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(const uint64_t);
40 static inline uint32_t hash_uint64_basis(const uint64_t x,
41 const uint32_t basis);
42 uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
44 static inline uint32_t hash_boolean(bool x, uint32_t basis);
45 uint32_t hash_double(double, uint32_t basis);
47 static inline uint32_t hash_pointer(const void *, uint32_t basis);
48 static inline uint32_t hash_string(const char *, uint32_t basis);
50 /* Murmurhash by Austin Appleby,
51 * from http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp.
53 * The upstream license there says:
55 * // MurmurHash3 was written by Austin Appleby, and is placed in the public
56 * // domain. The author hereby disclaims copyright to this source code.
58 * See hash_words() for sample usage. */
60 static inline uint32_t mhash_add__(uint32_t hash, uint32_t data)
63 data = hash_rot(data, 15);
68 static inline uint32_t mhash_add(uint32_t hash, uint32_t data)
70 hash = mhash_add__(hash, data);
71 hash = hash_rot(hash, 13);
72 return hash * 5 + 0xe6546b64;
75 static inline uint32_t mhash_finish(uint32_t hash, uint32_t n_bytes)
86 #if !(defined(__SSE4_2__) && defined(__x86_64__))
87 /* Mhash-based implemantation. */
89 static inline uint32_t hash_add(uint32_t hash, uint32_t data)
91 return mhash_add(hash, data);
94 static inline uint32_t hash_finish(uint32_t hash, uint32_t final)
96 return mhash_finish(hash, final);
99 /* Returns the hash of the 'n' 32-bit words at 'p', starting from 'basis'.
100 * 'p' must be properly aligned.
102 * This is inlined for the compiler to have access to the 'n_words', which
103 * in many cases is a constant. */
104 static inline uint32_t
105 hash_words_inline(const uint32_t p[], size_t n_words, uint32_t basis)
111 for (i = 0; i < n_words; i++) {
112 hash = hash_add(hash, p[i]);
114 return hash_finish(hash, n_words * 4);
117 static inline uint32_t
118 hash_words64_inline(const uint64_t p[], size_t n_words, uint64_t basis)
120 return hash_words_inline((uint32_t *)p, n_words * 2,
121 (uint32_t)basis ^ basis >> 32);
124 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
126 /* Often pointers are hashed simply by casting to integer type, but that
127 * has pitfalls since the lower bits of a pointer are often all 0 for
128 * alignment reasons. It's hard to guess where the entropy really is, so
129 * we give up here and just use a high-quality hash function.
131 * The double cast suppresses a warning on 64-bit systems about casting to
132 * an integer to different size. That's OK in this case, since most of the
133 * entropy in the pointer is almost certainly in the lower 32 bits. */
134 return hash_int((uint32_t) (uintptr_t) p, basis);
137 static inline uint32_t hash_2words(uint32_t x, uint32_t y)
139 return hash_finish(hash_add(hash_add(x, 0), y), 8);
142 static inline uint32_t hash_uint64(const uint64_t x)
144 return hash_2words((uint32_t)(x >> 32), (uint32_t)x);
147 static inline uint32_t hash_uint64_basis(const uint64_t x,
148 const uint32_t basis)
150 return hash_3words((uint32_t)(x >> 32), (uint32_t)x, basis);
153 #else /* __SSE4_2__ && __x86_64__ */
154 #include <smmintrin.h>
156 static inline uint32_t hash_add(uint32_t hash, uint32_t data)
158 return _mm_crc32_u32(hash, data);
161 static inline uint32_t hash_finish(uint64_t hash, uint64_t final)
163 /* The finishing multiplier 0x805204f3 has been experimentally
164 * derived to pass the testsuite hash tests. */
165 hash = _mm_crc32_u64(hash, final) * 0x805204f3;
166 return hash ^ (uint32_t)hash >> 16; /* Increase entropy in LSBs. */
169 /* Returns the hash of the 'n' 32-bit words at 'p_', starting from 'basis'.
170 * We access 'p_' as a uint64_t pointer, which is fine for __SSE_4_2__.
172 * This is inlined for the compiler to have access to the 'n_words', which
173 * in many cases is a constant. */
174 static inline uint32_t
175 hash_words_inline(const uint32_t p_[], size_t n_words, uint32_t basis)
177 const uint64_t *p = (const void *)p_;
178 uint64_t hash1 = basis;
180 uint64_t hash3 = n_words;
181 const uint32_t *endp = (const uint32_t *)p + n_words;
182 const uint64_t *limit = p + n_words / 2 - 3;
185 hash1 = _mm_crc32_u64(hash1, p[0]);
186 hash2 = _mm_crc32_u64(hash2, p[1]);
187 hash3 = _mm_crc32_u64(hash3, p[2]);
190 switch (endp - (const uint32_t *)p) {
192 hash1 = _mm_crc32_u32(hash1, *(const uint32_t *)&p[0]);
195 hash1 = _mm_crc32_u64(hash1, p[0]);
198 hash1 = _mm_crc32_u64(hash1, p[0]);
199 hash2 = _mm_crc32_u32(hash2, *(const uint32_t *)&p[1]);
202 hash1 = _mm_crc32_u64(hash1, p[0]);
203 hash2 = _mm_crc32_u64(hash2, p[1]);
206 hash1 = _mm_crc32_u64(hash1, p[0]);
207 hash2 = _mm_crc32_u64(hash2, p[1]);
208 hash3 = _mm_crc32_u32(hash3, *(const uint32_t *)&p[2]);
211 return hash_finish(hash1, hash2 << 32 | hash3);
214 /* A simpler version for 64-bit data.
215 * 'n_words' is the count of 64-bit words, basis is 64 bits. */
216 static inline uint32_t
217 hash_words64_inline(const uint64_t p[], size_t n_words, uint64_t basis)
219 uint64_t hash1 = (uint32_t)basis;
220 uint64_t hash2 = basis >> 32;
221 uint64_t hash3 = n_words;
222 const uint64_t *endp = p + n_words;
223 const uint64_t *limit = endp - 3;
226 hash1 = _mm_crc32_u64(hash1, p[0]);
227 hash2 = _mm_crc32_u64(hash2, p[1]);
228 hash3 = _mm_crc32_u64(hash3, p[2]);
233 hash1 = _mm_crc32_u64(hash1, p[0]);
236 hash1 = _mm_crc32_u64(hash1, p[0]);
237 hash2 = _mm_crc32_u64(hash2, p[1]);
240 return hash_finish(hash1, hash2 << 32 | hash3);
243 static inline uint32_t hash_uint64_basis(const uint64_t x,
244 const uint32_t basis)
246 /* '23' chosen to mix bits enough for the test-hash to pass. */
247 return hash_finish(_mm_crc32_u64(basis, x), 23);
250 static inline uint32_t hash_uint64(const uint64_t x)
252 return hash_uint64_basis(x, 0);
255 static inline uint32_t hash_2words(uint32_t x, uint32_t y)
257 return hash_uint64((uint64_t)y << 32 | x);
260 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
262 return hash_uint64_basis((uint64_t) (uintptr_t) p, basis);
266 uint32_t hash_words__(const uint32_t p[], size_t n_words, uint32_t basis);
267 uint32_t hash_words64__(const uint64_t p[], size_t n_words, uint64_t basis);
269 /* Inline the larger hash functions only when 'n_words' is known to be
270 * compile-time constant. */
272 static inline uint32_t
273 hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
275 if (__builtin_constant_p(n_words)) {
276 return hash_words_inline(p, n_words, basis);
278 return hash_words__(p, n_words, basis);
282 static inline uint32_t
283 hash_words64(const uint64_t p[], size_t n_words, uint64_t basis)
285 if (__builtin_constant_p(n_words)) {
286 return hash_words64_inline(p, n_words, basis);
288 return hash_words64__(p, n_words, basis);
294 static inline uint32_t
295 hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
297 return hash_words__(p, n_words, basis);
300 static inline uint32_t
301 hash_words64(const uint64_t p[], size_t n_words, uint64_t basis)
303 return hash_words64__(p, n_words, basis);
307 static inline uint32_t hash_string(const char *s, uint32_t basis)
309 return hash_bytes(s, strlen(s), basis);
312 static inline uint32_t hash_int(uint32_t x, uint32_t basis)
314 return hash_2words(x, basis);
317 /* An attempt at a useful 1-bit hash function. Has not been analyzed for
319 static inline uint32_t hash_boolean(bool x, uint32_t basis)
321 const uint32_t P0 = 0xc2b73583; /* This is hash_int(1, 0). */
322 const uint32_t P1 = 0xe90f1258; /* This is hash_int(2, 0). */
323 return (x ? P0 : P1) ^ hash_rot(basis, 1);