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Re: Implementation Proposal for Subfile GSoC

Gerhard Sittig wrote:
>>> OS Level - System Calls
>> Is the API you suggest compatible with any other operating system?
> The "other" systems which have this kind of feature seem to be
> - MacOS and its "resource forks"
> - Windows (NT style) and "alternative data streams"
> - Linux and its support for NTFS ADS (don't know about MacOS resource
>   forks handling on Linux)

   ..and OS/2 -- which called them "Extended attributes". Each time I
run an application which wants to create thumbnails, and stores them in
separate files in some obscure directory, I think "Wow! Welcome back
1990!". :-/

   Two things to note about my experiences with OS/2 and extended
   - IBM chose to make extended attributes available on FAT partitions,
by keeping some special EA-file(s) in the root of that particular
partition. These extended attributes were frequently lost for various
reasons. Didn't work well at all. Also, consider what happens when you
start moving around files on such a partition from a system which
doesn't know it should be updating those database files. (In dual-boot
cases). So don't make the mistake of implementing some fall-back method
for generic-filesystem-compatibility, unless you've _really_ thought it
   - The archivers I used understood them without any problems. I even
believe that the tar-files I created with some EMX-based tar would store
extended attributes. Extended attributes were never lost unless I sent
archives to friends with systems which were non-OS/2 (obviously). And
EA's never caused me any problems.

   I love extended attributes. I really wish I had them for NetBSD. But
I would prefer if the format was somewhat usable other platforms too.

   OTOH -- extended attributes are "extra data", and doesn't fit all
that good together with the "everything is a file" philosophy, which I
have come to enjoy in my later years. :-/

   The EA API:s in OS/2 were closely integrated with the other "normal"
file management API's. But to read and write EA's you had to parse and
build EA buffers in memory, and send/get the whole chunks. It was not

Kind regards,
Jan Danielsson

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