C / C++ / MFC

30-Jun-03 21:52

Hi Guys,
I am writing a windows service to start / stop certain utility applications. The utilities are in Vb (Please don't ask me why a background process was programmed in vb, I don't know that myself). I used CreateProcess to start them, that was fine.
Now the problem arises when I want to stop them. I can't use TerminateProcess because the applications may be in the middle of something and I want to wait till they finish the job at hand. So I decided to use messages.
I tried PostThreadMessage. The problem I have was that on the utilities' side, if I used GetMessage then it waits for the message which makes the application hang and if I used PeekMessage then in some cases it was missing the Message altogether.
Finally I thought of using a dummy subclassed form and sending the message to to form. It's working now, but it seems like a mess to me. I'm pretty sure there's a better way. Any suggestions?
thanks.
P

"It was when I found out I could make mistakes that I knew I was on to something."
-Ornette Coleman

Toni7830-Jun-03 22:03

30-Jun-03 22:03

Take a look two or three messages down "how do i Detect if an external program has finished excuting(shellexec)?" and read Rage's and cmk's messages. I think, they apply to you as well.

// Afterall, I realized that even my comment lines have bugs

When one cannot invent, one must at least improve (in bed).-My latest fortune cookie

parths30-Jun-03 22:09

30-Jun-03 22:09

I am waiting for them to finish.
Actually, I don't just want to wait for the programs to finish. I actually want to tell them to wrap up whatever they are doing and end.

"It was when I found out I could make mistakes that I knew I was on to something."
-Ornette Coleman

Ryan Binns30-Jun-03 22:53

Ryan Binns

30-Jun-03 22:53

PostThreadMessage()/PeekMessage() should work. Messages can not get lost if they're being sent to the correct thread, as long as you specify NULL (or 0 in VB) for the HWND parameter, and PM_REMOVE as the flags parameter. My VB is a bit rusty, but:

If PeekMessage(msg, 0, 0, 0, PM_REMOVE) = True Then
    If msg.message = MY_MESSAGE Then
        ExitProcess 0  ' Exit the process
    End If
End If

Where msg is the MSG structure variable and MY_MESSAGE is the value of the message that you are sending. I can't remember if the PM_REMOVE constant is declared like that, or whether it has a different name. Of course, if a different message is received, then it will need to be processed as well. If PeekMessage() returns False, then a message did not exist.

Hope this helps,

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

parths30-Jun-03 23:27

30-Jun-03 23:27

Thanks a lot. That's exactly what I had done.
But PeekMessage doesn't wait for the next message to arrive.
As a result, if the message arrives when the program might be in the middle of a transaction.
Could it be that by the time I call PeekMessage again the Message get processed (maybe by some default message handler which cannot comprehend the meaning of my user defined message?)

"It was when I found out I could make mistakes that I knew I was on to something."
-Ornette Coleman

Ryan Binns30-Jun-03 23:44

Ryan Binns

30-Jun-03 23:44

parths wrote:
But PeekMessage doesn't wait for the next message to arrive.

That's correct. If you need this, then you need to use GetMessage().

parths wrote:
Could it be that by the time I call PeekMessage again the Message get processed (maybe by some default message handler which cannot comprehend the meaning of my user defined message?)

Absolutely. If you're using more than one message loop, then you have to make sure all the message loops know about the message. It will probably be easier to code your main message loop similar to this:

Do While GetMessage(msg, 0, 0, 0) = True
    If msg.message = MY_MESSAGE Then
        ExitProcess 0
    Else
        TranslateMessage msg
        DispatchMessage msg
    End If
Loop

This should work (I think Wink | ;)

)

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

parths30-Jun-03 23:58

30-Jun-03 23:58

Thanks,
I had tried GetMessage, but then it doesn't return till it gets a message (any message) (right?), and that's a problem too because then I can't continue processing until I get a message. So I'll have to keep sending dummy messages to the app.
I'll look for possible 'hidden' Message handlers, but is it possible that VB has it's own message handler which sort of peeks at all the messages coming into the app before forwarding them to the program message handlers or individual message handlers? I'm guessing that is what calls the VB event handler functions

"It was when I found out I could make mistakes that I knew I was on to something."
-Ornette Coleman

Alt+Return == Strange Sound Sfx

Ryan Binns1-Jul-03 0:13

Ryan Binns

1-Jul-03 0:13

parths wrote:
I had tried GetMessage, but then it doesn't return till it gets a message (any message) (right?), and that's a problem too because then I can't continue processing until I get a message. So I'll have to keep sending dummy messages to the app.

Not necessarily. Modify the message loop so it uses PeekMessage() instead of GetMessage() and do the processing after the PeekMessage() handling:

Do While True
    If PeekMessage(msg, 0, 0, 0, PM_REMOVE) = True Then
        If msg.message = MY_MESSAGE Then
            ExitProcess 0
        Else
            TranslateMessage msg
            DispatchMessage msg
        End If
    End If
    ' Do your processing here
Loop

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

Mathias S.30-Jun-03 21:40

Mathias S.

30-Jun-03 21:40

In a controller I made I want to catch if user presses alt+return.
and I do it in OnSysKeyDown and everything works. BUT somehow a ‘boing’ sound is getting played.
Like if I pressed some illegal key combo.
How can I Stop it. It gets on my nerves.
(You get the same sound if you stand in IE and press alt+return )

Create a dynaset Recordset from an Excel sheet

Andy@30-Jun-03 21:31

Andy@

30-Jun-03 21:31

Hello,

i must read values from an Excel sheet, which becomes updated by another program. So i tried to open the Excel-File with CDaoDatabase and open a CDaoRecordset with the OpenType "dbOpenDynaset".

I can reed the values from the sheet, but the recordset wasn´t updated, if the values from the sheet have changed. I must open and close the recordset again.

Another thing is, that i get the message, that the Excel-File is blocked by another user", when i try to open the Excel-File.
But the attribut bExclusive from the CDaoDatabase::Open is set to FALSE.

Thanks
Andy

Re: Create a dynaset Recordset from an Excel sheet

Olli9-Jul-03 3:42

Olli

9-Jul-03 3:42

Hi Andy!

Thought I should take a short look for the news...

Andy@ wrote:
Another thing is, that i get the message, that the Excel-File is blocked by another user", when i try to open the Excel-File.

I think you should open it as a snapshot, but then you don't have an actual update...
Did you check that xt54 stuff??
There was a good class for that...

Hope it helps a little...

Greetings from a strange world!
Olli!

Olli
"Ooooooh, they have the internet on computers now!"
Homer Simpson

Beer | [beer] + Java | [Coffee] = NULL :=> Dead | X|

Re: Create a dynaset Recordset from an Excel sheet

Andy@9-Jul-03 4:17

Andy@

9-Jul-03 4:17

Hi Olli!

Nice to hear about you.

I use the xt54 stuff, it´s good to create a snapshot.
So i can get a actual update when i open and close the recordset cyclically. But this only works when i first open the file with excel and then change the values.

But when i create a test app which use a dynaset recordset for writing data and another dynaset recordset for reading data, i get the actual update.

So i must find out, how exactly the datas become changed in the excel sheet.

Greetings

Andy

how do i Detect if an external program has finished excuting(shellexec)?

Member 40481330-Jun-03 20:35

Member 404813

30-Jun-03 20:35

I want to execute several external programs in a que. I have to execute one program and wait for it to finish and excute another. Is there a way to detect if a external running program has finished?

Thanks

Re: how do i Detect if an external program has finished excuting(shellexec)?

Toni7830-Jun-03 20:44

Re: how do i Detect if an external program has finished excuting(shellexec)?

30-Jun-03 20:44

Now this might sound way off because I don't know what you're trying to do, but you could write a batch file "somefile.bat" and there you can put the names of your programs. I don't know if you're familiar with batch files so for example to execute notepad, paint, and minesweeper one after the other you could just write
c:\windows\notepad
c:\windows\paint
c:\windows\winmine
paint won't start until notepad closes and so on. So you can just try to execute this batch file from your program and you won't have to worry about the checking them (unless you want the opposite).

// Afterall, I realized that even my comment lines have bugs

When one cannot invent, one must at least improve (in bed).-My latest fortune cookie

Rage30-Jun-03 20:48

Rage

30-Jun-03 20:48

Use CreateProcess instead of ShellExecute, and use WaitForSingleObject like this :

// Init structs for process
STARTUPINFO lpsi;
lpsi.cb=sizeof(STARTUPINFO);
lpsi.cbReserved2=0;
lpsi.lpReserved2=0;
lpsi.lpReserved=0;
lpsi.lpDesktop=NULL;
lpsi.lpTitle="Doing something ...";
lpsi.dwFlags=STARTF_USESHOWWINDOW;
lpsi.wShowWindow=SW_SHOWMAXIMIZED;

PROCESS_INFORMATION lppi;

if (CreateProcess(NULL,(LPTSTR)path.operator LPCTSTR), NULL, NULL, FALSE, NORMAL_PRIORITY_CLASS, NULL, m_TotalCompPath.operator LPCTSTR(),&lpsi,&lppi)==0)
        // Error launching
    else
    {
        WaitForSingleObject(lppi.hProcess,INFINITE);
    }

~RaGE();

Re: how do i Detect if an external program has finished excuting(shellexec)?

cmk30-Jun-03 20:52

cmk

30-Jun-03 20:52

WaitForSingleObject() will allow you to wait on a process handle.
It uses the handle from CreateProcess() or OpenProcess().
The handle is signaled when the process terminates and is non-signaled while running.

...cmk

Checksum

Toni7830-Jun-03 19:27

30-Jun-03 19:27

I know how to make a checksum and the other day I was wondering if it is possible to have an exe perform a checksum on itself. I know that it is possible but, there is a catch to it. I realize that you could use a dll function to find the checksum of the exe, or you can put it in the registry, or who knows what other methods you could use. My question is the following:
Let's say that you have a single executable file. Is it possible to have this file perform a checksum on itself but without geting the checksum number from external sources (i.e. files, registry, dlls, etc.)? I was thinking that you cannot hardcode it in the source code because you don't know what the checksum would be until you compile the code, but then again, after you compile it, you can't change the exe because the checksum would change as well. It seems impossible to me to perform a checksum check without any help from external resources. As I came up with this problem in my head a couple of days ago I realized that I should stop thinking (and hopefully reach nirvana) because this problem is driving me crazy.

// Afterall, I realized that even my comment lines have bugs

When one cannot invent, one must at least improve (in bed).-My latest fortune cookie

Michael Dunn30-Jun-03 19:52

Michael Dunn

30-Jun-03 19:52

A common method is to store the checksum in an unused field in the EXE header. To calculate the checksum, you either ignore the EXE header entirely, or start calculating it at the byte following that field.
I can't remember where the field is off the top of my head, but it shouldn't be too hard to find with Google

--Mike--
"So where does that leave us? Well, it leaves us right back where we started, only more confused than before." -- Matt Gullett
Ericahist | Homepage | RightClick-Encrypt | 1ClickPicGrabber

Toni7830-Jun-03 20:04

30-Jun-03 20:04

So simple and so amazing. Thank you very much for your reply. I never thought about the fact that I can start reading the exe at any location.

// Afterall, I realized that even my comment lines have bugs

When one cannot invent, one must at least improve (in bed).-My latest fortune cookie

kakan30-Jun-03 20:03

kakan

30-Jun-03 20:03

The "normal" way to do it is this:
1.
Write your program, which includes your checksum algorithm.
2.
Put in a constant string of a known length. This string must have an unique identifier (which can later be found, browsing through the exe file).
I.e. "____xyz____zyx____AAAA".
(This string is 22 bytes long + the null, making it 23.)
The "AAAA"-part is later gonna be replaced with the real checksum code (assuming that the checksum will be 4 bytes long).

3.
Write the check code (still in your program), working like this:
Open the exe file, read through it and calculate the checksum, but DON'T count the constant string! Instead, when the string is found, read the "AAAA"-part and interpret it as an integer (likely an unsigned int, depending on the checksum algorithm). Close the exe-file.

4.
Compare the calculated checksum with the checksum from the "AAAA"-part. If a match, the it is OK.

5.
Write another program, a;) checksum generator (re-use the code in step 3), but this time, when the ID is found, save the file offset to the "AAAA"-part. (Remember, don't count the ID-string!)
When the checksum is calculated, seek to the saved offset to the "AAAA"-part, convert the checksum to a string, and write it to the exe-file.

Of course, you must recalculate the checksum every time you compile your program.

Good luck.
kakan

Toni7830-Jun-03 20:15

30-Jun-03 20:15

Wow! That is a brilliant idea. Now, why couldn't I think of that? Thank you very much for your reply.

// Afterall, I realized that even my comment lines have bugs

When one cannot invent, one must at least improve (in bed).-My latest fortune cookie