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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 21:19:14 2007" />
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11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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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>
… …
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
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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>
… …
568 599
569 600
570 601
571 602
572</div> 603</div>
573<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 604<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
574<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 605<div id="ANATOMY_OF_A_WATCHER_CONTENT">
575<p>A watcher is a structure that you create and register to record your 606<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 607interest 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> 608become 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) 609<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
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741events but its callback has not yet been invoked). As long as a watcher 772events 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 773is 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 774<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> 775libev (e.g. you cnanot <code>free ()</code> it).</p>
745 </dd> 776 </dd>
746 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 777 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 778 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 779 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 780 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 781 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 782 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 783 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 784(modulo threads).</p>
785 </dd>
786 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
787 <dt>int ev_priority (ev_TYPE *watcher)</dt>
788 <dd>
789 <p>Set and query the priority of the watcher. The priority is a small
790integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
791(default: <code>-2</code>). Pending watchers with higher priority will be invoked
792before watchers with lower priority, but priority will not keep watchers
793from being executed (except for <code>ev_idle</code> watchers).</p>
794 <p>This means that priorities are <i>only</i> used for ordering callback
795invocation after new events have been received. This is useful, for
796example, to reduce latency after idling, or more often, to bind two
797watchers on the same event and make sure one is called first.</p>
798 <p>If you need to suppress invocation when higher priority events are pending
799you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
800 <p>The default priority used by watchers when no priority has been set is
801always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
802 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
803fine, as long as you do not mind that the priority value you query might
804or might not have been adjusted to be within valid range.</p>
754 </dd> 805 </dd>
755</dl> 806</dl>
756 807
757 808
758 809
… …
783 struct my_io *w = (struct my_io *)w_; 834 struct my_io *w = (struct my_io *)w_;
784 ... 835 ...
785 } 836 }
786 837
787</pre> 838</pre>
788<p>More interesting and less C-conformant ways of catsing your callback type 839<p>More interesting and less C-conformant ways of casting your callback type
789have been omitted....</p> 840instead have been omitted.</p>
841<p>Another common scenario is having some data structure with multiple
842watchers:</p>
843<pre> struct my_biggy
844 {
845 int some_data;
846 ev_timer t1;
847 ev_timer t2;
848 }
790 849
850</pre>
851<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
852you need to use <code>offsetof</code>:</p>
853<pre> #include &lt;stddef.h&gt;
791 854
855 static void
856 t1_cb (EV_P_ struct ev_timer *w, int revents)
857 {
858 struct my_biggy big = (struct my_biggy *
859 (((char *)w) - offsetof (struct my_biggy, t1));
860 }
792 861
862 static void
863 t2_cb (EV_P_ struct ev_timer *w, int revents)
864 {
865 struct my_biggy big = (struct my_biggy *
866 (((char *)w) - offsetof (struct my_biggy, t2));
867 }
793 868
794 869
870
871
872</pre>
873
795</div> 874</div>
796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 875<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
797<div id="WATCHER_TYPES_CONTENT"> 876<div id="WATCHER_TYPES_CONTENT">
798<p>This section describes each watcher in detail, but will not repeat 877<p>This section describes each watcher in detail, but will not repeat
799information given in the last section. Any initialisation/set macros, 878information given in the last section. Any initialisation/set macros,
800functions and members specific to the watcher type are explained.</p> 879functions and members specific to the watcher type are explained.</p>
801<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, 880<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
… …
841this situation even with a relatively standard program structure. Thus 920this 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 921it 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> 922<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 923<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 924play 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 925whether 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 926such as poll (fortunately in our Xlib example, Xlib already does this on
848its own, so its quite safe to use).</p> 927its own, so its quite safe to use).</p>
849<dl> 928<dl>
850 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 929 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
851 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 930 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
922 </dd> 1001 </dd>
923 <dt>ev_timer_again (loop)</dt> 1002 <dt>ev_timer_again (loop)</dt>
924 <dd> 1003 <dd>
925 <p>This will act as if the timer timed out and restart it again if it is 1004 <p>This will act as if the timer timed out and restart it again if it is
926repeating. The exact semantics are:</p> 1005repeating. The exact semantics are:</p>
1006 <p>If the timer is pending, its pending status is cleared.</p>
927 <p>If the timer is started but nonrepeating, stop it.</p> 1007 <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 1008 <p>If the timer is repeating, either start it if necessary (with the
929value), or reset the running timer to the repeat value.</p> 1009<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 1010 <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 1011example: 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, 1012timeout, 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 1013seconds 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 1014configure 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 1015<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 1016you 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 1017socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
938need be.</p> 1018automatically restart it if need be.</p>
939 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1019 <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> 1020altogether 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.); 1021<pre> ev_timer_init (timer, callback, 0., 5.);
942 ev_timer_again (loop, timer); 1022 ev_timer_again (loop, timer);
943 ... 1023 ...
944 timer-&gt;again = 17.; 1024 timer-&gt;again = 17.;
945 ev_timer_again (loop, timer); 1025 ev_timer_again (loop, timer);
946 ... 1026 ...
947 timer-&gt;again = 10.; 1027 timer-&gt;again = 10.;
948 ev_timer_again (loop, timer); 1028 ev_timer_again (loop, timer);
949 1029
950</pre> 1030</pre>
951 <p>This is more efficient then stopping/starting the timer eahc time you want 1031 <p>This is more slightly efficient then stopping/starting the timer each time
952to modify its timeout value.</p> 1032you want to modify its timeout value.</p>
953 </dd> 1033 </dd>
954 <dt>ev_tstamp repeat [read-write]</dt> 1034 <dt>ev_tstamp repeat [read-write]</dt>
955 <dd> 1035 <dd>
956 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1036 <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), 1037or <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 1298<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 1299not 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 1300not 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 1301otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p> 1302the stat buffer having unspecified contents.</p>
1303<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1304relative and your working directory changes, the behaviour is undefined.</p>
1223<p>Since there is no standard to do this, the portable implementation simply 1305<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 1306calls <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 1307can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1308a 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 1309unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also 1310five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats 1311impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p> 1312usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers, 1313<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be 1314as even with OS-supported change notifications, this can be
1233resource-intensive.</p> 1315resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but 1316<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> 1317implemented (implementing kqueue support is left as an exercise for the
1318reader). Inotify will be used to give hints only and should not change the
1319semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1320to fall back to regular polling again even with inotify, but changes are
1321usually detected immediately, and if the file exists there will be no
1322polling.</p>
1236<dl> 1323<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1324 <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> 1325 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd> 1326 <dd>
1240 <p>Configures the watcher to wait for status changes of the given 1327 <p>Configures the watcher to wait for status changes of the given
… …
1303</pre> 1390</pre>
1304 1391
1305</div> 1392</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> 1393<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"> 1394<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 1395<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 1396priority are pending (prepare, check and other idle watchers do not
1310as your process is busy handling sockets or timeouts (or even signals, 1397count).</p>
1311imagine) it will not be triggered. But when your process is idle all idle 1398<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 - 1399(or even signals, imagine) of the same or higher priority it will not be
1400triggered. But when your process is idle (or only lower-priority watchers
1401are pending), the idle watchers are being called once per event loop
1313until stopped, that is, or your process receives more events and becomes 1402iteration - until stopped, that is, or your process receives more events
1314busy.</p> 1403and becomes busy again with higher priority stuff.</p>
1315<p>The most noteworthy effect is that as long as any idle watchers are 1404<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> 1405active, the process will not block when waiting for new events.</p>
1317<p>Apart from keeping your process non-blocking (which is a useful 1406<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 1407effect 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 1408&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1409 1498
1410 // create io watchers for each fd and a timer before blocking 1499 // create io watchers for each fd and a timer before blocking
1411 static void 1500 static void
1412 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1501 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1413 { 1502 {
1414 int timeout = 3600000;truct pollfd fds [nfd]; 1503 int timeout = 3600000;
1504 struct pollfd fds [nfd];
1415 // actual code will need to loop here and realloc etc. 1505 // actual code will need to loop here and realloc etc.
1416 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1506 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1417 1507
1418 /* the callback is illegal, but won't be called as we stop during check */ 1508 /* the callback is illegal, but won't be called as we stop during check */
1419 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1509 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
… …
1560 1650
1561 1651
1562 1652
1563 1653
1564</div> 1654</div>
1565<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1655<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1566<div id="OTHER_FUNCTIONS_CONTENT"> 1656<div id="OTHER_FUNCTIONS_CONTENT">
1567<p>There are some other functions of possible interest. Described. Here. Now.</p> 1657<p>There are some other functions of possible interest. Described. Here. Now.</p>
1568<dl> 1658<dl>
1569 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1659 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1570 <dd> 1660 <dd>
… …
1617 1707
1618 1708
1619 1709
1620 1710
1621</div> 1711</div>
1622<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1712<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1623<div id="LIBEVENT_EMULATION_CONTENT"> 1713<div id="LIBEVENT_EMULATION_CONTENT">
1624<p>Libev offers a compatibility emulation layer for libevent. It cannot 1714<p>Libev offers a compatibility emulation layer for libevent. It cannot
1625emulate the internals of libevent, so here are some usage hints:</p> 1715emulate the internals of libevent, so here are some usage hints:</p>
1626<dl> 1716<dl>
1627 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1717 <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 1727 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1638to use the libev header file and library.</dt> 1728to use the libev header file and library.</dt>
1639</dl> 1729</dl>
1640 1730
1641</div> 1731</div>
1642<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1732<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1643<div id="C_SUPPORT_CONTENT"> 1733<div id="C_SUPPORT_CONTENT">
1644<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1734<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 1735you to use some convinience methods to start/stop watchers and also change
1646the callback model to a model using method callbacks on objects.</p> 1736the callback model to a model using method callbacks on objects.</p>
1647<p>To use it,</p> 1737<p>To use it,</p>
1648<pre> #include &lt;ev++.h&gt; 1738<pre> #include &lt;ev++.h&gt;
1649 1739
1650</pre> 1740</pre>
1651<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1741<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 1742of 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> 1743put 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 1744options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1655<code>EV_MULTIPLICITY</code>.</p> 1745<p>Care has been taken to keep the overhead low. The only data member the C++
1746classes add (compared to plain C-style watchers) is the event loop pointer
1747that the watcher is associated with (or no additional members at all if
1748you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1749<p>Currently, functions, and static and non-static member functions can be
1750used as callbacks. Other types should be easy to add as long as they only
1751need one additional pointer for context. If you need support for other
1752types of functors please contact the author (preferably after implementing
1753it).</p>
1656<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1754<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1657<dl> 1755<dl>
1658 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1756 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1659 <dd> 1757 <dd>
1660 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1758 <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 1769which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1672defines by many implementations.</p> 1770defines by many implementations.</p>
1673 <p>All of those classes have these methods:</p> 1771 <p>All of those classes have these methods:</p>
1674 <p> 1772 <p>
1675 <dl> 1773 <dl>
1676 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1774 <dt>ev::TYPE::TYPE ()</dt>
1677 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1775 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1678 <dt>ev::TYPE::~TYPE</dt> 1776 <dt>ev::TYPE::~TYPE</dt>
1679 <dd> 1777 <dd>
1680 <p>The constructor takes a pointer to an object and a method pointer to 1778 <p>The constructor (optionally) takes an event loop to associate the watcher
1681the event handler callback to call in this class. The constructor calls 1779with. 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 1780 <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 1781<code>set</code> method before starting it.</p>
1684automatically associates the default loop with this watcher.</p> 1782 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1783method to set a callback before you can start the watcher.</p>
1784 <p>(The reason why you have to use a method is a limitation in C++ which does
1785not allow explicit template arguments for constructors).</p>
1685 <p>The destructor automatically stops the watcher if it is active.</p> 1786 <p>The destructor automatically stops the watcher if it is active.</p>
1787 </dd>
1788 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1789 <dd>
1790 <p>This method sets the callback method to call. The method has to have a
1791signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1792first argument and the <code>revents</code> as second. The object must be given as
1793parameter and is stored in the <code>data</code> member of the watcher.</p>
1794 <p>This method synthesizes efficient thunking code to call your method from
1795the C callback that libev requires. If your compiler can inline your
1796callback (i.e. it is visible to it at the place of the <code>set</code> call and
1797your compiler is good :), then the method will be fully inlined into the
1798thunking function, making it as fast as a direct C callback.</p>
1799 <p>Example: simple class declaration and watcher initialisation</p>
1800<pre> struct myclass
1801 {
1802 void io_cb (ev::io &amp;w, int revents) { }
1803 }
1804
1805 myclass obj;
1806 ev::io iow;
1807 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1808
1809</pre>
1810 </dd>
1811 <dt>w-&gt;set (void (*function)(watcher &amp;w, int), void *data = 0)</dt>
1812 <dd>
1813 <p>Also sets a callback, but uses a static method or plain function as
1814callback. The optional <code>data</code> argument will be stored in the watcher's
1815<code>data</code> member and is free for you to use.</p>
1816 <p>See the method-<code>set</code> above for more details.</p>
1686 </dd> 1817 </dd>
1687 <dt>w-&gt;set (struct ev_loop *)</dt> 1818 <dt>w-&gt;set (struct ev_loop *)</dt>
1688 <dd> 1819 <dd>
1689 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1820 <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> 1821do this when the watcher is inactive (and not pending either).</p>
1691 </dd> 1822 </dd>
1692 <dt>w-&gt;set ([args])</dt> 1823 <dt>w-&gt;set ([args])</dt>
1693 <dd> 1824 <dd>
1694 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1825 <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 1826called at least once. Unlike the C counterpart, an active watcher gets
1696automatically stopped and restarted.</p> 1827automatically stopped and restarted when reconfiguring it with this
1828method.</p>
1697 </dd> 1829 </dd>
1698 <dt>w-&gt;start ()</dt> 1830 <dt>w-&gt;start ()</dt>
1699 <dd> 1831 <dd>
1700 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1832 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1701constructor already takes the loop.</p> 1833constructor already stores the event loop.</p>
1702 </dd> 1834 </dd>
1703 <dt>w-&gt;stop ()</dt> 1835 <dt>w-&gt;stop ()</dt>
1704 <dd> 1836 <dd>
1705 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1837 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1706 </dd> 1838 </dd>
… …
1730 1862
1731 myclass (); 1863 myclass ();
1732 } 1864 }
1733 1865
1734 myclass::myclass (int fd) 1866 myclass::myclass (int fd)
1735 : io (this, &amp;myclass::io_cb),
1736 idle (this, &amp;myclass::idle_cb)
1737 { 1867 {
1868 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1869 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1870
1738 io.start (fd, ev::READ); 1871 io.start (fd, ev::READ);
1739 } 1872 }
1740 1873
1741 1874
1742 1875
1743 1876
1744</pre> 1877</pre>
1745 1878
1746</div> 1879</div>
1747<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p> 1880<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1748<div id="MACRO_MAGIC_CONTENT"> 1881<div id="MACRO_MAGIC_CONTENT">
1749<p>Libev can be compiled with a variety of options, the most fundemantal is 1882<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 1883<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1751callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1884callbacks 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 1885<p>To make it easier to write programs that cope with either variant, the
1753following macros are defined:</p> 1886following macros are defined:</p>
1754<dl> 1887<dl>
1755 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1888 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1784 <dd> 1917 <dd>
1785 <p>Similar to the other two macros, this gives you the value of the default 1918 <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> 1919loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1787 </dd> 1920 </dd>
1788</dl> 1921</dl>
1789<p>Example: Declare and initialise a check watcher, working regardless of 1922<p>Example: Declare and initialise a check watcher, utilising the above
1790wether multiple loops are supported or not.</p> 1923macros so it will work regardless of whether multiple loops are supported
1924or not.</p>
1791<pre> static void 1925<pre> static void
1792 check_cb (EV_P_ ev_timer *w, int revents) 1926 check_cb (EV_P_ ev_timer *w, int revents)
1793 { 1927 {
1794 ev_check_stop (EV_A_ w); 1928 ev_check_stop (EV_A_ w);
1795 } 1929 }
… …
1797 ev_check check; 1931 ev_check check;
1798 ev_check_init (&amp;check, check_cb); 1932 ev_check_init (&amp;check, check_cb);
1799 ev_check_start (EV_DEFAULT_ &amp;check); 1933 ev_check_start (EV_DEFAULT_ &amp;check);
1800 ev_loop (EV_DEFAULT_ 0); 1934 ev_loop (EV_DEFAULT_ 0);
1801 1935
1802
1803
1804
1805</pre> 1936</pre>
1806 1937
1807</div> 1938</div>
1808<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1939<h1 id="EMBEDDING">EMBEDDING</h1>
1809<div id="EMBEDDING_CONTENT"> 1940<div id="EMBEDDING_CONTENT">
1810<p>Libev can (and often is) directly embedded into host 1941<p>Libev can (and often is) directly embedded into host
1811applications. Examples of applications that embed it include the Deliantra 1942applications. Examples of applications that embed it include the Deliantra
1812Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1943Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1813and rxvt-unicode.</p> 1944and rxvt-unicode.</p>
… …
1850 ev_vars.h 1981 ev_vars.h
1851 ev_wrap.h 1982 ev_wrap.h
1852 1983
1853 ev_win32.c required on win32 platforms only 1984 ev_win32.c required on win32 platforms only
1854 1985
1855 ev_select.c only when select backend is enabled (which is by default) 1986 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) 1987 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) 1988 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) 1989 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) 1990 ev_port.c only when the solaris port backend is enabled (disabled by default)
1860 1991
… …
1987 </dd> 2118 </dd>
1988 <dt>EV_USE_DEVPOLL</dt> 2119 <dt>EV_USE_DEVPOLL</dt>
1989 <dd> 2120 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p> 2121 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd> 2122 </dd>
2123 <dt>EV_USE_INOTIFY</dt>
2124 <dd>
2125 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2126interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2127be detected at runtime.</p>
2128 </dd>
1992 <dt>EV_H</dt> 2129 <dt>EV_H</dt>
1993 <dd> 2130 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2131 <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 2132undefined 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> 2133can 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 2156will have the <code>struct ev_loop *</code> as first argument, and you can create
2020additional independent event loops. Otherwise there will be no support 2157additional independent event loops. Otherwise there will be no support
2021for multiple event loops and there is no first event loop pointer 2158for multiple event loops and there is no first event loop pointer
2022argument. Instead, all functions act on the single default loop.</p> 2159argument. Instead, all functions act on the single default loop.</p>
2023 </dd> 2160 </dd>
2161 <dt>EV_MINPRI</dt>
2162 <dt>EV_MAXPRI</dt>
2163 <dd>
2164 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2165<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2166provide for more priorities by overriding those symbols (usually defined
2167to be <code>-2</code> and <code>2</code>, respectively).</p>
2168 <p>When doing priority-based operations, libev usually has to linearly search
2169all the priorities, so having many of them (hundreds) uses a lot of space
2170and time, so using the defaults of five priorities (-2 .. +2) is usually
2171fine.</p>
2172 <p>If your embedding app does not need any priorities, defining these both to
2173<code>0</code> will save some memory and cpu.</p>
2174 </dd>
2024 <dt>EV_PERIODIC_ENABLE</dt> 2175 <dt>EV_PERIODIC_ENABLE</dt>
2025 <dd> 2176 <dd>
2026 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2177 <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 2178defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2028code.</p> 2179code.</p>
2029 </dd> 2180 </dd>
2181 <dt>EV_IDLE_ENABLE</dt>
2182 <dd>
2183 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2184defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2185code.</p>
2186 </dd>
2030 <dt>EV_EMBED_ENABLE</dt> 2187 <dt>EV_EMBED_ENABLE</dt>
2031 <dd> 2188 <dd>
2032 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2189 <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> 2190defined to be <code>0</code>, then they are not.</p>
2034 </dd> 2191 </dd>
… …
2051 <dt>EV_PID_HASHSIZE</dt> 2208 <dt>EV_PID_HASHSIZE</dt>
2052 <dd> 2209 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2210 <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 2211pid. 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 2212than enough. If you need to manage thousands of children you might want to
2056increase this value.</p> 2213increase this value (<i>must</i> be a power of two).</p>
2214 </dd>
2215 <dt>EV_INOTIFY_HASHSIZE</dt>
2216 <dd>
2217 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2218inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2219usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2220watchers you might want to increase this value (<i>must</i> be a power of
2221two).</p>
2057 </dd> 2222 </dd>
2058 <dt>EV_COMMON</dt> 2223 <dt>EV_COMMON</dt>
2059 <dd> 2224 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2225 <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 2226this 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 2253the <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 2254interface) 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 2255will be compiled. It is pretty complex because it provides its own header
2091file.</p> 2256file.</p>
2092 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2257 <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> 2258that everybody includes and which overrides some configure choices:</p>
2259<pre> #define EV_MINIMAL 1
2094<pre> #define EV_USE_POLL 0 2260 #define EV_USE_POLL 0
2095 #define EV_MULTIPLICITY 0 2261 #define EV_MULTIPLICITY 0
2096 #define EV_PERIODICS 0 2262 #define EV_PERIODIC_ENABLE 0
2263 #define EV_STAT_ENABLE 0
2264 #define EV_FORK_ENABLE 0
2097 #define EV_CONFIG_H &lt;config.h&gt; 2265 #define EV_CONFIG_H &lt;config.h&gt;
2266 #define EV_MINPRI 0
2267 #define EV_MAXPRI 0
2098 2268
2099 #include &quot;ev++.h&quot; 2269 #include &quot;ev++.h&quot;
2100 2270
2101</pre> 2271</pre>
2102 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2272 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2107 2277
2108 2278
2109</pre> 2279</pre>
2110 2280
2111</div> 2281</div>
2112<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2282<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2113<div id="COMPLEXITIES_CONTENT"> 2283<div id="COMPLEXITIES_CONTENT">
2114 <p>In this section the complexities of (many of) the algorithms used inside 2284 <p>In this section the complexities of (many of) the algorithms used inside
2115libev will be explained. For complexity discussions about backends see the 2285libev will be explained. For complexity discussions about backends see the
2116documentation for <code>ev_default_init</code>.</p> 2286documentation for <code>ev_default_init</code>.</p>
2287 <p>All of the following are about amortised time: If an array needs to be
2288extended, libev needs to realloc and move the whole array, but this
2289happens asymptotically never with higher number of elements, so O(1) might
2290mean it might do a lengthy realloc operation in rare cases, but on average
2291it is much faster and asymptotically approaches constant time.</p>
2117 <p> 2292 <p>
2118 <dl> 2293 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2294 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2295 <dd>
2296 <p>This means that, when you have a watcher that triggers in one hour and
2297there are 100 watchers that would trigger before that then inserting will
2298have to skip those 100 watchers.</p>
2299 </dd>
2120 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2300 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2301 <dd>
2302 <p>That means that for changing a timer costs less than removing/adding them
2303as only the relative motion in the event queue has to be paid for.</p>
2304 </dd>
2121 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2305 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2306 <dd>
2307 <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> 2308=item Stopping check/prepare/idle watchers: O(1)</p>
2309 </dd>
2123 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2310 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2311 <dd>
2312 <p>These watchers are stored in lists then need to be walked to find the
2313correct watcher to remove. The lists are usually short (you don't usually
2314have many watchers waiting for the same fd or signal).</p>
2315 </dd>
2124 <dt>Finding the next timer per loop iteration: O(1)</dt> 2316 <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> 2317 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2318 <dd>
2319 <p>A change means an I/O watcher gets started or stopped, which requires
2320libev to recalculate its status (and possibly tell the kernel).</p>
2321 </dd>
2126 <dt>Activating one watcher: O(1)</dt> 2322 <dt>Activating one watcher: O(1)</dt>
2323 <dt>Priority handling: O(number_of_priorities)</dt>
2324 <dd>
2325 <p>Priorities are implemented by allocating some space for each
2326priority. When doing priority-based operations, libev usually has to
2327linearly search all the priorities.</p>
2328 </dd>
2127 </dl> 2329 </dl>
2128 </p> 2330 </p>
2129 2331
2130 2332
2131 2333
2132 2334
2133 2335
2134</div> 2336</div>
2135<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2337<h1 id="AUTHOR">AUTHOR</h1>
2136<div id="AUTHOR_CONTENT"> 2338<div id="AUTHOR_CONTENT">
2137 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2339 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
2138 2340
2139</div> 2341</div>
2140</div></body> 2342</div></body>

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