Re: [Tracker] PATCH: Faster PNG extractor

[Philip Van Hoof <philip codeminded be>]

Op 28/06/2013 8:30, Jonatan Pålsson 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