Re: Convert CString to LONG.

From:
"Giovanni Dicanio" <giovanni.dicanio@invalid.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
Thu, 26 Jun 2008 11:02:31 +0200
Message-ID:
<OMh1Hv21IHA.4572@TK2MSFTNGP03.phx.gbl>
"Control Freq" <nick@nhthomas.freeserve.co.uk> ha scritto nel messaggio
news:347dfda4-8d31-46c7-b3b6-37abf7e8d432@y38g2000hsy.googlegroups.com...

   // Get user input.
   TCHAR Command[100];
   cin.getline(Command, sizeof(Command), '\n');


I think that istream::getline has char* as input parameter.
So, the correct and coherent way should be:

  char Command[ 100 ];
  cin.getline( Command, sizeof( Command ) );

  // ... or you may want to use
  // _countof( Command ) which is == sizeof( Command )
  // in this case of char-based string

There is also a Unicode wide-version of istream: wistream.

....Actually, both istream and wistream are a template specialization of
basic_istream template:

  typedef basic_istream<wchar_t, char_traits<wchar_t> > wistream;

The Unicode version of cin is wcin.

There is also a std::getline function, to be used something like this:

  string command;
  getline( cin, command, '\n' );

The Unicode version should be:

  wstring command;
  getline( wcin, command, L'\n' );

   // Convert to a CString.
   CString Item(Command);


I think that CString has a conversion constructor, which takes a char string
and convert to TCHAR string (i.e. in Unicode builds, when TCHAR expands to
wchar_t, this constructor converts from const char * ANSI string to wchar_t
Unicode string).
So, the above code should be fine.

   TCHAR *StopString;
   // Try to convert to an integer.
   errno = 0;
   LONG Value = strtol(Item, &StopString, 10);


No, the above code is not Unicode-aware. If you use TCHAR, you should use
_tcstol instead of strtol (strtol is fine if you use char, not TCHAR).
So, you should have:

  long value = _tcstol( Item, &StopString, 10 );

     // Invalid argument, or out of range.
     cerr << endl << _T("Invalid. The number is out of range.") <<


If you use cerr, you should use ANSI strings, e.g.

  cerr << endl << "Invalid. The number is out of range."
         << endl << endl;

If you use wcerr, you can use Unicode strings (with L prefix).
The point is that the _T() decorator does not play well with C++ standard
library... it's more a Windows-specific stuff.

Another option would be to use sscanf (or Unicode-aware _stscanf):

<code>

  int ParseInt( LPCTSTR s )
  {
      ASSERT( s != NULL );
      int n;
      _stscanf( s, "%d", &n );

      ... check parsing error

      return n;
  }

  CString item;
  int n = ParseInt( item );

</code>

HTH,
Giovanni

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