This is xnu-8019. See this file in:
/*-
 * Copyright 1994, 1995 Massachusetts Institute of Technology
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby
 * granted, provided that both the above copyright notice and this
 * permission notice appear in all copies, that both the above
 * copyright notice and this permission notice appear in all
 * supporting documentation, and that the name of M.I.T. not be used
 * in advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.  M.I.T. makes
 * no representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied
 * warranty.
 *
 * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
 * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
 * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
#include <sys/param.h>
#include <sys/systm.h>

#include <netinet/in.h>

char *
inet_ntoa(struct in_addr ina)
{
	static char buf[4 * sizeof "123"];
	unsigned char *ucp = (unsigned char *)&ina;

	snprintf(buf, sizeof(buf), "%d.%d.%d.%d",
	    ucp[0] & 0xff,
	    ucp[1] & 0xff,
	    ucp[2] & 0xff,
	    ucp[3] & 0xff);
	return buf;
}

char *
inet_ntoa_r(struct in_addr ina, char *buf, size_t buflen)
{
	unsigned char *ucp = (unsigned char *)&ina;

	snprintf(buf, buflen, "%d.%d.%d.%d",
	    ucp[0] & 0xff,
	    ucp[1] & 0xff,
	    ucp[2] & 0xff,
	    ucp[3] & 0xff);
	return buf;
}