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/*
* Copyright (c) 2008, 2009, 2010, 2012 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "jhash.h"
#include <string.h>
#include "unaligned.h"
/* This is the public domain lookup3 hash by Bob Jenkins from
* http://burtleburtle.net/bob/c/lookup3.c, modified for style. */
static inline uint32_t
jhash_rot(uint32_t x, int k)
{
return (x << k) | (x >> (32 - k));
}
static inline void
jhash_mix(uint32_t *a, uint32_t *b, uint32_t *c)
{
*a -= *c; *a ^= jhash_rot(*c, 4); *c += *b;
*b -= *a; *b ^= jhash_rot(*a, 6); *a += *c;
*c -= *b; *c ^= jhash_rot(*b, 8); *b += *a;
*a -= *c; *a ^= jhash_rot(*c, 16); *c += *b;
*b -= *a; *b ^= jhash_rot(*a, 19); *a += *c;
*c -= *b; *c ^= jhash_rot(*b, 4); *b += *a;
}
static inline void
jhash_final(uint32_t *a, uint32_t *b, uint32_t *c)
{
*c ^= *b; *c -= jhash_rot(*b, 14);
*a ^= *c; *a -= jhash_rot(*c, 11);
*b ^= *a; *b -= jhash_rot(*a, 25);
*c ^= *b; *c -= jhash_rot(*b, 16);
*a ^= *c; *a -= jhash_rot(*c, 4);
*b ^= *a; *b -= jhash_rot(*a, 14);
*c ^= *b; *c -= jhash_rot(*b, 24);
}
/* Returns the Jenkins hash of the 'n' 32-bit words at 'p', starting from
* 'basis'. 'p' must be properly aligned.
*
* Use hash_words() instead, unless you're computing a hash function whose
* value is exposed "on the wire" so we don't want to change it. */
uint32_t
jhash_words(const uint32_t *p, size_t n, uint32_t basis)
{
uint32_t a, b, c;
a = b = c = 0xdeadbeef + (((uint32_t) n) << 2) + basis;
while (n > 3) {
a += p[0];
b += p[1];
c += p[2];
jhash_mix(&a, &b, &c);
n -= 3;
p += 3;
}
switch (n) {
case 3:
c += p[2];
/* fall through */
case 2:
b += p[1];
/* fall through */
case 1:
a += p[0];
jhash_final(&a, &b, &c);
/* fall through */
case 0:
break;
}
return c;
}
/* Returns the Jenkins hash of the 'n' bytes at 'p', starting from 'basis'.
*
* Use hash_bytes() instead, unless you're computing a hash function whose
* value is exposed "on the wire" so we don't want to change it. */
uint32_t
jhash_bytes(const void *p_, size_t n, uint32_t basis)
{
const uint32_t *p = p_;
uint32_t a, b, c;
a = b = c = 0xdeadbeef + n + basis;
while (n >= 12) {
a += get_unaligned_u32(p);
b += get_unaligned_u32(p + 1);
c += get_unaligned_u32(p + 2);
jhash_mix(&a, &b, &c);
n -= 12;
p += 3;
}
if (n) {
uint32_t tmp[3];
tmp[0] = tmp[1] = tmp[2] = 0;
memcpy(tmp, p, n);
a += tmp[0];
b += tmp[1];
c += tmp[2];
jhash_final(&a, &b, &c);
}
return c;
}
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