diff options
Diffstat (limited to 'ev.pod')
| -rw-r--r-- | ev.pod | 30 |
1 files changed, 21 insertions, 9 deletions
@@ -1076,11 +1076,11 @@ to trigger "at" some specific point in time. For example, if you tell a periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () + 10.>) and then reset your system clock to the last year, then it will take a year to trigger the event (unlike an C<ev_timer>, which would trigger -roughly 10 seconds later and of course not if you reset your system time -again). +roughly 10 seconds later). They can also be used to implement vastly more complex timers, such as -triggering an event on eahc midnight, local time. +triggering an event on each midnight, local time or other, complicated, +rules. As with timers, the callback is guarenteed to be invoked only when the time (C<at>) has been passed, but if multiple periodic timers become ready @@ -1097,18 +1097,18 @@ operation, and we will explain them from simplest to complex: =over 4 -=item * absolute timer (interval = reschedule_cb = 0) +=item * absolute timer (at = time, interval = reschedule_cb = 0) In this configuration the watcher triggers an event at the wallclock time C<at> and doesn't repeat. It will not adjust when a time jump occurs, that is, if it is to be run at January 1st 2011 then it will run when the system time reaches or surpasses this time. -=item * non-repeating interval timer (interval > 0, reschedule_cb = 0) +=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) In this mode the watcher will always be scheduled to time out at the next -C<at + N * interval> time (for some integer N) and then repeat, regardless -of any time jumps. +C<at + N * interval> time (for some integer N, which can also be negative) +and then repeat, regardless of any time jumps. This can be used to create timers that do not drift with respect to system time: @@ -1124,7 +1124,11 @@ Another way to think about it (for the mathematically inclined) is that C<ev_periodic> will try to run the callback in this mode at the next possible time where C<time = at (mod interval)>, regardless of any time jumps. -=item * manual reschedule mode (reschedule_cb = callback) +For numerical stability it is preferable that the C<at> value is near +C<ev_now ()> (the current time), but there is no range requirement for +this value. + +=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) In this mode the values for C<interval> and C<at> are both being ignored. Instead, each time the periodic watcher gets scheduled, the @@ -1134,7 +1138,7 @@ current time as second argument. NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, or make any event loop modifications>. If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by -starting a prepare watcher). +starting an C<ev_prepare> watcher, which is legal). Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now)>, e.g.: @@ -1167,6 +1171,14 @@ when you changed some parameters or the reschedule callback would return a different time than the last time it was called (e.g. in a crond like program when the crontabs have changed). +=item ev_tstamp offset [read-write] + +When repeating, this contains the offset value, otherwise this is the +absolute point in time (the C<at> value passed to C<ev_periodic_set>). + +Can be modified any time, but changes only take effect when the periodic +timer fires or C<ev_periodic_again> is being called. + =item ev_tstamp interval [read-write] The current interval value. Can be modified any time, but changes only |