[osg-users] Refactoring DatabasePager NeedToRemove string flagging technique

Robert Osfield robert.osfield at gmail.com
Mon Nov 2 08:10:44 PST 2009

Hi Guys,

I just can't contribute to complex threads right now as I need all my
interlect to get the GLES/GL port right, so I won't even try to chip
in.  Please just be patient and hang back from hacking code that
requires my input on to get a full understanding.


On Mon, Nov 2, 2009 at 4:05 PM, Chris 'Xenon' Hanson
<xenon at alphapixel.com> wrote:
> Jean-Sébastien Guay wrote:
>> This doesn't really help you, but I wanted to be more detailed than just
>> saying "I agree".
>  Thanks for th insight, everyone.
>  I'm kind of an old-school C-flavor programmer, so my instinctive response is rather
> C-like. I don't like bloating people's in-memory objects, so I'd lean towards defining a
> 32-bit flag member on class Node called something like _ephemeralInternalStateFlags. This
> would not be saved or restored, and the definitions of each flag bit would be enumerated
> as 1<<n enums in the Node class header. Code outside of the OSG core distribution would be
> prohibited (by policy, can't really enforce it in the compiler) from defining and
> utilizing these flag bits, but code within OSG core could. The first bit allocated would
> be used to replace the NeedToRemove indicator.
>  Also, while the read-modify-write cycle used to toggle just one bit of a flag is not as
> fast as the blind-write cycle used when you dedicate a whole boolean variable (and consume
> more memory), both the setting operation AND the testing operation should be faster than
> the current string-marking technique.
>  If Robert has no objections to this solution, I'll code it up quick and share it.
>  I'm also concerned about the amount of very similar-but-not-quite-the-same code between
> DatabasePager::capped_removeExpiredSubgraphs and
> DatabasePager::expiry_removeExpiredSubgraphs. I'd like to refactor that to DRY (Don't
> Repeat Yourself) it out a bit as I'm implementing some code of my own that needs to
> cleanly dispose of some PagedLOD children. But, I don't understand why there are
> differences in the disposal technique between them (one calls
> _fileRequestQueue->updateBlock() directly, one sets a local flag and calls updateBlock()
> at the end of the operation, etc).
>> J-S
> --
> Chris 'Xenon' Hanson, omo sanza lettere                  Xenon AlphaPixel.com
> PixelSense Landsat processing now available! http://www.alphapixel.com/demos/
> "There is no Truth. There is only Perception. To Perceive is to Exist." - Xen

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