On Dienstag, 20. Oktober 2009 13:57:08 [email protected] wrote:
> Hi,
>
> I help currently someone wanting to build his own ZIM parser.
> I know this is not necessary... but he wants to do it and I find this is
> interesting to have someone trying to do that.
>
> I have remarked that on the wiki nothing is written about the compression:
> * How do we know if a cluster is compressed or not ?
> * What are the possible value (for different compression methods) ?
>
> Regards
> Emmanuel
>
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Hi,
unfortunately there are several areas, which are not specified completely. But
luckily this compression flag is at least partly ;-)
The first byte in a cluster specifies the compression. The value is:
0 default (no compression)
1 none (also no compression, I don't know, why vlado specified
this in zeno,
but I take ist over to zim)
2 zip (zlib)
3 bzip2 (currently used in writer)
4 lzma (not implemented in reader or writer due to lack of
compression
library)
You can find the flag here: http://openzim.org/ZIM_File_Format#Clusters. The
actual values are not documentated but can be found in the header zim/zim.h as
a enum.
It is really no necessary to implement a parser but it does not hurt. It helps
discussing ideas for improvements. And it helps pushing zim as a standard, if
we encourage people to work with it.
Tommi
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