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torrentclient.cpp Example File
network/torrent/torrentclient.cpp

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 #include "connectionmanager.h"
 #include "filemanager.h"
 #include "metainfo.h"
 #include "torrentclient.h"
 #include "torrentserver.h"
 #include "trackerclient.h"
 #include "peerwireclient.h"
 #include "ratecontroller.h"

 #include <QtCore>
 #include <QNetworkInterface>

 // These constants could also be configurable by the user.
 static const int ServerMinPort = 6881;
 static const int ServerMaxPort = /* 6889 */ 7000;
 static const int BlockSize = 16384;
 static const int MaxBlocksInProgress = 5;
 static const int MaxBlocksInMultiMode = 2;
 static const int MaxConnectionPerPeer = 1;
 static const int RateControlWindowLength = 10;
 static const int RateControlTimerDelay = 1000;
 static const int MinimumTimeBeforeRevisit = 30;
 static const int MaxUploads = 4;
 static const int UploadScheduleInterval = 10000;
 static const int EndGamePieces = 5;

 class TorrentPiece {
 public:
     int index;
     int length;
     QBitArray completedBlocks;
     QBitArray requestedBlocks;
     bool inProgress;
 };

 class TorrentClientPrivate
 {
 public:
     TorrentClientPrivate(TorrentClient *qq);

     // State / error
     void setError(TorrentClient::Error error);
     void setState(TorrentClient::State state);
     TorrentClient::Error error;
     TorrentClient::State state;
     QString errorString;
     QString stateString;

     // Where to save data
     QString destinationFolder;
     MetaInfo metaInfo;

     // Announce tracker and file manager
     QByteArray peerId;
     QByteArray infoHash;
     TrackerClient trackerClient;
     FileManager fileManager;

     // Connections
     QList<PeerWireClient *> connections;
     QList<TorrentPeer *> peers;
     bool schedulerCalled;
     void callScheduler();
     bool connectingToClients;
     void callPeerConnector();
     int uploadScheduleTimer;

     // Pieces
     QMap<int, PeerWireClient *> readIds;
     QMultiMap<PeerWireClient *, TorrentPiece *> payloads;
     QMap<int, TorrentPiece *> pendingPieces;
     QBitArray completedPieces;
     QBitArray incompletePieces;
     int pieceCount;

     // Progress
     int lastProgressValue;
     qint64 downloadedBytes;
     qint64 uploadedBytes;
     int downloadRate[RateControlWindowLength];
     int uploadRate[RateControlWindowLength];
     int transferRateTimer;

     TorrentClient *q;
 };

 TorrentClientPrivate::TorrentClientPrivate(TorrentClient *qq)
     : trackerClient(qq), q(qq)
 {
     error = TorrentClient::UnknownError;
     state = TorrentClient::Idle;
     errorString = QT_TRANSLATE_NOOP(TorrentClient, "Unknown error");
     stateString = QT_TRANSLATE_NOOP(TorrentClient, "Idle");
     schedulerCalled = false;
     connectingToClients = false;
     uploadScheduleTimer = 0;
     lastProgressValue = -1;
     pieceCount = 0;
     downloadedBytes = 0;
     uploadedBytes = 0;
     memset(downloadRate, 0, sizeof(downloadRate));
     memset(uploadRate, 0, sizeof(uploadRate));
     transferRateTimer = 0;
 }

 void TorrentClientPrivate::setError(TorrentClient::Error errorCode)
 {
     this->error = errorCode;
     switch (error) {
     case TorrentClient::UnknownError:
         errorString = QT_TRANSLATE_NOOP(TorrentClient, "Unknown error");
         break;
     case TorrentClient::TorrentParseError:
         errorString = QT_TRANSLATE_NOOP(TorrentClient, "Invalid torrent data");
         break;
     case TorrentClient::InvalidTrackerError:
         errorString = QT_TRANSLATE_NOOP(TorrentClient, "Unable to connect to tracker");
         break;
     case TorrentClient::FileError:
         errorString = QT_TRANSLATE_NOOP(TorrentClient, "File error");
         break;
     case TorrentClient::ServerError:
         errorString = QT_TRANSLATE_NOOP(TorrentClient, "Unable to initialize server");
         break;
     }
     emit q->error(errorCode);
 }

 void TorrentClientPrivate::setState(TorrentClient::State state)
 {
     this->state = state;
     switch (state) {
     case TorrentClient::Idle:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Idle");
         break;
     case TorrentClient::Paused:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Paused");
         break;
     case TorrentClient::Stopping:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Stopping");
         break;
     case TorrentClient::Preparing:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Preparing");
         break;
     case TorrentClient::Searching:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Searching");
         break;
     case TorrentClient::Connecting:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Connecting");
         break;
     case TorrentClient::WarmingUp:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Warming up");
         break;
     case TorrentClient::Downloading:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Downloading");
         break;
     case TorrentClient::Endgame:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Finishing");
         break;
     case TorrentClient::Seeding:
         stateString = QT_TRANSLATE_NOOP(TorrentClient, "Seeding");
         break;
     }
     emit q->stateChanged(state);
 }

 void TorrentClientPrivate::callScheduler()
 {
     if (!schedulerCalled) {
         schedulerCalled = true;
         QMetaObject::invokeMethod(q, "scheduleDownloads", Qt::QueuedConnection);
     }
 }

 void TorrentClientPrivate::callPeerConnector()
 {
     if (!connectingToClients) {
         connectingToClients = true;
         QTimer::singleShot(10000, q, SLOT(connectToPeers()));
     }
 }

 TorrentClient::TorrentClient(QObject *parent)
     : QObject(parent), d(new TorrentClientPrivate(this))
 {
     // Connect the file manager
     connect(&d->fileManager, SIGNAL(dataRead(int, int, int, const QByteArray &)),
             this, SLOT(sendToPeer(int, int, int, const QByteArray &)));
     connect(&d->fileManager, SIGNAL(verificationProgress(int)),
             this, SLOT(updateProgress(int)));
     connect(&d->fileManager, SIGNAL(verificationDone()),
             this, SLOT(fullVerificationDone()));
     connect(&d->fileManager, SIGNAL(pieceVerified(int, bool)),
             this, SLOT(pieceVerified(int, bool)));
     connect(&d->fileManager, SIGNAL(error()),
             this, SLOT(handleFileError()));

     // Connect the tracker client
     connect(&d->trackerClient, SIGNAL(peerListUpdated(const QList<TorrentPeer> &)),
             this, SLOT(addToPeerList(const QList<TorrentPeer> &)));
     connect(&d->trackerClient, SIGNAL(stopped()),
             this, SIGNAL(stopped()));
 }

 TorrentClient::~TorrentClient()
 {
     qDeleteAll(d->peers);
     qDeleteAll(d->pendingPieces);
     delete d;
 }

 bool TorrentClient::setTorrent(const QString &fileName)
 {
     QFile file(fileName);
     if (!file.open(QIODevice::ReadOnly) || !setTorrent(file.readAll())) {
         d->setError(TorrentParseError);
         return false;
     }
     return true;
 }

 bool TorrentClient::setTorrent(const QByteArray &torrentData)
 {
     if (!d->metaInfo.parse(torrentData)) {
         d->setError(TorrentParseError);
         return false;
     }

     // Calculate SHA1 hash of the "info" section in the torrent
     QByteArray infoValue = d->metaInfo.infoValue();
     d->infoHash = QCryptographicHash::hash(infoValue, QCryptographicHash::Sha1);

     return true;
 }

 MetaInfo TorrentClient::metaInfo() const
 {
     return d->metaInfo;
 }

 void TorrentClient::setDestinationFolder(const QString &directory)
 {
     d->destinationFolder = directory;
 }

 QString TorrentClient::destinationFolder() const
 {
     return d->destinationFolder;
 }

 void TorrentClient::setDumpedState(const QByteArray &dumpedState)
 {
     // Recover partially completed pieces
     QDataStream stream(dumpedState);

     quint16 version = 0;
     stream >> version;
     if (version != 2)
         return;

     stream >> d->completedPieces;

     while (!stream.atEnd()) {
         int index;
         int length;
         QBitArray completed;
         stream >> index >> length >> completed;
         if (stream.status() != QDataStream::Ok) {
             d->completedPieces.clear();
             break;
         }

         TorrentPiece *piece = new TorrentPiece;
         piece->index = index;
         piece->length = length;
         piece->completedBlocks = completed;
         piece->requestedBlocks.resize(completed.size());
         piece->inProgress = false;
         d->pendingPieces[index] = piece;
     }
 }

 QByteArray TorrentClient::dumpedState() const
 {
     QByteArray partials;
     QDataStream stream(&partials, QIODevice::WriteOnly);

     stream << quint16(2);
     stream << d->completedPieces;

     // Save the state of all partially downloaded pieces into a format
     // suitable for storing in settings.
     QMap<int, TorrentPiece *>::ConstIterator it = d->pendingPieces.constBegin();
     while (it != d->pendingPieces.constEnd()) {
         TorrentPiece *piece = it.value();
         if (blocksLeftForPiece(piece) > 0 && blocksLeftForPiece(piece) < piece->completedBlocks.size()) {
             stream << piece->index;
             stream << piece->length;
             stream << piece->completedBlocks;
         }
         ++it;
     }

     return partials;
 }

 qint64 TorrentClient::progress() const
 {
     return d->lastProgressValue;
 }

 void TorrentClient::setDownloadedBytes(qint64 bytes)
 {
     d->downloadedBytes = bytes;
 }

 qint64 TorrentClient::downloadedBytes() const
 {
     return d->downloadedBytes;
 }

 void TorrentClient::setUploadedBytes(qint64 bytes)
 {
     d->uploadedBytes = bytes;
 }

 qint64 TorrentClient::uploadedBytes() const
 {
     return d->uploadedBytes;
 }

 int TorrentClient::connectedPeerCount() const
 {
     int tmp = 0;
     foreach (PeerWireClient *client, d->connections) {
         if (client->state() == QAbstractSocket::ConnectedState)
             ++tmp;
     }
     return tmp;
 }

 int TorrentClient::seedCount() const
 {
     int tmp = 0;
     foreach (PeerWireClient *client, d->connections) {
         if (client->availablePieces().count(true) == d->pieceCount)
             ++tmp;
     }
     return tmp;
 }

 TorrentClient::State TorrentClient::state() const
 {
     return d->state;
 }

 QString TorrentClient::stateString() const
 {
     return d->stateString;
 }

 TorrentClient::Error TorrentClient::error() const
 {
     return d->error;
 }

 QString TorrentClient::errorString() const
 {
     return d->errorString;
 }

 QByteArray TorrentClient::peerId() const
 {
     return d->peerId;
 }

 QByteArray TorrentClient::infoHash() const
 {
     return d->infoHash;
 }

 void TorrentClient::start()
 {
     if (d->state != Idle)
         return;

     TorrentServer::instance()->addClient(this);

     // Initialize the file manager
     d->setState(Preparing);
     d->fileManager.setMetaInfo(d->metaInfo);
     d->fileManager.setDestinationFolder(d->destinationFolder);
     d->fileManager.setCompletedPieces(d->completedPieces);
     d->fileManager.start(QThread::LowestPriority);
     d->fileManager.startDataVerification();
 }

 void TorrentClient::stop()
 {
     if (d->state == Stopping)
         return;

     TorrentServer::instance()->removeClient(this);

     // Update the state
     State oldState = d->state;
     d->setState(Stopping);

     // Stop the timer
     if (d->transferRateTimer) {
         killTimer(d->transferRateTimer);
         d->transferRateTimer = 0;
     }

     // Abort all existing connections
     foreach (PeerWireClient *client, d->connections) {
         RateController::instance()->removeSocket(client);
         ConnectionManager::instance()->removeConnection(client);
         client->abort();
     }
     d->connections.clear();

     // Perhaps stop the tracker
     if (oldState > Preparing) {
         d->trackerClient.stop();
     } else {
         d->setState(Idle);
         emit stopped();
     }
 }

 void TorrentClient::setPaused(bool paused)
 {
     if (paused) {
         // Abort all connections, and set the max number of
         // connections to 0. Keep the list of peers, so we can quickly
         // resume later.
         d->setState(Paused);
         foreach (PeerWireClient *client, d->connections)
             client->abort();
         d->connections.clear();
         TorrentServer::instance()->removeClient(this);
     } else {
         // Restore the max number of connections, and start the peer
         // connector. We should also quickly start receiving incoming
         // connections.
         d->setState(d->completedPieces.count(true) == d->fileManager.pieceCount()
                     ? Seeding : Searching);
         connectToPeers();
         TorrentServer::instance()->addClient(this);
     }
 }

 void TorrentClient::timerEvent(QTimerEvent *event)
 {
     if (event->timerId() == d->uploadScheduleTimer) {
         // Update the state of who's choked and who's not
         scheduleUploads();
         return;
     }

     if (event->timerId() != d->transferRateTimer) {
         QObject::timerEvent(event);
         return;
     }

     // Calculate average upload/download rate
     qint64 uploadBytesPerSecond = 0;
     qint64 downloadBytesPerSecond = 0;
     for (int i = 0; i < RateControlWindowLength; ++i) {
         uploadBytesPerSecond += d->uploadRate[i];
         downloadBytesPerSecond += d->downloadRate[i];
     }
     uploadBytesPerSecond /= qint64(RateControlWindowLength);
     downloadBytesPerSecond /= qint64(RateControlWindowLength);
     for (int i = RateControlWindowLength - 2; i >= 0; --i) {
         d->uploadRate[i + 1] = d->uploadRate[i];
         d->downloadRate[i + 1] = d->downloadRate[i];
     }
     d->uploadRate[0] = 0;
     d->downloadRate[0] = 0;
     emit uploadRateUpdated(int(uploadBytesPerSecond));
     emit downloadRateUpdated(int(downloadBytesPerSecond));

     // Stop the timer if there is no activity.
     if (downloadBytesPerSecond == 0 && uploadBytesPerSecond == 0) {
         killTimer(d->transferRateTimer);
         d->transferRateTimer = 0;
     }
 }

 void TorrentClient::sendToPeer(int readId, int pieceIndex, int begin, const QByteArray &data)
 {
     // Send the requested block to the peer if the client connection
     // still exists; otherwise do nothing. This slot is called by the
     // file manager after it has read a block of data.
     PeerWireClient *client = d->readIds.value(readId);
     if (client) {
         if ((client->peerWireState() & PeerWireClient::ChokingPeer) == 0)
             client->sendBlock(pieceIndex, begin, data);
     }
     d->readIds.remove(readId);
 }

 void TorrentClient::fullVerificationDone()
 {
     // Update our list of completed and incomplete pieces.
     d->completedPieces = d->fileManager.completedPieces();
     d->incompletePieces.resize(d->completedPieces.size());
     d->pieceCount = d->completedPieces.size();
     for (int i = 0; i < d->fileManager.pieceCount(); ++i) {
         if (!d->completedPieces.testBit(i))
             d->incompletePieces.setBit(i);
     }

     updateProgress();

     // If the checksums show that what the dumped state thought was
     // partial was in fact complete, then we trust the checksums.
     QMap<int, TorrentPiece *>::Iterator it = d->pendingPieces.begin();
     while (it != d->pendingPieces.end()) {
         if (d->completedPieces.testBit(it.key()))
             it = d->pendingPieces.erase(it);
         else
             ++it;
     }

     d->uploadScheduleTimer = startTimer(UploadScheduleInterval);

     // Start the server
     TorrentServer *server = TorrentServer::instance();
     if (!server->isListening()) {
         // Set up the peer wire server
         for (int i = ServerMinPort; i <= ServerMaxPort; ++i) {
             if (server->listen(QHostAddress::Any, i))
                 break;
         }
         if (!server->isListening()) {
             d->setError(ServerError);
             return;
         }
     }

     d->setState(d->completedPieces.count(true) == d->pieceCount ? Seeding : Searching);

     // Start the tracker client
     d->trackerClient.start(d->metaInfo);
 }

 void TorrentClient::pieceVerified(int pieceIndex, bool ok)
 {
     TorrentPiece *piece = d->pendingPieces.value(pieceIndex);

     // Remove this piece from all payloads
     QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.begin();
     while (it != d->payloads.end()) {
         if (it.value()->index == pieceIndex)
             it = d->payloads.erase(it);
         else
             ++it;
     }

     if (!ok) {
         // If a piece did not pass the SHA1 check, we'll simply clear
         // its state, and the scheduler will re-request it
         piece->inProgress = false;
         piece->completedBlocks.fill(false);
         piece->requestedBlocks.fill(false);
         d->callScheduler();
         return;
     }

     // Update the peer list so we know who's still interesting.
     foreach (TorrentPeer *peer, d->peers) {
         if (!peer->interesting)
             continue;
         bool interesting = false;
         for (int i = 0; i < d->pieceCount; ++i) {
             if (peer->pieces.testBit(i) && d->incompletePieces.testBit(i)) {
                 interesting = true;
                 break;
             }
         }
         peer->interesting = interesting;
     }

     // Delete the piece and update our structures.
     delete piece;
     d->pendingPieces.remove(pieceIndex);
     d->completedPieces.setBit(pieceIndex);
     d->incompletePieces.clearBit(pieceIndex);

     // Notify connected peers.
     foreach (PeerWireClient *client, d->connections) {
         if (client->state() == QAbstractSocket::ConnectedState
             && !client->availablePieces().testBit(pieceIndex)) {
             client->sendPieceNotification(pieceIndex);
         }
     }

     // Notify the tracker if we've entered Seeding status; otherwise
     // call the scheduler.
     int completed = d->completedPieces.count(true);
     if (completed == d->pieceCount) {
         if (d->state != Seeding) {
             d->setState(Seeding);
             d->trackerClient.startSeeding();
         }
     } else {
         if (completed == 1)
             d->setState(Downloading);
         else if (d->incompletePieces.count(true) < 5 && d->pendingPieces.size() > d->incompletePieces.count(true))
             d->setState(Endgame);
         d->callScheduler();
     }

     updateProgress();
 }

 void TorrentClient::handleFileError()
 {
     if (d->state == Paused)
         return;
     setPaused(true);
     emit error(FileError);
 }

 void TorrentClient::connectToPeers()
 {
     d->connectingToClients = false;

     if (d->state == Stopping || d->state == Idle || d->state == Paused)
         return;

     if (d->state == Searching)
         d->setState(Connecting);

     // Find the list of peers we are not currently connected to, where
     // the more interesting peers are listed more than once.
     QList<TorrentPeer *> weighedPeers = weighedFreePeers();

     // Start as many connections as we can
     while (!weighedPeers.isEmpty() && ConnectionManager::instance()->canAddConnection()
            && (qrand() % (ConnectionManager::instance()->maxConnections() / 2))) {
         PeerWireClient *client = new PeerWireClient(ConnectionManager::instance()->clientId(), this);
         RateController::instance()->addSocket(client);
         ConnectionManager::instance()->addConnection(client);

         initializeConnection(client);
         d->connections << client;

         // Pick a random peer from the list of weighed peers.
         TorrentPeer *peer = weighedPeers.takeAt(qrand() % weighedPeers.size());
         weighedPeers.removeAll(peer);
         peer->connectStart = QDateTime::currentDateTime().toTime_t();
         peer->lastVisited = peer->connectStart;

         // Connect to the peer.
         client->setPeer(peer);
         client->connectToHost(peer->address, peer->port);
     }
 }

 QList<TorrentPeer *> TorrentClient::weighedFreePeers() const
 {
     QList<TorrentPeer *> weighedPeers;

     // Generate a list of peers that we want to connect to.
     uint now = QDateTime::currentDateTime().toTime_t();
     QList<TorrentPeer *> freePeers;
     QMap<QString, int> connectionsPerPeer;
     foreach (TorrentPeer *peer, d->peers) {
         bool busy = false;
         foreach (PeerWireClient *client, d->connections) {
             if (client->state() == PeerWireClient::ConnectedState
                 && client->peerAddress() == peer->address
                 && client->peerPort() == peer->port) {
                 if (++connectionsPerPeer[peer->address.toString()] >= MaxConnectionPerPeer) {
                     busy = true;
                     break;
                 }
             }
         }
         if (!busy && (now - peer->lastVisited) > uint(MinimumTimeBeforeRevisit))
             freePeers << peer;
     }

     // Nothing to connect to
     if (freePeers.isEmpty())
         return weighedPeers;

     // Assign points based on connection speed and pieces available.
     QList<QPair<int, TorrentPeer *> > points;
     foreach (TorrentPeer *peer, freePeers) {
         int tmp = 0;
         if (peer->interesting) {
             tmp += peer->numCompletedPieces;
             if (d->state == Seeding)
                 tmp = d->pieceCount - tmp;
             if (!peer->connectStart) // An unknown peer is as interesting as a seed
                 tmp += d->pieceCount;

             // 1/5 of the total score for each second below 5 it takes to
             // connect.
             if (peer->connectTime < 5)
                 tmp += (d->pieceCount / 10) * (5 - peer->connectTime);
         }
         points << QPair<int, TorrentPeer *>(tmp, peer);
     }
     qSort(points);

     // Minimize the list so the point difference is never more than 1.
     typedef QPair<int,TorrentPeer*> PointPair;
     QMultiMap<int, TorrentPeer *> pointMap;
     int lowestScore = 0;
     int lastIndex = 0;
     foreach (PointPair point, points) {
         if (point.first > lowestScore) {
             lowestScore = point.first;
             ++lastIndex;
         }
         pointMap.insert(lastIndex, point.second);
     }

     // Now make up a list of peers where the ones with more points are
     // listed many times.
     QMultiMap<int, TorrentPeer *>::ConstIterator it = pointMap.constBegin();
     while (it != pointMap.constEnd()) {
         for (int i = 0; i < it.key() + 1; ++i)
             weighedPeers << it.value();
         ++it;
     }

     return weighedPeers;
 }

 void TorrentClient::setupIncomingConnection(PeerWireClient *client)
 {
     // Connect signals
     initializeConnection(client);

     // Initialize this client
     RateController::instance()->addSocket(client);
     d->connections << client;

     client->initialize(d->infoHash, d->pieceCount);
     client->sendPieceList(d->completedPieces);

     emit peerInfoUpdated();

     if (d->state == Searching || d->state == Connecting) {
         int completed = d->completedPieces.count(true);
         if (completed == 0)
             d->setState(WarmingUp);
         else if (d->incompletePieces.count(true) < 5 && d->pendingPieces.size() > d->incompletePieces.count(true))
             d->setState(Endgame);
     }

     if (d->connections.isEmpty())
         scheduleUploads();
 }

 void TorrentClient::setupOutgoingConnection()
 {
     PeerWireClient *client = qobject_cast<PeerWireClient *>(sender());

     // Update connection statistics.
     foreach (TorrentPeer *peer, d->peers) {
         if (peer->port == client->peerPort() && peer->address == client->peerAddress()) {
             peer->connectTime = peer->lastVisited - peer->connectStart;
             break;
         }
     }

     // Send handshake and piece list
     client->initialize(d->infoHash, d->pieceCount);
     client->sendPieceList(d->completedPieces);

     emit peerInfoUpdated();

     if (d->state == Searching || d->state == Connecting) {
         int completed = d->completedPieces.count(true);
         if (completed == 0)
             d->setState(WarmingUp);
         else if (d->incompletePieces.count(true) < 5 && d->pendingPieces.size() > d->incompletePieces.count(true))
             d->setState(Endgame);
     }
 }

 void TorrentClient::initializeConnection(PeerWireClient *client)
 {
     connect(client, SIGNAL(connected()),
             this, SLOT(setupOutgoingConnection()));
     connect(client, SIGNAL(disconnected()),
             this, SLOT(removeClient()));
     connect(client, SIGNAL(error(QAbstractSocket::SocketError)),
             this, SLOT(removeClient()));
     connect(client, SIGNAL(piecesAvailable(const QBitArray &)),
             this, SLOT(peerPiecesAvailable(const QBitArray &)));
     connect(client, SIGNAL(blockRequested(int, int, int)),
             this, SLOT(peerRequestsBlock(int, int, int)));
     connect(client, SIGNAL(blockReceived(int, int, const QByteArray &)),
             this, SLOT(blockReceived(int, int, const QByteArray &)));
     connect(client, SIGNAL(choked()),
             this, SLOT(peerChoked()));
     connect(client, SIGNAL(unchoked()),
             this, SLOT(peerUnchoked()));
     connect(client, SIGNAL(bytesWritten(qint64)),
             this, SLOT(peerWireBytesWritten(qint64)));
     connect(client, SIGNAL(bytesReceived(qint64)),
             this, SLOT(peerWireBytesReceived(qint64)));
 }

 void TorrentClient::removeClient()
 {
     PeerWireClient *client = static_cast<PeerWireClient *>(sender());

     // Remove the host from our list of known peers if the connection
     // failed.
     if (client->peer() && client->error() == QAbstractSocket::ConnectionRefusedError)
         d->peers.removeAll(client->peer());

     // Remove the client from RateController and all structures.
     RateController::instance()->removeSocket(client);
     d->connections.removeAll(client);
     QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.find(client);
     while (it != d->payloads.end() && it.key() == client) {
         TorrentPiece *piece = it.value();
         piece->inProgress = false;
         piece->requestedBlocks.fill(false);
         it = d->payloads.erase(it);
     }

     // Remove pending read requests.
     QMapIterator<int, PeerWireClient *> it2(d->readIds);
     while (it2.findNext(client))
         d->readIds.remove(it2.key());

     // Delete the client later.
     disconnect(client, SIGNAL(disconnected()), this, SLOT(removeClient()));
     client->deleteLater();
     ConnectionManager::instance()->removeConnection(client);

     emit peerInfoUpdated();
     d->callPeerConnector();
 }

 void TorrentClient::peerPiecesAvailable(const QBitArray &pieces)
 {
     PeerWireClient *client = qobject_cast<PeerWireClient *>(sender());

     // Find the peer in our list of announced peers. If it's there,
     // then we can use the piece list into to gather statistics that
     // help us decide what peers to connect to.
     TorrentPeer *peer = 0;
     QList<TorrentPeer *>::Iterator it = d->peers.begin();
     while (it != d->peers.end()) {
         if ((*it)->address == client->peerAddress() && (*it)->port == client->peerPort()) {
             peer = *it;
             break;
         }
         ++it;
     }

     // If the peer is a seed, and we are in seeding mode, then the
     // peer is uninteresting.
     if (pieces.count(true) == d->pieceCount) {
         if (peer)
             peer->seed = true;
         emit peerInfoUpdated();
         if (d->state == Seeding) {
             client->abort();
             return;
         } else {
             if (peer)
                 peer->interesting = true;
             if ((client->peerWireState() & PeerWireClient::InterestedInPeer) == 0)
                 client->sendInterested();
             d->callScheduler();
             return;
         }
     }

     // Update our list of available pieces.
     if (peer) {
         peer->pieces = pieces;
         peer->numCompletedPieces = pieces.count(true);
     }

     // Check for interesting pieces, and tell the peer whether we are
     // interested or not.
     bool interested = false;
     int piecesSize = pieces.size();
     for (int pieceIndex = 0; pieceIndex < piecesSize; ++pieceIndex) {
         if (!pieces.testBit(pieceIndex))
             continue;
         if (!d->completedPieces.testBit(pieceIndex)) {
             interested = true;
             if ((client->peerWireState() & PeerWireClient::InterestedInPeer) == 0) {
                 if (peer)
                     peer->interesting = true;
                 client->sendInterested();
             }

             QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.find(client);
             int inProgress = 0;
             while (it != d->payloads.end() && it.key() == client) {
                 if (it.value()->inProgress)
                     inProgress += it.value()->requestedBlocks.count(true);
                 ++it;
             }
             if (!inProgress)
                 d->callScheduler();
             break;
         }
     }
     if (!interested && (client->peerWireState() & PeerWireClient::InterestedInPeer)) {
         if (peer)
             peer->interesting = false;
         client->sendNotInterested();
     }
 }

 void TorrentClient::peerRequestsBlock(int pieceIndex, int begin, int length)
 {
     PeerWireClient *client = qobject_cast<PeerWireClient *>(sender());

     // Silently ignore requests from choked peers
     if (client->peerWireState() & PeerWireClient::ChokingPeer)
         return;

     // Silently ignore requests for pieces we don't have.
     if (!d->completedPieces.testBit(pieceIndex))
         return;

     // Request the block from the file manager
     d->readIds.insert(d->fileManager.read(pieceIndex, begin, length),
                       qobject_cast<PeerWireClient *>(sender()));
 }

 void TorrentClient::blockReceived(int pieceIndex, int begin, const QByteArray &data)
 {
     PeerWireClient *client = qobject_cast<PeerWireClient *>(sender());
     if (data.size() == 0) {
         client->abort();
         return;
     }

     // Ignore it if we already have this block.
     int blockBit = begin / BlockSize;
     TorrentPiece *piece = d->pendingPieces.value(pieceIndex);
     if (!piece || piece->completedBlocks.testBit(blockBit)) {
         // Discard blocks that we already have, and fill up the pipeline.
         requestMore(client);
         return;
     }

     // If we are in warmup or endgame mode, cancel all duplicate
     // requests for this block.
     if (d->state == WarmingUp || d->state == Endgame) {
         QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.begin();
         while (it != d->payloads.end()) {
             PeerWireClient *otherClient = it.key();
             if (otherClient != client && it.value()->index == pieceIndex) {
                 if (otherClient->incomingBlocks().contains(TorrentBlock(pieceIndex, begin, data.size())))
                     it.key()->cancelRequest(pieceIndex, begin, data.size());
             }
             ++it;
         }
     }

     if (d->state != Downloading && d->state != Endgame && d->completedPieces.count(true) > 0)
         d->setState(Downloading);

     // Store this block
     d->fileManager.write(pieceIndex, begin, data);
     piece->completedBlocks.setBit(blockBit);
     piece->requestedBlocks.clearBit(blockBit);

     if (blocksLeftForPiece(piece) == 0) {
         // Ask the file manager to verify the newly downloaded piece
         d->fileManager.verifyPiece(piece->index);

         // Remove this piece from all payloads
         QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.begin();
         while (it != d->payloads.end()) {
             if (!it.value() || it.value()->index == piece->index)
                 it = d->payloads.erase(it);
             else
                 ++it;
         }
     }

     // Fill up the pipeline.
     requestMore(client);
 }

 void TorrentClient::peerWireBytesWritten(qint64 size)
 {
     if (!d->transferRateTimer)
         d->transferRateTimer = startTimer(RateControlTimerDelay);

     d->uploadRate[0] += size;
     d->uploadedBytes += size;
     emit dataSent(size);
 }

 void TorrentClient::peerWireBytesReceived(qint64 size)
 {
     if (!d->transferRateTimer)
         d->transferRateTimer = startTimer(RateControlTimerDelay);

     d->downloadRate[0] += size;
     d->downloadedBytes += size;
     emit dataSent(size);
 }

 int TorrentClient::blocksLeftForPiece(const TorrentPiece *piece) const
 {
     int blocksLeft = 0;
     int completedBlocksSize = piece->completedBlocks.size();
     for (int i = 0; i < completedBlocksSize; ++i) {
         if (!piece->completedBlocks.testBit(i))
             ++blocksLeft;
     }
     return blocksLeft;
 }

 void TorrentClient::scheduleUploads()
 {
     // Generate a list of clients sorted by their transfer
     // speeds.  When leeching, we sort by download speed, and when
     // seeding, we sort by upload speed. Seeds are left out; there's
     // no use in unchoking them.
     QList<PeerWireClient *> allClients = d->connections;
     QMultiMap<int, PeerWireClient *> transferSpeeds;
     foreach (PeerWireClient *client, allClients) {
         if (client->state() == QAbstractSocket::ConnectedState
             && client->availablePieces().count(true) != d->pieceCount) {
             if (d->state == Seeding) {
                 transferSpeeds.insert(client->uploadSpeed(), client);
             } else {
                 transferSpeeds.insert(client->downloadSpeed(), client);
             }
         }
     }

     // Unchoke the top 'MaxUploads' downloaders (peers that we are
     // uploading to) and choke all others.
     int maxUploaders = MaxUploads;
     QMapIterator<int, PeerWireClient *> it(transferSpeeds);
     it.toBack();
     while (it.hasPrevious()) {
         PeerWireClient *client = it.previous().value();
         bool interested = (client->peerWireState() & PeerWireClient::PeerIsInterested);

         if (maxUploaders) {
             allClients.removeAll(client);
             if (client->peerWireState() & PeerWireClient::ChokingPeer)
                 client->unchokePeer();
             --maxUploaders;
             continue;
         }

         if ((client->peerWireState() & PeerWireClient::ChokingPeer) == 0) {
             if ((qrand() % 10) == 0)
                 client->abort();
             else
                 client->chokePeer();
             allClients.removeAll(client);
         }
         if (!interested)
             allClients.removeAll(client);
     }

     // Only interested peers are left in allClients. Unchoke one
     // random peer to allow it to compete for a position among the
     // downloaders.  (This is known as an "optimistic unchoke".)
     if (!allClients.isEmpty()) {
         PeerWireClient *client = allClients[qrand() % allClients.size()];
         if (client->peerWireState() & PeerWireClient::ChokingPeer)
             client->unchokePeer();
     }
 }

 void TorrentClient::scheduleDownloads()
 {
     d->schedulerCalled = false;

     if (d->state == Stopping || d->state == Paused || d->state == Idle)
         return;

     // Check what each client is doing, and assign payloads to those
     // who are either idle or done.
     foreach (PeerWireClient *client, d->connections)
         schedulePieceForClient(client);
 }

 void TorrentClient::schedulePieceForClient(PeerWireClient *client)
 {
     // Only schedule connected clients.
     if (client->state() != QTcpSocket::ConnectedState)
         return;

     // The peer has choked us; try again later.
     if (client->peerWireState() & PeerWireClient::ChokedByPeer)
         return;

     // Make a list of all the client's pending pieces, and count how
     // many blocks have been requested.
     QList<int> currentPieces;
     bool somePiecesAreNotInProgress = false;
     TorrentPiece *lastPendingPiece = 0;
     QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.find(client);
     while (it != d->payloads.end() && it.key() == client) {
         lastPendingPiece = it.value();
         if (lastPendingPiece->inProgress) {
             currentPieces << lastPendingPiece->index;
         } else {
             somePiecesAreNotInProgress = true;
         }
         ++it;
     }

     // Skip clients that already have too many blocks in progress.
     if (client->incomingBlocks().size() >= ((d->state == Endgame || d->state == WarmingUp)
                                             ? MaxBlocksInMultiMode : MaxBlocksInProgress))
         return;

     // If all pieces are in progress, but we haven't filled up our
     // block requesting quota, then we need to schedule another piece.
     if (!somePiecesAreNotInProgress || client->incomingBlocks().size() > 0)
         lastPendingPiece = 0;
     TorrentPiece *piece = lastPendingPiece;

     // In warmup state, all clients request blocks from the same pieces.
     if (d->state == WarmingUp && d->pendingPieces.size() >= 4) {
         piece = d->payloads.value(client);
         if (!piece) {
             QList<TorrentPiece *> values = d->pendingPieces.values();
             piece = values.value(qrand() % values.size());
             piece->inProgress = true;
             d->payloads.insert(client, piece);
         }
         if (piece->completedBlocks.count(false) == client->incomingBlocks().size())
             return;
     }

     // If no pieces are currently in progress, schedule a new one.
     if (!piece) {
         // Build up a list of what pieces that we have not completed
         // are available to this client.
         QBitArray incompletePiecesAvailableToClient = d->incompletePieces;

         // Remove all pieces that are marked as being in progress
         // already (i.e., pieces that this or other clients are
         // already waiting for). A special rule applies to warmup and
         // endgame mode; there, we allow several clients to request
         // the same piece. In endgame mode, this only applies to
         // clients that are currently uploading (more than 1.0KB/s).
         if ((d->state == Endgame && client->uploadSpeed() < 1024) || d->state != WarmingUp) {
             QMap<int, TorrentPiece *>::ConstIterator it = d->pendingPieces.constBegin();
             while (it != d->pendingPieces.constEnd()) {
                 if (it.value()->inProgress)
                     incompletePiecesAvailableToClient.clearBit(it.key());
                 ++it;
             }
         }

         // Remove all pieces that the client cannot download.
         incompletePiecesAvailableToClient &= client->availablePieces();

         // Remove all pieces that this client has already requested.
         foreach (int i, currentPieces)
             incompletePiecesAvailableToClient.clearBit(i);

         // Only continue if more pieces can be scheduled. If no pieces
         // are available and no blocks are in progress, just leave
         // the connection idle; it might become interesting later.
         if (incompletePiecesAvailableToClient.count(true) == 0)
             return;

         // Check if any of the partially completed pieces can be
         // recovered, and if so, pick a random one of them.
         QList<TorrentPiece *> partialPieces;
         QMap<int, TorrentPiece *>::ConstIterator it = d->pendingPieces.constBegin();
         while (it != d->pendingPieces.constEnd()) {
             TorrentPiece *tmp = it.value();
             if (incompletePiecesAvailableToClient.testBit(it.key())) {
                 if (!tmp->inProgress || d->state == WarmingUp || d->state == Endgame) {
                     partialPieces << tmp;
                     break;
                 }
             }
             ++it;
         }
         if (!partialPieces.isEmpty())
             piece = partialPieces.value(qrand() % partialPieces.size());

         if (!piece) {
             // Pick a random piece 3 out of 4 times; otherwise, pick either
             // one of the most common or the least common pieces available,
             // depending on the state we're in.
             int pieceIndex = 0;
             if (d->state == WarmingUp || (qrand() & 4) == 0) {
                 int *occurrances = new int[d->pieceCount];
                 memset(occurrances, 0, d->pieceCount * sizeof(int));

                 // Count how many of each piece are available.
                 foreach (PeerWireClient *peer, d->connections) {
                     QBitArray peerPieces = peer->availablePieces();
                     int peerPiecesSize = peerPieces.size();
                     for (int i = 0; i < peerPiecesSize; ++i) {
                         if (peerPieces.testBit(i))
                             ++occurrances[i];
                     }
                 }

                 // Find the rarest or most common pieces.
                 int numOccurrances = d->state == WarmingUp ? 0 : 99999;
                 QList<int> piecesReadyForDownload;
                 for (int i = 0; i < d->pieceCount; ++i) {
                     if (d->state == WarmingUp) {
                         // Add common pieces
                         if (occurrances[i] >= numOccurrances
                             && incompletePiecesAvailableToClient.testBit(i)) {
                             if (occurrances[i] > numOccurrances)
                                 piecesReadyForDownload.clear();
                             piecesReadyForDownload.append(i);
                             numOccurrances = occurrances[i];
                         }
                     } else {
                         // Add rare pieces
                         if (occurrances[i] <= numOccurrances
                             && incompletePiecesAvailableToClient.testBit(i)) {
                             if (occurrances[i] < numOccurrances)
                                 piecesReadyForDownload.clear();
                             piecesReadyForDownload.append(i);
                             numOccurrances = occurrances[i];
                         }
                     }
                 }

                 // Select one piece randomly
                 pieceIndex = piecesReadyForDownload.at(qrand() % piecesReadyForDownload.size());
                 delete [] occurrances;
             } else {
                 // Make up a list of available piece indices, and pick
                 // a random one.
                 QList<int> values;
                 int incompletePiecesAvailableToClientSize = incompletePiecesAvailableToClient.size();
                 for (int i = 0; i < incompletePiecesAvailableToClientSize; ++i) {
                     if (incompletePiecesAvailableToClient.testBit(i))
                         values << i;
                 }
                 pieceIndex = values.at(qrand() % values.size());
             }

             // Create a new TorrentPiece and fill in all initial
             // properties.
             piece = new TorrentPiece;
             piece->index = pieceIndex;
             piece->length = d->fileManager.pieceLengthAt(pieceIndex);
             int numBlocks = piece->length / BlockSize;
             if (piece->length % BlockSize)
                 ++numBlocks;
             piece->completedBlocks.resize(numBlocks);
             piece->requestedBlocks.resize(numBlocks);
             d->pendingPieces.insert(pieceIndex, piece);
         }

         piece->inProgress = true;
         d->payloads.insert(client, piece);
     }

     // Request more blocks from all pending pieces.
     requestMore(client);
 }

 void TorrentClient::requestMore(PeerWireClient *client)
 {
     // Make a list of all pieces this client is currently waiting for,
     // and count the number of blocks in progress.
     QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.find(client);
     int numBlocksInProgress = client->incomingBlocks().size();
     QList<TorrentPiece *> piecesInProgress;
     while (it != d->payloads.end() && it.key() == client) {
         TorrentPiece *piece = it.value();
         if (piece->inProgress || (d->state == WarmingUp || d->state == Endgame))
             piecesInProgress << piece;
         ++it;
     }

     // If no pieces are in progress, call the scheduler.
     if (piecesInProgress.isEmpty() && d->incompletePieces.count(true)) {
         d->callScheduler();
         return;
     }

     // If too many pieces are in progress, there's nothing to do.
     int maxInProgress = ((d->state == Endgame || d->state == WarmingUp)
                          ? MaxBlocksInMultiMode : MaxBlocksInProgress);
     if (numBlocksInProgress == maxInProgress)
         return;

     // Starting with the first piece that we're waiting for, request
     // blocks until the quota is filled up.
     foreach (TorrentPiece *piece, piecesInProgress) {
         numBlocksInProgress += requestBlocks(client, piece, maxInProgress - numBlocksInProgress);
         if (numBlocksInProgress == maxInProgress)
             break;
     }

     // If we still didn't fill up the quota, we need to schedule more
     // pieces.
     if (numBlocksInProgress < maxInProgress && d->state != WarmingUp)
         d->callScheduler();
 }

 int TorrentClient::requestBlocks(PeerWireClient *client, TorrentPiece *piece, int maxBlocks)
 {
     // Generate the list of incomplete blocks for this piece.
     QVector<int> bits;
     int completedBlocksSize = piece->completedBlocks.size();
     for (int i = 0; i < completedBlocksSize; ++i) {
         if (!piece->completedBlocks.testBit(i) && !piece->requestedBlocks.testBit(i))
             bits << i;
     }

     // Nothing more to request.
     if (bits.size() == 0) {
         if (d->state != WarmingUp && d->state != Endgame)
             return 0;
         bits.clear();
         for (int i = 0; i < completedBlocksSize; ++i) {
             if (!piece->completedBlocks.testBit(i))
                 bits << i;
         }
     }

     if (d->state == WarmingUp || d->state == Endgame) {
         // By randomizing the list of blocks to request, we
         // significantly speed up the warmup and endgame modes, where
         // the same blocks are requested from multiple peers. The
         // speedup comes from an increased chance of receiving
         // different blocks from the different peers.
         for (int i = 0; i < bits.size(); ++i) {
             int a = qrand() % bits.size();
             int b = qrand() % bits.size();
             int tmp = bits[a];
             bits[a] = bits[b];
             bits[b] = tmp;
         }
     }

     // Request no more blocks than we've been asked to.
     int blocksToRequest = qMin(maxBlocks, bits.size());

     // Calculate the offset and size of each block, and send requests.
     for (int i = 0; i < blocksToRequest; ++i) {
         int blockSize = BlockSize;
         if ((piece->length % BlockSize) && bits.at(i) == completedBlocksSize - 1)
             blockSize = piece->length % BlockSize;
         client->requestBlock(piece->index, bits.at(i) * BlockSize, blockSize);
         piece->requestedBlocks.setBit(bits.at(i));
     }

     return blocksToRequest;
 }

 void TorrentClient::peerChoked()
 {
     PeerWireClient *client = qobject_cast<PeerWireClient *>(sender());
     if (!client)
         return;

     // When the peer chokes us, we immediately forget about all blocks
     // we've requested from it. We also remove the piece from out
     // payload, making it available to other clients.
     QMultiMap<PeerWireClient *, TorrentPiece *>::Iterator it = d->payloads.find(client);
     while (it != d->payloads.end() && it.key() == client) {
         it.value()->inProgress = false;
         it.value()->requestedBlocks.fill(false);
         it = d->payloads.erase(it);
     }
 }

 void TorrentClient::peerUnchoked()
 {
     PeerWireClient *client = qobject_cast<PeerWireClient *>(sender());
     if (!client)
         return;

     // We got unchoked, which means we can request more blocks.
     if (d->state != Seeding)
         d->callScheduler();
 }

 void TorrentClient::addToPeerList(const QList<TorrentPeer> &peerList)
 {
     // Add peers we don't already know of to our list of peers.
     QList<QHostAddress> addresses =  QNetworkInterface::allAddresses();
     foreach (TorrentPeer peer, peerList) {
         if (addresses.contains(peer.address)
             && peer.port == TorrentServer::instance()->serverPort()) {
             // Skip our own server.
             continue;
         }

         bool known = false;
         foreach (TorrentPeer *knownPeer, d->peers) {
             if (knownPeer->port == peer.port
                 && knownPeer->address == peer.address) {
                 known = true;
                 break;
             }
         }
         if (!known) {
             TorrentPeer *newPeer = new TorrentPeer;
             *newPeer = peer;
             newPeer->interesting = true;
             newPeer->seed = false;
             newPeer->lastVisited = 0;
             newPeer->connectStart = 0;
             newPeer->connectTime = 999999;
             newPeer->pieces.resize(d->pieceCount);
             newPeer->numCompletedPieces = 0;
             d->peers << newPeer;
         }
     }

     // If we've got more peers than we can connect to, we remove some
     // of the peers that have no (or low) activity.
     int maxPeers = ConnectionManager::instance()->maxConnections() * 3;
     if (d->peers.size() > maxPeers) {
         // Find what peers are currently connected & active
         QSet<TorrentPeer *> activePeers;
         foreach (TorrentPeer *peer, d->peers) {
             foreach (PeerWireClient *client, d->connections) {
                 if (client->peer() == peer && (client->downloadSpeed() + client->uploadSpeed()) > 1024)
                     activePeers << peer;
             }
         }

         // Remove inactive peers from the peer list until we're below
         // the max connections count.
         QList<int> toRemove;
         for (int i = 0; i < d->peers.size() && (d->peers.size() - toRemove.size()) > maxPeers; ++i) {
             if (!activePeers.contains(d->peers.at(i)))
                 toRemove << i;
         }
         QListIterator<int> toRemoveIterator(toRemove);
         toRemoveIterator.toBack();
         while (toRemoveIterator.hasPrevious())
             d->peers.removeAt(toRemoveIterator.previous());

         // If we still have too many peers, remove the oldest ones.
         while (d->peers.size() > maxPeers)
             d->peers.takeFirst();
     }

     if (d->state != Paused && d->state != Stopping && d->state != Idle) {
         if (d->state == Searching || d->state == WarmingUp)
             connectToPeers();
         else
             d->callPeerConnector();
     }
 }

 void TorrentClient::trackerStopped()
 {
     d->setState(Idle);
     emit stopped();
 }

 void TorrentClient::updateProgress(int progress)
 {
     if (progress == -1 && d->pieceCount > 0) {
         int newProgress = (d->completedPieces.count(true) * 100) / d->pieceCount;
         if (d->lastProgressValue != newProgress) {
             d->lastProgressValue = newProgress;
             emit progressUpdated(newProgress);
         }
     } else if (d->lastProgressValue != progress) {
         d->lastProgressValue = progress;
         emit progressUpdated(progress);
     }
 }