2 * Copyright (c) 2008, 2009, 2010, 2012, 2013, 2014 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);
36 void hash_bytes128(const void *_, size_t n_bytes, uint32_t basis,
39 static inline uint32_t hash_int(uint32_t x, uint32_t basis);
40 static inline uint32_t hash_2words(uint32_t, uint32_t);
41 static inline uint32_t hash_uint64(const uint64_t);
42 static inline uint32_t hash_uint64_basis(const uint64_t x,
43 const uint32_t basis);
44 uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
46 static inline uint32_t hash_boolean(bool x, uint32_t basis);
47 uint32_t hash_double(double, uint32_t basis);
49 static inline uint32_t hash_pointer(const void *, uint32_t basis);
50 static inline uint32_t hash_string(const char *, uint32_t basis);
52 /* Murmurhash by Austin Appleby,
53 * from http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp.
55 * The upstream license there says:
57 * // MurmurHash3 was written by Austin Appleby, and is placed in the public
58 * // domain. The author hereby disclaims copyright to this source code.
60 * See hash_words() for sample usage. */
62 static inline uint32_t mhash_add__(uint32_t hash, uint32_t data)
65 data = hash_rot(data, 15);
70 static inline uint32_t mhash_add(uint32_t hash, uint32_t data)
72 hash = mhash_add__(hash, data);
73 hash = hash_rot(hash, 13);
74 return hash * 5 + 0xe6546b64;
77 static inline uint32_t mhash_finish(uint32_t hash)
87 #if !(defined(__SSE4_2__) && defined(__x86_64__))
88 /* Mhash-based implementation. */
90 static inline uint32_t hash_add(uint32_t hash, uint32_t data)
92 return mhash_add(hash, data);
95 static inline uint32_t hash_add64(uint32_t hash, uint64_t data)
97 return hash_add(hash_add(hash, data), data >> 32);
100 static inline uint32_t hash_finish(uint32_t hash, uint32_t final)
102 return mhash_finish(hash ^ final);
105 /* Returns the hash of the 'n' 32-bit words at 'p', starting from 'basis'.
106 * 'p' must be properly aligned.
108 * This is inlined for the compiler to have access to the 'n_words', which
109 * in many cases is a constant. */
110 static inline uint32_t
111 hash_words_inline(const uint32_t p[], size_t n_words, uint32_t basis)
117 for (i = 0; i < n_words; i++) {
118 hash = hash_add(hash, p[i]);
120 return hash_finish(hash, n_words * 4);
123 static inline uint32_t
124 hash_words64_inline(const uint64_t p[], size_t n_words, uint32_t basis)
130 for (i = 0; i < n_words; i++) {
131 hash = hash_add64(hash, p[i]);
133 return hash_finish(hash, n_words * 8);
136 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
138 /* Often pointers are hashed simply by casting to integer type, but that
139 * has pitfalls since the lower bits of a pointer are often all 0 for
140 * alignment reasons. It's hard to guess where the entropy really is, so
141 * we give up here and just use a high-quality hash function.
143 * The double cast suppresses a warning on 64-bit systems about casting to
144 * an integer to different size. That's OK in this case, since most of the
145 * entropy in the pointer is almost certainly in the lower 32 bits. */
146 return hash_int((uint32_t) (uintptr_t) p, basis);
149 static inline uint32_t hash_2words(uint32_t x, uint32_t y)
151 return hash_finish(hash_add(hash_add(x, 0), y), 8);
154 static inline uint32_t hash_uint64_basis(const uint64_t x,
155 const uint32_t basis)
157 return hash_finish(hash_add64(basis, x), 8);
160 static inline uint32_t hash_uint64(const uint64_t x)
162 return hash_uint64_basis(x, 0);
165 #else /* __SSE4_2__ && __x86_64__ */
166 #include <smmintrin.h>
168 static inline uint32_t hash_add(uint32_t hash, uint32_t data)
170 return _mm_crc32_u32(hash, data);
173 /* Add the halves of 'data' in the memory order. */
174 static inline uint32_t hash_add64(uint32_t hash, uint64_t data)
176 return _mm_crc32_u64(hash, data);
179 static inline uint32_t hash_finish(uint64_t hash, uint64_t final)
181 /* The finishing multiplier 0x805204f3 has been experimentally
182 * derived to pass the testsuite hash tests. */
183 hash = _mm_crc32_u64(hash, final) * 0x805204f3;
184 return hash ^ (uint32_t)hash >> 16; /* Increase entropy in LSBs. */
187 /* Returns the hash of the 'n' 32-bit words at 'p_', starting from 'basis'.
188 * We access 'p_' as a uint64_t pointer, which is fine for __SSE_4_2__.
190 * This is inlined for the compiler to have access to the 'n_words', which
191 * in many cases is a constant. */
192 static inline uint32_t
193 hash_words_inline(const uint32_t p_[], size_t n_words, uint32_t basis)
195 const uint64_t *p = (const void *)p_;
196 uint64_t hash1 = basis;
198 uint64_t hash3 = n_words;
199 const uint32_t *endp = (const uint32_t *)p + n_words;
200 const uint64_t *limit = p + n_words / 2 - 3;
203 hash1 = _mm_crc32_u64(hash1, p[0]);
204 hash2 = _mm_crc32_u64(hash2, p[1]);
205 hash3 = _mm_crc32_u64(hash3, p[2]);
208 switch (endp - (const uint32_t *)p) {
210 hash1 = _mm_crc32_u32(hash1, *(const uint32_t *)&p[0]);
213 hash1 = _mm_crc32_u64(hash1, p[0]);
216 hash1 = _mm_crc32_u64(hash1, p[0]);
217 hash2 = _mm_crc32_u32(hash2, *(const uint32_t *)&p[1]);
220 hash1 = _mm_crc32_u64(hash1, p[0]);
221 hash2 = _mm_crc32_u64(hash2, p[1]);
224 hash1 = _mm_crc32_u64(hash1, p[0]);
225 hash2 = _mm_crc32_u64(hash2, p[1]);
226 hash3 = _mm_crc32_u32(hash3, *(const uint32_t *)&p[2]);
229 return hash_finish(hash1, hash2 << 32 | hash3);
232 /* A simpler version for 64-bit data.
233 * 'n_words' is the count of 64-bit words, basis is 64 bits. */
234 static inline uint32_t
235 hash_words64_inline(const uint64_t p[], size_t n_words, uint32_t basis)
237 uint64_t hash1 = basis;
239 uint64_t hash3 = n_words;
240 const uint64_t *endp = p + n_words;
241 const uint64_t *limit = endp - 3;
244 hash1 = _mm_crc32_u64(hash1, p[0]);
245 hash2 = _mm_crc32_u64(hash2, p[1]);
246 hash3 = _mm_crc32_u64(hash3, p[2]);
251 hash1 = _mm_crc32_u64(hash1, p[0]);
254 hash1 = _mm_crc32_u64(hash1, p[0]);
255 hash2 = _mm_crc32_u64(hash2, p[1]);
258 return hash_finish(hash1, hash2 << 32 | hash3);
261 static inline uint32_t hash_uint64_basis(const uint64_t x,
262 const uint32_t basis)
264 /* '23' chosen to mix bits enough for the test-hash to pass. */
265 return hash_finish(hash_add64(basis, x), 23);
268 static inline uint32_t hash_uint64(const uint64_t x)
270 return hash_uint64_basis(x, 0);
273 static inline uint32_t hash_2words(uint32_t x, uint32_t y)
275 return hash_uint64((uint64_t)y << 32 | x);
278 static inline uint32_t hash_pointer(const void *p, uint32_t basis)
280 return hash_uint64_basis((uint64_t) (uintptr_t) p, basis);
284 uint32_t hash_words__(const uint32_t p[], size_t n_words, uint32_t basis);
285 uint32_t hash_words64__(const uint64_t p[], size_t n_words, uint32_t basis);
287 /* Inline the larger hash functions only when 'n_words' is known to be
288 * compile-time constant. */
290 static inline uint32_t
291 hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
293 if (__builtin_constant_p(n_words)) {
294 return hash_words_inline(p, n_words, basis);
296 return hash_words__(p, n_words, basis);
300 static inline uint32_t
301 hash_words64(const uint64_t p[], size_t n_words, uint32_t basis)
303 if (__builtin_constant_p(n_words)) {
304 return hash_words64_inline(p, n_words, basis);
306 return hash_words64__(p, n_words, basis);
312 static inline uint32_t
313 hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
315 return hash_words__(p, n_words, basis);
318 static inline uint32_t
319 hash_words64(const uint64_t p[], size_t n_words, uint32_t basis)
321 return hash_words64__(p, n_words, basis);
325 static inline uint32_t hash_string(const char *s, uint32_t basis)
327 return hash_bytes(s, strlen(s), basis);
330 static inline uint32_t hash_int(uint32_t x, uint32_t basis)
332 return hash_2words(x, basis);
335 /* An attempt at a useful 1-bit hash function. Has not been analyzed for
337 static inline uint32_t hash_boolean(bool x, uint32_t basis)
339 const uint32_t P0 = 0xc2b73583; /* This is hash_int(1, 0). */
340 const uint32_t P1 = 0xe90f1258; /* This is hash_int(2, 0). */
341 return (x ? P0 : P1) ^ hash_rot(basis, 1);