1.\"- 2.\" Copyright (c) 2017 Dag-Erling Smørgrav 3.\" All rights reserved. 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 AUTHOR 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 AUTHOR 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.\" $FreeBSD$ 27.\" 28.Dd September 25, 2017 29.Dt RATECHECK 9 30.Os 31.Sh NAME 32.Nm ratecheck , 33.Nm ppsratecheck 34.Nd "event rate limiting" 35.Sh SYNOPSIS 36.In sys/time.h 37.Ft int 38.Fn ratecheck "struct timeval *lasttime" "struct timeval *mininterval" 39.Ft int 40.Fn ppsratecheck "struct timeval *lasttime" "int *curpps" "int maxpps" 41.Sh DESCRIPTION 42The 43.Nm ratecheck 44and 45.Nm ppsratecheck 46functions facilitate rate-limiting of arbitrary events. 47The former enforces a minimum interval between events while the latter 48enforces a maximum number of events per second. 49.Pp 50The 51.Nm ratecheck 52function compares the current time to the value pointed to by 53.Fa lasttime . 54If the difference is equal to or greater than 55.Fa mininterval , 56it returns a non-zero value and updates 57.Fa lasttime 58to the current time. 59Otherwise, it returns zero. 60.Pp 61The 62.Nm ppsratecheck 63function first compares the current time 64to 65.Fa lasttime . 66If at least a full second has passed, the value pointed to by the 67.Fa curpps 68argument is reset to 1 and 69.Fa lasttime 70is updated to the current time. 71Otherwise, 72.Fa curpps 73is incremented and 74.Fa lasttime 75is left untouched. 76In either case, 77.Nm ppsratecheck 78returns a non-zero value if and only if the updated 79.Fa curpps 80is less than or equal to 81.Fa maxpps 82or 83.Fa maxpps 84is negative. 85.Sh SEE ALSO 86.Xr counter 9 87.Sh HISTORY 88The 89.Nm ratecheck 90and 91.Nm ppsratecheck 92functions first appeared in 93.Fx 5.1 . 94