2 files changed, 131 insertions, 0 deletions
diff --git a/lib/nes/common/CMakeLists.txt b/lib/nes/common/CMakeLists.txt
index 69ae435..553d468 100644
--- a/lib/nes/common/CMakeLists.txt
+++ b/lib/nes/common/CMakeLists.txt
@@ -3,4 +3,5 @@ target_sources(
 	PRIVATE
 		debug.hh
 		rgb.hh
+		list.hh
 		display.hh)
 \ No newline at end of file
diff --git a/lib/nes/common/list.hh b/lib/nes/common/list.hh
new file mode 100644
index 0000000..5f0d258
--- /dev/null
+++ b/lib/nes/common/list.hh
@@ -0,0 +1,130 @@
+#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*() -> 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
+\ No newline at end of file