File indexing completed on 2024-05-05 17:50:04

 /*
    Copyright (C) 2018 Andreas Hartmetz <ahartmetz@gmail.com>
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.
 
    This library 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
    Library General Public License for more details.
 
    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LGPL.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
 
    Alternatively, this file is available under the Mozilla Public License
    Version 1.1.  You may obtain a copy of the License at
    http://www.mozilla.org/MPL/
 */
 
 #ifndef IIOEVENTSOURCE_H
 #define IIOEVENTSOURCE_H
 
 #include "iovaluetypes.h"
 #include "types.h"
 
 class IIoEventListener;
 
 // TODO: explain the context for this - layered sources and listeners and such
 
 // There is one subtle problem that needs to be solved regarding IIoEventListener::fileDescriptor().
 // Event sources are expected to use some kind of hash / map FileDescriptor -> IIoEventListener, so
 // an IIoEventListener cannot unregister after closing the file descriptor. Even keeping the old
 // value around doesn't help - the file descriptor could be reused very soon by any other part of the
 // current process.
 // So the lowest level implementation of close() must immediately unregister the IIoEventListener
 // leading to the I/O operation leading to the close(). That lowest level IIoEventListener must also
 // unregister itself, etc, up to the highest level IIoEventSource (usually EventDispatcherPrivate).
 
 class IIoEventSource
 {
 public:
     virtual ~IIoEventSource();
 
     // Contract: an IIoEventSource may have different IIoEventListeners listening to read and write
     // As a further restriction, a listener must always remove I/O interest from its old source
     // before enabling it on its new source.
     void addIoListener(IIoEventListener *iol);
     void removeIoListener(IIoEventListener *iol);
 
 protected:
     // add / remove only make sense for stateful APIs such as Linux epoll, so they don't have to be
     // implemented - the defaults just call updateIoInterestInternal().
     virtual void addIoListenerInternal(IIoEventListener *iol, uint32 ioRw);
     virtual void removeIoListenerInternal(IIoEventListener *iol);
     virtual void updateIoInterestInternal(IIoEventListener *iol, uint32 ioRw) = 0;
 
 private:
     friend class IIoEventListener;
     // called from IIoEventListener when its m_ioInterest changed
     void updateIoInterest(IIoEventListener *iol);
 };
 
 #endif // IIOEVENTSOURCE_H