//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2020 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program 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 Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#ifndef OPENVPN_COMMON_LINK_H
#define OPENVPN_COMMON_LINK_H

#include <utility>

namespace openvpn {

  // Link creates a sender-receiver relationship between two objects.
  // SEND is the sender interface, while RECV is the receiver interface.
  // The receiver class should publicly inherit from Link and implement
  // the receiver interface.
  // Multiple inheritance of Link is intended for objects that play a
  // receiver role for multiple interfaces (such as the server-side
  // client instance object), and for this reason RECV common base
  // classes such as RC should be virtually inherited.
  // Usage of Link may create a memory reference cycle between
  // Link-derived objects and the SEND object.  Therefore be sure
  // to manually break cycles as part of an explicit stop() method.
  template <typename SEND, typename RECV>
  class Link : public RECV
  {
  protected:
    Link() {}
    Link(typename SEND::Ptr send_arg) : send(std::move(send_arg)) {}
    Link(SEND* send_arg) : send(send_arg) {}

    typename SEND::Ptr send;
  };

}

#endif