--- /dev/null
+/*
+ * 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)->MEMBER != NULL; \
+ ASSIGN_CONTAINER(NODE, (NODE)->MEMBER.s, MEMBER))
+
+struct hindex_node *hindex_node_with_hash(const struct hindex *, size_t hash);
+
+/* Iteration. */
+
+/* Iterates through every node in HINDEX. */
+#define HINDEX_FOR_EACH(NODE, MEMBER, HINDEX) \
+ for (ASSIGN_CONTAINER(NODE, hindex_first(HINDEX), MEMBER); \
+ &(NODE)->MEMBER != NULL; \
+ 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)->MEMBER != NULL \
+ ? ASSIGN_CONTAINER(NEXT, hindex_next(HINDEX, &(NODE)->MEMBER), MEMBER) \
+ : 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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