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Help:C++ streams to access a binary file

• • Reply

  8 months ago

  by russbude

  Russell Brown

  Cornwall, United Kingdom

  Joined 11 months ago

  Can anybody help me!!  I am learning Visual C++ 6. I am trying to learn how to use C++ streams to store/retrieve variables of differing data types into/from a single binary file.

  A book which I have got about VC++ 6.0 mentions "Serialization of application".  In it, you create an AppWizard application giving your application name "Serialize". The application is a SDI application using Document/View architecture where the view class is based on CFormView class.

   I have created my own custom class called CPerson (a generic class) with its base class CObject so that I can hold the class in an object array. After that, I have made the class serializable as follows:

       class CPerson: public COject

       {   DECLARE_SERIAL (CPerson)

          private:   int m_iAge;  CString m_sName;

          public:

                void Serialize(CArchive &ar) {

                           CObject::Serialize(ar);

                           if (ar.IsStoring()) ar << m_sName << m_iAge;

                          else ar >> m_sName >> m_iAge;

                 }

       };

   

  Then in the header for the document class (i.e. SerializeDoc.h), I have declared the variables as follows:

       class SerializeDoc: public CDocument

       {     private:  CObArray m_oaPeople; int m_iCurPosition;

             public:

                 void   Serialize(CArchive &ar) { //Pass the serialization on to the object array

                              m_oaPeople.Serialize(ar);

                  }

        };

   

  My application creates CPerson objects in the document (object) and add them to the object array as follows:

           CPerson  *pPerson = new CPerson();

                        :

           m_oaPeople.Add(pPerson);

                       :

  With a SDI or MDI application, the functionality to save, open a file and exit the window is located on the application menu.  So it seems that I do not have to write such functionlity to do them myself.

  Question)

  Is there a way to give a file a name myself (a binary file), open/create it and then save or retrieve variables of different data types into or from it, without relying on the application menus?  Like fopen(), fclose(), fread(), fwrite() and so on as in C? What I mean is "How can I open/create/read/write/close a file in VC++ as we do in C using streams?"   How can I save or retrieve the data into or from a single binary file, if I disable the application menus (in a SDI application) which allow me to open or save a file?

   

   

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• • Reply

  8 months ago

  by Mohammad Rastkar

  Mohammad Rastkar

  Shiraz, Iran

  Joined 2 years ago

  Hi Chong,

  This approach, uses 'CArchive' and 'CFile' classes (you don't need to include anything). An example will show that all :

  • Save to a file :

  {

  CFile f1( "c:\\test.dat", CFile::modeCreate | CFile::modeWrite );

  CArchive ar1( &f1, CArchive::store );

   

  int num = 58;

  CString str( "String" ); ar1 << num << str;

   

  ar1.Close();

  f1.Close();

  }

  • Load from a file :

  {

  f1.Open ( "c:\\test.dat", CFile::modeRead );

  CArchive ar2( &f1, CArchive::load );

   

  int num;

  CString str;

  ar2 >> num >> str;

   

  ar2.Close();

  f1.Close();

  }

  • Remove/Rename a file :

  You can use static functions of class 'CFile' to remove/rename files :

  CFile::Remove( "c:\test.dat" );

  CFile::Rename( "c:\old.dat", "c:\new.dat" );

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• • Reply

  8 months ago

  by russbude

  Russell Brown

  Cornwall, United Kingdom

  Joined 11 months ago

  Hi my friend Mohammad

  Thanks for helping me once again.  I need your advice once again.  Using the instructions which you have given me, I have wrriten a code to read a file.  The code is below!!  I am wondering  if there are other ways to read a file!!  If you do know them, could you let me know.

  All the best

  Chong

  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

  {

  //To read a file to the end of it 

  CFile rfile("test.dat",CFile::modeRead);

  CArchive ar(&rfile, CArchive::load);

  CString sName[SomeLargeNumber];

  int iAge[SomeLargeNumber];

  int i = 0;

  try {

       while (TRUE) {

            ar >> sName[i] >> iAge[i++];

       } // while

  } // try

   

  catch (CArchiveException *e) {

       if (e->m_cause == CArchiveException::endOfFile) {

            AfxMessageBox("File has been read");

       } else

            AfxMessageBox("Something is wrong");

       e->Delete( );

  }  //catch

  ar.Close( );

  rfile.Close( );

      :

  }

  ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

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• • Reply

  8 months ago

  by Mohammad Rastkar

  Mohammad Rastkar

  Shiraz, Iran

  Joined 2 years ago

  Please read my article :

  File Handling in VC++6

  Great Times!

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