1/*
2 * Copyright (c) 2003-2003
3 *	Fraunhofer Institute for Open Communication Systems (FhG Fokus).
4 * 	All rights reserved.
5 *
6 * Author: Hartmut Brandt <harti@freebsd.org>
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * $Begemot: libunimsg/netnatm/misc/unimsg_common.c,v 1.3 2004/07/08 08:22:03 brandt Exp $
30 */
31
32#include <netnatm/unimsg.h>
33
34/*
35 * Make sure there is enough space in front of the data for
36 * len bytes, and update the read pointer.
37 */
38int
39uni_msg_prepend(struct uni_msg *msg, size_t len)
40{
41	size_t need;
42
43	if (uni_msg_leading(msg) >= len) {
44		msg->b_rptr -= len;
45		return (0);
46	}
47	need = len - uni_msg_leading(msg);
48	if (uni_msg_ensure(msg, need))
49		return (-1);
50	memcpy(msg->b_rptr + need, msg->b_rptr, uni_msg_len(msg));
51	msg->b_rptr += need - len;
52	msg->b_wptr += need;
53	return (0);
54}
55