Man Linux: Main Page and Category List

NAME

       gg-queue,   GG_SLIST_HEAD,  GG_SLIST_HEAD_INITIALIZER,  GG_SLIST_ENTRY,
       GG_SLIST_INIT2,      GG_SLIST_INSERT_AFTER,       GG_SLIST_INSERT_HEAD,
       GG_SLIST_REMOVE_HEAD,         GG_SLIST_REMOVE,        GG_SLIST_FOREACH,
       GG_SLIST_EMPTY,   GG_SLIST_FIRST,    GG_SLIST_NEXT,    GG_SIMPLEQ_HEAD,
       GG_SIMPLEQ_HEAD_INITIALIZER,     GG_SIMPLEQ_ENTRY,     GG_SIMPLEQ_INIT,
       GG_SIMPLEQ_INSERT_HEAD,                         GG_SIMPLEQ_INSERT_TAIL,
       GG_SIMPLEQ_INSERT_AFTER,   GG_SIMPLEQ_REMOVE_HEAD,   GG_SIMPLEQ_REMOVE,
       GG_SIMPLEQ_FOREACH,         GG_SIMPLEQ_EMPTY,         GG_SIMPLEQ_FIRST,
       GG_SIMPLEQ_NEXT, GG_LIST_HEAD, GG_LIST_HEAD_INITIALIZER, GG_LIST_ENTRY,
       GG_LIST_INIT,       GG_LIST_INSERT_AFTER,        GG_LIST_INSERT_BEFORE,
       GG_LIST_INSERT_HEAD,  GG_LIST_REMOVE,  GG_LIST_FOREACH,  GG_LIST_EMPTY,
       GG_LIST_FIRST, GG_LIST_NEXT, GG_TAILQ_HEAD,  GG_TAILQ_HEAD_INITIALIZER,
       GG_TAILQ_ENTRY,           GG_TAILQ_INIT,          GG_TAILQ_INSERT_HEAD,
       GG_TAILQ_INSERT_TAIL,  GG_TAILQ_INSERT_AFTER,   GG_TAILQ_INSERT_BEFORE,
       GG_TAILQ_REMOVE,       GG_TAILQ_FOREACH,      GG_TAILQ_FOREACH_REVERSE,
       GG_TAILQ_EMPTY,    GG_TAILQ_FIRST,    GG_TAILQ_NEXT,     GG_TAILQ_LAST,
       GG_TAILQ_PREV,       GG_CIRCLEQ_HEAD,      GG_CIRCLEQ_HEAD_INITIALIZER,
       GG_CIRCLEQ_ENTRY,       GG_CIRCLEQ_INIT,       GG_CIRCLEQ_INSERT_AFTER,
       GG_CIRCLEQ_INSERT_BEFORE,                       GG_CIRCLEQ_INSERT_HEAD,
       GG_CIRCLEQ_INSERT_TAIL,     GG_CIRCLEQ_REMOVE,      GG_CIRCLEQ_FOREACH,
       GG_CIRCLEQ_FOREACH_REVERSE,     GG_CIRCLEQ_EMPTY,     GG_CIRCLEQ_FIRST,
       GG_CIRCLEQ_LAST, GG_CIRCLEQ_NEXT, GG_CIRCLEQ_PREV - implementations  of
       singly-linked  lists,  simple  queues, lists, tail queues, and circular
       queues

SYNOPSIS

       #include <ggi/gg-queue.h>

       GG_SLIST_HEAD(HEADNAME, TYPE);

       GG_SLIST_HEAD_INITIALIZER(head);

       GG_SLIST_ENTRY(TYPE);

       GG_SLIST_INIT(GG_SLIST_HEAD *head);

       GG_SLIST_INSERT_AFTER(TYPE *listelm, TYPE *elm, GG_SLIST_ENTRY NAME);

       GG_SLIST_INSERT_HEAD(GG_SLIST_HEAD *head, TYPE *elm, GG_SLIST_ENTRY NAME);

       GG_SLIST_REMOVE_HEAD(GG_SLIST_HEAD *head, GG_SLIST_ENTRY NAME);

       GG_SLIST_REMOVE(GG_SLIST_HEAD *head, TYPE *elm, TYPE, GG_SLIST_ENTRY NAME);

       GG_SLIST_FOREACH(TYPE *var, GG_SLIST_HEAD *head, GG_SLIST_ENTRY NAME);

       int
       GG_SLIST_EMPTY(GG_SLIST_HEAD *head);

       TYPE *
       GG_SLIST_FIRST(GG_SLIST_HEAD *head);

       TYPE *
       GG_SLIST_NEXT(TYPE *elm, GG_SLIST_ENTRY NAME);

       GG_SIMPLEQ_HEAD(HEADNAME, TYPE);

       GG_SIMPLEQ_HEAD_INITIALIZER(head);

       GG_SIMPLEQ_ENTRY(TYPE);

       GG_SIMPLEQ_INIT(GG_SIMPLEQ_HEAD *head);

       GG_SIMPLEQ_INSERT_HEAD(GG_SIMPLEQ_HEAD *head, TYPE *elm, GG_SIMPLEQ_ENTRY NAME);

       GG_SIMPLEQ_INSERT_TAIL(GG_SIMPLEQ_HEAD *head, TYPE *elm, GG_SIMPLEQ_ENTRY NAME);

       GG_SIMPLEQ_INSERT_AFTER(GG_SIMPLEQ_HEAD *head, TYPE *listelm, TYPE *elm,
                  GG_SIMPLEQ_ENTRY NAME);

       GG_SIMPLEQ_REMOVE_HEAD(GG_SIMPLEQ_HEAD *head, GG_SIMPLEQ_ENTRY NAME);

       GG_SIMPLEQ_REMOVE(GG_SIMPLEQ_HEAD *head, TYPE *elm, TYPE, GG_SIMPLEQ_ENTRY NAME);

       GG_SIMPLEQ_FOREACH(TYPE *var, GG_SIMPLEQ_HEAD *head, GG_SIMPLEQ_ENTRY NAME);

       int
       GG_SIMPLEQ_EMPTY(GG_SIMPLEQ_HEAD *head);

       TYPE *
       GG_SIMPLEQ_FIRST(GG_SIMPLEQ_HEAD *head);

       TYPE *
       GG_SIMPLEQ_NEXT(TYPE *elm, GG_SIMPLEQ_ENTRY NAME);

       GG_LIST_HEAD(HEADNAME, TYPE);

       GG_LIST_HEAD_INITIALIZER(head);

       GG_LIST_ENTRY(TYPE);

       GG_LIST_INIT(GG_LIST_HEAD *head);

       GG_LIST_INSERT_AFTER(TYPE *listelm, TYPE *elm, GG_LIST_ENTRY NAME);

       GG_LIST_INSERT_BEFORE(TYPE *listelm, TYPE *elm, GG_LIST_ENTRY NAME);

       GG_LIST_INSERT_HEAD(GG_LIST_HEAD *head, TYPE *elm, GG_LIST_ENTRY NAME);

       GG_LIST_REMOVE(TYPE *elm, GG_LIST_ENTRY NAME);

       GG_LIST_FOREACH(TYPE *var, GG_LIST_HEAD *head, GG_LIST_ENTRY NAME);

       int
       GG_LIST_EMPTY(GG_LIST_HEAD *head);

       TYPE *
       GG_LIST_FIRST(GG_LIST_HEAD *head);

       TYPE *
       GG_LIST_NEXT(TYPE *elm, GG_LIST_ENTRY NAME);

       GG_TAILQ_HEAD(HEADNAME, TYPE);

       GG_TAILQ_HEAD_INITIALIZER(head);

       GG_TAILQ_ENTRY(TYPE);

       GG_TAILQ_INIT(GG_TAILQ_HEAD *head);

       GG_TAILQ_INSERT_HEAD(GG_TAILQ_HEAD *head, TYPE *elm, GG_TAILQ_ENTRY NAME);

       GG_TAILQ_INSERT_TAIL(GG_TAILQ_HEAD *head, TYPE *elm, GG_TAILQ_ENTRY NAME);

       GG_TAILQ_INSERT_AFTER(GG_TAILQ_HEAD *head, TYPE *listelm, TYPE *elm,
                  GG_TAILQ_ENTRY NAME);

       GG_TAILQ_INSERT_BEFORE(TYPE *listelm, TYPE *elm, GG_TAILQ_ENTRY NAME);

       GG_TAILQ_REMOVE(GG_TAILQ_HEAD *head, TYPE *elm, GG_TAILQ_ENTRY NAME);

       GG_TAILQ_FOREACH(TYPE *var, GG_TAILQ_HEAD *head, GG_TAILQ_ENTRY NAME);

       GG_TAILQ_FOREACH_REVERSE(TYPE *var, GG_TAILQ_HEAD *head, HEADNAME,
                  GG_TAILQ_ENTRY NAME);

       int
       GG_TAILQ_EMPTY(GG_TAILQ_HEAD *head);

       TYPE *
       GG_TAILQ_FIRST(GG_TAILQ_HEAD *head);

       TYPE *
       GG_TAILQ_NEXT(TYPE *elm, GG_TAILQ_ENTRY NAME);

       TYPE *
       GG_TAILQ_LAST(GG_TAILQ_HEAD *head, HEADNAME);

       TYPE *
       GG_TAILQ_PREV(TYPE *elm, HEADNAME, GG_TAILQ_ENTRY NAME);

       GG_CIRCLEQ_HEAD(HEADNAME, TYPE);

       GG_CIRCLEQ_HEAD_INITIALIZER(head);

       GG_CIRCLEQ_ENTRY(TYPE);

       GG_CIRCLEQ_INIT(GG_CIRCLEQ_HEAD *head);

       GG_CIRCLEQ_INSERT_AFTER(GG_CIRCLEQ_HEAD *head, TYPE *listelm, TYPE *elm,
                  GG_CIRCLEQ_ENTRY NAME);

       GG_CIRCLEQ_INSERT_BEFORE(GG_CIRCLEQ_HEAD *head, TYPE *listelm, TYPE *elm,
                  GG_CIRCLEQ_ENTRY NAME);

       GG_CIRCLEQ_INSERT_HEAD(GG_CIRCLEQ_HEAD *head, TYPE *elm, GG_CIRCLEQ_ENTRY NAME);

       GG_CIRCLEQ_INSERT_TAIL(GG_CIRCLEQ_HEAD *head, TYPE *elm, GG_CIRCLEQ_ENTRY NAME);

       GG_CIRCLEQ_REMOVE(GG_CIRCLEQ_HEAD *head, TYPE *elm, GG_CIRCLEQ_ENTRY NAME);

       GG_CIRCLEQ_FOREACH(TYPE *var, GG_CIRCLEQ_HEAD *head, GG_CIRCLEQ_ENTRY NAME);

       GG_CIRCLEQ_FOREACH_REVERSE(TYPE *var, GG_CIRCLEQ_HEAD *head,
                  GG_CIRCLEQ_ENTRY NAME);

       int
       GG_CIRCLEQ_EMPTY(GG_CIRCLEQ_HEAD *head);

       TYPE *
       GG_CIRCLEQ_FIRST(GG_CIRCLEQ_HEAD *head);

       TYPE *
       GG_CIRCLEQ_LAST(GG_CIRCLEQ_HEAD *head);

       TYPE *
       GG_CIRCLEQ_NEXT(TYPE *elm, GG_CIRCLEQ_ENTRY NAME);

       TYPE *
       GG_CIRCLEQ_PREV(TYPE *elm, GG_CIRCLEQ_ENTRY NAME);

DESCRIPTION

       These macros define and operate  on  five  types  of  data  structures:
       singly-  linked  lists, simple queues, lists, tail queues, and circular
       queues.  All five structures support the following functionality:

       1   Insertion of a new entry at the head of the list.

       2   Insertion of a new entry before or after any element in the list.

       3   Removal of any entry in the list.

       4   Forward traversal through the list.

       Singly-linked lists are the simplest of the five  data  structures  and
       support  only  the  above functionality.  Singly-linked lists are ideal
       for applications with large datasets and few or  no  removals,  or  for
       implementing a LIFO queue.

       Simple queues add the following functionality:

       1   Entries can be added at the end of a list.

       However:

       1   Entries may not be added before any element in the list.

       2   All list insertions and removals must specify the head of the list.

       3   Each head entry requires two pointers rather than one.

       Simple queues are ideal for applications with large datasets and few or
       no removals, or for implementing a FIFO  queue.

       All  doubly  linked  types  of data structures (lists, tail queues, and
       circle queues) additionally allow:

       1   Insertion of a new entry before any element in the list.

       2   O(1) removal of any entry in the list.

       However:

       1   Each element requires two pointers rather than one.

       2   Code size and execution time of operations (except for removal)  is
           about twice that of the singly-linked data-structures.

       Linked  lists are the simplest of the doubly linked data structures and
       support only the above functionality over singly-linked lists.

       Tail queues add the following functionality:

       1   Entries can be added at the end of a list.

       However:

       1   All list insertions and removals, except insertion  before  another
           element, must specify the head of the list.

       2   Each head entry requires two pointers rather than one.

       3   Code  size is about 15% greater and operations run about 20% slower
           than lists.

       Circular queues add the following functionality:

       1   Entries can be added at the end of a list.

       2   They may be traversed backwards, from tail to head.

       However:

       1   All list insertions and removals must specify the head of the list.

       2   Each head entry requires two pointers rather than one.

       3   The termination condition for traversal is more complex.

       4   Code  size is about 40% greater and operations run about 45% slower
           than lists.

       In the macro definitions, TYPE is the name of a user defined structure,
       that  must  contain  a  field  of type GG_LIST_ENTRY, GG_SIMPLEQ_ENTRY,
       GG_SLIST_ENTRY, GG_TAILQ_ENTRY, or GG_CIRCLEQ_ENTRY,  named  NAME.  The
       argument  HEADNAME is the name of a user defined structure that must be
       declared using the macros GG_LIST_HEAD, GG_SIMPLEQ_HEAD, GG_SLIST_HEAD,
       GG_TAILQ_HEAD,  or  GG_CIRCLEQ_HEAD. See the examples below for further
       explanation of how these macros are used.

SINGLY-LINKED LISTS

       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 GG_SLIST_HEAD structure is
       declared as follows:

       GG_SLIST_HEAD(HEADNAME, TYPE) head;

       where HEADNAME is the name of the structure to be defined, and 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.)

       The macro GG_SLIST_HEAD_INITIALIZER evaluates to an initializer for the
       list head.

       The  macro GG_SLIST_EMPTY evaluates to true if there are no elements in
       the list.

       The  macro  GG_SLIST_ENTRY  declares  a  structure  that  connects  the
       elements in the list.

       The  macro GG_SLIST_FIRST returns the first element in the list or NULL
       if the list is empty.

       The macro GG_SLIST_FOREACH traverses the list referenced by head in the
       forward direction, assigning each element in turn to var.

       The macro GG_SLIST_INIT initializes the list referenced by head.

       The  macro GG_SLIST_INSERT_HEAD inserts the new element elm at the head
       of the list.

       The macro GG_SLIST_INSERT_AFTER inserts the new element elm  after  the
       element listelm.

       The macro GG_SLIST_NEXT returns the next element in the list.

       The macro GG_SLIST_REMOVE removes the element elm from the list.

       The  macro GG_SLIST_REMOVE_HEAD removes the first element 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 GG_SLIST_REMOVE macro.

SINGLY-LINKED LIST EXAMPLE

       GG_SLIST_HEAD(slisthead, entry) head =
           GG_SLIST_HEAD_INITIALIZER(head);
       struct slisthead *headp;                /* Singly-linked List head. */
       struct entry {
               ...
               GG_SLIST_ENTRY(entry) entries;  /* Singly-linked List. */
               ...
       } *n1, *n2, *n3, *np;

       GG_SLIST_INIT(&head);                   /* Initialize the list. */

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

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

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

       n3 = GG_SLIST_FIRST(&head);
       GG_SLIST_REMOVE_HEAD(&head, entries);   /* Deletion from the head. */
       free(n3);
                                               /* Forward traversal. */
       GG_SLIST_FOREACH(np, &head, entries)
               np-> ...

       while (!GG_SLIST_EMPTY(&head)) {        /* List Deletion. */
               n1 = GG_SLIST_FIRST(&head);
               GG_SLIST_REMOVE_HEAD(&head, entries);
               free(n1);
       }

SIMPLE QUEUES

       A simple queue is headed by a structure defined by the  GG_SIMPLEQ_HEAD
       macro.   This  structure  contains a pair of pointers, one to the first
       element in the simple queue and the other to the last  element  in  the
       simple  queue.   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 queue after an
       existing element, at the head of the queue, or at the end of the queue.
       A GG_SIMPLEQ_HEAD structure is declared as follows:

       GG_SIMPLEQ_HEAD(HEADNAME, TYPE) head;

       where  HEADNAME is the name of the structure to be defined, and TYPE is
       the type of the elements to be linked into the simple queue.  A pointer
       to the head of the simple queue can later be declared as:

       struct HEADNAME *headp;

       (The names head and headp are user selectable.)

       The  macro  GG_SIMPLEQ_ENTRYk  declares  a  structure that connects the
       elements in the simple queue.

       The macro GG_SIMPLEQ_HEAD_INITIALIZER provides a  value  which  can  be
       used  to initialize a simple queue head at compile time, and is used at
       the point that the simple queue head variable is declared, like:

       struct HEADNAME head = GG_SIMPLEQ_HEAD_INITIALIZER(head);

       The macro GG_SIMPLEQ_INIT initializes the simple  queue  referenced  by
       head.

       The  macro  GG_SIMPLEQ_INSERT_HEAD  inserts  the new element elm at the
       head of the simple queue.

       The macro GG_SIMPLEQ_INSERT_TAIL inserts the new element elm at the end
       of the simple queue.

       The macro GG_SIMPLEQ_INSERT_AFTER inserts the new element elm after the
       ele- ment listelm.

       The macro GG_SIMPLEQ_REMOVE removes elm from the simple queue.

       The macro GG_SIMPLEQ_REMOVE_HEAD removes the  first  element  from  the
       head  of  the  simple  queue.   For  optimum efficiency, elements being
       removed from the head of the queue should  explicitly  use  this  macro
       instead of the generic GG_SIMPLQ_REMOVE macro.

       The  macro GG_SIMPLEQ_EMPTY return true if the simple queue head has no
       elements.

       The macro GG_SIMPLEQ_FIRST returns the  first  element  of  the  simple
       queue head.

       The  macro  GG_SIMPLEQ_FOREACH  traverses  the tail queue referenced by
       head in the forward direction, assigning each element in turn to var.

       The macro GG_SIMPLEQ_NEXT returns the element after the element elm.

SIMPLE QUEUE EXAMPLE

       GG_SIMPLEQ_HEAD(simplehead, entry) head;
       struct simplehead *headp;               /* Simple queue head. */
       struct entry {
               ...
               GG_SIMPLEQ_ENTRY(entry) entries;/* Simple queue. */
               ...
       } *n1, *n2, *np;

       GG_SIMPLEQ_INIT(&head);                 /* Initialize the queue. */

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

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

       n2 = malloc(sizeof(struct entry));      /* Insert after. */
       GG_SIMPLEQ_INSERT_AFTER(&head, n1, n2, entries);
                                               /* Forward traversal. */
       GG_SIMPLEQ_FOREACH(np, &head, entries)
               np-> ...
                                               /* Delete. */
       while (GG_SIMPLEQ_FIRST(&head) != NULL)
               GG_SIMPLEQ_REMOVE_HEAD(&head, entries);
       if (GG_SIMPLEQ_EMPTY(&head))            /* Test for emptiness. */
               printf("nothing to do\n");

LISTS

       A list is headed by a structure  defined  by  the  GG_LIST_HEAD  macro.
       This  structure  contains  a single pointer to the first element on the
       list.  The elements are doubly linked so that an arbitrary element  can
       be  removed  without traversing the list.  New elements can be added to
       the list after an existing element, before an existing element,  or  at
       the head of the list. A LIST_HEAD structure is declared as follows:

       GG_LIST_HEAD(HEADNAME, TYPE) head;

       where  HEADNAME is the name of the structure to be defined, and 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.)

       The macro GG_LIST_ENTRY declares a structure that connects the elements
       in the list.

       The macro GG_LIST_HEAD_INITIALIZER provides a value which can  be  used
       to  initialize  a  list  head at compile time, and is used at the point
       that the list head variable is declared, like:

       struct HEADNAME head = GG_LIST_HEAD_INITIALIZER(head);

       The macro GG_LIST_INIT initializes the list referenced by head.

       The macro GG_LIST_INSERT_HEAD inserts the new element elm at  the  head
       of the list.

       The  macro  GG_LIST_INSERT_AFTER  inserts the new element elm after the
       element listelm.

       The macro GG_LIST_INSERT_BEFORE inserts the new element elm before  the
       element listelm.

       The macro GG_LIST_REMOVE removes the element elm from the list.

       The macro GG_LIST_EMPTY return true if the list head has no elements.

       The macro GG_LIST_FIRST returns the first element of the list head.

       The  macro GG_LIST_FOREACH traverses the list referenced by head in the
       forward direction, assigning each element in turn to var.

       The macro GG_LIST_NEXT returns the element after the element elm.

LIST EXAMPLE

       GG_LIST_HEAD(listhead, entry) head;
       struct listhead *headp;                 /* List head. */
       struct entry {
               ...
               GG_LIST_ENTRY(entry) entries;   /* List. */
               ...
       } *n1, *n2, *np;

       GG_LIST_INIT(&head);                    /* Initialize the list. */

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

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

       n2 = malloc(sizeof(struct entry));      /* Insert before. */
       GG_LIST_INSERT_BEFORE(n1, n2, entries);
                                               /* Forward traversal. */
       GG_LIST_FOREACH(np, &head, entries)
               np-> ...
                                               /* Delete. */
       while (GG_LIST_FIRST(&head) != NULL)
               GG_LIST_REMOVE(LIST_FIRST(&head), entries);
       if (GG_LIST_EMPTY(&head))               /* Test for emptiness. */
               printf("nothing to do\n");

TAIL QUEUES

       A tail queue is headed by a  structure  defined  by  the  GG_TAILQ_HEAD
       macro.   This  structure  contains a pair of pointers, one to the first
       element in the tail queue and the other to the last element in the tail
       queue.  The elements are doubly linked so that an arbitrary element can
       be removed without traversing the tail queue. New elements can be added
       to  the queue after an existing element, before an existing element, at
       the head of the queue,  or  at  the  end  the  queue.  A  GG_TAILQ_HEAD
       structure is declared as follows:

       TAILQ_HEAD(HEADNAME, TYPE) head;

       where  HEADNAME is the name of the structure to be defined, and 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.)

       The  macro  GG_TAILQ_ENTRY  declares  a  structure  that  connects  the
       elements in the tail queue.

       The macro GG_TAILQ_HEAD_INITIALIZER provides a value which can be  used
       to  initialize  a  tail  queue head at compile time, and is used at the
       point that the tail queue head variable is declared, like:

       struct HEADNAME head = GG_TAILQ_HEAD_INITIALIZER(head);

       The macro GG_TAILQ_INIT initializes the tail queue referenced by  head.

       The  macro GG_TAILQ_INSERT_HEAD inserts the new element elm at the head
       of the tail queue.

       The macro GG_TAILQ_INSERT_TAIL inserts the new element elm at  the  end
       of the tail queue.

       The  macro  GG_TAILQ_INSERT_AFTER inserts the new element elm after the
       element listelm.

       The macro GG_TAILQ_INSERT_BEFORE inserts the new element elm before the
       element listelm.

       The  macro GG_TAILQ_REMOVE removes the element elm from the tail queue.

       The macro GG_TAILQ_EMPTY return true if the  tail  queue  head  has  no
       elements.

       The  macro  GG_TAILQ_FIRST  returns the first element of the tail queue
       head.

       The macro GG_TAILQ_FOREACH traverses the tail queue referenced by  head
       in the forward direction, assigning each element in turn to var.

       The  macro GG_TAILQ_FOREACH_REVERSE traverses the tail queue referenced
       by head in the reverse direction, assigning each  element  in  turn  to
       var.

       The macro GG_TAILQ_NEXT returns the element after the element elm

TAIL QUEUE EXAMPLE

       GG_TAILQ_HEAD(tailhead, entry) head;
       struct tailhead *headp;                 /* Tail queue head. */
       struct entry {
               ...
               GG_TAILQ_ENTRY(entry) entries;  /* Tail queue. */
               ...
       } *n1, *n2, *np;

       GG_TAILQ_INIT(&head);                   /* Initialize the queue. */

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

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

       n2 = malloc(sizeof(struct entry));      /* Insert after. */
       GG_TAILQ_INSERT_AFTER(&head, n1, n2, entries);

       n2 = malloc(sizeof(struct entry));      /* Insert before. */
       GG_TAILQ_INSERT_BEFORE(n1, n2, entries);
                                               /* Forward traversal. */
       GG_TAILQ_FOREACH(np, &head, entries)
               np-> ...
                                               /* Reverse traversal. */
       GG_TAILQ_FOREACH_REVERSE(np, &head, tailhead, entries)
               np-> ...
                                               /* Delete. */
       while (GG_TAILQ_FIRST(&head) != NULL)
               GG_TAILQ_REMOVE(&head, GG_TAILQ_FIRST(&head), entries);
       if (GG_TAILQ_EMPTY(&head))              /* Test for emptiness. */
               printf("nothing to do\n");

CIRCULAR QUEUES

       A   circular   queue   is   headed   by  a  structure  defined  by  the
       GG_CIRCLEQ_HEAD macro.  This structure contains a pair of pointers, one
       to  the  first  element in the circular queue and the other to the last
       element in the circular queue.  The elements are doubly linked so  that
       an  arbitrary element can be removed without traversing the queue.  New
       elements can be added to the queue after an existing element, before an
       existing element, at the head of the queue, or at the end of the queue.
       A GG_CIRCLEQ_HEAD structure is declared as follows:

       GG_CIRCLEQ_HEAD(HEADNAME, TYPE) head;

       where HEADNAME is the name of the structure to be defined, and TYPE  is
       the  type  of  the  elements  to  be linked into the circular queue.  A
       pointer to the head of the circular queue can later be declared as:

       struct HEADNAME *headp;

       (The names head and headp are user selectable.)

       The macro GG_CIRCLEQ_ENTRY  declares  a  structure  that  connects  the
       elements in the circular queue.

       The  macro  GG_CIRCLEQ_HEAD_INITIALIZER  provides  a value which can be
       used to initialize a circular queue head at compile time, and  is  used
       at the point that the circular queue head variable is declared, like:

       struct HEADNAME head = GG_CIRCLEQ_HEAD_INITIALIZER(head);

       The  macro GG_CIRCLEQ_INIT initializes the circular queue referenced by
       head.

       The macro GG_CIRCLEQ_INSERT_HEAD inserts the new  element  elm  at  the
       head of the circular queue.

       The macro GG_CIRCLEQ_INSERT_TAIL inserts the new element elm at the end
       of the circular queue.

       The macro GG_CIRCLEQ_INSERT_AFTER inserts the new element elm after the
       element listelm.

       The  macro  GG_CIRCLEQ_INSERT_BEFORE inserts the new element elm before
       the element listelm.

       The macro GG_CIRCLEQ_REMOVE removes the element elm from  the  circular
       queue.

       The  macro  GG_CIRCLEQ_EMPTY return true if the circular queue head has
       no elements.

       The macro GG_CIRCLEQ_FIRST returns the first element  of  the  circular
       queue head.

       The  macro  GG_CICRLEQ_FOREACH traverses the circle queue referenced by
       head in the forward direction, assigning each element in turn to var.

       The  macro  GG_CICRLEQ_FOREACH_REVERSE  traverses  the   circle   queue
       referenced  by head in the reverse direction, assigning each element in
       turn to var.

       The macro GG_CIRCLEQ_LAST returns the  last  element  of  the  circular
       queue head.

       The macro GG_CIRCLEQ_NEXT returns the element after the element elm.

       The macro GG_CIRCLEQ_PREV returns the element before the element elm.

CIRCULAR QUEUE EXAMPLE

       GG_CIRCLEQ_HEAD(circleq, entry) head;
       struct circleq *headp;                  /* Circular queue head. */
       struct entry {
              ...
              GG_CIRCLEQ_ENTRY(entry) entries; /* Circular queue. */
              ...
       } *n1, *n2, *np;

       GG_CIRCLEQ_INIT(&head);                 /* Initialize the circular queue. */

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

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

       n2 = malloc(sizeof(struct entry));      /* Insert after. */
       GG_CIRCLEQ_INSERT_AFTER(&head, n1, n2, entries);

       n2 = malloc(sizeof(struct entry));      /* Insert before. */
       GG_CIRCLEQ_INSERT_BEFORE(&head, n1, n2, entries);
                                               /* Forward traversal. */
       GG_CIRCLEQ_FOREACH(np, &head, entries)
               np-> ...
                                               /* Reverse traversal. */
       GG_CIRCLEQ_FOREACH_REVERSE(np, &head, entries)
               np-> ...
                                               /* Delete. */
       while (GG_CIRCLEQ_FIRST(&head) != (void *)&head)
               GG_CIRCLEQ_REMOVE(&head, GG_CIRCLEQ_FIRST(&head), entries);
       if (GG_CIRCLEQ_EMPTY(&head))            /* Test for emptiness. */
               printf("nothing to do\n");

SEE ALSO

       gg-tree(3)