/*	$OpenBSD: strlcat.c,v 1.15 2015/03/02 21:41:08 millert Exp $	*/

/*
 * Copyright (c) 1998, 2015 Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/**
 * @file strlcat.c
 * @author Todd C. Miller
 * @date 1998, 2015
 * @copyright ISC License
 */

#include <sys/types.h>
#include <string.h>

#ifndef strlcat
/**
 * Safe version of strncat() from OpenBSD
 * @param dst   Destination string
 * @param src   Source string
 * @param dsize Total maximum size of @p dst
 *
 * Appends @p src to string @p dst of size @p dsize (unlike strncat(),
 * @p dsize is the full size of @p dst, not space left).  At most
 * dsize-1 characters will be copied.  Always NUL terminates (unless
 * dsize <= strlen(dst)).
 *
 * @returns strlen(src) + MIN(dsize, strlen(initial dst)).  
 *          If retval >= dsize, truncation occurred.
 */
size_t
strlcat(char *dst, const char *src, size_t dsize)
{
	const char *odst = dst;
	const char *osrc = src;
	size_t n = dsize;
	size_t dlen;

	/* Find the end of dst and adjust bytes left but don't go past end. */
	while (n-- != 0 && *dst != '\0')
		dst++;
	dlen = dst - odst;
	n = dsize - dlen;

	if (n-- == 0)
		return(dlen + strlen(src));
	while (*src != '\0') {
		if (n != 0) {
			*dst++ = *src;
			n--;
		}
		src++;
	}
	*dst = '\0';

	return(dlen + (src - osrc));	/* count does not include NUL */
}
#endif