libzmq/src/xsub.cpp

/*
    Copyright (c) 2007-2013 Contributors as noted in the AUTHORS file

    This file is part of 0MQ.

    0MQ is free software; you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    0MQ is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <string.h>

#include "xsub.hpp"
#include "err.hpp"

zmq::xsub_t::xsub_t (class ctx_t *parent_, uint32_t tid_, int sid_) :
    socket_base_t (parent_, tid_, sid_),
    has_message (false),
    more (false)
{
    options.type = ZMQ_XSUB;

    //  When socket is being closed down we don't want to wait till pending
    //  subscription commands are sent to the wire.
    options.linger = 0;

    int rc = message.init ();
    errno_assert (rc == 0);
}

zmq::xsub_t::~xsub_t ()
{
    int rc = message.close ();
    errno_assert (rc == 0);
}

void zmq::xsub_t::xattach_pipe (pipe_t *pipe_, bool subscribe_to_all_)
{
    // subscribe_to_all_ is unused
    (void) subscribe_to_all_;

    zmq_assert (pipe_);
    fq.attach (pipe_);
    dist.attach (pipe_);

    //  Send all the cached subscriptions to the new upstream peer.
    subscriptions.apply (send_subscription, pipe_);
    pipe_->flush ();
}

void zmq::xsub_t::xread_activated (pipe_t *pipe_)
{
    fq.activated (pipe_);
}

void zmq::xsub_t::xwrite_activated (pipe_t *pipe_)
{
    dist.activated (pipe_);
}

void zmq::xsub_t::xpipe_terminated (pipe_t *pipe_)
{
    fq.pipe_terminated (pipe_);
    dist.pipe_terminated (pipe_);
}

void zmq::xsub_t::xhiccuped (pipe_t *pipe_)
{
    //  Send all the cached subscriptions to the hiccuped pipe.
    subscriptions.apply (send_subscription, pipe_);
    pipe_->flush ();
}

int zmq::xsub_t::xsend (msg_t *msg_)
{
    size_t size = msg_->size ();
    unsigned char *data = (unsigned char *) msg_->data ();

    if (size > 0 && *data == 1) {
        //  Process subscribe message
        //  This used to filter out duplicate subscriptions,
        //  however this is alread done on the XPUB side and
        //  doing it here as well breaks ZMQ_XPUB_VERBOSE
        //  when there are forwarding devices involved.
        subscriptions.add (data + 1, size - 1);
        return dist.send_to_all (msg_);
    }
    else 
    if (size > 0 && *data == 0) {
        //  Process unsubscribe message
        if (subscriptions.rm (data + 1, size - 1))
            return dist.send_to_all (msg_);
    }
    else 
        //  User message sent upstream to XPUB socket
        return dist.send_to_all (msg_);

    int rc = msg_->close ();
    errno_assert (rc == 0);
    rc = msg_->init ();
    errno_assert (rc == 0);

    return 0;
}

bool zmq::xsub_t::xhas_out ()
{
    //  Subscription can be added/removed anytime.
    return true;
}

int zmq::xsub_t::xrecv (msg_t *msg_)
{
    //  If there's already a message prepared by a previous call to zmq_poll,
    //  return it straight ahead.
    if (has_message) {
        int rc = msg_->move (message);
        errno_assert (rc == 0);
        has_message = false;
        more = msg_->flags () & msg_t::more ? true : false;
        return 0;
    }

    //  TODO: This can result in infinite loop in the case of continuous
    //  stream of non-matching messages which breaks the non-blocking recv
    //  semantics.
    while (true) {

        //  Get a message using fair queueing algorithm.
        int rc = fq.recv (msg_);

        //  If there's no message available, return immediately.
        //  The same when error occurs.
        if (rc != 0)
            return -1;

        //  Check whether the message matches at least one subscription.
        //  Non-initial parts of the message are passed 
        if (more || !options.filter || match (msg_)) {
            more = msg_->flags () & msg_t::more ? true : false;
            return 0;
        }

        //  Message doesn't match. Pop any remaining parts of the message
        //  from the pipe.
        while (msg_->flags () & msg_t::more) {
            rc = fq.recv (msg_);
            errno_assert (rc == 0);
        }
    }
}

bool zmq::xsub_t::xhas_in ()
{
    //  There are subsequent parts of the partly-read message available.
    if (more)
        return true;

    //  If there's already a message prepared by a previous call to zmq_poll,
    //  return straight ahead.
    if (has_message)
        return true;

    //  TODO: This can result in infinite loop in the case of continuous
    //  stream of non-matching messages.
    while (true) {

        //  Get a message using fair queueing algorithm.
        int rc = fq.recv (&message);

        //  If there's no message available, return immediately.
        //  The same when error occurs.
        if (rc != 0) {
            errno_assert (errno == EAGAIN);
            return false;
        }

        //  Check whether the message matches at least one subscription.
        if (!options.filter || match (&message)) {
            has_message = true;
            return true;
        }

        //  Message doesn't match. Pop any remaining parts of the message
        //  from the pipe.
        while (message.flags () & msg_t::more) {
            rc = fq.recv (&message);
            errno_assert (rc == 0);
        }
    }
}

bool zmq::xsub_t::match (msg_t *msg_)
{
    return subscriptions.check ((unsigned char*) msg_->data (), msg_->size ());
}

void zmq::xsub_t::send_subscription (unsigned char *data_, size_t size_,
    void *arg_)
{
    pipe_t *pipe = (pipe_t*) arg_;

    //  Create the subsctription message.
    msg_t msg;
    int rc = msg.init_size (size_ + 1);
    errno_assert (rc == 0);
    unsigned char *data = (unsigned char*) msg.data ();
    data [0] = 1;
    memcpy (data + 1, data_, size_);

    //  Send it to the pipe.
    bool sent = pipe->write (&msg);
    //  If we reached the SNDHWM, and thus cannot send the subscription, drop
    //  the subscription message instead. This matches the behaviour of
    //  zmq_setsockopt(ZMQ_SUBSCRIBE, ...), which also drops subscriptions
    //  when the SNDHWM is reached.
    if (!sent)
        msg.close ();
}