xref: /illumos-gate/usr/src/common/util/ffs.c (revision 7257d1b4)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 /*
30  * Common implementation of ffs for kernel, mdb, and libc.  Note that mdb
31  * renames ffs into mdb_ffs to avoid user-space clashes with the signature of
32  * ffs(3C).
33  */
34 
35 #if defined(_KERNEL) || defined(ffs)
36 #include <sys/int_types.h>
37 #define	arg_t	uintmax_t
38 #else
39 #define	arg_t	int
40 #include "lint.h"
41 #endif
42 
43 int
ffs(arg_t bits)44 ffs(arg_t bits)
45 {
46 	int i;
47 
48 	if (bits == 0)
49 		return (0);
50 	for (i = 1; ; i++, bits >>= 1) {
51 		if (bits & 1)
52 			break;
53 	}
54 	return (i);
55 }
56