Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!munnari.oz.au!ariel!ucsvc.ucs.unimelb.edu.au!luga!latcs1!stephens
From: stephens@latcs1.lat.oz.au (Philip J Stephens)
Newsgroups: comp.sys.apple2
Subject: Re: Heatseeker
Message-ID: <1991Jun25.075538.5389@latcs1.lat.oz.au>
Date: 25 Jun 91 07:55:38 GMT
References: <1991Jun22.023810.26366@mcs.anl.gov> <16484@smoke.brl.mil> <91175.213841ART100@psuvm.psu.edu>
Organization: Comp Sci, La Trobe Uni, Australia
Lines: 32

Andy Tefft writes:
>Now we have a program that apparently uses non-standard
>methods of accessing files (i.e. not the normal prodos mli calls, otherwise
>it would be as slow as any other program) which has not yet been thoroughly
>tested.

  The program will be safe *provided* that it gets it's information
about the directory and file structures by following the proper
pointers and such from the volume directory on a ProDOS disk, as the
MLI calls do.  It's speed will probably come from optimizing the
actual reading and writing of a file once the info has been gathered
in the normal (safe) fashion. e.g. once it gets the list of blocks
that the file occupies, it could reorder these in sequential order
based on the fastest interleave and **WHAM**, read it all in as fast
as the drive can take it, converting the "6-bit" disk bytes into normal
bytes on the fly.  Writing the blocks to the target disk would just be
the reversed process (yes, I know something about disk drives too,
after having disassembled the RWTS and Locksmith fast disk copy :-)
  I personally must congratulate the author of Heatseeker on taking
the time to write such a utility as this; I'm sure that if he already
understands what the fastest way of reading and writing to a disk is,
he has probably spent the time to understand how a ProDOS disk is
structured in order to make it compatible with current (and future)
versions of the OS.  Or the least he would do is ensure that it only
works up to version X.

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<  Philip J. Stephens                ><   "Many views yield the truth."       >
<  Hons. student, Computer Science   ><   "Therefore, be not alone."          >
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