xref: /freebsd/share/man/man9/ratecheck.9 (revision 95ee2897e98f5d444f26ed2334cc7c439f9c16c6)
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28.Dd March 11, 2022
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" "const 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