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56 lines
1.3 KiB
C
56 lines
1.3 KiB
C
/* SPDX-License-Identifier: LGPL-2.1
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*
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* Based on Paul Hsieh's (LGPG 2.1) hash function
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* From: http://www.azillionmonkeys.com/qed/hash.html
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*/
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#define get16bits(d) (*((const __u16 *) (d)))
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static __always_inline
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__u32 SuperFastHash (const char *data, int len, __u32 initval) {
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__u32 hash = initval;
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__u32 tmp;
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int rem;
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if (len <= 0 || data == NULL) return 0;
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rem = len & 3;
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len >>= 2;
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/* Main loop */
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#pragma clang loop unroll(full)
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for (;len > 0; len--) {
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hash += get16bits (data);
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tmp = (get16bits (data+2) << 11) ^ hash;
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hash = (hash << 16) ^ tmp;
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data += 2*sizeof (__u16);
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hash += hash >> 11;
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}
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/* Handle end cases */
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switch (rem) {
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case 3: hash += get16bits (data);
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hash ^= hash << 16;
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hash ^= ((signed char)data[sizeof (__u16)]) << 18;
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hash += hash >> 11;
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break;
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case 2: hash += get16bits (data);
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hash ^= hash << 11;
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hash += hash >> 17;
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break;
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case 1: hash += (signed char)*data;
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hash ^= hash << 10;
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hash += hash >> 1;
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}
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/* Force "avalanching" of final 127 bits */
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hash ^= hash << 3;
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hash += hash >> 5;
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hash ^= hash << 4;
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hash += hash >> 17;
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hash ^= hash << 25;
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hash += hash >> 6;
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return hash;
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}
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