我们知道shared_ptr是C++11的新标准，可以自动回收动态内存。同时它也可以管理其它资源。
比如网络编程里的连接。
语法
shared_ptr语法如下：
shared_ptr<T> p(q, d)
p接管了内置指针q所指对象的所有权。q必须保证能强制转换为T*类型。
p将调用回调函数d来代替delete回收资源。
应用
struct destination
{
string ip;
int port;
destination(string _ip, int _port): ip(_ip), port(_port){};
};
struct connection
{
string ip;
int port;
connection(string _ip, int _port): ip(_ip), port(_port){};
};
connection connect(destination *d)
{
shared_ptr<connection> pConn(new connection(d->ip, d->port));
cout << "creating connection(" << pConn.use_count() << ")" << endl;
return *pConn;
}
connection disconnect(connection& p)
{
cout << "connection close(" << p.ip << ":" << p.port << ")" << endl;
}
void deleter(connection* p)
{
disconnect(*p);
}
void f(destination &d)
{
connection c = connect(&d);
//shared_ptr<connection> p(&c, deleter);
shared_ptr<connection> p(&c, [](connection* p)
{disconnect(*p);});
cout << "Resource has been reaped\n";
}
int main()
{
destination des("202.201.13.12", 8888);
f(des);
}
如上所示，当f退出时，p被销毁，connection会被正确关闭。
程序打印结果：
creating connection(1)
Resource has been reaped
connection close(202.201.13.12:8888)
Reference
[1].C++ Primer. P416.