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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" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 12 09:57:02 2007" /> 9 <meta name="created" content="Fri Nov 23 06:14:47 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
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>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
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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99to the double type in C.</p> 101to 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">
106<p>These functions can be called anytime, even before initialising the
107library 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
112<code>ev_now</code> function is usually faster and also often returns the timestamp
113you 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
… …
116version of the library your program was compiled against.</p> 122version of the library your program was compiled against.</p>
117 <p>Usually, it's a good idea to terminate if the major versions mismatch, 123 <p>Usually, it's a good idea to terminate if the major versions mismatch,
118as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
119compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
120not a problem.</p> 126not a problem.</p>
127 </dd>
128 <dt>unsigned int ev_supported_backends ()</dt>
129 <dd>
130 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
131value) compiled into this binary of libev (independent of their
132availability on the system you are running on). See <code>ev_default_loop</code> for
133a description of the set values.</p>
134 </dd>
135 <dt>unsigned int ev_recommended_backends ()</dt>
136 <dd>
137 <p>Return the set of all backends compiled into this binary of libev and also
138recommended for this platform. This set is often smaller than the one
139returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
140most BSDs and will not be autodetected unless you explicitly request it
141(assuming you know what you are doing). This is the set of backends that
142<code>EVFLAG_AUTO</code> will probe for.</p>
121 </dd> 143 </dd>
122 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
123 <dd> 145 <dd>
124 <p>Sets the allocation function to use (the prototype is similar to the 146 <p>Sets the allocation function to use (the prototype is similar to the
125realloc C function, the semantics are identical). It is used to allocate 147realloc C function, the semantics are identical). It is used to allocate
… …
158 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 180 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159 <dd> 181 <dd>
160 <p>This will initialise the default event loop if it hasn't been initialised 182 <p>This will initialise the default event loop if it hasn't been initialised
161yet and return it. If the default loop could not be initialised, returns 183yet and return it. If the default loop could not be initialised, returns
162false. If it already was initialised it simply returns it (and ignores the 184false. If it already was initialised it simply returns it (and ignores the
163flags).</p> 185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
164 <p>If you don't know what event loop to use, use the one returned from this 186 <p>If you don't know what event loop to use, use the one returned from this
165function.</p> 187function.</p>
166 <p>The flags argument can be used to specify special behaviour or specific 188 <p>The flags argument can be used to specify special behaviour or specific
167backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 189backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p>
168 <p>It supports the following flags:</p> 190 <p>It supports the following flags:</p>
169 <p> 191 <p>
170 <dl> 192 <dl>
171 <dt><code>EVFLAG_AUTO</code></dt> 193 <dt><code>EVFLAG_AUTO</code></dt>
172 <dd> 194 <dd>
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180<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 202<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181override the flags completely if it is found in the environment. This is 203override the flags completely if it is found in the environment. This is
182useful to try out specific backends to test their performance, or to work 204useful to try out specific backends to test their performance, or to work
183around bugs.</p> 205around bugs.</p>
184 </dd> 206 </dd>
185 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> 207 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
186 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> 208 <dd>
187 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> 209 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
188 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> 210libev tries to roll its own fd_set with no limits on the number of fds,
189 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> 211but if that fails, expect a fairly low limit on the number of fds when
190 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> 212using this backend. It doesn't scale too well (O(highest_fd)), but its usually
213the fastest backend for a low number of fds.</p>
191 <dd> 214 </dd>
192 <p>If one or more of these are ored into the flags value, then only these 215 <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
193backends will be tried (in the reverse order as given here). If one are 216 <dd>
194specified, any backend will do.</p> 217 <p>And this is your standard poll(2) backend. It's more complicated than
218select, but handles sparse fds better and has no artificial limit on the
219number of fds you can use (except it will slow down considerably with a
220lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
221 </dd>
222 <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
223 <dd>
224 <p>For few fds, this backend is a bit little slower than poll and select,
225but it scales phenomenally better. While poll and select usually scale like
226O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
227either O(1) or O(active_fds).</p>
228 <p>While stopping and starting an I/O watcher in the same iteration will
229result in some caching, there is still a syscall per such incident
230(because the fd could point to a different file description now), so its
231best to avoid that. Also, dup()ed file descriptors might not work very
232well if you register events for both fds.</p>
233 </dd>
234 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
235 <dd>
236 <p>Kqueue deserves special mention, as at the time of this writing, it
237was broken on all BSDs except NetBSD (usually it doesn't work with
238anything but sockets and pipes, except on Darwin, where of course its
239completely useless). For this reason its not being &quot;autodetected&quot; unless
240you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>
241 <p>It scales in the same way as the epoll backend, but the interface to the
242kernel is more efficient (which says nothing about its actual speed, of
243course). While starting and stopping an I/O watcher does not cause an
244extra syscall as with epoll, it still adds up to four event changes per
245incident, so its best to avoid that.</p>
246 </dd>
247 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
248 <dd>
249 <p>This is not implemented yet (and might never be).</p>
250 </dd>
251 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
252 <dd>
253 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
254it's really slow, but it still scales very well (O(active_fds)).</p>
255 </dd>
256 <dt><code>EVBACKEND_ALL</code></dt>
257 <dd>
258 <p>Try all backends (even potentially broken ones that wouldn't be tried
259with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
260<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
195 </dd> 261 </dd>
196 </dl> 262 </dl>
197 </p> 263 </p>
264 <p>If one or more of these are ored into the flags value, then only these
265backends will be tried (in the reverse order as given here). If none are
266specified, most compiled-in backend will be tried, usually in reverse
267order of their flag values :)</p>
198 </dd> 268 </dd>
199 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 269 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200 <dd> 270 <dd>
201 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 271 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
202always distinct from the default loop. Unlike the default loop, it cannot 272always distinct from the default loop. Unlike the default loop, it cannot
… …
218 <dd> 288 <dd>
219 <p>This function reinitialises the kernel state for backends that have 289 <p>This function reinitialises the kernel state for backends that have
220one. Despite the name, you can call it anytime, but it makes most sense 290one. Despite the name, you can call it anytime, but it makes most sense
221after forking, in either the parent or child process (or both, but that 291after forking, in either the parent or child process (or both, but that
222again makes little sense).</p> 292again makes little sense).</p>
223 <p>You <i>must</i> call this function after forking if and only if you want to 293 <p>You <i>must</i> call this function in the child process after forking if and
224use the event library in both processes. If you just fork+exec, you don't 294only if you want to use the event library in both processes. If you just
225have to call it.</p> 295fork+exec, you don't have to call it.</p>
226 <p>The function itself is quite fast and it's usually not a problem to call 296 <p>The function itself is quite fast and it's usually not a problem to call
227it just in case after a fork. To make this easy, the function will fit in 297it just in case after a fork. To make this easy, the function will fit in
228quite nicely into a call to <code>pthread_atfork</code>:</p> 298quite nicely into a call to <code>pthread_atfork</code>:</p>
229<pre> pthread_atfork (0, 0, ev_default_fork); 299<pre> pthread_atfork (0, 0, ev_default_fork);
230 300
231</pre> 301</pre>
302 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
303without calling this function, so if you force one of those backends you
304do not need to care.</p>
232 </dd> 305 </dd>
233 <dt>ev_loop_fork (loop)</dt> 306 <dt>ev_loop_fork (loop)</dt>
234 <dd> 307 <dd>
235 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 308 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
236<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 309<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
237after fork, and how you do this is entirely your own problem.</p> 310after fork, and how you do this is entirely your own problem.</p>
238 </dd> 311 </dd>
239 <dt>unsigned int ev_method (loop)</dt> 312 <dt>unsigned int ev_backend (loop)</dt>
240 <dd> 313 <dd>
241 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 314 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242use.</p> 315use.</p>
243 </dd> 316 </dd>
244 <dt>ev_tstamp ev_now (loop)</dt> 317 <dt>ev_tstamp ev_now (loop)</dt>
245 <dd> 318 <dd>
246 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 319 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
… …
264your process until at least one new event arrives, and will return after 337your process until at least one new event arrives, and will return after
265one iteration of the loop.</p> 338one iteration of the loop.</p>
266 <p>This flags value could be used to implement alternative looping 339 <p>This flags value could be used to implement alternative looping
267constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 340constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
268more generic mechanism.</p> 341more generic mechanism.</p>
342 <p>Here are the gory details of what ev_loop does:</p>
343<pre> 1. If there are no active watchers (reference count is zero), return.
344 2. Queue and immediately call all prepare watchers.
345 3. If we have been forked, recreate the kernel state.
346 4. Update the kernel state with all outstanding changes.
347 5. Update the &quot;event loop time&quot;.
348 6. Calculate for how long to block.
349 7. Block the process, waiting for events.
350 8. Update the &quot;event loop time&quot; and do time jump handling.
351 9. Queue all outstanding timers.
352 10. Queue all outstanding periodics.
353 11. If no events are pending now, queue all idle watchers.
354 12. Queue all check watchers.
355 13. Call all queued watchers in reverse order (i.e. check watchers first).
356 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
357 was used, return, otherwise continue with step #1.
358
359</pre>
269 </dd> 360 </dd>
270 <dt>ev_unloop (loop, how)</dt> 361 <dt>ev_unloop (loop, how)</dt>
271 <dd> 362 <dd>
272 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 363 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273has processed all outstanding events). The <code>how</code> argument must be either 364has 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 365<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> 366<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276 </dd> 367 </dd>
277 <dt>ev_ref (loop)</dt> 368 <dt>ev_ref (loop)</dt>
278 <dt>ev_unref (loop)</dt> 369 <dt>ev_unref (loop)</dt>
279 <dd> 370 <dd>
… …
326with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 417with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
327*)</code>), and you can stop watching for events at any time by calling the 418*)</code>), and you can stop watching for events at any time by calling the
328corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 419corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
329<p>As long as your watcher is active (has been started but not stopped) you 420<p>As long as your watcher is active (has been started but not stopped) you
330must not touch the values stored in it. Most specifically you must never 421must not touch the values stored in it. Most specifically you must never
331reinitialise it or call its set method.</p> 422reinitialise it or call its set macro.</p>
332<p>You can check whether an event is active by calling the <code>ev_is_active 423<p>You can check whether an event is active by calling the <code>ev_is_active
333(watcher *)</code> macro. To see whether an event is outstanding (but the 424(watcher *)</code> macro. To see whether an event is outstanding (but the
334callback for it has not been called yet) you can use the <code>ev_is_pending 425callback for it has not been called yet) you can use the <code>ev_is_pending
335(watcher *)</code> macro.</p> 426(watcher *)</code> macro.</p>
336<p>Each and every callback receives the event loop pointer as first, the 427<p>Each and every callback receives the event loop pointer as first, the
… …
438<p>I/O watchers check whether a file descriptor is readable or writable 529<p>I/O watchers check whether a file descriptor is readable or writable
439in each iteration of the event loop (This behaviour is called 530in each iteration of the event loop (This behaviour is called
440level-triggering because you keep receiving events as long as the 531level-triggering because you keep receiving events as long as the
441condition persists. Remember you can stop the watcher if you don't want to 532condition persists. Remember you can stop the watcher if you don't want to
442act on the event and neither want to receive future events).</p> 533act 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 534<p>In general you can register as many read and/or write event watchers per
444fd as you want (as long as you don't confuse yourself). Setting all file 535fd as you want (as long as you don't confuse yourself). Setting all file
445descriptors to non-blocking mode is also usually a good idea (but not 536descriptors to non-blocking mode is also usually a good idea (but not
446required if you know what you are doing).</p> 537required if you know what you are doing).</p>
447<p>You have to be careful with dup'ed file descriptors, though. Some backends 538<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 539(the linux epoll backend is a notable example) cannot handle dup'ed file
449descriptors correctly if you register interest in two or more fds pointing 540descriptors correctly if you register interest in two or more fds pointing
450to the same file/socket etc. description.</p> 541to the same underlying file/socket etc. description (that is, they share
542the same underlying &quot;file open&quot;).</p>
451<p>If you must do this, then force the use of a known-to-be-good backend 543<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 544(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453EVMETHOD_POLL).</p> 545<code>EVBACKEND_POLL</code>).</p>
454<dl> 546<dl>
455 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 547 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 548 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
457 <dd> 549 <dd>
458 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 550 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
… …
465<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 557<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"> 558<div id="code_ev_timer_code_relative_and_opti-2">
467<p>Timer watchers are simple relative timers that generate an event after a 559<p>Timer watchers are simple relative timers that generate an event after a
468given time, and optionally repeating in regular intervals after that.</p> 560given 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 561<p>The timers are based on real time, that is, if you register an event that
470times out after an hour and youreset your system clock to last years 562times out after an hour and you reset your system clock to last years
471time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 563time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
472detecting time jumps is hard, and soem inaccuracies are unavoidable (the 564detecting time jumps is hard, and some inaccuracies are unavoidable (the
473monotonic clock option helps a lot here).</p> 565monotonic clock option helps a lot here).</p>
474<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 566<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475time. This is usually the right thing as this timestamp refers to the time 567time. This is usually the right thing as this timestamp refers to the time
476of the event triggering whatever timeout you are modifying/starting. If 568of the event triggering whatever timeout you are modifying/starting. If
477you suspect event processing to be delayed and you *need* to base the timeout 569you suspect event processing to be delayed and you <i>need</i> to base the timeout
478ion the current time, use something like this to adjust for this:</p> 570on the current time, use something like this to adjust for this:</p>
479<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.); 571<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
480 572
481</pre> 573</pre>
574<p>The callback is guarenteed to be invoked only when its timeout has passed,
575but if multiple timers become ready during the same loop iteration then
576order of execution is undefined.</p>
482<dl> 577<dl>
483 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 578 <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> 579 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485 <dd> 580 <dd>
486 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 581 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
488timer will automatically be configured to trigger again <code>repeat</code> seconds 583timer will automatically be configured to trigger again <code>repeat</code> seconds
489later, again, and again, until stopped manually.</p> 584later, again, and again, until stopped manually.</p>
490 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 585 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
491configure a timer to trigger every 10 seconds, then it will trigger at 586configure a timer to trigger every 10 seconds, then it will trigger at
492exactly 10 second intervals. If, however, your program cannot keep up with 587exactly 10 second intervals. If, however, your program cannot keep up with
493the timer (ecause it takes longer than those 10 seconds to do stuff) the 588the timer (because it takes longer than those 10 seconds to do stuff) the
494timer will not fire more than once per event loop iteration.</p> 589timer will not fire more than once per event loop iteration.</p>
495 </dd> 590 </dd>
496 <dt>ev_timer_again (loop)</dt> 591 <dt>ev_timer_again (loop)</dt>
497 <dd> 592 <dd>
498 <p>This will act as if the timer timed out and restart it again if it is 593 <p>This will act as if the timer timed out and restart it again if it is
… …
524take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 619take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525roughly 10 seconds later and of course not if you reset your system time 620roughly 10 seconds later and of course not if you reset your system time
526again).</p> 621again).</p>
527<p>They can also be used to implement vastly more complex timers, such as 622<p>They can also be used to implement vastly more complex timers, such as
528triggering an event on eahc midnight, local time.</p> 623triggering an event on eahc midnight, local time.</p>
624<p>As with timers, the callback is guarenteed to be invoked only when the
625time (<code>at</code>) has been passed, but if multiple periodic timers become ready
626during the same loop iteration then order of execution is undefined.</p>
529<dl> 627<dl>
530 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 628 <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> 629 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532 <dd> 630 <dd>
533 <p>Lots of arguments, lets sort it out... There are basically three modes of 631 <p>Lots of arguments, lets sort it out... There are basically three modes of
534operation, and we will explain them from simplest to complex:</p> 632operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539 <p> 633 <p>
540 <dl> 634 <dl>
541 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 635 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542 <dd> 636 <dd>
543 <p>In this configuration the watcher triggers an event at the wallclock time 637 <p>In this configuration the watcher triggers an event at the wallclock time
… …
567 <dd> 661 <dd>
568 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 662 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
569ignored. Instead, each time the periodic watcher gets scheduled, the 663ignored. Instead, each time the periodic watcher gets scheduled, the
570reschedule callback will be called with the watcher as first, and the 664reschedule callback will be called with the watcher as first, and the
571current time as second argument.</p> 665current time as second argument.</p>
572 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 666 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573periodic watcher, ever, or make any event loop modifications</i>. If you need 667ever, or make any event loop modifications</i>. If you need to stop it,
574to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> 668return <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 669starting a prepare watcher).</p>
576passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 670 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
578ev_tstamp now)</code>, e.g.:</p> 671ev_tstamp now)</code>, e.g.:</p>
579<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 672<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580 { 673 {
581 return now + 60.; 674 return now + 60.;
… …
584</pre> 677</pre>
585 <p>It must return the next time to trigger, based on the passed time value 678 <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 679(that is, the lowest time value larger than to the second argument). It
587will usually be called just before the callback will be triggered, but 680will usually be called just before the callback will be triggered, but
588might be called at other times, too.</p> 681might be called at other times, too.</p>
682 <p>NOTE: <i>This callback must always return a time that is later than the
683passed <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 684 <p>This can be used to create very complex timers, such as a timer that
590triggers on each midnight, local time. To do this, you would calculate the 685triggers on each midnight, local time. To do this, you would calculate the
591next midnight after <code>now</code> and return the timestamp value for this. How you do this 686next midnight after <code>now</code> and return the timestamp value for this. How
592is, again, up to you (but it is not trivial).</p> 687you do this is, again, up to you (but it is not trivial, which is the main
688reason I omitted it as an example).</p>
593 </dd> 689 </dd>
594 </dl> 690 </dl>
595 </p> 691 </p>
596 </dd> 692 </dd>
597 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 693 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
670 766
671</div> 767</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> 768<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"> 769<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: 770<p>Prepare and check watchers are usually (but not always) used in tandem:
675Prepare watchers get invoked before the process blocks and check watchers 771prepare watchers get invoked before the process blocks and check watchers
676afterwards.</p> 772afterwards.</p>
677<p>Their main purpose is to integrate other event mechanisms into libev. This 773<p>Their main purpose is to integrate other event mechanisms into libev. This
678could be used, for example, to track variable changes, implement your own 774could be used, for example, to track variable changes, implement your own
679watchers, integrate net-snmp or a coroutine library and lots more.</p> 775watchers, 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 776<p>This is done by examining in each prepare call which file descriptors need
681to be watched by the other library, registering <code>ev_io</code> watchers for 777to be watched by the other library, registering <code>ev_io</code> watchers for
682them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 778them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683provide just this functionality). Then, in the check watcher you check for 779provide just this functionality). Then, in the check watcher you check for
684any events that occured (by checking the pending status of all watchers 780any events that occured (by checking the pending status of all watchers
685and stopping them) and call back into the library. The I/O and timer 781and stopping them) and call back into the library. The I/O and timer
686callbacks will never actually be called (but must be valid neverthelles, 782callbacks will never actually be called (but must be valid nevertheless,
687because you never know, you know?).</p> 783because you never know, you know?).</p>
688<p>As another example, the Perl Coro module uses these hooks to integrate 784<p>As another example, the Perl Coro module uses these hooks to integrate
689coroutines into libev programs, by yielding to other active coroutines 785coroutines into libev programs, by yielding to other active coroutines
690during each prepare and only letting the process block if no coroutines 786during each prepare and only letting the process block if no coroutines
691are ready to run (its actually more complicated, it only runs coroutines 787are ready to run (it's actually more complicated: it only runs coroutines
692with priority higher than the event loop and one lower priority once, 788with priority higher than or equal to the event loop and one coroutine
693using idle watchers to keep the event loop from blocking if lower-priority 789of lower priority, but only once, using idle watchers to keep the event
694coroutines exist, thus mapping low-priority coroutines to idle/background 790loop from blocking if lower-priority coroutines are active, thus mapping
695tasks).</p> 791low-priority coroutines to idle/background tasks).</p>
696<dl> 792<dl>
697 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 793 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
698 <dt>ev_check_init (ev_check *, callback)</dt> 794 <dt>ev_check_init (ev_check *, callback)</dt>
699 <dd> 795 <dd>
700 <p>Initialises and configures the prepare or check watcher - they have no 796 <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> 807 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712 <dd> 808 <dd>
713 <p>This function combines a simple timer and an I/O watcher, calls your 809 <p>This function combines a simple timer and an I/O watcher, calls your
714callback on whichever event happens first and automatically stop both 810callback on whichever event happens first and automatically stop both
715watchers. This is useful if you want to wait for a single event on an fd 811watchers. This is useful if you want to wait for a single event on an fd
716or timeout without havign to allocate/configure/start/stop/free one or 812or timeout without having to allocate/configure/start/stop/free one or
717more watchers yourself.</p> 813more watchers yourself.</p>
718 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events 814 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and 815is 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> 816<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 817 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and 818started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of 819repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724dubious value.</p> 820dubious value.</p>
725 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets 821 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
726passed an events set like normal event callbacks (with a combination of 822passed 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> 823<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728value passed to <code>ev_once</code>:</p> 824value passed to <code>ev_once</code>:</p>
729<pre> static void stdin_ready (int revents, void *arg) 825<pre> static void stdin_ready (int revents, void *arg)
730 { 826 {
731 if (revents &amp; EV_TIMEOUT) 827 if (revents &amp; EV_TIMEOUT)
… …
754 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 850 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
755 </dd> 851 </dd>
756</dl> 852</dl>
757 853
758</div> 854</div>
855<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
856<div id="LIBEVENT_EMULATION_CONTENT">
857<p>Libev offers a compatibility emulation layer for libevent. It cannot
858emulate the internals of libevent, so here are some usage hints:</p>
859<dl>
860 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
861 <dt>* The following members are fully supported: ev_base, ev_callback,
862ev_arg, ev_fd, ev_res, ev_events.</dt>
863 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
864maintained by libev, it does not work exactly the same way as in libevent (consider
865it a private API).</dt>
866 <dt>* Priorities are not currently supported. Initialising priorities
867will fail and all watchers will have the same priority, even though there
868is an ev_pri field.</dt>
869 <dt>* Other members are not supported.</dt>
870 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
871to use the libev header file and library.</dt>
872</dl>
873
874</div>
875<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
876<div id="C_SUPPORT_CONTENT">
877<p>TBD.</p>
878
879</div>
759<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 880<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760<div id="AUTHOR_CONTENT"> 881<div id="AUTHOR_CONTENT">
761<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 882<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
762 883
763</div> 884</div>

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