function to test the key/value pairs for a certain property
user data to pass to the function
Return: The value of the first key/value pair is returned, for which @predicate evaluates to %TRUE. If no pair with the requested property is found, %NULL is returned.
2.4
Calls the given function for key/value pairs in the #GHashTable until @predicate returns %TRUE. The function is passed the key and value of each pair, and the given @user_data parameter. The hash table may not be modified while iterating over it (you can't add/remove items).
Note, that hash tables are really only optimized for forward lookups, i.e. g_hash_table_lookup(). So code that frequently issues g_hash_table_find() or g_hash_table_foreach() (e.g. in the order of once per every entry in a hash table) should probably be reworked to use additional or different data structures for reverse lookups (keep in mind that an O(n) find/foreach operation issued for all n values in a hash table ends up needing O(n*n) operations).