1/*	$NetBSD: swab.c,v 1.18 2011/01/04 17:14:07 martin Exp $	*/
2
3/*
4 * Copyright (c) 1988, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Jeffrey Mogul.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/cdefs.h>
36#if defined(LIBC_SCCS) && !defined(lint)
37#if 0
38static char sccsid[] = "@(#)swab.c	8.1 (Berkeley) 6/4/93";
39#else
40__RCSID("$NetBSD: swab.c,v 1.18 2011/01/04 17:14:07 martin Exp $");
41#endif
42#endif /* LIBC_SCCS and not lint */
43
44#include <assert.h>
45#include <unistd.h>
46
47void
48swab(const void * __restrict from, void * __restrict to, ssize_t len)
49{
50	char temp;
51	const char *fp;
52	char *tp;
53
54	if (len <= 1)
55		return;
56
57	_DIAGASSERT(from != NULL);
58	_DIAGASSERT(to != NULL);
59
60	len /= 2;
61	fp = (const char *)from;
62	tp = (char *)to;
63#define	STEP	temp = *fp++,*tp++ = *fp++,*tp++ = temp
64
65	if (__predict_false(len == 1)) {
66		STEP;
67		return;
68	}
69
70	/* round to multiple of 8 */
71	while ((--len % 8) != 0)
72		STEP;
73	len /= 8;
74	if (len == 0)
75		return;
76	while (len-- != 0) {
77		STEP; STEP; STEP; STEP;
78		STEP; STEP; STEP; STEP;
79	}
80}
81