hashmap

Hashmap implementation in C using linked list for collision resolution.

Usage

Create

To create a hashmap call the hashmap_create function:

hashmap *map = hashmap_create(12, NULL, NULL);

If you use a string type key, just pass NULL to use the default hash algorithm and compare function. Otherwise, you can also use your own algorithm and function.

Set

To set an entry in the hashmap use the hashmap_set function:

hashmap_set(map, "k1", "v1");
char *pre = hashmap_set(map, "k1", "v2"); // return "v1"

Get

To get an entry from a hashmap use the hashmap_get function:

void *value = hashmap_get(map, "k1");

Remove

To remove an entry from a hashmap use the hashmap_remove function:

char *removed = hashmap_remove(map, "k1");

Iterate

You can iterate over all the entries stored in the hashmap with the hashmap_iterate function:

static bool iterator(void *key, void *value, void *context) {
  printf("k: %s, v: %s\n", key, value);
  if (strcmp(key, "k3") == 0) {
    *(bool *)context = true;
    // Stop here
    return false;
  }
  return true;
}

bool found;
hashmap_iterate(map, iterator, &found);

You can early exit from the iteration of the hashmap by returning false from your callback function.

Get Number of Entries

To get the number of entries stored in the hashmap use the hashmap_count function:

size_t count = hashmap_count(map);

Free

To Free a hashmap when you are finished with it use the hashmap_free function:

hashmap_free(map);
map = NULL;

This does not free the keys or values themselves.

Thread Safety

For thread safety when getting and setting, use the hashmap_lock and hashmap_unlock functions:

hashmap_lock(map);
hashmap_set(map, "k1", "v1");
hashmap_unlock(map);