Yeah, point taken. The new interface is checked in!
Eddie
Ian Rose wrote:
>
> Eddie Kohler wrote:
>> Hi Ian,
>>
>> It's this way because even if a file descriptor was selected for both
>> reading and writing, selected() is called only once.
>
> True, but you could just use flags right? So the function could be
> redefined as Element::selected(int fd, int ops)
>
> and called like
> elt->selected(fd, Element::SELECT_READ)
> or elt->selected(fd, Element::SELECT_WRITE)
> or elt->selected(fd, Element::SELECT_READ | Element::SELECT_WRITE)
>
>>
>> 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.
>
> Also true, but if it was really that important to someone, they could
> always do that re-checking themselves. E.g. if their selected() was
> called for reading, they could also check the fd for writing "just in
> case". That seems rather inefficient to me, but I guess there could be
> some apps that really want to know ASAP when the fd is ready.
>
>> I don't feel that strongly.
>
> I think that adding a second function something like the following would
> retain existing functionality - do you agree?
>
> (in element.hh)
> virtual void selected(int fd, int ops);
>
> (in element.cc)
> void
> Element::selected(int fd, int ops)
> {
> selected(fd);
> }
>
>
>>
>> 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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