Help Writing a Plugin for File Checksums

lucask · 08-07-2017, 04:25 PM

Hello. I'm trying to write a Calibre plugin that will compute MD5 checksums of ebooks and store them in a custom column. I tried writing one following the examples in the manual (attached) but I clearly don't know what I'm doing as the code does nothing. I'd appreciate if anyone with some Python would give a few pointers regarding what I'm not doing right. Thank you.

BetterRed · 08-07-2017, 05:21 PM

Moderator Notice
@lucask - I moved your thread to the Development sub-forum.

If you read the PLEASE READ BEFORE ... sticky you'll understand why

BR

kovidgoyal · 08-07-2017, 11:01 PM

The indentation of the run method is incorrect. And for metadatawriter plugins you need to implement the set_metadata method, not the run method.

Also I'm not sure what you are expecting to do here. If you want to add metadata based on newly added book files to the calibre databse you need to create a filetype plugin not a metadatawriter plugin.

Create a filetype plugin and implement either the postimport() or postadd() methods in it.

lucask · 08-24-2017, 01:02 AM

Thank you for responding. I have been trying for an embarrassingly long time to understand and implement your suggestion and had the following questions.
1. I intend to apply this plugin to an existing library, not to newly imported books. Should I still try to write postadd() and/or postimport() methods?
2. I have not yet had a successful test, so I don't know if the way I attempt to write to a user-defined column is right. In the GUI these columns are preceded by pound signs (as in #genre). When writing such plugins, is it, for instance 'mi.genre = ((some_code))' or 'mi.#genre = ((some_code))?

Thank you for your time.

kovidgoyal · 08-24-2017, 01:24 AM

If you want to apply it to an existing library you will need to create a user interface plugin. I suggest simply adapting an existing plugin such as the Word Count plugin.

davidfor · 08-24-2017, 02:37 AM

Yes, the Count Pages plugin would be a good example for this. It already iterates over the selected books, does some processing on them in a background and then passes the result back to the foreground for updating into a column.

But, I don't know what the point of calculating a checksum for the books in the library is. There are plenty of things you can do that will change the files in a way to invalidate the checksum (edit, convert, polish, update metadata). And if you send the book outside the library calibre updates the metadata, including the cover, and that won't match the checksum.

pdurrant · 08-24-2017, 06:16 AM

Perhaps a checksum of the contents of the HTML/CSS/Images, and not of the metadata?

botmtl · 10-07-2017, 06:31 PM

I think having the checksum for the file as it was when it was first imported can still be really useful. I had some plans for something like this for myself.

The context is the key. I regularly grab free books off amazon. When I do, it's not rare that I grab a whole bunch of them in one sitting. That collection of books has gotten pretty big over time. After downloading the books and importing them to calibre, I clean up the tiles, the authors, do the cover thing... basically I work so much on them that on the next batch import, I end up with with duplicates. Having the original checksum (to prevent reimporting books I already imported) would be great in this case and an up-to-date checksum would be useless.

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08-07-2017, 05:21 PM	#2
BetterRed null operator (he/him) Posts: 20,550 Karma: 26954694 Join Date: Mar 2012 Location: Sydney Australia Device: none	Moderator Notice @lucask - I moved your thread to the Development sub-forum. If you read the PLEASE READ BEFORE ... sticky you'll understand why BR

08-07-2017, 11:01 PM	#3
kovidgoyal creator of calibre Posts: 43,842 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	The indentation of the run method is incorrect. And for metadatawriter plugins you need to implement the set_metadata method, not the run method. Also I'm not sure what you are expecting to do here. If you want to add metadata based on newly added book files to the calibre databse you need to create a filetype plugin not a metadatawriter plugin. Create a filetype plugin and implement either the postimport() or postadd() methods in it.

08-24-2017, 01:02 AM	#4
lucask Junior Member Posts: 2 Karma: 10 Join Date: Aug 2017 Location: Uganda Device: none	Thank you for responding. I have been trying for an embarrassingly long time to understand and implement your suggestion and had the following questions. 1. I intend to apply this plugin to an existing library, not to newly imported books. Should I still try to write postadd() and/or postimport() methods? 2. I have not yet had a successful test, so I don't know if the way I attempt to write to a user-defined column is right. In the GUI these columns are preceded by pound signs (as in #genre). When writing such plugins, is it, for instance 'mi.genre = ((some_code))' or 'mi.#genre = ((some_code))? Thank you for your time.

08-24-2017, 01:24 AM	#5
kovidgoyal creator of calibre Posts: 43,842 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	If you want to apply it to an existing library you will need to create a user interface plugin. I suggest simply adapting an existing plugin such as the Word Count plugin.

08-24-2017, 02:37 AM	#6
davidfor Grand Sorcerer Posts: 24,907 Karma: 47303748 Join Date: Jul 2011 Location: Sydney, Australia Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos	Yes, the Count Pages plugin would be a good example for this. It already iterates over the selected books, does some processing on them in a background and then passes the result back to the foreground for updating into a column. But, I don't know what the point of calculating a checksum for the books in the library is. There are plenty of things you can do that will change the files in a way to invalidate the checksum (edit, convert, polish, update metadata). And if you send the book outside the library calibre updates the metadata, including the cover, and that won't match the checksum.

08-24-2017, 06:16 AM	#7
pdurrant The Grand Mouse 高貴的老鼠 Posts: 71,495 Karma: 306214458 Join Date: Jul 2007 Location: Norfolk, England Device: Kindle Voyage	Perhaps a checksum of the contents of the HTML/CSS/Images, and not of the metadata?

10-07-2017, 06:31 PM	#8
botmtl Enthusiast Posts: 43 Karma: 70238 Join Date: Jun 2014 Device: none	I think having the checksum for the file as it was when it was first imported can still be really useful. I had some plans for something like this for myself. The context is the key. I regularly grab free books off amazon. When I do, it's not rare that I grab a whole bunch of them in one sitting. That collection of books has gotten pretty big over time. After downloading the books and importing them to calibre, I clean up the tiles, the authors, do the cover thing... basically I work so much on them that on the next batch import, I end up with with duplicates. Having the original checksum (to prevent reimporting books I already imported) would be great in this case and an up-to-date checksum would be useless.