text: /*
   * Doubly-linked list
   * Copyright (c) 2009, Jouni Malinen <j@w1.fi>
   *
   * This software may be distributed under the terms of the BSD license.
   * See README for more details.
   */
  
  #ifndef LIST_H
  #define LIST_H
  
  /**
   * struct dl_list - Doubly-linked list
   */
  struct dl_list {
    struct dl_list *next;
    struct dl_list *prev;
  };
  
  static inline void dl_list_init(struct dl_list *list) {
    list->next = list;
    list->prev = list;
  }
  
  static inline void dl_list_add(struct dl_list *list, struct dl_list *item) {
    item->next = list->next;
    item->prev = list;
    list->next->prev = item;
    list->next = item;
  }
  
  static inline void dl_list_add_tail(struct dl_list *list,
                                      struct dl_list *item) {
    dl_list_add(list->prev, item);
  }
  
  static inline void dl_list_del(struct dl_list *item) {
    item->next->prev = item->prev;
    item->prev->next = item->next;
    item->next = NULL;
    item->prev = NULL;
  }
  
  static inline int dl_list_empty(struct dl_list *list) {
    return list->next == list;
  }
  
  static inline unsigned int dl_list_len(struct dl_list *list) {
    struct dl_list *item;
    int count = 0;
    for (item = list->next; item != list; item = item->next)
      count++;
    return count;
  }
  
  #ifndef offsetof
  #define offsetof(type, member) ((long)&((type *)0)->member)
  #endif
  
  #define dl_list_entry(item, type, member)                                      \
    ((type *)((char *)item - offsetof(type, member)))
  
  #define dl_list_first(list, type, member)                                      \
    (dl_list_empty((list)) ? NULL : dl_list_entry((list)->next, type, member))
  
  #define dl_list_last(list, type, member)                                       \
    (dl_list_empty((list)) ? NULL : dl_list_entry((list)->prev, type, member))
  
  #define dl_list_for_each(item, list, type, member)                             \
    for (item = dl_list_entry((list)->next, type, member);                       \
         &item->member != (list);                                                \
         item = dl_list_entry(item->member.next, type, member))
  
  #define dl_list_for_each_safe(item, n, list, type, member)                     \
    for (item = dl_list_entry((list)->next, type, member),                       \
        n = dl_list_entry(item->member.next, type, member);                      \
         &item->member != (list);                                                \
         item = n, n = dl_list_entry(n->member.next, type, member))
  
  #define dl_list_for_each_reverse(item, list, type, member)                     \
    for (item = dl_list_entry((list)->prev, type, member);                       \
         &item->member != (list);                                                \
         item = dl_list_entry(item->member.prev, type, member))
  
  #define DEFINE_DL_LIST(name) struct dl_list name = {&(name), &(name)}
  
  #endif /* LIST_H */
  