select.hpp

/*
    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/>.
*/

#ifndef __ZMQ_SELECT_HPP_INCLUDED__
#define __ZMQ_SELECT_HPP_INCLUDED__

//  poller.hpp decides which polling mechanism to use.
#include "poller.hpp"
#if defined ZMQ_USE_SELECT

#include <stddef.h>
#include <vector>
#include <map>

#if defined ZMQ_HAVE_WINDOWS
#elif defined ZMQ_HAVE_OPENVMS
#include <sys/types.h>
#include <sys/time.h>
#else
#include <sys/select.h>
#endif

#include "ctx.hpp"
#include "fd.hpp"
#include "thread.hpp"
#include "poller_base.hpp"

namespace zmq
{
struct i_poll_events;

//  Implements socket polling mechanism using POSIX.1-2001 select()
//  function.

class select_t : public worker_poller_base_t
{
  public:
    typedef fd_t handle_t;

    select_t (const thread_ctx_t &ctx_);
    ~select_t ();

    //  "poller" concept.
    handle_t add_fd (fd_t fd_, zmq::i_poll_events *events_);
    void rm_fd (handle_t handle_);
    void set_pollin (handle_t handle_);
    void reset_pollin (handle_t handle_);
    void set_pollout (handle_t handle_);
    void reset_pollout (handle_t handle_);
    void stop ();

    static int max_fds ();

  private:
    //  Main event loop.
    void loop ();

    //  Internal state.
    struct fds_set_t
    {
        fds_set_t ();
        fds_set_t (const fds_set_t &other_);
        fds_set_t &operator= (const fds_set_t &other_);
        //  Convenience method to descriptor from all sets.
        void remove_fd (const fd_t &fd_);

        fd_set read;
        fd_set write;
        fd_set error;
    };

    struct fd_entry_t
    {
        fd_t fd;
        zmq::i_poll_events *events;
    };
    typedef std::vector<fd_entry_t> fd_entries_t;

    void trigger_events (const fd_entries_t &fd_entries_,
                         const fds_set_t &local_fds_set_,
                         int event_count_);

    struct family_entry_t
    {
        family_entry_t ();

        fd_entries_t fd_entries;
        fds_set_t fds_set;
        bool has_retired;
    };

    void select_family_entry (family_entry_t &family_entry_,
                              int max_fd_,
                              bool use_timeout_,
                              struct timeval &tv_);

#if defined ZMQ_HAVE_WINDOWS
    typedef std::map<u_short, family_entry_t> family_entries_t;

    struct wsa_events_t
    {
        wsa_events_t ();
        ~wsa_events_t ();

        //  read, write, error and readwrite
        WSAEVENT events[4];
    };

    family_entries_t family_entries;
    // See loop for details.
    family_entries_t::iterator current_family_entry_it;

    int try_retire_fd_entry (family_entries_t::iterator family_entry_it,
                             zmq::fd_t &handle_);

    static const size_t fd_family_cache_size = 8;
    std::pair<fd_t, u_short> fd_family_cache[fd_family_cache_size];

    u_short get_fd_family (fd_t fd_);

    //  Socket's family or AF_UNSPEC on error.
    static u_short determine_fd_family (fd_t fd_);
#else
    //  on non-Windows, we can treat all fds as one family
    family_entry_t family_entry;
    fd_t maxfd;
#endif

    void cleanup_retired ();
    bool cleanup_retired (family_entry_t &family_entry_);

    //  Checks if an fd_entry_t is retired.
    static bool is_retired_fd (const fd_entry_t &entry);

    static fd_entries_t::iterator
    find_fd_entry_by_handle (fd_entries_t &fd_entries, handle_t handle_);

    select_t (const select_t &);
    const select_t &operator= (const select_t &);
};

typedef select_t poller_t;
}

#endif

#endif