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.Dd September 25, 2017 .Dt RATECHECK 9 .Os .Sh NAME .Nm ratecheck , .Nm ppsratecheck .Nd "event rate limiting" .Sh SYNOPSIS n 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.

p 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.

p 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 .