[Click] Element::selected()

[Eddie Kohler]

Hi Ian,

It's this way because even if a file descriptor was selected for both reading 
and writing, selected() is called only once.

It might be useful to say whether reading or writing was enabled...but of 
course in between select()'s return and the call of selected(), something 
might have happened to make the fd selectable in other ways.  I don't feel 
that strongly.

Eddie


Ian Rose wrote:
> Hi list,
> 
> Is there any rational for why Element::selected() doesn't tell you what 
> the file descriptor was selected for (reading vs. writing)?  Or is there 
> a way to get this info that I don't know about?  It seems to me that if 
> you have a FD that you are both reading and writing to (like a socket) 
> you are pretty much stuck with something like:
> 
> void
> Foo::selected(int fd)
> {
>     // perhaps fd was selected for writes...
>     int rv = send(fd, ...);
>     if (rv == -1) {
>         if (errno == EAGAIN) {
>             // oops - I guess fd was actually selected for reads
>             int rv = recv(fd, ...);
>             (etc)
>         } else {
>             // this is a "real" send failure
>         }
>     }
>     // send succeeded!
>     (etc)
> }
> 
> Seems kinda ugly and inefficient to me...  Am I missing something?
> 
> I guess an alternative is to call select() on your fd to figure out 
> which it was selected for, but that's rather redundant!
> 
> - Ian
> 
> 
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