… | |
… | |
1151 | |
1151 | |
1152 | Timer watchers are simple relative timers that generate an event after a |
1152 | Timer watchers are simple relative timers that generate an event after a |
1153 | given time, and optionally repeating in regular intervals after that. |
1153 | given time, and optionally repeating in regular intervals after that. |
1154 | |
1154 | |
1155 | The timers are based on real time, that is, if you register an event that |
1155 | The timers are based on real time, that is, if you register an event that |
1156 | times out after an hour and you reset your system clock to last years |
1156 | times out after an hour and you reset your system clock to january last |
1157 | time, it will still time out after (roughly) and hour. "Roughly" because |
1157 | year, it will still time out after (roughly) and hour. "Roughly" because |
1158 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1158 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1159 | monotonic clock option helps a lot here). |
1159 | monotonic clock option helps a lot here). |
1160 | |
1160 | |
1161 | The relative timeouts are calculated relative to the C<ev_now ()> |
1161 | The relative timeouts are calculated relative to the C<ev_now ()> |
1162 | time. This is usually the right thing as this timestamp refers to the time |
1162 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1164 | you suspect event processing to be delayed and you I<need> to base the timeout |
1164 | you suspect event processing to be delayed and you I<need> to base the timeout |
1165 | on the current time, use something like this to adjust for this: |
1165 | on the current time, use something like this to adjust for this: |
1166 | |
1166 | |
1167 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1167 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1168 | |
1168 | |
1169 | The callback is guarenteed to be invoked only when its timeout has passed, |
1169 | The callback is guarenteed to be invoked only after its timeout has passed, |
1170 | but if multiple timers become ready during the same loop iteration then |
1170 | but if multiple timers become ready during the same loop iteration then |
1171 | order of execution is undefined. |
1171 | order of execution is undefined. |
1172 | |
1172 | |
1173 | =head3 Watcher-Specific Functions and Data Members |
1173 | =head3 Watcher-Specific Functions and Data Members |
1174 | |
1174 | |
… | |
… | |
1176 | |
1176 | |
1177 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1177 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1178 | |
1178 | |
1179 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1179 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1180 | |
1180 | |
1181 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1181 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
1182 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1182 | is C<0.>, then it will automatically be stopped once the timeout is |
1183 | timer will automatically be configured to trigger again C<repeat> seconds |
1183 | reached. If it is positive, then the timer will automatically be |
1184 | later, again, and again, until stopped manually. |
1184 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1185 | until stopped manually. |
1185 | |
1186 | |
1186 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1187 | The timer itself will do a best-effort at avoiding drift, that is, if |
1187 | configure a timer to trigger every 10 seconds, then it will trigger at |
1188 | you configure a timer to trigger every 10 seconds, then it will normally |
1188 | exactly 10 second intervals. If, however, your program cannot keep up with |
1189 | trigger at exactly 10 second intervals. If, however, your program cannot |
1189 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1190 | keep up with the timer (because it takes longer than those 10 seconds to |
1190 | timer will not fire more than once per event loop iteration. |
1191 | do stuff) the timer will not fire more than once per event loop iteration. |
1191 | |
1192 | |
1192 | =item ev_timer_again (loop, ev_timer *) |
1193 | =item ev_timer_again (loop, ev_timer *) |
1193 | |
1194 | |
1194 | This will act as if the timer timed out and restart it again if it is |
1195 | This will act as if the timer timed out and restart it again if it is |
1195 | repeating. The exact semantics are: |
1196 | repeating. The exact semantics are: |
… | |
… | |
1272 | Periodic watchers are also timers of a kind, but they are very versatile |
1273 | Periodic watchers are also timers of a kind, but they are very versatile |
1273 | (and unfortunately a bit complex). |
1274 | (and unfortunately a bit complex). |
1274 | |
1275 | |
1275 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1276 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1276 | but on wallclock time (absolute time). You can tell a periodic watcher |
1277 | but on wallclock time (absolute time). You can tell a periodic watcher |
1277 | to trigger "at" some specific point in time. For example, if you tell a |
1278 | to trigger after some specific point in time. For example, if you tell a |
1278 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1279 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1279 | + 10.>) and then reset your system clock to the last year, then it will |
1280 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1281 | clock to january of the previous year, then it will take more than year |
1280 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1282 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1281 | roughly 10 seconds later). |
1283 | roughly 10 seconds later as it uses a relative timeout). |
1282 | |
1284 | |
1283 | They can also be used to implement vastly more complex timers, such as |
1285 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1284 | triggering an event on each midnight, local time or other, complicated, |
1286 | such as triggering an event on each "midnight, local time", or other |
1285 | rules. |
1287 | complicated, rules. |
1286 | |
1288 | |
1287 | As with timers, the callback is guarenteed to be invoked only when the |
1289 | As with timers, the callback is guarenteed to be invoked only when the |
1288 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1290 | time (C<at>) has passed, but if multiple periodic timers become ready |
1289 | during the same loop iteration then order of execution is undefined. |
1291 | during the same loop iteration then order of execution is undefined. |
1290 | |
1292 | |
1291 | =head3 Watcher-Specific Functions and Data Members |
1293 | =head3 Watcher-Specific Functions and Data Members |
1292 | |
1294 | |
1293 | =over 4 |
1295 | =over 4 |
… | |
… | |
1301 | |
1303 | |
1302 | =over 4 |
1304 | =over 4 |
1303 | |
1305 | |
1304 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1306 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1305 | |
1307 | |
1306 | In this configuration the watcher triggers an event at the wallclock time |
1308 | In this configuration the watcher triggers an event after the wallclock |
1307 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1309 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1308 | that is, if it is to be run at January 1st 2011 then it will run when the |
1310 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1309 | system time reaches or surpasses this time. |
1311 | run when the system time reaches or surpasses this time. |
1310 | |
1312 | |
1311 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1313 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1312 | |
1314 | |
1313 | In this mode the watcher will always be scheduled to time out at the next |
1315 | In this mode the watcher will always be scheduled to time out at the next |
1314 | C<at + N * interval> time (for some integer N, which can also be negative) |
1316 | C<at + N * interval> time (for some integer N, which can also be negative) |
1315 | and then repeat, regardless of any time jumps. |
1317 | and then repeat, regardless of any time jumps. |
1316 | |
1318 | |
1317 | This can be used to create timers that do not drift with respect to system |
1319 | This can be used to create timers that do not drift with respect to system |
1318 | time: |
1320 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1321 | the hour: |
1319 | |
1322 | |
1320 | ev_periodic_set (&periodic, 0., 3600., 0); |
1323 | ev_periodic_set (&periodic, 0., 3600., 0); |
1321 | |
1324 | |
1322 | This doesn't mean there will always be 3600 seconds in between triggers, |
1325 | This doesn't mean there will always be 3600 seconds in between triggers, |
1323 | but only that the the callback will be called when the system time shows a |
1326 | but only that the the callback will be called when the system time shows a |
… | |
… | |
1328 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1331 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1329 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1332 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1330 | |
1333 | |
1331 | For numerical stability it is preferable that the C<at> value is near |
1334 | For numerical stability it is preferable that the C<at> value is near |
1332 | C<ev_now ()> (the current time), but there is no range requirement for |
1335 | C<ev_now ()> (the current time), but there is no range requirement for |
1333 | this value. |
1336 | this value, and in fact is often specified as zero. |
|
|
1337 | |
|
|
1338 | Note also that there is an upper limit to how often a timer can fire (cpu |
|
|
1339 | speed for example), so if C<interval> is very small then timing stability |
|
|
1340 | will of course detoriate. Libev itself tries to be exact to be about one |
|
|
1341 | millisecond (if the OS supports it and the machine is fast enough). |
1334 | |
1342 | |
1335 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1343 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1336 | |
1344 | |
1337 | In this mode the values for C<interval> and C<at> are both being |
1345 | In this mode the values for C<interval> and C<at> are both being |
1338 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1346 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1339 | reschedule callback will be called with the watcher as first, and the |
1347 | reschedule callback will be called with the watcher as first, and the |
1340 | current time as second argument. |
1348 | current time as second argument. |
1341 | |
1349 | |
1342 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1350 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1343 | ever, or make any event loop modifications>. If you need to stop it, |
1351 | ever, or make ANY event loop modifications whatsoever>. |
1344 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
1345 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1346 | |
1352 | |
|
|
1353 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1354 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1355 | only event loop modification you are allowed to do). |
|
|
1356 | |
1347 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1357 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1348 | ev_tstamp now)>, e.g.: |
1358 | *w, ev_tstamp now)>, e.g.: |
1349 | |
1359 | |
1350 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1360 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1351 | { |
1361 | { |
1352 | return now + 60.; |
1362 | return now + 60.; |
1353 | } |
1363 | } |
… | |
… | |
1355 | It must return the next time to trigger, based on the passed time value |
1365 | It must return the next time to trigger, based on the passed time value |
1356 | (that is, the lowest time value larger than to the second argument). It |
1366 | (that is, the lowest time value larger than to the second argument). It |
1357 | will usually be called just before the callback will be triggered, but |
1367 | will usually be called just before the callback will be triggered, but |
1358 | might be called at other times, too. |
1368 | might be called at other times, too. |
1359 | |
1369 | |
1360 | NOTE: I<< This callback must always return a time that is later than the |
1370 | NOTE: I<< This callback must always return a time that is higher than or |
1361 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1371 | equal to the passed C<now> value >>. |
1362 | |
1372 | |
1363 | This can be used to create very complex timers, such as a timer that |
1373 | This can be used to create very complex timers, such as a timer that |
1364 | triggers on each midnight, local time. To do this, you would calculate the |
1374 | triggers on "next midnight, local time". To do this, you would calculate the |
1365 | next midnight after C<now> and return the timestamp value for this. How |
1375 | next midnight after C<now> and return the timestamp value for this. How |
1366 | you do this is, again, up to you (but it is not trivial, which is the main |
1376 | you do this is, again, up to you (but it is not trivial, which is the main |
1367 | reason I omitted it as an example). |
1377 | reason I omitted it as an example). |
1368 | |
1378 | |
1369 | =back |
1379 | =back |
… | |
… | |
3352 | =back |
3362 | =back |
3353 | |
3363 | |
3354 | If you know of other additional requirements drop me a note. |
3364 | If you know of other additional requirements drop me a note. |
3355 | |
3365 | |
3356 | |
3366 | |
|
|
3367 | =head1 VALGRIND |
|
|
3368 | |
|
|
3369 | Valgrind has a special section here because it is a popular tool that is |
|
|
3370 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3371 | |
|
|
3372 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3373 | in libev, then check twice: If valgrind reports something like: |
|
|
3374 | |
|
|
3375 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3376 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3377 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3378 | |
|
|
3379 | then there is no memory leak. Similarly, under some circumstances, |
|
|
3380 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3381 | might be confused (it is a very good tool, but only a tool). |
|
|
3382 | |
|
|
3383 | If you are unsure about something, feel free to contact the mailing list |
|
|
3384 | with the full valgrind report and an explanation on why you think this is |
|
|
3385 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
|
|
3386 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3387 | properly. |
|
|
3388 | |
|
|
3389 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3390 | I suggest using suppression lists. |
|
|
3391 | |
|
|
3392 | |
3357 | =head1 AUTHOR |
3393 | =head1 AUTHOR |
3358 | |
3394 | |
3359 | Marc Lehmann <libev@schmorp.de>. |
3395 | Marc Lehmann <libev@schmorp.de>. |
3360 | |
3396 | |