This is xnu-8019. See this file in:
/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996,1999 by Internet Software Consortium.
 *
 * 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 ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC 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.
 */
#if defined(LIBC_SCCS) && !defined(lint)
static const char rcsid[] = "$Id: inet_pton.c,v 1.3.18.2 2005/07/28 07:38:07 marka Exp $";
#endif /* LIBC_SCCS and not lint */

#include <string.h>

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/systm.h>

#include <netinet/in.h>

/*%
 * WARNING: Don't even consider trying to compile this on a system where
 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
 */

static int      inet_pton4(const char *src, u_char *dst);
static int      inet_pton6(const char *src, u_char *dst);

/* int
 * inet_pton(af, src, dst)
 *	convert from presentation format (which usually means ASCII printable)
 *	to network format (which is usually some kind of binary format).
 * return:
 *	1 if the address was valid for the specified address family
 *	0 if the address wasn't valid (`dst' is untouched in this case)
 *	-1 if some other error occurred (`dst' is untouched in this case, too)
 * author:
 *	Paul Vixie, 1996.
 */
int
inet_pton(int af, const char *src, void *dst)
{
	switch (af) {
	case AF_INET:
		return inet_pton4(src, dst);
	case AF_INET6:
		return inet_pton6(src, dst);
	default:
		return -1;
	}
	/* NOTREACHED */
}

/* int
 * inet_pton4(src, dst)
 *	like inet_aton() but without all the hexadecimal and shorthand.
 * return:
 *	1 if `src' is a valid dotted quad, else 0.
 * notice:
 *	does not touch `dst' unless it's returning 1.
 * author:
 *	Paul Vixie, 1996.
 */
static int
inet_pton4(const char *src, u_char *dst)
{
	static const char digits[] = "0123456789";
	int saw_digit, octets, ch;
#define NS_INADDRSZ     4
	u_char tmp[NS_INADDRSZ], *tp;

	saw_digit = 0;
	octets = 0;
	*(tp = tmp) = 0;
	while ((ch = *src++) != '\0') {
		const char *pch;

		if ((pch = strchr(digits, ch)) != NULL) {
			u_int new = *tp * 10 + (u_int)(pch - digits);

			if (saw_digit && *tp == 0) {
				return 0;
			}
			if (new > 255) {
				return 0;
			}
			*tp = (u_char)new;
			if (!saw_digit) {
				if (++octets > 4) {
					return 0;
				}
				saw_digit = 1;
			}
		} else if (ch == '.' && saw_digit) {
			if (octets == 4) {
				return 0;
			}
			*++tp = 0;
			saw_digit = 0;
		} else {
			return 0;
		}
	}
	if (octets < 4) {
		return 0;
	}
	memcpy(dst, tmp, NS_INADDRSZ);
	return 1;
}

/* int
 * inet_pton6(src, dst)
 *	convert presentation level address to network order binary form.
 * return:
 *	1 if `src' is a valid [RFC1884 2.2] address, else 0.
 * notice:
 *	(1) does not touch `dst' unless it's returning 1.
 *	(2) :: in a full address is silently ignored.
 * credit:
 *	inspired by Mark Andrews.
 * author:
 *	Paul Vixie, 1996.
 */
static int
inet_pton6(const char *src, u_char *dst)
{
	static const char xdigits_l[] = "0123456789abcdef",
	    xdigits_u[] = "0123456789ABCDEF";
#define NS_IN6ADDRSZ    16
#define NS_INT16SZ      2
	u_char tmp[NS_IN6ADDRSZ], *tp, *endp, *colonp;
	const char *xdigits, *curtok;
	int ch, seen_xdigits;
	u_int val;

	memset((tp = tmp), '\0', NS_IN6ADDRSZ);
	endp = tp + NS_IN6ADDRSZ;
	colonp = NULL;
	/* Leading :: requires some special handling. */
	if (*src == ':') {
		if (*++src != ':') {
			return 0;
		}
	}
	curtok = src;
	seen_xdigits = 0;
	val = 0;
	while ((ch = *src++) != '\0') {
		const char *pch;

		if ((pch = strchr((xdigits = xdigits_l), ch)) == NULL) {
			pch = strchr((xdigits = xdigits_u), ch);
		}
		if (pch != NULL) {
			val <<= 4;
			val |= (pch - xdigits);
			if (++seen_xdigits > 4) {
				return 0;
			}
			continue;
		}
		if (ch == ':') {
			curtok = src;
			if (!seen_xdigits) {
				if (colonp) {
					return 0;
				}
				colonp = tp;
				continue;
			} else if (*src == '\0') {
				return 0;
			}
			if (tp + NS_INT16SZ > endp) {
				return 0;
			}
			*tp++ = (u_char) (val >> 8) & 0xff;
			*tp++ = (u_char) val & 0xff;
			seen_xdigits = 0;
			val = 0;
			continue;
		}
		if (ch == '.' && ((tp + NS_INADDRSZ) <= endp) &&
		    inet_pton4(curtok, tp) > 0) {
			tp += NS_INADDRSZ;
			seen_xdigits = 0;
			break;  /*%< '\\0' was seen by inet_pton4(). */
		}
		return 0;
	}
	if (seen_xdigits) {
		if (tp + NS_INT16SZ > endp) {
			return 0;
		}
		*tp++ = (u_char) (val >> 8) & 0xff;
		*tp++ = (u_char) val & 0xff;
	}
	if (colonp != NULL) {
		/*
		 * Since some memmove()'s erroneously fail to handle
		 * overlapping regions, we'll do the shift by hand.
		 */
		const long n = tp - colonp;
		int i;

		if (tp == endp) {
			return 0;
		}
		for (i = 1; i <= n; i++) {
			endp[-i] = colonp[n - i];
			colonp[n - i] = 0;
		}
		tp = endp;
	}
	if (tp != endp) {
		return 0;
	}
	memcpy(dst, tmp, NS_IN6ADDRSZ);
	return 1;
}