/* SPDX-License-Identifier: LGPL-2.1
 *
 * Based on Paul Hsieh's (LGPG 2.1) hash function
 * From: http://www.azillionmonkeys.com/qed/hash.html
 */

#define get16bits(d) (*((const __u16 *) (d)))

static __always_inline
__u32 SuperFastHash (const char *data, int len, __u32 initval) {
        __u32 hash = initval;
        __u32 tmp;
        int rem;

        if (len <= 0 || data == NULL) return 0;

        rem = len & 3;
        len >>= 2;

        /* Main loop */
#pragma clang loop unroll(full)
        for (;len > 0; len--) {
                hash  += get16bits (data);
                tmp    = (get16bits (data+2) << 11) ^ hash;
                hash   = (hash << 16) ^ tmp;
                data  += 2*sizeof (__u16);
                hash  += hash >> 11;
        }

        /* Handle end cases */
        switch (rem) {
        case 3: hash += get16bits (data);
                hash ^= hash << 16;
                hash ^= ((signed char)data[sizeof (__u16)]) << 18;
                hash += hash >> 11;
                break;
        case 2: hash += get16bits (data);
                hash ^= hash << 11;
                hash += hash >> 17;
                break;
        case 1: hash += (signed char)*data;
                hash ^= hash << 10;
                hash += hash >> 1;
        }

        /* Force "avalanching" of final 127 bits */
        hash ^= hash << 3;
        hash += hash >> 5;
        hash ^= hash << 4;
        hash += hash >> 17;
        hash ^= hash << 25;
        hash += hash >> 6;

        return hash;
}