deskflow/src/lib/net/SocketMultiplexer.h

/*
 * Deskflow -- mouse and keyboard sharing utility
 * SPDX-FileCopyrightText: (C) 2012 - 2016 Symless Ltd.
 * SPDX-FileCopyrightText: (C) 2004 Chris Schoeneman
 * SPDX-License-Identifier: GPL-2.0-only WITH LicenseRef-OpenSSL-Exception
 */

#pragma once

#include "arch/IArchNetwork.h"
#include "common/StdList.h"
#include "common/StdMap.h"

template <class T> class CondVar;
class Mutex;
class Thread;
class ISocket;
class ISocketMultiplexerJob;

//! Socket multiplexer
/*!
A socket multiplexer services multiple sockets simultaneously.
*/
class SocketMultiplexer
{
public:
  SocketMultiplexer();
  SocketMultiplexer(SocketMultiplexer const &) = delete;
  SocketMultiplexer(SocketMultiplexer &&) = delete;
  ~SocketMultiplexer();

  SocketMultiplexer &operator=(SocketMultiplexer const &) = delete;
  SocketMultiplexer &operator=(SocketMultiplexer &&) = delete;

  //! @name manipulators
  //@{

  void addSocket(ISocket *, ISocketMultiplexerJob *);

  void removeSocket(ISocket *);

  //@}
  //! @name accessors
  //@{

  // maybe belongs on ISocketMultiplexer
  static SocketMultiplexer *getInstance();

  //@}

private:
  // list of jobs.  we use a list so we can safely iterate over it
  // while other threads modify it.
  using SocketJobs = std::list<ISocketMultiplexerJob *>;
  using JobCursor = SocketJobs::iterator;
  using SocketJobMap = std::map<ISocket *, JobCursor>;

  // service sockets.  the service thread will only access m_sockets
  // and m_update while m_pollable and m_polling are true.  all other
  // threads must only modify these when m_pollable and m_polling are
  // false.  only the service thread sets m_polling.
  void serviceThread(void *);

  // create, iterate, and destroy a cursor.  a cursor is used to
  // safely iterate through the job list while other threads modify
  // the list.  it works by inserting a dummy item in the list and
  // moving that item through the list.  the dummy item will never
  // be removed by other edits so an iterator pointing at the item
  // remains valid until we remove the dummy item in deleteCursor().
  // nextCursor() finds the next non-dummy item, moves our dummy
  // item just past it, and returns an iterator for the non-dummy
  // item.  all cursor calls lock the mutex for their duration.
  JobCursor newCursor();
  JobCursor nextCursor(JobCursor);
  void deleteCursor(JobCursor);

  // lock out locking the job list.  this blocks if another thread
  // has already locked out locking.  once it returns, only the
  // calling thread will be able to lock the job list after any
  // current lock is released.
  void lockJobListLock();

  // lock the job list.  this blocks if the job list is already
  // locked.  the calling thread must have called requestJobLock.
  void lockJobList();

  // unlock the job list and the lock out on locking.
  void unlockJobList();

private:
  Mutex *m_mutex;
  Thread *m_thread;
  bool m_update;
  CondVar<bool> *m_jobsReady;
  CondVar<bool> *m_jobListLock;
  CondVar<bool> *m_jobListLockLocked;
  Thread *m_jobListLocker;
  Thread *m_jobListLockLocker;

  SocketJobs m_socketJobs;
  SocketJobMap m_socketJobMap;
  ISocketMultiplexerJob *m_cursorMark;
};