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

        /****************************************************************************
        **
        ** Copyright (C) 2004-2006 Trolltech ASA. All rights reserved.
        **
        ** This file is part of the documentation of the Qt Toolkit.
        **
        ** This file may be used under the terms of the GNU General Public
        ** License version 2.0 as published by the Free Software Foundation
        ** and appearing in the file LICENSE.GPL included in the packaging of
        ** this file.  Please review the following information to ensure GNU
        ** General Public Licensing requirements will be met:
        ** http://www.trolltech.com/products/qt/opensource.html
        **
        ** If you are unsure which license is appropriate for your use, please
        ** review the following information:
        ** http://www.trolltech.com/products/qt/licensing.html or contact the
        ** sales department at sales@trolltech.com.
        **
        ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        **
        ****************************************************************************/

        #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>

        extern "C" {
        #include "3rdparty/sha1.h"
        }

        // 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();
            SHA1Context sha;
            SHA1Reset(&sha);
            SHA1Input(&sha, (const unsigned char *)infoValue.constData(), infoValue.size());
            SHA1Result(&sha);
            unsigned char *digest = (unsigned char *)sha.Message_Digest;
            d->infoHash.resize(20);

            for (int i = 0; i < 5; ++i) {
        #if Q_BYTE_ORDER == Q_BIG_ENDIAN
                d->infoHash[i * 4 + 3] = digest[i * 4 + 3];
                d->infoHash[i * 4 + 2] = digest[i * 4 + 2];
                d->infoHash[i * 4 + 1] = digest[i * 4 + 1];
                d->infoHash[i * 4 + 0] = digest[i * 4 + 0];
        #else
                d->infoHash[i * 4 + 0] = digest[i * 4 + 3];
                d->infoHash[i * 4 + 1] = digest[i * 4 + 2];
                d->infoHash[i * 4 + 2] = digest[i * 4 + 1];
                d->infoHash[i * 4 + 3] = digest[i * 4 + 0];
        #endif
            }

            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)
                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.setUploadCount(d->uploadedBytes);
            d->trackerClient.setDownloadCount(d->downloadedBytes);
            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.start(d->metaInfo);
                }
            } 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()
                   && (rand() % (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(rand() % 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 ((rand() % 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[rand() % 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(rand() % 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(rand() % 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 || (rand() & 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(rand() % 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(rand() % 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 = rand() % bits.size();
                    int b = rand() % 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.
            foreach (TorrentPeer peer, peerList) {
                if (peer.address == TorrentServer::instance()->serverAddress()
                    && peer.port == TorrentServer::instance()->serverPort())
                    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);
            }
        }