智能指针类(ScopedPointer和SharedPointer)

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智能指针类(ScopedPointer和SharedPointer)

当ScopedPoniter对象销毁时，会自动释放所指堆空间对象。
当SharedPointer对象销毁时，会自动将引用计数减1，只有当引用计数为0时才会释放堆空间对象。

• Pointer类 接口类
• ScopedPointer类 不可拷贝
• SharedPointer类 带引用计数

---

//Pointer.h
template <typename T>
class Pointer: public Object
{
protected:
    T* m_pointer;
public:
    Pointer(T* p = NULL) : m_pointer (p)
    { }

    T* operator ->()
    { return  m_pointer; }

    T& operator * ()
    { return *m_pointer;}

    bool isNull()
    { return (m_pointer == NULL); }

    T* get() const
    { return m_pointer;}

    virtual ~Pointer() = 0;

};

template <typename T>
Pointer<T>::~Pointer()
{ }

//ScopedPointer.h
template<typename T>
class ScopedPointer : public Pointer<T>
{
private:
    ScopedPointer(const ScopedPointer<T>&);
    ScopedPointer<T>& operator = (const ScopedPointer<T>&);

    void operator==( ScopedPointer const& ) const;
    void operator!=( ScopedPointer const& ) const;
public:
    ScopedPointer(T* p = NULL): Pointer<T>(p)
    {}

    void reset(T* p = NULL)
    {
        ScopedPointer<T>(p).swap(*this);
    }

    void swap(ScopedPointer & b)
    {
        T * tmp = b.m_pointer;
        b.m_pointer = this->m_pointer;
        this->m_pointer = tmp;
    }

    ~ScopedPointer()
    {
        checked_delete<T>(this->m_pointer);
    }

};

//SharedPointer.h
 template<typename T>
class SharedPointer: public Pointer<T>
{
public:
    SharedPointer(T* p=NULL): Pointer<T>(NULL),m_ref(NULL)
    {
       assign(p);
    }

    SharedPointer(const SharedPointer<T>& obj):Pointer<T>(NULL)
    {
        assign(obj);
    }

    SharedPointer<T>& operator = (const SharedPointer<T>& obj)
    {
        if(&obj != this)
        {
            clear();
            assign(obj);
        }
        return *this;
    }

    void reset(T* p=NULL)
    {
        clear();
        assign(p);
    }

    ~SharedPointer()
    {
        clear();
    }

    int useCount() const
    {
        return (m_ref == NULL) ? 0 : *m_ref;
    }

    bool unique() const
    {
        return useCount() == 1;
    }

private:
    void assign(const SharedPointer<T>& obj)
    {
        this->m_ref = obj.m_ref;
        this->m_pointer = obj.m_pointer;
        if(this->m_ref)
        {
            (*this->m_ref)++;
        }
    }

    void assign(T* p)
    {
        if(p)
        {
            this->m_ref = static_cast<int*>(new int(0));
            if(this->m_ref)
            {
                this->m_pointer = p;
                *(this->m_ref) = 1;
            }
            else
            {
                THROW_EXCEPTION(NoEnoughtMemoryException,"no memory to reate SharedPointer object ..");
            }
        }
    }

    void clear()
    {
        T* toDel =this->m_pointer;
        int* ref = this->m_ref;

        this->m_pointer = NULL;
        this->m_ref = NULL;

        if(ref)
        {
            (*ref)--;
            if(*ref == 0)
            {
                delete ref;
                checked_delete<T>(toDel);
            }
        }
    }

protected:
    int* m_ref;

};
template <typename T>
bool operator ==(const SharedPointer<T>& l,const SharedPointer<T>& r)
{
    return (l.get() == r.get());
}

template <typename T>
bool operator !=(const SharedPointer<T>& l,const SharedPointer<T>& r)
{
    return !(l == r);
}