os/strlcat.c

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