Andrew's git - gitweb.git/blob

   1/*
   2 * Generic implementation of hash-based key value mappings.
   3 */
   4#include "cache.h"
   5#include "hashmap.h"
   6
   7#define FNV32_BASE ((unsigned int) 0x811c9dc5)
   8#define FNV32_PRIME ((unsigned int) 0x01000193)
   9
  10unsigned int strhash(const char *str)
  11{
  12        unsigned int c, hash = FNV32_BASE;
  13        while ((c = (unsigned char) *str++))
  14                hash = (hash * FNV32_PRIME) ^ c;
  15        return hash;
  16}
  17
  18unsigned int strihash(const char *str)
  19{
  20        unsigned int c, hash = FNV32_BASE;
  21        while ((c = (unsigned char) *str++)) {
  22                if (c >= 'a' && c <= 'z')
  23                        c -= 'a' - 'A';
  24                hash = (hash * FNV32_PRIME) ^ c;
  25        }
  26        return hash;
  27}
  28
  29unsigned int memhash(const void *buf, size_t len)
  30{
  31        unsigned int hash = FNV32_BASE;
  32        unsigned char *ucbuf = (unsigned char *) buf;
  33        while (len--) {
  34                unsigned int c = *ucbuf++;
  35                hash = (hash * FNV32_PRIME) ^ c;
  36        }
  37        return hash;
  38}
  39
  40unsigned int memihash(const void *buf, size_t len)
  41{
  42        unsigned int hash = FNV32_BASE;
  43        unsigned char *ucbuf = (unsigned char *) buf;
  44        while (len--) {
  45                unsigned int c = *ucbuf++;
  46                if (c >= 'a' && c <= 'z')
  47                        c -= 'a' - 'A';
  48                hash = (hash * FNV32_PRIME) ^ c;
  49        }
  50        return hash;
  51}
  52
  53/*
  54 * Incoporate another chunk of data into a memihash
  55 * computation.
  56 */
  57unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
  58{
  59        unsigned int hash = hash_seed;
  60        unsigned char *ucbuf = (unsigned char *) buf;
  61        while (len--) {
  62                unsigned int c = *ucbuf++;
  63                if (c >= 'a' && c <= 'z')
  64                        c -= 'a' - 'A';
  65                hash = (hash * FNV32_PRIME) ^ c;
  66        }
  67        return hash;
  68}
  69
  70#define HASHMAP_INITIAL_SIZE 64
  71/* grow / shrink by 2^2 */
  72#define HASHMAP_RESIZE_BITS 2
  73/* load factor in percent */
  74#define HASHMAP_LOAD_FACTOR 80
  75
  76static void alloc_table(struct hashmap *map, unsigned int size)
  77{
  78        map->tablesize = size;
  79        map->table = xcalloc(size, sizeof(struct hashmap_entry *));
  80
  81        /* calculate resize thresholds for new size */
  82        map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
  83        if (size <= HASHMAP_INITIAL_SIZE)
  84                map->shrink_at = 0;
  85        else
  86                /*
  87                 * The shrink-threshold must be slightly smaller than
  88                 * (grow-threshold / resize-factor) to prevent erratic resizing,
  89                 * thus we divide by (resize-factor + 1).
  90                 */
  91                map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
  92}
  93
  94static inline int entry_equals(const struct hashmap *map,
  95                const struct hashmap_entry *e1, const struct hashmap_entry *e2,
  96                const void *keydata)
  97{
  98        return (e1 == e2) ||
  99               (e1->hash == e2->hash &&
 100                !map->cmpfn(map->cmpfn_data, e1, e2, keydata));
 101}
 102
 103static inline unsigned int bucket(const struct hashmap *map,
 104                const struct hashmap_entry *key)
 105{
 106        return key->hash & (map->tablesize - 1);
 107}
 108
 109int hashmap_bucket(const struct hashmap *map, unsigned int hash)
 110{
 111        return hash & (map->tablesize - 1);
 112}
 113
 114static void rehash(struct hashmap *map, unsigned int newsize)
 115{
 116        unsigned int i, oldsize = map->tablesize;
 117        struct hashmap_entry **oldtable = map->table;
 118
 119        if (map->disallow_rehash)
 120                return;
 121
 122        alloc_table(map, newsize);
 123        for (i = 0; i < oldsize; i++) {
 124                struct hashmap_entry *e = oldtable[i];
 125                while (e) {
 126                        struct hashmap_entry *next = e->next;
 127                        unsigned int b = bucket(map, e);
 128                        e->next = map->table[b];
 129                        map->table[b] = e;
 130                        e = next;
 131                }
 132        }
 133        free(oldtable);
 134}
 135
 136static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
 137                const struct hashmap_entry *key, const void *keydata)
 138{
 139        struct hashmap_entry **e = &map->table[bucket(map, key)];
 140        while (*e && !entry_equals(map, *e, key, keydata))
 141                e = &(*e)->next;
 142        return e;
 143}
 144
 145static int always_equal(const void *unused_cmp_data,
 146                        const void *unused1,
 147                        const void *unused2,
 148                        const void *unused_keydata)
 149{
 150        return 0;
 151}
 152
 153void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
 154                const void *cmpfn_data, size_t initial_size)
 155{
 156        unsigned int size = HASHMAP_INITIAL_SIZE;
 157
 158        memset(map, 0, sizeof(*map));
 159
 160        map->cmpfn = equals_function ? equals_function : always_equal;
 161        map->cmpfn_data = cmpfn_data;
 162
 163        /* calculate initial table size and allocate the table */
 164        initial_size = (unsigned int) ((uint64_t) initial_size * 100
 165                        / HASHMAP_LOAD_FACTOR);
 166        while (initial_size > size)
 167                size <<= HASHMAP_RESIZE_BITS;
 168        alloc_table(map, size);
 169}
 170
 171void hashmap_free(struct hashmap *map, int free_entries)
 172{
 173        if (!map || !map->table)
 174                return;
 175        if (free_entries) {
 176                struct hashmap_iter iter;
 177                struct hashmap_entry *e;
 178                hashmap_iter_init(map, &iter);
 179                while ((e = hashmap_iter_next(&iter)))
 180                        free(e);
 181        }
 182        free(map->table);
 183        memset(map, 0, sizeof(*map));
 184}
 185
 186void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)
 187{
 188        return *find_entry_ptr(map, key, keydata);
 189}
 190
 191void *hashmap_get_next(const struct hashmap *map, const void *entry)
 192{
 193        struct hashmap_entry *e = ((struct hashmap_entry *) entry)->next;
 194        for (; e; e = e->next)
 195                if (entry_equals(map, entry, e, NULL))
 196                        return e;
 197        return NULL;
 198}
 199
 200void hashmap_add(struct hashmap *map, void *entry)
 201{
 202        unsigned int b = bucket(map, entry);
 203
 204        /* add entry */
 205        ((struct hashmap_entry *) entry)->next = map->table[b];
 206        map->table[b] = entry;
 207
 208        /* fix size and rehash if appropriate */
 209        map->size++;
 210        if (map->size > map->grow_at)
 211                rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
 212}
 213
 214void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)
 215{
 216        struct hashmap_entry *old;
 217        struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
 218        if (!*e)
 219                return NULL;
 220
 221        /* remove existing entry */
 222        old = *e;
 223        *e = old->next;
 224        old->next = NULL;
 225
 226        /* fix size and rehash if appropriate */
 227        map->size--;
 228        if (map->size < map->shrink_at)
 229                rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
 230        return old;
 231}
 232
 233void *hashmap_put(struct hashmap *map, void *entry)
 234{
 235        struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
 236        hashmap_add(map, entry);
 237        return old;
 238}
 239
 240void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
 241{
 242        iter->map = map;
 243        iter->tablepos = 0;
 244        iter->next = NULL;
 245}
 246
 247void *hashmap_iter_next(struct hashmap_iter *iter)
 248{
 249        struct hashmap_entry *current = iter->next;
 250        for (;;) {
 251                if (current) {
 252                        iter->next = current->next;
 253                        return current;
 254                }
 255
 256                if (iter->tablepos >= iter->map->tablesize)
 257                        return NULL;
 258
 259                current = iter->map->table[iter->tablepos++];
 260        }
 261}
 262
 263struct pool_entry {
 264        struct hashmap_entry ent;
 265        size_t len;
 266        unsigned char data[FLEX_ARRAY];
 267};
 268
 269static int pool_entry_cmp(const void *unused_cmp_data,
 270                          const struct pool_entry *e1,
 271                          const struct pool_entry *e2,
 272                          const unsigned char *keydata)
 273{
 274        return e1->data != keydata &&
 275               (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
 276}
 277
 278const void *memintern(const void *data, size_t len)
 279{
 280        static struct hashmap map;
 281        struct pool_entry key, *e;
 282
 283        /* initialize string pool hashmap */
 284        if (!map.tablesize)
 285                hashmap_init(&map, (hashmap_cmp_fn) pool_entry_cmp, NULL, 0);
 286
 287        /* lookup interned string in pool */
 288        hashmap_entry_init(&key, memhash(data, len));
 289        key.len = len;
 290        e = hashmap_get(&map, &key, data);
 291        if (!e) {
 292                /* not found: create it */
 293                FLEX_ALLOC_MEM(e, data, data, len);
 294                hashmap_entry_init(e, key.ent.hash);
 295                e->len = len;
 296                hashmap_add(&map, e);
 297        }
 298        return e->data;
 299}