设计基于锁的并发数据结构-1. 线程安全的栈容器

#include <exception>
#include <memory>
#include <mutex>
#include <stack>

struct empty_stack : std::exception {
	const char *what () const throw();
};

template <typename T>
class threadsafe_stack {
private:
	std::stack<T> m_data;
	mutable std::mutex m_mutex;

public:
	threadsafe_stack()
	{
	}

	threadsafe_stack (const threadsafe_stack &other)
	{
		std::lock_guard<std::mutex> lock (m_mutex);
		m_data = other.m_data;
	}

	threadsafe_stack &operator= (const threadsafe_stack &) = delete;

	void push (T new_value)
	{
		std::lock_guard<std::mutex> lock (m_mutex);
		m_data.push (std::move (new_value));
	}

	std::shared_ptr<T> pop ()
	{
		std::lock_guard<std::mutex> lock (m_mutex);
		if (m_data.empty())
			throw empty_stack();
		const std::shared_ptr<T> res (std::make_shared<T> (std::move (m_data.top())));
		m_data.pop();
		return res;
	}

	void pop (T &value)
	{
		std::lock_guard<std::mutex> lock (m_mutex);
		if (m_data.empty())
			throw empty_stack();
		value = std::move (m_data.top());
		m_data.pop();
	}

	bool empty () const
	{
		std::lock_guard<std::mutex> lock (m_mutex);
		return m_data.empty();
	}
};