strlcat.c

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/*      $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.
 */

#include "ruby/missing.h"
#include <sys/types.h>
#include <string.h>

/*
 * 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.
 */
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 */
}