C / C++ / MFC

integrating a function...

27-Dec-04 14:38

From the MSDN documentation on the GetDC function

After painting with a common DC, the ReleaseDC function must be called to release the DC. Class and private DCs do
not have to be released. ReleaseDC must be called from the same thread that called GetDC. The number of DCs is
limited only by available memory.

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

aaadetos27-Dec-04 12:07

aaadetos

27-Dec-04 12:07

The following code below is from a text on numerical recipes in C++...Its purpose is to evaluate the integral of a function, "func", using the Gaussian Quadrature formula, viz:

<br />
double qgaus(double func, double a, double b)<br />
{<br />
	//elements of the integral<br />
	double xr,xm,dx,s;	//s unrelated to Laplace<br />
	//at abscissas x and with weights w,<br />
	double x[] = {0.1488743389816312,0.4333953941292472,<br />
		0.6794095682990244,0.8650633666889845,0.9739065285171717};<br />
	double w[] = {0.2955242247147529,0.2692667193099963,<br />
		0.2190863625159821,0.1494513491505806,0.0666713443086881};<br />
<br />
	xm = 0.5*(b+a);<br />
	xr = 0.5*(b-a);<br />
	s = 0;<br />
	<br />
	//performing the integration on func<br />
	for(int j=0;j<5;j++)<br />
	{<br />
		dx = xr*x[j];<br />
		s += w[j]*(func(xm+dx)+func(xm-dx));<br />
	}<br />
	return s *= xr;<br />
}

Im trying to adapt the code to integrate my function, "func", which returns an array of values, viz:

<br />
void function(double (*func)[nSize],CKuchukDlg *pDialog)<br />
{<br />
	enum{nSize = 100};<br />
	double Ip[nSize],p[nSize],gh[1][nSize];<br />
	double alpha[nSize],beta[nSize];	//this 's' is unrelated to Laplace's<br />
<br />
	for(int t=0;t<nSize;t++)<br />
	{<br />
		if(t==0)<br />
		{<br />
				alpha[0] = beta[0] = 1;<br />
				p[0] = sqrt(pow(alpha[0],2.0)+pow(beta[0],2.0));<br />
<br />
				homo(gh,nSize,pDialog);<br />
				Integrals(Ip,nSize);<br />
<br />
				func[0][0] = (gh[0][0] * Ip[0])/p[0];<br />
		}<br />
		else<br />
		{<br />
			alpha[t] = beta[t] = 2*t*PI;<br />
<br />
			homo(gh,nSize,pDialog);<br />
			Integrals(Ip,nSize);<br />
		<br />
			p[t] = sqrt(pow(alpha[t],2.0)+pow(beta[t],2.0));<br />
		<br />
			func[0][t] = (gh[0][t] * Ip[t])/p[t];<br />
		}<br />
	}<br />
}<br />

Can anyone please show me how I may do this? I have tried a number of ways, but I keep running into errors. Thank you!

const pointer

act_x27-Dec-04 10:48

act_x

27-Dec-04 10:48

I need to refer something on C++ and found this

#include <iostream>
using namespace std;

int main()
{
int foo = 4;
int bar = 16;

// ptr - non-constant pointer, non-constant data
//
int* ptr = &foo;

*ptr = 6; // OK: Data is non-constant, so it can be
// changed via ptr

ptr = &bar; // The pointer is non-constant, so it may
*ptr = 22; // point to other data And change it

// ptr_to_const - non-constant pointer, constant data
//
const int* ptr_to_const = &foo;

return 0;
}

When i read this
const int* ptr_to_const = &foo;
Non constant pointer to constant data ;
But foo isnt declared as constant .
Why does the compiler not warn me of this ?

Re: const pointer

Prakash Nadar27-Dec-04 18:38

Prakash Nadar

27-Dec-04 18:38

Read this
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclang98/html/_pluslang_const_and_volatile_pointers.asp[^]

-prakash

Re: const pointer

Dennis Gourjii28-Dec-04 0:09

Dennis Gourjii

28-Dec-04 0:09

A pointer to constant data needs to be initialized, that's what this line does, and no specification says the "initializer" must be constant. Using pointers to constant data is in essence declaring an intention not to modify that data, nothing more. Sure, if you try to modify it, no warning will be shown - it'll be an Error!
The other possible case is declaring a constant pointer. You certainly can initialize it, but not make it point anywhere else afterwards.

Re: const pointer

Henry miller28-Dec-04 4:42

Henry miller

28-Dec-04 4:42

Because prt_to_const is a promise that you won't modify the data through ptr_to_const, not that the data it points to cannot change by other means!

One good reason to use const is to force other code to not change something. A class might return a ptr_to_const, that points to private internal class data. The class itself might modify the data via some function call latter, but it would be a mistake to let anything other than the class modify that internal data.

Callback Function

RedDragon2k27-Dec-04 10:13

RedDragon2k

27-Dec-04 10:13

Hi Everyone

I have a DLL which should later monitor a specified app. But how can I notify my Main Program that something has change ?

starts Routine
-----------------------------
|
\/ ^
|------| |----------------|
| DLL | | Main Program |
|------| |----------------|
| ^
| |
--------------------------
should notify the program if something changes

So i thought about a callback function, but i don't know how i can realize this
Please help ???

MFG
RedDragon2kx

Unix and C are the ultimate computer viruses.

Visit me: www.programming.info.ms

Tom Wright27-Dec-04 10:30

27-Dec-04 10:30

maybe in your dll you need to have an function that you can call that will check your app. Pass a message to the app and have the app send a message back with it's status.

I guess you need to ask your self.

1. How is this dll going to be loaded. From another application or your main app?
2. What is it that you are monitoring. Whether the main app is still running?
3. What is the purpose of the dll? Will it tell me something about the main app that will make it (the dll) do something else?
4. Is the main app something you wrote or someone else wrote?

Tom Wright
tawright915@yahoo.com

RedDragon2k27-Dec-04 10:43

RedDragon2k

27-Dec-04 10:43

So I have 3 Apps:
The first App is the MainApp which loads the DLL
The second "App" is the DLL which montiors the third App
The third App is some app which gets monitored by the DLL

While all apps are still running the DLL monitors the third App. And when the third App for e.g. calls WM_PAINT the Main App should get notified by the DLL.

Unix and C are the ultimate computer viruses.

Visit me: www.programming.info.ms

Tom Wright27-Dec-04 12:00

27-Dec-04 12:00

Much clearer. What you want to do is create a hook in your dll, so that you can monitor any messages that are being sent to that app. There are a ton of articles on window hooks.

Tom Wright
tawright915@yahoo.com

passing a struct with WM_COPYDATA

Dennis Gourjii28-Dec-04 0:15

Dennis Gourjii

28-Dec-04 0:15

Any interprocess communication technique will do. I would recommend using a memory-mapped file or thread messages, but that's up to you. For a list of effective IPC mechanisms refer to J.Richter's "Programming Windows", it's worth reading anyway.

Tom Wright27-Dec-04 9:14

27-Dec-04 9:14

I'm having a problem passing a structure with WM_COPYDATA. Can anyone give an example of how to do this on the sending side an the receiving side?

Thanks

Tom Wright
tawright915@yahoo.com

PJ Arends27-Dec-04 11:01

27-Dec-04 11:01

How are you currently doing it? Are you passing the address of your struct in the lpData member of the COPYDATASTRUCT?

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

Tom Wright27-Dec-04 11:33

27-Dec-04 11:33

yes. Here is my function that send the message from a thread I created:

<br />
	typedef struct tagCONNSTATUS {<br />
		int nConnID;<br />
		CString sThreadID;<br />
		CString sConnStatus;<br />
	}CONNSTATUS;<br />
	CONNSTATUS ConnStatus;<br />
	<br />
	ConnStatus.nConnID = ConnID;<br />
	ConnStatus.sThreadID = thdID;<br />
	ConnStatus.sConnStatus = "Connected";<br />
<br />
	COPYDATASTRUCT myData;<br />
	myData.dwData = 0;<br />
	myData.cbData = sizeof(ConnStatus);<br />
	myData.lpData = &ConnStatus;<br />
	<br />
	//LRESULT copyDataResult;<br />
	<br />
	if (!SendMessage(myHandle->m_hWnd, WM_COPYDATA, 0, (LPARAM)&myData))<br />
		MessageBox(NULL, "Error Posting Connection Message", "Error on PostMessage", MB_OK | MB_ICONEXCLAMATION);<br />
<br />

Here is the function that receives the message in my main application:

<br />
BOOL CLAMsgSwDlg::OnCopyData(CWnd* pWnd, COPYDATASTRUCT* pCopyDataStruct)<br />
{<br />
	//CString recvString = (LPCSTR) (pCopyDataStruct->lpData);<br />
	//int recvStringLen = pCopyDataStruct->cbData;<br />
	typedef struct tagCONNSTATUS {<br />
		int nConnID;<br />
		CString sThreadID;<br />
		CString sConnStatus;<br />
	}CONNSTATUS;<br />
<br />
	//CString recvString = (LPCSTR) (pCopyDataStruct->lpData);<br />
	(DWORD)((CONNSTATUS*)(pCopyDataStruct->lpData))->nConnID;<br />
	(LPCSTR)((CONNSTATUS*)(pCopyDataStruct->lpData))->sThreadID;<br />
	(LPCSTR)((CONNSTATUS*)(pCopyDataStruct->lpData))->sConnStatus;<br />
<br />
	CONNSTATUS ConnStatus;<br />
	AfxMessageBox(ConnStatus.sConnStatus);<br />
	AfxMessageBox(ConnStatus.sThreadID);<br />
<br />
	//return CLAMsgSwDlg::OnCopyData(pWnd, pCopyDataStruct);<br />
	return 1;<br />
}<br />
<br />

When my message boxes pop up they show nothing.

Tom Wright
tawright915@yahoo.com

PJ Arends27-Dec-04 11:53

27-Dec-04 11:53

Tom Wright wrote:
typedef struct tagCONNSTATUS {
int nConnID;
CString sThreadID;
CString sConnStatus;
}CONNSTATUS;
CONNSTATUS ConnStatus;

AFAIK the problem is with the CStrings. They contain pointers to the actual string data, and you can not pass pointers across process boundaries as the pointers will have no meaning to the recieving process.

You have to build your structure in such a way that it does not contain any pointers.
For example:

typedef struct tagCONNSTATUS {
   int nConnID;
   TCHAR sThreadID[128];
   TCHAR sConnStatus[128];
} CONNSTATUS;

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

Tom Wright28-Dec-04 11:55

28-Dec-04 11:55

Yeah I'm still getting nothing. I've tried it where I'm passing a test string from a CString object and that worked. However I cannot get a structure to pass coreectly. Not sure what I have set wrong.

Thanks for the help anyway. I'll keep plugging a long.

Tom Wright
tawright915@yahoo.com

PJ Arends28-Dec-04 16:09

28-Dec-04 16:09

The concept is not difficult. All it does is copy cbData bytes from the memory at lpData.

If you want to see a working example, take a look at http://www.codeproject.com/tools/imageviewer.asp[^]. The sending code is in the ViewerDll project; ImageView function. The receiving code is in the ViewerApp project; OnCopyData function.

I am willing to provide more help if you need it, just ask.

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

Tom Wright29-Dec-04 3:54

29-Dec-04 3:54

I figured it out. I needed to do a memcpy on the receving side. Once I did that I was able to receive all the data in my struct.

<br />
	typedef struct tagCONNSTATUS {<br />
		int nConnID;<br />
		TCHAR sThreadID[128];<br />
		TCHAR sConnStatus[128];<br />
	}CONNSTATUS;<br />
<br />
	CONNSTATUS ConnStatus;<br />
	memcpy(&ConnStatus, pCopyDataStruct->lpData, sizeof(ConnStatus));<br />
	m_lClientConn.SetItemText(ConnStatus.nConnID, 3, ConnStatus.sConnStatus);<br />

Thanks for the help.

Tom Wright
tawright915@yahoo.com

CStatusBar

Anthony988727-Dec-04 8:40

Anthony9887

27-Dec-04 8:40

I'm trying to insert a status bar control inside a the activex window in OnCreate. It only appears if i resize the window, also how can i change it from being indented(Pushed In) i would like it closer to what the Mainframe window looks like.

Thanks

Re: CStatusBar

Tom Wright27-Dec-04 10:35