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

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     #include "filemanager.h"
     #include "metainfo.h"

     #include <QByteArray>
     #include <QDir>
     #include <QFile>
     #include <QTimer>
     #include <QTimerEvent>

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

     FileManager::FileManager(QObject *parent)
         : QThread(parent)
     {
         quit = false;
         totalLength = 0;
         readId = 0;
         startVerification = false;
         wokeUp = false;
         newFile = false;
         numPieces = 0;
         verifiedPieces.fill(false);
     }

     FileManager::~FileManager()
     {
         quit = true;
         cond.wakeOne();
         wait();

         foreach (QFile *file, files) {
             file->close();
             delete file;
         }
     }

     int FileManager::read(int pieceIndex, int offset, int length)
     {
         ReadRequest request;
         request.pieceIndex = pieceIndex;
         request.offset = offset;
         request.length = length;

         QMutexLocker locker(&mutex);
         request.id = readId++;
         readRequests << request;

         if (!wokeUp) {
             wokeUp = true;
             QMetaObject::invokeMethod(this, "wakeUp", Qt::QueuedConnection);
         }

         return request.id;
     }

     void FileManager::write(int pieceIndex, int offset, const QByteArray &data)
     {
         WriteRequest request;
         request.pieceIndex = pieceIndex;
         request.offset = offset;
         request.data = data;

         QMutexLocker locker(&mutex);
         writeRequests << request;

         if (!wokeUp) {
             wokeUp = true;
             QMetaObject::invokeMethod(this, "wakeUp", Qt::QueuedConnection);
         }
     }

     void FileManager::verifyPiece(int pieceIndex)
     {
         QMutexLocker locker(&mutex);
         pendingVerificationRequests << pieceIndex;
         startVerification = true;

         if (!wokeUp) {
             wokeUp = true;
             QMetaObject::invokeMethod(this, "wakeUp", Qt::QueuedConnection);
         }
     }

     int FileManager::pieceLengthAt(int pieceIndex) const
     {
         QMutexLocker locker(&mutex);
         return (sha1s.size() == pieceIndex + 1)
             ? (totalLength % pieceLength) : pieceLength;
     }

     QBitArray FileManager::completedPieces() const
     {
         QMutexLocker locker(&mutex);
         return verifiedPieces;
     }

     void FileManager::setCompletedPieces(const QBitArray &pieces)
     {
         QMutexLocker locker(&mutex);
         verifiedPieces = pieces;
     }

     QString FileManager::errorString() const
     {
         return errString;
     }

     void FileManager::run()
     {
         if (!generateFiles())
             return;

         do {
             {
                 // Go to sleep if there's nothing to do.
                 QMutexLocker locker(&mutex);
                 if (!quit && readRequests.isEmpty() && writeRequests.isEmpty() && !startVerification)
                     cond.wait(&mutex);
             }

             // Read pending read requests
             mutex.lock();
             QList<ReadRequest> newReadRequests = readRequests;
             readRequests.clear();
             mutex.unlock();
             while (!newReadRequests.isEmpty()) {
                 ReadRequest request = newReadRequests.takeFirst();
                 QByteArray block = readBlock(request.pieceIndex, request.offset, request.length);
                 emit dataRead(request.id, request.pieceIndex, request.offset, block);
             }

             // Write pending write requests
             mutex.lock();
             QList<WriteRequest> newWriteRequests = writeRequests;
             writeRequests.clear();
             while (!quit && !newWriteRequests.isEmpty()) {
                 WriteRequest request = newWriteRequests.takeFirst();
                 writeBlock(request.pieceIndex, request.offset, request.data);
             }

             // Process pending verification requests
             if (startVerification) {
                 newPendingVerificationRequests = pendingVerificationRequests;
                 pendingVerificationRequests.clear();
                 verifyFileContents();
                 startVerification = false;
             }
             mutex.unlock();
             newPendingVerificationRequests.clear();

         } while (!quit);

         // Write pending write requests
         mutex.lock();
         QList<WriteRequest> newWriteRequests = writeRequests;
         writeRequests.clear();
         mutex.unlock();
         while (!newWriteRequests.isEmpty()) {
             WriteRequest request = newWriteRequests.takeFirst();
             writeBlock(request.pieceIndex, request.offset, request.data);
         }
     }

     void FileManager::startDataVerification()
     {
         QMutexLocker locker(&mutex);
         startVerification = true;
         cond.wakeOne();
     }

     bool FileManager::generateFiles()
     {
         numPieces = -1;

         // Set up the thread local data
         if (metaInfo.fileForm() == MetaInfo::SingleFileForm) {
             QMutexLocker locker(&mutex);
             MetaInfoSingleFile singleFile = metaInfo.singleFile();

             QString prefix;
             if (!destinationPath.isEmpty()) {
                 prefix = destinationPath;
                 if (!prefix.endsWith("/"))
                     prefix += "/";
                 QDir dir;
                 if (!dir.mkpath(prefix)) {
                     errString = tr("Failed to create directory %1").arg(prefix);
                     emit error();
                     return false;
                 }
             }
             QFile *file = new QFile(prefix + singleFile.name);
             if (!file->open(QFile::ReadWrite)) {
                 errString = tr("Failed to open/create file %1: %2")
                             .arg(file->fileName()).arg(file->errorString());
                 emit error();
                 return false;
             }

             if (file->size() != singleFile.length) {
                 newFile = true;
                 if (!file->resize(singleFile.length)) {
                     errString = tr("Failed to resize file %1: %2")
                                 .arg(file->fileName()).arg(file->errorString());
                     emit error();
                     return false;
                 }
             }
             fileSizes << file->size();
             files << file;
             file->close();

             pieceLength = singleFile.pieceLength;
             totalLength = singleFile.length;
             sha1s = singleFile.sha1Sums;
         } else {
             QMutexLocker locker(&mutex);
             QDir dir;
             QString prefix;

             if (!destinationPath.isEmpty()) {
                 prefix = destinationPath;
                 if (!prefix.endsWith("/"))
                     prefix += "/";
             }
             if (!metaInfo.name().isEmpty()) {
                 prefix += metaInfo.name();
                 if (!prefix.endsWith("/"))
                     prefix += "/";
             }
             if (!dir.mkpath(prefix)) {
                 errString = tr("Failed to create directory %1").arg(prefix);
                 emit error();
                 return false;
             }

             foreach (const MetaInfoMultiFile &entry, metaInfo.multiFiles()) {
                 QString filePath = QFileInfo(prefix + entry.path).path();
                 if (!QFile::exists(filePath)) {
                     if (!dir.mkpath(filePath)) {
                         errString = tr("Failed to create directory %1").arg(filePath);
                         emit error();
                         return false;
                     }
                 }

                 QFile *file = new QFile(prefix + entry.path);
                 if (!file->open(QFile::ReadWrite)) {
                     errString = tr("Failed to open/create file %1: %2")
                                 .arg(file->fileName()).arg(file->errorString());
                     emit error();
                     return false;
                 }

                 if (file->size() != entry.length) {
                     newFile = true;
                     if (!file->resize(entry.length)) {
                         errString = tr("Failed to resize file %1: %2")
                                     .arg(file->fileName()).arg(file->errorString());
                         emit error();
                         return false;
                     }
                 }
                 fileSizes << file->size();
                 files << file;
                 file->close();

                 totalLength += entry.length;
             }

             sha1s = metaInfo.sha1Sums();
             pieceLength = metaInfo.pieceLength();
         }
         numPieces = sha1s.size();
         return true;
     }

     QByteArray FileManager::readBlock(int pieceIndex, int offset, int length)
     {
         QByteArray block;
         qint64 startReadIndex = (quint64(pieceIndex) * pieceLength) + offset;
         qint64 currentIndex = 0;

         for (int i = 0; !quit && i < files.size() && length > 0; ++i) {
             QFile *file = files[i];
             qint64 currentFileSize = fileSizes.at(i);
             if ((currentIndex + currentFileSize) > startReadIndex) {
                 if (!file->isOpen()) {
                     if (!file->open(QFile::ReadWrite)) {
                         errString = tr("Failed to read from file %1: %2")
                             .arg(file->fileName()).arg(file->errorString());
                         emit error();
                         break;
                     }
                 }

                 file->seek(startReadIndex - currentIndex);
                 QByteArray chunk = file->read(qMin<qint64>(length, currentFileSize - file->pos()));
                 file->close();

                 block += chunk;
                 length -= chunk.size();
                 startReadIndex += chunk.size();
                 if (length < 0) {
                     errString = tr("Failed to read from file %1 (read %3 bytes): %2")
                                 .arg(file->fileName()).arg(file->errorString()).arg(length);
                     emit error();
                     break;
                 }
             }
             currentIndex += currentFileSize;
         }
         return block;
     }

     bool FileManager::writeBlock(int pieceIndex, int offset, const QByteArray &data)
     {
         qint64 startWriteIndex = (qint64(pieceIndex) * pieceLength) + offset;
         qint64 currentIndex = 0;
         int bytesToWrite = data.size();
         int written = 0;

         for (int i = 0; !quit && i < files.size(); ++i) {
             QFile *file = files[i];
             qint64 currentFileSize = fileSizes.at(i);

             if ((currentIndex + currentFileSize) > startWriteIndex) {
                 if (!file->isOpen()) {
                     if (!file->open(QFile::ReadWrite)) {
                         errString = tr("Failed to write to file %1: %2")
                             .arg(file->fileName()).arg(file->errorString());
                         emit error();
                         break;
                     }
                 }

                 file->seek(startWriteIndex - currentIndex);
                 qint64 bytesWritten = file->write(data.constData() + written,
                                                   qMin<qint64>(bytesToWrite, currentFileSize - file->pos()));
                 file->close();

                 if (bytesWritten <= 0) {
                     errString = tr("Failed to write to file %1: %2")
                                 .arg(file->fileName()).arg(file->errorString());
                     emit error();
                     return false;
                 }

                 written += bytesWritten;
                 startWriteIndex += bytesWritten;
                 bytesToWrite -= bytesWritten;
                 if (bytesToWrite == 0)
                     break;
             }
             currentIndex += currentFileSize;
         }
         return true;
     }

     void FileManager::verifyFileContents()
     {
         // Verify all pieces the first time
         if (newPendingVerificationRequests.isEmpty()) {
             if (verifiedPieces.count(true) == 0) {
                 verifiedPieces.resize(sha1s.size());

                 int oldPercent = 0;
                 if (!newFile) {
                     int numPieces = sha1s.size();

                     for (int index = 0; index < numPieces; ++index) {
                         verifySinglePiece(index);

                         int percent = ((index + 1) * 100) / numPieces;
                         if (oldPercent != percent) {
                             emit verificationProgress(percent);
                             oldPercent = percent;
                         }
                     }
                 }
             }
             emit verificationDone();
             return;
         }

         // Verify all pending pieces
         foreach (int index, newPendingVerificationRequests)
             emit pieceVerified(index, verifySinglePiece(index));
     }

     bool FileManager::verifySinglePiece(int pieceIndex)
     {
         QByteArray block = readBlock(pieceIndex, 0, pieceLength);

         SHA1Context sha;
         SHA1Reset(&sha);
         SHA1Input(&sha, (const unsigned char *)block.constData(), block.size());
         SHA1Result(&sha);

         QByteArray sha1Sum(20, ' ');
         unsigned char *digest = (unsigned char *)sha.Message_Digest;
         for (int i = 0; i < 5; ++i) {
     #if Q_BYTE_ORDER == Q_BIG_ENDIAN
             sha1Sum[i * 4 + 3] = digest[i * 4 + 3];
             sha1Sum[i * 4 + 2] = digest[i * 4 + 2];
             sha1Sum[i * 4 + 1] = digest[i * 4 + 1];
             sha1Sum[i * 4 + 0] = digest[i * 4 + 0];
     #else
             sha1Sum[i * 4 + 0] = digest[i * 4 + 3];
             sha1Sum[i * 4 + 1] = digest[i * 4 + 2];
             sha1Sum[i * 4 + 2] = digest[i * 4 + 1];
             sha1Sum[i * 4 + 3] = digest[i * 4 + 0];
     #endif
         }

         if (sha1Sum != sha1s.at(pieceIndex))
             return false;
         verifiedPieces.setBit(pieceIndex);
         return true;
     }

     void FileManager::wakeUp()
     {
         QMutexLocker locker(&mutex);
         wokeUp = false;
         cond.wakeOne();
     }