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Groups > comp.sys.apple2.programmer > #3052

Re: ProDOS 2.4

From Kelvin Sherlock <email@domain.com>
Newsgroups comp.sys.apple2.programmer
Subject Re: ProDOS 2.4
Date 2016-09-07 20:11 -0400
Organization A noiseless patient Spider
Message-ID <nqqaaj$82n$1@dont-email.me> (permalink)
References <c712d26a-a49d-49d2-a7d1-b3c3117b99e6@googlegroups.com>

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On 2016-09-07 20:37:28 +0000, Michael Pohoreski said:

> On Wednesday, September 7, 2016 at 3:23:55 AM UTC-7, Oliver Schmidt wrote:
>> As already written I'd look into removing:
>> 
>> 1) Writing sparse files. Already existing spares files should be read 
>> correctly.
> 
> Does anyone know what applications actually used sparse files?

Davex Disk Images do.

> The first 512 bytes of a Davex archived volume are a header, 
described under "File Format" in this Note. After the header comes 512 
bytes for each block on the saved volume, from zero on up. For blocks 
that are unused, you can just set the file mark ahead 512 bytes instead 
of writing 512 zero bytes--this way the unused blocks do not take up 
disk space, so the resulting file is only a few blocks larger than the 
number of used blocks on the original volume.

> This file format is suitable for ProDOS, but it is less useful on a 
file system (such as AppleShare) that does not allow for sparse files. 
A Davex archived volume file on an AppleShare server always takes up 
more blocks than the original volume contains.

Anyhow, I was under the impression that sparsification only happens 
when gaps are created with setmark or seteof. Removing the sparse code 
and zero-filling those blocks isn't necessarily an improvement.

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Thread

ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-08-17 00:01 -0700
  Re: ProDOS 2.4 Michael J. Mahon <mjmahon@aol.com> - 2016-08-17 17:53 -0500
    Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-08-17 22:43 -0700
      Re: ProDOS 2.4 dempson@actrix.gen.nz (David Empson) - 2016-08-18 17:47 +1200
        Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-08-17 23:06 -0700
          Re: ProDOS 2.4 David Schmidt <schmidtd@my-deja.com> - 2016-08-18 07:16 -0400
            Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-08-18 07:24 -0700
              Re: ProDOS 2.4 dempson@actrix.gen.nz (David Empson) - 2016-08-19 10:38 +1200
              Re: ProDOS 2.4 gids.rs@sasktel.net - 2016-08-18 22:33 -0700
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-08-19 14:05 -0700
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-09-05 19:42 -0700
                Re: ProDOS 2.4 Hugh Hood <hughhood@earthlink.net> - 2016-09-05 22:12 -0500
                Re: ProDOS 2.4 Hugh Hood <hughhood@earthlink.net> - 2016-09-06 00:05 -0500
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-09-06 08:40 -0700
                Re: ProDOS 2.4 Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-09-06 09:37 -0700
                Re: ProDOS 2.4 gids.rs@sasktel.net - 2016-09-06 13:26 -0700
                Re: ProDOS 2.4 David Schmenk <dschmenk@gmail.com> - 2016-09-06 14:08 -0700
                Re: ProDOS 2.4 Oliver Schmidt <ol.sc@web.de> - 2016-09-07 03:23 -0700
                Re: ProDOS 2.4 Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-09-07 13:37 -0700
                Re: ProDOS 2.4 Kelvin Sherlock <email@domain.com> - 2016-09-07 20:11 -0400
                Re: ProDOS 2.4 Michael J. Mahon <mjmahon@aol.com> - 2016-09-07 19:33 -0500
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-09-07 17:18 -0700
                Re: ProDOS 2.4 Oliver Schmidt <ol.sc@web.de> - 2016-09-08 01:37 -0700
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-09-08 08:49 -0700
                Re: ProDOS 2.4 Oliver Schmidt <ol.sc@web.de> - 2016-09-09 02:57 -0700
                Re: ProDOS 2.4 Steve Nickolas <usotsuki@buric.co> - 2016-09-09 06:06 -0400
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-09-09 08:29 -0700
                Re: ProDOS 2.4 sicklittlemonkey <nick.westgate@gmail.com> - 2016-09-15 18:21 -0700
                Re: ProDOS 2.4 David Schmenk <dschmenk@gmail.com> - 2016-09-08 07:06 -0700
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-09-08 09:25 -0700
                Re: ProDOS 2.4 David Schmenk <dschmenk@gmail.com> - 2016-09-08 12:31 -0700
                Re: ProDOS 2.4 Oliver Schmidt <ol.sc@web.de> - 2016-09-09 04:16 -0700
                Re: ProDOS 2.4 John Brooks <jbrooks@blueshiftinc.com> - 2016-09-09 09:02 -0700
                Re: ProDOS 2.4 ol.sc@web.de (Oliver Schmidt) - 2016-09-11 12:56 +0000
                Re: ProDOS 2.4 Oliver Schmidt <ol.sc@web.de> - 2016-09-09 02:09 -0700
                Re: ProDOS 2.4 Michael J. Mahon <mjmahon@aol.com> - 2016-09-07 19:33 -0500

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