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 }
122
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