Re: passing a variable inside thread - C / C++ / MFC Discussion Boards

Rajesh R Subramanian24-Dec-09 2:21

24-Dec-09 2:21

Either SendMessage can be used, or if you're afraid of the sender being taken into a deadlock, consider SendMessageTimeout[^]

But more importantly, why is it that your DLL needs to continuously raise events and clobber the message queue? May be if you could explain your scenario, someone here might be able to suggest a better alternative.

I say it because if you increase the message queue size on one computer, your program will still not work on another computer whose message queue size is the default! This is not a pretty sight.

“Follow your bliss.” – Joseph Campbell

error "a required resource was unavailable".

Le@rner23-Dec-09 22:41

Le@rner

23-Dec-09 22:41

HI all,

i m receiving this error,when i print records with large number of pages like 50 or above.

when i debug the code i m note able to find out this error.

please help me for this.

thanks in advance.

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not only plan, but also believe.

passing a variable inside thread

Le@rner23-Dec-09 18:46

Le@rner

23-Dec-09 18:46

Hi all,

I want to pass a CString variable to my worker thread.

How can i do it...

Thanks in advance

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

Re: passing a variable inside thread

Adam Roderick J23-Dec-09 18:59

Adam Roderick J

23-Dec-09 18:59

Change Allocation to Heap if scope of thread is unknown
pass the TCHAR*.
CString csTemp( "Sample data" );
LPTSTR lpszData = new TCHAR[csTemp.GetLength()+1];
_tcscpy(lpszData , csTemp)

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Re: passing a variable inside thread

Rajesh R Subramanian23-Dec-09 21:57

Rajesh R Subramanian

23-Dec-09 21:57

Adam Roderick J 09 wrote:
Change Allocation to Heap if scope of thread is unknown
pass the TCHAR*.
CString csTemp( "Sample data" );
LPTSTR lpszData = new TCHAR[csTemp.GetLength()+1];
_tcscpy(lpszData , csTemp)

While a pointer to the CString object on the heap itself can be passed to the thread, why bother creating a character array on the heap and deal with allocation size manually? Smile | :)

Adam Roderick J 09 wrote:
LPTSTR lpszData = new TCHAR[csTemp.GetLength()+1];

That won't work as expected with Unicode strings.

“Follow your bliss.” – Joseph Campbell

Re: passing a variable inside thread

CPallini23-Dec-09 22:25

CPallini

23-Dec-09 22:25

Rajesh R Subramanian wrote:
Adam Roderick J 09 wrote:
LPTSTR lpszData = new TCHAR[csTemp.GetLength()+1];

That won't work as expected with Unicode strings.

Why not?

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.
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[My articles]

Re: passing a variable inside thread

Rajesh R Subramanian23-Dec-09 22:32

Rajesh R Subramanian

23-Dec-09 22:32

CPallini wrote:
csTemp.GetLength()+1

Because of the +1 part, which makes a wrong assumption of the size of an Unicode character! It could have been multiplied by sizeof(TCHAR), that would make it work, but is not very clean (IMHO).

There's generally no reason to write C-Style code with manual memory allocation (deciding the size, etc.,) while using MFC, or even C++. Using a CString instead is much more elegant.

“Follow your bliss.” – Joseph Campbell

Re: passing a variable inside thread

Adam Roderick J23-Dec-09 22:39

Adam Roderick J

23-Dec-09 22:39

I think, there is a small misunderstanding.
for MBCS
LPTSTR lpszData = new TCHAR[csTemp.GetLength()+1];
Here we are allocating for TCHAR so it will allocate 2 bytes for every new operator.
so if
csTemp = _T("ab" )
size allocation with above allocation will be 4 +2 =6 bytes.
Smile | :)

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Re: passing a variable inside thread

CPallini23-Dec-09 23:05

CPallini

23-Dec-09 23:05

Rajesh R Subramanian wrote:
Because of the +1 part, which makes a wrong assumption of the size of an Unicode character! It could have been multiplied by sizeof(TCHAR), that would make it work, but is not very clean (IMHO).

Nope:

LPTSTR lpszData = new TCHAR[csTemp.GetLength()+1];

Looks correct to me, whatever CString is of wide characters or not.

Rajesh R Subramanian wrote:
It could have been multiplied by sizeof(TCHAR)

It is already taken into accout by the new operator.
Smile | :)

Re: passing a variable inside thread

Adam Roderick J23-Dec-09 22:34

Adam Roderick J

23-Dec-09 22:34

For first case the reason is performance, CString is a bit heavy Smile | :)

2.That won't work as expected with Unicode strings.
Why it wont work?
Can you please give me the reason. Wink | ;)

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Re: passing a variable inside thread

Rajesh R Subramanian24-Dec-09 1:38

Rajesh R Subramanian

24-Dec-09 1:38

With #2, my apologies. I overlooked the whole thing.

But I don't think you need optimise for performance by not using CString (C'mon, you're already using MFC). There will be absolutely no usable performance gain.

“Follow your bliss.” – Joseph Campbell

Re: passing a variable inside thread

Rajesh R Subramanian23-Dec-09 21:49

Rajesh R Subramanian

23-Dec-09 21:49

The variable you pass to the thread should be put on the heap. You could use it from within the thread and delete if it is not needed any more.

UINT ThreadFunc(LPVOID p)
{
  CString *pStr = (CString*)p;
  //use pStr here
  //delete pStr if it should be.
  return FALSE;
}

CMyDlg::SpawnThread()
{
  CString *pSz = new CString(_T("Some value"));
  AfxBeginThread(ThreadFunc, pSz);
}

“Follow your bliss.” – Joseph Campbell

upload larger file using Ftp in c+ Builder problem

raj157623-Dec-09 18:37

raj1576

23-Dec-09 18:37

Hi,

I am using TIdFTP component from the c++ builder to upload the file on to the ftp. It works fine for small files but when I upload the file like 4GB then it upload only 700 mb almost, then terminate. So Please tell me how upload larger files using TIdFTP.

I want to attach my window to the parent window so that on resizing or minimizing the parent window, the child window should be resized and moved appropriately

manoharbalu23-Dec-09 18:30

manoharbalu

23-Dec-09 18:30

I am using a MDI application. In the main window there need to be two panes, left pane and the right pane. The left pane displays some static information which will not change at all. But the right pane needs to display dynamic information which will get updated at frequent intervals of time.

I placed a modeless dialog after removing the minimise, maximize and close button from the top on the right pane using the SetWindowPos() which showed the data and gets updated at frequent intervals of time. So i was able to open other dialog windows in the application by this setup.

The Problem is when I use the "Restore down" button of the parent window, the parent window and the dialog window gets separated and shown. Also the parent window becomes resized in size(became a small window) whereas the modeless dialog window remain the same.

Now what I want is a separate pane window, in the mainwindow which should be minimized according to the main window and should remain in the same position in the parent window.

Please provide me sample code for this.

Re: I want to attach my window to the parent window so that on resizing or minimizing the parent window, the child window should be resized and moved appropriately

Richard MacCutchan23-Dec-09 22:20

Richard MacCutchan

23-Dec-09 22:20

The dialog is not 'attached' to the MDI frame in the same way that a view would be, so you will need to hide and restore it manually when the parent changes. I think the only way to get this to happen automatically is to use a window that derives from CView(), and is correctly attached to the frame window.

how to disable keyboard accelerators temporarily in a mdi application

Prasann Mayekar23-Dec-09 17:04

Prasann Mayekar

23-Dec-09 17:04

i am displaying a rich edit control in an mdi application. during which i want to disable my keyboard accelerators to avoid the unnecessary commands invocation as a result.
once i finish working with the edit control, i want to enable them again.

would like to know the way if any.

thanks

Re: how to disable keyboard accelerators temporarily in a mdi application

Adam Roderick J23-Dec-09 17:23

Adam Roderick J

23-Dec-09 17:23

Please check DestroyAcceleratorTable[^]

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FindFirstChangeNotification

Still learning how to code23-Dec-09 11:20

Still learning how to code

23-Dec-09 11:20

Is there an equivalent function to FindFirstChangeNotification that works across a home network ? Confused | :confused:

Doug

Re: FindFirstChangeNotification

Garth J Lancaster23-Dec-09 13:19

Garth J Lancaster

23-Dec-09 13:19

hmmmm - how do you mean

DougButtimer wrote:
across a home network

In general, iirc, FindFirstChangeNotification can only be used on a local PC and cant even be used to watch net shares. Any time Ive needed to 'achieve similar' across a network Ive used ftp to list a directory at time-0 'initial snapshiot', then compared that to ftp lists at time+n where n is 'polled'/refreshed at desired intervals - eg 5 or 15 minutes

sorry, likely doesnt help much

'g'

Re: FindFirstChangeNotification

Still learning how to code23-Dec-09 22:23

Still learning how to code

23-Dec-09 22:23

Hi Garth, Just after I had made this posting, I realised that I'd hit this problem once before and hadn't found a solution then either, so your reply wasn't unexpected ! Yes, I think that I'll have to resort to some solution along your lines ! Thanks, and a very happy Christmas to you !

Doug

Re: FindFirstChangeNotification

Garth J Lancaster23-Dec-09 22:38

Garth J Lancaster

23-Dec-09 22:38

I thought of 2 possibilities 'a bit better' than comparing ftp listings

Both really depend on how many files/events you are looking for - one might work for instance with creation of a particular file or a 'low volume' change system than the other - what about :-

1) use FindFirstChangeNotification on the machine you are watching, but add the [possibly filtered] events to a log file ... everytime you ftp from the 'monitoring machine', you grab the log file and erase it

2) use a tcp pub/sub system, the monitored machine publishes [again, possibly filtered] events from FindFirstChangeNotification to subscriber(s) - the monitor machine(s) 'subscribe' to particular events composing of {source machine name, add/change/delete, file(s)} for example - a lot more work, but extensible and applicable to multiple machines you might want to monitor from

not much I know

'g'

Re: FindFirstChangeNotification

Garth J Lancaster23-Dec-09 23:02

Garth J Lancaster

23-Dec-09 23:02

Im going to undo everything I just said - I just did some more reading - if you follow http://msdn.microsoft.com/en-us/library/system.io.filesystemwatcher(VS.80).aspx[^] it says you can monitor UNC paths !!!

'g'

Re: FindFirstChangeNotification

Still learning how to code24-Dec-09 3:49

Still learning how to code

24-Dec-09 3:49

Garth, Unfortunately, being a novice, I'm not "in to" Net Framework !! Thanks for your research, nevertheless

Doug

Re: FindFirstChangeNotification

Garth J Lancaster24-Dec-09 11:04

Garth J Lancaster

24-Dec-09 11:04

yes, but .NET uses ReadDirectoryChangesW - which if you look at this :- CDirectoryChangeWatcher - ReadDirectoryChangesW all wrapped up[^] shows how its possible to use it from c++ - and there are other examples 'out there'

Smile | :)

'g'

Re: FindFirstChangeNotification

Still learning how to code24-Dec-09 20:27

Still learning how to code

24-Dec-09 20:27

Hi Garth, I think that the real problem is that the folder that I want to watch is on a NAS disk and so the "This code will only work on Windows NT, Windows 2000, or Windows XP, and the directory you wish to watch must also reside on a WindowsNT, Windows 2000, or Windows XP computer" is going to make it a non-starter. I've now implemented a polling _findfirst/_findnext strategy which, although a bit basic, works fine !! (Just hope that the NAS disk can stand the traffic !!) Many thanks for your determination to find me a solution !!! Cheers !

Doug

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