- * This callback function returns the hashcode of a key.
- *
- * \param this is a pointer to the itemkeyfun record from where this
- * callback got invoked
- *
- * \param key is the key to produce a hascode for
- *
- * \returns the hashcode which is a vector_index (i.e. unsigned long)
- *
- * The hashcode is used for indexing into the backing vector for
- * finding the an item via its key. The same key must map consistently
- * to the same hashcode while the hashtable contains an item with that
- * key. Different keys map map to the same hashcode, in which case the
- * vector placement is made at the first empty or hole slot following
- * the hashcode index.