/* $NetBSD: swab.c,v 1.18.56.1 2023/02/22 18:47:00 martin Exp $ */ /*- * Copyright (c) 2022 The NetBSD Foundation, Inc. * All rights reserved. * * 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. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ #include #if defined(LIBC_SCCS) && !defined(lint) __RCSID("$NetBSD: swab.c,v 1.18.56.1 2023/02/22 18:47:00 martin Exp $"); #endif #include #include void swab(const void *__restrict src, void *__restrict dst, ssize_t nbytes) { const char *p = src; char *q = dst; size_t n; _DIAGASSERT(src != NULL); _DIAGASSERT(dst != NULL); if (nbytes <= 1) return; /* * Round nbytes/2 down; we ignore the last byte altogether if * nbytes is odd. This way, if the destination array is * uninitialized, sanitizers will recognize the last byte as * still uninitialized and flag it as undefined. */ for (n = nbytes/2; n --> 0; p += 2, q += 2) { /* * According to POSIX (2018), the behaviour is * undefined if src and dst overlap. However, there * are uses in-tree (xsrc/external/mit/xfwp/dist/io.c) * that rely on swab(ptr, ptr, n) to do the swabbing * in-place. So make sure this works if src == dst. */ const char p0 = p[0], p1 = p[1]; q[0] = p1; q[1] = p0; } }