Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/3/84; site maynard.UUCP
Path: utzoo!linus!alliant!maynard!campbell
From: campbell@maynard.UUCP (Larry Campbell)
Newsgroups: net.micro.amiga,net.unix-wizards
Subject: Re: Speed of seeks
Message-ID: <297@maynard.UUCP>
Date: Fri, 16-May-86 20:06:01 EDT
Article-I.D.: maynard.297
Posted: Fri May 16 20:06:01 1986
Date-Received: Sun, 18-May-86 15:29:33 EDT
References: <12593@ucla-cs.ARPA> <645@baylor.UUCP>
Distribution: net
Organization: The Boston Software Works Inc., Maynard, MA
Lines: 18
Xref: linus net.micro.amiga:6897 net.unix-wizards:15066

> Incidentally, despite the poor design of the files a seek() does not have to
> read every sector... a mistake often made by library writers is to try to
> make seek offsets simple integers. According to the library, the argument
> to an absolute seek() (lseek(fd, off, 0) or lseek(fd, off, 2)) only needs
> to be the returned value from a tell() call: it may indeed be a magic cookie
> like a sector/offset pair (and in fact "magic cookie" is the way it's described
> in the manual). It is under RSX/11M and on the ATARI 800.
> -- Peter da Silva
> -- UUCP: ...!shell!{baylor,graffiti}!peter; MCI: PDASILVA; CIS: 70216,1076

Wrongo.  First, the manual describes the offset as a long (NOT a "simple
integer" nor a "magic cookie").  Second, if the offsets AREN'T integers,
then almost any database library or package won't work (like dbm(3)),
because they often hash keys into offsets in the index file.
-- 
Larry Campbell                                 The Boston Software Works, Inc.
ARPA: maynard.UUCP:campbell@harvard.ARPA       120 Fulton Street
UUCP: {harvard,cbosgd}!wjh12!maynard!campbell  Boston MA 02109