Andrew's git - gitweb.git/blob

   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
  11extern unsigned int strhash(const char *buf);
  12extern unsigned int strihash(const char *buf);
  13extern unsigned int memhash(const void *buf, size_t len);
  14extern unsigned int memihash(const void *buf, size_t len);
  15extern unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len);
  16
  17static 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
  30struct hashmap_entry {
  31        struct hashmap_entry *next;
  32        unsigned int hash;
  33};
  34
  35typedef int (*hashmap_cmp_fn)(const void *entry, const void *entry_or_key,
  36                const void *keydata);
  37
  38struct 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
  45struct hashmap_iter {
  46        struct hashmap *map;
  47        struct hashmap_entry *next;
  48        unsigned int tablepos;
  49};
  50
  51/* hashmap functions */
  52
  53extern void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
  54                size_t initial_size);
  55extern void hashmap_free(struct hashmap *map, int free_entries);
  56
  57/* hashmap_entry functions */
  58
  59static 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}
  65extern void *hashmap_get(const struct hashmap *map, const void *key,
  66                const void *keydata);
  67extern void *hashmap_get_next(const struct hashmap *map, const void *entry);
  68extern void hashmap_add(struct hashmap *map, void *entry);
  69extern void *hashmap_put(struct hashmap *map, void *entry);
  70extern void *hashmap_remove(struct hashmap *map, const void *key,
  71                const void *keydata);
  72
  73static 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
  81int 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 */
  99static inline void hashmap_disallow_rehash(struct hashmap *map, unsigned value)
 100{
 101        map->disallow_rehash = value;
 102}
 103
 104/* hashmap_iter functions */
 105
 106extern void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter);
 107extern void *hashmap_iter_next(struct hashmap_iter *iter);
 108static 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
 117extern const void *memintern(const void *data, size_t len);
 118static inline const char *strintern(const char *string)
 119{
 120        return memintern(string, strlen(string));
 121}
 122
 123#endif