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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="Sat Nov 24 05:58:35 2007" /> 9 <meta name="created" content="Fri Dec 7 20:23:46 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>
24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 25<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 26<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27</ul> 29</ul>
28</li> 30</li>
29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
30<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> 34<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> 35<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> 38<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> 39<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
37<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li> 40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
38</ul> 42</ul>
39</li> 43</li>
40<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
41<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
42<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
47<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
48<li><a href="#EMBEDDING">EMBEDDING</a>
49<ul><li><a href="#FILESETS">FILESETS</a>
50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
53</ul>
54</li>
55<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
56<li><a href="#EXAMPLES">EXAMPLES</a></li>
57</ul>
58</li>
59<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
43<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
44</li> 61</li>
45</ul><hr /> 62</ul><hr />
46<!-- INDEX END --> 63<!-- INDEX END -->
47 64
48<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
49<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
50<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>
51 68
52</div> 69</div>
53<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
54<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
55<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
56 73
57</pre> 74</pre>
58 75
59</div> 76</div>
60<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>
61<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>
62<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
63file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
64these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
65<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
66(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
… …
69watchers</i>, which are relatively small C structures you initialise with the 134watchers</i>, which are relatively small C structures you initialise with the
70details 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
71watcher.</p> 136watcher.</p>
72 137
73</div> 138</div>
74<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
75<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
76<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
77kqueue mechanisms for file descriptor events, relative timers, absolute 142BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
78timers with customised rescheduling, signal events, process status change 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
79events (related to SIGCHLD), and event watchers dealing with the event 144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
80loop 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
81fast (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
82it to libevent for example).</p> 153for example).</p>
83 154
84</div> 155</div>
85<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
86<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
87<p>Libev is very configurable. In this manual the default configuration 158<p>Libev is very configurable. In this manual the default configuration will
88will be described, which supports multiple event loops. For more info 159be described, which supports multiple event loops. For more info about
89about various configuration options please have a look at the file 160various configuration options please have a look at <strong>EMBED</strong> section in
90<cite>README.embed</cite> in the libev distribution. If libev was configured without 161this manual. If libev was configured without support for multiple event
91support for multiple event loops, then all functions taking an initial 162loops, then all functions taking an initial argument of name <code>loop</code>
92argument 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>
93will not have this argument.</p>
94 164
95</div> 165</div>
96<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
97<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
98<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
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
100the 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
101called <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
102to 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
103it, you should treat it as such.</p> 173it, you should treat it as such.</p>
104 174
105
106
107
108
109</div> 175</div>
110<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 176<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
111<div id="GLOBAL_FUNCTIONS_CONTENT"> 177<div id="GLOBAL_FUNCTIONS_CONTENT">
112<p>These functions can be called anytime, even before initialising the 178<p>These functions can be called anytime, even before initialising the
113library in any way.</p> 179library in any way.</p>
114<dl> 180<dl>
115 <dt>ev_tstamp ev_time ()</dt> 181 <dt>ev_tstamp ev_time ()</dt>
… …
128version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
129 <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,
130as this indicates an incompatible change. Minor versions are usually 196as this indicates an incompatible change. Minor versions are usually
131compatible to older versions, so a larger minor version alone is usually 197compatible to older versions, so a larger minor version alone is usually
132not a problem.</p> 198not a problem.</p>
133 <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
134version:</p> 200version.</p>
135<pre> assert ((&quot;libev version mismatch&quot;, 201<pre> assert ((&quot;libev version mismatch&quot;,
136 ev_version_major () == EV_VERSION_MAJOR 202 ev_version_major () == EV_VERSION_MAJOR
137 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 203 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
138 204
139</pre> 205</pre>
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169recommended ones.</p> 235recommended ones.</p>
170 <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>
171 </dd> 237 </dd>
172 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
173 <dd> 239 <dd>
174 <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
175realloc C function, the semantics are identical). It is used to allocate 241semantics is identical - to the realloc C function). It is used to
176and free memory (no surprises here). If it returns zero when memory 242allocate and free memory (no surprises here). If it returns zero when
177needs to be allocated, the library might abort or take some potentially 243memory needs to be allocated, the library might abort or take some
178destructive action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
179 <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,
180free 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,
181or 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>
182 <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
183retries: better than mine).</p> 250retries).</p>
184<pre> static void * 251<pre> static void *
185 persistent_realloc (void *ptr, long size) 252 persistent_realloc (void *ptr, size_t size)
186 { 253 {
187 for (;;) 254 for (;;)
188 { 255 {
189 void *newptr = realloc (ptr, size); 256 void *newptr = realloc (ptr, size);
190 257
… …
207indicating the system call or subsystem causing the problem. If this 274indicating the system call or subsystem causing the problem. If this
208callback 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
209matter what, when it returns. That is, libev will generally retry the 276matter what, when it returns. That is, libev will generally retry the
210requested 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
211(such as abort).</p> 278(such as abort).</p>
212 <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>
213<pre> static void 280<pre> static void
214 fatal_error (const char *msg) 281 fatal_error (const char *msg)
215 { 282 {
216 perror (msg); 283 perror (msg);
217 abort (); 284 abort ();
… …
223</pre> 290</pre>
224 </dd> 291 </dd>
225</dl> 292</dl>
226 293
227</div> 294</div>
228<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>
229<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 296<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
230<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
231types 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
232events, and dynamically created loops which do not.</p> 299events, and dynamically created loops which do not.</p>
233<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
… …
262<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
263override 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
264useful 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
265around bugs.</p> 332around bugs.</p>
266 </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>
267 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
268 <dd> 352 <dd>
269 <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
270libev 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,
271but 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
… …
353 <dd> 437 <dd>
354 <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
355always distinct from the default loop. Unlike the default loop, it cannot 439always distinct from the default loop. Unlike the default loop, it cannot
356handle 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
357undefined behaviour (or a failed assertion if assertions are enabled).</p> 441undefined behaviour (or a failed assertion if assertions are enabled).</p>
358 <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>
359<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);
360 if (!epoller) 444 if (!epoller)
361 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;);
362 446
363</pre> 447</pre>
364 </dd> 448 </dd>
365 <dt>ev_default_destroy ()</dt> 449 <dt>ev_default_destroy ()</dt>
366 <dd> 450 <dd>
367 <p>Destroys the default loop again (frees all memory and kernel state 451 <p>Destroys the default loop again (frees all memory and kernel state
368etc.). This stops all registered event watchers (by not touching them in 452etc.). None of the active event watchers will be stopped in the normal
369any way whatsoever, although you cannot rely on this :).</p> 453sense, so e.g. <code>ev_is_active</code> might still return true. It is your
454responsibility to either stop all watchers cleanly yoursef <i>before</i>
455calling this function, or cope with the fact afterwards (which is usually
456the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
457for example).</p>
370 </dd> 458 </dd>
371 <dt>ev_loop_destroy (loop)</dt> 459 <dt>ev_loop_destroy (loop)</dt>
372 <dd> 460 <dd>
373 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 461 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
374earlier call to <code>ev_loop_new</code>.</p> 462earlier call to <code>ev_loop_new</code>.</p>
… …
395 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
396 <dd> 484 <dd>
397 <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
398<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
399after 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>
400 </dd> 497 </dd>
401 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
402 <dd> 499 <dd>
403 <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
404use.</p> 501use.</p>
… …
452 be handled here by queueing them when their watcher gets executed. 549 be handled here by queueing them when their watcher gets executed.
453 - 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
454 were used, return, otherwise continue with step *. 551 were used, return, otherwise continue with step *.
455 552
456</pre> 553</pre>
457 <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
458anymore.</p> 555anymore.</p>
459<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
460 ... 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..)
461 ev_loop (my_loop, 0); 558 ev_loop (my_loop, 0);
462 ... jobs done. yeah! 559 ... jobs done. yeah!
… …
481example, 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
482visible 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
483no 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
484way 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
485libraries. 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>
486 <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>
487running when nothing else is active.</p> 584running when nothing else is active.</p>
488<pre> struct dv_signal exitsig; 585<pre> struct ev_signal exitsig;
489 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 586 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
490 ev_signal_start (myloop, &amp;exitsig); 587 ev_signal_start (loop, &amp;exitsig);
491 evf_unref (myloop); 588 evf_unref (loop);
492 589
493</pre> 590</pre>
494 <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>
495<pre> ev_ref (myloop); 592<pre> ev_ref (loop);
496 ev_signal_stop (myloop, &amp;exitsig); 593 ev_signal_stop (loop, &amp;exitsig);
497 594
498</pre> 595</pre>
499 </dd> 596 </dd>
500</dl> 597</dl>
501 598
599
600
601
602
502</div> 603</div>
503<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>
504<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 605<div id="ANATOMY_OF_A_WATCHER_CONTENT">
505<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
506interest 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
507become 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>
508<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)
… …
535with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 636with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
536*)</code>), and you can stop watching for events at any time by calling the 637*)</code>), and you can stop watching for events at any time by calling the
537corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 638corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
538<p>As long as your watcher is active (has been started but not stopped) you 639<p>As long as your watcher is active (has been started but not stopped) you
539must not touch the values stored in it. Most specifically you must never 640must not touch the values stored in it. Most specifically you must never
540reinitialise it or call its set macro.</p> 641reinitialise it or call its <code>set</code> macro.</p>
541<p>You can check whether an event is active by calling the <code>ev_is_active
542(watcher *)</code> macro. To see whether an event is outstanding (but the
543callback for it has not been called yet) you can use the <code>ev_is_pending
544(watcher *)</code> macro.</p>
545<p>Each and every callback receives the event loop pointer as first, the 642<p>Each and every callback receives the event loop pointer as first, the
546registered watcher structure as second, and a bitset of received events as 643registered watcher structure as second, and a bitset of received events as
547third argument.</p> 644third argument.</p>
548<p>The received events usually include a single bit per event type received 645<p>The received events usually include a single bit per event type received
549(you can receive multiple events at the same time). The possible bit masks 646(you can receive multiple events at the same time). The possible bit masks
… …
569 </dd> 666 </dd>
570 <dt><code>EV_CHILD</code></dt> 667 <dt><code>EV_CHILD</code></dt>
571 <dd> 668 <dd>
572 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 669 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
573 </dd> 670 </dd>
671 <dt><code>EV_STAT</code></dt>
672 <dd>
673 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
674 </dd>
574 <dt><code>EV_IDLE</code></dt> 675 <dt><code>EV_IDLE</code></dt>
575 <dd> 676 <dd>
576 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 677 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
577 </dd> 678 </dd>
578 <dt><code>EV_PREPARE</code></dt> 679 <dt><code>EV_PREPARE</code></dt>
… …
583<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 684<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
584received events. Callbacks of both watcher types can start and stop as 685received events. Callbacks of both watcher types can start and stop as
585many watchers as they want, and all of them will be taken into account 686many watchers as they want, and all of them will be taken into account
586(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 687(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
587<code>ev_loop</code> from blocking).</p> 688<code>ev_loop</code> from blocking).</p>
689 </dd>
690 <dt><code>EV_EMBED</code></dt>
691 <dd>
692 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
693 </dd>
694 <dt><code>EV_FORK</code></dt>
695 <dd>
696 <p>The event loop has been resumed in the child process after fork (see
697<code>ev_fork</code>).</p>
588 </dd> 698 </dd>
589 <dt><code>EV_ERROR</code></dt> 699 <dt><code>EV_ERROR</code></dt>
590 <dd> 700 <dd>
591 <p>An unspecified error has occured, the watcher has been stopped. This might 701 <p>An unspecified error has occured, the watcher has been stopped. This might
592happen because the watcher could not be properly started because libev 702happen because the watcher could not be properly started because libev
… …
598your callbacks is well-written it can just attempt the operation and cope 708your callbacks is well-written it can just attempt the operation and cope
599with the error from read() or write(). This will not work in multithreaded 709with the error from read() or write(). This will not work in multithreaded
600programs, though, so beware.</p> 710programs, though, so beware.</p>
601 </dd> 711 </dd>
602</dl> 712</dl>
713
714</div>
715<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
716<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
717<p>In the following description, <code>TYPE</code> stands for the watcher type,
718e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
719<dl>
720 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
721 <dd>
722 <p>This macro initialises the generic portion of a watcher. The contents
723of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
724the generic parts of the watcher are initialised, you <i>need</i> to call
725the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
726type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
727which rolls both calls into one.</p>
728 <p>You can reinitialise a watcher at any time as long as it has been stopped
729(or never started) and there are no pending events outstanding.</p>
730 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
731int revents)</code>.</p>
732 </dd>
733 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
734 <dd>
735 <p>This macro initialises the type-specific parts of a watcher. You need to
736call <code>ev_init</code> at least once before you call this macro, but you can
737call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
738macro on a watcher that is active (it can be pending, however, which is a
739difference to the <code>ev_init</code> macro).</p>
740 <p>Although some watcher types do not have type-specific arguments
741(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
742 </dd>
743 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
744 <dd>
745 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
746calls into a single call. This is the most convinient method to initialise
747a watcher. The same limitations apply, of course.</p>
748 </dd>
749 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
750 <dd>
751 <p>Starts (activates) the given watcher. Only active watchers will receive
752events. If the watcher is already active nothing will happen.</p>
753 </dd>
754 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
755 <dd>
756 <p>Stops the given watcher again (if active) and clears the pending
757status. It is possible that stopped watchers are pending (for example,
758non-repeating timers are being stopped when they become pending), but
759<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
760you want to free or reuse the memory used by the watcher it is therefore a
761good idea to always call its <code>ev_TYPE_stop</code> function.</p>
762 </dd>
763 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
764 <dd>
765 <p>Returns a true value iff the watcher is active (i.e. it has been started
766and not yet been stopped). As long as a watcher is active you must not modify
767it.</p>
768 </dd>
769 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
770 <dd>
771 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
772events but its callback has not yet been invoked). As long as a watcher
773is pending (but not active) you must not call an init function on it (but
774<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
775libev (e.g. you cnanot <code>free ()</code> it).</p>
776 </dd>
777 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
778 <dd>
779 <p>Returns the callback currently set on the watcher.</p>
780 </dd>
781 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
782 <dd>
783 <p>Change the callback. You can change the callback at virtually any time
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>
805 </dd>
806</dl>
807
808
809
810
603 811
604</div> 812</div>
605<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 813<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
606<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 814<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
607<p>Each watcher has, by default, a member <code>void *data</code> that you can change 815<p>Each watcher has, by default, a member <code>void *data</code> that you can change
… …
626 struct my_io *w = (struct my_io *)w_; 834 struct my_io *w = (struct my_io *)w_;
627 ... 835 ...
628 } 836 }
629 837
630</pre> 838</pre>
631<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
632have 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 }
633 849
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;
634 854
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 }
635 861
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 }
636 868
637 869
870
871
872</pre>
873
638</div> 874</div>
639<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 875<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
640<div id="WATCHER_TYPES_CONTENT"> 876<div id="WATCHER_TYPES_CONTENT">
641<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
642information given in the last section.</p> 878information given in the last section. Any initialisation/set macros,
879functions and members specific to the watcher type are explained.</p>
880<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
881while the watcher is active, you can look at the member and expect some
882sensible content, but you must not modify it (you can modify it while the
883watcher is stopped to your hearts content), or <i>[read-write]</i>, which
884means you can expect it to have some sensible content while the watcher
885is active, but you can also modify it. Modifying it may not do something
886sensible or take immediate effect (or do anything at all), but libev will
887not crash or malfunction in any way.</p>
643 888
644 889
645 890
646 891
647 892
648</div> 893</div>
649<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 894<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
650<div id="code_ev_io_code_is_this_file_descrip-2"> 895<div id="code_ev_io_code_is_this_file_descrip-2">
651<p>I/O watchers check whether a file descriptor is readable or writable 896<p>I/O watchers check whether a file descriptor is readable or writable
652in each iteration of the event loop (This behaviour is called 897in each iteration of the event loop, or, more precisely, when reading
653level-triggering because you keep receiving events as long as the 898would not block the process and writing would at least be able to write
654condition persists. Remember you can stop the watcher if you don't want to 899some data. This behaviour is called level-triggering because you keep
655act on the event and neither want to receive future events).</p> 900receiving events as long as the condition persists. Remember you can stop
901the watcher if you don't want to act on the event and neither want to
902receive future events.</p>
656<p>In general you can register as many read and/or write event watchers per 903<p>In general you can register as many read and/or write event watchers per
657fd as you want (as long as you don't confuse yourself). Setting all file 904fd as you want (as long as you don't confuse yourself). Setting all file
658descriptors to non-blocking mode is also usually a good idea (but not 905descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing).</p> 906required if you know what you are doing).</p>
660<p>You have to be careful with dup'ed file descriptors, though. Some backends 907<p>You have to be careful with dup'ed file descriptors, though. Some backends
661(the linux epoll backend is a notable example) cannot handle dup'ed file 908(the linux epoll backend is a notable example) cannot handle dup'ed file
662descriptors correctly if you register interest in two or more fds pointing 909descriptors correctly if you register interest in two or more fds pointing
663to the same underlying file/socket etc. description (that is, they share 910to the same underlying file/socket/etc. description (that is, they share
664the same underlying &quot;file open&quot;).</p> 911the same underlying &quot;file open&quot;).</p>
665<p>If you must do this, then force the use of a known-to-be-good backend 912<p>If you must do this, then force the use of a known-to-be-good backend
666(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 913(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
667<code>EVBACKEND_POLL</code>).</p> 914<code>EVBACKEND_POLL</code>).</p>
915<p>Another thing you have to watch out for is that it is quite easy to
916receive &quot;spurious&quot; readyness notifications, that is your callback might
917be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
918because there is no data. Not only are some backends known to create a
919lot of those (for example solaris ports), it is very easy to get into
920this situation even with a relatively standard program structure. Thus
921it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
922<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
923<p>If you cannot run the fd in non-blocking mode (for example you should not
924play around with an Xlib connection), then you have to seperately re-test
925whether a file descriptor is really ready with a known-to-be good interface
926such as poll (fortunately in our Xlib example, Xlib already does this on
927its own, so its quite safe to use).</p>
668<dl> 928<dl>
669 <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>
670 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 930 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
671 <dd> 931 <dd>
672 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 932 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
673events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 933rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
674EV_WRITE</code> to receive the given events.</p> 934<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
675 <p>Please note that most of the more scalable backend mechanisms (for example 935 </dd>
676epoll and solaris ports) can result in spurious readyness notifications 936 <dt>int fd [read-only]</dt>
677for file descriptors, so you practically need to use non-blocking I/O (and 937 <dd>
678treat callback invocation as hint only), or retest separately with a safe 938 <p>The file descriptor being watched.</p>
679interface before doing I/O (XLib can do this), or force the use of either 939 </dd>
680<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 940 <dt>int events [read-only]</dt>
681problem. Also note that it is quite easy to have your callback invoked 941 <dd>
682when the readyness condition is no longer valid even when employing 942 <p>The events being watched.</p>
683typical ways of handling events, so its a good idea to use non-blocking
684I/O unconditionally.</p>
685 </dd> 943 </dd>
686</dl> 944</dl>
687<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
688readable, but only once. Since it is likely line-buffered, you could 946readable, but only once. Since it is likely line-buffered, you could
689attempt to read a whole line in the callback:</p> 947attempt to read a whole line in the callback.</p>
690<pre> static void 948<pre> static void
691 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)
692 { 950 {
693 ev_io_stop (loop, w); 951 ev_io_stop (loop, w);
694 .. 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
… …
705 963
706 964
707</pre> 965</pre>
708 966
709</div> 967</div>
710<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 968<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
711<div id="code_ev_timer_code_relative_and_opti-2"> 969<div id="code_ev_timer_code_relative_and_opti-2">
712<p>Timer watchers are simple relative timers that generate an event after a 970<p>Timer watchers are simple relative timers that generate an event after a
713given time, and optionally repeating in regular intervals after that.</p> 971given time, and optionally repeating in regular intervals after that.</p>
714<p>The timers are based on real time, that is, if you register an event that 972<p>The timers are based on real time, that is, if you register an event that
715times out after an hour and you reset your system clock to last years 973times out after an hour and you reset your system clock to last years
… …
743 </dd> 1001 </dd>
744 <dt>ev_timer_again (loop)</dt> 1002 <dt>ev_timer_again (loop)</dt>
745 <dd> 1003 <dd>
746 <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
747repeating. The exact semantics are:</p> 1005repeating. The exact semantics are:</p>
1006 <p>If the timer is pending, its pending status is cleared.</p>
748 <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>
749 <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
750value), 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>
751 <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
752example: Imagine you have a tcp connection and you want a so-called idle 1011example: Imagine you have a tcp connection and you want a so-called idle
753timeout, that is, you want to be called when there have been, say, 60 1012timeout, that is, you want to be called when there have been, say, 60
754seconds of inactivity on the socket. The easiest way to do this is to 1013seconds of inactivity on the socket. The easiest way to do this is to
755configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 1014configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
756time you successfully read or write some data. If you go into an idle 1015<code>ev_timer_again</code> each time you successfully read or write some data. If
757state where you do not expect data to travel on the socket, you can stop 1016you go into an idle state where you do not expect data to travel on the
1017socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
758the timer, and again will automatically restart it if need be.</p> 1018automatically restart it if need be.</p>
1019 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
1020altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
1021<pre> ev_timer_init (timer, callback, 0., 5.);
1022 ev_timer_again (loop, timer);
1023 ...
1024 timer-&gt;again = 17.;
1025 ev_timer_again (loop, timer);
1026 ...
1027 timer-&gt;again = 10.;
1028 ev_timer_again (loop, timer);
1029
1030</pre>
1031 <p>This is more slightly efficient then stopping/starting the timer each time
1032you want to modify its timeout value.</p>
1033 </dd>
1034 <dt>ev_tstamp repeat [read-write]</dt>
1035 <dd>
1036 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
1037or <code>ev_timer_again</code> is called and determines the next timeout (if any),
1038which is also when any modifications are taken into account.</p>
759 </dd> 1039 </dd>
760</dl> 1040</dl>
761<p>Example: create a timer that fires after 60 seconds.</p> 1041<p>Example: Create a timer that fires after 60 seconds.</p>
762<pre> static void 1042<pre> static void
763 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)
764 { 1044 {
765 .. one minute over, w is actually stopped right here 1045 .. one minute over, w is actually stopped right here
766 } 1046 }
… …
768 struct ev_timer mytimer; 1048 struct ev_timer mytimer;
769 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1049 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
770 ev_timer_start (loop, &amp;mytimer); 1050 ev_timer_start (loop, &amp;mytimer);
771 1051
772</pre> 1052</pre>
773<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
774inactivity.</p> 1054inactivity.</p>
775<pre> static void 1055<pre> static void
776 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)
777 { 1057 {
778 .. ten seconds without any activity 1058 .. ten seconds without any activity
… …
791 1071
792 1072
793</pre> 1073</pre>
794 1074
795</div> 1075</div>
796<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1076<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
797<div id="code_ev_periodic_code_to_cron_or_not-2"> 1077<div id="code_ev_periodic_code_to_cron_or_not-2">
798<p>Periodic watchers are also timers of a kind, but they are very versatile 1078<p>Periodic watchers are also timers of a kind, but they are very versatile
799(and unfortunately a bit complex).</p> 1079(and unfortunately a bit complex).</p>
800<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1080<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
801but on wallclock time (absolute time). You can tell a periodic watcher 1081but on wallclock time (absolute time). You can tell a periodic watcher
802to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1082to trigger &quot;at&quot; some specific point in time. For example, if you tell a
803periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 1083periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
804+ 10.&gt;) and then reset your system clock to the last year, then it will 1084+ 10.</code>) and then reset your system clock to the last year, then it will
805take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1085take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
806roughly 10 seconds later and of course not if you reset your system time 1086roughly 10 seconds later and of course not if you reset your system time
807again).</p> 1087again).</p>
808<p>They can also be used to implement vastly more complex timers, such as 1088<p>They can also be used to implement vastly more complex timers, such as
809triggering an event on eahc midnight, local time.</p> 1089triggering an event on eahc midnight, local time.</p>
… …
881 <p>Simply stops and restarts the periodic watcher again. This is only useful 1161 <p>Simply stops and restarts the periodic watcher again. This is only useful
882when you changed some parameters or the reschedule callback would return 1162when you changed some parameters or the reschedule callback would return
883a different time than the last time it was called (e.g. in a crond like 1163a different time than the last time it was called (e.g. in a crond like
884program when the crontabs have changed).</p> 1164program when the crontabs have changed).</p>
885 </dd> 1165 </dd>
1166 <dt>ev_tstamp interval [read-write]</dt>
1167 <dd>
1168 <p>The current interval value. Can be modified any time, but changes only
1169take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1170called.</p>
1171 </dd>
1172 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1173 <dd>
1174 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1175switched off. Can be changed any time, but changes only take effect when
1176the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1177 </dd>
886</dl> 1178</dl>
887<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
888system clock is divisible by 3600. The callback invocation times have 1180system clock is divisible by 3600. The callback invocation times have
889potentially a lot of jittering, but good long-term stability.</p> 1181potentially a lot of jittering, but good long-term stability.</p>
890<pre> static void 1182<pre> static void
891 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)
892 { 1184 {
… …
896 struct ev_periodic hourly_tick; 1188 struct ev_periodic hourly_tick;
897 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1189 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
898 ev_periodic_start (loop, &amp;hourly_tick); 1190 ev_periodic_start (loop, &amp;hourly_tick);
899 1191
900</pre> 1192</pre>
901<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>
902<pre> #include &lt;math.h&gt; 1194<pre> #include &lt;math.h&gt;
903 1195
904 static ev_tstamp 1196 static ev_tstamp
905 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1197 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
906 { 1198 {
… …
908 } 1200 }
909 1201
910 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);
911 1203
912</pre> 1204</pre>
913<p>Example: call a callback every hour, starting now:</p> 1205<p>Example: Call a callback every hour, starting now:</p>
914<pre> struct ev_periodic hourly_tick; 1206<pre> struct ev_periodic hourly_tick;
915 ev_periodic_init (&amp;hourly_tick, clock_cb, 1207 ev_periodic_init (&amp;hourly_tick, clock_cb,
916 fmod (ev_now (loop), 3600.), 3600., 0); 1208 fmod (ev_now (loop), 3600.), 3600., 0);
917 ev_periodic_start (loop, &amp;hourly_tick); 1209 ev_periodic_start (loop, &amp;hourly_tick);
918 1210
… …
920 1212
921 1213
922</pre> 1214</pre>
923 1215
924</div> 1216</div>
925<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1217<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
926<div id="code_ev_signal_code_signal_me_when_a-2"> 1218<div id="code_ev_signal_code_signal_me_when_a-2">
927<p>Signal watchers will trigger an event when the process receives a specific 1219<p>Signal watchers will trigger an event when the process receives a specific
928signal one or more times. Even though signals are very asynchronous, libev 1220signal one or more times. Even though signals are very asynchronous, libev
929will try it's best to deliver signals synchronously, i.e. as part of the 1221will try it's best to deliver signals synchronously, i.e. as part of the
930normal event processing, like any other event.</p> 1222normal event processing, like any other event.</p>
… …
939 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1231 <dt>ev_signal_set (ev_signal *, int signum)</dt>
940 <dd> 1232 <dd>
941 <p>Configures the watcher to trigger on the given signal number (usually one 1233 <p>Configures the watcher to trigger on the given signal number (usually one
942of the <code>SIGxxx</code> constants).</p> 1234of the <code>SIGxxx</code> constants).</p>
943 </dd> 1235 </dd>
1236 <dt>int signum [read-only]</dt>
1237 <dd>
1238 <p>The signal the watcher watches out for.</p>
1239 </dd>
944</dl> 1240</dl>
945 1241
946 1242
947 1243
948 1244
949 1245
950</div> 1246</div>
951<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1247<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
952<div id="code_ev_child_code_wait_for_pid_stat-2"> 1248<div id="code_ev_child_code_watch_out_for_pro-2">
953<p>Child watchers trigger when your process receives a SIGCHLD in response to 1249<p>Child watchers trigger when your process receives a SIGCHLD in response to
954some child status changes (most typically when a child of yours dies).</p> 1250some child status changes (most typically when a child of yours dies).</p>
955<dl> 1251<dl>
956 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1252 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
957 <dt>ev_child_set (ev_child *, int pid)</dt> 1253 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
961at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1257at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
962the status word (use the macros from <code>sys/wait.h</code> and see your systems 1258the status word (use the macros from <code>sys/wait.h</code> and see your systems
963<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1259<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
964process causing the status change.</p> 1260process causing the status change.</p>
965 </dd> 1261 </dd>
1262 <dt>int pid [read-only]</dt>
1263 <dd>
1264 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1265 </dd>
1266 <dt>int rpid [read-write]</dt>
1267 <dd>
1268 <p>The process id that detected a status change.</p>
1269 </dd>
1270 <dt>int rstatus [read-write]</dt>
1271 <dd>
1272 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1273<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1274 </dd>
966</dl> 1275</dl>
967<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1276<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
968<pre> static void 1277<pre> static void
969 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)
970 { 1279 {
971 ev_unloop (loop, EVUNLOOP_ALL); 1280 ev_unloop (loop, EVUNLOOP_ALL);
972 } 1281 }
… …
979 1288
980 1289
981</pre> 1290</pre>
982 1291
983</div> 1292</div>
1293<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1294<div id="code_ev_stat_code_did_the_file_attri-2">
1295<p>This watches a filesystem path for attribute changes. That is, it calls
1296<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1297compared to the last time, invoking the callback if it did.</p>
1298<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1299not exist&quot; is a status change like any other. The condition &quot;path does
1300not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1301otherwise always forced to be at least one) and all the other fields of
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>
1305<p>Since there is no standard to do this, the portable implementation simply
1306calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1307can specify a recommended polling interval for this case. If you specify
1308a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1309unspecified default</i> value will be used (which you can expect to be around
1310five seconds, although this might change dynamically). Libev will also
1311impose a minimum interval which is currently around <code>0.1</code>, but thats
1312usually overkill.</p>
1313<p>This watcher type is not meant for massive numbers of stat watchers,
1314as even with OS-supported change notifications, this can be
1315resource-intensive.</p>
1316<p>At the time of this writing, only the Linux inotify interface is
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>
1323<dl>
1324 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1325 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1326 <dd>
1327 <p>Configures the watcher to wait for status changes of the given
1328<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1329be detected and should normally be specified as <code>0</code> to let libev choose
1330a suitable value. The memory pointed to by <code>path</code> must point to the same
1331path for as long as the watcher is active.</p>
1332 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1333relative to the attributes at the time the watcher was started (or the
1334last change was detected).</p>
1335 </dd>
1336 <dt>ev_stat_stat (ev_stat *)</dt>
1337 <dd>
1338 <p>Updates the stat buffer immediately with new values. If you change the
1339watched path in your callback, you could call this fucntion to avoid
1340detecting this change (while introducing a race condition). Can also be
1341useful simply to find out the new values.</p>
1342 </dd>
1343 <dt>ev_statdata attr [read-only]</dt>
1344 <dd>
1345 <p>The most-recently detected attributes of the file. Although the type is of
1346<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1347suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1348was some error while <code>stat</code>ing the file.</p>
1349 </dd>
1350 <dt>ev_statdata prev [read-only]</dt>
1351 <dd>
1352 <p>The previous attributes of the file. The callback gets invoked whenever
1353<code>prev</code> != <code>attr</code>.</p>
1354 </dd>
1355 <dt>ev_tstamp interval [read-only]</dt>
1356 <dd>
1357 <p>The specified interval.</p>
1358 </dd>
1359 <dt>const char *path [read-only]</dt>
1360 <dd>
1361 <p>The filesystem path that is being watched.</p>
1362 </dd>
1363</dl>
1364<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1365<pre> static void
1366 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1367 {
1368 /* /etc/passwd changed in some way */
1369 if (w-&gt;attr.st_nlink)
1370 {
1371 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1372 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1373 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1374 }
1375 else
1376 /* you shalt not abuse printf for puts */
1377 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1378 &quot;if this is windows, they already arrived\n&quot;);
1379 }
1380
1381 ...
1382 ev_stat passwd;
1383
1384 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1385 ev_stat_start (loop, &amp;passwd);
1386
1387
1388
1389
1390</pre>
1391
1392</div>
984<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>
985<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">
986<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
987(prepare, check and other idle watchers do not count). That is, as long 1396priority are pending (prepare, check and other idle watchers do not
988as your process is busy handling sockets or timeouts (or even signals, 1397count).</p>
989imagine) 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
990watchers 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
991until stopped, that is, or your process receives more events and becomes 1402iteration - until stopped, that is, or your process receives more events
992busy.</p> 1403and becomes busy again with higher priority stuff.</p>
993<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
994active, the process will not block when waiting for new events.</p> 1405active, the process will not block when waiting for new events.</p>
995<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
996effect 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
997&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
… …
1002 <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
1003kind. 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,
1004believe me.</p> 1415believe me.</p>
1005 </dd> 1416 </dd>
1006</dl> 1417</dl>
1007<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
1008callback, free it. Alos, use no error checking, as usual.</p> 1419callback, free it. Also, use no error checking, as usual.</p>
1009<pre> static void 1420<pre> static void
1010 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)
1011 { 1422 {
1012 free (w); 1423 free (w);
1013 // now do something you wanted to do when the program has 1424 // now do something you wanted to do when the program has
… …
1022 1433
1023 1434
1024</pre> 1435</pre>
1025 1436
1026</div> 1437</div>
1027<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1438<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1028<div id="code_ev_prepare_code_and_code_ev_che-2"> 1439<div id="code_ev_prepare_code_and_code_ev_che-2">
1029<p>Prepare and check watchers are usually (but not always) used in tandem: 1440<p>Prepare and check watchers are usually (but not always) used in tandem:
1030prepare watchers get invoked before the process blocks and check watchers 1441prepare watchers get invoked before the process blocks and check watchers
1031afterwards.</p> 1442afterwards.</p>
1443<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1444the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1445watchers. Other loops than the current one are fine, however. The
1446rationale behind this is that you do not need to check for recursion in
1447those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1448<code>ev_check</code> so if you have one watcher of each kind they will always be
1449called in pairs bracketing the blocking call.</p>
1032<p>Their main purpose is to integrate other event mechanisms into libev and 1450<p>Their main purpose is to integrate other event mechanisms into libev and
1033their use is somewhat advanced. This could be used, for example, to track 1451their use is somewhat advanced. This could be used, for example, to track
1034variable changes, implement your own watchers, integrate net-snmp or a 1452variable changes, implement your own watchers, integrate net-snmp or a
1035coroutine library and lots more.</p> 1453coroutine library and lots more. They are also occasionally useful if
1454you cache some data and want to flush it before blocking (for example,
1455in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1456watcher).</p>
1036<p>This is done by examining in each prepare call which file descriptors need 1457<p>This is done by examining in each prepare call which file descriptors need
1037to be watched by the other library, registering <code>ev_io</code> watchers for 1458to be watched by the other library, registering <code>ev_io</code> watchers for
1038them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1459them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1039provide just this functionality). Then, in the check watcher you check for 1460provide just this functionality). Then, in the check watcher you check for
1040any events that occured (by checking the pending status of all watchers 1461any events that occured (by checking the pending status of all watchers
… …
1056 <p>Initialises and configures the prepare or check watcher - they have no 1477 <p>Initialises and configures the prepare or check watcher - they have no
1057parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1478parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1058macros, but using them is utterly, utterly and completely pointless.</p> 1479macros, but using them is utterly, utterly and completely pointless.</p>
1059 </dd> 1480 </dd>
1060</dl> 1481</dl>
1061<p>Example: *TODO*.</p> 1482<p>Example: To include a library such as adns, you would add IO watchers
1483and a timeout watcher in a prepare handler, as required by libadns, and
1484in a check watcher, destroy them and call into libadns. What follows is
1485pseudo-code only of course:</p>
1486<pre> static ev_io iow [nfd];
1487 static ev_timer tw;
1062 1488
1489 static void
1490 io_cb (ev_loop *loop, ev_io *w, int revents)
1491 {
1492 // set the relevant poll flags
1493 // could also call adns_processreadable etc. here
1494 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1495 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1496 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1497 }
1063 1498
1499 // create io watchers for each fd and a timer before blocking
1500 static void
1501 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1502 {
1503 int timeout = 3600000;
1504 struct pollfd fds [nfd];
1505 // actual code will need to loop here and realloc etc.
1506 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1064 1507
1508 /* the callback is illegal, but won't be called as we stop during check */
1509 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1510 ev_timer_start (loop, &amp;tw);
1065 1511
1512 // create on ev_io per pollfd
1513 for (int i = 0; i &lt; nfd; ++i)
1514 {
1515 ev_io_init (iow + i, io_cb, fds [i].fd,
1516 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1517 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1066 1518
1519 fds [i].revents = 0;
1520 iow [i].data = fds + i;
1521 ev_io_start (loop, iow + i);
1522 }
1523 }
1524
1525 // stop all watchers after blocking
1526 static void
1527 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1528 {
1529 ev_timer_stop (loop, &amp;tw);
1530
1531 for (int i = 0; i &lt; nfd; ++i)
1532 ev_io_stop (loop, iow + i);
1533
1534 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1535 }
1536
1537
1538
1539
1540</pre>
1541
1067</div> 1542</div>
1068<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1543<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1069<div id="code_ev_embed_code_when_one_backend_-2"> 1544<div id="code_ev_embed_code_when_one_backend_-2">
1070<p>This is a rather advanced watcher type that lets you embed one event loop 1545<p>This is a rather advanced watcher type that lets you embed one event loop
1071into another.</p> 1546into another (currently only <code>ev_io</code> events are supported in the embedded
1547loop, other types of watchers might be handled in a delayed or incorrect
1548fashion and must not be used).</p>
1072<p>There are primarily two reasons you would want that: work around bugs and 1549<p>There are primarily two reasons you would want that: work around bugs and
1073prioritise I/O.</p> 1550prioritise I/O.</p>
1074<p>As an example for a bug workaround, the kqueue backend might only support 1551<p>As an example for a bug workaround, the kqueue backend might only support
1075sockets on some platform, so it is unusable as generic backend, but you 1552sockets on some platform, so it is unusable as generic backend, but you
1076still want to make use of it because you have many sockets and it scales 1553still want to make use of it because you have many sockets and it scales
… …
1081<p>As for prioritising I/O: rarely you have the case where some fds have 1558<p>As for prioritising I/O: rarely you have the case where some fds have
1082to be watched and handled very quickly (with low latency), and even 1559to be watched and handled very quickly (with low latency), and even
1083priorities and idle watchers might have too much overhead. In this case 1560priorities and idle watchers might have too much overhead. In this case
1084you would put all the high priority stuff in one loop and all the rest in 1561you would put all the high priority stuff in one loop and all the rest in
1085a second one, and embed the second one in the first.</p> 1562a second one, and embed the second one in the first.</p>
1563<p>As long as the watcher is active, the callback will be invoked every time
1564there might be events pending in the embedded loop. The callback must then
1565call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1566their callbacks (you could also start an idle watcher to give the embedded
1567loop strictly lower priority for example). You can also set the callback
1568to <code>0</code>, in which case the embed watcher will automatically execute the
1569embedded loop sweep.</p>
1086<p>As long as the watcher is started it will automatically handle events. The 1570<p>As long as the watcher is started it will automatically handle events. The
1087callback will be invoked whenever some events have been handled. You can 1571callback will be invoked whenever some events have been handled. You can
1088set the callback to <code>0</code> to avoid having to specify one if you are not 1572set the callback to <code>0</code> to avoid having to specify one if you are not
1089interested in that.</p> 1573interested in that.</p>
1090<p>Also, there have not currently been made special provisions for forking: 1574<p>Also, there have not currently been made special provisions for forking:
… …
1117 else 1601 else
1118 loop_lo = loop_hi; 1602 loop_lo = loop_hi;
1119 1603
1120</pre> 1604</pre>
1121<dl> 1605<dl>
1122 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> 1606 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1123 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *loop)</dt> 1607 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1608 <dd>
1609 <p>Configures the watcher to embed the given loop, which must be
1610embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1611invoked automatically, otherwise it is the responsibility of the callback
1612to invoke it (it will continue to be called until the sweep has been done,
1613if you do not want thta, you need to temporarily stop the embed watcher).</p>
1124 <dd> 1614 </dd>
1125 <p>Configures the watcher to embed the given loop, which must be embeddable.</p> 1615 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1616 <dd>
1617 <p>Make a single, non-blocking sweep over the embedded loop. This works
1618similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1619apropriate way for embedded loops.</p>
1620 </dd>
1621 <dt>struct ev_loop *loop [read-only]</dt>
1622 <dd>
1623 <p>The embedded event loop.</p>
1126 </dd> 1624 </dd>
1127</dl> 1625</dl>
1128 1626
1129 1627
1130 1628
1131 1629
1132 1630
1133</div> 1631</div>
1134<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1632<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
1633<div id="code_ev_fork_code_the_audacity_to_re-2">
1634<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1635whoever is a good citizen cared to tell libev about it by calling
1636<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1637event loop blocks next and before <code>ev_check</code> watchers are being called,
1638and only in the child after the fork. If whoever good citizen calling
1639<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1640handlers will be invoked, too, of course.</p>
1641<dl>
1642 <dt>ev_fork_init (ev_signal *, callback)</dt>
1643 <dd>
1644 <p>Initialises and configures the fork watcher - it has no parameters of any
1645kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1646believe me.</p>
1647 </dd>
1648</dl>
1649
1650
1651
1652
1653
1654</div>
1655<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1135<div id="OTHER_FUNCTIONS_CONTENT"> 1656<div id="OTHER_FUNCTIONS_CONTENT">
1136<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>
1137<dl> 1658<dl>
1138 <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>
1139 <dd> 1660 <dd>
… …
1163 1684
1164 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1685 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1165 1686
1166</pre> 1687</pre>
1167 </dd> 1688 </dd>
1168 <dt>ev_feed_event (loop, watcher, int events)</dt> 1689 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
1169 <dd> 1690 <dd>
1170 <p>Feeds the given event set into the event loop, as if the specified event 1691 <p>Feeds the given event set into the event loop, as if the specified event
1171had happened for the specified watcher (which must be a pointer to an 1692had happened for the specified watcher (which must be a pointer to an
1172initialised but not necessarily started event watcher).</p> 1693initialised but not necessarily started event watcher).</p>
1173 </dd> 1694 </dd>
1174 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1695 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
1175 <dd> 1696 <dd>
1176 <p>Feed an event on the given fd, as if a file descriptor backend detected 1697 <p>Feed an event on the given fd, as if a file descriptor backend detected
1177the given events it.</p> 1698the given events it.</p>
1178 </dd> 1699 </dd>
1179 <dt>ev_feed_signal_event (loop, int signum)</dt> 1700 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
1180 <dd> 1701 <dd>
1181 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1702 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1703loop!).</p>
1182 </dd> 1704 </dd>
1183</dl> 1705</dl>
1184 1706
1185 1707
1186 1708
1187 1709
1188 1710
1189</div> 1711</div>
1190<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1712<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1191<div id="LIBEVENT_EMULATION_CONTENT"> 1713<div id="LIBEVENT_EMULATION_CONTENT">
1192<p>Libev offers a compatibility emulation layer for libevent. It cannot 1714<p>Libev offers a compatibility emulation layer for libevent. It cannot
1193emulate the internals of libevent, so here are some usage hints:</p> 1715emulate the internals of libevent, so here are some usage hints:</p>
1194<dl> 1716<dl>
1195 <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>
… …
1205 <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
1206to use the libev header file and library.</dt> 1728to use the libev header file and library.</dt>
1207</dl> 1729</dl>
1208 1730
1209</div> 1731</div>
1210<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1732<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1211<div id="C_SUPPORT_CONTENT"> 1733<div id="C_SUPPORT_CONTENT">
1212<p>TBD.</p> 1734<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1735you to use some convinience methods to start/stop watchers and also change
1736the callback model to a model using method callbacks on objects.</p>
1737<p>To use it,</p>
1738<pre> #include &lt;ev++.h&gt;
1213 1739
1740</pre>
1741<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1742and puts all of its definitions (many of them macros) into the global
1743namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1744<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1745<code>EV_MULTIPLICITY</code>.</p>
1746<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1747<dl>
1748 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1749 <dd>
1750 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1751macros from <cite>ev.h</cite>.</p>
1752 </dd>
1753 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1754 <dd>
1755 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1756 </dd>
1757 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1758 <dd>
1759 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1760the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1761which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1762defines by many implementations.</p>
1763 <p>All of those classes have these methods:</p>
1764 <p>
1765 <dl>
1766 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1767 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1768 <dt>ev::TYPE::~TYPE</dt>
1769 <dd>
1770 <p>The constructor takes a pointer to an object and a method pointer to
1771the event handler callback to call in this class. The constructor calls
1772<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1773before starting it. If you do not specify a loop then the constructor
1774automatically associates the default loop with this watcher.</p>
1775 <p>The destructor automatically stops the watcher if it is active.</p>
1776 </dd>
1777 <dt>w-&gt;set (struct ev_loop *)</dt>
1778 <dd>
1779 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1780do this when the watcher is inactive (and not pending either).</p>
1781 </dd>
1782 <dt>w-&gt;set ([args])</dt>
1783 <dd>
1784 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1785called at least once. Unlike the C counterpart, an active watcher gets
1786automatically stopped and restarted.</p>
1787 </dd>
1788 <dt>w-&gt;start ()</dt>
1789 <dd>
1790 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1791constructor already takes the loop.</p>
1792 </dd>
1793 <dt>w-&gt;stop ()</dt>
1794 <dd>
1795 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1796 </dd>
1797 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1798 <dd>
1799 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1800<code>ev_TYPE_again</code> function.</p>
1801 </dd>
1802 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1803 <dd>
1804 <p>Invokes <code>ev_embed_sweep</code>.</p>
1805 </dd>
1806 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1807 <dd>
1808 <p>Invokes <code>ev_stat_stat</code>.</p>
1809 </dd>
1810 </dl>
1811 </p>
1812 </dd>
1813</dl>
1814<p>Example: Define a class with an IO and idle watcher, start one of them in
1815the constructor.</p>
1816<pre> class myclass
1817 {
1818 ev_io io; void io_cb (ev::io &amp;w, int revents);
1819 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1820
1821 myclass ();
1822 }
1823
1824 myclass::myclass (int fd)
1825 : io (this, &amp;myclass::io_cb),
1826 idle (this, &amp;myclass::idle_cb)
1827 {
1828 io.start (fd, ev::READ);
1829 }
1830
1831
1832
1833
1834</pre>
1835
1214</div> 1836</div>
1215<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1837<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1838<div id="MACRO_MAGIC_CONTENT">
1839<p>Libev can be compiled with a variety of options, the most fundemantal is
1840<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1841callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1842<p>To make it easier to write programs that cope with either variant, the
1843following macros are defined:</p>
1844<dl>
1845 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1846 <dd>
1847 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1848loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1849<code>EV_A_</code> is used when other arguments are following. Example:</p>
1850<pre> ev_unref (EV_A);
1851 ev_timer_add (EV_A_ watcher);
1852 ev_loop (EV_A_ 0);
1853
1854</pre>
1855 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1856which is often provided by the following macro.</p>
1857 </dd>
1858 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1859 <dd>
1860 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1861loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1862<code>EV_P_</code> is used when other parameters are following. Example:</p>
1863<pre> // this is how ev_unref is being declared
1864 static void ev_unref (EV_P);
1865
1866 // this is how you can declare your typical callback
1867 static void cb (EV_P_ ev_timer *w, int revents)
1868
1869</pre>
1870 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1871suitable for use with <code>EV_A</code>.</p>
1872 </dd>
1873 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1874 <dd>
1875 <p>Similar to the other two macros, this gives you the value of the default
1876loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1877 </dd>
1878</dl>
1879<p>Example: Declare and initialise a check watcher, utilising the above
1880macros so it will work regardless of whether multiple loops are supported
1881or not.</p>
1882<pre> static void
1883 check_cb (EV_P_ ev_timer *w, int revents)
1884 {
1885 ev_check_stop (EV_A_ w);
1886 }
1887
1888 ev_check check;
1889 ev_check_init (&amp;check, check_cb);
1890 ev_check_start (EV_DEFAULT_ &amp;check);
1891 ev_loop (EV_DEFAULT_ 0);
1892
1893</pre>
1894
1895</div>
1896<h1 id="EMBEDDING">EMBEDDING</h1>
1897<div id="EMBEDDING_CONTENT">
1898<p>Libev can (and often is) directly embedded into host
1899applications. Examples of applications that embed it include the Deliantra
1900Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1901and rxvt-unicode.</p>
1902<p>The goal is to enable you to just copy the neecssary files into your
1903source directory without having to change even a single line in them, so
1904you can easily upgrade by simply copying (or having a checked-out copy of
1905libev somewhere in your source tree).</p>
1906
1907</div>
1908<h2 id="FILESETS">FILESETS</h2>
1909<div id="FILESETS_CONTENT">
1910<p>Depending on what features you need you need to include one or more sets of files
1911in your app.</p>
1912
1913</div>
1914<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1915<div id="CORE_EVENT_LOOP_CONTENT">
1916<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1917configuration (no autoconf):</p>
1918<pre> #define EV_STANDALONE 1
1919 #include &quot;ev.c&quot;
1920
1921</pre>
1922<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1923single C source file only to provide the function implementations. To use
1924it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1925done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1926where you can put other configuration options):</p>
1927<pre> #define EV_STANDALONE 1
1928 #include &quot;ev.h&quot;
1929
1930</pre>
1931<p>Both header files and implementation files can be compiled with a C++
1932compiler (at least, thats a stated goal, and breakage will be treated
1933as a bug).</p>
1934<p>You need the following files in your source tree, or in a directory
1935in your include path (e.g. in libev/ when using -Ilibev):</p>
1936<pre> ev.h
1937 ev.c
1938 ev_vars.h
1939 ev_wrap.h
1940
1941 ev_win32.c required on win32 platforms only
1942
1943 ev_select.c only when select backend is enabled (which is enabled by default)
1944 ev_poll.c only when poll backend is enabled (disabled by default)
1945 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1946 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1947 ev_port.c only when the solaris port backend is enabled (disabled by default)
1948
1949</pre>
1950<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1951to compile this single file.</p>
1952
1953</div>
1954<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1955<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1956<p>To include the libevent compatibility API, also include:</p>
1957<pre> #include &quot;event.c&quot;
1958
1959</pre>
1960<p>in the file including <cite>ev.c</cite>, and:</p>
1961<pre> #include &quot;event.h&quot;
1962
1963</pre>
1964<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1965<p>You need the following additional files for this:</p>
1966<pre> event.h
1967 event.c
1968
1969</pre>
1970
1971</div>
1972<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1973<div id="AUTOCONF_SUPPORT_CONTENT">
1974<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1975whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1976<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1977include <cite>config.h</cite> and configure itself accordingly.</p>
1978<p>For this of course you need the m4 file:</p>
1979<pre> libev.m4
1980
1981</pre>
1982
1983</div>
1984<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1985<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1986<p>Libev can be configured via a variety of preprocessor symbols you have to define
1987before including any of its files. The default is not to build for multiplicity
1988and only include the select backend.</p>
1989<dl>
1990 <dt>EV_STANDALONE</dt>
1991 <dd>
1992 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1993keeps libev from including <cite>config.h</cite>, and it also defines dummy
1994implementations for some libevent functions (such as logging, which is not
1995supported). It will also not define any of the structs usually found in
1996<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1997 </dd>
1998 <dt>EV_USE_MONOTONIC</dt>
1999 <dd>
2000 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
2001monotonic clock option at both compiletime and runtime. Otherwise no use
2002of the monotonic clock option will be attempted. If you enable this, you
2003usually have to link against librt or something similar. Enabling it when
2004the functionality isn't available is safe, though, althoguh you have
2005to make sure you link against any libraries where the <code>clock_gettime</code>
2006function is hiding in (often <cite>-lrt</cite>).</p>
2007 </dd>
2008 <dt>EV_USE_REALTIME</dt>
2009 <dd>
2010 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
2011realtime clock option at compiletime (and assume its availability at
2012runtime if successful). Otherwise no use of the realtime clock option will
2013be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
2014(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
2015in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
2016 </dd>
2017 <dt>EV_USE_SELECT</dt>
2018 <dd>
2019 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
2020<code>select</code>(2) backend. No attempt at autodetection will be done: if no
2021other method takes over, select will be it. Otherwise the select backend
2022will not be compiled in.</p>
2023 </dd>
2024 <dt>EV_SELECT_USE_FD_SET</dt>
2025 <dd>
2026 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
2027structure. This is useful if libev doesn't compile due to a missing
2028<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
2029exotic systems. This usually limits the range of file descriptors to some
2030low limit such as 1024 or might have other limitations (winsocket only
2031allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
2032influence the size of the <code>fd_set</code> used.</p>
2033 </dd>
2034 <dt>EV_SELECT_IS_WINSOCKET</dt>
2035 <dd>
2036 <p>When defined to <code>1</code>, the select backend will assume that
2037select/socket/connect etc. don't understand file descriptors but
2038wants osf handles on win32 (this is the case when the select to
2039be used is the winsock select). This means that it will call
2040<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
2041it is assumed that all these functions actually work on fds, even
2042on win32. Should not be defined on non-win32 platforms.</p>
2043 </dd>
2044 <dt>EV_USE_POLL</dt>
2045 <dd>
2046 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
2047backend. Otherwise it will be enabled on non-win32 platforms. It
2048takes precedence over select.</p>
2049 </dd>
2050 <dt>EV_USE_EPOLL</dt>
2051 <dd>
2052 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
2053<code>epoll</code>(7) backend. Its availability will be detected at runtime,
2054otherwise another method will be used as fallback. This is the
2055preferred backend for GNU/Linux systems.</p>
2056 </dd>
2057 <dt>EV_USE_KQUEUE</dt>
2058 <dd>
2059 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2060<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2061otherwise another method will be used as fallback. This is the preferred
2062backend for BSD and BSD-like systems, although on most BSDs kqueue only
2063supports some types of fds correctly (the only platform we found that
2064supports ptys for example was NetBSD), so kqueue might be compiled in, but
2065not be used unless explicitly requested. The best way to use it is to find
2066out whether kqueue supports your type of fd properly and use an embedded
2067kqueue loop.</p>
2068 </dd>
2069 <dt>EV_USE_PORT</dt>
2070 <dd>
2071 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
207210 port style backend. Its availability will be detected at runtime,
2073otherwise another method will be used as fallback. This is the preferred
2074backend for Solaris 10 systems.</p>
2075 </dd>
2076 <dt>EV_USE_DEVPOLL</dt>
2077 <dd>
2078 <p>reserved for future expansion, works like the USE symbols above.</p>
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>
2086 <dt>EV_H</dt>
2087 <dd>
2088 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
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
2090can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2091 </dd>
2092 <dt>EV_CONFIG_H</dt>
2093 <dd>
2094 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2095<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2096<code>EV_H</code>, above.</p>
2097 </dd>
2098 <dt>EV_EVENT_H</dt>
2099 <dd>
2100 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2101of how the <cite>event.h</cite> header can be found.</p>
2102 </dd>
2103 <dt>EV_PROTOTYPES</dt>
2104 <dd>
2105 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2106prototypes, but still define all the structs and other symbols. This is
2107occasionally useful if you want to provide your own wrapper functions
2108around libev functions.</p>
2109 </dd>
2110 <dt>EV_MULTIPLICITY</dt>
2111 <dd>
2112 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2113will have the <code>struct ev_loop *</code> as first argument, and you can create
2114additional independent event loops. Otherwise there will be no support
2115for multiple event loops and there is no first event loop pointer
2116argument. Instead, all functions act on the single default loop.</p>
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>
2132 <dt>EV_PERIODIC_ENABLE</dt>
2133 <dd>
2134 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2135defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2136code.</p>
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>
2144 <dt>EV_EMBED_ENABLE</dt>
2145 <dd>
2146 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2147defined to be <code>0</code>, then they are not.</p>
2148 </dd>
2149 <dt>EV_STAT_ENABLE</dt>
2150 <dd>
2151 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2152defined to be <code>0</code>, then they are not.</p>
2153 </dd>
2154 <dt>EV_FORK_ENABLE</dt>
2155 <dd>
2156 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2157defined to be <code>0</code>, then they are not.</p>
2158 </dd>
2159 <dt>EV_MINIMAL</dt>
2160 <dd>
2161 <p>If you need to shave off some kilobytes of code at the expense of some
2162speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2163some inlining decisions, saves roughly 30% codesize of amd64.</p>
2164 </dd>
2165 <dt>EV_PID_HASHSIZE</dt>
2166 <dd>
2167 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2168pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2169than enough. If you need to manage thousands of children you might want to
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>
2179 </dd>
2180 <dt>EV_COMMON</dt>
2181 <dd>
2182 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2183this macro to a something else you can include more and other types of
2184members. You have to define it each time you include one of the files,
2185though, and it must be identical each time.</p>
2186 <p>For example, the perl EV module uses something like this:</p>
2187<pre> #define EV_COMMON \
2188 SV *self; /* contains this struct */ \
2189 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2190
2191</pre>
2192 </dd>
2193 <dt>EV_CB_DECLARE (type)</dt>
2194 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2195 <dt>ev_set_cb (ev, cb)</dt>
2196 <dd>
2197 <p>Can be used to change the callback member declaration in each watcher,
2198and the way callbacks are invoked and set. Must expand to a struct member
2199definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2200their default definitions. One possible use for overriding these is to
2201avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2202method calls instead of plain function calls in C++.</p>
2203
2204</div>
2205<h2 id="EXAMPLES">EXAMPLES</h2>
2206<div id="EXAMPLES_CONTENT">
2207 <p>For a real-world example of a program the includes libev
2208verbatim, you can have a look at the EV perl module
2209(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2210the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2211interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2212will be compiled. It is pretty complex because it provides its own header
2213file.</p>
2214 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2215that everybody includes and which overrides some configure choices:</p>
2216<pre> #define EV_MINIMAL 1
2217 #define EV_USE_POLL 0
2218 #define EV_MULTIPLICITY 0
2219 #define EV_PERIODIC_ENABLE 0
2220 #define EV_STAT_ENABLE 0
2221 #define EV_FORK_ENABLE 0
2222 #define EV_CONFIG_H &lt;config.h&gt;
2223 #define EV_MINPRI 0
2224 #define EV_MAXPRI 0
2225
2226 #include &quot;ev++.h&quot;
2227
2228</pre>
2229 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2230<pre> #include &quot;ev_cpp.h&quot;
2231 #include &quot;ev.c&quot;
2232
2233
2234
2235
2236</pre>
2237
2238</div>
2239<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2240<div id="COMPLEXITIES_CONTENT">
2241 <p>In this section the complexities of (many of) the algorithms used inside
2242libev will be explained. For complexity discussions about backends see the
2243documentation for <code>ev_default_init</code>.</p>
2244 <p>All of the following are about amortised time: If an array needs to be
2245extended, libev needs to realloc and move the whole array, but this
2246happens asymptotically never with higher number of elements, so O(1) might
2247mean it might do a lengthy realloc operation in rare cases, but on average
2248it is much faster and asymptotically approaches constant time.</p>
2249 <p>
2250 <dl>
2251 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2252 <dd>
2253 <p>This means that, when you have a watcher that triggers in one hour and
2254there are 100 watchers that would trigger before that then inserting will
2255have to skip those 100 watchers.</p>
2256 </dd>
2257 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2258 <dd>
2259 <p>That means that for changing a timer costs less than removing/adding them
2260as only the relative motion in the event queue has to be paid for.</p>
2261 </dd>
2262 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2263 <dd>
2264 <p>These just add the watcher into an array or at the head of a list.
2265=item Stopping check/prepare/idle watchers: O(1)</p>
2266 </dd>
2267 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2268 <dd>
2269 <p>These watchers are stored in lists then need to be walked to find the
2270correct watcher to remove. The lists are usually short (you don't usually
2271have many watchers waiting for the same fd or signal).</p>
2272 </dd>
2273 <dt>Finding the next timer per loop iteration: O(1)</dt>
2274 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2275 <dd>
2276 <p>A change means an I/O watcher gets started or stopped, which requires
2277libev to recalculate its status (and possibly tell the kernel).</p>
2278 </dd>
2279 <dt>Activating one watcher: O(1)</dt>
2280 <dt>Priority handling: O(number_of_priorities)</dt>
2281 <dd>
2282 <p>Priorities are implemented by allocating some space for each
2283priority. When doing priority-based operations, libev usually has to
2284linearly search all the priorities.</p>
2285 </dd>
2286 </dl>
2287 </p>
2288
2289
2290
2291
2292
2293</div>
2294<h1 id="AUTHOR">AUTHOR</h1>
1216<div id="AUTHOR_CONTENT"> 2295<div id="AUTHOR_CONTENT">
1217<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2296 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1218 2297
1219</div> 2298</div>
1220</div></body> 2299</div></body>
1221</html> 2300</html>

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