shared_ptr模拟代码

17-06-26 来源：[db:作者]
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shared_ptr模拟代码。
#include 
//#include 
#include
using namespace std;
template
class shared_ptr
{
        T* m_ptr = NULL;
        int* m_inf = NULL;
        shared_ptr(){}
public:
        shared_ptr(T* ptr)
        {
                m_inf = new int;
                *m_inf = 1;
                m_ptr = ptr;
        }
        shared_ptr(const shared_ptr& from)
        {
                deconstruct();
                m_inf = from.m_inf;
                m_ptr = from.m_ptr;
                (*m_inf)++;
        }
        shared_ptr& operator=(const shared_ptr& from)
        {
                deconstruct();
                m_inf = from.m_inf;
                m_ptr = from.m_ptr;
                (*m_inf)++;
        }
        ~shared_ptr()
        {
                deconstruct();
        }
        void deconstruct()
        {
                if(m_inf != NULL)
                {
                        (*m_inf)--;
                        if(*m_inf == 0)
                        {
                                delete m_ptr;
                                delete m_inf;
                                m_ptr = NULL;
                                m_inf = NULL;
                        }
                }
        }
        T* operator->()
        {
                return m_ptr;
        }
        int use_count()
        {
                return *m_inf;
        }
};

template
static shared_ptr make_shared(int val)
{
        return shared_ptr(new T(val));
}

class A
{
        int m_v;
public:
        A(int v) { cout << "new: " << (m_v = v) << endl; }
        ~A() { cout << "delete: " << m_v << endl; }
        void DisPlay() { cout << "display " << m_v << endl; }
};

shared_ptr TestSharePtr()
{
        auto p = make_shared(123);
        cout << p.use_count() << endl;
        auto p2 = p;
        cout << p.use_count() << endl;
        //
        p2 = make_shared(456);
        cout << p.use_count() << endl;
        return p;
}

int main()
{
        auto rst = TestSharePtr();
        cout << "after call" << endl;
        rst->DisPlay();
        return 0;
}
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