Re: SocketService and SocketPort

[David Sugar]

Did this get missed earlier?  We get a HUGE amount of junk mail attempts 
through this list.  It's very easy to miss a real pending message.  I would 
like to think about this...I know how I originally was thinking of what later 
became SocketService; it was based on the coding model I was originally using 
for channel ports in ACS. 

On Sunday 06 October 2002 04:30, Byrial Jensen wrote:
> [Note: I sent my first message to the list a week ago when I was not
> yet subscribed to the list. I got a mesage back that it awaited
> moderator approval because it was posted by a non-member. However the
> moderator seems to be sleeping - at least I never saw my message at
> the list.]
>
> I have programmed a simple tcp proxy-server using Common C++ and
> have some experience and suggestions with regard to SocketService
> and SocketPort I would like to share:
>
>   - There is currently no way to create SocketPorts for non-server
>     connections. I would like a SocketPort constructor which creates
>     an outgoing client tcp connection as I need a lot of such
>     connections in a proxy server.
>
>   - The virtual callback functions of the SocketPort class (expired,
>     pending, output) may /not/ delete the current SocketPort object
>     (*this) because SocketService::run will still use a pointer
>     (SocketPort *port) to the object /after/ the return of these
>     callback functions and thus use deallocated memory.
>
>     This is not documented and it is disobeyed by the tcpservice.cpp
>     demo program. So the demo program contains undefined behaviour!
>
>     I would like that the callback functions are allowed to not only
>     delete the current SocketPort object, but also to create new
>     SocketPorts attached to the same SocketService and to delete
>     other SocketPorts than *this, as this is useful in a proxy
>     server. I have done it this way in my code (here implemented
>     only inside "#ifdef CCXX_USE_POLL"):
>
> diff -udrpb commoncpp2-1.0.2-org/include/cc++/socket.h
> commoncpp2-1.0.2/include/cc++/socket.h ---
> commoncpp2-1.0.2-org/include/cc++/socket.h    Tue Aug 27 04:11:07 2002 +++
> commoncpp2-1.0.2/include/cc++/socket.h        Sun Oct  6 09:22:21 2002 @@ 
> -1814,6
> +1814,7 @@ private:
>       bool detect_pending;
>       bool detect_output;
>       bool detect_disconnect;
> +     volatile bool recent_changes;
>
>       friend class SocketService;
>
> diff -udrpb commoncpp2-1.0.2-org/src/port.cpp commoncpp2-1.0.2/src/port.cpp
> --- commoncpp2-1.0.2-org/src/port.cpp Thu Jul 18 16:52:25 2002
> +++ commoncpp2-1.0.2/src/port.cpp     Sun Oct  6 09:34:06 2002
> @@ -403,6 +403,7 @@ void SocketService::attach(SocketPort *p
>
>       ++count;
>       if(!first) first = port;
> +     recent_changes = true;
>
>       // start thread if necessary
>       if (count == 1)
> @@ -438,6 +439,7 @@ void SocketService::detach(SocketPort *p
>       port->service = NULL;
>
>       --count;
> +     recent_changes = true;
>       leaveMutex();
>       update();
>  }
> @@ -533,6 +535,7 @@ void SocketService::run(void)
>
>               MUTEX_START
>               onEvent();
> +             recent_changes = false;
>               port = first;
>               while(port)
>               {
> @@ -544,19 +547,22 @@ void SocketService::run(void)
>                                       port->detect_disconnect = false;
>                                       p_ufd->events &= ~POLLHUP;
>
> -                                     SocketPort* p = port;
> -                                     port = port->next;
> -                                     detach(p);
> -                                     reallocate = true;
> -                                     p->disconnect();
> -                                     continue;
> +                                     port->disconnect();
> +                                     if (recent_changes)
> +                                             break;
>                               }
>
> -                             if ( ( POLLIN | POLLPRI ) & p_ufd->revents )
> +                             if ( ( POLLIN | POLLPRI ) & p_ufd->revents ) {
>                                       port->pending();
> +                                     if (recent_changes)
> +                                             break;
> +                             }
>
> -                             if ( POLLOUT & p_ufd->revents )
> +                             if ( POLLOUT & p_ufd->revents ) {
>                                       port->output();
> +                                     if (recent_changes)
> +                                             break;
> +                             }
>
>                       } else {
>                               reallocate = true;
> @@ -573,6 +579,8 @@ retry:
>                       {
>                               port->endTimer();
>                               port->expired();
> +                             if (recent_changes)
> +                                     break;
>                               goto retry;
>                       }
>
>   - It would be more effective if SocketService::Run used the return
>     values from the poll/select system calls.
>
>   - TCPSocket does not support onAccept as claimed in the
>     documentation. Yes, the function exists but it is not called by
>     the SocketPort(SocketService *svc, TCPSocket &tcp) constructor.
>
> Best regards
> Byrial
>
>
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