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 struct lxc_list {
  28         void *elem;
  29         struct lxc_list *next;
  30         struct lxc_list *prev;
  31 };
  32
  33 #define lxc_init_list(l) { .next = l, .prev = l }
  34
  35 /*
  36  * Iterate through an lxc list. An example for an idiom would be:
  37  *
  38  * struct lxc_list *iterator;
  39  * type *tmp; // where "type" can be an int, char * etc.
  40  * lxc_list_for_each(iterator, list) {
  41  *        tmp = iterator->elem;
  42  *        // Do stuff with tmp.
  43  * }
  44  * free(iterator);
  45  */
  46 #define lxc_list_for_each(__iterator, __list)                           \
  47         for (__iterator = (__list)->next;                               \
  48              __iterator != __list;                                      \
  49              __iterator = __iterator->next)
  50
  51 /*
  52  * Iterate safely through an lxc list. An example for an appropriate use case
  53  * would be:
  54  *
  55  * struct lxc_list *iterator;
  56  * lxc_list_for_each_safe(iterator, list, list->next) {
  57  *        tmp = iterator->elem;
  58  *        // Do stuff with tmp.
  59  * }
  60  * free(iterator);
  61  */
  62 #define lxc_list_for_each_safe(__iterator, __list, __next)              \
  63         for (__iterator = (__list)->next, __next = __iterator->next;    \
  64              __iterator != __list;                                      \
  65              __iterator = __next, __next = __next->next)
  66
  67 /* Initalize list. */
  68 static inline void lxc_list_init(struct lxc_list *list)
  69 {
  70         list->elem = NULL;
  71         list->next = list->prev = list;
  72 }
  73
  74 /* Add an element to a list. See lxc_list_add() and lxc_list_add_tail() for an
  75  * idiom. */
  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,
 101                                   struct lxc_list *prev,
 102                                   struct lxc_list *next)
 103 {
 104         next->prev = new;
 105         new->next = next;
 106         new->prev = prev;
 107         prev->next = new;
 108 }
 109
 110 /*
 111  * Idiom to add an element to the beginning of an lxc list:
 112  *
 113  *      struct lxc_list *tmp = malloc(sizeof(*tmp));
 114  *      if (tmp == NULL)
 115  *              return 1;
 116  *      lxc_list_add_elem(tmp, elem);
 117  *      lxc_list_add(list, tmp);
 118  */
 119 static inline void lxc_list_add(struct lxc_list *head, struct lxc_list *list)
 120 {
 121         __lxc_list_add(list, head, head->next);
 122 }
 123
 124 /*
 125  * Idiom to add an element to the end of an lxc list:
 126  *
 127  *      struct lxc_list *tmp = malloc(sizeof(*tmp));
 128  *      if (tmp == NULL)
 129  *              return 1;
 130  *      lxc_list_add_elem(tmp, elem);
 131  *      lxc_list_add_tail(list, tmp);
 132  */
 133 static inline void lxc_list_add_tail(struct lxc_list *head,
 134                                      struct lxc_list *list)
 135 {
 136         __lxc_list_add(list, head->prev, head);
 137 }
 138
 139 /*
 140  * Idiom to free an lxc list:
 141  *
 142  * lxc_list_for_each_safe(iterator, list, list->next) {
 143  *        lxc_list_del(iterator);
 144  *        free(iterator);
 145  * }
 146  * free(iterator);
 147  */
 148 static inline void lxc_list_del(struct lxc_list *list)
 149 {
 150         struct lxc_list *next, *prev;
 151
 152         next = list->next;
 153         prev = list->prev;
 154         next->prev = prev;
 155         prev->next = next;
 156 }
 157
 158 /* Return length of the list. */
 159 static inline size_t lxc_list_len(struct lxc_list *list)
 160 {
 161          size_t i = 0;
 162          struct lxc_list *iter;
 163          lxc_list_for_each(iter, list) {
 164                 i++;
 165          }
 166
 167          return i;
 168 }
 169
 170 #endif