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      1 /* Ring definitions. */
      2 #define	qr(a_type)							\
      3 struct {								\
      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