Messages in this thread |  | | From | "" <> | Subject | RE: [PATCH 1/4] exfat: Simplify exfat_utf8_d_hash() for code points above U+FFFF | Date | Mon, 6 Apr 2020 09:37:38 +0000 |
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> > If you want to get an unbiased hash value by specifying an 8 or 16-bit > > value, > > Hello! In exfat we have sequence of 21-bit values (not 8, not 16).
hash_32() generates a less-biased hash, even for 21-bit characters.
The hash of partial_name_hash() for the filename with the following character is ... - 21-bit(surrogate pair): the upper 3-bits of hash tend to be 0. - 16-bit(mostly CJKV): the upper 8-bits of hash tend to be 0. - 8-bit(mostly latin): the upper 16-bits of hash tend to be 0.
I think the more frequently used latin/CJKV characters are more important when considering the hash efficiency of surrogate pair characters.
The hash of partial_name_hash() for 8/16-bit characters is also biased. However, it works well.
Surrogate pair characters are used less frequently, and the hash of partial_name_hash() has less bias than for 8/16 bit characters.
So I think there is no problem with your patch.
> Did you mean hash_32() function from linux/hash.h?
Oops. I forgot '_'. hash_32() is correct.
--- Kohada Tetsuhiro <Kohada.Tetsuhiro@dc.MitsubishiElectric.co.jp>
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