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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 | |
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196 | See the description of C<ev_embed> watchers for more info. |
196 | See the description of C<ev_embed> watchers for more info. |
197 | |
197 | |
198 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
198 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
199 | |
199 | |
200 | Sets the allocation function to use (the prototype is similar - the |
200 | Sets the allocation function to use (the prototype is similar - the |
201 | semantics is identical - to the realloc C function). It is used to |
201 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
202 | allocate and free memory (no surprises here). If it returns zero when |
202 | used to allocate and free memory (no surprises here). If it returns zero |
203 | memory needs to be allocated, the library might abort or take some |
203 | when memory needs to be allocated (C<size != 0>), the library might abort |
204 | potentially destructive action. The default is your system realloc |
204 | or take some potentially destructive action. |
205 | function. |
205 | |
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206 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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207 | correct C<realloc> semantics, libev will use a wrapper around the system |
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208 | C<realloc> and C<free> functions by default. |
206 | |
209 | |
207 | You could override this function in high-availability programs to, say, |
210 | You could override this function in high-availability programs to, say, |
208 | free some memory if it cannot allocate memory, to use a special allocator, |
211 | free some memory if it cannot allocate memory, to use a special allocator, |
209 | or even to sleep a while and retry until some memory is available. |
212 | or even to sleep a while and retry until some memory is available. |
210 | |
213 | |
211 | Example: Replace the libev allocator with one that waits a bit and then |
214 | Example: Replace the libev allocator with one that waits a bit and then |
212 | retries). |
215 | retries (example requires a standards-compliant C<realloc>). |
213 | |
216 | |
214 | static void * |
217 | static void * |
215 | persistent_realloc (void *ptr, size_t size) |
218 | persistent_realloc (void *ptr, size_t size) |
216 | { |
219 | { |
217 | for (;;) |
220 | for (;;) |
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256 | |
259 | |
257 | An event loop is described by a C<struct ev_loop *>. The library knows two |
260 | An event loop is described by a C<struct ev_loop *>. The library knows two |
258 | types of such loops, the I<default> loop, which supports signals and child |
261 | types of such loops, the I<default> loop, which supports signals and child |
259 | events, and dynamically created loops which do not. |
262 | events, and dynamically created loops which do not. |
260 | |
263 | |
261 | If you use threads, a common model is to run the default event loop |
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262 | in your main thread (or in a separate thread) and for each thread you |
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263 | create, you also create another event loop. Libev itself does no locking |
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264 | whatsoever, so if you mix calls to the same event loop in different |
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265 | threads, make sure you lock (this is usually a bad idea, though, even if |
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266 | done correctly, because it's hideous and inefficient). |
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267 | |
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268 | =over 4 |
264 | =over 4 |
269 | |
265 | |
270 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
266 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
271 | |
267 | |
272 | This will initialise the default event loop if it hasn't been initialised |
268 | This will initialise the default event loop if it hasn't been initialised |
… | |
… | |
274 | false. If it already was initialised it simply returns it (and ignores the |
270 | false. If it already was initialised it simply returns it (and ignores the |
275 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
271 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
276 | |
272 | |
277 | If you don't know what event loop to use, use the one returned from this |
273 | If you don't know what event loop to use, use the one returned from this |
278 | function. |
274 | function. |
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275 | |
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276 | Note that this function is I<not> thread-safe, so if you want to use it |
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277 | from multiple threads, you have to lock (note also that this is unlikely, |
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278 | as loops cannot bes hared easily between threads anyway). |
279 | |
279 | |
280 | The default loop is the only loop that can handle C<ev_signal> and |
280 | The default loop is the only loop that can handle C<ev_signal> and |
281 | C<ev_child> watchers, and to do this, it always registers a handler |
281 | C<ev_child> watchers, and to do this, it always registers a handler |
282 | for C<SIGCHLD>. If this is a problem for your app you can either |
282 | for C<SIGCHLD>. If this is a problem for your app you can either |
283 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
283 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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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 |
… | |
… | |
354 | For few fds, this backend is a bit little slower than poll and select, |
354 | For few fds, this backend is a bit little slower than poll and select, |
355 | but it scales phenomenally better. While poll and select usually scale |
355 | but it scales phenomenally better. While poll and select usually scale |
356 | like O(total_fds) where n is the total number of fds (or the highest fd), |
356 | like O(total_fds) where n is the total number of fds (or the highest fd), |
357 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
357 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
358 | of shortcomings, such as silently dropping events in some hard-to-detect |
358 | of shortcomings, such as silently dropping events in some hard-to-detect |
359 | cases and rewiring a syscall per fd change, no fork support and bad |
359 | cases and requiring a syscall per fd change, no fork support and bad |
360 | support for dup. |
360 | support for dup. |
361 | |
361 | |
362 | While stopping, setting and starting an I/O watcher in the same iteration |
362 | While stopping, setting and starting an I/O watcher in the same iteration |
363 | will result in some caching, there is still a syscall per such incident |
363 | will result in some caching, there is still a syscall per such incident |
364 | (because the fd could point to a different file description now), so its |
364 | (because the fd could point to a different file description now), so its |
… | |
… | |
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 | |
… | |
… | |
465 | |
465 | |
466 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
466 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
467 | always distinct from the default loop. Unlike the default loop, it cannot |
467 | always distinct from the default loop. Unlike the default loop, it cannot |
468 | handle signal and child watchers, and attempts to do so will be greeted by |
468 | handle signal and child watchers, and attempts to do so will be greeted by |
469 | undefined behaviour (or a failed assertion if assertions are enabled). |
469 | undefined behaviour (or a failed assertion if assertions are enabled). |
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470 | |
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471 | Note that this function I<is> thread-safe, and the recommended way to use |
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472 | libev with threads is indeed to create one loop per thread, and using the |
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473 | default loop in the "main" or "initial" thread. |
470 | |
474 | |
471 | Example: Try to create a event loop that uses epoll and nothing else. |
475 | Example: Try to create a event loop that uses epoll and nothing else. |
472 | |
476 | |
473 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
477 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
474 | if (!epoller) |
478 | if (!epoller) |
… | |
… | |
1028 | If you must do this, then force the use of a known-to-be-good backend |
1032 | If you must do this, then force the use of a known-to-be-good backend |
1029 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1033 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1030 | C<EVBACKEND_POLL>). |
1034 | C<EVBACKEND_POLL>). |
1031 | |
1035 | |
1032 | Another thing you have to watch out for is that it is quite easy to |
1036 | Another thing you have to watch out for is that it is quite easy to |
1033 | receive "spurious" readyness notifications, that is your callback might |
1037 | receive "spurious" readiness notifications, that is your callback might |
1034 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1038 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1035 | because there is no data. Not only are some backends known to create a |
1039 | because there is no data. Not only are some backends known to create a |
1036 | lot of those (for example solaris ports), it is very easy to get into |
1040 | lot of those (for example solaris ports), it is very easy to get into |
1037 | this situation even with a relatively standard program structure. Thus |
1041 | this situation even with a relatively standard program structure. Thus |
1038 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1042 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
… | |
… | |
1147 | |
1151 | |
1148 | 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 |
1149 | given time, and optionally repeating in regular intervals after that. |
1153 | given time, and optionally repeating in regular intervals after that. |
1150 | |
1154 | |
1151 | 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 |
1152 | 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 |
1153 | 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 |
1154 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1158 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1155 | monotonic clock option helps a lot here). |
1159 | monotonic clock option helps a lot here). |
1156 | |
1160 | |
1157 | The relative timeouts are calculated relative to the C<ev_now ()> |
1161 | The relative timeouts are calculated relative to the C<ev_now ()> |
1158 | 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 |
… | |
… | |
1160 | 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 |
1161 | 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: |
1162 | |
1166 | |
1163 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1167 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1164 | |
1168 | |
1165 | 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, |
1166 | 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 |
1167 | order of execution is undefined. |
1171 | order of execution is undefined. |
1168 | |
1172 | |
1169 | =head3 Watcher-Specific Functions and Data Members |
1173 | =head3 Watcher-Specific Functions and Data Members |
1170 | |
1174 | |
… | |
… | |
1172 | |
1176 | |
1173 | =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) |
1174 | |
1178 | |
1175 | =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) |
1176 | |
1180 | |
1177 | 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> |
1178 | 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 |
1179 | timer will automatically be configured to trigger again C<repeat> seconds |
1183 | reached. If it is positive, then the timer will automatically be |
1180 | later, again, and again, until stopped manually. |
1184 | configured to trigger again C<repeat> seconds later, again, and again, |
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|
1185 | until stopped manually. |
1181 | |
1186 | |
1182 | 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 |
1183 | 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 |
1184 | exactly 10 second intervals. If, however, your program cannot keep up with |
1189 | trigger at exactly 10 second intervals. If, however, your program cannot |
1185 | 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 |
1186 | 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. |
1187 | |
1192 | |
1188 | =item ev_timer_again (loop, ev_timer *) |
1193 | =item ev_timer_again (loop, ev_timer *) |
1189 | |
1194 | |
1190 | 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 |
1191 | repeating. The exact semantics are: |
1196 | repeating. The exact semantics are: |
… | |
… | |
1268 | 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 |
1269 | (and unfortunately a bit complex). |
1274 | (and unfortunately a bit complex). |
1270 | |
1275 | |
1271 | 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) |
1272 | 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 |
1273 | 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 |
1274 | 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 () |
1275 | + 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 |
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|
1281 | clock to january of the previous year, then it will take more than year |
1276 | 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 |
1277 | roughly 10 seconds later). |
1283 | roughly 10 seconds later as it uses a relative timeout). |
1278 | |
1284 | |
1279 | 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, |
1280 | triggering an event on each midnight, local time or other, complicated, |
1286 | such as triggering an event on each "midnight, local time", or other |
1281 | rules. |
1287 | complicated, rules. |
1282 | |
1288 | |
1283 | 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 |
1284 | 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 |
1285 | during the same loop iteration then order of execution is undefined. |
1291 | during the same loop iteration then order of execution is undefined. |
1286 | |
1292 | |
1287 | =head3 Watcher-Specific Functions and Data Members |
1293 | =head3 Watcher-Specific Functions and Data Members |
1288 | |
1294 | |
1289 | =over 4 |
1295 | =over 4 |
… | |
… | |
1297 | |
1303 | |
1298 | =over 4 |
1304 | =over 4 |
1299 | |
1305 | |
1300 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1306 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1301 | |
1307 | |
1302 | In this configuration the watcher triggers an event at the wallclock time |
1308 | In this configuration the watcher triggers an event after the wallclock |
1303 | 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 |
1304 | 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 |
1305 | system time reaches or surpasses this time. |
1311 | run when the system time reaches or surpasses this time. |
1306 | |
1312 | |
1307 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1313 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1308 | |
1314 | |
1309 | 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 |
1310 | 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) |
1311 | and then repeat, regardless of any time jumps. |
1317 | and then repeat, regardless of any time jumps. |
1312 | |
1318 | |
1313 | 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 |
1314 | time: |
1320 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
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|
1321 | the hour: |
1315 | |
1322 | |
1316 | ev_periodic_set (&periodic, 0., 3600., 0); |
1323 | ev_periodic_set (&periodic, 0., 3600., 0); |
1317 | |
1324 | |
1318 | 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, |
1319 | 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 |
… | |
… | |
1324 | 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 |
1325 | 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. |
1326 | |
1333 | |
1327 | 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 |
1328 | 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 |
1329 | 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 |
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|
1339 | speed for example), so if C<interval> is very small then timing stability |
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|
1340 | will of course detoriate. Libev itself tries to be exact to be about one |
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|
1341 | millisecond (if the OS supports it and the machine is fast enough). |
1330 | |
1342 | |
1331 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1343 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1332 | |
1344 | |
1333 | 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 |
1334 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1346 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1335 | 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 |
1336 | current time as second argument. |
1348 | current time as second argument. |
1337 | |
1349 | |
1338 | 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, |
1339 | ever, or make any event loop modifications>. If you need to stop it, |
1351 | ever, or make ANY event loop modifications whatsoever>. |
1340 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
1341 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1342 | |
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 | |
1343 | 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 |
1344 | ev_tstamp now)>, e.g.: |
1358 | *w, ev_tstamp now)>, e.g.: |
1345 | |
1359 | |
1346 | 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) |
1347 | { |
1361 | { |
1348 | return now + 60.; |
1362 | return now + 60.; |
1349 | } |
1363 | } |
… | |
… | |
1351 | 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 |
1352 | (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 |
1353 | 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 |
1354 | might be called at other times, too. |
1368 | might be called at other times, too. |
1355 | |
1369 | |
1356 | 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 |
1357 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1371 | equal to the passed C<now> value >>. |
1358 | |
1372 | |
1359 | 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 |
1360 | 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 |
1361 | 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 |
1362 | 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 |
1363 | reason I omitted it as an example). |
1377 | reason I omitted it as an example). |
1364 | |
1378 | |
1365 | =back |
1379 | =back |
… | |
… | |
1369 | Simply stops and restarts the periodic watcher again. This is only useful |
1383 | Simply stops and restarts the periodic watcher again. This is only useful |
1370 | when you changed some parameters or the reschedule callback would return |
1384 | when you changed some parameters or the reschedule callback would return |
1371 | a different time than the last time it was called (e.g. in a crond like |
1385 | a different time than the last time it was called (e.g. in a crond like |
1372 | program when the crontabs have changed). |
1386 | program when the crontabs have changed). |
1373 | |
1387 | |
|
|
1388 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1389 | |
|
|
1390 | When active, returns the absolute time that the watcher is supposed to |
|
|
1391 | trigger next. |
|
|
1392 | |
1374 | =item ev_tstamp offset [read-write] |
1393 | =item ev_tstamp offset [read-write] |
1375 | |
1394 | |
1376 | When repeating, this contains the offset value, otherwise this is the |
1395 | When repeating, this contains the offset value, otherwise this is the |
1377 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1396 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1378 | |
1397 | |
… | |
… | |
1388 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1407 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1389 | |
1408 | |
1390 | The current reschedule callback, or C<0>, if this functionality is |
1409 | The current reschedule callback, or C<0>, if this functionality is |
1391 | switched off. Can be changed any time, but changes only take effect when |
1410 | switched off. Can be changed any time, but changes only take effect when |
1392 | the periodic timer fires or C<ev_periodic_again> is being called. |
1411 | the periodic timer fires or C<ev_periodic_again> is being called. |
1393 | |
|
|
1394 | =item ev_tstamp at [read-only] |
|
|
1395 | |
|
|
1396 | When active, contains the absolute time that the watcher is supposed to |
|
|
1397 | trigger next. |
|
|
1398 | |
1412 | |
1399 | =back |
1413 | =back |
1400 | |
1414 | |
1401 | =head3 Examples |
1415 | =head3 Examples |
1402 | |
1416 | |
… | |
… | |
1606 | as even with OS-supported change notifications, this can be |
1620 | as even with OS-supported change notifications, this can be |
1607 | resource-intensive. |
1621 | resource-intensive. |
1608 | |
1622 | |
1609 | At the time of this writing, only the Linux inotify interface is |
1623 | At the time of this writing, only the Linux inotify interface is |
1610 | implemented (implementing kqueue support is left as an exercise for the |
1624 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1625 | reader, note, however, that the author sees no way of implementing ev_stat |
1611 | reader). Inotify will be used to give hints only and should not change the |
1626 | semantics with kqueue). Inotify will be used to give hints only and should |
1612 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1627 | not change the semantics of C<ev_stat> watchers, which means that libev |
1613 | to fall back to regular polling again even with inotify, but changes are |
1628 | sometimes needs to fall back to regular polling again even with inotify, |
1614 | usually detected immediately, and if the file exists there will be no |
1629 | but changes are usually detected immediately, and if the file exists there |
1615 | polling. |
1630 | will be no polling. |
1616 | |
1631 | |
1617 | =head3 ABI Issues (Largefile Support) |
1632 | =head3 ABI Issues (Largefile Support) |
1618 | |
1633 | |
1619 | Libev by default (unless the user overrides this) uses the default |
1634 | Libev by default (unless the user overrides this) uses the default |
1620 | compilation environment, which means that on systems with optionally |
1635 | compilation environment, which means that on systems with optionally |
… | |
… | |
1630 | When C<inotify (7)> support has been compiled into libev (generally only |
1645 | When C<inotify (7)> support has been compiled into libev (generally only |
1631 | available on Linux) and present at runtime, it will be used to speed up |
1646 | available on Linux) and present at runtime, it will be used to speed up |
1632 | change detection where possible. The inotify descriptor will be created lazily |
1647 | change detection where possible. The inotify descriptor will be created lazily |
1633 | when the first C<ev_stat> watcher is being started. |
1648 | when the first C<ev_stat> watcher is being started. |
1634 | |
1649 | |
1635 | Inotify presense does not change the semantics of C<ev_stat> watchers |
1650 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1636 | except that changes might be detected earlier, and in some cases, to avoid |
1651 | except that changes might be detected earlier, and in some cases, to avoid |
1637 | making regular C<stat> calls. Even in the presense of inotify support |
1652 | making regular C<stat> calls. Even in the presence of inotify support |
1638 | there are many cases where libev has to resort to regular C<stat> polling. |
1653 | there are many cases where libev has to resort to regular C<stat> polling. |
1639 | |
1654 | |
1640 | (There is no support for kqueue, as apparently it cannot be used to |
1655 | (There is no support for kqueue, as apparently it cannot be used to |
1641 | implement this functionality, due to the requirement of having a file |
1656 | implement this functionality, due to the requirement of having a file |
1642 | descriptor open on the object at all times). |
1657 | descriptor open on the object at all times). |
… | |
… | |
1645 | |
1660 | |
1646 | The C<stat ()> syscall only supports full-second resolution portably, and |
1661 | The C<stat ()> syscall only supports full-second resolution portably, and |
1647 | even on systems where the resolution is higher, many filesystems still |
1662 | even on systems where the resolution is higher, many filesystems still |
1648 | only support whole seconds. |
1663 | only support whole seconds. |
1649 | |
1664 | |
1650 | That means that, if the time is the only thing that changes, you might |
1665 | That means that, if the time is the only thing that changes, you can |
1651 | miss updates: on the first update, C<ev_stat> detects a change and calls |
1666 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1652 | your callback, which does something. When there is another update within |
1667 | calls your callback, which does something. When there is another update |
1653 | the same second, C<ev_stat> will be unable to detect it. |
1668 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1669 | data does not change. |
1654 | |
1670 | |
1655 | The solution to this is to delay acting on a change for a second (or till |
1671 | The solution to this is to delay acting on a change for slightly more |
1656 | the next second boundary), using a roughly one-second delay C<ev_timer> |
1672 | than a second (or till slightly after the next full second boundary), using |
1657 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
1673 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1658 | is added to work around small timing inconsistencies of some operating |
1674 | ev_timer_again (loop, w)>). |
1659 | systems. |
1675 | |
|
|
1676 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1677 | of some operating systems (where the second counter of the current time |
|
|
1678 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1679 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1680 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1681 | update file times then there will be a small window where the kernel uses |
|
|
1682 | the previous second to update file times but libev might already execute |
|
|
1683 | the timer callback). |
1660 | |
1684 | |
1661 | =head3 Watcher-Specific Functions and Data Members |
1685 | =head3 Watcher-Specific Functions and Data Members |
1662 | |
1686 | |
1663 | =over 4 |
1687 | =over 4 |
1664 | |
1688 | |
… | |
… | |
1670 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1694 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1671 | be detected and should normally be specified as C<0> to let libev choose |
1695 | be detected and should normally be specified as C<0> to let libev choose |
1672 | a suitable value. The memory pointed to by C<path> must point to the same |
1696 | a suitable value. The memory pointed to by C<path> must point to the same |
1673 | path for as long as the watcher is active. |
1697 | path for as long as the watcher is active. |
1674 | |
1698 | |
1675 | The callback will be receive C<EV_STAT> when a change was detected, |
1699 | The callback will receive C<EV_STAT> when a change was detected, relative |
1676 | relative to the attributes at the time the watcher was started (or the |
1700 | to the attributes at the time the watcher was started (or the last change |
1677 | last change was detected). |
1701 | was detected). |
1678 | |
1702 | |
1679 | =item ev_stat_stat (loop, ev_stat *) |
1703 | =item ev_stat_stat (loop, ev_stat *) |
1680 | |
1704 | |
1681 | Updates the stat buffer immediately with new values. If you change the |
1705 | Updates the stat buffer immediately with new values. If you change the |
1682 | watched path in your callback, you could call this fucntion to avoid |
1706 | watched path in your callback, you could call this function to avoid |
1683 | detecting this change (while introducing a race condition). Can also be |
1707 | detecting this change (while introducing a race condition if you are not |
1684 | useful simply to find out the new values. |
1708 | the only one changing the path). Can also be useful simply to find out the |
|
|
1709 | new values. |
1685 | |
1710 | |
1686 | =item ev_statdata attr [read-only] |
1711 | =item ev_statdata attr [read-only] |
1687 | |
1712 | |
1688 | The most-recently detected attributes of the file. Although the type is of |
1713 | The most-recently detected attributes of the file. Although the type is |
1689 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1714 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1690 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
1715 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1716 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1691 | was some error while C<stat>ing the file. |
1717 | some error while C<stat>ing the file. |
1692 | |
1718 | |
1693 | =item ev_statdata prev [read-only] |
1719 | =item ev_statdata prev [read-only] |
1694 | |
1720 | |
1695 | The previous attributes of the file. The callback gets invoked whenever |
1721 | The previous attributes of the file. The callback gets invoked whenever |
1696 | C<prev> != C<attr>. |
1722 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1723 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1724 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1697 | |
1725 | |
1698 | =item ev_tstamp interval [read-only] |
1726 | =item ev_tstamp interval [read-only] |
1699 | |
1727 | |
1700 | The specified interval. |
1728 | The specified interval. |
1701 | |
1729 | |
… | |
… | |
1755 | } |
1783 | } |
1756 | |
1784 | |
1757 | ... |
1785 | ... |
1758 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1786 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1759 | ev_stat_start (loop, &passwd); |
1787 | ev_stat_start (loop, &passwd); |
1760 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1788 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1761 | |
1789 | |
1762 | |
1790 | |
1763 | =head2 C<ev_idle> - when you've got nothing better to do... |
1791 | =head2 C<ev_idle> - when you've got nothing better to do... |
1764 | |
1792 | |
1765 | Idle watchers trigger events when no other events of the same or higher |
1793 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1853 | |
1881 | |
1854 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1882 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1855 | priority, to ensure that they are being run before any other watchers |
1883 | priority, to ensure that they are being run before any other watchers |
1856 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1884 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1857 | too) should not activate ("feed") events into libev. While libev fully |
1885 | too) should not activate ("feed") events into libev. While libev fully |
1858 | supports this, they will be called before other C<ev_check> watchers |
1886 | supports this, they might get executed before other C<ev_check> watchers |
1859 | did their job. As C<ev_check> watchers are often used to embed other |
1887 | did their job. As C<ev_check> watchers are often used to embed other |
1860 | (non-libev) event loops those other event loops might be in an unusable |
1888 | (non-libev) event loops those other event loops might be in an unusable |
1861 | state until their C<ev_check> watcher ran (always remind yourself to |
1889 | state until their C<ev_check> watcher ran (always remind yourself to |
1862 | coexist peacefully with others). |
1890 | coexist peacefully with others). |
1863 | |
1891 | |
… | |
… | |
1878 | =head3 Examples |
1906 | =head3 Examples |
1879 | |
1907 | |
1880 | There are a number of principal ways to embed other event loops or modules |
1908 | There are a number of principal ways to embed other event loops or modules |
1881 | into libev. Here are some ideas on how to include libadns into libev |
1909 | into libev. Here are some ideas on how to include libadns into libev |
1882 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1910 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1883 | use for an actually working example. Another Perl module named C<EV::Glib> |
1911 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1884 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
1912 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1885 | into the Glib event loop). |
1913 | Glib event loop). |
1886 | |
1914 | |
1887 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1915 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1888 | and in a check watcher, destroy them and call into libadns. What follows |
1916 | and in a check watcher, destroy them and call into libadns. What follows |
1889 | is pseudo-code only of course. This requires you to either use a low |
1917 | is pseudo-code only of course. This requires you to either use a low |
1890 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1918 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
… | |
… | |
2280 | |
2308 | |
2281 | This call incurs the overhead of a syscall only once per loop iteration, |
2309 | This call incurs the overhead of a syscall only once per loop iteration, |
2282 | so while the overhead might be noticable, it doesn't apply to repeated |
2310 | so while the overhead might be noticable, it doesn't apply to repeated |
2283 | calls to C<ev_async_send>. |
2311 | calls to C<ev_async_send>. |
2284 | |
2312 | |
|
|
2313 | =item bool = ev_async_pending (ev_async *) |
|
|
2314 | |
|
|
2315 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2316 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2317 | event loop. |
|
|
2318 | |
|
|
2319 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2320 | the loop iterates next and checks for the watcher to have become active, |
|
|
2321 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2322 | quickly check wether invoking the loop might be a good idea. |
|
|
2323 | |
|
|
2324 | Not that this does I<not> check wether the watcher itself is pending, only |
|
|
2325 | wether it has been requested to make this watcher pending. |
|
|
2326 | |
2285 | =back |
2327 | =back |
2286 | |
2328 | |
2287 | |
2329 | |
2288 | =head1 OTHER FUNCTIONS |
2330 | =head1 OTHER FUNCTIONS |
2289 | |
2331 | |
… | |
… | |
2360 | |
2402 | |
2361 | =item * Priorities are not currently supported. Initialising priorities |
2403 | =item * Priorities are not currently supported. Initialising priorities |
2362 | will fail and all watchers will have the same priority, even though there |
2404 | will fail and all watchers will have the same priority, even though there |
2363 | is an ev_pri field. |
2405 | is an ev_pri field. |
2364 | |
2406 | |
|
|
2407 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2408 | first base created (== the default loop) gets the signals. |
|
|
2409 | |
2365 | =item * Other members are not supported. |
2410 | =item * Other members are not supported. |
2366 | |
2411 | |
2367 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2412 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2368 | to use the libev header file and library. |
2413 | to use the libev header file and library. |
2369 | |
2414 | |
… | |
… | |
2611 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2656 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2612 | |
2657 | |
2613 | Similar to the other two macros, this gives you the value of the default |
2658 | Similar to the other two macros, this gives you the value of the default |
2614 | loop, if multiple loops are supported ("ev loop default"). |
2659 | loop, if multiple loops are supported ("ev loop default"). |
2615 | |
2660 | |
|
|
2661 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2662 | |
|
|
2663 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2664 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2665 | is undefined when the default loop has not been initialised by a previous |
|
|
2666 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2667 | |
|
|
2668 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2669 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
|
|
2670 | |
2616 | =back |
2671 | =back |
2617 | |
2672 | |
2618 | Example: Declare and initialise a check watcher, utilising the above |
2673 | Example: Declare and initialise a check watcher, utilising the above |
2619 | macros so it will work regardless of whether multiple loops are supported |
2674 | macros so it will work regardless of whether multiple loops are supported |
2620 | or not. |
2675 | or not. |
… | |
… | |
2715 | |
2770 | |
2716 | libev.m4 |
2771 | libev.m4 |
2717 | |
2772 | |
2718 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2773 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2719 | |
2774 | |
2720 | Libev can be configured via a variety of preprocessor symbols you have to define |
2775 | Libev can be configured via a variety of preprocessor symbols you have to |
2721 | before including any of its files. The default is not to build for multiplicity |
2776 | define before including any of its files. The default in the absense of |
2722 | and only include the select backend. |
2777 | autoconf is noted for every option. |
2723 | |
2778 | |
2724 | =over 4 |
2779 | =over 4 |
2725 | |
2780 | |
2726 | =item EV_STANDALONE |
2781 | =item EV_STANDALONE |
2727 | |
2782 | |
… | |
… | |
2753 | =item EV_USE_NANOSLEEP |
2808 | =item EV_USE_NANOSLEEP |
2754 | |
2809 | |
2755 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2810 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2756 | and will use it for delays. Otherwise it will use C<select ()>. |
2811 | and will use it for delays. Otherwise it will use C<select ()>. |
2757 | |
2812 | |
|
|
2813 | =item EV_USE_EVENTFD |
|
|
2814 | |
|
|
2815 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2816 | available and will probe for kernel support at runtime. This will improve |
|
|
2817 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2818 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2819 | 2.7 or newer, otherwise disabled. |
|
|
2820 | |
2758 | =item EV_USE_SELECT |
2821 | =item EV_USE_SELECT |
2759 | |
2822 | |
2760 | If undefined or defined to be C<1>, libev will compile in support for the |
2823 | If undefined or defined to be C<1>, libev will compile in support for the |
2761 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2824 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2762 | other method takes over, select will be it. Otherwise the select backend |
2825 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
2798 | |
2861 | |
2799 | =item EV_USE_EPOLL |
2862 | =item EV_USE_EPOLL |
2800 | |
2863 | |
2801 | If defined to be C<1>, libev will compile in support for the Linux |
2864 | If defined to be C<1>, libev will compile in support for the Linux |
2802 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2865 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2803 | otherwise another method will be used as fallback. This is the |
2866 | otherwise another method will be used as fallback. This is the preferred |
2804 | preferred backend for GNU/Linux systems. |
2867 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2868 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2805 | |
2869 | |
2806 | =item EV_USE_KQUEUE |
2870 | =item EV_USE_KQUEUE |
2807 | |
2871 | |
2808 | If defined to be C<1>, libev will compile in support for the BSD style |
2872 | If defined to be C<1>, libev will compile in support for the BSD style |
2809 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2873 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2828 | |
2892 | |
2829 | =item EV_USE_INOTIFY |
2893 | =item EV_USE_INOTIFY |
2830 | |
2894 | |
2831 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2895 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2832 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2896 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2833 | be detected at runtime. |
2897 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2898 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2834 | |
2899 | |
2835 | =item EV_ATOMIC_T |
2900 | =item EV_ATOMIC_T |
2836 | |
2901 | |
2837 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2902 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2838 | access is atomic with respect to other threads or signal contexts. No such |
2903 | access is atomic with respect to other threads or signal contexts. No such |
… | |
… | |
2925 | defined to be C<0>, then they are not. |
2990 | defined to be C<0>, then they are not. |
2926 | |
2991 | |
2927 | =item EV_MINIMAL |
2992 | =item EV_MINIMAL |
2928 | |
2993 | |
2929 | If you need to shave off some kilobytes of code at the expense of some |
2994 | If you need to shave off some kilobytes of code at the expense of some |
2930 | speed, define this symbol to C<1>. Currently only used for gcc to override |
2995 | speed, define this symbol to C<1>. Currently this is used to override some |
2931 | some inlining decisions, saves roughly 30% codesize of amd64. |
2996 | inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
|
|
2997 | much smaller 2-heap for timer management over the default 4-heap. |
2932 | |
2998 | |
2933 | =item EV_PID_HASHSIZE |
2999 | =item EV_PID_HASHSIZE |
2934 | |
3000 | |
2935 | C<ev_child> watchers use a small hash table to distribute workload by |
3001 | C<ev_child> watchers use a small hash table to distribute workload by |
2936 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3002 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
2942 | C<ev_stat> watchers use a small hash table to distribute workload by |
3008 | C<ev_stat> watchers use a small hash table to distribute workload by |
2943 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
3009 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2944 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3010 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2945 | watchers you might want to increase this value (I<must> be a power of |
3011 | watchers you might want to increase this value (I<must> be a power of |
2946 | two). |
3012 | two). |
|
|
3013 | |
|
|
3014 | =item EV_USE_4HEAP |
|
|
3015 | |
|
|
3016 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3017 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3018 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3019 | noticably faster performance with many (thousands) of watchers. |
|
|
3020 | |
|
|
3021 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3022 | (disabled). |
|
|
3023 | |
|
|
3024 | =item EV_HEAP_CACHE_AT |
|
|
3025 | |
|
|
3026 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3027 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3028 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3029 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3030 | but avoids random read accesses on heap changes. This improves performance |
|
|
3031 | noticably with with many (hundreds) of watchers. |
|
|
3032 | |
|
|
3033 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3034 | (disabled). |
2947 | |
3035 | |
2948 | =item EV_COMMON |
3036 | =item EV_COMMON |
2949 | |
3037 | |
2950 | By default, all watchers have a C<void *data> member. By redefining |
3038 | By default, all watchers have a C<void *data> member. By redefining |
2951 | this macro to a something else you can include more and other types of |
3039 | this macro to a something else you can include more and other types of |
… | |
… | |
3025 | |
3113 | |
3026 | #include "ev_cpp.h" |
3114 | #include "ev_cpp.h" |
3027 | #include "ev.c" |
3115 | #include "ev.c" |
3028 | |
3116 | |
3029 | |
3117 | |
|
|
3118 | =head1 THREADS AND COROUTINES |
|
|
3119 | |
|
|
3120 | =head2 THREADS |
|
|
3121 | |
|
|
3122 | Libev itself is completely threadsafe, but it uses no locking. This |
|
|
3123 | means that you can use as many loops as you want in parallel, as long as |
|
|
3124 | only one thread ever calls into one libev function with the same loop |
|
|
3125 | parameter. |
|
|
3126 | |
|
|
3127 | Or put differently: calls with different loop parameters can be done in |
|
|
3128 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3129 | done serially (but can be done from different threads, as long as only one |
|
|
3130 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3131 | per loop). |
|
|
3132 | |
|
|
3133 | If you want to know which design is best for your problem, then I cannot |
|
|
3134 | help you but by giving some generic advice: |
|
|
3135 | |
|
|
3136 | =over 4 |
|
|
3137 | |
|
|
3138 | =item * most applications have a main thread: use the default libev loop |
|
|
3139 | in that thread, or create a seperate thread running only the default loop. |
|
|
3140 | |
|
|
3141 | This helps integrating other libraries or software modules that use libev |
|
|
3142 | themselves and don't care/know about threading. |
|
|
3143 | |
|
|
3144 | =item * one loop per thread is usually a good model. |
|
|
3145 | |
|
|
3146 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3147 | exists, but it is always a good start. |
|
|
3148 | |
|
|
3149 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3150 | loop is handed through multiple threads in a kind of round-robbin fashion. |
|
|
3151 | |
|
|
3152 | Chosing a model is hard - look around, learn, know that usually you cna do |
|
|
3153 | better than you currently do :-) |
|
|
3154 | |
|
|
3155 | =item * often you need to talk to some other thread which blocks in the |
|
|
3156 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3157 | threads safely (or from signal contexts...). |
|
|
3158 | |
|
|
3159 | =back |
|
|
3160 | |
|
|
3161 | =head2 COROUTINES |
|
|
3162 | |
|
|
3163 | Libev is much more accomodating to coroutines ("cooperative threads"): |
|
|
3164 | libev fully supports nesting calls to it's functions from different |
|
|
3165 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3166 | different coroutines and switch freely between both coroutines running the |
|
|
3167 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3168 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3169 | |
|
|
3170 | Care has been invested into making sure that libev does not keep local |
|
|
3171 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3172 | switches. |
|
|
3173 | |
|
|
3174 | |
3030 | =head1 COMPLEXITIES |
3175 | =head1 COMPLEXITIES |
3031 | |
3176 | |
3032 | In this section the complexities of (many of) the algorithms used inside |
3177 | In this section the complexities of (many of) the algorithms used inside |
3033 | libev will be explained. For complexity discussions about backends see the |
3178 | libev will be explained. For complexity discussions about backends see the |
3034 | documentation for C<ev_default_init>. |
3179 | documentation for C<ev_default_init>. |
… | |
… | |
3064 | correct watcher to remove. The lists are usually short (you don't usually |
3209 | correct watcher to remove. The lists are usually short (you don't usually |
3065 | have many watchers waiting for the same fd or signal). |
3210 | have many watchers waiting for the same fd or signal). |
3066 | |
3211 | |
3067 | =item Finding the next timer in each loop iteration: O(1) |
3212 | =item Finding the next timer in each loop iteration: O(1) |
3068 | |
3213 | |
3069 | By virtue of using a binary heap, the next timer is always found at the |
3214 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3070 | beginning of the storage array. |
3215 | fixed position in the storage array. |
3071 | |
3216 | |
3072 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3217 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3073 | |
3218 | |
3074 | A change means an I/O watcher gets started or stopped, which requires |
3219 | A change means an I/O watcher gets started or stopped, which requires |
3075 | libev to recalculate its status (and possibly tell the kernel, depending |
3220 | libev to recalculate its status (and possibly tell the kernel, depending |
… | |
… | |
3104 | model. Libev still offers limited functionality on this platform in |
3249 | model. Libev still offers limited functionality on this platform in |
3105 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3250 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3106 | descriptors. This only applies when using Win32 natively, not when using |
3251 | descriptors. This only applies when using Win32 natively, not when using |
3107 | e.g. cygwin. |
3252 | e.g. cygwin. |
3108 | |
3253 | |
|
|
3254 | Lifting these limitations would basically require the full |
|
|
3255 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3256 | things, then note that glib does exactly that for you in a very portable |
|
|
3257 | way (note also that glib is the slowest event library known to man). |
|
|
3258 | |
3109 | There is no supported compilation method available on windows except |
3259 | There is no supported compilation method available on windows except |
3110 | embedding it into other applications. |
3260 | embedding it into other applications. |
3111 | |
3261 | |
3112 | Due to the many, low, and arbitrary limits on the win32 platform and the |
3262 | Due to the many, low, and arbitrary limits on the win32 platform and |
3113 | abysmal performance of winsockets, using a large number of sockets is not |
3263 | the abysmal performance of winsockets, using a large number of sockets |
3114 | recommended (and not reasonable). If your program needs to use more than |
3264 | is not recommended (and not reasonable). If your program needs to use |
3115 | a hundred or so sockets, then likely it needs to use a totally different |
3265 | more than a hundred or so sockets, then likely it needs to use a totally |
3116 | implementation for windows, as libev offers the POSIX model, which cannot |
3266 | different implementation for windows, as libev offers the POSIX readiness |
3117 | be implemented efficiently on windows (microsoft monopoly games). |
3267 | notification model, which cannot be implemented efficiently on windows |
|
|
3268 | (microsoft monopoly games). |
3118 | |
3269 | |
3119 | =over 4 |
3270 | =over 4 |
3120 | |
3271 | |
3121 | =item The winsocket select function |
3272 | =item The winsocket select function |
3122 | |
3273 | |
… | |
… | |
3136 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3287 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3137 | complexity in the O(n²) range when using win32. |
3288 | complexity in the O(n²) range when using win32. |
3138 | |
3289 | |
3139 | =item Limited number of file descriptors |
3290 | =item Limited number of file descriptors |
3140 | |
3291 | |
3141 | Windows has numerous arbitrary (and low) limits on things. Early versions |
3292 | Windows has numerous arbitrary (and low) limits on things. |
3142 | of winsocket's select only supported waiting for a max. of C<64> handles |
3293 | |
|
|
3294 | Early versions of winsocket's select only supported waiting for a maximum |
3143 | (probably owning to the fact that all windows kernels can only wait for |
3295 | of C<64> handles (probably owning to the fact that all windows kernels |
3144 | C<64> things at the same time internally; microsoft recommends spawning a |
3296 | can only wait for C<64> things at the same time internally; microsoft |
3145 | chain of threads and wait for 63 handles and the previous thread in each). |
3297 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3298 | previous thread in each. Great). |
3146 | |
3299 | |
3147 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3300 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3148 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3301 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3149 | call (which might be in libev or elsewhere, for example, perl does its own |
3302 | call (which might be in libev or elsewhere, for example, perl does its own |
3150 | select emulation on windows). |
3303 | select emulation on windows). |
… | |
… | |
3162 | calling select (O(n²)) will likely make this unworkable. |
3315 | calling select (O(n²)) will likely make this unworkable. |
3163 | |
3316 | |
3164 | =back |
3317 | =back |
3165 | |
3318 | |
3166 | |
3319 | |
|
|
3320 | =head1 PORTABILITY REQUIREMENTS |
|
|
3321 | |
|
|
3322 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3323 | additional extensions: |
|
|
3324 | |
|
|
3325 | =over 4 |
|
|
3326 | |
|
|
3327 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3328 | |
|
|
3329 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3330 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3331 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3332 | believed to be sufficiently portable. |
|
|
3333 | |
|
|
3334 | =item C<sigprocmask> must work in a threaded environment |
|
|
3335 | |
|
|
3336 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3337 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3338 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3339 | thread" or will block signals process-wide, both behaviours would |
|
|
3340 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3341 | C<pthread_sigmask> could complicate things, however. |
|
|
3342 | |
|
|
3343 | The most portable way to handle signals is to block signals in all threads |
|
|
3344 | except the initial one, and run the default loop in the initial thread as |
|
|
3345 | well. |
|
|
3346 | |
|
|
3347 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3348 | |
|
|
3349 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3350 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3351 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3352 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3353 | millions of watchers. |
|
|
3354 | |
|
|
3355 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3356 | |
|
|
3357 | The type C<double> is used to represent timestamps. It is required to |
|
|
3358 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3359 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3360 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3361 | |
|
|
3362 | =back |
|
|
3363 | |
|
|
3364 | If you know of other additional requirements drop me a note. |
|
|
3365 | |
|
|
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 | |
3167 | =head1 AUTHOR |
3393 | =head1 AUTHOR |
3168 | |
3394 | |
3169 | Marc Lehmann <libev@schmorp.de>. |
3395 | Marc Lehmann <libev@schmorp.de>. |
3170 | |
3396 | |