#ifndef SHARED_PTR_H_#define SHARED_PTR_H_#ifndef NULL#define NULL 0#endifnamespace util{    template <class T>    class shared_ptr;    template <class T>    class shared_data    {      private:        friend class shared_ptr<T>;        explicit shared_data(T *pT): _M_ptr(pT)        {            _M_nCount = 1;        }        ~shared_data()        {            delete _M_ptr;        }        void operator++()        {            ++_M_nCount;        }        void operator--()        {            --_M_nCount;            if (_M_nCount == 0)            {                delete this;            }        }        T &operator *()const        {            return  *_M_ptr;        }        T *operator->()const        {            return _M_ptr;        }        bool operator == (T *pT)const        {            return _M_ptr == pT;        }        T *get()        {            return _M_ptr;        }        int use_count()        {            return _M_nCount;        }      private:        T *_M_ptr;        unsigned int _M_nCount;    };    template <class T>    class shared_ptr    {        typedef shared_data<T> element;      public:        explicit shared_ptr(T *pT): _M_pD(NULL)        {            _M_pD = new element(pT);        }        explicit shared_ptr(): _M_pD(NULL)		{        }        // copy constructor        shared_ptr(const shared_ptr < T >  &rT)        {            _M_pD = rT.get_element();            if (_M_pD != NULL)            {                ++(*_M_pD);            }        }        ~shared_ptr()        {            if (_M_pD != NULL)            {                --(*_M_pD);            }        }        // assignment operator        shared_ptr < T >  &operator = (const shared_ptr < T >  &rT)        {            if (_M_pD != NULL)            {                --(*_M_pD);            }            _M_pD = rT.get_element();            if (_M_pD != NULL)            {                ++(*_M_pD);            }            return  *this;        }        // assignment operator        shared_ptr < T >  &operator = (shared_ptr < T >  &rT)        {            if (_M_pD != NULL)            {                --(*_M_pD);            }            _M_pD = rT.get_element();            if (_M_pD != NULL)            {                ++(*_M_pD);            }            return  *this;        }        T &operator *()const        {            return _M_pD->operator *();        }        T *operator->()const        {            return _M_pD->operator->();        }		bool operator == (shared_ptr < T >  &rT)const        {            return rT.get_element() == _M_pD;        }        bool operator == (T *pT)const        {            if (_M_pD == NULL)            {                return pT == NULL;            }            return  *_M_pD == pT;        }        T *get()        {            if (_M_pD == NULL)            {                return NULL;            }            else            {                return _M_pD->get();            }        }        void release()        {            if (_M_pD != NULL)            {                --(*_M_pD);                _M_pD = NULL;            }        }        void reset(T *pT)        {            if (_M_pD != NULL)            {                --(*_M_pD);                _M_pD = NULL;            }            _M_pD = new element(pT);        }      private:        element *get_element()const        {            return _M_pD;        }        element *_M_pD;    };}#endif