智能指针之scoped_ptr源码剖析

//scoped_ptr指针的简单实现
//scoped_ptr不能转让所有权
//重点是reset函数的写法
#if 0
//how to use scoped_ptr
#include <boost/smart_ptr.hpp>
using namespace boost;
using namespace std;

struct posixFile
{
posixFile(const char* fileName)
{
cout << "open file : " << fileName << endl;
}

~posixFile()
{
cout << "close file"	<< endl;
}
};

int main()
{
scoped_ptr<int> p(new int);
if(p)
{
*p = 100;
cout << *p << endl;
}
p.reset();
assert(p == 0);
if(!p)
{
cout << "p == NULL"	<< endl;

//每种智能指针只能管理一种类型的的指针，操作时要注意智能指针所管
//的类型
scoped_ptr<posixFile> pos(new posixFile("/home/lhg/1.txt"));
}
return 0;
}
#endif

#if 0
#include <iostream>
#include <boost/smart_ptr.hpp>
using namespace boost;
using namespace std;
//自动指针auto_ptr和scoped_ptr的区别
//示例
int main()
{
auto_ptr<int> ap(new int(10));
scoped_ptr<int> sp(ap); //这步是怎么实现的
assert(ap.get() == 0);

ap.reset(new int(20));
cout << *ap << "," << *sp << endl;

auto_ptr<int> ap2;
ap2 = ap;
assert(ap.get() == 0);
}
#endif

#if 1
//下来是源码剖析
//scoped_ptr
#include <iostream>
using namespace std;

template <class T>
class scoped_ptr
{
private :
T* px;
scoped_ptr(scoped_ptr<T> const&);
scoped_ptr& operator=(const scoped_ptr<T> &);

public :
scoped_ptr(T * p = 0) : px(p) {}
~scoped_ptr()
{
delete px;
}
T& operator*()
{
return *get();
}
T* operator->() const
{
return get();
}
T* get() const
{
return px;
}

        //重点是reset函数的写法
        //copy-swap手法   异常安全   effective C++ 条款11
        typedef scoped_ptr<T> this_type;
void reset(T * p = 0)
{
this_type(p).swap(*this);
}

void swap(scoped_ptr<T>& b)
{
T * temp = b.px;
b.px = px;
px = temp;
}
};

int main()
{
int *p = new int(10);
int *q = new int(100);
scoped_ptr<int> sp(p);
cout << *sp << endl;
sp.reset(q);
cout << *sp << endl;

return 0;
}

#endif