Review Request 125762: External extractor plugin support for KFileMetaData

[Boudhayan Gupta]

> On Oct. 24, 2015, 6 p.m., Vishesh Handa wrote:
> > I still have many thoughts regarding this particular approach, and third party plugins in general. I'm trying to write them into a cohesive blob.

Do you mean the entire current extractor interface, or just this patch?

What do you mean, "write them into a cohesive blob"? Do you mean all the plugins would be compiled into one giant SO/DLL?

I wrote this patch because it was a 4-hour job, but if you want to overhaul the entire plugin API I suppose the SOC project would be a better place to do it.


> On Oct. 24, 2015, 6 p.m., Vishesh Handa wrote:
> > src/extractors/externalextractor.cpp, line 69
> > <https://git.reviewboard.kde.org/r/125762/diff/4/?file=412432#file412432line69>
> >
> >     Why move from the C++ for syntax to Q_FOREACH? There doesn't seem to be any advantage in this case.

I was told on IRC (IIRC, by Luca Beltrame) that we still can't use range-based for loops in frameworks because of compiler requirements. My initial patch used range-based for loops.


- Boudhayan


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On Oct. 24, 2015, 5:49 p.m., Boudhayan Gupta wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/125762/
> -----------------------------------------------------------
> 
> (Updated Oct. 24, 2015, 5:49 p.m.)
> 
> 
> Review request for Baloo, KDE Frameworks, Pinak Ahuja, and Vishesh Handa.
> 
> 
> Repository: kfilemetadata
> 
> 
> Description
> -------
> 
> This patch introduces support for external metadata extractors in KFileMetaData
> 
> The external extractors themselves can be written in any language, provided that it can be executed as a standalone executable (compiled or script with a hashbang), with command line arguments, and can output data to stdout.
> 
> The extractors are executed like so:
> 
> * `extractor --mimetypes` - outputs a list of mimetypes supported by the extractor, one per line.
> * `extractor filename` - outputs a json document with the metadata. The keys are such that they can be directly used with PropertyInfo::fromName().
> 
> At the KFileMetaData end, an additional internal plugin (ExternalExtractor) is provided that forms a conduit between external extractors and the internal API. This plugin looks for executables called kfilemetadata_extractor_<something> in /usr/bin to find external extractors, and executes them with the --mimetypes arg to find the list of mimetypes each extractor supports. ExternalExtractor then claims to support all of these mimetypes, and then delegates to the extractor executable when doing the actual extraction.
> 
> 
> Diffs
> -----
> 
>   README.md 19b1a26 
>   src/extractors/CMakeLists.txt 5dd223e 
>   src/extractors/externalextractor.h PRE-CREATION 
>   src/extractors/externalextractor.cpp PRE-CREATION 
> 
> Diff: https://git.reviewboard.kde.org/r/125762/diff/
> 
> 
> Testing
> -------
> 
> Tested with the sample executable file extractor (as attched, written in python) with the dump manual test in KFileMetaData. Works.
> 
> 
> File Attachments
> ----------------
> 
> kfilemetadata_extractor_executable
>   https://git.reviewboard.kde.org/media/uploaded/files/2015/10/23/146b657f-31d9-4117-a82f-ef966a6339d4__kfilemetadata_extractor_executable
> 
> 
> Thanks,
> 
> Boudhayan Gupta
> 
>

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