带引用计数的智能指针实现

    自己实现的智能指针：

    优点：有引用计数，可以实现指针间共享一个对象。

    缺点：不能实现数组的动态分配。

    auto_cptr.h:

#ifndef _AUTO_CPTR_H_#define _AUTO_CPTR_H_//#define __debug// auto_cptr.h// 带引用计数的智能指针#include <iostream>using namespace std;template <typename T>class auto_cptr{public:    auto_cptr():p(0),count(0)    {        #ifdef __debug        cout<<"auto_cptr():empty construction of auto_cptr"<<endl;        #endif    }        template <typename U>    explicit auto_cptr(U *pu):p( (T*)pu ),count(0)    {        if(pu)        {            count=new size_t;            *count = 1;            #ifdef __debug            cout<<"auto_cptr(U *pu): construction of auto_cptr, obj="<<p<<", count="<<get_count()<<"  "<<endl;            #endif        }else        {            #ifdef __debug            cout<<"auto_cptr(U *pu): construction of auto_cptr, null=null"<<endl;            #endif        }    }        auto_cptr(const auto_cptr<T>& cp):p( 0 ),count(0)    {        copyfrom(cp);        #ifdef __debug        cout<<"auto_cptr(const auto_cptr<T>& cp):copy construction of auto_cptr.obj="        <<p<<", count="<<get_count()<<"  "<<endl;        #endif    }        auto_cptr<T>& operator=(const auto_cptr <T>&cp)    {        if(&cp==this)            return *this;        copyfrom(cp);        #ifdef __debug        cout<<"auto_cptr::operator=:operator"<<"obj="<<p<<", count="<<get_count()<<"  "<<endl;        #endif                return *this;    }    ~auto_cptr()    {        #ifdef __debug        cout<<"~auto_cptr()"<<endl;        #endif        minus();    }        friend bool operator==(const auto_cptr<T>&p1,const auto_cptr<T>&p2)    {        return p1.p==p2.p && p1.count==p2.count;    }    friend bool operator!=(const auto_cptr<T>&p1,const auto_cptr<T>&p2)    {        return !(p1==p2);    }        T *operator->() {return &(operator*());}    T &operator*() {return *p;}        size_t get_count()    {        return count?*count:0;    }        T* get_pvalue()    {        return p;    }    private:    void copyfrom(const auto_cptr<T> &cp)    {        minus();        if(cp.p)        {             p=cp.p;            count=cp.count;            ++(*count);        }        }         void minus()    {        if(p==0)            return;        --(*count);        if(*count<=0)        {            #ifdef __debug            cout<<"auto_cptr::minus(): delete "<<endl;            #endif            delete p;            delete count;        }else        {            #ifdef __debug            cout<<"auto_cptr::minus():not delete, p="<<p<<", count="<<get_count()<<"  "<<endl;            #endif        }                p=0;        count=0;    }    private:    T  *p;    size_t *count;};#endif

测试：main.c:

#include <iostream>#define __debug   // 打印智能指针的调试信息#include "auto_cptr.h"using namespace std;// 测试类class A{public:    A(){cout<<"empty construction"<<endl;}    A(int a_){cout<<"non-empty construction"<<endl;_a=a_;}    ~A(){cout<<"deconstruction"<<endl;}    void display(){cout<<"A::display()"<<endl;}    friend ostream &operator<<(ostream &os, const A&a);        private:    int _a;};ostream &operator<<(ostream &os, const A&a){    cout<<a._a;    return os;}int main(){        auto_cptr<A> p1=auto_cptr<A> (new A(5) );    auto_cptr<A> p2=p1; // 拷贝构造    auto_cptr<A>p3;     // 空的智能指针    p3=p2;              // 智能指针的赋值        p2=auto_cptr<A>();  // 空对象赋值给p2    cout<<"指针指向的对象值: "<<*p3<<endl;              // operator *    cout<<"通过智能指针调用函数： ";   p3->display();    // operator ->            return 0;}

运行：

chen@chen-book1:~$ gcc c.cpp -lstdc++ -o cpp -gchen@chen-book1:~$ ./cppnon-empty constructionauto_cptr(U *pu): construction of auto_cptr, obj=0x9c3c008, count=1  auto_cptr(const auto_cptr<T>& cp):copy construction of auto_cptr.obj=0x9c3c008, count=2  auto_cptr():empty construction of auto_cptrauto_cptr::operator=:operatorobj=0x9c3c008, count=3  auto_cptr():empty construction of auto_cptrauto_cptr::minus():not delete, p=0x9c3c008, count=2  auto_cptr::operator=:operatorobj=0, count=0  ~auto_cptr()指针指向的对象值: 5通过智能指针调用函数： A::display()~auto_cptr()auto_cptr::minus():not delete, p=0x9c3c008, count=1  ~auto_cptr()~auto_cptr()auto_cptr::minus(): delete deconstructionchen@chen-book1:~$