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| 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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