slist(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | STANDARDS | HISTORY | BUGS | EXAMPLES | SEE ALSO | COLOPHON

SLIST(3)                Library Functions Manual                SLIST(3)

NAME         top

       SLIST_EMPTY, SLIST_ENTRY, SLIST_FIRST, SLIST_FOREACH, SLIST_HEAD,
       SLIST_HEAD_INITIALIZER, SLIST_INIT, SLIST_INSERT_AFTER,
       SLIST_INSERT_HEAD, SLIST_NEXT, SLIST_REMOVE, SLIST_REMOVE_HEAD -
       implementation of a singly linked list

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <sys/queue.h>

       SLIST_ENTRY(TYPE);

       SLIST_HEAD(HEADNAME, TYPE);
       SLIST_HEAD SLIST_HEAD_INITIALIZER(SLIST_HEAD head);
       void SLIST_INIT(SLIST_HEAD *head);

       int SLIST_EMPTY(SLIST_HEAD *head);

       void SLIST_INSERT_HEAD(SLIST_HEAD *head,
                               struct TYPE *elm, SLIST_ENTRY NAME);
       void SLIST_INSERT_AFTER(struct TYPE *listelm,
                               struct TYPE *elm, SLIST_ENTRY NAME);

       struct TYPE *SLIST_FIRST(SLIST_HEAD *head);
       struct TYPE *SLIST_NEXT(struct TYPE *elm, SLIST_ENTRY NAME);

       SLIST_FOREACH(struct TYPE *var, SLIST_HEAD *head, SLIST_ENTRY NAME);

       void SLIST_REMOVE(SLIST_HEAD *head, struct TYPE *elm,
                               SLIST_ENTRY NAME);
       void SLIST_REMOVE_HEAD(SLIST_HEAD *head,
                               SLIST_ENTRY NAME);

DESCRIPTION         top

       These macros define and operate on singly linked lists.

       In the macro definitions, TYPE is the name of a user-defined
       structure, that must contain a field of type SLIST_ENTRY, named
       NAME.  The argument HEADNAME is the name of a user-defined
       structure that must be declared using the macro SLIST_HEAD().

   Creation
       A singly linked list is headed by a structure defined by the
       SLIST_HEAD() macro.  This structure contains a single pointer to
       the first element on the list.  The elements are singly linked
       for minimum space and pointer manipulation overhead at the
       expense of O(n) removal for arbitrary elements.  New elements can
       be added to the list after an existing element or at the head of
       the list.  An SLIST_HEAD structure is declared as follows:

           SLIST_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 list.  A
       pointer to the head of the list can later be declared as:

           struct HEADNAME *headp;

       (The names head and headp are user selectable.)

       SLIST_ENTRY() declares a structure that connects the elements in
       the list.

       SLIST_HEAD_INITIALIZER() evaluates to an initializer for the list
       head.

       SLIST_INIT() initializes the list referenced by head.

       SLIST_EMPTY() evaluates to true if there are no elements in the
       list.

   Insertion
       SLIST_INSERT_HEAD() inserts the new element elm at the head of
       the list.

       SLIST_INSERT_AFTER() inserts the new element elm after the
       element listelm.

   Traversal
       SLIST_FIRST() returns the first element in the list, or NULL if
       the list is empty.

       SLIST_NEXT() returns the next element in the list.

       SLIST_FOREACH() traverses the list referenced by head in the
       forward direction, assigning each element in turn to var.

   Removal
       SLIST_REMOVE() removes the element elm from the list.

       SLIST_REMOVE_HEAD() removes the element elm from the head of the
       list.  For optimum efficiency, elements being removed from the
       head of the list should explicitly use this macro instead of the
       generic SLIST_REMOVE().

RETURN VALUE         top

       SLIST_EMPTY() returns nonzero if the list is empty, and zero if
       the list contains at least one entry.

       SLIST_FIRST(), and SLIST_NEXT() return a pointer to the first or
       next TYPE structure, respectively.

       SLIST_HEAD_INITIALIZER() returns an initializer that can be
       assigned to the list head.

STANDARDS         top

       BSD.

HISTORY         top

       4.4BSD.

BUGS         top

       SLIST_FOREACH() doesn't allow var to be removed or freed within
       the loop, as it would interfere with the traversal.
       SLIST_FOREACH_SAFE(), which is present on the BSDs but is not
       present in glibc, fixes this limitation by allowing var to safely
       be removed from the list and freed from within the loop without
       interfering with the traversal.

EXAMPLES         top

       #include <stddef.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/queue.h>

       struct entry {
           int data;
           SLIST_ENTRY(entry) entries;             /* Singly linked list */
       };

       SLIST_HEAD(slisthead, entry);

       int
       main(void)
       {
           struct entry *n1, *n2, *n3, *np;
           struct slisthead head;                  /* Singly linked list
                                                      head */

           SLIST_INIT(&head);                      /* Initialize the queue */

           n1 = malloc(sizeof(struct entry));      /* Insert at the head */
           SLIST_INSERT_HEAD(&head, n1, entries);

           n2 = malloc(sizeof(struct entry));      /* Insert after */
           SLIST_INSERT_AFTER(n1, n2, entries);

           SLIST_REMOVE(&head, n2, entry, entries);/* Deletion */
           free(n2);

           n3 = SLIST_FIRST(&head);
           SLIST_REMOVE_HEAD(&head, entries);      /* Deletion from the head */
           free(n3);

           for (unsigned int i = 0; i < 5; i++) {
               n1 = malloc(sizeof(struct entry));
               SLIST_INSERT_HEAD(&head, n1, entries);
               n1->data = i;
           }

                                                   /* Forward traversal */
           SLIST_FOREACH(np, &head, entries)
               printf("%i\n", np->data);

           while (!SLIST_EMPTY(&head)) {           /* List deletion */
               n1 = SLIST_FIRST(&head);
               SLIST_REMOVE_HEAD(&head, entries);
               free(n1);
           }
           SLIST_INIT(&head);

           exit(EXIT_SUCCESS);
       }

SEE ALSO         top

       insque(3), queue(7)

COLOPHON         top

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Linux man-pages 6.9.1          2024-06-15                       SLIST(3)

Pages that refer to this page: queue(7)