2010-06-21 01:57:59 +04:00
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.\" $NetBSD: ilog2.3,v 1.3 2010/06/20 21:57:59 joerg Exp $ $
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2010-06-08 12:51:08 +04:00
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.\"
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.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jukka Ruohonen.
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.\"
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd June 8, 2010
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.Dt ILOG2 3
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2010-06-21 01:57:59 +04:00
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.Os
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2010-06-08 12:51:08 +04:00
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.Sh NAME
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.Nm ilog2
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.Nd integer logarithm
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.Sh SYNOPSIS
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.In sys/bitops.h
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.Ft size
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.Fn ilog2 "size x"
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.Sh DESCRIPTION
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The
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.Fn ilog2
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macro returns an integer (binary) logarithm of
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.Fa x .
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It is the logarithm for base 2; the binary logarithm of
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.Fa x
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is the power to which the number 2 must be raised to obtain the value
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.Fa x .
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.Pp
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The type of the input parameter should be either
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.Vt uint32_t
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or
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.Vt uint64_t .
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.Sh ERRORS
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A value \-1 is returned on error.
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.Sh SEE ALSO
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.Xr log2 3 ,
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2010-06-08 13:00:51 +04:00
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.Xr imax 9 ,
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.Xr powerof2 9
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2010-06-08 12:51:08 +04:00
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.Sh HISTORY
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The
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.Fn ilog2
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macro first appeared in
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.Nx 5.0 .
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