inet_addr.c

操作系统SunOS 4.1.3版本的源码

#if !defined(lint) && defined(SCCSIDS)
static	char sccsid[] = "@(#)inet_addr.c 1.1 92/07/30 SMI"; /* from UCB 4.5 82/11/14 */
#endif

#include <sys/types.h>
#include <ctype.h>
#include <netinet/in.h>

/*
 * Internet address interpretation routine.
 * All the network library routines call this
 * routine to interpret entries in the data bases
 * which are expected to be an address.
 * The value returned is in network order.
 */
u_long
inet_addr(cp)
	register char *cp;
{
	register u_long val, base, n;
	register char c;
	u_long parts[4], *pp = parts;

again:
	/*
	 * Collect number up to ``.''.
	 * Values are specified as for C:
	 * 0x=hex, 0=octal, other=decimal.
	 */
	val = 0; base = 10;
	if (*cp == '0') {
		if (*++cp == 'x' || *cp == 'X')
			base = 16, cp++;
		else
			base = 8;
	}
	while (c = *cp) {
		if (isdigit(c)) {
			if ((c - '0') >= base)
			    break;
			val = (val * base) + (c - '0');
			cp++;
			continue;
		}
		if (base == 16 && isxdigit(c)) {
			val = (val << 4) + (c + 10 - (islower(c) ? 'a' : 'A'));
			cp++;
			continue;
		}
		break;
	}
	if (*cp == '.') {
		/*
		 * Internet format:
		 *	a.b.c.d
		 *	a.b.c	(with c treated as 16-bits)
		 *	a.b	(with b treated as 24 bits)
		 */
		if (pp >= parts + 4)
			return (-1);
		*pp++ = val, cp++;
		goto again;
	}
	/*
	 * Check for trailing characters.
	 */
	if (*cp && !isspace(*cp))
		return (-1);
	*pp++ = val;
	/*
	 * Concoct the address according to
	 * the number of parts specified.
	 */
	n = pp - parts;
	switch (n) {

	case 1:				/* a -- 32 bits */
		val = parts[0];
		break;

	case 2:				/* a.b -- 8.24 bits */
		val = (parts[0] << 24) | (parts[1] & 0xffffff);
		break;

	case 3:				/* a.b.c -- 8.8.16 bits */
		val = (parts[0] << 24) | ((parts[1] & 0xff) << 16) |
			(parts[2] & 0xffff);
		break;

	case 4:				/* a.b.c.d -- 8.8.8.8 bits */
		val = (parts[0] << 24) | ((parts[1] & 0xff) << 16) |
		      ((parts[2] & 0xff) << 8) | (parts[3] & 0xff);
		break;

	default:
		return (-1);
	}
	val = htonl(val);
	return (val);
}