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15.8.1.cpp
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15.8.1.cpp
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#include <iostream>
#include <stdexcept>
using namespace std;
class CBase
{
public:
CBase(){}
virtual ~CBase(){}
CBase(const CBase& obj){ }
CBase& operator=(const CBase& obj)
{
if(this != &obj)
{
//todo
}
return *this;
}
virtual void Show() {cout << "CBase::Show" << endl; }
virtual CBase* Clone() const { return new CBase(*this); }
};
class CDerived1 : public CBase
{
public:
CDerived1() : CBase() {}
virtual ~CDerived1() { }
CDerived1(const CDerived1& obj) : CBase(obj) { }
CDerived1& operator=(const CDerived1& obj)
{
if(this != &obj)
{
//todo
CBase::operator=(obj);
}
return *this;
}
virtual void Show() { cout << "CDerived1::Show()" << endl; }
virtual CDerived1* Clone() const { return new CDerived1(*this); }
};
class CDerived2 : public CBase
{
public:
CDerived2() : CBase() {}
virtual ~CDerived2() {}
CDerived2(const CDerived2& obj) : CBase(obj) {}
CDerived2& operator=(const CDerived2& obj)
{
if(this != &obj)
{
//todo
CBase::operator=(obj);
}
return *this;
}
virtual void Show() { cout << "CDerived2::Show()" << endl; }
virtual CDerived2* Clone() const { return new CDerived2(*this); }
};
class CAutoPtr
{
public:
//construct
CAutoPtr() : m_pPtr(0), m_pUse(new std::size_t(1)) { }
//construct
CAutoPtr(const CBase& obj) : m_pPtr(obj.Clone()), m_pUse(new std::size_t(1)) {}
//destruct
virtual ~CAutoPtr() { Decr_use(); }
//copy construct
CAutoPtr(const CAutoPtr& ptr) : m_pPtr(ptr.m_pPtr), m_pUse(ptr.m_pUse) { ++*m_pUse; }
//operator=
CAutoPtr& operator=(const CAutoPtr& ptr)
{
++(*ptr.m_pUse); //right val ref add 1
Decr_use();
m_pPtr = ptr.m_pPtr;
m_pUse = ptr.m_pUse;
}
void Decr_use()
{
if(--*m_pUse == 0)
{
delete m_pPtr;
m_pPtr = 0;
delete m_pUse;
m_pUse = 0;
}
}
const CBase* operator->() const
{
if(m_pPtr)
return m_pPtr;
else
throw std::logic_error("error");
}
const CBase& operator*() const
{
if(m_pPtr)
return *m_pPtr;
else
throw std::logic_error("error");
}
protected:
CBase* m_pPtr;
std::size_t* m_pUse;
};
int main()
{
CAutoPtr ptr1;
CDerived1 d1;
CAutoPtr ptr2(d1);
ptr1 = ptr2;
return 0;
}