Re: Cache and FAT

[Behdad Esfahbod <behdad@xxxxxxxxxx>]

On 12/09/2009 04:57 AM, Mikhail Gusarov wrote:
>
> Twas brillig at 21:18:18 08.12.2009 UTC-05 when behdad@xxxxxxxxxx did gyre and gimble:
>
>   >>  1) scan directory and subdirectories and use max(mtimes, ctimes) of
>   >>  all files as mtime of directory.
>
>   BE>  Would be a PITA.
>
>   >>  2) add "hash" field to directory cache which is hash of all
>   >>      subdirectories' hashes and directory contents.
>
>   BE>  Isn't option #1 superior to this?  And doesn't need a change to the
>   BE>  cache format.
>
> I've came up with the following scenario:
>
> dir/
>    foo.ttf (mtime=5,ctime=5)
>
> otherdir/
>    bar.ttf (mtime=4,ctime=4)
>
> mv otherdir/bar.ttf dir =>
>
> dir/
>    foo.ttf (mtime=5,ctime=5)
>    bar.ttf (mtime=4,ctime=4)
>
> First variant will fail to detect new font in dir/ in this case, as
> Windows does not change any timestamp on moved file.
>
> Also, it should be possible to reuse mtime field in cache file for a
> hash (32-bit one, as cryptographical sthrength is not necessary here).

Right.  Since we only compare mtime for equality, we can simply use it as the 
directory hash.

Thanks,
behdad
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