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.
29 /* This is the public domain lookup3 hash by Bob Jenkins from
30 * http://burtleburtle.net/bob/c/lookup3.c, modified for style. */
32 static inline uint32_t
33 hash_rot(uint32_t x, int k)
35 return (x << k) | (x >> (32 - k));
39 hash_mix(uint32_t *a, uint32_t *b, uint32_t *c)
41 *a -= *c; *a ^= hash_rot(*c, 4); *c += *b;
42 *b -= *a; *b ^= hash_rot(*a, 6); *a += *c;
43 *c -= *b; *c ^= hash_rot(*b, 8); *b += *a;
44 *a -= *c; *a ^= hash_rot(*c, 16); *c += *b;
45 *b -= *a; *b ^= hash_rot(*a, 19); *a += *c;
46 *c -= *b; *c ^= hash_rot(*b, 4); *b += *a;
50 hash_final(uint32_t *a, uint32_t *b, uint32_t *c)
52 *c ^= *b; *c -= hash_rot(*b, 14);
53 *a ^= *c; *a -= hash_rot(*c, 11);
54 *b ^= *a; *b -= hash_rot(*a, 25);
55 *c ^= *b; *c -= hash_rot(*b, 16);
56 *a ^= *c; *a -= hash_rot(*c, 4);
57 *b ^= *a; *b -= hash_rot(*a, 14);
58 *c ^= *b; *c -= hash_rot(*b, 24);
61 uint32_t hash_words(const uint32_t *, size_t n_word, uint32_t basis);
62 uint32_t hash_2words(uint32_t, uint32_t);
63 uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
64 uint32_t hash_bytes(const void *, size_t n_bytes, uint32_t basis);
66 static inline uint32_t hash_string(const char *s, uint32_t basis)
68 return hash_bytes(s, strlen(s), basis);
71 /* This is Bob Jenkins' integer hash from
72 * http://burtleburtle.net/bob/hash/integer.html, modified for style.
74 * This hash is faster than hash_2words(), but it isn't as good when 'basis' is
75 * important. So use this function for speed or hash_2words() for hash
77 static inline uint32_t hash_int(uint32_t x, uint32_t basis)
90 /* An attempt at a useful 1-bit hash function. Has not been analyzed for
92 static inline uint32_t hash_boolean(bool x, uint32_t basis)
94 const uint32_t P0 = 0xc2b73583; /* This is hash_int(1, 0). */
95 const uint32_t P1 = 0xe90f1258; /* This is hash_int(2, 0). */
96 return (x ? P0 : P1) ^ hash_rot(basis, 1);
99 static inline uint32_t hash_double(double x, uint32_t basis)
102 BUILD_ASSERT_DECL(sizeof x == sizeof value);
104 memcpy(value, &x, sizeof value);
105 return hash_3words(value[0], value[1], basis);
108 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
110 /* Often pointers are hashed simply by casting to integer type, but that
111 * has pitfalls since the lower bits of a pointer are often all 0 for
112 * alignment reasons. It's hard to guess where the entropy really is, so
113 * we give up here and just use a high-quality hash function.
115 * The double cast suppresses a warning on 64-bit systems about casting to
116 * an integer to different size. That's OK in this case, since most of the
117 * entropy in the pointer is almost certainly in the lower 32 bits. */
118 return hash_int((uint32_t) (uintptr_t) p, basis);