Cancel read on socket

[leonp at plris.com (Leon Pollak)]

On Wednesday, 28 ?May 2008, Ralf Corsepius wrote:
> On Wed, 2008-05-28 at 09:22 +0300, Leon Pollak wrote:
> > On Wednesday, 28 ?May 2008, Chris Johns wrote:
> > > Joel Sherrill wrote:
> > > > Without thinking about compatibility at all, shouldn't it be
> > > > possible to add an RTEMS specific IOCTL which forced
> > > > a read() to return an error like ECANCELED?
> Think along these lines from POSIX:
> ...
> If a read() is interrupted by a signal before it reads any data, it
> shall return -1 with errno set to [EINTR].
>
> If a read() is interrupted by a signal after it has successfully read
> some data, it shall return the number of bytes read.
> ...
>
> How would you handle canceling io?
Well, IMHO, this is simple - as I asked to cancel this io its results are not 
interesting for me even if there was already some data received.

And, BTW, what is the principal difference between this and the timeout case?
I mean, that timeout occurred exactly before the data arrived?

> In addition to that, I am opposed to adding anything proprietary to a
> standardized API.
Here is the good point.
And I should not speak about this, if there was no precedent - CancelIo in 
Windows. Yes, I don't like MS at all, but they did it much later then 
Berkley/BSD - still may be they already saw this need...:-)

And besides, BSD stack was designed mostly not for RT applications where 
requirements are not so hard... IMHO...

Thanks.
-- 
Leon