2 * Copyright (c) 1993,94 Winning Strategies, Inc.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by Winning Strategies, Inc.
16 * 4. The name of the author may not be used to endorse or promote products
17 * derived from this software without specific prior written permission
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 * $FreeBSD: src/lib/libc/i386/string/swab.S,v 1.5 1999/08/27 23:59:35 peter Exp $
31 * $DragonFly: src/lib/libc/i386/string/swab.S,v 1.3 2003/12/06 03:11:36 drhodus Exp $
38 * swab (const void *src, void *dst, size_t len)
39 * copy len bytes from src to dst, swapping adjacent bytes
41 * On the i486, this code is negligibly faster than the code generated
42 * by gcc at about half the size. If my i386 databook is correct, it
43 * should be considerably faster than the gcc code on a i386.
46 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
56 cld # set direction forward
59 testl $7,%ecx # copy first group of 1 to 7 words
60 jz L2 # while swaping alternate bytes.
69 L2: shrl $3,%ecx # copy remainder 8 words at a time
70 jz L4 # while swapping alternate bytes.