hashmap.h

   1 #ifndef HASHMAP_H
   2 #define HASHMAP_H
   3
   4 /*
   5  * Generic implementation of hash-based key-value mappings.
   6  * See Documentation/technical/api-hashmap.txt.
   7  */
   8
   9 /* FNV-1 functions */
  10
  11 extern unsigned int strhash(const char *buf);
  12 extern unsigned int strihash(const char *buf);
  13 extern unsigned int memhash(const void *buf, size_t len);
  14 extern unsigned int memihash(const void *buf, size_t len);
  15 extern unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len);
  16
  17 static inline unsigned int sha1hash(const unsigned char *sha1)
  18 {
  19         /*
  20          * Equivalent to 'return *(unsigned int *)sha1;', but safe on
  21          * platforms that don't support unaligned reads.
  22          */
  23         unsigned int hash;
  24         memcpy(&hash, sha1, sizeof(hash));
  25         return hash;
  26 }
  27
  28 /* data structures */
  29
  30 struct hashmap_entry {
  31         struct hashmap_entry *next;
  32         unsigned int hash;
  33 };
  34
  35 typedef int (*hashmap_cmp_fn)(const void *entry, const void *entry_or_key,
  36                 const void *keydata);
  37
  38 struct hashmap {
  39         struct hashmap_entry **table;
  40         hashmap_cmp_fn cmpfn;
  41         unsigned int size, tablesize, grow_at, shrink_at;
  42         unsigned disallow_rehash : 1;
  43 };
  44
  45 struct hashmap_iter {
  46         struct hashmap *map;
  47         struct hashmap_entry *next;
  48         unsigned int tablepos;
  49 };
  50
  51 /* hashmap functions */
  52
  53 extern void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
  54                 size_t initial_size);
  55 extern void hashmap_free(struct hashmap *map, int free_entries);
  56
  57 /* hashmap_entry functions */
  58
  59 static inline void hashmap_entry_init(void *entry, unsigned int hash)
  60 {
  61         struct hashmap_entry *e = entry;
  62         e->hash = hash;
  63         e->next = NULL;
  64 }
  65 extern void *hashmap_get(const struct hashmap *map, const void *key,
  66                 const void *keydata);
  67 extern void *hashmap_get_next(const struct hashmap *map, const void *entry);
  68 extern void hashmap_add(struct hashmap *map, void *entry);
  69 extern void *hashmap_put(struct hashmap *map, void *entry);
  70 extern void *hashmap_remove(struct hashmap *map, const void *key,
  71                 const void *keydata);
  72
  73 static inline void *hashmap_get_from_hash(const struct hashmap *map,
  74                 unsigned int hash, const void *keydata)
  75 {
  76         struct hashmap_entry key;
  77         hashmap_entry_init(&key, hash);
  78         return hashmap_get(map, &key, keydata);
  79 }
  80
  81 int hashmap_bucket(const struct hashmap *map, unsigned int hash);
  82
  83 /*
  84  * Disallow/allow rehashing of the hashmap.
  85  * This is useful if the caller knows that the hashmap
  86  * needs multi-threaded access.  The caller is still
  87  * required to guard/lock searches and inserts in a
  88  * manner appropriate to their usage.  This simply
  89  * prevents the table from being unexpectedly re-mapped.
  90  *
  91  * If is up to the caller to ensure that the hashmap is
  92  * initialized to a reasonable size to prevent poor
  93  * performance.
  94  *
  95  * When value=1, prevent future rehashes on adds and deleted.
  96  * When value=0, allow future rehahses.  This DOES NOT force
  97  * a rehash now.
  98  */
  99 static inline void hashmap_disallow_rehash(struct hashmap *map, unsigned value)
 100 {
 101         map->disallow_rehash = value;
 102 }
 103
 104 /* hashmap_iter functions */
 105
 106 extern void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter);
 107 extern void *hashmap_iter_next(struct hashmap_iter *iter);
 108 static inline void *hashmap_iter_first(struct hashmap *map,
 109                 struct hashmap_iter *iter)
 110 {
 111         hashmap_iter_init(map, iter);
 112         return hashmap_iter_next(iter);
 113 }
 114
 115 /* string interning */
 116
 117 extern const void *memintern(const void *data, size_t len);
 118 static inline const char *strintern(const char *string)
 119 {
 120         return memintern(string, strlen(string));
 121 }
 122
 123 #endif