2 * Copyright (c) 2008, 2009, 2010, 2012 Nicira, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
20 #include "unaligned.h"
22 /* This is the public domain lookup3 hash by Bob Jenkins from
23 * http://burtleburtle.net/bob/c/lookup3.c, modified for style. */
25 static inline uint32_t
26 jhash_rot(uint32_t x, int k)
28 return (x << k) | (x >> (32 - k));
32 jhash_mix(uint32_t *a, uint32_t *b, uint32_t *c)
34 *a -= *c; *a ^= jhash_rot(*c, 4); *c += *b;
35 *b -= *a; *b ^= jhash_rot(*a, 6); *a += *c;
36 *c -= *b; *c ^= jhash_rot(*b, 8); *b += *a;
37 *a -= *c; *a ^= jhash_rot(*c, 16); *c += *b;
38 *b -= *a; *b ^= jhash_rot(*a, 19); *a += *c;
39 *c -= *b; *c ^= jhash_rot(*b, 4); *b += *a;
43 jhash_final(uint32_t *a, uint32_t *b, uint32_t *c)
45 *c ^= *b; *c -= jhash_rot(*b, 14);
46 *a ^= *c; *a -= jhash_rot(*c, 11);
47 *b ^= *a; *b -= jhash_rot(*a, 25);
48 *c ^= *b; *c -= jhash_rot(*b, 16);
49 *a ^= *c; *a -= jhash_rot(*c, 4);
50 *b ^= *a; *b -= jhash_rot(*a, 14);
51 *c ^= *b; *c -= jhash_rot(*b, 24);
54 /* Returns the Jenkins hash of the 'n' 32-bit words at 'p', starting from
55 * 'basis'. 'p' must be properly aligned.
57 * Use hash_words() instead, unless you're computing a hash function whose
58 * value is exposed "on the wire" so we don't want to change it. */
60 jhash_words(const uint32_t *p, size_t n, uint32_t basis)
64 a = b = c = 0xdeadbeef + (((uint32_t) n) << 2) + basis;
70 jhash_mix(&a, &b, &c);
84 jhash_final(&a, &b, &c);
92 /* Returns the Jenkins hash of the 'n' bytes at 'p', starting from 'basis'.
94 * Use jhash_bytes() instead, unless you're computing a hash function whose
95 * value is exposed "on the wire" so we don't want to change it. */
97 jhash_bytes(const void *p_, size_t n, uint32_t basis)
99 const uint8_t *p = p_;
102 a = b = c = 0xdeadbeef + n + basis;
105 a += get_unaligned_u32((uint32_t *) p);
106 b += get_unaligned_u32((uint32_t *) (p + 4));
107 c += get_unaligned_u32((uint32_t *) (p + 8));
108 jhash_mix(&a, &b, &c);
116 tmp[0] = tmp[1] = tmp[2] = 0;
121 jhash_final(&a, &b, &c);