mirror of
https://github.com/openvswitch/ovs
synced 2025-10-19 14:37:21 +00:00
e0edde6fee
Replaced all instances of Nicira Networks(, Inc) to Nicira, Inc. Feature #10593 Signed-off-by: Raju Subramanian <rsubramanian@nicira.com> Signed-off-by: Ben Pfaff <blp@nicira.com>
126 lines
3.8 KiB
C
126 lines
3.8 KiB
C
/*
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* Copyright (c) 2008, 2009, 2010, 2012 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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/* This is the public domain lookup3 hash by Bob Jenkins from
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* http://burtleburtle.net/bob/c/lookup3.c, modified for style. */
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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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static inline void
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hash_mix(uint32_t *a, uint32_t *b, uint32_t *c)
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{
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*a -= *c; *a ^= hash_rot(*c, 4); *c += *b;
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*b -= *a; *b ^= hash_rot(*a, 6); *a += *c;
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*c -= *b; *c ^= hash_rot(*b, 8); *b += *a;
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*a -= *c; *a ^= hash_rot(*c, 16); *c += *b;
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*b -= *a; *b ^= hash_rot(*a, 19); *a += *c;
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*c -= *b; *c ^= hash_rot(*b, 4); *b += *a;
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}
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static inline void
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hash_final(uint32_t *a, uint32_t *b, uint32_t *c)
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{
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*c ^= *b; *c -= hash_rot(*b, 14);
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*a ^= *c; *a -= hash_rot(*c, 11);
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*b ^= *a; *b -= hash_rot(*a, 25);
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*c ^= *b; *c -= hash_rot(*b, 16);
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*a ^= *c; *a -= hash_rot(*c, 4);
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*b ^= *a; *b -= hash_rot(*a, 14);
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*c ^= *b; *c -= hash_rot(*b, 24);
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}
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uint32_t hash_words(const uint32_t *, size_t n_word, uint32_t basis);
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uint32_t hash_2words(uint32_t, uint32_t);
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uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
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uint32_t hash_bytes(const void *, size_t n_bytes, uint32_t basis);
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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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/* This is Bob Jenkins' integer hash from
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* http://burtleburtle.net/bob/hash/integer.html, modified for style.
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*
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* This hash is faster than hash_2words(), but it isn't as good when 'basis' is
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* important. So use this function for speed or hash_2words() for hash
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* quality. */
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static inline uint32_t hash_int(uint32_t x, uint32_t basis)
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{
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x -= x << 6;
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x ^= x >> 17;
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x -= x << 9;
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x ^= x << 4;
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x += basis;
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x -= x << 3;
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x ^= x << 10;
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x ^= x >> 15;
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return x;
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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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static inline uint32_t hash_double(double x, uint32_t basis)
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{
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uint32_t value[2];
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BUILD_ASSERT_DECL(sizeof x == sizeof value);
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memcpy(value, &x, sizeof value);
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return hash_3words(value[0], value[1], basis);
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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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#ifdef __cplusplus
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}
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#endif
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#endif /* hash.h */
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