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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="Fri Dec 7 19:03:06 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;
… …
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>Libev is an event loop: you register interest in certain events (such as a 124<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 125file descriptor being readable or a timeout occuring), and it will manage
126these event sources and provide your program with events.</p> 126these 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 127<p>To do this, it must take more or less complete control over your process
… …
131watchers</i>, which are relatively small C structures you initialise with the 131watchers</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 132details of the event, and then hand it over to libev by <i>starting</i> the
133watcher.</p> 133watcher.</p>
134 134
135</div> 135</div>
136<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
137<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the 138<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 139BSD-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>), 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous 142with customised rescheduling (<code>ev_periodic</code>), synchronous signals
142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and 143(<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>, 144watchers 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 145<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 146file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p> 147(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this 148<p>It also is quite fast (see this
148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent 149<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
149for example).</p> 150for example).</p>
150 151
151</div> 152</div>
152<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
153<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
154<p>Libev is very configurable. In this manual the default configuration will 155<p>Libev is very configurable. In this manual the default configuration will
155be described, which supports multiple event loops. For more info about 156be described, which supports multiple event loops. For more info about
156various configuration options please have a look at <strong>EMBED</strong> section in 157various configuration options please have a look at <strong>EMBED</strong> section in
157this manual. If libev was configured without support for multiple event 158this manual. If libev was configured without support for multiple event
158loops, then all functions taking an initial argument of name <code>loop</code> 159loops, 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> 160(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
160 161
161</div> 162</div>
162<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
163<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
164<p>Libev represents time as a single floating point number, representing the 165<p>Libev represents time as a single floating point number, representing the
165(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
166the beginning of 1970, details are complicated, don't ask). This type is 167the 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 168called <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 169to the <code>double</code> type in C, and when you need to do any calculations on
169it, you should treat it as such.</p> 170it, you should treat it as such.</p>
170 171
171</div> 172</div>
172<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
173<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
174<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
175library in any way.</p> 176library in any way.</p>
176<dl> 177<dl>
177 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
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229might be supported on the current system, you would need to look at 230might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 231<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 232recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 234 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 236 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 237 <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 238semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 239allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 240memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
241 <p>You could override this function in high-availability programs to, say, 243 <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, 244free 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> 245or 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 246 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 247retries).</p>
… …
285</pre> 287</pre>
286 </dd> 288 </dd>
287</dl> 289</dl>
288 290
289</div> 291</div>
290<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 292<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
291<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 293<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 294<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 295types of such loops, the <i>default</i> loop, which supports signals and child
294events, and dynamically created loops which do not.</p> 296events, and dynamically created loops which do not.</p>
295<p>If you use threads, a common model is to run the default event loop 297<p>If you use threads, a common model is to run the default event loop
… …
323or setgid) then libev will <i>not</i> look at the environment variable 325or setgid) then libev will <i>not</i> look at the environment variable
324<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 326<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
325override the flags completely if it is found in the environment. This is 327override 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 328useful to try out specific backends to test their performance, or to work
327around bugs.</p> 329around bugs.</p>
330 </dd>
331 <dt><code>EVFLAG_FORKCHECK</code></dt>
332 <dd>
333 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
334a fork, you can also make libev check for a fork in each iteration by
335enabling this flag.</p>
336 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
337and thus this might slow down your event loop if you do a lot of loop
338iterations and little real work, but is usually not noticeable (on my
339Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
340without a syscall and thus <i>very</i> fast, but my Linux system also has
341<code>pthread_atfork</code> which is even faster).</p>
342 <p>The big advantage of this flag is that you can forget about fork (and
343forget about forgetting to tell libev about forking) when you use this
344flag.</p>
345 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
346environment variable.</p>
328 </dd> 347 </dd>
329 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 348 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
330 <dd> 349 <dd>
331 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 350 <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, 351libev tries to roll its own fd_set with no limits on the number of fds,
… …
462 <dd> 481 <dd>
463 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 482 <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 483<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> 484after fork, and how you do this is entirely your own problem.</p>
466 </dd> 485 </dd>
486 <dt>unsigned int ev_loop_count (loop)</dt>
487 <dd>
488 <p>Returns the count of loop iterations for the loop, which is identical to
489the number of times libev did poll for new events. It starts at <code>0</code> and
490happily wraps around with enough iterations.</p>
491 <p>This value can sometimes be useful as a generation counter of sorts (it
492&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
493<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
494 </dd>
467 <dt>unsigned int ev_backend (loop)</dt> 495 <dt>unsigned int ev_backend (loop)</dt>
468 <dd> 496 <dd>
469 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 497 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
470use.</p> 498use.</p>
471 </dd> 499 </dd>
… …
568 596
569 597
570 598
571 599
572</div> 600</div>
573<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 601<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
574<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 602<div id="ANATOMY_OF_A_WATCHER_CONTENT">
575<p>A watcher is a structure that you create and register to record your 603<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 604interest 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> 605become 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) 606<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
741events but its callback has not yet been invoked). As long as a watcher 769events 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 770is 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 771<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
744libev (e.g. you cnanot <code>free ()</code> it).</p> 772libev (e.g. you cnanot <code>free ()</code> it).</p>
745 </dd> 773 </dd>
746 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 774 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 775 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 776 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 777 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 778 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 779 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 780 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 781(modulo threads).</p>
782 </dd>
783 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
784 <dt>int ev_priority (ev_TYPE *watcher)</dt>
785 <dd>
786 <p>Set and query the priority of the watcher. The priority is a small
787integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
788(default: <code>-2</code>). Pending watchers with higher priority will be invoked
789before watchers with lower priority, but priority will not keep watchers
790from being executed (except for <code>ev_idle</code> watchers).</p>
791 <p>This means that priorities are <i>only</i> used for ordering callback
792invocation after new events have been received. This is useful, for
793example, to reduce latency after idling, or more often, to bind two
794watchers on the same event and make sure one is called first.</p>
795 <p>If you need to suppress invocation when higher priority events are pending
796you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
797 <p>The default priority used by watchers when no priority has been set is
798always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
799 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
800fine, as long as you do not mind that the priority value you query might
801or might not have been adjusted to be within valid range.</p>
754 </dd> 802 </dd>
755</dl> 803</dl>
756 804
757 805
758 806
… …
783 struct my_io *w = (struct my_io *)w_; 831 struct my_io *w = (struct my_io *)w_;
784 ... 832 ...
785 } 833 }
786 834
787</pre> 835</pre>
788<p>More interesting and less C-conformant ways of catsing your callback type 836<p>More interesting and less C-conformant ways of casting your callback type
789have been omitted....</p> 837instead have been omitted.</p>
838<p>Another common scenario is having some data structure with multiple
839watchers:</p>
840<pre> struct my_biggy
841 {
842 int some_data;
843 ev_timer t1;
844 ev_timer t2;
845 }
790 846
847</pre>
848<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
849you need to use <code>offsetof</code>:</p>
850<pre> #include &lt;stddef.h&gt;
791 851
852 static void
853 t1_cb (EV_P_ struct ev_timer *w, int revents)
854 {
855 struct my_biggy big = (struct my_biggy *
856 (((char *)w) - offsetof (struct my_biggy, t1));
857 }
792 858
859 static void
860 t2_cb (EV_P_ struct ev_timer *w, int revents)
861 {
862 struct my_biggy big = (struct my_biggy *
863 (((char *)w) - offsetof (struct my_biggy, t2));
864 }
793 865
794 866
867
868
869</pre>
870
795</div> 871</div>
796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 872<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
797<div id="WATCHER_TYPES_CONTENT"> 873<div id="WATCHER_TYPES_CONTENT">
798<p>This section describes each watcher in detail, but will not repeat 874<p>This section describes each watcher in detail, but will not repeat
799information given in the last section. Any initialisation/set macros, 875information given in the last section. Any initialisation/set macros,
800functions and members specific to the watcher type are explained.</p> 876functions and members specific to the watcher type are explained.</p>
801<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, 877<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
… …
841this situation even with a relatively standard program structure. Thus 917this 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 918it 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> 919<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 920<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 921play 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 922whether 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 923such as poll (fortunately in our Xlib example, Xlib already does this on
848its own, so its quite safe to use).</p> 924its own, so its quite safe to use).</p>
849<dl> 925<dl>
850 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 926 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
851 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 927 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
922 </dd> 998 </dd>
923 <dt>ev_timer_again (loop)</dt> 999 <dt>ev_timer_again (loop)</dt>
924 <dd> 1000 <dd>
925 <p>This will act as if the timer timed out and restart it again if it is 1001 <p>This will act as if the timer timed out and restart it again if it is
926repeating. The exact semantics are:</p> 1002repeating. The exact semantics are:</p>
1003 <p>If the timer is pending, its pending status is cleared.</p>
927 <p>If the timer is started but nonrepeating, stop it.</p> 1004 <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 1005 <p>If the timer is repeating, either start it if necessary (with the
929value), or reset the running timer to the repeat value.</p> 1006<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 1007 <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 1008example: 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, 1009timeout, 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 1010seconds 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 1011configure 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 1012<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 1013you 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 1014socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
938need be.</p> 1015automatically restart it if need be.</p>
939 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1016 <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> 1017altogether 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.); 1018<pre> ev_timer_init (timer, callback, 0., 5.);
942 ev_timer_again (loop, timer); 1019 ev_timer_again (loop, timer);
943 ... 1020 ...
944 timer-&gt;again = 17.; 1021 timer-&gt;again = 17.;
945 ev_timer_again (loop, timer); 1022 ev_timer_again (loop, timer);
946 ... 1023 ...
947 timer-&gt;again = 10.; 1024 timer-&gt;again = 10.;
948 ev_timer_again (loop, timer); 1025 ev_timer_again (loop, timer);
949 1026
950</pre> 1027</pre>
951 <p>This is more efficient then stopping/starting the timer eahc time you want 1028 <p>This is more slightly efficient then stopping/starting the timer each time
952to modify its timeout value.</p> 1029you want to modify its timeout value.</p>
953 </dd> 1030 </dd>
954 <dt>ev_tstamp repeat [read-write]</dt> 1031 <dt>ev_tstamp repeat [read-write]</dt>
955 <dd> 1032 <dd>
956 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1033 <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), 1034or <code>ev_timer_again</code> is called and determines the next timeout (if any),
… …
1218<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1295<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 1296not 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 1297not 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 1298otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p> 1299the stat buffer having unspecified contents.</p>
1300<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1301relative and your working directory changes, the behaviour is undefined.</p>
1223<p>Since there is no standard to do this, the portable implementation simply 1302<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 1303calls <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 1304can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1305a 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 1306unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also 1307five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats 1308impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p> 1309usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers, 1310<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be 1311as even with OS-supported change notifications, this can be
1233resource-intensive.</p> 1312resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but 1313<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> 1314implemented (implementing kqueue support is left as an exercise for the
1315reader). Inotify will be used to give hints only and should not change the
1316semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1317to fall back to regular polling again even with inotify, but changes are
1318usually detected immediately, and if the file exists there will be no
1319polling.</p>
1236<dl> 1320<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1321 <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> 1322 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd> 1323 <dd>
1240 <p>Configures the watcher to wait for status changes of the given 1324 <p>Configures the watcher to wait for status changes of the given
… …
1303</pre> 1387</pre>
1304 1388
1305</div> 1389</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> 1390<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"> 1391<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 1392<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 1393priority are pending (prepare, check and other idle watchers do not
1310as your process is busy handling sockets or timeouts (or even signals, 1394count).</p>
1311imagine) it will not be triggered. But when your process is idle all idle 1395<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 - 1396(or even signals, imagine) of the same or higher priority it will not be
1397triggered. But when your process is idle (or only lower-priority watchers
1398are pending), the idle watchers are being called once per event loop
1313until stopped, that is, or your process receives more events and becomes 1399iteration - until stopped, that is, or your process receives more events
1314busy.</p> 1400and becomes busy again with higher priority stuff.</p>
1315<p>The most noteworthy effect is that as long as any idle watchers are 1401<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> 1402active, the process will not block when waiting for new events.</p>
1317<p>Apart from keeping your process non-blocking (which is a useful 1403<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 1404effect 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 1405&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1409 1495
1410 // create io watchers for each fd and a timer before blocking 1496 // create io watchers for each fd and a timer before blocking
1411 static void 1497 static void
1412 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1498 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1413 { 1499 {
1414 int timeout = 3600000;truct pollfd fds [nfd]; 1500 int timeout = 3600000;
1501 struct pollfd fds [nfd];
1415 // actual code will need to loop here and realloc etc. 1502 // actual code will need to loop here and realloc etc.
1416 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1503 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1417 1504
1418 /* the callback is illegal, but won't be called as we stop during check */ 1505 /* the callback is illegal, but won't be called as we stop during check */
1419 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1506 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
… …
1560 1647
1561 1648
1562 1649
1563 1650
1564</div> 1651</div>
1565<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1652<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1566<div id="OTHER_FUNCTIONS_CONTENT"> 1653<div id="OTHER_FUNCTIONS_CONTENT">
1567<p>There are some other functions of possible interest. Described. Here. Now.</p> 1654<p>There are some other functions of possible interest. Described. Here. Now.</p>
1568<dl> 1655<dl>
1569 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1656 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1570 <dd> 1657 <dd>
… …
1617 1704
1618 1705
1619 1706
1620 1707
1621</div> 1708</div>
1622<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1709<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1623<div id="LIBEVENT_EMULATION_CONTENT"> 1710<div id="LIBEVENT_EMULATION_CONTENT">
1624<p>Libev offers a compatibility emulation layer for libevent. It cannot 1711<p>Libev offers a compatibility emulation layer for libevent. It cannot
1625emulate the internals of libevent, so here are some usage hints:</p> 1712emulate the internals of libevent, so here are some usage hints:</p>
1626<dl> 1713<dl>
1627 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1714 <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 1724 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1638to use the libev header file and library.</dt> 1725to use the libev header file and library.</dt>
1639</dl> 1726</dl>
1640 1727
1641</div> 1728</div>
1642<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1729<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1643<div id="C_SUPPORT_CONTENT"> 1730<div id="C_SUPPORT_CONTENT">
1644<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1731<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 1732you to use some convinience methods to start/stop watchers and also change
1646the callback model to a model using method callbacks on objects.</p> 1733the callback model to a model using method callbacks on objects.</p>
1647<p>To use it,</p> 1734<p>To use it,</p>
… …
1742 1829
1743 1830
1744</pre> 1831</pre>
1745 1832
1746</div> 1833</div>
1747<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p> 1834<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1748<div id="MACRO_MAGIC_CONTENT"> 1835<div id="MACRO_MAGIC_CONTENT">
1749<p>Libev can be compiled with a variety of options, the most fundemantal is 1836<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 1837<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1751callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1838callbacks 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 1839<p>To make it easier to write programs that cope with either variant, the
1753following macros are defined:</p> 1840following macros are defined:</p>
1754<dl> 1841<dl>
1755 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1842 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1784 <dd> 1871 <dd>
1785 <p>Similar to the other two macros, this gives you the value of the default 1872 <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> 1873loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1787 </dd> 1874 </dd>
1788</dl> 1875</dl>
1789<p>Example: Declare and initialise a check watcher, working regardless of 1876<p>Example: Declare and initialise a check watcher, utilising the above
1790wether multiple loops are supported or not.</p> 1877macros so it will work regardless of whether multiple loops are supported
1878or not.</p>
1791<pre> static void 1879<pre> static void
1792 check_cb (EV_P_ ev_timer *w, int revents) 1880 check_cb (EV_P_ ev_timer *w, int revents)
1793 { 1881 {
1794 ev_check_stop (EV_A_ w); 1882 ev_check_stop (EV_A_ w);
1795 } 1883 }
… …
1797 ev_check check; 1885 ev_check check;
1798 ev_check_init (&amp;check, check_cb); 1886 ev_check_init (&amp;check, check_cb);
1799 ev_check_start (EV_DEFAULT_ &amp;check); 1887 ev_check_start (EV_DEFAULT_ &amp;check);
1800 ev_loop (EV_DEFAULT_ 0); 1888 ev_loop (EV_DEFAULT_ 0);
1801 1889
1802
1803
1804
1805</pre> 1890</pre>
1806 1891
1807</div> 1892</div>
1808<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1893<h1 id="EMBEDDING">EMBEDDING</h1>
1809<div id="EMBEDDING_CONTENT"> 1894<div id="EMBEDDING_CONTENT">
1810<p>Libev can (and often is) directly embedded into host 1895<p>Libev can (and often is) directly embedded into host
1811applications. Examples of applications that embed it include the Deliantra 1896applications. Examples of applications that embed it include the Deliantra
1812Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1897Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1813and rxvt-unicode.</p> 1898and rxvt-unicode.</p>
… …
1850 ev_vars.h 1935 ev_vars.h
1851 ev_wrap.h 1936 ev_wrap.h
1852 1937
1853 ev_win32.c required on win32 platforms only 1938 ev_win32.c required on win32 platforms only
1854 1939
1855 ev_select.c only when select backend is enabled (which is by default) 1940 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) 1941 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) 1942 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) 1943 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) 1944 ev_port.c only when the solaris port backend is enabled (disabled by default)
1860 1945
… …
1987 </dd> 2072 </dd>
1988 <dt>EV_USE_DEVPOLL</dt> 2073 <dt>EV_USE_DEVPOLL</dt>
1989 <dd> 2074 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p> 2075 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd> 2076 </dd>
2077 <dt>EV_USE_INOTIFY</dt>
2078 <dd>
2079 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2080interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2081be detected at runtime.</p>
2082 </dd>
1992 <dt>EV_H</dt> 2083 <dt>EV_H</dt>
1993 <dd> 2084 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2085 <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 2086undefined 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> 2087can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
2025 <dd> 2116 <dd>
2026 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2117 <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 2118defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2028code.</p> 2119code.</p>
2029 </dd> 2120 </dd>
2121 <dt>EV_IDLE_ENABLE</dt>
2122 <dd>
2123 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2124defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2125code.</p>
2126 </dd>
2030 <dt>EV_EMBED_ENABLE</dt> 2127 <dt>EV_EMBED_ENABLE</dt>
2031 <dd> 2128 <dd>
2032 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2129 <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> 2130defined to be <code>0</code>, then they are not.</p>
2034 </dd> 2131 </dd>
… …
2051 <dt>EV_PID_HASHSIZE</dt> 2148 <dt>EV_PID_HASHSIZE</dt>
2052 <dd> 2149 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2150 <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 2151pid. 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 2152than enough. If you need to manage thousands of children you might want to
2056increase this value.</p> 2153increase this value (<i>must</i> be a power of two).</p>
2154 </dd>
2155 <dt>EV_INOTIFY_HASHSIZE</dt>
2156 <dd>
2157 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2158inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2159usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2160watchers you might want to increase this value (<i>must</i> be a power of
2161two).</p>
2057 </dd> 2162 </dd>
2058 <dt>EV_COMMON</dt> 2163 <dt>EV_COMMON</dt>
2059 <dd> 2164 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2165 <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 2166this 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 2193the <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 2194interface) 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 2195will be compiled. It is pretty complex because it provides its own header
2091file.</p> 2196file.</p>
2092 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2197 <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> 2198that everybody includes and which overrides some configure choices:</p>
2199<pre> #define EV_MINIMAL 1
2094<pre> #define EV_USE_POLL 0 2200 #define EV_USE_POLL 0
2095 #define EV_MULTIPLICITY 0 2201 #define EV_MULTIPLICITY 0
2096 #define EV_PERIODICS 0 2202 #define EV_PERIODIC_ENABLE 0
2203 #define EV_STAT_ENABLE 0
2204 #define EV_FORK_ENABLE 0
2097 #define EV_CONFIG_H &lt;config.h&gt; 2205 #define EV_CONFIG_H &lt;config.h&gt;
2206 #define EV_MINPRI 0
2207 #define EV_MAXPRI 0
2098 2208
2099 #include &quot;ev++.h&quot; 2209 #include &quot;ev++.h&quot;
2100 2210
2101</pre> 2211</pre>
2102 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2212 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2107 2217
2108 2218
2109</pre> 2219</pre>
2110 2220
2111</div> 2221</div>
2112<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2222<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2113<div id="COMPLEXITIES_CONTENT"> 2223<div id="COMPLEXITIES_CONTENT">
2114 <p>In this section the complexities of (many of) the algorithms used inside 2224 <p>In this section the complexities of (many of) the algorithms used inside
2115libev will be explained. For complexity discussions about backends see the 2225libev will be explained. For complexity discussions about backends see the
2116documentation for <code>ev_default_init</code>.</p> 2226documentation for <code>ev_default_init</code>.</p>
2117 <p> 2227 <p>
2118 <dl> 2228 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2229 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2120 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2230 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2121 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2231 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2122 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2232 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2123 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2233 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2124 <dt>Finding the next timer per loop iteration: O(1)</dt> 2234 <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> 2235 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2126 <dt>Activating one watcher: O(1)</dt> 2236 <dt>Activating one watcher: O(1)</dt>
2127 </dl> 2237 </dl>
2128 </p> 2238 </p>
… …
2130 2240
2131 2241
2132 2242
2133 2243
2134</div> 2244</div>
2135<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2245<h1 id="AUTHOR">AUTHOR</h1>
2136<div id="AUTHOR_CONTENT"> 2246<div id="AUTHOR_CONTENT">
2137 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2247 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
2138 2248
2139</div> 2249</div>
2140</div></body> 2250</div></body>

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