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BD-R with UDF filesystem - FS redirector with 64-bit sizes (Miscellaneous)

posted by ecm Homepage E-mail, Düsseldorf, Germany, 22.12.2020, 12:50

> Khusraw's DOS port of MPLAYER can play (unencypted) Blu-ray discs, but only
> if formatted in ISO9660 standard, as there's no UDF driver. The problem is
> in MS-DOS, filesizes > 2GB aren't readable due to signed longint
> limitation.
>
> There's an experimental exFAT reader for DOS as well, but the problem again
> is that filesizes > 2GB aren't readable, so that completely defeats the
> purpose of having an exFAT driver in the first place. The raw assembly code
> of MSDOS.SYS and / or IO.SYS needs to be modified somehow. Even if
> possible, I do not know if filesizes > 4GB can be directly supported.
>
> Same issues for the R. Loew drivers (I think?), or did he somehow magically
> erase and / or patch the 32-bit longint limitations on filesizes as well as
> increase sector sizes and capacities of drives beyond the 2TB limit? I'm
> not sure, as I've not personally tested those drivers.
It is possible for a file system redirector (like for ISO 9660, UDF, exFAT, NTFS, or dosemu's host FS) to support 64-bit file sizes and seeks in a manner compatible to the FAT+ support of Enhanced DR-DOS. That means expanding the SFTs with extension fields (can be stored in file handle tables of the redirector), hooking the new-style interrupt 21h service 7142h for large seeking, and service 42h to make old-style seeking somewhat aware of the large size support. I did this for dosemu2's mfs. Technologically it works, but it was rejected on other grounds.

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