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

Cool! The open-fd-input-port is a great function.

Inotify cannot handle subtrees. I will try to make it more convenience.
I plan to make a tool like guard - https://github.com/guard/guard

It's useful to run unit tests while some files are changed.

Thanks,
Haiwei


On 30 January 2013 20:52, Laurent <laurent.orseau at gmail.com> wrote:

> 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)))<http://docs.racket-lang.org/inside/Ports_and_the_Filesystem.html?q=to%20port#%28idx._%28gentag._480._%28lib._scribblings/inside/inside..scrbl%29%29%29>
>>
>> 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
>> >
>> >
>> >
>> > ____________________
>> >   Racket Users list:
>> >   http://lists.racket-lang.org/users
>> >
>> ____________________
>>   Racket Users list:
>>   http://lists.racket-lang.org/users
>>
>
>
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