update swab() to match the current posix definition. "rationale: none."

rewrite the function to be simpler as well. the compiler can unroll the
loop for us if necessary.
ok schwarze

1 files changed, 24 insertions, 50 deletions

diff --git a/src/lib/libc/string/swab.c b/src/lib/libc/string/swab.c
index b74db7e62a..c7d7d72ce0 100644
--- a/src/lib/libc/string/swab.c
+++ b/src/lib/libc/string/swab.c
@@ -1,61 +1,35 @@
-/*      $OpenBSD: swab.c,v 1.8 2008/03/15 21:54:09 ray Exp $ */
+/*      $OpenBSD: swab.c,v 1.9 2014/12/11 23:05:38 tedu Exp $ */
 /*
- * Copyright (c) 1988 Regents of the University of California.
- * All rights reserved.
+ * Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
  *
- * This code is derived from software contributed to Berkeley by
- * Jeffrey Mogul.
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
  *
- * 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. 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.
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
-
 #include <unistd.h>
 
 void
-swab(const void *from, void *to, size_t len)
+swab(const void *__restrict from, void *__restrict to, ssize_t len)
 {
-        size_t n;
-        char *fp, *tp;
-        char temp;
+        const unsigned char *src = from;
+        unsigned char *dst = to;
+        unsigned char t0, t1;
 
-        n = (len / 2) + 1;
-        fp = (char *)from;
-        tp = (char *)to;
-#define STEP do {       \
-        temp = *fp++;   \
-        *tp++ = *fp++;  \
-        *tp++ = temp;   \
-} while (0)
-        /* round to multiple of 8 */
-        while ((--n) & 07)
-                STEP;
-        n >>= 3;
-        if (n == 0)
-                return;
-        while (n-- != 0) {
-                STEP; STEP; STEP; STEP;
-                STEP; STEP; STEP; STEP;
+        while (len > 1) {
+                t0 = src[0];
+                t1 = src[1];
+                dst[0] = t1;
+                dst[1] = t0;
+                src += 2;
+                dst += 2;
+                len -= 2;
         }
 }