[Interest] QFile subclass that does HFS compression?

Thiago Macieira thiago.macieira at intel.com
Thu Dec 20 00:57:08 CET 2018

On Wednesday, 19 December 2018 14:00:50 PST René J. V. Bertin wrote:
> Thiago Macieira wrote:
> > Transparent compression is fine.
> But that's only because there is also transparent decompression, otherwise
> you'd be in exactly the same boat.


> Ultimately I don't think it matters where the compression takes place, in
> filesystem code or in userland code. As long as the fact that compression
> takes place is completely hidden from code that needs to work the same way
> when there is no compression.
> I'm going to try to let this rest (until I learn of a way where you don't
> need to keep the entire compressed resource fork in memory as long as the
> file is open for writing).

Almost all the compression libraries support streaming mode. Some will have a 
pull mechanism, where it will ask you for a number of bytes; others will have 
a way for you to detect the next block's size so it can be decoded. Usually, 
memory usage in the decoder is not that big, but it might rise to a megabyte 
or two for large, well-compressed files.

Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center

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