Gets the value corresponding to the given key, creating it if
necessary. It first checks if the value already exists in the
GCache, by using the key_equal_func function passed to
g_cache_new(). If it does already exist it is returned, and its
reference count is increased by one. If the value does not currently
exist, if is created by calling the value_new_func. The key is
duplicated by calling key_dup_func and the duplicated key and value
are inserted into the GCache.
Gets the value corresponding to the given key, creating it if necessary. It first checks if the value already exists in the GCache, by using the key_equal_func function passed to g_cache_new(). If it does already exist it is returned, and its reference count is increased by one. If the value does not currently exist, if is created by calling the value_new_func. The key is duplicated by calling key_dup_func and the duplicated key and value are inserted into the GCache.