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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="Fri Nov 23 16:26:06 2007" /> 9 <meta name="created" content="Sat Nov 24 08:13:46 2007" />
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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 -->
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 21<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
26<ul><li><a href="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</a></li>
26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 27<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27</ul> 28</ul>
28</li> 29</li>
29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 30<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
30<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> 31<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>
31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> 33<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> 34<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 35<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</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_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> 37<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>
38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li>
37</ul> 39</ul>
38</li> 40</li>
39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
96<div id="TIME_REPRESENTATION_CONTENT"> 98<div id="TIME_REPRESENTATION_CONTENT">
97<p>Libev represents time as a single floating point number, representing the 99<p>Libev represents time as a single floating point number, representing the
98(fractional) number of seconds since the (POSIX) epoch (somewhere near 100(fractional) number of seconds since the (POSIX) epoch (somewhere near
99the beginning of 1970, details are complicated, don't ask). This type is 101the beginning of 1970, details are complicated, don't ask). This type is
100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 102called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
101to the double type in C.</p> 103to the <code>double</code> type in C, and when you need to do any calculations on
104it, you should treat it as such.</p>
105
106
107
108
102 109
103</div> 110</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 111<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT"> 112<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the 113<p>These functions can be called anytime, even before initialising the
122version of the library your program was compiled against.</p> 129version of the library your program was compiled against.</p>
123 <p>Usually, it's a good idea to terminate if the major versions mismatch, 130 <p>Usually, it's a good idea to terminate if the major versions mismatch,
124as this indicates an incompatible change. Minor versions are usually 131as this indicates an incompatible change. Minor versions are usually
125compatible to older versions, so a larger minor version alone is usually 132compatible to older versions, so a larger minor version alone is usually
126not a problem.</p> 133not a problem.</p>
134 <p>Example: make sure we haven't accidentally been linked against the wrong
135version:</p>
136<pre> assert ((&quot;libev version mismatch&quot;,
137 ev_version_major () == EV_VERSION_MAJOR
138 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
139
140</pre>
127 </dd> 141 </dd>
128 <dt>unsigned int ev_supported_backends ()</dt> 142 <dt>unsigned int ev_supported_backends ()</dt>
129 <dd> 143 <dd>
130 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> 144 <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 145value) compiled into this binary of libev (independent of their
132availability on the system you are running on). See <code>ev_default_loop</code> for 146availability on the system you are running on). See <code>ev_default_loop</code> for
133a description of the set values.</p> 147a description of the set values.</p>
148 <p>Example: make sure we have the epoll method, because yeah this is cool and
149a must have and can we have a torrent of it please!!!11</p>
150<pre> assert ((&quot;sorry, no epoll, no sex&quot;,
151 ev_supported_backends () &amp; EVBACKEND_EPOLL));
152
153</pre>
134 </dd> 154 </dd>
135 <dt>unsigned int ev_recommended_backends ()</dt> 155 <dt>unsigned int ev_recommended_backends ()</dt>
136 <dd> 156 <dd>
137 <p>Return the set of all backends compiled into this binary of libev and also 157 <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 158recommended 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 159returned 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 160most 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 161(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> 162libev will probe for if you specify no backends explicitly.</p>
163 </dd>
164 <dt>unsigned int ev_embeddable_backends ()</dt>
165 <dd>
166 <p>Returns the set of backends that are embeddable in other event loops. This
167is the theoretical, all-platform, value. To find which backends
168might be supported on the current system, you would need to look at
169<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
170recommended ones.</p>
171 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
143 </dd> 172 </dd>
144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 173 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
145 <dd> 174 <dd>
146 <p>Sets the allocation function to use (the prototype is similar to the 175 <p>Sets the allocation function to use (the prototype is similar to the
147realloc C function, the semantics are identical). It is used to allocate 176realloc C function, the semantics are identical). It is used to allocate
149needs to be allocated, the library might abort or take some potentially 178needs to be allocated, the library might abort or take some potentially
150destructive action. The default is your system realloc function.</p> 179destructive action. The default is your system realloc function.</p>
151 <p>You could override this function in high-availability programs to, say, 180 <p>You could override this function in high-availability programs to, say,
152free some memory if it cannot allocate memory, to use a special allocator, 181free some memory if it cannot allocate memory, to use a special allocator,
153or even to sleep a while and retry until some memory is available.</p> 182or even to sleep a while and retry until some memory is available.</p>
183 <p>Example: replace the libev allocator with one that waits a bit and then
184retries: better than mine).</p>
185<pre> static void *
186 persistent_realloc (void *ptr, long size)
187 {
188 for (;;)
189 {
190 void *newptr = realloc (ptr, size);
191
192 if (newptr)
193 return newptr;
194
195 sleep (60);
196 }
197 }
198
199 ...
200 ev_set_allocator (persistent_realloc);
201
202</pre>
154 </dd> 203 </dd>
155 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 204 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
156 <dd> 205 <dd>
157 <p>Set the callback function to call on a retryable syscall error (such 206 <p>Set the callback function to call on a retryable syscall error (such
158as failed select, poll, epoll_wait). The message is a printable string 207as failed select, poll, epoll_wait). The message is a printable string
159indicating the system call or subsystem causing the problem. If this 208indicating the system call or subsystem causing the problem. If this
160callback is set, then libev will expect it to remedy the sitution, no 209callback is set, then libev will expect it to remedy the sitution, no
161matter what, when it returns. That is, libev will generally retry the 210matter what, when it returns. That is, libev will generally retry the
162requested operation, or, if the condition doesn't go away, do bad stuff 211requested operation, or, if the condition doesn't go away, do bad stuff
163(such as abort).</p> 212(such as abort).</p>
213 <p>Example: do the same thing as libev does internally:</p>
214<pre> static void
215 fatal_error (const char *msg)
216 {
217 perror (msg);
218 abort ();
219 }
220
221 ...
222 ev_set_syserr_cb (fatal_error);
223
224</pre>
164 </dd> 225 </dd>
165</dl> 226</dl>
166 227
167</div> 228</div>
168<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 229<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
293 <dd> 354 <dd>
294 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 355 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
295always distinct from the default loop. Unlike the default loop, it cannot 356always distinct from the default loop. Unlike the default loop, it cannot
296handle signal and child watchers, and attempts to do so will be greeted by 357handle signal and child watchers, and attempts to do so will be greeted by
297undefined behaviour (or a failed assertion if assertions are enabled).</p> 358undefined behaviour (or a failed assertion if assertions are enabled).</p>
359 <p>Example: try to create a event loop that uses epoll and nothing else.</p>
360<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
361 if (!epoller)
362 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
363
364</pre>
298 </dd> 365 </dd>
299 <dt>ev_default_destroy ()</dt> 366 <dt>ev_default_destroy ()</dt>
300 <dd> 367 <dd>
301 <p>Destroys the default loop again (frees all memory and kernel state 368 <p>Destroys the default loop again (frees all memory and kernel state
302etc.). This stops all registered event watchers (by not touching them in 369etc.). This stops all registered event watchers (by not touching them in
338use.</p> 405use.</p>
339 </dd> 406 </dd>
340 <dt>ev_tstamp ev_now (loop)</dt> 407 <dt>ev_tstamp ev_now (loop)</dt>
341 <dd> 408 <dd>
342 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 409 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
343got events and started processing them. This timestamp does not change 410received events and started processing them. This timestamp does not
344as long as callbacks are being processed, and this is also the base time 411change as long as callbacks are being processed, and this is also the base
345used for relative timers. You can treat it as the timestamp of the event 412time used for relative timers. You can treat it as the timestamp of the
346occuring (or more correctly, the mainloop finding out about it).</p> 413event occuring (or more correctly, libev finding out about it).</p>
347 </dd> 414 </dd>
348 <dt>ev_loop (loop, int flags)</dt> 415 <dt>ev_loop (loop, int flags)</dt>
349 <dd> 416 <dd>
350 <p>Finally, this is it, the event handler. This function usually is called 417 <p>Finally, this is it, the event handler. This function usually is called
351after you initialised all your watchers and you want to start handling 418after you initialised all your watchers and you want to start handling
352events.</p> 419events.</p>
353 <p>If the flags argument is specified as <code>0</code>, it will not return until 420 <p>If the flags argument is specified as <code>0</code>, it will not return until
354either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 421either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
422 <p>Please note that an explicit <code>ev_unloop</code> is usually better than
423relying on all watchers to be stopped when deciding when a program has
424finished (especially in interactive programs), but having a program that
425automatically loops as long as it has to and no longer by virtue of
426relying on its watchers stopping correctly is a thing of beauty.</p>
355 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 427 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
356those events and any outstanding ones, but will not block your process in 428those events and any outstanding ones, but will not block your process in
357case there are no events and will return after one iteration of the loop.</p> 429case there are no events and will return after one iteration of the loop.</p>
358 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 430 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
359neccessary) and will handle those and any outstanding ones. It will block 431neccessary) and will handle those and any outstanding ones. It will block
381 be handled here by queueing them when their watcher gets executed. 453 be handled here by queueing them when their watcher gets executed.
382 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 454 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
383 were used, return, otherwise continue with step *. 455 were used, return, otherwise continue with step *.
384 456
385</pre> 457</pre>
458 <p>Example: queue some jobs and then loop until no events are outsanding
459anymore.</p>
460<pre> ... queue jobs here, make sure they register event watchers as long
461 ... as they still have work to do (even an idle watcher will do..)
462 ev_loop (my_loop, 0);
463 ... jobs done. yeah!
464
465</pre>
386 </dd> 466 </dd>
387 <dt>ev_unloop (loop, how)</dt> 467 <dt>ev_unloop (loop, how)</dt>
388 <dd> 468 <dd>
389 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 469 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
390has processed all outstanding events). The <code>how</code> argument must be either 470has processed all outstanding events). The <code>how</code> argument must be either
402example, libev itself uses this for its internal signal pipe: It is not 482example, libev itself uses this for its internal signal pipe: It is not
403visible to the libev user and should not keep <code>ev_loop</code> from exiting if 483visible to the libev user and should not keep <code>ev_loop</code> from exiting if
404no event watchers registered by it are active. It is also an excellent 484no event watchers registered by it are active. It is also an excellent
405way to do this for generic recurring timers or from within third-party 485way to do this for generic recurring timers or from within third-party
406libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 486libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
487 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
488running when nothing else is active.</p>
489<pre> struct dv_signal exitsig;
490 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
491 ev_signal_start (myloop, &amp;exitsig);
492 evf_unref (myloop);
493
494</pre>
495 <p>Example: for some weird reason, unregister the above signal handler again.</p>
496<pre> ev_ref (myloop);
497 ev_signal_stop (myloop, &amp;exitsig);
498
499</pre>
407 </dd> 500 </dd>
408</dl> 501</dl>
409 502
410</div> 503</div>
411<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 504<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
443with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 536with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
444*)</code>), and you can stop watching for events at any time by calling the 537*)</code>), and you can stop watching for events at any time by calling the
445corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 538corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
446<p>As long as your watcher is active (has been started but not stopped) you 539<p>As long as your watcher is active (has been started but not stopped) you
447must not touch the values stored in it. Most specifically you must never 540must not touch the values stored in it. Most specifically you must never
448reinitialise it or call its set macro.</p> 541reinitialise it or call its <code>set</code> macro.</p>
449<p>You can check whether an event is active by calling the <code>ev_is_active
450(watcher *)</code> macro. To see whether an event is outstanding (but the
451callback for it has not been called yet) you can use the <code>ev_is_pending
452(watcher *)</code> macro.</p>
453<p>Each and every callback receives the event loop pointer as first, the 542<p>Each and every callback receives the event loop pointer as first, the
454registered watcher structure as second, and a bitset of received events as 543registered watcher structure as second, and a bitset of received events as
455third argument.</p> 544third argument.</p>
456<p>The received events usually include a single bit per event type received 545<p>The received events usually include a single bit per event type received
457(you can receive multiple events at the same time). The possible bit masks 546(you can receive multiple events at the same time). The possible bit masks
506your callbacks is well-written it can just attempt the operation and cope 595your callbacks is well-written it can just attempt the operation and cope
507with the error from read() or write(). This will not work in multithreaded 596with the error from read() or write(). This will not work in multithreaded
508programs, though, so beware.</p> 597programs, though, so beware.</p>
509 </dd> 598 </dd>
510</dl> 599</dl>
600
601</div>
602<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2>
603<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2">
604<p>In the following description, <code>TYPE</code> stands for the watcher type,
605e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
606<dl>
607 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
608 <dd>
609 <p>This macro initialises the generic portion of a watcher. The contents
610of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
611the generic parts of the watcher are initialised, you <i>need</i> to call
612the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
613type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
614which rolls both calls into one.</p>
615 <p>You can reinitialise a watcher at any time as long as it has been stopped
616(or never started) and there are no pending events outstanding.</p>
617 <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
618int revents)</code>.</p>
619 </dd>
620 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
621 <dd>
622 <p>This macro initialises the type-specific parts of a watcher. You need to
623call <code>ev_init</code> at least once before you call this macro, but you can
624call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
625macro on a watcher that is active (it can be pending, however, which is a
626difference to the <code>ev_init</code> macro).</p>
627 <p>Although some watcher types do not have type-specific arguments
628(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
629 </dd>
630 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
631 <dd>
632 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
633calls into a single call. This is the most convinient method to initialise
634a watcher. The same limitations apply, of course.</p>
635 </dd>
636 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
637 <dd>
638 <p>Starts (activates) the given watcher. Only active watchers will receive
639events. If the watcher is already active nothing will happen.</p>
640 </dd>
641 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
642 <dd>
643 <p>Stops the given watcher again (if active) and clears the pending
644status. It is possible that stopped watchers are pending (for example,
645non-repeating timers are being stopped when they become pending), but
646<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
647you want to free or reuse the memory used by the watcher it is therefore a
648good idea to always call its <code>ev_TYPE_stop</code> function.</p>
649 </dd>
650 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
651 <dd>
652 <p>Returns a true value iff the watcher is active (i.e. it has been started
653and not yet been stopped). As long as a watcher is active you must not modify
654it.</p>
655 </dd>
656 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
657 <dd>
658 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
659events but its callback has not yet been invoked). As long as a watcher
660is pending (but not active) you must not call an init function on it (but
661<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
662libev (e.g. you cnanot <code>free ()</code> it).</p>
663 </dd>
664 <dt>callback = ev_cb (ev_TYPE *watcher)</dt>
665 <dd>
666 <p>Returns the callback currently set on the watcher.</p>
667 </dd>
668 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
669 <dd>
670 <p>Change the callback. You can change the callback at virtually any time
671(modulo threads).</p>
672 </dd>
673</dl>
674
675
676
677
511 678
512</div> 679</div>
513<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 680<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
514<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 681<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
515<p>Each watcher has, by default, a member <code>void *data</code> that you can change 682<p>Each watcher has, by default, a member <code>void *data</code> that you can change
546</div> 713</div>
547<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 714<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
548<div id="WATCHER_TYPES_CONTENT"> 715<div id="WATCHER_TYPES_CONTENT">
549<p>This section describes each watcher in detail, but will not repeat 716<p>This section describes each watcher in detail, but will not repeat
550information given in the last section.</p> 717information given in the last section.</p>
718
719
720
721
551 722
552</div> 723</div>
553<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 724<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
554<div id="code_ev_io_code_is_this_file_descrip-2"> 725<div id="code_ev_io_code_is_this_file_descrip-2">
555<p>I/O watchers check whether a file descriptor is readable or writable 726<p>I/O watchers check whether a file descriptor is readable or writable
586when the readyness condition is no longer valid even when employing 757when the readyness condition is no longer valid even when employing
587typical ways of handling events, so its a good idea to use non-blocking 758typical ways of handling events, so its a good idea to use non-blocking
588I/O unconditionally.</p> 759I/O unconditionally.</p>
589 </dd> 760 </dd>
590</dl> 761</dl>
762<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
763readable, but only once. Since it is likely line-buffered, you could
764attempt to read a whole line in the callback:</p>
765<pre> static void
766 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
767 {
768 ev_io_stop (loop, w);
769 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
770 }
771
772 ...
773 struct ev_loop *loop = ev_default_init (0);
774 struct ev_io stdin_readable;
775 ev_io_init (&amp;stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
776 ev_io_start (loop, &amp;stdin_readable);
777 ev_loop (loop, 0);
778
779
780
781
782</pre>
591 783
592</div> 784</div>
593<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 785<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
594<div id="code_ev_timer_code_relative_and_opti-2"> 786<div id="code_ev_timer_code_relative_and_opti-2">
595<p>Timer watchers are simple relative timers that generate an event after a 787<p>Timer watchers are simple relative timers that generate an event after a
639time you successfully read or write some data. If you go into an idle 831time you successfully read or write some data. If you go into an idle
640state where you do not expect data to travel on the socket, you can stop 832state where you do not expect data to travel on the socket, you can stop
641the timer, and again will automatically restart it if need be.</p> 833the timer, and again will automatically restart it if need be.</p>
642 </dd> 834 </dd>
643</dl> 835</dl>
836<p>Example: create a timer that fires after 60 seconds.</p>
837<pre> static void
838 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839 {
840 .. one minute over, w is actually stopped right here
841 }
842
843 struct ev_timer mytimer;
844 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
845 ev_timer_start (loop, &amp;mytimer);
846
847</pre>
848<p>Example: create a timeout timer that times out after 10 seconds of
849inactivity.</p>
850<pre> static void
851 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
852 {
853 .. ten seconds without any activity
854 }
855
856 struct ev_timer mytimer;
857 ev_timer_init (&amp;mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
858 ev_timer_again (&amp;mytimer); /* start timer */
859 ev_loop (loop, 0);
860
861 // and in some piece of code that gets executed on any &quot;activity&quot;:
862 // reset the timeout to start ticking again at 10 seconds
863 ev_timer_again (&amp;mytimer);
864
865
866
867
868</pre>
644 869
645</div> 870</div>
646<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 871<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
647<div id="code_ev_periodic_code_to_cron_or_not-2"> 872<div id="code_ev_periodic_code_to_cron_or_not-2">
648<p>Periodic watchers are also timers of a kind, but they are very versatile 873<p>Periodic watchers are also timers of a kind, but they are very versatile
732when you changed some parameters or the reschedule callback would return 957when you changed some parameters or the reschedule callback would return
733a different time than the last time it was called (e.g. in a crond like 958a different time than the last time it was called (e.g. in a crond like
734program when the crontabs have changed).</p> 959program when the crontabs have changed).</p>
735 </dd> 960 </dd>
736</dl> 961</dl>
962<p>Example: call a callback every hour, or, more precisely, whenever the
963system clock is divisible by 3600. The callback invocation times have
964potentially a lot of jittering, but good long-term stability.</p>
965<pre> static void
966 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
967 {
968 ... its now a full hour (UTC, or TAI or whatever your clock follows)
969 }
970
971 struct ev_periodic hourly_tick;
972 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
973 ev_periodic_start (loop, &amp;hourly_tick);
974
975</pre>
976<p>Example: the same as above, but use a reschedule callback to do it:</p>
977<pre> #include &lt;math.h&gt;
978
979 static ev_tstamp
980 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
981 {
982 return fmod (now, 3600.) + 3600.;
983 }
984
985 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
986
987</pre>
988<p>Example: call a callback every hour, starting now:</p>
989<pre> struct ev_periodic hourly_tick;
990 ev_periodic_init (&amp;hourly_tick, clock_cb,
991 fmod (ev_now (loop), 3600.), 3600., 0);
992 ev_periodic_start (loop, &amp;hourly_tick);
993
994
995
996
997</pre>
737 998
738</div> 999</div>
739<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1000<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
740<div id="code_ev_signal_code_signal_me_when_a-2"> 1001<div id="code_ev_signal_code_signal_me_when_a-2">
741<p>Signal watchers will trigger an event when the process receives a specific 1002<p>Signal watchers will trigger an event when the process receives a specific
755 <p>Configures the watcher to trigger on the given signal number (usually one 1016 <p>Configures the watcher to trigger on the given signal number (usually one
756of the <code>SIGxxx</code> constants).</p> 1017of the <code>SIGxxx</code> constants).</p>
757 </dd> 1018 </dd>
758</dl> 1019</dl>
759 1020
1021
1022
1023
1024
760</div> 1025</div>
761<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1026<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
762<div id="code_ev_child_code_wait_for_pid_stat-2"> 1027<div id="code_ev_child_code_wait_for_pid_stat-2">
763<p>Child watchers trigger when your process receives a SIGCHLD in response to 1028<p>Child watchers trigger when your process receives a SIGCHLD in response to
764some child status changes (most typically when a child of yours dies).</p> 1029some child status changes (most typically when a child of yours dies).</p>
772the status word (use the macros from <code>sys/wait.h</code> and see your systems 1037the status word (use the macros from <code>sys/wait.h</code> and see your systems
773<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1038<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
774process causing the status change.</p> 1039process causing the status change.</p>
775 </dd> 1040 </dd>
776</dl> 1041</dl>
1042<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1043<pre> static void
1044 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1045 {
1046 ev_unloop (loop, EVUNLOOP_ALL);
1047 }
1048
1049 struct ev_signal signal_watcher;
1050 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1051 ev_signal_start (loop, &amp;sigint_cb);
1052
1053
1054
1055
1056</pre>
777 1057
778</div> 1058</div>
779<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1059<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
780<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1060<div id="code_ev_idle_code_when_you_ve_got_no-2">
781<p>Idle watchers trigger events when there are no other events are pending 1061<p>Idle watchers trigger events when there are no other events are pending
797 <p>Initialises and configures the idle watcher - it has no parameters of any 1077 <p>Initialises and configures the idle watcher - it has no parameters of any
798kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1078kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
799believe me.</p> 1079believe me.</p>
800 </dd> 1080 </dd>
801</dl> 1081</dl>
1082<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
1083callback, free it. Alos, use no error checking, as usual.</p>
1084<pre> static void
1085 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1086 {
1087 free (w);
1088 // now do something you wanted to do when the program has
1089 // no longer asnything immediate to do.
1090 }
1091
1092 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1093 ev_idle_init (idle_watcher, idle_cb);
1094 ev_idle_start (loop, idle_cb);
1095
1096
1097
1098
1099</pre>
802 1100
803</div> 1101</div>
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> 1102<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
805<div id="code_ev_prepare_code_and_code_ev_che-2"> 1103<div id="code_ev_prepare_code_and_code_ev_che-2">
806<p>Prepare and check watchers are usually (but not always) used in tandem: 1104<p>Prepare and check watchers are usually (but not always) used in tandem:
807prepare watchers get invoked before the process blocks and check watchers 1105prepare watchers get invoked before the process blocks and check watchers
808afterwards.</p> 1106afterwards.</p>
809<p>Their main purpose is to integrate other event mechanisms into libev. This 1107<p>Their main purpose is to integrate other event mechanisms into libev and
810could be used, for example, to track variable changes, implement your own 1108their use is somewhat advanced. This could be used, for example, to track
811watchers, integrate net-snmp or a coroutine library and lots more.</p> 1109variable changes, implement your own watchers, integrate net-snmp or a
1110coroutine library and lots more.</p>
812<p>This is done by examining in each prepare call which file descriptors need 1111<p>This is done by examining in each prepare call which file descriptors need
813to be watched by the other library, registering <code>ev_io</code> watchers for 1112to be watched by the other library, registering <code>ev_io</code> watchers for
814them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1113them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
815provide just this functionality). Then, in the check watcher you check for 1114provide just this functionality). Then, in the check watcher you check for
816any events that occured (by checking the pending status of all watchers 1115any events that occured (by checking the pending status of all watchers
832 <p>Initialises and configures the prepare or check watcher - they have no 1131 <p>Initialises and configures the prepare or check watcher - they have no
833parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1132parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
834macros, but using them is utterly, utterly and completely pointless.</p> 1133macros, but using them is utterly, utterly and completely pointless.</p>
835 </dd> 1134 </dd>
836</dl> 1135</dl>
1136<p>Example: *TODO*.</p>
1137
1138
1139
1140
1141
1142</div>
1143<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
1144<div id="code_ev_embed_code_when_one_backend_-2">
1145<p>This is a rather advanced watcher type that lets you embed one event loop
1146into another (currently only <code>ev_io</code> events are supported in the embedded
1147loop, other types of watchers might be handled in a delayed or incorrect
1148fashion and must not be used).</p>
1149<p>There are primarily two reasons you would want that: work around bugs and
1150prioritise I/O.</p>
1151<p>As an example for a bug workaround, the kqueue backend might only support
1152sockets on some platform, so it is unusable as generic backend, but you
1153still want to make use of it because you have many sockets and it scales
1154so nicely. In this case, you would create a kqueue-based loop and embed it
1155into your default loop (which might use e.g. poll). Overall operation will
1156be a bit slower because first libev has to poll and then call kevent, but
1157at least you can use both at what they are best.</p>
1158<p>As for prioritising I/O: rarely you have the case where some fds have
1159to be watched and handled very quickly (with low latency), and even
1160priorities and idle watchers might have too much overhead. In this case
1161you would put all the high priority stuff in one loop and all the rest in
1162a second one, and embed the second one in the first.</p>
1163<p>As long as the watcher is active, the callback will be invoked every time
1164there might be events pending in the embedded loop. The callback must then
1165call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1166their callbacks (you could also start an idle watcher to give the embedded
1167loop strictly lower priority for example). You can also set the callback
1168to <code>0</code>, in which case the embed watcher will automatically execute the
1169embedded loop sweep.</p>
1170<p>As long as the watcher is started it will automatically handle events. The
1171callback will be invoked whenever some events have been handled. You can
1172set the callback to <code>0</code> to avoid having to specify one if you are not
1173interested in that.</p>
1174<p>Also, there have not currently been made special provisions for forking:
1175when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
1176but you will also have to stop and restart any <code>ev_embed</code> watchers
1177yourself.</p>
1178<p>Unfortunately, not all backends are embeddable, only the ones returned by
1179<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
1180portable one.</p>
1181<p>So when you want to use this feature you will always have to be prepared
1182that you cannot get an embeddable loop. The recommended way to get around
1183this is to have a separate variables for your embeddable loop, try to
1184create it, and if that fails, use the normal loop for everything:</p>
1185<pre> struct ev_loop *loop_hi = ev_default_init (0);
1186 struct ev_loop *loop_lo = 0;
1187 struct ev_embed embed;
1188
1189 // see if there is a chance of getting one that works
1190 // (remember that a flags value of 0 means autodetection)
1191 loop_lo = ev_embeddable_backends () &amp; ev_recommended_backends ()
1192 ? ev_loop_new (ev_embeddable_backends () &amp; ev_recommended_backends ())
1193 : 0;
1194
1195 // if we got one, then embed it, otherwise default to loop_hi
1196 if (loop_lo)
1197 {
1198 ev_embed_init (&amp;embed, 0, loop_lo);
1199 ev_embed_start (loop_hi, &amp;embed);
1200 }
1201 else
1202 loop_lo = loop_hi;
1203
1204</pre>
1205<dl>
1206 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1207 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1208 <dd>
1209 <p>Configures the watcher to embed the given loop, which must be
1210embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1211invoked automatically, otherwise it is the responsibility of the callback
1212to invoke it (it will continue to be called until the sweep has been done,
1213if you do not want thta, you need to temporarily stop the embed watcher).</p>
1214 </dd>
1215 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1216 <dd>
1217 <p>Make a single, non-blocking sweep over the embedded loop. This works
1218similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1219apropriate way for embedded loops.</p>
1220 </dd>
1221</dl>
1222
1223
1224
1225
837 1226
838</div> 1227</div>
839<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1228<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
840<div id="OTHER_FUNCTIONS_CONTENT"> 1229<div id="OTHER_FUNCTIONS_CONTENT">
841<p>There are some other functions of possible interest. Described. Here. Now.</p> 1230<p>There are some other functions of possible interest. Described. Here. Now.</p>
868 1257
869 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1258 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
870 1259
871</pre> 1260</pre>
872 </dd> 1261 </dd>
873 <dt>ev_feed_event (loop, watcher, int events)</dt> 1262 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
874 <dd> 1263 <dd>
875 <p>Feeds the given event set into the event loop, as if the specified event 1264 <p>Feeds the given event set into the event loop, as if the specified event
876had happened for the specified watcher (which must be a pointer to an 1265had happened for the specified watcher (which must be a pointer to an
877initialised but not necessarily started event watcher).</p> 1266initialised but not necessarily started event watcher).</p>
878 </dd> 1267 </dd>
879 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1268 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
880 <dd> 1269 <dd>
881 <p>Feed an event on the given fd, as if a file descriptor backend detected 1270 <p>Feed an event on the given fd, as if a file descriptor backend detected
882the given events it.</p> 1271the given events it.</p>
883 </dd> 1272 </dd>
884 <dt>ev_feed_signal_event (loop, int signum)</dt> 1273 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
885 <dd> 1274 <dd>
886 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1275 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1276loop!).</p>
887 </dd> 1277 </dd>
888</dl> 1278</dl>
1279
1280
1281
1282
889 1283
890</div> 1284</div>
891<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1285<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
892<div id="LIBEVENT_EMULATION_CONTENT"> 1286<div id="LIBEVENT_EMULATION_CONTENT">
893<p>Libev offers a compatibility emulation layer for libevent. It cannot 1287<p>Libev offers a compatibility emulation layer for libevent. It cannot

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