計數指標，源碼雛形

跟auto_ptr對照一下，auto_ptr複製或轉移擁有權，看看計數指標有什麼不同，看看計數指標是怎麼實現的？

#include<iostream>#include<string>#include<deque>#include<algorithm>#include<vector>#include<list>using namespace std;template<typename T>class CountedPtr{private:T* ptr;long *count;public:explicit CountedPtr(T* p=0):ptr(p),count(new long(1)){}CountedPtr(const CountedPtr<T>& p)throw():ptr(p.ptr),count(p.count){++*count;}~CountedPtr()throw(){dispose();}CountedPtr<T>& operator=(const CountedPtr<T>& p)throw(){if(this!=&p){dispose();ptr=p.ptr;count=p.count;++*count;}return *this;}T& operator*()const throw(){return *ptr;}T* operator->()const throw(){return ptr;}private:void dispose(){if(--*count==0){delete count;delete ptr;}}};void dayin(CountedPtr<int> elem){cout<<*elem<<" ";}int main(){static int values[]={3,5,9,1,6,4};typedef CountedPtr<int> InPtr;deque<InPtr>d;list<InPtr>l;for(int i=0;i<sizeof(values)/sizeof(*values);++i){InPtr ptr(new int(values[i]));d.push_back(ptr);l.push_front(ptr);}for_each(d.begin(),d.end(),dayin);cout<<endl;for_each(l.begin(),l.end(),dayin);cout<<endl;*d[2]*=*d[2];(**d.begin())*=-1;(**d.begin())=0;for_each(d.begin(),d.end(),dayin);cout<<endl;for_each(l.begin(),l.end(),dayin);cout<<endl;system("pause");return 0;}