[lwip-users] Re: [lwip] Q: implementation for select()

[Dirk Koopman]

Erm...

Am I being a bit thick here or have I missed something?

All the 'socket' stuff is ultimately based on the 'low-level interface'.
The 'low-level interface' is a callback interface that gives you all the
information that 'select' does (and then some). Also, crucially, for an
embedded platform, it only executes 'user code' when there is something
for that to do.

Why not use that, rather than the 'socket' code? 

You won't need threads/semaphores either!

Dirk

On Tue, 2002-08-06 at 23:52, Sebastian Bauer wrote:
> Hi!
> 
> From: "Duncan Palmer" <address@hidden>
> >Add 2 lists of semaphores to each struct netconn - one to be used by
> >readfds
> >and one by writefds. Add fields to the struct netconn's to enable FD_SET
> >and
> >friends to be implemented.
> [...]
> >To implement readfd's: The select call will create a new semaphore and add
> >it
> >to the list of semaphores on all connections which correspond to its list
> >of
> >readfds. It will then wait on this semaphore. When new data comes in (i.e.
> >in
> >all the places where conn->recvmbox is posted to), signal all read
> >semaphores
> >on the connection. This will wake up the select call which can delete the
> >semaphore from all connections it was waiting from and return.
> 
> I'm not really familiar with the internals of lwip but this sounds well for
> me. The only problem I see is that how select() knows now (after it has been
> waken up) which netconn's received something? Or is it possible to check
> this? (checking if there is anything in conn->recvmbox without fetching).
> 
> Also is there really the need that the netconn's should have lists? Maybe
> just a refrence would be enough. I think only one task/process/thread can
> receive something from a netconn.
> That would make the implementation simpler.
> 
> But I will think a little bit more about tomorrow :)
> 
> Ciao,
> Sebastian
> 
> 
> 
> [This message was sent through the lwip discussion list.]


[This message was sent through the lwip discussion list.]