2 * Copyright (c) 2008, 2009, 2010, 2012, 2013 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 static inline uint32_t
30 hash_rot(uint32_t x, int k)
32 return (x << k) | (x >> (32 - k));
35 uint32_t hash_words(const uint32_t data[], size_t n_words, uint32_t basis);
36 uint32_t hash_bytes(const void *, size_t n_bytes, uint32_t basis);
38 static inline uint32_t hash_int(uint32_t x, uint32_t basis);
39 static inline uint32_t hash_2words(uint32_t, uint32_t);
40 uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
42 static inline uint32_t hash_boolean(bool x, uint32_t basis);
43 uint32_t hash_double(double, uint32_t basis);
45 static inline uint32_t hash_pointer(const void *, uint32_t basis);
46 static inline uint32_t hash_string(const char *, uint32_t basis);
48 /* Murmurhash by Austin Appleby,
49 * from http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp.
51 * The upstream license there says:
53 * // MurmurHash3 was written by Austin Appleby, and is placed in the public
54 * // domain. The author hereby disclaims copyright to this source code.
56 * See hash_words() for sample usage. */
58 static inline uint32_t mhash_add__(uint32_t hash, uint32_t data)
61 data = hash_rot(data, 15);
66 static inline uint32_t mhash_add(uint32_t hash, uint32_t data)
68 hash = mhash_add__(hash, data);
69 hash = hash_rot(hash, 13);
70 return hash * 5 + 0xe6546b64;
73 static inline uint32_t mhash_finish(uint32_t hash, size_t n_bytes)
84 static inline uint32_t hash_string(const char *s, uint32_t basis)
86 return hash_bytes(s, strlen(s), basis);
89 static inline uint32_t hash_int(uint32_t x, uint32_t basis)
91 return hash_2words(x, basis);
94 /* An attempt at a useful 1-bit hash function. Has not been analyzed for
96 static inline uint32_t hash_boolean(bool x, uint32_t basis)
98 const uint32_t P0 = 0xc2b73583; /* This is hash_int(1, 0). */
99 const uint32_t P1 = 0xe90f1258; /* This is hash_int(2, 0). */
100 return (x ? P0 : P1) ^ hash_rot(basis, 1);
103 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
105 /* Often pointers are hashed simply by casting to integer type, but that
106 * has pitfalls since the lower bits of a pointer are often all 0 for
107 * alignment reasons. It's hard to guess where the entropy really is, so
108 * we give up here and just use a high-quality hash function.
110 * The double cast suppresses a warning on 64-bit systems about casting to
111 * an integer to different size. That's OK in this case, since most of the
112 * entropy in the pointer is almost certainly in the lower 32 bits. */
113 return hash_int((uint32_t) (uintptr_t) p, basis);
116 static inline uint32_t hash_2words(uint32_t x, uint32_t y)
118 return mhash_finish(mhash_add(mhash_add(x, 0), y), 4);