From: thefadden@gmail.com   
      
   On Sunday, October 30, 2022 at 11:07:53 AM UTC-7, Kent Dickey wrote:   
   > Can you describe CiderPress's algorithm for determining sector order of    
   > a .dsk file?    
      
   "Complicated".   
      
   It tries DOS, ProDOS/Pascal, CP/M, and physical sector orders.  (CP/M ordering   
   is not really a thing, since nobody is creating disk images with CP/M   
   software... but we might as well collect the whole set.)  It tests the   
   filesystem for DOS, ProDOS, Pascal,   
    CP/M, RDOS, Gutenberg, and is probably checking for HFS even though I doubt   
   anybody put that on a 5.25" floppy.   
      
   The tests for DOS / ProDOS filesystems have to take into account non-5.25"   
   situations, like UNIDOS disks and DOS Master floppies, so there's a bunch of   
   auto-detect code that doesn't really apply to 5.25" disks.   
      
   The tricky part is finding the right thresholds for the filesystem check.  If   
   you find 15 catalog sectors in the right order on track 17, you're done.  If   
   you find 2, you've got the wrong order.  If you find 4... could be the wrong   
   order plus some lucky    
   bytes, could be a DOS disk with a custom short catalog track.  So you try each   
   order, and come up with a "yes definitely", "no definitely", or "maybe go with   
   this one if you can't find anything better".   
      
   The filename extension is used as a hint, but enough files were named the   
   wrong way that CiderPress doesn't pay much attention to it.  It does allow the   
   code to try the most likely order first, so if we get a "yes definitely" from   
   a filesystem we can    
   just stop looking.  Also, if we can't identify the filesystem, we can open the   
   sector editor with order indicated by the extension.   
      
   It Would Be Nice if CiderPress complained about incorrect or ambiguous   
   filename extensions to encourage people to correct them.   
      
   cf. https://retrocomputing.stackexchange.com/q/15054/56   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)