BF_FREE
bfs[current].counter = BF_FREE; /* free old one */
if (b->counter == BF_FREE) /* if it's empty */
if (b->counter != BF_FREE) /* nop if not free */
if (bfs[current].counter != BF_FREE) /* if not free */
b->counter = BF_FREE; /* reset flag */
bfs[1].counter = BF_FREE;