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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 1.13 2009/01/13 13:19:42 kib Exp $
	32	.\"
	33	.Dd October 26, 2008
	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	.Ft int
	54	.Fn ffsll "long long value"
	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 bit set
	67	(beginning with the least significant bit)
	68	in
	69	.Fa value
	70	and return the index of that bit.
	71	.Pp
	72	The
	73	.Fn fls ,
	74	.Fn flsl
	75	and
	76	.Fn flsll
	77	functions find the last bit set in
	78	.Fa value
	79	and return the index of that bit.
	80	.Pp
	81	Bits are numbered starting at 1 (the least significant bit).
	82	A return value of zero from any of these functions means that the
	83	argument was zero.
	84	.Sh SEE ALSO
	85	.Xr bitstring 3
	86	.Sh HISTORY
	87	The
	88	.Fn ffs
	89	function appeared in
	90	.Bx 4.3 .
	91	Its prototype existed previously in
	92	.In string.h
	93	before it was moved to
	94	.In strings.h
	95	for
	96	.St -p1003.1-2001
	97	compliance.
	98	.Pp
	99	The
	100	.Fn ffsl ,
	101	.Fn fls
	102	and
	103	.Fn flsl
	104	functions appeared in
	105	.Fx 5.3 .
	106	The
	107	.Fn ffsll
	108	and
	109	.Fn flsll
	110	functions appeared in
	111	.Fx 7.1 .