C / C++ / MFC

Le@rner wrote:

but when i open the file the content inside it is

Apþÿÿ ?ñÔÈSû! @

CStdioFile file;
CFileException e;
if(!file.Open(_T("C:\\file.txt"), CFile::modeCreate | CFile::modeWrite | CFile::typeText, &e))
{
	TRACE(_T("File could not be opened %d\n"), e.m_cause);
}
else
{
        char c = 'A';
	int i = -400;
	float f = 1.25f;
	double d = 3.14159265;
	
        CString str;
	str.Format(_T("%c %d %f %f"), c, i, f, d);
	
        file.WriteString(str);
	file.Close();
}

#include <fstream>

// Deal with both Unicode and Non-Unicode builds
#ifdef _UNICODE
	#define _tofstream std::wofstream
#else
	#define _tofstream std::ofstream
#endif

........

char c = 'A';
int i = -400;
float f = 1.25f;
double d = 3.14159265;
	
_tofstream fout;
fout.open(_T("C:\\file.txt"));
fout << c << _T(" ")<< i << _T(" ") << f << _T(" ")<< d;
fout.close();

Bram van Kampen wrote:

Then I placed the module containing the Above Code in a DLL, and CreateMutex never Fails

krmed wrote:

Calling GetLastError when the call did not fail is not recommended - the error code that you get will probably be from the last failed action.
You should only call GetLastError if the CreateMutex call failed - then it will give you a reliable error code.

krmed wrote:

Many users call GetLastError after calling other methods that don't set it unless there's an error.

krmed wrote:

Sorry about that.

Rajesh R Subramanian wrote:

Well, the call won't fail (the return value won't be NULL). It rather returns a handle to the existing mutex object. However, if you make an immediate call to GetLastError() (which you should do), you'd see that the error code has been set to ERROR_ALREADY_EXISTS.

Bram van Kampen wrote:

Why do you respond twice to this post!

Bram van Kampen wrote:

CString AppName=GetAppNameRoot();

Migounette wrote:

What is the goal of your mutex ?
Prevent multiple loads of the DLL or block for security reasons ?

Tell me more...

<br />
DLLEXPORT void OnceOnly(){<br />
// Protect against Two Instances on the Same Computer!<br />
        CString AppName=GetAppRootName();<br />
        CString MutexName=AppName+SG_UID;<br />
	<br />
        HANDLE exclusion = CreateMutex(NULL, FALSE, MutexName);<br />
     DWORD err = ::GetLastError();<br />
     if(err != 0){<br />
		 if(err == ERROR_ALREADY_EXISTS){<br />
			 CString Message;<br />
			 Message.Format("There is already an Instance of '%s' Running on This Computer\n\n"<br />
					 "Activate the Existing Instance instead",(LPCSTR)AppName);<br />
	    		 AfxMessageBox(Message);<br />
				 exit(0);<br />
		 }<br />
		 else{<br />
			 AfxMessageBox("An Error occurred whilst checking that No other instance of\n"<br />
				 "this program is running\n");<br />
			 exit(-1);<br />
		} // error <br />
	 }<br />