typedef struct ExQueue ExQueue;

ExQueue *ex_queue_new            (int      element_size);
char *   ex_queue_append         (ExQueue *queue,
				  int      n_elements);
char *   ex_queue_prepend        (ExQueue *queue,
				  int      n_elements);
char *   ex_queue_pop_head       (ExQueue *queue,
				  int      n_elements);
char *   ex_queue_pop_tail       (ExQueue *queue,
				  int      n_elements);
void     ex_queue_free           (ExQueue *queue);
int      ex_queue_get_n_elements (ExQueue *queue);