C / C++ / MFC

How to create a Unique numeric ID

18-Dec-07 3:40

I don't understand well you question. Do you put namespace around your CDialog inherited class?
Can you post the relevant code?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Re: namespace problem

jhwurmbach18-Dec-07 4:33

jhwurmbach

18-Dec-07 4:33

prithaa wrote:
I have declared a namespace for 3 of my classes and changed the declarations accordingly using : :

Why?
Adding

using namespace f;

did not help?

Let's think the unthinkable, let's do the undoable, let's prepare to grapple with the ineffable itself, and see if we may not eff it after all.
Douglas Adams, "Dirk Gently's Holistic Detective Agency"

Re: namespace problem

Member 75496018-Dec-07 8:11

Member 754960

18-Dec-07 8:11

Make sure you understand what the various message map macros expand to.

The message map is a static member variable of the class. If you wrap
the dialog class declaration in a namespace then wrap the dialog
implementation in that namespace.

Move the message map table definitions into the same namespace the
dialog class is declared in.

// header.h

namespace f {

class CAboutDlg : public CDialog
{
protected:
	//{{AFX_MSG(CAboutDlg)
	afx_msg void OnButton1();
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()
};

}	// namespace f

// source.cpp

namespace f {

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
	//{{AFX_MSG_MAP(CAboutDlg)
	ON_BN_CLICKED(IDC_BUTTON1, OnButton1)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

void CAboutDlg::OnButton1() 
{
}

}	// namespace f

SWDevil18-Dec-07 1:52

18-Dec-07 1:52

Hi,

I need to create a unique id which consists only of numbers (0-9), and needs to be of a certain length (not more than 37 chars).
How can I do this?
I know that here is GUID, but this creates a hexidecimal number.

Thanks

CPallini18-Dec-07 2:14

18-Dec-07 2:14

Well, I think it is far easier to change the GUID representation than writing your own algo to create a unique ID. Unfortunately, a 128-bit wide number (as GUID is) requires more than 38 decimal digits.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

SWDevil18-Dec-07 2:17

18-Dec-07 2:17

yes - that's exactly my problem Smile | :)

SWDevil18-Dec-07 2:23

18-Dec-07 2:23

yes - that's exactly my problem Smile | :)

If I use part of the GUID that is generated and convert that to decimal. will that still be globaly unique?

CPallini18-Dec-07 2:33

18-Dec-07 2:33

SWDevil wrote:
If I use part of the GUID that is generated and convert that to decimal. will that still be globaly unique?

No.

BTW why have you such a ~~requirement~~ constraint (just curious)?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

SWDevil18-Dec-07 2:42

18-Dec-07 2:42

The requirement is a 64 char string.
But there is a first part that I have to include, and for the second part I have to generate a unique ID.
Both parts together should not be mopre than 64 chars.

CPallini18-Dec-07 2:45

18-Dec-07 2:45

BTW, do you really need a Global Unique Identifier?
GUID exist because ID creation must be shared (anyone may create his unique IDs via Guidgen) and not bound to a centralized mechanism
(as the one assigning car license numbers), do you have such a strict requirement? Confused | :confused:

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

jhwurmbach18-Dec-07 4:42

jhwurmbach

18-Dec-07 4:42

Could you get away with using a timestamp (probably including milliseconds?)

Thats nowhere _globally_ unique, but unique to every point in space. And maybe that is enough?

SWDevil18-Dec-07 6:05

18-Dec-07 6:05

I am thinking of using GetTickCount, but I understand that this might return a negative value? Is this true?

Re: _CRT_SECURE_NO_WARNINGS

jhwurmbach18-Dec-07 6:22

jhwurmbach

18-Dec-07 6:22

SWDevil wrote:
...GetTickCount...might return a negative value?

No. It returns a DWORD, that is unsigned.
It wraps around after 49,7 days, though.
Win95 used to crash after that uptime. Not that it was generally able to stay up that long without crash anyway.

time64 returns the seconds since UTC. It wraps around somtimes in the year 3000
If you really need, you could mix in the milliseconds since startup (GetTickCount)

time64 relies on the computers clock being set - tampering with the clock *could* make your UID non-unique. That may or may not be a problem.

_CRT_SECURE_NO_WARNINGS

Anthony Appleyard18-Dec-07 0:26

Anthony Appleyard

18-Dec-07 0:26

I am adapting for Visual C++ 2008 an old Borland C++ 4.5 program that contains many old-type string handling statements. The compiler tells me to "use _CRT_SECURE_NO_WARNINGS" to suppress warnings about strcpy and sprintf etc, but the online help gives no examples of its use. "#define _CRT_SECURE_NO_WARNINGS" has no effect. "_CRT_SECURE_NO_WARNINGS" (without quotes) alone on a line is treated as an undeclared variable. "#pragma _CRT_SECURE_NO_WARNINGS" causes a warning "unknown pragma". Please how do I put _CRT_SECURE_NO_WARNINGS in to suppress those warnings?

CPallini18-Dec-07 0:40