LZMA compression for jpkg

[Chris Hegarty]

On 06/ 8/11 01:18 AM, Tom Marble wrote:
> On 06/07/2011 01:06 PM, Chris Hegarty wrote:
>> I have been looking into the possibility of using LZMA compression ( following on from Dalibors work last year ) for the jmod packages. Initial results look positive.
> It's true that we have an opportunity to do something new here!
>
> Note that the Java Module-System Requirements — DRAFT 12 [0]
> does list this as a goal (with pack200 for jars of course).
>
> While where considering compression techniques we might as
> well jump to xz (an improvement over lzma) [1].

Yes a very good point. I am planning to evaluate the xz (LZMA2) 
implementation that is part of the LZMA SDK. It may not help much with 
compression over LZMA, but certainly has other advantages.

>> I've been using a Java implementation from the latest LZMA 9.20 SDK [1]. I modified jpkg to use LZMA compression [...]
>> The debian packages that get built during the modules build are still smaller than these lzma-ized jmod files.
>
> With our current Jigsaw project in Debian we are looking at how
> to create policy compliant packages [2]. I highly suspect we
> will need to rethink the current approach of having jpkg doing
> the work and, instead, collaborating with native debhelper tools [3].
> Point being that we should probably avoid the current *.deb
> packaging as much of a baseline.

Currently jpkg calls native dpkg to create the debian packages, but it 
may be that debhelper, or a combination of debhelper and jpkg, is a 
better approach. I need to spend more time looking at the debhelper 
tools. Thanks for pointing this out.

-Chris.

> In this context it is important to note that classically
> Debian source packages used to accept only upstream tarballs
> in gzip but are evolving to include bzip2 and xz in
> later releases. [4]
>
> Regards,
>
> --Tom
>
> [0] http://openjdk.java.net/projects/jigsaw/doc/draft-java-module-system-requirements-12#java-native-module-file-format
> [1] http://tukaani.org/xz/
> [2] http://wiki.debian.org/SummerOfCode2011/Jigsaw
> [3] http://joey.kitenet.net/code/debhelper/
> [4] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=556407