Re: [Tracker] PATCH: Faster PNG extractor



Op 28/06/2013 8:30, Jonatan PÃ¥lsson schreef:

Hi Jonatan,

The main reason for not modifying the original extractor is that I want to keep it as a fallback if this new extractor fails due to an unexpected file structure. Since png-faster tries to skip to the end of the file by estimating the location of the metadata contained in the end of the file using the file size & IDAT chunk size, I predict it may fail more often than the original. Since tracker-extract handles these failures gracefully, this is not a problem however.
The best way I can see to get a similar functionality in to the 
existing extractor would be to modify libpng to allow skipping to the 
end of the file (right now there is a comment in the existing png 
extractor noting that this functionality is missing from the library), 
but since reading the PNG format is relatively simple I opted to put 
this functionality in the extractor rather than first patching libpng 
(I am not sure how much work this would be, either).
What are your thoughts on keeping png-faster as a separate, optional 
extractor module which can be enabled when extraction speed is of 
primary concern?
After reading this, my opinion is that we should keep it as separate 
modules. What do you think, Martyn?
Patching libpng is a longer term fine solution, too. Not sure how 
willing libpng maintainers will be, but for the time being we can deal 
with the opitmization this way.
Kind regards,

Philip



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