[Scons-dev] Documentation in EPUB-format

[Andrew Featherstone]

On 10/09/2013 09:18 AM, Dirk Bächle wrote:

> Andrew,

>

> thanks for the update on your progress. Sounds good so far...

>

> On 09.10.2013 00:26, Andrew Featherstone wrote:

>> Hi Dirk,

>>

>> Yes my tool takes care of zipping up and formatting the container 

>> correctly. Unfortunately the SCons Zip builder method doesn't support 

>> source files with different compression types; perhaps that's a 

>> separate feature that could be added. For now I'm using the Python 

>> zipfile module directly and achieving what's required.

>>

>

> I had a look at the Zip Builder too. From what I understood you should 

> be able to call it repeatedly, such that you append files to an 

> already existing archive. Wouldn't this open the possibility of 

> specifying different compression modes then?

Whilst that's true, I can't get the desired results. As a simple example 
where foo.txt and bar.txt are two files to be compressed using different 
compression algorithms

# SConstruct
import zipfile
Zip('out', 'foo.txt', ZIPCOMPRESSION=zipfile.ZIP_STORED)
Zip('out', 'bar.txt', ZIPCOMPRESSION=zipfile.ZIP_DEFLATED)

$ scons
scons: Reading SConscript files ...

scons: *** Two environments with different actions were specified for 
the same target: out.zip

Creating a intermediate target doesn't help, as the result is simply 
nested zip archives. E.g.

# SConstruct
import zipfile
Zip('tmp', 'foo.txt', ZIPCOMPRESSION=zipfile.ZIP_STORED)
Zip('outer', ['bar.txt', 'tmp.zip'], ZIPCOMPRESSION=zipfile.ZIP_DEFLATED)

results in outer.zip containing bar.txt compressed using the deflate 
algorithm, and an archive containing a single uncompressed foo.txt.

>

>

> The EPUB recipes on the Internet that I found used the simple "zip 

> -X9rD OEBPS" to archive the stuff together. So I'm wondering whether 

> it's really required to support special compression settings...

>

My understanding of the specification is that the mimetype file needs to 
be uncompressed. See 
http://www.idpf.org/epub/30/spec/epub30-ocf.html#sec-zip-container-mime 
. It's permitted for all files to be uncompressed, but that results in 
needlessly large EPUB files. I imagine that lots of EPUB readers are 
designed to be tolerant of recipes that compress everything, despite it 
being against the specification.

Regards,
Andrew