xref: /illumos-gate/usr/src/common/util/ffs.c (revision 7257d1b4)
17c478bd9Sstevel@tonic-gate /*
27c478bd9Sstevel@tonic-gate  * CDDL HEADER START
37c478bd9Sstevel@tonic-gate  *
47c478bd9Sstevel@tonic-gate  * The contents of this file are subject to the terms of the
569bb4bb4Scarlsonj  * Common Development and Distribution License (the "License").
669bb4bb4Scarlsonj  * You may not use this file except in compliance with the License.
77c478bd9Sstevel@tonic-gate  *
87c478bd9Sstevel@tonic-gate  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
97c478bd9Sstevel@tonic-gate  * or http://www.opensolaris.org/os/licensing.
107c478bd9Sstevel@tonic-gate  * See the License for the specific language governing permissions
117c478bd9Sstevel@tonic-gate  * and limitations under the License.
127c478bd9Sstevel@tonic-gate  *
137c478bd9Sstevel@tonic-gate  * When distributing Covered Code, include this CDDL HEADER in each
147c478bd9Sstevel@tonic-gate  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
157c478bd9Sstevel@tonic-gate  * If applicable, add the following below this CDDL HEADER, with the
167c478bd9Sstevel@tonic-gate  * fields enclosed by brackets "[]" replaced with your own identifying
177c478bd9Sstevel@tonic-gate  * information: Portions Copyright [yyyy] [name of copyright owner]
187c478bd9Sstevel@tonic-gate  *
197c478bd9Sstevel@tonic-gate  * CDDL HEADER END
207c478bd9Sstevel@tonic-gate  */
227c478bd9Sstevel@tonic-gate /*
23*7257d1b4Sraf  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
247c478bd9Sstevel@tonic-gate  * Use is subject to license terms.
257c478bd9Sstevel@tonic-gate  */
277c478bd9Sstevel@tonic-gate #pragma ident	"%Z%%M%	%I%	%E% SMI"
2969bb4bb4Scarlsonj /*
3069bb4bb4Scarlsonj  * Common implementation of ffs for kernel, mdb, and libc.  Note that mdb
3169bb4bb4Scarlsonj  * renames ffs into mdb_ffs to avoid user-space clashes with the signature of
3269bb4bb4Scarlsonj  * ffs(3C).
3369bb4bb4Scarlsonj  */
3569bb4bb4Scarlsonj #if defined(_KERNEL) || defined(ffs)
3669bb4bb4Scarlsonj #include <sys/int_types.h>
3769bb4bb4Scarlsonj #define	arg_t	uintmax_t
3869bb4bb4Scarlsonj #else
3969bb4bb4Scarlsonj #define	arg_t	int
40*7257d1b4Sraf #include "lint.h"
4169bb4bb4Scarlsonj #endif
437c478bd9Sstevel@tonic-gate int
ffs(arg_t bits)4469bb4bb4Scarlsonj ffs(arg_t bits)
457c478bd9Sstevel@tonic-gate {
4669bb4bb4Scarlsonj 	int i;
4869bb4bb4Scarlsonj 	if (bits == 0)
497c478bd9Sstevel@tonic-gate 		return (0);
5069bb4bb4Scarlsonj 	for (i = 1; ; i++, bits >>= 1) {
5169bb4bb4Scarlsonj 		if (bits & 1)
5269bb4bb4Scarlsonj 			break;
537c478bd9Sstevel@tonic-gate 	}
5469bb4bb4Scarlsonj 	return (i);
557c478bd9Sstevel@tonic-gate }