- Qt 5.5
- Qt Network
- Torrent Example
- torrentclient.cpp Example File
- Qt 5.5.1 Reference Documentation

# torrentclient.cpp Example File

torrent/torrentclient.cpp

    /****************************************************************************
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    ** This file is part of the examples of the Qt Toolkit.
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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>

    #include <algorithm>

    // 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;

    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,QByteArray)),
                this, SLOT(sendToPeer(int,int,int,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(QList<TorrentPeer>)),
                this, SLOT(addToPeerList(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);
        }
        std::sort(points.begin(), points.end());

        // 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(QBitArray)),
                this, SLOT(peerPiecesAvailable(QBitArray)));
        connect(client, SIGNAL(blockRequested(int,int,int)),
                this, SLOT(peerRequestsBlock(int,int,int)));
        connect(client, SIGNAL(blockReceived(int,int,QByteArray)),
                this, SLOT(blockReceived(int,int,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 *occurrences = new int[d->pieceCount];
                    memset(occurrences, 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))
                                ++occurrences[i];
                        }
                    }

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

                    // Select one piece randomly
                    pieceIndex = piecesReadyForDownload.at(qrand() % piecesReadyForDownload.size());
                    delete [] occurrences;
                } 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);
        }
    }