C / C++ / MFC

Re: How to auto generate the registry key value in MFC

20-Jul-09 20:37

Use the registry APIs instead of GetProfileString.
Look at the documentation for Registry Functions[^].

For example, you can create/open registry keys using RegCreateKeyEx, you can read registry values using RegQueryValueEx etc.

«_Superman_»
I love work. It gives me something to do between weekends.

Adam Roderick J20-Jul-09 21:09

Adam Roderick J

20-Jul-09 21:09

http://www.codeproject.com/KClass to handle the Windows Registry operations[^]B/winsdk/Windows_Registry.aspx

Callback to a Non static Member function in C++ need to be called from a DLL

San20-Jul-09 19:53

San

20-Jul-09 19:53

Hi All,

I need to implment a callback to a Nonstatic member function of a class.
Which will be invoked through a DLL.DLL is an independent library.No dependency with the class.
I Implemented with a static function. I need to know how it will be for a non static member function.

My code is as follows for static implementation. I need to change it for a non static .Please help.

class CCallbackTester
{
public:
static int __stdcall CompareInts(const byte* velem1, const byte* velem2);
};

int __stdcall CCallbackTester::CompareInts(const byte* velem1, const byte* velem2)
{
int elem1 = *(int*)velem1;
int elem2 = *(int*)velem2;

if(elem1 < elem2)
return -1;
if(elem1 > elem2)
return 1;

return 0;
}

int main(int argc, char* argv[])
{
int i;
int array[] = {22, 1, 3210, 2109, 1098};

Bubblesort((byte*)array, 5, sizeof(array[0]),
&CCallbackTester::CompareInts);

cout << "After the sorting\n";
for(i=0; i<5; i++)
cout << array[i] << '\n';
getch();
}

in DLL Bubblesort is as follows.
void DLLDIR CALLBACK Bubblesort(byte* array, int size, int elem_size, CompareFunction cmpFunc)
{
for(int i=0; i<size; i++)
{
for(int j=0; j<size-1; j++)
{
if(1 == (*cmpFunc)(array+j*elem_size, array+(j+1)*elem_size))
{
byte* temp = new byte[elem_size];
memcpy(temp, array+j*elem_size, elem_size);
memcpy(array+j*elem_size, array+(j+1)*elem_size, elem_size);
memcpy(array+(j+1)*elem_size, temp, elem_size);
delete [] temp;
}
}
}
}

Thanks
San

Re: Callback to a Non static Member function in C++ need to be called from a DLL

«_Superman_»20-Jul-09 20:31

Re: Callback to a Non static Member function in C++ need to be called from a DLL

20-Jul-09 20:31

A non-static member function is very much dependent on its class.
So you cannot use it for callbacks.

«_Superman_»
I love work. It gives me something to do between weekends.

Rick York21-Jul-09 6:54

Rick York

21-Jul-09 6:54

One way is to do this is like many callback procedures do - they pass along a user specified argument as a void pointer (PVOID). You can pass a pointer to one of your objects as the argument and use a static member of the same class for the callback procedure. Then in the callback procedure cast the void pointer to a pointer to your object and call your member method. As an example, your callback procedure could look something like this :

class YourClass
{
static int CompareCallback( ctchar * item1, ctchar * item2, void *ptr )
{
    if( ! ptr )
        return 0;
    YourClass * pObject = (YourClass *)ptr;
    return pObject->Compare( item1, item2 );
}
};

BTW : you can use this technique in a wide variety of callback scenarios like for thread procedures or window enumeration procedures or ...

How Do I Change StillCap Resolution

Tom Hubin20-Jul-09 19:49

Tom Hubin

20-Jul-09 19:49

Hello,

I have been working with the Watchport/V2 and Eyetoy webcams. All the reolutions and modes work fine with AmCap but I prefer the simplicity of StillCap for quick photos for a youngster's science project documentation.

The default resolution for StillCap seems to be 320x240 for images saved. I would prefer displaying and saving 640x480.

I used the Visual Studio 2003 Resource editor to increase the displayed size for the StillCap dialog box and the two webcam views.

I have poked around through the source code but cannot find where the camera resolution is set. How do I specify the webcam resolution to be 640x480, preferably as the default?

Thanx,
Tom

Font

kumar sanghvi20-Jul-09 17:40

kumar sanghvi

20-Jul-09 17:40

HI,
i have a TabCtrl which is created using Create function(using control variable) but not using resource...
Now how can i increase the font inside the TabCtrl

Re: Font

Randor 20-Jul-09 18:00

Randor

20-Jul-09 18:00

Have you tried using the WM_SETFONT Message[^]?

::SendMessage(hwndYourTab,WM_SETFONT,(WPARAM)GetStockObject(DEFAULT_GUI_FONT),0);

file share problem

york52820-Jul-09 16:55

20-Jul-09 16:55

I just wanna know how to share a big file, 3-4G

when using FileMapping, I only can share a file that not bigger than 1.5G

if bigger than that, I got an error of ERROR_NOT_ENOUGH_MEMORY

Thanks!

«_Superman_»20-Jul-09 18:10

20-Jul-09 18:10

What exactly do you mean by share a big file?

«_Superman_»
I love work. It gives me something to do between weekends.

york52820-Jul-09 18:41

20-Jul-09 18:41

I forgot.

It means to share a big file between multi-process

so all the processes can read the file

Thank you!~

«_Superman_»20-Jul-09 18:44

20-Jul-09 18:44

You could use CreateFile[^] with FILE_SHARE_READ|FILE_SHARE_WRITE as its share mode parameter.

«_Superman_»
I love work. It gives me something to do between weekends.

york52820-Jul-09 18:54

20-Jul-09 18:54

not that problem

when I create a file mapping that the file is bigger than 1.5Gb

the CreateFileMapping return ERROR_NOT_ENOUGH_MEMORY

And I was wondering if I can map a big file (3-4G) to share in one time

that's what I want

for example I have a 3G file and 100 people wanna read it

so I wanna share it

that's the situation

Thank you !~

«_Superman_»20-Jul-09 19:48

20-Jul-09 19:48

Instead of mapping the file to memory, all 100 people can read it from disk using CreateFile and the share flags.

«_Superman_»
I love work. It gives me something to do between weekends.

york52820-Jul-09 22:03

20-Jul-09 22:03

speed is important

IO is slower than file mapping

that's why I wanna use it

Best Wishes

One day I will get what I wish by working hard

Randor 20-Jul-09 18:43

Randor

20-Jul-09 18:43

I would recommend reading the Microsoft article Creating a File Mapping Object[^]

Specifically the 'File Mapping Size' section where it states the following:

The size of a file mapping object that is backed by a named file is limited by disk space. The size of a file view is limited to the largest available contiguous block of unreserved virtual memory. This is at most 2 GB minus the virtual memory already reserved by the process.

Best Wishes,
-David Delaune

york52820-Jul-09 18:59

20-Jul-09 18:59

Thank you so much

I read the book Programming Applications for Microsoft Windows by Jeffrey Richter

but biside file mapping

Is there another way to share a big file in one time

I always wanna find a better way

Smile | :)

Randor 20-Jul-09 19:17

Randor

20-Jul-09 19:17

I think you should re-evaluate your application requirements. Do you *really* need to share 3 Gigabytes of a file between multiple processes? Why not share small sections of the file as needed? Have a look at the sample:

Creating a View Within a File[^]

You could use a similar technique and share 250 megabytes or more of the file at a time.

Best Wishes,
-David Delaune

york52820-Jul-09 19:43

20-Jul-09 19:43

Thank you

I'll try that

Big Grin | :-D

Stuart Dootson20-Jul-09 23:30

Stuart Dootson

20-Jul-09 23:30

I'll second Randor's suggestion - I've used that technique on files about 1GB in size. I actually wrapped the whole mapping thing in a set of custom STL-style iterators that mapped bits of the file in and out on demand.

I've got a half-written article on the subject - I'll have to pull my finger out and finish it Smile | :)

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

SelvaKr20-Jul-09 20:25

SelvaKr

20-Jul-09 20:25

Just by going thru the link, i understood that, it talks about memory mapping files.
But i think process address space is limited to 4GB in 32 bit windows. (2GB-Process; 2GB-Kernel)
Hence if you need 3GB of space at a point from your application, you maynot be able to address it.
Check for /3GB switch (even though it is not advisable)... which may give you some more information to approach your problem...
As Randor pointed, u may have to unmap and map whenever required.

Selva

york52820-Jul-09 22:16