Pali Rohár <pali.rohar@xxxxxxxxx> writes: > On Monday 20 January 2020 21:07:12 OGAWA Hirofumi wrote: >> Pali Rohár <pali.rohar@xxxxxxxxx> writes: >> >> >> To be perfect, the table would have to emulate what Windows use. It can >> >> be unicode standard, or something other. >> > >> > Windows FAT32 implementation (fastfat.sys) is opensource. So it should >> > be possible to inspect code and figure out how it is working. >> > >> > I will try to look at it. >> >> I don't think the conversion library is not in fs driver though, >> checking implement itself would be good. > > Ok, I did some research. It took me it longer as I thought as lot of > stuff is undocumented and hard to find all relevant information. > > So... fastfat.sys is using ntos function RtlUpcaseUnicodeString() which > takes UTF-16 string and returns upper case UTF-16 string. There is no > mapping table in fastfat.sys driver itself. > > RtlUpcaseUnicodeString() is a ntos kernel function and after my research > it seems that this function is using only conversion table stored in > file l_intl.nls (from c:\windows\system32). > > Project wine describe this file as "unicode casing tables" and seems > that it can parse this file format. Even more it distributes its own > version of this file which looks like to be generated from official > Unicode UnicodeData.txt via Perl script make_unicode (part of wine). > > So question is... how much is MS changing l_intl.nls file in their > released Windows versions? > > I would try to decode what is format of that file l_intl.nls and try to > compare data in it from some Windows versions. > > Can we reuse upper case mapping table from that file? Regarding fs/unicode, we have some infrastructure to parse UCD files, handle unicode versioning, and store the data in a more compact structure. See the mkutf8data script. Right now, we only store the mapping of the code-point to the NFD + full casefold, but it would be possible to extend the parsing script to store the un-normalized uppercase version in the data structure. So, if l_intl.nls is generated from UnicodeData.txt, you might consider to extend fs/unicode to store it. We store the code-points in an optimized format to decode utf-8, but the infrastructure is half way there already. -- Gabriel Krisman Bertazi
