strlcat.c 1.71 KB
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/*	$OpenBSD: strlcat.c,v 1.15 2015/03/02 21:41:08 millert Exp $	*/
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/*
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 * Copyright (c) 1998, 2015 Todd C. Miller <Todd.Miller@courtesan.com>
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 *
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 * 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.
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 *
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 * 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.
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 */

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

/*
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 * Appends src to string dst of size dsize (unlike strncat, dsize is the
 * full size of 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.
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 */
size_t
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strlcat(char *dst, const char *src, size_t dsize)
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{
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	const char *odst = dst;
	const char *osrc = src;
	size_t n = dsize;
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	size_t dlen;

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	/* 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;
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	if (n-- == 0)
		return(dlen + strlen(src));
	while (*src != '\0') {
		if (n != 0) {
			*dst++ = *src;
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			n--;
		}
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		src++;
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	}
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	*dst = '\0';
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	return(dlen + (src - osrc));	/* count does not include NUL */
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}