xref: /freebsd/lib/libc/string/fls.c (revision 8a16b7a18f5d0b031f09832fd7752fba717e2a97)
1f434fe12SDag-Erling Smørgrav /*-
2*8a16b7a1SPedro F. Giffuni  * SPDX-License-Identifier: BSD-3-Clause
3*8a16b7a1SPedro F. Giffuni  *
4f434fe12SDag-Erling Smørgrav  * Copyright (c) 1990, 1993
5f434fe12SDag-Erling Smørgrav  *	The Regents of the University of California.  All rights reserved.
6f434fe12SDag-Erling Smørgrav  *
7f434fe12SDag-Erling Smørgrav  * Redistribution and use in source and binary forms, with or without
8f434fe12SDag-Erling Smørgrav  * modification, are permitted provided that the following conditions
9f434fe12SDag-Erling Smørgrav  * are met:
10f434fe12SDag-Erling Smørgrav  * 1. Redistributions of source code must retain the above copyright
11f434fe12SDag-Erling Smørgrav  *    notice, this list of conditions and the following disclaimer.
12f434fe12SDag-Erling Smørgrav  * 2. Redistributions in binary form must reproduce the above copyright
13f434fe12SDag-Erling Smørgrav  *    notice, this list of conditions and the following disclaimer in the
14f434fe12SDag-Erling Smørgrav  *    documentation and/or other materials provided with the distribution.
153fb3b97cSEd Maste  * 3. Neither the name of the University nor the names of its contributors
16f434fe12SDag-Erling Smørgrav  *    may be used to endorse or promote products derived from this software
17f434fe12SDag-Erling Smørgrav  *    without specific prior written permission.
18f434fe12SDag-Erling Smørgrav  *
19f434fe12SDag-Erling Smørgrav  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20f434fe12SDag-Erling Smørgrav  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21f434fe12SDag-Erling Smørgrav  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22f434fe12SDag-Erling Smørgrav  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23f434fe12SDag-Erling Smørgrav  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24f434fe12SDag-Erling Smørgrav  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25f434fe12SDag-Erling Smørgrav  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26f434fe12SDag-Erling Smørgrav  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27f434fe12SDag-Erling Smørgrav  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28f434fe12SDag-Erling Smørgrav  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29f434fe12SDag-Erling Smørgrav  * SUCH DAMAGE.
30f434fe12SDag-Erling Smørgrav  */
31f434fe12SDag-Erling Smørgrav 
32f434fe12SDag-Erling Smørgrav #include <sys/cdefs.h>
33f434fe12SDag-Erling Smørgrav __FBSDID("$FreeBSD$");
34f434fe12SDag-Erling Smørgrav 
35f434fe12SDag-Erling Smørgrav #include <strings.h>
36f434fe12SDag-Erling Smørgrav 
37f434fe12SDag-Erling Smørgrav /*
38f434fe12SDag-Erling Smørgrav  * Find Last Set bit
39f434fe12SDag-Erling Smørgrav  */
40f434fe12SDag-Erling Smørgrav int
41f434fe12SDag-Erling Smørgrav fls(int mask)
42f434fe12SDag-Erling Smørgrav {
43f434fe12SDag-Erling Smørgrav 	int bit;
44f434fe12SDag-Erling Smørgrav 
45f434fe12SDag-Erling Smørgrav 	if (mask == 0)
46f434fe12SDag-Erling Smørgrav 		return (0);
47f434fe12SDag-Erling Smørgrav 	for (bit = 1; mask != 1; bit++)
4829554ea5SDag-Erling Smørgrav 		mask = (unsigned int)mask >> 1;
49f434fe12SDag-Erling Smørgrav 	return (bit);
50f434fe12SDag-Erling Smørgrav }
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