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hash: Correct implementation of mhash_finish().

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With rotates instead of shifts, the upper and lower 16 bits of the returned
hash are always the same.

I noticed this while working on replacing Jenkins hash by murmurhash,
because some of the database unit tests started failing, e.g. "row
hashing (scalars)".

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>
This commit is contained in:
Ben Pfaff
2012-12-14 13:43:54 -08:00
parent 432fca235c
commit b2a52eedaa
1 changed files with 3 additions and 3 deletions
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6
lib/hash.h
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@@ -152,11 +152,11 @@ static inline uint32_t mhash_add(uint32_t hash, uint32_t data)
static inline uint32_t mhash_finish(uint32_t hash, size_t n)
{
hash ^= n * 4;
hash ^= hash_rot(hash, 16);
hash ^= hash >> 16;
hash *= 0x85ebca6b;
hash ^= hash_rot(hash, 13);
hash ^= hash >> 13;
hash *= 0xc2b2ae35;
hash ^= hash_rot(hash, 16);
hash ^= hash >> 16;
return hash;
}