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11395686 JDB |
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 | } |