/
hash.h
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/
hash.h
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/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright 2021 Authors of KubeArmor */
#ifndef __HASH_H
#define __HASH_H
#include "vmlinux.h"
/*
* This contains Jenkins hash algorithm modified for use in ebpf land:
* jenkins_rot(), jenkins_mix(), jenkins_final() and jenkins_hash()
*
* Inspiration sources:
*
* https://en.wikipedia.org/wiki/Jenkins_hash_function
* http://burtleburtle.net/bob/c/lookup3.c
* https://github.com/tildeleb/hashland/blob/46daf2d89bba924a4269f30949050748548effb1/jenkins/jenkins.go
*/
static inline u32
jenkins_rot(u32 x, u32 k)
{
return (x << k) | (x >> (32 - k));
}
static inline void
jenkins_mix(u32 *ap, u32 *bp, u32 *cp)
{
u32 a = *ap;
u32 b = *bp;
u32 c = *cp;
a -= c;
a ^= jenkins_rot(c, 4);
c += b;
b -= a;
b ^= jenkins_rot(a, 6);
a += c;
c -= b;
c ^= jenkins_rot(b, 8);
b += a;
a -= c;
a ^= jenkins_rot(c, 16);
c += b;
b -= a;
b ^= jenkins_rot(a, 19);
a += c;
c -= b;
c ^= jenkins_rot(b, 4);
b += a;
*ap = a;
*bp = b;
*cp = c;
}
static inline void
jenkins_final(u32 a, u32 b, u32 *cp)
{
u32 c = *cp;
c ^= b;
c -= jenkins_rot(b, 14);
a ^= c;
a -= jenkins_rot(c, 11);
b ^= a;
b -= jenkins_rot(a, 25);
c ^= b;
c -= jenkins_rot(b, 16);
a ^= c;
a -= jenkins_rot(c, 4);
b ^= a;
b -= jenkins_rot(a, 14);
c ^= b;
c -= jenkins_rot(b, 24);
*cp = c;
}
static u32
jenkins_hash(const char *key, size_t length, u32 initval)
{
const u8 *k = (const u8 *) key;
u32 a, b, c;
a = 0xdeadbeef + ((u32) length) + initval;
b = a;
c = a;
while (length > 12) {
a += *((u32 *) &k[0]);
b += *((u32 *) &k[4]);
c += *((u32 *) &k[8]);
jenkins_mix(&a, &b, &c);
length -= 12;
k += 12;
}
switch (length) {
case 12:
a += *((u32 *) &k[0]);
b += *((u32 *) &k[4]);
c += *((u32 *) &k[8]);
break;
case 11:
c += ((u32) k[10]) << 16;
/* fallthrough */
case 10:
c += ((u32) k[9]) << 8;
/* fallthrough */
case 9:
c += ((u32) k[8]);
/* fallthrough */
case 8:
a += *((u32 *) &k[0]);
b += *((u32 *) &k[4]);
break;
case 7:
b += ((u32) k[6]) << 16;
/* fallthrough */
case 6:
b += ((u32) k[5]) << 8;
/* fallthrough */
case 5:
b += ((u32) k[4]);
/* fallthrough */
case 4:
a += *((u32 *) &k[0]);
break;
case 3:
a += ((u32) k[2]) << 16;
/* fallthrough */
case 2:
a += ((u32) k[1]) << 8;
/* fallthrough */
case 1:
a += ((u32) k[0]);
break;
case 0:
return c;
}
jenkins_final(a, b, &c);
return c;
}
#endif /* __HASH_H */