mirror of
https://github.com/openvswitch/ovs
synced 2025-10-29 15:28:56 +00:00
0a96a21b6e
All of the callers of hash_words() and hash_words64() actually find it easier to pass in the number of bytes instead of the number of 32-bit or 64-bit words. These new functions allow the callers to be a little simpler. Signed-off-by: Ben Pfaff <blp@ovn.org> Acked-by: Jarno Rajahalme <jarno@ovn.org>
362 lines
10 KiB
C
362 lines
10 KiB
C
/*
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* Copyright (c) 2008, 2009, 2010, 2012, 2013, 2014, 2016 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef HASH_H
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#define HASH_H 1
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#include "util.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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static inline uint32_t
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hash_rot(uint32_t x, int k)
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{
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return (x << k) | (x >> (32 - k));
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}
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uint32_t hash_bytes(const void *, size_t n_bytes, uint32_t basis);
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/* The hash input must be a word larger than 128 bits. */
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void hash_bytes128(const void *_, size_t n_bytes, uint32_t basis,
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ovs_u128 *out);
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static inline uint32_t hash_int(uint32_t x, uint32_t basis);
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static inline uint32_t hash_2words(uint32_t, uint32_t);
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static inline uint32_t hash_uint64(const uint64_t);
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static inline uint32_t hash_uint64_basis(const uint64_t x,
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const uint32_t basis);
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uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
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static inline uint32_t hash_boolean(bool x, uint32_t basis);
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uint32_t hash_double(double, uint32_t basis);
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static inline uint32_t hash_pointer(const void *, uint32_t basis);
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static inline uint32_t hash_string(const char *, uint32_t basis);
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/* Murmurhash by Austin Appleby,
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* from http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp.
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*
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* The upstream license there says:
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*
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* // MurmurHash3 was written by Austin Appleby, and is placed in the public
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* // domain. The author hereby disclaims copyright to this source code.
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*
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* See hash_words() for sample usage. */
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static inline uint32_t mhash_add__(uint32_t hash, uint32_t data)
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{
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data *= 0xcc9e2d51;
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data = hash_rot(data, 15);
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data *= 0x1b873593;
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return hash ^ data;
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}
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static inline uint32_t mhash_add(uint32_t hash, uint32_t data)
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{
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hash = mhash_add__(hash, data);
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hash = hash_rot(hash, 13);
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return hash * 5 + 0xe6546b64;
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}
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static inline uint32_t mhash_finish(uint32_t hash)
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{
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hash ^= hash >> 16;
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hash *= 0x85ebca6b;
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hash ^= hash >> 13;
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hash *= 0xc2b2ae35;
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hash ^= hash >> 16;
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return hash;
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}
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#if !(defined(__SSE4_2__) && defined(__x86_64__))
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/* Mhash-based implementation. */
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static inline uint32_t hash_add(uint32_t hash, uint32_t data)
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{
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return mhash_add(hash, data);
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}
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static inline uint32_t hash_add64(uint32_t hash, uint64_t data)
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{
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return hash_add(hash_add(hash, data), data >> 32);
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}
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static inline uint32_t hash_finish(uint32_t hash, uint32_t final)
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{
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return mhash_finish(hash ^ final);
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}
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/* Returns the hash of the 'n' 32-bit words at 'p', starting from 'basis'.
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* 'p' must be properly aligned.
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*
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* This is inlined for the compiler to have access to the 'n_words', which
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* in many cases is a constant. */
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static inline uint32_t
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hash_words_inline(const uint32_t p[], size_t n_words, uint32_t basis)
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{
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uint32_t hash;
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size_t i;
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hash = basis;
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for (i = 0; i < n_words; i++) {
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hash = hash_add(hash, p[i]);
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}
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return hash_finish(hash, n_words * 4);
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}
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static inline uint32_t
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hash_words64_inline(const uint64_t p[], size_t n_words, uint32_t basis)
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{
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uint32_t hash;
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size_t i;
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hash = basis;
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for (i = 0; i < n_words; i++) {
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hash = hash_add64(hash, p[i]);
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}
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return hash_finish(hash, n_words * 8);
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}
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static inline uint32_t hash_pointer(const void *p, uint32_t basis)
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{
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/* Often pointers are hashed simply by casting to integer type, but that
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* has pitfalls since the lower bits of a pointer are often all 0 for
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* alignment reasons. It's hard to guess where the entropy really is, so
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* we give up here and just use a high-quality hash function.
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*
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* The double cast suppresses a warning on 64-bit systems about casting to
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* an integer to different size. That's OK in this case, since most of the
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* entropy in the pointer is almost certainly in the lower 32 bits. */
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return hash_int((uint32_t) (uintptr_t) p, basis);
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}
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static inline uint32_t hash_2words(uint32_t x, uint32_t y)
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{
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return hash_finish(hash_add(hash_add(x, 0), y), 8);
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}
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static inline uint32_t hash_uint64_basis(const uint64_t x,
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const uint32_t basis)
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{
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return hash_finish(hash_add64(basis, x), 8);
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}
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static inline uint32_t hash_uint64(const uint64_t x)
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{
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return hash_uint64_basis(x, 0);
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}
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#else /* __SSE4_2__ && __x86_64__ */
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#include <smmintrin.h>
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static inline uint32_t hash_add(uint32_t hash, uint32_t data)
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{
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return _mm_crc32_u32(hash, data);
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}
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/* Add the halves of 'data' in the memory order. */
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static inline uint32_t hash_add64(uint32_t hash, uint64_t data)
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{
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return _mm_crc32_u64(hash, data);
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}
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static inline uint32_t hash_finish(uint64_t hash, uint64_t final)
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{
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/* The finishing multiplier 0x805204f3 has been experimentally
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* derived to pass the testsuite hash tests. */
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hash = _mm_crc32_u64(hash, final) * 0x805204f3;
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return hash ^ (uint32_t)hash >> 16; /* Increase entropy in LSBs. */
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}
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/* Returns the hash of the 'n' 32-bit words at 'p_', starting from 'basis'.
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* We access 'p_' as a uint64_t pointer, which is fine for __SSE_4_2__.
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*
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* This is inlined for the compiler to have access to the 'n_words', which
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* in many cases is a constant. */
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static inline uint32_t
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hash_words_inline(const uint32_t p_[], size_t n_words, uint32_t basis)
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{
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const uint64_t *p = (const void *)p_;
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uint64_t hash1 = basis;
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uint64_t hash2 = 0;
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uint64_t hash3 = n_words;
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const uint32_t *endp = (const uint32_t *)p + n_words;
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const uint64_t *limit = p + n_words / 2 - 3;
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while (p <= limit) {
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hash1 = _mm_crc32_u64(hash1, p[0]);
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hash2 = _mm_crc32_u64(hash2, p[1]);
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hash3 = _mm_crc32_u64(hash3, p[2]);
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p += 3;
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}
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switch (endp - (const uint32_t *)p) {
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case 1:
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hash1 = _mm_crc32_u32(hash1, *(const uint32_t *)&p[0]);
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break;
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case 2:
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hash1 = _mm_crc32_u64(hash1, p[0]);
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break;
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case 3:
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hash1 = _mm_crc32_u64(hash1, p[0]);
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hash2 = _mm_crc32_u32(hash2, *(const uint32_t *)&p[1]);
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break;
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case 4:
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hash1 = _mm_crc32_u64(hash1, p[0]);
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hash2 = _mm_crc32_u64(hash2, p[1]);
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break;
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case 5:
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hash1 = _mm_crc32_u64(hash1, p[0]);
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hash2 = _mm_crc32_u64(hash2, p[1]);
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hash3 = _mm_crc32_u32(hash3, *(const uint32_t *)&p[2]);
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break;
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}
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return hash_finish(hash1, hash2 << 32 | hash3);
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}
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/* A simpler version for 64-bit data.
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* 'n_words' is the count of 64-bit words, basis is 64 bits. */
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static inline uint32_t
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hash_words64_inline(const uint64_t p[], size_t n_words, uint32_t basis)
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{
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uint64_t hash1 = basis;
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uint64_t hash2 = 0;
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uint64_t hash3 = n_words;
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const uint64_t *endp = p + n_words;
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const uint64_t *limit = endp - 3;
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while (p <= limit) {
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hash1 = _mm_crc32_u64(hash1, p[0]);
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hash2 = _mm_crc32_u64(hash2, p[1]);
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hash3 = _mm_crc32_u64(hash3, p[2]);
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p += 3;
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}
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switch (endp - p) {
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case 1:
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hash1 = _mm_crc32_u64(hash1, p[0]);
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break;
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case 2:
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hash1 = _mm_crc32_u64(hash1, p[0]);
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hash2 = _mm_crc32_u64(hash2, p[1]);
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break;
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}
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return hash_finish(hash1, hash2 << 32 | hash3);
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}
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static inline uint32_t hash_uint64_basis(const uint64_t x,
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const uint32_t basis)
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{
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/* '23' chosen to mix bits enough for the test-hash to pass. */
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return hash_finish(hash_add64(basis, x), 23);
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}
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static inline uint32_t hash_uint64(const uint64_t x)
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{
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return hash_uint64_basis(x, 0);
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}
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static inline uint32_t hash_2words(uint32_t x, uint32_t y)
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{
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return hash_uint64((uint64_t)y << 32 | x);
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}
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static inline uint32_t hash_pointer(const void *p, uint32_t basis)
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{
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return hash_uint64_basis((uint64_t) (uintptr_t) p, basis);
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}
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#endif
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uint32_t hash_words__(const uint32_t p[], size_t n_words, uint32_t basis);
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uint32_t hash_words64__(const uint64_t p[], size_t n_words, uint32_t basis);
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/* Inline the larger hash functions only when 'n_words' is known to be
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* compile-time constant. */
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#if __GNUC__ >= 4
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static inline uint32_t
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hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
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{
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if (__builtin_constant_p(n_words)) {
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return hash_words_inline(p, n_words, basis);
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} else {
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return hash_words__(p, n_words, basis);
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}
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}
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static inline uint32_t
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hash_words64(const uint64_t p[], size_t n_words, uint32_t basis)
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{
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if (__builtin_constant_p(n_words)) {
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return hash_words64_inline(p, n_words, basis);
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} else {
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return hash_words64__(p, n_words, basis);
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}
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}
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#else
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static inline uint32_t
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hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
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{
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return hash_words__(p, n_words, basis);
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}
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static inline uint32_t
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hash_words64(const uint64_t p[], size_t n_words, uint32_t basis)
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{
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return hash_words64__(p, n_words, basis);
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}
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#endif
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static inline uint32_t
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hash_bytes32(const uint32_t p[], size_t n_bytes, uint32_t basis)
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{
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return hash_words(p, n_bytes / 4, basis);
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}
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static inline uint32_t
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hash_bytes64(const uint64_t p[], size_t n_bytes, uint32_t basis)
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{
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return hash_words64(p, n_bytes / 8, basis);
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}
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static inline uint32_t hash_string(const char *s, uint32_t basis)
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{
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return hash_bytes(s, strlen(s), basis);
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}
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static inline uint32_t hash_int(uint32_t x, uint32_t basis)
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{
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return hash_2words(x, basis);
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}
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/* An attempt at a useful 1-bit hash function. Has not been analyzed for
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* quality. */
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static inline uint32_t hash_boolean(bool x, uint32_t basis)
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{
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const uint32_t P0 = 0xc2b73583; /* This is hash_int(1, 0). */
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const uint32_t P1 = 0xe90f1258; /* This is hash_int(2, 0). */
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return (x ? P0 : P1) ^ hash_rot(basis, 1);
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* hash.h */
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