Re: Help-octave Digest, Vol 157, Issue 40

[John Donoghue]

On 4/22/19 9:41 AM, address@hidden wrote:
> Message: 2
> Date: Sun, 21 Apr 2019 23:54:09 +0000
> From: "Ardid, Salva"<address@hidden>
> To:"address@hidden"  <address@hidden>
> Subject: Workaround missing functions in the zeromq package
> Message-ID: <address@hidden>
> Content-Type: text/plain; charset="utf-8"
>
> Hi,
>
> I started working to support Octave in Transplant using the zeromq package in 
> Octave Forge. It?s the first time I use anything related to ZMQ and I reached a 
> point where I?m stacked because Transplant uses zmq_msg_init, zmq_msg_recv, 
> zmq_msg_data and zmq_msg_close, which are not yet supported in Octave?s package.
>
> So, I wonder, would there be some way to implement the same functionality just 
> using zmq_recv?
>
> For the case it is useful, this is the piece of code I would need to adapt:
>
> msg = libstruct('zmq_msg_t', struct('hidden', zeros(1, 64, 'uint8')));
> calllib('libzmq', 'zmq_msg_init', msg); % always returns 0
> msglen = calllib('libzmq', 'zmq_msg_recv', msg, obj.socket, 0);
> assert(msglen >= 0, obj.errortext('zmq_msg_recv'));
> msgptr = calllib('libzmq', 'zmq_msg_data', msg);
> if not(msgptr.isNull)
>      setdatatype(msgptr, 'uint8Ptr', 1, msglen);
>      str = uint8(msgptr.Value);
> else
>      str = uint8([]);
> end
> err = calllib('libzmq', 'zmq_msg_close', msg);
> assert(err == 0, obj.errortext('zmq_msg_close'));
>
>
> [Transplant also uses zmq contexts, which are not supported in the Octave 
> package either. Although I?m not totally sure, I think this shouldn?t be 
> strictly needed to make it work]
>
> Any help on this is very much appreciated!
>
> Thanks in advance and best, Salva

the octave zmq package uses a zmq context within the package, but 
doesn't expose it to the user. The same goes for the zmq_msg_xxxx 
functions - they are used internally, but the user doesnt have direct 
access to them.

So the user (after creating the zmq socket) can just call,   msg = 
zmq_recv(sock, 100) to read up to 100 bytes to msg, rather than having 
to prep a msg_t.

The examples and documentation that come with the package give a 
overview of using it, and what calls are not required. [1]


[1] https://octave.sourceforge.io/zeromq/package_doc/