[Win32] HEEEEEEELLLLPPPP! I need to determine the cluster size on WinXP/NT/2k

[Sylwia]

Hi!

I need Your help. I implement a Python NT service and I need to
determine (on WinXP/2k/XP) a cluster size of the particular partition
(to find out how much space a file will occupy on that partition).

Till now I faced the following problems:

- The GetDiskFreeSpace() function is reliable in deriving cluster size
if it is a FAT16 drive. If it is a FAT32 drive, the Win32
GetDiskFreeSpace call is lying about cluster size.

-The newer GetDiskFreeSpaceEx call returns total and free space on the
drive, but does not provide a cluster size parameter at all!!!

-There's a small table that summarizes the default cluster size for
every range of FAT32 volume sizes, but there's no guarantee that the
user accepted the default when creating the partition (((

- There is a DOS function, Int 21h Function 7303h Get_ExtFreeSpace
(FAT32),
but it exists only in Windows 95 SR 2 and later. This can be called
through VWIN32.VXD using DeviceIoControl (unfortunately VWIN32 is
Win9x/Me specific driver and it's not available on Win2K/XP).

So is there any API that gets the FAT32 cluster size correctly in
WinNT/2k/XP?
Does anyone know of an API function that can tell me how much space a
file will occupy on the disk? It'll need to work with FAT, FAT32, and
NTFS.

Thank You in advance!

Farraige

 

[Peter Hansen]

So is there any API that gets the FAT32 cluster size correctly in
WinNT/2k/XP?
Does anyone know of an API function that can tell me how much space a
file will occupy on the disk? It'll need to work with FAT, FAT32, and
NTFS.

It appears you are quoting much of your information directly
from this page:

http://www.techweb.com/winmag/library/1998/0401/howto110.htm

The author appears to have reached the conclusion that there is
no workable solution for NT and friends...

-Peter

 

[Dennis Lee Bieber]

Does anyone know of an API function that can tell me how much space a
file will occupy on the disk? It'll need to work with FAT, FAT32, and
NTFS.

And what is it supposed to report on a compressed partition?
Until you compress the file, you won't know how much space it needs...
So far as I know, compression is done in a stream fashion as you write
the file to the drive.

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