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https://github.com/openvswitch/ovs
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78145f6edb
This patch sacrifices a few bits of hash quality from the 128-bit unique flow identifiers to make the UFIDs RFC4122-conformant as per the version 4 (random) UUID spec. Given that the 128-bit space is already quite large, this should not affect the spread of UFIDs in any meaningful way for hashing. Signed-off-by: Joe Stringer <joestringer@nicira.com> Acked-by: Ben Pfaff <blp@nicira.com>
84 lines
2.7 KiB
C
84 lines
2.7 KiB
C
/* Copyright (c) 2008, 2009, 2010 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 UUID_H
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#define UUID_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 "util.h"
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#define UUID_BIT 128 /* Number of bits in a UUID. */
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#define UUID_OCTET (UUID_BIT / 8) /* Number of bytes in a UUID. */
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/* A Universally Unique IDentifier (UUID) compliant with RFC 4122.
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*
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* Each of the parts is stored in host byte order, but the parts themselves are
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* ordered from left to right. That is, (parts[0] >> 24) is the first 8 bits
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* of the UUID when output in the standard form, and (parts[3] & 0xff) is the
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* final 8 bits. */
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struct uuid {
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uint32_t parts[4];
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};
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BUILD_ASSERT_DECL(sizeof(struct uuid) == UUID_OCTET);
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/* Formats a UUID as a string, in the conventional format.
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*
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* Example:
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* struct uuid uuid = ...;
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* printf("This UUID is "UUID_FMT"\n", UUID_ARGS(&uuid));
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*
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*/
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#define UUID_LEN 36
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#define UUID_FMT "%08x-%04x-%04x-%04x-%04x%08x"
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#define UUID_ARGS(UUID) \
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((unsigned int) ((UUID)->parts[0])), \
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((unsigned int) ((UUID)->parts[1] >> 16)), \
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((unsigned int) ((UUID)->parts[1] & 0xffff)), \
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((unsigned int) ((UUID)->parts[2] >> 16)), \
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((unsigned int) ((UUID)->parts[2] & 0xffff)), \
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((unsigned int) ((UUID)->parts[3]))
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/* Returns a hash value for 'uuid'. This hash value is the same regardless of
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* whether we are running on a 32-bit or 64-bit or big-endian or little-endian
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* architecture. */
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static inline size_t
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uuid_hash(const struct uuid *uuid)
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{
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return uuid->parts[0];
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}
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/* Returns true if 'a == b', false otherwise. */
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static inline bool
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uuid_equals(const struct uuid *a, const struct uuid *b)
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{
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return (a->parts[0] == b->parts[0]
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&& a->parts[1] == b->parts[1]
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&& a->parts[2] == b->parts[2]
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&& a->parts[3] == b->parts[3]);
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}
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void uuid_init(void);
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void uuid_generate(struct uuid *);
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void uuid_zero(struct uuid *);
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bool uuid_is_zero(const struct uuid *);
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int uuid_compare_3way(const struct uuid *, const struct uuid *);
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bool uuid_from_string(struct uuid *, const char *);
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bool uuid_from_string_prefix(struct uuid *, const char *);
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void uuid_set_bits_v4(struct uuid *);
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#endif /* uuid.h */
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