1.\" $NetBSD: mstohz.9,v 1.7 2010/03/01 17:21:02 jruoho Exp $ 2.\" 3.\" Copyright (c) 2002 Manuel Bouyer. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" 27.Dd February 10, 2010 28.Dt MSTOHZ 9 29.Os 30.Sh NAME 31.Nm mstohz 32.Nd convert between milliseconds and system clock ticks 33.Sh SYNOPSIS 34.In sys/param.h 35.Ft int 36.Fn mstohz "int ms" 37.Ft int 38.Fn hztoms "int hz" 39.Sh DESCRIPTION 40.Nm 41can be used to convert time in milliseconds to system clock ticks, as used 42by the 43.Xr callout 9 44facility, in an integer-overflow safe way. 45Conversely, 46.Fn hztoms 47converts system clock ticks to milliseconds. 48.Pp 49These macros are defined in the 50.Em \*[Lt]sys/param.h\*[Gt] 51header. 52Individual ports can have a processor-specific, more efficient 53version implemented in their 54.Em \*[Lt]machine/param.h\*[Gt] 55header as a define. 56.Sh RETURN VALUES 57The return value is either the number of clock ticks or milliseconds 58for the specified value. 59.Sh SEE ALSO 60.Xr callout 9 61.Sh BUGS 62Neither 63.Fn mstohz 64nor 65.Fn hztoms 66make use of expensive 64-bit integer arithmetic. 67The result from 68.Fn mstohz 69will be rounded down to one second if the parameter is larger 70than 131072 milliseconds. 71