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.\"-
.\" Copyright (c) 2017 Dag-Erling Smørgrav
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd September 25, 2017
.Dt RATECHECK 9
.Os
.Sh NAME
.Nm ratecheck ,
.Nm ppsratecheck
.Nd "event rate limiting"
.Sh SYNOPSIS
.In sys/time.h
.Ft int
.Fn ratecheck "struct timeval *lasttime" "struct timeval *mininterval"
.Ft int
.Fn ppsratecheck "struct timeval *lasttime" "int *curpps" "int maxpps"
.Sh DESCRIPTION
The
.Nm ratecheck
and
.Nm ppsratecheck
functions facilitate rate-limiting of arbitrary events.
The former enforces a minimum interval between events while the latter
enforces a maximum number of events per second.
.Pp
The
.Nm ratecheck
function compares the current time to the value pointed to by
.Fa lasttime .
If the difference is equal to or greater than
.Fa mininterval ,
it returns a non-zero value and updates
.Fa lasttime
to the current time.
Otherwise, it returns zero.
.Pp
The
.Nm ppsratecheck
function first compares the current time
to
.Fa lasttime .
If at least a full second has passed, the value pointed to by the
.Fa curpps
argument is reset to 1 and
.Fa lasttime
is updated to the current time.
Otherwise,
.Fa curpps
is incremented and
.Fa lasttime
is left untouched.
In either case,
.Nm ppsratecheck
returns a non-zero value if and only if the updated
.Fa curpps
is less than or equal to
.Fa maxpps
or
.Fa maxpps
is negative.
.Sh SEE ALSO
.Xr counter 9
.Sh HISTORY
The
.Nm ratecheck
and
.Nm ppsratecheck
functions first appeared in
.Fx 5.1 .
|
