i want to add a file to json structure and send it,i want to add that file to json using json array for example i reading file as binary an append to json array(use this code) :
Qt Code: 
  1. void send_file(QString file_path)
  2. {
  3.     cout<<"SEND FILE: "<<file_path.toStdString()<<"\n";
  4.  
  5.     QFile i_file(file_path.remove(file_path.count()-1,1));
  6.     i_file.open(QIODevice::ReadOnly);
  7.     if (i_file.isOpen())
  8.     {
  9.         QJsonObject packet;
  10.         packet["message_type"]="ANSWER_PACKET";
  11.         packet["sender"]=mac_address;
  12.         packet["reciver"]="control_panel";
  13.         packet["answer_type"]="PRIVATE";
  14.         packet["what"]="send_file";
  15.         packet["file_type"]="GENERAL";
  16.         packet["file_path"]=file_path;
  17.         QDataStream i_file_stream(&i_file);
  18.         QJsonArray i_array;
  19.         while (!i_file.atEnd())
  20.         {
  21.             int len=1048576;
  22.             char char_buffer[len];
  23.             int size_read=i_file_stream.readRawData(char_buffer,len);
  24.             if (size_read>0)
  25.             {
  26.                 QByteArray temp(char_buffer,size_read);
  27.                 i_array.append(temp.constData());
  28.             }
  29.         }
  30.  
  31.         packet["file_content"]=i_array;
  32.         QJsonDocument json_doc(packet);
  33.         QByteArray buffer=json_doc.toJson();
  34.  
  35.         cout<<QString(buffer).toStdString()<<"\n";
  36.         i_file.close();
  37.        send_packet(buffer);
  38.  
  39.     }
  40. }
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now,in another hand i using this code for deserializing and writing file:
Qt Code: 
  1. void settings_frame_widget::save_file(QJsonObject packet)
  2. {
  3.     QJsonArray i_array =packet["file_content"].toArray();
  4.     QByteArray file_buffer;
  5.  
  6.     foreach (QJsonValue item, i_array)
  7.     {
  8.         QByteArray temp=item.toVariant().toByteArray();
  9.         file_buffer.append(temp);
  10.     }
  11.     //Write File:
  12.     if (download_address!=QString())
  13.     {
  14.         QFile i_file(download_address);
  15.         i_file.open(QIODevice::WriteOnly);
  16.         if (i_file.isOpen())
  17.         {
  18.             QDataStream file_stream(&i_file);
  19.             file_stream<<file_buffer;
  20.         }
  21.         QMessageBox msgbox;
  22.         msgbox.setText("Download Finish!");
  23.         msgbox.exec();
  24.         i_file.close();
  25.         download_address=QString();
  26.     }
  27. }
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for example when i send sequential file like this:
Qt Code: 
  1. {
  2. 	"res1":{
  3. 		"isError":false,
  4. 		"key":"1234566",
  5. 		"data":{
  6. 			"messages":"O.K!"
  7. 		}
  8. 	}
  9. }
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when recive it and write to file , see a slacks byte in first of file,like this:
slack.jpg
this sudden cause of random access file is damaged...
what's the problem!?