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/*
* Copyright (c) 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef HINDEX_H
#define HINDEX_H 1
/* Hashed multimap.
*
* hindex is a hash table data structure that gracefully handles duplicates.
* With a high-quality hash function, insertion, deletion, and search are O(1)
* expected time, regardless of the number of duplicates for a given key. */
#include <stdbool.h>
#include <stdlib.h>
#include "util.h"
/* A hash index node, to embed inside the data structure being indexed.
*
* Nodes are linked together like this (the boxes are labeled with hash
* values):
*
* +--------+ d +--------+ d +--------+ d
* bucket---> | 6 |---->| 20 |---->| 15 |---->null
* +-|------+ +-|------+ +-|------+
* | ^ | | ^
* s| |d |s s| |d
* V | V V |
* +------|-+ null +------|-+
* | 6 | | 15 |
* +-|------+ +-|------+
* | ^ |
* s| |d s|
* V | V
* +------|-+ null
* | 6 |
* +-|------+
* |
* s|
* V
* null
*
* The basic usage is:
*
* - To visit the unique hash values in the hindex, follow the 'd'
* ("different") pointers starting from each bucket. The nodes visited
* this way are called "head" nodes, because they are at the head of the
* vertical chains.
*
* - To visit the nodes with hash value H, follow the 'd' pointers in the
* appropriate bucket until you find one with hash H, then follow the 's'
* ("same") pointers until you hit a null pointer. The non-head nodes
* visited this way are called "body" nodes.
*
* - The 'd' pointers in body nodes point back to the previous body node
* or, for the first body node, to the head node. (This makes it
* possible to remove a body node without traversing all the way downward
* from the head).
*/
struct hindex_node {
/* Hash value. */
size_t hash;
/* In a head node, the next head node (with a hash different from this
* node), or NULL if this is the last node in this bucket.
*
* In a body node, the previous head or body node (with the same hash as
* this node). Never null. */
struct hindex_node *d;
/* In a head or a body node, the next body node with the same hash as this
* node. NULL if this is the last node with this hash. */
struct hindex_node *s;
};
/* A hash index. */
struct hindex {
struct hindex_node **buckets; /* Must point to 'one' iff 'mask' == 0. */
struct hindex_node *one;
size_t mask; /* 0 or more lowest-order bits set, others cleared. */
size_t n_unique; /* Number of unique hashes (the number of head nodes). */
};
/* Initializer for an empty hash index. */
#define HINDEX_INITIALIZER(HINDEX) \
{ (struct hindex_node **const) &(HINDEX)->one, NULL, 0, 0 }
/* Initialization. */
void hindex_init(struct hindex *);
void hindex_destroy(struct hindex *);
void hindex_clear(struct hindex *);
void hindex_swap(struct hindex *a, struct hindex *b);
void hindex_moved(struct hindex *hindex);
static inline bool hindex_is_empty(const struct hindex *);
/* Adjusting capacity. */
void hindex_expand(struct hindex *);
void hindex_shrink(struct hindex *);
void hindex_reserve(struct hindex *, size_t capacity);
/* Insertion and deletion. */
void hindex_insert_fast(struct hindex *, struct hindex_node *, size_t hash);
void hindex_insert(struct hindex *, struct hindex_node *, size_t hash);
void hindex_remove(struct hindex *, struct hindex_node *);
/* Search.
*
* HINDEX_FOR_EACH_WITH_HASH iterates NODE over all of the nodes in HINDEX that
* have hash value equal to HASH. MEMBER must be the name of the 'struct
* hindex_node' member within NODE.
*
* The loop should not change NODE to point to a different node or insert or
* delete nodes in HINDEX (unless it "break"s out of the loop to terminate
* iteration).
*
* Evaluates HASH only once.
*/
#define HINDEX_FOR_EACH_WITH_HASH(NODE, MEMBER, HASH, HINDEX) \
for (ASSIGN_CONTAINER(NODE, hindex_node_with_hash(HINDEX, HASH), MEMBER); \
NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER); \
ASSIGN_CONTAINER(NODE, (NODE)->MEMBER.s, MEMBER))
/* Returns the head node in 'hindex' with the given 'hash', or a null pointer
* if no nodes have that hash value. */
static inline struct hindex_node *
hindex_node_with_hash(const struct hindex *hindex, size_t hash)
{
struct hindex_node *node = hindex->buckets[hash & hindex->mask];
while (node && node->hash != hash) {
node = node->d;
}
return node;
}
/* Iteration. */
/* Iterates through every node in HINDEX. */
#define HINDEX_FOR_EACH(NODE, MEMBER, HINDEX) \
for (ASSIGN_CONTAINER(NODE, hindex_first(HINDEX), MEMBER); \
NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER); \
ASSIGN_CONTAINER(NODE, hindex_next(HINDEX, &(NODE)->MEMBER), MEMBER))
/* Safe when NODE may be freed (not needed when NODE may be removed from the
* hash index but its members remain accessible and intact). */
#define HINDEX_FOR_EACH_SAFE(NODE, NEXT, MEMBER, HINDEX) \
for (ASSIGN_CONTAINER(NODE, hindex_first(HINDEX), MEMBER); \
(NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER) \
? ASSIGN_CONTAINER(NEXT, hindex_next(HINDEX, &(NODE)->MEMBER), MEMBER), 1 \
: 0); \
(NODE) = (NEXT))
struct hindex_node *hindex_first(const struct hindex *);
struct hindex_node *hindex_next(const struct hindex *,
const struct hindex_node *);
/* Returns true if 'hindex' currently contains no nodes, false otherwise. */
static inline bool
hindex_is_empty(const struct hindex *hindex)
{
return hindex->n_unique == 0;
}
#endif /* hindex.h */
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