common/lib/libc/string/strncat.c

   1 /*      $NetBSD: strncat.c,v 1.2 2013/12/27 20:26:53 christos Exp $     */
   2
   3 /*-
   4  * Copyright (c) 1990, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Chris Torek.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 #if 0
  38 static char sccsid[] = "@(#)strncat.c   8.1 (Berkeley) 6/4/93";
  39 #else
  40 __RCSID("$NetBSD: strncat.c,v 1.2 2013/12/27 20:26:53 christos Exp $");
  41 #endif
  42 #endif /* LIBC_SCCS and not lint */
  43
  44 #if !defined(_KERNEL) && !defined(_STANDALONE)
  45 #include <assert.h>
  46 #include <string.h>
  47 #else
  48 #include <lib/libkern/libkern.h>
  49 #endif
  50
  51 #ifdef _FORTIFY_SOURCE
  52 #undef strncat
  53 #endif
  54
  55 /*
  56  * Concatenate src on the end of dst.  At most strlen(dst)+n+1 bytes
  57  * are written at dst (at most n+1 bytes being appended).  Return dst.
  58  */
  59 char *
  60 strncat(char *dst, const char *src, size_t n)
  61 {
  62
  63         _DIAGASSERT(dst != NULL);
  64         _DIAGASSERT(src != NULL);
  65
  66         if (n != 0) {
  67                 char *d = dst;
  68                 const char *s = src;
  69
  70                 while (*d != 0)
  71                         d++;
  72                 do {
  73                         if ((*d = *s++) == 0)
  74                                 break;
  75                         d++;
  76                 } while (--n != 0);
  77                 *d = 0;
  78         }
  79         return (dst);
  80 }