Mathematical Overflow - C / C++ / MFC Discussion Boards

Re: Avoiding UDP client-side packet loss

Zoltan Csizmadia4-Feb-03 11:18

4-Feb-03 11:18

UDP is connectionless, so it's always possible you will lose packets. Try to use TCP sockets, or build some kind of protocol (using UDP) to avoid packet loss. You can play with the network card driver buffer settings, or using bigger packet size, or decrease the frequency.

If you are not using a real-time OS, you cannot be sure the OS will store all the incoming packets. Like a driver will run on higher priority than your process, and it's possible you'll lose packets.

Zolee

Re: Avoiding UDP client-side packet loss

Gisle Vanem5-Feb-03 0:39

Gisle Vanem

5-Feb-03 0:39

Note that if sending a UDP messages from several threads and before ARP resolution is done (because ARP entry has expired or is the first message sent), it will cause some (or all?) UDP messages to be lost.

This is (according to MSDN) due to the fact that there can only one pending ARP-reply per host-IP. Sorry I cannot find the ref. at the moment.

Remedy: call SendARP() before sendto().

Gisle V.

"If you feel paranoid it doesn't mean they're not after you!" -- Woody Allen

Can't use \n in my Edit box!!

Rickard Andersson²⁰4-Feb-03 10:43

Rickard Andersson²⁰

4-Feb-03 10:43

I've created an Edit box like this:

wndCmdEdit = CreateWindow("edit",
			  NULL,
			  WS_CHILD | WS_VISIBLE |
			  WS_BORDER | ES_LEFT | ES_MULTILINE,
			  5, 130,
			  385, 20,
			  hWnd,
			  (HMENU)IDC_MAINWNDEDIT,
			  hInst,
			  NULL);

But when I write text to it with "new line" char it adds a | instead of new line!!

Why??

Rickard Andersson@Suza Computing
C# and C++ programmer from SWEDEN!
UIN: 50302279
E-Mail: nikado@pc.nu
Speciality: I love C#, ASP.NET and C++!

Re: Can't use \n in my Edit box!!

Gary Kirkham4-Feb-03 10:45

Gary Kirkham

4-Feb-03 10:45

try \r\n

Gary Kirkham

A working Program is one that has only unobserved bugs

I thought I wanted a career, turns out I just wanted paychecks

Re: Can't use \n in my Edit box!!

Alvaro Mendez4-Feb-03 10:46

Alvaro Mendez

4-Feb-03 10:46

Because the newline character is not enough. It needs to also have a carriage-return character ('\r'). So the proper way to insert new lines is with "\r\n".

Regards,
Alvaro

All you need in this life is ignorance and confidence, and then success is sure. -- Mark Twain

Can somebody help me please?

MemLeak4-Feb-03 10:12

MemLeak

4-Feb-03 10:12

It's not the first time that I post this message. Look like nobody can help me...

I want to draw a transparent bitmap into a Dialogbar.

Here what I tried:

this is in my dialog bar class...

BOOL myDlgBar::Create(CWnd* pParentWnd)
{
if(!Create(pParentWnd, IDD_DLG_POSROOT, CBRS_RIGHT, IDD_DLG_POSROOT))
{
return 0; // fail to create
}

else
{

COLORMAP clr; //used to chnge my black color in my bitmap to white color

clr.from = RGB(0,0,0);//black
clr.to = RGB(255,255,255);//white

m_SLogo.Create(_T("my static"),WS_CHILD|WS_VISIBLE|SS_BITMAP|SS_CENTERIMAGE,
CRect(9,10,209,78), this, IDC_LOGOPOSROOT);

m_SLogo.SetBitmap(::CreateMappedBitmap(AfxGetInstanceHandle(), IDB_LOGO, 0, &clr, 1) );

return 1;
}
}

with CStatic m_SLogo;

IDC_LOGOPOSROOT is my picture class object in the resource editor with "frame" option
IDB_LOGO is my id of my bitmap in the ressource editor
IDD_DLG_POSROOT is the id of my dialog in the ressource editor

The result of this is that I can see my bitmap in my dialog bar but the black didn't change to white...

thanks

Everything's beautiful if you look at it long enough...

Re: Can somebody help me please?

includeh106-Feb-03 0:04

includeh10

6-Feb-03 0:04

i suggest:
1. creat a blank application and only test the fuction
or
2. use "find in file" to search the function in msdn samples (source are in CD).

i only remember that the function is very simple.

good luck

includeh10

Mathematical Overflow

Dov Sherman4-Feb-03 10:10

Dov Sherman

4-Feb-03 10:10

If I have:

int Multiply(int iA, int iB)<br />
{<br />
int iProduct = iA * iB;<br />
return iProduct;<br />
}

How can I test for multiplication overflow, the situation in which the correct result of iA * iB requires too many bits to fit into iProduct?

Re: Mathematical Overflow

Tim Smith4-Feb-03 10:25

Tim Smith

4-Feb-03 10:25

One method is to do the multiplication using __int64s and then testing for overflow.

__int64 result = __int64 (iA) * __int64 (iB);
if (result != (int) result)
    // OVERFLOW

However, this assumes int isn't an __int64.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: Mathematical Overflow

Alvaro Mendez4-Feb-03 10:39

Alvaro Mendez

4-Feb-03 10:39

Tim's is probably the simplest method.

You can also opt for trapping these kinds of problems using structured exception handling. In your case it looks like an Integer Overflow exception (0xC0000095).

Do a search for "_try" in MSDN and take a look at this article[^].

[edit]
Yet another option is to put the code inside a try/catch-all block:

int Multiply(int iA, int iB)
{
  try
  {
    return iA * iB;
  }
  catch (...)
  {
    // something bad happened; most likely an Integer Overflow
  }
}

[/edit]

Regards,
Alvaro

All you need in this life is ignorance and confidence, and then success is sure. -- Mark Twain

Re: Mathematical Overflow

eddie.breeveld28-Sep-04 1:51

eddie.breeveld

28-Sep-04 1:51

How do I enable integer overflow trapping? It doesn't seem to be on by default.

Eddie Breeveld

Re: Mathematical Overflow

Joaquín M López Muñoz4-Feb-03 10:49

Joaquín M López Muñoz

4-Feb-03 10:49

I guess this could do:

inline bool mult_overflow(int a,int b)
{
  return a!=0 && (a*b)/a!=b;
}

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: Mathematical Overflow

nde_plume4-Feb-03 11:26

nde_plume

4-Feb-03 11:26

int mult(int iA, int iB)
{
int product = iA * iB;
if(iB != 0 || product / iB != iA)
throw MathException;
return product;
}

I believe this works.

using HWND vs CWnd* with MFC.

Maximilien4-Feb-03 9:58

Maximilien

4-Feb-03 9:58

I always used CWnd when working with MFC, never really used HWND as I never really programmed fully Win32 applications.

Is there an advantage to use HWND to keep objects in containers ( for example ? ) instead of CWnd* ?

std::vector<HWND> hwndVector;
std::vector<CWnd*> cwndVector;

Thanks.

Max.

Re: using HWND vs CWnd* with MFC.

Joaquín M López Muñoz4-Feb-03 9:59

Joaquín M López Muñoz

4-Feb-03 9:59

As for the efficiency, none at all (both types of objects occupy the same space). Using HWND will tend to make things more complicat, specially in multithreaded code, where it is not easy to retrive the "true" CWnd attached to a given HWND. So, I'd say you're better off using CWnd *s.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: using HWND vs CWnd* with MFC.

David Salter4-Feb-03 10:20

David Salter

4-Feb-03 10:20

Joaquín M López Muñoz wrote:
Using HWND will tend to make things more complicat, specially in multithreaded code

But if you're passing Window handles between threads you have to use HWNDs as the CWnd/HWND mapping doesn't go across the thread boundary properly.

Re: using HWND vs CWnd* with MFC.

Joaquín M López Muñoz4-Feb-03 10:45

Joaquín M López Muñoz

4-Feb-03 10:45

It is the mapping HWND->CWnd that does not hold across threads, not the other way around. Handling a CWnd object from a thread other than the one which created the CWnd is just fine (modulo concurrency problems).

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: using HWND vs CWnd* with MFC.

Zoltan Csizmadia4-Feb-03 11:28

Zoltan Csizmadia

4-Feb-03 11:28

If you have a single-threaded application storing CWnd* is more practical, easier to use.

You CANNOT use the CWnd* in a different thread, than the thread, where the given CWnd* was created. What you can do is you pass the HWND for the given window to the thread, and in that thread you create your CWnd* using CWnd::FromHandle(hwnd), after that, you can use this CWnd* in this thread. So it's more practical to store HWND in this kind of environment.

I could give you some examples, when you could use CWnd* in a multithreaded application, but it's very wrong.

Zolee

Re: using HWND vs CWnd* with MFC.

Joaquín M López Muñoz4-Feb-03 11:34

Joaquín M López Muñoz

4-Feb-03 11:34

You CANNOT use the CWnd* in a different thread, than the thread, where the given CWnd*

I do not agree with that. Can you give some example in which using a CWnd * across threads is wrong and doing the same with a CWnd * obtained via CWnd::FromHandle is right?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Get app Path ?

Larsson4-Feb-03 9:55

Larsson

4-Feb-03 9:55

How can I get the app Path without geting the app name?

\Larsson

Re: Get app Path ?

Joaquín M López Muñoz4-Feb-03 9:56

Joaquín M López Muñoz

4-Feb-03 9:56

If you have the app path and name, use strrchr to look for the last ocurrence of \, insert a string-terminating 0 there and you're done.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: Get app Path ?

Larsson4-Feb-03 11:24

Larsson

4-Feb-03 11:24

Can you please send me a code to se what to do??

\Larsson

Re: Get app Path ?

Navin4-Feb-03 11:00

Navin

4-Feb-03 11:00

_splitpath

You can pick your friends, and you can pick your nose, but you can't pick your friend's nose.

Re: Get app Path ?

bryce4-Feb-03 12:16

bryce

4-Feb-03 12:16

somewhere useful

char * szDir = (char*) malloc(300);;
GetCurrentDirectory( 300,szDir);

and don't forget to....
free(szDir);

Bryce

Re: Get app Path ?

Steve Mayfield4-Feb-03 19:20

Steve Mayfield

4-Feb-03 19:20

Here is the routine I use:

CString CDemoApp::GetFullAppName() const
{
  char szFilename[_MAX_PATH] , szDrive[_MAX_DRIVE], szDir[_MAX_DIR], szFname[_MAX_FNAME], szExt[_MAX_EXT];

  GetModuleFileName(AfxGetInstanceHandle(), szFilename, _MAX_PATH);
  _splitpath(szFilename, szDrive, szDir, szFname, szExt);
  CString strAppPath(CString(szDrive) + CString(szDir) + CString(szFname));
  return strAppPath;
}

Steve

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