用c++简单实现智能指针 (三)

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& 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& operator = (const SP& 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;
}
};
在看看客户端的代码：
[cpp]
Collapse | Copy Code
void main()
{
SP p(new Person("Scott", 25));
p->Display();
{
SP q = p;
q->Display();
// Destructor of q will be called here..

SP r;
r = p;
r->Display();
// Destructor of r will be called here..
}
p->Display();
// Destructor of p will be called here
// and person pointer will be deleted
}

Collapse | Copy Code
void main()
{
SP p(new Person("Scott", 25));
p->Display();
{
SP q = p;
q->Display();
// Destructor of q will be called here..

SP r;
r = p;
r->Display();
// Destructor of r will be called here..
}
p->Display();
// Destructor of p will be called here
// and person pointer will be deleted
}