lib/hmap.h

   1 /*
   2  * Copyright (c) 2008, 2009, 2010 Nicira Networks.
   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) { &(HMAP)->one, NULL, 0, 0 }
  69
  70 /* Initialization. */
  71 void hmap_init(struct hmap *);
  72 void hmap_destroy(struct hmap *);
  73 void hmap_clear(struct hmap *);
  74 void hmap_swap(struct hmap *a, struct hmap *b);
  75 void hmap_moved(struct hmap *hmap);
  76 static inline size_t hmap_count(const struct hmap *);
  77 static inline bool hmap_is_empty(const struct hmap *);
  78
  79 /* Adjusting capacity. */
  80 void hmap_expand(struct hmap *);
  81 void hmap_shrink(struct hmap *);
  82 void hmap_reserve(struct hmap *, size_t capacity);
  83
  84 /* Insertion and deletion. */
  85 static inline void hmap_insert_fast(struct hmap *,
  86                                     struct hmap_node *, size_t hash);
  87 static inline void hmap_insert(struct hmap *, struct hmap_node *, size_t hash);
  88 static inline void hmap_remove(struct hmap *, struct hmap_node *);
  89
  90 void hmap_node_moved(struct hmap *, struct hmap_node *, struct hmap_node *);
  91 static inline void hmap_replace(struct hmap *, const struct hmap_node *old,
  92                                 struct hmap_node *new_node);
  93
  94 struct hmap_node *hmap_random_node(const struct hmap *);
  95
  96 /* Search.
  97  *
  98  * HMAP_FOR_EACH_WITH_HASH iterates NODE over all of the nodes in HMAP that
  99  * have hash value equal to HASH.  HMAP_FOR_EACH_IN_BUCKET iterates NODE over
 100  * all of the nodes in HMAP that would fall in the same bucket as HASH.  MEMBER
 101  * must be the name of the 'struct hmap_node' member within NODE.
 102  *
 103  * These macros may be used interchangeably to search for a particular value in
 104  * an hmap, see, e.g. shash_find() for an example.  Usually, using
 105  * HMAP_FOR_EACH_WITH_HASH provides an optimization, because comparing a hash
 106  * value is usually cheaper than comparing an entire hash map key.  But for
 107  * simple hash map keys, it makes sense to use HMAP_FOR_EACH_IN_BUCKET because
 108  * it avoids doing two comparisons when a single simple comparison suffices.
 109  *
 110  * The loop should not change NODE to point to a different node or insert or
 111  * delete nodes in HMAP (unless it "break"s out of the loop to terminate
 112  * iteration).
 113  *
 114  * HASH is only evaluated once.
 115  */
 116 #define HMAP_FOR_EACH_WITH_HASH(NODE, MEMBER, HASH, HMAP)               \
 117     for (ASSIGN_CONTAINER(NODE, hmap_first_with_hash(HMAP, HASH), MEMBER); \
 118          &(NODE)->MEMBER != NULL;                                       \
 119          ASSIGN_CONTAINER(NODE, hmap_next_with_hash(&(NODE)->MEMBER),   \
 120                           MEMBER))
 121 #define HMAP_FOR_EACH_IN_BUCKET(NODE, MEMBER, HASH, HMAP)               \
 122     for (ASSIGN_CONTAINER(NODE, hmap_first_in_bucket(HMAP, HASH), MEMBER); \
 123          &(NODE)->MEMBER != NULL;                                       \
 124          ASSIGN_CONTAINER(NODE, hmap_next_in_bucket(&(NODE)->MEMBER), MEMBER))
 125
 126 static inline struct hmap_node *hmap_first_with_hash(const struct hmap *,
 127                                                      size_t hash);
 128 static inline struct hmap_node *hmap_next_with_hash(const struct hmap_node *);
 129 static inline struct hmap_node *hmap_first_in_bucket(const struct hmap *,
 130                                                      size_t hash);
 131 static inline struct hmap_node *hmap_next_in_bucket(const struct hmap_node *);
 132
 133 /* Iteration. */
 134
 135 /* Iterates through every node in HMAP. */
 136 #define HMAP_FOR_EACH(NODE, MEMBER, HMAP)                               \
 137     for (ASSIGN_CONTAINER(NODE, hmap_first(HMAP), MEMBER);              \
 138          &(NODE)->MEMBER != NULL;                                       \
 139          ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER))
 140
 141 /* Safe when NODE may be freed (not needed when NODE may be removed from the
 142  * hash map but its members remain accessible and intact). */
 143 #define HMAP_FOR_EACH_SAFE(NODE, NEXT, MEMBER, HMAP)                    \
 144     for (ASSIGN_CONTAINER(NODE, hmap_first(HMAP), MEMBER);              \
 145          (&(NODE)->MEMBER != NULL                                       \
 146           ? ASSIGN_CONTAINER(NEXT, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER) \
 147           : 0);                                                         \
 148          (NODE) = (NEXT))
 149
 150 /* Continues an iteration from just after NODE. */
 151 #define HMAP_FOR_EACH_CONTINUE(NODE, MEMBER, HMAP)                      \
 152     for (ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER); \
 153          &(NODE)->MEMBER != NULL;                                       \
 154          ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER))
 155
 156 static inline struct hmap_node *hmap_first(const struct hmap *);
 157 static inline struct hmap_node *hmap_next(const struct hmap *,
 158                                           const struct hmap_node *);
 159
 160 struct hmap_node *hmap_at_position(const struct hmap *,
 161                                    uint32_t *bucket, uint32_t *offset);
 162
 163 /* Returns the number of nodes currently in 'hmap'. */
 164 static inline size_t
 165 hmap_count(const struct hmap *hmap)
 166 {
 167     return hmap->n;
 168 }
 169
 170 /* Returns the maximum number of nodes that 'hmap' may hold before it should be
 171  * rehashed. */
 172 static inline size_t
 173 hmap_capacity(const struct hmap *hmap)
 174 {
 175     return hmap->mask * 2 + 1;
 176 }
 177
 178 /* Returns true if 'hmap' currently contains no nodes,
 179  * false otherwise. */
 180 static inline bool
 181 hmap_is_empty(const struct hmap *hmap)
 182 {
 183     return hmap->n == 0;
 184 }
 185
 186 /* Inserts 'node', with the given 'hash', into 'hmap'.  'hmap' is never
 187  * expanded automatically. */
 188 static inline void
 189 hmap_insert_fast(struct hmap *hmap, struct hmap_node *node, size_t hash)
 190 {
 191     struct hmap_node **bucket = &hmap->buckets[hash & hmap->mask];
 192     node->hash = hash;
 193     node->next = *bucket;
 194     *bucket = node;
 195     hmap->n++;
 196 }
 197
 198 /* Inserts 'node', with the given 'hash', into 'hmap', and expands 'hmap' if
 199  * necessary to optimize search performance. */
 200 static inline void
 201 hmap_insert(struct hmap *hmap, struct hmap_node *node, size_t hash)
 202 {
 203     hmap_insert_fast(hmap, node, hash);
 204     if (hmap->n / 2 > hmap->mask) {
 205         hmap_expand(hmap);
 206     }
 207 }
 208
 209 /* Removes 'node' from 'hmap'.  Does not shrink the hash table; call
 210  * hmap_shrink() directly if desired. */
 211 static inline void
 212 hmap_remove(struct hmap *hmap, struct hmap_node *node)
 213 {
 214     struct hmap_node **bucket = &hmap->buckets[node->hash & hmap->mask];
 215     while (*bucket != node) {
 216         bucket = &(*bucket)->next;
 217     }
 218     *bucket = node->next;
 219     hmap->n--;
 220 }
 221
 222 /* Puts 'new_node' in the position in 'hmap' currently occupied by 'old_node'.
 223  * The 'new_node' must hash to the same value as 'old_node'.  The client is
 224  * responsible for ensuring that the replacement does not violate any
 225  * client-imposed invariants (e.g. uniqueness of keys within a map).
 226  *
 227  * Afterward, 'old_node' is not part of 'hmap', and the client is responsible
 228  * for freeing it (if this is desirable). */
 229 static inline void
 230 hmap_replace(struct hmap *hmap,
 231              const struct hmap_node *old_node, struct hmap_node *new_node)
 232 {
 233     struct hmap_node **bucket = &hmap->buckets[old_node->hash & hmap->mask];
 234     while (*bucket != old_node) {
 235         bucket = &(*bucket)->next;
 236     }
 237     *bucket = new_node;
 238     new_node->hash = old_node->hash;
 239     new_node->next = old_node->next;
 240 }
 241
 242 static inline struct hmap_node *
 243 hmap_next_with_hash__(const struct hmap_node *node, size_t hash)
 244 {
 245     while (node != NULL && node->hash != hash) {
 246         node = node->next;
 247     }
 248     return (struct hmap_node *) node;
 249 }
 250
 251 /* Returns the first node in 'hmap' with the given 'hash', or a null pointer if
 252  * no nodes have that hash value. */
 253 static inline struct hmap_node *
 254 hmap_first_with_hash(const struct hmap *hmap, size_t hash)
 255 {
 256     return hmap_next_with_hash__(hmap->buckets[hash & hmap->mask], hash);
 257 }
 258
 259 /* Returns the first node in 'hmap' in the bucket in which the given 'hash'
 260  * would land, or a null pointer if that bucket is empty. */
 261 static inline struct hmap_node *
 262 hmap_first_in_bucket(const struct hmap *hmap, size_t hash)
 263 {
 264     return hmap->buckets[hash & hmap->mask];
 265 }
 266
 267 /* Returns the next node in the same bucket as 'node', or a null pointer if
 268  * there are no more nodes in that bucket.
 269  *
 270  * If the hash map has been reallocated since 'node' was visited, some nodes
 271  * may be skipped; if new nodes with the same hash value have been added, they
 272  * will be skipped.  (Removing 'node' from the hash map does not prevent
 273  * calling this function, since node->next is preserved, although freeing
 274  * 'node' of course does.) */
 275 static inline struct hmap_node *
 276 hmap_next_in_bucket(const struct hmap_node *node)
 277 {
 278     return node->next;
 279 }
 280
 281 /* Returns the next node in the same hash map as 'node' with the same hash
 282  * value, or a null pointer if no more nodes have that hash value.
 283  *
 284  * If the hash map has been reallocated since 'node' was visited, some nodes
 285  * may be skipped; if new nodes with the same hash value have been added, they
 286  * will be skipped.  (Removing 'node' from the hash map does not prevent
 287  * calling this function, since node->next is preserved, although freeing
 288  * 'node' of course does.) */
 289 static inline struct hmap_node *
 290 hmap_next_with_hash(const struct hmap_node *node)
 291 {
 292     return hmap_next_with_hash__(node->next, node->hash);
 293 }
 294
 295 static inline struct hmap_node *
 296 hmap_next__(const struct hmap *hmap, size_t start)
 297 {
 298     size_t i;
 299     for (i = start; i <= hmap->mask; i++) {
 300         struct hmap_node *node = hmap->buckets[i];
 301         if (node) {
 302             return node;
 303         }
 304     }
 305     return NULL;
 306 }
 307
 308 /* Returns the first node in 'hmap', in arbitrary order, or a null pointer if
 309  * 'hmap' is empty. */
 310 static inline struct hmap_node *
 311 hmap_first(const struct hmap *hmap)
 312 {
 313     return hmap_next__(hmap, 0);
 314 }
 315
 316 /* Returns the next node in 'hmap' following 'node', in arbitrary order, or a
 317  * null pointer if 'node' is the last node in 'hmap'.
 318  *
 319  * If the hash map has been reallocated since 'node' was visited, some nodes
 320  * may be skipped or visited twice.  (Removing 'node' from the hash map does
 321  * not prevent calling this function, since node->next is preserved, although
 322  * freeing 'node' of course does.) */
 323 static inline struct hmap_node *
 324 hmap_next(const struct hmap *hmap, const struct hmap_node *node)
 325 {
 326     return (node->next
 327             ? node->next
 328             : hmap_next__(hmap, (node->hash & hmap->mask) + 1));
 329 }
 330
 331 #ifdef  __cplusplus
 332 }
 333 #endif
 334
 335 #endif /* hmap.h */