freebsd-skq/lib/libc/string/swab.c
robert 9920d9cacd - Convert the function definition to declare its arguments
in the ANSI-C format.
 - Change the code a bit to hopefully save some cycles.
   I.e. (simplified) change

     a = b + 1;
     while (--b & 0x7)
	/* ... */
   to
     a = b;
     for (; b & 0x7; b--)
	/* ... */
   and
     while (--a >= 0)
	/* ... */
   to
     for (; a > 0; a--)
	/* ... */
 - Equip two function arguments of swab() with the 'restrict'
   type qualifier in form of the '__restrict' macro.  This is
   specified by POSIX.1-2001.
2002-08-30 20:33:05 +00:00

64 lines
2.4 KiB
C

/*
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jeffrey Mogul.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)swab.c 8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <string.h>
void
swab(const void * __restrict from, void * __restrict to, size_t len)
{
unsigned long temp;
int n;
char *fp, *tp;
n = len >> 1;
fp = (char *)from;
tp = (char *)to;
#define STEP temp = *fp++,*tp++ = *fp++,*tp++ = temp
/* round to multiple of 8 */
for (; n & 0x7; --n)
STEP;
for (n >>= 3; n > 0; --n) {
STEP; STEP; STEP; STEP;
STEP; STEP; STEP; STEP;
}
}