swab(3): Rewrite this to be understandable.
And make the tests work, and exercise all lengths up to 100. Evidently the previous definition, presumably tightly optimized for 1980s-era compilers and CPUs, was too hard to understand, because it was incorrectly tested for two decades and broken for years. PR lib/57141 XXX pullup-8 XXX pullup-9 XXX pullup-10
This commit is contained in:
riastradh
parent
aab5fac668
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ddb0a7e7a7
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@ -1,11 +1,9 @@
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/* $NetBSD: swab.c,v 1.19 2022/12/28 14:32:04 kre Exp $ */
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/* $NetBSD: swab.c,v 1.20 2022/12/28 15:34:19 riastradh Exp $ */
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/*
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* Copyright (c) 1988, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Jeffrey Mogul.
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/*-
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* Copyright (c) 2022 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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@ -15,66 +13,58 @@
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#if defined(LIBC_SCCS) && !defined(lint)
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#if 0
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static char sccsid[] = "@(#)swab.c 8.1 (Berkeley) 6/4/93";
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#else
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__RCSID("$NetBSD: swab.c,v 1.19 2022/12/28 14:32:04 kre Exp $");
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__RCSID("$NetBSD: swab.c,v 1.20 2022/12/28 15:34:19 riastradh Exp $");
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#endif
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#endif /* LIBC_SCCS and not lint */
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#include <assert.h>
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#include <unistd.h>
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void
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swab(const void * __restrict from, void * __restrict to, ssize_t len)
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swab(const void *__restrict src, void *__restrict dst, ssize_t nbytes)
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{
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char temp;
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const char *fp;
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char *tp;
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const char *p = src;
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char *q = dst;
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size_t n;
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if (len <= 1)
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_DIAGASSERT(src != NULL);
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_DIAGASSERT(dst != NULL);
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if (nbytes <= 1)
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return;
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_DIAGASSERT(from != NULL);
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_DIAGASSERT(to != NULL);
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/*
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* Round nbytes/2 down; we ignore the last byte altogether if
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* nbytes is odd. This way, if the destination array is
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* uninitialized, sanitizers will recognize the last byte as
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* still uninitialized and flag it as undefined.
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*/
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for (n = nbytes/2; n --> 0; p += 2, q += 2) {
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/*
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* According to POSIX (2018), the behaviour is
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* undefined if src and dst overlap. However, there
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* are uses in-tree (xsrc/external/mit/xfwp/dist/io.c)
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* that rely on swab(ptr, ptr, n) to do the swabbing
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* in-place. So make sure this works if src == dst.
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*/
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const char p0 = p[0], p1 = p[1];
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len /= 2;
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fp = (const char *)from;
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tp = (char *)to;
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#define STEP temp = *fp++,*tp++ = *fp++,*tp++ = temp
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if (__predict_false(len == 1)) {
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STEP;
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return;
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}
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/* round to multiple of 8 */
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while ((len % 8) != 0)
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len--, STEP;
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len /= 8;
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if (len == 0)
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return;
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while (len-- != 0) {
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STEP; STEP; STEP; STEP;
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STEP; STEP; STEP; STEP;
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q[0] = p1;
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q[1] = p0;
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}
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}
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@ -1,4 +1,4 @@
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/* $NetBSD: t_swab.c,v 1.2 2011/07/07 08:27:36 jruoho Exp $ */
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/* $NetBSD: t_swab.c,v 1.3 2022/12/28 15:34:19 riastradh Exp $ */
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/*-
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* Copyright (c) 2001 The NetBSD Foundation, Inc.
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@ -39,15 +39,17 @@
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#define MAXCHK 100
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static void
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build(char *a, char *b, size_t n) {
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build(char *a, char *b, size_t n)
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{
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size_t i;
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n >>= 1;
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for (i = 0; i < n; i += 2) {
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b[i+1] = a[i] = (char)i;
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b[i] = a[i+1] = (char)(i+1);
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b[i + 1] = a[i] = (char)i;
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b[i] = a[i + 1] = (char)(i + 1);
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}
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for (n <<= 1; n < MAXCHK; n++)
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if (n & 1)
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a[n - 1] = b[n - 1] = (char)~1;
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for (; n < MAXCHK; n++)
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a[n] = b[n] = (char)~0;
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}
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@ -72,19 +74,23 @@ ATF_TC_BODY(swab_basic, tc)
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{
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char a[MAXCHK], b[MAXCHK], r[MAXCHK];
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size_t i;
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bool failed = false;
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for (i = 0; i < MAXCHK; i += 2) {
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for (i = 0; i < MAXCHK; i++) {
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build(a, b, i);
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(void)memset(r, ~0, MAXCHK);
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swab(a, r, i);
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if (i & 1) /* last byte unspecified if odd length */
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r[i - 1] = (char )~1;
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if (memcmp(b, r, MAXCHK) != 0) {
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fprintf(stderr, "pattern mismatch at %lu bytes",
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(unsigned long)i);
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printf("pattern mismatch at %zu bytes\n", i);
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dump("expect:", b, MAXCHK);
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dump("result:", r, MAXCHK);
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atf_tc_fail("Check stderr for details");
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failed = true;
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}
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}
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if (failed)
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atf_tc_fail_nonfatal("Check stdout for details");
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}
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ATF_TP_ADD_TCS(tp)
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