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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 21:26:46 2007" /> 9 <meta name="created" content="Sun Dec 9 20:30:11 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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60<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
61</li> 61</li>
62</ul><hr /> 62</ul><hr />
63<!-- INDEX END --> 63<!-- INDEX END -->
64 64
65<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
66<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
67<p>libev - a high performance full-featured event loop written in C</p> 67<p>libev - a high performance full-featured event loop written in C</p>
68 68
69</div> 69</div>
70<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
71<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
72<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
73 73
74</pre> 74</pre>
75 75
76</div> 76</div>
77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1><p><a href="#TOP" class="toplink">Top</a></p> 77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT"> 78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt; 79<pre> #include &lt;ev.h&gt;
80 80
81 ev_io stdin_watcher; 81 ev_io stdin_watcher;
82 ev_timer timeout_watcher; 82 ev_timer timeout_watcher;
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117 } 117 }
118 118
119</pre> 119</pre>
120 120
121</div> 121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 122<h1 id="DESCRIPTION">DESCRIPTION</h1>
123<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
124<p>The newest version of this document is also available as a html-formatted
125web page you might find easier to navigate when reading it for the first
126time: <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 127<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 128file descriptor being readable or a timeout occuring), and it will manage
126these event sources and provide your program with events.</p> 129these 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 130<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 131(or thread) by executing the <i>event loop</i> handler, and will then
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131watchers</i>, which are relatively small C structures you initialise with the 134watchers</i>, which are relatively small C structures you initialise with the
132details of the event, and then hand it over to libev by <i>starting</i> the 135details of the event, and then hand it over to libev by <i>starting</i> the
133watcher.</p> 136watcher.</p>
134 137
135</div> 138</div>
136<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
137<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the 141<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 142BSD-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>), 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous 145with customised rescheduling (<code>ev_periodic</code>), synchronous signals
142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and 146(<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>, 147watchers 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 148<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 149file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p> 150(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this 151<p>It also is quite fast (see this
148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent 152<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
149for example).</p> 153for example).</p>
150 154
151</div> 155</div>
152<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
153<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
154<p>Libev is very configurable. In this manual the default configuration will 158<p>Libev is very configurable. In this manual the default configuration will
155be described, which supports multiple event loops. For more info about 159be described, which supports multiple event loops. For more info about
156various configuration options please have a look at <strong>EMBED</strong> section in 160various configuration options please have a look at <strong>EMBED</strong> section in
157this manual. If libev was configured without support for multiple event 161this manual. If libev was configured without support for multiple event
158loops, then all functions taking an initial argument of name <code>loop</code> 162loops, then all functions taking an initial argument of name <code>loop</code>
159(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p> 163(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
160 164
161</div> 165</div>
162<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
163<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
164<p>Libev represents time as a single floating point number, representing the 168<p>Libev represents time as a single floating point number, representing the
165(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
166the beginning of 1970, details are complicated, don't ask). This type is 170the beginning of 1970, details are complicated, don't ask). This type is
167called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 171called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
168to the <code>double</code> type in C, and when you need to do any calculations on 172to the <code>double</code> type in C, and when you need to do any calculations on
169it, you should treat it as such.</p> 173it, you should treat it as such.</p>
170 174
171</div> 175</div>
172<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 176<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
173<div id="GLOBAL_FUNCTIONS_CONTENT"> 177<div id="GLOBAL_FUNCTIONS_CONTENT">
174<p>These functions can be called anytime, even before initialising the 178<p>These functions can be called anytime, even before initialising the
175library in any way.</p> 179library in any way.</p>
176<dl> 180<dl>
177 <dt>ev_tstamp ev_time ()</dt> 181 <dt>ev_tstamp ev_time ()</dt>
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229might be supported on the current system, you would need to look at 233might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 234<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 235recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 236 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 237 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 239 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 240 <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 241semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 242allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 243memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
241 <p>You could override this function in high-availability programs to, say, 246 <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, 247free 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> 248or 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 249 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 250retries).</p>
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285</pre> 290</pre>
286 </dd> 291 </dd>
287</dl> 292</dl>
288 293
289</div> 294</div>
290<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 295<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
291<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 296<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
292<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 297<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
293types of such loops, the <i>default</i> loop, which supports signals and child 298types of such loops, the <i>default</i> loop, which supports signals and child
294events, and dynamically created loops which do not.</p> 299events, and dynamically created loops which do not.</p>
295<p>If you use threads, a common model is to run the default event loop 300<p>If you use threads, a common model is to run the default event loop
… …
324<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
325override the flags completely if it is found in the environment. This is 330override 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 331useful to try out specific backends to test their performance, or to work
327around bugs.</p> 332around bugs.</p>
328 </dd> 333 </dd>
334 <dt><code>EVFLAG_FORKCHECK</code></dt>
335 <dd>
336 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
337a fork, you can also make libev check for a fork in each iteration by
338enabling this flag.</p>
339 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
340and thus this might slow down your event loop if you do a lot of loop
341iterations and little real work, but is usually not noticeable (on my
342Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
343without a syscall and thus <i>very</i> fast, but my Linux system also has
344<code>pthread_atfork</code> which is even faster).</p>
345 <p>The big advantage of this flag is that you can forget about fork (and
346forget about forgetting to tell libev about forking) when you use this
347flag.</p>
348 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
349environment variable.</p>
350 </dd>
329 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
330 <dd> 352 <dd>
331 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 353 <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, 354libev 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 355but if that fails, expect a fairly low limit on the number of fds when
… …
461 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
462 <dd> 484 <dd>
463 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 485 <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 486<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> 487after fork, and how you do this is entirely your own problem.</p>
488 </dd>
489 <dt>unsigned int ev_loop_count (loop)</dt>
490 <dd>
491 <p>Returns the count of loop iterations for the loop, which is identical to
492the number of times libev did poll for new events. It starts at <code>0</code> and
493happily wraps around with enough iterations.</p>
494 <p>This value can sometimes be useful as a generation counter of sorts (it
495&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
496<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
466 </dd> 497 </dd>
467 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
468 <dd> 499 <dd>
469 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 500 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
470use.</p> 501use.</p>
… …
498one iteration of the loop. This is useful if you are waiting for some 529one iteration of the loop. This is useful if you are waiting for some
499external event in conjunction with something not expressible using other 530external 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 531libev 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> 532usually a better approach for this kind of thing.</p>
502 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 533 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
534<pre> - Before the first iteration, call any pending watchers.
503<pre> * If there are no active watchers (reference count is zero), return. 535 * If there are no active watchers (reference count is zero), return.
504 - Queue prepare watchers and then call all outstanding watchers. 536 - Queue all prepare watchers and then call all outstanding watchers.
505 - If we have been forked, recreate the kernel state. 537 - If we have been forked, recreate the kernel state.
506 - Update the kernel state with all outstanding changes. 538 - Update the kernel state with all outstanding changes.
507 - Update the &quot;event loop time&quot;. 539 - Update the &quot;event loop time&quot;.
508 - Calculate for how long to block. 540 - Calculate for how long to block.
509 - Block the process, waiting for any events. 541 - Block the process, waiting for any events.
… …
568 600
569 601
570 602
571 603
572</div> 604</div>
573<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 605<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
574<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 606<div id="ANATOMY_OF_A_WATCHER_CONTENT">
575<p>A watcher is a structure that you create and register to record your 607<p>A watcher is a structure that you create and register to record your
576interest in some event. For instance, if you want to wait for STDIN to 608interest in some event. For instance, if you want to wait for STDIN to
577become readable, you would create an <code>ev_io</code> watcher for that:</p> 609become readable, you would create an <code>ev_io</code> watcher for that:</p>
578<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 610<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
738 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 770 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
739 <dd> 771 <dd>
740 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 772 <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 773events 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 774is 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 775<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> 776make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
777it).</p>
745 </dd> 778 </dd>
746 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 779 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 780 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 781 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 782 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 783 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 784 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 785 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 786(modulo threads).</p>
787 </dd>
788 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
789 <dt>int ev_priority (ev_TYPE *watcher)</dt>
790 <dd>
791 <p>Set and query the priority of the watcher. The priority is a small
792integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
793(default: <code>-2</code>). Pending watchers with higher priority will be invoked
794before watchers with lower priority, but priority will not keep watchers
795from being executed (except for <code>ev_idle</code> watchers).</p>
796 <p>This means that priorities are <i>only</i> used for ordering callback
797invocation after new events have been received. This is useful, for
798example, to reduce latency after idling, or more often, to bind two
799watchers on the same event and make sure one is called first.</p>
800 <p>If you need to suppress invocation when higher priority events are pending
801you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
802 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
803pending.</p>
804 <p>The default priority used by watchers when no priority has been set is
805always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
806 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
807fine, as long as you do not mind that the priority value you query might
808or might not have been adjusted to be within valid range.</p>
809 </dd>
810 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
811 <dd>
812 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
813<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
814can deal with that fact.</p>
815 </dd>
816 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
817 <dd>
818 <p>If the watcher is pending, this function returns clears its pending status
819and returns its <code>revents</code> bitset (as if its callback was invoked). If the
820watcher isn't pending it does nothing and returns <code>0</code>.</p>
754 </dd> 821 </dd>
755</dl> 822</dl>
756 823
757 824
758 825
… …
783 struct my_io *w = (struct my_io *)w_; 850 struct my_io *w = (struct my_io *)w_;
784 ... 851 ...
785 } 852 }
786 853
787</pre> 854</pre>
788<p>More interesting and less C-conformant ways of catsing your callback type 855<p>More interesting and less C-conformant ways of casting your callback type
789have been omitted....</p> 856instead have been omitted.</p>
857<p>Another common scenario is having some data structure with multiple
858watchers:</p>
859<pre> struct my_biggy
860 {
861 int some_data;
862 ev_timer t1;
863 ev_timer t2;
864 }
790 865
866</pre>
867<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
868you need to use <code>offsetof</code>:</p>
869<pre> #include &lt;stddef.h&gt;
791 870
871 static void
872 t1_cb (EV_P_ struct ev_timer *w, int revents)
873 {
874 struct my_biggy big = (struct my_biggy *
875 (((char *)w) - offsetof (struct my_biggy, t1));
876 }
792 877
878 static void
879 t2_cb (EV_P_ struct ev_timer *w, int revents)
880 {
881 struct my_biggy big = (struct my_biggy *
882 (((char *)w) - offsetof (struct my_biggy, t2));
883 }
793 884
794 885
886
887
888</pre>
889
795</div> 890</div>
796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 891<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
797<div id="WATCHER_TYPES_CONTENT"> 892<div id="WATCHER_TYPES_CONTENT">
798<p>This section describes each watcher in detail, but will not repeat 893<p>This section describes each watcher in detail, but will not repeat
799information given in the last section. Any initialisation/set macros, 894information given in the last section. Any initialisation/set macros,
800functions and members specific to the watcher type are explained.</p> 895functions and members specific to the watcher type are explained.</p>
801<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, 896<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
… …
841this situation even with a relatively standard program structure. Thus 936this 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 937it 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> 938<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 939<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 940play 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 941whether 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 942such as poll (fortunately in our Xlib example, Xlib already does this on
848its own, so its quite safe to use).</p> 943its own, so its quite safe to use).</p>
849<dl> 944<dl>
850 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 945 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
851 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 946 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
922 </dd> 1017 </dd>
923 <dt>ev_timer_again (loop)</dt> 1018 <dt>ev_timer_again (loop)</dt>
924 <dd> 1019 <dd>
925 <p>This will act as if the timer timed out and restart it again if it is 1020 <p>This will act as if the timer timed out and restart it again if it is
926repeating. The exact semantics are:</p> 1021repeating. The exact semantics are:</p>
1022 <p>If the timer is pending, its pending status is cleared.</p>
927 <p>If the timer is started but nonrepeating, stop it.</p> 1023 <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 1024 <p>If the timer is repeating, either start it if necessary (with the
929value), or reset the running timer to the repeat value.</p> 1025<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 1026 <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 1027example: 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, 1028timeout, 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 1029seconds 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 1030configure 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 1031<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 1032you 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 1033socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
938need be.</p> 1034automatically restart it if need be.</p>
939 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1035 <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> 1036altogether 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.); 1037<pre> ev_timer_init (timer, callback, 0., 5.);
942 ev_timer_again (loop, timer); 1038 ev_timer_again (loop, timer);
943 ... 1039 ...
944 timer-&gt;again = 17.; 1040 timer-&gt;again = 17.;
945 ev_timer_again (loop, timer); 1041 ev_timer_again (loop, timer);
946 ... 1042 ...
947 timer-&gt;again = 10.; 1043 timer-&gt;again = 10.;
948 ev_timer_again (loop, timer); 1044 ev_timer_again (loop, timer);
949 1045
950</pre> 1046</pre>
951 <p>This is more efficient then stopping/starting the timer eahc time you want 1047 <p>This is more slightly efficient then stopping/starting the timer each time
952to modify its timeout value.</p> 1048you want to modify its timeout value.</p>
953 </dd> 1049 </dd>
954 <dt>ev_tstamp repeat [read-write]</dt> 1050 <dt>ev_tstamp repeat [read-write]</dt>
955 <dd> 1051 <dd>
956 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1052 <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), 1053or <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 1097but 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 1098to 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 () 1099periodic 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 1100+ 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 1101take 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 1102roughly 10 seconds later).</p>
1007again).</p>
1008<p>They can also be used to implement vastly more complex timers, such as 1103<p>They can also be used to implement vastly more complex timers, such as
1009triggering an event on eahc midnight, local time.</p> 1104triggering an event on each midnight, local time or other, complicated,
1105rules.</p>
1010<p>As with timers, the callback is guarenteed to be invoked only when the 1106<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 1107time (<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> 1108during the same loop iteration then order of execution is undefined.</p>
1013<dl> 1109<dl>
1014 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1110 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
… …
1016 <dd> 1112 <dd>
1017 <p>Lots of arguments, lets sort it out... There are basically three modes of 1113 <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> 1114operation, and we will explain them from simplest to complex:</p>
1019 <p> 1115 <p>
1020 <dl> 1116 <dl>
1021 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1117 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1022 <dd> 1118 <dd>
1023 <p>In this configuration the watcher triggers an event at the wallclock time 1119 <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, 1120<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 1121that 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> 1122system time reaches or surpasses this time.</p>
1027 </dd> 1123 </dd>
1028 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1124 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1029 <dd> 1125 <dd>
1030 <p>In this mode the watcher will always be scheduled to time out at the next 1126 <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 1127<code>at + N * interval</code> time (for some integer N, which can also be negative)
1032of any time jumps.</p> 1128and 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 1129 <p>This can be used to create timers that do not drift with respect to system
1034time:</p> 1130time:</p>
1035<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1131<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1036 1132
1037</pre> 1133</pre>
… …
1040full hour (UTC), or more correctly, when the system time is evenly divisible 1136full hour (UTC), or more correctly, when the system time is evenly divisible
1041by 3600.</p> 1137by 3600.</p>
1042 <p>Another way to think about it (for the mathematically inclined) is that 1138 <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 1139<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> 1140time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1141 <p>For numerical stability it is preferable that the <code>at</code> value is near
1142<code>ev_now ()</code> (the current time), but there is no range requirement for
1143this value.</p>
1045 </dd> 1144 </dd>
1046 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1145 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1047 <dd> 1146 <dd>
1048 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1147 <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 1148ignored. Instead, each time the periodic watcher gets scheduled, the
1050reschedule callback will be called with the watcher as first, and the 1149reschedule callback will be called with the watcher as first, and the
1051current time as second argument.</p> 1150current time as second argument.</p>
1052 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1151 <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, 1152ever, 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 1153return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1055starting a prepare watcher).</p> 1154starting an <code>ev_prepare</code> watcher, which is legal).</p>
1056 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1155 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1057ev_tstamp now)</code>, e.g.:</p> 1156ev_tstamp now)</code>, e.g.:</p>
1058<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1157<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1059 { 1158 {
1060 return now + 60.; 1159 return now + 60.;
… …
1080 <dd> 1179 <dd>
1081 <p>Simply stops and restarts the periodic watcher again. This is only useful 1180 <p>Simply stops and restarts the periodic watcher again. This is only useful
1082when you changed some parameters or the reschedule callback would return 1181when 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 1182a different time than the last time it was called (e.g. in a crond like
1084program when the crontabs have changed).</p> 1183program when the crontabs have changed).</p>
1184 </dd>
1185 <dt>ev_tstamp offset [read-write]</dt>
1186 <dd>
1187 <p>When repeating, this contains the offset value, otherwise this is the
1188absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1189 <p>Can be modified any time, but changes only take effect when the periodic
1190timer fires or <code>ev_periodic_again</code> is being called.</p>
1085 </dd> 1191 </dd>
1086 <dt>ev_tstamp interval [read-write]</dt> 1192 <dt>ev_tstamp interval [read-write]</dt>
1087 <dd> 1193 <dd>
1088 <p>The current interval value. Can be modified any time, but changes only 1194 <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 1195take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
… …
1218<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1324<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 1325not 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 1326not 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 1327otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p> 1328the stat buffer having unspecified contents.</p>
1329<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1330relative and your working directory changes, the behaviour is undefined.</p>
1223<p>Since there is no standard to do this, the portable implementation simply 1331<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 1332calls <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 1333can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1334a 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 1335unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also 1336five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats 1337impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p> 1338usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers, 1339<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be 1340as even with OS-supported change notifications, this can be
1233resource-intensive.</p> 1341resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but 1342<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> 1343implemented (implementing kqueue support is left as an exercise for the
1344reader). Inotify will be used to give hints only and should not change the
1345semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1346to fall back to regular polling again even with inotify, but changes are
1347usually detected immediately, and if the file exists there will be no
1348polling.</p>
1236<dl> 1349<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1350 <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> 1351 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd> 1352 <dd>
1240 <p>Configures the watcher to wait for status changes of the given 1353 <p>Configures the watcher to wait for status changes of the given
… …
1303</pre> 1416</pre>
1304 1417
1305</div> 1418</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> 1419<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"> 1420<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 1421<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 1422priority are pending (prepare, check and other idle watchers do not
1310as your process is busy handling sockets or timeouts (or even signals, 1423count).</p>
1311imagine) it will not be triggered. But when your process is idle all idle 1424<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 - 1425(or even signals, imagine) of the same or higher priority it will not be
1426triggered. But when your process is idle (or only lower-priority watchers
1427are pending), the idle watchers are being called once per event loop
1313until stopped, that is, or your process receives more events and becomes 1428iteration - until stopped, that is, or your process receives more events
1314busy.</p> 1429and becomes busy again with higher priority stuff.</p>
1315<p>The most noteworthy effect is that as long as any idle watchers are 1430<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> 1431active, the process will not block when waiting for new events.</p>
1317<p>Apart from keeping your process non-blocking (which is a useful 1432<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 1433effect 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 1434&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1379are ready to run (it's actually more complicated: it only runs coroutines 1494are 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 1495with 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 1496of lower priority, but only once, using idle watchers to keep the event
1382loop from blocking if lower-priority coroutines are active, thus mapping 1497loop from blocking if lower-priority coroutines are active, thus mapping
1383low-priority coroutines to idle/background tasks).</p> 1498low-priority coroutines to idle/background tasks).</p>
1499<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1500priority, to ensure that they are being run before any other watchers
1501after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1502too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1503supports this, they will be called before other <code>ev_check</code> watchers did
1504their job. As <code>ev_check</code> watchers are often used to embed other event
1505loops those other event loops might be in an unusable state until their
1506<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1507others).</p>
1384<dl> 1508<dl>
1385 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1509 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1386 <dt>ev_check_init (ev_check *, callback)</dt> 1510 <dt>ev_check_init (ev_check *, callback)</dt>
1387 <dd> 1511 <dd>
1388 <p>Initialises and configures the prepare or check watcher - they have no 1512 <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> 1513parameters 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> 1514macros, but using them is utterly, utterly and completely pointless.</p>
1391 </dd> 1515 </dd>
1392</dl> 1516</dl>
1393<p>Example: To include a library such as adns, you would add IO watchers 1517<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 1518into libev. Here are some ideas on how to include libadns into libev
1519(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1520use for an actually working example. Another Perl module named <code>EV::Glib</code>
1521embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1522into the Glib event loop).</p>
1523<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 1524and in a check watcher, destroy them and call into libadns. What follows
1396pseudo-code only of course:</p> 1525is pseudo-code only of course. This requires you to either use a low
1526priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1527the callbacks for the IO/timeout watchers might not have been called yet.</p>
1397<pre> static ev_io iow [nfd]; 1528<pre> static ev_io iow [nfd];
1398 static ev_timer tw; 1529 static ev_timer tw;
1399 1530
1400 static void 1531 static void
1401 io_cb (ev_loop *loop, ev_io *w, int revents) 1532 io_cb (ev_loop *loop, ev_io *w, int revents)
1402 { 1533 {
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 } 1534 }
1409 1535
1410 // create io watchers for each fd and a timer before blocking 1536 // create io watchers for each fd and a timer before blocking
1411 static void 1537 static void
1412 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1538 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1413 { 1539 {
1414 int timeout = 3600000;truct pollfd fds [nfd]; 1540 int timeout = 3600000;
1541 struct pollfd fds [nfd];
1415 // actual code will need to loop here and realloc etc. 1542 // actual code will need to loop here and realloc etc.
1416 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1543 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1417 1544
1418 /* the callback is illegal, but won't be called as we stop during check */ 1545 /* the callback is illegal, but won't be called as we stop during check */
1419 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1546 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1420 ev_timer_start (loop, &amp;tw); 1547 ev_timer_start (loop, &amp;tw);
1421 1548
1422 // create on ev_io per pollfd 1549 // create one ev_io per pollfd
1423 for (int i = 0; i &lt; nfd; ++i) 1550 for (int i = 0; i &lt; nfd; ++i)
1424 { 1551 {
1425 ev_io_init (iow + i, io_cb, fds [i].fd, 1552 ev_io_init (iow + i, io_cb, fds [i].fd,
1426 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1553 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1427 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1554 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1428 1555
1429 fds [i].revents = 0; 1556 fds [i].revents = 0;
1430 iow [i].data = fds + i;
1431 ev_io_start (loop, iow + i); 1557 ev_io_start (loop, iow + i);
1432 } 1558 }
1433 } 1559 }
1434 1560
1435 // stop all watchers after blocking 1561 // stop all watchers after blocking
… …
1437 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1563 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1438 { 1564 {
1439 ev_timer_stop (loop, &amp;tw); 1565 ev_timer_stop (loop, &amp;tw);
1440 1566
1441 for (int i = 0; i &lt; nfd; ++i) 1567 for (int i = 0; i &lt; nfd; ++i)
1568 {
1569 // set the relevant poll flags
1570 // could also call adns_processreadable etc. here
1571 struct pollfd *fd = fds + i;
1572 int revents = ev_clear_pending (iow + i);
1573 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1574 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1575
1576 // now stop the watcher
1442 ev_io_stop (loop, iow + i); 1577 ev_io_stop (loop, iow + i);
1578 }
1443 1579
1444 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1580 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1581 }
1582
1583</pre>
1584<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1585in the prepare watcher and would dispose of the check watcher.</p>
1586<p>Method 3: If the module to be embedded supports explicit event
1587notification (adns does), you can also make use of the actual watcher
1588callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1589<pre> static void
1590 timer_cb (EV_P_ ev_timer *w, int revents)
1591 {
1592 adns_state ads = (adns_state)w-&gt;data;
1593 update_now (EV_A);
1594
1595 adns_processtimeouts (ads, &amp;tv_now);
1596 }
1597
1598 static void
1599 io_cb (EV_P_ ev_io *w, int revents)
1600 {
1601 adns_state ads = (adns_state)w-&gt;data;
1602 update_now (EV_A);
1603
1604 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1605 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1606 }
1607
1608 // do not ever call adns_afterpoll
1609
1610</pre>
1611<p>Method 4: Do not use a prepare or check watcher because the module you
1612want to embed is too inflexible to support it. Instead, youc na override
1613their poll function. The drawback with this solution is that the main
1614loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1615this.</p>
1616<pre> static gint
1617 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1618 {
1619 int got_events = 0;
1620
1621 for (n = 0; n &lt; nfds; ++n)
1622 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1623
1624 if (timeout &gt;= 0)
1625 // create/start timer
1626
1627 // poll
1628 ev_loop (EV_A_ 0);
1629
1630 // stop timer again
1631 if (timeout &gt;= 0)
1632 ev_timer_stop (EV_A_ &amp;to);
1633
1634 // stop io watchers again - their callbacks should have set
1635 for (n = 0; n &lt; nfds; ++n)
1636 ev_io_stop (EV_A_ iow [n]);
1637
1638 return got_events;
1445 } 1639 }
1446 1640
1447 1641
1448 1642
1449 1643
… …
1560 1754
1561 1755
1562 1756
1563 1757
1564</div> 1758</div>
1565<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1759<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1566<div id="OTHER_FUNCTIONS_CONTENT"> 1760<div id="OTHER_FUNCTIONS_CONTENT">
1567<p>There are some other functions of possible interest. Described. Here. Now.</p> 1761<p>There are some other functions of possible interest. Described. Here. Now.</p>
1568<dl> 1762<dl>
1569 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1763 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1570 <dd> 1764 <dd>
… …
1617 1811
1618 1812
1619 1813
1620 1814
1621</div> 1815</div>
1622<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1816<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1623<div id="LIBEVENT_EMULATION_CONTENT"> 1817<div id="LIBEVENT_EMULATION_CONTENT">
1624<p>Libev offers a compatibility emulation layer for libevent. It cannot 1818<p>Libev offers a compatibility emulation layer for libevent. It cannot
1625emulate the internals of libevent, so here are some usage hints:</p> 1819emulate the internals of libevent, so here are some usage hints:</p>
1626<dl> 1820<dl>
1627 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1821 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1637 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1831 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1638to use the libev header file and library.</dt> 1832to use the libev header file and library.</dt>
1639</dl> 1833</dl>
1640 1834
1641</div> 1835</div>
1642<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1836<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1643<div id="C_SUPPORT_CONTENT"> 1837<div id="C_SUPPORT_CONTENT">
1644<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1838<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1645you to use some convinience methods to start/stop watchers and also change 1839you to use some convinience methods to start/stop watchers and also change
1646the callback model to a model using method callbacks on objects.</p> 1840the callback model to a model using method callbacks on objects.</p>
1647<p>To use it,</p> 1841<p>To use it,</p>
1648<pre> #include &lt;ev++.h&gt; 1842<pre> #include &lt;ev++.h&gt;
1649 1843
1650</pre> 1844</pre>
1651<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1845<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 1846of 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> 1847put 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 1848options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1655<code>EV_MULTIPLICITY</code>.</p> 1849<p>Care has been taken to keep the overhead low. The only data member the C++
1850classes add (compared to plain C-style watchers) is the event loop pointer
1851that the watcher is associated with (or no additional members at all if
1852you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1853<p>Currently, functions, and static and non-static member functions can be
1854used as callbacks. Other types should be easy to add as long as they only
1855need one additional pointer for context. If you need support for other
1856types of functors please contact the author (preferably after implementing
1857it).</p>
1656<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1858<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1657<dl> 1859<dl>
1658 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1860 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1659 <dd> 1861 <dd>
1660 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1862 <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 1873which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1672defines by many implementations.</p> 1874defines by many implementations.</p>
1673 <p>All of those classes have these methods:</p> 1875 <p>All of those classes have these methods:</p>
1674 <p> 1876 <p>
1675 <dl> 1877 <dl>
1676 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1878 <dt>ev::TYPE::TYPE ()</dt>
1677 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1879 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1678 <dt>ev::TYPE::~TYPE</dt> 1880 <dt>ev::TYPE::~TYPE</dt>
1679 <dd> 1881 <dd>
1680 <p>The constructor takes a pointer to an object and a method pointer to 1882 <p>The constructor (optionally) takes an event loop to associate the watcher
1681the event handler callback to call in this class. The constructor calls 1883with. 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 1884 <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 1885<code>set</code> method before starting it.</p>
1684automatically associates the default loop with this watcher.</p> 1886 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1887method to set a callback before you can start the watcher.</p>
1888 <p>(The reason why you have to use a method is a limitation in C++ which does
1889not allow explicit template arguments for constructors).</p>
1685 <p>The destructor automatically stops the watcher if it is active.</p> 1890 <p>The destructor automatically stops the watcher if it is active.</p>
1891 </dd>
1892 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1893 <dd>
1894 <p>This method sets the callback method to call. The method has to have a
1895signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1896first argument and the <code>revents</code> as second. The object must be given as
1897parameter and is stored in the <code>data</code> member of the watcher.</p>
1898 <p>This method synthesizes efficient thunking code to call your method from
1899the C callback that libev requires. If your compiler can inline your
1900callback (i.e. it is visible to it at the place of the <code>set</code> call and
1901your compiler is good :), then the method will be fully inlined into the
1902thunking function, making it as fast as a direct C callback.</p>
1903 <p>Example: simple class declaration and watcher initialisation</p>
1904<pre> struct myclass
1905 {
1906 void io_cb (ev::io &amp;w, int revents) { }
1907 }
1908
1909 myclass obj;
1910 ev::io iow;
1911 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1912
1913</pre>
1914 </dd>
1915 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1916 <dd>
1917 <p>Also sets a callback, but uses a static method or plain function as
1918callback. The optional <code>data</code> argument will be stored in the watcher's
1919<code>data</code> member and is free for you to use.</p>
1920 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1921 <p>See the method-<code>set</code> above for more details.</p>
1922 <p>Example:</p>
1923<pre> static void io_cb (ev::io &amp;w, int revents) { }
1924 iow.set &lt;io_cb&gt; ();
1925
1926</pre>
1686 </dd> 1927 </dd>
1687 <dt>w-&gt;set (struct ev_loop *)</dt> 1928 <dt>w-&gt;set (struct ev_loop *)</dt>
1688 <dd> 1929 <dd>
1689 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1930 <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> 1931do this when the watcher is inactive (and not pending either).</p>
1691 </dd> 1932 </dd>
1692 <dt>w-&gt;set ([args])</dt> 1933 <dt>w-&gt;set ([args])</dt>
1693 <dd> 1934 <dd>
1694 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1935 <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 1936called at least once. Unlike the C counterpart, an active watcher gets
1696automatically stopped and restarted.</p> 1937automatically stopped and restarted when reconfiguring it with this
1938method.</p>
1697 </dd> 1939 </dd>
1698 <dt>w-&gt;start ()</dt> 1940 <dt>w-&gt;start ()</dt>
1699 <dd> 1941 <dd>
1700 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1942 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1701constructor already takes the loop.</p> 1943constructor already stores the event loop.</p>
1702 </dd> 1944 </dd>
1703 <dt>w-&gt;stop ()</dt> 1945 <dt>w-&gt;stop ()</dt>
1704 <dd> 1946 <dd>
1705 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1947 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1706 </dd> 1948 </dd>
… …
1730 1972
1731 myclass (); 1973 myclass ();
1732 } 1974 }
1733 1975
1734 myclass::myclass (int fd) 1976 myclass::myclass (int fd)
1735 : io (this, &amp;myclass::io_cb),
1736 idle (this, &amp;myclass::idle_cb)
1737 { 1977 {
1978 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1979 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1980
1738 io.start (fd, ev::READ); 1981 io.start (fd, ev::READ);
1739 } 1982 }
1740 1983
1741 1984
1742 1985
1743 1986
1744</pre> 1987</pre>
1745 1988
1746</div> 1989</div>
1747<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p> 1990<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1748<div id="MACRO_MAGIC_CONTENT"> 1991<div id="MACRO_MAGIC_CONTENT">
1749<p>Libev can be compiled with a variety of options, the most fundemantal is 1992<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 1993<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1751callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1994callbacks 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 1995<p>To make it easier to write programs that cope with either variant, the
1753following macros are defined:</p> 1996following macros are defined:</p>
1754<dl> 1997<dl>
1755 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1998 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1784 <dd> 2027 <dd>
1785 <p>Similar to the other two macros, this gives you the value of the default 2028 <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> 2029loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1787 </dd> 2030 </dd>
1788</dl> 2031</dl>
1789<p>Example: Declare and initialise a check watcher, working regardless of 2032<p>Example: Declare and initialise a check watcher, utilising the above
1790wether multiple loops are supported or not.</p> 2033macros so it will work regardless of whether multiple loops are supported
2034or not.</p>
1791<pre> static void 2035<pre> static void
1792 check_cb (EV_P_ ev_timer *w, int revents) 2036 check_cb (EV_P_ ev_timer *w, int revents)
1793 { 2037 {
1794 ev_check_stop (EV_A_ w); 2038 ev_check_stop (EV_A_ w);
1795 } 2039 }
… …
1797 ev_check check; 2041 ev_check check;
1798 ev_check_init (&amp;check, check_cb); 2042 ev_check_init (&amp;check, check_cb);
1799 ev_check_start (EV_DEFAULT_ &amp;check); 2043 ev_check_start (EV_DEFAULT_ &amp;check);
1800 ev_loop (EV_DEFAULT_ 0); 2044 ev_loop (EV_DEFAULT_ 0);
1801 2045
1802
1803
1804
1805</pre> 2046</pre>
1806 2047
1807</div> 2048</div>
1808<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 2049<h1 id="EMBEDDING">EMBEDDING</h1>
1809<div id="EMBEDDING_CONTENT"> 2050<div id="EMBEDDING_CONTENT">
1810<p>Libev can (and often is) directly embedded into host 2051<p>Libev can (and often is) directly embedded into host
1811applications. Examples of applications that embed it include the Deliantra 2052applications. Examples of applications that embed it include the Deliantra
1812Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2053Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1813and rxvt-unicode.</p> 2054and rxvt-unicode.</p>
… …
1850 ev_vars.h 2091 ev_vars.h
1851 ev_wrap.h 2092 ev_wrap.h
1852 2093
1853 ev_win32.c required on win32 platforms only 2094 ev_win32.c required on win32 platforms only
1854 2095
1855 ev_select.c only when select backend is enabled (which is by default) 2096 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) 2097 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) 2098 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) 2099 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) 2100 ev_port.c only when the solaris port backend is enabled (disabled by default)
1860 2101
… …
1987 </dd> 2228 </dd>
1988 <dt>EV_USE_DEVPOLL</dt> 2229 <dt>EV_USE_DEVPOLL</dt>
1989 <dd> 2230 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p> 2231 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd> 2232 </dd>
2233 <dt>EV_USE_INOTIFY</dt>
2234 <dd>
2235 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2236interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2237be detected at runtime.</p>
2238 </dd>
1992 <dt>EV_H</dt> 2239 <dt>EV_H</dt>
1993 <dd> 2240 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2241 <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 2242undefined 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> 2243can 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 2266will have the <code>struct ev_loop *</code> as first argument, and you can create
2020additional independent event loops. Otherwise there will be no support 2267additional independent event loops. Otherwise there will be no support
2021for multiple event loops and there is no first event loop pointer 2268for multiple event loops and there is no first event loop pointer
2022argument. Instead, all functions act on the single default loop.</p> 2269argument. Instead, all functions act on the single default loop.</p>
2023 </dd> 2270 </dd>
2271 <dt>EV_MINPRI</dt>
2272 <dt>EV_MAXPRI</dt>
2273 <dd>
2274 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2275<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2276provide for more priorities by overriding those symbols (usually defined
2277to be <code>-2</code> and <code>2</code>, respectively).</p>
2278 <p>When doing priority-based operations, libev usually has to linearly search
2279all the priorities, so having many of them (hundreds) uses a lot of space
2280and time, so using the defaults of five priorities (-2 .. +2) is usually
2281fine.</p>
2282 <p>If your embedding app does not need any priorities, defining these both to
2283<code>0</code> will save some memory and cpu.</p>
2284 </dd>
2024 <dt>EV_PERIODIC_ENABLE</dt> 2285 <dt>EV_PERIODIC_ENABLE</dt>
2025 <dd> 2286 <dd>
2026 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2287 <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 2288defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2028code.</p> 2289code.</p>
2029 </dd> 2290 </dd>
2291 <dt>EV_IDLE_ENABLE</dt>
2292 <dd>
2293 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2294defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2295code.</p>
2296 </dd>
2030 <dt>EV_EMBED_ENABLE</dt> 2297 <dt>EV_EMBED_ENABLE</dt>
2031 <dd> 2298 <dd>
2032 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2299 <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> 2300defined to be <code>0</code>, then they are not.</p>
2034 </dd> 2301 </dd>
… …
2051 <dt>EV_PID_HASHSIZE</dt> 2318 <dt>EV_PID_HASHSIZE</dt>
2052 <dd> 2319 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2320 <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 2321pid. 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 2322than enough. If you need to manage thousands of children you might want to
2056increase this value.</p> 2323increase this value (<i>must</i> be a power of two).</p>
2324 </dd>
2325 <dt>EV_INOTIFY_HASHSIZE</dt>
2326 <dd>
2327 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2328inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2329usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2330watchers you might want to increase this value (<i>must</i> be a power of
2331two).</p>
2057 </dd> 2332 </dd>
2058 <dt>EV_COMMON</dt> 2333 <dt>EV_COMMON</dt>
2059 <dd> 2334 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2335 <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 2336this 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 2363the <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 2364interface) 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 2365will be compiled. It is pretty complex because it provides its own header
2091file.</p> 2366file.</p>
2092 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2367 <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> 2368that everybody includes and which overrides some configure choices:</p>
2369<pre> #define EV_MINIMAL 1
2094<pre> #define EV_USE_POLL 0 2370 #define EV_USE_POLL 0
2095 #define EV_MULTIPLICITY 0 2371 #define EV_MULTIPLICITY 0
2096 #define EV_PERIODICS 0 2372 #define EV_PERIODIC_ENABLE 0
2373 #define EV_STAT_ENABLE 0
2374 #define EV_FORK_ENABLE 0
2097 #define EV_CONFIG_H &lt;config.h&gt; 2375 #define EV_CONFIG_H &lt;config.h&gt;
2376 #define EV_MINPRI 0
2377 #define EV_MAXPRI 0
2098 2378
2099 #include &quot;ev++.h&quot; 2379 #include &quot;ev++.h&quot;
2100 2380
2101</pre> 2381</pre>
2102 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2382 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2107 2387
2108 2388
2109</pre> 2389</pre>
2110 2390
2111</div> 2391</div>
2112<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2392<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2113<div id="COMPLEXITIES_CONTENT"> 2393<div id="COMPLEXITIES_CONTENT">
2114 <p>In this section the complexities of (many of) the algorithms used inside 2394 <p>In this section the complexities of (many of) the algorithms used inside
2115libev will be explained. For complexity discussions about backends see the 2395libev will be explained. For complexity discussions about backends see the
2116documentation for <code>ev_default_init</code>.</p> 2396documentation for <code>ev_default_init</code>.</p>
2397 <p>All of the following are about amortised time: If an array needs to be
2398extended, libev needs to realloc and move the whole array, but this
2399happens asymptotically never with higher number of elements, so O(1) might
2400mean it might do a lengthy realloc operation in rare cases, but on average
2401it is much faster and asymptotically approaches constant time.</p>
2117 <p> 2402 <p>
2118 <dl> 2403 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2404 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2405 <dd>
2406 <p>This means that, when you have a watcher that triggers in one hour and
2407there are 100 watchers that would trigger before that then inserting will
2408have to skip those 100 watchers.</p>
2409 </dd>
2120 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2410 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2411 <dd>
2412 <p>That means that for changing a timer costs less than removing/adding them
2413as only the relative motion in the event queue has to be paid for.</p>
2414 </dd>
2121 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2415 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2416 <dd>
2417 <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> 2418=item Stopping check/prepare/idle watchers: O(1)</p>
2419 </dd>
2123 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2420 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2421 <dd>
2422 <p>These watchers are stored in lists then need to be walked to find the
2423correct watcher to remove. The lists are usually short (you don't usually
2424have many watchers waiting for the same fd or signal).</p>
2425 </dd>
2124 <dt>Finding the next timer per loop iteration: O(1)</dt> 2426 <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> 2427 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2428 <dd>
2429 <p>A change means an I/O watcher gets started or stopped, which requires
2430libev to recalculate its status (and possibly tell the kernel).</p>
2431 </dd>
2126 <dt>Activating one watcher: O(1)</dt> 2432 <dt>Activating one watcher: O(1)</dt>
2433 <dt>Priority handling: O(number_of_priorities)</dt>
2434 <dd>
2435 <p>Priorities are implemented by allocating some space for each
2436priority. When doing priority-based operations, libev usually has to
2437linearly search all the priorities.</p>
2438 </dd>
2127 </dl> 2439 </dl>
2128 </p> 2440 </p>
2129 2441
2130 2442
2131 2443
2132 2444
2133 2445
2134</div> 2446</div>
2135<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2447<h1 id="AUTHOR">AUTHOR</h1>
2136<div id="AUTHOR_CONTENT"> 2448<div id="AUTHOR_CONTENT">
2137 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2449 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
2138 2450
2139</div> 2451</div>
2140</div></body> 2452</div></body>

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