… | |
… | |
64 | |
64 | |
65 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
66 | |
66 | |
67 | The newest version of this document is also available as an html-formatted |
67 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
68 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
70 | |
70 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
71 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
72 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
73 | these event sources and provide your program with events. |
74 | |
74 | |
… | |
… | |
336 | To get good performance out of this backend you need a high amount of |
336 | To get good performance out of this backend you need a high amount of |
337 | parallelity (most of the file descriptors should be busy). If you are |
337 | parallelity (most of the file descriptors should be busy). If you are |
338 | writing a server, you should C<accept ()> in a loop to accept as many |
338 | writing a server, you should C<accept ()> in a loop to accept as many |
339 | connections as possible during one iteration. You might also want to have |
339 | connections as possible during one iteration. You might also want to have |
340 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
340 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
341 | readyness notifications you get per iteration. |
341 | readiness notifications you get per iteration. |
342 | |
342 | |
343 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
343 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
344 | |
344 | |
345 | And this is your standard poll(2) backend. It's more complicated |
345 | And this is your standard poll(2) backend. It's more complicated |
346 | than select, but handles sparse fds better and has no artificial |
346 | than select, but handles sparse fds better and has no artificial |
… | |
… | |
425 | While this backend scales well, it requires one system call per active |
425 | While this backend scales well, it requires one system call per active |
426 | file descriptor per loop iteration. For small and medium numbers of file |
426 | file descriptor per loop iteration. For small and medium numbers of file |
427 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
427 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
428 | might perform better. |
428 | might perform better. |
429 | |
429 | |
430 | On the positive side, ignoring the spurious readyness notifications, this |
430 | On the positive side, ignoring the spurious readiness notifications, this |
431 | backend actually performed to specification in all tests and is fully |
431 | backend actually performed to specification in all tests and is fully |
432 | embeddable, which is a rare feat among the OS-specific backends. |
432 | embeddable, which is a rare feat among the OS-specific backends. |
433 | |
433 | |
434 | =item C<EVBACKEND_ALL> |
434 | =item C<EVBACKEND_ALL> |
435 | |
435 | |
… | |
… | |
689 | interval to a value near C<0.1> or so, which is often enough for |
689 | interval to a value near C<0.1> or so, which is often enough for |
690 | interactive servers (of course not for games), likewise for timeouts. It |
690 | interactive servers (of course not for games), likewise for timeouts. It |
691 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
691 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
692 | as this approsaches the timing granularity of most systems. |
692 | as this approsaches the timing granularity of most systems. |
693 | |
693 | |
|
|
694 | =item ev_loop_verify (loop) |
|
|
695 | |
|
|
696 | This function only does something when C<EV_VERIFY> support has been |
|
|
697 | compiled in. It tries to go through all internal structures and checks |
|
|
698 | them for validity. If anything is found to be inconsistent, it will print |
|
|
699 | an error message to standard error and call C<abort ()>. |
|
|
700 | |
|
|
701 | This can be used to catch bugs inside libev itself: under normal |
|
|
702 | circumstances, this function will never abort as of course libev keeps its |
|
|
703 | data structures consistent. |
|
|
704 | |
694 | =back |
705 | =back |
695 | |
706 | |
696 | |
707 | |
697 | =head1 ANATOMY OF A WATCHER |
708 | =head1 ANATOMY OF A WATCHER |
698 | |
709 | |
… | |
… | |
1032 | If you must do this, then force the use of a known-to-be-good backend |
1043 | If you must do this, then force the use of a known-to-be-good backend |
1033 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1044 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1034 | C<EVBACKEND_POLL>). |
1045 | C<EVBACKEND_POLL>). |
1035 | |
1046 | |
1036 | Another thing you have to watch out for is that it is quite easy to |
1047 | Another thing you have to watch out for is that it is quite easy to |
1037 | receive "spurious" readyness notifications, that is your callback might |
1048 | receive "spurious" readiness notifications, that is your callback might |
1038 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1049 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1039 | because there is no data. Not only are some backends known to create a |
1050 | because there is no data. Not only are some backends known to create a |
1040 | lot of those (for example solaris ports), it is very easy to get into |
1051 | lot of those (for example solaris ports), it is very easy to get into |
1041 | this situation even with a relatively standard program structure. Thus |
1052 | this situation even with a relatively standard program structure. Thus |
1042 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1053 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
… | |
… | |
1151 | |
1162 | |
1152 | Timer watchers are simple relative timers that generate an event after a |
1163 | Timer watchers are simple relative timers that generate an event after a |
1153 | given time, and optionally repeating in regular intervals after that. |
1164 | given time, and optionally repeating in regular intervals after that. |
1154 | |
1165 | |
1155 | The timers are based on real time, that is, if you register an event that |
1166 | 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 |
1167 | 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 |
1168 | year, it will still time out after (roughly) and hour. "Roughly" because |
1158 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1169 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1159 | monotonic clock option helps a lot here). |
1170 | monotonic clock option helps a lot here). |
1160 | |
1171 | |
1161 | The relative timeouts are calculated relative to the C<ev_now ()> |
1172 | 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 |
1173 | 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 |
1175 | 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: |
1176 | on the current time, use something like this to adjust for this: |
1166 | |
1177 | |
1167 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1178 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1168 | |
1179 | |
1169 | The callback is guarenteed to be invoked only when its timeout has passed, |
1180 | 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 |
1181 | but if multiple timers become ready during the same loop iteration then |
1171 | order of execution is undefined. |
1182 | order of execution is undefined. |
1172 | |
1183 | |
1173 | =head3 Watcher-Specific Functions and Data Members |
1184 | =head3 Watcher-Specific Functions and Data Members |
1174 | |
1185 | |
… | |
… | |
1176 | |
1187 | |
1177 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1188 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1178 | |
1189 | |
1179 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1190 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1180 | |
1191 | |
1181 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1192 | 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 |
1193 | 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 |
1194 | reached. If it is positive, then the timer will automatically be |
1184 | later, again, and again, until stopped manually. |
1195 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1196 | until stopped manually. |
1185 | |
1197 | |
1186 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1198 | 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 |
1199 | 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 |
1200 | 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 |
1201 | 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. |
1202 | do stuff) the timer will not fire more than once per event loop iteration. |
1191 | |
1203 | |
1192 | =item ev_timer_again (loop, ev_timer *) |
1204 | =item ev_timer_again (loop, ev_timer *) |
1193 | |
1205 | |
1194 | This will act as if the timer timed out and restart it again if it is |
1206 | This will act as if the timer timed out and restart it again if it is |
1195 | repeating. The exact semantics are: |
1207 | repeating. The exact semantics are: |
… | |
… | |
1272 | Periodic watchers are also timers of a kind, but they are very versatile |
1284 | Periodic watchers are also timers of a kind, but they are very versatile |
1273 | (and unfortunately a bit complex). |
1285 | (and unfortunately a bit complex). |
1274 | |
1286 | |
1275 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1287 | 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 |
1288 | 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 |
1289 | 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 () |
1290 | 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 |
1291 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1292 | 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 |
1293 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1281 | roughly 10 seconds later). |
1294 | roughly 10 seconds later as it uses a relative timeout). |
1282 | |
1295 | |
1283 | They can also be used to implement vastly more complex timers, such as |
1296 | 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, |
1297 | such as triggering an event on each "midnight, local time", or other |
1285 | rules. |
1298 | complicated, rules. |
1286 | |
1299 | |
1287 | As with timers, the callback is guarenteed to be invoked only when the |
1300 | 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 |
1301 | time (C<at>) has passed, but if multiple periodic timers become ready |
1289 | during the same loop iteration then order of execution is undefined. |
1302 | during the same loop iteration then order of execution is undefined. |
1290 | |
1303 | |
1291 | =head3 Watcher-Specific Functions and Data Members |
1304 | =head3 Watcher-Specific Functions and Data Members |
1292 | |
1305 | |
1293 | =over 4 |
1306 | =over 4 |
… | |
… | |
1301 | |
1314 | |
1302 | =over 4 |
1315 | =over 4 |
1303 | |
1316 | |
1304 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1317 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1305 | |
1318 | |
1306 | In this configuration the watcher triggers an event at the wallclock time |
1319 | 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, |
1320 | 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 |
1321 | 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. |
1322 | run when the system time reaches or surpasses this time. |
1310 | |
1323 | |
1311 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1324 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1312 | |
1325 | |
1313 | In this mode the watcher will always be scheduled to time out at the next |
1326 | 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) |
1327 | C<at + N * interval> time (for some integer N, which can also be negative) |
1315 | and then repeat, regardless of any time jumps. |
1328 | and then repeat, regardless of any time jumps. |
1316 | |
1329 | |
1317 | This can be used to create timers that do not drift with respect to system |
1330 | This can be used to create timers that do not drift with respect to system |
1318 | time: |
1331 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1332 | the hour: |
1319 | |
1333 | |
1320 | ev_periodic_set (&periodic, 0., 3600., 0); |
1334 | ev_periodic_set (&periodic, 0., 3600., 0); |
1321 | |
1335 | |
1322 | This doesn't mean there will always be 3600 seconds in between triggers, |
1336 | 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 |
1337 | 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 |
1342 | 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. |
1343 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1330 | |
1344 | |
1331 | For numerical stability it is preferable that the C<at> value is near |
1345 | 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 |
1346 | C<ev_now ()> (the current time), but there is no range requirement for |
1333 | this value. |
1347 | this value, and in fact is often specified as zero. |
|
|
1348 | |
|
|
1349 | Note also that there is an upper limit to how often a timer can fire (cpu |
|
|
1350 | speed for example), so if C<interval> is very small then timing stability |
|
|
1351 | will of course detoriate. Libev itself tries to be exact to be about one |
|
|
1352 | millisecond (if the OS supports it and the machine is fast enough). |
1334 | |
1353 | |
1335 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1354 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1336 | |
1355 | |
1337 | In this mode the values for C<interval> and C<at> are both being |
1356 | 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 |
1357 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1339 | reschedule callback will be called with the watcher as first, and the |
1358 | reschedule callback will be called with the watcher as first, and the |
1340 | current time as second argument. |
1359 | current time as second argument. |
1341 | |
1360 | |
1342 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1361 | 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, |
1362 | 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 | |
1363 | |
|
|
1364 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1365 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1366 | only event loop modification you are allowed to do). |
|
|
1367 | |
1347 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1368 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1348 | ev_tstamp now)>, e.g.: |
1369 | *w, ev_tstamp now)>, e.g.: |
1349 | |
1370 | |
1350 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1371 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1351 | { |
1372 | { |
1352 | return now + 60.; |
1373 | return now + 60.; |
1353 | } |
1374 | } |
… | |
… | |
1355 | It must return the next time to trigger, based on the passed time value |
1376 | 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 |
1377 | (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 |
1378 | will usually be called just before the callback will be triggered, but |
1358 | might be called at other times, too. |
1379 | might be called at other times, too. |
1359 | |
1380 | |
1360 | NOTE: I<< This callback must always return a time that is later than the |
1381 | 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. |
1382 | equal to the passed C<now> value >>. |
1362 | |
1383 | |
1363 | This can be used to create very complex timers, such as a timer that |
1384 | 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 |
1385 | 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 |
1386 | 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 |
1387 | 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). |
1388 | reason I omitted it as an example). |
1368 | |
1389 | |
1369 | =back |
1390 | =back |
… | |
… | |
1610 | as even with OS-supported change notifications, this can be |
1631 | as even with OS-supported change notifications, this can be |
1611 | resource-intensive. |
1632 | resource-intensive. |
1612 | |
1633 | |
1613 | At the time of this writing, only the Linux inotify interface is |
1634 | At the time of this writing, only the Linux inotify interface is |
1614 | implemented (implementing kqueue support is left as an exercise for the |
1635 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1636 | reader, note, however, that the author sees no way of implementing ev_stat |
1615 | reader). Inotify will be used to give hints only and should not change the |
1637 | semantics with kqueue). Inotify will be used to give hints only and should |
1616 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1638 | not change the semantics of C<ev_stat> watchers, which means that libev |
1617 | to fall back to regular polling again even with inotify, but changes are |
1639 | sometimes needs to fall back to regular polling again even with inotify, |
1618 | usually detected immediately, and if the file exists there will be no |
1640 | but changes are usually detected immediately, and if the file exists there |
1619 | polling. |
1641 | will be no polling. |
1620 | |
1642 | |
1621 | =head3 ABI Issues (Largefile Support) |
1643 | =head3 ABI Issues (Largefile Support) |
1622 | |
1644 | |
1623 | Libev by default (unless the user overrides this) uses the default |
1645 | Libev by default (unless the user overrides this) uses the default |
1624 | compilation environment, which means that on systems with optionally |
1646 | compilation environment, which means that on systems with optionally |
… | |
… | |
1649 | |
1671 | |
1650 | The C<stat ()> syscall only supports full-second resolution portably, and |
1672 | The C<stat ()> syscall only supports full-second resolution portably, and |
1651 | even on systems where the resolution is higher, many filesystems still |
1673 | even on systems where the resolution is higher, many filesystems still |
1652 | only support whole seconds. |
1674 | only support whole seconds. |
1653 | |
1675 | |
1654 | That means that, if the time is the only thing that changes, you might |
1676 | That means that, if the time is the only thing that changes, you can |
1655 | miss updates: on the first update, C<ev_stat> detects a change and calls |
1677 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1656 | your callback, which does something. When there is another update within |
1678 | calls your callback, which does something. When there is another update |
1657 | the same second, C<ev_stat> will be unable to detect it. |
1679 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1680 | data does not change. |
1658 | |
1681 | |
1659 | The solution to this is to delay acting on a change for a second (or till |
1682 | The solution to this is to delay acting on a change for slightly more |
1660 | the next second boundary), using a roughly one-second delay C<ev_timer> |
1683 | than a second (or till slightly after the next full second boundary), using |
1661 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
1684 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1662 | is added to work around small timing inconsistencies of some operating |
1685 | ev_timer_again (loop, w)>). |
1663 | systems. |
1686 | |
|
|
1687 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1688 | of some operating systems (where the second counter of the current time |
|
|
1689 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1690 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1691 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1692 | update file times then there will be a small window where the kernel uses |
|
|
1693 | the previous second to update file times but libev might already execute |
|
|
1694 | the timer callback). |
1664 | |
1695 | |
1665 | =head3 Watcher-Specific Functions and Data Members |
1696 | =head3 Watcher-Specific Functions and Data Members |
1666 | |
1697 | |
1667 | =over 4 |
1698 | =over 4 |
1668 | |
1699 | |
… | |
… | |
1674 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1705 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1675 | be detected and should normally be specified as C<0> to let libev choose |
1706 | be detected and should normally be specified as C<0> to let libev choose |
1676 | a suitable value. The memory pointed to by C<path> must point to the same |
1707 | a suitable value. The memory pointed to by C<path> must point to the same |
1677 | path for as long as the watcher is active. |
1708 | path for as long as the watcher is active. |
1678 | |
1709 | |
1679 | The callback will be receive C<EV_STAT> when a change was detected, |
1710 | The callback will receive C<EV_STAT> when a change was detected, relative |
1680 | relative to the attributes at the time the watcher was started (or the |
1711 | to the attributes at the time the watcher was started (or the last change |
1681 | last change was detected). |
1712 | was detected). |
1682 | |
1713 | |
1683 | =item ev_stat_stat (loop, ev_stat *) |
1714 | =item ev_stat_stat (loop, ev_stat *) |
1684 | |
1715 | |
1685 | Updates the stat buffer immediately with new values. If you change the |
1716 | Updates the stat buffer immediately with new values. If you change the |
1686 | watched path in your callback, you could call this fucntion to avoid |
1717 | watched path in your callback, you could call this function to avoid |
1687 | detecting this change (while introducing a race condition). Can also be |
1718 | detecting this change (while introducing a race condition if you are not |
1688 | useful simply to find out the new values. |
1719 | the only one changing the path). Can also be useful simply to find out the |
|
|
1720 | new values. |
1689 | |
1721 | |
1690 | =item ev_statdata attr [read-only] |
1722 | =item ev_statdata attr [read-only] |
1691 | |
1723 | |
1692 | The most-recently detected attributes of the file. Although the type is of |
1724 | The most-recently detected attributes of the file. Although the type is |
1693 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1725 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1694 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
1726 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1727 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1695 | was some error while C<stat>ing the file. |
1728 | some error while C<stat>ing the file. |
1696 | |
1729 | |
1697 | =item ev_statdata prev [read-only] |
1730 | =item ev_statdata prev [read-only] |
1698 | |
1731 | |
1699 | The previous attributes of the file. The callback gets invoked whenever |
1732 | The previous attributes of the file. The callback gets invoked whenever |
1700 | C<prev> != C<attr>. |
1733 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1734 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1735 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1701 | |
1736 | |
1702 | =item ev_tstamp interval [read-only] |
1737 | =item ev_tstamp interval [read-only] |
1703 | |
1738 | |
1704 | The specified interval. |
1739 | The specified interval. |
1705 | |
1740 | |
… | |
… | |
1759 | } |
1794 | } |
1760 | |
1795 | |
1761 | ... |
1796 | ... |
1762 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1797 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1763 | ev_stat_start (loop, &passwd); |
1798 | ev_stat_start (loop, &passwd); |
1764 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1799 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1765 | |
1800 | |
1766 | |
1801 | |
1767 | =head2 C<ev_idle> - when you've got nothing better to do... |
1802 | =head2 C<ev_idle> - when you've got nothing better to do... |
1768 | |
1803 | |
1769 | Idle watchers trigger events when no other events of the same or higher |
1804 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1857 | |
1892 | |
1858 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1893 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1859 | priority, to ensure that they are being run before any other watchers |
1894 | priority, to ensure that they are being run before any other watchers |
1860 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1895 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1861 | too) should not activate ("feed") events into libev. While libev fully |
1896 | too) should not activate ("feed") events into libev. While libev fully |
1862 | supports this, they will be called before other C<ev_check> watchers |
1897 | supports this, they might get executed before other C<ev_check> watchers |
1863 | did their job. As C<ev_check> watchers are often used to embed other |
1898 | did their job. As C<ev_check> watchers are often used to embed other |
1864 | (non-libev) event loops those other event loops might be in an unusable |
1899 | (non-libev) event loops those other event loops might be in an unusable |
1865 | state until their C<ev_check> watcher ran (always remind yourself to |
1900 | state until their C<ev_check> watcher ran (always remind yourself to |
1866 | coexist peacefully with others). |
1901 | coexist peacefully with others). |
1867 | |
1902 | |
… | |
… | |
1882 | =head3 Examples |
1917 | =head3 Examples |
1883 | |
1918 | |
1884 | There are a number of principal ways to embed other event loops or modules |
1919 | There are a number of principal ways to embed other event loops or modules |
1885 | into libev. Here are some ideas on how to include libadns into libev |
1920 | into libev. Here are some ideas on how to include libadns into libev |
1886 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1921 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1887 | use for an actually working example. Another Perl module named C<EV::Glib> |
1922 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1888 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
1923 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1889 | into the Glib event loop). |
1924 | Glib event loop). |
1890 | |
1925 | |
1891 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1926 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1892 | and in a check watcher, destroy them and call into libadns. What follows |
1927 | and in a check watcher, destroy them and call into libadns. What follows |
1893 | is pseudo-code only of course. This requires you to either use a low |
1928 | is pseudo-code only of course. This requires you to either use a low |
1894 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1929 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
… | |
… | |
2966 | defined to be C<0>, then they are not. |
3001 | defined to be C<0>, then they are not. |
2967 | |
3002 | |
2968 | =item EV_MINIMAL |
3003 | =item EV_MINIMAL |
2969 | |
3004 | |
2970 | If you need to shave off some kilobytes of code at the expense of some |
3005 | If you need to shave off some kilobytes of code at the expense of some |
2971 | speed, define this symbol to C<1>. Currently only used for gcc to override |
3006 | speed, define this symbol to C<1>. Currently this is used to override some |
2972 | some inlining decisions, saves roughly 30% codesize of amd64. |
3007 | inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
|
|
3008 | much smaller 2-heap for timer management over the default 4-heap. |
2973 | |
3009 | |
2974 | =item EV_PID_HASHSIZE |
3010 | =item EV_PID_HASHSIZE |
2975 | |
3011 | |
2976 | C<ev_child> watchers use a small hash table to distribute workload by |
3012 | C<ev_child> watchers use a small hash table to distribute workload by |
2977 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3013 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
2983 | C<ev_stat> watchers use a small hash table to distribute workload by |
3019 | C<ev_stat> watchers use a small hash table to distribute workload by |
2984 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
3020 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2985 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3021 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2986 | watchers you might want to increase this value (I<must> be a power of |
3022 | watchers you might want to increase this value (I<must> be a power of |
2987 | two). |
3023 | two). |
|
|
3024 | |
|
|
3025 | =item EV_USE_4HEAP |
|
|
3026 | |
|
|
3027 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3028 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3029 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3030 | noticably faster performance with many (thousands) of watchers. |
|
|
3031 | |
|
|
3032 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3033 | (disabled). |
|
|
3034 | |
|
|
3035 | =item EV_HEAP_CACHE_AT |
|
|
3036 | |
|
|
3037 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3038 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3039 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3040 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3041 | but avoids random read accesses on heap changes. This improves performance |
|
|
3042 | noticably with with many (hundreds) of watchers. |
|
|
3043 | |
|
|
3044 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3045 | (disabled). |
|
|
3046 | |
|
|
3047 | =item EV_VERIFY |
|
|
3048 | |
|
|
3049 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3050 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3051 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3052 | called. If set to C<2>, then the internal verification code will be |
|
|
3053 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3054 | verification code will be called very frequently, which will slow down |
|
|
3055 | libev considerably. |
|
|
3056 | |
|
|
3057 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3058 | C<0.> |
2988 | |
3059 | |
2989 | =item EV_COMMON |
3060 | =item EV_COMMON |
2990 | |
3061 | |
2991 | By default, all watchers have a C<void *data> member. By redefining |
3062 | By default, all watchers have a C<void *data> member. By redefining |
2992 | this macro to a something else you can include more and other types of |
3063 | this macro to a something else you can include more and other types of |
… | |
… | |
3162 | correct watcher to remove. The lists are usually short (you don't usually |
3233 | correct watcher to remove. The lists are usually short (you don't usually |
3163 | have many watchers waiting for the same fd or signal). |
3234 | have many watchers waiting for the same fd or signal). |
3164 | |
3235 | |
3165 | =item Finding the next timer in each loop iteration: O(1) |
3236 | =item Finding the next timer in each loop iteration: O(1) |
3166 | |
3237 | |
3167 | By virtue of using a binary heap, the next timer is always found at the |
3238 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3168 | beginning of the storage array. |
3239 | fixed position in the storage array. |
3169 | |
3240 | |
3170 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3241 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3171 | |
3242 | |
3172 | A change means an I/O watcher gets started or stopped, which requires |
3243 | A change means an I/O watcher gets started or stopped, which requires |
3173 | libev to recalculate its status (and possibly tell the kernel, depending |
3244 | libev to recalculate its status (and possibly tell the kernel, depending |
… | |
… | |
3202 | model. Libev still offers limited functionality on this platform in |
3273 | model. Libev still offers limited functionality on this platform in |
3203 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3274 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3204 | descriptors. This only applies when using Win32 natively, not when using |
3275 | descriptors. This only applies when using Win32 natively, not when using |
3205 | e.g. cygwin. |
3276 | e.g. cygwin. |
3206 | |
3277 | |
|
|
3278 | Lifting these limitations would basically require the full |
|
|
3279 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3280 | things, then note that glib does exactly that for you in a very portable |
|
|
3281 | way (note also that glib is the slowest event library known to man). |
|
|
3282 | |
3207 | There is no supported compilation method available on windows except |
3283 | There is no supported compilation method available on windows except |
3208 | embedding it into other applications. |
3284 | embedding it into other applications. |
3209 | |
3285 | |
3210 | Due to the many, low, and arbitrary limits on the win32 platform and the |
3286 | Due to the many, low, and arbitrary limits on the win32 platform and |
3211 | abysmal performance of winsockets, using a large number of sockets is not |
3287 | the abysmal performance of winsockets, using a large number of sockets |
3212 | recommended (and not reasonable). If your program needs to use more than |
3288 | is not recommended (and not reasonable). If your program needs to use |
3213 | a hundred or so sockets, then likely it needs to use a totally different |
3289 | more than a hundred or so sockets, then likely it needs to use a totally |
3214 | implementation for windows, as libev offers the POSIX model, which cannot |
3290 | different implementation for windows, as libev offers the POSIX readiness |
3215 | be implemented efficiently on windows (microsoft monopoly games). |
3291 | notification model, which cannot be implemented efficiently on windows |
|
|
3292 | (microsoft monopoly games). |
3216 | |
3293 | |
3217 | =over 4 |
3294 | =over 4 |
3218 | |
3295 | |
3219 | =item The winsocket select function |
3296 | =item The winsocket select function |
3220 | |
3297 | |
… | |
… | |
3234 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3311 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3235 | complexity in the O(n²) range when using win32. |
3312 | complexity in the O(n²) range when using win32. |
3236 | |
3313 | |
3237 | =item Limited number of file descriptors |
3314 | =item Limited number of file descriptors |
3238 | |
3315 | |
3239 | Windows has numerous arbitrary (and low) limits on things. Early versions |
3316 | Windows has numerous arbitrary (and low) limits on things. |
3240 | of winsocket's select only supported waiting for a max. of C<64> handles |
3317 | |
|
|
3318 | Early versions of winsocket's select only supported waiting for a maximum |
3241 | (probably owning to the fact that all windows kernels can only wait for |
3319 | of C<64> handles (probably owning to the fact that all windows kernels |
3242 | C<64> things at the same time internally; microsoft recommends spawning a |
3320 | can only wait for C<64> things at the same time internally; microsoft |
3243 | chain of threads and wait for 63 handles and the previous thread in each). |
3321 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3322 | previous thread in each. Great). |
3244 | |
3323 | |
3245 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3324 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3246 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3325 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3247 | call (which might be in libev or elsewhere, for example, perl does its own |
3326 | call (which might be in libev or elsewhere, for example, perl does its own |
3248 | select emulation on windows). |
3327 | select emulation on windows). |
… | |
… | |
3287 | |
3366 | |
3288 | The most portable way to handle signals is to block signals in all threads |
3367 | The most portable way to handle signals is to block signals in all threads |
3289 | except the initial one, and run the default loop in the initial thread as |
3368 | except the initial one, and run the default loop in the initial thread as |
3290 | well. |
3369 | well. |
3291 | |
3370 | |
|
|
3371 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3372 | |
|
|
3373 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3374 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3375 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3376 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3377 | millions of watchers. |
|
|
3378 | |
|
|
3379 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3380 | |
|
|
3381 | The type C<double> is used to represent timestamps. It is required to |
|
|
3382 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3383 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3384 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3385 | |
3292 | =back |
3386 | =back |
3293 | |
3387 | |
3294 | If you know of other additional requirements drop me a note. |
3388 | If you know of other additional requirements drop me a note. |
3295 | |
3389 | |
3296 | |
3390 | |
|
|
3391 | =head1 VALGRIND |
|
|
3392 | |
|
|
3393 | Valgrind has a special section here because it is a popular tool that is |
|
|
3394 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3395 | |
|
|
3396 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3397 | in libev, then check twice: If valgrind reports something like: |
|
|
3398 | |
|
|
3399 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3400 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3401 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3402 | |
|
|
3403 | then there is no memory leak. Similarly, under some circumstances, |
|
|
3404 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3405 | might be confused (it is a very good tool, but only a tool). |
|
|
3406 | |
|
|
3407 | If you are unsure about something, feel free to contact the mailing list |
|
|
3408 | with the full valgrind report and an explanation on why you think this is |
|
|
3409 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
|
|
3410 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3411 | properly. |
|
|
3412 | |
|
|
3413 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3414 | I suggest using suppression lists. |
|
|
3415 | |
|
|
3416 | |
3297 | =head1 AUTHOR |
3417 | =head1 AUTHOR |
3298 | |
3418 | |
3299 | Marc Lehmann <libev@schmorp.de>. |
3419 | Marc Lehmann <libev@schmorp.de>. |
3300 | |
3420 | |