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Old 10-28-2015, 09:42 AM   #1
lisabeeren
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Accessing the author of a KF8 book

Hi,

I'm trying to retrieve the author from an instance of

Code:
from calibre.ebooks.mobi.reader.mobi6 import MobiReader
but i'm having difficulty finding it. i can get the title from the:

Code:
book.book_header.title
but the author seems less straight forward.

could someone point me in the right direction?

with thanks
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Old 10-28-2015, 09:44 AM   #2
kovidgoyal
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metadata/meta.py
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Old 10-28-2015, 10:03 AM   #3
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thanks!
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Old 10-28-2015, 12:20 PM   #4
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hi, me again :P

looking at metadata/meta.py, the code calls:

get_file_type_metadata() from calibre.customize.ui

calibre/customize/ui.py contains a lot of plugin stuff, so presumably it works its way through the plugin system for each file type.

in the case of kf8, i assume it ends up in the get_metadata() function of `calibre/ebooks/metadata/mobi.py`

this function's job is to place all the meta information in MetaInformation object called mi, see below:

Code:
    if mh.exth is not None:
        if mh.exth.mi is not None:
            mi = mh.exth.mi
    else:
        size = 1024**3
        if hasattr(stream, 'seek') and hasattr(stream, 'tell'):
            pos = stream.tell()
            stream.seek(0, 2)
            size = stream.tell()
            stream.seek(pos)
        if size < 4*1024*1024:
            with TemporaryDirectory('_mobi_meta_reader') as tdir:
                with CurrentDir(tdir):
                    mr = MobiReader(stream, log)
                    parse_cache = {}
                    mr.extract_content(tdir, parse_cache)
                    if mr.embedded_mi is not None:
                        mi = mr.embedded_mi
none of the books i have satisfy the first if-statement, so they fall through to the else. this creates a MobileReader object, and calls extract_content() on that. now the very first (or second) thing that extract_content() calls is:

Code:
self.check_for_drm()
which throws an exception in the case of DRM. this being the case, does that mean that many books (at least all the ones i have), you cannot access the author without first removing the DRM?

with thanks
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Old 10-28-2015, 12:58 PM   #5
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Just do

get_metadata(open(filename, 'rb'), stream_type='mobi')

That will work exactly like reading metadata in all of calibre.
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Old 10-28-2015, 01:01 PM   #6
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yup, i get that. i'm just trying to understand the internals.

but my question was whether i'm understanding the code correctly, and whether it's possible to read the author when the book has DRM.

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Old 10-28-2015, 01:05 PM   #7
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If you want to answer that question, get hold of a book with DRM and add it to calibre or use the ebook-metadata command line tool and see if calibre reads metadata. As far as I recall metadata in MOBI files is not DRMed.
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Old 10-28-2015, 02:07 PM   #8
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hmm, yes, you're right. it is still able to read the author, etc. when the book has DRM... though i have no idea where calibre does this :P

i did find a way of getting the author though, the fetchEXTHFields() function of the moby.py MetadataReader doesn't read the author, but i can modify it so it does:

Code:
   def fetchEXTHFields(self):
        stream = self.stream
        record0 = self.record0

        # 20:24 = mobiHeaderLength, 16=PDBHeader size
        exth_off = unpack('>I', record0[20:24])[0] + 16 + record0.start
        image_base, = unpack('>I', record0[108:112])

        # Fetch EXTH block
        exth = self.exth = StreamSlicer(stream, exth_off, record0.stop)
        nitems, = unpack('>I', exth[8:12])
        pos = 12
        # Store any EXTH fields not specifiable in GUI
        for i in xrange(nitems):
            id, size = unpack('>II', exth[pos:pos + 8])
            content = exth[pos + 8: pos + size]
            pos += size

            self.original_exth_records[id] = content

            if id == 100: # added this
                print(content)  # content is the author
thanks for your help!
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Old 10-29-2015, 10:20 AM   #9
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OK! i just thought i'd fill you in, i've got it all to work!

it turns out i'd failed to include the EXTHHeader class definition in my project (i've been separating some of this code from the rest of calibre, so i don't have a 60+ meg dependency

of course, this was just being caught and reported as an "Invalid EXTH header". once i got this included properly, and stripped out the dependencies, my project can read all the metadata, extract covers, etc.

so it all works! thanks for your help
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