safe_list.c

   1 /*
   2  * safe_list - linked list protected against recursive iteration with deletes
   3  *
   4  * Copyright (C) 2013 Felix Fietkau <nbd@openwrt.org>
   5  *
   6  * Permission to use, copy, modify, and/or distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include "safe_list.h"
  20
  21 struct safe_list_iterator {
  22         struct safe_list_iterator **head;
  23         struct safe_list_iterator *next_i;
  24         struct safe_list *next;
  25 };
  26
  27 static void
  28 __safe_list_set_iterator(struct safe_list *list,
  29                          struct safe_list_iterator *i)
  30 {
  31         struct safe_list_iterator *next_i;
  32         struct safe_list *next;
  33
  34         next = list_entry(list->list.next, struct safe_list, list);
  35         next_i = next->i;
  36
  37         next->i = i;
  38         i->next = next;
  39         i->head = &next->i;
  40
  41         i->next_i = next_i;
  42         if (next_i)
  43                 next_i->head = &i->next_i;
  44 }
  45
  46 static void
  47 __safe_list_del_iterator(struct safe_list_iterator *i)
  48 {
  49         *i->head = i->next_i;
  50         if (i->next_i)
  51                 i->next_i->head = i->head;
  52 }
  53
  54 static void
  55 __safe_list_move_iterator(struct safe_list *list,
  56                           struct safe_list_iterator *i)
  57 {
  58         __safe_list_del_iterator(i);
  59         __safe_list_set_iterator(list, i);
  60 }
  61
  62 int safe_list_for_each(struct safe_list *head,
  63                        int (*cb)(void *ctx, struct safe_list *list),
  64                        void *ctx)
  65 {
  66         struct safe_list_iterator i;
  67         struct safe_list *cur;
  68         int ret = 0;
  69
  70         for (cur = list_entry(head->list.next, struct safe_list, list),
  71              __safe_list_set_iterator(cur, &i);
  72              cur != head;
  73              cur = i.next, __safe_list_move_iterator(cur, &i)) {
  74                 ret = cb(ctx, cur);
  75                 if (ret)
  76                         break;
  77         }
  78
  79         __safe_list_del_iterator(&i);
  80         return ret;
  81 }
  82
  83 void safe_list_add(struct safe_list *list, struct safe_list *head)
  84 {
  85         list->i = NULL;
  86         list_add_tail(&list->list, &head->list);
  87 }
  88
  89 void safe_list_add_first(struct safe_list *list, struct safe_list *head)
  90 {
  91         list->i = NULL;
  92         list_add(&list->list, &head->list);
  93 }
  94
  95 void safe_list_del(struct safe_list *list)
  96 {
  97         struct safe_list_iterator *i, *next_i, **tail;
  98         struct safe_list *next;
  99
 100         next = list_entry(list->list.next, struct safe_list, list);
 101         list_del(&list->list);
 102
 103         if (!list->i)
 104                 return;
 105
 106         next_i = next->i;
 107         tail = &next->i;
 108
 109         for (i = list->i; i; i = i->next_i) {
 110                 tail = &i->next_i;
 111                 i->next = next;
 112         }
 113
 114         next->i = list->i;
 115         list->i->head = &next->i;
 116         *tail = next_i;
 117         if (next_i)
 118                 next_i->head = tail;
 119
 120         list->i = NULL;
 121 }