Merge commit '86cc97e55fe346502462284d2e636a2b3708163e' as 'Sources/OpenVPN3'

Sources/OpenVPN3/openvpn/common/link.hpp

@@ -0,0 +1,53 @@
+//    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) 2012-2017 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