1 /* SPDX-License-Identifier: LGPL-2.1
2 *
3 * Based on Paul Hsieh's (LGPG 2.1) hash function
4 * From: http://www.azillionmonkeys.com/qed/hash.html
5 */
6
7 #define get16bits(d) (*((const __u16 *) (d)))
8
9 static __always_inline
10 __u32 SuperFastHash (const char *data, int len, __u32 initval) {
11 __u32 hash = initval;
12 __u32 tmp;
13 int rem;
14
15 if (len <= 0 || data == NULL) return 0;
16
17 rem = len & 3;
18 len >>= 2;
19
20 /* Main loop */
21 #pragma clang loop unroll(full)
22 for (;len > 0; len--) {
23 hash += get16bits (data);
24 tmp = (get16bits (data+2) << 11) ^ hash;
25 hash = (hash << 16) ^ tmp;
26 data += 2*sizeof (__u16);
27 hash += hash >> 11;
28 }
29
30 /* Handle end cases */
31 switch (rem) {
32 case 3: hash += get16bits (data);
33 hash ^= hash << 16;
34 hash ^= ((signed char)data[sizeof (__u16)]) << 18;
35 hash += hash >> 11;
36 break;
37 case 2: hash += get16bits (data);
38 hash ^= hash << 11;
39 hash += hash >> 17;
40 break;
41 case 1: hash += (signed char)*data;
42 hash ^= hash << 10;
43 hash += hash >> 1;
44 }
45
46 /* Force "avalanching" of final 127 bits */
47 hash ^= hash << 3;
48 hash += hash >> 5;
49 hash ^= hash << 4;
50 hash += hash >> 17;
51 hash ^= hash << 25;
52 hash += hash >> 6;
53
54 return hash;
55 }
56
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