libzmq/src/pipe.cpp

/*
    Copyright (c) 2007-2016 Contributors as noted in the AUTHORS file

    This file is part of libzmq, the ZeroMQ core engine in C++.

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

    As a special exception, the Contributors give you permission to link
    this library with independent modules to produce an executable,
    regardless of the license terms of these independent modules, and to
    copy and distribute the resulting executable under terms of your choice,
    provided that you also meet, for each linked independent module, the
    terms and conditions of the license of that module. An independent
    module is a module which is not derived from or based on this library.
    If you modify this library, you must extend this exception to your
    version of the library.

    libzmq 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 "precompiled.hpp"
#include <new>
#include <stddef.h>

#include "macros.hpp"
#include "pipe.hpp"
#include "err.hpp"

#include "ypipe.hpp"
#include "ypipe_conflate.hpp"

int zmq::pipepair (class object_t *parents_ [2], class pipe_t* pipes_ [2],
    int hwms_ [2], bool conflate_ [2])
{
    //   Creates two pipe objects. These objects are connected by two ypipes,
    //   each to pass messages in one direction.

    typedef ypipe_t <msg_t, message_pipe_granularity> upipe_normal_t;
    typedef ypipe_conflate_t <msg_t> upipe_conflate_t;

    pipe_t::upipe_t *upipe1;
    if(conflate_ [0])
        upipe1 = new (std::nothrow) upipe_conflate_t ();
    else
        upipe1 = new (std::nothrow) upipe_normal_t ();
    alloc_assert (upipe1);

    pipe_t::upipe_t *upipe2;
    if(conflate_ [1])
        upipe2 = new (std::nothrow) upipe_conflate_t ();
    else
        upipe2 = new (std::nothrow) upipe_normal_t ();
    alloc_assert (upipe2);

    pipes_ [0] = new (std::nothrow) pipe_t (parents_ [0], upipe1, upipe2,
        hwms_ [1], hwms_ [0], conflate_ [0]);
    alloc_assert (pipes_ [0]);
    pipes_ [1] = new (std::nothrow) pipe_t (parents_ [1], upipe2, upipe1,
        hwms_ [0], hwms_ [1], conflate_ [1]);
    alloc_assert (pipes_ [1]);

    pipes_ [0]->set_peer (pipes_ [1]);
    pipes_ [1]->set_peer (pipes_ [0]);

    return 0;
}

zmq::pipe_t::pipe_t (object_t *parent_, upipe_t *inpipe_, upipe_t *outpipe_,
      int inhwm_, int outhwm_, bool conflate_) :
    object_t (parent_),
    inpipe (inpipe_),
    outpipe (outpipe_),
    in_active (true),
    out_active (true),
    hwm (outhwm_),
    lwm (compute_lwm (inhwm_)),
    inhwmboost(0),
    outhwmboost(0),
    msgs_read (0),
    msgs_written (0),
    peers_msgs_read (0),
    peer (NULL),
    sink (NULL),
    state (active),
    delay (true),
    routing_id(0),
    conflate (conflate_)
{
}

zmq::pipe_t::~pipe_t ()
{
}

void zmq::pipe_t::set_peer (pipe_t *peer_)
{
    //  Peer can be set once only.
    zmq_assert (!peer);
    peer = peer_;
}

void zmq::pipe_t::set_event_sink (i_pipe_events *sink_)
{
    // Sink can be set once only.
    zmq_assert (!sink);
    sink = sink_;
}

void zmq::pipe_t::set_routing_id (uint32_t routing_id_)
{
    routing_id = routing_id_;
}

uint32_t zmq::pipe_t::get_routing_id ()
{
    return routing_id;
}

void zmq::pipe_t::set_identity (const blob_t &identity_)
{
    identity = identity_;
}

zmq::blob_t zmq::pipe_t::get_identity ()
{
    return identity;
}

zmq::blob_t zmq::pipe_t::get_credential () const
{
    return credential;
}

bool zmq::pipe_t::check_read ()
{
    if (unlikely (!in_active))
        return false;
    if (unlikely (state != active && state != waiting_for_delimiter))
        return false;

    //  Check if there's an item in the pipe.
    if (!inpipe->check_read ()) {
        in_active = false;
        return false;
    }

    //  If the next item in the pipe is message delimiter,
    //  initiate termination process.
    if (inpipe->probe (is_delimiter)) {
        msg_t msg;
        bool ok = inpipe->read (&msg);
        zmq_assert (ok);
        process_delimiter ();
        return false;
    }

    return true;
}

bool zmq::pipe_t::read (msg_t *msg_)
{
    if (unlikely (!in_active))
        return false;
    if (unlikely (state != active && state != waiting_for_delimiter))
        return false;

read_message:
    if (!inpipe->read (msg_)) {
        in_active = false;
        return false;
    }

    //  If this is a credential, save a copy and receive next message.
    if (unlikely (msg_->is_credential ())) {
        const unsigned char *data = static_cast <const unsigned char *> (msg_->data ());
        credential = blob_t (data, msg_->size ());
        const int rc = msg_->close ();
        zmq_assert (rc == 0);
        goto read_message;
    }

    //  If delimiter was read, start termination process of the pipe.
    if (msg_->is_delimiter ()) {
        process_delimiter ();
        return false;
    }

    if (!(msg_->flags () & msg_t::more) && !msg_->is_identity ())
        msgs_read++;

    if (lwm > 0 && msgs_read % lwm == 0)
        send_activate_write (peer, msgs_read);

    return true;
}

bool zmq::pipe_t::check_write ()
{
    if (unlikely (!out_active || state != active))
        return false;

    bool full = !check_hwm();

    if (unlikely (full)) {
        out_active = false;
        return false;
    }

    return true;
}

bool zmq::pipe_t::write (msg_t *msg_)
{
    if (unlikely (!check_write ()))
        return false;

    bool more = msg_->flags () & msg_t::more ? true : false;
    const bool is_identity = msg_->is_identity ();
    outpipe->write (*msg_, more);
    if (!more && !is_identity)
        msgs_written++;

    return true;
}

void zmq::pipe_t::rollback ()
{
    //  Remove incomplete message from the outbound pipe.
    msg_t msg;
    if (outpipe) {
        while (outpipe->unwrite (&msg)) {
            zmq_assert (msg.flags () & msg_t::more);
            int rc = msg.close ();
            errno_assert (rc == 0);
        }
    }
}

void zmq::pipe_t::flush ()
{
    //  The peer does not exist anymore at this point.
    if (state == term_ack_sent)
        return;

    if (outpipe && !outpipe->flush ())
        send_activate_read (peer);
}

void zmq::pipe_t::process_activate_read ()
{
    if (!in_active && (state == active || state == waiting_for_delimiter)) {
        in_active = true;
        sink->read_activated (this);
    }
}

void zmq::pipe_t::process_activate_write (uint64_t msgs_read_)
{
    //  Remember the peer's message sequence number.
    peers_msgs_read = msgs_read_;

    if (!out_active && state == active) {
        out_active = true;
        sink->write_activated (this);
    }
}

void zmq::pipe_t::process_hiccup (void *pipe_)
{
    //  Destroy old outpipe. Note that the read end of the pipe was already
    //  migrated to this thread.
    zmq_assert (outpipe);
    outpipe->flush ();
    msg_t msg;
    while (outpipe->read (&msg)) {
       if (!(msg.flags () & msg_t::more))
            msgs_written--;
       int rc = msg.close ();
       errno_assert (rc == 0);
    }
    LIBZMQ_DELETE(outpipe);

    //  Plug in the new outpipe.
    zmq_assert (pipe_);
    outpipe = (upipe_t*) pipe_;
    out_active = true;

    //  If appropriate, notify the user about the hiccup.
    if (state == active)
        sink->hiccuped (this);
}

void zmq::pipe_t::process_pipe_term ()
{
    zmq_assert (state == active
            ||  state == delimiter_received
            ||  state == term_req_sent1);

    //  This is the simple case of peer-induced termination. If there are no
    //  more pending messages to read, or if the pipe was configured to drop
    //  pending messages, we can move directly to the term_ack_sent state.
    //  Otherwise we'll hang up in waiting_for_delimiter state till all
    //  pending messages are read.
    if (state == active) {
        if (delay)
            state = waiting_for_delimiter;
        else {
            state = term_ack_sent;
            outpipe = NULL;
            send_pipe_term_ack (peer);
        }
    }

    //  Delimiter happened to arrive before the term command. Now we have the
    //  term command as well, so we can move straight to term_ack_sent state.
    else
    if (state == delimiter_received) {
        state = term_ack_sent;
        outpipe = NULL;
        send_pipe_term_ack (peer);
    }

    //  This is the case where both ends of the pipe are closed in parallel.
    //  We simply reply to the request by ack and continue waiting for our
    //  own ack.
    else
    if (state == term_req_sent1) {
        state = term_req_sent2;
        outpipe = NULL;
        send_pipe_term_ack (peer);
    }
}

void zmq::pipe_t::process_pipe_term_ack ()
{
    //  Notify the user that all the references to the pipe should be dropped.
    zmq_assert (sink);
    sink->pipe_terminated (this);

    //  In term_ack_sent and term_req_sent2 states there's nothing to do.
    //  Simply deallocate the pipe. In term_req_sent1 state we have to ack
    //  the peer before deallocating this side of the pipe.
    //  All the other states are invalid.
    if (state == term_req_sent1) {
        outpipe = NULL;
        send_pipe_term_ack (peer);
    }
    else
        zmq_assert (state == term_ack_sent || state == term_req_sent2);

    //  We'll deallocate the inbound pipe, the peer will deallocate the outbound
    //  pipe (which is an inbound pipe from its point of view).
    //  First, delete all the unread messages in the pipe. We have to do it by
    //  hand because msg_t doesn't have automatic destructor. Then deallocate
    //  the ypipe itself.

    if (!conflate) {
        msg_t msg;
        while (inpipe->read (&msg)) {
            int rc = msg.close ();
            errno_assert (rc == 0);
        }
    }

    LIBZMQ_DELETE(inpipe);

    //  Deallocate the pipe object
    delete this;
}

void zmq::pipe_t::set_nodelay ()
{
    this->delay = false;
}

void zmq::pipe_t::terminate (bool delay_)
{
    //  Overload the value specified at pipe creation.
    delay = delay_;

    //  If terminate was already called, we can ignore the duplicate invocation.
    if (state == term_req_sent1 || state == term_req_sent2) {
        return;
    }
    //  If the pipe is in the final phase of async termination, it's going to
    //  closed anyway. No need to do anything special here.
    else if (state == term_ack_sent) {
        return;
    }
    //  The simple sync termination case. Ask the peer to terminate and wait
    //  for the ack.
    else if (state == active) {
        send_pipe_term (peer);
        state = term_req_sent1;
    }
    //  There are still pending messages available, but the user calls
    //  'terminate'. We can act as if all the pending messages were read.
    else if (state == waiting_for_delimiter && !delay) {
        outpipe = NULL;
        send_pipe_term_ack (peer);
        state = term_ack_sent;
    }
    //  If there are pending messages still available, do nothing.
    else if (state == waiting_for_delimiter) {
    }
    //  We've already got delimiter, but not term command yet. We can ignore
    //  the delimiter and ack synchronously terminate as if we were in
    //  active state.
    else if (state == delimiter_received) {
        send_pipe_term (peer);
        state = term_req_sent1;
    }
    //  There are no other states.
    else {
        zmq_assert (false);
    }

    //  Stop outbound flow of messages.
    out_active = false;

    if (outpipe) {

        //  Drop any unfinished outbound messages.
        rollback ();

        //  Write the delimiter into the pipe. Note that watermarks are not
        //  checked; thus the delimiter can be written even when the pipe is full.
        msg_t msg;
        msg.init_delimiter ();
        outpipe->write (msg, false);
        flush ();
    }
}

bool zmq::pipe_t::is_delimiter (const msg_t &msg_)
{
    return msg_.is_delimiter ();
}

int zmq::pipe_t::compute_lwm (int hwm_)
{
    //  Compute the low water mark. Following point should be taken
    //  into consideration:
    //
    //  1. LWM has to be less than HWM.
    //  2. LWM cannot be set to very low value (such as zero) as after filling
    //     the queue it would start to refill only after all the messages are
    //     read from it and thus unnecessarily hold the progress back.
    //  3. LWM cannot be set to very high value (such as HWM-1) as it would
    //     result in lock-step filling of the queue - if a single message is
    //     read from a full queue, writer thread is resumed to write exactly one
    //     message to the queue and go back to sleep immediately. This would
    //     result in low performance.
    //
    //  Given the 3. it would be good to keep HWM and LWM as far apart as
    //  possible to reduce the thread switching overhead to almost zero.
    //  Let's make LWM 1/2 of HWM.
    int result = (hwm_ + 1) / 2;

    return result;
}

void zmq::pipe_t::process_delimiter ()
{
    zmq_assert (state == active
            ||  state == waiting_for_delimiter);

    if (state == active)
        state = delimiter_received;
    else {
        outpipe = NULL;
        send_pipe_term_ack (peer);
        state = term_ack_sent;
    }
}

void zmq::pipe_t::hiccup ()
{
    //  If termination is already under way do nothing.
    if (state != active)
        return;

    //  We'll drop the pointer to the inpipe. From now on, the peer is
    //  responsible for deallocating it.
    inpipe = NULL;

    //  Create new inpipe.
    if (conflate)
        inpipe = new (std::nothrow)ypipe_conflate_t <msg_t>();
    else
        inpipe = new (std::nothrow)ypipe_t <msg_t, message_pipe_granularity>();

    alloc_assert (inpipe);
    in_active = true;

    //  Notify the peer about the hiccup.
    send_hiccup (peer, (void*) inpipe);
}

void zmq::pipe_t::set_hwms (int inhwm_, int outhwm_)
{
    int in = inhwm_ + inhwmboost;
    int out = outhwm_ + outhwmboost;

    // if either send or recv side has hwm <= 0 it means infinite so we should set hwms infinite
    if (inhwm_ <= 0 || inhwmboost <= 0)
        in = 0;

    if (outhwm_ <= 0 || outhwmboost <= 0)
        out = 0;

    lwm = compute_lwm(in);
    hwm = out;
}

void zmq::pipe_t::set_hwms_boost(int inhwmboost_, int outhwmboost_)
{
    inhwmboost = inhwmboost_;
    outhwmboost = outhwmboost_;
}

bool zmq::pipe_t::check_hwm () const
{
    bool full = hwm > 0 && msgs_written - peers_msgs_read >= uint64_t (hwm);
    return( !full );
}