C / C++ / MFC

30-Jul-04 5:36

Ok, i just im making a binder
and i am using the CreateFile(), ReadFile(), and WriteFile() functions

now it took me long enough to figure out you cant read 28KB file into a buffer and write it all at once

Problem 1
As you should be able to guess im going to split the output by a string (no problem since i already wrote a function for that) but if im reading in segments then well you know it could cut into that string im splitting by

Problem 2
SetFilePointer doesnt seem to be working for me
if i could get this to work i have an idea that m
might (i stress might) solve my problems

Jaime Stuardo30-Jul-04 5:55

Jaime Stuardo

30-Jul-04 5:55

Didn't the third parameter of ReadFile work (nNumberOfBytesToRead)?

Jaime

Archer28230-Jul-04 5:59

30-Jul-04 5:59

Yes the third parameter of ReadFile has alwase worked. i am sorry but i dont really see what that has to do with either of my problems

David Crow30-Jul-04 6:31

David Crow

30-Jul-04 6:31

»Archer282« wrote:
now it took me long enough to figure out you cant read 28KB file into a buffer and write it all at once

Sure you can. I've used these functions before to read in a file 10x larger than that. No problem.

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Michael P Butler30-Jul-04 6:32

Michael P Butler

30-Jul-04 6:32

»Archer282« wrote:
now it took me long enough to figure out you cant read 28KB file into a buffer and write it all at once

Really. I've read and written larger files in the past. What problems did you encounter?

Michael

CP Blog [^]

Archer28230-Jul-04 6:41

30-Jul-04 6:41

well at first i just read all of it into one buffer
i defined it like so

char *szBuffer;

and then wrote all of it right after reading
everytime i would get the blue screen of death
then if i returned to windows it would be locked up

i looked at an example on MSDN which read and wrote the data in segments, i have had success doing it this way (no problems, except for the ones i mentioned)

note: when i did this in segments i defined my buffer like
char szBuffer[1024];

could this have been a problem?

if it will help i clean up and post the old code that was wasnt working

avenger_sb2530-Jul-04 8:13

avenger_sb25

30-Jul-04 8:13

>>well at first i just read all of it into one buffer. i defined it like so
>>char *szBuffer;

Well Mr. Hotshot, are you allocating memory for szBuffer ??? before using it with your file-handling-functions.... IF NO.... god help you Dead | X|

.
If yes... sorry.
USE malloc or new to alllocate appropriate amount of memory.

>>note: when i did this in segments i defined my buffer like
>>char szBuffer[1024];

look closely... here you alocate the buffer's size to be 1024 bytes. BUT in char* szBuffer.... YOU MAY NOT BE ALLOCATING ANY MEMORY and the 'BLUE SCREEN' loves programmers like you. Poke tongue | ;-P

.... i hope i helped;)

...Avenger

Remember... testing & debugging are always part of programming ...so exterminate those stinking bugs

Archer28230-Jul-04 6:57

30-Jul-04 6:57

Funny how right when i go and ask for help my problem seem to be solved before i get an answer

I kinda reverted my code to the way it was when i gettting the bsod and now it seems to be working just fine

and i manged to get SetFilePointer() to go to the end but i had to use GetFileSize()

Logically you would think you could go to the end by doing

SetFilePointer( hFile, 0, NULL, FILE_END );

but i cant it get it to work doing that
infact i cant even get it to go anywhere from FILE_END

just occured to me could that be becuase i only used GENERIC_WRITE access?

darkbyte30-Jul-04 14:20

darkbyte

30-Jul-04 14:20

Well, here's an idea to stop all those kind helping people from answering for nothing: Big Grin | :-D

Once you realize you solved your problem, you could edit your original post and change its title, appending "<--solved" to it.

This would also have the added advantage of giving a clue to people having the same kind of question that they might find their answer in that thread.

Anyone agrees with me ?

Resource Exception

NadAzur30-Jul-04 4:43

NadAzur

30-Jul-04 4:43

Hi,

my application will always have this error after running for a while. The app regularly pops up modeless dialog and closing it after a while. This cycle repeats itself. The background property page will always do OnPaint when this modeless dialog pop up and closes.

Need advise on what could be the problem and how to resolve it. Thanks.

Jaime Stuardo30-Jul-04 4:52

Jaime Stuardo

30-Jul-04 4:52

post some code so we will be able to guide you.

Jaime

NadAzur30-Jul-04 5:25

NadAzur

30-Jul-04 5:25

please see below for portion of code

pDC->GetClipBox(&m_rect);
CreateCompatibleDC(pDC);
m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
m_pOldBitmap = SelectObject(&m_bitmap); // ASSERT here
setWindowOrg(m_rect.left, m_rect.top);

Thanks.

Jaime Stuardo30-Jul-04 5:40

Jaime Stuardo

30-Jul-04 5:40

Are you placing it in OnPaint method? if you are, that CreateCompatibleDC used is the global ::CreateCompatibleDC that expects a HDC as the parameter. That way, be sure the pDC is casted correctly to an HDC. By using the global API function, you will be returned an HDC for the new DC, which MUST be deleted when the DC is no longer needed.

Second, You are creating a compatible DC but you are not using it. You just continue using the old one.

Third, are you DeleteObject the bitmap you are creating?

Finally, if you are implementing a sort of double buffering, why not using a well tested class such as CMemDC which you can find in CodeProject? This class does all those affairs by you.

Jaime

NadAzur30-Jul-04 19:16

NadAzur

30-Jul-04 19:16

Hi Jaime,

thanks for your reply. Actually I'm already using CMemDC and those codes are from there and the ASSERT happen in that class.

This is the CGridCtrl Class from by Chris Maunder.
void CGridCtrl::OnDraw(CDC& DrawDC)
{
CMemDC dc(&DrawDC);
#else // Use normal DC - this helps in debugging
void CGridCtrl::OnDraw(CDC& dc)
{
#endif
CRect rect;
int row,col;

CRect clipRect;
if (dc.GetClipBox(&clipRect) == ERROR) return;

EraseBkgnd(&dc); // OnEraseBkgnd does nothing, so erase bkgnd here.
// This necessary since we may be using a Memory DC.

int nFixedRowHeight = GetFixedRowHeight();
int nFixedColWidth = GetFixedColumnWidth();
......
}

Hope this is clearer. Thanks.