Support for RAR

[kwrobot]

Original issue 40 created by Google Code user ondra.pelech on 2009-10-05T16:05:49.000Z:

Hi,

it would be great if libarchive supported the RAR format; even if it would
be passworded archive.

This is just a wish/enhancement, not a bug; and I know it's probably not
easy to implement and may take a long time. And thanks for this great
project, I use it through GNOME's gvfs-mount.

[kwrobot]

Comment #1 originally posted by Google Code user cwilso11 on 2009-10-06T02:10:33.000Z:

I'm pretty sure that won't happen. The RAR format decoders are free-as-in-beer but
not free-as-in-speech AND if you use the "free" decoder you are agreeing never to try
to reverse-engineer and create your own encoder.  Needless to say (but I'll say it
anyway) the RARlabs encoders are not free in any sense.

Now, libarchive is BSDish, not GPLish, so maybe that's of less concern to Tim...

[kwrobot]

Comment #2 originally posted by kientzle on 2009-10-06T03:14:48.000Z:

The deeper problem is that the existing RAR code almost certainly will not integrate
cleanly into libarchive.  So RAR support would probably require at least refactoring
the existing RAR code and may require rewriting parts of it more-or-less from
scratch.  This hasn't been a problem for well-documented open formats such as ZIP and
ISO9660 but could be a problem for RAR.

My suggestion:  Talk to the RAR developers and ask them if they would help with such
a project.  If they don't want to build a libarchive module themselves (libarchive's
internal API is pretty stable at this point, so this could be a reasonable approach),
they may be willing to provide enough documentation for someone else to implement
such a module.  It never hurts to ask!

Note: The distribution of such a module would also be a little tricky.  I've tried to
keep the libarchive distribution entirely BSD-licensed.  If the RAR developers insist
on a more restrictive license, they could either distribute their own fork of
libarchive or I could try to come up with a way to organize the libarchive
distribution so that there was a well-defined area for code with different licenses.
 I have no objection at all to someone distributing their own fork and would be
entirely open to discussing the latter approach.

[kwrobot]

Comment #3 originally posted by Google Code user ondra.pelech on 2009-10-06T10:24:09.000Z:

I knew it won't be easy... :)
the idea came from VLC, that's capable of playing movies inside RAR archive(s), and
my wish of Totem being able to do this too. One way of doing this was through
mounting the RAR(s) with gvfs (with libarchive) and than playing it. The other way is
writing a special plugin for GStreamer. Both ways are pretty difficult... I will
probably try to takl to GStreamer guys too.
Anyway, I will contact RARlabs and track the progress of the negotiation here...

[kwrobot]

Comment #4 originally posted by Google Code user ondra.pelech on 2009-10-09T22:28:27.000Z:

reply:
Eugene Roshal

Hello,

Sorry, we do not plan to make such libarchive module and we do not
have any additional documentation about RAR format. All what we have
now is the brief archive headers description in technote.txt
and unrar source code available in "RAR extras" on www.rarlab.com.

If libarchive team will decide to make such module, I can answer to
their questions related to any unclear parts of unrar source code
by email.

Eugene

[kwrobot]

Comment #5 originally posted by Google Code user ondra.pelech on 2009-10-09T22:45:11.000Z:

package containing "technote.txt": http://www.rarlab.com/rar/rarlinux-3.9.0.tar.gz
unrar source code: http://www.rarlab.com/rar/unrarsrc-3.9.6.tar.gz
email: roshal(at)rarlab.com

[kwrobot]

Comment #6 originally posted by kientzle on 2009-10-10T03:59:05.000Z:

The unrar sources are not useful.  Because of the unusual license restrictions on
them, we cannot use any part of them in libarchive.  In fact, anyone who has read
them carefully cannot be allowed to work on RAR support for libarchive.  (I myself
downloaded, skimmed the readme, technote, and copyright notices, then deleted them
from my local system.)

The format described in the technote.txt is relatively simple to implement in
libarchive from scratch.  Anyone who has worked with libarchive even a little should
be able to use that technote to implement a reader for the RAR format.

The decompression is trickier.  Because of the license terms, we can't copy any of
the unrar source code.  Which means libarchive would have to link against a separate
library that implemented the RAR decompression algorithm.  As far as I know, no such
library exists.   Without that, there's very little that could be done.

[kwrobot]

Comment #7 originally posted by Google Code user azuwis on 2009-10-14T08:04:25.000Z:

[7zip][1] has a rar module make it able to extract RAR files. But it's certainly not
a library.

The source code is in p7zip_9.04_src_all.tar.bz2/CPP/7zip/Archive/Rar, can this code
be reused?

[1]: http://p7zip.sourceforge.net/

[kwrobot]

Comment #8 originally posted by kientzle on 2009-10-29T03:44:39.000Z:

<empty>

[kwrobot]

Comment #9 originally posted by Google Code user a.henriksson on 2009-12-21T12:43:38.000Z:

p7zip seems to have bundled the (non-free) unrar source code, so it's probably not
any help.