shared_ptr 简单实现

template 
class Shared_ptr {
public:
    Shared_ptr(): count(new unsigned int(1)), val(new T()) {}

    Shared_ptr(T* p): count(new unsigned int(1)), val(p) {}

    Shared_ptr(const Shared_ptr& sp): count(sp.count), val(sp.val){
        ++*count;
    }

    ~Shared_ptr() {
        Release();
    }

    T& operator *() {
        return *val;
    }

    Shared_ptr& operator = (const Shared_ptr& p) {
        ++ *p.count;
        Release();
        count = p.count;
        val = p.val;
        return *this;
    }

    void Release() {
        if (--*count == 0) {
            delete val;
            delete count;
        }
    }

private:
    unsigned int *count;
    T *val;
};