#ifndef stack_h
#define stack_h 1

#include <exception>
#include <mutex>

template<class T> class stack
{
public:
	using empty = std::exception;

	 stack(): head(nullptr) {}

	~stack() { while (head) pop(); }

	void push(const T& t)
	{
		std::lock_guard<std::mutex> l(m);
		head = new node{head, t};
	}

	T pop()
	{
		std::lock_guard<std::mutex> l(m);
		if (head != nullptr)
		{
			node *n = head;
			head = n->next;
			T t = n->data;
			delete n;
			return t;
		}
		throw empty();
	}

private:
	struct node
	{
		node* next;
		T data;
	};

	std::mutex m;
	node* head;
};

#endif // stack_h