Re: Strange behavior in bit fields in "C++" - C / C++ / MFC Discussion Boards

manoharbalu4-Jan-09 22:30

4-Jan-09 22:30

I am sure, I am using the DoModal() function.

My application has a mainwindow, which opens a first modal dialog, which in turn opens a second modal dialog. When I click on the main window after opening the first modal dialog alone, the focus is not going to the main window. When I open the second modal dialog from the first modal dialog and then click on the application main window, now also the main window is not getting the focus. But the problem is when i Click on the first modal dialog, when the second modal dialog is still open, the focus is going to the first modal dialog which is not supposed to be.
Pls provide the solution to prevent this behaviour.

Note: The first modal dialog was previously derived from CPropertyPage which i have changed it to derive from CDialog.

Re: Modal dialog problem

Chandrasekharan P4-Jan-09 23:34

Chandrasekharan P

4-Jan-09 23:34

Tried with an example the way you have explained. its working fine for me.

Re: Modal dialog problem

Code-o-mat5-Jan-09 0:49

Code-o-mat

5-Jan-09 0:49

Could it be that the parent of your second modal dialog is your main window rather then the first modal dialog?

> The problem with computers is that they do what you tell them to do and not what you want them to do. <

Re: Modal dialog problem

Nibu babu thomas4-Jan-09 21:55

Nibu babu thomas

4-Jan-09 21:55

manohar_balu wrote:
another modal dialog using DoModal() function. When I open the dialog (modal) from the parent modal dialog, it opens fine. But when I click on the Parent modal dialog I am able to gain focus on the Parent modal dialog which is not supposed to be.

Is this the problem?

http://www.codeproject.com/KB/dialog/notmodaldialogs.aspx[^]

Nibu babu thomas
Microsoft MVP for VC++

Code must be written to be read, not by the compiler, but by another human being.

Programming Blog: http://nibuthomas.wordpress.com

Strange behavior in bit fields in "C++"

Joseph Marzbani4-Jan-09 19:07

Joseph Marzbani

4-Jan-09 19:07

NOTE: I'm using an "Intel" machine to test the following codes.

I have an array of 48 Bytes named aArray and as you know it looks like some thing like this in memory:

100011011001110110110101 ...

Now, I want to separate six-bit chunks from the begin, useing bit fields as the follow:

struct CHUNKS
{
        unsigend  __int32    FirstChunk:6;
        unsigend  __int32    SecondChunk:6;
        unsigend  __int32    ThirdChunk:6;
        unsigend  __int32    FourthChunk:6;
}*pChunk = NULL;

for(int iCountor=0; iCountor<48; iCountor+=3)
{
        pChunk = (CHUNKS*) (aArray + iCountor);
        ...
}

What I expect is this:

Suppose aArray = 10001101 10011101 10110101 ...
and Say iCountor is equal to 0 at the moment.
pChunk->FirstChunk ... pChunk->FourthChunk should be as follow:

100011 011001 110110 110101

But that's not the case! pChunk->FirstChunk ... pChunk->FourthChunk are as follow:

pChunk->FirstChunk is equal to 001101 as follow:<br />
10<big>001101</big>  10011101  10110101<br />
<br />
pChunk->SecondChunk is equal to 110110 as follow:<br />
<big>10</big>001101  1001<big>1101</big>  10110101<br />
<br />
pChunk->ThirdChunk is equal to 011001 as follow:<br />
10001101  <big>1001</big>1101  101101<big>01</big><br />
<br />
pChunk->FourthChunk is equal to 101101 as follow:<br />
10001101  10011101  <big>101101</big>01

As you can see and I guess, no body can make anything of this situation.

Thank you masters!

Re: Strange behavior in bit fields in "C++"

KarstenK4-Jan-09 21:00

KarstenK

4-Jan-09 21:00

Please read about LSB und MSB this is also to tricky for me. Dead | X|

Greetings from Germany

Re: Strange behavior in bit fields in "C++"

Sameerkumar Namdeo4-Jan-09 21:01

Sameerkumar Namdeo

4-Jan-09 21:01

the struct CHUNKS, i guess will require no more than 24 bits, i.e one single unsigned int(32 bits = 4 bytes) will be enough.

give a try for this one,

CHUNKS st;
memcpy(&st, aArray, 4);
pChunk = &st;

now try to access

pChunk->FirstChunk & pChunk->FourthChunk

Re: Strange behavior in bit fields in "C++"

CPallini4-Jan-09 23:08

CPallini

4-Jan-09 23:08

Due to bit alignment in bytes, I think you cannot avoid a bit of bitwise manipulation. Roll eyes | :rolleyes:

For instance

#include <iostream>
#include <iomanip>
using namespace std;


// 10001101 10011101 10110101
// 11111110 11011100 10111010

void main()
{
  unsigned char aArray[]={0x8D, 0x9D, 0xB5, 0xFE, 0xDC, 0xBA};

  unsigned char bChunk[4];

  cout << setbase(16);
  for(int iIndex=0; iIndex<6; iIndex+=3)
  {
    bChunk[0] = aArray[iIndex] >> 2;
    bChunk[1] = (aArray[iIndex] << 4)  & 0x3F | aArray[iIndex+1] >> 4;
    bChunk[2] = (aArray[iIndex+1] << 2 ) & 0x3F | aArray[iIndex+2] >> 6;
    bChunk[3] = aArray[iIndex+2] & 0x3F;
    cout << (int)bChunk[0] << " " << (int)bChunk[1] << " " << (int)bChunk[2] << " " << (int)bChunk[3] << endl;
  }
}

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.

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[My articles]

Re: Strange behavior in bit fields in "C++"

Stuart Dootson5-Jan-09 0:13

Stuart Dootson

5-Jan-09 0:13

Like you, this behaviour seems a little unintuitive to me. Intel chips are little-endian (i.e. least-significant bytes first), but I thought that within a byte, a bit-field would extract the most significant bits first. Obviously not - as documented[^], Microsoft treat bytes as least-significant bit first as well.

Your only way round this is to do some bit manipulation yourself - the easiest way is probably to use bit-fields to extract the bits and glue them together again in methods of the struct - something like this:

struct CHUNKS
{
   unsigned  int FirstChunk() const { return firstChunk; }
   unsigned  int SecondChunk() const { return (secondChunkMSB<<4)|secondChunkLSB; }
   unsigned  int ThirdChunk() const { return (thirdChunkMSB<<2)|thirdChunkLSB; }
   unsigned  int FourthChunk() const { return fourthChunk; }
private:
   unsigned int secondChunkMSB:2;
   unsigned int firstChunk:6;

   unsigned int thirdChunkMSB:4;
   unsigned int secondChunkLSB:4;

   unsigned int fourthChunk:6;
   unsigned int thirdChunkLSB:2;
}*pChunk = NULL;

This does give the expected results for your test data.

memset?

dec824-Jan-09 18:53

dec82

4-Jan-09 18:53

What is the relevance of these code in C#? Thanks

unsigned char HartSendBuffer [200];
memset(SendBuffer,'\0',sizeof(SendBuffer));

Re: memset?

dec824-Jan-09 19:18

dec82

4-Jan-09 19:18

sorry, they are should be :
unsigned char SendBuffer [200];
memset(SendBuffer,'\0',sizeof(SendBuffer));

Re: memset?

CPallini4-Jan-09 20:00

CPallini

4-Jan-09 20:00

an82 wrote:
What is the relevance of these code in C#?

It is the relevance that C code has to C# language...

BTW: What about documentation [^]?

Smile | :)

Re: memset?

ThatsAlok5-Jan-09 0:45

ThatsAlok

5-Jan-09 0:45

are you using unmanaged programming in the C#. anyways it make whole sendbuffer to zero!

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
Never mind - my own stupidity is the source of every "problem" - Mixture

cheers,
Alok Gupta
VC Forum Q&A :- I/IV
Support CRY- Child Relief and You

My modal dialog loses focus to the parent dialog

manoharbalu4-Jan-09 18:30

manoharbalu

4-Jan-09 18:30

I have created modal dialog using DoModal() function. But my dialog loses focus when I click on the Parent dialog. How to prevent this..?

Re: My modal dialog loses focus to the parent dialog

David Crow5-Jan-09 8:10

David Crow

5-Jan-09 8:10

manohar_balu wrote:
How to prevent this..?

By using Spy++ to see what window the dialog is modal to.

"Love people and use things, not love things and use people." - Unknown

"The brick walls are there for a reason...to stop the people who don't want it badly enough." - Randy Pausch

File Exists

rdop4-Jan-09 18:14

rdop

4-Jan-09 18:14

Hi All

How can i check file is Exists or not?I am creating a file but before create a file i want to check File name is exists or not.Plz help me

Re: File Exists

Naveen4-Jan-09 18:20

Naveen

4-Jan-09 18:20

Use PathFileExists [^] function

nave

[OpenedFileFinder] [My Blog]

Re: File Exists

Hamid_RT4-Jan-09 18:35

Hamid_RT

4-Jan-09 18:35

You can use of FindFirstFile.

Of one Essence is the human race
thus has Creation put the base
One Limb impacted is sufficient
For all Others to feel the Mace
(Saadi )

Re: File Exists

KarstenK4-Jan-09 21:01

KarstenK

4-Jan-09 21:01

if you find a file you got to close the handle. Blush | :O

Greetings from Germany

Re: File Exists

Hamid_RT4-Jan-09 21:14

Hamid_RT

4-Jan-09 21:14

Sure!

Of one Essence is the human race
thus has Creation put the base
One Limb impacted is sufficient
For all Others to feel the Mace
(Saadi )

Re: File Exists

ThatsAlok5-Jan-09 0:19

ThatsAlok

5-Jan-09 0:19

Hamid. wrote:
Sure!

hummm

cheers,
Alok Gupta
VC Forum Q&A :- I/IV
Support CRY- Child Relief and You

Re: File Exists

Sameerkumar Namdeo4-Jan-09 21:04

Sameerkumar Namdeo

4-Jan-09 21:04

_taccess()

Re: File Exists

ThatsAlok5-Jan-09 0:20

ThatsAlok

5-Jan-09 0:20

ccpptrain wrote:
_taccess()

good! but i think, if i use it, it will increase my dependency on C runtime library. though they are fast but more error prone so beware while using it.

cheers,
Alok Gupta
VC Forum Q&A :- I/IV
Support CRY- Child Relief and You

How to create a custom list control in MFC ?

shah1864-Jan-09 18:08

shah186

4-Jan-09 18:08

How to create a custom list control in MFC which has following implemented :

Multicolumn sorting(time , text , numbers) .
Column coloring and dragging .
Set cell padding.
Subitem editing .

Please provide me with the code for the custom list control.

Re: How to create a custom list control in MFC ?

Hamid_RT4-Jan-09 18:36

Hamid_RT

4-Jan-09 18:36

Is this[^] helpful?

Of one Essence is the human race
thus has Creation put the base
One Limb impacted is sufficient
For all Others to feel the Mace
(Saadi )

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.