.\" Copyright (c) 2000 Kelly Yancey
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.\"    $FreeBSD: src/share/man/man9/tvtohz.9,v 1.1.4.2 2001/12/17 11:30:19 ru Exp $
.\"    $DragonFly: src/share/man/man9/tvtohz.9,v 1.4 2007/11/14 18:27:52 swildner Exp $
.\"
.Dd June 30, 2007
.Dt TVTOHZ 9
.Os
.Sh NAME
.Nm tvtohz_high ,
.Nm tvtohz_low
.Nd convert time interval to tick count
.Sh SYNOPSIS
.In sys/time.h
.Ft int
.Fn tvtohz_high "struct timeval *tv"
.Ft int
.Fn tvtohz_low "struct timeval *tv"
.Sh DESCRIPTION
The
.Fn tvtohz_high
and
.Fn tvtohz_low
functions accept a single argument
.Fa tv
which specifies the time interval over which to calculate the number
of system ticks that would elapse.
.Sh RETURN VALUES
The
.Fn tvtohz_high
function returns the integral number of system ticks expected to elapse
in the given interval.
The return value is intended to be used in a clock interrupt timed operation
and guaranteed to meet or exceed the requested time.
The minimum return value is 1 tick and the function will average the
calculation up.
If any value greater than 0 microseconds is supplied, a value of at least 2
will be returned to ensure that a near-term clock interrupt does not cause
the timeout to occur (degenerately) early.
.Pp
The
.Fn tvtohz_low
function returns the uncompensated number of system ticks for the specified
amount of time.
A return value of 0 is possible if
.Fa tv
converts to less than 1 tick.
.Pp
If the reprensentation overflows, both functions return
.Dv INT_MAX .
.Sh FILES
.Pa sys/kern/kern_clock.c
.Sh SEE ALSO
.Xr callout 9 ,
.Xr microtime 9 ,
.Xr microuptime 9
.Sh HISTORY
The
.Nm tvtohz
function first appeared in
.Fx 3.0 .
It was split into
.Nm
and
.Nm tvtohz_low
by
.An Matt Dillon
in
.Dx 1.0 .
.Sh AUTHORS
.An -nosplit
This manual page was originally written by
.An Kelly Yancey Aq kbyanc@posi.net
and later updated by
.An Sascha Wildner .