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
38 static 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
47 void
swab(const void * __restrict from,void * __restrict to,ssize_t len)48 swab(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