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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="Tue Nov 27 21:29:04 2007" /> 9 <meta name="created" content="Wed Dec 12 18:55:04 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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27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li> 27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
29</ul> 29</ul>
30</li> 30</li>
31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
32<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> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a>
33<ul><li><a href="#The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</a></li>
34<li><a href="#Watcher_Specific_Functions">Watcher-Specific Functions</a></li>
35</ul>
36</li>
33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 37<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a>
38<ul><li><a href="#Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</a></li>
39</ul>
40</li>
34<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> 41<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a>
42<ul><li><a href="#Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</a></li>
43</ul>
44</li>
35<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li> 45<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a>
46<ul><li><a href="#Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</a></li>
47</ul>
48</li>
36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 49<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a>
50<ul><li><a href="#Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</a></li>
51</ul>
52</li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li> 53<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a>
54<ul><li><a href="#Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</a></li>
55</ul>
56</li>
38<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> 57<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>
58<ul><li><a href="#Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</a></li>
59</ul>
60</li>
39<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> 61<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>
62<ul><li><a href="#Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</a></li>
63</ul>
64</li>
40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 65<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a>
66<ul><li><a href="#Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</a></li>
67</ul>
68</li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li> 69<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
42</ul> 70</ul>
43</li> 71</li>
44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 72<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 73<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
… …
119</pre> 147</pre>
120 148
121</div> 149</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1> 150<h1 id="DESCRIPTION">DESCRIPTION</h1>
123<div id="DESCRIPTION_CONTENT"> 151<div id="DESCRIPTION_CONTENT">
152<p>The newest version of this document is also available as a html-formatted
153web page you might find easier to navigate when reading it for the first
154time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
124<p>Libev is an event loop: you register interest in certain events (such as a 155<p>Libev is an event loop: you register interest in certain events (such as a
125file descriptor being readable or a timeout occuring), and it will manage 156file descriptor being readable or a timeout occuring), and it will manage
126these event sources and provide your program with events.</p> 157these event sources and provide your program with events.</p>
127<p>To do this, it must take more or less complete control over your process 158<p>To do this, it must take more or less complete control over your process
128(or thread) by executing the <i>event loop</i> handler, and will then 159(or thread) by executing the <i>event loop</i> handler, and will then
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133watcher.</p> 164watcher.</p>
134 165
135</div> 166</div>
136<h1 id="FEATURES">FEATURES</h1> 167<h1 id="FEATURES">FEATURES</h1>
137<div id="FEATURES_CONTENT"> 168<div id="FEATURES_CONTENT">
138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the 169<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
139bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms 170BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
140for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>), 171for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
172(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous 173with customised rescheduling (<code>ev_periodic</code>), synchronous signals
142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and 174(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
143event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, 175watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
144<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as 176<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
145file watchers (<code>ev_stat</code>) and even limited support for fork events 177file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p> 178(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this 179<p>It also is quite fast (see this
148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent 180<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
… …
181you actually want to know.</p> 213you actually want to know.</p>
182 </dd> 214 </dd>
183 <dt>int ev_version_major ()</dt> 215 <dt>int ev_version_major ()</dt>
184 <dt>int ev_version_minor ()</dt> 216 <dt>int ev_version_minor ()</dt>
185 <dd> 217 <dd>
186 <p>You can find out the major and minor version numbers of the library 218 <p>You can find out the major and minor ABI version numbers of the library
187you linked against by calling the functions <code>ev_version_major</code> and 219you linked against by calling the functions <code>ev_version_major</code> and
188<code>ev_version_minor</code>. If you want, you can compare against the global 220<code>ev_version_minor</code>. If you want, you can compare against the global
189symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 221symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
190version of the library your program was compiled against.</p> 222version of the library your program was compiled against.</p>
223 <p>These version numbers refer to the ABI version of the library, not the
224release version.</p>
191 <p>Usually, it's a good idea to terminate if the major versions mismatch, 225 <p>Usually, it's a good idea to terminate if the major versions mismatch,
192as this indicates an incompatible change. Minor versions are usually 226as this indicates an incompatible change. Minor versions are usually
193compatible to older versions, so a larger minor version alone is usually 227compatible to older versions, so a larger minor version alone is usually
194not a problem.</p> 228not a problem.</p>
195 <p>Example: Make sure we haven't accidentally been linked against the wrong 229 <p>Example: Make sure we haven't accidentally been linked against the wrong
196version.</p> 230version.</p>
197<pre> assert ((&quot;libev version mismatch&quot;, 231<pre> assert ((&quot;libev version mismatch&quot;,
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229might be supported on the current system, you would need to look at 263might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 264<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 265recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 266 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 267 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 268 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 269 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 270 <p>Sets the allocation function to use (the prototype is similar - the
237identical to the realloc C function). It is used to allocate and free 271semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 272allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 273memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 274potentially destructive action. The default is your system realloc
275function.</p>
241 <p>You could override this function in high-availability programs to, say, 276 <p>You could override this function in high-availability programs to, say,
242free some memory if it cannot allocate memory, to use a special allocator, 277free some memory if it cannot allocate memory, to use a special allocator,
243or even to sleep a while and retry until some memory is available.</p> 278or even to sleep a while and retry until some memory is available.</p>
244 <p>Example: Replace the libev allocator with one that waits a bit and then 279 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 280retries).</p>
… …
324<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 359<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
325override the flags completely if it is found in the environment. This is 360override the flags completely if it is found in the environment. This is
326useful to try out specific backends to test their performance, or to work 361useful to try out specific backends to test their performance, or to work
327around bugs.</p> 362around bugs.</p>
328 </dd> 363 </dd>
364 <dt><code>EVFLAG_FORKCHECK</code></dt>
365 <dd>
366 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
367a fork, you can also make libev check for a fork in each iteration by
368enabling this flag.</p>
369 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
370and thus this might slow down your event loop if you do a lot of loop
371iterations and little real work, but is usually not noticeable (on my
372Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
373without a syscall and thus <i>very</i> fast, but my Linux system also has
374<code>pthread_atfork</code> which is even faster).</p>
375 <p>The big advantage of this flag is that you can forget about fork (and
376forget about forgetting to tell libev about forking) when you use this
377flag.</p>
378 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
379environment variable.</p>
380 </dd>
329 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 381 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
330 <dd> 382 <dd>
331 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 383 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
332libev tries to roll its own fd_set with no limits on the number of fds, 384libev tries to roll its own fd_set with no limits on the number of fds,
333but if that fails, expect a fairly low limit on the number of fds when 385but if that fails, expect a fairly low limit on the number of fds when
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461 <dt>ev_loop_fork (loop)</dt> 513 <dt>ev_loop_fork (loop)</dt>
462 <dd> 514 <dd>
463 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 515 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
464<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 516<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
465after fork, and how you do this is entirely your own problem.</p> 517after fork, and how you do this is entirely your own problem.</p>
518 </dd>
519 <dt>unsigned int ev_loop_count (loop)</dt>
520 <dd>
521 <p>Returns the count of loop iterations for the loop, which is identical to
522the number of times libev did poll for new events. It starts at <code>0</code> and
523happily wraps around with enough iterations.</p>
524 <p>This value can sometimes be useful as a generation counter of sorts (it
525&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
526<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
466 </dd> 527 </dd>
467 <dt>unsigned int ev_backend (loop)</dt> 528 <dt>unsigned int ev_backend (loop)</dt>
468 <dd> 529 <dd>
469 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 530 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
470use.</p> 531use.</p>
… …
498one iteration of the loop. This is useful if you are waiting for some 559one iteration of the loop. This is useful if you are waiting for some
499external event in conjunction with something not expressible using other 560external event in conjunction with something not expressible using other
500libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 561libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
501usually a better approach for this kind of thing.</p> 562usually a better approach for this kind of thing.</p>
502 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 563 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
564<pre> - Before the first iteration, call any pending watchers.
503<pre> * If there are no active watchers (reference count is zero), return. 565 * If there are no active watchers (reference count is zero), return.
504 - Queue prepare watchers and then call all outstanding watchers. 566 - Queue all prepare watchers and then call all outstanding watchers.
505 - If we have been forked, recreate the kernel state. 567 - If we have been forked, recreate the kernel state.
506 - Update the kernel state with all outstanding changes. 568 - Update the kernel state with all outstanding changes.
507 - Update the &quot;event loop time&quot;. 569 - Update the &quot;event loop time&quot;.
508 - Calculate for how long to block. 570 - Calculate for how long to block.
509 - Block the process, waiting for any events. 571 - Block the process, waiting for any events.
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738 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 800 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
739 <dd> 801 <dd>
740 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 802 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
741events but its callback has not yet been invoked). As long as a watcher 803events but its callback has not yet been invoked). As long as a watcher
742is pending (but not active) you must not call an init function on it (but 804is pending (but not active) you must not call an init function on it (but
743<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 805<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
744libev (e.g. you cnanot <code>free ()</code> it).</p> 806make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
807it).</p>
745 </dd> 808 </dd>
746 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 809 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 810 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 811 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 812 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 813 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 814 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 815 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 816(modulo threads).</p>
817 </dd>
818 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
819 <dt>int ev_priority (ev_TYPE *watcher)</dt>
820 <dd>
821 <p>Set and query the priority of the watcher. The priority is a small
822integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
823(default: <code>-2</code>). Pending watchers with higher priority will be invoked
824before watchers with lower priority, but priority will not keep watchers
825from being executed (except for <code>ev_idle</code> watchers).</p>
826 <p>This means that priorities are <i>only</i> used for ordering callback
827invocation after new events have been received. This is useful, for
828example, to reduce latency after idling, or more often, to bind two
829watchers on the same event and make sure one is called first.</p>
830 <p>If you need to suppress invocation when higher priority events are pending
831you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
832 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
833pending.</p>
834 <p>The default priority used by watchers when no priority has been set is
835always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
836 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
837fine, as long as you do not mind that the priority value you query might
838or might not have been adjusted to be within valid range.</p>
839 </dd>
840 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
841 <dd>
842 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
843<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
844can deal with that fact.</p>
845 </dd>
846 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
847 <dd>
848 <p>If the watcher is pending, this function returns clears its pending status
849and returns its <code>revents</code> bitset (as if its callback was invoked). If the
850watcher isn't pending it does nothing and returns <code>0</code>.</p>
754 </dd> 851 </dd>
755</dl> 852</dl>
756 853
757 854
758 855
… …
783 struct my_io *w = (struct my_io *)w_; 880 struct my_io *w = (struct my_io *)w_;
784 ... 881 ...
785 } 882 }
786 883
787</pre> 884</pre>
788<p>More interesting and less C-conformant ways of catsing your callback type 885<p>More interesting and less C-conformant ways of casting your callback type
789have been omitted....</p> 886instead have been omitted.</p>
887<p>Another common scenario is having some data structure with multiple
888watchers:</p>
889<pre> struct my_biggy
890 {
891 int some_data;
892 ev_timer t1;
893 ev_timer t2;
894 }
790 895
896</pre>
897<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
898you need to use <code>offsetof</code>:</p>
899<pre> #include &lt;stddef.h&gt;
791 900
901 static void
902 t1_cb (EV_P_ struct ev_timer *w, int revents)
903 {
904 struct my_biggy big = (struct my_biggy *
905 (((char *)w) - offsetof (struct my_biggy, t1));
906 }
792 907
908 static void
909 t2_cb (EV_P_ struct ev_timer *w, int revents)
910 {
911 struct my_biggy big = (struct my_biggy *
912 (((char *)w) - offsetof (struct my_biggy, t2));
913 }
793 914
915
916
917
918</pre>
794 919
795</div> 920</div>
796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1> 921<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
797<div id="WATCHER_TYPES_CONTENT"> 922<div id="WATCHER_TYPES_CONTENT">
798<p>This section describes each watcher in detail, but will not repeat 923<p>This section describes each watcher in detail, but will not repeat
… …
841this situation even with a relatively standard program structure. Thus 966this situation even with a relatively standard program structure. Thus
842it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 967it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
843<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 968<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
844<p>If you cannot run the fd in non-blocking mode (for example you should not 969<p>If you cannot run the fd in non-blocking mode (for example you should not
845play around with an Xlib connection), then you have to seperately re-test 970play around with an Xlib connection), then you have to seperately re-test
846wether a file descriptor is really ready with a known-to-be good interface 971whether a file descriptor is really ready with a known-to-be good interface
847such as poll (fortunately in our Xlib example, Xlib already does this on 972such as poll (fortunately in our Xlib example, Xlib already does this on
848its own, so its quite safe to use).</p> 973its own, so its quite safe to use).</p>
974
975</div>
976<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
977<div id="The_special_problem_of_disappearing_-2">
978<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
979descriptor (either by calling <code>close</code> explicitly or by any other means,
980such as <code>dup</code>). The reason is that you register interest in some file
981descriptor, but when it goes away, the operating system will silently drop
982this interest. If another file descriptor with the same number then is
983registered with libev, there is no efficient way to see that this is, in
984fact, a different file descriptor.</p>
985<p>To avoid having to explicitly tell libev about such cases, libev follows
986the following policy: Each time <code>ev_io_set</code> is being called, libev
987will assume that this is potentially a new file descriptor, otherwise
988it is assumed that the file descriptor stays the same. That means that
989you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
990descriptor even if the file descriptor number itself did not change.</p>
991<p>This is how one would do it normally anyway, the important point is that
992the libev application should not optimise around libev but should leave
993optimisations to libev.</p>
994
995
996
997
998
999</div>
1000<h3 id="Watcher_Specific_Functions">Watcher-Specific Functions</h3>
1001<div id="Watcher_Specific_Functions_CONTENT">
849<dl> 1002<dl>
850 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 1003 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
851 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 1004 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
852 <dd> 1005 <dd>
853 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 1006 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
… …
904 1057
905</pre> 1058</pre>
906<p>The callback is guarenteed to be invoked only when its timeout has passed, 1059<p>The callback is guarenteed to be invoked only when its timeout has passed,
907but if multiple timers become ready during the same loop iteration then 1060but if multiple timers become ready during the same loop iteration then
908order of execution is undefined.</p> 1061order of execution is undefined.</p>
1062
1063</div>
1064<h3 id="Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</h3>
1065<div id="Watcher_Specific_Functions_and_Data_-2">
909<dl> 1066<dl>
910 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 1067 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
911 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 1068 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
912 <dd> 1069 <dd>
913 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 1070 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
922 </dd> 1079 </dd>
923 <dt>ev_timer_again (loop)</dt> 1080 <dt>ev_timer_again (loop)</dt>
924 <dd> 1081 <dd>
925 <p>This will act as if the timer timed out and restart it again if it is 1082 <p>This will act as if the timer timed out and restart it again if it is
926repeating. The exact semantics are:</p> 1083repeating. The exact semantics are:</p>
1084 <p>If the timer is pending, its pending status is cleared.</p>
927 <p>If the timer is started but nonrepeating, stop it.</p> 1085 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
928 <p>If the timer is repeating, either start it if necessary (with the repeat 1086 <p>If the timer is repeating, either start it if necessary (with the
929value), or reset the running timer to the repeat value.</p> 1087<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
930 <p>This sounds a bit complicated, but here is a useful and typical 1088 <p>This sounds a bit complicated, but here is a useful and typical
931example: Imagine you have a tcp connection and you want a so-called 1089example: Imagine you have a tcp connection and you want a so-called idle
932idle timeout, that is, you want to be called when there have been, 1090timeout, that is, you want to be called when there have been, say, 60
933say, 60 seconds of inactivity on the socket. The easiest way to do 1091seconds of inactivity on the socket. The easiest way to do this is to
934this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling 1092configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
935<code>ev_timer_again</code> each time you successfully read or write some data. If 1093<code>ev_timer_again</code> each time you successfully read or write some data. If
936you go into an idle state where you do not expect data to travel on the 1094you go into an idle state where you do not expect data to travel on the
937socket, you can stop the timer, and again will automatically restart it if 1095socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
938need be.</p> 1096automatically restart it if need be.</p>
939 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1097 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
940and only ever use the <code>repeat</code> value:</p> 1098altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
941<pre> ev_timer_init (timer, callback, 0., 5.); 1099<pre> ev_timer_init (timer, callback, 0., 5.);
942 ev_timer_again (loop, timer); 1100 ev_timer_again (loop, timer);
943 ... 1101 ...
944 timer-&gt;again = 17.; 1102 timer-&gt;again = 17.;
945 ev_timer_again (loop, timer); 1103 ev_timer_again (loop, timer);
946 ... 1104 ...
947 timer-&gt;again = 10.; 1105 timer-&gt;again = 10.;
948 ev_timer_again (loop, timer); 1106 ev_timer_again (loop, timer);
949 1107
950</pre> 1108</pre>
951 <p>This is more efficient then stopping/starting the timer eahc time you want 1109 <p>This is more slightly efficient then stopping/starting the timer each time
952to modify its timeout value.</p> 1110you want to modify its timeout value.</p>
953 </dd> 1111 </dd>
954 <dt>ev_tstamp repeat [read-write]</dt> 1112 <dt>ev_tstamp repeat [read-write]</dt>
955 <dd> 1113 <dd>
956 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1114 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
957or <code>ev_timer_again</code> is called and determines the next timeout (if any), 1115or <code>ev_timer_again</code> is called and determines the next timeout (if any),
… …
1001but on wallclock time (absolute time). You can tell a periodic watcher 1159but on wallclock time (absolute time). You can tell a periodic watcher
1002to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1160to trigger &quot;at&quot; some specific point in time. For example, if you tell a
1003periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1161periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
1004+ 10.</code>) and then reset your system clock to the last year, then it will 1162+ 10.</code>) and then reset your system clock to the last year, then it will
1005take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1163take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
1006roughly 10 seconds later and of course not if you reset your system time 1164roughly 10 seconds later).</p>
1007again).</p>
1008<p>They can also be used to implement vastly more complex timers, such as 1165<p>They can also be used to implement vastly more complex timers, such as
1009triggering an event on eahc midnight, local time.</p> 1166triggering an event on each midnight, local time or other, complicated,
1167rules.</p>
1010<p>As with timers, the callback is guarenteed to be invoked only when the 1168<p>As with timers, the callback is guarenteed to be invoked only when the
1011time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1169time (<code>at</code>) has been passed, but if multiple periodic timers become ready
1012during the same loop iteration then order of execution is undefined.</p> 1170during the same loop iteration then order of execution is undefined.</p>
1171
1172</div>
1173<h3 id="Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</h3>
1174<div id="Watcher_Specific_Functions_and_Data_-2">
1013<dl> 1175<dl>
1014 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1176 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
1015 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 1177 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
1016 <dd> 1178 <dd>
1017 <p>Lots of arguments, lets sort it out... There are basically three modes of 1179 <p>Lots of arguments, lets sort it out... There are basically three modes of
1018operation, and we will explain them from simplest to complex:</p> 1180operation, and we will explain them from simplest to complex:</p>
1019 <p> 1181 <p>
1020 <dl> 1182 <dl>
1021 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1183 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1022 <dd> 1184 <dd>
1023 <p>In this configuration the watcher triggers an event at the wallclock time 1185 <p>In this configuration the watcher triggers an event at the wallclock time
1024<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1186<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
1025that is, if it is to be run at January 1st 2011 then it will run when the 1187that is, if it is to be run at January 1st 2011 then it will run when the
1026system time reaches or surpasses this time.</p> 1188system time reaches or surpasses this time.</p>
1027 </dd> 1189 </dd>
1028 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1190 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1029 <dd> 1191 <dd>
1030 <p>In this mode the watcher will always be scheduled to time out at the next 1192 <p>In this mode the watcher will always be scheduled to time out at the next
1031<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1193<code>at + N * interval</code> time (for some integer N, which can also be negative)
1032of any time jumps.</p> 1194and then repeat, regardless of any time jumps.</p>
1033 <p>This can be used to create timers that do not drift with respect to system 1195 <p>This can be used to create timers that do not drift with respect to system
1034time:</p> 1196time:</p>
1035<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1197<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1036 1198
1037</pre> 1199</pre>
… …
1040full hour (UTC), or more correctly, when the system time is evenly divisible 1202full hour (UTC), or more correctly, when the system time is evenly divisible
1041by 3600.</p> 1203by 3600.</p>
1042 <p>Another way to think about it (for the mathematically inclined) is that 1204 <p>Another way to think about it (for the mathematically inclined) is that
1043<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1205<code>ev_periodic</code> will try to run the callback in this mode at the next possible
1044time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1206time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1207 <p>For numerical stability it is preferable that the <code>at</code> value is near
1208<code>ev_now ()</code> (the current time), but there is no range requirement for
1209this value.</p>
1045 </dd> 1210 </dd>
1046 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1211 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1047 <dd> 1212 <dd>
1048 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1213 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
1049ignored. Instead, each time the periodic watcher gets scheduled, the 1214ignored. Instead, each time the periodic watcher gets scheduled, the
1050reschedule callback will be called with the watcher as first, and the 1215reschedule callback will be called with the watcher as first, and the
1051current time as second argument.</p> 1216current time as second argument.</p>
1052 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1217 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
1053ever, or make any event loop modifications</i>. If you need to stop it, 1218ever, or make any event loop modifications</i>. If you need to stop it,
1054return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1219return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1055starting a prepare watcher).</p> 1220starting an <code>ev_prepare</code> watcher, which is legal).</p>
1056 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1221 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1057ev_tstamp now)</code>, e.g.:</p> 1222ev_tstamp now)</code>, e.g.:</p>
1058<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1223<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1059 { 1224 {
1060 return now + 60.; 1225 return now + 60.;
… …
1080 <dd> 1245 <dd>
1081 <p>Simply stops and restarts the periodic watcher again. This is only useful 1246 <p>Simply stops and restarts the periodic watcher again. This is only useful
1082when you changed some parameters or the reschedule callback would return 1247when you changed some parameters or the reschedule callback would return
1083a different time than the last time it was called (e.g. in a crond like 1248a different time than the last time it was called (e.g. in a crond like
1084program when the crontabs have changed).</p> 1249program when the crontabs have changed).</p>
1250 </dd>
1251 <dt>ev_tstamp offset [read-write]</dt>
1252 <dd>
1253 <p>When repeating, this contains the offset value, otherwise this is the
1254absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1255 <p>Can be modified any time, but changes only take effect when the periodic
1256timer fires or <code>ev_periodic_again</code> is being called.</p>
1085 </dd> 1257 </dd>
1086 <dt>ev_tstamp interval [read-write]</dt> 1258 <dt>ev_tstamp interval [read-write]</dt>
1087 <dd> 1259 <dd>
1088 <p>The current interval value. Can be modified any time, but changes only 1260 <p>The current interval value. Can be modified any time, but changes only
1089take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1261take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
… …
1144first watcher gets started will libev actually register a signal watcher 1316first watcher gets started will libev actually register a signal watcher
1145with the kernel (thus it coexists with your own signal handlers as long 1317with the kernel (thus it coexists with your own signal handlers as long
1146as you don't register any with libev). Similarly, when the last signal 1318as you don't register any with libev). Similarly, when the last signal
1147watcher for a signal is stopped libev will reset the signal handler to 1319watcher for a signal is stopped libev will reset the signal handler to
1148SIG_DFL (regardless of what it was set to before).</p> 1320SIG_DFL (regardless of what it was set to before).</p>
1321
1322</div>
1323<h3 id="Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</h3>
1324<div id="Watcher_Specific_Functions_and_Data_-2-2">
1149<dl> 1325<dl>
1150 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt> 1326 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt>
1151 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1327 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1152 <dd> 1328 <dd>
1153 <p>Configures the watcher to trigger on the given signal number (usually one 1329 <p>Configures the watcher to trigger on the given signal number (usually one
… …
1166</div> 1342</div>
1167<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2> 1343<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1168<div id="code_ev_child_code_watch_out_for_pro-2"> 1344<div id="code_ev_child_code_watch_out_for_pro-2">
1169<p>Child watchers trigger when your process receives a SIGCHLD in response to 1345<p>Child watchers trigger when your process receives a SIGCHLD in response to
1170some child status changes (most typically when a child of yours dies).</p> 1346some child status changes (most typically when a child of yours dies).</p>
1347
1348</div>
1349<h3 id="Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</h3>
1350<div id="Watcher_Specific_Functions_and_Data_-2-3">
1171<dl> 1351<dl>
1172 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1352 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1173 <dt>ev_child_set (ev_child *, int pid)</dt> 1353 <dt>ev_child_set (ev_child *, int pid)</dt>
1174 <dd> 1354 <dd>
1175 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 1355 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
… …
1218<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1398<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1219not exist&quot; is a status change like any other. The condition &quot;path does 1399not exist&quot; is a status change like any other. The condition &quot;path does
1220not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is 1400not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1221otherwise always forced to be at least one) and all the other fields of 1401otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p> 1402the stat buffer having unspecified contents.</p>
1403<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1404relative and your working directory changes, the behaviour is undefined.</p>
1223<p>Since there is no standard to do this, the portable implementation simply 1405<p>Since there is no standard to do this, the portable implementation simply
1224calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You 1406calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1225can specify a recommended polling interval for this case. If you specify 1407can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1408a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1227unspecified default</i> value will be used (which you can expect to be around 1409unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also 1410five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats 1411impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p> 1412usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers, 1413<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be 1414as even with OS-supported change notifications, this can be
1233resource-intensive.</p> 1415resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but 1416<p>At the time of this writing, only the Linux inotify interface is
1235if demand increases, at least a kqueue and inotify backend will be added.</p> 1417implemented (implementing kqueue support is left as an exercise for the
1418reader). Inotify will be used to give hints only and should not change the
1419semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1420to fall back to regular polling again even with inotify, but changes are
1421usually detected immediately, and if the file exists there will be no
1422polling.</p>
1423
1424</div>
1425<h3 id="Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</h3>
1426<div id="Watcher_Specific_Functions_and_Data_-2-4">
1236<dl> 1427<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1428 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1238 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> 1429 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd> 1430 <dd>
1240 <p>Configures the watcher to wait for status changes of the given 1431 <p>Configures the watcher to wait for status changes of the given
… …
1303</pre> 1494</pre>
1304 1495
1305</div> 1496</div>
1306<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1497<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1307<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1498<div id="code_ev_idle_code_when_you_ve_got_no-2">
1308<p>Idle watchers trigger events when there are no other events are pending 1499<p>Idle watchers trigger events when no other events of the same or higher
1309(prepare, check and other idle watchers do not count). That is, as long 1500priority are pending (prepare, check and other idle watchers do not
1310as your process is busy handling sockets or timeouts (or even signals, 1501count).</p>
1311imagine) it will not be triggered. But when your process is idle all idle 1502<p>That is, as long as your process is busy handling sockets or timeouts
1312watchers are being called again and again, once per event loop iteration - 1503(or even signals, imagine) of the same or higher priority it will not be
1504triggered. But when your process is idle (or only lower-priority watchers
1505are pending), the idle watchers are being called once per event loop
1313until stopped, that is, or your process receives more events and becomes 1506iteration - until stopped, that is, or your process receives more events
1314busy.</p> 1507and becomes busy again with higher priority stuff.</p>
1315<p>The most noteworthy effect is that as long as any idle watchers are 1508<p>The most noteworthy effect is that as long as any idle watchers are
1316active, the process will not block when waiting for new events.</p> 1509active, the process will not block when waiting for new events.</p>
1317<p>Apart from keeping your process non-blocking (which is a useful 1510<p>Apart from keeping your process non-blocking (which is a useful
1318effect on its own sometimes), idle watchers are a good place to do 1511effect on its own sometimes), idle watchers are a good place to do
1319&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1512&quot;pseudo-background processing&quot;, or delay processing stuff to after the
1320event loop has handled all outstanding events.</p> 1513event loop has handled all outstanding events.</p>
1514
1515</div>
1516<h3 id="Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</h3>
1517<div id="Watcher_Specific_Functions_and_Data_-2-5">
1321<dl> 1518<dl>
1322 <dt>ev_idle_init (ev_signal *, callback)</dt> 1519 <dt>ev_idle_init (ev_signal *, callback)</dt>
1323 <dd> 1520 <dd>
1324 <p>Initialises and configures the idle watcher - it has no parameters of any 1521 <p>Initialises and configures the idle watcher - it has no parameters of any
1325kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1522kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
… …
1379are ready to run (it's actually more complicated: it only runs coroutines 1576are ready to run (it's actually more complicated: it only runs coroutines
1380with priority higher than or equal to the event loop and one coroutine 1577with priority higher than or equal to the event loop and one coroutine
1381of lower priority, but only once, using idle watchers to keep the event 1578of lower priority, but only once, using idle watchers to keep the event
1382loop from blocking if lower-priority coroutines are active, thus mapping 1579loop from blocking if lower-priority coroutines are active, thus mapping
1383low-priority coroutines to idle/background tasks).</p> 1580low-priority coroutines to idle/background tasks).</p>
1581<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1582priority, to ensure that they are being run before any other watchers
1583after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1584too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1585supports this, they will be called before other <code>ev_check</code> watchers did
1586their job. As <code>ev_check</code> watchers are often used to embed other event
1587loops those other event loops might be in an unusable state until their
1588<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1589others).</p>
1590
1591</div>
1592<h3 id="Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</h3>
1593<div id="Watcher_Specific_Functions_and_Data_-2-6">
1384<dl> 1594<dl>
1385 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1595 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1386 <dt>ev_check_init (ev_check *, callback)</dt> 1596 <dt>ev_check_init (ev_check *, callback)</dt>
1387 <dd> 1597 <dd>
1388 <p>Initialises and configures the prepare or check watcher - they have no 1598 <p>Initialises and configures the prepare or check watcher - they have no
1389parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1599parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1390macros, but using them is utterly, utterly and completely pointless.</p> 1600macros, but using them is utterly, utterly and completely pointless.</p>
1391 </dd> 1601 </dd>
1392</dl> 1602</dl>
1393<p>Example: To include a library such as adns, you would add IO watchers 1603<p>There are a number of principal ways to embed other event loops or modules
1394and a timeout watcher in a prepare handler, as required by libadns, and 1604into libev. Here are some ideas on how to include libadns into libev
1605(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1606use for an actually working example. Another Perl module named <code>EV::Glib</code>
1607embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1608into the Glib event loop).</p>
1609<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1395in a check watcher, destroy them and call into libadns. What follows is 1610and in a check watcher, destroy them and call into libadns. What follows
1396pseudo-code only of course:</p> 1611is pseudo-code only of course. This requires you to either use a low
1612priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1613the callbacks for the IO/timeout watchers might not have been called yet.</p>
1397<pre> static ev_io iow [nfd]; 1614<pre> static ev_io iow [nfd];
1398 static ev_timer tw; 1615 static ev_timer tw;
1399 1616
1400 static void 1617 static void
1401 io_cb (ev_loop *loop, ev_io *w, int revents) 1618 io_cb (ev_loop *loop, ev_io *w, int revents)
1402 { 1619 {
1403 // set the relevant poll flags
1404 // could also call adns_processreadable etc. here
1405 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1406 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1407 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1408 } 1620 }
1409 1621
1410 // create io watchers for each fd and a timer before blocking 1622 // create io watchers for each fd and a timer before blocking
1411 static void 1623 static void
1412 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1624 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1413 { 1625 {
1414 int timeout = 3600000;truct pollfd fds [nfd]; 1626 int timeout = 3600000;
1627 struct pollfd fds [nfd];
1415 // actual code will need to loop here and realloc etc. 1628 // actual code will need to loop here and realloc etc.
1416 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1629 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1417 1630
1418 /* the callback is illegal, but won't be called as we stop during check */ 1631 /* the callback is illegal, but won't be called as we stop during check */
1419 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1632 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1420 ev_timer_start (loop, &amp;tw); 1633 ev_timer_start (loop, &amp;tw);
1421 1634
1422 // create on ev_io per pollfd 1635 // create one ev_io per pollfd
1423 for (int i = 0; i &lt; nfd; ++i) 1636 for (int i = 0; i &lt; nfd; ++i)
1424 { 1637 {
1425 ev_io_init (iow + i, io_cb, fds [i].fd, 1638 ev_io_init (iow + i, io_cb, fds [i].fd,
1426 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1639 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1427 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1640 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1428 1641
1429 fds [i].revents = 0; 1642 fds [i].revents = 0;
1430 iow [i].data = fds + i;
1431 ev_io_start (loop, iow + i); 1643 ev_io_start (loop, iow + i);
1432 } 1644 }
1433 } 1645 }
1434 1646
1435 // stop all watchers after blocking 1647 // stop all watchers after blocking
… …
1437 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1649 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1438 { 1650 {
1439 ev_timer_stop (loop, &amp;tw); 1651 ev_timer_stop (loop, &amp;tw);
1440 1652
1441 for (int i = 0; i &lt; nfd; ++i) 1653 for (int i = 0; i &lt; nfd; ++i)
1654 {
1655 // set the relevant poll flags
1656 // could also call adns_processreadable etc. here
1657 struct pollfd *fd = fds + i;
1658 int revents = ev_clear_pending (iow + i);
1659 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1660 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1661
1662 // now stop the watcher
1442 ev_io_stop (loop, iow + i); 1663 ev_io_stop (loop, iow + i);
1664 }
1443 1665
1444 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1666 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1667 }
1668
1669</pre>
1670<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1671in the prepare watcher and would dispose of the check watcher.</p>
1672<p>Method 3: If the module to be embedded supports explicit event
1673notification (adns does), you can also make use of the actual watcher
1674callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1675<pre> static void
1676 timer_cb (EV_P_ ev_timer *w, int revents)
1677 {
1678 adns_state ads = (adns_state)w-&gt;data;
1679 update_now (EV_A);
1680
1681 adns_processtimeouts (ads, &amp;tv_now);
1682 }
1683
1684 static void
1685 io_cb (EV_P_ ev_io *w, int revents)
1686 {
1687 adns_state ads = (adns_state)w-&gt;data;
1688 update_now (EV_A);
1689
1690 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1691 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1692 }
1693
1694 // do not ever call adns_afterpoll
1695
1696</pre>
1697<p>Method 4: Do not use a prepare or check watcher because the module you
1698want to embed is too inflexible to support it. Instead, youc na override
1699their poll function. The drawback with this solution is that the main
1700loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1701this.</p>
1702<pre> static gint
1703 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1704 {
1705 int got_events = 0;
1706
1707 for (n = 0; n &lt; nfds; ++n)
1708 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1709
1710 if (timeout &gt;= 0)
1711 // create/start timer
1712
1713 // poll
1714 ev_loop (EV_A_ 0);
1715
1716 // stop timer again
1717 if (timeout &gt;= 0)
1718 ev_timer_stop (EV_A_ &amp;to);
1719
1720 // stop io watchers again - their callbacks should have set
1721 for (n = 0; n &lt; nfds; ++n)
1722 ev_io_stop (EV_A_ iow [n]);
1723
1724 return got_events;
1445 } 1725 }
1446 1726
1447 1727
1448 1728
1449 1729
… …
1510 } 1790 }
1511 else 1791 else
1512 loop_lo = loop_hi; 1792 loop_lo = loop_hi;
1513 1793
1514</pre> 1794</pre>
1795
1796</div>
1797<h3 id="Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</h3>
1798<div id="Watcher_Specific_Functions_and_Data_-2-7">
1515<dl> 1799<dl>
1516 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1800 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1517 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1801 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1518 <dd> 1802 <dd>
1519 <p>Configures the watcher to embed the given loop, which must be 1803 <p>Configures the watcher to embed the given loop, which must be
… …
1646the callback model to a model using method callbacks on objects.</p> 1930the callback model to a model using method callbacks on objects.</p>
1647<p>To use it,</p> 1931<p>To use it,</p>
1648<pre> #include &lt;ev++.h&gt; 1932<pre> #include &lt;ev++.h&gt;
1649 1933
1650</pre> 1934</pre>
1651<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1935<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1652and puts all of its definitions (many of them macros) into the global 1936of them macros) into the global namespace. All C++ specific things are
1653namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1937put into the <code>ev</code> namespace. It should support all the same embedding
1654<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1938options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1655<code>EV_MULTIPLICITY</code>.</p> 1939<p>Care has been taken to keep the overhead low. The only data member the C++
1940classes add (compared to plain C-style watchers) is the event loop pointer
1941that the watcher is associated with (or no additional members at all if
1942you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1943<p>Currently, functions, and static and non-static member functions can be
1944used as callbacks. Other types should be easy to add as long as they only
1945need one additional pointer for context. If you need support for other
1946types of functors please contact the author (preferably after implementing
1947it).</p>
1656<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1948<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1657<dl> 1949<dl>
1658 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1950 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1659 <dd> 1951 <dd>
1660 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1952 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1671which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1963which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1672defines by many implementations.</p> 1964defines by many implementations.</p>
1673 <p>All of those classes have these methods:</p> 1965 <p>All of those classes have these methods:</p>
1674 <p> 1966 <p>
1675 <dl> 1967 <dl>
1676 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1968 <dt>ev::TYPE::TYPE ()</dt>
1677 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1969 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1678 <dt>ev::TYPE::~TYPE</dt> 1970 <dt>ev::TYPE::~TYPE</dt>
1679 <dd> 1971 <dd>
1680 <p>The constructor takes a pointer to an object and a method pointer to 1972 <p>The constructor (optionally) takes an event loop to associate the watcher
1681the event handler callback to call in this class. The constructor calls 1973with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1682<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1974 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1683before starting it. If you do not specify a loop then the constructor 1975<code>set</code> method before starting it.</p>
1684automatically associates the default loop with this watcher.</p> 1976 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1977method to set a callback before you can start the watcher.</p>
1978 <p>(The reason why you have to use a method is a limitation in C++ which does
1979not allow explicit template arguments for constructors).</p>
1685 <p>The destructor automatically stops the watcher if it is active.</p> 1980 <p>The destructor automatically stops the watcher if it is active.</p>
1981 </dd>
1982 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1983 <dd>
1984 <p>This method sets the callback method to call. The method has to have a
1985signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1986first argument and the <code>revents</code> as second. The object must be given as
1987parameter and is stored in the <code>data</code> member of the watcher.</p>
1988 <p>This method synthesizes efficient thunking code to call your method from
1989the C callback that libev requires. If your compiler can inline your
1990callback (i.e. it is visible to it at the place of the <code>set</code> call and
1991your compiler is good :), then the method will be fully inlined into the
1992thunking function, making it as fast as a direct C callback.</p>
1993 <p>Example: simple class declaration and watcher initialisation</p>
1994<pre> struct myclass
1995 {
1996 void io_cb (ev::io &amp;w, int revents) { }
1997 }
1998
1999 myclass obj;
2000 ev::io iow;
2001 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
2002
2003</pre>
2004 </dd>
2005 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
2006 <dd>
2007 <p>Also sets a callback, but uses a static method or plain function as
2008callback. The optional <code>data</code> argument will be stored in the watcher's
2009<code>data</code> member and is free for you to use.</p>
2010 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
2011 <p>See the method-<code>set</code> above for more details.</p>
2012 <p>Example:</p>
2013<pre> static void io_cb (ev::io &amp;w, int revents) { }
2014 iow.set &lt;io_cb&gt; ();
2015
2016</pre>
1686 </dd> 2017 </dd>
1687 <dt>w-&gt;set (struct ev_loop *)</dt> 2018 <dt>w-&gt;set (struct ev_loop *)</dt>
1688 <dd> 2019 <dd>
1689 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 2020 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1690do this when the watcher is inactive (and not pending either).</p> 2021do this when the watcher is inactive (and not pending either).</p>
1691 </dd> 2022 </dd>
1692 <dt>w-&gt;set ([args])</dt> 2023 <dt>w-&gt;set ([args])</dt>
1693 <dd> 2024 <dd>
1694 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 2025 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1695called at least once. Unlike the C counterpart, an active watcher gets 2026called at least once. Unlike the C counterpart, an active watcher gets
1696automatically stopped and restarted.</p> 2027automatically stopped and restarted when reconfiguring it with this
2028method.</p>
1697 </dd> 2029 </dd>
1698 <dt>w-&gt;start ()</dt> 2030 <dt>w-&gt;start ()</dt>
1699 <dd> 2031 <dd>
1700 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 2032 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1701constructor already takes the loop.</p> 2033constructor already stores the event loop.</p>
1702 </dd> 2034 </dd>
1703 <dt>w-&gt;stop ()</dt> 2035 <dt>w-&gt;stop ()</dt>
1704 <dd> 2036 <dd>
1705 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 2037 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1706 </dd> 2038 </dd>
… …
1730 2062
1731 myclass (); 2063 myclass ();
1732 } 2064 }
1733 2065
1734 myclass::myclass (int fd) 2066 myclass::myclass (int fd)
1735 : io (this, &amp;myclass::io_cb),
1736 idle (this, &amp;myclass::idle_cb)
1737 { 2067 {
2068 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
2069 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
2070
1738 io.start (fd, ev::READ); 2071 io.start (fd, ev::READ);
1739 } 2072 }
1740 2073
1741 2074
1742 2075
… …
1745 2078
1746</div> 2079</div>
1747<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 2080<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1748<div id="MACRO_MAGIC_CONTENT"> 2081<div id="MACRO_MAGIC_CONTENT">
1749<p>Libev can be compiled with a variety of options, the most fundemantal is 2082<p>Libev can be compiled with a variety of options, the most fundemantal is
1750<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 2083<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1751callbacks have an initial <code>struct ev_loop *</code> argument.</p> 2084callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1752<p>To make it easier to write programs that cope with either variant, the 2085<p>To make it easier to write programs that cope with either variant, the
1753following macros are defined:</p> 2086following macros are defined:</p>
1754<dl> 2087<dl>
1755 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 2088 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1784 <dd> 2117 <dd>
1785 <p>Similar to the other two macros, this gives you the value of the default 2118 <p>Similar to the other two macros, this gives you the value of the default
1786loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2119loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1787 </dd> 2120 </dd>
1788</dl> 2121</dl>
1789<p>Example: Declare and initialise a check watcher, working regardless of 2122<p>Example: Declare and initialise a check watcher, utilising the above
1790wether multiple loops are supported or not.</p> 2123macros so it will work regardless of whether multiple loops are supported
2124or not.</p>
1791<pre> static void 2125<pre> static void
1792 check_cb (EV_P_ ev_timer *w, int revents) 2126 check_cb (EV_P_ ev_timer *w, int revents)
1793 { 2127 {
1794 ev_check_stop (EV_A_ w); 2128 ev_check_stop (EV_A_ w);
1795 } 2129 }
1796 2130
1797 ev_check check; 2131 ev_check check;
1798 ev_check_init (&amp;check, check_cb); 2132 ev_check_init (&amp;check, check_cb);
1799 ev_check_start (EV_DEFAULT_ &amp;check); 2133 ev_check_start (EV_DEFAULT_ &amp;check);
1800 ev_loop (EV_DEFAULT_ 0); 2134 ev_loop (EV_DEFAULT_ 0);
1801
1802
1803
1804 2135
1805</pre> 2136</pre>
1806 2137
1807</div> 2138</div>
1808<h1 id="EMBEDDING">EMBEDDING</h1> 2139<h1 id="EMBEDDING">EMBEDDING</h1>
… …
1850 ev_vars.h 2181 ev_vars.h
1851 ev_wrap.h 2182 ev_wrap.h
1852 2183
1853 ev_win32.c required on win32 platforms only 2184 ev_win32.c required on win32 platforms only
1854 2185
1855 ev_select.c only when select backend is enabled (which is by default) 2186 ev_select.c only when select backend is enabled (which is enabled by default)
1856 ev_poll.c only when poll backend is enabled (disabled by default) 2187 ev_poll.c only when poll backend is enabled (disabled by default)
1857 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2188 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1858 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2189 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1859 ev_port.c only when the solaris port backend is enabled (disabled by default) 2190 ev_port.c only when the solaris port backend is enabled (disabled by default)
1860 2191
… …
1987 </dd> 2318 </dd>
1988 <dt>EV_USE_DEVPOLL</dt> 2319 <dt>EV_USE_DEVPOLL</dt>
1989 <dd> 2320 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p> 2321 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd> 2322 </dd>
2323 <dt>EV_USE_INOTIFY</dt>
2324 <dd>
2325 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2326interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2327be detected at runtime.</p>
2328 </dd>
1992 <dt>EV_H</dt> 2329 <dt>EV_H</dt>
1993 <dd> 2330 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2331 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1995undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This 2332undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
1996can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2333can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
2019will have the <code>struct ev_loop *</code> as first argument, and you can create 2356will have the <code>struct ev_loop *</code> as first argument, and you can create
2020additional independent event loops. Otherwise there will be no support 2357additional independent event loops. Otherwise there will be no support
2021for multiple event loops and there is no first event loop pointer 2358for multiple event loops and there is no first event loop pointer
2022argument. Instead, all functions act on the single default loop.</p> 2359argument. Instead, all functions act on the single default loop.</p>
2023 </dd> 2360 </dd>
2361 <dt>EV_MINPRI</dt>
2362 <dt>EV_MAXPRI</dt>
2363 <dd>
2364 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2365<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2366provide for more priorities by overriding those symbols (usually defined
2367to be <code>-2</code> and <code>2</code>, respectively).</p>
2368 <p>When doing priority-based operations, libev usually has to linearly search
2369all the priorities, so having many of them (hundreds) uses a lot of space
2370and time, so using the defaults of five priorities (-2 .. +2) is usually
2371fine.</p>
2372 <p>If your embedding app does not need any priorities, defining these both to
2373<code>0</code> will save some memory and cpu.</p>
2374 </dd>
2024 <dt>EV_PERIODIC_ENABLE</dt> 2375 <dt>EV_PERIODIC_ENABLE</dt>
2025 <dd> 2376 <dd>
2026 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2377 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2027defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2378defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2028code.</p> 2379code.</p>
2029 </dd> 2380 </dd>
2381 <dt>EV_IDLE_ENABLE</dt>
2382 <dd>
2383 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2384defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2385code.</p>
2386 </dd>
2030 <dt>EV_EMBED_ENABLE</dt> 2387 <dt>EV_EMBED_ENABLE</dt>
2031 <dd> 2388 <dd>
2032 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2389 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2033defined to be <code>0</code>, then they are not.</p> 2390defined to be <code>0</code>, then they are not.</p>
2034 </dd> 2391 </dd>
… …
2051 <dt>EV_PID_HASHSIZE</dt> 2408 <dt>EV_PID_HASHSIZE</dt>
2052 <dd> 2409 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2410 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2054pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more 2411pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2055than enough. If you need to manage thousands of children you might want to 2412than enough. If you need to manage thousands of children you might want to
2056increase this value.</p> 2413increase this value (<i>must</i> be a power of two).</p>
2414 </dd>
2415 <dt>EV_INOTIFY_HASHSIZE</dt>
2416 <dd>
2417 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2418inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2419usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2420watchers you might want to increase this value (<i>must</i> be a power of
2421two).</p>
2057 </dd> 2422 </dd>
2058 <dt>EV_COMMON</dt> 2423 <dt>EV_COMMON</dt>
2059 <dd> 2424 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2425 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2061this macro to a something else you can include more and other types of 2426this macro to a something else you can include more and other types of
… …
2088the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2453the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2089interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2454interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2090will be compiled. It is pretty complex because it provides its own header 2455will be compiled. It is pretty complex because it provides its own header
2091file.</p> 2456file.</p>
2092 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2457 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2093that everybody includes and which overrides some autoconf choices:</p> 2458that everybody includes and which overrides some configure choices:</p>
2459<pre> #define EV_MINIMAL 1
2094<pre> #define EV_USE_POLL 0 2460 #define EV_USE_POLL 0
2095 #define EV_MULTIPLICITY 0 2461 #define EV_MULTIPLICITY 0
2096 #define EV_PERIODICS 0 2462 #define EV_PERIODIC_ENABLE 0
2463 #define EV_STAT_ENABLE 0
2464 #define EV_FORK_ENABLE 0
2097 #define EV_CONFIG_H &lt;config.h&gt; 2465 #define EV_CONFIG_H &lt;config.h&gt;
2466 #define EV_MINPRI 0
2467 #define EV_MAXPRI 0
2098 2468
2099 #include &quot;ev++.h&quot; 2469 #include &quot;ev++.h&quot;
2100 2470
2101</pre> 2471</pre>
2102 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2472 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2112<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2482<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2113<div id="COMPLEXITIES_CONTENT"> 2483<div id="COMPLEXITIES_CONTENT">
2114 <p>In this section the complexities of (many of) the algorithms used inside 2484 <p>In this section the complexities of (many of) the algorithms used inside
2115libev will be explained. For complexity discussions about backends see the 2485libev will be explained. For complexity discussions about backends see the
2116documentation for <code>ev_default_init</code>.</p> 2486documentation for <code>ev_default_init</code>.</p>
2487 <p>All of the following are about amortised time: If an array needs to be
2488extended, libev needs to realloc and move the whole array, but this
2489happens asymptotically never with higher number of elements, so O(1) might
2490mean it might do a lengthy realloc operation in rare cases, but on average
2491it is much faster and asymptotically approaches constant time.</p>
2117 <p> 2492 <p>
2118 <dl> 2493 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2494 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2495 <dd>
2496 <p>This means that, when you have a watcher that triggers in one hour and
2497there are 100 watchers that would trigger before that then inserting will
2498have to skip those 100 watchers.</p>
2499 </dd>
2120 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2500 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2501 <dd>
2502 <p>That means that for changing a timer costs less than removing/adding them
2503as only the relative motion in the event queue has to be paid for.</p>
2504 </dd>
2121 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2505 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2506 <dd>
2507 <p>These just add the watcher into an array or at the head of a list.
2122 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2508=item Stopping check/prepare/idle watchers: O(1)</p>
2509 </dd>
2123 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2510 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2511 <dd>
2512 <p>These watchers are stored in lists then need to be walked to find the
2513correct watcher to remove. The lists are usually short (you don't usually
2514have many watchers waiting for the same fd or signal).</p>
2515 </dd>
2124 <dt>Finding the next timer per loop iteration: O(1)</dt> 2516 <dt>Finding the next timer per loop iteration: O(1)</dt>
2125 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2517 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2518 <dd>
2519 <p>A change means an I/O watcher gets started or stopped, which requires
2520libev to recalculate its status (and possibly tell the kernel).</p>
2521 </dd>
2126 <dt>Activating one watcher: O(1)</dt> 2522 <dt>Activating one watcher: O(1)</dt>
2523 <dt>Priority handling: O(number_of_priorities)</dt>
2524 <dd>
2525 <p>Priorities are implemented by allocating some space for each
2526priority. When doing priority-based operations, libev usually has to
2527linearly search all the priorities.</p>
2528 </dd>
2127 </dl> 2529 </dl>
2128 </p> 2530 </p>
2129 2531
2130 2532
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