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Re: msdos kext and short file name issue

In article
<email@hidden>,
André-John Mas <email@hidden> wrote:

> I have noticed an inconsistency in the msdos driver, at least from
> the usage perspective. Create a number of files and folders
> on a removable medium, such as a USB Flashdisk on a Windows PC.
> Make some of them longer than 8 characters and some 8 characters
> and shorter, ensuring mixed case. Unmount the device and the
> mount it again. You should notice that Windows recognises the file
> names as they were typed.
>
> Now take that device and mount it with a Darwin build compatible
> with Darwin 6.2. The file names shorter or equal to 8 characters are
> shown in 'all caps', where the other file names retain their case
> formatting. This would seem to indicate that the values in the
> 'Win95 table' get ignored if the entry is 8 characters or less.

I just tried and was able to reproduce the behavior you described using
Mac OS X. I wrote up a bug for it.

I'm not quite sure what you mean by "Win95 table", but those names do
not have long name entries (which are also used to preserve the
upper/lower case of names). A name containing both upper and lower
case does have a long name entry which msdosfs does recognize and
return properly.

The one thing I did notice was a difference in values in a supposedly
unused/reserved field in the directory entry. Microsoft calls the
field DIR_NTRes. It is 12 bytes from the start of the directory entry
(immediately following the attributes byte). Names that were short and
all lower case had the value 0x18. Names that were short and all upper
case had the value 0x10. Names with mixed case had a long name entry
and DIR_NTRes was 0x00.

According to Microsoft's official documentation, this field is supposed
to be set to 0 and then never changed. Obviously, they are doing
something more. I haven't found any other documentation on this field.

-Mark
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