xref: /illumos-gate/usr/src/lib/libresolv2/common/isc/bitncmp.c (revision 4c28a617e3922d92a58e813a5b955eb526b9c386)
1 /*
2  * Copyright (C) 2004, 2005, 2008  Internet Systems Consortium, Inc. ("ISC")
3  * Copyright (C) 1996, 1999, 2001  Internet Software Consortium.
4  *
5  * Permission to use, copy, modify, and/or distribute this software for any
6  * purpose with or without fee is hereby granted, provided that the above
7  * copyright notice and this permission notice appear in all copies.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15  * PERFORMANCE OF THIS SOFTWARE.
16  */
17 
18 #include "port_before.h"
19 
20 #include <sys/types.h>
21 
22 #include <string.h>
23 
24 #include "port_after.h"
25 
26 #include <isc/misc.h>
27 
28 /*%
29  * int
30  * bitncmp(l, r, n)
31  *	compare bit masks l and r, for n bits.
32  * return:
33  *	-1, 1, or 0 in the libc tradition.
34  * note:
35  *	network byte order assumed.  this means 192.5.5.240/28 has
36  *	0x11110000 in its fourth octet.
37  * author:
38  *	Paul Vixie (ISC), June 1996
39  */
40 int
41 bitncmp(const void *l, const void *r, int n) {
42 	u_int lb, rb;
43 	int x, b;
44 
45 	b = n / 8;
46 	x = memcmp(l, r, b);
47 	if (x || (n % 8) == 0)
48 		return (x);
49 
50 	lb = ((const u_char *)l)[b];
51 	rb = ((const u_char *)r)[b];
52 	for (b = n % 8; b > 0; b--) {
53 		if ((lb & 0x80) != (rb & 0x80)) {
54 			if (lb & 0x80)
55 				return (1);
56 			return (-1);
57 		}
58 		lb <<= 1;
59 		rb <<= 1;
60 	}
61 	return (0);
62 }
63 
64 /*! \file */
65