def [](path, default = "")
      ptr = ffi_delegate.get(path, default)
      return nil if ptr.null?
      ptr.read_string
    end
def [](path, default = "")
      ptr = ffi_delegate.get(path, default)
      return nil if ptr.null?
      ptr.read_string
    end
Get the value of the current config item.
 @param path [String, #to_s] path to config item
 @param default [String, #to_s] default value to return if config item
   doesn't exist
 @return [String]
 @return [default] if config item doesn't exist
 @note The default value is not returned when the config item exists but
   just doesn't have a value. In that case, it'll return the empty
   string.