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Comparing libev/ev.3 (file contents):
Revision 1.45 by root, Sat Dec 8 22:11:14 2007 UTC vs.
Revision 1.46 by root, Sun Dec 9 19:42:57 2007 UTC

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127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-12-08" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-09" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
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1235but on wallclock time (absolute time). You can tell a periodic watcher 1235but on wallclock time (absolute time). You can tell a periodic watcher
1236to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1236to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
1237periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 1237periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1238+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will 1238+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
1239take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1239take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
1240roughly 10 seconds later and of course not if you reset your system time 1240roughly 10 seconds later).
1241again).
1242.PP 1241.PP
1243They can also be used to implement vastly more complex timers, such as 1242They can also be used to implement vastly more complex timers, such as
1244triggering an event on eahc midnight, local time. 1243triggering an event on each midnight, local time or other, complicated,
1244rules.
1245.PP 1245.PP
1246As with timers, the callback is guarenteed to be invoked only when the 1246As with timers, the callback is guarenteed to be invoked only when the
1247time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1247time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1248during the same loop iteration then order of execution is undefined. 1248during the same loop iteration then order of execution is undefined.
1249.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1249.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
… …
1253.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1253.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1254.PD 1254.PD
1255Lots of arguments, lets sort it out... There are basically three modes of 1255Lots of arguments, lets sort it out... There are basically three modes of
1256operation, and we will explain them from simplest to complex: 1256operation, and we will explain them from simplest to complex:
1257.RS 4 1257.RS 4
1258.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1258.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
1259.IX Item "absolute timer (interval = reschedule_cb = 0)" 1259.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
1260In this configuration the watcher triggers an event at the wallclock time 1260In this configuration the watcher triggers an event at the wallclock time
1261\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1261\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1262that is, if it is to be run at January 1st 2011 then it will run when the 1262that is, if it is to be run at January 1st 2011 then it will run when the
1263system time reaches or surpasses this time. 1263system time reaches or surpasses this time.
1264.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1264.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
1265.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1265.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
1266In this mode the watcher will always be scheduled to time out at the next 1266In this mode the watcher will always be scheduled to time out at the next
1267\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1267\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
1268of any time jumps. 1268and then repeat, regardless of any time jumps.
1269.Sp 1269.Sp
1270This can be used to create timers that do not drift with respect to system 1270This can be used to create timers that do not drift with respect to system
1271time: 1271time:
1272.Sp 1272.Sp
1273.Vb 1 1273.Vb 1
… …
1280by 3600. 1280by 3600.
1281.Sp 1281.Sp
1282Another way to think about it (for the mathematically inclined) is that 1282Another way to think about it (for the mathematically inclined) is that
1283\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1283\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1284time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1284time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1285.Sp
1286For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1287\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1288this value.
1285.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1289.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
1286.IX Item "manual reschedule mode (reschedule_cb = callback)" 1290.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
1287In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1291In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1288ignored. Instead, each time the periodic watcher gets scheduled, the 1292ignored. Instead, each time the periodic watcher gets scheduled, the
1289reschedule callback will be called with the watcher as first, and the 1293reschedule callback will be called with the watcher as first, and the
1290current time as second argument. 1294current time as second argument.
1291.Sp 1295.Sp
1292\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1296\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1293ever, or make any event loop modifications\fR. If you need to stop it, 1297ever, or make any event loop modifications\fR. If you need to stop it,
1294return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1298return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1295starting a prepare watcher). 1299starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1296.Sp 1300.Sp
1297Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1301Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1298ev_tstamp now)\*(C'\fR, e.g.: 1302ev_tstamp now)\*(C'\fR, e.g.:
1299.Sp 1303.Sp
1300.Vb 4 1304.Vb 4
… …
1324.IX Item "ev_periodic_again (loop, ev_periodic *)" 1328.IX Item "ev_periodic_again (loop, ev_periodic *)"
1325Simply stops and restarts the periodic watcher again. This is only useful 1329Simply stops and restarts the periodic watcher again. This is only useful
1326when you changed some parameters or the reschedule callback would return 1330when you changed some parameters or the reschedule callback would return
1327a different time than the last time it was called (e.g. in a crond like 1331a different time than the last time it was called (e.g. in a crond like
1328program when the crontabs have changed). 1332program when the crontabs have changed).
1333.IP "ev_tstamp offset [read\-write]" 4
1334.IX Item "ev_tstamp offset [read-write]"
1335When repeating, this contains the offset value, otherwise this is the
1336absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1337.Sp
1338Can be modified any time, but changes only take effect when the periodic
1339timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1329.IP "ev_tstamp interval [read\-write]" 4 1340.IP "ev_tstamp interval [read\-write]" 4
1330.IX Item "ev_tstamp interval [read-write]" 1341.IX Item "ev_tstamp interval [read-write]"
1331The current interval value. Can be modified any time, but changes only 1342The current interval value. Can be modified any time, but changes only
1332take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being 1343take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1333called. 1344called.

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