Subject: Re: [Boost-users] [Asio]Question about error_code when socket::close
From: Comet (cometliao_at_[hidden])
Date: 2010-05-17 06:29:59
> That is because you are most likely using the inefficient creation
> style, probably like this:
> shared_ptr<myClass> myPtr(new myClass(arg1,arg2));
> Which will also new a struct inside the shared_ptr that holds that
> pointer and bookkeeping information. If you have read the shared_ptr
> documentation, the efficient creation style is this:
> shared_ptr<myClass> myPtr = make_shared<myClass>(arg1,arg2);
> Which will new both your class and the bookkeeping information in the
> same place in memory, increasing both the speed of creation (only one
> new), and speed of accessing (better cache coherency).
> When creating your objects at the same time (literally) as the
> shared_ptr, that should fix most of those speed issues.
That's not the point, make_shared can be used only when the object is
created,but what I said is as follows:
class Session
: public boost::enable_shared_from_this<Session> {
public:
static void HandleRead(boost::weak_ptr<Session> session,
const boost::system::error_code& error,
size_t bytes_transferred) {
if (session.expired())
return;
...
}
void Read() {
// this line is very slow,
// because boost::bind(&Session::HandleRead,shared_from_this(), ...)
// causes extra new/delete operations
socket_.async_read_some(boost::asio::buffer(...),
boost::bind(&Session::HandleRead,
shared_from_this(),
_1, _2));
...
}
void Close() {
socket_.close();
}
private:
boost::asio::ip::tcp::socket socket_;
};
std::set<boost::shared_ptr<Session> > session_set;
boost::shared_ptr<Session> session
= boost::make_shared<Session>();
session_set.insert(session);
session->Read();
....
session->Close();
session_set->erase(session); // session is destroyed here,
if I replace
static void HandleRead(weak_prt ...) with void HandleRead(...)
and
boost::bind(&Session::HandleRead, shared_from_this()...), with
boost::bind(&Session::HandleRead, this, ...);
the question I asked emerges:
void HandleRead(const boost::system::error_code& error,
size_t bytes_transferred) {
if (error)
//should I erase shared_from_this() from session_set? this object
may have been destroyed...
}
....
session->Close();
session_set->erase(session); // session is destroyed here. if I don't
do this here, where should I do ? HandleRead may not be registered
ever...