1 /* $OpenBSD: strlcat.c,v 1.9 2019/01/25 00:19:26 millert Exp $ */
2
3 /*
4 * Copyright (c) 1998, 2015 Todd C. Miller <millert@openbsd.org>
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 <lib/libkern/libkern.h>
20
21 /*
22 * Appends src to string dst of size dsize (unlike strncat, dsize is the
23 * full size of dst, not space left). At most dsize-1 characters
24 * will be copied. Always NUL terminates (unless dsize <= strlen(dst)).
25 * Returns strlen(src) + MIN(dsize, strlen(initial dst)).
26 * If retval >= siz, truncation occurred.
27 */
28 size_t
strlcat(char * dst,const char * src,size_t dsize)29 strlcat(char *dst, const char *src, size_t dsize)
30 {
31 const char *odst = dst;
32 const char *osrc = src;
33 size_t n = dsize;
34 size_t dlen;
35
36 /* Find the end of dst and adjust bytes left but don't go past end. */
37 while (n-- != 0 && *dst != '\0')
38 dst++;
39 dlen = dst - odst;
40 n = dsize - dlen;
41
42 if (n-- == 0)
43 return(dlen + strlen(src));
44 while (*src != '\0') {
45 if (n != 0) {
46 *dst++ = *src;
47 n--;
48 }
49 src++;
50 }
51 *dst = '\0';
52
53 return(dlen + (src - osrc)); /* count does not include NUL */
54 }
55