C++

[Peter Dufault <dufault@xxxxxxx>]

On Friday, Jul 18, 2003, at 13:34 US/Eastern, Matthew Dillon wrote:

> :As I understand it mp_SendMsg is a function pointer in the message 
> port
> :structure. It gets filled in when the port is created.
> :
>
>     Precisely.  mp_SendMsg() is controlled by the target port and thus 
> is
>     responsible for any frontend optimizations and conversions, 
> including
>     chaining.  mp_SendMsg is the 'agent' for the target port.
>
>     This leads to all sorts of cool possibilities.  Inserting a shim
>     becomes very easy, you would provide your own port that hides the
>     real one and then you would do your own frontend processing.  For
>     example:
>
>     struct myport {
> 	MsgPort		port;
> 	MsgPort		*realport;
>     }t;
>
>     ...initialization of port...
>     myport->port.mp_SendMsg = myfunc;
>     myport->realport = originalport;
>
>     And then:
>
>     int
>     myfunc(struct myport *port, Msg *msg)
>     {
> 	if (message is something we want to play with) {
> 		...
> 	}
> 	/* else fall through to original port */
> 	return(port->realport->mp_SendMsg(port->realport, msg));
>     }
>
>     The port agent would be responsible for all sorts of things.  For
>     example, in the kernel on a port representing entry into the TCP 
> stack
>     the port agent would be responsible for partitioning the work 
> amoungst
>     available TCP stack worker threads and forwarding the message
Did you consider using a subset of C++ for the kernel?  I'm asking 
because of this example and because I personally would have had to 
consider it because of the hand-built repetitive infrastructure of pure 
C.

I can see many drawbacks (enforcing a subset, issues associated with 
many fingers in the pie, etc) and I want to know what you thought about 
it.