/*  $Id: inet_aton.c,v 1.1.1.1 2005/01/13 18:45:14 mcr Exp $
**
**  Replacement for a missing inet_aton.
**
**  Written by Russ Allbery <rra@stanford.edu>
**  This work is hereby placed in the public domain by its author.
**
**  Provides the same functionality as the standard library routine
**  inet_aton for those platforms that don't have it.  inet_aton is
**  thread-safe.
*/

#include "config.h"
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif

/* If we're running the test suite, rename inet_ntoa to avoid conflicts with
   the system version. */
#if TESTING
# define inet_aton test_inet_aton
int test_inet_aton(const char *, struct in_addr *);
#endif

int inet_aton(const char *s, struct in_addr *addr)
{
	unsigned long octet[4], address;
	const char *p;
	int base, i;
	int part = 0;

	if (s == NULL)
		return 0;

	/* Step through each period-separated part of the address.  If we see
	   more than four parts, the address is invalid. */
	for (p = s; *p != 0; part++) {
		if (part > 3)
			return 0;

		/* Determine the base of the section we're looking at.  Numbers are
		   represented the same as in C; octal starts with 0, hex starts
		   with 0x, and anything else is decimal. */
		if (*p == '0') {
			p++;
			if (*p == 'x') {
				p++;
				base = 16;
			} else {
				base = 8;
			}
		} else {
			base = 10;
		}

		/* Make sure there's actually a number.  (A section of just "0"
		   would set base to 8 and leave us pointing at a period; allow
		   that.) */
		if (*p == '.' && base != 8)
			return 0;

		octet[part] = 0;

		/* Now, parse this segment of the address.  For each digit, multiply
		   the result so far by the base and then add the value of the
		   digit.  Be careful of arithmetic overflow in cases where an
		   unsigned long is 32 bits; we need to detect it *before* we
		   multiply by the base since otherwise we could overflow and wrap
		   and then not detect the error. */
		for (; *p != 0 && *p != '.'; p++) {
			if (octet[part] > 0xffffffffUL / base)
				return 0;

			/* Use a switch statement to parse each digit rather than
			   assuming ASCII.  Probably pointless portability.... */
			switch (*p) {
			case '0':           i = 0;
				break;
			case '1':           i = 1;
				break;
			case '2':           i = 2;
				break;
			case '3':           i = 3;
				break;
			case '4':           i = 4;
				break;
			case '5':           i = 5;
				break;
			case '6':           i = 6;
				break;
			case '7':           i = 7;
				break;
			case '8':           i = 8;
				break;
			case '9':           i = 9;
				break;
			case 'A': case 'a': i = 10;
				break;
			case 'B': case 'b': i = 11;
				break;
			case 'C': case 'c': i = 12;
				break;
			case 'D': case 'd': i = 13;
				break;
			case 'E': case 'e': i = 14;
				break;
			case 'F': case 'f': i = 15;
				break;
			default:            return 0;
			}
			if (i >= base)
				return 0;

			octet[part] = (octet[part] * base) + i;
		}

		/* Advance over periods; the top of the loop will increment the
		   count of parts we've seen.  We need a check here to detect an
		   illegal trailing period. */
		if (*p == '.') {
			p++;
			if (*p == 0)
				return 0;
		}
	}
	if (part == 0)
		return 0;

	/* IPv4 allows three types of address specification:

	       a.b
	       a.b.c
	       a.b.c.d

	   If there are fewer than four segments, the final segment accounts for
	   all of the remaining portion of the address.  For example, in the a.b
	   form, b is the final 24 bits of the address.  We also allow a simple
	   number, which is interpreted as the 32-bit number corresponding to
	   the full IPv4 address.

	   The first for loop below ensures that any initial segments represent
	   only 8 bits of the address and builds the upper portion of the IPv4
	   address.  Then, the remaining segment is checked to make sure it's no
	   bigger than the remaining space in the address and then is added into
	   the result. */
	address = 0;
	for (i = 0; i < part - 1; i++) {
		if (octet[i] > 0xff)
			return 0;

		address |= octet[i] << (8 * (3 - i));
	}
	if (octet[i] > (0xffffffffUL >> (i * 8)))
		return 0;

	address |= octet[i];
	if (addr != NULL)
		addr->s_addr = htonl(address);
	return 1;
}
