Andrew's git - gitweb.git/blob

   1#ifndef HASH_H
   2#define HASH_H
   3
   4/*
   5 * These are some simple generic hash table helper functions.
   6 * Not necessarily suitable for all users, but good for things
   7 * where you want to just keep track of a list of things, and
   8 * have a good hash to use on them.
   9 *
  10 * It keeps the hash table at roughly 50-75% free, so the memory
  11 * cost of the hash table itself is roughly
  12 *
  13 *      3 * 2*sizeof(void *) * nr_of_objects
  14 *
  15 * bytes.
  16 *
  17 * FIXME: on 64-bit architectures, we waste memory. It would be
  18 * good to have just 32-bit pointers, requiring a special allocator
  19 * for hashed entries or something.
  20 */
  21struct hash_table_entry {
  22        unsigned int hash;
  23        void *ptr;
  24};
  25
  26struct hash_table {
  27        unsigned int size, nr;
  28        struct hash_table_entry *array;
  29};
  30
  31extern void *lookup_hash(unsigned int hash, const struct hash_table *table);
  32extern void **insert_hash(unsigned int hash, void *ptr, struct hash_table *table);
  33extern int for_each_hash(const struct hash_table *table, int (*fn)(void *, void *), void *data);
  34extern void free_hash(struct hash_table *table);
  35
  36static inline void init_hash(struct hash_table *table)
  37{
  38        table->size = 0;
  39        table->nr = 0;
  40        table->array = NULL;
  41}
  42
  43static inline void preallocate_hash(struct hash_table *table, unsigned int elts)
  44{
  45        assert(table->size == 0 && table->nr == 0 && table->array == NULL);
  46        table->size = elts * 2;
  47        table->array = xcalloc(sizeof(struct hash_table_entry), table->size);
  48}
  49
  50#endif