… | |
… | |
1074 | but on wallclock time (absolute time). You can tell a periodic watcher |
1074 | but on wallclock time (absolute time). You can tell a periodic watcher |
1075 | to trigger "at" some specific point in time. For example, if you tell a |
1075 | to trigger "at" some specific point in time. For example, if you tell a |
1076 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1076 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1077 | + 10.>) and then reset your system clock to the last year, then it will |
1077 | + 10.>) and then reset your system clock to the last year, then it will |
1078 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1078 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1079 | roughly 10 seconds later and of course not if you reset your system time |
1079 | roughly 10 seconds later). |
1080 | again). |
|
|
1081 | |
1080 | |
1082 | They can also be used to implement vastly more complex timers, such as |
1081 | They can also be used to implement vastly more complex timers, such as |
1083 | triggering an event on eahc midnight, local time. |
1082 | triggering an event on each midnight, local time or other, complicated, |
|
|
1083 | rules. |
1084 | |
1084 | |
1085 | As with timers, the callback is guarenteed to be invoked only when the |
1085 | As with timers, the callback is guarenteed to be invoked only when the |
1086 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1086 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1087 | during the same loop iteration then order of execution is undefined. |
1087 | during the same loop iteration then order of execution is undefined. |
1088 | |
1088 | |
… | |
… | |
1095 | Lots of arguments, lets sort it out... There are basically three modes of |
1095 | Lots of arguments, lets sort it out... There are basically three modes of |
1096 | operation, and we will explain them from simplest to complex: |
1096 | operation, and we will explain them from simplest to complex: |
1097 | |
1097 | |
1098 | =over 4 |
1098 | =over 4 |
1099 | |
1099 | |
1100 | =item * absolute timer (interval = reschedule_cb = 0) |
1100 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1101 | |
1101 | |
1102 | In this configuration the watcher triggers an event at the wallclock time |
1102 | In this configuration the watcher triggers an event at the wallclock time |
1103 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1103 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1104 | that is, if it is to be run at January 1st 2011 then it will run when the |
1104 | that is, if it is to be run at January 1st 2011 then it will run when the |
1105 | system time reaches or surpasses this time. |
1105 | system time reaches or surpasses this time. |
1106 | |
1106 | |
1107 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1107 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1108 | |
1108 | |
1109 | In this mode the watcher will always be scheduled to time out at the next |
1109 | In this mode the watcher will always be scheduled to time out at the next |
1110 | C<at + N * interval> time (for some integer N) and then repeat, regardless |
1110 | C<at + N * interval> time (for some integer N, which can also be negative) |
1111 | of any time jumps. |
1111 | and then repeat, regardless of any time jumps. |
1112 | |
1112 | |
1113 | This can be used to create timers that do not drift with respect to system |
1113 | This can be used to create timers that do not drift with respect to system |
1114 | time: |
1114 | time: |
1115 | |
1115 | |
1116 | ev_periodic_set (&periodic, 0., 3600., 0); |
1116 | ev_periodic_set (&periodic, 0., 3600., 0); |
… | |
… | |
1122 | |
1122 | |
1123 | Another way to think about it (for the mathematically inclined) is that |
1123 | Another way to think about it (for the mathematically inclined) is that |
1124 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1124 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1125 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1125 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1126 | |
1126 | |
|
|
1127 | For numerical stability it is preferable that the C<at> value is near |
|
|
1128 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1129 | this value. |
|
|
1130 | |
1127 | =item * manual reschedule mode (reschedule_cb = callback) |
1131 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1128 | |
1132 | |
1129 | In this mode the values for C<interval> and C<at> are both being |
1133 | In this mode the values for C<interval> and C<at> are both being |
1130 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1134 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1131 | reschedule callback will be called with the watcher as first, and the |
1135 | reschedule callback will be called with the watcher as first, and the |
1132 | current time as second argument. |
1136 | current time as second argument. |
1133 | |
1137 | |
1134 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1138 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1135 | ever, or make any event loop modifications>. If you need to stop it, |
1139 | ever, or make any event loop modifications>. If you need to stop it, |
1136 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1140 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1137 | starting a prepare watcher). |
1141 | starting an C<ev_prepare> watcher, which is legal). |
1138 | |
1142 | |
1139 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1143 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1140 | ev_tstamp now)>, e.g.: |
1144 | ev_tstamp now)>, e.g.: |
1141 | |
1145 | |
1142 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1146 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
… | |
… | |
1164 | |
1168 | |
1165 | Simply stops and restarts the periodic watcher again. This is only useful |
1169 | Simply stops and restarts the periodic watcher again. This is only useful |
1166 | when you changed some parameters or the reschedule callback would return |
1170 | when you changed some parameters or the reschedule callback would return |
1167 | a different time than the last time it was called (e.g. in a crond like |
1171 | a different time than the last time it was called (e.g. in a crond like |
1168 | program when the crontabs have changed). |
1172 | program when the crontabs have changed). |
|
|
1173 | |
|
|
1174 | =item ev_tstamp offset [read-write] |
|
|
1175 | |
|
|
1176 | When repeating, this contains the offset value, otherwise this is the |
|
|
1177 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
|
|
1178 | |
|
|
1179 | Can be modified any time, but changes only take effect when the periodic |
|
|
1180 | timer fires or C<ev_periodic_again> is being called. |
1169 | |
1181 | |
1170 | =item ev_tstamp interval [read-write] |
1182 | =item ev_tstamp interval [read-write] |
1171 | |
1183 | |
1172 | The current interval value. Can be modified any time, but changes only |
1184 | The current interval value. Can be modified any time, but changes only |
1173 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1185 | take effect when the periodic timer fires or C<ev_periodic_again> is being |