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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 17:57:37 2007" /> 9 <meta name="created" content="Wed Nov 28 12:27:27 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>
… …
31<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>
32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating 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>
33<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>
34<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>
35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process 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>
36<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>
37<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>
38<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>
39</ul> 42</ul>
40</li> 43</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<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>
44<li><a href="#EMBEDDING">EMBEDDING</a> 48<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a> 49<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
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50</li> 54</li>
51<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li> 55<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
52<li><a href="#EXAMPLES">EXAMPLES</a></li> 56<li><a href="#EXAMPLES">EXAMPLES</a></li>
53</ul> 57</ul>
54</li> 58</li>
59<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
55<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
56</li> 61</li>
57</ul><hr /> 62</ul><hr />
58<!-- INDEX END --> 63<!-- INDEX END -->
59 64
60<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
61<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
62<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>
63 68
64</div> 69</div>
65<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
66<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
67<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
68 73
69</pre> 74</pre>
70 75
71</div> 76</div>
72<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>
73<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
74<p>Libev is an event loop: you register interest in certain events (such as a 124<p>Libev is an event loop: you register interest in certain events (such as a
75file descriptor being readable or a timeout occuring), and it will manage 125file descriptor being readable or a timeout occuring), and it will manage
76these event sources and provide your program with events.</p> 126these event sources and provide your program with events.</p>
77<p>To do this, it must take more or less complete control over your process 127<p>To do this, it must take more or less complete control over your process
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81watchers</i>, which are relatively small C structures you initialise with the 131watchers</i>, which are relatively small C structures you initialise with the
82details of the event, and then hand it over to libev by <i>starting</i> the 132details of the event, and then hand it over to libev by <i>starting</i> the
83watcher.</p> 133watcher.</p>
84 134
85</div> 135</div>
86<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
87<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
88<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the
89kqueue mechanisms for file descriptor events, relative timers, absolute 139bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms
90timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>),
91events (related to SIGCHLD), and event watchers dealing with the event 141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous
92loop mechanism itself (idle, prepare and check watchers). It also is quite 142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and
143event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
144<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
145file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this
93fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
94it to libevent for example).</p> 149for example).</p>
95 150
96</div> 151</div>
97<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 152<h1 id="CONVENTIONS">CONVENTIONS</h1>
98<div id="CONVENTIONS_CONTENT"> 153<div id="CONVENTIONS_CONTENT">
99<p>Libev is very configurable. In this manual the default configuration 154<p>Libev is very configurable. In this manual the default configuration will
100will be described, which supports multiple event loops. For more info 155be described, which supports multiple event loops. For more info about
101about various configuration options please have a look at the file 156various configuration options please have a look at <strong>EMBED</strong> section in
102<cite>README.embed</cite> in the libev distribution. If libev was configured without 157this manual. If libev was configured without support for multiple event
103support for multiple event loops, then all functions taking an initial 158loops, then all functions taking an initial argument of name <code>loop</code>
104argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 159(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
105will not have this argument.</p>
106 160
107</div> 161</div>
108<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 162<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
109<div id="TIME_REPRESENTATION_CONTENT"> 163<div id="TIME_REPRESENTATION_CONTENT">
110<p>Libev represents time as a single floating point number, representing the 164<p>Libev represents time as a single floating point number, representing the
111(fractional) number of seconds since the (POSIX) epoch (somewhere near 165(fractional) number of seconds since the (POSIX) epoch (somewhere near
112the beginning of 1970, details are complicated, don't ask). This type is 166the beginning of 1970, details are complicated, don't ask). This type is
113called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 167called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
114to the <code>double</code> type in C, and when you need to do any calculations on 168to the <code>double</code> type in C, and when you need to do any calculations on
115it, you should treat it as such.</p> 169it, you should treat it as such.</p>
116 170
117
118
119
120
121</div> 171</div>
122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 172<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
123<div id="GLOBAL_FUNCTIONS_CONTENT"> 173<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the 174<p>These functions can be called anytime, even before initialising the
125library in any way.</p> 175library in any way.</p>
126<dl> 176<dl>
127 <dt>ev_tstamp ev_time ()</dt> 177 <dt>ev_tstamp ev_time ()</dt>
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140version of the library your program was compiled against.</p> 190version of the library your program was compiled against.</p>
141 <p>Usually, it's a good idea to terminate if the major versions mismatch, 191 <p>Usually, it's a good idea to terminate if the major versions mismatch,
142as this indicates an incompatible change. Minor versions are usually 192as this indicates an incompatible change. Minor versions are usually
143compatible to older versions, so a larger minor version alone is usually 193compatible to older versions, so a larger minor version alone is usually
144not a problem.</p> 194not a problem.</p>
145 <p>Example: make sure we haven't accidentally been linked against the wrong 195 <p>Example: Make sure we haven't accidentally been linked against the wrong
146version:</p> 196version.</p>
147<pre> assert ((&quot;libev version mismatch&quot;, 197<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR 198 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 199 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150 200
151</pre> 201</pre>
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179might be supported on the current system, you would need to look at 229might be supported on the current system, you would need to look at
180<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
181recommended ones.</p> 231recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 232 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
183 </dd> 233 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
185 <dd> 235 <dd>
186 <p>Sets the allocation function to use (the prototype is similar to the 236 <p>Sets the allocation function to use (the prototype and semantics are
187realloc C function, the semantics are identical). It is used to allocate 237identical to the realloc C function). It is used to allocate and free
188and free memory (no surprises here). If it returns zero when memory 238memory (no surprises here). If it returns zero when memory needs to be
189needs to be allocated, the library might abort or take some potentially 239allocated, the library might abort or take some potentially destructive
190destructive action. The default is your system realloc function.</p> 240action. The default is your system realloc function.</p>
191 <p>You could override this function in high-availability programs to, say, 241 <p>You could override this function in high-availability programs to, say,
192free some memory if it cannot allocate memory, to use a special allocator, 242free some memory if it cannot allocate memory, to use a special allocator,
193or even to sleep a while and retry until some memory is available.</p> 243or even to sleep a while and retry until some memory is available.</p>
194 <p>Example: replace the libev allocator with one that waits a bit and then 244 <p>Example: Replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p> 245retries).</p>
196<pre> static void * 246<pre> static void *
197 persistent_realloc (void *ptr, long size) 247 persistent_realloc (void *ptr, size_t size)
198 { 248 {
199 for (;;) 249 for (;;)
200 { 250 {
201 void *newptr = realloc (ptr, size); 251 void *newptr = realloc (ptr, size);
202 252
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219indicating the system call or subsystem causing the problem. If this 269indicating the system call or subsystem causing the problem. If this
220callback is set, then libev will expect it to remedy the sitution, no 270callback is set, then libev will expect it to remedy the sitution, no
221matter what, when it returns. That is, libev will generally retry the 271matter what, when it returns. That is, libev will generally retry the
222requested operation, or, if the condition doesn't go away, do bad stuff 272requested operation, or, if the condition doesn't go away, do bad stuff
223(such as abort).</p> 273(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p> 274 <p>Example: This is basically the same thing that libev does internally, too.</p>
225<pre> static void 275<pre> static void
226 fatal_error (const char *msg) 276 fatal_error (const char *msg)
227 { 277 {
228 perror (msg); 278 perror (msg);
229 abort (); 279 abort ();
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235</pre> 285</pre>
236 </dd> 286 </dd>
237</dl> 287</dl>
238 288
239</div> 289</div>
240<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 290<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
241<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 291<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
242<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 292<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
243types of such loops, the <i>default</i> loop, which supports signals and child 293types of such loops, the <i>default</i> loop, which supports signals and child
244events, and dynamically created loops which do not.</p> 294events, and dynamically created loops which do not.</p>
245<p>If you use threads, a common model is to run the default event loop 295<p>If you use threads, a common model is to run the default event loop
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365 <dd> 415 <dd>
366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 416 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
367always distinct from the default loop. Unlike the default loop, it cannot 417always distinct from the default loop. Unlike the default loop, it cannot
368handle signal and child watchers, and attempts to do so will be greeted by 418handle signal and child watchers, and attempts to do so will be greeted by
369undefined behaviour (or a failed assertion if assertions are enabled).</p> 419undefined behaviour (or a failed assertion if assertions are enabled).</p>
370 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 420 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
371<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 421<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller) 422 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 423 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374 424
375</pre> 425</pre>
… …
468 be handled here by queueing them when their watcher gets executed. 518 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 519 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *. 520 were used, return, otherwise continue with step *.
471 521
472</pre> 522</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding 523 <p>Example: Queue some jobs and then loop until no events are outsanding
474anymore.</p> 524anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long 525<pre> ... queue jobs here, make sure they register event watchers as long
476 ... as they still have work to do (even an idle watcher will do..) 526 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0); 527 ev_loop (my_loop, 0);
478 ... jobs done. yeah! 528 ... jobs done. yeah!
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497example, libev itself uses this for its internal signal pipe: It is not 547example, libev itself uses this for its internal signal pipe: It is not
498visible to the libev user and should not keep <code>ev_loop</code> from exiting if 548visible to the libev user and should not keep <code>ev_loop</code> from exiting if
499no event watchers registered by it are active. It is also an excellent 549no event watchers registered by it are active. It is also an excellent
500way to do this for generic recurring timers or from within third-party 550way to do this for generic recurring timers or from within third-party
501libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 551libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
502 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 552 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p> 553running when nothing else is active.</p>
504<pre> struct dv_signal exitsig; 554<pre> struct ev_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 555 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig); 556 ev_signal_start (loop, &amp;exitsig);
507 evf_unref (myloop); 557 evf_unref (loop);
508 558
509</pre> 559</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p> 560 <p>Example: For some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop); 561<pre> ev_ref (loop);
512 ev_signal_stop (myloop, &amp;exitsig); 562 ev_signal_stop (loop, &amp;exitsig);
513 563
514</pre> 564</pre>
515 </dd> 565 </dd>
516</dl> 566</dl>
517 567
518 568
519 569
520 570
521 571
522</div> 572</div>
523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 573<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
524<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 574<div id="ANATOMY_OF_A_WATCHER_CONTENT">
525<p>A watcher is a structure that you create and register to record your 575<p>A watcher is a structure that you create and register to record your
526interest in some event. For instance, if you want to wait for STDIN to 576interest in some event. For instance, if you want to wait for STDIN to
527become readable, you would create an <code>ev_io</code> watcher for that:</p> 577become readable, you would create an <code>ev_io</code> watcher for that:</p>
528<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 578<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
585 </dd> 635 </dd>
586 <dt><code>EV_CHILD</code></dt> 636 <dt><code>EV_CHILD</code></dt>
587 <dd> 637 <dd>
588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 638 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
589 </dd> 639 </dd>
640 <dt><code>EV_STAT</code></dt>
641 <dd>
642 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
643 </dd>
590 <dt><code>EV_IDLE</code></dt> 644 <dt><code>EV_IDLE</code></dt>
591 <dd> 645 <dd>
592 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 646 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
593 </dd> 647 </dd>
594 <dt><code>EV_PREPARE</code></dt> 648 <dt><code>EV_PREPARE</code></dt>
… …
599<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 653<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
600received events. Callbacks of both watcher types can start and stop as 654received events. Callbacks of both watcher types can start and stop as
601many watchers as they want, and all of them will be taken into account 655many watchers as they want, and all of them will be taken into account
602(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 656(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
603<code>ev_loop</code> from blocking).</p> 657<code>ev_loop</code> from blocking).</p>
658 </dd>
659 <dt><code>EV_EMBED</code></dt>
660 <dd>
661 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
662 </dd>
663 <dt><code>EV_FORK</code></dt>
664 <dd>
665 <p>The event loop has been resumed in the child process after fork (see
666<code>ev_fork</code>).</p>
604 </dd> 667 </dd>
605 <dt><code>EV_ERROR</code></dt> 668 <dt><code>EV_ERROR</code></dt>
606 <dd> 669 <dd>
607 <p>An unspecified error has occured, the watcher has been stopped. This might 670 <p>An unspecified error has occured, the watcher has been stopped. This might
608happen because the watcher could not be properly started because libev 671happen because the watcher could not be properly started because libev
… …
678events but its callback has not yet been invoked). As long as a watcher 741events but its callback has not yet been invoked). As long as a watcher
679is pending (but not active) you must not call an init function on it (but 742is pending (but not active) you must not call an init function on it (but
680<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 743<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
681libev (e.g. you cnanot <code>free ()</code> it).</p> 744libev (e.g. you cnanot <code>free ()</code> it).</p>
682 </dd> 745 </dd>
683 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 746 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
684 <dd> 747 <dd>
685 <p>Returns the callback currently set on the watcher.</p> 748 <p>Returns the callback currently set on the watcher.</p>
686 </dd> 749 </dd>
687 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
688 <dd> 751 <dd>
… …
720 struct my_io *w = (struct my_io *)w_; 783 struct my_io *w = (struct my_io *)w_;
721 ... 784 ...
722 } 785 }
723 786
724</pre> 787</pre>
725<p>More interesting and less C-conformant ways of catsing your callback type 788<p>More interesting and less C-conformant ways of casting your callback type
726have been omitted....</p> 789instead have been omitted.</p>
790<p>Another common scenario is having some data structure with multiple
791watchers:</p>
792<pre> struct my_biggy
793 {
794 int some_data;
795 ev_timer t1;
796 ev_timer t2;
797 }
727 798
799</pre>
800<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
801you need to use <code>offsetof</code>:</p>
802<pre> #include &lt;stddef.h&gt;
728 803
804 static void
805 t1_cb (EV_P_ struct ev_timer *w, int revents)
806 {
807 struct my_biggy big = (struct my_biggy *
808 (((char *)w) - offsetof (struct my_biggy, t1));
809 }
729 810
811 static void
812 t2_cb (EV_P_ struct ev_timer *w, int revents)
813 {
814 struct my_biggy big = (struct my_biggy *
815 (((char *)w) - offsetof (struct my_biggy, t2));
816 }
730 817
731 818
819
820
821</pre>
822
732</div> 823</div>
733<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 824<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
734<div id="WATCHER_TYPES_CONTENT"> 825<div id="WATCHER_TYPES_CONTENT">
735<p>This section describes each watcher in detail, but will not repeat 826<p>This section describes each watcher in detail, but will not repeat
736information given in the last section.</p> 827information given in the last section. Any initialisation/set macros,
828functions and members specific to the watcher type are explained.</p>
829<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
830while the watcher is active, you can look at the member and expect some
831sensible content, but you must not modify it (you can modify it while the
832watcher is stopped to your hearts content), or <i>[read-write]</i>, which
833means you can expect it to have some sensible content while the watcher
834is active, but you can also modify it. Modifying it may not do something
835sensible or take immediate effect (or do anything at all), but libev will
836not crash or malfunction in any way.</p>
737 837
738 838
739 839
740 840
741 841
… …
780 <dd> 880 <dd>
781 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 881 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
782rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or 882rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
783<code>EV_READ | EV_WRITE</code> to receive the given events.</p> 883<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
784 </dd> 884 </dd>
885 <dt>int fd [read-only]</dt>
886 <dd>
887 <p>The file descriptor being watched.</p>
888 </dd>
889 <dt>int events [read-only]</dt>
890 <dd>
891 <p>The events being watched.</p>
892 </dd>
785</dl> 893</dl>
786<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 894<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
787readable, but only once. Since it is likely line-buffered, you could 895readable, but only once. Since it is likely line-buffered, you could
788attempt to read a whole line in the callback:</p> 896attempt to read a whole line in the callback.</p>
789<pre> static void 897<pre> static void
790 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 898 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
791 { 899 {
792 ev_io_stop (loop, w); 900 ev_io_stop (loop, w);
793 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 901 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
846repeating. The exact semantics are:</p> 954repeating. The exact semantics are:</p>
847 <p>If the timer is started but nonrepeating, stop it.</p> 955 <p>If the timer is started but nonrepeating, stop it.</p>
848 <p>If the timer is repeating, either start it if necessary (with the repeat 956 <p>If the timer is repeating, either start it if necessary (with the repeat
849value), or reset the running timer to the repeat value.</p> 957value), or reset the running timer to the repeat value.</p>
850 <p>This sounds a bit complicated, but here is a useful and typical 958 <p>This sounds a bit complicated, but here is a useful and typical
851example: Imagine you have a tcp connection and you want a so-called idle 959example: Imagine you have a tcp connection and you want a so-called
852timeout, that is, you want to be called when there have been, say, 60 960idle timeout, that is, you want to be called when there have been,
853seconds of inactivity on the socket. The easiest way to do this is to 961say, 60 seconds of inactivity on the socket. The easiest way to do
854configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 962this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
855time you successfully read or write some data. If you go into an idle 963<code>ev_timer_again</code> each time you successfully read or write some data. If
856state where you do not expect data to travel on the socket, you can stop 964you go into an idle state where you do not expect data to travel on the
857the timer, and again will automatically restart it if need be.</p> 965socket, you can stop the timer, and again will automatically restart it if
966need be.</p>
967 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
968and only ever use the <code>repeat</code> value:</p>
969<pre> ev_timer_init (timer, callback, 0., 5.);
970 ev_timer_again (loop, timer);
971 ...
972 timer-&gt;again = 17.;
973 ev_timer_again (loop, timer);
974 ...
975 timer-&gt;again = 10.;
976 ev_timer_again (loop, timer);
977
978</pre>
979 <p>This is more efficient then stopping/starting the timer eahc time you want
980to modify its timeout value.</p>
981 </dd>
982 <dt>ev_tstamp repeat [read-write]</dt>
983 <dd>
984 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
985or <code>ev_timer_again</code> is called and determines the next timeout (if any),
986which is also when any modifications are taken into account.</p>
858 </dd> 987 </dd>
859</dl> 988</dl>
860<p>Example: create a timer that fires after 60 seconds.</p> 989<p>Example: Create a timer that fires after 60 seconds.</p>
861<pre> static void 990<pre> static void
862 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 991 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
863 { 992 {
864 .. one minute over, w is actually stopped right here 993 .. one minute over, w is actually stopped right here
865 } 994 }
… …
867 struct ev_timer mytimer; 996 struct ev_timer mytimer;
868 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 997 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
869 ev_timer_start (loop, &amp;mytimer); 998 ev_timer_start (loop, &amp;mytimer);
870 999
871</pre> 1000</pre>
872<p>Example: create a timeout timer that times out after 10 seconds of 1001<p>Example: Create a timeout timer that times out after 10 seconds of
873inactivity.</p> 1002inactivity.</p>
874<pre> static void 1003<pre> static void
875 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1004 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
876 { 1005 {
877 .. ten seconds without any activity 1006 .. ten seconds without any activity
… …
980 <p>Simply stops and restarts the periodic watcher again. This is only useful 1109 <p>Simply stops and restarts the periodic watcher again. This is only useful
981when you changed some parameters or the reschedule callback would return 1110when you changed some parameters or the reschedule callback would return
982a different time than the last time it was called (e.g. in a crond like 1111a different time than the last time it was called (e.g. in a crond like
983program when the crontabs have changed).</p> 1112program when the crontabs have changed).</p>
984 </dd> 1113 </dd>
1114 <dt>ev_tstamp interval [read-write]</dt>
1115 <dd>
1116 <p>The current interval value. Can be modified any time, but changes only
1117take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1118called.</p>
1119 </dd>
1120 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1121 <dd>
1122 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1123switched off. Can be changed any time, but changes only take effect when
1124the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1125 </dd>
985</dl> 1126</dl>
986<p>Example: call a callback every hour, or, more precisely, whenever the 1127<p>Example: Call a callback every hour, or, more precisely, whenever the
987system clock is divisible by 3600. The callback invocation times have 1128system clock is divisible by 3600. The callback invocation times have
988potentially a lot of jittering, but good long-term stability.</p> 1129potentially a lot of jittering, but good long-term stability.</p>
989<pre> static void 1130<pre> static void
990 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1131 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
991 { 1132 {
… …
995 struct ev_periodic hourly_tick; 1136 struct ev_periodic hourly_tick;
996 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1137 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
997 ev_periodic_start (loop, &amp;hourly_tick); 1138 ev_periodic_start (loop, &amp;hourly_tick);
998 1139
999</pre> 1140</pre>
1000<p>Example: the same as above, but use a reschedule callback to do it:</p> 1141<p>Example: The same as above, but use a reschedule callback to do it:</p>
1001<pre> #include &lt;math.h&gt; 1142<pre> #include &lt;math.h&gt;
1002 1143
1003 static ev_tstamp 1144 static ev_tstamp
1004 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1145 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1005 { 1146 {
… …
1007 } 1148 }
1008 1149
1009 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1150 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1010 1151
1011</pre> 1152</pre>
1012<p>Example: call a callback every hour, starting now:</p> 1153<p>Example: Call a callback every hour, starting now:</p>
1013<pre> struct ev_periodic hourly_tick; 1154<pre> struct ev_periodic hourly_tick;
1014 ev_periodic_init (&amp;hourly_tick, clock_cb, 1155 ev_periodic_init (&amp;hourly_tick, clock_cb,
1015 fmod (ev_now (loop), 3600.), 3600., 0); 1156 fmod (ev_now (loop), 3600.), 3600., 0);
1016 ev_periodic_start (loop, &amp;hourly_tick); 1157 ev_periodic_start (loop, &amp;hourly_tick);
1017 1158
… …
1038 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1179 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1039 <dd> 1180 <dd>
1040 <p>Configures the watcher to trigger on the given signal number (usually one 1181 <p>Configures the watcher to trigger on the given signal number (usually one
1041of the <code>SIGxxx</code> constants).</p> 1182of the <code>SIGxxx</code> constants).</p>
1042 </dd> 1183 </dd>
1184 <dt>int signum [read-only]</dt>
1185 <dd>
1186 <p>The signal the watcher watches out for.</p>
1187 </dd>
1043</dl> 1188</dl>
1044 1189
1045 1190
1046 1191
1047 1192
… …
1060at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1205at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1061the status word (use the macros from <code>sys/wait.h</code> and see your systems 1206the status word (use the macros from <code>sys/wait.h</code> and see your systems
1062<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1207<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1063process causing the status change.</p> 1208process causing the status change.</p>
1064 </dd> 1209 </dd>
1210 <dt>int pid [read-only]</dt>
1211 <dd>
1212 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1213 </dd>
1214 <dt>int rpid [read-write]</dt>
1215 <dd>
1216 <p>The process id that detected a status change.</p>
1217 </dd>
1218 <dt>int rstatus [read-write]</dt>
1219 <dd>
1220 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1221<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1222 </dd>
1065</dl> 1223</dl>
1066<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1224<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1067<pre> static void 1225<pre> static void
1068 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1226 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1069 { 1227 {
1070 ev_unloop (loop, EVUNLOOP_ALL); 1228 ev_unloop (loop, EVUNLOOP_ALL);
1071 } 1229 }
1072 1230
1073 struct ev_signal signal_watcher; 1231 struct ev_signal signal_watcher;
1074 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT); 1232 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1075 ev_signal_start (loop, &amp;sigint_cb); 1233 ev_signal_start (loop, &amp;sigint_cb);
1234
1235
1236
1237
1238</pre>
1239
1240</div>
1241<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1242<div id="code_ev_stat_code_did_the_file_attri-2">
1243<p>This watches a filesystem path for attribute changes. That is, it calls
1244<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1245compared to the last time, invoking the callback if it did.</p>
1246<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1247not exist&quot; is a status change like any other. The condition &quot;path does
1248not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1249otherwise always forced to be at least one) and all the other fields of
1250the stat buffer having unspecified contents.</p>
1251<p>Since there is no standard to do this, the portable implementation simply
1252calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1253can specify a recommended polling interval for this case. If you specify
1254a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1255unspecified default</i> value will be used (which you can expect to be around
1256five seconds, although this might change dynamically). Libev will also
1257impose a minimum interval which is currently around <code>0.1</code>, but thats
1258usually overkill.</p>
1259<p>This watcher type is not meant for massive numbers of stat watchers,
1260as even with OS-supported change notifications, this can be
1261resource-intensive.</p>
1262<p>At the time of this writing, only the Linux inotify interface is
1263implemented (implementing kqueue support is left as an exercise for the
1264reader). Inotify will be used to give hints only and should not change the
1265semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1266to fall back to regular polling again even with inotify, but changes are
1267usually detected immediately, and if the file exists there will be no
1268polling.</p>
1269<dl>
1270 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1271 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1272 <dd>
1273 <p>Configures the watcher to wait for status changes of the given
1274<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1275be detected and should normally be specified as <code>0</code> to let libev choose
1276a suitable value. The memory pointed to by <code>path</code> must point to the same
1277path for as long as the watcher is active.</p>
1278 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1279relative to the attributes at the time the watcher was started (or the
1280last change was detected).</p>
1281 </dd>
1282 <dt>ev_stat_stat (ev_stat *)</dt>
1283 <dd>
1284 <p>Updates the stat buffer immediately with new values. If you change the
1285watched path in your callback, you could call this fucntion to avoid
1286detecting this change (while introducing a race condition). Can also be
1287useful simply to find out the new values.</p>
1288 </dd>
1289 <dt>ev_statdata attr [read-only]</dt>
1290 <dd>
1291 <p>The most-recently detected attributes of the file. Although the type is of
1292<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1293suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1294was some error while <code>stat</code>ing the file.</p>
1295 </dd>
1296 <dt>ev_statdata prev [read-only]</dt>
1297 <dd>
1298 <p>The previous attributes of the file. The callback gets invoked whenever
1299<code>prev</code> != <code>attr</code>.</p>
1300 </dd>
1301 <dt>ev_tstamp interval [read-only]</dt>
1302 <dd>
1303 <p>The specified interval.</p>
1304 </dd>
1305 <dt>const char *path [read-only]</dt>
1306 <dd>
1307 <p>The filesystem path that is being watched.</p>
1308 </dd>
1309</dl>
1310<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1311<pre> static void
1312 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1313 {
1314 /* /etc/passwd changed in some way */
1315 if (w-&gt;attr.st_nlink)
1316 {
1317 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1318 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1319 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1320 }
1321 else
1322 /* you shalt not abuse printf for puts */
1323 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1324 &quot;if this is windows, they already arrived\n&quot;);
1325 }
1326
1327 ...
1328 ev_stat passwd;
1329
1330 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1331 ev_stat_start (loop, &amp;passwd);
1076 1332
1077 1333
1078 1334
1079 1335
1080</pre> 1336</pre>
… …
1101 <p>Initialises and configures the idle watcher - it has no parameters of any 1357 <p>Initialises and configures the idle watcher - it has no parameters of any
1102kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1358kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1103believe me.</p> 1359believe me.</p>
1104 </dd> 1360 </dd>
1105</dl> 1361</dl>
1106<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1362<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1107callback, free it. Alos, use no error checking, as usual.</p> 1363callback, free it. Also, use no error checking, as usual.</p>
1108<pre> static void 1364<pre> static void
1109 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1365 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1110 { 1366 {
1111 free (w); 1367 free (w);
1112 // now do something you wanted to do when the program has 1368 // now do something you wanted to do when the program has
… …
1126<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2> 1382<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1127<div id="code_ev_prepare_code_and_code_ev_che-2"> 1383<div id="code_ev_prepare_code_and_code_ev_che-2">
1128<p>Prepare and check watchers are usually (but not always) used in tandem: 1384<p>Prepare and check watchers are usually (but not always) used in tandem:
1129prepare watchers get invoked before the process blocks and check watchers 1385prepare watchers get invoked before the process blocks and check watchers
1130afterwards.</p> 1386afterwards.</p>
1387<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1388the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1389watchers. Other loops than the current one are fine, however. The
1390rationale behind this is that you do not need to check for recursion in
1391those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1392<code>ev_check</code> so if you have one watcher of each kind they will always be
1393called in pairs bracketing the blocking call.</p>
1131<p>Their main purpose is to integrate other event mechanisms into libev and 1394<p>Their main purpose is to integrate other event mechanisms into libev and
1132their use is somewhat advanced. This could be used, for example, to track 1395their use is somewhat advanced. This could be used, for example, to track
1133variable changes, implement your own watchers, integrate net-snmp or a 1396variable changes, implement your own watchers, integrate net-snmp or a
1134coroutine library and lots more.</p> 1397coroutine library and lots more. They are also occasionally useful if
1398you cache some data and want to flush it before blocking (for example,
1399in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1400watcher).</p>
1135<p>This is done by examining in each prepare call which file descriptors need 1401<p>This is done by examining in each prepare call which file descriptors need
1136to be watched by the other library, registering <code>ev_io</code> watchers for 1402to be watched by the other library, registering <code>ev_io</code> watchers for
1137them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1403them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1138provide just this functionality). Then, in the check watcher you check for 1404provide just this functionality). Then, in the check watcher you check for
1139any events that occured (by checking the pending status of all watchers 1405any events that occured (by checking the pending status of all watchers
… …
1155 <p>Initialises and configures the prepare or check watcher - they have no 1421 <p>Initialises and configures the prepare or check watcher - they have no
1156parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1422parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1157macros, but using them is utterly, utterly and completely pointless.</p> 1423macros, but using them is utterly, utterly and completely pointless.</p>
1158 </dd> 1424 </dd>
1159</dl> 1425</dl>
1160<p>Example: *TODO*.</p> 1426<p>Example: To include a library such as adns, you would add IO watchers
1427and a timeout watcher in a prepare handler, as required by libadns, and
1428in a check watcher, destroy them and call into libadns. What follows is
1429pseudo-code only of course:</p>
1430<pre> static ev_io iow [nfd];
1431 static ev_timer tw;
1161 1432
1433 static void
1434 io_cb (ev_loop *loop, ev_io *w, int revents)
1435 {
1436 // set the relevant poll flags
1437 // could also call adns_processreadable etc. here
1438 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1439 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1440 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1441 }
1162 1442
1443 // create io watchers for each fd and a timer before blocking
1444 static void
1445 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1446 {
1447 int timeout = 3600000;truct pollfd fds [nfd];
1448 // actual code will need to loop here and realloc etc.
1449 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1163 1450
1451 /* the callback is illegal, but won't be called as we stop during check */
1452 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1453 ev_timer_start (loop, &amp;tw);
1164 1454
1455 // create on ev_io per pollfd
1456 for (int i = 0; i &lt; nfd; ++i)
1457 {
1458 ev_io_init (iow + i, io_cb, fds [i].fd,
1459 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1460 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1461
1462 fds [i].revents = 0;
1463 iow [i].data = fds + i;
1464 ev_io_start (loop, iow + i);
1465 }
1466 }
1467
1468 // stop all watchers after blocking
1469 static void
1470 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1471 {
1472 ev_timer_stop (loop, &amp;tw);
1473
1474 for (int i = 0; i &lt; nfd; ++i)
1475 ev_io_stop (loop, iow + i);
1476
1477 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1478 }
1479
1480
1481
1482
1483</pre>
1165 1484
1166</div> 1485</div>
1167<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2> 1486<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1168<div id="code_ev_embed_code_when_one_backend_-2"> 1487<div id="code_ev_embed_code_when_one_backend_-2">
1169<p>This is a rather advanced watcher type that lets you embed one event loop 1488<p>This is a rather advanced watcher type that lets you embed one event loop
… …
1240 <dd> 1559 <dd>
1241 <p>Make a single, non-blocking sweep over the embedded loop. This works 1560 <p>Make a single, non-blocking sweep over the embedded loop. This works
1242similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1561similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1243apropriate way for embedded loops.</p> 1562apropriate way for embedded loops.</p>
1244 </dd> 1563 </dd>
1564 <dt>struct ev_loop *loop [read-only]</dt>
1565 <dd>
1566 <p>The embedded event loop.</p>
1567 </dd>
1245</dl> 1568</dl>
1246 1569
1247 1570
1248 1571
1249 1572
1250 1573
1251</div> 1574</div>
1252<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1575<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>
1576<div id="code_ev_fork_code_the_audacity_to_re-2">
1577<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1578whoever is a good citizen cared to tell libev about it by calling
1579<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1580event loop blocks next and before <code>ev_check</code> watchers are being called,
1581and only in the child after the fork. If whoever good citizen calling
1582<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1583handlers will be invoked, too, of course.</p>
1584<dl>
1585 <dt>ev_fork_init (ev_signal *, callback)</dt>
1586 <dd>
1587 <p>Initialises and configures the fork watcher - it has no parameters of any
1588kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1589believe me.</p>
1590 </dd>
1591</dl>
1592
1593
1594
1595
1596
1597</div>
1598<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1253<div id="OTHER_FUNCTIONS_CONTENT"> 1599<div id="OTHER_FUNCTIONS_CONTENT">
1254<p>There are some other functions of possible interest. Described. Here. Now.</p> 1600<p>There are some other functions of possible interest. Described. Here. Now.</p>
1255<dl> 1601<dl>
1256 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1602 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1257 <dd> 1603 <dd>
… …
1304 1650
1305 1651
1306 1652
1307 1653
1308</div> 1654</div>
1309<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1655<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1310<div id="LIBEVENT_EMULATION_CONTENT"> 1656<div id="LIBEVENT_EMULATION_CONTENT">
1311<p>Libev offers a compatibility emulation layer for libevent. It cannot 1657<p>Libev offers a compatibility emulation layer for libevent. It cannot
1312emulate the internals of libevent, so here are some usage hints:</p> 1658emulate the internals of libevent, so here are some usage hints:</p>
1313<dl> 1659<dl>
1314 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1660 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1324 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1670 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1325to use the libev header file and library.</dt> 1671to use the libev header file and library.</dt>
1326</dl> 1672</dl>
1327 1673
1328</div> 1674</div>
1329<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1675<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1330<div id="C_SUPPORT_CONTENT"> 1676<div id="C_SUPPORT_CONTENT">
1331<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1677<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1332you to use some convinience methods to start/stop watchers and also change 1678you to use some convinience methods to start/stop watchers and also change
1333the callback model to a model using method callbacks on objects.</p> 1679the callback model to a model using method callbacks on objects.</p>
1334<p>To use it,</p> 1680<p>To use it,</p>
… …
1398 </dd> 1744 </dd>
1399 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1745 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1400 <dd> 1746 <dd>
1401 <p>Invokes <code>ev_embed_sweep</code>.</p> 1747 <p>Invokes <code>ev_embed_sweep</code>.</p>
1402 </dd> 1748 </dd>
1749 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1750 <dd>
1751 <p>Invokes <code>ev_stat_stat</code>.</p>
1752 </dd>
1403 </dl> 1753 </dl>
1404 </p> 1754 </p>
1405 </dd> 1755 </dd>
1406</dl> 1756</dl>
1407<p>Example: Define a class with an IO and idle watcher, start one of them in 1757<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1419 idle (this, &amp;myclass::idle_cb) 1769 idle (this, &amp;myclass::idle_cb)
1420 { 1770 {
1421 io.start (fd, ev::READ); 1771 io.start (fd, ev::READ);
1422 } 1772 }
1423 1773
1424</pre>
1425 1774
1775
1776
1777</pre>
1778
1426</div> 1779</div>
1427<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1780<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1781<div id="MACRO_MAGIC_CONTENT">
1782<p>Libev can be compiled with a variety of options, the most fundemantal is
1783<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1784callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1785<p>To make it easier to write programs that cope with either variant, the
1786following macros are defined:</p>
1787<dl>
1788 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1789 <dd>
1790 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1791loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1792<code>EV_A_</code> is used when other arguments are following. Example:</p>
1793<pre> ev_unref (EV_A);
1794 ev_timer_add (EV_A_ watcher);
1795 ev_loop (EV_A_ 0);
1796
1797</pre>
1798 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1799which is often provided by the following macro.</p>
1800 </dd>
1801 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1802 <dd>
1803 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1804loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1805<code>EV_P_</code> is used when other parameters are following. Example:</p>
1806<pre> // this is how ev_unref is being declared
1807 static void ev_unref (EV_P);
1808
1809 // this is how you can declare your typical callback
1810 static void cb (EV_P_ ev_timer *w, int revents)
1811
1812</pre>
1813 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1814suitable for use with <code>EV_A</code>.</p>
1815 </dd>
1816 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1817 <dd>
1818 <p>Similar to the other two macros, this gives you the value of the default
1819loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1820 </dd>
1821</dl>
1822<p>Example: Declare and initialise a check watcher, working regardless of
1823wether multiple loops are supported or not.</p>
1824<pre> static void
1825 check_cb (EV_P_ ev_timer *w, int revents)
1826 {
1827 ev_check_stop (EV_A_ w);
1828 }
1829
1830 ev_check check;
1831 ev_check_init (&amp;check, check_cb);
1832 ev_check_start (EV_DEFAULT_ &amp;check);
1833 ev_loop (EV_DEFAULT_ 0);
1834
1835
1836
1837
1838</pre>
1839
1840</div>
1841<h1 id="EMBEDDING">EMBEDDING</h1>
1428<div id="EMBEDDING_CONTENT"> 1842<div id="EMBEDDING_CONTENT">
1429<p>Libev can (and often is) directly embedded into host 1843<p>Libev can (and often is) directly embedded into host
1430applications. Examples of applications that embed it include the Deliantra 1844applications. Examples of applications that embed it include the Deliantra
1431Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1845Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1432and rxvt-unicode.</p> 1846and rxvt-unicode.</p>
… …
1606 </dd> 2020 </dd>
1607 <dt>EV_USE_DEVPOLL</dt> 2021 <dt>EV_USE_DEVPOLL</dt>
1608 <dd> 2022 <dd>
1609 <p>reserved for future expansion, works like the USE symbols above.</p> 2023 <p>reserved for future expansion, works like the USE symbols above.</p>
1610 </dd> 2024 </dd>
2025 <dt>EV_USE_INOTIFY</dt>
2026 <dd>
2027 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2028interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2029be detected at runtime.</p>
2030 </dd>
1611 <dt>EV_H</dt> 2031 <dt>EV_H</dt>
1612 <dd> 2032 <dd>
1613 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2033 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1614undefined 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 2034undefined 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
1615can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2035can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1638will have the <code>struct ev_loop *</code> as first argument, and you can create 2058will have the <code>struct ev_loop *</code> as first argument, and you can create
1639additional independent event loops. Otherwise there will be no support 2059additional independent event loops. Otherwise there will be no support
1640for multiple event loops and there is no first event loop pointer 2060for multiple event loops and there is no first event loop pointer
1641argument. Instead, all functions act on the single default loop.</p> 2061argument. Instead, all functions act on the single default loop.</p>
1642 </dd> 2062 </dd>
1643 <dt>EV_PERIODICS</dt> 2063 <dt>EV_PERIODIC_ENABLE</dt>
1644 <dd> 2064 <dd>
1645 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2065 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1646otherwise not. This saves a few kb of code.</p> 2066defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2067code.</p>
2068 </dd>
2069 <dt>EV_EMBED_ENABLE</dt>
2070 <dd>
2071 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2072defined to be <code>0</code>, then they are not.</p>
2073 </dd>
2074 <dt>EV_STAT_ENABLE</dt>
2075 <dd>
2076 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2077defined to be <code>0</code>, then they are not.</p>
2078 </dd>
2079 <dt>EV_FORK_ENABLE</dt>
2080 <dd>
2081 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2082defined to be <code>0</code>, then they are not.</p>
2083 </dd>
2084 <dt>EV_MINIMAL</dt>
2085 <dd>
2086 <p>If you need to shave off some kilobytes of code at the expense of some
2087speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2088some inlining decisions, saves roughly 30% codesize of amd64.</p>
2089 </dd>
2090 <dt>EV_PID_HASHSIZE</dt>
2091 <dd>
2092 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2093pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2094than enough. If you need to manage thousands of children you might want to
2095increase this value (<i>must</i> be a power of two).</p>
2096 </dd>
2097 <dt>EV_INOTIFY_HASHSIZE</dt>
2098 <dd>
2099 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2100inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2101usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2102watchers you might want to increase this value (<i>must</i> be a power of
2103two).</p>
1647 </dd> 2104 </dd>
1648 <dt>EV_COMMON</dt> 2105 <dt>EV_COMMON</dt>
1649 <dd> 2106 <dd>
1650 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2107 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1651this macro to a something else you can include more and other types of 2108this macro to a something else you can include more and other types of
… …
1691</pre> 2148</pre>
1692 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2149 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1693<pre> #include &quot;ev_cpp.h&quot; 2150<pre> #include &quot;ev_cpp.h&quot;
1694 #include &quot;ev.c&quot; 2151 #include &quot;ev.c&quot;
1695 2152
1696</pre>
1697 2153
2154
2155
2156</pre>
2157
1698</div> 2158</div>
1699<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2159<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2160<div id="COMPLEXITIES_CONTENT">
2161 <p>In this section the complexities of (many of) the algorithms used inside
2162libev will be explained. For complexity discussions about backends see the
2163documentation for <code>ev_default_init</code>.</p>
2164 <p>
2165 <dl>
2166 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2167 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2168 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2169 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2170 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2171 <dt>Finding the next timer per loop iteration: O(1)</dt>
2172 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2173 <dt>Activating one watcher: O(1)</dt>
2174 </dl>
2175 </p>
2176
2177
2178
2179
2180
2181</div>
2182<h1 id="AUTHOR">AUTHOR</h1>
1700<div id="AUTHOR_CONTENT"> 2183<div id="AUTHOR_CONTENT">
1701 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2184 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1702 2185
1703</div> 2186</div>
1704</div></body> 2187</div></body>

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