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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 20:23:27 2007" /> 9 <meta name="created" content="Fri Dec 7 20:07:44 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 -->
15<h3 id="TOP">Index</h3> 15<h3 id="TOP">Index</h3>
16 16
17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 20<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 21<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 22<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 23<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 24<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
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59<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
60</li> 61</li>
61</ul><hr /> 62</ul><hr />
62<!-- INDEX END --> 63<!-- INDEX END -->
63 64
64<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
65<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
66<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>
67 68
68</div> 69</div>
69<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
70<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
71<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
72 73
73</pre> 74</pre>
74 75
75</div> 76</div>
76<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt;
80
81 ev_io stdin_watcher;
82 ev_timer timeout_watcher;
83
84 /* called when data readable on stdin */
85 static void
86 stdin_cb (EV_P_ struct ev_io *w, int revents)
87 {
88 /* puts (&quot;stdin ready&quot;); */
89 ev_io_stop (EV_A_ w); /* just a syntax example */
90 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
91 }
92
93 static void
94 timeout_cb (EV_P_ struct ev_timer *w, int revents)
95 {
96 /* puts (&quot;timeout&quot;); */
97 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
98 }
99
100 int
101 main (void)
102 {
103 struct ev_loop *loop = ev_default_loop (0);
104
105 /* initialise an io watcher, then start it */
106 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
107 ev_io_start (loop, &amp;stdin_watcher);
108
109 /* simple non-repeating 5.5 second timeout */
110 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
111 ev_timer_start (loop, &amp;timeout_watcher);
112
113 /* loop till timeout or data ready */
114 ev_loop (loop, 0);
115
116 return 0;
117 }
118
119</pre>
120
121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1>
77<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>
78<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
79file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
80these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
81<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
82(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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85watchers</i>, which are relatively small C structures you initialise with the 134watchers</i>, which are relatively small C structures you initialise with the
86details 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
87watcher.</p> 136watcher.</p>
88 137
89</div> 138</div>
90<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
91<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
92<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 141<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
93kqueue mechanisms for file descriptor events, relative timers, absolute 142BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
94timers with customised rescheduling, signal events, process status change 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
95events (related to SIGCHLD), and event watchers dealing with the event 144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
96loop mechanism itself (idle, prepare and check watchers). It also is quite 145with customised rescheduling (<code>ev_periodic</code>), synchronous signals
146(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
147watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
148<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
149file watchers (<code>ev_stat</code>) and even limited support for fork events
150(<code>ev_fork</code>).</p>
151<p>It also is quite fast (see this
97fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 152<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
98it to libevent for example).</p> 153for example).</p>
99 154
100</div> 155</div>
101<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
102<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
103<p>Libev is very configurable. In this manual the default configuration 158<p>Libev is very configurable. In this manual the default configuration will
104will be described, which supports multiple event loops. For more info 159be described, which supports multiple event loops. For more info about
105about various configuration options please have a look at the file 160various configuration options please have a look at <strong>EMBED</strong> section in
106<cite>README.embed</cite> in the libev distribution. If libev was configured without 161this manual. If libev was configured without support for multiple event
107support for multiple event loops, then all functions taking an initial 162loops, then all functions taking an initial argument of name <code>loop</code>
108argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 163(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
109will not have this argument.</p>
110 164
111</div> 165</div>
112<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
113<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
114<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
115(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
116the 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
117called <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
118to 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
119it, you should treat it as such.</p> 173it, you should treat it as such.</p>
120 174
121</div> 175</div>
122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 176<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
123<div id="GLOBAL_FUNCTIONS_CONTENT"> 177<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the 178<p>These functions can be called anytime, even before initialising the
125library in any way.</p> 179library in any way.</p>
126<dl> 180<dl>
127 <dt>ev_tstamp ev_time ()</dt> 181 <dt>ev_tstamp ev_time ()</dt>
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140version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
141 <p>Usually, it's a good idea to terminate if the major versions mismatch, 195 <p>Usually, it's a good idea to terminate if the major versions mismatch,
142as this indicates an incompatible change. Minor versions are usually 196as this indicates an incompatible change. Minor versions are usually
143compatible to older versions, so a larger minor version alone is usually 197compatible to older versions, so a larger minor version alone is usually
144not a problem.</p> 198not a problem.</p>
145 <p>Example: make sure we haven't accidentally been linked against the wrong 199 <p>Example: Make sure we haven't accidentally been linked against the wrong
146version:</p> 200version.</p>
147<pre> assert ((&quot;libev version mismatch&quot;, 201<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR 202 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 203 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150 204
151</pre> 205</pre>
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181recommended ones.</p> 235recommended ones.</p>
182 <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>
183 </dd> 237 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
185 <dd> 239 <dd>
186 <p>Sets the allocation function to use (the prototype is similar to the 240 <p>Sets the allocation function to use (the prototype is similar - the
187realloc C function, the semantics are identical). It is used to allocate 241semantics is identical - to the realloc C function). It is used to
188and free memory (no surprises here). If it returns zero when memory 242allocate and free memory (no surprises here). If it returns zero when
189needs to be allocated, the library might abort or take some potentially 243memory needs to be allocated, the library might abort or take some
190destructive action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
191 <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,
192free 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,
193or 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>
194 <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
195retries: better than mine).</p> 250retries).</p>
196<pre> static void * 251<pre> static void *
197 persistent_realloc (void *ptr, long size) 252 persistent_realloc (void *ptr, size_t size)
198 { 253 {
199 for (;;) 254 for (;;)
200 { 255 {
201 void *newptr = realloc (ptr, size); 256 void *newptr = realloc (ptr, size);
202 257
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219indicating the system call or subsystem causing the problem. If this 274indicating the system call or subsystem causing the problem. If this
220callback is set, then libev will expect it to remedy the sitution, no 275callback is set, then libev will expect it to remedy the sitution, no
221matter what, when it returns. That is, libev will generally retry the 276matter what, when it returns. That is, libev will generally retry the
222requested operation, or, if the condition doesn't go away, do bad stuff 277requested operation, or, if the condition doesn't go away, do bad stuff
223(such as abort).</p> 278(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p> 279 <p>Example: This is basically the same thing that libev does internally, too.</p>
225<pre> static void 280<pre> static void
226 fatal_error (const char *msg) 281 fatal_error (const char *msg)
227 { 282 {
228 perror (msg); 283 perror (msg);
229 abort (); 284 abort ();
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235</pre> 290</pre>
236 </dd> 291 </dd>
237</dl> 292</dl>
238 293
239</div> 294</div>
240<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>
241<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 296<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
242<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
243types 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
244events, and dynamically created loops which do not.</p> 299events, and dynamically created loops which do not.</p>
245<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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274<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
275override 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
276useful 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
277around bugs.</p> 332around bugs.</p>
278 </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>
279 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
280 <dd> 352 <dd>
281 <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
282libev 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,
283but 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
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365 <dd> 437 <dd>
366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 438 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
367always distinct from the default loop. Unlike the default loop, it cannot 439always distinct from the default loop. Unlike the default loop, it cannot
368handle signal and child watchers, and attempts to do so will be greeted by 440handle signal and child watchers, and attempts to do so will be greeted by
369undefined behaviour (or a failed assertion if assertions are enabled).</p> 441undefined behaviour (or a failed assertion if assertions are enabled).</p>
370 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 442 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
371<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 443<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller) 444 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 445 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374 446
375</pre> 447</pre>
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411 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
412 <dd> 484 <dd>
413 <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
414<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
415after 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>
416 </dd> 497 </dd>
417 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
418 <dd> 499 <dd>
419 <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
420use.</p> 501use.</p>
… …
468 be handled here by queueing them when their watcher gets executed. 549 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 550 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *. 551 were used, return, otherwise continue with step *.
471 552
472</pre> 553</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding 554 <p>Example: Queue some jobs and then loop until no events are outsanding
474anymore.</p> 555anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long 556<pre> ... queue jobs here, make sure they register event watchers as long
476 ... as they still have work to do (even an idle watcher will do..) 557 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0); 558 ev_loop (my_loop, 0);
478 ... jobs done. yeah! 559 ... jobs done. yeah!
… …
497example, libev itself uses this for its internal signal pipe: It is not 578example, libev itself uses this for its internal signal pipe: It is not
498visible to the libev user and should not keep <code>ev_loop</code> from exiting if 579visible to the libev user and should not keep <code>ev_loop</code> from exiting if
499no event watchers registered by it are active. It is also an excellent 580no event watchers registered by it are active. It is also an excellent
500way to do this for generic recurring timers or from within third-party 581way to do this for generic recurring timers or from within third-party
501libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 582libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
502 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 583 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p> 584running when nothing else is active.</p>
504<pre> struct dv_signal exitsig; 585<pre> struct ev_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 586 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig); 587 ev_signal_start (loop, &amp;exitsig);
507 evf_unref (myloop); 588 evf_unref (loop);
508 589
509</pre> 590</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p> 591 <p>Example: For some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop); 592<pre> ev_ref (loop);
512 ev_signal_stop (myloop, &amp;exitsig); 593 ev_signal_stop (loop, &amp;exitsig);
513 594
514</pre> 595</pre>
515 </dd> 596 </dd>
516</dl> 597</dl>
517 598
518 599
519 600
520 601
521 602
522</div> 603</div>
523<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>
524<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 605<div id="ANATOMY_OF_A_WATCHER_CONTENT">
525<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
526interest 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
527become 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>
528<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)
… …
691events 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
692is 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
693<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
694libev (e.g. you cnanot <code>free ()</code> it).</p> 775libev (e.g. you cnanot <code>free ()</code> it).</p>
695 </dd> 776 </dd>
696 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 777 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
697 <dd> 778 <dd>
698 <p>Returns the callback currently set on the watcher.</p> 779 <p>Returns the callback currently set on the watcher.</p>
699 </dd> 780 </dd>
700 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 781 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
701 <dd> 782 <dd>
702 <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
703(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>
704 </dd> 805 </dd>
705</dl> 806</dl>
706 807
707 808
708 809
… …
733 struct my_io *w = (struct my_io *)w_; 834 struct my_io *w = (struct my_io *)w_;
734 ... 835 ...
735 } 836 }
736 837
737</pre> 838</pre>
738<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
739have 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 }
740 849
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;
741 854
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 }
742 861
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 }
743 868
744 869
870
871
872</pre>
873
745</div> 874</div>
746<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 875<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
747<div id="WATCHER_TYPES_CONTENT"> 876<div id="WATCHER_TYPES_CONTENT">
748<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
749information given in the last section. Any initialisation/set macros, 878information given in the last section. Any initialisation/set macros,
750functions and members specific to the watcher type are explained.</p> 879functions and members specific to the watcher type are explained.</p>
751<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,
… …
791this situation even with a relatively standard program structure. Thus 920this situation even with a relatively standard program structure. Thus
792it 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
793<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>
794<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
795play 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
796wether 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
797such 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
798its own, so its quite safe to use).</p> 927its own, so its quite safe to use).</p>
799<dl> 928<dl>
800 <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>
801 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 930 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
811 <dt>int events [read-only]</dt> 940 <dt>int events [read-only]</dt>
812 <dd> 941 <dd>
813 <p>The events being watched.</p> 942 <p>The events being watched.</p>
814 </dd> 943 </dd>
815</dl> 944</dl>
816<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 945<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
817readable, but only once. Since it is likely line-buffered, you could 946readable, but only once. Since it is likely line-buffered, you could
818attempt to read a whole line in the callback:</p> 947attempt to read a whole line in the callback.</p>
819<pre> static void 948<pre> static void
820 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 949 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
821 { 950 {
822 ev_io_stop (loop, w); 951 ev_io_stop (loop, w);
823 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 952 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
872 </dd> 1001 </dd>
873 <dt>ev_timer_again (loop)</dt> 1002 <dt>ev_timer_again (loop)</dt>
874 <dd> 1003 <dd>
875 <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
876repeating. The exact semantics are:</p> 1005repeating. The exact semantics are:</p>
1006 <p>If the timer is pending, its pending status is cleared.</p>
877 <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>
878 <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
879value), 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>
880 <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
881example: 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
882idle 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
883say, 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
884this 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
885<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
886you 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
887socket, 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
888need be.</p> 1018automatically restart it if need be.</p>
889 <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>
890and 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>
891<pre> ev_timer_init (timer, callback, 0., 5.); 1021<pre> ev_timer_init (timer, callback, 0., 5.);
892 ev_timer_again (loop, timer); 1022 ev_timer_again (loop, timer);
893 ... 1023 ...
894 timer-&gt;again = 17.; 1024 timer-&gt;again = 17.;
895 ev_timer_again (loop, timer); 1025 ev_timer_again (loop, timer);
896 ... 1026 ...
897 timer-&gt;again = 10.; 1027 timer-&gt;again = 10.;
898 ev_timer_again (loop, timer); 1028 ev_timer_again (loop, timer);
899 1029
900</pre> 1030</pre>
901 <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
902to modify its timeout value.</p> 1032you want to modify its timeout value.</p>
903 </dd> 1033 </dd>
904 <dt>ev_tstamp repeat [read-write]</dt> 1034 <dt>ev_tstamp repeat [read-write]</dt>
905 <dd> 1035 <dd>
906 <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
907or <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),
908which is also when any modifications are taken into account.</p> 1038which is also when any modifications are taken into account.</p>
909 </dd> 1039 </dd>
910</dl> 1040</dl>
911<p>Example: create a timer that fires after 60 seconds.</p> 1041<p>Example: Create a timer that fires after 60 seconds.</p>
912<pre> static void 1042<pre> static void
913 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1043 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
914 { 1044 {
915 .. one minute over, w is actually stopped right here 1045 .. one minute over, w is actually stopped right here
916 } 1046 }
… …
918 struct ev_timer mytimer; 1048 struct ev_timer mytimer;
919 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1049 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
920 ev_timer_start (loop, &amp;mytimer); 1050 ev_timer_start (loop, &amp;mytimer);
921 1051
922</pre> 1052</pre>
923<p>Example: create a timeout timer that times out after 10 seconds of 1053<p>Example: Create a timeout timer that times out after 10 seconds of
924inactivity.</p> 1054inactivity.</p>
925<pre> static void 1055<pre> static void
926 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1056 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
927 { 1057 {
928 .. ten seconds without any activity 1058 .. ten seconds without any activity
… …
1044 <p>The current reschedule callback, or <code>0</code>, if this functionality is 1174 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1045switched off. Can be changed any time, but changes only take effect when 1175switched off. Can be changed any time, but changes only take effect when
1046the periodic timer fires or <code>ev_periodic_again</code> is being called.</p> 1176the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1047 </dd> 1177 </dd>
1048</dl> 1178</dl>
1049<p>Example: call a callback every hour, or, more precisely, whenever the 1179<p>Example: Call a callback every hour, or, more precisely, whenever the
1050system clock is divisible by 3600. The callback invocation times have 1180system clock is divisible by 3600. The callback invocation times have
1051potentially a lot of jittering, but good long-term stability.</p> 1181potentially a lot of jittering, but good long-term stability.</p>
1052<pre> static void 1182<pre> static void
1053 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1183 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1054 { 1184 {
… …
1058 struct ev_periodic hourly_tick; 1188 struct ev_periodic hourly_tick;
1059 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1189 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
1060 ev_periodic_start (loop, &amp;hourly_tick); 1190 ev_periodic_start (loop, &amp;hourly_tick);
1061 1191
1062</pre> 1192</pre>
1063<p>Example: the same as above, but use a reschedule callback to do it:</p> 1193<p>Example: The same as above, but use a reschedule callback to do it:</p>
1064<pre> #include &lt;math.h&gt; 1194<pre> #include &lt;math.h&gt;
1065 1195
1066 static ev_tstamp 1196 static ev_tstamp
1067 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1197 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1068 { 1198 {
… …
1070 } 1200 }
1071 1201
1072 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1202 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1073 1203
1074</pre> 1204</pre>
1075<p>Example: call a callback every hour, starting now:</p> 1205<p>Example: Call a callback every hour, starting now:</p>
1076<pre> struct ev_periodic hourly_tick; 1206<pre> struct ev_periodic hourly_tick;
1077 ev_periodic_init (&amp;hourly_tick, clock_cb, 1207 ev_periodic_init (&amp;hourly_tick, clock_cb,
1078 fmod (ev_now (loop), 3600.), 3600., 0); 1208 fmod (ev_now (loop), 3600.), 3600., 0);
1079 ev_periodic_start (loop, &amp;hourly_tick); 1209 ev_periodic_start (loop, &amp;hourly_tick);
1080 1210
… …
1141 <dd> 1271 <dd>
1142 <p>The process exit/trace status caused by <code>rpid</code> (see your systems 1272 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1143<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p> 1273<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1144 </dd> 1274 </dd>
1145</dl> 1275</dl>
1146<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1276<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1147<pre> static void 1277<pre> static void
1148 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1278 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1149 { 1279 {
1150 ev_unloop (loop, EVUNLOOP_ALL); 1280 ev_unloop (loop, EVUNLOOP_ALL);
1151 } 1281 }
… …
1168<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
1169not 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
1170not 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
1171otherwise 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
1172the 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>
1173<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
1174calls <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
1175can specify a recommended polling interval for this case. If you specify 1307can specify a recommended polling interval for this case. If you specify
1176a 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,
1177unspecified 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
1178five seconds, although this might change dynamically). Libev will also 1310five seconds, although this might change dynamically). Libev will also
1179impose 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
1180usually overkill.</p> 1312usually overkill.</p>
1181<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,
1182as even with OS-supported change notifications, this can be 1314as even with OS-supported change notifications, this can be
1183resource-intensive.</p> 1315resource-intensive.</p>
1184<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
1185if 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>
1186<dl> 1323<dl>
1187 <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>
1188 <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>
1189 <dd> 1326 <dd>
1190 <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
… …
1253</pre> 1390</pre>
1254 1391
1255</div> 1392</div>
1256<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>
1257<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">
1258<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
1259(prepare, check and other idle watchers do not count). That is, as long 1396priority are pending (prepare, check and other idle watchers do not
1260as your process is busy handling sockets or timeouts (or even signals, 1397count).</p>
1261imagine) 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
1262watchers 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
1263until stopped, that is, or your process receives more events and becomes 1402iteration - until stopped, that is, or your process receives more events
1264busy.</p> 1403and becomes busy again with higher priority stuff.</p>
1265<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
1266active, the process will not block when waiting for new events.</p> 1405active, the process will not block when waiting for new events.</p>
1267<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
1268effect 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
1269&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
… …
1274 <p>Initialises and configures the idle watcher - it has no parameters of any 1413 <p>Initialises and configures the idle watcher - it has no parameters of any
1275kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1414kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1276believe me.</p> 1415believe me.</p>
1277 </dd> 1416 </dd>
1278</dl> 1417</dl>
1279<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1418<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1280callback, free it. Alos, use no error checking, as usual.</p> 1419callback, free it. Also, use no error checking, as usual.</p>
1281<pre> static void 1420<pre> static void
1282 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1421 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1283 { 1422 {
1284 free (w); 1423 free (w);
1285 // now do something you wanted to do when the program has 1424 // now do something you wanted to do when the program has
… …
1359 1498
1360 // create io watchers for each fd and a timer before blocking 1499 // create io watchers for each fd and a timer before blocking
1361 static void 1500 static void
1362 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1501 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1363 { 1502 {
1364 int timeout = 3600000;truct pollfd fds [nfd]; 1503 int timeout = 3600000;
1504 struct pollfd fds [nfd];
1365 // actual code will need to loop here and realloc etc. 1505 // actual code will need to loop here and realloc etc.
1366 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 ()));
1367 1507
1368 /* 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 */
1369 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1509 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
… …
1510 1650
1511 1651
1512 1652
1513 1653
1514</div> 1654</div>
1515<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1655<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1516<div id="OTHER_FUNCTIONS_CONTENT"> 1656<div id="OTHER_FUNCTIONS_CONTENT">
1517<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>
1518<dl> 1658<dl>
1519 <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>
1520 <dd> 1660 <dd>
… …
1567 1707
1568 1708
1569 1709
1570 1710
1571</div> 1711</div>
1572<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1712<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1573<div id="LIBEVENT_EMULATION_CONTENT"> 1713<div id="LIBEVENT_EMULATION_CONTENT">
1574<p>Libev offers a compatibility emulation layer for libevent. It cannot 1714<p>Libev offers a compatibility emulation layer for libevent. It cannot
1575emulate the internals of libevent, so here are some usage hints:</p> 1715emulate the internals of libevent, so here are some usage hints:</p>
1576<dl> 1716<dl>
1577 <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>
… …
1587 <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
1588to use the libev header file and library.</dt> 1728to use the libev header file and library.</dt>
1589</dl> 1729</dl>
1590 1730
1591</div> 1731</div>
1592<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1732<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1593<div id="C_SUPPORT_CONTENT"> 1733<div id="C_SUPPORT_CONTENT">
1594<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
1595you 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
1596the callback model to a model using method callbacks on objects.</p> 1736the callback model to a model using method callbacks on objects.</p>
1597<p>To use it,</p> 1737<p>To use it,</p>
… …
1692 1832
1693 1833
1694</pre> 1834</pre>
1695 1835
1696</div> 1836</div>
1697<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p> 1837<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1698<div id="MACRO_MAGIC_CONTENT"> 1838<div id="MACRO_MAGIC_CONTENT">
1699<p>Libev can be compiled with a variety of options, the most fundemantal is 1839<p>Libev can be compiled with a variety of options, the most fundemantal is
1700<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1840<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1701callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1841callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1702<p>To make it easier to write programs that cope with either variant, the 1842<p>To make it easier to write programs that cope with either variant, the
1703following macros are defined:</p> 1843following macros are defined:</p>
1704<dl> 1844<dl>
1705 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1845 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1734 <dd> 1874 <dd>
1735 <p>Similar to the other two macros, this gives you the value of the default 1875 <p>Similar to the other two macros, this gives you the value of the default
1736loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 1876loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1737 </dd> 1877 </dd>
1738</dl> 1878</dl>
1739<p>Example: Declare and initialise a check watcher, working regardless of 1879<p>Example: Declare and initialise a check watcher, utilising the above
1740wether multiple loops are supported or not.</p> 1880macros so it will work regardless of whether multiple loops are supported
1881or not.</p>
1741<pre> static void 1882<pre> static void
1742 check_cb (EV_P_ ev_timer *w, int revents) 1883 check_cb (EV_P_ ev_timer *w, int revents)
1743 { 1884 {
1744 ev_check_stop (EV_A_ w); 1885 ev_check_stop (EV_A_ w);
1745 } 1886 }
… …
1747 ev_check check; 1888 ev_check check;
1748 ev_check_init (&amp;check, check_cb); 1889 ev_check_init (&amp;check, check_cb);
1749 ev_check_start (EV_DEFAULT_ &amp;check); 1890 ev_check_start (EV_DEFAULT_ &amp;check);
1750 ev_loop (EV_DEFAULT_ 0); 1891 ev_loop (EV_DEFAULT_ 0);
1751 1892
1752
1753
1754
1755</pre> 1893</pre>
1756 1894
1757</div> 1895</div>
1758<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1896<h1 id="EMBEDDING">EMBEDDING</h1>
1759<div id="EMBEDDING_CONTENT"> 1897<div id="EMBEDDING_CONTENT">
1760<p>Libev can (and often is) directly embedded into host 1898<p>Libev can (and often is) directly embedded into host
1761applications. Examples of applications that embed it include the Deliantra 1899applications. Examples of applications that embed it include the Deliantra
1762Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1900Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1763and rxvt-unicode.</p> 1901and rxvt-unicode.</p>
… …
1800 ev_vars.h 1938 ev_vars.h
1801 ev_wrap.h 1939 ev_wrap.h
1802 1940
1803 ev_win32.c required on win32 platforms only 1941 ev_win32.c required on win32 platforms only
1804 1942
1805 ev_select.c only when select backend is enabled (which is by default) 1943 ev_select.c only when select backend is enabled (which is enabled by default)
1806 ev_poll.c only when poll backend is enabled (disabled by default) 1944 ev_poll.c only when poll backend is enabled (disabled by default)
1807 ev_epoll.c only when the epoll backend is enabled (disabled by default) 1945 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1808 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 1946 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1809 ev_port.c only when the solaris port backend is enabled (disabled by default) 1947 ev_port.c only when the solaris port backend is enabled (disabled by default)
1810 1948
… …
1937 </dd> 2075 </dd>
1938 <dt>EV_USE_DEVPOLL</dt> 2076 <dt>EV_USE_DEVPOLL</dt>
1939 <dd> 2077 <dd>
1940 <p>reserved for future expansion, works like the USE symbols above.</p> 2078 <p>reserved for future expansion, works like the USE symbols above.</p>
1941 </dd> 2079 </dd>
2080 <dt>EV_USE_INOTIFY</dt>
2081 <dd>
2082 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2083interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2084be detected at runtime.</p>
2085 </dd>
1942 <dt>EV_H</dt> 2086 <dt>EV_H</dt>
1943 <dd> 2087 <dd>
1944 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2088 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1945undefined 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 2089undefined 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
1946can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2090can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1969will have the <code>struct ev_loop *</code> as first argument, and you can create 2113will have the <code>struct ev_loop *</code> as first argument, and you can create
1970additional independent event loops. Otherwise there will be no support 2114additional independent event loops. Otherwise there will be no support
1971for multiple event loops and there is no first event loop pointer 2115for multiple event loops and there is no first event loop pointer
1972argument. Instead, all functions act on the single default loop.</p> 2116argument. Instead, all functions act on the single default loop.</p>
1973 </dd> 2117 </dd>
2118 <dt>EV_MINPRI</dt>
2119 <dt>EV_MAXPRI</dt>
2120 <dd>
2121 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2122<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2123provide for more priorities by overriding those symbols (usually defined
2124to be <code>-2</code> and <code>2</code>, respectively).</p>
2125 <p>When doing priority-based operations, libev usually has to linearly search
2126all the priorities, so having many of them (hundreds) uses a lot of space
2127and time, so using the defaults of five priorities (-2 .. +2) is usually
2128fine.</p>
2129 <p>If your embedding app does not need any priorities, defining these both to
2130<code>0</code> will save some memory and cpu.</p>
2131 </dd>
1974 <dt>EV_PERIODIC_ENABLE</dt> 2132 <dt>EV_PERIODIC_ENABLE</dt>
1975 <dd> 2133 <dd>
1976 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2134 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1977defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2135defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1978code.</p> 2136code.</p>
1979 </dd> 2137 </dd>
2138 <dt>EV_IDLE_ENABLE</dt>
2139 <dd>
2140 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2141defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2142code.</p>
2143 </dd>
1980 <dt>EV_EMBED_ENABLE</dt> 2144 <dt>EV_EMBED_ENABLE</dt>
1981 <dd> 2145 <dd>
1982 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2146 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
1983defined to be <code>0</code>, then they are not.</p> 2147defined to be <code>0</code>, then they are not.</p>
1984 </dd> 2148 </dd>
… …
2001 <dt>EV_PID_HASHSIZE</dt> 2165 <dt>EV_PID_HASHSIZE</dt>
2002 <dd> 2166 <dd>
2003 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2167 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2004pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more 2168pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2005than enough. If you need to manage thousands of children you might want to 2169than enough. If you need to manage thousands of children you might want to
2006increase this value.</p> 2170increase this value (<i>must</i> be a power of two).</p>
2171 </dd>
2172 <dt>EV_INOTIFY_HASHSIZE</dt>
2173 <dd>
2174 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2175inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2176usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2177watchers you might want to increase this value (<i>must</i> be a power of
2178two).</p>
2007 </dd> 2179 </dd>
2008 <dt>EV_COMMON</dt> 2180 <dt>EV_COMMON</dt>
2009 <dd> 2181 <dd>
2010 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2182 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2011this macro to a something else you can include more and other types of 2183this macro to a something else you can include more and other types of
… …
2038the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2210the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2039interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2211interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2040will be compiled. It is pretty complex because it provides its own header 2212will be compiled. It is pretty complex because it provides its own header
2041file.</p> 2213file.</p>
2042 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2214 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2043that everybody includes and which overrides some autoconf choices:</p> 2215that everybody includes and which overrides some configure choices:</p>
2216<pre> #define EV_MINIMAL 1
2044<pre> #define EV_USE_POLL 0 2217 #define EV_USE_POLL 0
2045 #define EV_MULTIPLICITY 0 2218 #define EV_MULTIPLICITY 0
2046 #define EV_PERIODICS 0 2219 #define EV_PERIODIC_ENABLE 0
2220 #define EV_STAT_ENABLE 0
2221 #define EV_FORK_ENABLE 0
2047 #define EV_CONFIG_H &lt;config.h&gt; 2222 #define EV_CONFIG_H &lt;config.h&gt;
2223 #define EV_MINPRI 0
2224 #define EV_MAXPRI 0
2048 2225
2049 #include &quot;ev++.h&quot; 2226 #include &quot;ev++.h&quot;
2050 2227
2051</pre> 2228</pre>
2052 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2229 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2057 2234
2058 2235
2059</pre> 2236</pre>
2060 2237
2061</div> 2238</div>
2062<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2239<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2063<div id="COMPLEXITIES_CONTENT"> 2240<div id="COMPLEXITIES_CONTENT">
2064 <p>In this section the complexities of (many of) the algorithms used inside 2241 <p>In this section the complexities of (many of) the algorithms used inside
2065libev will be explained. For complexity discussions about backends see the 2242libev will be explained. For complexity discussions about backends see the
2066documentation for <code>ev_default_init</code>.</p> 2243documentation for <code>ev_default_init</code>.</p>
2067 <p> 2244 <p>
2068 <dl> 2245 <dl>
2069 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2246 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2247 <dd>
2248 <p>This means that, when you have a watcher that triggers in one hour and
2249there are 100 watchers that would trigger before that then inserting will
2250have to skip those 100 watchers.</p>
2251 </dd>
2070 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2252 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2253 <dd>
2254 <p>That means that for changing a timer costs less than removing/adding them
2255as only the relative motion in the event queue has to be paid for.</p>
2256 </dd>
2071 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2257 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2258 <dd>
2259 <p>These just add the watcher into an array or at the head of a list. If
2260the array needs to be extended libev needs to realloc and move the whole
2261array, but this happen asymptotically less and less with more watchers,
2262thus amortised O(1).</p>
2263 </dd>
2072 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2264 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2073 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2265 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2266 <dd>
2267 <p>These watchers are stored in lists then need to be walked to find the
2268correct watcher to remove. The lists are usually short (you don't usually
2269have many watchers waiting for the same fd or signal).</p>
2270 </dd>
2074 <dt>Finding the next timer per loop iteration: O(1)</dt> 2271 <dt>Finding the next timer per loop iteration: O(1)</dt>
2075 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2272 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2273 <dd>
2274 <p>A change means an I/O watcher gets started or stopped, which requires
2275libev to recalculate its status (and possibly tell the kernel).</p>
2276 </dd>
2076 <dt>Activating one watcher: O(1)</dt> 2277 <dt>Activating one watcher: O(1)</dt>
2278 <dt>Priority handling: O(number_of_priorities)</dt>
2279 <dd>
2280 <p>Priorities are implemented by allocating some space for each
2281priority. When doing priority-based operations, libev usually has to
2282linearly search all the priorities.</p>
2283 </dd>
2077 </dl> 2284 </dl>
2078 </p> 2285 </p>
2079 2286
2080 2287
2081 2288
2082 2289
2083 2290
2084</div> 2291</div>
2085<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2292<h1 id="AUTHOR">AUTHOR</h1>
2086<div id="AUTHOR_CONTENT"> 2293<div id="AUTHOR_CONTENT">
2087 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2294 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
2088 2295
2089</div> 2296</div>
2090</div></body> 2297</div></body>

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