Re: accessing registry using vc++ - C / C++ / MFC Discussion Boards

Mark Salsbery5-Mar-07 6:41

5-Mar-07 6:41

How can it get changed if only one thread ever changes it? How can you be sure it doesn't get
changed while computing the checksum? Is a critical section really that slow?

"Great job, team. Head back to base for debriefing and cocktails."
(Spottswoode "Team America")

Re: Atomic operations in Win32

Mr.Brainley5-Mar-07 6:59

Mr.Brainley

5-Mar-07 6:59

Here a scenarion. Thread A reads, Thread B writes, the pair consists of V1 and V2 of type int.

A reads V1

B writes V1
B writes V2

A reads V2

So now A has a pair that does not belong together. Now consider this :

A reads V1

B writes Checksum V1+V2
B writes V1
B writes V2

A reads V2

A checks the Sum -> does not match, so A tries the read again.

There are a lot more cases, but they all work out.
Using a CRITICAL_SECTION or any other kind of synchronization would mean traps into the OS and context-switches on the wait-operations. In cases where such an optimistic approach is possible, that means the probability of an error, and thus a second or even third read is very low, the performance is higher this way.

Re: Atomic operations in Win32

James R. Twine5-Mar-07 8:17

James R. Twine

5-Mar-07 8:17

   The spin count on a CS object can be utilitized to handle situations like this, but you really need to be on a multi-CPU/multi-core machine to really make use of it.

   If the CS is released during the spin count, no context-switch will take place. Given that simple operations are being done, I would bet that you would hit that situation more often than not.

   Peace!

-=- James
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Re: Atomic operations in Win32

Mark Salsbery5-Mar-07 10:16

Mark Salsbery

5-Mar-07 10:16

I just hijacked the thread for my own personal learnin'...

Can you explain what the heck you're talking about? Smile | :)

*edit* Google is my friend: Critical Section Objects[^] Roll eyes | :rolleyes:

Thanks!
Mark

"Great job, team. Head back to base for debriefing and cocktails."
(Spottswoode "Team America")

Re: Atomic operations in Win32

Stephen Hewitt5-Mar-07 11:37

Stephen Hewitt

5-Mar-07 11:37

Looks like you should do some research on "readers writer locks".

Steve

accessing registry using vc++

siddhesh13835-Mar-07 1:14

siddhesh1383

5-Mar-07 1:14

hi i need to read and write the registry values using vc++.
if anyone has any idea please forword itto me.

thanks.

Re: accessing registry using vc++

Rajesh R Subramanian5-Mar-07 1:15

Rajesh R Subramanian

5-Mar-07 1:15

Have a look at CRegKey on MSDN.

And please delete your previous message.

Glory follows virtue as if it were its shadow.
- Marcus Tullius Cicero

Re: accessing registry using vc++

Joan M5-Mar-07 1:36

Joan M

5-Mar-07 1:36

Here you have some samples...

CRegistry is a class that I use often in order to work with the registry... it's something that we had developed some time ago.

<br />
bool	CRegistry::SetKey(HKEY hKey, CString csSubkey, CString csValName, CString csVal)<br />
{<br />
	if(hKey != HKEY_CURRENT_USER)<br />
		return false;<br />
<br />
	if(csSubkey.IsEmpty() || csValName.IsEmpty() || csVal.IsEmpty())<br />
		return false;<br />
<br />
	HKEY hWkKey;<br />
	LONG lRetorn = RegOpenKeyEx(hKey,csSubkey,0,KEY_ALL_ACCESS,&hWkKey);<br />
	if(lRetorn == ERROR_SUCCESS)<br />
	{<br />
		int iLength = csVal.GetLength();<br />
		lRetorn = RegSetValueEx(hWkKey,<br />
									csValName,<br />
									0, <br />
									REG_SZ, <br />
									(BYTE *)csVal.GetBuffer(0),<br />
									iLength);<br />
<br />
		RegFlushKey(hWkKey);<br />
		RegCloseKey(hWkKey);<br />
<br />
		if( lRetorn == ERROR_SUCCESS)<br />
			return true;<br />
	}<br />
	return false;<br />
}<br />
<br />
bool	CRegistry::SetKey(HKEY hKey, CString csSubkey, CString csValName, int iVal)<br />
{<br />
	if(hKey != HKEY_CURRENT_USER)<br />
		return false;<br />
<br />
	if(csSubkey.IsEmpty() || csValName.IsEmpty())<br />
		return false;<br />
<br />
	HKEY hWkKey;<br />
	LONG lRetorn = RegOpenKeyEx(hKey,csSubkey,0,KEY_ALL_ACCESS,&hWkKey);<br />
	if(lRetorn == ERROR_SUCCESS)<br />
	{<br />
		int iLength = sizeof(iVal);<br />
		lRetorn = RegSetValueEx(hWkKey,<br />
									csValName,<br />
									0, <br />
									REG_DWORD, <br />
									(BYTE *)&iVal,<br />
									iLength);<br />
<br />
		RegFlushKey(hWkKey);<br />
		RegCloseKey(hWkKey);<br />
<br />
		if( lRetorn == ERROR_SUCCESS)<br />
			return true;<br />
	}<br />
	return false;<br />
}

Hope this helps...

Re: accessing registry using vc++

Michael Dunn5-Mar-07 12:39

Michael Dunn

5-Mar-07 12:39

Never use KEY_ALL_ACCESS unless you want the code to be usable only by administrators.

--Mike--
Visual C++ MVP Cool | :cool:

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Re: accessing registry using vc++

Joan M5-Mar-07 19:43

Joan M

5-Mar-07 19:43

Yes, you are right... Blush | :O

Sometimes this becomes a problem when I share code... as I make machine prototypes, and I prevent people who use my apps to reach the OS, then normally I don't have this kind of problems, I always work as an administrator.

Re: accessing registry using vc++

Hamid_RT5-Mar-07 5:51

Hamid_RT

5-Mar-07 5:51

See A Registry Class [^] and Registry Wrapper Class (cregistry)[^]

WhiteSky

adding registry hives in combo box

siddhesh13835-Mar-07 1:12

siddhesh1383

5-Mar-07 1:12

hi i want to access the registry hives in combo box in vc++ mfc dialog based application.
i have tried it but getting some errors.
could some body help me out.

thanks.

Re: adding registry hives in combo box

Hamid_RT5-Mar-07 5:51

Hamid_RT

5-Mar-07 5:51

What errors?

WhiteSky

Hiding Contorl's Scoll Bar

Ali Beirami5-Mar-07 1:07

Ali Beirami

5-Mar-07 1:07

Hi There Every Body,

How can I hide a control's Scroll Bar?Something like ListView.
When the count of it's items exceeds a number relative to its size control shows a scoll bar.Should I Send a special Message to control?Could I do somthing with ShowWindow(BOOL)?Theoritically when a handle or poiter to a window is grabbed It can be shown or hide by ShowWindow.Any Ideas?

Kind Regards:
Ali

Re: Hiding Contorl's Scoll Bar

prasad_som5-Mar-07 1:32

prasad_som

5-Mar-07 1:32

Have a look at window style WS_VSCROLL and List view style LVS_NOSCROLL.

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Hiding Contorl's Scoll Bar

Ali Beirami5-Mar-07 3:42

Ali Beirami

5-Mar-07 3:42

thanks dear prasad,

Unfortunately it is a DOTNET project(which is written previously) and I must modify it to do such behavior.I didnt find something useful in .NET documentation and decided to use C++.Can we modify the control after it is created?whould u please post some refrence.

thanks again a lot.

Kind Regards, Ali.

Re: Hiding Contorl's Scoll Bar

prasad_som5-Mar-07 3:46

prasad_som

5-Mar-07 3:46

Ali Beirami wrote:
Can we modify the control after it is created?

What do you mean by control. Isn't it a MFC window.
You can modify window style after its ceation. Look for ModifyStyle,ModifyStyleEx documentation.

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Hiding Contorl's Scoll Bar

Ali Beirami5-Mar-07 3:55

Ali Beirami

5-Mar-07 3:55

Thanks thanks,very useful.
Is there any SDK Function for changing style of a window(control Big Grin | :-D

)?I can NOT use MFC.
Thanks again buddy.thanks.

Re: Hiding Contorl's Scoll Bar

prasad_som5-Mar-07 4:00

prasad_som

5-Mar-07 4:00

Ali Beirami wrote:
Is there any SDK Function for changing style of a window

Yes, Look SetWindowLong. Your code would be on following line,

// Remove WS_VSCROLL style
DWORD dwStyle = ::GetWindowLong(hwnd, GWL_STYLE);
if (dwStyle & WS_VSCROLL)
  ::SetWindowLong(hwnd, GWL_STYLE, dwStyle & ~WS_VSCROLL);

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Hiding Contorl's Scoll Bar

Ali Beirami5-Mar-07 6:02

Ali Beirami

5-Mar-07 6:02

Thnx buddy , Prefect!

vc++ + model dialog box [modified]

rajeev20075-Mar-07 0:24

rajeev2007

5-Mar-07 0:24

how to create modeless dialog box. and
Which method is used to create model dialog box in mfc.

-- modified at 7:10 Monday 5th March, 2007

Re: vc++ + model dialog box

prasad_som5-Mar-07 1:05

prasad_som

5-Mar-07 1:05

Refer, Life Cycle of a Dialog Box[^].

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: vc++ + model dialog box

Joan M5-Mar-07 1:41

Joan M

5-Mar-07 1:41

A dialog is the object that comes from a class, so you have a variable that must be instantiated.

In a modeless dialog, you can use, for example, a pointer to that class, and then reserve memory for that variable using the new clause. Once this has been done you can use CreateDialog in order to create that dialog and once this is done, you can use showwindow...

if it is modal, it's far easier, you have that variable (e.g: CDialog Dlg;) and then you have only to call DoModal();

But I think that the best you can do is to document yourself a little bit more. It is very important to get the basics very clear before trying to go further.

Hope this helps.

plot Library?

$uresh $hanmugam4-Mar-07 23:45

$uresh $hanmugam

4-Mar-07 23:45

Hi all

I need to plot values on a graph. Say for example I have an two integer vector

4,2,3,5,6,7
0.564,0.656,1.6456;

now i want to plot these values. What's the best way to do that?

I saw a Plot Graphic Library on this webpage "http://www.codeproject.com/miscctrl/pgllib.asp" but it not work with in VS2005, it will give some error.

error C2923: 'std::list' : 'std::vector<hull::tlineapproximator<t>::SPoint>::const_iterator' is not a valid template type argument for parameter '_Ty'

at

typedef std::vector<spoint> PointContainer;
//! Key containers
typedef std::list<pointcontainer::const_iterator> KeyContainer;

Can anyone help me what's wrong with "pgllib".
Thanks in advance

Re: plot Library?

prasad_som5-Mar-07 0:06

prasad_som

5-Mar-07 0:06

Why you are spamming[^] the forum ? Can't you be little patience?

Prasad
Notifier using ATL | Operator new[],delete[][^]

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