ratecontroller.cpp Example File

  /****************************************************************************
  **
  ** Copyright (C) 2016 The Qt Company Ltd.
  ** Contact: https://www.qt.io/licensing/
  **
  ** This file is part of the examples of the Qt Toolkit.
  **
  ** $QT_BEGIN_LICENSE:BSD$
  ** Commercial License Usage
  ** Licensees holding valid commercial Qt licenses may use this file in
  ** accordance with the commercial license agreement provided with the
  ** Software or, alternatively, in accordance with the terms contained in
  ** a written agreement between you and The Qt Company. For licensing terms
  ** and conditions see https://www.qt.io/terms-conditions. For further
  ** information use the contact form at https://www.qt.io/contact-us.
  **
  ** BSD License Usage
  ** Alternatively, you may use this file under the terms of the BSD license
  ** as follows:
  **
  ** "Redistribution and use in source and binary forms, with or without
  ** modification, are permitted provided that the following conditions are
  ** met:
  **   * Redistributions of source code must retain the above copyright
  **     notice, this list of conditions and the following disclaimer.
  **   * Redistributions in binary form must reproduce the above copyright
  **     notice, this list of conditions and the following disclaimer in
  **     the documentation and/or other materials provided with the
  **     distribution.
  **   * Neither the name of The Qt Company Ltd nor the names of its
  **     contributors may be used to endorse or promote products derived
  **     from this software without specific prior written permission.
  **
  **
  ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
  **
  ** $QT_END_LICENSE$
  **
  ****************************************************************************/

  #include "peerwireclient.h"
  #include "ratecontroller.h"

  #include <QtCore>

  Q_GLOBAL_STATIC(RateController, rateController)

  RateController *RateController::instance()
  {
      return rateController();
  }

  void RateController::addSocket(PeerWireClient *socket)
  {
      connect(socket, SIGNAL(readyToTransfer()), this, SLOT(scheduleTransfer()));
      socket->setReadBufferSize(downLimit * 4);
      sockets << socket;
      scheduleTransfer();
  }

  void RateController::removeSocket(PeerWireClient *socket)
  {
      disconnect(socket, SIGNAL(readyToTransfer()), this, SLOT(scheduleTransfer()));
      socket->setReadBufferSize(0);
      sockets.remove(socket);
  }

  void RateController::setDownloadLimit(int bytesPerSecond)
  {
      downLimit = bytesPerSecond;
      foreach (PeerWireClient *socket, sockets)
          socket->setReadBufferSize(downLimit * 4);
  }

  void RateController::scheduleTransfer()
  {
      if (transferScheduled)
          return;
      transferScheduled = true;
      QTimer::singleShot(50, this, SLOT(transfer()));
  }

  void RateController::transfer()
  {
      transferScheduled = false;
      if (sockets.isEmpty())
          return;

      int msecs = 1000;
      if (!stopWatch.isNull())
          msecs = qMin(msecs, stopWatch.elapsed());

      qint64 bytesToWrite = (upLimit * msecs) / 1000;
      qint64 bytesToRead = (downLimit * msecs) / 1000;
      if (bytesToWrite == 0 && bytesToRead == 0) {
          scheduleTransfer();
          return;
      }

      QSet<PeerWireClient *> pendingSockets;
      foreach (PeerWireClient *client, sockets) {
          if (client->canTransferMore())
              pendingSockets << client;
      }
      if (pendingSockets.isEmpty())
          return;

      stopWatch.start();

      bool canTransferMore;
      do {
          canTransferMore = false;
          qint64 writeChunk = qMax<qint64>(1, bytesToWrite / pendingSockets.size());
          qint64 readChunk = qMax<qint64>(1, bytesToRead / pendingSockets.size());

          QSetIterator<PeerWireClient *> it(pendingSockets);
          while (it.hasNext() && (bytesToWrite > 0 || bytesToRead > 0)) {
              PeerWireClient *socket = it.next();
              if (socket->state() != QAbstractSocket::ConnectedState) {
                  pendingSockets.remove(socket);
                  continue;
              }

              bool dataTransferred = false;
              qint64 available = qMin<qint64>(socket->socketBytesAvailable(), readChunk);
              if (available > 0) {
                  qint64 readBytes = socket->readFromSocket(qMin<qint64>(available, bytesToRead));
                  if (readBytes > 0) {
                      bytesToRead -= readBytes;
                      dataTransferred = true;
                  }
              }

              if (upLimit * 2 > socket->bytesToWrite()) {
                  qint64 chunkSize = qMin<qint64>(writeChunk, bytesToWrite);
                  qint64 toWrite = qMin(upLimit * 2 - socket->bytesToWrite(), chunkSize);
                  if (toWrite > 0) {
                      qint64 writtenBytes = socket->writeToSocket(toWrite);
                      if (writtenBytes > 0) {
                          bytesToWrite -= writtenBytes;
                          dataTransferred = true;
                      }
                  }
              }

              if (dataTransferred && socket->canTransferMore())
                  canTransferMore = true;
              else
                  pendingSockets.remove(socket);
          }
      } while (canTransferMore && (bytesToWrite > 0 || bytesToRead > 0) && !pendingSockets.isEmpty());

      if (canTransferMore || bytesToWrite == 0 || bytesToRead == 0)
          scheduleTransfer();
  }