Date: Tue, 01 Aug 2006 23:35:03 -0700 From: Tim Kientzle <kientzle@freebsd.org> To: rick-freebsd@kiwi-computer.com Cc: freebsd-hackers@freebsd.org Subject: Re: [PATCH] adding two new options to 'cp' Message-ID: <44D04797.1040201@freebsd.org> In-Reply-To: <20060801174048.GE3413@megan.kiwi-computer.com> References: <44CE03D2.2050803@centtech.com> <17614.4005.407223.621637@bhuda.mired.org> <44CE199C.2020500@centtech.com> <17614.8289.134373.387558@bhuda.mired.org> <96b30c400607310847s1d2f845eo212b234d03f51e9a@mail.gmail.com> <17614.10982.499561.139268@bhuda.mired.org> <ealpn1$lan$1@sea.gmane.org> <20060801072611.GA717@turion.vk2pj.dyndns.org> <20060801171150.GB3413@megan.kiwi-computer.com> <44CF8F1A.5090506@centtech.com> <20060801174048.GE3413@megan.kiwi-computer.com>
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Rick C. Petty wrote: > > While we're at it, I think we should add the -S option to bsdtar. I'm > willing to do the work ... I have pretty strong ideas about sparse file support for bsdtar. The "cheap" solution is to handle it purely on extract: Detect blocks of zeros when restoring files and seek over them. That would be pretty easy to implement: just add another option to archive_read_extract() and implement the logic to skip over blocks of zeros. Archiving sparse files as such is harder, although I do have an outline of a technique which would not only handle sparse files, but also allow archiving files whose size is not known in advance (something the GNU tar approach doesn't support). I simply dislike the GNU tar approach, in part because it requires two passes over the file (the map of holes is required before the file is written). Again, if someone is really interested, let me know. Tim Kientzle
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