src/lxc/list.h

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2008
   5  *
   6  * Authors:
   7  * Daniel Lezcano <daniel.lezcano at free.fr>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #ifndef __LXC_LIST_H
  25 #define __LXC_LIST_H
  26
  27 #include <stdio.h>
  28
  29 struct lxc_list {
  30         void *elem;
  31         struct lxc_list *next;
  32         struct lxc_list *prev;
  33 };
  34
  35 #define lxc_init_list(l)                                                       \
  36         {                                                                      \
  37                 .next = l, .prev = l                                           \
  38         }
  39
  40 /*
  41  * Iterate through an lxc list. An example for an idiom would be:
  42  *
  43  * struct lxc_list *iterator;
  44  * lxc_list_for_each(iterator, list) {
  45  *        type *tmp;
  46  *        tmp = iterator->elem;
  47  * }
  48  */
  49 #define lxc_list_for_each(__iterator, __list)                                  \
  50         for (__iterator = (__list)->next; __iterator != __list;                \
  51              __iterator = __iterator->next)
  52
  53 /* Iterate safely through an lxc list. An example for an appropriate use case
  54  * would be:
  55  *
  56  * struct lxc_list *cur, *next;
  57  * lxc_list_for_each_safe(cur, list, next) {
  58  *        type *tmp;
  59  *        tmp = cur->elem;
  60  * }
  61  */
  62 #define lxc_list_for_each_safe(__iterator, __list, __next)                     \
  63         for (__iterator = (__list)->next, __next = __iterator->next;           \
  64              __iterator != __list; __iterator = __next, __next = __next->next)
  65
  66 /* Initialize list. */
  67 static inline void lxc_list_init(struct lxc_list *list)
  68 {
  69         list->elem = NULL;
  70         list->next = list->prev = list;
  71 }
  72
  73 /* Add an element to a list. See lxc_list_add() and lxc_list_add_tail() for an
  74  * idiom.
  75  */
  76 static inline void lxc_list_add_elem(struct lxc_list *list, void *elem)
  77 {
  78         list->elem = elem;
  79 }
  80
  81 /* Retrieve first element of list. */
  82 static inline void *lxc_list_first_elem(struct lxc_list *list)
  83 {
  84         return list->next->elem;
  85 }
  86
  87 /* Retrieve last element of list. */
  88 static inline void *lxc_list_last_elem(struct lxc_list *list)
  89 {
  90         return list->prev->elem;
  91 }
  92
  93 /* Determine if list is empty. */
  94 static inline int lxc_list_empty(struct lxc_list *list)
  95 {
  96         return list == list->next;
  97 }
  98
  99 /* Workhorse to be called from lxc_list_add() and lxc_list_add_tail(). */
 100 static inline void __lxc_list_add(struct lxc_list *new, struct lxc_list *prev,
 101                                   struct lxc_list *next)
 102 {
 103         next->prev = new;
 104         new->next = next;
 105         new->prev = prev;
 106         prev->next = new;
 107 }
 108
 109 /* Idiom to add an element to the beginning of an lxc list:
 110  *
 111  *      struct lxc_list *tmp = malloc(sizeof(*tmp));
 112  *      if (tmp == NULL)
 113  *              return 1;
 114  *      lxc_list_add_elem(tmp, elem);
 115  *      lxc_list_add(list, tmp);
 116  */
 117 static inline void lxc_list_add(struct lxc_list *head, struct lxc_list *list)
 118 {
 119         __lxc_list_add(list, head, head->next);
 120 }
 121
 122 /* Idiom to add an element to the end of an lxc list:
 123  *
 124  *      struct lxc_list *tmp = malloc(sizeof(*tmp));
 125  *      if (tmp == NULL)
 126  *              return 1;
 127  *      lxc_list_add_elem(tmp, elem);
 128  *      lxc_list_add_tail(list, tmp);
 129  */
 130 static inline void lxc_list_add_tail(struct lxc_list *head,
 131                                      struct lxc_list *list)
 132 {
 133         __lxc_list_add(list, head->prev, head);
 134 }
 135
 136 /* Idiom to remove an element from a list:
 137  * struct lxc_list *cur, *next;
 138  * lxc_list_for_each_safe(cur, list, next) {
 139  *        lxc_list_del(cur);
 140  *        free(cur->elem);
 141  *        free(cur);
 142  * }
 143  */
 144 static inline void lxc_list_del(struct lxc_list *list)
 145 {
 146         struct lxc_list *next, *prev;
 147
 148         next = list->next;
 149         prev = list->prev;
 150         next->prev = prev;
 151         prev->next = next;
 152 }
 153
 154 /* Return length of the list. */
 155 static inline size_t lxc_list_len(struct lxc_list *list)
 156 {
 157         size_t i = 0;
 158         struct lxc_list *iter;
 159
 160         lxc_list_for_each(iter, list) {
 161                 i++;
 162         }
 163
 164         return i;
 165 }
 166
 167 #endif /* __LXC_LIST_H */