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Note reversal of MFS and HFS

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The NuFX spec reversed the entries for MFS and HFS.  Not a significant
issue, but worth pointing out.
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Andy McFadden 2022-05-25 11:34:10 -07:00
parent 01abf8e920
commit 33a9e06ddc
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library/nufx-addendum.htm
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@ -24,12 +24,13 @@
<!--msnavigation--><msnavigation border="0" cellpadding="0" cellspacing="0" dir="ltr" width="100%"><tr><!--msnavigation--><msnavigation valign="top"><msnavigation border="0" cellpadding="0" cellspacing="0" width="100%"><msnavigation border="0" cellpadding="0" cellspacing="0" dir="ltr" width="100%"><tr><msnavigation valign="top"><msnavigation border="0" cellpadding="0" cellspacing="0" width="100%"><msnavigation border="0" cellpadding="0" cellspacing="0" width="100%"><tr><msnavigation valign="top">
<h6>NuFX Addendum - <b>By Andy McFadden - Last revised 2015/01/09</b></h6>
<h6>NuFX Addendum - <b>By Andy McFadden - Last revised 2022/05/25</b></h6>
<p align="left">This addendum clarifies and extends certain aspects of the <a href="FTN.e08002.htm"> NuFX
specification</a>.&nbsp; This is not an &quot;official&quot; modification
of the original document - it has not been reviewed and approved by
the original author - but anyone developing NuFX utilities would do
well to follow these recommendations.</p>
<h2 align="left">Purpose</h2>
<p align="left">The NuFX specification defines&nbsp;a very loose structure, and
leaves much to the imagination of the implementer.&nbsp; For example, &quot;If a
@ -428,20 +429,27 @@ or CRLF, and convert as needed for display.&nbsp; GS/ShrinkIt used a
proportional font, so there is no need to worry about formatting to preserve &quot;ASCII art&quot; in
comments.</p>
<p align="left">&nbsp;</p>
<h3 align="left">GS/OS option lists</h3>
<p align="left">Files archived from HFS AppleShare volumes come with
&quot;option lists&quot;, a GS/OS feature that provides a way for non-ProDOS
filesystem information to be preserved.&nbsp; GS/ShrinkIt tries to save this
information, but it doesn't seem to do a very good job.&nbsp; It appears to drop
a big chunk of the data without altering the size (e.g. the size field says 36
bytes, but there's only space for 18 bytes in the record header).</p>
filesystem information to be preserved (e.g. the HFS FInfo and FXInfo data).
GS/ShrinkIt tries to save this information, but it doesn't seem to do a very good job.
Sometimes it appears to drop some of the data without altering the size, e.g. the
size field says 36 bytes, but there's only space for 18 bytes in the record header.
(ProDOS technote #25 suggests this could relate to the ProDOS FSM on
a Macintosh with a //e card.)</p>
<p align="left">GS/ShrinkIt seems to work correctly whether the option list size
is correct or not, so other applications should do the same.</p>
<p>Side note: the NuFX specification reversed the values of MFS and HFS
in the file_sys_id definition. In practice, GS/ShrinkIt correctly uses the
GS/OS FST definitions: MFS=5, HFS=6.</p>
<p align="left"><b>Opening:</b> Assume the option_size field is correct
unless it exceeds attrib_count-2.&nbsp; If it's too large, clip it down to size.</p>
<p align="left"><b>Updating:</b> Always use the actual size.&nbsp; Do not
propagate incorrect values.&nbsp; Discarding existing option lists is
discouraged but allowed.</p>
<p align="left">&nbsp;</p>
<h3 align="left">Master EOF</h3>
<p align="left">For the most part, ShrinkIt correctly sets the MasterEOF field