C / C++ / MFC

21-Mar-09 3:49

Hi!

I have an array of pointers, which point to classes derived from the same class. I also have a pointer, that points to the array. Is there a simple way to find out to which element of the array this pointer points to, or shall i use a variable in the base class for this purpose?
Thanks

CPallini21-Mar-09 4:09

21-Mar-09 4:09

You may use RTTI [^].
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.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

korte2521-Mar-09 6:09

21-Mar-09 6:09

Actually, this solves another problem of mine, so thanks a lot Big Grin | :-D

However, I'd like to know, whether the pointer points to the 2nd, 5th, nth element of the array. If I understand the description correctly, type_info only gives me the name of the class my pointer-in-the-array points to (right?). First I thought of using sizof(), but my derived classes are of different sizes.

CPallini21-Mar-09 6:25

21-Mar-09 6:25

Please post the relevant code (I need to know the pointer relationship with the array).
Smile | :)

korte2521-Mar-09 6:57

21-Mar-09 6:57

I have a base class, let's say Car, and derived classes BMW, Mercedes, Renault, etc.
The array is: Car* p_Cars[2][16];
The pointer: Car** pCar;

for (int i = 0; i < 2; i++)
{
    for (int j = 0; j < 16; j++)
    {
        if (j==2 || j==3)
            p_Cars[i][j] = new BMW(i, j);
        else if (j==4 || j==5)
            p_Cars[i][j] = new Mercedes(i, j);
        .
                    .
                    .
    }
}

So I'd like to know, whether I can determine the element from its address.
I hope you understand my problem, i tried my best Sniff | :^)

CPallini21-Mar-09 7:41

21-Mar-09 7:41

A given value of pCar refers to the element p_Cars[i][j] (i.e. pCar == &p_Cars[i][j] holds true), provided i,j are computed as follows:

int k = (int) (pCar - &p_Cars[0][0]);
int i = k / 16;
int j = k % 16;

korte2521-Mar-09 7:44

21-Mar-09 7:44

thanks

CPallini21-Mar-09 7:48

21-Mar-09 7:48

You are welcome.
Smile | :)

Stuart Dootson21-Mar-09 12:29

Stuart Dootson

21-Mar-09 12:29

So....you have:

CBase* pArray[] = { whatever... };
CBase* pItem = address_of_some_item_in_the_array;

?

In that case:

const size_t index = pItem - pArray;

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

korte2522-Mar-09 2:30

How to use Borland C DLL in C#.NET

22-Mar-09 2:30

thx

CreateDirectoryW()

p_196021-Mar-09 3:47

p_1960

21-Mar-09 3:47

Hi,
May i know how to check if a folder or file exists and if not create a folder....

im using ...
CString csPath1="C:\\Temp\\myfolder";

if(_access (csPath1+_T("\\Test"), 0)==-1);
::CreateDirectoryW(csPath1+L"\\Test",NULL);

and im getting the below error....
'_access' :cannot convert parameter 1 from 'ATL::CStringT<BaseType,StringTraits>' to 'const char *'...

Please help me......(myproject is in unicode)

Re: CreateDirectoryW()

«_Superman_»21-Mar-09 4:05

«_Superman_»

21-Mar-09 4:05

Why do you need to check first?
CreateDirectory will return ERROR_ALREADY_EXISTS if the directory already exists.

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

Re: CreateDirectoryW()

p_196021-Mar-09 4:17

p_1960

21-Mar-09 4:17

Thanks for ur help and please let me know how can i check whether a file(not directory) exists....(my project is in unicode)........

Re: CreateDirectoryW()

Rajesh R Subramanian21-Mar-09 4:28

Rajesh R Subramanian

21-Mar-09 4:28

You can use PathFileExists()[^] function (works with both folders and files).

The page contains a sample as well - saves me from typing code. Do remember to include shlwapi.h and link to shlwapi.lib.

It is a crappy thing, but it's life -^ Carlo Pallini

dataminers21-Mar-09 3:28

dataminers

21-Mar-09 3:28

How can I use DLL file in C#.NET ? I create dll in Borland C++ Compiler 5.5.1 and using C language.

Following code is not work.

My C Code;
-----------------------------------------------------
//hello.dll
#include <windows.h>

extern "C"
{
void __declspec (dllexport) function1()
{

MessageBox (NULL, "test message","test title",0);
}
}

BOOL WINAPI DllMain (HINSTANCE, DWORD, LPVOID)
{
return TRUE;
}

My C# Code;
-----------------------------------------------------

[DllImport("C:\hello.dll")]
public static extern void function1();

private void button1_Click(object sender, EventArgs e)
{
function1();
}

Re: How to use Borland C DLL in C#.NET

dataminers21-Mar-09 3:49

dataminers

21-Mar-09 3:49

Ok, I try this; But I get this error: Entry Point Not Found

C DLL CODE
-----------------------------------------------

#include <windows.h>

BOOL __stdcall DllMain(HINSTANCE hInst, DWORD dwReason, LPVOID lpReserved) {
return TRUE;
}

__declspec(dllexport) void __stdcall Message(char* p_szMessage) {
MessageBox(NULL, p_szMessage, "Message from DLL", MB_OK);
}

C# DLL CODE
-----------------------------------------------

[DllImport("filename.dll")]
static extern void Message(string msg);

private void button1_Click(object sender, EventArgs e)
{
Message("Hello world");
}

Re: How to use Borland C DLL in C#.NET

CPallini21-Mar-09 4:03

Re: How to use Borland C DLL in C#.NET

21-Mar-09 4:03

What does it mean, specifically, 'it doesn't work' (i.e. more details needed)?

BTW you possibly would get better help at C# forum.

BTW2: I saw you've already cross-posted your question... Roll eyes | :rolleyes:

dataminers21-Mar-09 5:04

dataminers

21-Mar-09 5:04

cross-posted is forbidden? Because this question related about between c and c#.

How can I "dumpbin -exports dll" in borland c++ 5.5.1 compiler on command prompt?

Do you have any idea?

sending structure data on tcp socket

jalsa G21-Mar-09 2:55

jalsa G

21-Mar-09 2:55

Hi,

how do we send structure data on tcp socket ?

any code snippets ?

Jalsa

CPallini21-Mar-09 3:27

21-Mar-09 3:27

jalsa G wrote:
how do we send structure data on tcp socket ?

Just like any other binary data.
Smile | :)

«_Superman_»21-Mar-09 3:38

«_Superman_»

21-Mar-09 3:38

It doesn't matter what you're sending, just make sure the size of data is mentioned correctly.
You may need to typecast the data as char* 'cause that's what the function accepts.

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

CPallini21-Mar-09 4:13

21-Mar-09 4:13

«_Superman_» wrote:
It doesn't matter what you're sending

Provided you're not sending pointers... Roll eyes | :rolleyes:

--Carlo the Nitpick.

Rajesh R Subramanian21-Mar-09 4:33

Rajesh R Subramanian

21-Mar-09 4:33

Also, an old Greek mythic legend states that you cannot (and should not) send tomatoes on socket.

It is a crappy thing, but it's life -^ Carlo Pallini

CPallini21-Mar-09 5:11