bitncmp.c

/*
 * Copyright (C) 2004, 2005, 2008  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1996, 1999, 2001  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and/or 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: bitncmp.c,v 1.5 2008/11/14 02:36:51 marka Exp $";
#endif

#include <sys/types.h>
#include <string.h>

/*
 * int
 * bitncmp(l, r, n)
 *	compare bit masks l and r, for n bits.
 * return:
 *	-1, 1, or 0 in the libc tradition.
 * note:
 *	network byte order assumed.  this means 192.5.5.240/28 has
 *	0x11110000 in its fourth octet.
 * author:
 *	Paul Vixie (ISC), June 1996
 */
int
bitncmp(const void *l, const void *r, size_t n) {
	unsigned int lb, rb;
	size_t b;
	int x;

	b = n / 8;
	x = memcmp(l, r, b);
	if (x || (n % 8) == 0)
		return (x);

	lb = ((const unsigned char *)l)[b];
	rb = ((const unsigned char *)r)[b];
	for (b = n % 8; b > 0; b--) {
		if ((lb & 0x80) != (rb & 0x80)) {
			if (lb & 0x80)
				return (1);
			return (-1);
		}
		lb <<= 1;
		rb <<= 1;
	}
	return (0);
}