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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 example classes 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);
         }
     }