C / C++ / MFC

4-May-02 8:38

Where should I post my TurboC++ / ASM / BIOS question?

I need a way to wake up the BIOS chip on an AGP card under DOS environment.
Can anyone help ?? Blush | :O

Thank you!

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

Array of pointers

Rohde4-May-02 8:16

Rohde

4-May-02 8:16

Oh, damn I accidentally postd this in the Lounge...now heres it is. I'd appreciate ny help.

Can somebody help me. I'm trying to create an array of pointers. I'd do something like this:

int *array[SIZE];

But the array's large so I'd like to use the _new_ operator. How do I do that?

I've tried the following without luck:

int ** array = new int[size];

int * array = new *int[size];

Plz help

Nish Nishant4-May-02 8:29

Nish Nishant

4-May-02 8:29

int *array[SIZE];
for(int i=0;i<SIZE;i++)
    array[i] = new int;

Nish

The posting stats are now in PDF:-
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Feel free to make your comments.
Updated - May 04th, Saturday

Paul M Watt4-May-02 9:22

Paul M Watt

4-May-02 9:22

You were close:

int **array = new int*[SIZE];

That will allocate an array of integer pointers that has SIZE number of elements.

Just for everyone's knowledge, to access the pointers in this new array, you will need to do something like this:

int a = 10;
int b = 20;
int c = 30;
// you can point to existing integer buffers
array[0] = &a;
array[1] = &b;

// you can allocate new integers
array[2] = new int;
*array[2] = 50;

// you can allocate an array if integers to be held in this new pointer.
array[3] = new int[10];
array[3][0] = 100;

just remember to delete any memory that you allocate, even in the pointers inside of your allocated array.

Good Luck!

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

Maxwell Chen4-May-02 9:33

4-May-02 9:33

Some day I asked Bjarne Stroustrup a question to dynamically allocating square array ( 2 X 2 or 3 X 3 or 10 X 10 ... ), He told me to use vector!

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

Christian Graus4-May-02 11:34

Christian Graus

4-May-02 11:34

He's a wise man.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned. - Christopher Duncan - 18/04/2002

Maxwell Chen4-May-02 20:57

Setting Up Option Parameters :: C++

4-May-02 20:57

His way is nice!
But finally I approached my goal via a template class that wraps a low-level 2d int array.

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

valikac4-May-02 7:19

4-May-02 7:19

Hi.

I would like to create a generic class that wraps around, say, an API function. I need a way to pass into a function parameters such as FEATURE1 | FEATURE3. I believe that requires the use of bitwise AND, OR, and NOT similar to MFC programming style.

For example:

-----
// call function to initialize variables

SetVariableA(FEATURE1 | FEATURE 3) // I want feature1 and feature3
-----

Here is what SetVariableA(...) might look like

-----
enum STYLE {FEATURE1 = 0, FEATURE2, FEATURE3}

SetVariableA(...)
{
}
-----

Basically, I am not familiar with the use of enum with bitwise AND, OR, and NOT. Here is a what I would like to accomplish.

- user calls function to setup a feature: function(FEATURE1)
- function determines what feature the user wants

How would you implement some like the above using enum, bitwise AND, OR, and NOT?

Thanks,
Kuphryn

P.S. MFC programmers seem to use the bitwise AND, OR, and NOT

Ravi Bhavnani4-May-02 7:27

Ravi Bhavnani

4-May-02 7:27

setVariableA (UINT bitMask)
{
  enum STYLE styleIterator;
  for (enum STYLE styleIterator=FEATURE1; (styleIterator <= FEATURE3) styleIterator++) {
      if (bitMask & styleIterator) {
         // Handle case for feature "styleIterator"
         ...
      }
  }
}

/ravi

"There is always one more bug..."
http://www.ravib.com
ravib@ravib.com

Maxwell Chen4-May-02 8:14

4-May-02 8:14

Hi Ravi,

Your code doesn't compile, there're several errors. Check your code, compile it, and you will see!
Wink | ;)

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

valikac4-May-02 8:22

4-May-02 8:22

Thanks.

Your sample code helped me understand *almost* everything. I have two questions.

1) I assume enum STYLE is *defined* as global inside whatever class setVariableA(UINT bitMask) belongs to. Right?

-----
enum STYLE {FEATURE1 = 0, FEATURE2, FEATURE3}

class CArbitrary
{
public:
setVariableA(UINT bitMask);
};
-----

If yes: Will the class that declare CArbitrary understand what, for example, FEATURE1 actually is?

For example:

-----
setVariableA(FEATURE2);
-----
// FEATURE2 is defined is enum STYLE
// However, SetVariableA(UINT bitMask)
// UINT == enum STYLE?

2) In the code you posted, I cases (bitMask & FEATURE1), etc., but how about cases such as FEATURE1 | FEATURE3?

Thanks,
Kuphryn

Class scope....

Maxwell Chen4-May-02 8:28

4-May-02 8:28

Hi Kuphryn,

While wrapping such functions in a class, you use this way:

#include <iostreamᡊe9ac73-238b-46be-991d-0f050c37248dusing namespace std;

class MyCtrl
{
public:
	enum ST { enType1 = 0x01, enType2 = 0x02, enType3 = 0x04 };
	void SetVar(int style)
	{
		int tt;
		for(tt = enType1; tt <= enType3; tt = (tt << 1))
		{
			if(style & tt)
				cout << "Type " << tt / 2 + 1 << " implemented\n";
		}
	}
};

void main()
{
	MyCtrl	ctrl;
	ctrl.SetVar(MyCtrl::enType1 | MyCtrl::enType3);
}

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

Re: Class scope....

Ravi Bhavnani4-May-02 9:30

Ravi Bhavnani

4-May-02 9:30

Ugh. What was I thinking? Of course you have to bit shift (and not sequence thru like I did) a mask. Blush | :O

I'm going to hold doff posting until I'm sufficiently awake!

/ravi

"There is always one more bug..."
http://www.ravib.com
ravib@ravib.com

Re: Class scope....

Maxwell Chen4-May-02 9:37

4-May-02 9:37

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

Maxwell Chen4-May-02 8:19

4-May-02 8:19

I used to do this way......

#include <iostreamᡊe9ac73-238b-46be-991d-0f050c37248dusing namespace std;

enum ST { enType1 = 0x01, enType2 = 0x02, enType3 = 0x03 };

void SetVar(int style)
{
	int tt;
	for(tt = enType1; tt <= enType3; tt = (tt << 1))
	{
		if(style & tt)
			cout << "Type " << tt / 2 + 1 << " implemented\n";
	}
}

void main()
{
	SetVar(enType1 | enType3);
}

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

valikac4-May-02 8:24

4-May-02 8:24

Thanks.

Please read my reply above.

Kuphryn

PJ Arends4-May-02 8:31

PJ Arends

4-May-02 8:31

I would not use an enum, but rather just a set of defines for every flag

#define FEATURE1  0x00000001  // bit one
#define FEATURE2  0x00000002  // bit two
#define FEATURE3  0x00000004  // bit three
#define FEATURE4  0x00000008  // bit four
#define FEATURE5  0x00000010  // bit five
.
.
.

This will give you up to 32 flags.

Then, the parameter used to set the flags would be a DWORD

void SetVariableA (DWORD dwflags = 0);

You would call it this way

SetVariableA (FEATURE1 | FEATURE3);

Then, inside SetVariableA() you would check to see which flags have been set by using the bitwise AND ( & ) operator

void SetVariableA (DWORD dwFlags)
{
    if (dwFlags & FEATURE1)
    {
        // FEATURE1 flag set, do what has to be done
    }
    if (dwFlags & FEATURE2)
    {
.
.
.

HTH

---
CPUA 0x5041

Sonork 100.11743 Chicken Little

If a man is standing in the middle of the forest speaking and there is no woman around to hear him...is he still wrong?

valikac4-May-02 8:43

4-May-02 8:43

Thanks.

You, Ravi Bhavnani, and Maxwell Chen posted three very similar techniques. All seems important. Your technique, however, make use of #define instead of enum and DWORD instead of UINT.

1) Can you explain #define over enum and DWORD of UINT?
2) Can I use #define FEATURE1 1, #define FEATURE2 2, etc.. instead of hex?
3) I asked Maxwell Chen about calling the FEATURE1 *outside* of the class.

For example:

-----
int main()
{
...
SetVariableA(FEATURE1);
-----

How does mean know what FEATURE1, FEATURE2, etc. are?

Last, this question applies to everyone. In the function,

// SetVariableA (FEATURE1 | FEATURE3);

I believe that means you want FEATURE1 and you want FEATURE3. However, in the implementation of SetVariableA(UINT) or SetVariableA(DWORD), there are cases for (dwFlags & FEATURE1), (dwFlags & FEATURE2), etc. How about something like:

// FEATURE1 | FEATURE3

Oh. I think I know what is going on. For every "if cases" the statement sets *each* FEATURE accordingly. For example:

// SetVariableA (FEATURE1 | FEATURE3);

// SetVariableA(UINT flags) or SetVariableA(DWORD flags)
{
if (flags & FEATURE1) // applying to the call above, YES
if (flags & FEATURE2) // NO
if (flags & FEATURE3) // YES
}

Am I on track?

Kuphryn

PJ Arends4-May-02 9:12

PJ Arends

4-May-02 9:12

kuphryn wrote:
1) Can you explain #define over enum and DWORD of UINT?
with an enum, you can loop over the values, so technically it probably better, but I prefer #defines, They are easier IMO

On 32 bit systems, there is no difference between UINT and DWORD. On 16 bit systems UINT is 16 bits, DWORD is 32 bits

kuphryn wrote:
2) Can I use #define FEATURE1 1, #define FEATURE2 2, etc.. instead of hex?

Yes you can, but remember that you are setting the individual bits, so your values would be 1, 2, 4, 8, 16, 32, 64, 128 etc. using hex is just easier IMO.
just remember that the bitwise OR operator, when used with properly defined flags, acts as a plus operator.
ie :
1 | 2 == 3
1 | 4 == 5
2 | 4 == 6
1 | 2 | 4 == 7
...

kuphryn wrote:
How does mean know what FEATURE1, FEATURE2, etc. are

that is why I put the defines in the header file. Just include the header file in which ever file you use the flags.

kuphryn wrote:
Am I on track?
Yes. Be sure to read up on bitwise operators in MSDN.

HTH

---
CPUA 0x5041

Sonork 100.11743 Chicken Little

If a man is standing in the middle of the forest speaking and there is no woman around to hear him...is he still wrong?

Maxwell Chen4-May-02 9:28

4-May-02 9:28

I wrote something wrong, so I deleted it.

#define preprocessor directive affetcs everywhere after the compiler "sees" it.

Enum is something like you are creating some integral type. Those members of a certain enum type, you may take them as integral number, like int, short.
The compiler optimizes the size, if all members in a enum type are less than maximum value of short, then they are short. Else they are taken as int or long... If beyond maximum of (unsigned) int or long, you get a error compiling msg!

Bjarne recommends C++ programmers less using MACROs.

Maxwell Chen
People say "No news is good news". Then, no code is good code!?

Re: Thanks

valikac4-May-02 9:30

4-May-02 9:30

Okay. Thanks everyone.

I will start out using #define and DWORD.

Kuphryn

Re: Thanks

Todd Smith6-May-02 12:49

Todd Smith

6-May-02 12:49

You can see the value of an enum in the debugger. With a define you cannot.

typedef enum
{
    FEATURE1 = 0x0001,
    FEATURE2 = 0x0002,
    FEATURE3 = 0x0004,
    FEATURE4 = 0x0008,
    FEATURE5 = 0x0010,
    // etc...

} FEATURES;

Todd Smith

Re: Hex

valikac4-May-02 9:54