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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;" />
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9 <meta name="created" content="Mon Nov 12 09:58:24 2007" /> 9 <meta name="created" content="Fri Nov 23 16:26:06 2007" />
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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
142libev will probe for if you specify no backends explicitly.</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 <code>EVFLAG_AUTO</code>).</p>
168 <p>It supports the following flags:</p> 190 <p>The following flags are supported:</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>
173 <p>The default flags value. Use this if you have no clue (it's the right 195 <p>The default flags value. Use this if you have no clue (it's the right
… …
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 <p>Please note that epoll sometimes generates spurious notifications, so you
234need to use non-blocking I/O or other means to avoid blocking when no data
235(or space) is available.</p>
236 </dd>
237 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
238 <dd>
239 <p>Kqueue deserves special mention, as at the time of this writing, it
240was broken on all BSDs except NetBSD (usually it doesn't work with
241anything but sockets and pipes, except on Darwin, where of course its
242completely useless). For this reason its not being &quot;autodetected&quot;
243unless you explicitly specify it explicitly in the flags (i.e. using
244<code>EVBACKEND_KQUEUE</code>).</p>
245 <p>It scales in the same way as the epoll backend, but the interface to the
246kernel is more efficient (which says nothing about its actual speed, of
247course). While starting and stopping an I/O watcher does not cause an
248extra syscall as with epoll, it still adds up to four event changes per
249incident, so its best to avoid that.</p>
250 </dd>
251 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
252 <dd>
253 <p>This is not implemented yet (and might never be).</p>
254 </dd>
255 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
256 <dd>
257 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
258it's really slow, but it still scales very well (O(active_fds)).</p>
259 <p>Please note that solaris ports can result in a lot of spurious
260notifications, so you need to use non-blocking I/O or other means to avoid
261blocking when no data (or space) is available.</p>
262 </dd>
263 <dt><code>EVBACKEND_ALL</code></dt>
264 <dd>
265 <p>Try all backends (even potentially broken ones that wouldn't be tried
266with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
267<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
195 </dd> 268 </dd>
196 </dl> 269 </dl>
197 </p> 270 </p>
271 <p>If one or more of these are ored into the flags value, then only these
272backends will be tried (in the reverse order as given here). If none are
273specified, most compiled-in backend will be tried, usually in reverse
274order of their flag values :)</p>
275 <p>The most typical usage is like this:</p>
276<pre> if (!ev_default_loop (0))
277 fatal (&quot;could not initialise libev, bad $LIBEV_FLAGS in environment?&quot;);
278
279</pre>
280 <p>Restrict libev to the select and poll backends, and do not allow
281environment settings to be taken into account:</p>
282<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
283
284</pre>
285 <p>Use whatever libev has to offer, but make sure that kqueue is used if
286available (warning, breaks stuff, best use only with your own private
287event loop and only if you know the OS supports your types of fds):</p>
288<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
289
290</pre>
198 </dd> 291 </dd>
199 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 292 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200 <dd> 293 <dd>
201 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 294 <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 295always distinct from the default loop. Unlike the default loop, it cannot
… …
218 <dd> 311 <dd>
219 <p>This function reinitialises the kernel state for backends that have 312 <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 313one. 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 314after forking, in either the parent or child process (or both, but that
222again makes little sense).</p> 315again makes little sense).</p>
223 <p>You <i>must</i> call this function after forking if and only if you want to 316 <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 317only if you want to use the event library in both processes. If you just
225have to call it.</p> 318fork+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 319 <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 320it 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> 321quite nicely into a call to <code>pthread_atfork</code>:</p>
229<pre> pthread_atfork (0, 0, ev_default_fork); 322<pre> pthread_atfork (0, 0, ev_default_fork);
230 323
231</pre> 324</pre>
325 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
326without calling this function, so if you force one of those backends you
327do not need to care.</p>
232 </dd> 328 </dd>
233 <dt>ev_loop_fork (loop)</dt> 329 <dt>ev_loop_fork (loop)</dt>
234 <dd> 330 <dd>
235 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 331 <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 332<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> 333after fork, and how you do this is entirely your own problem.</p>
238 </dd> 334 </dd>
239 <dt>unsigned int ev_method (loop)</dt> 335 <dt>unsigned int ev_backend (loop)</dt>
240 <dd> 336 <dd>
241 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 337 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242use.</p> 338use.</p>
243 </dd> 339 </dd>
244 <dt>ev_tstamp ev_now (loop)</dt> 340 <dt>ev_tstamp ev_now (loop)</dt>
245 <dd> 341 <dd>
246 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 342 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
… …
252 <dt>ev_loop (loop, int flags)</dt> 348 <dt>ev_loop (loop, int flags)</dt>
253 <dd> 349 <dd>
254 <p>Finally, this is it, the event handler. This function usually is called 350 <p>Finally, this is it, the event handler. This function usually is called
255after you initialised all your watchers and you want to start handling 351after you initialised all your watchers and you want to start handling
256events.</p> 352events.</p>
257 <p>If the flags argument is specified as 0, it will not return until either 353 <p>If the flags argument is specified as <code>0</code>, it will not return until
258no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 354either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
259 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 355 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
260those events and any outstanding ones, but will not block your process in 356those events and any outstanding ones, but will not block your process in
261case there are no events and will return after one iteration of the loop.</p> 357case there are no events and will return after one iteration of the loop.</p>
262 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 358 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
263neccessary) and will handle those and any outstanding ones. It will block 359neccessary) and will handle those and any outstanding ones. It will block
264your process until at least one new event arrives, and will return after 360your process until at least one new event arrives, and will return after
265one iteration of the loop.</p> 361one iteration of the loop. This is useful if you are waiting for some
266 <p>This flags value could be used to implement alternative looping 362external event in conjunction with something not expressible using other
267constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 363libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268more generic mechanism.</p> 364usually a better approach for this kind of thing.</p>
365 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
366<pre> * If there are no active watchers (reference count is zero), return.
367 - Queue prepare watchers and then call all outstanding watchers.
368 - If we have been forked, recreate the kernel state.
369 - Update the kernel state with all outstanding changes.
370 - Update the &quot;event loop time&quot;.
371 - Calculate for how long to block.
372 - Block the process, waiting for any events.
373 - Queue all outstanding I/O (fd) events.
374 - Update the &quot;event loop time&quot; and do time jump handling.
375 - Queue all outstanding timers.
376 - Queue all outstanding periodics.
377 - If no events are pending now, queue all idle watchers.
378 - Queue all check watchers.
379 - Call all queued watchers in reverse order (i.e. check watchers first).
380 Signals and child watchers are implemented as I/O watchers, and will
381 be handled here by queueing them when their watcher gets executed.
382 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
383 were used, return, otherwise continue with step *.
384
385</pre>
269 </dd> 386 </dd>
270 <dt>ev_unloop (loop, how)</dt> 387 <dt>ev_unloop (loop, how)</dt>
271 <dd> 388 <dd>
272 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 389 <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 390has 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 391<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> 392<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276 </dd> 393 </dd>
277 <dt>ev_ref (loop)</dt> 394 <dt>ev_ref (loop)</dt>
278 <dt>ev_unref (loop)</dt> 395 <dt>ev_unref (loop)</dt>
279 <dd> 396 <dd>
… …
326with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 443with 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 444*)</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> 445corresponding 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 446<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 447must not touch the values stored in it. Most specifically you must never
331reinitialise it or call its set method.</p> 448reinitialise it or call its set macro.</p>
332<p>You can check whether an event is active by calling the <code>ev_is_active 449<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 450(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 451callback for it has not been called yet) you can use the <code>ev_is_pending
335(watcher *)</code> macro.</p> 452(watcher *)</code> macro.</p>
336<p>Each and every callback receives the event loop pointer as first, the 453<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 555<p>I/O watchers check whether a file descriptor is readable or writable
439in each iteration of the event loop (This behaviour is called 556in each iteration of the event loop (This behaviour is called
440level-triggering because you keep receiving events as long as the 557level-triggering because you keep receiving events as long as the
441condition persists. Remember you can stop the watcher if you don't want to 558condition 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> 559act 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 560<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 561fd 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 562descriptors to non-blocking mode is also usually a good idea (but not
446required if you know what you are doing).</p> 563required if you know what you are doing).</p>
447<p>You have to be careful with dup'ed file descriptors, though. Some backends 564<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 565(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 566descriptors correctly if you register interest in two or more fds pointing
450to the same file/socket etc. description.</p> 567to the same underlying file/socket etc. description (that is, they share
568the 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 569<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 570(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453EVMETHOD_POLL).</p> 571<code>EVBACKEND_POLL</code>).</p>
454<dl> 572<dl>
455 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 573 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 574 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
457 <dd> 575 <dd>
458 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 576 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
459events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 577events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
460EV_WRITE</code> to receive the given events.</p> 578EV_WRITE</code> to receive the given events.</p>
579 <p>Please note that most of the more scalable backend mechanisms (for example
580epoll and solaris ports) can result in spurious readyness notifications
581for file descriptors, so you practically need to use non-blocking I/O (and
582treat callback invocation as hint only), or retest separately with a safe
583interface before doing I/O (XLib can do this), or force the use of either
584<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
585problem. Also note that it is quite easy to have your callback invoked
586when the readyness condition is no longer valid even when employing
587typical ways of handling events, so its a good idea to use non-blocking
588I/O unconditionally.</p>
461 </dd> 589 </dd>
462</dl> 590</dl>
463 591
464</div> 592</div>
465<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 593<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"> 594<div id="code_ev_timer_code_relative_and_opti-2">
467<p>Timer watchers are simple relative timers that generate an event after a 595<p>Timer watchers are simple relative timers that generate an event after a
468given time, and optionally repeating in regular intervals after that.</p> 596given 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 597<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 598times 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 599time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
472detecting time jumps is hard, and soem inaccuracies are unavoidable (the 600detecting time jumps is hard, and some inaccuracies are unavoidable (the
473monotonic clock option helps a lot here).</p> 601monotonic clock option helps a lot here).</p>
474<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 602<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 603time. This is usually the right thing as this timestamp refers to the time
476of the event triggering whatever timeout you are modifying/starting. If 604of the event triggering whatever timeout you are modifying/starting. If
477you suspect event processing to be delayed and you *need* to base the timeout 605you 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> 606on 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.); 607<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
480 608
481</pre> 609</pre>
610<p>The callback is guarenteed to be invoked only when its timeout has passed,
611but if multiple timers become ready during the same loop iteration then
612order of execution is undefined.</p>
482<dl> 613<dl>
483 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 614 <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> 615 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485 <dd> 616 <dd>
486 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 617 <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 619timer will automatically be configured to trigger again <code>repeat</code> seconds
489later, again, and again, until stopped manually.</p> 620later, again, and again, until stopped manually.</p>
490 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 621 <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 622configure a timer to trigger every 10 seconds, then it will trigger at
492exactly 10 second intervals. If, however, your program cannot keep up with 623exactly 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 624the 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> 625timer will not fire more than once per event loop iteration.</p>
495 </dd> 626 </dd>
496 <dt>ev_timer_again (loop)</dt> 627 <dt>ev_timer_again (loop)</dt>
497 <dd> 628 <dd>
498 <p>This will act as if the timer timed out and restart it again if it is 629 <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 655take 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 656roughly 10 seconds later and of course not if you reset your system time
526again).</p> 657again).</p>
527<p>They can also be used to implement vastly more complex timers, such as 658<p>They can also be used to implement vastly more complex timers, such as
528triggering an event on eahc midnight, local time.</p> 659triggering an event on eahc midnight, local time.</p>
660<p>As with timers, the callback is guarenteed to be invoked only when the
661time (<code>at</code>) has been passed, but if multiple periodic timers become ready
662during the same loop iteration then order of execution is undefined.</p>
529<dl> 663<dl>
530 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 664 <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> 665 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532 <dd> 666 <dd>
533 <p>Lots of arguments, lets sort it out... There are basically three modes of 667 <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> 668operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539 <p> 669 <p>
540 <dl> 670 <dl>
541 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 671 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542 <dd> 672 <dd>
543 <p>In this configuration the watcher triggers an event at the wallclock time 673 <p>In this configuration the watcher triggers an event at the wallclock time
… …
567 <dd> 697 <dd>
568 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 698 <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 699ignored. Instead, each time the periodic watcher gets scheduled, the
570reschedule callback will be called with the watcher as first, and the 700reschedule callback will be called with the watcher as first, and the
571current time as second argument.</p> 701current time as second argument.</p>
572 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 702 <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 703ever, 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> 704return <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 705starting 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, 706 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
578ev_tstamp now)</code>, e.g.:</p> 707ev_tstamp now)</code>, e.g.:</p>
579<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 708<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580 { 709 {
581 return now + 60.; 710 return now + 60.;
… …
584</pre> 713</pre>
585 <p>It must return the next time to trigger, based on the passed time value 714 <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 715(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 716will usually be called just before the callback will be triggered, but
588might be called at other times, too.</p> 717might be called at other times, too.</p>
718 <p>NOTE: <i>This callback must always return a time that is later than the
719passed <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 720 <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 721triggers 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 722next midnight after <code>now</code> and return the timestamp value for this. How
592is, again, up to you (but it is not trivial).</p> 723you do this is, again, up to you (but it is not trivial, which is the main
724reason I omitted it as an example).</p>
593 </dd> 725 </dd>
594 </dl> 726 </dl>
595 </p> 727 </p>
596 </dd> 728 </dd>
597 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 729 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
670 802
671</div> 803</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> 804<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"> 805<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: 806<p>Prepare and check watchers are usually (but not always) used in tandem:
675Prepare watchers get invoked before the process blocks and check watchers 807prepare watchers get invoked before the process blocks and check watchers
676afterwards.</p> 808afterwards.</p>
677<p>Their main purpose is to integrate other event mechanisms into libev. This 809<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 810could be used, for example, to track variable changes, implement your own
679watchers, integrate net-snmp or a coroutine library and lots more.</p> 811watchers, 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 812<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 813to 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 814them 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 815provide just this functionality). Then, in the check watcher you check for
684any events that occured (by checking the pending status of all watchers 816any 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 817and stopping them) and call back into the library. The I/O and timer
686callbacks will never actually be called (but must be valid neverthelles, 818callbacks will never actually be called (but must be valid nevertheless,
687because you never know, you know?).</p> 819because you never know, you know?).</p>
688<p>As another example, the Perl Coro module uses these hooks to integrate 820<p>As another example, the Perl Coro module uses these hooks to integrate
689coroutines into libev programs, by yielding to other active coroutines 821coroutines into libev programs, by yielding to other active coroutines
690during each prepare and only letting the process block if no coroutines 822during each prepare and only letting the process block if no coroutines
691are ready to run (its actually more complicated, it only runs coroutines 823are ready to run (it's actually more complicated: it only runs coroutines
692with priority higher than the event loop and one lower priority once, 824with 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 825of lower priority, but only once, using idle watchers to keep the event
694coroutines exist, thus mapping low-priority coroutines to idle/background 826loop from blocking if lower-priority coroutines are active, thus mapping
695tasks).</p> 827low-priority coroutines to idle/background tasks).</p>
696<dl> 828<dl>
697 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 829 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
698 <dt>ev_check_init (ev_check *, callback)</dt> 830 <dt>ev_check_init (ev_check *, callback)</dt>
699 <dd> 831 <dd>
700 <p>Initialises and configures the prepare or check watcher - they have no 832 <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> 843 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712 <dd> 844 <dd>
713 <p>This function combines a simple timer and an I/O watcher, calls your 845 <p>This function combines a simple timer and an I/O watcher, calls your
714callback on whichever event happens first and automatically stop both 846callback 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 847watchers. 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 848or timeout without having to allocate/configure/start/stop/free one or
717more watchers yourself.</p> 849more watchers yourself.</p>
718 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events 850 <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 851is 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> 852<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 853 <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 854started. 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 855repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724dubious value.</p> 856dubious value.</p>
725 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets 857 <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 858passed 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> 859<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> 860value passed to <code>ev_once</code>:</p>
729<pre> static void stdin_ready (int revents, void *arg) 861<pre> static void stdin_ready (int revents, void *arg)
730 { 862 {
731 if (revents &amp; EV_TIMEOUT) 863 if (revents &amp; EV_TIMEOUT)
… …
754 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 886 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
755 </dd> 887 </dd>
756</dl> 888</dl>
757 889
758</div> 890</div>
891<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
892<div id="LIBEVENT_EMULATION_CONTENT">
893<p>Libev offers a compatibility emulation layer for libevent. It cannot
894emulate the internals of libevent, so here are some usage hints:</p>
895<dl>
896 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
897 <dt>* The following members are fully supported: ev_base, ev_callback,
898ev_arg, ev_fd, ev_res, ev_events.</dt>
899 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
900maintained by libev, it does not work exactly the same way as in libevent (consider
901it a private API).</dt>
902 <dt>* Priorities are not currently supported. Initialising priorities
903will fail and all watchers will have the same priority, even though there
904is an ev_pri field.</dt>
905 <dt>* Other members are not supported.</dt>
906 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
907to use the libev header file and library.</dt>
908</dl>
909
910</div>
911<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
912<div id="C_SUPPORT_CONTENT">
913<p>TBD.</p>
914
915</div>
759<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 916<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760<div id="AUTHOR_CONTENT"> 917<div id="AUTHOR_CONTENT">
761<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 918<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
762 919
763</div> 920</div>

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