zmq::send always releases its message about cppzmq HOT 4 CLOSED

@yerden The sending will happen on an other thread. So you are just queuing the message. With zmq_send you can quckly assemble a message (even on the stack) and put it to the queue and then move on, releasing that message on your thread. The sending thread will release the copy of that message when it not needed anymore. In case of zmq_send_const you have to keep in memory the original message until the sending moment. And you have to find out when it happens somehow.

from cppzmq.

The implementation of zmq_send_const is kind of pointless. It constructs a message internally, uses it, and allows it to be destroyed.

I believe this is a poor implementation as it isn't really const as advertised. And thus this mess shouldn't be pushed into the C++ interface.

I am closing this ticket.

from cppzmq.

I think you misread the code. The zmq_send_const

    zmq_msg_t msg;
    int rc = zmq_msg_init_data (&msg, (void *)buf_, len_, NULL, NULL);

but the zmq_send

   zmq_msg_t msg;
    if (zmq_msg_init_size (&msg, len_))
        return -1;

    //  We explicitly allow a send from NULL, size zero
    if (len_) {
        assert (buf_);
        memcpy (zmq_msg_data (&msg), buf_, len_);
    }

So the zmq_send do a complete copy with malloc + memcpy but the zmq_send_const just use a buf_ and len_ variables for sending. There is a huge performance difference between the two version.

from cppzmq.

@hun-nemethpeter sorry for bringing it to sunlight but what are the benefits of calling zmq_send over zmq_send_const? What's the matter with malloc + memcpy? When zmq_send_const returns, can I modify the specified (and "sent") buffer?

from cppzmq.