libc/string/swab.c

1.18.56.1    martin /*	$NetBSD: swab.c,v 1.18.56.1 2023/02/22 18:47:00 martin Exp $	*/
      1.4  christos
1.18.56.1    martin
1.18.56.1    martin /*-
1.18.56.1    martin  * Copyright (c) 2022 The NetBSD Foundation, Inc.
1.18.56.1    martin  * All rights reserved.
      1.1       cgd  *
      1.1       cgd  * Redistribution and use in source and binary forms, with or without
      1.1       cgd  * modification, are permitted provided that the following conditions
      1.1       cgd  * are met:
      1.1       cgd  * 1. Redistributions of source code must retain the above copyright
      1.1       cgd  *    notice, this list of conditions and the following disclaimer.
      1.1       cgd  * 2. Redistributions in binary form must reproduce the above copyright
      1.1       cgd  *    notice, this list of conditions and the following disclaimer in the
      1.1       cgd  *    documentation and/or other materials provided with the distribution.
      1.1       cgd  *
1.18.56.1    martin  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
1.18.56.1    martin  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
1.18.56.1    martin  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
1.18.56.1    martin  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
1.18.56.1    martin  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
1.18.56.1    martin  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
1.18.56.1    martin  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
1.18.56.1    martin  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
1.18.56.1    martin  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
1.18.56.1    martin  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
1.18.56.1    martin  * POSSIBILITY OF SUCH DAMAGE.
      1.1       cgd  */
      1.1       cgd
      1.4  christos #include <sys/cdefs.h>
      1.1       cgd #if defined(LIBC_SCCS) && !defined(lint)
1.18.56.1    martin __RCSID("$NetBSD: swab.c,v 1.18.56.1 2023/02/22 18:47:00 martin Exp $");
      1.4  christos #endif
      1.1       cgd
      1.8     lukem #include <assert.h>
      1.5    kleink #include <unistd.h>
      1.1       cgd
      1.1       cgd void
1.18.56.1    martin swab(const void *__restrict src, void *__restrict dst, ssize_t nbytes)
      1.1       cgd {
1.18.56.1    martin 	const char *p = src;
1.18.56.1    martin 	char *q = dst;
1.18.56.1    martin 	size_t n;
     1.13  christos
1.18.56.1    martin 	_DIAGASSERT(src != NULL);
1.18.56.1    martin 	_DIAGASSERT(dst != NULL);
      1.1       cgd
1.18.56.1    martin 	if (nbytes <= 1)
     1.18    martin 		return;
     1.18    martin
1.18.56.1    martin 	/*
1.18.56.1    martin 	 * Round nbytes/2 down; we ignore the last byte altogether if
1.18.56.1    martin 	 * nbytes is odd.  This way, if the destination array is
1.18.56.1    martin 	 * uninitialized, sanitizers will recognize the last byte as
1.18.56.1    martin 	 * still uninitialized and flag it as undefined.
1.18.56.1    martin 	 */
1.18.56.1    martin 	for (n = nbytes/2; n --> 0; p += 2, q += 2) {
1.18.56.1    martin 		/*
1.18.56.1    martin 		 * According to POSIX (2018), the behaviour is
1.18.56.1    martin 		 * undefined if src and dst overlap.  However, there
1.18.56.1    martin 		 * are uses in-tree (xsrc/external/mit/xfwp/dist/io.c)
1.18.56.1    martin 		 * that rely on swab(ptr, ptr, n) to do the swabbing
1.18.56.1    martin 		 * in-place.  So make sure this works if src == dst.
1.18.56.1    martin 		 */
1.18.56.1    martin 		const char p0 = p[0], p1 = p[1];
1.18.56.1    martin
1.18.56.1    martin 		q[0] = p1;
1.18.56.1    martin 		q[1] = p0;
      1.1       cgd 	}
      1.1       cgd }