101 lines
2.9 KiB
Groff
101 lines
2.9 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek.
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)ffs.3 8.2 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd January 13, 2004
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.Dt FFS 3
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.Os
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.Sh NAME
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.Nm ffs ,
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.Nm ffsl ,
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.Nm fls ,
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.Nm flsl
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.Nd find first or last bit set in a bit string
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In strings.h
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.Ft int
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.Fn ffs "int value"
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.Ft int
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.Fn ffsl "long value"
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.Ft int
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.Fn fls "int value"
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.Ft int
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.Fn flsl "long value"
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.Sh DESCRIPTION
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The
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.Fn ffs
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and
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.Fn ffsl
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functions find the first bit set in
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.Fa value
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and return the index of that bit.
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.Pp
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The
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.Fn fls
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and
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.Fn flsl
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functions find the last bit set in
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.Fa value
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and return the index of that bit.
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.Pp
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Bits are numbered starting from 1, starting at the right-most
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(least significant) bit.
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A return value of zero from any of these functions means that the
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argument was zero.
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.Sh SEE ALSO
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.Xr bitstring 3
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.Sh HISTORY
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The
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.Fn ffs
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function appeared in
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.Bx 4.3 .
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Its prototype existed previously in
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.In string.h
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before it was moved to
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.In strings.h
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for
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.St -p1003.1-2001
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compliance.
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.Pp
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The
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.Fn ffsl ,
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.Fn fls
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and
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.Fn flsl
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functions appeared in
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.Fx 5.3 .
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