[racket] How to invoke a blocking foreign function without blocking whole racket?

For the record, Kevin Tew's function makes it easy to use:
https://github.com/kazzmir/x11-racket/blob/master/fd.rkt

For example, that's what I use in my own version of libinotify FFI:
https://github.com/Metaxal/linux-tools/blob/master/inotify.rkt

Laurent


On Wed, Jan 30, 2013 at 12:28 PM, Tim Brown <tim at timb.net> wrote:

> Resend... original (and previous resend!) sent from an address not
> valid for the list.
>
> ---------- Forwarded message ----------
> From: Tim Brown <tim.brown at timb.net>
> Date: 30 January 2013 10:01
> Subject: Re: [racket] How to invoke a blocking foreign function
> without blocking whole racket?
> To: Haiwei Zhou <highfly22 at gmail.com>
> Cc: users at racket-lang.org
>
>
> There are internal FFI calls: scheme_make_fd_input_port and
> scheme_make_fd_output_port, documented in
>
> http://docs.racket-lang.org/inside/Ports_and_the_Filesystem.html?q=to%20port#(idx._(gentag._480._(lib._scribblings/inside/inside..scrbl)))
>
> If you would normally be able to poll (or select) from the port, then
> a little bit of work will allow you to tie your IO closer to the
> racket events system.
>
> There are more involved variants, I've mostly only needed this level
> of access at the racket level; servicing the known-to-be ready fd is
> done by your FFI library.
>
> Tim
>
> On 30 Jan 2013 09:44, "Haiwei Zhou" <highfly22 at gmail.com> wrote:
> >
> > Finally, I figured out the callback from this letter:
> http://lists.racket-lang.org/users/archive/2010-July/040409.html . I wish
> I red this letter early.
> >
> > After realized that the foreign function blocks the caller thread, I
> used dynamic-place to create worker thread. The code is here :
> https://github.com/highfly22/alert/blob/master/inotify.rkt
> >
> > Racket is amazing simple after you know the bloody details.
> >
> > Haiwei
> >
> >
> > On 30 January 2013 14:23, Haiwei Zhou <highfly22 at gmail.com> wrote:
> >>
> >> Hi,
> >>
> >>  I try to wrap inotify API. After adding a watcher, I try to read
> events from file descriptor. But the racket thread is blocking until the
> read operation is done. Here is the definition of read.
> >>
> >> (define _read (get-ffi-obj "read" libc (_fun #:async-apply (lambda (f)
> (f))
> >>                                              #:save-errno 'posix
> >>                                             _fd_t
> >>                                             (output : (_bytes o size))
> >>                                             (size : _uint32)
> >>                                             -> (r : _int32)
> >>                                             -> (values r saved-errno
> output))))
> >>
> >> I am confused by the term callback. Is the callback called in the
> racket thread or another OS thread?
> >>
> >> Thanks,
> >> Haiwei
> >
> >
> >
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