Date: Wed, 5 Apr 1995 17:33:43 -0500 (CDT) From: "Clay D. Hopperdietzel" <hoppy@appsmiths.com> To: hackers@FreeBSD.org Subject: Re: new install(1) utility Message-ID: <199504052233.RAA22470@anvil.appsmiths.com> In-Reply-To: <199504052134.HAA31128@godzilla.zeta.org.au> from "Bruce Evans" at Apr 6, 95 07:33:44 am
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:: :: >> > obvious if they don't match, and doing cksums on both files would be :: >> > much faster than the 'cmp' IMHO. :: >> :: >> Funny you should mention, I just ran some experiments (for CTM), and the :: >> fastest thing you can do is to mmap both files and memcmp them... :: :: There are many reasons why checksumming might be slower, especially if it :: isn't implemented carefully. Checksumming can only be faster if you can :: usually avoid reading the target. A non-hashed database in a single file :: would be very slow. You would have to use a hashed database. Writing :: the database would add a lot of overhead. This would be more of a :: problem for install than for ctm since files are unfortunately often :: installed one at a time so the database would have to be opened and :: closed a lot. Not to mention the fact that the memcmp() is going to bail at the first difference...probably avoiding most of the I/O to begin with. =============================================================================== Clay D. Hopperdietzel hoppy@appsmiths.com AppSmiths, Inc. Voice (713) 578-0154 Fax (713) 578-6182 15915 Katy Fwy, Suite 470 Where do *I* Want to Go Today? Houston, Texas 77094 FreeBSD!
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