智能指针一个简单例子

/*
* The Code Project Open License (CPOL) 1.02
*
*/
class RC
{
private:
    int count; // Reference count
public:
    void AddRef()
    {
        // Increment the reference count
        count++;
    }
    int Release()
    {
        // Decrement the reference count and
        // return the reference count.
        return --count;
    }
};

template < typename T > class SP
{
private:
    T*    pData;       // pointer
    RC* reference; // Reference count

public:
    SP() : pData(0), reference(0) 
    {
        // Create a new reference 
        reference = new RC();
        // Increment the reference count
        reference->AddRef();
    }

    SP(T* pValue) : pData(pValue), reference(0)
    {
        // Create a new reference 
        reference = new RC();
        // Increment the reference count
        reference->AddRef();
    }

    SP(const SP<T>& sp) : pData(sp.pData), reference(sp.reference)
    {
        // Copy constructor
        // Copy the data and reference pointer
        // and increment the reference count
        reference->AddRef();
    }

    ~SP()
    {
        // Destructor
        // Decrement the reference count
        // if reference become zero delete the data
        if(reference->Release() == 0)
        {
            delete pData;
            delete reference;
        }
    }

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

    T* operator-> ()
    {
        return pData;
    }
    
    SP<T>& operator = (const SP<T>& sp)
    {
        // Assignment operator
        if (this != &sp) // Avoid self assignment
        {
            // Decrement the old reference count
            // if reference become zero delete the old data
            if(reference->Release() == 0)
            {
                delete pData;
                delete reference;
            }
            // Copy the data and reference pointer
            // and increment the reference count
            pData = sp.pData;
            reference = sp.reference;
            reference->AddRef();
        }
        return *this;
    }
};

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