C / C++ / MFC

Re: HANDLE - what exactly is it ? [modified]

2-Jun-06 10:16

Hello again Smile | :)

I have a question : What is a handle ?
Is it something like pointer ?

What is difference for example between HWND and a Cwnd ?

Please give me some explicit explanations.

Thank you.

Maxwell Chen2-Jun-06 10:57

Maxwell Chen

2-Jun-06 10:57

big_denny_200 wrote:
What is a handle ?

A handle is a unique serial number for Windows (and managed by Windows) to identify an instance (or a system object like a window, an event, a timer, a mutex, ... ).

big_denny_200 wrote:
What is difference for example between HWND and a Cwnd ?

HWND is a handle: the concept to Windows programming.
CWnd is a class type: the concept to C++ language. This type is defined in MFC Library.

-- modified at 16:58 Friday 2nd June, 2006

class CWnd has a data member of type HWND.

Maxwell Chen

How to learn develop in C++ and VOIP ?

Yanshof2-Jun-06 8:47

Yanshof

2-Jun-06 8:47

Hi All,

I need help to find some info of how to develop in visual C++ and VOIP .

I looked in this site and didn't find something really helpful.

Please help me.

Thanks.

Re: How to learn develop in C++ and VOIP ?

led mike2-Jun-06 8:55

led mike

2-Jun-06 8:55

If you are not an experienced Visual C++ developer I suggest you tackle that problem first and in isolation from the VIOP problem.

Re: How to learn develop in C++ and VOIP ? [modified]

Yanshof2-Jun-06 10:39

Yanshof

2-Jun-06 10:39

I know C++ and i have a lot of experience with visual C++.
I just need some example to know and learn how to use the classes of VOIP.

I don't know nothing about VOIP - and i want to learn - i thought that with some code example i could learn.

Can someone help me ?

-- modified at 16:43 Friday 2nd June, 2006

Re: How to learn develop in C++ and VOIP ? [modified]

Maxwell Chen2-Jun-06 11:04

Maxwell Chen

2-Jun-06 11:04

yanshof wrote:
some example to know and learn how to use the classes of VOIP.

Maybe try THIS LIBRARY[^].

Maxwell Chen

string issues again [modified]

big_denny_2002-Jun-06 8:21

Re: string issues again [modified]

2-Jun-06 8:21

Hello again Smile | :)

Please someone explain me next situation

I have next code :

...
      const UINT SIZE = 5;

	TCHAR strDest[SIZE];

	LPCTSTR strSource = _T("cool");

	_tcscpy_s(strDest,sizeof(strDest)/sizeof(TCHAR), strSource);
	
	CString s(strDest);

	MessageBox(s);
...

Everything works fine, but I get some differences in Debug and Release builds.

Specifficaly, in Release build, in debugger when I look at contents of strDest after _tcscpy_sfunction, I see that, first 4 bytes of it are occupied by come strange characters and 5th byte is 'c', but anyway the resule is displayed correctly in Message box.

In Debug build everything happens as expected : first 4 bytes are occupied by 'c' 'o' 'o' 'l' and 5th byte is '\0'

Why is this difference ?

thank you.

I have VS2005

-- modified at 14:21 Friday 2nd June, 2006

Zac Howland2-Jun-06 8:30

Re: Driver creation problem

2-Jun-06 8:30

The first 4 bytes of a CString are taken up by an DWORD (unsigned long) that holds the size of the buffer. You should see that in both the Debug and Release builds, but the Debugger may move the pointer to the first part of the character buffer when it is built in Debug. If you check the memory at &strDest, you should see similar results for both.

Also, if you intend to place the results of 1 CString into another, you don't need a character buffer.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Re: string issues again

Anton Mikhalyov2-Jun-06 21:38

Anton Mikhalyov

2-Jun-06 21:38

Looks like that this is bug in visual studio debugger

This strange symbols are nothing else than the pointer to the "cool" string in your resource section(.rdata usually) of executable. In debugger window you see destination buffer address decremented by 4 bytes. I don't know why this happens, but I think that this is bug.

Driver creation problem

Sharath862-Jun-06 7:34

Sharath86

2-Jun-06 7:34

I am creating a service along with a sys file to aid me in writing to the parallel port data byte. Iam using the code segement given below.

Ser = CreateService (Mgr,
"hwinterface",
"hwinterface",
SERVICE_ALL_ACCESS,
SERVICE_KERNEL_DRIVER,
SERVICE_SYSTEM_START,
SERVICE_ERROR_NORMAL,
"System32\\Drivers\\hwinterface.sys",
NULL,
NULL,
NULL,
NULL,
NULL
);

How ever if i change the term "hwinterface" to say "mydriver". It stops working neither does the sys file get created nor does it interface with the port. Furthermore, the Description of the file is set as buzz driver and copyright is to Buzz corporation why is this happening and how do i change the service name and its associated attributes to say Description: "My ParallelPortDriver"
Copyright to "MYcompany".

any help in this regard would be great.

sharath

Maxwell Chen2-Jun-06 11:28

Maxwell Chen

2-Jun-06 11:28

Sharath86 wrote:
if i change the term "hwinterface" to say "mydriver". It stops working neither does the sys file get created nor does it interface with the port.

The "service name" (the argument for CreateService API) should match the Symbolic Link Name registered from somewhere in AddDevice in the driver.

The reason for the above is because it (CreateService) creates a link. A link must have a concrete destination (aka in the driver).

On the other hand, the "display name" argument for CreateService API can have a different name.

Maxwell Chen

Binary Trees

Mridang Agarwalla2-Jun-06 7:30

Mridang Agarwalla

2-Jun-06 7:30

Hi Guys,
I have this exam on Data Structures in C. I need some help wiht Binary Trees. I found the follwing code for Binary Tree Traversal abnd its perfect. It's a recursive implementattion. I need a non recursive version too. Could someone tell me where I coulfd find it.

<br />
/* Pre-order traversal */<br />
<br />
void Pre_order (struct NODE *Node)<br />
{<br />
        if (Node)<br />
        {<br />
                printf(" %c", Node->Info);<br />
                Pre_order(Node->Left_Child);<br />
                Pre_order(Node->Right_Child);<br />
        }<br />
}<br />
<br />
/* In-order traversal */<br />
<br />
void In_order (struct NODE *Node)<br />
{<br />
        if (Node)<br />
        {<br />
                In_order(Node->Left_Child);<br />
                printf(" %c", Node->Info);<br />
                In_order(Node->Right_Child);<br />
        }<br />
}<br />
<br />
/* Post-order traversal */<br />
<br />
void Post_order (struct NODE *Node)<br />
{<br />
        if (Node)<br />
        {<br />
                Post_order(Node->Left_Child);<br />
                Post_order(Node->Right_Child);<br />
                printf(" %c", Node->Info);<br />
        }<br />
}<br />

Re: Binary Trees

Zac Howland2-Jun-06 9:07

managed String in Visual C++ / call a function like void f(int& x, String* s)

2-Jun-06 9:07

Non-recursive traversals use a stack similar to the following (going off memory here, so it may not be exact):

<br />
void traverse (struct NODE *Node)<br />
{<br />
	stack<NODE*> travStack;<br />
	NODE* cur = Node;<br />
	while (NULL != cur)<br />
	{<br />
		travStack.push(cur);<br />
		printf(" %c", cur->Info);	// for Pre-order<br />
		cur = cur->Left_Child;<br />
		printf(" %c", cur->Info);	// for In-order<br />
		while (NULL == cur && FALSE == travStack.empty())<br />
		{<br />
			cur = travStack.pop();<br />
			cur = cur->Right_Child;<br />
		}<br />
		printf(" %c", cur->Info);	// for Post-order<br />
	}<br />
}<br />

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Re: Binary Trees

David Crow2-Jun-06 9:43

David Crow

2-Jun-06 9:43

Good luck on your exam Roll eyes | :rolleyes:

"The largest fire starts but with the smallest spark." - David Crow

karlheinzsteinhart2-Jun-06 6:05

karlheinzsteinhart

2-Jun-06 6:05

Hi,
I have some problems with managed Strings as function parameter.

See:

void f(int& x, String* s)
{
x=10;
s="hello"
return;
}

.....
String *s ="start";
int x= 0;
f(x,s);
....

Problem:
s doesn't get the new vale "hello"
is it possible to use a managed String in a function by reference ??
Thx

Re: managed String in Visual C++ / call a function like void f(int& x, String* s)

C^hris L^osinger2-Jun-06 7:05

C^hris L^osinger

2-Jun-06 7:05

try the Managed C++ forum : http://www.codeproject.com/script/comments/forums.asp?forumid=3785[^]

Cleek | Image Toolkits | Thumbnail maker

wcscpy_s issues [modified]

big_denny_2002-Jun-06 5:13

2-Jun-06 5:13

Hi all

Please help, I have next code :

I am building in Unicode

TCHAR array[100];

CString strText = _T("Cool");

_tcscpy_s(array,//Location of destination string buffer
          sizeof(array),// Size of the destination string buffer.
          strText//Null-terminated source string buffer.
         )

But the program halts and hangs, when performs _tcscpy_s method.

thank you

-- modified at 11:16 Friday 2nd June, 2006

Nish Nishant2-Jun-06 5:22

Nish Nishant

2-Jun-06 5:22

There's no problem in the snippet of code you have shown. The error, presumably, lies elsewhere.

Regards,
Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications.
Also visit the Ultimate Toolbox blog (New)

David Crow2-Jun-06 5:33

David Crow

2-Jun-06 5:33

big_denny_200 wrote:
But the program halts and hangs, when performs _tcscpy_s method.

How are you verifying this?

"The largest fire starts but with the smallest spark." - David Crow

Viorel.2-Jun-06 5:33

Viorel.

2-Jun-06 5:33

Since _tcscpy_s is expanded to wcscpy_s call in Unicode version, you must specify the size of destination buffer in 2-byte unicode characters, not in bytes. Universal solution can look like this:

_tcscpy_s(array,
          sizeof(array) / sizeof(TCHAR),
          strText);

You got halts even if the source string was short enought, because -- in Debug version -- this function fills the buffer with 0xFD value.

-- modified at 11:33 Friday 2nd June, 2006

Zac Howland2-Jun-06 5:36

2-Jun-06 5:36

Try explicitly casting the CString object:

<br />
TCHAR array[100];<br />
<br />
CString strText = _T("Cool");<br />
<br />
_tcscpy_s(array,//Location of destination string buffer<br />
          sizeof(array),// Size of the destination string buffer.<br />
          (LPCTSTR)strText//Null-terminated source string buffer.<br />
         );<br />

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Viorel.2-Jun-06 5:42

Viorel.

2-Jun-06 5:42

(Actually, explicit casting from CString to LPCTSTR is not required even in printf-like calls -- at least in VS 6.0).

big_denny_2002-Jun-06 6:03

2-Jun-06 6:03

Could you be more explicit ?

MSDN says, that second parameter of wcscpy_s must specify size of destination buffer in bytes, therefore in Unicode build destination size will be 100 * sizeof(TCHAR) (which is equal to sizeof(array)), but in you case it will be 100(which is not the size of destination buffer)

I am little confused.

thanks

-- modified at 12:02 Friday 2nd June, 2006

Zac Howland2-Jun-06 6:02

Re: wcscpy_s issues [modified] Viorel Bejan

2-Jun-06 6:02

It shouldn't be, but I've run into problems with it converting (implicitly) to char* instead of wchar_t* when I didn't explicitly cast it.

Looking back at the code again, I think he will run into another problem though. In non-UNICODE builds, he shouldn't notice anything, but in UNICODE builds, the sizeof(array) will actually return twice the size of the actual buffer. I believe the wstcpy_s function requires array size in elements, not bytes (I'll have to double-check that though). If I'm correct, he would just need to change that line from sizeof(array) to sizeof(array) / sizeof(TCHAR).

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

big_denny_2002-Jun-06 6:07