gnome-vfs-mime-magic query

["Eugene O'Connor" <eugene oconnor sun com>]

Can anyone help me to understand what the &pattern_mask is in the
gnome-vfs-mime-magic file? Perhaps someone could explain with an
example, maybe this one:

0	string		BMxxxx\000\000 &0xffff00000000ffff	image/bmp

What does the mask actually do?

This is for the MIME type chapter of the GNOME 2.0 System Administration
Guide, the first couple of chapters of which are available at
http://www.gnome.org/learn/admin-guide/2.0/.

Thanks,
Eugene