Rewriting the FIFO code

[Corinna Vinschen]

On Jan 22 20:44, Ken Brown wrote:
> On 12/26/2018 2:03 PM, Corinna Vinschen wrote:
> > On Dec 26 14:00, Ken Brown wrote:
> >> Thanks for the encouragement, and Happy Holidays to you too.  One question: In
> >> the new AF_UNIX socket code you mostly used NT functions, but the existing FIFO
> >> code uses Win32 functions.  Do you prefer NT functions for new code?
> > 
> > The NT functions have some advantages over the Win32 functions.
> > For instance, WaitNamedPipe is not interruptible, while
> > NtFsControlFile(FSCTL_PIPE_WAIT) can be called asynchronously
> > and then you can just wait for an event object via cygwait
> > (see fhandler_socket_unix::wait_pipe_thread).
> > 
> > So, in theory I'd prefer NT functions, but if you feel uncomfortable
> > and just want to implement away, feel free to go ahead with Win32
> > functions.
> 
> I've decided to use Win32 functions for now, not because of discomfort but 
> because it allowed me to use more of the existing code.  I can always change 
> that later.

Sounds good to me.  Just... can we make the fifo pipes PIPE_NOWAIT, by
any chance and make fhandler_fifo a derived class of fhandler_base?

In the long run I'd like to get rid of the dreaded
fhandler_base_overlapped class.  It doesn't reflect POSIX nowait
semantics correctly and using nonblocking pipes would drop the need for
code like fhandler_base_overlapped::close.  Normal pipes should also run
nonblocking ideally.

> I've got enough working now that I think my patches could use some review.  But 
> there's still a lot more to do.  I've attached the patches, but I could send 
> them to cygwin-patches instead if you prefer.

I'd like to get 2.12.0 out of the door and then we can start pulling
your stuff, whenever you think the patches are ready for that.  In 
that case, send them to the patches list.

I reviewed the patches just visually for now, but this looks good to me
so far, except for my begging above :}


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
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