Improving type detection

[Kohei Yoshida]

Hi Maxim,

On Thu, 2014-05-01 at 15:44 +0300, Maxim Monastirsky wrote:

> https://gerrit.libreoffice.org/9221
> https://gerrit.libreoffice.org/9222
> https://gerrit.libreoffice.org/9223
> 
> Any kind of feedback would be appreciated!

So, I looked over those changes, and I do like the changes. :-)  I
believe they will greatly improve the maintainability of the type
detection code not to mention several bugs they fix.

I believe these changes pass "make check"?  If so, let's go ahead to
push those changes in.

While we are on this subject, I've also received (quite some time ago)
some feedback from the developer & maintainer of some of the external
import filter libraries that we use.  Those libraries do handle type
detection that are plugged into our type detection system, and they are
all zip-based formats.  He was concerned about having to "detect" zip
storage over and over again which he rightly said was not great for
performance.

So I was thinking about perhaps introducing an additional boolean
property with the MediaDescriptor - something like "ZipStorageDetected"
which, when true, the subsequent detection code can choose to skip
detecting for zip archive.

Anyway, this is perhaps for a future project.  I'd like to throw this in
since you are working in this area, in case you can come up with a
clever way to plug such functionality in for your next project. ;-)

Kohei