Unusual characters in filenames and shared folders
 

I was experimenting with creating files with unusual characters in their names, and seeing how those characters map to the filenames WinUAE creates in the host shared folder. (Some characters are shown differently, I'll post about that later.)

There are some issues with the º character (hex $BA). I can't reproduce that character properly typing here, but it looks like a superscript o with an underline below it. Pressing Alt-B with the Amiga GB keymap types it. Whether or not that character is legal in filenames varies:

• Kickstart 1.x ROM filesystem: illegal
• Kickstart 1.x RAM-handler: illegal
• Kickstart 2.x, 3.x ROM filesystem: illegal
• Kickstart 2.x, 3.x RAM handler: legal
• FFS 40.1 (probably all earlier versions too): illegal
• FFS 45.13: legal
• WinUAE shared folder: legal

If you try to copy a file with that character in its name to an FFS pre-v45 partition or RAM: under Kickstart 1.x you'll get an error 210, object name invalid. Because of that it might be a good idea to make the º character illegal for WinUAE shared folders. Or at least, disallow creation of files with that character. (On the other hand, maybe those characters are supposed to be legal but were incorrectly rejected by the 1.x RAM-handler and earlier FFS versions?)

The same issue seems to apply to the ¯ character (hex $AF, Shift-Alt-N in the GB keymap).

Because this is AmigaOS filesystem specific limit, not AmigaDOS limit, I don't see any reason for restrictions. Different filesystems can have different limits.

That makes sense.

I wonder why only $AF and $BA are not allowed. Hopefully I'll get around to looking at the FFS code to see why some time.

If anyone's interested in checking how various Kickstart and/or filesystem versions handle filenames with those characters in, here's a test ADF. I created it using a 901120-byte HDF with FFS 45.13 in WinUAE. The ROM filesystem 40.1 won't allow files with those characters in their names to be created, but you can open and write to existing files.