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	1	.\" Copyright (c) 1990, 1991, 1993
	2	.\" The Regents of the University of California. All rights reserved.
	3	.\"
	4	.\" This code is derived from software contributed to Berkeley by
	5	.\" Chris Torek.
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 4. Neither the name of the University nor the names of its contributors
	15	.\" may be used to endorse or promote products derived from this software
	16	.\" without specific prior written permission.
	17	.\"
	18	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	19	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	20	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	21	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	22	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	23	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	24	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	25	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	26	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	27	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	28	.\" SUCH DAMAGE.
	29	.\"
	30	.\" @(#)ffs.3 8.2 (Berkeley) 4/19/94
	31	.\" $FreeBSD: src/lib/libc/string/ffs.3,v 1.15 2012/09/30 03:25:04 eadler Exp $
	32	.\"
	33	.Dd September 29, 2012
	34	.Dt FFS 3
	35	.Os
	36	.Sh NAME
	37	.Nm ffs ,
	38	.Nm ffsl ,
	39	.Nm ffsll ,
	40	.Nm fls ,
	41	.Nm flsl ,
	42	.Nm flsll
	43	.Nd find first or last bit set in a bit string
	44	.Sh LIBRARY
	45	.Lb libc
	46	.Sh SYNOPSIS
	47	.In strings.h
	48	.Ft int
	49	.Fn ffs "int value"
	50	.Ft int
	51	.Fn ffsl "long value"
	52	.Ft int
	53	.Fn ffsll "long long value"
	54	.Ft int
	55	.Fn fls "int value"
	56	.Ft int
	57	.Fn flsl "long value"
	58	.Ft int
	59	.Fn flsll "long long value"
	60	.Sh DESCRIPTION
	61	The
	62	.Fn ffs ,
	63	.Fn ffsl
	64	and
	65	.Fn ffsll
	66	functions find the first (least significant) bit set
	67	in
	68	.Fa value
	69	and return the index of that bit.
	70	.Pp
	71	The
	72	.Fn fls ,
	73	.Fn flsl
	74	and
	75	.Fn flsll
	76	functions find the last (most significant) bit set in
	77	.Fa value
	78	and return the index of that bit.
	79	.Pp
	80	Bits are numbered starting at 1, the least significant bit.
	81	A return value of zero from any of these functions means that the
	82	argument was zero.
	83	.Sh SEE ALSO
	84	.Xr bitstring 3
	85	.Sh HISTORY
	86	The
	87	.Fn ffs
	88	function appeared in
	89	.Bx 4.3 .
	90	Its prototype existed previously in
	91	.In string.h
	92	before it was moved to
	93	.In strings.h
	94	for
	95	.St -p1003.1-2001
	96	compliance.
	97	.Pp
	98	The
	99	.Fn ffsl ,
	100	.Fn fls
	101	and
	102	.Fn flsl
	103	functions appeared in
	104	.Fx 5.3 .
	105	The
	106	.Fn ffsll
	107	and
	108	.Fn flsll
	109	functions appeared in
	110	.Fx 7.1 .