glibc/misc/insremque.c

54 lines
1.6 KiB
C

/* Copyright (C) 1992-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <stddef.h>
#include <search.h>
/* Insert ELEM into a doubly-linked list, after PREV. */
void
insque (void *elem, void *prev)
{
if (prev == NULL)
{
((struct qelem *) elem)->q_forw = NULL;
((struct qelem *) elem)->q_back = NULL;
}
else
{
struct qelem *next = ((struct qelem *) prev)->q_forw;
((struct qelem *) prev)->q_forw = (struct qelem *) elem;
if (next != NULL)
next->q_back = (struct qelem *) elem;
((struct qelem *) elem)->q_forw = next;
((struct qelem *) elem)->q_back = (struct qelem *) prev;
}
}
/* Unlink ELEM from the doubly-linked list that it is in. */
void
remque (void *elem)
{
struct qelem *next = ((struct qelem *) elem)->q_forw;
struct qelem *prev = ((struct qelem *) elem)->q_back;
if (next != NULL)
next->q_back = prev;
if (prev != NULL)
prev->q_forw = (struct qelem *) next;
}