#include <sys/queue.h> STAILQ_ENTRY(TYPE); STAILQ_HEAD(HEADNAME, TYPE); STAILQ_HEAD STAILQ_HEAD_INITIALIZER(STAILQ_HEAD head); void STAILQ_INIT(STAILQ_HEAD *head); int STAILQ_EMPTY(STAILQ_HEAD *head); void STAILQ_INSERT_HEAD(STAILQ_HEAD *head, struct TYPE *elm, STAILQ_ENTRY NAME); void STAILQ_INSERT_TAIL(STAILQ_HEAD *head, struct TYPE *elm, STAILQ_ENTRY NAME); void STAILQ_INSERT_AFTER(STAILQ_HEAD *head, struct TYPE *listelm, struct TYPE *elm, STAILQ_ENTRY NAME); struct TYPE *STAILQ_FIRST(STAILQ_HEAD *head); struct TYPE *STAILQ_NEXT(struct TYPE *elm, STAILQ_ENTRY NAME); STAILQ_FOREACH(struct TYPE *var, STAILQ_HEAD *head, STAILQ_ENTRY NAME); void STAILQ_REMOVE(STAILQ_HEAD *head, struct TYPE *elm, TYPE, STAILQ_ENTRY NAME); void STAILQ_REMOVE_HEAD(STAILQ_HEAD *head, STAILQ_ENTRY NAME); void STAILQ_CONCAT(STAILQ_HEAD *head1, STAILQ_HEAD *head2);Note: Identical macros prefixed with SIMPLEQ instead of STAILQ exist; see NOTES.
In the macro definitions, TYPE is the name of a user-defined structure, that must contain a field of type STAILQ_ENTRY, named NAME. The argument HEADNAME is the name of a user-defined structure that must be declared using the macro STAILQ_HEAD().
STAILQ_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 tail queue. A pointer to the head of the tail queue can later be declared as:
struct HEADNAME *headp;
(The names head and headp are user selectable.)
STAILQ_ENTRY() declares a structure that connects the elements in the tail queue.
STAILQ_HEAD_INITIALIZER() evaluates to an initializer for the tail queue head.
STAILQ_INIT() initializes the tail queue referenced by head.
STAILQ_EMPTY() evaluates to true if there are no items on the tail queue.
STAILQ_INSERT_TAIL() inserts the new element elm at the end of the tail queue.
STAILQ_INSERT_AFTER() inserts the new element elm after the element listelm.
STAILQ_NEXT() returns the next item on the tail queue, or NULL this item is the last.
STAILQ_FOREACH() traverses the tail queue referenced by head in the forward direction, assigning each element in turn to var.
STAILQ_REMOVE_HEAD() removes the element at the head of the tail queue. For optimum efficiency, elements being removed from the head of the tail queue should use this macro explicitly rather than the generic STAILQ_REMOVE() macro.
STAILQ_FIRST(), and STAILQ_NEXT() return a pointer to the first or next TYPE structure, respectively.
STAILQ_HEAD_INITIALIZER() returns an initializer that can be assigned to the queue head.
struct entry {
int data;
STAILQ_ENTRY(entry) entries; /* Singly linked tail queue */
};
STAILQ_HEAD(stailhead, entry);
int
main(void)
{
struct entry *n1, *n2, *n3, *np;
struct stailhead head; /* Singly linked tail queue
head */
STAILQ_INIT(&head); /* Initialize the queue */
n1 = malloc(sizeof(struct entry)); /* Insert at the head */
STAILQ_INSERT_HEAD(&head, n1, entries);
n1 = malloc(sizeof(struct entry)); /* Insert at the tail */
STAILQ_INSERT_TAIL(&head, n1, entries);
n2 = malloc(sizeof(struct entry)); /* Insert after */
STAILQ_INSERT_AFTER(&head, n1, n2, entries);
STAILQ_REMOVE(&head, n2, entry, entries); /* Deletion */
free(n2);
n3 = STAILQ_FIRST(&head);
STAILQ_REMOVE_HEAD(&head, entries); /* Deletion from the head */
free(n3);
n1 = STAILQ_FIRST(&head);
n1->data = 0;
for (int i = 1; i < 5; i++) {
n1 = malloc(sizeof(struct entry));
STAILQ_INSERT_HEAD(&head, n1, entries);
n1->data = i;
}
/* Forward traversal */
STAILQ_FOREACH(np, &head, entries)
printf("%i\n", np->data);
/* TailQ deletion */
n1 = STAILQ_FIRST(&head);
while (n1 != NULL) {
n2 = STAILQ_NEXT(n1, entries);
free(n1);
n1 = n2;
}
STAILQ_INIT(&head);