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strlcat.c (1759B)


      1 /*	$OpenBSD: strlcat.c,v 1.19 2019/01/25 00:19:25 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 <sys/types.h>
     20 #include <string.h>
     21 
     22 #include "util.h"
     23 
     24 /*
     25  * Appends src to string dst of size dsize (unlike strncat, dsize is the
     26  * full size of dst, not space left).  At most dsize-1 characters
     27  * will be copied.  Always NUL terminates (unless dsize <= strlen(dst)).
     28  * Returns strlen(src) + MIN(dsize, strlen(initial dst)).
     29  * If retval >= dsize, truncation occurred.
     30  */
     31 size_t
     32 strlcat(char *dst, const char *src, size_t dsize)
     33 {
     34 	const char *odst = dst;
     35 	const char *osrc = src;
     36 	size_t n = dsize;
     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 && *dst != '\0')
     41 		dst++;
     42 	dlen = dst - odst;
     43 	n = dsize - dlen;
     44 
     45 	if (n-- == 0)
     46 		return(dlen + strlen(src));
     47 	while (*src != '\0') {
     48 		if (n != 0) {
     49 			*dst++ = *src;
     50 			n--;
     51 		}
     52 		src++;
     53 	}
     54 	*dst = '\0';
     55 
     56 	return(dlen + (src - osrc));	/* count does not include NUL */
     57 }