Menu item is displyed as "@xyz@"... - C / C++ / MFC Discussion Boards

Re: Number of waiting threads

LionAM2-Apr-08 6:20

LionAM

2-Apr-08 6:20

Thank you for your answer.

VuNic wrote:
WaitForSingleObject waits for only one object.

But multiple threads can wait for one object - and I would like to know how many. The problem is:

when I use a (synchronized) counter before the WaitForSingleObject,
how do I know if the Thread has already reached it and is waiting
or was interrupted before - I can not unlock the counter atomically
with the WaitForSingleObject call...

Alex

Re: Number of waiting threads

Mark Salsbery2-Apr-08 6:38

Mark Salsbery

2-Apr-08 6:38

LionAM wrote:
how do I know if the Thread has already reached it and is waiting or was interrupted before

There's no way reliably. What thread would be examining this thread to see where it's at?

What are you trying to do and how is this counter involved? There may be a simpler solution Smile | :)

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Number of waiting threads

LionAM2-Apr-08 10:42

LionAM

2-Apr-08 10:42

I wanted to implement a multiple reader/single writer lock.
The counter counts the number of waiting readers (which
then wait until the event is set).
If a writer unlocks, it sets (or pulses if there are writers
waiting) the event so that all waiting readers can resume -
but only if they already wait.

Alex

Re: Number of waiting threads

Mark Salsbery2-Apr-08 13:34

Mark Salsbery

2-Apr-08 13:34

The lack of an atomic lock/counter-adjust API makes it tricky.

There's a ton of solutions on the web (e.g. search "reader writer lock") that vary in performance and whether
they favor the reader thread(s) or the writer thread(s).

Even if you're looking to design your own, they're worth looking at IMO.

Here's an interesting article: Implementing a Reader-Writer lock[^]
along with its companion article: Analysis of Reader-Writer lock[^]

Here's a simple example - straight forward, if performance isn't a major concern: Reader/Writer Lock[^]

Hope that helps a bit,
Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Number of waiting threads

LionAM4-Apr-08 2:55

LionAM

4-Apr-08 2:55

I have found a very simple and short solution, using only
two "fast critical sections" (interlocked bool) and one
(interlocked) counter - and less than 20 lines of code.

Alex

Re: Number of waiting threads

Mark Salsbery4-Apr-08 6:49

Mark Salsbery

4-Apr-08 6:49

Cool!

As long as it meets your performance requirements and doesn't deadlock Smile | :)

Like I mentioned, there's lots of ways to do it - with "big" performance differences between
the solutions.

Glad you found a solution!

Cheers,
Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Number of waiting threads

Mark Salsbery2-Apr-08 6:01

Mark Salsbery

2-Apr-08 6:01

AFAIK, no, not with Windows synchronization objects.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Menu item is displyed as "@xyz@"...

ptr_Electron2-Apr-08 5:05

ptr_Electron

2-Apr-08 5:05

Friends, I am working on the code, wrote by somebody.. I added a new menu Item in the resource.. say "xyz", during the
runtime it is shown as "@xyz@".. I need it as "xyz",

how to handle this friends..

Re: Menu item is displyed as "@xyz@"...

led mike2-Apr-08 5:11

led mike

2-Apr-08 5:11

ptr_Electron wrote:
how to handle this friends

Fix it friend

led mike

Re: Menu item is displyed as "@xyz@"...

ptr_Electron2-Apr-08 5:39

ptr_Electron

2-Apr-08 5:39

Thanks for ur responce friend

Re: Menu item is displyed as "@xyz@"...

Hamid_RT7-Apr-08 4:08

Hamid_RT

7-Apr-08 4:08

Did you use of ANSI code?

reg., CImage sources (UNICODE COMPATIBLE) to load GIF, JPEG

ganesa moorthy2-Apr-08 4:50

ganesa moorthy

2-Apr-08 4:50

Where we can get CImage sources (UNICODE COMPATIBLE) to load GIF, JPEG in our application ? Confused | :confused:

Anyone Please help on this.

Thanks a Lot Rose | [Rose]

Thanks a lot

Re: reg., CImage sources (UNICODE COMPATIBLE) to load GIF, JPEG

Mark Salsbery2-Apr-08 6:08

Mark Salsbery

2-Apr-08 6:08

The source code is included with Visual Studio.

CImage uses GDI+ to load and save images. The loaded GDI+ image is converted to a DIBsection, which is
wrapped by the CImage class.

The loading code is similar to this (without the conversion to a DIBSection):

    ULONG dwToken;
    Gdiplus::GdiplusStartupInput input;
    Gdiplus::GdiplusStartupOutput output;
    Gdiplus::Status status = Gdiplus::GdiplusStartup(&dwToken, &input, &output);
    if(status == Gdiplus::Ok)
    {
        Gdiplus::Bitmap *pSrcBitmap = new Gdiplus::Bitmap(L"C:\\test.jpg", FALSE);

        <font color="Green">//... use the bitmap ...</font>

        delete pSrcBitmap;

        Gdiplus::GdiplusShutdown(dwToken);
    }

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: reg., CImage sources (UNICODE COMPATIBLE) to load GIF, JPEG

ganesa moorthy3-Apr-08 19:36

ganesa moorthy

3-Apr-08 19:36

Actually i am sure, there is no manual for CImage, in MS Visual Studio though it is included. If so what header i need to include to proceed?

Thanks for your response! Rose | [Rose]

Thanks a lot

Re: reg., CImage sources (UNICODE COMPATIBLE) to load GIF, JPEG

Mark Salsbery4-Apr-08 6:04

Mark Salsbery

4-Apr-08 6:04

atlimage.h in VS 2008 - most of it is inline.

It used to be an MFC class so it was a different header file before.

What version of Visual Studio are you using?

If you don't have a VS version that has the class, you can always use GDI+ directly, as I showed in the sample code.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: reg., CImage sources (UNICODE COMPATIBLE) to load GIF, JPEG

Hamid_RT7-Apr-08 4:07

Hamid_RT

7-Apr-08 4:07

you can find it on the its header file.

Mixed metaphor problem

Matthew Faithfull2-Apr-08 4:22

Matthew Faithfull

2-Apr-08 4:22

Does anyone here know a way of using the value of a constant class member in an #if condition.
What I'd like to do for example is :-

<br />
class CSomething<br />
{<br />
  public:<br />
<br />
  //...<br />
  enum<br />
  {<br />
    E_IsCool = 1;<br />
  };<br />
};<br />
<br />
//Then later conditional compilation based on E_IsCool<br />
<br />
#if (CSomething::E_IsCool)<br />
//Insert cool code here<br />
#else<br />
//Insert uncool code here<br />
#endif<br />
<br />

This may seem unnecessary when there is only one CSomething but I have several different ones, some cool some not and then a typedef is used to give one of them the name that is actually used. I'm trying to avoid peppering the classes with #defines and #undefs

Nothing is exactly what it seems but everything with seems can be unpicked.

Re: Mixed metaphor problem

Nemanja Trifunovic2-Apr-08 4:42

Nemanja Trifunovic

2-Apr-08 4:42

I think some template meataprogramming[^] would serve you better than the preprocessor #if

Programming Blog

utf8-cpp

Re: Mixed metaphor problem [modified]

Matthew Faithfull2-Apr-08 4:50

Matthew Faithfull

2-Apr-08 4:50

Yes it would normally and I've been thinking about using it. There is one small snag though. What if the conditional code is something like this:-

<br />
#if (CSomething::E_IsCool)<br />
#define _LONG_SUFFIX(_X) _X#L<br />
#else<br />
#define _LONG_SUFFIX(_X) _X<br />
#endif<br />

I can't find any way to pull in things like this that seem to have to be macros conditionally at the moment and I'm only really sold on going the template-mp route if I can do it all that way. Unsure | :~

Nothing is exactly what it seems but everything with seems can be unpicked.

modified on Wednesday, April 2, 2008 10:59 AM

Re: Mixed metaphor problem

CPallini2-Apr-08 4:50

CPallini

2-Apr-08 4:50

Matthew Faithfull wrote:
This may seem unnecessary when there is only one CSomething but I have several different ones, some cool some not and then a typedef is used to give one of them the name that is actually used

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

Re: Mixed metaphor problem

Matthew Faithfull2-Apr-08 5:06

Matthew Faithfull

2-Apr-08 5:06

I was trying to keep the example simple, obviously I failed Smile | :)

<br />
class CSomething<br />
{<br />
public:<br />
<br />
  //...<br />
  enum<br />
  {<br />
    E_IsCool = 1;<br />
  };<br />
};<br />
<br />
<br />
#ifdef USE_MYSOMETHING<br />
typedef CMySomething CSomething<br />
#else<br />
//Other CSomething alternatives<br />
#endif<br />
<br />
<br />
//Then later conditional compilation based on E_IsCool<br />
<br />
#if (CMySomething::E_IsCool)<br />
#define _LONG_SUFFIX(_X) _X#L<br />
#else<br />
//Insert uncool code here<br />
#define _LONG_SUFFIX(_X) _X<br />
#endif<br />
<br />

This is closer to what I'm really doing which is somewhat more complicated. It has to work on different compilers as that really is the point of this so any template tricks will need to be MSVC6 friendly

Nothing is exactly what it seems but everything with seems can be unpicked.

Re: Mixed metaphor problem

led mike2-Apr-08 5:10

led mike

2-Apr-08 5:10

Wow. So you don't know what a "pre" processor is in the context of a compiler?

led mike

Re: Mixed metaphor problem

Matthew Faithfull2-Apr-08 5:16

Matthew Faithfull

2-Apr-08 5:16

Yes Mike I do know and am not expecting the example code I posted to work. I need something functionally equivalent to what it would do if it did work, i.e. if the PRE-processor was C++ aware. If you're telling me there's no way to control conditional compilation using compile time constants then just come out and say so.

Nothing is exactly what it seems but everything with seems can be unpicked.

Re: Mixed metaphor problem

led mike2-Apr-08 5:31

led mike

2-Apr-08 5:31

Matthew Faithfull wrote:
Yes Mike I do know

What, then why have you asked this question? I mean if you know then you know so why ask the question? Wait, now I remember trying to have a logical discussion with you in the SoapBox, never mind.

led mike

Re: Mixed metaphor problem

Matthew Faithfull2-Apr-08 5:50

Matthew Faithfull

2-Apr-08 5:50

Yes, you didn't understand the use of a metaphor then and you clearly still don't.

Nothing is exactly what it seems but everything with seems can be unpicked.

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