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gg-queue.3.gz

gg-queue(3)                      GGI                     gg-queue(3)



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_SIM‐
       PLEQ_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_CIR‐
       CLEQ_INSERT_TAIL,   GG_CIRCLEQ_REMOVE,    GG_CIRCLEQ_FOREACH,
       GG_CIRCLEQ_FOREACH_REVERSE,     GG_CIRCLEQ_EMPTY,     GG_CIR‐
       CLEQ_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  struc‐
       tures:  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  struc‐
       tures  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_CIR‐
       CLEQ_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 initial‐
       izer 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 ele‐
       ments are singly linked for minimum space and pointer manipu‐
       lation  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  fol‐
       lows:

       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  con‐
       nects 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 refer‐
       enced 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_SIM‐
       PLQ_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 refer‐
       enced by head in the forward direction, assigning  each  ele‐
       ment in turn to var.

       The  macro GG_SIMPLEQ_NEXT returns the element after the ele‐
       ment 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  exist‐
       ing  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  refer‐
       enced  by  head in the forward direction, assigning each ele‐
       ment 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 fol‐
       lows:

       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 ref‐
       erenced 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 ref‐
       erenced by head in the forward direction, assigning each ele‐
       ment 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  ele‐
       ment elm.

       The macro GG_CIRCLEQ_PREV returns the element before the ele‐
       ment 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)



libgg-1.0.x                  2005-08-26                  gg-queue(3)
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