Click here to Skip to main content

C / C++ / MFC

Re: Mixed metaphor problem

Matthew Faithfull2-Apr-08 12:16

Matthew Faithfull

2-Apr-08 12:16

Yes, I realize the preprocessor isn't going to cut it. I wondered if there was any other mechanism to get the compiler to conditionally ignore/notice chunks of code with a similar effect to the preprocessor but during actual compilation. For the moment I've worked round it but in the longer run that's going to mean defining things in multiple places which is not exactly splendid. Anyway you can see how it works out as this is part of what will almost certainly be my next article, the Compiler abstraction library I ranted at Marc Clifton about nearly a year ago, expect it any time in the next 12 months Laugh | :laugh:

Laugh | :laugh:

Thanks.

Nothing is exactly what it seems but everything with seems can be unpicked.

check file opened or not?

George_George2-Apr-08 3:55

2-Apr-08 3:55

Hello everyone,

On Windows platform, which API could be used to check whether a file is opened (either by other thread or process or even the same thread) or not?

C++ is fine.

thanks in advance,
George

Re: check file opened or not?

David Crow2-Apr-08 4:16

2-Apr-08 4:16

One such way is with a device driver (like the one created for use with FileMon and Handle).

You can also check out NetFileEnum().

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

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: check file opened or not?

George_George2-Apr-08 20:40

2-Apr-08 20:40

Hi DavidCrow,

After reading the MSDN document for NetFileEnum, I am confused. The description is,

--------------------
The NetFileEnum function returns information about some or all open files on a server, depending on the parameters specified.
--------------------

Server means? I just want to find all the used (open) files on the local machine. Any ideas or comments?

regards,
George

Re: check file opened or not?

David Crow3-Apr-08 3:06

3-Apr-08 3:06

George_George wrote:
Server means? I just want to find all the used (open) files on the local machine. Any ideas or comments?

servername
[in] Pointer to a Unicode (Windows NT/2000/XP) or ANSI (Windows 95/98/Me) string specifying the name of the remote server on which the function is to execute. The string must begin with \\. If this parameter is NULL, the local computer is used.

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

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: check file opened or not?

George_George3-Apr-08 3:39

3-Apr-08 3:39

Thanks DavidCrow,

But does it relates to my original question? I just want to find whether a local file is opened or not. Any comments?

regards,
George

Re: check file opened or not?

David Crow3-Apr-08 3:45

3-Apr-08 3:45

George_George wrote:
But does it relates to my original question?

Only you can determine if NetFileEnum() will meet your needs.

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

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: check file opened or not?

George_George3-Apr-08 4:04

3-Apr-08 4:04

Hi DavidCrow,

This function will find all open files... But I only want to find whether a specific file is open or not, file name is known. The NetFileEnum function is fine, but too heavy for me.

I think using OpenFile with exclusive shared mode option is fine. Any comments?

regards,
George

Re: check file opened or not? [modified]

JudyL_MD3-Apr-08 5:28

3-Apr-08 5:28

George_George wrote:
I think using OpenFile with exclusive shared mode option is fine. Any comments

That will only tell you if the file is already open with exclusive access. It will not tell you if the file is already open with shared access. AFAIK, there is no user-mode way to tell that, unless David's previous answer can do that (I haven't ever needed to use the Net set of functions).

Judy

modified on Thursday, April 3, 2008 4:19 PM

Re: check file opened or not?

George_George3-Apr-08 21:18

3-Apr-08 21:18

Thanks Judy,

I think I should use ::OpenFile() with OF_SHARE_EXCLUSIVE -- the best choice. Right?

regards,
George

Re: check file opened or not?

JudyL_MD4-Apr-08 1:56

4-Apr-08 1:56

If you want to test every file under scrutiny, yes that will work. I'd try David's enum suggestion if you're looking to get a list.

Judy

Re: check file opened or not?

George_George4-Apr-08 2:19

4-Apr-08 2:19

Thanks Judy,

I only need to test for a specific file. I think OpenFile is enough, agree? Smile | :)

Smile | :)

regards,
George

Re: check file opened or not?

JudyL_MD4-Apr-08 2:23

4-Apr-08 2:23

Yes, using OF_SHARE_EXCLUSIVE

Re: check file opened or not?

George_George4-Apr-08 2:44

4-Apr-08 2:44

Thanks JudyL_FL,

Question answered.

regards,
George

Re: check file opened or not?

led mike2-Apr-08 4:28

2-Apr-08 4:28

George_George wrote:
which API could be used to check whether a file is opened

Depends on your definition of "file is opened". An application can be displaying the contents of a file and even allowing the user to edit the contents without having an active file handle to the disk file used to persist the data. In that case there is no API that's going to tell you that, period.

led mike

Re: check file opened or not?

George_George2-Apr-08 20:37

2-Apr-08 20:37

Open I can it is used by other thread/process, they may not open the file in exclusive mode, but I need to detect whether it is used (open) or not. Any ideas?

regards,
George

Re: check file opened or not?

basementman2-Apr-08 4:55

2-Apr-08 4:55

You can try opening the file in exclusive mode.

onwards and upwards...

Re: check file opened or not?

George_George2-Apr-08 20:38

2-Apr-08 20:38

Thanks basementman!

You mean OF_SHARE_EXCLUSIVE mode of OpenFile?

regards,
George

Re: check file opened or not?

Hamid_RT7-Apr-08 4:07

7-Apr-08 4:07

I think http://www.angelfire.com/country/aldev0/cpphowto/cpp_BinaryFileIO.html[^] is helpful for you.

Re: check file opened or not?

George_George7-Apr-08 4:10

7-Apr-08 4:10

Thanks Hamid,

I looked through the link, does it relates to my original question?

regards,
George

Re: check file opened or not?

Hamid_RT7-Apr-08 4:29

7-Apr-08 4:29

I think its helpful about files,right?

Re: check file opened or not?

George_George7-Apr-08 4:38

7-Apr-08 4:38

Thanks Hamid,

It is helpful. But not direct relates to my original question. Smile | :)

Smile | :)

regards,
George

Re: check file opened or not?

Hamid_RT7-Apr-08 5:07

7-Apr-08 5:07

Smile | :)

Wrong DLL output

parth.p2-Apr-08 3:15

2-Apr-08 3:15

Hi,
I have a DLL written in C and I am calling it from VB and I am using Visual Studio 6. The problem I have is that I'm trying to receive RANDOM number from C and add to my VB form. But the number received is not random or is way to big than what I pass into the parameter.

Here's the Code for .CPP

<br />
#include "stdafx.h"<br />
#include <stdlib.h><br />
#include <stdio.h><br />
#include <time.h><br />
<br />
<br />
<br />
BOOL APIENTRY DllMain( HANDLE hModule, <br />
                       DWORD  ul_reason_for_call, <br />
                       LPVOID lpReserved<br />
					 )<br />
{<br />
    return TRUE;<br />
}<br />
<br />
int _stdcall rndNum(int iMaxNum)<br />
{<br />
	int iNum;<br />
	//srand( (unsigned)iMaxNum );<br />
<br />
<br />
	srand( (unsigned)time( NULL ) );		<br />
<br />
<br />
	iNum =  rand() % iMaxNum;<br />
	<br />
	return iNum;<br />
<br />
}<br />
</time.h></stdio.h></stdlib.h>

.DEF file

<br />
LIBRARY CdllRndNum<br />
<br />
EXPORTS<br />
rndNum @1<br />

VB Code

<br />
Private Declare Function rndNum Lib "F:\Year - 2\CdllRndNum\Debug\CdllRndNum.dll" (ByRef iMaxNum As Integer) As Integer<br />
<br />
Sub AddNums()<br />
Dim i As Integer<br />
For i = 0 To 40<br />
    <br />
    List1.AddItem rndNum(100)<br />
<br />
Next i<br />
<br />
End Sub<br />

Result VB:

28156
28156
28156
28156
28156 and same and same again....

Result C:

Number is 30
Number is 43
Number is 16
Number is 24
Number is 25
Number is 63
Number is 62
Number is 84
Number is 40
Number is 64
Number is 77
Number is 79
Press any key to continue

The C code gives me perfect results in C Console app. But not in VB. Anyone any idea what is going wrong?? Confused | :confused:

Confused | :confused:

Confused | :confused:

Confused | :confused:

- Stop thinking in terms of limitations and start thinking in terms of possibilities -

Re: Wrong DLL output

Cedric Moonen2-Apr-08 3:18

2-Apr-08 3:18

I am far from being a VB expert, but shouldn't you pass the integer ByVal instead of ByRef ? Did you try to debug the dll to see which number you receive and what you are returning ?

Cédric Moonen
Software developer

Charting control [v1.3]

General News Suggestion Question Bug Answer Joke Praise Rant Admin

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