#include <sys/queue.h>
TAILQ_ENTRY(TYPE);
TAILQ_HEAD(HEADNAME, TYPE);
TAILQ_HEAD TAILQ_HEAD_INITIALIZER(TAILQ_HEAD head);
void TAILQ_INIT(TAILQ_HEAD *head);
int TAILQ_EMPTY(TAILQ_HEAD *head);
void TAILQ_INSERT_HEAD(TAILQ_HEAD *head,
struct TYPE *elm, TAILQ_ENTRY NAME);
void TAILQ_INSERT_TAIL(TAILQ_HEAD *head,
struct TYPE *elm, TAILQ_ENTRY NAME);
void TAILQ_INSERT_BEFORE(struct TYPE *listelm,
struct TYPE *elm, TAILQ_ENTRY NAME);
void TAILQ_INSERT_AFTER(TAILQ_HEAD *head, struct TYPE *listelm,
struct TYPE *elm, TAILQ_ENTRY NAME);
struct TYPE *TAILQ_FIRST(TAILQ_HEAD *head);
struct TYPE *TAILQ_LAST(TAILQ_HEAD *head, HEADNAME);
struct TYPE *TAILQ_PREV(struct TYPE *elm, HEADNAME, TAILQ_ENTRY NAME);
struct TYPE *TAILQ_NEXT(struct TYPE *elm, TAILQ_ENTRY NAME);
TAILQ_FOREACH(struct TYPE *var, TAILQ_HEAD *head,
TAILQ_ENTRY NAME);
TAILQ_FOREACH_REVERSE(struct TYPE *var, TAILQ_HEAD *head, HEADNAME,
TAILQ_ENTRY NAME);
void TAILQ_REMOVE(TAILQ_HEAD *head, struct TYPE *elm,
TAILQ_ENTRY NAME);
void TAILQ_CONCAT(TAILQ_HEAD *head1, TAILQ_HEAD *head2,
TAILQ_ENTRY NAME);
In the macro definitions, TYPE is the name of a user defined structure, that must contain a field of type TAILQ_ENTRY, named NAME. The argument HEADNAME is the name of a user defined structure that must be declared using the macro TAILQ_HEAD().
TAILQ_HEAD(HEADNAME, TYPE) head;
where struct HEADNAME is the structure to be defined, and struct TYPE is the type of the elements to be linked into the queue. A pointer to the head of the queue can later be declared as:
struct HEADNAME *headp;
(The names head and headp are user selectable.)
TAILQ_ENTRY() declares a structure that connects the elements in the queue.
TAILQ_HEAD_INITIALIZER() evaluates to an initializer for the queue head.
TAILQ_INIT() initializes the queue referenced by
TAILQ_EMPTY() evaluates to true if there are no items on the queue. head.
TAILQ_INSERT_TAIL() inserts the new element elm at the end of the queue.
TAILQ_INSERT_BEFORE() inserts the new element elm before the element listelm.
TAILQ_INSERT_AFTER() inserts the new element elm after the element listelm.
TAILQ_LAST() returns the last item on the queue. If the queue is empty the return value is NULL.
TAILQ_PREV() returns the previous item on the queue, or NULL if this item is the first.
TAILQ_NEXT() returns the next item on the queue, or NULL if this item is the last.
TAILQ_FOREACH() traverses the queue referenced by head in the forward direction, assigning each element in turn to var. var is set to NULL if the loop completes normally, or if there were no elements.
TAILQ_FOREACH_REVERSE() traverses the queue referenced by head in the reverse direction, assigning each element in turn to var.
TAILQ_FIRST(), TAILQ_LAST(), TAILQ_PREV(), and TAILQ_NEXT() return a pointer to the first, last, previous, or next TYPE structure, respectively.
TAILQ_HEAD_INITIALIZER() returns an initializer that can be assigned to the queue head.
struct entry {
int data;
TAILQ_ENTRY(entry) entries; /* Tail queue */
};
TAILQ_HEAD(tailhead, entry);
int
main(void)
{
struct entry *n1, *n2, *n3, *np;
struct tailhead head; /* Tail queue head */
int i;
TAILQ_INIT(&head); /* Initialize the queue */
n1 = malloc(sizeof(struct entry)); /* Insert at the head */
TAILQ_INSERT_HEAD(&head, n1, entries);
n1 = malloc(sizeof(struct entry)); /* Insert at the tail */
TAILQ_INSERT_TAIL(&head, n1, entries);
n2 = malloc(sizeof(struct entry)); /* Insert after */
TAILQ_INSERT_AFTER(&head, n1, n2, entries);
n3 = malloc(sizeof(struct entry)); /* Insert before */
TAILQ_INSERT_BEFORE(n2, n3, entries);
TAILQ_REMOVE(&head, n2, entries); /* Deletion */
free(n2);
/* Forward traversal */
i = 0;
TAILQ_FOREACH(np, &head, entries)
np->data = i++;
/* Reverse traversal */
TAILQ_FOREACH_REVERSE(np, &head, tailhead, entries)
printf("%i\n", np->data);
/* TailQ deletion */
n1 = TAILQ_FIRST(&head);
while (n1 != NULL) {
n2 = TAILQ_NEXT(n1, entries);
free(n1);
n1 = n2;
}
TAILQ_INIT(&head);