Before calling isc_buffer_putmem(), there is a condition to check that 'buf_size' is greater than 0. At this point 'buf_size' is guaranteed to be greater than zero, so either the condition is redundant, or 'unprocessed_size' should be checked instead, which seems more logical, because calling isc_buffer_putmem() with 'unprocessed_size' being zero is not useful, although harmless.