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
9static __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