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Commit 11395686 authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by Daniel Borkmann
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samples/bpf: add Paul Hsieh's (LGPL 2.1) hash function SuperFastHash 



Adjusted function call API to take an initval. This allow the API
user to set the initial value, as a seed. This could also be used for
inputting the previous hash.

Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent eb91e4d4

samples/bpf/hash_func01.h

0 → 100644
+55 −0
Original line number Diff line number Diff line 
/* 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;

}