lib/libc/string/strlcat.c

   1 /*      $OpenBSD: strlcat.c,v 1.13 2005/08/08 08:05:37 espie Exp $      */
   2
   3 /*
   4  * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  *
  18  * $FreeBSD: head/lib/libc/string/strlcat.c 189133 2009-02-28 05:15:02Z das $
  19  */
  20
  21 #include <sys/types.h>
  22 #include <string.h>
  23
  24 /*
  25  * Appends src to string dst of size siz (unlike strncat, siz is the
  26  * full size of dst, not space left).  At most siz-1 characters
  27  * will be copied.  Always NUL terminates (unless siz <= strlen(dst)).
  28  * Returns strlen(src) + MIN(siz, strlen(initial dst)).
  29  * If retval >= siz, truncation occurred.
  30  */
  31 size_t
  32 strlcat(char * __restrict dst, const char * __restrict src, size_t siz)
  33 {
  34         char *d = dst;
  35         const char *s = src;
  36         size_t n = siz;
  37         size_t dlen;
  38
  39         /* Find the end of dst and adjust bytes left but don't go past end */
  40         while (n-- != 0 && *d != '\0')
  41                 d++;
  42         dlen = d - dst;
  43         n = siz - dlen;
  44
  45         if (n == 0)
  46                 return(dlen + strlen(s));
  47         while (*s != '\0') {
  48                 if (n != 1) {
  49                         *d++ = *s;
  50                         n--;
  51                 }
  52                 s++;
  53         }
  54         *d = '\0';
  55
  56         return(dlen + (s - src));       /* count does not include NUL */
  57 }