Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!ames!ucbcad!ucbvax!jade!eris!mwm From: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer) Newsgroups: comp.sys.amiga Subject: Re: Sparse files. Message-ID: <3711@jade.BERKELEY.EDU> Date: Mon, 25-May-87 03:37:26 EDT Article-I.D.: jade.3711 Posted: Mon May 25 03:37:26 1987 Date-Received: Tue, 26-May-87 01:25:45 EDT References: <8705232024.AA15280@cogsci.berkeley.edu> Sender: usenet@jade.BERKELEY.EDU Reply-To: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer) Organization: Missionaria Phonibalonica Lines: 47 In article <8705232024.AA15280@cogsci.berkeley.edu> bryce@COGSCI.BERKELEY.EDU (Bryce Nesbitt) writes: <1> Can anything other than a sector editor produce a sparse file? Doesn't looke like it. The last sentence for the Seek() entry in the AmigaDOS Developer's Manual says: You cannot Seek beyond the end of a file. Trying to do so verifies this (Me, believe manuals? Hah! I've been hacking Unix long enough to know better than that!). Suddenly I feel like I'm stranded on a VMS system.... <2> Is there *any* use for a sparse file at the filesystem level? < Name *one* use that could not be better served in another manner, Almost any sparse data structure stored on disk likes spares files. Take a look at the dbm code, for instance. It hashes the key to produce a block address to store data at. Or personal example: I needed to store short (~120 bytes) records on a three-character key. So you cram the bytes together, multiply by record size, and do a seek (roughly, anyway). The alternative data structure we considered was a trie, which also wanted a sparse data file. [Thinking about it, an Amiga would have been damn near _perfect_ for that project, barring the lack of sparse files. But working around that would have been easier than the workarounds the amiga would have prevented. To bad it didn't exist then.] As a more esoteric example, if your OS supports sparse address spaces in a process, then saving/restarting some interpreted language systems gets easier. If you can demonstrate better (by some measure other than "doesn't use sparse files") ways to do the sparse data applications, I'd like to hear about them. < I'm curious! Ah, but what color are you when you're curious? Or is this just a case of "enquiring minds want to know"?