C / C++ / MFC

6-Aug-03 1:06

Hi,

This is probably going to seem a very dumb and easy question to many (I hope!), but I am a novice with C++ so please bear with me...

I have an application that saves certain settings to file, and loads them on opening. All of these settings are just simple strings and integers, so at the moment I just save them to a (renamed) INI file using WritePrivateProfileString() and load them using GetPrivateProfileString() and GetPrivateProfileInt(). However, using these instructions means that anyone using my program can open the INI file in a text editor and look at the stored information. Ideally, I would like to create saved files that can't be opened in a text editor.

Could anybody tell me how to do this, please? (I am using the Windows API but *not* using MFC.) If somebody could show me a function (or tell me where to look) that creates a save file, and then can save strings and integers to it, and also a function on how I would then read the information back (load it), I would be very grateful. (One advantage with using the PrivateProfile functions is that I can read whatever value I want arbitrarily without having to load the info of the whole fle - can this functionality be maintained in a custom file?)

Many thanks,
KB

Dangleberry6-Aug-03 1:16

Dangleberry

6-Aug-03 1:16

CreateFile in MSDN has all your answers for creating and opening files. WriteFile and ReadFile can do just what you want with them. When you master that, get onto File Mapping in memory for fast access to file data Smile | :)

lawrence20006-Aug-03 3:13

lawrence2000

6-Aug-03 3:13

I think you can use register after i watched your requirement .

i'm a software engineer

David Crow6-Aug-03 3:19

David Crow

6-Aug-03 3:19

Kayembi wrote:
However, using these instructions means that anyone using my program can open the INI file in a text editor and look at the stored information.

Is this a bad thing? If the settings are related to your application, what's the harm?

Ideally, Win32 programs use the registry instead of text-based INI files. It's no more secure, at least not to any experienced person, but it does give your application more flexibility.

Kayembi6-Aug-03 4:06

6-Aug-03 4:06

Thanks for the replies.

I can live with INI files - it's not really a bad thing - but I just think it would be a little more "professional" if people can't look in the file. Also, I may need to store a password in there, in which case (although I could encrypt it in an INI file), a non-readable file would be better.

Thanks again for the replies, I'm looking into all the suggestions on the MSDN site and trying to work it all out... It's still a bit complex for me as I'm still learning, but I'm trying...

Cheers,
KB

David Crow6-Aug-03 4:18

David Crow

6-Aug-03 4:18

Kayembi wrote:
but I just think it would be a little more "professional" if people can't look in the file.

Sometimes editing a file outside the app is the only way to get it to work.

Kayembi wrote:
Also, I may need to store a password in there...

A very bad design.

Kayembi6-Aug-03 4:45

6-Aug-03 4:45

"A Very bad design" - you're right; I think I have eliminated the need for a password to be stored in the file, fortunately.

Maybe you're right about leaving the files as INI files... The main reason I want to do it is that there is information in there that, if changed, will definitely cause the program to crash, or at least behave oddly. This is probably bad design again... Essentially I am writing a launcher app and a wizard. Through the wizard, users can choose different styles and settings for the launcher app. It then copies the launcher app, with the files it is launching, and the settings file (which is the file I am trying to save/load, currently an INI) to a new directory. Thus all of the settings they chose through the wizard (JPG to display while launching, titlebar name etc) are all saved in the INI file, and the launcher reads that in order to find the files it need to launch and to find the picture files it needs to display, etc.

In an ideal world there would be no need for an INI or saved file at all - all the information would be stored inside a newly generated launcher executable, along with the JPG files that have been selected for use by the launcher. This would be tidier and more professional, but as I have no idea where to begin in trying something like that, I have to instead go the route of external files and an INI (or save file of another format).

Many thanks for all your help, I really appreciate it,
KB

David Crow6-Aug-03 4:57

David Crow

6-Aug-03 4:57

Kayembi wrote:
The main reason I want to do it is that there is information in there that, if changed, will definitely cause the program to crash, or at least behave oddly. This is probably bad design again...

A well-behaved app would indeed not crash, but should instead detect when "bad data" is present and respond accordingly. For example, if you were storing the window coordinates of the app when it was last shut down (t=0, r=1024, b=768, l=0) so that it could be positioned in the same spot next time, and someone changed those coordinates to something non-sense (t=768, r=1024, b=0, l=0), the app would know to correct the problem, or use some default values at the very least.

Kayembi6-Aug-03 5:27

6-Aug-03 5:27

Thanks. I guess I need to add lots of error-handling code to sort this out. I ought to get into good habits now, so thanks for the advice.
Cheers,
KB

Timer Callback

LittleYellowBird6-Aug-03 0:31

6-Aug-03 0:31

Hi,

I'm trying to use a timer call back function but I can't get it to compile.

I set up the timer for a 1 second interval like this:-
m_uSampleTimerID = SetTimer( 1,1000,TimerTakeSample );

My function is declared like this:-
void CALLBACK EXPORT COxygraphView::TimerTakeSample(HWND hWnd, UINT nMsg, UINT nTimerID, DWORD dwTime)

BUT the SetTime command gives the following error:-
:\Oxygraph\OxygraphView.cpp(575) : error C2664: 'SetTimer' : cannot convert parameter 3 from 'void (struct HWND__ *,unsigned int,unsigned int,unsigned long)' to 'void (__stdcall *)(struct HWND__ *,unsigned int,unsigned int,unsigned l
ong)'

This is all in the View part of an MFC app. It doesn't seem to like the return type of the function.

Any ideas what's wrong with it?

Thanks

Ali

Member 4242596-Aug-03 0:41

Member 424259

6-Aug-03 0:41

Hey can i suggest u one thing..
Check out if u like this thing
instead of calling a call back function
just go to class wizard map the WM_TIMER for the view class
then call the set timer function with parameters(1000, timeasperuwant, NULL)
in this case the Functiopn mapped for WM_TIMER will be called..
please check out and let me know
bye

Thanx
TAKE CARE

Member 4242596-Aug-03 0:42

Member 424259

6-Aug-03 0:42

this thing will work if u calling the set timer function in the view class itself..

Thanx
TAKE CARE

LittleYellowBird6-Aug-03 1:12

6-Aug-03 1:12

Thanks for the suggestion. In fact I have got my code working like that at the moment, but I have several timers and I wanted to assign each one its own handling function.

Thanks anyway Smile | :)

Ali

ivor bigun6-Aug-03 0:58

ivor bigun

6-Aug-03 0:58

The problem is with the declaration of your TimerTakeSample function. I think its probably got something to do with that EXPORT (try removing it?) because the CALLBACK simply defines the function type as an _stdcall* and so that should compile.

LittleYellowBird6-Aug-03 1:09

6-Aug-03 1:09

Thanks for the suggestion, I've tried it but the compiler still doesn't want to know (still the same error message).

Thanks anyway Smile | :)

Ali

ivor bigun6-Aug-03 1:08

ivor bigun

6-Aug-03 1:08

The actual problem is that the compiler is expecting a void (_stdcall*) (arglist...)function and your function has somehow been defined as a mere void (arglist...) function hence the error. Since the CALLBACK statement defines the (_stdcall*) you should not be having this issue, unless the EXPORT statement is doing something dopy (so try removing it), or the TimerTakeSample referred to in the SetTimer function is being linked to a different function? try specifying COxygraphView::TimerTakeSample(blah...) in your SetTimer function to make sure your linkage is correct (can't tell from your example where the SetTimer is being called from). I'm sure the answer will reveal itself Smile | :)

Ryan Binns6-Aug-03 1:11

Ryan Binns

6-Aug-03 1:11

The function must be declared as static

Hope this helps,

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

ivor bigun6-Aug-03 1:31

ivor bigun

6-Aug-03 1:31

Haha, yes the declaration should be static void CALLBACK etc. well done ryan Smile | :)

Phil Speller6-Aug-03 1:53

Phil Speller

6-Aug-03 1:53

To expand on Ryan's post - it's all to do with pointers to member functions. Take a look at this[^] site - it will explain all!

Phil

LittleYellowBird6-Aug-03 2:09

6-Aug-03 2:09

Thanks, the link looks really helpful, looks like I need to do some reading!

Smile | :)

Ali

LittleYellowBird6-Aug-03 2:12

6-Aug-03 2:12

You're right changing the funstionto static gets rid of the compiler error. However, now I have more errors calling functions from the timer function. Looks like I need to read up on static functions!

Thanks for the help, much appreciated Smile | :)

Ali

Ryan Binns6-Aug-03 2:19

Ryan Binns

6-Aug-03 2:19

You're welcome Smile | :)

Alison Pentland wrote:
However, now I have more errors calling functions from the timer function. Looks like I need to read up on static functions!

Good idea Wink | ;)

Your errors at the moment are probably because you're calling non-static members from your static function. You can't do that Smile | :)

. The general way of using static functions as callbacks is to pass a pointer to the object as the lParam value that gets passed to the callback function, and then using that pointer to access the other class members.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

Phil Speller6-Aug-03 3:04

Phil Speller

6-Aug-03 3:04

Declaring a member function of class as static will remove the need for an instance of the class to be associated with it - i.e. no this pointer. What this means is that it can't access any of the normal member functions/variables - precisely because there is no associated this pointer. However, supply the static function with a pointer to an instance of the class and you can access all functions/variables (even private ones) via that pointer - because the static function is still declared in the scope of the class.

In terms of pointers to functions, because a static member function has no associated this pointer you can obtain it's address directly (just like a C function) - this is why Ryan's suggestion worked. Any normal member function must have an associated this pointer with it, so even when you take the address of a member function you must still use it with a pointer to an instance of the class as well.

class CMyClass<br />
{<br />
public:<br />
  void MyFn (void);<br />
  static void MyStaticFn (CMyClass *);<br />
};<br />
<br />
typedef void(* FnPtr)(CMyClass*);  // C style fn pointer<br />
typedef void(CMyClass::* MemberFnPtr)();  // C++ style fn pointer<br />
<br />
CMyClass* pMyClass = new CMyClass;<br />
<br />
MemberFnPtr pMFn = &CMyClass::MyFn;<br />
pMyClass->MyFn();           // Calling as normal<br />
pMyClass->*pMFn();          // Calling via pointer to member fn<br />
<br />
FnPtr pFn = &CMyClass::MyStaticFn;<br />
(*pFn)( pMyClass );         // Calling static member fn

[edit]
You could try using the nIDEvent parameter of SetTimer to hold the pointer to your class instance - cast it back to the correct type and use within your static fn.
[/edit]

Hope this helps,

Phil