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;
}
};