C / C++ / MFC

Re: Stack or heap pointer?

22-Apr-05 2:56

Hello,

I was wondering, is there a way to determine if a pointer points to data on the heap or on the stack?

I know that you can see if the pointer points 'near' the value of the ESP register, but thats not what I'm looking for...

I also got the blogging virus..[^]

James R. Twine22-Apr-05 3:45

James R. Twine

22-Apr-05 3:45

   I remember something about all heap memory having a certain bit set (high bit, bit 6, bit 7?), but I do not remember which it one, or if it is even really true.

   Tip: if you are trying to figure out delete this functionality, be careful...!

   Peace!

-=- James

If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
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Re: Stack or heap pointer?

Bob Stanneveld24-Apr-05 20:26

Re: Stack or heap pointer?

24-Apr-05 20:26

Thanks for your reply!

James R. Twine wrote:
Tip: if you are trying to figure out delete this functionality, be careful...!

This is exactly what I'm trying to do. I alreay implemented the "feature" but it the cost was to disable all the rest for safety reasons. (copy constructor, public destructor, etc..) I want these functions to be available for flexibility, but I think that I have to make a choice...

If I could get the upper bound and the lower boud of the heap address range, than I just could....

I also got the blogging virus..[^]

22491722-Apr-05 7:44

224917

22-Apr-05 7:44

These functions may help : GetProcessHeaps() then a HeapWalk()/HeapValidate(). In case of debug build _CrtIsValidHeapPointer.

suhredayan
There is no spoon.

ListCtrl Won't Sort - Help !

Jethro6322-Apr-05 2:45

Jethro63

22-Apr-05 2:45

Hi:

I am trying to write an extended ListCtrl class for my own use and as a self-learning exercise. I have a perplexing problem here and I have tried to reduce it to the simplest of possible terms.

The two key code segments are as follows:

A button handler which requests that the list box items be sorted:

void CReportWiseDlg::OnSortBtn()
{
m_nrcDemo.SetRedraw( FALSE );
m_nrcDemo.SortItems( TempCmpFunc, (LPARAM)&m_nrcDemo );
m_nrcDemo.SetRedraw( TRUE );
}

And the CALLBACK function that provides the compare operation. In this case, I wanted to sort by column two which contains floating point values (which I have to convert, of course):

int CALLBACK TempCmpFunc(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
CNiceReportCtrl* pListCtrl = (CNiceReportCtrl *)lParamSort;
CString strItem1, strItem2;
int nItem1, nItem2;

nItem1 = (int)lParam1;
nItem2 = (int)lParam2;

strItem1 = pListCtrl->GetItemText(nItem1, 2);
strItem2 = pListCtrl->GetItemText(nItem2, 2);

double f1, f2;
f1 = atof( (LPCTSTR)strItem1 );
f2 = atof( (LPCTSTR)strItem2 );

if (f1 < f2)
return 1;
else if (f1 > f2)
return -1;
else
return 0;
}

Now, when I click my sort button, I can see my OnSortBtn routine get called. Furthermore, I can see my CALLBACK function getting called several times. For a List box with 8 rows, I counted 13 calls to my CALLBACK. The problem is that every single time the CALLBACK is called, the lParam1 and lParam2 input parameters are ALWAYS equal to ZERO. The net result of this is that the list does not get sorted. It stays exactly the same.

I just followed the example code provided on the MSDN disks for CListCtrl::SortItems. It all looked pretty straight-forward.

Can anybody suggest what might be going on?

Thank you in advance for your help.
Mark

Re: ListCtrl Won't Sort - Help !

Stlan22-Apr-05 3:49

Stlan

22-Apr-05 3:49

If I remember correctly, lParam1 and lParam2 of the sorting callback function, do not contain the index of the items to compare, but instead they refer to the user data of those two items (You know, it's the custom value you can associate to any item by calling the function SetItemData)

Re: ListCtrl Won't Sort - Help !

David Crow22-Apr-05 8:02

David Crow

22-Apr-05 8:02

Stlan wrote:
If I remember correctly...

You are correct. Most folks do not know that the control calls GetItemData() before calling their compare function. This is why SetItemData() is needed.

"Ideas are a dime a dozen. People who put them into action are priceless." - Unknown

Chat - Using Threads?

DKT_22-Apr-05 2:12

DKT_

22-Apr-05 2:12

Hi guys,

I once coded a chat program. Server - Client based. It worked like a charm. But the only problem was, that the sever app worked in an endless loop to receive messages and wait for new connections. This raises the cpu to 50 and more per cent.
How can I avoid that? I thought about using threads. But this doesnt seem to solve the problem. What can I do? And if I should use threads, which function to take? There are alot out there.

I am working with visual C++ but NOT with MFC.

DKT

Jack Puppy22-Apr-05 2:36

Jack Puppy

22-Apr-05 2:36

Try the Winsock Programmer's FAQ

In particular, read
Which I/O Strategy Should I Use?

If I remember correctly, there should be sample C code of the various techinques somewhere on that site.

Pssst. You see that little light on your monitor? That's actually a government installed spy camera. Smile and wave to big brother!

Anonymous22-Apr-05 2:45

22-Apr-05 2:45

Wow. Thats nice! I will read that!

Thank you!

DKT

ThatsAlok22-Apr-05 2:38

ThatsAlok

22-Apr-05 2:38

are you using Blocking sockets or Non blocking Socket!

It seems you are using nonblocking sockets which incresing the load on CPU!. try recode you client server using Blocking socket this may help you drop down your cpu usage

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta

Anonymous22-Apr-05 2:47

22-Apr-05 2:47

Yeah, I used nonblocking mode. But if I switch to blocking mode, then the whole app stands, and waits for an incoming connection. For this I need threads I think, right?

DKT

Bob Stanneveld22-Apr-05 2:53

22-Apr-05 2:53

Yes, you can use one thread to wait for a connection, and spawn a new thread for every connection received.

There are some good thread pool articles and thread articles around here on CP..

I also got the blogging virus..[^]

Anonymous22-Apr-05 3:02

22-Apr-05 3:02

Yeah, I was already looking for those tutorials. But most articles come up with their own class. And the others work with the MFC. I couldnt find an article that fits my wishes, therefor I am here.

I have to look once again!

So, the best way is the following:

Create a thread that accepts incoming connections
This one creates a new thread for each connected client, who will handle his stuff, like sending and receiving data.

Is that correct?

DKT

Bob Stanneveld22-Apr-05 3:41

22-Apr-05 3:41

Yes that is the easy way to go. It is not bad if your chat server doesn't have a high load and very many connections.

If you do have a high load chat server, you can start a few threads that handle work asynchronously. That is more complex though.

This[^] CThread class by Dominik Filipp is a very nice one.

I also got the blogging virus..[^]

Anonymous25-Apr-05 0:18

25-Apr-05 0:18

Hi again,

I have one problem: If I want to create a thread, I cant add params to the thread function. But thats what I need, at least to pass the HWND of my Dialogbox. Is there no way to implement that?

DKT

Bob Stanneveld25-Apr-05 4:40

25-Apr-05 4:40

if you are using raw thread api's you can pass one parameter to the CreateThread api. This could be your HWND.

If you are using a thread class, derive your own class, set all the parameters as member variables before you run the class...

I also got the blogging virus..[^]