[Unison-hackers] Unison and extended attributes (xattr) on Tiger?

[Geoffrey Alan Washburn]

Benjamin Pierce wrote:

> This is something we've dealt with already for some somewhat similar  
> cases -- e.g., the TYPE and CREATOR fields on OSX, which I believe  
> are handled fairly cleanly, and resource forks, which we didn't  
> succeed in handling at especially cleanly (the possible presence of  
> resource forks pollutes a lot of code in a lot of modules).  So  
> there's a good and a bad precedent.  :-)

	Extended attributes are now used to implement resource forks (as of 
MacOS 10.4), and extended attributes are available on Linux and several 
other Unixes (for ACLs among other things) so it would probably make 
things a bit cleaner to remove the resource fork code and add extended 
attribute support.

> For the UI, I guess the main issue is how big the information is --  
> can it just go in the same place as the permission bits, or does it  
> need to be summarized in some way?

	I'm not aware of any limits on the size of the data an extended 
attribute can hold (other than perhaps size_t).  Looking at the man 
pages, I can't see anything about a limit on the length of an attribute 
name.  It is probably reasonable to assume they are less than 255 UTF8 
characters.