C / C++ / MFC

14-Dec-09 10:43

In my VS c++ console app i have the main thread processing input obtained by other secondary threads. The secondary threads use WaitForSingleObject to wait on either tcp input or wait to get the mutex back. These mutexes are used to control access to global buffers. Each secondary thread writes to a specific global buffer and when complete gives up the mutex. The main thread uses WaitForMultipleObjects to determine which buffer to read from, then, when done, turns the mutex back over to the secondary thread.

Problem is if the apps start up when there's a lot of data(messages) backed up I initially get a lot of reported empty buffers in the beginning and later when I get buffers they (the corresponding mutex) seem to be ignored by the main thread. This is what my log file shows. It may be that even my log file sequencing is questionable at this point.
Starting the processes like this would not be the norm but still it should all work even under these conditions.
Is it possible I have some kind of synchronization problem between the main and secondary threads? More details provided upon request.
Thanks

Migounette14-Dec-09 11:53

Migounette

14-Dec-09 11:53

More information is needed in order to help you.
A common error when we use WaitForMultipleObject is the bWaitAll is not set correctly or an invalid handled is passed to the function.

Check this, if none of the above answers correspond to your issue.

Please provide us more information

Alan Kurlansky15-Dec-09 3:09

15-Dec-09 3:09

Thanks for the hints. I created the threads as follows:
HANDLE   mutexFIXHandle;
HANDLE   mutexSetAlertTimer;
HANDLE     mutexSetAWAYHandle;
mutexFIXHandle     = CreateMutex(NULL, false, NULL);
mutexSetAlertTimer = CreateMutex(NULL, false, NULL);
mutexSetAWAYHandle = CreateMutex(NULL, false, NULL);

Based on first reply I changed this to and will retest:

mutexFIXHandle     = CreateMutex(SYNCHRONIZE, false, NULL);
mutexSetAlertTimer = CreateMutex(SYNCHRONIZE, false, NULL);
mutexSetAWAYHandle = CreateMutex(SYNCHRONIZE, false, NULL);
   //
   // for waitformutlipleobjects
   //
HANDLE ghEvents[3];
ghEvents[0] =     mutexFIXHandle;
ghEvents[1] =     mutexSetAlertTimer;
ghEvents[2] =     mutexSetAWAYHandle;
The skeleton of the WaitForMultipleObjects looks like this:
while (1) {
   waitRval =   WaitForMultipleObjects( 3, ghEvents, FALSE,   2000);

     if (waitRval == WAIT_OBJECT_0) {
                     // process event
                     ReleaseMutex(mutexFIXHandle);
            }
            else if (waitRval == (WAIT_OBJECT_0 + 1) ) {
                     // process event
                     ReleaseMutex(mutexSetAlertTimer);
            }
            else if (waitRval == (WAIT_OBJECT_0 + 2) ) {
                        // process event
                        ReleaseMutex(mutexSetAWAYHandle);
            }
            else if (waitRval == WAIT_TIMEOUT) {
                     //printf("Wait timed out\n");
            }
            else {
                     // log something
            }
}

Alan Kurlansky15-Dec-09 3:23

15-Dec-09 3:23

I also needed to do this to get it to compile:
mutexFIXHandle = CreateMutex((LPSECURITY_ATTRIBUTES)SYNCHRONIZE, false, NULL);
mutexSetAlertTimer = CreateMutex((LPSECURITY_ATTRIBUTES)SYNCHRONIZE, false, NULL);
mutexSetAWAYHandle = CreateMutex((LPSECURITY_ATTRIBUTES)SYNCHRONIZE, false, NULL);

Alan Kurlansky15-Dec-09 3:55

Playing an AVI video from memory

15-Dec-09 3:55

Using (LPSECURITY_ATTRIBUTES)SYNCHRONIZE causes the program to crash. So I'm back to using NULL.

zzelephant14-Dec-09 10:10

zzelephant

14-Dec-09 10:10

Hello,

I need to integrate a video player / video API into my MFC / C++ application. It needs to be able to take video data stored as byte arrays in memory and display it in a preview window.

Is DirectShow the appropriate framework to use for this? As far as I have been able to tell, I would need to write a custom source filter which appears to be non trivial.

Is there a simpler way to do this?

Thanks!

akhtar nasary14-Dec-09 8:45

akhtar nasary

14-Dec-09 8:45

hi my name is akhtar gul <small><pre><code> D'Oh! | :doh:

Re: hi

loyal ginger14-Dec-09 9:05

loyal ginger

14-Dec-09 9:05

Your first message is pretty hard to comprehend.

Re: hi

CPallini14-Dec-09 10:14

Split images into several regions.

14-Dec-09 10:14

Hi Akhtar,
What is your problem? The name?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

franckesh14-Dec-09 5:06

franckesh

14-Dec-09 5:06

Hi,
I would like to compare some (black& white) images region by region. I want to know how to split an image into many regions with Qt.

franck

Re: Split images into several regions.

Tim Craig14-Dec-09 14:23

Tim Craig

14-Dec-09 14:23

As far as I know, Qt is a GUI framework and not an imageprocessing library. If you're looking for a lot of image processing functions, try OpenCV.

You measure democracy by the freedom it gives its dissidents, not the freedom it gives its assimilated conformists.

How to control LEDs using Parallel Port and Turbo C?

--xtiAN_002--14-Dec-09 3:53

--xtiAN_002--

14-Dec-09 3:53

Hello to everyone!

I need some help. How can I control 8 LEDs using parallel port and Turbo C? I have read this article http://www.codeproject.com/KB/cs/csppleds.aspx but it is written in C# language and since I only know C language, I don't know how to program it.

Please help me for the source code in Turbo C. Any help will higly appreciated. Thanks in advance.

Re: How to control LEDs using Parallel Port and Turbo C?

transoft14-Dec-09 4:35

transoft

14-Dec-09 4:35

Using following function to load the dll.

HMODULE hUsbLib = LoadLibrary("inpout32.dll");

GetProcAddress(hUsbLib, "Output");

Rect

kumar sanghvi14-Dec-09 2:29

kumar sanghvi

14-Dec-09 2:29

HI,
Is it possible to draw rect using Normalised coordinates like 0.399567,0.000000,1.000000,0.399369

CPallini14-Dec-09 2:56

14-Dec-09 2:56

GDI+ allows this. Anyway why bother? Simply properly scale the rectagle before drawing it.
Smile | :)

kumar sanghvi14-Dec-09 17:39

kumar sanghvi

14-Dec-09 17:39

pls let me know how can i do that...

loyal ginger14-Dec-09 18:02

loyal ginger

14-Dec-09 18:02

GDI+ uses floating point coordinates. You just need to use GDI+.

kumar sanghvi14-Dec-09 18:37

kumar sanghvi

14-Dec-09 18:37

Let me be more clear...

Suppose i want to draw segments(rect) on a Dialog and the given coordinates of the segemnt is
0.499567,0.000000,1.000000,0.499369 (these coordinates are independent of the width and height of the Dialog Rect) then how to draw the segment with the given coordinates.....

Failed to initialize COM library error

Cedric Moonen14-Dec-09 21:04

Cedric Moonen

14-Dec-09 21:04

Do you sometimes read the answers that are given to you ?

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

Le@rner14-Dec-09 1:22

Le@rner

14-Dec-09 1:22

Hi all,

I have made a exe using VS-2008.
I am trying to run that exe on another pc which not having VS-2008 inatalled on it (having OS - win xp with sp3), in my exe i have initialised COM using this code.

hres =  CoInitializeEx(0, COINIT_MULTITHREADED); 
    if (FAILED(hres))
    {
        AfxMessageBox(_T("Failed to initialize COM library") );
		return;                  // Program has failed.
    }

But every time i run my exe on this machine it gives "Failed to initialize COM library".

Do i need to install anything extra on this machine...

Or what other problem there might be?

Can anybody help me in this...

Thanks in advance

To accomplish great things, we must not only act, but also dream;
not only plan, but also believe.

CPallini14-Dec-09 1:38

14-Dec-09 1:38

You should check better the function return value (make your program reporting it). See the documentation for details [^].
Smile | :)

Durga_Devi14-Dec-09 2:07

Durga_Devi

14-Dec-09 2:07

HI,

For the function CoInitializeEx(), dont check for the returned code.
Because if the COM has been initialized on the calling thread, the return code will be failed i.e S_FALSE.
Just call the CoInitializeEx() and proceed to next.

CPallini14-Dec-09 2:17

14-Dec-09 2:17

DurgaDevi_hr wrote:
For the function CoInitializeEx(), dont check for the returned code.
Because if the COM has been initialized on the calling thread, the return code will be failed i.e S_FALSE.

Your point is wrong.

In fact, CoInitializeEx() may return S_FALSE the way you depicted. However FAILED(S_FALSE) evaluates to false.
Smile | :)