1/* Ring definitions. */
2#define	qr(a_type)							\
3struct {								\
4	a_type	*qre_next;						\
5	a_type	*qre_prev;						\
6}
7
8/* Ring functions. */
9#define	qr_new(a_qr, a_field) do {					\
10	(a_qr)->a_field.qre_next = (a_qr);				\
11	(a_qr)->a_field.qre_prev = (a_qr);				\
12} while (0)
13
14#define	qr_next(a_qr, a_field) ((a_qr)->a_field.qre_next)
15
16#define	qr_prev(a_qr, a_field) ((a_qr)->a_field.qre_prev)
17
18#define	qr_before_insert(a_qrelm, a_qr, a_field) do {			\
19	(a_qr)->a_field.qre_prev = (a_qrelm)->a_field.qre_prev;		\
20	(a_qr)->a_field.qre_next = (a_qrelm);				\
21	(a_qr)->a_field.qre_prev->a_field.qre_next = (a_qr);		\
22	(a_qrelm)->a_field.qre_prev = (a_qr);				\
23} while (0)
24
25#define	qr_after_insert(a_qrelm, a_qr, a_field)				\
26    do									\
27    {									\
28	(a_qr)->a_field.qre_next = (a_qrelm)->a_field.qre_next;		\
29	(a_qr)->a_field.qre_prev = (a_qrelm);				\
30	(a_qr)->a_field.qre_next->a_field.qre_prev = (a_qr);		\
31	(a_qrelm)->a_field.qre_next = (a_qr);				\
32    } while (0)
33
34#define	qr_meld(a_qr_a, a_qr_b, a_field) do {				\
35	void *t;							\
36	(a_qr_a)->a_field.qre_prev->a_field.qre_next = (a_qr_b);	\
37	(a_qr_b)->a_field.qre_prev->a_field.qre_next = (a_qr_a);	\
38	t = (a_qr_a)->a_field.qre_prev;					\
39	(a_qr_a)->a_field.qre_prev = (a_qr_b)->a_field.qre_prev;	\
40	(a_qr_b)->a_field.qre_prev = t;					\
41} while (0)
42
43/* qr_meld() and qr_split() are functionally equivalent, so there's no need to
44 * have two copies of the code. */
45#define	qr_split(a_qr_a, a_qr_b, a_field)				\
46	qr_meld((a_qr_a), (a_qr_b), a_field)
47
48#define	qr_remove(a_qr, a_field) do {					\
49	(a_qr)->a_field.qre_prev->a_field.qre_next			\
50	    = (a_qr)->a_field.qre_next;					\
51	(a_qr)->a_field.qre_next->a_field.qre_prev			\
52	    = (a_qr)->a_field.qre_prev;					\
53	(a_qr)->a_field.qre_next = (a_qr);				\
54	(a_qr)->a_field.qre_prev = (a_qr);				\
55} while (0)
56
57#define	qr_foreach(var, a_qr, a_field)					\
58	for ((var) = (a_qr);						\
59	    (var) != NULL;						\
60	    (var) = (((var)->a_field.qre_next != (a_qr))		\
61	    ? (var)->a_field.qre_next : NULL))
62
63#define	qr_reverse_foreach(var, a_qr, a_field)				\
64	for ((var) = ((a_qr) != NULL) ? qr_prev(a_qr, a_field) : NULL;	\
65	    (var) != NULL;						\
66	    (var) = (((var) != (a_qr))					\
67	    ? (var)->a_field.qre_prev : NULL))
68