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# trackerclient.cpp Example File
network/torrent/trackerclient.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 "bencodeparser.h"
        #include "connectionmanager.h"
        #include "torrentclient.h"
        #include "torrentserver.h"
        #include "trackerclient.h"

        #include <QtCore>

        quint32 qntoh(quint32 source)
        {
        #if Q_BYTE_ORDER == Q_BIG_ENDIAN
            return source;
        #else
            return 0
                | ((source & 0x000000ff) << 24)
                | ((source & 0x0000ff00) << 8)
                | ((source & 0x00ff0000) >> 8)
                | ((source & 0xff000000) >> 24);
        #endif
        }

        TrackerClient::TrackerClient(TorrentClient *downloader, QObject *parent)
            : QObject(parent), torrentDownloader(downloader)
        {
            length = 0;
            uploadedBytes = 0;
            downloadedBytes = 0;
            requestInterval = 5 * 60;
            requestIntervalTimer = -1;
            firstTrackerRequest = true;
            lastTrackerRequest = false;

            connect(&http, SIGNAL(done(bool)), this, SLOT(httpRequestDone(bool)));
        }

        void TrackerClient::start(const MetaInfo &info)
        {
            metaInfo = info;
            QTimer::singleShot(0, this, SLOT(fetchPeerList()));

            if (metaInfo.fileForm() == MetaInfo::SingleFileForm) {
                length = metaInfo.singleFile().length;
            } else {
                QList<MetaInfoMultiFile> files = metaInfo.multiFiles();
                for (int i = 0; i < files.size(); ++i)
                    length += files.at(i).length;
            }
        }

        void TrackerClient::stop()
        {
            lastTrackerRequest = true;
            http.abort();
            fetchPeerList();
        }

        void TrackerClient::timerEvent(QTimerEvent *event)
        {
            if (event->timerId() == requestIntervalTimer) {
                if (http.state() == QHttp::Unconnected)
                    fetchPeerList();
            } else {
                QObject::timerEvent(event);
            }
        }

        void TrackerClient::fetchPeerList()
        {
            // Prepare connection details
            QUrl url(metaInfo.announceUrl());

            QByteArray infoHash = torrentDownloader->infoHash();
            unsigned int *messageDigest = (unsigned int *)infoHash.constData();

            // Percent encode the hash
            QByteArray encodedSum;
            const char hex[] = "0123456789ABCDEF";
            unsigned char chars[4];

            for (int i = 0; i < 5; ++i) {
                unsigned int digest = qntoh(messageDigest[i]);
                chars[0] = (digest & 0xff000000) >> 24;
                chars[1] = (digest & 0x00ff0000) >> 16;
                chars[2] = (digest & 0x0000ff00) >> 8;
                chars[3] = (digest & 0x000000ff);

                for (int j = 0; j < 4; ++j) {
                    unsigned char c = chars[j];
                    if ((c >= '0' && c <= '9')
                        || (c >= 'a' && c <= 'z')
                        || (c >= 'A' && c <= 'Z'))
                        encodedSum += c;
                    else switch (c) {
                    case '$': case '-': case '_': case '.':
                    case '+': case '!': case '*': case '\'':
                    case '(': case ')':
                        encodedSum += c;
                        break;
                    default: {
                        encodedSum += "%";
                        encodedSum += hex[(c & 0xf0) >> 4];
                        encodedSum += hex[c & 0xf];
                        break;
                    }
                    }
                }
            }

            bool seeding = (torrentDownloader->state() == TorrentClient::Seeding);
            QByteArray query;
            query += url.path().toLatin1();
            query += "?";
            query += "info_hash=" + encodedSum;
            query += "&peer_id=" + ConnectionManager::instance()->clientId();
            query += "&port=" + QByteArray::number(TorrentServer::instance()->serverPort());
            query += "&uploaded=" + QByteArray::number(uploadedBytes);
            query += "&downloaded=" + QByteArray::number(downloadedBytes);
            query += "&left="+ QByteArray::number(seeding ? 0 : qMax<int>(0, length - downloadedBytes));
            query += "&compact=1";
            if (seeding) {
                query += "&event=completed";
            } else if (firstTrackerRequest) {
                firstTrackerRequest = false;
                query += "&event=started";
            } else if (lastTrackerRequest) {
                query += "&event=stopped";
            }
            if (!trackerId.isEmpty())
                query += "&trackerid=" + trackerId;

            http.setHost(url.host(), url.port() == -1 ? 80 : url.port());
            if (!url.userName().isEmpty())
                http.setUser(url.userName(), url.password());

            http.get(query);
        }

        void TrackerClient::httpRequestDone(bool error)
        {
            if (lastTrackerRequest) {
                emit stopped();
                return;
            }

            if (error) {
                emit connectionError(http.error());
                return;
            }

            QByteArray response = http.readAll();
            http.abort();

            BencodeParser parser;
            if (!parser.parse(response)) {
                qWarning("Error parsing bencode response from tracker: %s",
                         qPrintable(parser.errorString()));
                http.abort();
                return;
            }

            QMap<QByteArray, QVariant> dict = parser.dictionary();

            if (dict.contains("failure reason")) {
                // no other items are present
                emit failure(QString::fromUtf8(dict.value("failure reason").toByteArray()));
                return;
            }

            if (dict.contains("warning message")) {
                // continue processing
                emit warning(QString::fromUtf8(dict.value("warning message").toByteArray()));
            }

            if (dict.contains("tracker id")) {
                // store it
                trackerId = dict.value("tracker id").toByteArray();
            }

            if (dict.contains("interval")) {
                // Mandatory item
                if (requestIntervalTimer != -1)
                    killTimer(requestIntervalTimer);
                requestIntervalTimer = startTimer(dict.value("interval").toInt() * 1000);
            }

            if (dict.contains("peers")) {
                // store it
                peers.clear();
                QVariant peerEntry = dict.value("peers");
                if (peerEntry.type() == QVariant::List) {
                    QList<QVariant> peerTmp = peerEntry.toList();
                    for (int i = 0; i < peerTmp.size(); ++i) {
                        TorrentPeer tmp;
                        QMap<QByteArray, QVariant> peer = qVariantValue<QMap<QByteArray, QVariant> >(peerTmp.at(i));
                        tmp.id = QString::fromUtf8(peer.value("peer id").toByteArray());
                        tmp.address.setAddress(QString::fromUtf8(peer.value("ip").toByteArray()));
                        tmp.port = peer.value("port").toInt();
                        peers << tmp;
                    }
                } else {
                    QByteArray peerTmp = peerEntry.toByteArray();
                    for (int i = 0; i < peerTmp.size(); i += 6) {
                        TorrentPeer tmp;
                        uchar *data = (uchar *)peerTmp.constData() + i;
                        tmp.port = (int(data[4]) << 8) + data[5];
                        uint ipAddress = 0;
                        ipAddress += uint(data[0]) << 24;
                        ipAddress += uint(data[1]) << 16;
                        ipAddress += uint(data[2]) << 8;
                        ipAddress += uint(data[3]);
                        tmp.address.setAddress(ipAddress);
                        peers << tmp;
                    }
                }
                emit peerListUpdated(peers);
            }
        }