Making rsync compile under Mac OS X 10.3.9 with extended attributes

[Robert DuToit]

Matt,
I would be happy to implement and test any of these things on OS 10.3  
thru 10.5. the only hitch is I am only applescript savvy with a  
smattering of OBJ-c. so can help if someone tells me what to do, what  
code to implement etc.  But this is probably where Vitorio comes in-  
he sounds eager to get something going.  Rob


On Jan 26, 2008, at 4:43 PM, Matt McCutchen wrote:

> On Sat, 2008-01-26 at 15:52 -0500, Matt McCutchen wrote:
>> Rsync is
>> unlikely to be able to manipulate xattrs on 10.3 unless we can figure
>> out what the old API is and add it as another case in
>> lib/sysxattrs.{c,h} .
>
> I poked around some more.  Here is my current understanding of the  
> xattr
> situation:
>
> - All versions of Mac OS X support certain Mac-specific attributes,
> including resource fork, finder flags, and creation time.  The
> getattrlist and setattrlist functions access most of these:
>
> http://developer.apple.com/documentation/Darwin/Reference/ManPages/man2/getattrlist.2.html
> http://developer.apple.com/documentation/Darwin/Reference/ManPages/man2/setattrlist.2.html
>
> - Mac OS 10.4+ supports arbitrarily named xattrs through the getxattr
> interface.  Its implementation of this interface also exposes most of
> the Mac-specific attributes as xattrs with specific names, allowing
> rsync to preserve them as it would any other xattr.
>
> - Oddly, the creation time is not exposed at the 10.4+ getxattr level.
> Thus, osx-create-time.diff adds a special case at rsync's getxattr
> abstraction level to expose the creation time (accessed via
> {get,set}attrlist) as an xattr named "com.apple.crtime96".  This  
> name is
> rsync-specific and was chosen by Wayne.  It will be stored on non-Mac
> filesystems to which Mac files have been copied, so we have to be
> careful about changing it later.
>
> - 10.3 does not support arbitrarily named xattrs and does not provide
> the getxattr interface.  To make rsync preserve the Mac-specific
> attributes, we would need to write code to access each one  
> individually
> using {get,set}attrlist, like osx-create-time.diff does for creation
> times.  Probably the most natural approach is to wire these up to
> rsync's getxattr abstraction level using the same names by which they
> are exposed by 10.4+.  This way, rsync copies between 10.3 and 10.4  
> will
> just work.
>
> The operation of the current rsync getxattr abstraction layer to  
> read an
> xattr named N can be described as follows (the top three lines coming
> from osx-create-time.diff):
>
> if (mac && N == "com.apple.crtime96")
> 	getattrlist(ATTR_CMN_CRTIME);
> else
> 	getxattr(N);
>
> To fully support Mac OS 10.3 attributes, we will need an extra  
> configure
> test to distinguish 10.3 from 10.4+ and an abstraction layer like  
> this:
>
> if (mac && N == "com.apple.crtime96")
> 	getattrlist(ATTR_CMN_CRTIME);
> else if (mac < 10.4) {
> 	if (N == "com.apple.FinderInfo")
> 		getattrlist(ATTR_CMN_FNDRINFO);
> 	else if (N == "com.apple.ResourceFork")
> 		// I'm not sure of the API to access the resource fork.
> 	// More cases here?
> 	else
> 		// No other xattrs exist.
> } else
> 	getxattr(N);
>
> See also the following message by Wesley Terpstra for some related
> ideas, including how attributes might interact with --fake-super:
>
> http://lists.samba.org/archive/rsync/2007-October/018892.html
>
> Please correct me if any of the above is wrong.  And...does anyone who
> has a Mac feel like implementing this?
>
> Matt
>