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Reading a file with Qt

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  • SamurayHS Offline
    SamurayHS Offline
    SamurayH
    wrote on last edited by
    #4

    Hi @EL-jos,
    Be sure that your paquet contains the file's content, the problem could be with qDebug or the QtCreator's console.If you want to check that out you can use qlabel or qtextBrowser (it will consume some cpu for larger files), or QByteArray::mid.

    QLabel *label = new QLabel(paquet);
    label->showMaximized();
    //--------------------------
    qDebug() << paquet.mid(0,100);
    

    I don't know if it's a length limitation by qDebug, but I don't think so since it isn't mentioned in the documentation.
    You're not the first one, check out that thread to, I took the second line of code from it.

    "قال رسول الله صلى الله عليه وسلم : " أحب الناس إلى الله أنفعهم للناس

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    • M Offline
      M Offline
      mchinand
      wrote on last edited by
      #5

      What is the size of paquet after you have read from your file? Does it match the size of the file in bytes? qDebug() has a limited buffer that is probably the issue in this case. Is there other processing of this data that you do after reading it in? Does that still work? Also, if you are reading in a text file, you might want to use QTextStream instead of QByteArray.

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      • Christian EhrlicherC Offline
        Christian EhrlicherC Offline
        Christian Ehrlicher
        Lifetime Qt Champion
        wrote on last edited by
        #6

        @EL-jos said in Reading a file with Qt:

            while(!fichier.atEnd()){
        
                paquet = fichier.readAll();// full reading of our byte file
            }
        

        When here readAll() does not return the complete content with the first call, you will not read all... you want paquet += ...

        Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
        Visit the Qt Academy at https://academy.qt.io/catalog

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        5
        • E Offline
          E Offline
          EL-jos
          wrote on last edited by
          #7

          Thanks for your help because I just noticed that my file was serialized in the QByteArray except the console could not display it in its entirety because of its buffer.

          But there is a new problem: when I try to send my QByteArray that contains my serialize file, when the QByteArray arrives at the server it loses all its data so its bytes.

          Please how to fix this problem?
          Knowing that I use the TCP protocol.

          JonBJ 1 Reply Last reply
          0
          • E EL-jos

            Thanks for your help because I just noticed that my file was serialized in the QByteArray except the console could not display it in its entirety because of its buffer.

            But there is a new problem: when I try to send my QByteArray that contains my serialize file, when the QByteArray arrives at the server it loses all its data so its bytes.

            Please how to fix this problem?
            Knowing that I use the TCP protocol.

            JonBJ Offline
            JonBJ Offline
            JonB
            wrote on last edited by
            #8

            @EL-jos
            From the information you've supplied on the new problem, I would guess some code is wrong somewhere.

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            • E Offline
              E Offline
              EL-jos
              wrote on last edited by
              #9

              Here's my code on the client side:

              void Controleur::on_pushButton_clicked()
              {
                  QString chemin = QFileDialog::getOpenFileName(this,"Chemin du fichier");
                  cheminFichier->setText(chemin);
              
                  QFile fichier(chemin);
                  QFileInfo info(fichier);
                  QString extension = info.suffix();
              
                  if(fichier.exists()){
              
                     qDebug() <<"LE fichier existe bel est bienet et voici son extension: " << extension;
              
                     int reponse = QMessageBox::question(this,"Confirmation d'envie du fichier", "êtes-vous sûr d'<strong>envoyer</strong> le fichier: " + fichier.fileName(), QMessageBox::Yes | QMessageBox::No);
                     if(reponse == QMessageBox::Yes){
              
                         qDebug("Donc vous souhaitez envoyer le fichier dans le réseau.");
              
                         fichier.open(QIODevice::ReadOnly);
                         if(fichier.isOpen()){
              
                             qDebug() << "Fichier ouvert et voici le nom: " << fichier.fileName();
              
                             QByteArray paquetFichier;
              
                             while(!fichier.atEnd()){
              
                                 paquetFichier = fichier.readAll();// lecture entier de notre fichier en octet
                             }
              
                             fichier.close();
              
                             if(!paquetFichier.isEmpty()){
              
                                qDebug() << "Les données ont été bien sérialiser dans le paquet en octets.";
                                qDebug() << paquetFichier;
                             }
              
              
                             QByteArray paquetEnvoieFichier;
                             QDataStream outFichier(&paquetEnvoieFichier,QIODevice::WriteOnly);
              
                             outFichier << (quint16) 0;
                             outFichier << (quint16) 6;
                             outFichier << extension;
                             outFichier << paquetFichier;
                             outFichier.device()->seek(0);
                             outFichier << (quint16) (paquetEnvoieFichier.size() - sizeof(quint16));
                             m_client->getSocket()->write(paquetEnvoieFichier);
                         }// Fin fichier isOpen
                        } // Fin MessageBox::YES
                     } // Fin si le fichier existe
              }
              
              

              and this is the one for reading

              if(id == (quint16) 6){
              
                      qDebug() << "réception d'un fichier venant du serveur.";
              
                      QString extension;
                      QByteArray  paquetReception;
              
                      in >> extension;
                      in >> paquetReception;
              
                      qDebug() << "voici l'extension du fichier: " << extension <<" le paquet est: " <<paquetReception;
              
                      QFile fichier("AutreFichier."+ extension);
                      fichier.open(QIODevice::WriteOnly);
              
                      if(fichier.isOpen()){
              
                          qDebug("Le fichier de la copie se -t- ouvert en écriture seul.");
                          qDebug() << "avec l'extension: " + extension;
              
                          QDataStream outAutreFichier(&fichier);
                          outAutreFichier << paquetReception;
                      }
              
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              • Christian EhrlicherC Offline
                Christian EhrlicherC Offline
                Christian Ehrlicher
                Lifetime Qt Champion
                wrote on last edited by
                #10

                My comment is still not fixed... and now - what do you think will happen when your file size is greater than 65535 bytes?

                outFichier << (quint16) (paquetEnvoieFichier.size() - sizeof(quint16));
                And then you don't write the data directly to a file but stream it as QDataStream - this will add some more information in the front which is definitly not what you want... use
                QFile::write(QByteArray())

                And when sending data via network, readyRead() will for sure not contain the whole content - at least not when you're sending 6MB. Please take a look at the QTcpServer/Client examples (and avoid using QDataStream here - it's not needed at all...)

                Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                Visit the Qt Academy at https://academy.qt.io/catalog

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                • E Offline
                  E Offline
                  EL-jos
                  wrote on last edited by
                  #11

                  Yes I have this problem because I noticed that if my file size is larger than 65535 bytes, the server does not receive all the information. But how do we solve this problem?

                  Then if I use Qdatastream this to first write the identifier of my message because the one that says if it is a text message (5), if it is a new connection (3), if it is a disconnect (4) and for the file the identifier value is (7) to tell the server that it is a file. Here the QDATASTREAM allows me to write a screen like this:

                  *Message size

                  *Identifier

                  *Message

                  So if I don't use a Qdatastream how can I write in my QByteArray?

                  Translated with www.DeepL.com/Translator

                  aha_1980A 1 Reply Last reply
                  0
                  • E EL-jos

                    Yes I have this problem because I noticed that if my file size is larger than 65535 bytes, the server does not receive all the information. But how do we solve this problem?

                    Then if I use Qdatastream this to first write the identifier of my message because the one that says if it is a text message (5), if it is a new connection (3), if it is a disconnect (4) and for the file the identifier value is (7) to tell the server that it is a file. Here the QDATASTREAM allows me to write a screen like this:

                    *Message size

                    *Identifier

                    *Message

                    So if I don't use a Qdatastream how can I write in my QByteArray?

                    Translated with www.DeepL.com/Translator

                    aha_1980A Offline
                    aha_1980A Offline
                    aha_1980
                    Lifetime Qt Champion
                    wrote on last edited by
                    #12

                    Hi @EL-jos,

                    What do you want to do exactly?

                    For file transfer, decicated protocols exists, e.g. FTP or HTTP. To me it looks like your are re-inventing the wheel?

                    Regards

                    Qt has to stay free or it will die.

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                    0
                    • E Offline
                      E Offline
                      EL-jos
                      wrote on last edited by EL-jos
                      #13

                      Concretely I want my client to send a file to my server and the server after receiving the file, that it sends this file to all the client that are connected to it.
                      Because it is a chat software then I also want the client to be able to send a file to another client via a server.

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                      • Christian EhrlicherC Offline
                        Christian EhrlicherC Offline
                        Christian Ehrlicher
                        Lifetime Qt Champion
                        wrote on last edited by
                        #14

                        Please take a look at the examples (again...) how to send large data ... http://doc.qt.io/qt-5/qtnetwork-loopback-example.html

                        Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                        Visit the Qt Academy at https://academy.qt.io/catalog

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                        2
                        • E Offline
                          E Offline
                          EL-jos
                          wrote on last edited by
                          #15

                          Okay Thanks, I'll read this example and then I'll come back to you to give you the follow-up.

                          Thank you

                          1 Reply Last reply
                          0
                          • E Offline
                            E Offline
                            EL-jos
                            wrote on last edited by
                            #16

                            Hi,
                            after several studies of the example given by the Qt documentation, I don't know where and how to send my file to the server?

                            then in the example given by the Qt documentation, just sends the same 64KB packet several times until it tints 50MB . and the server and the client are in the same project but in my case the client and the server are different projects

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                            • SGaistS Offline
                              SGaistS Offline
                              SGaist
                              Lifetime Qt Champion
                              wrote on last edited by
                              #17

                              Hi,

                              Are you writing both the client and server parts ?

                              Interested in AI ? www.idiap.ch
                              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                              0
                              • E Offline
                                E Offline
                                EL-jos
                                wrote on last edited by
                                #18

                                Yes, do you want me to mail them?

                                1 Reply Last reply
                                0
                                • SGaistS Offline
                                  SGaistS Offline
                                  SGaist
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #19

                                  It was regarding your last remark about the server and client being in the same project. Since you are writing both, then it doesn't matter that they are in different projects.

                                  Interested in AI ? www.idiap.ch
                                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  1 Reply Last reply
                                  1
                                  • E Offline
                                    E Offline
                                    EL-jos
                                    wrote on last edited by
                                    #20

                                    Hey, everybody,

                                    Still in the example given by the Qt documentation for the exchange of large documents between the client and the server in a chatt software, I could separate the client and the server in different projects which is not the case in the example given by the Qt documentation.

                                    So here's my question:

                                    Just that there I do not know how to adapt this example to my chatt software to be able to send large files between client and server?

                                    Translated with www.DeepL.com/Translator

                                    1 Reply Last reply
                                    0
                                    • SGaistS Offline
                                      SGaistS Offline
                                      SGaist
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #21

                                      There's nothing special to do, if you implement the client and the server the same way as the exemple, then it's also going to work the same.

                                      Interested in AI ? www.idiap.ch
                                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                      0
                                      • E Offline
                                        E Offline
                                        EL-jos
                                        wrote on last edited by
                                        #22

                                        Theoretically yes, but in practice this is not the case.

                                        mrjjM 1 Reply Last reply
                                        0
                                        • E EL-jos

                                          Theoretically yes, but in practice this is not the case.

                                          mrjjM Offline
                                          mrjjM Offline
                                          mrjj
                                          Lifetime Qt Champion
                                          wrote on last edited by
                                          #23

                                          @EL-jos
                                          Hi
                                          As mr @Christian-Ehrlicher noted higher up.
                                          You are using quint16 for size handling
                                          Try
                                          #include <limits.h>
                                          qDebug() << std::numeric_limits<quint16>::max();

                                          and you will see the magic 65535 as maximum value.

                                          1 Reply Last reply
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