Re: Mqtt support in guile?

I'm not seeing all of the context, but I think this should work

   (define (my-msg-handler mos data msg)
      (display (pointer->string (cdata*-ref msg 'message) (cdata*-ref 
msg 'messagesize)))
     (newline))

   (mosquitto_message_callback_set mosq my-msg-handler)

in my-msg-handler, mos will be <cdata struct-mosquitto* 0xdeadbeef>, 
data will be of type <pointer > and msg will be of type <cdata 
struct-mosquitto_message* 0xdeadbeef>

A lot of the plumbing you are doing comes for free in the 
ffi/mosquitto.scm code.  You should not have be writining 
pointer->procedure code or using (make-cdata ...) from the callback 
arguments.

On 11/1/24 8:10 AM, Mikael Djurfeldt wrote:
> BTW,
>
> I did:
>
> (mosquitto_message_callback_set mosq (procedure->pointer void 
> receive-message (list '* '* '*)))
>
> Is it correct to pass '* as argument type for the struct 
> mosquitto_message pointer (3rd arg)?
>
> On Fri, Nov 1, 2024 at 4:08 PM Mikael Djurfeldt <[email protected]> 
> wrote:
>
>     Thanks!
>
>     Doing the (make-cdata struct-mosquitto_message* message) as well
>     as changing cdata-ref to cdata*-ref works fine.
>
>     Obviously, what someone should do is to write a nice schemey
>     interface on top of what you get with (ffi mosquitto).
>
>     Best regards,
>     Mikael
>
>     On Fri, Nov 1, 2024 at 3:05 PM Matt Wette <[email protected]>
>     wrote:
>
>         And one more thing.   There is a manual for cdata.  There is a
>         link on
>         this page
>
>         https://www.nongnu.org/nyacc/
>
>
>         On 11/1/24 6:37 AM, Matt Wette wrote:
>         > I got this wrong.  Sorry!   This is it.  What I gave
>         previously was
>         > the old fh syntax.
>         >
>         > (msg (make-cdata struct-mosquitto_message* message))
>         >
>         >
>         >
>         > On 11/1/24 6:32 AM, Matt Wette wrote:
>         >> assuming message is a Guile pointer:
>         >>
>         >> (define (receive-message mosq obj message)
>         >>   (let ((msg (make-struct-mosquitto_message* message))
>         >>           (size (cdata-ref msg '* 'payloadsize))
>         >>          (payload (cdata-ref msg '* 'payload))
>         >>   (pointer->string payload size)))
>         >>
>         >>
>         >> On 10/31/24 4:49 PM, Mikael Djurfeldt wrote:
>         >>> Hi Matt,
>         >>>
>         >>> This is very nice indeed! :-)
>         >>>
>         >>> I got a small client working, but I found the unpacking of
>         values in
>         >>> the message callback function a bit cumbersome.  I now have:
>         >>>
>         >>> (define (pointer->struct-mosquitto_message pointer)
>         >>>   (let* ((size (ctype-size struct-mosquitto_message))
>         >>>          (bvec (pointer->bytevector pointer size)))
>         >>>          (Xcdata-ref bvec 0 struct-mosquitto_message)))
>         ;The only
>         >>> way I found that worked! :)
>         >>>
>         >>> (define (receive-message mosq obj message)
>         >>>   (let* ((message (pointer->struct-mosquitto_message message))
>         >>>          (payload (cdata-ref message 'payload))
>         >>>          (size (cdata-ref message 'payloadlen))
>         >>>          (payload (pointer->string payload size)))
>         >>>     (display payload)
>         >>>     (newline)))
>         >>>
>         >>> Is there some more convenient/right way to do that?
>         >>>
>         >>> Best regards,
>         >>> Mikael
>         >>>
>         >>> On Thu, Oct 31, 2024 at 1:02 PM Matt Wette
>         <[email protected]>
>         >>> wrote:
>         >>>
>         >>>     On 10/31/24 1:48 AM, Ricardo G. Herdt wrote:
>         >>>     > Hi,
>         >>>     >
>         >>>     > never did it myself, but you can create some bindings to
>         >>>     libmosquitto
>         >>>     > for your usecase. There are bindings for chicken,
>         one can take
>         >>> some
>         >>>     > inspiration from there:
>         >>> http://wiki.call-cc.org/eggref/5/mosquitto#api
>         >>>     >
>         >>>     > Regards,
>         >>>     >
>         >>>     > Ricardo
>         >>>     >
>         >>>     > Am 31.10.2024 03:24 schrieb Alan Wedel:
>         >>>     >> I have been working on a controller that uses a
>         >>> microcontroller to
>         >>>     >> read some sensors and publish their data to a mqtt
>         broker. I
>         >>> would
>         >>>     >> like to have a guile program subscribe to the mqtt
>         broker and
>         >>>     log the
>         >>>     >> sensor readings to a file. Is there anyone using
>         guile with
>         >>>     mqtt like
>         >>>     >> this? If so, how are you doing it?
>         >>>     >
>         >>>
>         >>>     Here is a dot-ffi file for mosquitto using nyacc:
>         >>>
>         >>>        (define-ffi-module (ffi mosquitto)
>         >>>          #:pkg-config "libmosquitto"
>         >>>          #:include '("mosquitto.h"))
>         >>>
>         >>>
>         >>>     I just uploaded nyacc-2.01.2, needed to compile above.
>         >>>
>         >>>     refs:
>         >>> https://savannah.nongnu.org/projects/nyacc
>         >>> https://www.nongnu.org/nyacc/nyacc-fh-ug.html
>         >>>
>         >>>     Matt
>         >>>
>         >>>
>         >>>
>         >>>
>         >>>
>         >
>         >
>