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Date: Tue, 20 Jul 2004 18:10:51 +1000
From: Peter Jeremy <PeterJeremy@optushome.com.au>
To: Tim Kientzle <tim@kientzle.com>
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cc: Andrey Chernov <ache@nagual.pp.ru>
cc: current@freebsd.org
Subject: Re: NEW TAR
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On Mon, 2004-Jul-19 21:29:54 -0700, Tim Kientzle wrote:
>I have some ideas about sparse file handling,
>but they're not gtar-compatible.  (The gtar
>approach has a number of drawbacks.  The primary
>one being that on many systems it requires reading
>the entire file twice, once to find holes and again
>to actually archive the file.

Actually, it's not possible to accurately determine the holes in a
file by reading it - you can't differentiate between a hole and a
allocated block of zeroes.  What you need is a (new) syscall that
invokes a new VOP_... and returns a bitmap of allocated blocks.  This
would be non-trival unfortunately.

-- 
Peter Jeremy