C / C++ / MFC

20-Dec-07 5:28

As a wizard, you should be able to conjure this up using your How to be a Wizard in 21 Days book that came in your Welcome Package when you joined the Wizard club.

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

virtual member?

Stan the man20-Dec-07 2:52

Stan the man

20-Dec-07 2:52

Hi.

I am not sure how to explain this but I want to declare a member in a base class. IN a class derived from this, I want to be able to be able to override the member with another class that is derived from that original member.

Ex:

class CBase
{
virtual CTest m_test;

}

class CBase1 : public CBase
{

virtual CTest1 m_test;

}

CTest1 is derived from CTest.

I want to be able to almost use the same name in each class and just add more fuunctionality in the CBase1 class, but CBase will still be able to call fuctions from m_test. Then in CBase1, it can call additional functions available in CTest1... This is like a virtual function but I want to do it for a member variable or something.

I am not sure if I explained it right. Anyone can give me an idea?

Thanks.

Stan the man

image processing toolkits | batch image processing

C^hris L^osinger20-Dec-07 3:01

C^hris L^osinger

20-Dec-07 3:01

there's no such thing as a virtual member.

but, can you make CTest a base class of CTest1 ? then you can override members in CTest to add that additional functionality.

Stan the man20-Dec-07 3:07

Stan the man

20-Dec-07 3:07

Hi Chris.

Yes, that is not a problem. The one thing is that if the (virtual) member/class is already declared in another base class. Then this base class I derive another class. But for this class, I need a slightly different functionality of that "virtual" member/class. But I do not want to disturb the function of the original (virtual) member/ class in that other base class.

You know my meaning? I want to "replace" that class with another class which has identical functions but with some changes...

Thanks.

Stan the man

Maximilien20-Dec-07 3:06

Maximilien

20-Dec-07 3:06

I'm not certain I understand what you want to achieve, but my gut feeling is that you cannot do that.

maybe if you create a base class for CTest and CTest1 and keep a pointer to that class instead of CTest and CTest1 ?

// not tested, and probably will not work as-is 
class CTestBase {};
class CTest : public CTestBase {};
class CTest1 : public CTestBase {};

// and have 

class CBase 
{
 CBase() { m_pTest = new CTest;};
 CTestBase* m_pTest;
};

class Cbase1 : public CBase 
{
 CBase1() { m_pTest = new CTest1;};
 CTestBase* m_pTest;
};

but you will probably need to use something like CBase::m_pTest and CBase1::m_pTest to resolve potential name conflicts.

Maximilien Lincourt
Your Head A Splode - Strong Bad

Stan the man20-Dec-07 3:11

Stan the man

20-Dec-07 3:11

HI Max.

Thanks for the comment. I think I can use something like this. Don't know why I did not think of it.

Thanks.

Stan the man

Re: Convert string to long

Matthew Faithfull20-Dec-07 3:12

Matthew Faithfull

20-Dec-07 3:12

I think there's a bit of an OO design issue going on here. Perhaps you need some data hiding...

<br />
class CBase<br />
{<br />
public:<br />
  virtual int AccessorFunctionThatDealsWithTest();<br />
<br />
private:<br />
  CTest m_test;<br />
};<br />
<br />
class CDerived1 : public CBase<br />
{<br />
public:<br />
  int AccessorFunctionThatDealsWithTest();//override of CBase virtual function<br />
<br />
private:<br />
  CSomeOtherTest m_test;<br />
};<br />

If you do this then it matters not if CTest and CSomeOtherTest are related, they can be but the 'user' of CBase:CDerived1 hierarchy doesn't have to know or care because the AccessorFunctionThatDealsWithTest() interface is the same even though its implementation might be entirely different. Now that makes me Big Grin | :-D

Nothing is exactly what it seems but everything with seems can be unpicked.

Convert string to long

SWDevil20-Dec-07 2:41

SWDevil

20-Dec-07 2:41

Hi,

How can I convert a string to long, so that the long value will be exactly the same value as the string?

When I use the following code:

CString str= "39436573472344";
long temp = atol(str);

The value of temp is 2147483647.
How can I get the value of temp to be the same as the string?

Thanks.

CPallini20-Dec-07 2:53

CPallini

20-Dec-07 2:53

The numeric value corrensponding to your string simply doesn't fit inside a variable of type long; in such cases the atol returns LONG_MAX (i.e. 2147483647).
You can use _strtoi64 function and a variable of type __int64 that holds values up to 9223372036854775807.
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.

[my articles]

Re: Convert string to long

Matthew Faithfull20-Dec-07 3:03

Matthew Faithfull

20-Dec-07 3:03

Your problem here is that the number is too large to be stored in 32 bit signed long. You'll need a 64 bit integer type for this one, _int64 _atoi64( const char *string ); should do the trick or its UNICODE equivalent.

Nothing is exactly what it seems but everything with seems can be unpicked.

Detection of databases

tom groezer20-Dec-07 2:14

tom groezer

20-Dec-07 2:14

I'm developing a C++ program that should check whether SQL 2k5, Exchange 2k7, Oracle 10g are installed on the system. Based on whether one of it is installed the program shall invoke a different C++ function. The check shall be made by probing for certain registry keys/values by the C++ main program.
I would like to know which keys/values are set by the installation of

SQL 2k5
Exchange 2k7
Oracle 10g.

Also are there registy keys/values probing is foolproof enough to guarantee the successfull calling of the appropriate function?

On a sidenote are there any registry keys/values that are common and same for all the above three databases irrespective of different flavours. The idea is that the same registry check works for all the different version of a database.

Re: Detection of databases

David Crow20-Dec-07 2:28

how to format a pen drive?

20-Dec-07 2:28

This should give you a starting point.

Shayantani20-Dec-07 1:27

Shayantani

20-Dec-07 1:27

I work in C,C++ Windows platform. I am to write code to format a pendrive. I searched and found DeviceIOControl() that seemed to fulfill my purpose. But I cannot proceed any further. Plz help me in this regard.

thanx
Shayantani

Re: how to format a pen drive? [modified]

kakan20-Dec-07 2:08

kakan

20-Dec-07 2:08

One way, generally, is to use the function FormatEx() from fmifs.dll.
I have been using it for years, but yesterday, I tried to use it for formatting an USB stick/pendrive.
The format itself seemed to work very well, but I got "delayed write error" when I tried to write big files to the pen drive after formatting it (with FormatEx).
I ended up with using Windows normal Format, and after that, the pen drive seemed to work as before.
I suspect the cause of the problem is in the second parameter to the FormatEx() function.
It seems as there are just two known values (outside MS) out of 24! (The known values are FMIFS_FLOPPY and FMIFS_HARDDISK). Another value might do the trick.

So your DeviceIOControl() call might be a way to do it. It seems possible that the formatting code is included with the driver. Might be worth to investigate further.
You say "I cannot proceed any further". Why? What's the problem?

<edit>I'm going on Xmas leave now. Back on the 7:th of January (GMT+1)

Alcohol. The cause of, and the solution to, all of life's problems - Homer Simpson

modified on Thursday, December 20, 2007 11:18:08 AM

Really Not An Easy Ques. !!!!!!!!

AhmedOsamaMoh20-Dec-07 1:13

AhmedOsamaMoh

20-Dec-07 1:13

Dear All

how can i get the size of a function (its code size in the memory in bytes) from its pointer (its function pointer)

function like

double add (double , double)

i tried sizeof by many ways and no result Unsure | :~

any tips

thanks all

bye

CPallini20-Dec-07 1:58

CPallini

20-Dec-07 1:58

You cannot.
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.

[my articles]

AhmedOsamaMoh20-Dec-07 2:28

AhmedOsamaMoh

20-Dec-07 2:28

what if i want to copy the function code from the memory to a file?? !!

thanks

David Crow20-Dec-07 2:35

20-Dec-07 2:35

Why would you need/want this? Even if it were possible, the "code" you'd end up with would be machine code.

CPallini20-Dec-07 2:38

CPallini

20-Dec-07 2:38

IMHO (I'm not expert about), you need to hack DLL (or executable) internals, i.e. you need to know PE file format, have a look at http://msdn.microsoft.com/msdnmag/issues/02/02/PE/default.aspx[^]
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.

[my articles]

Matthew Faithfull20-Dec-07 2:46

Matthew Faithfull

20-Dec-07 2:46

The only way would be a loop that reads through the assembly code looking for the next ret. This would only work with simple functions having only one ret. Once you put the code in a file it would be useless anyway because code with jump instructions in it (most code) is usually address dependent. ie. if you don't load the code back at the same address it won't work anymore. As you can never gaurentee to do this in any future instance of the process it would be of no use to have the unbased machine code in a file, except possibly for comparison to detect a code modifying virus attack or something. There are better ways to do that anyway like security cookie checks which are already built into every function for you by the MS Compiler. See the /GS compiler switch. If you want to know more have a look at some disassemblers which turn compiled code back into something almost readable.

Nothing is exactly what it seems but everything with seems can be unpicked.

Member 75496020-Dec-07 4:27

Member 754960

20-Dec-07 4:27

Caveat: This is dubious practice. The memory layout is not guaranteed and should not be relied upon. Pointer arithmatic is not good. It is mostly just an "irresistible" question.

Given the above: an old technique is to use two function pointers

void functionA()
{
	// whatever
}
void functionB()
{
	// whatever
}

void dontdothis()
{
	void * p1 = functionA;
	void * p2 = functionB;
	char * p3 = static_cast<char *>(p1);
	char * p4 = static_cast<char *>(p2);
	size_t sizeFn = p4 - p3;
}

There is little, if anything, that can be done with this.

AhmedOsamaMoh20-Dec-07 5:44

AhmedOsamaMoh

20-Dec-07 5:44

can u kindly explain more what the meaning by ur code ??

you just sub. two addr of two pointer of two function !! how this be the size and size of which one ..

i really misunderstand

thx

David Crow20-Dec-07 5:51

20-Dec-07 5:51

Assuming the two functions are back-to-back in memory, you can simply take the difference of their addresses to obtain the size. In other words, if functionA() is at 0x1234 and functionB() is at 0x2345, then the size of functionA() would be 4,369 bytes.