C / C++ / MFC

3-Oct-01 10:39

Another wild guess Wink | ;)

Have you been playing around with the schema number in the IMPLEMENT_SERIAL macro? There's an MSDN article that says something about a bug relating to using a schema number 0.
Maybe you can try to switch to another schema number and see what happens.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Deleting a file

RobJones3-Oct-01 9:28

3-Oct-01 9:28

Is their a good way to check if a file exists?

I have a application that creates a text file called source.txt and once an event takes place I remove it.. the problem is if something happens and for some reason the file doesn't get created it pops up an error stating that the file doesn't exist.. I was wondering what the best way would be to do a "if exists" delete it "if not" pop up a msg stating that something went wrong..

Thanks, Big Grin | :-D

Rob

Joaquín M López Muñoz3-Oct-01 9:46

3-Oct-01 9:46

Use DeleteFile(); it the file does not exist, the function returns FALSE and GetLastError() yields ERROR_FILE_NOT_FOUND.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Joaquín M López Muñoz3-Oct-01 9:48

3-Oct-01 9:48

Check also ERROR_PATH_NOT_FOUND and ERROR_ACCESS_DENIED

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

RobJones3-Oct-01 11:39

3-Oct-01 11:39

Is this a good way of implementing what you have suggested?

DeleteFile("Source.txt");
DeleteFile("Time.txt");

DWORD dw = GetLastError(); 
if(GetLastError() != FALSE)
{
	MessageBox("File Not Found!","Error", MB_OK);
}

It seems to work ok.

Thanks

Rob

Joaquín M López Muñoz3-Oct-01 11:58

3-Oct-01 11:58

Is this a good way of implementing what you have suggested?

No, it is not. DeleteFile() returns either TRUE or FALSE, and only in the latter case can you use GetLastError() to know the detailed cause of the failure:

BOOL bResult=DeleteFile("Source.txt");
if(!bResult){
  DWORD dw=GetLastError();
  if(dw==ERROR_FILE_NOT_FOUND){
    MessageBox("File Not Found!","Error", MB_OK);
  }
  else{
    // DeleteFile failed, but it was not because the file didn't
    // exist. Other expected results are ERROR_PATH_NOT_FOUND and
    // ERROR_ACCESS_DENIED, though you cannot in general assume
    // that the error code will be always one of these.
    // Do whatever you consider appropriate in this situtation
  }
}

This way of signaling errors (i.e., returning a BOOL and storing in case of failure an error code to be retrieved with GetLastError() ) is typical of many Win32 functions, so you might find it useful to get acquantied with it.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

RobJones3-Oct-01 12:53

3-Oct-01 12:53

Thank you very much! I'm pretty new to programing and this kind of information helps alot!!!

Thanks again for you time,
Big Grin | :-D

Rob

Bernhard3-Oct-01 23:26

Bernhard

3-Oct-01 23:26

http://www.codeproject.com/useritems/cwin32error.asp

that's an article bout how you can handle GetLastError Message.. i think it is a really interesting discussion in the discussion below the article.. maybe your interested..

happy learning

bernhard

stolen sig #15:
"The content of this post is not necessarily the opinion of my yadda yadda yadda."

RobJones4-Oct-01 7:10

How do I get a process' opened files names

4-Oct-01 7:10

Thanks!!

I will take a look at the article.. I'm very interested in learning anything new.

Thanks again,

Rob

Saving file with MCI

3-Oct-01 9:16

I have a subroutine in a Visual C++ program using Microsoft's MCI that
records to a file named dummy.wav that already exists on C drive. If the
program is also on C drive all works well. However, if I put the program
on D drive, but still leave dummy.wav on C drive, the subroutine opens
c:\dummy.wav but will not save to it the first time the subroutine is
called. Instead it writes a temporary file of the type ~$mc331C.tmp to the
root of C. On calling the subroutine a second time, it works properly. MCI
does not report any errors when the subroutine is run. Can anyone explain
why it doesn't work the on the first call?

char strcmd[100];

wsprintf(strcmd,"open %s %s","c:\\dummy.wav","wait");
if (mciSendString(strcmd,NULL,NULL,NULL))
AfxMessageBox("error opening dummy.wav",MB_OK,NULL);

wsprintf(strcmd,"record %s %s %s","c:\\dummy.wav","from 0 overwrite to 1000","wait");
if (mciSendString(strcmd,NULL,NULL,NULL))
AfxMessageBox("error recording dummy.wav",MB_OK,NULL);

wsprintf(strcmd,"save %s %s","c:\\dummy.wav","wait");
if(mciSendString(strcmd,NULL,NULL,NULL))
AfxMessageBox("error saving dummy.wav",MB_OK,NULL);

wsprintf(strcmd,"close %s %s","c:\\dummy.wav", "wait");
if (mciSendString(strcmd,NULL,NULL,NULL))
AfxMessageBox("error closing dummy.wav",MB_OK,NULL);

Note: if I execute the program with a .pif style shortcut, the behaviour is
as described above, except that when I quit the program and then restart it,
it works properly on the first call to the subroutine, unless I reboot the
computer. However, if I execute the program with a standard Win98 or Me
shortcut, the call to the subroutine fails on the first try and succeeds on
subsequent calls every time the program is executed from the shortcut icon.

Le centriste3-Oct-01 9:03

Le centriste

3-Oct-01 9:03

I would like to be able to programmatically query a process' opened files (don't confuse with EnumProcessModules). I know it is possible (TaskInfo2000 does it). Can I do that using a Win32 or Shell function/object? I wasn't able to figure out yet.

Tx

Problem with CDaoRecordset "Too few parameters. Expected 1"

Cheickna3-Oct-01 8:21

Cheickna

3-Oct-01 8:21

Hi,

I Use Visual C++ 6.0 and an access Database.
I want to execute a SQL statement with CDaoRecordset. This error message occurs : "Too few parameters. Expected 1" when i use Open method.
My SQL statement is longer than 256 characters ( about 1100 ). The problem is here it seems.
If i run This query directly in Microsoft Access, it work.

Is there any method to execute un SQL Statement like this in DAO ( CDaoDatabase ) ???

Thanks in advance

Regards,

Re: Problem with CDaoRecordset "Too few parameters. Expected 1"

Carlos Antollini3-Oct-01 8:35

Carlos Antollini

3-Oct-01 8:35

Show me the line....

Cheers!!! Big Grin | :-D

Carlos Antollini.

How to check a FTP connection's validation?

Chaos Lawful3-Oct-01 6:46

Re: How to check a FTP connection's validation?

3-Oct-01 6:46

I use CFtpConnection to process FTP connections. But how can I check whether the connection is still opened when I get a CFtpConnection pointer? There will be many accidents to break the connection(The master closed the FTP server, net-wire broken, etc.). X|Show me some solutions, please.

Law is meaningless without chaos.
Chaos without Law is equal to destruction.
Chaos and Law create our rich and colorful world.

Carlos Antollini3-Oct-01 8:37

Carlos Antollini

3-Oct-01 8:37

I had the same Problem, I found a solution, doing something over the FTP Server, like a change Dir, or a FindFile, etc...

Cheers!!! Big Grin | :-D

Carlos Antollini.

AfxbeginThread

meirav3-Oct-01 6:44

meirav

3-Oct-01 6:44

In an Mfc programm ( dialog based) i created a thread through the AfxBeginThread function .
I need that the specific class that was created will
get access to another class ( the main Dlg class)????

(i tried to use pointer but no good !)

meirav

Chaos Lawful3-Oct-01 6:56

3-Oct-01 6:56

You should not pass dialog pointer to the thread because it may be invalid. I think you can use GetSafeHwnd() to get the handle of the main dialog and pass it to the thread. In the thread you can use FromHandle() to get back the main dialog pointer and then you can access the main dialog class.
Here is an example:

UINT ThreadProc(LPVOID);// the thread proc

HWND hWnd; // for handle of main dialog

BOOL C???Dlg::OnInitDialog()
{
...// some codes
hWnd=GetSafeHwnd();
...// other codes
}

void C???Dlg::OnButton1() // Button1 is a sample button
{
AfxBeginThread(ThreadProc,NULL);
}

UINT ThreadProc(LPVOID lpData)
{
C???Dlg *pDlg=(C???Dlg*)C???Dlg::FromHandle(hWnd); // get the main dlg pointer
...// do what you want to do
}

You can also pass the handle through the thread proc's lpData pointer, then you don't have to declare the hWnd as a external variable. Smile | :)

Law is meaningless without chaos.
Chaos without Law is equal to destruction.
Chaos and Law create our rich and colorful world.

meirav3-Oct-01 19:53

meirav

3-Oct-01 19:53

Thank you for your answer,
i tried what you suggest me , but there is one problem:
when i pass the LPVOID to the ThreadProc (I did it on ThreadProc::InitInstance) using the debug i saw that he never get at all to this Function .
(without the LPVOID it did get there )
it will be a great help if you can help me.

Chaos Lawful3-Oct-01 19:56

3-Oct-01 19:56

Could you show me your codes? I think that would be a great help.;)

Law is meaningless without chaos.
Chaos without Law is equal to destruction.
Chaos and Law create our rich and colorful world.

meirav3-Oct-01 19:59

meirav

3-Oct-01 19:59

Hi,I did exacly the code you suggested in your reply above.
I can send the programm i did (it is very short ) if it is needed.

Chaos Lawful3-Oct-01 22:21