32 #define INIT_LIST(list) \  argument
33 	do { (list).head = NULL; (list).tail = NULL; } while (0)
46 #define HEAD(list) ((list).head)  argument
47 #define TAIL(list) ((list).tail)  argument
48 #define EMPTY(list) ((list).head == NULL)  argument
50 #define PREPEND(list, elt, link) \  argument
53 		if ((list).head != NULL) \
54 			(list).head->link.prev = (elt); \
56 			(list).tail = (elt); \
58 		(elt)->link.next = (list).head; \
59 		(list).head = (elt); \
62 #define APPEND(list, elt, link) \  argument
65 		if ((list).tail != NULL) \
66 			(list).tail->link.next = (elt); \
68 			(list).head = (elt); \
69 		(elt)->link.prev = (list).tail; \
71 		(list).tail = (elt); \
74 #define UNLINK_TYPE(list, elt, link, type) \  argument
80 			INSIST((list).tail == (elt)); \
81 			(list).tail = (elt)->link.prev; \
86 			INSIST((list).head == (elt)); \
87 			(list).head = (elt)->link.next; \
91 #define UNLINK(list, elt, link) \  argument
92 	UNLINK_TYPE(list, elt, link, void)
97 #define INSERT_BEFORE(list, before, elt, link) \  argument
101 			PREPEND(list, elt, link); \
110 #define INSERT_AFTER(list, after, elt, link) \  argument
114 			APPEND(list, elt, link); \
123 #define ENQUEUE(list, elt, link) APPEND(list, elt, link)  argument
124 #define DEQUEUE(list, elt, link) UNLINK(list, elt, link)  argument