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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="Mon Nov 26 11:20:35 2007" /> 9 <meta name="created" content="Wed Nov 28 12:31:29 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>
… …
56<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
57</li> 61</li>
58</ul><hr /> 62</ul><hr />
59<!-- INDEX END --> 63<!-- INDEX END -->
60 64
61<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
62<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
63<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>
64 68
65</div> 69</div>
66<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
67<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
68<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
69 73
70</pre> 74</pre>
71 75
72</div> 76</div>
73<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>
74<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
75<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
76file descriptor being readable or a timeout occuring), and it will manage 125file descriptor being readable or a timeout occuring), and it will manage
77these event sources and provide your program with events.</p> 126these event sources and provide your program with events.</p>
78<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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82watchers</i>, which are relatively small C structures you initialise with the 131watchers</i>, which are relatively small C structures you initialise with the
83details 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
84watcher.</p> 133watcher.</p>
85 134
86</div> 135</div>
87<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
88<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
89<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
90kqueue mechanisms for file descriptor events, relative timers, absolute 139BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
91timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
92events (related to SIGCHLD), and event watchers dealing with the event 141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
93loop mechanism itself (idle, prepare and check watchers). It also is quite 142with customised rescheduling (<code>ev_periodic</code>), synchronous signals
143(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
144watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
145<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
146file watchers (<code>ev_stat</code>) and even limited support for fork events
147(<code>ev_fork</code>).</p>
148<p>It also is quite fast (see this
94fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 149<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
95it to libevent for example).</p> 150for example).</p>
96 151
97</div> 152</div>
98<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
99<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
100<p>Libev is very configurable. In this manual the default configuration 155<p>Libev is very configurable. In this manual the default configuration will
101will be described, which supports multiple event loops. For more info 156be described, which supports multiple event loops. For more info about
102about various configuration options please have a look at the file 157various configuration options please have a look at <strong>EMBED</strong> section in
103<cite>README.embed</cite> in the libev distribution. If libev was configured without 158this manual. If libev was configured without support for multiple event
104support for multiple event loops, then all functions taking an initial 159loops, then all functions taking an initial argument of name <code>loop</code>
105argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 160(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
106will not have this argument.</p>
107 161
108</div> 162</div>
109<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
110<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
111<p>Libev represents time as a single floating point number, representing the 165<p>Libev represents time as a single floating point number, representing the
112(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
113the beginning of 1970, details are complicated, don't ask). This type is 167the beginning of 1970, details are complicated, don't ask). This type is
114called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 168called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
115to the <code>double</code> type in C, and when you need to do any calculations on 169to the <code>double</code> type in C, and when you need to do any calculations on
116it, you should treat it as such.</p> 170it, you should treat it as such.</p>
117 171
118
119
120
121
122</div> 172</div>
123<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
124<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
125<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
126library in any way.</p> 176library in any way.</p>
127<dl> 177<dl>
128 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
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141version of the library your program was compiled against.</p> 191version of the library your program was compiled against.</p>
142 <p>Usually, it's a good idea to terminate if the major versions mismatch, 192 <p>Usually, it's a good idea to terminate if the major versions mismatch,
143as this indicates an incompatible change. Minor versions are usually 193as this indicates an incompatible change. Minor versions are usually
144compatible to older versions, so a larger minor version alone is usually 194compatible to older versions, so a larger minor version alone is usually
145not a problem.</p> 195not a problem.</p>
146 <p>Example: make sure we haven't accidentally been linked against the wrong 196 <p>Example: Make sure we haven't accidentally been linked against the wrong
147version:</p> 197version.</p>
148<pre> assert ((&quot;libev version mismatch&quot;, 198<pre> assert ((&quot;libev version mismatch&quot;,
149 ev_version_major () == EV_VERSION_MAJOR 199 ev_version_major () == EV_VERSION_MAJOR
150 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 200 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
151 201
152</pre> 202</pre>
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180might be supported on the current system, you would need to look at 230might be supported on the current system, you would need to look at
181<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 231<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
182recommended ones.</p> 232recommended ones.</p>
183 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
184 </dd> 234 </dd>
185 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
186 <dd> 236 <dd>
187 <p>Sets the allocation function to use (the prototype is similar to the 237 <p>Sets the allocation function to use (the prototype and semantics are
188realloc C function, the semantics are identical). It is used to allocate 238identical to the realloc C function). It is used to allocate and free
189and free memory (no surprises here). If it returns zero when memory 239memory (no surprises here). If it returns zero when memory needs to be
190needs to be allocated, the library might abort or take some potentially 240allocated, the library might abort or take some potentially destructive
191destructive action. The default is your system realloc function.</p> 241action. The default is your system realloc function.</p>
192 <p>You could override this function in high-availability programs to, say, 242 <p>You could override this function in high-availability programs to, say,
193free some memory if it cannot allocate memory, to use a special allocator, 243free some memory if it cannot allocate memory, to use a special allocator,
194or even to sleep a while and retry until some memory is available.</p> 244or even to sleep a while and retry until some memory is available.</p>
195 <p>Example: replace the libev allocator with one that waits a bit and then 245 <p>Example: Replace the libev allocator with one that waits a bit and then
196retries: better than mine).</p> 246retries).</p>
197<pre> static void * 247<pre> static void *
198 persistent_realloc (void *ptr, long size) 248 persistent_realloc (void *ptr, size_t size)
199 { 249 {
200 for (;;) 250 for (;;)
201 { 251 {
202 void *newptr = realloc (ptr, size); 252 void *newptr = realloc (ptr, size);
203 253
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220indicating the system call or subsystem causing the problem. If this 270indicating the system call or subsystem causing the problem. If this
221callback is set, then libev will expect it to remedy the sitution, no 271callback is set, then libev will expect it to remedy the sitution, no
222matter what, when it returns. That is, libev will generally retry the 272matter what, when it returns. That is, libev will generally retry the
223requested operation, or, if the condition doesn't go away, do bad stuff 273requested operation, or, if the condition doesn't go away, do bad stuff
224(such as abort).</p> 274(such as abort).</p>
225 <p>Example: do the same thing as libev does internally:</p> 275 <p>Example: This is basically the same thing that libev does internally, too.</p>
226<pre> static void 276<pre> static void
227 fatal_error (const char *msg) 277 fatal_error (const char *msg)
228 { 278 {
229 perror (msg); 279 perror (msg);
230 abort (); 280 abort ();
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236</pre> 286</pre>
237 </dd> 287 </dd>
238</dl> 288</dl>
239 289
240</div> 290</div>
241<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 291<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
242<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 292<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
243<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 293<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
244types of such loops, the <i>default</i> loop, which supports signals and child 294types of such loops, the <i>default</i> loop, which supports signals and child
245events, and dynamically created loops which do not.</p> 295events, and dynamically created loops which do not.</p>
246<p>If you use threads, a common model is to run the default event loop 296<p>If you use threads, a common model is to run the default event loop
… …
366 <dd> 416 <dd>
367 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 417 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
368always distinct from the default loop. Unlike the default loop, it cannot 418always distinct from the default loop. Unlike the default loop, it cannot
369handle signal and child watchers, and attempts to do so will be greeted by 419handle signal and child watchers, and attempts to do so will be greeted by
370undefined behaviour (or a failed assertion if assertions are enabled).</p> 420undefined behaviour (or a failed assertion if assertions are enabled).</p>
371 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 421 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
372<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 422<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
373 if (!epoller) 423 if (!epoller)
374 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 424 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
375 425
376</pre> 426</pre>
… …
469 be handled here by queueing them when their watcher gets executed. 519 be handled here by queueing them when their watcher gets executed.
470 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 520 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
471 were used, return, otherwise continue with step *. 521 were used, return, otherwise continue with step *.
472 522
473</pre> 523</pre>
474 <p>Example: queue some jobs and then loop until no events are outsanding 524 <p>Example: Queue some jobs and then loop until no events are outsanding
475anymore.</p> 525anymore.</p>
476<pre> ... queue jobs here, make sure they register event watchers as long 526<pre> ... queue jobs here, make sure they register event watchers as long
477 ... as they still have work to do (even an idle watcher will do..) 527 ... as they still have work to do (even an idle watcher will do..)
478 ev_loop (my_loop, 0); 528 ev_loop (my_loop, 0);
479 ... jobs done. yeah! 529 ... jobs done. yeah!
… …
498example, libev itself uses this for its internal signal pipe: It is not 548example, libev itself uses this for its internal signal pipe: It is not
499visible to the libev user and should not keep <code>ev_loop</code> from exiting if 549visible to the libev user and should not keep <code>ev_loop</code> from exiting if
500no event watchers registered by it are active. It is also an excellent 550no event watchers registered by it are active. It is also an excellent
501way to do this for generic recurring timers or from within third-party 551way to do this for generic recurring timers or from within third-party
502libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 552libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
503 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 553 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
504running when nothing else is active.</p> 554running when nothing else is active.</p>
505<pre> struct dv_signal exitsig; 555<pre> struct ev_signal exitsig;
506 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 556 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
507 ev_signal_start (myloop, &amp;exitsig); 557 ev_signal_start (loop, &amp;exitsig);
508 evf_unref (myloop); 558 evf_unref (loop);
509 559
510</pre> 560</pre>
511 <p>Example: for some weird reason, unregister the above signal handler again.</p> 561 <p>Example: For some weird reason, unregister the above signal handler again.</p>
512<pre> ev_ref (myloop); 562<pre> ev_ref (loop);
513 ev_signal_stop (myloop, &amp;exitsig); 563 ev_signal_stop (loop, &amp;exitsig);
514 564
515</pre> 565</pre>
516 </dd> 566 </dd>
517</dl> 567</dl>
518 568
519 569
520 570
521 571
522 572
523</div> 573</div>
524<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 574<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
525<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 575<div id="ANATOMY_OF_A_WATCHER_CONTENT">
526<p>A watcher is a structure that you create and register to record your 576<p>A watcher is a structure that you create and register to record your
527interest in some event. For instance, if you want to wait for STDIN to 577interest in some event. For instance, if you want to wait for STDIN to
528become readable, you would create an <code>ev_io</code> watcher for that:</p> 578become readable, you would create an <code>ev_io</code> watcher for that:</p>
529<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 579<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
586 </dd> 636 </dd>
587 <dt><code>EV_CHILD</code></dt> 637 <dt><code>EV_CHILD</code></dt>
588 <dd> 638 <dd>
589 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 639 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
590 </dd> 640 </dd>
641 <dt><code>EV_STAT</code></dt>
642 <dd>
643 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
644 </dd>
591 <dt><code>EV_IDLE</code></dt> 645 <dt><code>EV_IDLE</code></dt>
592 <dd> 646 <dd>
593 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 647 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
594 </dd> 648 </dd>
595 <dt><code>EV_PREPARE</code></dt> 649 <dt><code>EV_PREPARE</code></dt>
… …
600<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 654<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
601received events. Callbacks of both watcher types can start and stop as 655received events. Callbacks of both watcher types can start and stop as
602many watchers as they want, and all of them will be taken into account 656many watchers as they want, and all of them will be taken into account
603(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 657(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
604<code>ev_loop</code> from blocking).</p> 658<code>ev_loop</code> from blocking).</p>
659 </dd>
660 <dt><code>EV_EMBED</code></dt>
661 <dd>
662 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
663 </dd>
664 <dt><code>EV_FORK</code></dt>
665 <dd>
666 <p>The event loop has been resumed in the child process after fork (see
667<code>ev_fork</code>).</p>
605 </dd> 668 </dd>
606 <dt><code>EV_ERROR</code></dt> 669 <dt><code>EV_ERROR</code></dt>
607 <dd> 670 <dd>
608 <p>An unspecified error has occured, the watcher has been stopped. This might 671 <p>An unspecified error has occured, the watcher has been stopped. This might
609happen because the watcher could not be properly started because libev 672happen because the watcher could not be properly started because libev
… …
679events but its callback has not yet been invoked). As long as a watcher 742events but its callback has not yet been invoked). As long as a watcher
680is pending (but not active) you must not call an init function on it (but 743is pending (but not active) you must not call an init function on it (but
681<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 744<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
682libev (e.g. you cnanot <code>free ()</code> it).</p> 745libev (e.g. you cnanot <code>free ()</code> it).</p>
683 </dd> 746 </dd>
684 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 747 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
685 <dd> 748 <dd>
686 <p>Returns the callback currently set on the watcher.</p> 749 <p>Returns the callback currently set on the watcher.</p>
687 </dd> 750 </dd>
688 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 751 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
689 <dd> 752 <dd>
… …
721 struct my_io *w = (struct my_io *)w_; 784 struct my_io *w = (struct my_io *)w_;
722 ... 785 ...
723 } 786 }
724 787
725</pre> 788</pre>
726<p>More interesting and less C-conformant ways of catsing your callback type 789<p>More interesting and less C-conformant ways of casting your callback type
727have been omitted....</p> 790instead have been omitted.</p>
791<p>Another common scenario is having some data structure with multiple
792watchers:</p>
793<pre> struct my_biggy
794 {
795 int some_data;
796 ev_timer t1;
797 ev_timer t2;
798 }
728 799
800</pre>
801<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
802you need to use <code>offsetof</code>:</p>
803<pre> #include &lt;stddef.h&gt;
729 804
805 static void
806 t1_cb (EV_P_ struct ev_timer *w, int revents)
807 {
808 struct my_biggy big = (struct my_biggy *
809 (((char *)w) - offsetof (struct my_biggy, t1));
810 }
730 811
812 static void
813 t2_cb (EV_P_ struct ev_timer *w, int revents)
814 {
815 struct my_biggy big = (struct my_biggy *
816 (((char *)w) - offsetof (struct my_biggy, t2));
817 }
731 818
732 819
820
821
822</pre>
823
733</div> 824</div>
734<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 825<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
735<div id="WATCHER_TYPES_CONTENT"> 826<div id="WATCHER_TYPES_CONTENT">
736<p>This section describes each watcher in detail, but will not repeat 827<p>This section describes each watcher in detail, but will not repeat
737information given in the last section.</p> 828information given in the last section. Any initialisation/set macros,
829functions and members specific to the watcher type are explained.</p>
830<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
831while the watcher is active, you can look at the member and expect some
832sensible content, but you must not modify it (you can modify it while the
833watcher is stopped to your hearts content), or <i>[read-write]</i>, which
834means you can expect it to have some sensible content while the watcher
835is active, but you can also modify it. Modifying it may not do something
836sensible or take immediate effect (or do anything at all), but libev will
837not crash or malfunction in any way.</p>
738 838
739 839
740 840
741 841
742 842
… …
781 <dd> 881 <dd>
782 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 882 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
783rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or 883rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
784<code>EV_READ | EV_WRITE</code> to receive the given events.</p> 884<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
785 </dd> 885 </dd>
886 <dt>int fd [read-only]</dt>
887 <dd>
888 <p>The file descriptor being watched.</p>
889 </dd>
890 <dt>int events [read-only]</dt>
891 <dd>
892 <p>The events being watched.</p>
893 </dd>
786</dl> 894</dl>
787<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 895<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
788readable, but only once. Since it is likely line-buffered, you could 896readable, but only once. Since it is likely line-buffered, you could
789attempt to read a whole line in the callback:</p> 897attempt to read a whole line in the callback.</p>
790<pre> static void 898<pre> static void
791 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 899 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
792 { 900 {
793 ev_io_stop (loop, w); 901 ev_io_stop (loop, w);
794 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 902 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
847repeating. The exact semantics are:</p> 955repeating. The exact semantics are:</p>
848 <p>If the timer is started but nonrepeating, stop it.</p> 956 <p>If the timer is started but nonrepeating, stop it.</p>
849 <p>If the timer is repeating, either start it if necessary (with the repeat 957 <p>If the timer is repeating, either start it if necessary (with the repeat
850value), or reset the running timer to the repeat value.</p> 958value), or reset the running timer to the repeat value.</p>
851 <p>This sounds a bit complicated, but here is a useful and typical 959 <p>This sounds a bit complicated, but here is a useful and typical
852example: Imagine you have a tcp connection and you want a so-called idle 960example: Imagine you have a tcp connection and you want a so-called
853timeout, that is, you want to be called when there have been, say, 60 961idle timeout, that is, you want to be called when there have been,
854seconds of inactivity on the socket. The easiest way to do this is to 962say, 60 seconds of inactivity on the socket. The easiest way to do
855configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 963this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
856time you successfully read or write some data. If you go into an idle 964<code>ev_timer_again</code> each time you successfully read or write some data. If
857state where you do not expect data to travel on the socket, you can stop 965you go into an idle state where you do not expect data to travel on the
858the timer, and again will automatically restart it if need be.</p> 966socket, you can stop the timer, and again will automatically restart it if
967need be.</p>
968 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
969and only ever use the <code>repeat</code> value:</p>
970<pre> ev_timer_init (timer, callback, 0., 5.);
971 ev_timer_again (loop, timer);
972 ...
973 timer-&gt;again = 17.;
974 ev_timer_again (loop, timer);
975 ...
976 timer-&gt;again = 10.;
977 ev_timer_again (loop, timer);
978
979</pre>
980 <p>This is more efficient then stopping/starting the timer eahc time you want
981to modify its timeout value.</p>
982 </dd>
983 <dt>ev_tstamp repeat [read-write]</dt>
984 <dd>
985 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
986or <code>ev_timer_again</code> is called and determines the next timeout (if any),
987which is also when any modifications are taken into account.</p>
859 </dd> 988 </dd>
860</dl> 989</dl>
861<p>Example: create a timer that fires after 60 seconds.</p> 990<p>Example: Create a timer that fires after 60 seconds.</p>
862<pre> static void 991<pre> static void
863 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 992 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
864 { 993 {
865 .. one minute over, w is actually stopped right here 994 .. one minute over, w is actually stopped right here
866 } 995 }
… …
868 struct ev_timer mytimer; 997 struct ev_timer mytimer;
869 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 998 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
870 ev_timer_start (loop, &amp;mytimer); 999 ev_timer_start (loop, &amp;mytimer);
871 1000
872</pre> 1001</pre>
873<p>Example: create a timeout timer that times out after 10 seconds of 1002<p>Example: Create a timeout timer that times out after 10 seconds of
874inactivity.</p> 1003inactivity.</p>
875<pre> static void 1004<pre> static void
876 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1005 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
877 { 1006 {
878 .. ten seconds without any activity 1007 .. ten seconds without any activity
… …
981 <p>Simply stops and restarts the periodic watcher again. This is only useful 1110 <p>Simply stops and restarts the periodic watcher again. This is only useful
982when you changed some parameters or the reschedule callback would return 1111when you changed some parameters or the reschedule callback would return
983a different time than the last time it was called (e.g. in a crond like 1112a different time than the last time it was called (e.g. in a crond like
984program when the crontabs have changed).</p> 1113program when the crontabs have changed).</p>
985 </dd> 1114 </dd>
1115 <dt>ev_tstamp interval [read-write]</dt>
1116 <dd>
1117 <p>The current interval value. Can be modified any time, but changes only
1118take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1119called.</p>
1120 </dd>
1121 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1122 <dd>
1123 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1124switched off. Can be changed any time, but changes only take effect when
1125the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1126 </dd>
986</dl> 1127</dl>
987<p>Example: call a callback every hour, or, more precisely, whenever the 1128<p>Example: Call a callback every hour, or, more precisely, whenever the
988system clock is divisible by 3600. The callback invocation times have 1129system clock is divisible by 3600. The callback invocation times have
989potentially a lot of jittering, but good long-term stability.</p> 1130potentially a lot of jittering, but good long-term stability.</p>
990<pre> static void 1131<pre> static void
991 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1132 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
992 { 1133 {
… …
996 struct ev_periodic hourly_tick; 1137 struct ev_periodic hourly_tick;
997 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1138 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
998 ev_periodic_start (loop, &amp;hourly_tick); 1139 ev_periodic_start (loop, &amp;hourly_tick);
999 1140
1000</pre> 1141</pre>
1001<p>Example: the same as above, but use a reschedule callback to do it:</p> 1142<p>Example: The same as above, but use a reschedule callback to do it:</p>
1002<pre> #include &lt;math.h&gt; 1143<pre> #include &lt;math.h&gt;
1003 1144
1004 static ev_tstamp 1145 static ev_tstamp
1005 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1146 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1006 { 1147 {
… …
1008 } 1149 }
1009 1150
1010 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1151 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1011 1152
1012</pre> 1153</pre>
1013<p>Example: call a callback every hour, starting now:</p> 1154<p>Example: Call a callback every hour, starting now:</p>
1014<pre> struct ev_periodic hourly_tick; 1155<pre> struct ev_periodic hourly_tick;
1015 ev_periodic_init (&amp;hourly_tick, clock_cb, 1156 ev_periodic_init (&amp;hourly_tick, clock_cb,
1016 fmod (ev_now (loop), 3600.), 3600., 0); 1157 fmod (ev_now (loop), 3600.), 3600., 0);
1017 ev_periodic_start (loop, &amp;hourly_tick); 1158 ev_periodic_start (loop, &amp;hourly_tick);
1018 1159
… …
1039 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1180 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1040 <dd> 1181 <dd>
1041 <p>Configures the watcher to trigger on the given signal number (usually one 1182 <p>Configures the watcher to trigger on the given signal number (usually one
1042of the <code>SIGxxx</code> constants).</p> 1183of the <code>SIGxxx</code> constants).</p>
1043 </dd> 1184 </dd>
1185 <dt>int signum [read-only]</dt>
1186 <dd>
1187 <p>The signal the watcher watches out for.</p>
1188 </dd>
1044</dl> 1189</dl>
1045 1190
1046 1191
1047 1192
1048 1193
… …
1061at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1206at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1062the status word (use the macros from <code>sys/wait.h</code> and see your systems 1207the status word (use the macros from <code>sys/wait.h</code> and see your systems
1063<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1208<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1064process causing the status change.</p> 1209process causing the status change.</p>
1065 </dd> 1210 </dd>
1211 <dt>int pid [read-only]</dt>
1212 <dd>
1213 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1214 </dd>
1215 <dt>int rpid [read-write]</dt>
1216 <dd>
1217 <p>The process id that detected a status change.</p>
1218 </dd>
1219 <dt>int rstatus [read-write]</dt>
1220 <dd>
1221 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1222<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1223 </dd>
1066</dl> 1224</dl>
1067<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1225<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1068<pre> static void 1226<pre> static void
1069 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1227 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1070 { 1228 {
1071 ev_unloop (loop, EVUNLOOP_ALL); 1229 ev_unloop (loop, EVUNLOOP_ALL);
1072 } 1230 }
1073 1231
1074 struct ev_signal signal_watcher; 1232 struct ev_signal signal_watcher;
1075 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT); 1233 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1076 ev_signal_start (loop, &amp;sigint_cb); 1234 ev_signal_start (loop, &amp;sigint_cb);
1235
1236
1237
1238
1239</pre>
1240
1241</div>
1242<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1243<div id="code_ev_stat_code_did_the_file_attri-2">
1244<p>This watches a filesystem path for attribute changes. That is, it calls
1245<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1246compared to the last time, invoking the callback if it did.</p>
1247<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1248not exist&quot; is a status change like any other. The condition &quot;path does
1249not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1250otherwise always forced to be at least one) and all the other fields of
1251the stat buffer having unspecified contents.</p>
1252<p>Since there is no standard to do this, the portable implementation simply
1253calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1254can specify a recommended polling interval for this case. If you specify
1255a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1256unspecified default</i> value will be used (which you can expect to be around
1257five seconds, although this might change dynamically). Libev will also
1258impose a minimum interval which is currently around <code>0.1</code>, but thats
1259usually overkill.</p>
1260<p>This watcher type is not meant for massive numbers of stat watchers,
1261as even with OS-supported change notifications, this can be
1262resource-intensive.</p>
1263<p>At the time of this writing, only the Linux inotify interface is
1264implemented (implementing kqueue support is left as an exercise for the
1265reader). Inotify will be used to give hints only and should not change the
1266semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1267to fall back to regular polling again even with inotify, but changes are
1268usually detected immediately, and if the file exists there will be no
1269polling.</p>
1270<dl>
1271 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1272 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1273 <dd>
1274 <p>Configures the watcher to wait for status changes of the given
1275<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1276be detected and should normally be specified as <code>0</code> to let libev choose
1277a suitable value. The memory pointed to by <code>path</code> must point to the same
1278path for as long as the watcher is active.</p>
1279 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1280relative to the attributes at the time the watcher was started (or the
1281last change was detected).</p>
1282 </dd>
1283 <dt>ev_stat_stat (ev_stat *)</dt>
1284 <dd>
1285 <p>Updates the stat buffer immediately with new values. If you change the
1286watched path in your callback, you could call this fucntion to avoid
1287detecting this change (while introducing a race condition). Can also be
1288useful simply to find out the new values.</p>
1289 </dd>
1290 <dt>ev_statdata attr [read-only]</dt>
1291 <dd>
1292 <p>The most-recently detected attributes of the file. Although the type is of
1293<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1294suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1295was some error while <code>stat</code>ing the file.</p>
1296 </dd>
1297 <dt>ev_statdata prev [read-only]</dt>
1298 <dd>
1299 <p>The previous attributes of the file. The callback gets invoked whenever
1300<code>prev</code> != <code>attr</code>.</p>
1301 </dd>
1302 <dt>ev_tstamp interval [read-only]</dt>
1303 <dd>
1304 <p>The specified interval.</p>
1305 </dd>
1306 <dt>const char *path [read-only]</dt>
1307 <dd>
1308 <p>The filesystem path that is being watched.</p>
1309 </dd>
1310</dl>
1311<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1312<pre> static void
1313 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1314 {
1315 /* /etc/passwd changed in some way */
1316 if (w-&gt;attr.st_nlink)
1317 {
1318 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1319 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1320 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1321 }
1322 else
1323 /* you shalt not abuse printf for puts */
1324 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1325 &quot;if this is windows, they already arrived\n&quot;);
1326 }
1327
1328 ...
1329 ev_stat passwd;
1330
1331 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1332 ev_stat_start (loop, &amp;passwd);
1077 1333
1078 1334
1079 1335
1080 1336
1081</pre> 1337</pre>
… …
1102 <p>Initialises and configures the idle watcher - it has no parameters of any 1358 <p>Initialises and configures the idle watcher - it has no parameters of any
1103kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1359kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1104believe me.</p> 1360believe me.</p>
1105 </dd> 1361 </dd>
1106</dl> 1362</dl>
1107<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1363<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1108callback, free it. Alos, use no error checking, as usual.</p> 1364callback, free it. Also, use no error checking, as usual.</p>
1109<pre> static void 1365<pre> static void
1110 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1366 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1111 { 1367 {
1112 free (w); 1368 free (w);
1113 // now do something you wanted to do when the program has 1369 // now do something you wanted to do when the program has
… …
1304 <dd> 1560 <dd>
1305 <p>Make a single, non-blocking sweep over the embedded loop. This works 1561 <p>Make a single, non-blocking sweep over the embedded loop. This works
1306similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1562similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1307apropriate way for embedded loops.</p> 1563apropriate way for embedded loops.</p>
1308 </dd> 1564 </dd>
1565 <dt>struct ev_loop *loop [read-only]</dt>
1566 <dd>
1567 <p>The embedded event loop.</p>
1568 </dd>
1309</dl> 1569</dl>
1310 1570
1311 1571
1312 1572
1313 1573
1314 1574
1315</div> 1575</div>
1316<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1576<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>
1577<div id="code_ev_fork_code_the_audacity_to_re-2">
1578<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1579whoever is a good citizen cared to tell libev about it by calling
1580<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1581event loop blocks next and before <code>ev_check</code> watchers are being called,
1582and only in the child after the fork. If whoever good citizen calling
1583<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1584handlers will be invoked, too, of course.</p>
1585<dl>
1586 <dt>ev_fork_init (ev_signal *, callback)</dt>
1587 <dd>
1588 <p>Initialises and configures the fork watcher - it has no parameters of any
1589kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1590believe me.</p>
1591 </dd>
1592</dl>
1593
1594
1595
1596
1597
1598</div>
1599<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1317<div id="OTHER_FUNCTIONS_CONTENT"> 1600<div id="OTHER_FUNCTIONS_CONTENT">
1318<p>There are some other functions of possible interest. Described. Here. Now.</p> 1601<p>There are some other functions of possible interest. Described. Here. Now.</p>
1319<dl> 1602<dl>
1320 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1603 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1321 <dd> 1604 <dd>
… …
1368 1651
1369 1652
1370 1653
1371 1654
1372</div> 1655</div>
1373<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1656<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1374<div id="LIBEVENT_EMULATION_CONTENT"> 1657<div id="LIBEVENT_EMULATION_CONTENT">
1375<p>Libev offers a compatibility emulation layer for libevent. It cannot 1658<p>Libev offers a compatibility emulation layer for libevent. It cannot
1376emulate the internals of libevent, so here are some usage hints:</p> 1659emulate the internals of libevent, so here are some usage hints:</p>
1377<dl> 1660<dl>
1378 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1661 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1388 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1671 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1389to use the libev header file and library.</dt> 1672to use the libev header file and library.</dt>
1390</dl> 1673</dl>
1391 1674
1392</div> 1675</div>
1393<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1676<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1394<div id="C_SUPPORT_CONTENT"> 1677<div id="C_SUPPORT_CONTENT">
1395<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1678<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1396you to use some convinience methods to start/stop watchers and also change 1679you to use some convinience methods to start/stop watchers and also change
1397the callback model to a model using method callbacks on objects.</p> 1680the callback model to a model using method callbacks on objects.</p>
1398<p>To use it,</p> 1681<p>To use it,</p>
… …
1462 </dd> 1745 </dd>
1463 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1746 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1464 <dd> 1747 <dd>
1465 <p>Invokes <code>ev_embed_sweep</code>.</p> 1748 <p>Invokes <code>ev_embed_sweep</code>.</p>
1466 </dd> 1749 </dd>
1750 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1751 <dd>
1752 <p>Invokes <code>ev_stat_stat</code>.</p>
1753 </dd>
1467 </dl> 1754 </dl>
1468 </p> 1755 </p>
1469 </dd> 1756 </dd>
1470</dl> 1757</dl>
1471<p>Example: Define a class with an IO and idle watcher, start one of them in 1758<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1483 idle (this, &amp;myclass::idle_cb) 1770 idle (this, &amp;myclass::idle_cb)
1484 { 1771 {
1485 io.start (fd, ev::READ); 1772 io.start (fd, ev::READ);
1486 } 1773 }
1487 1774
1488</pre>
1489 1775
1776
1777
1778</pre>
1779
1490</div> 1780</div>
1491<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1781<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1782<div id="MACRO_MAGIC_CONTENT">
1783<p>Libev can be compiled with a variety of options, the most fundemantal is
1784<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1785callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1786<p>To make it easier to write programs that cope with either variant, the
1787following macros are defined:</p>
1788<dl>
1789 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1790 <dd>
1791 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1792loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1793<code>EV_A_</code> is used when other arguments are following. Example:</p>
1794<pre> ev_unref (EV_A);
1795 ev_timer_add (EV_A_ watcher);
1796 ev_loop (EV_A_ 0);
1797
1798</pre>
1799 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1800which is often provided by the following macro.</p>
1801 </dd>
1802 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1803 <dd>
1804 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1805loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1806<code>EV_P_</code> is used when other parameters are following. Example:</p>
1807<pre> // this is how ev_unref is being declared
1808 static void ev_unref (EV_P);
1809
1810 // this is how you can declare your typical callback
1811 static void cb (EV_P_ ev_timer *w, int revents)
1812
1813</pre>
1814 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1815suitable for use with <code>EV_A</code>.</p>
1816 </dd>
1817 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1818 <dd>
1819 <p>Similar to the other two macros, this gives you the value of the default
1820loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1821 </dd>
1822</dl>
1823<p>Example: Declare and initialise a check watcher, working regardless of
1824wether multiple loops are supported or not.</p>
1825<pre> static void
1826 check_cb (EV_P_ ev_timer *w, int revents)
1827 {
1828 ev_check_stop (EV_A_ w);
1829 }
1830
1831 ev_check check;
1832 ev_check_init (&amp;check, check_cb);
1833 ev_check_start (EV_DEFAULT_ &amp;check);
1834 ev_loop (EV_DEFAULT_ 0);
1835
1836
1837
1838
1839</pre>
1840
1841</div>
1842<h1 id="EMBEDDING">EMBEDDING</h1>
1492<div id="EMBEDDING_CONTENT"> 1843<div id="EMBEDDING_CONTENT">
1493<p>Libev can (and often is) directly embedded into host 1844<p>Libev can (and often is) directly embedded into host
1494applications. Examples of applications that embed it include the Deliantra 1845applications. Examples of applications that embed it include the Deliantra
1495Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1846Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1496and rxvt-unicode.</p> 1847and rxvt-unicode.</p>
… …
1670 </dd> 2021 </dd>
1671 <dt>EV_USE_DEVPOLL</dt> 2022 <dt>EV_USE_DEVPOLL</dt>
1672 <dd> 2023 <dd>
1673 <p>reserved for future expansion, works like the USE symbols above.</p> 2024 <p>reserved for future expansion, works like the USE symbols above.</p>
1674 </dd> 2025 </dd>
2026 <dt>EV_USE_INOTIFY</dt>
2027 <dd>
2028 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2029interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2030be detected at runtime.</p>
2031 </dd>
1675 <dt>EV_H</dt> 2032 <dt>EV_H</dt>
1676 <dd> 2033 <dd>
1677 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2034 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1678undefined 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 2035undefined 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
1679can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2036can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1702will have the <code>struct ev_loop *</code> as first argument, and you can create 2059will have the <code>struct ev_loop *</code> as first argument, and you can create
1703additional independent event loops. Otherwise there will be no support 2060additional independent event loops. Otherwise there will be no support
1704for multiple event loops and there is no first event loop pointer 2061for multiple event loops and there is no first event loop pointer
1705argument. Instead, all functions act on the single default loop.</p> 2062argument. Instead, all functions act on the single default loop.</p>
1706 </dd> 2063 </dd>
1707 <dt>EV_PERIODICS</dt> 2064 <dt>EV_PERIODIC_ENABLE</dt>
1708 <dd> 2065 <dd>
1709 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2066 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1710otherwise not. This saves a few kb of code.</p> 2067defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2068code.</p>
2069 </dd>
2070 <dt>EV_EMBED_ENABLE</dt>
2071 <dd>
2072 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2073defined to be <code>0</code>, then they are not.</p>
2074 </dd>
2075 <dt>EV_STAT_ENABLE</dt>
2076 <dd>
2077 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2078defined to be <code>0</code>, then they are not.</p>
2079 </dd>
2080 <dt>EV_FORK_ENABLE</dt>
2081 <dd>
2082 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2083defined to be <code>0</code>, then they are not.</p>
2084 </dd>
2085 <dt>EV_MINIMAL</dt>
2086 <dd>
2087 <p>If you need to shave off some kilobytes of code at the expense of some
2088speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2089some inlining decisions, saves roughly 30% codesize of amd64.</p>
2090 </dd>
2091 <dt>EV_PID_HASHSIZE</dt>
2092 <dd>
2093 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2094pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2095than enough. If you need to manage thousands of children you might want to
2096increase this value (<i>must</i> be a power of two).</p>
2097 </dd>
2098 <dt>EV_INOTIFY_HASHSIZE</dt>
2099 <dd>
2100 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2101inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2102usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2103watchers you might want to increase this value (<i>must</i> be a power of
2104two).</p>
1711 </dd> 2105 </dd>
1712 <dt>EV_COMMON</dt> 2106 <dt>EV_COMMON</dt>
1713 <dd> 2107 <dd>
1714 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2108 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1715this macro to a something else you can include more and other types of 2109this macro to a something else you can include more and other types of
… …
1761 2155
1762 2156
1763</pre> 2157</pre>
1764 2158
1765</div> 2159</div>
1766<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2160<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
1767<div id="COMPLEXITIES_CONTENT"> 2161<div id="COMPLEXITIES_CONTENT">
1768 <p>In this section the complexities of (many of) the algorithms used inside 2162 <p>In this section the complexities of (many of) the algorithms used inside
1769libev will be explained. For complexity discussions about backends see the 2163libev will be explained. For complexity discussions about backends see the
1770documentation for <code>ev_default_init</code>.</p> 2164documentation for <code>ev_default_init</code>.</p>
1771 <p> 2165 <p>
1772 <dl> 2166 <dl>
1773 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2167 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
1774 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2168 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
1775 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2169 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
1776 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2170 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
1777 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2171 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
1778 <dt>Finding the next timer per loop iteration: O(1)</dt> 2172 <dt>Finding the next timer per loop iteration: O(1)</dt>
1779 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2173 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
1780 <dt>Activating one watcher: O(1)</dt> 2174 <dt>Activating one watcher: O(1)</dt>
1781 </dl> 2175 </dl>
1782 </p> 2176 </p>
… …
1784 2178
1785 2179
1786 2180
1787 2181
1788</div> 2182</div>
1789<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2183<h1 id="AUTHOR">AUTHOR</h1>
1790<div id="AUTHOR_CONTENT"> 2184<div id="AUTHOR_CONTENT">
1791 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2185 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1792 2186
1793</div> 2187</div>
1794</div></body> 2188</div></body>

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