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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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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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35 | <li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> |
35 | <li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> |
36 | <li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> |
36 | <li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> |
37 | </ul> |
37 | </ul> |
38 | </li> |
38 | </li> |
39 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
39 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
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40 | <li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
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41 | <li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
40 | <li><a href="#AUTHOR">AUTHOR</a> |
42 | <li><a href="#AUTHOR">AUTHOR</a> |
41 | </li> |
43 | </li> |
42 | </ul><hr /> |
44 | </ul><hr /> |
43 | <!-- INDEX END --> |
45 | <!-- INDEX END --> |
44 | |
46 | |
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99 | to the double type in C.</p> |
101 | to the double type in C.</p> |
100 | |
102 | |
101 | </div> |
103 | </div> |
102 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
104 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
103 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
105 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
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106 | <p>These functions can be called anytime, even before initialising the |
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107 | library in any way.</p> |
104 | <dl> |
108 | <dl> |
105 | <dt>ev_tstamp ev_time ()</dt> |
109 | <dt>ev_tstamp ev_time ()</dt> |
106 | <dd> |
110 | <dd> |
107 | <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> |
108 | </dd> |
114 | </dd> |
109 | <dt>int ev_version_major ()</dt> |
115 | <dt>int ev_version_major ()</dt> |
110 | <dt>int ev_version_minor ()</dt> |
116 | <dt>int ev_version_minor ()</dt> |
111 | <dd> |
117 | <dd> |
112 | <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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180 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
186 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
181 | 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 |
182 | 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 |
183 | around bugs.</p> |
189 | around bugs.</p> |
184 | </dd> |
190 | </dd> |
185 | <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> |
186 | <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> |
187 | <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> |
200 | <dd> |
188 | <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> |
201 | <p>And this is your standard poll(2) backend. It's more complicated than |
189 | <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> |
202 | select, but handles sparse fds better and has no artificial limit on the |
190 | <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> |
191 | <dd> |
205 | </dd> |
192 | <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> |
193 | backends will be tried (in the reverse order as given here). If one are |
207 | <dd> |
194 | 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). Since this is a mask, you |
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243 | can do stuff like <code>EVMETHOD_ALL & ~EVMETHOD_KQUEUE</code>.</p> |
195 | </dd> |
244 | </dd> |
196 | </dl> |
245 | </dl> |
197 | </p> |
246 | </p> |
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247 | <p>If one or more of these are ored into the flags value, then only these |
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248 | backends will be tried (in the reverse order as given here). If none are |
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249 | specified, most compiled-in backend will be tried, usually in reverse |
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250 | order of their flag values :)</p> |
198 | </dd> |
251 | </dd> |
199 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
252 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
200 | <dd> |
253 | <dd> |
201 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
254 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
202 | always distinct from the default loop. Unlike the default loop, it cannot |
255 | always distinct from the default loop. Unlike the default loop, it cannot |
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264 | your process until at least one new event arrives, and will return after |
317 | your process until at least one new event arrives, and will return after |
265 | one iteration of the loop.</p> |
318 | one iteration of the loop.</p> |
266 | <p>This flags value could be used to implement alternative looping |
319 | <p>This flags value could be used to implement alternative looping |
267 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
320 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
268 | more generic mechanism.</p> |
321 | more generic mechanism.</p> |
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322 | <p>Here are the gory details of what ev_loop does:</p> |
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323 | <pre> 1. If there are no active watchers (reference count is zero), return. |
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324 | 2. Queue and immediately call all prepare watchers. |
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325 | 3. If we have been forked, recreate the kernel state. |
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326 | 4. Update the kernel state with all outstanding changes. |
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327 | 5. Update the "event loop time". |
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328 | 6. Calculate for how long to block. |
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329 | 7. Block the process, waiting for events. |
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330 | 8. Update the "event loop time" and do time jump handling. |
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331 | 9. Queue all outstanding timers. |
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332 | 10. Queue all outstanding periodics. |
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333 | 11. If no events are pending now, queue all idle watchers. |
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334 | 12. Queue all check watchers. |
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335 | 13. Call all queued watchers in reverse order (i.e. check watchers first). |
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336 | 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
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337 | was used, return, otherwise continue with step #1. |
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338 | |
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339 | </pre> |
269 | </dd> |
340 | </dd> |
270 | <dt>ev_unloop (loop, how)</dt> |
341 | <dt>ev_unloop (loop, how)</dt> |
271 | <dd> |
342 | <dd> |
272 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
343 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
273 | has processed all outstanding events). The <code>how</code> argument must be either |
344 | has processed all outstanding events). The <code>how</code> argument must be either |
274 | <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or |
345 | <code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or |
275 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
346 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
276 | </dd> |
347 | </dd> |
277 | <dt>ev_ref (loop)</dt> |
348 | <dt>ev_ref (loop)</dt> |
278 | <dt>ev_unref (loop)</dt> |
349 | <dt>ev_unref (loop)</dt> |
279 | <dd> |
350 | <dd> |
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438 | <p>I/O watchers check whether a file descriptor is readable or writable |
509 | <p>I/O watchers check whether a file descriptor is readable or writable |
439 | in each iteration of the event loop (This behaviour is called |
510 | in each iteration of the event loop (This behaviour is called |
440 | level-triggering because you keep receiving events as long as the |
511 | level-triggering because you keep receiving events as long as the |
441 | condition persists. Remember you can stop the watcher if you don't want to |
512 | condition persists. Remember you can stop the watcher if you don't want to |
442 | act on the event and neither want to receive future events).</p> |
513 | act on the event and neither want to receive future events).</p> |
443 | <p>In general you can register as many read and/or write event watchers oer |
514 | <p>In general you can register as many read and/or write event watchers per |
444 | fd as you want (as long as you don't confuse yourself). Setting all file |
515 | fd as you want (as long as you don't confuse yourself). Setting all file |
445 | descriptors to non-blocking mode is also usually a good idea (but not |
516 | descriptors to non-blocking mode is also usually a good idea (but not |
446 | required if you know what you are doing).</p> |
517 | required if you know what you are doing).</p> |
447 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
518 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
448 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
519 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
449 | descriptors correctly if you register interest in two or more fds pointing |
520 | descriptors correctly if you register interest in two or more fds pointing |
450 | to the same file/socket etc. description.</p> |
521 | to the same underlying file/socket etc. description (that is, they share |
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522 | the same underlying "file open").</p> |
451 | <p>If you must do this, then force the use of a known-to-be-good backend |
523 | <p>If you must do this, then force the use of a known-to-be-good backend |
452 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
524 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
453 | EVMETHOD_POLL).</p> |
525 | EVMETHOD_POLL).</p> |
454 | <dl> |
526 | <dl> |
455 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
527 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
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465 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
537 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
466 | <div id="code_ev_timer_code_relative_and_opti-2"> |
538 | <div id="code_ev_timer_code_relative_and_opti-2"> |
467 | <p>Timer watchers are simple relative timers that generate an event after a |
539 | <p>Timer watchers are simple relative timers that generate an event after a |
468 | given time, and optionally repeating in regular intervals after that.</p> |
540 | given time, and optionally repeating in regular intervals after that.</p> |
469 | <p>The timers are based on real time, that is, if you register an event that |
541 | <p>The timers are based on real time, that is, if you register an event that |
470 | times out after an hour and youreset your system clock to last years |
542 | times out after an hour and you reset your system clock to last years |
471 | time, it will still time out after (roughly) and hour. "Roughly" because |
543 | time, it will still time out after (roughly) and hour. "Roughly" because |
472 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
544 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
473 | monotonic clock option helps a lot here).</p> |
545 | monotonic clock option helps a lot here).</p> |
474 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
546 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
475 | time. This is usually the right thing as this timestamp refers to the time |
547 | time. This is usually the right thing as this timestamp refers to the time |
476 | of the event triggering whatever timeout you are modifying/starting. If |
548 | of the event triggering whatever timeout you are modifying/starting. If |
477 | you suspect event processing to be delayed and you *need* to base the timeout |
549 | you suspect event processing to be delayed and you <i>need</i> to base the timeout |
478 | ion the current time, use something like this to adjust for this:</p> |
550 | on the current time, use something like this to adjust for this:</p> |
479 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
551 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
480 | |
552 | |
481 | </pre> |
553 | </pre> |
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554 | <p>The callback is guarenteed to be invoked only when its timeout has passed, |
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555 | but if multiple timers become ready during the same loop iteration then |
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556 | order of execution is undefined.</p> |
482 | <dl> |
557 | <dl> |
483 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
558 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
484 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
559 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
485 | <dd> |
560 | <dd> |
486 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
561 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
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488 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
563 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
489 | later, again, and again, until stopped manually.</p> |
564 | later, again, and again, until stopped manually.</p> |
490 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
565 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
491 | configure a timer to trigger every 10 seconds, then it will trigger at |
566 | configure a timer to trigger every 10 seconds, then it will trigger at |
492 | exactly 10 second intervals. If, however, your program cannot keep up with |
567 | exactly 10 second intervals. If, however, your program cannot keep up with |
493 | the timer (ecause it takes longer than those 10 seconds to do stuff) the |
568 | the timer (because it takes longer than those 10 seconds to do stuff) the |
494 | timer will not fire more than once per event loop iteration.</p> |
569 | timer will not fire more than once per event loop iteration.</p> |
495 | </dd> |
570 | </dd> |
496 | <dt>ev_timer_again (loop)</dt> |
571 | <dt>ev_timer_again (loop)</dt> |
497 | <dd> |
572 | <dd> |
498 | <p>This will act as if the timer timed out and restart it again if it is |
573 | <p>This will act as if the timer timed out and restart it again if it is |
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524 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
599 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
525 | roughly 10 seconds later and of course not if you reset your system time |
600 | roughly 10 seconds later and of course not if you reset your system time |
526 | again).</p> |
601 | again).</p> |
527 | <p>They can also be used to implement vastly more complex timers, such as |
602 | <p>They can also be used to implement vastly more complex timers, such as |
528 | triggering an event on eahc midnight, local time.</p> |
603 | triggering an event on eahc midnight, local time.</p> |
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604 | <p>As with timers, the callback is guarenteed to be invoked only when the |
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605 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
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606 | during the same loop iteration then order of execution is undefined.</p> |
529 | <dl> |
607 | <dl> |
530 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
608 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
531 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
609 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
532 | <dd> |
610 | <dd> |
533 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
611 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
534 | operation, and we will explain them from simplest to complex:</p> |
612 | operation, and we will explain them from simplest to complex:</p> |
535 | |
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536 | |
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537 | |
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538 | |
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539 | <p> |
613 | <p> |
540 | <dl> |
614 | <dl> |
541 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
615 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
542 | <dd> |
616 | <dd> |
543 | <p>In this configuration the watcher triggers an event at the wallclock time |
617 | <p>In this configuration the watcher triggers an event at the wallclock time |
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567 | <dd> |
641 | <dd> |
568 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
642 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
569 | ignored. Instead, each time the periodic watcher gets scheduled, the |
643 | ignored. Instead, each time the periodic watcher gets scheduled, the |
570 | reschedule callback will be called with the watcher as first, and the |
644 | reschedule callback will be called with the watcher as first, and the |
571 | current time as second argument.</p> |
645 | current time as second argument.</p> |
572 | <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other |
646 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
573 | periodic watcher, ever, or make any event loop modifications</i>. If you need |
647 | ever, or make any event loop modifications</i>. If you need to stop it, |
574 | to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> |
648 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
575 | <p>Also, <i>this callback must always return a time that is later than the |
649 | starting a prepare watcher).</p> |
576 | passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p> |
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577 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
650 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
578 | ev_tstamp now)</code>, e.g.:</p> |
651 | ev_tstamp now)</code>, e.g.:</p> |
579 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
652 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
580 | { |
653 | { |
581 | return now + 60.; |
654 | return now + 60.; |
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584 | </pre> |
657 | </pre> |
585 | <p>It must return the next time to trigger, based on the passed time value |
658 | <p>It must return the next time to trigger, based on the passed time value |
586 | (that is, the lowest time value larger than to the second argument). It |
659 | (that is, the lowest time value larger than to the second argument). It |
587 | will usually be called just before the callback will be triggered, but |
660 | will usually be called just before the callback will be triggered, but |
588 | might be called at other times, too.</p> |
661 | might be called at other times, too.</p> |
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|
662 | <p>NOTE: <i>This callback must always return a time that is later than the |
|
|
663 | passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p> |
589 | <p>This can be used to create very complex timers, such as a timer that |
664 | <p>This can be used to create very complex timers, such as a timer that |
590 | triggers on each midnight, local time. To do this, you would calculate the |
665 | triggers on each midnight, local time. To do this, you would calculate the |
591 | next midnight after <code>now</code> and return the timestamp value for this. How you do this |
666 | next midnight after <code>now</code> and return the timestamp value for this. How |
592 | is, again, up to you (but it is not trivial).</p> |
667 | you do this is, again, up to you (but it is not trivial, which is the main |
|
|
668 | reason I omitted it as an example).</p> |
593 | </dd> |
669 | </dd> |
594 | </dl> |
670 | </dl> |
595 | </p> |
671 | </p> |
596 | </dd> |
672 | </dd> |
597 | <dt>ev_periodic_again (loop, ev_periodic *)</dt> |
673 | <dt>ev_periodic_again (loop, ev_periodic *)</dt> |
… | |
… | |
670 | |
746 | |
671 | </div> |
747 | </div> |
672 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
748 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
673 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
749 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
674 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
750 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
675 | Prepare watchers get invoked before the process blocks and check watchers |
751 | prepare watchers get invoked before the process blocks and check watchers |
676 | afterwards.</p> |
752 | afterwards.</p> |
677 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
753 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
678 | could be used, for example, to track variable changes, implement your own |
754 | could be used, for example, to track variable changes, implement your own |
679 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
755 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
680 | <p>This is done by examining in each prepare call which file descriptors need |
756 | <p>This is done by examining in each prepare call which file descriptors need |
681 | to be watched by the other library, registering <code>ev_io</code> watchers for |
757 | to be watched by the other library, registering <code>ev_io</code> watchers for |
682 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
758 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
683 | provide just this functionality). Then, in the check watcher you check for |
759 | provide just this functionality). Then, in the check watcher you check for |
684 | any events that occured (by checking the pending status of all watchers |
760 | any events that occured (by checking the pending status of all watchers |
685 | and stopping them) and call back into the library. The I/O and timer |
761 | and stopping them) and call back into the library. The I/O and timer |
686 | callbacks will never actually be called (but must be valid neverthelles, |
762 | callbacks will never actually be called (but must be valid nevertheless, |
687 | because you never know, you know?).</p> |
763 | because you never know, you know?).</p> |
688 | <p>As another example, the Perl Coro module uses these hooks to integrate |
764 | <p>As another example, the Perl Coro module uses these hooks to integrate |
689 | coroutines into libev programs, by yielding to other active coroutines |
765 | coroutines into libev programs, by yielding to other active coroutines |
690 | during each prepare and only letting the process block if no coroutines |
766 | during each prepare and only letting the process block if no coroutines |
691 | are ready to run (its actually more complicated, it only runs coroutines |
767 | are ready to run (it's actually more complicated: it only runs coroutines |
692 | with priority higher than the event loop and one lower priority once, |
768 | with priority higher than or equal to the event loop and one coroutine |
693 | using idle watchers to keep the event loop from blocking if lower-priority |
769 | of lower priority, but only once, using idle watchers to keep the event |
694 | coroutines exist, thus mapping low-priority coroutines to idle/background |
770 | loop from blocking if lower-priority coroutines are active, thus mapping |
695 | tasks).</p> |
771 | low-priority coroutines to idle/background tasks).</p> |
696 | <dl> |
772 | <dl> |
697 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
773 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
698 | <dt>ev_check_init (ev_check *, callback)</dt> |
774 | <dt>ev_check_init (ev_check *, callback)</dt> |
699 | <dd> |
775 | <dd> |
700 | <p>Initialises and configures the prepare or check watcher - they have no |
776 | <p>Initialises and configures the prepare or check watcher - they have no |
… | |
… | |
711 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
787 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
712 | <dd> |
788 | <dd> |
713 | <p>This function combines a simple timer and an I/O watcher, calls your |
789 | <p>This function combines a simple timer and an I/O watcher, calls your |
714 | callback on whichever event happens first and automatically stop both |
790 | callback on whichever event happens first and automatically stop both |
715 | watchers. This is useful if you want to wait for a single event on an fd |
791 | watchers. This is useful if you want to wait for a single event on an fd |
716 | or timeout without havign to allocate/configure/start/stop/free one or |
792 | or timeout without having to allocate/configure/start/stop/free one or |
717 | more watchers yourself.</p> |
793 | more watchers yourself.</p> |
718 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
794 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
719 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
795 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
720 | <code>events</code> set will be craeted and started.</p> |
796 | <code>events</code> set will be craeted and started.</p> |
721 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
797 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
722 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
798 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
723 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
799 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
724 | dubious value.</p> |
800 | dubious value.</p> |
725 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
801 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
726 | passed an events set like normal event callbacks (with a combination of |
802 | passed an <code>revents</code> set like normal event callbacks (a combination of |
727 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
803 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
728 | value passed to <code>ev_once</code>:</p> |
804 | value passed to <code>ev_once</code>:</p> |
729 | <pre> static void stdin_ready (int revents, void *arg) |
805 | <pre> static void stdin_ready (int revents, void *arg) |
730 | { |
806 | { |
731 | if (revents & EV_TIMEOUT) |
807 | if (revents & EV_TIMEOUT) |
… | |
… | |
754 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
830 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
755 | </dd> |
831 | </dd> |
756 | </dl> |
832 | </dl> |
757 | |
833 | |
758 | </div> |
834 | </div> |
|
|
835 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
|
|
836 | <div id="LIBEVENT_EMULATION_CONTENT"> |
|
|
837 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
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|
838 | emulate the internals of libevent, so here are some usage hints:</p> |
|
|
839 | <dl> |
|
|
840 | <dt>* Use it by including <event.h>, as usual.</dt> |
|
|
841 | <dt>* The following members are fully supported: ev_base, ev_callback, |
|
|
842 | ev_arg, ev_fd, ev_res, ev_events.</dt> |
|
|
843 | <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is |
|
|
844 | maintained by libev, it does not work exactly the same way as in libevent (consider |
|
|
845 | it a private API).</dt> |
|
|
846 | <dt>* Priorities are not currently supported. Initialising priorities |
|
|
847 | will fail and all watchers will have the same priority, even though there |
|
|
848 | is an ev_pri field.</dt> |
|
|
849 | <dt>* Other members are not supported.</dt> |
|
|
850 | <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need |
|
|
851 | to use the libev header file and library.</dt> |
|
|
852 | </dl> |
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|
853 | |
|
|
854 | </div> |
|
|
855 | <h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> |
|
|
856 | <div id="C_SUPPORT_CONTENT"> |
|
|
857 | <p>TBD.</p> |
|
|
858 | |
|
|
859 | </div> |
759 | <h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> |
860 | <h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> |
760 | <div id="AUTHOR_CONTENT"> |
861 | <div id="AUTHOR_CONTENT"> |
761 | <p>Marc Lehmann <libev@schmorp.de>.</p> |
862 | <p>Marc Lehmann <libev@schmorp.de>.</p> |
762 | |
863 | |
763 | </div> |
864 | </div> |