C / C++ / MFC Discussion Boards

Help with understanding the use of a buf[]

Anonymous30-Jun-03 4:00

30-Jun-03 4:00

I don't quite understand how a buffer works.

I have a PCI card that uses reflective memory
Reflective memory is memory that is connected through a daisy chain on fiber optics, when one PC writes to the memory on the PCI card then the rest of the computers on the daisy chain can read what was written in realtime or as close as you can get to it.

I hope that makes sense.

I am able to choose at what offset I want to start writing data to the PCI cards memory.
ex. offset 0x40 from the beginning of the cards memory.

Then on another PC I can go read the data at that offset 0x40.

The data structure that I have created is that needs to be written to memory is:

The data is continious.

<br />
<br />
//this will get written at offset 0x40<br />
 struct TSimHeader<br />
	{<br />
		int SimWriteFlag;			<br />
		int DisplayReadFlag;				<br />
		int SignalCount;		<br />
		int SimStatus;<br />
		long TimeStamp;<br />
	};<br />
<br />
//this will get written right after TSimHeader<br />
struct TSimSignal<br />
	{<br />
		double Min[45];	  <br />
		double Max[45];	  <br />
		double Value[45]; <br />
		char   *Name[45];<br />
		char   *Unit[45];<br />
	};<br />

The functions that read and write the data use a buffer to write and read from (char or int or double or long buf[1024])

How can I put these 2 structures in this buffer so that on the otherside when I read in the data I am able to parse it back out of the structure?

Thanks,
sj Smile | :)

Re: Help with understanding the use of a buf[]

Trollslayer30-Jun-03 5:37

Trollslayer

30-Jun-03 5:37

How about creating a structure

struct TSimBlock<br />
{<br />
TSimHeader header;<br />
TSimSignal signal;<br />
}<br />

then a variable

<br />
TSimBlock *BlockPtr;<br />

then set TBlockPtr to point to the data in the card on the other side and read it for eaxmple by

<br />
i = BlockPtr->header.SimWriteFlag;<br />

Hope I've got all the indirection right, haven't run the code myself.

Elaine Rose | [Rose]

The tigress is here Big Grin | :-D

Re: Help with understanding the use of a buf[]

johnstonsk30-Jun-03 6:20

johnstonsk

30-Jun-03 6:20

Makes sense. I just created a type exactly like the struct that was written.
I then casted the data to the struct type on the other side.
I am then able to read the data just as I was writing it.

Thanks,
For showing me the way.

Sj Smile | :)

Custom Draw in CListCtrl - how to change background of icons?

Dominik Reichl30-Jun-03 3:07

Dominik Reichl

30-Jun-03 3:07

Hello,

I am trying to colorize specific rows of my list control. For this I use the OnCustomDraw member function of CListCtrl to select the color before Windows draws the item. This works very nice, except that the icon's background isn't drawn correctly.

See this screenshot:
http://home.tiscali.de/reichl/temp.jpg[^]

As you can see, the row is highlighted correctly, but the icon's background remains white.

How can I draw the icon's background? Confused | :confused:

-Dominik

_outp(0x64, 0xAD);
and
__asm mov al, 0xAD __asm out 0x64, al
do the same... but what do they do??

Re: Custom Draw in CListCtrl - how to change background of icons?

Ryan Binns30-Jun-03 4:12

Ryan Binns

30-Jun-03 4:12

Did you try drawing the background in OnCustomDraw() during the CDDS_ITEMPREPAINT notification? If that doesn't work, try an earlier notification, such as CDDS_ITEMPOSTERASE or even CDDS_ITEMPREERASE (not recommended, but it might work).

Or is the problem that Windows is drawing the white background no matter what you do? If that's the case, the best thing to do would probably be to get the control to draw in a memory DC and change the colour yourself, although that would probably require full owner-draw.

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

Re: Custom Draw in CListCtrl - how to change background of icons?

Dominik Reichl30-Jun-03 6:28

Dominik Reichl

30-Jun-03 6:28

I tried preerase and posterase, but both don't work. The background remains white. Seems as I really have to draw it myself Dead | X|

Anyway, thanks for your help
-Dominik

_outp(0x64, 0xAD);
and
__asm mov al, 0xAD __asm out 0x64, al
do the same... but what do they do??

Re: Custom Draw in CListCtrl - how to change background of icons?

Ryan Binns30-Jun-03 17:14

Ryan Binns

30-Jun-03 17:14

OK, I just happened to look at Michael Dunn's article on list view custom draw (http://www.codeproject.com/listctrl/lvcustomdraw.asp[^]) and he does this by redrawing the icon in CDDS_ITEMPOSTPAINT and returning CDRF_SKIPDEFAULT. It flickers a bit, but not too much.

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

Re: Custom Draw in CListCtrl - how to change background of icons?

Dominik Reichl1-Jul-03 0:15

Dominik Reichl

1-Jul-03 0:15

Ok, I'll try this.

Thanks
-Dominik

_outp(0x64, 0xAD);
and
__asm mov al, 0xAD __asm out 0x64, al
do the same... but what do they do??

Re: Custom Draw in CListCtrl - how to change background of icons?

basementman30-Jun-03 4:35

basementman

30-Jun-03 4:35

You could specify an overlay mask which would colorize the background as you wish.

onwards and upwards...

List Box

Jay Hova30-Jun-03 2:57

Jay Hova

30-Jun-03 2:57

Hi,

Still learning and playing with MFC... Smile | :)

Is there a way that I can set the number of columns in a list box? Also, if this is possible how do you put column headings in a list box?

Thanks in advance.

Re: List Box

Michael P Butler30-Jun-03 3:07

Michael P Butler

30-Jun-03 3:07

Have a look at CListCtrl instead. There are some good samples here http://www.codeproject.com/listctrl/[^]

Michael

'War is at best barbarism...Its glory is all moonshine. It is only those who have neither fired a shot nor heard the shrieks and groans of the wounded who cry aloud for blood, more vengeance, more desolation. War is hell.' - General William Sherman, 1879

Is GetItemText limited to 256 bytes for CString ?

Wormhole523030-Jun-03 2:51

Wormhole5230

30-Jun-03 2:51

There are two types of function to extract a text in the list item in CListCtrl.

One is
CString GetItemText( int nItem, int nSubItem ),
and the other is
int GetItemText( int nItem, int nSubItem, LPTSTR lpszText, int nLen ).

In case of using the first function,
it looks like it can only extract 256 bytes,
even the text is over 256 bytes.

It is OK for second function.

I don't know why the length is limited for CString.

Any idea to resolve this problem with CString?

Should I use second function?

Thanks.

Re: Is GetItemText limited to 256 bytes for CSting ?

Trollslayer30-Jun-03 3:40

Trollslayer

30-Jun-03 3:40

Perhaps the first function uses the second with a length value of 256 ?
Probably easiest to write your own function which is equivalent to the first but with a larger length limit.

Elaine Rose | [Rose]

The tigress is here Big Grin | :-D

Re: Is GetItemText limited to 256 bytes for CSting ?

Wormhole523030-Jun-03 4:16

Wormhole5230

30-Jun-03 4:16

OK, that's no problem but what happened to CString, is it bug or not?

Thanks.

Re: Is GetItemText limited to 256 bytes for CSting ?

Trollslayer30-Jun-03 5:41

Trollslayer

30-Jun-03 5:41

Its not a bug in CString, its the function that returns CString. They have to call the original function and in the course of that add the length parameter. And thinking that 256 chars would have been enough....
If you look at the library code there will be a GetBuffer(256) statement with the length also set to 256. Make sure these match in your code or you could get an overflow.

Elaine Rose | [Rose]

The tigress is here Big Grin | :-D

Re: Is GetItemText limited to 256 bytes for CSting ?

David Crow30-Jun-03 6:04

David Crow

30-Jun-03 6:04

What are you using to verify the length of the CString object? Have you stepped into CListCtrl::GetItemText() to watch how it is behaving?

Re: Is GetItemText limited to 256 bytes for CSting ?

Wormhole523030-Jun-03 6:19

Wormhole5230

30-Jun-03 6:19

I just used GetLength() to check the length of the returned CString object.
The return value is 256.
The length of the text in the CListCtrl is surely over 256 bytes.
The second function can extract whole text when the last parameter nLen
is large enought to hold whole text.

Thanks.

Re: Is GetItemText limited to 256 bytes for CSting ?

David Crow30-Jun-03 6:29

David Crow

30-Jun-03 6:29

Ok, but did you step through the MFC code?

Re: Is GetItemText limited to 256 bytes for CSting ?

Wormhole523030-Jun-03 6:55

Wormhole5230

30-Jun-03 6:55

With your advice, I looked at the MFC code.

The function was defined as follows.

CString CListCtrl::GetItemText(int nItem, int nSubItem) const
{
ASSERT(::IsWindow(m_hWnd));
LVITEM lvi;
memset(&lvi, 0, sizeof(LVITEM));
lvi.iSubItem = nSubItem;
CString str;
int nLen = 128;
int nRes;
do
{
nLen *= 2;
lvi.cchTextMax = nLen;
lvi.pszText = str.GetBufferSetLength(nLen);
nRes = (int)::SendMessage(m_hWnd, LVM_GETITEMTEXT, (WPARAM)nItem,
(LPARAM)&lvi);
} while (nRes == nLen-1);
str.ReleaseBuffer();
return str;
}

At first look at, it looks like to extract whole text using do-while statement.
But in my code, nRes is 256, so do-while is applied only one time.

Re: Is GetItemText limited to 256 bytes for CSting ?

David Crow30-Jun-03 7:22

David Crow

30-Jun-03 7:22

I used the following code snippet and both TRACE() calls output 300:

CString str;<br />
int len;<br />
str  = "12345678901234567890123456789012345678901234567890";<br />
str += "12345678901234567890123456789012345678901234567890";<br />
str += "12345678901234567890123456789012345678901234567890";<br />
str += "12345678901234567890123456789012345678901234567890";<br />
str += "12345678901234567890123456789012345678901234567890";<br />
str += "12345678901234567890123456789012345678901234567890";<br />
len = str.GetLength();<br />
TRACE("len = %d\n", len);<br />
ctrlList.InsertItem(0, str);<br />
str.Empty();<br />
str = ctrlList.GetItemText(0, 0);<br />
len = str.GetLength();<br />
TRACE("len = %d\n", len);

Re: You are right and I am right too.

Wormhole523030-Jun-03 7:40

Wormhole5230

30-Jun-03 7:40

You are right.

I found it worked well in alphanumeric text.
I'm a Korean. When the string is Korean, it fails.

Thanks.

Re: You are right and I am right too.

David Crow30-Jun-03 7:45

David Crow

30-Jun-03 7:45

Makes me wonder if you aren't having a Unicode problem.

Re: You are right and I am right too.

Wormhole523030-Jun-03 8:03

Wormhole5230

30-Jun-03 8:03

OK, it looks like it definitely related to data-type mapping.
I will check it later because of the lack of time.

Thank you for your consideration. Smile | :)

Can I use the DECLARE_DYNAMIC macro for a CList derived class?

Charles Liu30-Jun-03 2:46

Charles Liu

30-Jun-03 2:46

I got a class derived from CList, as
class CPointList : public CList<CPoint*,CPoint*&>
{
...
}
I want to declare it DYNAMIC, but as i wrote this in .cpp
IMPLEMENT_DYNAMIC(CPointList,CList<CPoint*,CPoint*&>
The compiler gave an error:
warning C4002: too many actual parameters for macro 'IMPLEMENT_DYNAMIC'
How can I declare it to be dynamic?

Re: Can I use the DECLARE_DYNAMIC macro for a CList derived class?

Ryan Binns30-Jun-03 3:24

Ryan Binns

30-Jun-03 3:24

Charles Liu wrote:
How can I declare it to be dynamic?

Yes, but instead of CList<CPoint*,CPoint*&>, you need to use CObject. CList is not DECLARE_DYNAMIC(), so you can't specify it as the base class.

Doing this means that you can tell what class the CPointList is, but it will appear to be a direct descendent of CObject, ie. RUNTIME_CLASS(CPointList)->GetBaseClass() will return RUNTIME_CLASS(CObject).

BTW, the reason the compiler tells you it has too many parameters is because the preprocessor doesn't care about C syntax - it just splits the macro at the commas. It does not care (and does not know) that the second comma is inside a template definition, and assumes it to be separating parameters. The only comma is treats differently is one that's inside a string.

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

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