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      1 /*	$NetBSD: dd_swab.c,v 1.2 2021/10/08 14:44:48 christos 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  * from: NetBSD: swab.c,v 1.18 2011/01/04 17:14:07 martin Exp
     35  */
     36 
     37 /* This copy has no restrict on it, that dd wants */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 #if 0
     42 static char sccsid[] = "@(#)swab.c	8.1 (Berkeley) 6/4/93";
     43 #else
     44 __RCSID("$NetBSD: dd_swab.c,v 1.2 2021/10/08 14:44:48 christos Exp $");
     45 #endif
     46 #endif /* LIBC_SCCS and not lint */
     47 
     48 #include <sys/types.h>
     49 
     50 #include "dd.h"
     51 #include "extern.h"
     52 
     53 void
     54 dd_swab(const void * from, void * to, ssize_t len)
     55 {
     56 	char temp;
     57 	const char *fp;
     58 	char *tp;
     59 
     60 	if (len <= 1)
     61 		return;
     62 
     63 	len /= 2;
     64 	fp = (const char *)from;
     65 	tp = (char *)to;
     66 #define	STEP	temp = *fp++,*tp++ = *fp++,*tp++ = temp
     67 
     68 	if (__predict_false(len == 1)) {
     69 		STEP;
     70 		return;
     71 	}
     72 
     73 	/* round to multiple of 8 */
     74 	for (; (len % 8) != 0; --len)
     75 		STEP;
     76 	len /= 8;
     77 	if (len == 0)
     78 		return;
     79 	while (len-- != 0) {
     80 		STEP; STEP; STEP; STEP;
     81 		STEP; STEP; STEP; STEP;
     82 	}
     83 }
     84