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