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4 | <head> |
4 | <head> |
5 | <title>libev</title> |
5 | <title>libev</title> |
6 | <meta name="description" content="Pod documentation for libev" /> |
6 | <meta name="description" content="Pod documentation for libev" /> |
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9 | <meta name="created" content="Mon Nov 12 20:19:59 2007" /> |
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13 | <div class="pod"> |
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14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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106 | <p>These functions can be called anytime, even before initialising the |
106 | <p>These functions can be called anytime, even before initialising the |
107 | library in any way.</p> |
107 | library in any way.</p> |
108 | <dl> |
108 | <dl> |
109 | <dt>ev_tstamp ev_time ()</dt> |
109 | <dt>ev_tstamp ev_time ()</dt> |
110 | <dd> |
110 | <dd> |
111 | <p>Returns the current time as libev would use it.</p> |
111 | <p>Returns the current time as libev would use it. Please note that the |
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112 | <code>ev_now</code> function is usually faster and also often returns the timestamp |
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113 | you actually want to know.</p> |
112 | </dd> |
114 | </dd> |
113 | <dt>int ev_version_major ()</dt> |
115 | <dt>int ev_version_major ()</dt> |
114 | <dt>int ev_version_minor ()</dt> |
116 | <dt>int ev_version_minor ()</dt> |
115 | <dd> |
117 | <dd> |
116 | <p>You can find out the major and minor version numbers of the library |
118 | <p>You can find out the major and minor version numbers of the library |
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184 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
186 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
185 | override the flags completely if it is found in the environment. This is |
187 | override the flags completely if it is found in the environment. This is |
186 | useful to try out specific backends to test their performance, or to work |
188 | useful to try out specific backends to test their performance, or to work |
187 | around bugs.</p> |
189 | around bugs.</p> |
188 | </dd> |
190 | </dd> |
189 | <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> |
191 | <dt><code>EVMETHOD_SELECT</code> (value 1, portable select backend)</dt> |
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192 | <dd> |
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193 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
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194 | libev tries to roll its own fd_set with no limits on the number of fds, |
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195 | but if that fails, expect a fairly low limit on the number of fds when |
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196 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
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197 | the fastest backend for a low number of fds.</p> |
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198 | </dd> |
190 | <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> |
199 | <dt><code>EVMETHOD_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt> |
191 | <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> |
200 | <dd> |
192 | <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> |
201 | <p>And this is your standard poll(2) backend. It's more complicated than |
193 | <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> |
202 | select, but handles sparse fds better and has no artificial limit on the |
194 | <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> |
203 | number of fds you can use (except it will slow down considerably with a |
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204 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p> |
195 | <dd> |
205 | </dd> |
196 | <p>If one or more of these are ored into the flags value, then only these |
206 | <dt><code>EVMETHOD_EPOLL</code> (value 4, Linux)</dt> |
197 | backends will be tried (in the reverse order as given here). If one are |
207 | <dd> |
198 | specified, any backend will do.</p> |
208 | <p>For few fds, this backend is a bit little slower than poll and select, |
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209 | but it scales phenomenally better. While poll and select usually scale like |
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210 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
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211 | either O(1) or O(active_fds).</p> |
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212 | <p>While stopping and starting an I/O watcher in the same iteration will |
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213 | result in some caching, there is still a syscall per such incident |
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214 | (because the fd could point to a different file description now), so its |
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215 | best to avoid that. Also, dup()ed file descriptors might not work very |
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216 | well if you register events for both fds.</p> |
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217 | </dd> |
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218 | <dt><code>EVMETHOD_KQUEUE</code> (value 8, most BSD clones)</dt> |
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219 | <dd> |
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220 | <p>Kqueue deserves special mention, as at the time of this writing, it |
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221 | was broken on all BSDs except NetBSD (usually it doesn't work with |
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222 | anything but sockets and pipes, except on Darwin, where of course its |
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223 | completely useless). For this reason its not being "autodetected" unless |
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224 | you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p> |
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225 | <p>It scales in the same way as the epoll backend, but the interface to the |
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226 | kernel is more efficient (which says nothing about its actual speed, of |
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227 | course). While starting and stopping an I/O watcher does not cause an |
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228 | extra syscall as with epoll, it still adds up to four event changes per |
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229 | incident, so its best to avoid that.</p> |
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230 | </dd> |
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231 | <dt><code>EVMETHOD_DEVPOLL</code> (value 16, Solaris 8)</dt> |
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232 | <dd> |
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233 | <p>This is not implemented yet (and might never be).</p> |
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234 | </dd> |
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235 | <dt><code>EVMETHOD_PORT</code> (value 32, Solaris 10)</dt> |
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236 | <dd> |
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237 | <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
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238 | it's really slow, but it still scales very well (O(active_fds)).</p> |
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239 | </dd> |
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240 | <dt><code>EVMETHOD_ALL</code></dt> |
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241 | <dd> |
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242 | <p>Try all backends (even potentially broken ones that wouldn't be tried |
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243 | with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
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244 | <code>EVMETHOD_ALL & ~EVMETHOD_KQUEUE</code>.</p> |
199 | </dd> |
245 | </dd> |
200 | </dl> |
246 | </dl> |
201 | </p> |
247 | </p> |
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248 | <p>If one or more of these are ored into the flags value, then only these |
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249 | backends will be tried (in the reverse order as given here). If none are |
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250 | specified, most compiled-in backend will be tried, usually in reverse |
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251 | order of their flag values :)</p> |
202 | </dd> |
252 | </dd> |
203 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
253 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
204 | <dd> |
254 | <dd> |
205 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
255 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
206 | always distinct from the default loop. Unlike the default loop, it cannot |
256 | always distinct from the default loop. Unlike the default loop, it cannot |
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222 | <dd> |
272 | <dd> |
223 | <p>This function reinitialises the kernel state for backends that have |
273 | <p>This function reinitialises the kernel state for backends that have |
224 | one. Despite the name, you can call it anytime, but it makes most sense |
274 | one. Despite the name, you can call it anytime, but it makes most sense |
225 | after forking, in either the parent or child process (or both, but that |
275 | after forking, in either the parent or child process (or both, but that |
226 | again makes little sense).</p> |
276 | again makes little sense).</p> |
227 | <p>You <i>must</i> call this function after forking if and only if you want to |
277 | <p>You <i>must</i> call this function in the child process after forking if and |
228 | use the event library in both processes. If you just fork+exec, you don't |
278 | only if you want to use the event library in both processes. If you just |
229 | have to call it.</p> |
279 | fork+exec, you don't have to call it.</p> |
230 | <p>The function itself is quite fast and it's usually not a problem to call |
280 | <p>The function itself is quite fast and it's usually not a problem to call |
231 | it just in case after a fork. To make this easy, the function will fit in |
281 | it just in case after a fork. To make this easy, the function will fit in |
232 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
282 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
233 | <pre> pthread_atfork (0, 0, ev_default_fork); |
283 | <pre> pthread_atfork (0, 0, ev_default_fork); |
234 | |
284 | |
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268 | your process until at least one new event arrives, and will return after |
318 | your process until at least one new event arrives, and will return after |
269 | one iteration of the loop.</p> |
319 | one iteration of the loop.</p> |
270 | <p>This flags value could be used to implement alternative looping |
320 | <p>This flags value could be used to implement alternative looping |
271 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
321 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
272 | more generic mechanism.</p> |
322 | more generic mechanism.</p> |
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323 | <p>Here are the gory details of what ev_loop does:</p> |
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324 | <pre> 1. If there are no active watchers (reference count is zero), return. |
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325 | 2. Queue and immediately call all prepare watchers. |
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326 | 3. If we have been forked, recreate the kernel state. |
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327 | 4. Update the kernel state with all outstanding changes. |
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328 | 5. Update the "event loop time". |
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329 | 6. Calculate for how long to block. |
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330 | 7. Block the process, waiting for events. |
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331 | 8. Update the "event loop time" and do time jump handling. |
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332 | 9. Queue all outstanding timers. |
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333 | 10. Queue all outstanding periodics. |
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334 | 11. If no events are pending now, queue all idle watchers. |
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335 | 12. Queue all check watchers. |
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336 | 13. Call all queued watchers in reverse order (i.e. check watchers first). |
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337 | 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
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338 | was used, return, otherwise continue with step #1. |
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339 | |
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340 | </pre> |
273 | </dd> |
341 | </dd> |
274 | <dt>ev_unloop (loop, how)</dt> |
342 | <dt>ev_unloop (loop, how)</dt> |
275 | <dd> |
343 | <dd> |
276 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
344 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
277 | has processed all outstanding events). The <code>how</code> argument must be either |
345 | has processed all outstanding events). The <code>how</code> argument must be either |
278 | <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or |
346 | <code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or |
279 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
347 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
280 | </dd> |
348 | </dd> |
281 | <dt>ev_ref (loop)</dt> |
349 | <dt>ev_ref (loop)</dt> |
282 | <dt>ev_unref (loop)</dt> |
350 | <dt>ev_unref (loop)</dt> |
283 | <dd> |
351 | <dd> |
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472 | <p>Timer watchers are simple relative timers that generate an event after a |
540 | <p>Timer watchers are simple relative timers that generate an event after a |
473 | given time, and optionally repeating in regular intervals after that.</p> |
541 | given time, and optionally repeating in regular intervals after that.</p> |
474 | <p>The timers are based on real time, that is, if you register an event that |
542 | <p>The timers are based on real time, that is, if you register an event that |
475 | times out after an hour and you reset your system clock to last years |
543 | times out after an hour and you reset your system clock to last years |
476 | time, it will still time out after (roughly) and hour. "Roughly" because |
544 | time, it will still time out after (roughly) and hour. "Roughly" because |
477 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
545 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
478 | monotonic clock option helps a lot here).</p> |
546 | monotonic clock option helps a lot here).</p> |
479 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
547 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
480 | time. This is usually the right thing as this timestamp refers to the time |
548 | time. This is usually the right thing as this timestamp refers to the time |
481 | of the event triggering whatever timeout you are modifying/starting. If |
549 | of the event triggering whatever timeout you are modifying/starting. If |
482 | you suspect event processing to be delayed and you *need* to base the timeout |
550 | you suspect event processing to be delayed and you <i>need</i> to base the timeout |
483 | on the current time, use something like this to adjust for this:</p> |
551 | on the current time, use something like this to adjust for this:</p> |
484 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
552 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
485 | |
553 | |
486 | </pre> |
554 | </pre> |
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555 | <p>The callback is guarenteed to be invoked only when its timeout has passed, |
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556 | but if multiple timers become ready during the same loop iteration then |
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557 | order of execution is undefined.</p> |
487 | <dl> |
558 | <dl> |
488 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
559 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
489 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
560 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
490 | <dd> |
561 | <dd> |
491 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
562 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
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529 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
600 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
530 | roughly 10 seconds later and of course not if you reset your system time |
601 | roughly 10 seconds later and of course not if you reset your system time |
531 | again).</p> |
602 | again).</p> |
532 | <p>They can also be used to implement vastly more complex timers, such as |
603 | <p>They can also be used to implement vastly more complex timers, such as |
533 | triggering an event on eahc midnight, local time.</p> |
604 | triggering an event on eahc midnight, local time.</p> |
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605 | <p>As with timers, the callback is guarenteed to be invoked only when the |
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606 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
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607 | during the same loop iteration then order of execution is undefined.</p> |
534 | <dl> |
608 | <dl> |
535 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
609 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
536 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
610 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
537 | <dd> |
611 | <dd> |
538 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
612 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
539 | operation, and we will explain them from simplest to complex:</p> |
613 | operation, and we will explain them from simplest to complex:</p> |
540 | |
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541 | |
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542 | |
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543 | |
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544 | <p> |
614 | <p> |
545 | <dl> |
615 | <dl> |
546 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
616 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
547 | <dd> |
617 | <dd> |
548 | <p>In this configuration the watcher triggers an event at the wallclock time |
618 | <p>In this configuration the watcher triggers an event at the wallclock time |