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changed moo_hash_bytes() to use fnv-1 hash

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hyunghwan.chung 2019-03-01 09:13:34 +00:00
parent c9e2a9c68f
commit 5737422376
1 changed files with 30 additions and 3 deletions
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33
moo/lib/utl.c
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@ -216,18 +216,45 @@ moo_uint128_t moo_hton128 (moo_uint128_t x)
* utobcstr -> ucstr to bcstr * utobcstr -> ucstr to bcstr
*/ */
#if MOO_SIZEOF_OOW_T == 4
# define FNV_MAGIC_INIT (0x811c9dc5)
# define FNV_MAGIC_PRIME (0x01000193)
#elif MOO_SIZEOF_OOW_T == 8
# define FNV_MAGIC_INIT (0xCBF29CE484222325)
# define FNV_MAGIC_PRIME (0x100000001B3)
#elif MOO_SIZEOF_OOW_T == 16
# define FNV_MAGIC_INIT (0x6C62272E07BB014262B821756295C58D)
# define FNV_MAGIC_PRIME (0x1000000000000000000013B)
#endif
moo_oow_t moo_hash_bytes (const moo_oob_t* ptr, moo_oow_t len) moo_oow_t moo_hash_bytes (const moo_oob_t* ptr, moo_oow_t len)
{ {
moo_oow_t h = 0; moo_oow_t h;
const moo_uint8_t* bp, * be; const moo_uint8_t* bp, * be;
bp = ptr; be = bp + len; bp = ptr; be = bp + len;
/* this hash doesn't produce good distribution */ /* this hash doesn't produce good distribution */
/*while (bp < be) h = h * 31 + *bp++; */ /*
h = 0
while (bp < be) h = h * 31 + *bp++;
*/
/* SDBM hash is know to produce good overall distribution for many different data sets */ #if defined(FNV_MAGIC_INIT)
/* FNV-1 hash */
h = FNV_MAGIC_INIT;
while (bp < be)
{
h ^= (moo_oow_t)(*bp++);
h *= FNV_MAGIC_PRIME;
}
#else
/* SDBM hash is known to produce good overall distribution
* for many different data sets */
h = 0;
while (bp < be) h = (h << 6) + (h << 16) - h + *bp++; while (bp < be) h = (h << 6) + (h << 16) - h + *bp++;
#endif
/* constrain the hash value to be representable in a small integer /* constrain the hash value to be representable in a small integer
* for convenience sake */ * for convenience sake */