Re: reading string from a text file from vc++ without MFC support

From:

MrAsm <mrasm@usa.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Sat, 16 Jun 2007 07:01:36 GMT

Message-ID:

<9l0773dm3hbqp7eof8q5gdjrrngqekl4mk@4ax.com>

On Fri, 15 Jun 2007 22:28:32 -0700, rindam2002@yahoo.com wrote:

need need to again read the file.here is y code which is working fine
for writing to file:
                FILE *fp=NULL;
        fp=_wfopen(lstr,_T("w+"));//lstr is having the path to the file
        fwrite( strTitleCurrentDate, sizeof(TCHAR), strTitle.GetLength()/
** sizeof( TCHAR )*/, fp );
        fclose( fp );
this code is working fine but

The previous code is not good.

You are using _T and Unicode (_wfopen) in a wrong way.
_wfopen is the Unicode version of fopen, its prototype is:

FILE *_wfopen(
    const wchar_t *filename,
    const wchar_t *mode
);

So 'mode' is a Unicode string (wchar_t *) in _wfopen, so you should
use L"w+", not _T("w+"), with _wfopen.

Or, if you want to use Unicode-aware style consistently, you can
write:

  // Assume 'lstr' is a TCHAR-string (e.g. a CString)
  FILE * fp = _tfopen( lstr, _T("w+") );

Your original code would compile only in Unicode builds, but is
inconsistent with TCHAR convention.

Moreover, the fwrite line does not very much make sense:

fwrite( strTitleCurrentDate, sizeof(TCHAR), strTitle.GetLength()/
** sizeof( TCHAR )*/, fp );

You are writing 'strTitleCurrentData' characters, but you are giving
fwrite the length of 'strTitle'... are these variables the *same*
string? If so, why are you using two different variables for the same
string? The code is confusing...

Moreover, if 'strTitleCurrentDate' is of type CString, I would prefer
to explicitly cast to LPCTSTR to access string character pointer.

Finally, are you aware that you are writing only the string characters
but *no* the final _T('\0') of the string? In fact, GetLength returns
the number of TCHARs in the string, excluding the terminating
_T('\0').

CString strTitle1;
newBuffer=strTitle1.GetBuffer(strTitle1.GetLength()*
sizeof( TCHAR ));

'strTitle1' is initialized to an empty string by the default
constructor. So 'strTitle1.GetLength()' is 0, so you are passing 0 to
GetBuffer.
Is that what you really want??

LPTSTR lstr=strPath2.GetBuffer(strTitle.GetLength()* sizeof( TCHAR ));
FILE *fp=NULL;
fp=_wfopen(lstr,_T("a+"));

You have the same Unicode/_T (_wfopen/_T("a+")) mismatch as above.

while(!feof(fp))
fread( newBuffer, sizeof(char), 100/** sizeof( TCHAR )*/, fp );
fclose( fp );

You called GetBuffer above, but you didn't release the buffer with
ReleaseBuffer.
Moreover, where is the 'newBuffer' memory?
Where is defined that 'newBuffer' is 100 bytes?
Why are you using 'char' and not 'TCHAR'?

IMHO, the code has several inconsistent things...
You should really clean it up.

You might consider using more modern C++ I/O stream classes to manage
files; they are easier than C FILE*, are more robust (e.g. the
destructor will close the file, while with C FILE * you may forget to
call fclose, etc.)

If you want to write to a file, you may use code as follow:

  // Your file object
  std::ofstream file( "TheFileName.txt" );

  // You may check result with file.is_open()
  // if ( file.is_open() ...

  // Write to file:
  file << "This is the first line.\n";
  file << "Hello...\n";
  ... and so on

  // You may call file.close() or let the
  // class destructor close the file when
  // 'file' variable goes out of scope.

If you want to read from a file, line by line:

  std::string line;
  std::ifstream file("Data.txt");
  // if (! file.is_open()) --> error

  // Line reading loop
  while ( ! file.feof() )
  {
    std::getline( file, line );
    std::cout << "Line read: " << line << std::endl;
  }

  // file.close() or delegate to destructor

There is also the MFC CStdioFile class, but I would prefer a
substitute from CodeProject (or Tom's much better version):

http://www.codeproject.com/file/stdiofileex.asp

MrAsm