lib/hmap.h

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2012 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef HMAP_H
  18 #define HMAP_H 1
  19
  20 #include <stdbool.h>
  21 #include <stdlib.h>
  22 #include "util.h"
  23
  24 #ifdef  __cplusplus
  25 extern "C" {
  26 #endif
  27
  28 /* A hash map node, to be embedded inside the data structure being mapped. */
  29 struct hmap_node {
  30     size_t hash;                /* Hash value. */
  31     struct hmap_node *next;     /* Next in linked list. */
  32 };
  33
  34 /* Returns the hash value embedded in 'node'. */
  35 static inline size_t hmap_node_hash(const struct hmap_node *node)
  36 {
  37     return node->hash;
  38 }
  39
  40 #define HMAP_NODE_NULL ((struct hmap_node *) 1)
  41 #define HMAP_NODE_NULL_INITIALIZER { 0, HMAP_NODE_NULL }
  42
  43 /* Returns true if 'node' has been set to null by hmap_node_nullify() and has
  44  * not been un-nullified by being inserted into an hmap. */
  45 static inline bool
  46 hmap_node_is_null(const struct hmap_node *node)
  47 {
  48     return node->next == HMAP_NODE_NULL;
  49 }
  50
  51 /* Marks 'node' with a distinctive value that can be tested with
  52  * hmap_node_is_null().  */
  53 static inline void
  54 hmap_node_nullify(struct hmap_node *node)
  55 {
  56     node->next = HMAP_NODE_NULL;
  57 }
  58
  59 /* A hash map. */
  60 struct hmap {
  61     struct hmap_node **buckets; /* Must point to 'one' iff 'mask' == 0. */
  62     struct hmap_node *one;
  63     size_t mask;
  64     size_t n;
  65 };
  66
  67 /* Initializer for an empty hash map. */
  68 #define HMAP_INITIALIZER(HMAP) \
  69     { (struct hmap_node **const) &(HMAP)->one, NULL, 0, 0 }
  70
  71 /* Initialization. */
  72 void hmap_init(struct hmap *);
  73 void hmap_destroy(struct hmap *);
  74 void hmap_clear(struct hmap *);
  75 void hmap_swap(struct hmap *a, struct hmap *b);
  76 void hmap_moved(struct hmap *hmap);
  77 static inline size_t hmap_count(const struct hmap *);
  78 static inline bool hmap_is_empty(const struct hmap *);
  79
  80 /* Adjusting capacity. */
  81 void hmap_expand(struct hmap *);
  82 void hmap_shrink(struct hmap *);
  83 void hmap_reserve(struct hmap *, size_t capacity);
  84
  85 /* Insertion and deletion. */
  86 static inline void hmap_insert_fast(struct hmap *,
  87                                     struct hmap_node *, size_t hash);
  88 static inline void hmap_insert(struct hmap *, struct hmap_node *, size_t hash);
  89 static inline void hmap_remove(struct hmap *, struct hmap_node *);
  90
  91 void hmap_node_moved(struct hmap *, struct hmap_node *, struct hmap_node *);
  92 static inline void hmap_replace(struct hmap *, const struct hmap_node *old,
  93                                 struct hmap_node *new_node);
  94
  95 struct hmap_node *hmap_random_node(const struct hmap *);
  96
  97 /* Search.
  98  *
  99  * HMAP_FOR_EACH_WITH_HASH iterates NODE over all of the nodes in HMAP that
 100  * have hash value equal to HASH.  HMAP_FOR_EACH_IN_BUCKET iterates NODE over
 101  * all of the nodes in HMAP that would fall in the same bucket as HASH.  MEMBER
 102  * must be the name of the 'struct hmap_node' member within NODE.
 103  *
 104  * These macros may be used interchangeably to search for a particular value in
 105  * an hmap, see, e.g. shash_find() for an example.  Usually, using
 106  * HMAP_FOR_EACH_WITH_HASH provides an optimization, because comparing a hash
 107  * value is usually cheaper than comparing an entire hash map key.  But for
 108  * simple hash map keys, it makes sense to use HMAP_FOR_EACH_IN_BUCKET because
 109  * it avoids doing two comparisons when a single simple comparison suffices.
 110  *
 111  * The loop should not change NODE to point to a different node or insert or
 112  * delete nodes in HMAP (unless it "break"s out of the loop to terminate
 113  * iteration).
 114  *
 115  * HASH is only evaluated once.
 116  */
 117 #define HMAP_FOR_EACH_WITH_HASH(NODE, MEMBER, HASH, HMAP)               \
 118     for (ASSIGN_CONTAINER(NODE, hmap_first_with_hash(HMAP, HASH), MEMBER); \
 119          &(NODE)->MEMBER != NULL;                                       \
 120          ASSIGN_CONTAINER(NODE, hmap_next_with_hash(&(NODE)->MEMBER),   \
 121                           MEMBER))
 122 #define HMAP_FOR_EACH_IN_BUCKET(NODE, MEMBER, HASH, HMAP)               \
 123     for (ASSIGN_CONTAINER(NODE, hmap_first_in_bucket(HMAP, HASH), MEMBER); \
 124          &(NODE)->MEMBER != NULL;                                       \
 125          ASSIGN_CONTAINER(NODE, hmap_next_in_bucket(&(NODE)->MEMBER), MEMBER))
 126
 127 static inline struct hmap_node *hmap_first_with_hash(const struct hmap *,
 128                                                      size_t hash);
 129 static inline struct hmap_node *hmap_next_with_hash(const struct hmap_node *);
 130 static inline struct hmap_node *hmap_first_in_bucket(const struct hmap *,
 131                                                      size_t hash);
 132 static inline struct hmap_node *hmap_next_in_bucket(const struct hmap_node *);
 133
 134 bool hmap_contains(const struct hmap *, const struct hmap_node *);
 135
 136 /* Iteration. */
 137
 138 /* Iterates through every node in HMAP. */
 139 #define HMAP_FOR_EACH(NODE, MEMBER, HMAP)                               \
 140     for (ASSIGN_CONTAINER(NODE, hmap_first(HMAP), MEMBER);              \
 141          &(NODE)->MEMBER != NULL;                                       \
 142          ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER))
 143
 144 /* Safe when NODE may be freed (not needed when NODE may be removed from the
 145  * hash map but its members remain accessible and intact). */
 146 #define HMAP_FOR_EACH_SAFE(NODE, NEXT, MEMBER, HMAP)                    \
 147     for (ASSIGN_CONTAINER(NODE, hmap_first(HMAP), MEMBER);              \
 148          (&(NODE)->MEMBER != NULL                                       \
 149           ? ASSIGN_CONTAINER(NEXT, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER) \
 150           : 0);                                                         \
 151          (NODE) = (NEXT))
 152
 153 /* Continues an iteration from just after NODE. */
 154 #define HMAP_FOR_EACH_CONTINUE(NODE, MEMBER, HMAP)                      \
 155     for (ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER); \
 156          &(NODE)->MEMBER != NULL;                                       \
 157          ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER))
 158
 159 static inline struct hmap_node *hmap_first(const struct hmap *);
 160 static inline struct hmap_node *hmap_next(const struct hmap *,
 161                                           const struct hmap_node *);
 162
 163 struct hmap_node *hmap_at_position(const struct hmap *,
 164                                    uint32_t *bucket, uint32_t *offset);
 165
 166 /* Returns the number of nodes currently in 'hmap'. */
 167 static inline size_t
 168 hmap_count(const struct hmap *hmap)
 169 {
 170     return hmap->n;
 171 }
 172
 173 /* Returns the maximum number of nodes that 'hmap' may hold before it should be
 174  * rehashed. */
 175 static inline size_t
 176 hmap_capacity(const struct hmap *hmap)
 177 {
 178     return hmap->mask * 2 + 1;
 179 }
 180
 181 /* Returns true if 'hmap' currently contains no nodes,
 182  * false otherwise. */
 183 static inline bool
 184 hmap_is_empty(const struct hmap *hmap)
 185 {
 186     return hmap->n == 0;
 187 }
 188
 189 /* Inserts 'node', with the given 'hash', into 'hmap'.  'hmap' is never
 190  * expanded automatically. */
 191 static inline void
 192 hmap_insert_fast(struct hmap *hmap, struct hmap_node *node, size_t hash)
 193 {
 194     struct hmap_node **bucket = &hmap->buckets[hash & hmap->mask];
 195     node->hash = hash;
 196     node->next = *bucket;
 197     *bucket = node;
 198     hmap->n++;
 199 }
 200
 201 /* Inserts 'node', with the given 'hash', into 'hmap', and expands 'hmap' if
 202  * necessary to optimize search performance. */
 203 static inline void
 204 hmap_insert(struct hmap *hmap, struct hmap_node *node, size_t hash)
 205 {
 206     hmap_insert_fast(hmap, node, hash);
 207     if (hmap->n / 2 > hmap->mask) {
 208         hmap_expand(hmap);
 209     }
 210 }
 211
 212 /* Removes 'node' from 'hmap'.  Does not shrink the hash table; call
 213  * hmap_shrink() directly if desired. */
 214 static inline void
 215 hmap_remove(struct hmap *hmap, struct hmap_node *node)
 216 {
 217     struct hmap_node **bucket = &hmap->buckets[node->hash & hmap->mask];
 218     while (*bucket != node) {
 219         bucket = &(*bucket)->next;
 220     }
 221     *bucket = node->next;
 222     hmap->n--;
 223 }
 224
 225 /* Puts 'new_node' in the position in 'hmap' currently occupied by 'old_node'.
 226  * The 'new_node' must hash to the same value as 'old_node'.  The client is
 227  * responsible for ensuring that the replacement does not violate any
 228  * client-imposed invariants (e.g. uniqueness of keys within a map).
 229  *
 230  * Afterward, 'old_node' is not part of 'hmap', and the client is responsible
 231  * for freeing it (if this is desirable). */
 232 static inline void
 233 hmap_replace(struct hmap *hmap,
 234              const struct hmap_node *old_node, struct hmap_node *new_node)
 235 {
 236     struct hmap_node **bucket = &hmap->buckets[old_node->hash & hmap->mask];
 237     while (*bucket != old_node) {
 238         bucket = &(*bucket)->next;
 239     }
 240     *bucket = new_node;
 241     new_node->hash = old_node->hash;
 242     new_node->next = old_node->next;
 243 }
 244
 245 static inline struct hmap_node *
 246 hmap_next_with_hash__(const struct hmap_node *node, size_t hash)
 247 {
 248     while (node != NULL && node->hash != hash) {
 249         node = node->next;
 250     }
 251     return CONST_CAST(struct hmap_node *, node);
 252 }
 253
 254 /* Returns the first node in 'hmap' with the given 'hash', or a null pointer if
 255  * no nodes have that hash value. */
 256 static inline struct hmap_node *
 257 hmap_first_with_hash(const struct hmap *hmap, size_t hash)
 258 {
 259     return hmap_next_with_hash__(hmap->buckets[hash & hmap->mask], hash);
 260 }
 261
 262 /* Returns the first node in 'hmap' in the bucket in which the given 'hash'
 263  * would land, or a null pointer if that bucket is empty. */
 264 static inline struct hmap_node *
 265 hmap_first_in_bucket(const struct hmap *hmap, size_t hash)
 266 {
 267     return hmap->buckets[hash & hmap->mask];
 268 }
 269
 270 /* Returns the next node in the same bucket as 'node', or a null pointer if
 271  * there are no more nodes in that bucket.
 272  *
 273  * If the hash map has been reallocated since 'node' was visited, some nodes
 274  * may be skipped; if new nodes with the same hash value have been added, they
 275  * will be skipped.  (Removing 'node' from the hash map does not prevent
 276  * calling this function, since node->next is preserved, although freeing
 277  * 'node' of course does.) */
 278 static inline struct hmap_node *
 279 hmap_next_in_bucket(const struct hmap_node *node)
 280 {
 281     return node->next;
 282 }
 283
 284 /* Returns the next node in the same hash map as 'node' with the same hash
 285  * value, or a null pointer if no more nodes have that hash value.
 286  *
 287  * If the hash map has been reallocated since 'node' was visited, some nodes
 288  * may be skipped; if new nodes with the same hash value have been added, they
 289  * will be skipped.  (Removing 'node' from the hash map does not prevent
 290  * calling this function, since node->next is preserved, although freeing
 291  * 'node' of course does.) */
 292 static inline struct hmap_node *
 293 hmap_next_with_hash(const struct hmap_node *node)
 294 {
 295     return hmap_next_with_hash__(node->next, node->hash);
 296 }
 297
 298 static inline struct hmap_node *
 299 hmap_next__(const struct hmap *hmap, size_t start)
 300 {
 301     size_t i;
 302     for (i = start; i <= hmap->mask; i++) {
 303         struct hmap_node *node = hmap->buckets[i];
 304         if (node) {
 305             return node;
 306         }
 307     }
 308     return NULL;
 309 }
 310
 311 /* Returns the first node in 'hmap', in arbitrary order, or a null pointer if
 312  * 'hmap' is empty. */
 313 static inline struct hmap_node *
 314 hmap_first(const struct hmap *hmap)
 315 {
 316     return hmap_next__(hmap, 0);
 317 }
 318
 319 /* Returns the next node in 'hmap' following 'node', in arbitrary order, or a
 320  * null pointer if 'node' is the last node in 'hmap'.
 321  *
 322  * If the hash map has been reallocated since 'node' was visited, some nodes
 323  * may be skipped or visited twice.  (Removing 'node' from the hash map does
 324  * not prevent calling this function, since node->next is preserved, although
 325  * freeing 'node' of course does.) */
 326 static inline struct hmap_node *
 327 hmap_next(const struct hmap *hmap, const struct hmap_node *node)
 328 {
 329     return (node->next
 330             ? node->next
 331             : hmap_next__(hmap, (node->hash & hmap->mask) + 1));
 332 }
 333
 334 #ifdef  __cplusplus
 335 }
 336 #endif
 337
 338 #endif /* hmap.h */