C / C++ / MFC

12-Apr-04 3:30

Use PostMessage() to communicate between them.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

copy constructor

packetlos12-Apr-04 3:12

packetlos

12-Apr-04 3:12

Hi there,

If I add a CArray such as CByteArray to a struct like so:

<br />
typedef struct DATAGRAM<br />
{<br />
   // other types here...<br />
   CByteArray pkt_data; 	// Packet data<br />
} DATAGRAM;<br />

and then try and assign something of type DATAGRAM to type DATAGRAM i get the following compile error:
C2558: struct 'DATAGRAM' : no copy constructor available or copy constructor is declared 'explicit'

I know this is because because CByteArray is of dynamic type so I need to provide a copy constructor. So my question is do I need to provide one for DATAGRAM or do I really need to provide one for CByteArray and if so could somebody post a code snippet to help me out?

Cheers

Packetlos

toxcct12-Apr-04 3:50

toxcct

12-Apr-04 3:50

isn't it because you use a struct instead of a class ?

i know C++ enlarge structures capabilities, but i wonder if that's possible...

TOXCCT >>> GEII power

antlers12-Apr-04 5:01

antlers

12-Apr-04 5:01

You don't need to provide one for CByteArray if you provide one for DATAGRAM (that does not rely on CByteArray having a copy constructor)

packetlos12-Apr-04 5:17

packetlos

12-Apr-04 5:17

Thanks toxcct and antlers,

toxcct was right that there in as far as I can see a way to provide a constructor for the struct, therefore I converted it to a class and used CByteArray's .Copy() to provide the assignment.

Smile | :)

Tim Smith12-Apr-04 6:23

Tim Smith

12-Apr-04 6:23

There is little difference between a class and a structure. The only difference is that the default protection is private for a class and public for a structure.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

toxcct12-Apr-04 9:07

toxcct

12-Apr-04 9:07

that's what i was thinking, but in another side, i did never see struct with member functions...
so, here was my doubt.

TOXCCT >>> GEII power

John R. Shaw12-Apr-04 11:05

John R. Shaw

12-Apr-04 11:05

Remember that a struct in C++ is a class that defaults to public access and a normal class defaults to private access. Since DATAGRAM has a dynamic member it does require a copy constructor:

struct DATAGRAM
{
    // other types here...
    CByteArray pkt_data;

    // ctor
    DATAGRAM(DATAGRAM& dg)
    {
        // copy other type here...
        pkt_data.Copy(dg.pkt_data); // Copy packet data
    }
};

Note: I did not use a typedef because it is not needed in C++.

Good Luck! Smile | :)

Now if the blasted Mad | :mad:

power does not go out again, you'll get this message!

INTP

How can stor a listbox strings with serialization?

Paul Ranson13-Apr-04 2:03

Paul Ranson

13-Apr-04 2:03

I recommend you use a more modern design of container, perhaps std::vector<unsigned char>. These containers provide a copy constructor so that the compiler default copy constructor for your class will work.

I don't think you should be having to work out how to copy a CByteArray efficiently, or even correctly.

Paul

Mehdi_Hosseinpour12-Apr-04 2:59

Mehdi_Hosseinpour

12-Apr-04 2:59

I want to store listbox strings in to a file with serialization and load strings from this file with serialization.

Mehdi Hosseinpour

Re: How can stor a listbox strings with serialization?

David Crow12-Apr-04 3:39

Re: How can stor a listbox strings with serialization?

12-Apr-04 3:39

Something like:

CString str;
CFile file;
file.Open(..., CFile::modeWrite);
CArchive ar(&file, CArchive::store);
for (int x = 0; x < listbox.GetCount(); x++)
{
    listbox.GetText(x, str);
    ar << str;
}
ar.Close();
file.Close();

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Ravi Bhavnani12-Apr-04 9:10

Ravi Bhavnani

12-Apr-04 9:10

Might want to ar << listbox.GetCount(); first. Smile | :)

/ravi

My new year's resolution: 2048 x 1536
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Re: How can stor a listbox strings with serialization?

David Crow12-Apr-04 9:13

Re: How can stor a listbox strings with serialization?

12-Apr-04 9:13

Of course. I never indicated it was a complete working code example, hence the "Something like" qualifier. When typing this stuff from memory, small details often get omitted.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Ravi Bhavnani12-Apr-04 9:09

Ravi Bhavnani

12-Apr-04 9:09

See this[^] series of articles.

/ravi

My new year's resolution: 2048 x 1536
Home | Articles | Freeware | Music
ravib@ravib.com

Not able to navigate data between vc++ project and USB device.

Pankaj Bhalla12-Apr-04 2:59

Pankaj Bhalla

12-Apr-04 2:59

Hi All.

The problem I am facing is a bit different. Even I do not know, whether the problem is related to Embedded programming or can be solved with VC++ MFC itself.

I want to send and recieve data between my vc++ application and a USB device. Thats the main issue.

Can anyone tell from where to start or if anyone can help me with the coding that should be done...I will be very thankfull for that help.

Thanks and regards,

Pankaj Bhalla
pankajbhalla@mantraonline.com

Pankaj Bhalla
Consultant - VC++

Re: Not able to navigate data between vc++ project and USB device.

Darshan Jani12-Apr-04 7:21

Darshan Jani

12-Apr-04 7:21

Which USB Device you are talking about.
Please Clarify.

Re: Not able to navigate data between vc++ project and USB device.

Pankaj Bhalla13-Apr-04 0:15

Pankaj Bhalla

13-Apr-04 0:15

Hello Darshan.

Thanks for your consideration and time. Actually, the USB device is itself, under the process of creation. So, not sure about the device, but if you can then please tell me general steps we have to take to make it possible. I mean the articles or any other source from where I can get more information about this issue. If you can the please tell me the MFC classes we can use or any info. about MFC and USB devices.

Thanks and Regards,

Pankaj Bhalla

GDI

Ni@m12-Apr-04 2:42

Ni@m

12-Apr-04 2:42

Where can I download GDI+ librarys and headers?

Re: GDI

Indrawati12-Apr-04 2:50

Indrawati

12-Apr-04 2:50

You can get it from:

http://www.microsoft.com/msdownload/platformsdk/sdkupdate/

I think it's in the core SDK part.

freeing memory for an array

kfaday12-Apr-04 2:38

kfaday

12-Apr-04 2:38

I've got a char array

<br />
char *vec;<br />

and i allocate memory for a number of elemets

<br />
vec = (char*) malloc ((sizeof(char))*(number_of_elemets));<br />

i do that in main.
then i call a free function

<br />
free_mem (vec);<br />

the function code is:

<br />
void free_mem (char *vec,number_of _elements)<br />
{   <br />
        for (i=0;i<(number_of _elements);i++)<br />
	{<br />
                 	free (vec[i]);<br />
	}<br />
}<br />

it gives me errors
what's wrong?
thanks!!

Anonymous12-Apr-04 2:45

Anonymous

12-Apr-04 2:45

try this:

char *vec;
vec = new char[number_of_elements];

kfaday12-Apr-04 2:49

kfaday

12-Apr-04 2:49

it's only ansi c, i can't use c++

Indrawati12-Apr-04 2:53

Indrawati

12-Apr-04 2:53

I think you can just use free(vec), not free(vec[i]). Or maybe the error occurs because you forgot to pass the number_of_elements argument when you call free_mem?

David Crow12-Apr-04 3:43