lib/libc/string/swab.c

   1 /*
   2  * Copyright (c) 1988, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Jeffrey Mogul.
   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  * 3. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)swab.c   8.1 (Berkeley) 6/4/93
  33  * $FreeBSD: head/lib/libc/string/swab.c 251069 2013-05-28 20:57:40Z emaste $
  34  */
  35
  36 #include <unistd.h>
  37
  38 void
  39 swab(const void * __restrict from, void * __restrict to, ssize_t len)
  40 {
  41         unsigned long temp;
  42         int n;
  43         char *fp, *tp;
  44
  45         if (len <= 0)
  46                 return;
  47         n = len >> 1;
  48         fp = (char *)from;
  49         tp = (char *)to;
  50 #define STEP    temp = *fp++,*tp++ = *fp++,*tp++ = temp
  51         /* round to multiple of 8 */
  52         for (; n & 0x7; --n)
  53                 STEP;
  54         for (n >>= 3; n > 0; --n) {
  55                 STEP; STEP; STEP; STEP;
  56                 STEP; STEP; STEP; STEP;
  57         }
  58 }