75 lines
2.4 KiB
Groff
75 lines
2.4 KiB
Groff
.\" $NetBSD: mstohz.9,v 1.9 2011/04/08 07:55:04 jruoho Exp $
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.\"
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.\" Copyright (c) 2002 Manuel Bouyer.
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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 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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.\"
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.Dd April 8, 2011
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.Dt MSTOHZ 9
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.Os
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.Sh NAME
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.Nm mstohz ,
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.Nm hztoms
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.Nd convert between milliseconds and system clock ticks
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.Sh SYNOPSIS
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.In sys/param.h
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.Ft int
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.Fn mstohz "int ms"
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.Ft int
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.Fn hztoms "int hz"
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.Sh DESCRIPTION
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The
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.Fn mstohz
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macro can be used to convert time
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in milliseconds to system clock ticks, as used
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by the
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.Xr callout 9
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facility, in an integer-overflow safe way.
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Conversely,
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.Fn hztoms
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converts system clock ticks to milliseconds.
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.Pp
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These macros are defined in the
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.Em \*[Lt]sys/param.h\*[Gt]
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header.
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Individual ports can have a processor-specific, more efficient
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version implemented in their
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.Em \*[Lt]machine/param.h\*[Gt]
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header as a define.
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.Sh RETURN VALUES
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The return value is either the number of clock ticks or milliseconds
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for the specified value.
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.Sh SEE ALSO
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.Xr param 3 ,
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.Xr callout 9
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.Sh BUGS
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Neither
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.Fn mstohz
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nor
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.Fn hztoms
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make use of expensive 64-bit integer arithmetic.
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The result from
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.Fn mstohz
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will be rounded down to one second if the parameter is larger
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than 131072 milliseconds.
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