PX4-Autopilot/src/include/containers/List.hpp

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/**
 * @file List.hpp
 *
 * An intrusive linked list.
 */

#pragma once

#include <stdlib.h>

template<class T>
class ListNode
{
public:

	void setSibling(T sibling) { _list_node_sibling = sibling; }
	const T getSibling() const { return _list_node_sibling; }

protected:

	T _list_node_sibling{nullptr};

};

template<class T>
class List
{
public:

	void add(T newNode)
	{
		if (_head == nullptr) {
			// list is empty, add as head
			_head = newNode;
			return;

		} else {
			// find last node and add to end
			T node = _head;

			while (node != nullptr) {
				if (node->getSibling() == nullptr) {
					// found last node, now add newNode
					node->setSibling(newNode);
					return;
				}

				node = node->getSibling();
			}
		}
	}

	bool remove(T removeNode)
	{
		if (removeNode == nullptr) {
			return false;
		}

		// base case
		if (removeNode == _head) {
			if (_head != nullptr) {
				_head = _head->getSibling();
			}

			removeNode->setSibling(nullptr);

			return true;
		}

		for (T node = getHead(); node != nullptr; node = node->getSibling()) {
			// is sibling the node to remove?
			if (node->getSibling() == removeNode) {
				// replace sibling
				if (node->getSibling() != nullptr) {
					node->setSibling(node->getSibling()->getSibling());

				} else {
					node->setSibling(nullptr);
				}

				removeNode->setSibling(nullptr);

				return true;
			}
		}

		return false;
	}

	struct Iterator {
		T node;
		explicit Iterator(T v) : node(v) {}

		operator T() const { return node; }
		operator T &() { return node; }
		const T &operator* () const { return node; }
		Iterator &operator++ ()
		{
			if (node) {
				node = node->getSibling();
			}

			return *this;
		}
	};

	Iterator begin() { return Iterator(getHead()); }
	Iterator end() { return Iterator(nullptr); }

	const T getHead() const { return _head; }

	bool empty() const { return getHead() == nullptr; }

	size_t size() const
	{
		size_t sz = 0;

		for (auto node = getHead(); node != nullptr; node = node->getSibling()) {
			sz++;
		}

		return sz;
	}

	void deleteNode(T node)
	{
		if (remove(node)) {
			// only delete if node was successfully removed
			delete node;
		}
	}

	void clear()
	{
		auto node = getHead();

		while (node != nullptr) {
			auto next = node->getSibling();
			delete node;
			node = next;
		}

		_head = nullptr;
	}

protected:

	T _head{nullptr};
};