FreeLists / openbeosstorage / [openbeosstorage] Re: Disk Device API: Some semantical questions

["Ingo Weinhold" <bonefish@xxxxxxxxxxxxxxx>]

On Sat, 12 Jul 2003 12:44:55 -0700 Tyler Dauwalder <tyler@xxxxxxxxxxxxx
> wrote:
> On 2003-07-11 at 11:42:47 [-0700], Ingo Weinhold wrote:
[...]
> > > For VisitEachPartition(), the "device" parameter allows you
> > > to specify a single device on which to visit all partitions, 
> > > IIRC,
> > > but
> > > that doesn't make much sense for VisitEachDevice().
> > 
> > The BDiskDevice* parameter passed to the partition visiting methods 
> > is
> > an output parameter as well. Since a BPartition object can only 
> > exist,
> > if it belongs to a BDiskDevice, there must also be a BDiskDevice, 
> > if 
> > we
> > want to return a BPartition*. And that's the function of the device
> > parameter; it is set to the device that contains the found 
> > partition.
> > 
> > If that is confusing, we can still change the visiting methods to 
> > just
> > return a partition_id (all of them) instead of a bool and have no
> > further parameters. Then the caller can get a device/partition 
> > object
> > via Get{DiskDevice,Partition}WithID().
> 
> The only confusing part is that one is * and one is a **; that's what 
> threw me off originally. Wouldn't using the partition_id be a bit 
> more 
> expensive, since you'd have to look up the appropriate partition 
> again? 
> Or are you hashing the ids?

Yes, it would be more expensive. The device data had to be refetched 
from the kernel.

> Regardless, I think the way it's set up 
> currently is fine as long as it's properly documented, which it will 
> be. :-)

Which it already is. :-) The methods are virtually unchanged since the 
first iteration of the Disk Device API and so are their comments. Some 
methods still have the old comments, although their signature and/or 
their semantics have changed, though. I will document things properly, 
when the API is more stable...

CU, Ingo