1 /*
2  * Copyright (c) 1998, 2015 Todd C. Miller <millert@openbsd.org>
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 THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/types.h>
18 #include <string.h>
19 
20 /*
21  * Appends src to string dst of size dsize (unlike strncat, dsize is the
22  * full size of dst, not space left).  At most dsize-1 characters
23  * will be copied.  Always NUL terminates (unless dsize <= strlen(dst)).
24  * Returns strlen(src) + MIN(dsize, strlen(initial dst)).
25  * If retval >= dsize, truncation occurred.
26  */
27 size_t
28 strlcat(char *dst, const char *src, size_t dsize)
29 {
30 	const char *odst = dst;
31 	const char *osrc = src;
32 	size_t n = dsize;
33 	size_t dlen;
34 
35 	/* Find the end of dst and adjust bytes left but don't go past end. */
36 	while (n-- != 0 && *dst != '\0')
37 		dst++;
38 	dlen = dst - odst;
39 	n = dsize - dlen;
40 
41 	if (n-- == 0)
42 		return(dlen + strlen(src));
43 	while (*src != '\0') {
44 		if (n != 0) {
45 			*dst++ = *src;
46 			n--;
47 		}
48 		src++;
49 	}
50 	*dst = '\0';
51 
52 	return(dlen + (src - osrc));	/* count does not include NUL */
53 }