C / C++ / MFC Discussion Boards

achandra0073-Jul-03 6:14

3-Jul-03 6:14

Hi
I have a GUI application that does this:

<br />
GUI Thread<br />
 AfxBeginThread(...); // Worker Thread 1<br />
 AfxBeginThread(...); // Worker Thread 2<br />

I want to capture when both the threads have returned and then enable the Cancel button. What is the most effective way of doing that? I have looked at WaitForMultipleObjects but probably do no know how to implement it.

Thanks in advance
ashish

Re: Multithread question

RobJones3-Jul-03 6:17

RobJones

3-Jul-03 6:17

You could create a function (in your GUI) to receive a PostMessage from the thread.. that way your application doesn't hang while waiting for the threads to finish.. I could post some code if you want..

Rob

Whoever said nothing's impossible never tried slamming a revolving door!

Re: Multithread question

achandra0073-Jul-03 6:33

achandra007

3-Jul-03 6:33

Thanks...could you please post.

Re: Multithread question

RobJones3-Jul-03 6:42

RobJones

3-Jul-03 6:42

I havent compiled any of this so there could be mistakes.. This will allow your threads to post messages to the main GUI..

// In your .cpp after the includes..
#define UWM_THREAD_A_DONE WM_APP+1
#define UWM_THREAD_B_DONE WM_APP+2
 
// In your .cpp MessageMap
ON_MESSAGE(UWM_THREAD_A_DONE, OnThreadADone)
ON_MESSAGE(UWM_THREAD_B_DONE, OnThreadBDone)
 
// In your .h
LRESULT OnThreadADone (WPARAM wParam, LPARAM lParam);
LRESULT OnThreadBDone (WPARAM wParam, LPARAM lParam);
 
// Functions for receiving the PostMessage (in .cpp)
// Received a Thread A Done message..
LRESULT CMainFrame::OnThreadADone(WPARAM wParam, LPARAM lParam)
{
	// Do what ever you want.. Thread A has closed..
	return TRUE;
}
 
// Received a Thread B Done message..
LRESULT CMainFrame::OnThreadBDone(WPARAM wParam, LPARAM lParam)
{
	// Do what ever you want.. Thread B has closed..
	return TRUE;
}
 
Inside the Thread "A" do a PostMessage(UWM_THREAD_A_DONE,0,0);

Hope it helps..
Rob

Whoever said nothing's impossible never tried slamming a revolving door!

Re: Multithread question

John M. Drescher3-Jul-03 6:29

John M. Drescher

3-Jul-03 6:29

The following code can be used to test if the threads are still running:

HANDLE hThreads[2];

hThreads[0] = //Handle of first thread
hThreads[1] = //Handle of second thread

DWORD dwCode = WaitForMultipleObjects(2,hThreads,TRUE,0);

if ( dwCode == WAIT_TIMEOUT ) {
// Then at least one thread is still running.
}

[EDIT]
The 0 in the last parameter of WaitForMultipleObjects indicates to test and return immediately if you want to wait longer you can enter a value or INFINITE to wait until both threads end.
[/EDIT]

John

Re: Multithread question

achandra0073-Jul-03 6:40

achandra007

3-Jul-03 6:40

John

I actually want both threads to finish, not one of them. So if I use TRUE for Parm 3 of WaitForMultipleObjects, then as soon as one thread exists, won't my statement return?

I acutally tried this:

<br />
HANDLE hEvents[2] = {NULL,NULL};<br />
CWinThread	*pThread1,*pThread2;<br />
<br />
try<br />
{	<br />
     m_bRestartMode = IsRestartMode();<br />
		<br />
     if(!m_bRestartMode)<br />
		{<br />
			//if(GetBulkDataMSARemote() == SAL2UNI_RETCODE_SUCC)<br />
			if(GetPendingANI() == SAL2UNI_RETCODE_SUCC)<br />
			{<br />
				pThread1 = AfxBeginThread(BeginWorker,(LPVOID)this);<br />
				pThread2 = AfxBeginThread(CRMWorker,(LPVOID)this);<br />
//				DoProcessing();<br />
			}<br />
		}<br />
		else<br />
		{<br />
			if(Restart())<br />
			{<br />
				pThread1 = AfxBeginThread(BeginWorker,(LPVOID)this);<br />
				pThread2 = AfxBeginThread(CRMWorker,(LPVOID)this);<br />
//				DoProcessing();<br />
			}<br />
		}<br />
<br />
		hEvents[0] = pThread1->m_hThread;<br />
		hEvents[1] = pThread2->m_hThread;<br />
			<br />
	}<br />
	catch(CDaoException *daoe)<br />
	{<br />
			CString sErrorMsg,sErrNo;<br />
			CDaoErrorInfo *errInfo = daoe->m_pErrorInfo;<br />
			<br />
			<br />
			sErrNo.Format("%d", errInfo->m_lErrorCode);<br />
			sErrorMsg = "Error No.: " + sErrNo + " - " + errInfo->m_strDescription;<br />
			sErrorMsg += " occurred in application " + errInfo->m_strSource;<br />
			LogActivity(CA_MSG_SEVERITY_INFORMATION,sErrorMsg);<br />
			daoe->Delete();<br />
	<br />
	}<br />
<br />
	WaitForMultipleObjects(2,hEvents,FALSE,INFINITE);<br />
	LogActivity(CA_MSG_SEVERITY_INFORMATION,"Both threads returned");<br />
<br />

And my code just got hung....none of the two worker threads did any work and I never got to LogActivity(...) below WaitForMultipleObjects.

Thanks
ashish

Re: Multithread question

RobJones3-Jul-03 6:53

RobJones

3-Jul-03 6:53

He was probably assuming that you were running this in a loop.. checking every so often to see if both the threads exited.. You could set the Infinate flag and not even use the loop.. then it would wait until both exited.. Could be infinate if for some reason one of your threads hung..

HANDLE hThreads[2];
 
hThreads[0] = //Handle of first thread
hThreads[1] = //Handle of second thread
 
 
while(true)
{
	DWORD dwCode = WaitForMultipleObjects(2,hThreads,TRUE,100); // CHECK EVERY 100 ms
	 
	if ( dwCode == WAIT_TIMEOUT ) 
	{
		// Then at least one thread is still running.
	}
	else
	{
		// Both threads are finished.. Do what ever..
		// Stop the loop
		break;
	}
}

Whoever said nothing's impossible never tried slamming a revolving door!

Re: Multithread question

John M. Drescher3-Jul-03 6:57

John M. Drescher

3-Jul-03 6:57

achandra007 wrote:
So if I use TRUE for Parm 3 of WaitForMultipleObjects, then as soon as one thread exists, won't my statement return?

You do want TRUE for param 3 because that means to wait for both threads to finish. Are you sure that the threads are finishing? I have used this technique in the past with CreateThread() but not AfxBeginThread but the result should be the same.

John

Peer to Peer network implementation in V C++

EEder3-Jul-03 5:46

EEder

3-Jul-03 5:46

I am currently looking for the highest quality, easiest to implement, most secure and most reliable peer to peer c++ package avaliable to implement peer to peer networking in c++.

The company I work for already has a very robust and complex program which operates under a client-server network architecture. I am exploring migrating that architecture to peer to peer.

I have so far come across what appear to be the three best packages avaliable online:

1) P2PToolkit - www.p2ptoolkit.com
2) Howl - http://www.swampwolf.com/products/
3) JXTA-C - http://jxta-c.jxta.org/servlets/ProjectHome

Obviously, there is always the option of coding it up ourselves and not using a pre-defined package but I estimate that would take more time and money than necessary.

We have done some initial testing of P2PToolkit sample programs and have found them to be extremely unstable and unreliable. Then again, those were just the sample programs given online. HOWL seems encouraging as it uses the Zeroconf "standard" adopted by Apple Computer, but there is a discouraging amount of documentation avaliable.

I am very excited by the JXTA program and we have other projects which have used it in java-implementations of peer to peer networking. JXTA-C would be a definite choice, especially in light of its claims of interoperability, except according to the JXTA-C program site, its not finished and has not had any kind of final release. In fact, according to the program site, the majority of the project hasn't been touched in at least a year, which implies forward progress stopped in some way.

Does anyone out there have any suggestions about any of the three aforementioned Peer to Peer packages, either from experience or knowledge? Has anyone worked on a large scale project involving peer to peer networking and could share their experience?

Thanks in advance.

-EEder

Re: Peer to Peer network implementation in V C++

AlexO3-Jul-03 7:03

AlexO

3-Jul-03 7:03

Well, it is really project specific. While "peer to peer" is a beautiful term, it can mean million different things. Judging by your java reference I assume you prefer RMI, in which case why don't you go with Corba (COM/ DCOM) or even RPC?

Re: Peer to Peer network implementation in V C++

EEder3-Jul-03 8:14

EEder

3-Jul-03 8:14

Actually, my Java reference was to a different, although similar, project. Although the potential of that project and my current one being able to easily operate together if need be (part of my reason for being excited about JXTA) is nice.

I did use the term 'peer-to-peer' loosely and thats becuase I think its a pretty standard 'peer-to-peer' application. I'm looking for -

1) Self realizing network - discovery of peers when they arrive on the network, although a nameserver may be necessary.
2) standard message sending, data transfer
3) security is a factor, although not a driving one

The project currently handles all the data transfer properly, it just does it between a client and server.

Thanks for the comments!

how to change float to char*

Angel Kid3-Jul-03 5:40

Angel Kid

3-Jul-03 5:40

HI,Guys
I tried all methods I know,but it seems all the methods don't work?Could anyone help me?

YES, I am here.

Re: how to change float to char*

AlexO3-Jul-03 5:44

AlexO

3-Jul-03 5:44

float f =-89.567;
char * a = (char*)f;

Thanks

Angel Kid3-Jul-03 5:58

Angel Kid

3-Jul-03 5:58

thank you very much

YES, I am here.

Re: how to change float to char*

Ryan Binns3-Jul-03 15:39

Ryan Binns

3-Jul-03 15:39

That won't work at all.

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"

Re: how to change float to char*

Harald Krause3-Jul-03 5:48

Harald Krause

3-Jul-03 5:48

char buffer[100];
sprintf(buffer,"%f",floatvalue);

bb |~ bb

Thanks

Angel Kid3-Jul-03 5:59

Angel Kid

3-Jul-03 5:59

thank you.But it seems that must include the file stdio.h

YES, I am here.

Re: how to change float to char*

John M. Drescher3-Jul-03 6:04

John M. Drescher

3-Jul-03 6:04

When I look at the answers I see that both answers are completly different. The first casts the float to a char* so that you can look at the bits of how the processor encoded the float. I am not sure why you would want that.
[EDIT]
Also if you want that you should use BYTE or unsigned char instead.
[/EDIT]

The second returns a string that represents the float number. This is more likely what you want.

Which one are you looking for?

John

Convert BSTR to char*

RvD20023-Jul-03 5:18

RvD2002

3-Jul-03 5:18

<br />
char* ConvertBSTR(BSTR text)<br />
{<br />
	return (char*)_T(text);<br />
}<br />

I've got this function, but when I call:

<br />
char* temp;<br />
temp=ConvertBSTR(BSTRTEXT);<br />
MessageBox(NULL,temp,"",MB_OK);<br />

It only converts the first character Frown | :(

Does somebody know how to resolve this problem???

Re: Convert BSTR to char*

Ryan Binns3-Jul-03 5:27

Ryan Binns

3-Jul-03 5:27

[edit] This solution won't work because the converted string is actually on the stack, so the returned string will be invalid. The macros will have to be used inline, not in separate functions [/edit]

You can't use a BSTR like that. A BSTR is a unicode string. To convert BSTR to a char*, use the ATL conversion macros:

[edit]You have to include "atlconv.h" first[/edit]

char *ConvertBSTR(BSTR text)
{
   USES_CONVERSION;
   return W2A(text);
}

In your case, you only need a const char*, so you can do this

const char *ConvertBSTR(BSTR text)
{
   USES_CONVERSION;
   return W2CA(text);
}

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"

Re: Convert BSTR to char*

RvD20023-Jul-03 6:36

RvD2002

3-Jul-03 6:36

No, still doesn't work Frown | :(

Any other options?

Re: Convert BSTR to char*

Michael Dunn3-Jul-03 6:48

Michael Dunn

3-Jul-03 6:48

That won't work because the converted string is stored on the stack, and it goes out of scope as soon as the function returns. Use the macros inline, instead of in separate functions like that.

--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

Re: Convert BSTR to char*

RvD20023-Jul-03 6:52

RvD2002

3-Jul-03 6:52

That's the problem, the macro's won't work here... and they are to slow Frown | :(

I'm making a game engine so that need to be fast Big Grin | :-D

With COM, that's the reason for using a BSTR. And now I call a DirectX function that needs a LPCWSTR. So I have to convert it, but how??? :S

Re: Convert BSTR to char*

Michael Dunn3-Jul-03 7:27

Michael Dunn

3-Jul-03 7:27

You can pass a BSTR to a function expecting a LPCWSTR, because both strings are in the same format (zero-terminated Unicode string)

--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

Re: Convert BSTR to char*

RvD20023-Jul-03 7:32

RvD2002

3-Jul-03 7:32

But then I get the error that the format isn't right

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.