#ifndef SINGLETON_DCLP_HPP
#define SINGLETON_DCLP_HPP

#include <mutex>

template<typename T>
class Singleton_DCLP
{
public:

	Singleton_DCLP() {};
	virtual ~Singleton_DCLP()
	{
		if (m_instance)
			delete m_instance;
	};

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


	/** c++-11 has the "atomic initializers" and this can be replaced with:
	 *
	 * static T getInstance()
	 * {
	 *     static Singleton instance;
         *     return instance;
	 * }
	 *
	 * But that is not supported in Visual Studio 2012 SP4
	 * https://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11/
	 */
	static T* getInstance()
	{
		if (!m_instance) {
			std::lock_guard<std::mutex> guard(m_lock);
			if (!m_instance) {
				volatile T *temp = new T();
				m_instance = (T*)temp;
			}
		}
		return (T*)m_instance;
	}

private:
	static std::mutex m_lock;
	static volatile T* m_instance;
};

template<class T> std::mutex Singleton_DCLP<T>::m_lock;
template<class T> volatile T* Singleton_DCLP<T>::m_instance = 0;


#endif // SINGLETON_DCLP_HPP