1/* Copyright (C) 1992-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <stddef.h>
19#include <search.h>
20
21/* Insert ELEM into a doubly-linked list, after PREV. */
22
23void
24insque (void *elem, void *prev)
25{
26 if (prev == NULL)
27 {
28 ((struct qelem *) elem)->q_forw = NULL;
29 ((struct qelem *) elem)->q_back = NULL;
30 }
31 else
32 {
33 struct qelem *next = ((struct qelem *) prev)->q_forw;
34 ((struct qelem *) prev)->q_forw = (struct qelem *) elem;
35 if (next != NULL)
36 next->q_back = (struct qelem *) elem;
37 ((struct qelem *) elem)->q_forw = next;
38 ((struct qelem *) elem)->q_back = (struct qelem *) prev;
39 }
40}
41
42/* Unlink ELEM from the doubly-linked list that it is in. */
43
44void
45remque (void *elem)
46{
47 struct qelem *next = ((struct qelem *) elem)->q_forw;
48 struct qelem *prev = ((struct qelem *) elem)->q_back;
49 if (next != NULL)
50 next->q_back = prev;
51 if (prev != NULL)
52 prev->q_forw = (struct qelem *) next;
53}
54