1 /* $OpenBSD: strlcat.c,v 1.18 2016/10/16 17:37:39 dtucker Exp $ */
2
3 /*
4 * Copyright (c) 1998, 2015 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
19 #include <sys/types.h>
20 #include <string.h>
21
22 /*
23 * Appends src to string dst of size dsize (unlike strncat, dsize is the
24 * full size of dst, not space left). At most dsize-1 characters
25 * will be copied. Always NUL terminates (unless dsize <= strlen(dst)).
26 * Returns strlen(src) + MIN(dsize, strlen(initial dst)).
27 * If retval >= dsize, truncation occurred.
28 */
29 size_t
strlcat(char * dst,const char * src,size_t dsize)30 strlcat(char *dst, const char *src, size_t dsize)
31 {
32 const char *odst = dst;
33 const char *osrc = src;
34 size_t n = dsize;
35 size_t dlen;
36
37 /* Find the end of dst and adjust bytes left but don't go past end. */
38 while (n-- != 0 && *dst != '\0')
39 dst++;
40 dlen = dst - odst;
41 n = dsize - dlen;
42
43 if (n-- == 0)
44 return (dlen + strlen(src));
45 while (*src != '\0') {
46 if (n != 0) {
47 *dst++ = *src;
48 n--;
49 }
50 src++;
51 }
52 *dst = '\0';
53
54 return (dlen + (src - osrc)); /* count does not include NUL */
55 }