On Oct 15, 2007, at 12:13 PM, Wesley W. Terpstra wrote:
On Oct 15, 2007, at 1:55 AM, Wayne Davison wrote:
The name of the attribute was changed to com.apple.crtime96 (for
the moment) . Since it is not an official com.apple.* value, I
didn't want to use a name that Apple might choose in the future.
The name should probably go in the rsync.* namespace, but I'd need
to move the code for reading and writing the value out of lib/
sysxattrs.c into xattrs.c to do that (I believe).
Yeah, I suppose it should go in the rsync namespace too.
I notice that rsync is starting to converge towards a particular use
of xattrs:
Copy meta-data that has an analogous concept on the remote host.
If -X is specified, copy anything that has no analogue into an
extended attribute.
In looking over the bsd flags patch, I notice that it is relatively
complicated and still doesn't move the data into an xattr on a system
which has no support.
I wonder if the right command-line options might be something like this:
-X ... enables copying of user extended attributes
--flags ... enables copying of bsd flags
--osx (or similar) ... enables copying of osx related meta-data
(ResourceFork/FinderInfo/CreationDate)
-A ... enables copying of ACL information
-M ... maps any unsupported meta-data into an extended attribute on
the remote side (in the rsync namespace)
-Q ... silently drop unsupported meta-data
I'm not sure if --flags and --osx should be implied by -p, but I
think so.
Then, use a pseudo-design pattern where every type of meta-data rsync
can get/set has do_{get,set}_{acls,flags,owner,group,...}. A platform
also provides a sys_supports_{acls,flags,...}(filename). This returns
true/false if the meta-data is supported for that file (filesystems
differ, as do platforms). Then, if the method could ever return true,
the platform must provide matching sys_{set,get,could_set}_....
(filename) methods. could_set reports if there are sufficient
permissions for the operation to succeed.
A design pattern like this could be used to easily extend rsync
whenever new types of meta-data appear. For each piece of meta-data,
the do_{get,set} methods look like this:
do_set_X(file, ...):
if (sys_supports_X(file)) {
if (fake_super and NOT sys_could_set_X(file)) {
return set_xattr(file, X, ...)
} else {
return sys_set_X(file, ...)
}
} else {
if (-M) {
return set_xattr(file, X, ...)
} else if (! -Q) {
warning: meta-data X is unsupported on platform Y for file, use -
Q to silence this warning, or -M to map it into an xattr.
return
}
}
do_get_X:
if (sys_supports_X(file)) {
if (fake_super and NOT sys_could_set_X(file)) {
return get_xattr(file, X)
} else {
return sys_get_X(file)
}
} else {
if (-M) {
return get_xattr(file, X)
}
if (! -Q) {
if (exist_xattr(file, X)) warning: discarding meta-data X that
was stored in an xattr
}
return nothing_to_sync
}
Real implementations would be complicated by meta-data that is
partially convertible. For example, file permissions and ACLs. But
logically, from a user point of view, one wants the above behaviour.
What do you think?
--
To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync
Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
