def list_domains
    domains_count = 0
    domains_count = num_of_domains
    return [] if domains_count == 0

    array_names_ptr = FFI::MemoryPointer.new(:pointer, domains_count)
    domains_count = FFI::Connection.virConnectListDefinedDomains(@connection, array_names_ptr, domains_count)

    string_ptr = array_names_ptr.read_pointer
    string_ptr.null? ? [] : string_ptr.get_array_of_string(0, domains_count).compact
  ensure
    array_names_ptr.free if domains_count > 0
  end