Support of named attributes in jdk7

[Alan Bateman]

Jean-Pierre André wrote:
> Hi,
>
> I am working with the ntfs-3g project, aiming at providing NTFS
> storage for multiple OS (Linux, MacOSX, Solaris, etc.), and I am
> currently fulfilling the development of extended attributes.
>
> A specific concern for us, as pluggable storage devices tend now to be
> formatted as NTFS off the box, is that the files created on a platform
> can be directly used when the plugged into another platform, even
> of a different type.
>
> As jdk7 is apparently extending the io class to support named
> attributes, we would like our implementation to be such that a Java
> application running on any platform and using NTFS could process
> the data written by the same application on another platform.
>
> The main problem is to comply with the rules for naming the attributes
> on each platform, and we think these naming rules should be hidden
> from the Java programmer. On Linux specifically, the prefix "user."
> should not be apparent.
>
> As a consequence, we (at ntfs-3g) have to make adaptations so that
> the extended attributes are stored the same way on NTFS from either
> Windows, Linux, Solaris or Mac OS X. Currently we map the extended
> attributes to alternative data streams.
>
> Attached is a chart trying to explain this, and we would like to know
> whether jdk7 supports a similar view.
>
> Home page of the ntfs-3g project : http://www.ntfs-3g.org
> Implementation of extended attributes :
> http://pagesperso-orange.fr/b.andre/extend-attr.html
>
> Regards
>
> Jean-Pierre
I think this is reasonable and arguably a poor implementation choice on 
my part to have required the namespace be included in the name. With 
that fixed then the translations work as per the interface boundaries in 
your slide.

One thing that isn't clear to me about ntfs-3g is the conversion to/from 
Unicode for both file names and extended attribute names when accessing 
NTFS. The extended attribute names in our API are provided by the 
application as Unicode strings and so are encoded to bytes for the 
*xattr calls.  I assume ntfs-3g then encodes these bytes to UTF-16/UCS-2 
that NTFS uses. Can you say more about this? (just wondering if 
round-trips are going to be a problem).

-Alan.