safe_list.c

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/*
 * safe_list - linked list protected against recursive iteration with deletes
 *
 * Copyright (C) 2013 Felix Fietkau <nbd@openwrt.org>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
#include "safe_list.h"
 
struct safe_list_iterator {
        struct safe_list_iterator **head;
        struct safe_list_iterator *next_i;
        struct safe_list *next;
};
 
static void
__safe_list_set_iterator(struct safe_list *list,
                         struct safe_list_iterator *i)
{
        struct safe_list_iterator *next_i;
        struct safe_list *next;
 
        next = list_entry(list->list.next, struct safe_list, list);
        next_i = next->i;
 
        next->i = i;
        i->next = next;
        i->head = &next->i;
 
        i->next_i = next_i;
        if (next_i)
                next_i->head = &i->next_i;
}
 
static void
__safe_list_del_iterator(struct safe_list_iterator *i)
{
        *i->head = i->next_i;
        if (i->next_i)
                i->next_i->head = i->head;
}
 
static void
__safe_list_move_iterator(struct safe_list *list,
                          struct safe_list_iterator *i)
{
        __safe_list_del_iterator(i);
        __safe_list_set_iterator(list, i);
}
 
int safe_list_for_each(struct safe_list *head,
                       int (*cb)(void *ctx, struct safe_list *list),
                       void *ctx)
{
        struct safe_list_iterator i;
        struct safe_list *cur;
        int ret = 0;
 
        for (cur = list_entry(head->list.next, struct safe_list, list),
             __safe_list_set_iterator(cur, &i);
             cur != head;
             cur = i.next, __safe_list_move_iterator(cur, &i)) {
                ret = cb(ctx, cur);
                if (ret)
                        break;
        }
 
        __safe_list_del_iterator(&i);
        return ret;
}
 
void safe_list_add(struct safe_list *list, struct safe_list *head)
{
        list->i = NULL;
        list_add_tail(&list->list, &head->list);
}
 
void safe_list_add_first(struct safe_list *list, struct safe_list *head)
{
        list->i = NULL;
        list_add(&list->list, &head->list);
}
 
void safe_list_del(struct safe_list *list)
{
        struct safe_list_iterator *i, *next_i, **tail;
        struct safe_list *next;
 
        next = list_entry(list->list.next, struct safe_list, list);
        list_del(&list->list);
 
        if (!list->i)
                return;
 
        next_i = next->i;
        tail = &next->i;
 
        for (i = list->i; i; i = i->next_i) {
                tail = &i->next_i;
                i->next = next;
        }
 
        next->i = list->i;
        list->i->head = &next->i;
        *tail = next_i;
        if (next_i)
                next_i->head = tail;
 
        list->i = NULL;
}