zmq.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/>.
*/

// "Tell them I was a writer.
//  A maker of software.
//  A humanist. A father.
//  And many things.
//  But above all, a writer.
//  Thank You. :)"
//  - Pieter Hintjens

#include "precompiled.hpp"
#define ZMQ_TYPE_UNSAFE

#include "macros.hpp"
#include "poller.hpp"

#if !defined ZMQ_HAVE_POLLER
//  On AIX platform, poll.h has to be included first to get consistent
//  definition of pollfd structure (AIX uses 'reqevents' and 'retnevents'
//  instead of 'events' and 'revents' and defines macros to map from POSIX-y
//  names to AIX-specific names).
#if defined ZMQ_POLL_BASED_ON_POLL && !defined ZMQ_HAVE_WINDOWS
#include <poll.h>
#endif

#include "polling_util.hpp"
#endif

// TODO: determine if this is an issue, since zmq.h is being loaded from pch.
// zmq.h must be included *after* poll.h for AIX to build properly
//#include "../include/zmq.h"

#if !defined ZMQ_HAVE_WINDOWS
#include <unistd.h>
#ifdef ZMQ_HAVE_VXWORKS
#include <strings.h>
#endif
#endif

// XSI vector I/O
#if defined ZMQ_HAVE_UIO
#include <sys/uio.h>
#else
struct iovec
{
    void *iov_base;
    size_t iov_len;
};
#endif

#include <string.h>
#include <stdlib.h>
#include <new>
#include <climits>

#include "proxy.hpp"
#include "socket_base.hpp"
#include "stdint.hpp"
#include "config.hpp"
#include "likely.hpp"
#include "clock.hpp"
#include "ctx.hpp"
#include "err.hpp"
#include "msg.hpp"
#include "fd.hpp"
#include "metadata.hpp"
#include "socket_poller.hpp"
#include "timers.hpp"
#include "ip.hpp"
#include "address.hpp"

#if defined ZMQ_HAVE_OPENPGM
#define __PGM_WININT_H__
#include <pgm/pgm.h>
#endif

//  Compile time check whether msg_t fits into zmq_msg_t.
typedef char
  check_msg_t_size[sizeof (zmq::msg_t) == sizeof (zmq_msg_t) ? 1 : -1];


void zmq_version (int *major_, int *minor_, int *patch_)
{
    *major_ = ZMQ_VERSION_MAJOR;
    *minor_ = ZMQ_VERSION_MINOR;
    *patch_ = ZMQ_VERSION_PATCH;
}


const char *zmq_strerror (int errnum_)
{
    return zmq::errno_to_string (errnum_);
}

int zmq_errno (void)
{
    return errno;
}


//  New context API

void *zmq_ctx_new (void)
{
    //  We do this before the ctx constructor since its embedded mailbox_t
    //  object needs the network to be up and running (at least on Windows).
    if (!zmq::initialize_network ()) {
        return NULL;
    }

    //  Create 0MQ context.
    zmq::ctx_t *ctx = new (std::nothrow) zmq::ctx_t;
    if (ctx) {
        if (!ctx->valid ()) {
            delete ctx;
            return NULL;
        }
    }
    return ctx;
}

int zmq_ctx_term (void *ctx_)
{
    if (!ctx_ || !(static_cast<zmq::ctx_t *> (ctx_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    int rc = (static_cast<zmq::ctx_t *> (ctx_))->terminate ();
    int en = errno;

    //  Shut down only if termination was not interrupted by a signal.
    if (!rc || en != EINTR) {
        zmq::shutdown_network ();
    }

    errno = en;
    return rc;
}

int zmq_ctx_shutdown (void *ctx_)
{
    if (!ctx_ || !(static_cast<zmq::ctx_t *> (ctx_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }
    return (static_cast<zmq::ctx_t *> (ctx_))->shutdown ();
}

int zmq_ctx_set (void *ctx_, int option_, int optval_)
{
    if (!ctx_ || !(static_cast<zmq::ctx_t *> (ctx_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }
    return (static_cast<zmq::ctx_t *> (ctx_))->set (option_, optval_);
}

int zmq_ctx_get (void *ctx_, int option_)
{
    if (!ctx_ || !(static_cast<zmq::ctx_t *> (ctx_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }
    return (static_cast<zmq::ctx_t *> (ctx_))->get (option_);
}

//  Stable/legacy context API

void *zmq_init (int io_threads_)
{
    if (io_threads_ >= 0) {
        void *ctx = zmq_ctx_new ();
        zmq_ctx_set (ctx, ZMQ_IO_THREADS, io_threads_);
        return ctx;
    }
    errno = EINVAL;
    return NULL;
}

int zmq_term (void *ctx_)
{
    return zmq_ctx_term (ctx_);
}

int zmq_ctx_destroy (void *ctx_)
{
    return zmq_ctx_term (ctx_);
}


// Sockets

static zmq::socket_base_t *as_socket_base_t (void *s_)
{
    zmq::socket_base_t *s = static_cast<zmq::socket_base_t *> (s_);
    if (!s_ || !s->check_tag ()) {
        errno = ENOTSOCK;
        return NULL;
    }
    return s;
}

void *zmq_socket (void *ctx_, int type_)
{
    if (!ctx_ || !(static_cast<zmq::ctx_t *> (ctx_))->check_tag ()) {
        errno = EFAULT;
        return NULL;
    }
    zmq::ctx_t *ctx = static_cast<zmq::ctx_t *> (ctx_);
    zmq::socket_base_t *s = ctx->create_socket (type_);
    return (void *) s;
}

int zmq_close (void *s_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    s->close ();
    return 0;
}

int zmq_setsockopt (void *s_,
                    int option_,
                    const void *optval_,
                    size_t optvallen_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->setsockopt (option_, optval_, optvallen_);
}

int zmq_getsockopt (void *s_, int option_, void *optval_, size_t *optvallen_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->getsockopt (option_, optval_, optvallen_);
}

int zmq_socket_monitor (void *s_, const char *addr_, int events_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->monitor (addr_, events_);
}

int zmq_join (void *s_, const char *group_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->join (group_);
}

int zmq_leave (void *s_, const char *group_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->leave (group_);
}

int zmq_bind (void *s_, const char *addr_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->bind (addr_);
}

int zmq_connect (void *s_, const char *addr_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->connect (addr_);
}

int zmq_unbind (void *s_, const char *addr_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->term_endpoint (addr_);
}

int zmq_disconnect (void *s_, const char *addr_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s->term_endpoint (addr_);
}

// Sending functions.

static inline int
s_sendmsg (zmq::socket_base_t *s_, zmq_msg_t *msg_, int flags_)
{
    size_t sz = zmq_msg_size (msg_);
    int rc = s_->send (reinterpret_cast<zmq::msg_t *> (msg_), flags_);
    if (unlikely (rc < 0))
        return -1;

    //  This is what I'd like to do, my C++ fu is too weak -- PH 2016/02/09
    //  int max_msgsz = s_->parent->get (ZMQ_MAX_MSGSZ);
    size_t max_msgsz = INT_MAX;

    //  Truncate returned size to INT_MAX to avoid overflow to negative values
    return static_cast<int> (sz < max_msgsz ? sz : max_msgsz);
}

/*  To be deprecated once zmq_msg_send() is stable                           */
int zmq_sendmsg (void *s_, zmq_msg_t *msg_, int flags_)
{
    return zmq_msg_send (msg_, s_, flags_);
}

int zmq_send (void *s_, const void *buf_, size_t len_, int flags_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    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_);
    }
    int rc = s_sendmsg (s, &msg, flags_);
    if (unlikely (rc < 0)) {
        int err = errno;
        int rc2 = zmq_msg_close (&msg);
        errno_assert (rc2 == 0);
        errno = err;
        return -1;
    }
    //  Note the optimisation here. We don't close the msg object as it is
    //  empty anyway. This may change when implementation of zmq_msg_t changes.
    return rc;
}

int zmq_send_const (void *s_, const void *buf_, size_t len_, int flags_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    zmq_msg_t msg;
    int rc =
      zmq_msg_init_data (&msg, const_cast<void *> (buf_), len_, NULL, NULL);
    if (rc != 0)
        return -1;

    rc = s_sendmsg (s, &msg, flags_);
    if (unlikely (rc < 0)) {
        int err = errno;
        int rc2 = zmq_msg_close (&msg);
        errno_assert (rc2 == 0);
        errno = err;
        return -1;
    }
    //  Note the optimisation here. We don't close the msg object as it is
    //  empty anyway. This may change when implementation of zmq_msg_t changes.
    return rc;
}


// Send multiple messages.
// TODO: this function has no man page
//
// If flag bit ZMQ_SNDMORE is set the vector is treated as
// a single multi-part message, i.e. the last message has
// ZMQ_SNDMORE bit switched off.
//
int zmq_sendiov (void *s_, iovec *a_, size_t count_, int flags_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    if (unlikely (count_ <= 0 || !a_)) {
        errno = EINVAL;
        return -1;
    }

    int rc = 0;
    zmq_msg_t msg;

    for (size_t i = 0; i < count_; ++i) {
        rc = zmq_msg_init_size (&msg, a_[i].iov_len);
        if (rc != 0) {
            rc = -1;
            break;
        }
        memcpy (zmq_msg_data (&msg), a_[i].iov_base, a_[i].iov_len);
        if (i == count_ - 1)
            flags_ = flags_ & ~ZMQ_SNDMORE;
        rc = s_sendmsg (s, &msg, flags_);
        if (unlikely (rc < 0)) {
            int err = errno;
            int rc2 = zmq_msg_close (&msg);
            errno_assert (rc2 == 0);
            errno = err;
            rc = -1;
            break;
        }
    }
    return rc;
}

// Receiving functions.

static int s_recvmsg (zmq::socket_base_t *s_, zmq_msg_t *msg_, int flags_)
{
    int rc = s_->recv (reinterpret_cast<zmq::msg_t *> (msg_), flags_);
    if (unlikely (rc < 0))
        return -1;

    //  Truncate returned size to INT_MAX to avoid overflow to negative values
    size_t sz = zmq_msg_size (msg_);
    return static_cast<int> (sz < INT_MAX ? sz : INT_MAX);
}

/*  To be deprecated once zmq_msg_recv() is stable                           */
int zmq_recvmsg (void *s_, zmq_msg_t *msg_, int flags_)
{
    return zmq_msg_recv (msg_, s_, flags_);
}


int zmq_recv (void *s_, void *buf_, size_t len_, int flags_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    zmq_msg_t msg;
    int rc = zmq_msg_init (&msg);
    errno_assert (rc == 0);

    int nbytes = s_recvmsg (s, &msg, flags_);
    if (unlikely (nbytes < 0)) {
        int err = errno;
        rc = zmq_msg_close (&msg);
        errno_assert (rc == 0);
        errno = err;
        return -1;
    }

    //  An oversized message is silently truncated.
    size_t to_copy = size_t (nbytes) < len_ ? size_t (nbytes) : len_;

    //  We explicitly allow a null buffer argument if len is zero
    if (to_copy) {
        assert (buf_);
        memcpy (buf_, zmq_msg_data (&msg), to_copy);
    }
    rc = zmq_msg_close (&msg);
    errno_assert (rc == 0);

    return nbytes;
}

// Receive a multi-part message
//
// Receives up to *count_ parts of a multi-part message.
// Sets *count_ to the actual number of parts read.
// ZMQ_RCVMORE is set to indicate if a complete multi-part message was read.
// Returns number of message parts read, or -1 on error.
//
// Note: even if -1 is returned, some parts of the message
// may have been read. Therefore the client must consult
// *count_ to retrieve message parts successfully read,
// even if -1 is returned.
//
// The iov_base* buffers of each iovec *a_ filled in by this
// function may be freed using free().
// TODO: this function has no man page
//
int zmq_recviov (void *s_, iovec *a_, size_t *count_, int flags_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    if (unlikely (!count_ || *count_ <= 0 || !a_)) {
        errno = EINVAL;
        return -1;
    }

    size_t count = *count_;
    int nread = 0;
    bool recvmore = true;

    *count_ = 0;

    for (size_t i = 0; recvmore && i < count; ++i) {
        zmq_msg_t msg;
        int rc = zmq_msg_init (&msg);
        errno_assert (rc == 0);

        int nbytes = s_recvmsg (s, &msg, flags_);
        if (unlikely (nbytes < 0)) {
            int err = errno;
            rc = zmq_msg_close (&msg);
            errno_assert (rc == 0);
            errno = err;
            nread = -1;
            break;
        }

        a_[i].iov_len = zmq_msg_size (&msg);
        a_[i].iov_base = static_cast<char *> (malloc (a_[i].iov_len));
        if (unlikely (!a_[i].iov_base)) {
            errno = ENOMEM;
            return -1;
        }
        memcpy (a_[i].iov_base, static_cast<char *> (zmq_msg_data (&msg)),
                a_[i].iov_len);
        // Assume zmq_socket ZMQ_RVCMORE is properly set.
        const zmq::msg_t *p_msg = reinterpret_cast<const zmq::msg_t *> (&msg);
        recvmore = p_msg->flags () & zmq::msg_t::more;
        rc = zmq_msg_close (&msg);
        errno_assert (rc == 0);
        ++*count_;
        ++nread;
    }
    return nread;
}

// Message manipulators.

int zmq_msg_init (zmq_msg_t *msg_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))->init ();
}

int zmq_msg_init_size (zmq_msg_t *msg_, size_t size_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))->init_size (size_);
}

int zmq_msg_init_data (
  zmq_msg_t *msg_, void *data_, size_t size_, zmq_free_fn *ffn_, void *hint_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))
      ->init_data (data_, size_, ffn_, hint_);
}

int zmq_msg_send (zmq_msg_t *msg_, void *s_, int flags_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s_sendmsg (s, msg_, flags_);
}

int zmq_msg_recv (zmq_msg_t *msg_, void *s_, int flags_)
{
    zmq::socket_base_t *s = as_socket_base_t (s_);
    if (!s)
        return -1;
    return s_recvmsg (s, msg_, flags_);
}

int zmq_msg_close (zmq_msg_t *msg_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))->close ();
}

int zmq_msg_move (zmq_msg_t *dest_, zmq_msg_t *src_)
{
    return (reinterpret_cast<zmq::msg_t *> (dest_))
      ->move (*reinterpret_cast<zmq::msg_t *> (src_));
}

int zmq_msg_copy (zmq_msg_t *dest_, zmq_msg_t *src_)
{
    return (reinterpret_cast<zmq::msg_t *> (dest_))
      ->copy (*reinterpret_cast<zmq::msg_t *> (src_));
}

void *zmq_msg_data (zmq_msg_t *msg_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))->data ();
}

size_t zmq_msg_size (const zmq_msg_t *msg_)
{
    return ((zmq::msg_t *) msg_)->size ();
}

int zmq_msg_more (const zmq_msg_t *msg_)
{
    return zmq_msg_get (msg_, ZMQ_MORE);
}

int zmq_msg_get (const zmq_msg_t *msg_, int property_)
{
    const char *fd_string;

    switch (property_) {
        case ZMQ_MORE:
            return (((zmq::msg_t *) msg_)->flags () & zmq::msg_t::more) ? 1 : 0;
        case ZMQ_SRCFD:
            fd_string = zmq_msg_gets (msg_, "__fd");
            if (fd_string == NULL)
                return -1;

            return atoi (fd_string);
        case ZMQ_SHARED:
            return (((zmq::msg_t *) msg_)->is_cmsg ())
                       || (((zmq::msg_t *) msg_)->flags () & zmq::msg_t::shared)
                     ? 1
                     : 0;
        default:
            errno = EINVAL;
            return -1;
    }
}

int zmq_msg_set (zmq_msg_t *, int, int)
{
    //  No properties supported at present
    errno = EINVAL;
    return -1;
}

int zmq_msg_set_routing_id (zmq_msg_t *msg_, uint32_t routing_id_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))
      ->set_routing_id (routing_id_);
}

uint32_t zmq_msg_routing_id (zmq_msg_t *msg_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))->get_routing_id ();
}

int zmq_msg_set_group (zmq_msg_t *msg_, const char *group_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))->set_group (group_);
}

const char *zmq_msg_group (zmq_msg_t *msg_)
{
    return (reinterpret_cast<zmq::msg_t *> (msg_))->group ();
}

//  Get message metadata string

const char *zmq_msg_gets (const zmq_msg_t *msg_, const char *property_)
{
    const zmq::metadata_t *metadata =
      reinterpret_cast<const zmq::msg_t *> (msg_)->metadata ();
    const char *value = NULL;
    if (metadata)
        value = metadata->get (std::string (property_));
    if (value)
        return value;

    errno = EINVAL;
    return NULL;
}

    // Polling.

#if defined ZMQ_HAVE_POLLER
inline int zmq_poller_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
{
    // implement zmq_poll on top of zmq_poller
    int rc;
    zmq_poller_event_t *events;
    zmq::socket_poller_t poller;
    events = new (std::nothrow) zmq_poller_event_t[nitems_];
    alloc_assert (events);

    bool repeat_items = false;
    //  Register sockets with poller
    for (int i = 0; i < nitems_; i++) {
        items_[i].revents = 0;

        bool modify = false;
        short e = items_[i].events;
        if (items_[i].socket) {
            //  Poll item is a 0MQ socket.
            for (int j = 0; j < i; ++j) {
                // Check for repeat entries
                if (items_[j].socket == items_[i].socket) {
                    repeat_items = true;
                    modify = true;
                    e |= items_[j].events;
                }
            }
            if (modify) {
                rc = zmq_poller_modify (&poller, items_[i].socket, e);
            } else {
                rc = zmq_poller_add (&poller, items_[i].socket, NULL, e);
            }
            if (rc < 0) {
                delete[] events;
                return rc;
            }
        } else {
            //  Poll item is a raw file descriptor.
            for (int j = 0; j < i; ++j) {
                // Check for repeat entries
                if (!items_[j].socket && items_[j].fd == items_[i].fd) {
                    repeat_items = true;
                    modify = true;
                    e |= items_[j].events;
                }
            }
            if (modify) {
                rc = zmq_poller_modify_fd (&poller, items_[i].fd, e);
            } else {
                rc = zmq_poller_add_fd (&poller, items_[i].fd, NULL, e);
            }
            if (rc < 0) {
                delete[] events;
                return rc;
            }
        }
    }

    //  Wait for events
    rc = zmq_poller_wait_all (&poller, events, nitems_, timeout_);
    if (rc < 0) {
        delete[] events;
        if (zmq_errno () == EAGAIN) {
            return 0;
        }
        return rc;
    }

    //  Transform poller events into zmq_pollitem events.
    //  items_ contains all items, while events only contains fired events.
    //  If no sockets are repeated (likely), the two are still co-ordered, so step through the items
    //  checking for matches only on the first event.
    //  If there are repeat items, they cannot be assumed to be co-ordered,
    //  so each pollitem must check fired events from the beginning.
    int j_start = 0, found_events = rc;
    for (int i = 0; i < nitems_; i++) {
        for (int j = j_start; j < found_events; ++j) {
            if ((items_[i].socket && items_[i].socket == events[j].socket)
                || (!(items_[i].socket || events[j].socket)
                    && items_[i].fd == events[j].fd)) {
                items_[i].revents = events[j].events & items_[i].events;
                if (!repeat_items) {
                    // no repeats, we can ignore events we've already seen
                    j_start++;
                }
                break;
            }
            if (!repeat_items) {
                // no repeats, never have to look at j > j_start
                break;
            }
        }
    }

    //  Cleanup
    delete[] events;
    return rc;
}
#endif // ZMQ_HAVE_POLLER

int zmq_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
{
#if defined ZMQ_HAVE_POLLER
    // if poller is present, use that if there is at least 1 thread-safe socket,
    // otherwise fall back to the previous implementation as it's faster.
    for (int i = 0; i != nitems_; i++) {
        if (items_[i].socket
            && as_socket_base_t (items_[i].socket)->is_thread_safe ()) {
            return zmq_poller_poll (items_, nitems_, timeout_);
        }
    }
#endif // ZMQ_HAVE_POLLER
#if defined ZMQ_POLL_BASED_ON_POLL || defined ZMQ_POLL_BASED_ON_SELECT
    if (unlikely (nitems_ < 0)) {
        errno = EINVAL;
        return -1;
    }
    if (unlikely (nitems_ == 0)) {
        if (timeout_ == 0)
            return 0;
#if defined ZMQ_HAVE_WINDOWS
        Sleep (timeout_ > 0 ? timeout_ : INFINITE);
        return 0;
#elif defined ZMQ_HAVE_VXWORKS
        struct timespec ns_;
        ns_.tv_sec = timeout_ / 1000;
        ns_.tv_nsec = timeout_ % 1000 * 1000000;
        return nanosleep (&ns_, 0);
#else
        return usleep (timeout_ * 1000);
#endif
    }
    if (!items_) {
        errno = EFAULT;
        return -1;
    }

    zmq::clock_t clock;
    uint64_t now = 0;
    uint64_t end = 0;
#if defined ZMQ_POLL_BASED_ON_POLL
    zmq::fast_vector_t<pollfd, ZMQ_POLLITEMS_DFLT> pollfds (nitems_);

    //  Build pollset for poll () system call.
    for (int i = 0; i != nitems_; i++) {
        //  If the poll item is a 0MQ socket, we poll on the file descriptor
        //  retrieved by the ZMQ_FD socket option.
        if (items_[i].socket) {
            size_t zmq_fd_size = sizeof (zmq::fd_t);
            if (zmq_getsockopt (items_[i].socket, ZMQ_FD, &pollfds[i].fd,
                                &zmq_fd_size)
                == -1) {
                return -1;
            }
            pollfds[i].events = items_[i].events ? POLLIN : 0;
        }
        //  Else, the poll item is a raw file descriptor. Just convert the
        //  events to normal POLLIN/POLLOUT for poll ().
        else {
            pollfds[i].fd = items_[i].fd;
            pollfds[i].events =
              (items_[i].events & ZMQ_POLLIN ? POLLIN : 0)
              | (items_[i].events & ZMQ_POLLOUT ? POLLOUT : 0)
              | (items_[i].events & ZMQ_POLLPRI ? POLLPRI : 0);
        }
    }
#else
    //  Ensure we do not attempt to select () on more than FD_SETSIZE
    //  file descriptors.
    //  TODO since this function is called by a client, we could return errno EINVAL/ENOMEM/... here
    zmq_assert (nitems_ <= FD_SETSIZE);

    zmq::optimized_fd_set_t pollset_in (nitems_);
    FD_ZERO (pollset_in.get ());
    zmq::optimized_fd_set_t pollset_out (nitems_);
    FD_ZERO (pollset_out.get ());
    zmq::optimized_fd_set_t pollset_err (nitems_);
    FD_ZERO (pollset_err.get ());

    zmq::fd_t maxfd = 0;

    //  Build the fd_sets for passing to select ().
    for (int i = 0; i != nitems_; i++) {
        //  If the poll item is a 0MQ socket we are interested in input on the
        //  notification file descriptor retrieved by the ZMQ_FD socket option.
        if (items_[i].socket) {
            size_t zmq_fd_size = sizeof (zmq::fd_t);
            zmq::fd_t notify_fd;
            if (zmq_getsockopt (items_[i].socket, ZMQ_FD, &notify_fd,
                                &zmq_fd_size)
                == -1)
                return -1;
            if (items_[i].events) {
                FD_SET (notify_fd, pollset_in.get ());
                if (maxfd < notify_fd)
                    maxfd = notify_fd;
            }
        }
        //  Else, the poll item is a raw file descriptor. Convert the poll item
        //  events to the appropriate fd_sets.
        else {
            if (items_[i].events & ZMQ_POLLIN)
                FD_SET (items_[i].fd, pollset_in.get ());
            if (items_[i].events & ZMQ_POLLOUT)
                FD_SET (items_[i].fd, pollset_out.get ());
            if (items_[i].events & ZMQ_POLLERR)
                FD_SET (items_[i].fd, pollset_err.get ());
            if (maxfd < items_[i].fd)
                maxfd = items_[i].fd;
        }
    }

    zmq::optimized_fd_set_t inset (nitems_);
    zmq::optimized_fd_set_t outset (nitems_);
    zmq::optimized_fd_set_t errset (nitems_);
#endif

    bool first_pass = true;
    int nevents = 0;

    while (true) {
#if defined ZMQ_POLL_BASED_ON_POLL

        //  Compute the timeout for the subsequent poll.
        zmq::timeout_t timeout =
          zmq::compute_timeout (first_pass, timeout_, now, end);

        //  Wait for events.
        {
            int rc = poll (&pollfds[0], nitems_, timeout);
            if (rc == -1 && errno == EINTR) {
                return -1;
            }
            errno_assert (rc >= 0);
        }
        //  Check for the events.
        for (int i = 0; i != nitems_; i++) {
            items_[i].revents = 0;

            //  The poll item is a 0MQ socket. Retrieve pending events
            //  using the ZMQ_EVENTS socket option.
            if (items_[i].socket) {
                size_t zmq_events_size = sizeof (uint32_t);
                uint32_t zmq_events;
                if (zmq_getsockopt (items_[i].socket, ZMQ_EVENTS, &zmq_events,
                                    &zmq_events_size)
                    == -1) {
                    return -1;
                }
                if ((items_[i].events & ZMQ_POLLOUT)
                    && (zmq_events & ZMQ_POLLOUT))
                    items_[i].revents |= ZMQ_POLLOUT;
                if ((items_[i].events & ZMQ_POLLIN)
                    && (zmq_events & ZMQ_POLLIN))
                    items_[i].revents |= ZMQ_POLLIN;
            }
            //  Else, the poll item is a raw file descriptor, simply convert
            //  the events to zmq_pollitem_t-style format.
            else {
                if (pollfds[i].revents & POLLIN)
                    items_[i].revents |= ZMQ_POLLIN;
                if (pollfds[i].revents & POLLOUT)
                    items_[i].revents |= ZMQ_POLLOUT;
                if (pollfds[i].revents & POLLPRI)
                    items_[i].revents |= ZMQ_POLLPRI;
                if (pollfds[i].revents & ~(POLLIN | POLLOUT | POLLPRI))
                    items_[i].revents |= ZMQ_POLLERR;
            }

            if (items_[i].revents)
                nevents++;
        }

#else

        //  Compute the timeout for the subsequent poll.
        timeval timeout;
        timeval *ptimeout;
        if (first_pass) {
            timeout.tv_sec = 0;
            timeout.tv_usec = 0;
            ptimeout = &timeout;
        } else if (timeout_ < 0)
            ptimeout = NULL;
        else {
            timeout.tv_sec = static_cast<long> ((end - now) / 1000);
            timeout.tv_usec = static_cast<long> ((end - now) % 1000 * 1000);
            ptimeout = &timeout;
        }

        //  Wait for events. Ignore interrupts if there's infinite timeout.
        while (true) {
            memcpy (inset.get (), pollset_in.get (),
                    zmq::valid_pollset_bytes (*pollset_in.get ()));
            memcpy (outset.get (), pollset_out.get (),
                    zmq::valid_pollset_bytes (*pollset_out.get ()));
            memcpy (errset.get (), pollset_err.get (),
                    zmq::valid_pollset_bytes (*pollset_err.get ()));
#if defined ZMQ_HAVE_WINDOWS
            int rc =
              select (0, inset.get (), outset.get (), errset.get (), ptimeout);
            if (unlikely (rc == SOCKET_ERROR)) {
                errno = zmq::wsa_error_to_errno (WSAGetLastError ());
                wsa_assert (errno == ENOTSOCK);
                return -1;
            }
#else
            int rc = select (maxfd + 1, inset.get (), outset.get (),
                             errset.get (), ptimeout);
            if (unlikely (rc == -1)) {
                errno_assert (errno == EINTR || errno == EBADF);
                return -1;
            }
#endif
            break;
        }

        //  Check for the events.
        for (int i = 0; i != nitems_; i++) {
            items_[i].revents = 0;

            //  The poll item is a 0MQ socket. Retrieve pending events
            //  using the ZMQ_EVENTS socket option.
            if (items_[i].socket) {
                size_t zmq_events_size = sizeof (uint32_t);
                uint32_t zmq_events;
                if (zmq_getsockopt (items_[i].socket, ZMQ_EVENTS, &zmq_events,
                                    &zmq_events_size)
                    == -1)
                    return -1;
                if ((items_[i].events & ZMQ_POLLOUT)
                    && (zmq_events & ZMQ_POLLOUT))
                    items_[i].revents |= ZMQ_POLLOUT;
                if ((items_[i].events & ZMQ_POLLIN)
                    && (zmq_events & ZMQ_POLLIN))
                    items_[i].revents |= ZMQ_POLLIN;
            }
            //  Else, the poll item is a raw file descriptor, simply convert
            //  the events to zmq_pollitem_t-style format.
            else {
                if (FD_ISSET (items_[i].fd, inset.get ()))
                    items_[i].revents |= ZMQ_POLLIN;
                if (FD_ISSET (items_[i].fd, outset.get ()))
                    items_[i].revents |= ZMQ_POLLOUT;
                if (FD_ISSET (items_[i].fd, errset.get ()))
                    items_[i].revents |= ZMQ_POLLERR;
            }

            if (items_[i].revents)
                nevents++;
        }
#endif

        //  If timeout is zero, exit immediately whether there are events or not.
        if (timeout_ == 0)
            break;

        //  If there are events to return, we can exit immediately.
        if (nevents)
            break;

        //  At this point we are meant to wait for events but there are none.
        //  If timeout is infinite we can just loop until we get some events.
        if (timeout_ < 0) {
            if (first_pass)
                first_pass = false;
            continue;
        }

        //  The timeout is finite and there are no events. In the first pass
        //  we get a timestamp of when the polling have begun. (We assume that
        //  first pass have taken negligible time). We also compute the time
        //  when the polling should time out.
        if (first_pass) {
            now = clock.now_ms ();
            end = now + timeout_;
            if (now == end)
                break;
            first_pass = false;
            continue;
        }

        //  Find out whether timeout have expired.
        now = clock.now_ms ();
        if (now >= end)
            break;
    }

    return nevents;
#else
    //  Exotic platforms that support neither poll() nor select().
    errno = ENOTSUP;
    return -1;
#endif
}

//  The poller functionality

void *zmq_poller_new (void)
{
    zmq::socket_poller_t *poller = new (std::nothrow) zmq::socket_poller_t;
    if (!poller) {
        errno = ENOMEM;
    }
    return poller;
}

int zmq_poller_destroy (void **poller_p_)
{
    if (poller_p_) {
        zmq::socket_poller_t *const poller =
          static_cast<zmq::socket_poller_t *> (*poller_p_);
        if (poller && poller->check_tag ()) {
            delete poller;
            *poller_p_ = NULL;
            return 0;
        }
    }
    errno = EFAULT;
    return -1;
}


static int check_poller (void *const poller_)
{
    if (!poller_
        || !(static_cast<zmq::socket_poller_t *> (poller_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    return 0;
}

static int check_events (const short events_)
{
    if (events_ & ~(ZMQ_POLLIN | ZMQ_POLLOUT | ZMQ_POLLERR | ZMQ_POLLPRI)) {
        errno = EINVAL;
        return -1;
    }
    return 0;
}

static int check_poller_registration_args (void *const poller_, void *const s_)
{
    if (-1 == check_poller (poller_))
        return -1;

    if (!s_ || !(static_cast<zmq::socket_base_t *> (s_))->check_tag ()) {
        errno = ENOTSOCK;
        return -1;
    }

    return 0;
}

static int check_poller_fd_registration_args (void *const poller_,
                                              const zmq::fd_t fd_)
{
    if (-1 == check_poller (poller_))
        return -1;

    if (fd_ == zmq::retired_fd) {
        errno = EBADF;
        return -1;
    }

    return 0;
}

int zmq_poller_add (void *poller_, void *s_, void *user_data_, short events_)
{
    if (-1 == check_poller_registration_args (poller_, s_)
        || -1 == check_events (events_))
        return -1;

    zmq::socket_base_t *socket = static_cast<zmq::socket_base_t *> (s_);

    return (static_cast<zmq::socket_poller_t *> (poller_))
      ->add (socket, user_data_, events_);
}

int zmq_poller_add_fd (void *poller_,
                       zmq::fd_t fd_,
                       void *user_data_,
                       short events_)
{
    if (-1 == check_poller_fd_registration_args (poller_, fd_)
        || -1 == check_events (events_))
        return -1;

    return (static_cast<zmq::socket_poller_t *> (poller_))
      ->add_fd (fd_, user_data_, events_);
}


int zmq_poller_modify (void *poller_, void *s_, short events_)
{
    if (-1 == check_poller_registration_args (poller_, s_)
        || -1 == check_events (events_))
        return -1;

    zmq::socket_base_t *socket = static_cast<zmq::socket_base_t *> (s_);

    return (static_cast<zmq::socket_poller_t *> (poller_))
      ->modify (socket, events_);
}

int zmq_poller_modify_fd (void *poller_, zmq::fd_t fd_, short events_)
{
    if (-1 == check_poller_fd_registration_args (poller_, fd_)
        || -1 == check_events (events_))
        return -1;

    return (static_cast<zmq::socket_poller_t *> (poller_))
      ->modify_fd (fd_, events_);
}

int zmq_poller_remove (void *poller_, void *s_)
{
    if (-1 == check_poller_registration_args (poller_, s_))
        return -1;

    zmq::socket_base_t *socket = static_cast<zmq::socket_base_t *> (s_);

    return (static_cast<zmq::socket_poller_t *> (poller_))->remove (socket);
}

int zmq_poller_remove_fd (void *poller_, zmq::fd_t fd_)
{
    if (-1 == check_poller_fd_registration_args (poller_, fd_))
        return -1;

    return (static_cast<zmq::socket_poller_t *> (poller_))->remove_fd (fd_);
}

int zmq_poller_wait (void *poller_, zmq_poller_event_t *event_, long timeout_)
{
    int rc = zmq_poller_wait_all (poller_, event_, 1, timeout_);

    if (rc < 0 && event_) {
        // TODO this is not portable... zmq_poller_event_t contains pointers,
        // for which nullptr does not need to be represented by all-zeroes
        memset (event_, 0, sizeof (zmq_poller_event_t));
    }
    // wait_all returns number of events, but we return 0 for any success
    return rc >= 0 ? 0 : rc;
}

int zmq_poller_wait_all (void *poller_,
                         zmq_poller_event_t *events_,
                         int n_events_,
                         long timeout_)
{
    if (-1 == check_poller (poller_))
        return -1;

    if (!events_) {
        errno = EFAULT;
        return -1;
    }
    if (n_events_ < 0) {
        errno = EINVAL;
        return -1;
    }

    int rc =
      (static_cast<zmq::socket_poller_t *> (poller_))
        ->wait (reinterpret_cast<zmq::socket_poller_t::event_t *> (events_),
                n_events_, timeout_);

    return rc;
}

//  Peer-specific state

int zmq_socket_get_peer_state (void *s_,
                               const void *routing_id_,
                               size_t routing_id_size_)
{
    const zmq::socket_base_t *const s = as_socket_base_t (s_);
    if (!s)
        return -1;

    return s->get_peer_state (routing_id_, routing_id_size_);
}

//  Timers

void *zmq_timers_new (void)
{
    zmq::timers_t *timers = new (std::nothrow) zmq::timers_t;
    alloc_assert (timers);
    return timers;
}

int zmq_timers_destroy (void **timers_p_)
{
    void *timers = *timers_p_;
    if (!timers || !(static_cast<zmq::timers_t *> (timers))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }
    delete (static_cast<zmq::timers_t *> (timers));
    *timers_p_ = NULL;
    return 0;
}

int zmq_timers_add (void *timers_,
                    size_t interval_,
                    zmq_timer_fn handler_,
                    void *arg_)
{
    if (!timers_ || !(static_cast<zmq::timers_t *> (timers_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    return (static_cast<zmq::timers_t *> (timers_))
      ->add (interval_, handler_, arg_);
}

int zmq_timers_cancel (void *timers_, int timer_id_)
{
    if (!timers_ || !(static_cast<zmq::timers_t *> (timers_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    return (static_cast<zmq::timers_t *> (timers_))->cancel (timer_id_);
}

int zmq_timers_set_interval (void *timers_, int timer_id_, size_t interval_)
{
    if (!timers_ || !(static_cast<zmq::timers_t *> (timers_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    return (static_cast<zmq::timers_t *> (timers_))
      ->set_interval (timer_id_, interval_);
}

int zmq_timers_reset (void *timers_, int timer_id_)
{
    if (!timers_ || !(static_cast<zmq::timers_t *> (timers_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    return (static_cast<zmq::timers_t *> (timers_))->reset (timer_id_);
}

long zmq_timers_timeout (void *timers_)
{
    if (!timers_ || !(static_cast<zmq::timers_t *> (timers_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    return (static_cast<zmq::timers_t *> (timers_))->timeout ();
}

int zmq_timers_execute (void *timers_)
{
    if (!timers_ || !(static_cast<zmq::timers_t *> (timers_))->check_tag ()) {
        errno = EFAULT;
        return -1;
    }

    return (static_cast<zmq::timers_t *> (timers_))->execute ();
}

//  The proxy functionality

int zmq_proxy (void *frontend_, void *backend_, void *capture_)
{
    if (!frontend_ || !backend_) {
        errno = EFAULT;
        return -1;
    }
    return zmq::proxy (static_cast<zmq::socket_base_t *> (frontend_),
                       static_cast<zmq::socket_base_t *> (backend_),
                       static_cast<zmq::socket_base_t *> (capture_));
}

int zmq_proxy_steerable (void *frontend_,
                         void *backend_,
                         void *capture_,
                         void *control_)
{
    if (!frontend_ || !backend_) {
        errno = EFAULT;
        return -1;
    }
    return zmq::proxy (static_cast<zmq::socket_base_t *> (frontend_),
                       static_cast<zmq::socket_base_t *> (backend_),
                       static_cast<zmq::socket_base_t *> (capture_),
                       static_cast<zmq::socket_base_t *> (control_));
}

//  The deprecated device functionality

int zmq_device (int /* type */, void *frontend_, void *backend_)
{
    return zmq::proxy (static_cast<zmq::socket_base_t *> (frontend_),
                       static_cast<zmq::socket_base_t *> (backend_), NULL);
}

//  Probe library capabilities; for now, reports on transport and security

int zmq_has (const char *capability_)
{
#if !defined(ZMQ_HAVE_WINDOWS) && !defined(ZMQ_HAVE_OPENVMS)
    if (strcmp (capability_, zmq::protocol_name::ipc) == 0)
        return true;
#endif
#if defined(ZMQ_HAVE_OPENPGM)
    if (strcmp (capability_, "pgm") == 0)
        return true;
#endif
#if defined(ZMQ_HAVE_TIPC)
    if (strcmp (capability_, zmq::protocol_name::tipc) == 0)
        return true;
#endif
#if defined(ZMQ_HAVE_NORM)
    if (strcmp (capability_, "norm") == 0)
        return true;
#endif
#if defined(ZMQ_HAVE_CURVE)
    if (strcmp (capability_, "curve") == 0)
        return true;
#endif
#if defined(HAVE_LIBGSSAPI_KRB5)
    if (strcmp (capability_, "gssapi") == 0)
        return true;
#endif
#if defined(ZMQ_HAVE_VMCI)
    if (strcmp (capability_, zmq::protocol_name::vmci) == 0)
        return true;
#endif
#if defined(ZMQ_BUILD_DRAFT_API)
    if (strcmp (capability_, "draft") == 0)
        return true;
#endif
    //  Whatever the application asked for, we don't have
    return false;
}