[sword-devel] Compression formats

[Greg Hellings]

7z is a file format, not a compression format. As such, it is not really
relevant to SWORD, except as a possible method for distributing archives of
files (e.g. in lieu of a tar.gz of the conf files or a zip of an entire
module). For those few specific cases where we distribute archives, 7z does
not benefit us as much as either zip or tar, since those two are supported
native formats in our target operating systems.

7z does support more efficient compression algorithms than, for example,
zip files support. However, since our modules are typically already
compressed we are more in need of an easily accessible archive format. 7z
is an archive format, but it's not as easily accessible as zip. Compressing
an already compressed file generally yields very poor, if any, improvement
on the existing compression.

Thus, 7z isn't really useful for SWORD's purposes. We already support its
better algorithms (LZMA) in the engine for compressing the modules. Our
additional needs are simply to distribute archive files of those compressed
modules, where our goal is ease of access to the format rather than
re-compressing the modules. The only additional benefit of compressing the
modules in the archive is compression of the conf file. On the whole, the
relative size of that component is miniscule compared to the module it's
accompanying, so gzip or zip compression is more than sufficient to tack
onto the archive file.

--Greg

On Mon, Apr 17, 2017 at 10:43 AM, David Haslam <dfhmch at googlemail.com>
wrote:

> Have the SWORD developers ever considered adding support for the *7z* open
> compression format?
>
> See http://www.7-zip.org/7z.html
>
> Best regards,
>
> David
>
>
>
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