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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="Sat Dec 8 15:27:35 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
… …
600programs, though, so beware.</p> 710programs, though, so beware.</p>
601 </dd> 711 </dd>
602</dl> 712</dl>
603 713
604</div> 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), you must not change its priority, and you must
775make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
776it).</p>
777 </dd>
778 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
779 <dd>
780 <p>Returns the callback currently set on the watcher.</p>
781 </dd>
782 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
783 <dd>
784 <p>Change the callback. You can change the callback at virtually any time
785(modulo threads).</p>
786 </dd>
787 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
788 <dt>int ev_priority (ev_TYPE *watcher)</dt>
789 <dd>
790 <p>Set and query the priority of the watcher. The priority is a small
791integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
792(default: <code>-2</code>). Pending watchers with higher priority will be invoked
793before watchers with lower priority, but priority will not keep watchers
794from being executed (except for <code>ev_idle</code> watchers).</p>
795 <p>This means that priorities are <i>only</i> used for ordering callback
796invocation after new events have been received. This is useful, for
797example, to reduce latency after idling, or more often, to bind two
798watchers on the same event and make sure one is called first.</p>
799 <p>If you need to suppress invocation when higher priority events are pending
800you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
801 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
802pending.</p>
803 <p>The default priority used by watchers when no priority has been set is
804always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
805 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
806fine, as long as you do not mind that the priority value you query might
807or might not have been adjusted to be within valid range.</p>
808 </dd>
809 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
810 <dd>
811 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
812<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
813can deal with that fact.</p>
814 </dd>
815 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
816 <dd>
817 <p>If the watcher is pending, this function returns clears its pending status
818and returns its <code>revents</code> bitset (as if its callback was invoked). If the
819watcher isn't pending it does nothing and returns <code>0</code>.</p>
820 </dd>
821</dl>
822
823
824
825
826
827</div>
605<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 828<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"> 829<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 830<p>Each watcher has, by default, a member <code>void *data</code> that you can change
608and read at any time, libev will completely ignore it. This can be used 831and read at any time, libev will completely ignore it. This can be used
609to associate arbitrary data with your watcher. If you need more data and 832to associate arbitrary data with your watcher. If you need more data and
… …
626 struct my_io *w = (struct my_io *)w_; 849 struct my_io *w = (struct my_io *)w_;
627 ... 850 ...
628 } 851 }
629 852
630</pre> 853</pre>
631<p>More interesting and less C-conformant ways of catsing your callback type 854<p>More interesting and less C-conformant ways of casting your callback type
632have been omitted....</p> 855instead have been omitted.</p>
856<p>Another common scenario is having some data structure with multiple
857watchers:</p>
858<pre> struct my_biggy
859 {
860 int some_data;
861 ev_timer t1;
862 ev_timer t2;
863 }
633 864
865</pre>
866<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
867you need to use <code>offsetof</code>:</p>
868<pre> #include &lt;stddef.h&gt;
634 869
870 static void
871 t1_cb (EV_P_ struct ev_timer *w, int revents)
872 {
873 struct my_biggy big = (struct my_biggy *
874 (((char *)w) - offsetof (struct my_biggy, t1));
875 }
635 876
877 static void
878 t2_cb (EV_P_ struct ev_timer *w, int revents)
879 {
880 struct my_biggy big = (struct my_biggy *
881 (((char *)w) - offsetof (struct my_biggy, t2));
882 }
636 883
637 884
885
886
887</pre>
888
638</div> 889</div>
639<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 890<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
640<div id="WATCHER_TYPES_CONTENT"> 891<div id="WATCHER_TYPES_CONTENT">
641<p>This section describes each watcher in detail, but will not repeat 892<p>This section describes each watcher in detail, but will not repeat
642information given in the last section.</p> 893information given in the last section. Any initialisation/set macros,
894functions and members specific to the watcher type are explained.</p>
895<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
896while the watcher is active, you can look at the member and expect some
897sensible content, but you must not modify it (you can modify it while the
898watcher is stopped to your hearts content), or <i>[read-write]</i>, which
899means you can expect it to have some sensible content while the watcher
900is active, but you can also modify it. Modifying it may not do something
901sensible or take immediate effect (or do anything at all), but libev will
902not crash or malfunction in any way.</p>
643 903
644 904
645 905
646 906
647 907
648</div> 908</div>
649<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 909<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"> 910<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 911<p>I/O watchers check whether a file descriptor is readable or writable
652in each iteration of the event loop (This behaviour is called 912in each iteration of the event loop, or, more precisely, when reading
653level-triggering because you keep receiving events as long as the 913would 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 914some data. This behaviour is called level-triggering because you keep
655act on the event and neither want to receive future events).</p> 915receiving events as long as the condition persists. Remember you can stop
916the watcher if you don't want to act on the event and neither want to
917receive future events.</p>
656<p>In general you can register as many read and/or write event watchers per 918<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 919fd 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 920descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing).</p> 921required if you know what you are doing).</p>
660<p>You have to be careful with dup'ed file descriptors, though. Some backends 922<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 923(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 924descriptors correctly if you register interest in two or more fds pointing
663to the same underlying file/socket etc. description (that is, they share 925to the same underlying file/socket/etc. description (that is, they share
664the same underlying &quot;file open&quot;).</p> 926the 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 927<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 928(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
667<code>EVBACKEND_POLL</code>).</p> 929<code>EVBACKEND_POLL</code>).</p>
930<p>Another thing you have to watch out for is that it is quite easy to
931receive &quot;spurious&quot; readyness notifications, that is your callback might
932be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
933because there is no data. Not only are some backends known to create a
934lot of those (for example solaris ports), it is very easy to get into
935this situation even with a relatively standard program structure. Thus
936it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
937<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
938<p>If you cannot run the fd in non-blocking mode (for example you should not
939play around with an Xlib connection), then you have to seperately re-test
940whether a file descriptor is really ready with a known-to-be good interface
941such as poll (fortunately in our Xlib example, Xlib already does this on
942its own, so its quite safe to use).</p>
668<dl> 943<dl>
669 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 944 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
670 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 945 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
671 <dd> 946 <dd>
672 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 947 <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 | 948rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
674EV_WRITE</code> to receive the given events.</p> 949<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 950 </dd>
676epoll and solaris ports) can result in spurious readyness notifications 951 <dt>int fd [read-only]</dt>
677for file descriptors, so you practically need to use non-blocking I/O (and 952 <dd>
678treat callback invocation as hint only), or retest separately with a safe 953 <p>The file descriptor being watched.</p>
679interface before doing I/O (XLib can do this), or force the use of either 954 </dd>
680<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 955 <dt>int events [read-only]</dt>
681problem. Also note that it is quite easy to have your callback invoked 956 <dd>
682when the readyness condition is no longer valid even when employing 957 <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> 958 </dd>
686</dl> 959</dl>
687<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 960<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 961readable, but only once. Since it is likely line-buffered, you could
689attempt to read a whole line in the callback:</p> 962attempt to read a whole line in the callback.</p>
690<pre> static void 963<pre> static void
691 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 964 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
692 { 965 {
693 ev_io_stop (loop, w); 966 ev_io_stop (loop, w);
694 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 967 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
705 978
706 979
707</pre> 980</pre>
708 981
709</div> 982</div>
710<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 983<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"> 984<div id="code_ev_timer_code_relative_and_opti-2">
712<p>Timer watchers are simple relative timers that generate an event after a 985<p>Timer watchers are simple relative timers that generate an event after a
713given time, and optionally repeating in regular intervals after that.</p> 986given 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 987<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 988times out after an hour and you reset your system clock to last years
… …
743 </dd> 1016 </dd>
744 <dt>ev_timer_again (loop)</dt> 1017 <dt>ev_timer_again (loop)</dt>
745 <dd> 1018 <dd>
746 <p>This will act as if the timer timed out and restart it again if it is 1019 <p>This will act as if the timer timed out and restart it again if it is
747repeating. The exact semantics are:</p> 1020repeating. The exact semantics are:</p>
1021 <p>If the timer is pending, its pending status is cleared.</p>
748 <p>If the timer is started but nonrepeating, stop it.</p> 1022 <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 1023 <p>If the timer is repeating, either start it if necessary (with the
750value), or reset the running timer to the repeat value.</p> 1024<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 1025 <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 1026example: 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 1027timeout, 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 1028seconds 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 1029configure 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 1030<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 1031you go into an idle state where you do not expect data to travel on the
1032socket, 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> 1033automatically restart it if need be.</p>
1034 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
1035altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
1036<pre> ev_timer_init (timer, callback, 0., 5.);
1037 ev_timer_again (loop, timer);
1038 ...
1039 timer-&gt;again = 17.;
1040 ev_timer_again (loop, timer);
1041 ...
1042 timer-&gt;again = 10.;
1043 ev_timer_again (loop, timer);
1044
1045</pre>
1046 <p>This is more slightly efficient then stopping/starting the timer each time
1047you want to modify its timeout value.</p>
1048 </dd>
1049 <dt>ev_tstamp repeat [read-write]</dt>
1050 <dd>
1051 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
1052or <code>ev_timer_again</code> is called and determines the next timeout (if any),
1053which is also when any modifications are taken into account.</p>
759 </dd> 1054 </dd>
760</dl> 1055</dl>
761<p>Example: create a timer that fires after 60 seconds.</p> 1056<p>Example: Create a timer that fires after 60 seconds.</p>
762<pre> static void 1057<pre> static void
763 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1058 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
764 { 1059 {
765 .. one minute over, w is actually stopped right here 1060 .. one minute over, w is actually stopped right here
766 } 1061 }
… …
768 struct ev_timer mytimer; 1063 struct ev_timer mytimer;
769 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1064 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
770 ev_timer_start (loop, &amp;mytimer); 1065 ev_timer_start (loop, &amp;mytimer);
771 1066
772</pre> 1067</pre>
773<p>Example: create a timeout timer that times out after 10 seconds of 1068<p>Example: Create a timeout timer that times out after 10 seconds of
774inactivity.</p> 1069inactivity.</p>
775<pre> static void 1070<pre> static void
776 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1071 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
777 { 1072 {
778 .. ten seconds without any activity 1073 .. ten seconds without any activity
… …
791 1086
792 1087
793</pre> 1088</pre>
794 1089
795</div> 1090</div>
796<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1091<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"> 1092<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 1093<p>Periodic watchers are also timers of a kind, but they are very versatile
799(and unfortunately a bit complex).</p> 1094(and unfortunately a bit complex).</p>
800<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1095<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 1096but 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 1097to 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 () 1098periodic 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 1099+ 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 1100take 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 1101roughly 10 seconds later and of course not if you reset your system time
807again).</p> 1102again).</p>
808<p>They can also be used to implement vastly more complex timers, such as 1103<p>They can also be used to implement vastly more complex timers, such as
809triggering an event on eahc midnight, local time.</p> 1104triggering an event on eahc midnight, local time.</p>
… …
881 <p>Simply stops and restarts the periodic watcher again. This is only useful 1176 <p>Simply stops and restarts the periodic watcher again. This is only useful
882when you changed some parameters or the reschedule callback would return 1177when 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 1178a different time than the last time it was called (e.g. in a crond like
884program when the crontabs have changed).</p> 1179program when the crontabs have changed).</p>
885 </dd> 1180 </dd>
1181 <dt>ev_tstamp interval [read-write]</dt>
1182 <dd>
1183 <p>The current interval value. Can be modified any time, but changes only
1184take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1185called.</p>
1186 </dd>
1187 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1188 <dd>
1189 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1190switched off. Can be changed any time, but changes only take effect when
1191the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1192 </dd>
886</dl> 1193</dl>
887<p>Example: call a callback every hour, or, more precisely, whenever the 1194<p>Example: Call a callback every hour, or, more precisely, whenever the
888system clock is divisible by 3600. The callback invocation times have 1195system clock is divisible by 3600. The callback invocation times have
889potentially a lot of jittering, but good long-term stability.</p> 1196potentially a lot of jittering, but good long-term stability.</p>
890<pre> static void 1197<pre> static void
891 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1198 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
892 { 1199 {
… …
896 struct ev_periodic hourly_tick; 1203 struct ev_periodic hourly_tick;
897 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1204 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
898 ev_periodic_start (loop, &amp;hourly_tick); 1205 ev_periodic_start (loop, &amp;hourly_tick);
899 1206
900</pre> 1207</pre>
901<p>Example: the same as above, but use a reschedule callback to do it:</p> 1208<p>Example: The same as above, but use a reschedule callback to do it:</p>
902<pre> #include &lt;math.h&gt; 1209<pre> #include &lt;math.h&gt;
903 1210
904 static ev_tstamp 1211 static ev_tstamp
905 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1212 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
906 { 1213 {
… …
908 } 1215 }
909 1216
910 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1217 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
911 1218
912</pre> 1219</pre>
913<p>Example: call a callback every hour, starting now:</p> 1220<p>Example: Call a callback every hour, starting now:</p>
914<pre> struct ev_periodic hourly_tick; 1221<pre> struct ev_periodic hourly_tick;
915 ev_periodic_init (&amp;hourly_tick, clock_cb, 1222 ev_periodic_init (&amp;hourly_tick, clock_cb,
916 fmod (ev_now (loop), 3600.), 3600., 0); 1223 fmod (ev_now (loop), 3600.), 3600., 0);
917 ev_periodic_start (loop, &amp;hourly_tick); 1224 ev_periodic_start (loop, &amp;hourly_tick);
918 1225
… …
920 1227
921 1228
922</pre> 1229</pre>
923 1230
924</div> 1231</div>
925<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1232<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"> 1233<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 1234<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 1235signal 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 1236will try it's best to deliver signals synchronously, i.e. as part of the
930normal event processing, like any other event.</p> 1237normal event processing, like any other event.</p>
… …
939 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1246 <dt>ev_signal_set (ev_signal *, int signum)</dt>
940 <dd> 1247 <dd>
941 <p>Configures the watcher to trigger on the given signal number (usually one 1248 <p>Configures the watcher to trigger on the given signal number (usually one
942of the <code>SIGxxx</code> constants).</p> 1249of the <code>SIGxxx</code> constants).</p>
943 </dd> 1250 </dd>
1251 <dt>int signum [read-only]</dt>
1252 <dd>
1253 <p>The signal the watcher watches out for.</p>
1254 </dd>
944</dl> 1255</dl>
945 1256
946 1257
947 1258
948 1259
949 1260
950</div> 1261</div>
951<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1262<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"> 1263<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 1264<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> 1265some child status changes (most typically when a child of yours dies).</p>
955<dl> 1266<dl>
956 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1267 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
957 <dt>ev_child_set (ev_child *, int pid)</dt> 1268 <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 1272at 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 1273the 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 1274<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
964process causing the status change.</p> 1275process causing the status change.</p>
965 </dd> 1276 </dd>
1277 <dt>int pid [read-only]</dt>
1278 <dd>
1279 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1280 </dd>
1281 <dt>int rpid [read-write]</dt>
1282 <dd>
1283 <p>The process id that detected a status change.</p>
1284 </dd>
1285 <dt>int rstatus [read-write]</dt>
1286 <dd>
1287 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1288<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1289 </dd>
966</dl> 1290</dl>
967<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1291<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
968<pre> static void 1292<pre> static void
969 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1293 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
970 { 1294 {
971 ev_unloop (loop, EVUNLOOP_ALL); 1295 ev_unloop (loop, EVUNLOOP_ALL);
972 } 1296 }
… …
979 1303
980 1304
981</pre> 1305</pre>
982 1306
983</div> 1307</div>
1308<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1309<div id="code_ev_stat_code_did_the_file_attri-2">
1310<p>This watches a filesystem path for attribute changes. That is, it calls
1311<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1312compared to the last time, invoking the callback if it did.</p>
1313<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1314not exist&quot; is a status change like any other. The condition &quot;path does
1315not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1316otherwise always forced to be at least one) and all the other fields of
1317the stat buffer having unspecified contents.</p>
1318<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1319relative and your working directory changes, the behaviour is undefined.</p>
1320<p>Since there is no standard to do this, the portable implementation simply
1321calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1322can specify a recommended polling interval for this case. If you specify
1323a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1324unspecified default</i> value will be used (which you can expect to be around
1325five seconds, although this might change dynamically). Libev will also
1326impose a minimum interval which is currently around <code>0.1</code>, but thats
1327usually overkill.</p>
1328<p>This watcher type is not meant for massive numbers of stat watchers,
1329as even with OS-supported change notifications, this can be
1330resource-intensive.</p>
1331<p>At the time of this writing, only the Linux inotify interface is
1332implemented (implementing kqueue support is left as an exercise for the
1333reader). Inotify will be used to give hints only and should not change the
1334semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1335to fall back to regular polling again even with inotify, but changes are
1336usually detected immediately, and if the file exists there will be no
1337polling.</p>
1338<dl>
1339 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1340 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1341 <dd>
1342 <p>Configures the watcher to wait for status changes of the given
1343<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1344be detected and should normally be specified as <code>0</code> to let libev choose
1345a suitable value. The memory pointed to by <code>path</code> must point to the same
1346path for as long as the watcher is active.</p>
1347 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1348relative to the attributes at the time the watcher was started (or the
1349last change was detected).</p>
1350 </dd>
1351 <dt>ev_stat_stat (ev_stat *)</dt>
1352 <dd>
1353 <p>Updates the stat buffer immediately with new values. If you change the
1354watched path in your callback, you could call this fucntion to avoid
1355detecting this change (while introducing a race condition). Can also be
1356useful simply to find out the new values.</p>
1357 </dd>
1358 <dt>ev_statdata attr [read-only]</dt>
1359 <dd>
1360 <p>The most-recently detected attributes of the file. Although the type is of
1361<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1362suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1363was some error while <code>stat</code>ing the file.</p>
1364 </dd>
1365 <dt>ev_statdata prev [read-only]</dt>
1366 <dd>
1367 <p>The previous attributes of the file. The callback gets invoked whenever
1368<code>prev</code> != <code>attr</code>.</p>
1369 </dd>
1370 <dt>ev_tstamp interval [read-only]</dt>
1371 <dd>
1372 <p>The specified interval.</p>
1373 </dd>
1374 <dt>const char *path [read-only]</dt>
1375 <dd>
1376 <p>The filesystem path that is being watched.</p>
1377 </dd>
1378</dl>
1379<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1380<pre> static void
1381 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1382 {
1383 /* /etc/passwd changed in some way */
1384 if (w-&gt;attr.st_nlink)
1385 {
1386 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1387 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1388 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1389 }
1390 else
1391 /* you shalt not abuse printf for puts */
1392 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1393 &quot;if this is windows, they already arrived\n&quot;);
1394 }
1395
1396 ...
1397 ev_stat passwd;
1398
1399 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1400 ev_stat_start (loop, &amp;passwd);
1401
1402
1403
1404
1405</pre>
1406
1407</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> 1408<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"> 1409<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 1410<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 1411priority are pending (prepare, check and other idle watchers do not
988as your process is busy handling sockets or timeouts (or even signals, 1412count).</p>
989imagine) it will not be triggered. But when your process is idle all idle 1413<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 - 1414(or even signals, imagine) of the same or higher priority it will not be
1415triggered. But when your process is idle (or only lower-priority watchers
1416are pending), the idle watchers are being called once per event loop
991until stopped, that is, or your process receives more events and becomes 1417iteration - until stopped, that is, or your process receives more events
992busy.</p> 1418and becomes busy again with higher priority stuff.</p>
993<p>The most noteworthy effect is that as long as any idle watchers are 1419<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> 1420active, the process will not block when waiting for new events.</p>
995<p>Apart from keeping your process non-blocking (which is a useful 1421<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 1422effect 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 1423&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 1428 <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, 1429kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1004believe me.</p> 1430believe me.</p>
1005 </dd> 1431 </dd>
1006</dl> 1432</dl>
1007<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1433<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> 1434callback, free it. Also, use no error checking, as usual.</p>
1009<pre> static void 1435<pre> static void
1010 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1436 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1011 { 1437 {
1012 free (w); 1438 free (w);
1013 // now do something you wanted to do when the program has 1439 // now do something you wanted to do when the program has
… …
1022 1448
1023 1449
1024</pre> 1450</pre>
1025 1451
1026</div> 1452</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> 1453<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"> 1454<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: 1455<p>Prepare and check watchers are usually (but not always) used in tandem:
1030prepare watchers get invoked before the process blocks and check watchers 1456prepare watchers get invoked before the process blocks and check watchers
1031afterwards.</p> 1457afterwards.</p>
1458<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1459the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1460watchers. Other loops than the current one are fine, however. The
1461rationale behind this is that you do not need to check for recursion in
1462those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1463<code>ev_check</code> so if you have one watcher of each kind they will always be
1464called in pairs bracketing the blocking call.</p>
1032<p>Their main purpose is to integrate other event mechanisms into libev and 1465<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 1466their use is somewhat advanced. This could be used, for example, to track
1034variable changes, implement your own watchers, integrate net-snmp or a 1467variable changes, implement your own watchers, integrate net-snmp or a
1035coroutine library and lots more.</p> 1468coroutine library and lots more. They are also occasionally useful if
1469you cache some data and want to flush it before blocking (for example,
1470in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1471watcher).</p>
1036<p>This is done by examining in each prepare call which file descriptors need 1472<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 1473to 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 1474them 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 1475provide just this functionality). Then, in the check watcher you check for
1040any events that occured (by checking the pending status of all watchers 1476any events that occured (by checking the pending status of all watchers
… …
1056 <p>Initialises and configures the prepare or check watcher - they have no 1492 <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> 1493parameters 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> 1494macros, but using them is utterly, utterly and completely pointless.</p>
1059 </dd> 1495 </dd>
1060</dl> 1496</dl>
1061<p>Example: *TODO*.</p> 1497<p>Example: To include a library such as adns, you would add IO watchers
1498and a timeout watcher in a prepare handler, as required by libadns, and
1499in a check watcher, destroy them and call into libadns. What follows is
1500pseudo-code only of course:</p>
1501<pre> static ev_io iow [nfd];
1502 static ev_timer tw;
1062 1503
1504 static void
1505 io_cb (ev_loop *loop, ev_io *w, int revents)
1506 {
1507 // set the relevant poll flags
1508 // could also call adns_processreadable etc. here
1509 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1510 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1511 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1512 }
1063 1513
1514 // create io watchers for each fd and a timer before blocking
1515 static void
1516 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1517 {
1518 int timeout = 3600000;
1519 struct pollfd fds [nfd];
1520 // actual code will need to loop here and realloc etc.
1521 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1064 1522
1523 /* the callback is illegal, but won't be called as we stop during check */
1524 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1525 ev_timer_start (loop, &amp;tw);
1065 1526
1527 // create on ev_io per pollfd
1528 for (int i = 0; i &lt; nfd; ++i)
1529 {
1530 ev_io_init (iow + i, io_cb, fds [i].fd,
1531 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1532 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1066 1533
1534 fds [i].revents = 0;
1535 iow [i].data = fds + i;
1536 ev_io_start (loop, iow + i);
1537 }
1538 }
1539
1540 // stop all watchers after blocking
1541 static void
1542 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1543 {
1544 ev_timer_stop (loop, &amp;tw);
1545
1546 for (int i = 0; i &lt; nfd; ++i)
1547 ev_io_stop (loop, iow + i);
1548
1549 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1550 }
1551
1552
1553
1554
1555</pre>
1556
1067</div> 1557</div>
1068<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1558<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"> 1559<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 1560<p>This is a rather advanced watcher type that lets you embed one event loop
1071into another.</p> 1561into another (currently only <code>ev_io</code> events are supported in the embedded
1562loop, other types of watchers might be handled in a delayed or incorrect
1563fashion and must not be used).</p>
1072<p>There are primarily two reasons you would want that: work around bugs and 1564<p>There are primarily two reasons you would want that: work around bugs and
1073prioritise I/O.</p> 1565prioritise I/O.</p>
1074<p>As an example for a bug workaround, the kqueue backend might only support 1566<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 1567sockets 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 1568still 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 1573<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 1574to be watched and handled very quickly (with low latency), and even
1083priorities and idle watchers might have too much overhead. In this case 1575priorities 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 1576you 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> 1577a second one, and embed the second one in the first.</p>
1578<p>As long as the watcher is active, the callback will be invoked every time
1579there might be events pending in the embedded loop. The callback must then
1580call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1581their callbacks (you could also start an idle watcher to give the embedded
1582loop strictly lower priority for example). You can also set the callback
1583to <code>0</code>, in which case the embed watcher will automatically execute the
1584embedded loop sweep.</p>
1086<p>As long as the watcher is started it will automatically handle events. The 1585<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 1586callback 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 1587set the callback to <code>0</code> to avoid having to specify one if you are not
1089interested in that.</p> 1588interested in that.</p>
1090<p>Also, there have not currently been made special provisions for forking: 1589<p>Also, there have not currently been made special provisions for forking:
… …
1117 else 1616 else
1118 loop_lo = loop_hi; 1617 loop_lo = loop_hi;
1119 1618
1120</pre> 1619</pre>
1121<dl> 1620<dl>
1122 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> 1621 <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> 1622 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1623 <dd>
1624 <p>Configures the watcher to embed the given loop, which must be
1625embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1626invoked automatically, otherwise it is the responsibility of the callback
1627to invoke it (it will continue to be called until the sweep has been done,
1628if you do not want thta, you need to temporarily stop the embed watcher).</p>
1124 <dd> 1629 </dd>
1125 <p>Configures the watcher to embed the given loop, which must be embeddable.</p> 1630 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1631 <dd>
1632 <p>Make a single, non-blocking sweep over the embedded loop. This works
1633similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1634apropriate way for embedded loops.</p>
1635 </dd>
1636 <dt>struct ev_loop *loop [read-only]</dt>
1637 <dd>
1638 <p>The embedded event loop.</p>
1126 </dd> 1639 </dd>
1127</dl> 1640</dl>
1128 1641
1129 1642
1130 1643
1131 1644
1132 1645
1133</div> 1646</div>
1134<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1647<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>
1648<div id="code_ev_fork_code_the_audacity_to_re-2">
1649<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1650whoever is a good citizen cared to tell libev about it by calling
1651<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1652event loop blocks next and before <code>ev_check</code> watchers are being called,
1653and only in the child after the fork. If whoever good citizen calling
1654<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1655handlers will be invoked, too, of course.</p>
1656<dl>
1657 <dt>ev_fork_init (ev_signal *, callback)</dt>
1658 <dd>
1659 <p>Initialises and configures the fork watcher - it has no parameters of any
1660kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1661believe me.</p>
1662 </dd>
1663</dl>
1664
1665
1666
1667
1668
1669</div>
1670<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1135<div id="OTHER_FUNCTIONS_CONTENT"> 1671<div id="OTHER_FUNCTIONS_CONTENT">
1136<p>There are some other functions of possible interest. Described. Here. Now.</p> 1672<p>There are some other functions of possible interest. Described. Here. Now.</p>
1137<dl> 1673<dl>
1138 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1674 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1139 <dd> 1675 <dd>
… …
1163 1699
1164 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1700 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1165 1701
1166</pre> 1702</pre>
1167 </dd> 1703 </dd>
1168 <dt>ev_feed_event (loop, watcher, int events)</dt> 1704 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
1169 <dd> 1705 <dd>
1170 <p>Feeds the given event set into the event loop, as if the specified event 1706 <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 1707had happened for the specified watcher (which must be a pointer to an
1172initialised but not necessarily started event watcher).</p> 1708initialised but not necessarily started event watcher).</p>
1173 </dd> 1709 </dd>
1174 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1710 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
1175 <dd> 1711 <dd>
1176 <p>Feed an event on the given fd, as if a file descriptor backend detected 1712 <p>Feed an event on the given fd, as if a file descriptor backend detected
1177the given events it.</p> 1713the given events it.</p>
1178 </dd> 1714 </dd>
1179 <dt>ev_feed_signal_event (loop, int signum)</dt> 1715 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
1180 <dd> 1716 <dd>
1181 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1717 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1718loop!).</p>
1182 </dd> 1719 </dd>
1183</dl> 1720</dl>
1184 1721
1185 1722
1186 1723
1187 1724
1188 1725
1189</div> 1726</div>
1190<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1727<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1191<div id="LIBEVENT_EMULATION_CONTENT"> 1728<div id="LIBEVENT_EMULATION_CONTENT">
1192<p>Libev offers a compatibility emulation layer for libevent. It cannot 1729<p>Libev offers a compatibility emulation layer for libevent. It cannot
1193emulate the internals of libevent, so here are some usage hints:</p> 1730emulate the internals of libevent, so here are some usage hints:</p>
1194<dl> 1731<dl>
1195 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1732 <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 1742 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1206to use the libev header file and library.</dt> 1743to use the libev header file and library.</dt>
1207</dl> 1744</dl>
1208 1745
1209</div> 1746</div>
1210<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1747<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1211<div id="C_SUPPORT_CONTENT"> 1748<div id="C_SUPPORT_CONTENT">
1212<p>TBD.</p> 1749<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1750you to use some convinience methods to start/stop watchers and also change
1751the callback model to a model using method callbacks on objects.</p>
1752<p>To use it,</p>
1753<pre> #include &lt;ev++.h&gt;
1213 1754
1755</pre>
1756<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1757of them macros) into the global namespace. All C++ specific things are
1758put into the <code>ev</code> namespace. It should support all the same embedding
1759options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1760<p>Care has been taken to keep the overhead low. The only data member the C++
1761classes add (compared to plain C-style watchers) is the event loop pointer
1762that the watcher is associated with (or no additional members at all if
1763you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1764<p>Currently, functions, and static and non-static member functions can be
1765used as callbacks. Other types should be easy to add as long as they only
1766need one additional pointer for context. If you need support for other
1767types of functors please contact the author (preferably after implementing
1768it).</p>
1769<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1770<dl>
1771 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1772 <dd>
1773 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1774macros from <cite>ev.h</cite>.</p>
1775 </dd>
1776 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1777 <dd>
1778 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1779 </dd>
1780 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1781 <dd>
1782 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1783the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1784which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1785defines by many implementations.</p>
1786 <p>All of those classes have these methods:</p>
1787 <p>
1788 <dl>
1789 <dt>ev::TYPE::TYPE ()</dt>
1790 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1791 <dt>ev::TYPE::~TYPE</dt>
1792 <dd>
1793 <p>The constructor (optionally) takes an event loop to associate the watcher
1794with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1795 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1796<code>set</code> method before starting it.</p>
1797 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1798method to set a callback before you can start the watcher.</p>
1799 <p>(The reason why you have to use a method is a limitation in C++ which does
1800not allow explicit template arguments for constructors).</p>
1801 <p>The destructor automatically stops the watcher if it is active.</p>
1802 </dd>
1803 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1804 <dd>
1805 <p>This method sets the callback method to call. The method has to have a
1806signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1807first argument and the <code>revents</code> as second. The object must be given as
1808parameter and is stored in the <code>data</code> member of the watcher.</p>
1809 <p>This method synthesizes efficient thunking code to call your method from
1810the C callback that libev requires. If your compiler can inline your
1811callback (i.e. it is visible to it at the place of the <code>set</code> call and
1812your compiler is good :), then the method will be fully inlined into the
1813thunking function, making it as fast as a direct C callback.</p>
1814 <p>Example: simple class declaration and watcher initialisation</p>
1815<pre> struct myclass
1816 {
1817 void io_cb (ev::io &amp;w, int revents) { }
1818 }
1819
1820 myclass obj;
1821 ev::io iow;
1822 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1823
1824</pre>
1825 </dd>
1826 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1827 <dd>
1828 <p>Also sets a callback, but uses a static method or plain function as
1829callback. The optional <code>data</code> argument will be stored in the watcher's
1830<code>data</code> member and is free for you to use.</p>
1831 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1832 <p>See the method-<code>set</code> above for more details.</p>
1833 <p>Example:</p>
1834<pre> static void io_cb (ev::io &amp;w, int revents) { }
1835 iow.set &lt;io_cb&gt; ();
1836
1837</pre>
1838 </dd>
1839 <dt>w-&gt;set (struct ev_loop *)</dt>
1840 <dd>
1841 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1842do this when the watcher is inactive (and not pending either).</p>
1843 </dd>
1844 <dt>w-&gt;set ([args])</dt>
1845 <dd>
1846 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1847called at least once. Unlike the C counterpart, an active watcher gets
1848automatically stopped and restarted when reconfiguring it with this
1849method.</p>
1850 </dd>
1851 <dt>w-&gt;start ()</dt>
1852 <dd>
1853 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1854constructor already stores the event loop.</p>
1855 </dd>
1856 <dt>w-&gt;stop ()</dt>
1857 <dd>
1858 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1859 </dd>
1860 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1861 <dd>
1862 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1863<code>ev_TYPE_again</code> function.</p>
1864 </dd>
1865 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1866 <dd>
1867 <p>Invokes <code>ev_embed_sweep</code>.</p>
1868 </dd>
1869 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1870 <dd>
1871 <p>Invokes <code>ev_stat_stat</code>.</p>
1872 </dd>
1873 </dl>
1874 </p>
1875 </dd>
1876</dl>
1877<p>Example: Define a class with an IO and idle watcher, start one of them in
1878the constructor.</p>
1879<pre> class myclass
1880 {
1881 ev_io io; void io_cb (ev::io &amp;w, int revents);
1882 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1883
1884 myclass ();
1885 }
1886
1887 myclass::myclass (int fd)
1888 {
1889 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1890 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1891
1892 io.start (fd, ev::READ);
1893 }
1894
1895
1896
1897
1898</pre>
1899
1214</div> 1900</div>
1215<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1901<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1902<div id="MACRO_MAGIC_CONTENT">
1903<p>Libev can be compiled with a variety of options, the most fundemantal is
1904<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1905callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1906<p>To make it easier to write programs that cope with either variant, the
1907following macros are defined:</p>
1908<dl>
1909 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1910 <dd>
1911 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1912loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1913<code>EV_A_</code> is used when other arguments are following. Example:</p>
1914<pre> ev_unref (EV_A);
1915 ev_timer_add (EV_A_ watcher);
1916 ev_loop (EV_A_ 0);
1917
1918</pre>
1919 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1920which is often provided by the following macro.</p>
1921 </dd>
1922 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1923 <dd>
1924 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1925loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1926<code>EV_P_</code> is used when other parameters are following. Example:</p>
1927<pre> // this is how ev_unref is being declared
1928 static void ev_unref (EV_P);
1929
1930 // this is how you can declare your typical callback
1931 static void cb (EV_P_ ev_timer *w, int revents)
1932
1933</pre>
1934 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1935suitable for use with <code>EV_A</code>.</p>
1936 </dd>
1937 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1938 <dd>
1939 <p>Similar to the other two macros, this gives you the value of the default
1940loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1941 </dd>
1942</dl>
1943<p>Example: Declare and initialise a check watcher, utilising the above
1944macros so it will work regardless of whether multiple loops are supported
1945or not.</p>
1946<pre> static void
1947 check_cb (EV_P_ ev_timer *w, int revents)
1948 {
1949 ev_check_stop (EV_A_ w);
1950 }
1951
1952 ev_check check;
1953 ev_check_init (&amp;check, check_cb);
1954 ev_check_start (EV_DEFAULT_ &amp;check);
1955 ev_loop (EV_DEFAULT_ 0);
1956
1957</pre>
1958
1959</div>
1960<h1 id="EMBEDDING">EMBEDDING</h1>
1961<div id="EMBEDDING_CONTENT">
1962<p>Libev can (and often is) directly embedded into host
1963applications. Examples of applications that embed it include the Deliantra
1964Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1965and rxvt-unicode.</p>
1966<p>The goal is to enable you to just copy the neecssary files into your
1967source directory without having to change even a single line in them, so
1968you can easily upgrade by simply copying (or having a checked-out copy of
1969libev somewhere in your source tree).</p>
1970
1971</div>
1972<h2 id="FILESETS">FILESETS</h2>
1973<div id="FILESETS_CONTENT">
1974<p>Depending on what features you need you need to include one or more sets of files
1975in your app.</p>
1976
1977</div>
1978<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1979<div id="CORE_EVENT_LOOP_CONTENT">
1980<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1981configuration (no autoconf):</p>
1982<pre> #define EV_STANDALONE 1
1983 #include &quot;ev.c&quot;
1984
1985</pre>
1986<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1987single C source file only to provide the function implementations. To use
1988it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1989done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1990where you can put other configuration options):</p>
1991<pre> #define EV_STANDALONE 1
1992 #include &quot;ev.h&quot;
1993
1994</pre>
1995<p>Both header files and implementation files can be compiled with a C++
1996compiler (at least, thats a stated goal, and breakage will be treated
1997as a bug).</p>
1998<p>You need the following files in your source tree, or in a directory
1999in your include path (e.g. in libev/ when using -Ilibev):</p>
2000<pre> ev.h
2001 ev.c
2002 ev_vars.h
2003 ev_wrap.h
2004
2005 ev_win32.c required on win32 platforms only
2006
2007 ev_select.c only when select backend is enabled (which is enabled by default)
2008 ev_poll.c only when poll backend is enabled (disabled by default)
2009 ev_epoll.c only when the epoll backend is enabled (disabled by default)
2010 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2011 ev_port.c only when the solaris port backend is enabled (disabled by default)
2012
2013</pre>
2014<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
2015to compile this single file.</p>
2016
2017</div>
2018<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
2019<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
2020<p>To include the libevent compatibility API, also include:</p>
2021<pre> #include &quot;event.c&quot;
2022
2023</pre>
2024<p>in the file including <cite>ev.c</cite>, and:</p>
2025<pre> #include &quot;event.h&quot;
2026
2027</pre>
2028<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
2029<p>You need the following additional files for this:</p>
2030<pre> event.h
2031 event.c
2032
2033</pre>
2034
2035</div>
2036<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
2037<div id="AUTOCONF_SUPPORT_CONTENT">
2038<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
2039whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
2040<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
2041include <cite>config.h</cite> and configure itself accordingly.</p>
2042<p>For this of course you need the m4 file:</p>
2043<pre> libev.m4
2044
2045</pre>
2046
2047</div>
2048<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
2049<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
2050<p>Libev can be configured via a variety of preprocessor symbols you have to define
2051before including any of its files. The default is not to build for multiplicity
2052and only include the select backend.</p>
2053<dl>
2054 <dt>EV_STANDALONE</dt>
2055 <dd>
2056 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
2057keeps libev from including <cite>config.h</cite>, and it also defines dummy
2058implementations for some libevent functions (such as logging, which is not
2059supported). It will also not define any of the structs usually found in
2060<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
2061 </dd>
2062 <dt>EV_USE_MONOTONIC</dt>
2063 <dd>
2064 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
2065monotonic clock option at both compiletime and runtime. Otherwise no use
2066of the monotonic clock option will be attempted. If you enable this, you
2067usually have to link against librt or something similar. Enabling it when
2068the functionality isn't available is safe, though, althoguh you have
2069to make sure you link against any libraries where the <code>clock_gettime</code>
2070function is hiding in (often <cite>-lrt</cite>).</p>
2071 </dd>
2072 <dt>EV_USE_REALTIME</dt>
2073 <dd>
2074 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
2075realtime clock option at compiletime (and assume its availability at
2076runtime if successful). Otherwise no use of the realtime clock option will
2077be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
2078(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
2079in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
2080 </dd>
2081 <dt>EV_USE_SELECT</dt>
2082 <dd>
2083 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
2084<code>select</code>(2) backend. No attempt at autodetection will be done: if no
2085other method takes over, select will be it. Otherwise the select backend
2086will not be compiled in.</p>
2087 </dd>
2088 <dt>EV_SELECT_USE_FD_SET</dt>
2089 <dd>
2090 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
2091structure. This is useful if libev doesn't compile due to a missing
2092<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
2093exotic systems. This usually limits the range of file descriptors to some
2094low limit such as 1024 or might have other limitations (winsocket only
2095allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
2096influence the size of the <code>fd_set</code> used.</p>
2097 </dd>
2098 <dt>EV_SELECT_IS_WINSOCKET</dt>
2099 <dd>
2100 <p>When defined to <code>1</code>, the select backend will assume that
2101select/socket/connect etc. don't understand file descriptors but
2102wants osf handles on win32 (this is the case when the select to
2103be used is the winsock select). This means that it will call
2104<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
2105it is assumed that all these functions actually work on fds, even
2106on win32. Should not be defined on non-win32 platforms.</p>
2107 </dd>
2108 <dt>EV_USE_POLL</dt>
2109 <dd>
2110 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
2111backend. Otherwise it will be enabled on non-win32 platforms. It
2112takes precedence over select.</p>
2113 </dd>
2114 <dt>EV_USE_EPOLL</dt>
2115 <dd>
2116 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
2117<code>epoll</code>(7) backend. Its availability will be detected at runtime,
2118otherwise another method will be used as fallback. This is the
2119preferred backend for GNU/Linux systems.</p>
2120 </dd>
2121 <dt>EV_USE_KQUEUE</dt>
2122 <dd>
2123 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2124<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2125otherwise another method will be used as fallback. This is the preferred
2126backend for BSD and BSD-like systems, although on most BSDs kqueue only
2127supports some types of fds correctly (the only platform we found that
2128supports ptys for example was NetBSD), so kqueue might be compiled in, but
2129not be used unless explicitly requested. The best way to use it is to find
2130out whether kqueue supports your type of fd properly and use an embedded
2131kqueue loop.</p>
2132 </dd>
2133 <dt>EV_USE_PORT</dt>
2134 <dd>
2135 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
213610 port style backend. Its availability will be detected at runtime,
2137otherwise another method will be used as fallback. This is the preferred
2138backend for Solaris 10 systems.</p>
2139 </dd>
2140 <dt>EV_USE_DEVPOLL</dt>
2141 <dd>
2142 <p>reserved for future expansion, works like the USE symbols above.</p>
2143 </dd>
2144 <dt>EV_USE_INOTIFY</dt>
2145 <dd>
2146 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2147interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2148be detected at runtime.</p>
2149 </dd>
2150 <dt>EV_H</dt>
2151 <dd>
2152 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
2153undefined 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
2154can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2155 </dd>
2156 <dt>EV_CONFIG_H</dt>
2157 <dd>
2158 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2159<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2160<code>EV_H</code>, above.</p>
2161 </dd>
2162 <dt>EV_EVENT_H</dt>
2163 <dd>
2164 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2165of how the <cite>event.h</cite> header can be found.</p>
2166 </dd>
2167 <dt>EV_PROTOTYPES</dt>
2168 <dd>
2169 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2170prototypes, but still define all the structs and other symbols. This is
2171occasionally useful if you want to provide your own wrapper functions
2172around libev functions.</p>
2173 </dd>
2174 <dt>EV_MULTIPLICITY</dt>
2175 <dd>
2176 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2177will have the <code>struct ev_loop *</code> as first argument, and you can create
2178additional independent event loops. Otherwise there will be no support
2179for multiple event loops and there is no first event loop pointer
2180argument. Instead, all functions act on the single default loop.</p>
2181 </dd>
2182 <dt>EV_MINPRI</dt>
2183 <dt>EV_MAXPRI</dt>
2184 <dd>
2185 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2186<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2187provide for more priorities by overriding those symbols (usually defined
2188to be <code>-2</code> and <code>2</code>, respectively).</p>
2189 <p>When doing priority-based operations, libev usually has to linearly search
2190all the priorities, so having many of them (hundreds) uses a lot of space
2191and time, so using the defaults of five priorities (-2 .. +2) is usually
2192fine.</p>
2193 <p>If your embedding app does not need any priorities, defining these both to
2194<code>0</code> will save some memory and cpu.</p>
2195 </dd>
2196 <dt>EV_PERIODIC_ENABLE</dt>
2197 <dd>
2198 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2199defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2200code.</p>
2201 </dd>
2202 <dt>EV_IDLE_ENABLE</dt>
2203 <dd>
2204 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2205defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2206code.</p>
2207 </dd>
2208 <dt>EV_EMBED_ENABLE</dt>
2209 <dd>
2210 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2211defined to be <code>0</code>, then they are not.</p>
2212 </dd>
2213 <dt>EV_STAT_ENABLE</dt>
2214 <dd>
2215 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2216defined to be <code>0</code>, then they are not.</p>
2217 </dd>
2218 <dt>EV_FORK_ENABLE</dt>
2219 <dd>
2220 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2221defined to be <code>0</code>, then they are not.</p>
2222 </dd>
2223 <dt>EV_MINIMAL</dt>
2224 <dd>
2225 <p>If you need to shave off some kilobytes of code at the expense of some
2226speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2227some inlining decisions, saves roughly 30% codesize of amd64.</p>
2228 </dd>
2229 <dt>EV_PID_HASHSIZE</dt>
2230 <dd>
2231 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2232pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2233than enough. If you need to manage thousands of children you might want to
2234increase this value (<i>must</i> be a power of two).</p>
2235 </dd>
2236 <dt>EV_INOTIFY_HASHSIZE</dt>
2237 <dd>
2238 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2239inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2240usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2241watchers you might want to increase this value (<i>must</i> be a power of
2242two).</p>
2243 </dd>
2244 <dt>EV_COMMON</dt>
2245 <dd>
2246 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2247this macro to a something else you can include more and other types of
2248members. You have to define it each time you include one of the files,
2249though, and it must be identical each time.</p>
2250 <p>For example, the perl EV module uses something like this:</p>
2251<pre> #define EV_COMMON \
2252 SV *self; /* contains this struct */ \
2253 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2254
2255</pre>
2256 </dd>
2257 <dt>EV_CB_DECLARE (type)</dt>
2258 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2259 <dt>ev_set_cb (ev, cb)</dt>
2260 <dd>
2261 <p>Can be used to change the callback member declaration in each watcher,
2262and the way callbacks are invoked and set. Must expand to a struct member
2263definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2264their default definitions. One possible use for overriding these is to
2265avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2266method calls instead of plain function calls in C++.</p>
2267
2268</div>
2269<h2 id="EXAMPLES">EXAMPLES</h2>
2270<div id="EXAMPLES_CONTENT">
2271 <p>For a real-world example of a program the includes libev
2272verbatim, you can have a look at the EV perl module
2273(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2274the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2275interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2276will be compiled. It is pretty complex because it provides its own header
2277file.</p>
2278 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2279that everybody includes and which overrides some configure choices:</p>
2280<pre> #define EV_MINIMAL 1
2281 #define EV_USE_POLL 0
2282 #define EV_MULTIPLICITY 0
2283 #define EV_PERIODIC_ENABLE 0
2284 #define EV_STAT_ENABLE 0
2285 #define EV_FORK_ENABLE 0
2286 #define EV_CONFIG_H &lt;config.h&gt;
2287 #define EV_MINPRI 0
2288 #define EV_MAXPRI 0
2289
2290 #include &quot;ev++.h&quot;
2291
2292</pre>
2293 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2294<pre> #include &quot;ev_cpp.h&quot;
2295 #include &quot;ev.c&quot;
2296
2297
2298
2299
2300</pre>
2301
2302</div>
2303<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2304<div id="COMPLEXITIES_CONTENT">
2305 <p>In this section the complexities of (many of) the algorithms used inside
2306libev will be explained. For complexity discussions about backends see the
2307documentation for <code>ev_default_init</code>.</p>
2308 <p>All of the following are about amortised time: If an array needs to be
2309extended, libev needs to realloc and move the whole array, but this
2310happens asymptotically never with higher number of elements, so O(1) might
2311mean it might do a lengthy realloc operation in rare cases, but on average
2312it is much faster and asymptotically approaches constant time.</p>
2313 <p>
2314 <dl>
2315 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2316 <dd>
2317 <p>This means that, when you have a watcher that triggers in one hour and
2318there are 100 watchers that would trigger before that then inserting will
2319have to skip those 100 watchers.</p>
2320 </dd>
2321 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2322 <dd>
2323 <p>That means that for changing a timer costs less than removing/adding them
2324as only the relative motion in the event queue has to be paid for.</p>
2325 </dd>
2326 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2327 <dd>
2328 <p>These just add the watcher into an array or at the head of a list.
2329=item Stopping check/prepare/idle watchers: O(1)</p>
2330 </dd>
2331 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2332 <dd>
2333 <p>These watchers are stored in lists then need to be walked to find the
2334correct watcher to remove. The lists are usually short (you don't usually
2335have many watchers waiting for the same fd or signal).</p>
2336 </dd>
2337 <dt>Finding the next timer per loop iteration: O(1)</dt>
2338 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2339 <dd>
2340 <p>A change means an I/O watcher gets started or stopped, which requires
2341libev to recalculate its status (and possibly tell the kernel).</p>
2342 </dd>
2343 <dt>Activating one watcher: O(1)</dt>
2344 <dt>Priority handling: O(number_of_priorities)</dt>
2345 <dd>
2346 <p>Priorities are implemented by allocating some space for each
2347priority. When doing priority-based operations, libev usually has to
2348linearly search all the priorities.</p>
2349 </dd>
2350 </dl>
2351 </p>
2352
2353
2354
2355
2356
2357</div>
2358<h1 id="AUTHOR">AUTHOR</h1>
1216<div id="AUTHOR_CONTENT"> 2359<div id="AUTHOR_CONTENT">
1217<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2360 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1218 2361
1219</div> 2362</div>
1220</div></body> 2363</div></body>
1221</html> 2364</html>

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