+uint64_t ht_count (hashtable_t *ht);
+
+typedef struct ll list_t;
+list_t * ll_alloc (void);
+
+uint64_t ll_lookup (list_t *ll, uint64_t key);
+uint64_t ll_add (list_t *ll, uint64_t key, uint64_t value);
+uint64_t ll_remove (list_t *ll, uint64_t key);
+void ll_print (list_t *ll);
+
+typedef struct sl skiplist_t;
+skiplist_t * sl_alloc (void);
+
+uint64_t sl_lookup (skiplist_t *sl, uint64_t key);
+uint64_t sl_add (skiplist_t *sl, uint64_t key, uint64_t value);
+uint64_t sl_remove (skiplist_t *sl, uint64_t key);
+void sl_print (skiplist_t *sl);