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Subject: Re: [PATCH 1/4] exfat: Simplify exfat_utf8_d_hash() for code points
 above U+FFFF
Thread-Topic: Re: [PATCH 1/4] exfat: Simplify exfat_utf8_d_hash() for code
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> I guess it was designed for 8bit types, not for long (64bit types) and
> I'm not sure how effective it is even for 16bit types for which it is
> already used.

In partial_name_hash (), when 8bit value or 16bit value is specified,=20
upper 8-12bits tend to be 0.

> So question is, what should we do for either 21bit number (one Unicode
> code point =3D equivalent of UTF-32) or for sequence of 16bit numbers
> (UTF-16)?

If you want to get an unbiased hash value by specifying an 8 or 16-bit valu=
e,
the hash32() function is a good choice.
ex1: Prepare by hash32 () function.
   hash =3D partial_name_hash (hash32 (val16,32), hash);
ex2: Use the hash32() function directly.
   hash + =3D hash32 (val16,32);

> partial_name_hash(unsigned long c, unsigned long prevhash)
> {
>	return (prevhash + (c << 4) + (c >> 4)) * 11;
> }

Another way may replace partial_name_hash().

	return prevhash + hash32(c,32)