Re: Ido mode on Windows: please turn off cache

[Herbert Euler]

I got another idea of dealing with this.  Please think about whether
it is appropriate.

I have tested it again to be sure, that if the file system is NTFS the
modification time will be updated, while if the file system is FAT32
it will not.  Again, I did not check the FAT file system.  If this is
the key to the problem, we can check some other infomation in addition
to the modification time, to determine whether a directory is updated.

The `file-attributes' function returns a list, the third and fourth
element of which are file uid and file gid.  These two fields are
different on NTFS and FAT32.  Please take a comparison:

   (file-attributes "c:/")   ;; On FAT32 file system
        ==> (t 1 0 0 (0 0) (0 0) (0 0) 0 "drwxrwxrwx" nil 0 (7756 . 6145))

   (file-attributes "c:/")   ;; On NTFS file system
        ==> (t 1 5 5 (0 0) (0 0) (0 0) 0 "drwxrwxrwx" nil 0 (9440 . 10983))

Note that the uid and gid are different for the two file systems.  I
have tested many logical drives, all FAT32 drives come with (0 0), and
all NTFS drives come with (5 5).

What about this idea?  If the OS is w32, and if the uid and gid are (0
0), it means reading from FAT32 file system, so the cache should be
disabled; if they are (5 5), it means reading from NTFS file system,
then the cache should be enabled?

Regards,
Guanpeng Xu

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