lib/hmap.h

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2012, 2013, 2015 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_at(struct hmap *, const char *where);
  82 #define hmap_expand(HMAP) hmap_expand_at(HMAP, OVS_SOURCE_LOCATOR)
  83
  84 void hmap_shrink_at(struct hmap *, const char *where);
  85 #define hmap_shrink(HMAP) hmap_shrink_at(HMAP, OVS_SOURCE_LOCATOR)
  86
  87 void hmap_reserve_at(struct hmap *, size_t capacity, const char *where);
  88 #define hmap_reserve(HMAP, CAPACITY) \
  89     hmap_reserve_at(HMAP, CAPACITY, OVS_SOURCE_LOCATOR)
  90
  91 /* Insertion and deletion. */
  92 static inline void hmap_insert_at(struct hmap *, struct hmap_node *,
  93                                   size_t hash, const char *where);
  94 #define hmap_insert(HMAP, NODE, HASH) \
  95     hmap_insert_at(HMAP, NODE, HASH, OVS_SOURCE_LOCATOR)
  96
  97 static inline void hmap_insert_fast(struct hmap *,
  98                                     struct hmap_node *, size_t hash);
  99 static inline void hmap_remove(struct hmap *, struct hmap_node *);
 100
 101 void hmap_node_moved(struct hmap *, struct hmap_node *, struct hmap_node *);
 102 static inline void hmap_replace(struct hmap *, const struct hmap_node *old,
 103                                 struct hmap_node *new_node);
 104
 105 struct hmap_node *hmap_random_node(const struct hmap *);
 106
 107 /* Search.
 108  *
 109  * HMAP_FOR_EACH_WITH_HASH iterates NODE over all of the nodes in HMAP that
 110  * have hash value equal to HASH.  HMAP_FOR_EACH_IN_BUCKET iterates NODE over
 111  * all of the nodes in HMAP that would fall in the same bucket as HASH.  MEMBER
 112  * must be the name of the 'struct hmap_node' member within NODE.
 113  *
 114  * These macros may be used interchangeably to search for a particular value in
 115  * an hmap, see, e.g. shash_find() for an example.  Usually, using
 116  * HMAP_FOR_EACH_WITH_HASH provides an optimization, because comparing a hash
 117  * value is usually cheaper than comparing an entire hash map key.  But for
 118  * simple hash map keys, it makes sense to use HMAP_FOR_EACH_IN_BUCKET because
 119  * it avoids doing two comparisons when a single simple comparison suffices.
 120  *
 121  * The loop should not change NODE to point to a different node or insert or
 122  * delete nodes in HMAP (unless it "break"s out of the loop to terminate
 123  * iteration).
 124  *
 125  * HASH is only evaluated once.
 126  *
 127  *
 128  * Warning
 129  * -------
 130  *
 131  * When the loop terminates, &NODE->MEMBER will equal NULL.  Unless MEMBER is
 132  * the first member in its struct, this means that NODE itself will not be
 133  * NULL.
 134  *
 135  * (This is true for all of the HMAP_FOR_EACH_*() macros.)
 136  */
 137 #define HMAP_FOR_EACH_WITH_HASH(NODE, MEMBER, HASH, HMAP)               \
 138     for (INIT_CONTAINER(NODE, hmap_first_with_hash(HMAP, HASH), MEMBER); \
 139          NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER);                  \
 140          ASSIGN_CONTAINER(NODE, hmap_next_with_hash(&(NODE)->MEMBER),   \
 141                           MEMBER))
 142 #define HMAP_FOR_EACH_IN_BUCKET(NODE, MEMBER, HASH, HMAP)               \
 143     for (INIT_CONTAINER(NODE, hmap_first_in_bucket(HMAP, HASH), MEMBER); \
 144          NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER);                  \
 145          ASSIGN_CONTAINER(NODE, hmap_next_in_bucket(&(NODE)->MEMBER), MEMBER))
 146
 147 static inline struct hmap_node *hmap_first_with_hash(const struct hmap *,
 148                                                      size_t hash);
 149 static inline struct hmap_node *hmap_next_with_hash(const struct hmap_node *);
 150 static inline struct hmap_node *hmap_first_in_bucket(const struct hmap *,
 151                                                      size_t hash);
 152 static inline struct hmap_node *hmap_next_in_bucket(const struct hmap_node *);
 153
 154 bool hmap_contains(const struct hmap *, const struct hmap_node *);
 155
 156 /* Iteration. */
 157
 158 /* Iterates through every node in HMAP. */
 159 #define HMAP_FOR_EACH(NODE, MEMBER, HMAP)                               \
 160     for (INIT_CONTAINER(NODE, hmap_first(HMAP), MEMBER);                \
 161          NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER);                  \
 162          ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER))
 163
 164 /* Safe when NODE may be freed (not needed when NODE may be removed from the
 165  * hash map but its members remain accessible and intact). */
 166 #define HMAP_FOR_EACH_SAFE(NODE, NEXT, MEMBER, HMAP)                    \
 167     for (INIT_CONTAINER(NODE, hmap_first(HMAP), MEMBER);                \
 168          (NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER)                  \
 169           ? INIT_CONTAINER(NEXT, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER), 1 \
 170           : 0);                                                         \
 171          (NODE) = (NEXT))
 172
 173 /* Continues an iteration from just after NODE. */
 174 #define HMAP_FOR_EACH_CONTINUE(NODE, MEMBER, HMAP)                      \
 175     for (ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER); \
 176          NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER);                  \
 177          ASSIGN_CONTAINER(NODE, hmap_next(HMAP, &(NODE)->MEMBER), MEMBER))
 178
 179 static inline struct hmap_node *hmap_first(const struct hmap *);
 180 static inline struct hmap_node *hmap_next(const struct hmap *,
 181                                           const struct hmap_node *);
 182
 183 struct hmap_node *hmap_at_position(const struct hmap *,
 184                                    uint32_t *bucket, uint32_t *offset);
 185
 186 /* Returns the number of nodes currently in 'hmap'. */
 187 static inline size_t
 188 hmap_count(const struct hmap *hmap)
 189 {
 190     return hmap->n;
 191 }
 192
 193 /* Returns the maximum number of nodes that 'hmap' may hold before it should be
 194  * rehashed. */
 195 static inline size_t
 196 hmap_capacity(const struct hmap *hmap)
 197 {
 198     return hmap->mask * 2 + 1;
 199 }
 200
 201 /* Returns true if 'hmap' currently contains no nodes,
 202  * false otherwise.
 203  * Note: While hmap in general is not thread-safe without additional locking,
 204  * hmap_is_empty() is. */
 205 static inline bool
 206 hmap_is_empty(const struct hmap *hmap)
 207 {
 208     return hmap->n == 0;
 209 }
 210
 211 /* Inserts 'node', with the given 'hash', into 'hmap'.  'hmap' is never
 212  * expanded automatically. */
 213 static inline void
 214 hmap_insert_fast(struct hmap *hmap, struct hmap_node *node, size_t hash)
 215 {
 216     struct hmap_node **bucket = &hmap->buckets[hash & hmap->mask];
 217     node->hash = hash;
 218     node->next = *bucket;
 219     *bucket = node;
 220     hmap->n++;
 221 }
 222
 223 /* Inserts 'node', with the given 'hash', into 'hmap', and expands 'hmap' if
 224  * necessary to optimize search performance.
 225  *
 226  * ('where' is used in debug logging.  Commonly one would use hmap_insert() to
 227  * automatically provide the caller's source file and line number for
 228  * 'where'.) */
 229 static inline void
 230 hmap_insert_at(struct hmap *hmap, struct hmap_node *node, size_t hash,
 231                const char *where)
 232 {
 233     hmap_insert_fast(hmap, node, hash);
 234     if (hmap->n / 2 > hmap->mask) {
 235         hmap_expand_at(hmap, where);
 236     }
 237 }
 238
 239 /* Removes 'node' from 'hmap'.  Does not shrink the hash table; call
 240  * hmap_shrink() directly if desired. */
 241 static inline void
 242 hmap_remove(struct hmap *hmap, struct hmap_node *node)
 243 {
 244     struct hmap_node **bucket = &hmap->buckets[node->hash & hmap->mask];
 245     while (*bucket != node) {
 246         bucket = &(*bucket)->next;
 247     }
 248     *bucket = node->next;
 249     hmap->n--;
 250 }
 251
 252 /* Puts 'new_node' in the position in 'hmap' currently occupied by 'old_node'.
 253  * The 'new_node' must hash to the same value as 'old_node'.  The client is
 254  * responsible for ensuring that the replacement does not violate any
 255  * client-imposed invariants (e.g. uniqueness of keys within a map).
 256  *
 257  * Afterward, 'old_node' is not part of 'hmap', and the client is responsible
 258  * for freeing it (if this is desirable). */
 259 static inline void
 260 hmap_replace(struct hmap *hmap,
 261              const struct hmap_node *old_node, struct hmap_node *new_node)
 262 {
 263     struct hmap_node **bucket = &hmap->buckets[old_node->hash & hmap->mask];
 264     while (*bucket != old_node) {
 265         bucket = &(*bucket)->next;
 266     }
 267     *bucket = new_node;
 268     new_node->hash = old_node->hash;
 269     new_node->next = old_node->next;
 270 }
 271
 272 static inline struct hmap_node *
 273 hmap_next_with_hash__(const struct hmap_node *node, size_t hash)
 274 {
 275     while (node != NULL && node->hash != hash) {
 276         node = node->next;
 277     }
 278     return CONST_CAST(struct hmap_node *, node);
 279 }
 280
 281 /* Returns the first node in 'hmap' with the given 'hash', or a null pointer if
 282  * no nodes have that hash value. */
 283 static inline struct hmap_node *
 284 hmap_first_with_hash(const struct hmap *hmap, size_t hash)
 285 {
 286     return hmap_next_with_hash__(hmap->buckets[hash & hmap->mask], hash);
 287 }
 288
 289 /* Returns the first node in 'hmap' in the bucket in which the given 'hash'
 290  * would land, or a null pointer if that bucket is empty. */
 291 static inline struct hmap_node *
 292 hmap_first_in_bucket(const struct hmap *hmap, size_t hash)
 293 {
 294     return hmap->buckets[hash & hmap->mask];
 295 }
 296
 297 /* Returns the next node in the same bucket as 'node', or a null pointer if
 298  * there are no more nodes in that bucket.
 299  *
 300  * If the hash map has been reallocated since 'node' was visited, some nodes
 301  * may be skipped; if new nodes with the same hash value have been added, they
 302  * will be skipped.  (Removing 'node' from the hash map does not prevent
 303  * calling this function, since node->next is preserved, although freeing
 304  * 'node' of course does.) */
 305 static inline struct hmap_node *
 306 hmap_next_in_bucket(const struct hmap_node *node)
 307 {
 308     return node->next;
 309 }
 310
 311 /* Returns the next node in the same hash map as 'node' with the same hash
 312  * value, or a null pointer if no more nodes have that hash value.
 313  *
 314  * If the hash map has been reallocated since 'node' was visited, some nodes
 315  * may be skipped; if new nodes with the same hash value have been added, they
 316  * will be skipped.  (Removing 'node' from the hash map does not prevent
 317  * calling this function, since node->next is preserved, although freeing
 318  * 'node' of course does.) */
 319 static inline struct hmap_node *
 320 hmap_next_with_hash(const struct hmap_node *node)
 321 {
 322     return hmap_next_with_hash__(node->next, node->hash);
 323 }
 324
 325 static inline struct hmap_node *
 326 hmap_next__(const struct hmap *hmap, size_t start)
 327 {
 328     size_t i;
 329     for (i = start; i <= hmap->mask; i++) {
 330         struct hmap_node *node = hmap->buckets[i];
 331         if (node) {
 332             return node;
 333         }
 334     }
 335     return NULL;
 336 }
 337
 338 /* Returns the first node in 'hmap', in arbitrary order, or a null pointer if
 339  * 'hmap' is empty. */
 340 static inline struct hmap_node *
 341 hmap_first(const struct hmap *hmap)
 342 {
 343     return hmap_next__(hmap, 0);
 344 }
 345
 346 /* Returns the next node in 'hmap' following 'node', in arbitrary order, or a
 347  * null pointer if 'node' is the last node in 'hmap'.
 348  *
 349  * If the hash map has been reallocated since 'node' was visited, some nodes
 350  * may be skipped or visited twice.  (Removing 'node' from the hash map does
 351  * not prevent calling this function, since node->next is preserved, although
 352  * freeing 'node' of course does.) */
 353 static inline struct hmap_node *
 354 hmap_next(const struct hmap *hmap, const struct hmap_node *node)
 355 {
 356     return (node->next
 357             ? node->next
 358             : hmap_next__(hmap, (node->hash & hmap->mask) + 1));
 359 }
 360
 361 #ifdef  __cplusplus
 362 }
 363 #endif
 364
 365 #endif /* hmap.h */