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#pragma once
namespace nes
{
/// An intrusive doubly-linked list.
template<typename T>
class list
{
public:
/// Base class of nodes in the list.
class node
{
friend list;
list* list_{ nullptr };
T* prev_{ nullptr };
T* next_{ nullptr };
public:
virtual ~node() = default;
node(node const&) = delete;
node(node&&) = delete;
auto operator=(node const&) -> node& = delete;
auto operator=(node&&) -> node& = delete;
protected:
explicit node() = default;
};
/// An iterator for the linked list.
class iterator
{
friend list;
T* current_{ nullptr };
public:
auto operator==(iterator const& other) -> bool { return current_ == other.current_; }
auto operator!=(iterator const& other) -> bool { return current_ != other.current_; }
auto operator*() const -> T* { return current_; }
auto operator++() -> iterator&
{
if (current_)
{
node& current_node = *current_;
current_ = current_node.next_;
}
return *this;
}
auto operator++(int) -> iterator
{
auto res = *this;
++*this;
return res;
}
private:
explicit iterator() = default;
explicit iterator(T* current)
: current_{ current }
{
}
};
private:
T* head_{ nullptr };
T* tail_{ nullptr };
public:
explicit list() = default;
~list()
{
while (begin() != end()) { remove(begin()); }
}
list(list const&) = delete;
list(list&&) = delete;
auto operator=(list const&) -> list& = delete;
auto operator=(list&&) -> list& = delete;
auto begin() const -> iterator { return iterator{ head_ }; }
auto end() const -> iterator { return iterator{}; }
/// Add an item to the end of the list, removing it from any other list it may be in.
auto append(T& item) -> void
{
node& item_node = item;
if (item_node.list_) { item_node.list_->remove(item); }
item_node.list_ = this;
if (tail_)
{
item_node.prev_ = tail_;
tail_->next_ = &item;
}
else
{
head_ = &item;
}
tail_ = &item;
}
/// Remove an item from the list.
auto remove(T& item) -> void
{
node& item_node = item;
if (!item_node.list_) { return; }
if (head_ == &item) { head_ = item_node.next_; }
if (tail_ == &item) { tail_ = item_node.prev_; }
if (item_node.prev_) { item_node.prev_->next_ = item_node.next_; }
if (item_node.next_) { item_node.next_->prev_ = item_node.prev_; }
item_node.next_ = nullptr;
item_node.prev_ = nullptr;
item_node.list_ = nullptr;
}
/// Remove an item from the list by its iterator.
auto remove(iterator it) -> void
{
if (it != end()) { remove(**it); }
}
};
} // namespace nes
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