C++智能指针的简单实现

[code]template <typename T> class U_Ptr
{
    template <typename T> friend class lxlshared_ptr;
    T *tp;
    size_t use;
    U_Ptr(T *p) : tp(p), use(1) {}
    ~U_Ptr() {delete tp;}
};

template <typename T> class lxlshared_ptr
{
public:
    lxlshared_ptr(T *p) : ptr(new U_Ptr<T>(p)) {}
    lxlshared_ptr(const lxlshared_ptr &orig) : ptr(orig.ptr) {++ptr->use;}
    lxlshared_ptr& operator= (const lxlshared_ptr&);
    ~lxlshared_ptr()
    {
        if (--ptr->use == 0)
            delete ptr;
    }
    long use_count() const {return ptr->use;}
    T& operator* () {return *ptr->tp;}
    T* operator-> () {return ptr->tp;}
    friend bool operator== (const lxlshared_ptr &lhs, const lxlshared_ptr &rhs) {return lhs.ptr == rhs.ptr;}
    friend bool operator!= (const lxlshared_ptr &lhs, const lxlshared_ptr &rhs) {return !(lhs == rhs);}
private:
    U_Ptr<T> *ptr;
};

template <typename T> lxlshared_ptr<T>& lxlshared_ptr<T>::operator= (const lxlshared_ptr<T> &rhs)
{
    ++rhs.ptr->use;
    if (--ptr->use == 0)
        delete ptr;
    ptr = rhs.ptr;
    return *this;
}