containers add IntrusiveQueue and testing

src/include/containers/IntrusiveQueue.hpp

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+/****************************************************************************
+ *
+ *   Copyright (C) 2019 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+#include <stdlib.h>
+
+template<class T>
+class IntrusiveQueue
+{
+public:
+
+	bool empty() const { return _head == nullptr; }
+
+	T front() const { return _head; }
+	T back() const { return _tail; }
+
+	size_t size() const
+	{
+		size_t sz = 0;
+
+		for (auto node = front(); node != nullptr; node = node->next_intrusive_queue_node()) {
+			sz++;
+		}
+
+		return sz;
+	}
+
+	void push(T newNode)
+	{
+		// error, node already queued or already inserted
+		if ((newNode->next_intrusive_queue_node() != nullptr) || (newNode == _tail)) {
+			return;
+		}
+
+		if (_head == nullptr) {
+			_head = newNode;
+		}
+
+		if (_tail != nullptr) {
+			_tail->set_next_intrusive_queue_node(newNode);
+		}
+
+		_tail = newNode;
+	}
+
+	T pop()
+	{
+		T ret = _head;
+
+		if (!empty()) {
+			if (_head != _tail) {
+				_head = _head->next_intrusive_queue_node();
+
+			} else {
+				// only one item left
+				_head = nullptr;
+				_tail = nullptr;
+			}
+
+			// clear next in popped (in might be re-inserted later)
+			ret->set_next_intrusive_queue_node(nullptr);
+		}
+
+		return ret;
+	}
+
+private:
+
+	T _head{nullptr};
+	T _tail{nullptr};
+
+};
+
+template<class T>
+class IntrusiveQueueNode
+{
+private:
+	friend IntrusiveQueue<T>;
+
+	T next_intrusive_queue_node() const { return _next_intrusive_queue_node; }
+	void set_next_intrusive_queue_node(T new_next) { _next_intrusive_queue_node = new_next; }
+
+	T _next_intrusive_queue_node{nullptr};
+};