear();
                _listHead = std::move(a_rhs._listHead);
            }
            return *this;
        }
 
        TES_HEAP_REDEFINE_NEW();
 
        [[nodiscard]] inline reference front()
        {
            assert(!empty());
            return *begin();
        }
 
        [[nodiscard]] inline const_reference front() const
        {
            assert(!empty());
            return *begin();
        }
 
        [[nodiscard]] inline iterator       begin() { return empty() ? end() : iterator(get_head()); }
        [[nodiscard]] inline const_iterator begin() const { return empty() ? end() : const_iterator(get_head()); }
        [[nodiscard]] inline const_iterator cbegin() const { return begin(); }
 
        [[nodiscard]] constexpr iterator       end() noexcept { return iterator(nullptr); }
        [[nodiscard]] constexpr const_iterator end() const noexcept { return const_iterator(nullptr); }
        [[nodiscard]] constexpr const_iterator cend() const noexcept { return end(); }
 
        [[nodiscard]] inline bool empty() const { return !_listHead.next && !_listHead.item; }
 
        inline void clear()
        {
            erase_after_impl(get_head(), nullptr);
            if (static_cast<bool>(_listHead.item)) {
                std::destroy_at(std::addressof(_listHead.item));
            }
        }
 
        inline iterator insert_after(const_iterator a_pos, const_reference a_value)
        {
            auto node = new Node(a_value);
            return insert_after_impl(
                a_pos.get_current(),
                std::make_pair(node, node));
        }
 
        inline iterator insert_after(const_iterator a_pos, value_type&& a_value)
        {
            auto node = new Node(std::move(a_value));
            return insert_after_impl(
                a_pos.get_current(),
                std::make_pair(node, node));
        }
 
        inline iterator insert_after(const_iterator a_pos, size_type a_count, const_reference a_value)
        {
            if (a_count <= 0) {
                return a_pos;
            }
 
            return insert_after_impl(
                a_pos.get_current(),
                alloc_copies(a_count, a_value));
        }
 
        inline iterator erase_after(const_iterator a_pos)
        {
            if (a_pos == cend()) {
                return end();
            }
 
            auto node = a_pos.get_current();
            erase_after_impl(node, node->next);
            return node->next;
        }
 
        inline iterator erase_after(const_iterator a_first, const_iterator a_last)
        {
            assert(a_first.comes_before(a_last));
 
            auto head = a_first.get_current();
            auto tail = a_last.get_current();
 
            erase_after_impl(head, tail);
            return tail;
        }
 
        inline void push_front(const_reference a_value) { emplace_front_impl(a_value); }
        inline void push_front(value_type&& a_value) { emplace_front_impl(std::move(a_value)); }
 
        template <class... Args>
        inline reference emplace_front(Args&&... a_args)
        {
            emplace_front_impl(std::forward<Args>(a_args)...);
            return front();
        }
 
        inline void pop_front()
        {
            assert(!empty());
 
            std::destroy_at(std::addressof(_listHead.item));
            auto node = _listHead.next;
            if (node) {
                _listHead.next = node->next;
                std::construct_at(std::addressof(_listHead.item), std::move(node->item));
                delete node;
            }
        }
 
        inline void resize(size_type a_count) { resize(a_count, value_type{}); }
        inline void resize(size_type a_count, const value_type& a_value) { resize_impl(a_count, a_value); }
 
    protected:
        [[nodiscard]] constexpr Node*       get_head() noexcept { return std::addressof(_listHead); }
        [[nodiscard]] constexpr const Node* get_head() const noexcept { return std::addressof(_listHead); }
 
        [[nodiscard]] inline std::pair<Node*, Node*> alloc_copies(size_type a_count, const_reference a_value)
        {
            assert(a_count > 0);
 
            auto head = new Node(a_value);
            auto tail = head;
            for (size_type i = 1; i < a_count; ++i) {
                tail->next = new Node(a_value);
                tail = tail->next;
            }
 
            return std::make_pair(head, tail);
        }
 
        inline void copy_from(const BSSimpleList& a_rhs)
        {
            auto lhs = get_head();
            auto rhs = a_rhs.get_head();
 
            lhs->item = rhs->item;
            while (rhs->next) {
                rhs = rhs->next;
                lhs->next = new Node(rhs->item);
                lhs = lhs->next;
            }
        }
 
        [[nodiscard]] inline Node* insert_after_impl(Node* a_pos, std::pair<Node*, Node*> a_values)
        {
            auto [head, tail] = a_values;
 
            assert(a_pos);
            assert(head && tail);
 
            tail->next = a_pos->next;
            a_pos->next = head;
            return tail;
        }
 
        inline void erase_after_impl(Node* a_head, Node* a_tail)
        {
            if (a_head && a_head != a_tail) {
                auto iter = a_head->next;
                auto tmp = iter;
                while (iter != a_tail) {
                    tmp = iter;
                    iter = iter->next;
                    delete tmp;
                }
                a_head->next = a_tail;
            }
        }
 
        template <class... Args>
        inline void emplace_front_impl(Args&&... a_args)
        {
            if (static_cast<bool>(_listHead.item)) {
                auto node = new Node(std::move(_listHead));
                _listHead.next = node;
            }
 
            std::destroy_at(std::addressof(_listHead.item));
            std::construct_at(std::addressof(_listHead.item), std::forward<Args>(a_args)...);
        }
 
        inline void resize_impl(size_type a_count, const_reference a_value)
        {
            if (a_count <= 0) {
                clear();
            }
 
            auto      iter = begin();
            auto      last = end();
            size_type elems = 1;
            while (iter != last && elems != a_count) {
                ++iter;
                ++elems;
            }
 
            if (elems < a_count) {
                // need to grow
                insert_after(iter, a_count - elems, a_value);
            } else if (iter != last) {
                // need to shrink
                erase_after(iter, last);
            } else {
                // already required size
            }
        }
 
        // members
        Node _listHead;  // 00
 
        // T                _item;  // 00
        // BSSimpleList<T>* _next;  // ??
    };
}