C / C++ / MFC

Re: Why can't i read from a cd-rom drive when i have opened it with CreateFIle?

15-Jun-02 12:22

I know, but it can't hurt, can it?

Amit Dey15-Jun-02 14:24

Re: Why can't i read from a cd-rom drive when i have opened it with CreateFIle?

15-Jun-02 14:24

sonork: 100:18407

You yard yellow years yieldingly; you yanked your yearning yoke.

-Jeremy Falcon

Amit Dey15-Jun-02 14:22

15-Jun-02 14:22

Here's some code to help you out.

void CCDReadDlg::ReadCD()
{
DWORD dwSize = 2048;
DWORD dwBytesRead;
LPBYTE lpBuffer;
HANDLE hFile;
hFile = CreateFile("\\\\.\\F:", GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile != INVALID_HANDLE_VALUE)
{
lpBuffer =(unsigned char*) VirtualAlloc (NULL, dwSize,
MEM_COMMIT|MEM_RESERVE,
PAGE_READWRITE);
//In CDFS(i.e.ISO9660 format) sector size is 2048.
//the first 16 sectors are always filled with 0's
//To get something meaningful first skip to 16th sector and then read
//course the propah way is to first use DeviceIoControl calls
//to lock the media and finally unlock it after reading... Smile | :)

.
SetFilePointer (hFile, dwSize*16,
NULL, FILE_BEGIN);
if (ReadFile (hFile, lpBuffer, dwSize, &dwBytesRead, NULL))
{
//you buffer should have a volume descriptor
//to begin with

//do something
}
VirtualFree (lpBuffer, 0, MEM_RELEASE);

}
CloseHandle(hFile);
}

sonork: 100:18407

You yard yellow years yieldingly; you yanked your yearning yoke.

-Jeremy Falcon

strange...

redeemer15-Jun-02 14:43

15-Jun-02 14:43

dwBytesRead is 0 and lpBuffer is empty. But the ReadFile function returns 1 so there shouldn't be anything wrong... strange

Re: strange...

Amit Dey15-Jun-02 15:07

15-Jun-02 15:07

dwBytesRead is 2048 for me(with media present in CDROM ofcourse) i.e. 1 sector(just what I want) and lpBuffer contains the CDROM volume description as expected.

You yard yellow years yieldingly; you yanked your yearning yoke.-Jeremy Falcon-CPite.

Amit Dey

sonork: 100:18407
msn: visualcdev

Re: strange...

Amit Dey15-Jun-02 15:12

15-Jun-02 15:12

Is your CDROM drive setup correctly? Do you have any other cdfs drivers like Adaptec DirectCD on your system? course, you are trying this code on Win2K/NT...right?

hmmm....

You yard yellow years yieldingly; you yanked your yearning yoke.-Jeremy Falcon-CPite.

Amit Dey

sonork: 100:18407
msn: visualcdev

toolbar on desktop

slah15-Jun-02 11:16

slah

15-Jun-02 11:16

HI i want to have a toolbar on desktop, but CreateToolbarEx()
needs a window handle as a parent. I have passed the desktop handle by calling GetDesktopWindow but it doesn't work. Is there any solution to the problem.

Re: toolbar on desktop

Amit Dey15-Jun-02 11:58

Re: DataBase via Internet

15-Jun-02 11:58

You'd want to use an appbar. Please lookup codeproject for an article and code on appbars.

sonork: 100:18407

You yard yellow years yieldingly; you yanked your yearning yoke.

-Jeremy Falcon

DataBase via Internet

laphijia15-Jun-02 7:24

laphijia

15-Jun-02 7:24

I made a Visual C++ application that uses ADO to query a database, and to update the changes.
I send some simple SQL statement to the database (an Access DB until now), like SELECT, UPDATE, etc.

Now I would like to make this through the internet.
I mean I run my program on my computer and it query the database that instead is on another computer, and it connects to it via tha Internet.

Where I can find a guide on how to do it?
Thankyou.

P.S.
I also think that I will need to use SQL Server or Oracle to store my database remotely, ad than use this server. Are there any service that offers this kind of hosting for free, so that I can start experimenting, without the hassle of installing my own SQL Server or ORACLE ?

Thank you very much.

"Nelle cose del mondo non e' il sapere ma il volere che puo'."

Jason Henderson15-Jun-02 7:44

Jason Henderson

15-Jun-02 7:44

You can do this any number of ways.
Here is how we currently do it at work:

Create an XML file on the client describing the data.
Send the XML to an ASP page which then passes it on to a COM object.
The COM object parses the entire XML and adds the data to the db.
You could also use an ISAPI DLL to parse the data.
(BTW, you need to have IIS running on the computer you are sending to.)

Jason Henderson
_{quasi-homepage}
^articles
_{"Like it or not, I'm right!"}

How to make a button usable when a for statement is running. (Non-MFC)

redeemer15-Jun-02 6:58

Re: How to make a button usable when a for statement is running. (Non-MFC)

15-Jun-02 6:58

If i have a function that uses a for loop that does very much and the action could take up to 5 minutes. How do i, if i have a cancel button on the form, make that cancel button usable? Cause i can't use it while the for loop is running. I saw something in the faq about multithreading but i don't know how to use it.

Thanks in advance.

Jason Henderson15-Jun-02 7:49

Jason Henderson

15-Jun-02 7:49

I think this will work:

void Yield()
{
   MSG msg;
   if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
   {
      TranslateMessage(&msg);
      DispatchMessage(&msg);
   }
}

for ...
{
   // your code
   Yield();
}

Jason Henderson
_{quasi-homepage}
^articles
_{"Like it or not, I'm right!"}

Re: How to make a button usable when a for statement is running. (Non-MFC)

redeemer15-Jun-02 8:29

Writing a filesystem driver?

15-Jun-02 8:29

Thankyou, works perfectly.

clintsinger15-Jun-02 6:16

clintsinger

15-Jun-02 6:16

Hi all,

I want to make a file system driver to access BeOS partitions from windows 2000. I am having a hard time learning how to get access to the partition info and how to mount a drive so that I can then access the foreign file system.

I guess after I am successfull in mounting a drive (including all the code to read and write) I will need to make it a shell extension so that it shows up transparently in Explorer? Is that right?

Any pointers to tutorials, source code, etc. would be greatly appreciated.

Cheers,
Clint

Amit Dey15-Jun-02 12:00

15-Jun-02 12:00

I think you will find open source filesystem drivers for NTFS,ext2(Linux) at sourceforge.net very illuminating.There are a couple of Beos ports to NTFS drivers too(I think).

sonork: 100:18407

You yard yellow years yieldingly; you yanked your yearning yoke.

-Jeremy Falcon

Mike Nordell16-Jun-02 5:27

16-Jun-02 5:27

Then you're in for a treat. Not!

MS has the FSD SDK for $5k (or is it perhaps $10k+ nowadays?) with no support, sparse documentation and no promises they won't change everything behind your back even from service-pack to service-pack, making this one of the "great developer experiences" that MS loves to force down our throats with a rough 2-by-4 without any K-Y.

Good luck, I really think you need it.

I guess after I am successfull in mounting a drive (including all the code to read and write) I will need to make it a shell extension so that it shows up transparently in Explorer? Is that right?

No. Once you have the filesystem mounted it's just like any other filesystem (except that you can't use half of the features in BFS on this DOS-emulation platform). You perhaps could get access to the attributes using the NT-only syntax for alternate file streams "filename:stream_name", but since you'd be the only one using it (since it's incompatible with everything except NTFS almost no-one ever uses it) you'd (obviously) have to write your own programs to access that too.

The only place I can point you to is http://ntfsd.org

++luck;

clintsinger16-Jun-02 13:21

clintsinger

16-Jun-02 13:21

Thanks for you information. I am too poor to afford anything so I guess the FSD SDK is out of the question.

One thing I would like clarification on is about the dos-emulation layer you mentioned. I am aware that there is an emulation layer but are you saying I could write a driver for dos and use it to access another filesystem from within win2k?

Thanks again,
Clint

Mike Nordell17-Jun-02 17:49

17-Jun-02 17:49

One thing I would like clarification on is about the dos-emulation layer you mentioned.

I forgot to add the <sarcasm> tag. I was referring to the fact that Win32 is little more than MS-DOS with longer filenames when it comes to filesystem and filename handling.
I'm sorry if it got your hopes up.

Heaps and DisableHeapLookAside

18-Jun-02 10:20

Doh... I should have known better. I didn't dismiss the idea because I did read bout something like that years ago where int 0x21 was extended for Win95 to support the long file names and such. I guess I just thought there might be something for mounting partitions.

If you have done anything like this could you please check out my last post. I have source code to read from the disk sectors but it fails on ReadFile.

Thanks again,
Clint

stereo15-Jun-02 5:58

stereo

15-Jun-02 5:58

I'm having the most difficult time determining the cause of a bug somewhere
in the heap manager (I'm guessing?).

I'm using Windows 2000 SP2, with MSVC 6.0 SP5, and ATL 3.0.

In my application, *sometimes*, when adding a treeview item, the memory
allocated internally by comctl32.dll for the item is later overwritten by a
call to RegQueryKeyValueEx(). As a result the treeview is corrupted, and
the application becomes unstable. The default process heap is being used in
both allocations, and both allocations are happening on the same thread.

Here is an assembly listing of the code before and after the call to
HeapAlloc() in comctl32:

_text:7179A8ED push 24h ; dwBytes
_text:7179A8EF push 8 ; dwFlags
_text:7179A8F1 push dword ptr [edi+94h] ; hHeap

Values at ESP before the call ... 130000 seems to be the default heap
00130000 00000008 00000024

_text:7179A8F7 call ds:HeapAlloc

eax after the call to HeapAlloc() is 172de0

Now, after the treeview item is added, the _ATL_DEBUG_INTERFACES macro
queries the registry for the value of an interface name ... and this code is
in advapi32.dll!RegQueryKeyValueEx:

_text:77DB2B3E push ecx
_text:77DB2B3F push edx
_text:77DB2B40 push dword ptr [eax+18h]

ESP before the call:
00130000 00000000 00000024

_text:77DB2B43 call ds:__imp__RtlAllocateHeap@12

eax after the call to __imp__RtlAllocateHeap@12() is 172de0!

How on earth can HeapAlloc() be returning the same value twice?

Now the interesting part is that if I define the DisableHeapLookAside value
in the Image File Execution Options, everything works fine, and HeapAlloc()
never returns duplicate values. If I do a HeapValidate() on the treeview
hItem value, sometimes it fixes it. I've also instrumented all my code with
Boundschecker, and it reported no memory corruption issues.

After checking the KB, I found article Q195009, which describes the Heap
Manager change in NT4 SP4 ... and goes on to say that sometimes the cause of
this bug is when an application uses memory previously freed. So I set some
breakpoints on HeapFree() calls, but never saw the pointer being freed
between the two calls to HeapAlloc().

My real question is why is this happening to begin with, and what does
DisableHeapLookAside do to cause the problem to go away?

Thanks in advance,

Scott.

Mike Nordell16-Jun-02 5:52

16-Jun-02 5:52

You also have to monitor HeapReAlloc in addition to HeapFree.

Before jumping to conclusions, have you tried this with a "checked build" and/or using e.g Purify or something similar to really rule out the possibility that your application is overwriting some heap memory it doesn't own? If you're longing for an adventure you might even replace the malloc/free implementation functions from the CRT with your own functions that use a private heap.

If it is beyond all dubt ruled out that the a memory overflow bug is introduced by your app, one can only conclude that it has to be a bug in the NT heap manager and you should notify MS of this ASAP.

If this is an MS bug I could guess that they don't have a (nasty enough) regression test for HeapReAlloc and the heap lookaside combination (which I personaly think is a fairly reasonable guess).

The following assumes the bug is not in your code:

My real question is why is this happening to begin with

Bugs in the heap manager implementation.

what does
DisableHeapLookAside do to cause the problem to go away?

Answering that question would probably involve explaining how their NT4sp4+ and NT5+ heap manager works in such a detailed way that one could write it oneself. That would probably violate some kind of "trade secrets". Smile | :)

Please check HeapReAlloc also and report back. This can become interesting (unless it's a bug in your code)!

stereo16-Jun-02 6:12

stereo

16-Jun-02 6:12

Hi,

Thanks for the reply ... I was wondering if my question was even going to get one Smile | :)

I've done a full instrumentation of all the entire using Boundschecker, and no memory overwrites turned up. Maybe I should have mentioned in my original post that not a lot of code is being executed in the time it takes HeapAlloc() to spit out the duplicate pointer.

Basically, the structure of code is like:

Call one event sink
Insert the treeview item (first pointer)
Enumerate the treeview using TVM_GETNEXTITEM to ensure the item was added
Call next event sink
ATL event tracing (duplicate pointer)

I'd estimate that there were about ~30 calls to HeapAlloc in the time between the duplicate pointer returns.

I didn't check calls to HeapReAlloc, but I'll do that and post my results.

Fortunately, at work we have an MSDN subscription which includes 2 developer support calls, and I've been authorized to use one of them for this particular instance ... so hopefully I'll get an answer sometime soon.

Thanks for the help,

Scott

Mike Nordell16-Jun-02 6:42

16-Jun-02 6:42

Just a though that struck me. If you can write some code before that "ATL event tracing (duplicate pointer)", and you can duplicate the bug even if you break into a debugger (which it seems you can), what about using a local variable and set it (using the debugger) to point to the memory you think is already allocated (but the "second" allocation returns) and just call IsBadReadPtr/IsBadWritePtr on it?

OK, checking HeapReAlloc isn't gonna hurt, but it never hurts to exhaust all options before that "support" call either. Smile | :)

How do i put a new line in an Edit control? (non-MFC)

stereo16-Jun-02 6:50

stereo

16-Jun-02 6:50

Well,

I after adding the treeview item, I set a breakpoint on all HeapReAlloc() calls, and it was hit one time, on a call to realloc(), which is using the CRT heap ... aside from that, the GetProcessHeap() heap wasn't touched by any HeapReAlloc calls.

I tried your last suggestion ... I took the HTREEITEM returned by the TVM_INSERTITEM (which actually points to a 0x24 byte internal structure ... gotta love reverse engineering MS dll's) and called IsBadReadPtr(hItem, 0x24), and it returned 0 so ... hmmm ...

If you can think of anything else, let me know ... I feel as though I've tried every thing conceivable Frown | :(

Thanks,

Scott.

redeemer15-Jun-02 6:01