C / C++ / MFC

Files: What is more efficient?

7-Dec-02 4:50

For that, I would have to modestly point you to my article: CDataFile[^] Poke tongue | ;-P

That should help. I will update it to write the file back out in the next release.

- Nitron

"Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

AlexMarbus6-Dec-02 12:51

AlexMarbus

6-Dec-02 12:51

Suppose I receive raw data from a source. This source already placed it in memory for me and I only know the raw data doesn't exceed 10 megabytes. It's running on a computer with 512MB RAM or more.. What is more efficient if I want to write this raw data to a file :

- Create a buffer of xxx bytes
- Write the 10 MB to file at once

Confused | :confused:

--
Alex Marbus
www.marbus.net
But then again, I could be wrong.

Nitron6-Dec-02 13:36

6-Dec-02 13:36

What format do you want the data in? ASCII or just a proprietary serialization?

- Nitron

"Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

AlexMarbus6-Dec-02 13:37

AlexMarbus

6-Dec-02 13:37

ASCII, actually it's always plain text (well, some Base64 encoding might be there but that's text after all Smile | :)

)

--
Alex Marbus
www.marbus.net
But then again, I could be wrong.

Michael Dunn6-Dec-02 14:13

Michael Dunn

6-Dec-02 14:13

I'd say just write the whole thing at once and let the OS's caching code worry about how best to write it out to disk.

--Mike--
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How to tell if a file is opened?

AlexMarbus6-Dec-02 14:19

AlexMarbus

6-Dec-02 14:19

Thanks, Mike.. that was actually the answer I wanted to hear Smile | :)

--
Alex Marbus
www.marbus.net
But then again, I could be wrong.

Jonathan Gilligan6-Dec-02 12:34

Jonathan Gilligan

6-Dec-02 12:34

Is there a good way to tell whether some process has a given file open.

I am writing an application that allows the user to open a file in an arbitrary external editor. I start the editor in a spawned process with P_NOWAIT or P_DETACH flags, and want to figure out whether the editor has closed the file. Since the user can arbitrarily choose the editor, I can't make any assumptions about DDE or similar calls to the editor to query the status of the file.

The user may close the file in the editor without closing the editor, so I can't simply check whether the given PID has exited.

Thus, my question is: given a PID (process id) and a filename (full path), is there a Win32 API method of determining whether the process PID currently has the given file open?

Thanks,
Jonathan

Why couldn't Science, in the long run, serve
As well as one's uncleared lunch-table or
Mme X en Culottes de Matador? James Merrill

Re: How to tell if a file is opened?

Ravi Bhavnani6-Dec-02 13:06

Ravi Bhavnani

6-Dec-02 13:06

You can test if a file is open by trying to open it for exclusive access with no sharing. It the file exists but the open fails, another process has opened it.

/ravi

Let's put "civil" back in "civilization"
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ravib@ravib.com

Re: How to tell if a file is opened?

Jonathan Gilligan6-Dec-02 13:27

Jonathan Gilligan

6-Dec-02 13:27

Cool! Elegant solution. Thanks.

Mystery Progress Bars in Shell Context Menu Extension DLL

Sheri Steeves6-Dec-02 11:28

Sheri Steeves

6-Dec-02 11:28

I have a small but annoying problem I'm hoping someone here can help me with. I've built a small shell context menu extension dll. When my item is invoked from the menu, I create my dialog box with progress bars , set up the list of files and send them off to the dialog, which then processes them. The wierd behaviour starts when I have two shell windows ( My Computer windows ), and I run some files from each window at the same time. The underlying process is built so that the second dialog will sit waiting, ready to go, while the first one finishes - that part is ok. What is strange is that as the dialog in the first window is processing, and updating it's progress bars, the progress bars in the other dialog are also being updated.

Any clues? Thanks in advance for any help.

Restore focus to child window in CScrollView

Sara Burns6-Dec-02 10:54

Sara Burns

6-Dec-02 10:54

Using VC++ 6.0 and MFC
I am dynamically creating child windows in a derivative of CScrollView. This is working really well.

How can I save the child window which has the focus when another application is activated so that this can be restored when the focus is returned to my application.

Example is when user switches to Explorer then back to my app using the buttons in the start bar.

I have tried a few methods but they do not seem to behave consistently. Any suggestions will be very welcome.

Sara

Windows 2000 VS. NT

Shay Harel6-Dec-02 10:41

Shay Harel

6-Dec-02 10:41

Hi,

If I draw a rectangle on a dialog using this code it draws a nice rectangle with black frame on NT but nothing on 2000, any idea ?

CRect rect;
CClientDC dc (dlg); //get our device context
dlg->GetClientRect (&rect); //get the pointer to our window
CBrush brush (RGB (192,192,192));
dc.SelectObject(&brush);

dc.Rectangle(20,30,40,70);

Poke tongue | ;-P

When do you build a DLL?

Nitron6-Dec-02 10:16

6-Dec-02 10:16

How many Dialogs and stuff do you usually have before you start putting them into DLL's? Also, do you put more than just the dialogs into DLL's? When would I consider building a class as a DLL?

- Nitron

"Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

Paul M Watt6-Dec-02 10:24

Paul M Watt

6-Dec-02 10:24

I think the main criteria for putting stuff in a DLL is its ability to share the content of the DLL.

or

If the data is rarely used, and your program would benefit from only loading the DLL when it is needed.

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!

Nitron6-Dec-02 10:40

6-Dec-02 10:40

So if my application is pretty much canned in one main class and no one else interfaces with it, forget the DLL? Except if I have some functions and classes which aren't used often, so put them away into the DLL to avoid the overhead when they are not in use...

I guess if you don't have an explicit reason for a DLL, you probably don't need one?

- Nitron

"Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

Paul M Watt6-Dec-02 10:47

Paul M Watt

6-Dec-02 10:47

Nitron wrote:
I guess if you don't have an explicit reason for a DLL, you probably don't need one?

Yep. I see applications that go over 2 MB in size. Alot of that is resources and images, but still your EXEs can get as large as you want.

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!

Nitron6-Dec-02 10:56