Re: [coldsync-hackers] ColdSync 1.5.0 snapshot (and RFC)

[Andrew Arensburger <arensb+CShackers@ooblick.com>]

On Sat, 11 Nov 2000, J.D. Smith wrote:
> >         - Added John-David Smith's Install conduits.
> 
> Thanks for including this, Andrew.  I've been using it with success for
> over a month (though I've yet to test if your main() redesign might have
> broken anything).  

	I guess I should point out that I tentatively deleted your install
mode, when I realized that it was essentially the same as restore mode.
	Or would there be a point in having a mode that installs files,
but runs pre-Install conduits on them first? (but doesn't perform a full
Sync). Perhaps a sysadmin could use this to initialize a user's Palm?

	One other new feature in 1.5 that I forgot to mention earlier is
that ColdSync reads a site-wide /etc/coldsync.conf file. This file is in
the same format as .coldsyncrc . It is intended to allow a sysadmin to
provide hints and impose some policy (e.g., it can prevent any
user-defined conduit from running).

> >         Question: Let's say that your site administrator has just
> >   dropped a copy of the corporate directory in your
> >   ~/.palm/install/AddressDB.pdb . However, you prefer to use the
> >   SuperAddressBook application, so you write an Install conduit to
> >   convert ~/.palm/install/AddressDB.pdb to
> >   ~/.palm/install/SuperAB.pdb. After ColdSync runs the Install
> >   conduits for AddressDB.pdb, should it also run the Install conduits
> >   for SuperAB.pdb ? Or should it assume that if you just created it,
> >   then you know what you're doing?
> 
> The latter, absolutely.  Otherwise you could end up with loops.

	Depends on the implementation (see below). If install conduits are
run on newly-created databases, then this can trigger all sorts of complex
and wonderful behavior (and I definitely believe in giving people enough
rope to shoot themselves, though it shouldn't be easy to do so
accidentally).

> >         Question: currently, if an Install conduit deletes its input
> >   database, that means that it has taken care of installing it (or
> >   whatever). What if you have two conduits:
> >         conduit install {
> >                 type: Foox/Barx;
> >                 path: /conduits/first;
> >         }
> >         conduit install {
> >                 type: Foox/Barx;
> >                 path: /conduits/second;
> >         }
> >   If /conduits/first deletes its input database, should
> >   /conduits/second still run?
> 
> Maybe try:
> 
> this-round=all install conduits
> LOOP UNTIL this-round is empty, or no files remain:
> Clear "next-round".
> Loop over install/ files (generate the list anew each time):
> 1) if install conduit from "this-round" matches file, run it
> 2) if another install conduit from "this-round" matches, don't run it,
> but instead save it to a list of further conduits to run (next-round).
> Set this-round to next-round. 
> END LOOP

	If I'm reading this correctly, it contradicts what you said
earlier: if an install conduit creates a new file, then install conduits
will be run on the new file.
	Secondly, the logic here is backwards from what is easily
implementable: it's easier to read a file, then apply each matching
conduit, than it is to look at a conduit and see which files match. But I
understand that you weren't talking about implementation details.
	Also, from a purely pragmatic standpoint, if the two conduits are
ordinary Perl scripts that use ColdSync.pm, then the second one will barf
because its input file doesn't exist.

> Another possibility: let the conduit writers deal with this.  Of course,
> the user may just chain together two install conduits he shouldn't
> have... it's somewhat of a tough call.

	I think this is the sanest approach: "Here's a file. Do something
with it. If there's anything left when you're done, I'll install it." The
conduit mechanism is flexible enough to do all sorts of reasonable (and
unreasonable) things. So I guess the logic becomes:

	all-files = all files in ~/.palm/install;
	for each F in all-files, do:
		for each conduit C, do:
			if C applies to F, then:
				run C with input F;
			fi
		done;
	done;

	all-files = all files in ~/.palm/install;
	for each F in all-files, do:
		install F;
	done;

The list of files must be generated before any install conduits are
run. If you use the obvious implementation
	while (readdir() != NULL)
then you run the risk of running install conduits on databases that didn't
exist before. But not always, and inconsistency would be bad.

-- 
Andrew Arensburger                      This message *does* represent the
arensb@ooblick.com			views of ooblick.com
     "Bother!" said Pooh, as he shot A.A. Milne for being a git.


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