"tar tfv /dev/cd0" speedup patch

[Tim Kientzle]

Joerg Sonnenberger wrote:
> On Thu, Feb 18, 2010 at 07:34:59PM +0100, Juergen Lock wrote:
>>  Ok here is a new version of the patch with these things fixed and the
>> Linux case added:  (Linux case not tested yet, and yes I did this on
>> stable/8.)
> 
> Why the check at all? Shouldn't devices that don't allow seek fail that?
> E.g. for devices, just try to seek ahead and fallback to normal reading?

That was the initial implementation in libarchive, but
I had a number of reports of that not working for
tape drives.  I recently dug out and connected an
old DDS drive I had in the closet, so I should
probably try again and see if I misunderstood
something along the way.

Tim