56 lines
1.3 KiB
C
56 lines
1.3 KiB
C
|
/* SPDX-License-Identifier: LGPL-2.1
|
||
|
|
*
|
||
|
|
* Based on Paul Hsieh's (LGPG 2.1) hash function
|
||
|
|
* From: http://www.azillionmonkeys.com/qed/hash.html
|
||
|
|
*/
|
||
|
|
|
||
|
|
#define get16bits(d) (*((const __u16 *) (d)))
|
||
|
|
|
||
|
|
static __always_inline
|
||
|
|
__u32 SuperFastHash (const char *data, int len, __u32 initval) {
|
||
|
|
__u32 hash = initval;
|
||
|
|
__u32 tmp;
|
||
|
|
int rem;
|
||
|
|
|
||
|
|
if (len <= 0 || data == NULL) return 0;
|
||
|
|
|
||
|
|
rem = len & 3;
|
||
|
|
len >>= 2;
|
||
|
|
|
||
|
|
/* Main loop */
|
||
|
|
#pragma clang loop unroll(full)
|
||
|
|
for (;len > 0; len--) {
|
||
|
|
hash += get16bits (data);
|
||
|
|
tmp = (get16bits (data+2) << 11) ^ hash;
|
||
|
|
hash = (hash << 16) ^ tmp;
|
||
|
|
data += 2*sizeof (__u16);
|
||
|
|
hash += hash >> 11;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Handle end cases */
|
||
|
|
switch (rem) {
|
||
|
|
case 3: hash += get16bits (data);
|
||
|
|
hash ^= hash << 16;
|
||
|
|
hash ^= ((signed char)data[sizeof (__u16)]) << 18;
|
||
|
|
hash += hash >> 11;
|
||
|
|
break;
|
||
|
|
case 2: hash += get16bits (data);
|
||
|
|
hash ^= hash << 11;
|
||
|
|
hash += hash >> 17;
|
||
|
|
break;
|
||
|
|
case 1: hash += (signed char)*data;
|
||
|
|
hash ^= hash << 10;
|
||
|
|
hash += hash >> 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Force "avalanching" of final 127 bits */
|
||
|
|
hash ^= hash << 3;
|
||
|
|
hash += hash >> 5;
|
||
|
|
hash ^= hash << 4;
|
||
|
|
hash += hash >> 17;
|
||
|
|
hash ^= hash << 25;
|
||
|
|
hash += hash >> 6;
|
||
|
|
|
||
|
|
return hash;
|
||
|
|
}
|