C / C++ / MFC

16-Nov-09 6:24

I am writing a Windows application in Visual C++. I want to make a program loop take exactly a thirtieth of a second per loop. Please how can I make the program find the time since the program started running, or similar, accurate to a millisecond or a microsecond? I have found many time-related functions, but all giving the time to the nearest whole second.

Iain Clarke, Warrior Programmer

Iain Clarke, Warrior Programmer16-Nov-09 6:32

16-Nov-09 6:32

GetTickCount will report with ms accuracy - but it's lumpier than that. It used to change at ~19ms intervals, but I think it's finer.

If you want *exactly* 1/3 of a second, then windows is the wrong OS for you.

After that, it boils down to your exactness. You could use SetTimer (..., 333, ...), or waitable timers, or...

Do you want no less that 333ms between events, 3 events pretty evenly per second, but you can handle some jitter?

Short version: Define "exact".

Iain.

I have now moved to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), or need contract work done, give me a job! http://cv.imcsoft.co.uk/[^]

OT-Hey Warrior!

CPallini16-Nov-09 9:36

Iain Clarke, Warrior Programmer

16-Nov-09 9:36

Hey warrior, how goes on the great invasion of Sweden?
Big Grin | :-D

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]

Re: OT-Hey Warrior!

Iain Clarke, Warrior Programmer16-Nov-09 21:43

16-Nov-09 21:43

Going great - see the change in my sig!

Iain.

I have now moved to Sweden for love (awwww).

image processing toolkits | batch image processing

C^hris L^osinger16-Nov-09 7:09

C^hris L^osinger

16-Nov-09 7:09

QueryPerformanceCounter can give better resolution than GetTickCount or 'time()' or SetTimer. but you will never get a loop that takes exactly 1/30s in Windows - you can get close, on average. but not exactly, all the time. Windows just isn't that kind of OS.

Jeff Archer16-Nov-09 17:11

Jeff Archer

16-Nov-09 17:11

Use the MultiMedia timer with a callback function. It is the most accurate timing you can have in Windows.
Lookup the following in the VC++ help:

TIMECAPS
timeGetDevCaps
timeBeginPeriod
timeSetEvent

Anthony Appleyard16-Nov-09 23:34

16-Nov-09 23:34

This "event setting" sounds complicated, like trapping errors. My program uses this method, and it seems to work:

NEXTFRAME: t=GetTickCount();
            InvalidateRect(wn,0,0); RedrawWindow(wn,0,0,RDW_UPDATENOW);
            for(j=0;j<4;j++) {if(!isdigit(MFN[i+j])) goto DEF; FN[j]=MFN[i+j];}
            fn=(FN[0]-'0')*1000+(FN[1]-'0')*100+(FN[2]-'0')*10+FN[3]-'0'+1;
            if(fn>9999) goto DEF;     
     FN[3]++; if(FN[3]>'9') {FN[3]='0'; FN[2]++;}
            if(FN[2]>'9') {FN[2]='0'; FN[1]++;}
            if(FN[1]>'9') {FN[1]='0'; FN[0]++;}
     MFN[i]=FN[0]; MFN[i+1]=FN[1]; MFN[i+2]=FN[2]; MFN[i+3]=FN[3];
     if(!readfile(I,MFN,wn)) goto DEF; // read from file MFN to image I, running under Windows window wn.
            do {} while(GetTickCount()-t<33); goto NEXTFRAME;}

;

but the loop in the last line looks like it ties up the computer until time comes to display the next frame, instead of letting aniother process run.

Anthony Appleyard16-Nov-09 23:41

16-Nov-09 23:41

I would have thought that, in these times when desktop computers can run at a gigahertz and more, that it would be routinely easy for a C++ program to time events by the microsecond.

Jeff Archer17-Nov-09 2:34

Jeff Archer

17-Nov-09 2:34

It's really not that complicated once you have done it a couple of times. The do while loop that you are using is extremely wasteful in terms of CPU utilization. The proper way to block a thread is with WaitForMultipleObjects. Also, you should never block the main thread of your application. The best solution would really be to use a background thread to draw on a BITMAP and use use BitBlt to transfer the image to the screen every 333 ms.
As a side note the values returned by GetTickCount are really only accurate to 15.2 ms so using it to time 33 ms isn't going to work well on a loaded machine. The advantage of the multimedia timer is that you can truely have 1 ms accuracy. And by using a background thread and proper thread synchronization your code will scale properly on faster and multi core machines and still work correcly on a slower or heavly loaded machine.

Re: Timing

Anthony Appleyard17-Nov-09 19:09

How to add a dual interface to a non-ATL, non-MFC Application [closed]

17-Nov-09 19:09

In this case I need to wait not 333ms absolutely, but (333ms minus (the time taken to read that frame from a file)).

jmen@moc16-Nov-09 2:15

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 2:15

Hello VC++ gurus,
I have to add a dual interface to a non-MFC, non-ATL application.
I have a non-ATL, non-MFC enabled project and a plain Win32 application. Now, this Win32 exe must expose some services through an IDispatch interface.
My question: Can I somehow use ATL to help me with that IDispatch implementation? Event if the project is a non-ATL project?
Note: My Win32 exe must act as Local Server (CLSCTX = CLSCTX_LOCAL_SERVER) here.

I'll appreciate your help a lot.
Regards

P.S.: Thanks to all how replied to this thread.
I'll try to use ATL in my non-ATL project: use CComObjectRootEx, CComCoClass, IDispatchImpl and CAtlModuleT<base> etc. straight away. So far, it looks OK.
Regards,
Joerg

Richard MacCutchan16-Nov-09 3:05

Richard MacCutchan

16-Nov-09 3:05

Getting the most out of IDispatch[^] may have the answer you are looking for.

Re: How to add a dual interface to a non-ATL, non-MFC Application

jmen@moc16-Nov-09 3:57

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 3:57

Thanks. Now, let me try to understand the XYZDispatchDriver: does it assume that the IDispatch Interface has been defined (in an IDL) and a coclass has been implemented? Or, is this created dynamically on the fly?
In my situation, I do not yet have IDL defined, class implemented.
Regards,
Joerg

Richard MacCutchan16-Nov-09 4:14

Richard MacCutchan

16-Nov-09 4:14

Sorry, I'm not a COM expert, I just remembered this article from my own studies on the subject. You could try posting your question at the end of the article as it will then go to the author, who probably is an expert.

Re: How to add a dual interface to a non-ATL, non-MFC Application

jmen@moc16-Nov-09 4:22

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 4:22

Thanks anyway. Smile | :)

CPallini16-Nov-09 5:42

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 5:42

See here [^].
Smile | :)

jmen@moc16-Nov-09 5:54

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 5:54

I've seen that; just trying to be lazy and avoid all that handwriting... Is there a "lazy way"?

CPallini16-Nov-09 6:13

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 6:13

jmen@moc wrote:
Is there a "lazy way"?
Quote Selected Text

Yes: ATL (Active Template Laziness). Smile | :)

Nemanja Trifunovic16-Nov-09 7:05

Nemanja Trifunovic

16-Nov-09 7:05

CPallini wrote:
Yes: ATL

Using ATL once you know it is "laziness" (in a good way), but learning it?

utf8-cpp

Re: How to add a dual interface to a non-ATL, non-MFC Application

CPallini16-Nov-09 8:36

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 8:36

I don't need a code obfuscator: I'm writing a template library wrapping COM.
--The ATL's author, former Klingon developer.

I don't need to learn it, I just need to use it.
--The VB6 developer

Big Grin | :-D

jmen@moc16-Nov-09 8:38

Re: How to add a dual interface to a non-ATL, non-MFC Application

16-Nov-09 8:38

You mean, I can add ATL templates, macros and an ATL IDispatch implementation, eveen if my project is not an ATL Project? Would be good enough for me.
Regards, Joerg

CPallini16-Nov-09 9:38

16-Nov-09 9:38

I suppose (note: suppose) it would be simpler transforming you project in a ATL one.
Smile | :)

Re: Off topic

Richard MacCutchan16-Nov-09 7:34

Richard MacCutchan

16-Nov-09 7:34

A message in Italian in the .NET Framework forum; can you help with it?

Re: Off topic

CPallini16-Nov-09 9:22