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Hello. I wrote a dll for use with a VB front-end. The DLL runs mainly in a while loop which takes full control over the one thread VB allows, which ultimately freezes the VB form. I was wondering if adding multi-threading to the DLL would help. Theorhetically, I would think that it might. For example, VB App loads DLL in one thread, DLL creates new thread for while loop processing, thus the VB form should be able to function.
Here would be an example of my DLL layout:
while() {
for() {
if () {
}
}
}
So, I suppose I would need to through the entire while loop in its own thread, but I have no idea how. I have never multithreaded before, so I would really appreciate an example, if possible.
I thank you in advance.
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First, it would help if you specified what VB you are talking about, VB6 or .NET.
Second, it strikes me as extremely poor design to use a continuously looping thread. For such a thing, one usually uses a design that uses wait functions and alertable threads.
Why don't you describe what kind of processing the thread is actually doing, and I'm sure there is some way to redesign it so that it works better.
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I am using VB6. As of now, the while loop is non-alertable, but will be before I am through. But, would be open to an example of that as well. However, that was an intention before the release. The thread is processing packet data as it comes off the wire. I need it to continously loop until user says stop.
let me know if you need more info. thanks in advance.
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borono wrote: The thread is processing packet data as it comes off the wire.
Well what do you mean by "the wire?" Is the thread talking directly to a device driver? Are you referring to TCP/IP sockets? There are numerous examples of how to accomplish overlapped I/O with TCP/IP sockets.
The theory with overlapped I/O, is that you create a worker thread that enters a wait state, waiting for data to arrive on one or more sockets. When the system alerts the thread that data has arrived, then the thread wakes up, and performs the necessary processing.
Just look up Overlapped IO in the MSDN. If you have questions about implementing it in your DLL, I and many others on this board can help you with that.
Rich
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thats what I have now, the thread sits in a wait state waiting for data. I am talking directly to the device. I just can not stop it altogether at this point, without totally killing the process. I figure I can do this. I can create another vb project, solely to load my dll for capturing and that should work. However, I would rather do it properly with multiple threads.
How would I through the entire while loop in its own thread separate from the main thread, in my dll?
thanks in advance.
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Well, the easy way out of your problem would be to call CreateThread in your DllMain function, so that your device polling happens on this second thread, and your main thread is free to return to the VB form.
DWORD ThreadId = 0;
HANDLE ThreadHandle = CreateThread( NULL, NULL, ProcessingFunction, lpParameter, NULL, &ThreadId );
Then your processing function would be declared as follows:
DWORD WINAPI ProcessingFunction(
LPVOID lpParameter
);
Just put all your processing code into the ProcessingFunction, and you will have it running on a separate thread. But you will be responsible for communicating to the second thread when it needs to quit.
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Oh no, now I am lost. Bare with me, I am currently sitting with two-ply jammed up both nostrils, sick as a dog, trying to keep up with you. Plus, this is all new knowledge to me, so I of course have questions.
With:
DWORD WINAPI ProcessingFunction(LPVOID lpParameter);
Would it go into my function:
char* _stdcall cap(char *adp) {
//place here
}
...?
Also, I don't have a DLLMAin function, because I thought it was not necessary when calling the DLL from VB. Is it alright to create one? Not sure how it looks.
Plus, doesn't the API cause leaks? I would rather avoid that, if possible. Doesn't look like I will be multi-threading anytime soon. So, here is another question, perhaps easier to explain. I also need to send the stats back to the VB app... how can I do that without sending a return, which ends the entire function. I just want to know how many protocols have been identified while capturing, without killing the entire thing. I'm not even going to guess, I have no idea what to do.
sorry for the slow comprhension rate today, I am normally quicker than this.
best regards
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borono wrote: Also, I don't have a DLLMAin function
Did you write this DLL? What language was used to write the DLL?
borono wrote: Plus, doesn't the API cause leaks?
What kind of "leaks" are you talking about? And NO, the API by itself does not cause memory leaks.
If you want to create additional threads, you are going to have to use the Win32 API. I don't know of any way in VB6 to create additional threads.
borono wrote: I also need to send the stats back to the VB app
For this, I would suggest looking up how to implement something called a "callback function" in your VB6 app. Then have the thread in your DLL periodically call the callback function with the necessary data.
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Hi Borono,
Sorry I didn't get chance to answer your E-mail yet. I was going to suggest running your dll in a thread, though it looks like you figured it out already. The only problems you may encounter is alerting the VB side about events happening in the thread.
I'm not sure how VB handles handles a message loop, or if there is one, but I would suggest creating a GetMessage() function in your dll which the VB can constantly call. Thus retrieving any notifications from the thread and acting on them.
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thanks waldermort, that sounds like a good idea, GetMessage(). I actually tried using a separate function, which of course didn't work. I am trying. Yes, I think multi-threading is the answer here as well, I have a bit of research to do. thanks again and no worries about the email, I got up early today, am sick with nothing better to do and started stirring a bit, thought I would get going on it. Glad you jumped in. I think I am just upsetting the other gentlemen. 
best regards
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You were not upsetting me. I was already upset. Sorry if I came across gruff.
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no problem my friend, no harm done. In fact, your suggestion on callbacks was quite successful. Just in case anyone needs the same, here is how you perform the callback from DLL to VB.
First you need to write the DLL. Create the new project, "simple project". Then paste this code:
extern "C" void __stdcall TestCallback( void (*cb) (int*) )
{
int nrMsg = 123 ;
cb( &nrMsg );
}
Create a def file and place this in it:
LIBRARY MYDLLNAME
EXPORTS
TestCallback @1
Note: you have to do this for VB, also notice the _stdcall, again a must for VB.
Then compile the DLL and place in the VB project directory.
Create a new VB project and add a module and command button.
In module:
Option Explicit
'
Declare Sub TestCallback Lib "mydll.dll" (ByVal funcptr As Long)
'
Sub CallbackFunction(ByRef numb As Long)
MsgBox "Success: " + Str(numb)
End Sub
In form:
Private sub Command1_Click()
TestCallback AddressOf CallbackFunction
end sub
Now compile the project and run. Should return 123.
gdlk, hope this was clear. now off to multi-threading. thanks
best regards
-- modified at 23:42 Friday 7th April, 2006
Update: multi-threading complete. I did what you said and it works great, can start and stop it at will now, easier than I thought it would be. thanks a lot.
this is solved, regards
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Hello,
Does anyone have any experience with using or creating alternative shells for Windows 2K, XP ??
Basically, my question is I want to know how simple or complex it would be to have Winlogon run my program instead of Explorer, so that my program can do some things, and then turn around and launch Explorer as the main shell.
I have found a registry key that looks like it might be a simple way to launch my program:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
This key contains a value called "Shell" that currently says "Explorer.exe". Do you think that all I have to do is replace that value with my program, or do you think I have to develop a custom GINA dll and all that stuff?
Any thoughtful comments would be appreciated,
Rich
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I receive event 1,
I would like to set a timer to the millisecond
When i receive event 2,
I would like to stop that timer.
Anyone know what i should use?
Also, if i decide to get the current time to the millisecond after the 1st event, then do the same for the second event.
Then i can subtract the two and get the difference in time
Anyone know how to do that as well?
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SetTimer() would send you WM_Timer messages, but handling this with a resolution of (less than) a millisecond is asking a bit much.
If you can afford to rely on DirectX, timeSetEvent() would be the way to go.
It provides you with the possibility to be called with a much higher accuracy.
Measuring even shorter durations is easy:
You ::QueryPerformanceCounter() on event1.
You ::QueryPerformanceCounter() on event2.
The difference is your duration between the events.
Be sure to ask ::QueryPerformanceFrequency() about if and with which frequencies the timer runs.
"We trained hard, but it seemed that every time we were beginning to form up into teams we would be reorganised. I was to learn later in life that we tend to meet any new situation by reorganising: and a wonderful method it can be for creating the illusion of progress, while producing confusion, inefficiency and demoralisation."
-- Caius Petronius, Roman Consul, 66 A.D.
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This question has been asked and answered many times. What is it that you are not understanding?
"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain
"There is no death, only a change of worlds." - Native American Proverb
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This previous response was the only response that gave me something to try to the nearest millisecond. Other responses, simply said that this cannot be done to accuracy with a windows OS. I have looked at a few other API calls but they all give time to the nearest second..
This current response gave me (QueryPerformanceCounter) to try that i had never tried to achieve millisecond time...
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hi, can somebody help me to determine the source code for chain code?
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what is chain code ?
what is it supposed to do ?
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Hi there,
I receive some data as packets in XML format and I need to verify thier type for further implementation, and I can understand what kind of data I am dealing with as I need to send the data to different palces through socket (for example: if the data I receive is transaction request, send it to that bank through IP add ......., if data is sign on send it to host,....). Is anyone know how I can do it?
TNX
nahitan
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I am working on an application which will going to use OpenGL in 2 different locations.
#1. in DialogBar
#2. in CView
I implemented OpenGL for both, and they are working well when one of them is disabled. My problem is when both are active, confliction happens like they are trying to use opengl setup properties of each other like..if Dialog is wireframe CView turns into wireframe mode then crashes..
How can I prevent this, and let them work without touching each other.is Multi-threaded 2 different engine needed? ( As the example I gave above..they are using different views so I cant use 1 engine for both view. )
I am missknowledged about this type of OpenGL problems..
Any suggestion, articles are all welcome...and I ll be very glad...
thanks...
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Hi all,
I'd like have some MDI child windows (Form View) like model dialogs, so that after closing the dialog only, I should even be able to access the main window (toolbar/menu/close button).
How to make it possible?
Thanks in advance,
Sarvan AL
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So - what you want is a modal dialogue with a FormView(-derivation) inside?
There should be a few examples lying around here on CP.
"We trained hard, but it seemed that every time we were beginning to form up into teams we would be reorganised. I was to learn later in life that we tend to meet any new situation by reorganising: and a wonderful method it can be for creating the illusion of progress, while producing confusion, inefficiency and demoralisation."
-- Caius Petronius, Roman Consul, 66 A.D.
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