1.\" $NetBSD: mstohz.9,v 1.8 2010/07/01 15:06:55 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 July 1, 2010 28.Dt MSTOHZ 9 29.Os 30.Sh NAME 31.Nm mstohz , 32.Nm hztoms 33.Nd convert between milliseconds and system clock ticks 34.Sh SYNOPSIS 35.In sys/param.h 36.Ft int 37.Fn mstohz "int ms" 38.Ft int 39.Fn hztoms "int hz" 40.Sh DESCRIPTION 41The 42.Fn mstohz 43macro can be used to convert time 44in milliseconds to system clock ticks, as used 45by the 46.Xr callout 9 47facility, in an integer-overflow safe way. 48Conversely, 49.Fn hztoms 50converts system clock ticks to milliseconds. 51.Pp 52These macros are defined in the 53.Em \*[Lt]sys/param.h\*[Gt] 54header. 55Individual ports can have a processor-specific, more efficient 56version implemented in their 57.Em \*[Lt]machine/param.h\*[Gt] 58header as a define. 59.Sh RETURN VALUES 60The return value is either the number of clock ticks or milliseconds 61for the specified value. 62.Sh SEE ALSO 63.Xr callout 9 64.Sh BUGS 65Neither 66.Fn mstohz 67nor 68.Fn hztoms 69make use of expensive 64-bit integer arithmetic. 70The result from 71.Fn mstohz 72will be rounded down to one second if the parameter is larger 73than 131072 milliseconds. 74