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_bytes(const void *, size_t n_bytes, uint32_t basis);
37 static inline uint32_t hash_int(uint32_t x, uint32_t basis);
38 static inline uint32_t hash_2words(uint32_t, uint32_t);
39 static inline uint32_t hash_uint64(uint64_t);
40 static inline uint32_t hash_uint64_basis(uint64_t x, uint32_t basis);
41 uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
43 static inline uint32_t hash_boolean(bool x, uint32_t basis);
44 uint32_t hash_double(double, uint32_t basis);
46 static inline uint32_t hash_pointer(const void *, uint32_t basis);
47 static inline uint32_t hash_string(const char *, uint32_t basis);
49 /* Murmurhash by Austin Appleby,
50 * from http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp.
52 * The upstream license there says:
54 * // MurmurHash3 was written by Austin Appleby, and is placed in the public
55 * // domain. The author hereby disclaims copyright to this source code.
57 * See hash_words() for sample usage. */
59 static inline uint32_t mhash_add__(uint32_t hash, uint32_t data)
62 data = hash_rot(data, 15);
67 static inline uint32_t mhash_add(uint32_t hash, uint32_t data)
69 hash = mhash_add__(hash, data);
70 hash = hash_rot(hash, 13);
71 return hash * 5 + 0xe6546b64;
74 static inline uint32_t mhash_finish(uint32_t hash, uint32_t n_bytes)
85 #if !(defined(__SSE4_2__) && defined(__x86_64__))
86 /* Mhash-based implemantation. */
88 static inline uint32_t hash_add(uint32_t hash, uint32_t data)
90 return mhash_add(hash, data);
93 static inline uint32_t hash_finish(uint32_t hash, uint32_t final)
95 return mhash_finish(hash, final);
98 /* Returns the hash of the 'n' 32-bit words at 'p', starting from 'basis'.
99 * 'p' must be properly aligned.
101 * This is inlined for the compiler to have access to the 'n_words', which
102 * in many cases is a constant. */
103 static inline uint32_t
104 hash_words_inline(const uint32_t p[], size_t n_words, uint32_t basis)
110 for (i = 0; i < n_words; i++) {
111 hash = hash_add(hash, p[i]);
113 return hash_finish(hash, n_words * 4);
116 static inline uint32_t
117 hash_words64_inline(const uint64_t p[], size_t n_words, uint64_t basis)
119 return hash_words_inline((uint32_t *)p, n_words * 2,
120 (uint32_t)basis ^ basis >> 32);
123 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
125 /* Often pointers are hashed simply by casting to integer type, but that
126 * has pitfalls since the lower bits of a pointer are often all 0 for
127 * alignment reasons. It's hard to guess where the entropy really is, so
128 * we give up here and just use a high-quality hash function.
130 * The double cast suppresses a warning on 64-bit systems about casting to
131 * an integer to different size. That's OK in this case, since most of the
132 * entropy in the pointer is almost certainly in the lower 32 bits. */
133 return hash_int((uint32_t) (uintptr_t) p, basis);
136 static inline uint32_t hash_2words(uint32_t x, uint32_t y)
138 return hash_finish(hash_add(hash_add(x, 0), y), 8);
141 static inline uint32_t hash_uint64(const uint64_t x)
143 return hash_2words((uint32_t)(x >> 32), (uint32_t)x);
146 static inline uint32_t hash_uint64_basis(const uint64_t x,
147 const uint32_t basis)
149 return hash_3words((uint32_t)(x >> 32), (uint32_t)x, basis);
152 #else /* __SSE4_2__ && __x86_64__ */
153 #include <smmintrin.h>
155 static inline uint32_t hash_add(uint32_t hash, uint32_t data)
157 return _mm_crc32_u32(hash, data);
160 static inline uint32_t hash_finish(uint64_t hash, uint64_t final)
162 /* The finishing multiplier 0x805204f3 has been experimentally
163 * derived to pass the testsuite hash tests. */
164 hash = _mm_crc32_u64(hash, final) * 0x805204f3;
165 return hash ^ (uint32_t)hash >> 16; /* Increase entropy in LSBs. */
168 /* Returns the hash of the 'n' 32-bit words at 'p_', starting from 'basis'.
169 * We access 'p_' as a uint64_t pointer, which is fine for __SSE_4_2__.
171 * This is inlined for the compiler to have access to the 'n_words', which
172 * in many cases is a constant. */
173 static inline uint32_t
174 hash_words_inline(const uint32_t p_[], size_t n_words, uint32_t basis)
176 const uint64_t *p = (const void *)p_;
177 uint64_t hash1 = basis;
179 uint64_t hash3 = n_words;
180 const uint32_t *endp = (const uint32_t *)p + n_words;
181 const uint64_t *limit = p + n_words / 2 - 3;
184 hash1 = _mm_crc32_u64(hash1, p[0]);
185 hash2 = _mm_crc32_u64(hash2, p[1]);
186 hash3 = _mm_crc32_u64(hash3, p[2]);
189 switch (endp - (const uint32_t *)p) {
191 hash1 = _mm_crc32_u32(hash1, *(const uint32_t *)&p[0]);
194 hash1 = _mm_crc32_u64(hash1, p[0]);
197 hash1 = _mm_crc32_u64(hash1, p[0]);
198 hash2 = _mm_crc32_u32(hash2, *(const uint32_t *)&p[1]);
201 hash1 = _mm_crc32_u64(hash1, p[0]);
202 hash2 = _mm_crc32_u64(hash2, p[1]);
205 hash1 = _mm_crc32_u64(hash1, p[0]);
206 hash2 = _mm_crc32_u64(hash2, p[1]);
207 hash3 = _mm_crc32_u32(hash3, *(const uint32_t *)&p[2]);
210 return hash_finish(hash1, hash2 << 32 | hash3);
213 /* A simpler version for 64-bit data.
214 * 'n_words' is the count of 64-bit words, basis is 64 bits. */
215 static inline uint32_t
216 hash_words64_inline(const uint64_t p[], size_t n_words, uint64_t basis)
218 uint64_t hash1 = (uint32_t)basis;
219 uint64_t hash2 = basis >> 32;
220 uint64_t hash3 = n_words;
221 const uint64_t *endp = p + n_words;
222 const uint64_t *limit = endp - 3;
225 hash1 = _mm_crc32_u64(hash1, p[0]);
226 hash2 = _mm_crc32_u64(hash2, p[1]);
227 hash3 = _mm_crc32_u64(hash3, p[2]);
232 hash1 = _mm_crc32_u64(hash1, p[0]);
235 hash1 = _mm_crc32_u64(hash1, p[0]);
236 hash2 = _mm_crc32_u64(hash2, p[1]);
239 return hash_finish(hash1, hash2 << 32 | hash3);
242 static inline uint32_t hash_uint64_basis(const uint64_t x,
243 const uint32_t basis)
245 /* '23' chosen to mix bits enough for the test-hash to pass. */
246 return hash_finish(_mm_crc32_u64(basis, x), 23);
249 static inline uint32_t hash_uint64(const uint64_t x)
251 return hash_uint64_basis(x, 0);
254 static inline uint32_t hash_2words(uint32_t x, uint32_t y)
256 return hash_uint64((uint64_t)y << 32 | x);
259 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
261 return hash_uint64_basis((uint64_t) (uintptr_t) p, basis);
265 uint32_t hash_words__(const uint32_t p[], size_t n_words, uint32_t basis);
266 uint32_t hash_words64__(const uint64_t p[], size_t n_words, uint64_t basis);
268 /* Inline the larger hash functions only when 'n_words' is known to be
269 * compile-time constant. */
271 static inline uint32_t
272 hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
274 if (__builtin_constant_p(n_words)) {
275 return hash_words_inline(p, n_words, basis);
277 return hash_words__(p, n_words, basis);
281 static inline uint32_t
282 hash_words64(const uint64_t p[], size_t n_words, uint64_t basis)
284 if (__builtin_constant_p(n_words)) {
285 return hash_words64_inline(p, n_words, basis);
287 return hash_words64__(p, n_words, basis);
293 static inline uint32_t
294 hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
296 return hash_words__(p, n_words, basis);
299 static inline uint32_t
300 hash_words64(const uint64_t p[], size_t n_words, uint64_t basis)
302 return hash_words64__(p, n_words, basis);
306 static inline uint32_t hash_string(const char *s, uint32_t basis)
308 return hash_bytes(s, strlen(s), basis);
311 static inline uint32_t hash_int(uint32_t x, uint32_t basis)
313 return hash_2words(x, basis);
316 /* An attempt at a useful 1-bit hash function. Has not been analyzed for
318 static inline uint32_t hash_boolean(bool x, uint32_t basis)
320 const uint32_t P0 = 0xc2b73583; /* This is hash_int(1, 0). */
321 const uint32_t P1 = 0xe90f1258; /* This is hash_int(2, 0). */
322 return (x ? P0 : P1) ^ hash_rot(basis, 1);