[openbeosstorage] Re: DiskDevice API v2.1



Somebody wrote:

> But anyway, it *is* a problem, and we will not be=20
> able to solve it completely (and efficiently when=20
> complete), due to the heavy usage of entry=3D3D5Frefs=20
> in BeOS.

An offset in the in-memory data structure representing
a volume/partition/whatever can efficiently and simply
solve this problem assuming that you are simply going=20
to move everything linearly.

You don't even have to remember which entry_refs were
from before the move.  You can treat them all the same
by subtracting the offset every time you create an
entry_ref.

Space hit: one field (int64?)
Time hit: an addition per entry_ref access
          a subtraction per entry_ref creation

Doing an addition each time is probably cheaper than
figuring out if you have to update an entry_ref and
doing the "right thing" on the fly.  It's also less
complicated than keeping track of all current=20
entry_refs and updating them during the move.

I assume entry_refs store the absolute position from
the start of the disk and not the relative position
from the start of the volume or this wouldn't be an
issue, right?

Andrew

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