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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 10:52:13 2007" /> 9 <meta name="created" content="Thu Nov 29 13:21:20 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>
… …
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>), the Linux <code>inotify</code> interface
91events (related to SIGCHLD), and event watchers dealing with the event 141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
92loop 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
93fast (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
94it to libevent for example).</p> 150for example).</p>
95 151
96</div> 152</div>
97<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
98<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
99<p>Libev is very configurable. In this manual the default configuration 155<p>Libev is very configurable. In this manual the default configuration will
100will be described, which supports multiple event loops. For more info 156be described, which supports multiple event loops. For more info about
101about various configuration options please have a look at the file 157various 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 158this manual. If libev was configured without support for multiple event
103support for multiple event loops, then all functions taking an initial 159loops, 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>) 160(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
105will not have this argument.</p>
106 161
107</div> 162</div>
108<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
109<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
110<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
111(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
112the 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
113called <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
114to 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
115it, you should treat it as such.</p> 170it, you should treat it as such.</p>
116 171
117
118
119
120
121</div> 172</div>
122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
123<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
125library in any way.</p> 176library in any way.</p>
126<dl> 177<dl>
127 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
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140version of the library your program was compiled against.</p> 191version of the library your program was compiled against.</p>
141 <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,
142as this indicates an incompatible change. Minor versions are usually 193as this indicates an incompatible change. Minor versions are usually
143compatible to older versions, so a larger minor version alone is usually 194compatible to older versions, so a larger minor version alone is usually
144not a problem.</p> 195not a problem.</p>
145 <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
146version:</p> 197version.</p>
147<pre> assert ((&quot;libev version mismatch&quot;, 198<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR 199 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 200 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150 201
151</pre> 202</pre>
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181recommended ones.</p> 232recommended ones.</p>
182 <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>
183 </dd> 234 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
185 <dd> 236 <dd>
186 <p>Sets the allocation function to use (the prototype is similar to the 237 <p>Sets the allocation function to use (the prototype is similar - the
187realloc C function, the semantics are identical). It is used to allocate 238semantics is identical - to the realloc C function). It is used to
188and free memory (no surprises here). If it returns zero when memory 239allocate and free memory (no surprises here). If it returns zero when
189needs to be allocated, the library might abort or take some potentially 240memory needs to be allocated, the library might abort or take some
190destructive action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
191 <p>You could override this function in high-availability programs to, say, 243 <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, 244free 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> 245or 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 246 <p>Example: Replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p> 247retries).</p>
196<pre> static void * 248<pre> static void *
197 persistent_realloc (void *ptr, long size) 249 persistent_realloc (void *ptr, size_t size)
198 { 250 {
199 for (;;) 251 for (;;)
200 { 252 {
201 void *newptr = realloc (ptr, size); 253 void *newptr = realloc (ptr, size);
202 254
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219indicating the system call or subsystem causing the problem. If this 271indicating the system call or subsystem causing the problem. If this
220callback is set, then libev will expect it to remedy the sitution, no 272callback is set, then libev will expect it to remedy the sitution, no
221matter what, when it returns. That is, libev will generally retry the 273matter what, when it returns. That is, libev will generally retry the
222requested operation, or, if the condition doesn't go away, do bad stuff 274requested operation, or, if the condition doesn't go away, do bad stuff
223(such as abort).</p> 275(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p> 276 <p>Example: This is basically the same thing that libev does internally, too.</p>
225<pre> static void 277<pre> static void
226 fatal_error (const char *msg) 278 fatal_error (const char *msg)
227 { 279 {
228 perror (msg); 280 perror (msg);
229 abort (); 281 abort ();
… …
235</pre> 287</pre>
236 </dd> 288 </dd>
237</dl> 289</dl>
238 290
239</div> 291</div>
240<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 292<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
241<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 293<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 294<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 295types of such loops, the <i>default</i> loop, which supports signals and child
244events, and dynamically created loops which do not.</p> 296events, and dynamically created loops which do not.</p>
245<p>If you use threads, a common model is to run the default event loop 297<p>If you use threads, a common model is to run the default event loop
… …
365 <dd> 417 <dd>
366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 418 <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 419always 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 420handle signal and child watchers, and attempts to do so will be greeted by
369undefined behaviour (or a failed assertion if assertions are enabled).</p> 421undefined 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> 422 <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); 423<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller) 424 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 425 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374 426
375</pre> 427</pre>
… …
468 be handled here by queueing them when their watcher gets executed. 520 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 521 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *. 522 were used, return, otherwise continue with step *.
471 523
472</pre> 524</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding 525 <p>Example: Queue some jobs and then loop until no events are outsanding
474anymore.</p> 526anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long 527<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..) 528 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0); 529 ev_loop (my_loop, 0);
478 ... jobs done. yeah! 530 ... jobs done. yeah!
… …
497example, libev itself uses this for its internal signal pipe: It is not 549example, 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 550visible 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 551no 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 552way 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> 553libraries. 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> 554 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p> 555running when nothing else is active.</p>
504<pre> struct dv_signal exitsig; 556<pre> struct ev_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 557 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig); 558 ev_signal_start (loop, &amp;exitsig);
507 evf_unref (myloop); 559 evf_unref (loop);
508 560
509</pre> 561</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p> 562 <p>Example: For some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop); 563<pre> ev_ref (loop);
512 ev_signal_stop (myloop, &amp;exitsig); 564 ev_signal_stop (loop, &amp;exitsig);
513 565
514</pre> 566</pre>
515 </dd> 567 </dd>
516</dl> 568</dl>
517 569
518 570
519 571
520 572
521 573
522</div> 574</div>
523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 575<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
524<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 576<div id="ANATOMY_OF_A_WATCHER_CONTENT">
525<p>A watcher is a structure that you create and register to record your 577<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 578interest 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> 579become 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) 580<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
585 </dd> 637 </dd>
586 <dt><code>EV_CHILD</code></dt> 638 <dt><code>EV_CHILD</code></dt>
587 <dd> 639 <dd>
588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 640 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
589 </dd> 641 </dd>
642 <dt><code>EV_STAT</code></dt>
643 <dd>
644 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
645 </dd>
590 <dt><code>EV_IDLE</code></dt> 646 <dt><code>EV_IDLE</code></dt>
591 <dd> 647 <dd>
592 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 648 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
593 </dd> 649 </dd>
594 <dt><code>EV_PREPARE</code></dt> 650 <dt><code>EV_PREPARE</code></dt>
… …
599<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 655<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 656received 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 657many 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 658(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
603<code>ev_loop</code> from blocking).</p> 659<code>ev_loop</code> from blocking).</p>
660 </dd>
661 <dt><code>EV_EMBED</code></dt>
662 <dd>
663 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
664 </dd>
665 <dt><code>EV_FORK</code></dt>
666 <dd>
667 <p>The event loop has been resumed in the child process after fork (see
668<code>ev_fork</code>).</p>
604 </dd> 669 </dd>
605 <dt><code>EV_ERROR</code></dt> 670 <dt><code>EV_ERROR</code></dt>
606 <dd> 671 <dd>
607 <p>An unspecified error has occured, the watcher has been stopped. This might 672 <p>An unspecified error has occured, the watcher has been stopped. This might
608happen because the watcher could not be properly started because libev 673happen because the watcher could not be properly started because libev
… …
678events but its callback has not yet been invoked). As long as a watcher 743events 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 744is 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 745<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> 746libev (e.g. you cnanot <code>free ()</code> it).</p>
682 </dd> 747 </dd>
683 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 748 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
684 <dd> 749 <dd>
685 <p>Returns the callback currently set on the watcher.</p> 750 <p>Returns the callback currently set on the watcher.</p>
686 </dd> 751 </dd>
687 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 752 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
688 <dd> 753 <dd>
… …
720 struct my_io *w = (struct my_io *)w_; 785 struct my_io *w = (struct my_io *)w_;
721 ... 786 ...
722 } 787 }
723 788
724</pre> 789</pre>
725<p>More interesting and less C-conformant ways of catsing your callback type 790<p>More interesting and less C-conformant ways of casting your callback type
726have been omitted....</p> 791instead have been omitted.</p>
792<p>Another common scenario is having some data structure with multiple
793watchers:</p>
794<pre> struct my_biggy
795 {
796 int some_data;
797 ev_timer t1;
798 ev_timer t2;
799 }
727 800
801</pre>
802<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
803you need to use <code>offsetof</code>:</p>
804<pre> #include &lt;stddef.h&gt;
728 805
806 static void
807 t1_cb (EV_P_ struct ev_timer *w, int revents)
808 {
809 struct my_biggy big = (struct my_biggy *
810 (((char *)w) - offsetof (struct my_biggy, t1));
811 }
729 812
813 static void
814 t2_cb (EV_P_ struct ev_timer *w, int revents)
815 {
816 struct my_biggy big = (struct my_biggy *
817 (((char *)w) - offsetof (struct my_biggy, t2));
818 }
730 819
731 820
821
822
823</pre>
824
732</div> 825</div>
733<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 826<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
734<div id="WATCHER_TYPES_CONTENT"> 827<div id="WATCHER_TYPES_CONTENT">
735<p>This section describes each watcher in detail, but will not repeat 828<p>This section describes each watcher in detail, but will not repeat
736information given in the last section.</p> 829information given in the last section. Any initialisation/set macros,
830functions and members specific to the watcher type are explained.</p>
831<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
832while the watcher is active, you can look at the member and expect some
833sensible content, but you must not modify it (you can modify it while the
834watcher is stopped to your hearts content), or <i>[read-write]</i>, which
835means you can expect it to have some sensible content while the watcher
836is active, but you can also modify it. Modifying it may not do something
837sensible or take immediate effect (or do anything at all), but libev will
838not crash or malfunction in any way.</p>
737 839
738 840
739 841
740 842
741 843
… …
780 <dd> 882 <dd>
781 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 883 <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 884rceeive 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> 885<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
784 </dd> 886 </dd>
887 <dt>int fd [read-only]</dt>
888 <dd>
889 <p>The file descriptor being watched.</p>
890 </dd>
891 <dt>int events [read-only]</dt>
892 <dd>
893 <p>The events being watched.</p>
894 </dd>
785</dl> 895</dl>
786<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 896<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 897readable, but only once. Since it is likely line-buffered, you could
788attempt to read a whole line in the callback:</p> 898attempt to read a whole line in the callback.</p>
789<pre> static void 899<pre> static void
790 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 900 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
791 { 901 {
792 ev_io_stop (loop, w); 902 ev_io_stop (loop, w);
793 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 903 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
842 </dd> 952 </dd>
843 <dt>ev_timer_again (loop)</dt> 953 <dt>ev_timer_again (loop)</dt>
844 <dd> 954 <dd>
845 <p>This will act as if the timer timed out and restart it again if it is 955 <p>This will act as if the timer timed out and restart it again if it is
846repeating. The exact semantics are:</p> 956repeating. The exact semantics are:</p>
957 <p>If the timer is pending, its pending status is cleared.</p>
847 <p>If the timer is started but nonrepeating, stop it.</p> 958 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
848 <p>If the timer is repeating, either start it if necessary (with the repeat 959 <p>If the timer is repeating, either start it if necessary (with the
849value), or reset the running timer to the repeat value.</p> 960<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
850 <p>This sounds a bit complicated, but here is a useful and typical 961 <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 962example: Imagine you have a tcp connection and you want a so-called idle
852timeout, that is, you want to be called when there have been, say, 60 963timeout, that is, you want to be called when there have been, say, 60
853seconds of inactivity on the socket. The easiest way to do this is to 964seconds of inactivity on the socket. The easiest way to do this is to
854configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 965configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
855time you successfully read or write some data. If you go into an idle 966<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 967you go into an idle state where you do not expect data to travel on the
968socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
857the timer, and again will automatically restart it if need be.</p> 969automatically restart it if need be.</p>
970 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
971altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
972<pre> ev_timer_init (timer, callback, 0., 5.);
973 ev_timer_again (loop, timer);
974 ...
975 timer-&gt;again = 17.;
976 ev_timer_again (loop, timer);
977 ...
978 timer-&gt;again = 10.;
979 ev_timer_again (loop, timer);
980
981</pre>
982 <p>This is more slightly efficient then stopping/starting the timer each time
983you want to modify its timeout value.</p>
984 </dd>
985 <dt>ev_tstamp repeat [read-write]</dt>
986 <dd>
987 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
988or <code>ev_timer_again</code> is called and determines the next timeout (if any),
989which is also when any modifications are taken into account.</p>
858 </dd> 990 </dd>
859</dl> 991</dl>
860<p>Example: create a timer that fires after 60 seconds.</p> 992<p>Example: Create a timer that fires after 60 seconds.</p>
861<pre> static void 993<pre> static void
862 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 994 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
863 { 995 {
864 .. one minute over, w is actually stopped right here 996 .. one minute over, w is actually stopped right here
865 } 997 }
… …
867 struct ev_timer mytimer; 999 struct ev_timer mytimer;
868 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1000 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
869 ev_timer_start (loop, &amp;mytimer); 1001 ev_timer_start (loop, &amp;mytimer);
870 1002
871</pre> 1003</pre>
872<p>Example: create a timeout timer that times out after 10 seconds of 1004<p>Example: Create a timeout timer that times out after 10 seconds of
873inactivity.</p> 1005inactivity.</p>
874<pre> static void 1006<pre> static void
875 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1007 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
876 { 1008 {
877 .. ten seconds without any activity 1009 .. ten seconds without any activity
… …
980 <p>Simply stops and restarts the periodic watcher again. This is only useful 1112 <p>Simply stops and restarts the periodic watcher again. This is only useful
981when you changed some parameters or the reschedule callback would return 1113when 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 1114a different time than the last time it was called (e.g. in a crond like
983program when the crontabs have changed).</p> 1115program when the crontabs have changed).</p>
984 </dd> 1116 </dd>
1117 <dt>ev_tstamp interval [read-write]</dt>
1118 <dd>
1119 <p>The current interval value. Can be modified any time, but changes only
1120take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1121called.</p>
1122 </dd>
1123 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1124 <dd>
1125 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1126switched off. Can be changed any time, but changes only take effect when
1127the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1128 </dd>
985</dl> 1129</dl>
986<p>Example: call a callback every hour, or, more precisely, whenever the 1130<p>Example: Call a callback every hour, or, more precisely, whenever the
987system clock is divisible by 3600. The callback invocation times have 1131system clock is divisible by 3600. The callback invocation times have
988potentially a lot of jittering, but good long-term stability.</p> 1132potentially a lot of jittering, but good long-term stability.</p>
989<pre> static void 1133<pre> static void
990 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1134 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
991 { 1135 {
… …
995 struct ev_periodic hourly_tick; 1139 struct ev_periodic hourly_tick;
996 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1140 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
997 ev_periodic_start (loop, &amp;hourly_tick); 1141 ev_periodic_start (loop, &amp;hourly_tick);
998 1142
999</pre> 1143</pre>
1000<p>Example: the same as above, but use a reschedule callback to do it:</p> 1144<p>Example: The same as above, but use a reschedule callback to do it:</p>
1001<pre> #include &lt;math.h&gt; 1145<pre> #include &lt;math.h&gt;
1002 1146
1003 static ev_tstamp 1147 static ev_tstamp
1004 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1148 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1005 { 1149 {
… …
1007 } 1151 }
1008 1152
1009 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1153 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1010 1154
1011</pre> 1155</pre>
1012<p>Example: call a callback every hour, starting now:</p> 1156<p>Example: Call a callback every hour, starting now:</p>
1013<pre> struct ev_periodic hourly_tick; 1157<pre> struct ev_periodic hourly_tick;
1014 ev_periodic_init (&amp;hourly_tick, clock_cb, 1158 ev_periodic_init (&amp;hourly_tick, clock_cb,
1015 fmod (ev_now (loop), 3600.), 3600., 0); 1159 fmod (ev_now (loop), 3600.), 3600., 0);
1016 ev_periodic_start (loop, &amp;hourly_tick); 1160 ev_periodic_start (loop, &amp;hourly_tick);
1017 1161
… …
1038 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1182 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1039 <dd> 1183 <dd>
1040 <p>Configures the watcher to trigger on the given signal number (usually one 1184 <p>Configures the watcher to trigger on the given signal number (usually one
1041of the <code>SIGxxx</code> constants).</p> 1185of the <code>SIGxxx</code> constants).</p>
1042 </dd> 1186 </dd>
1187 <dt>int signum [read-only]</dt>
1188 <dd>
1189 <p>The signal the watcher watches out for.</p>
1190 </dd>
1043</dl> 1191</dl>
1044 1192
1045 1193
1046 1194
1047 1195
… …
1060at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1208at 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 1209the 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 1210<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1063process causing the status change.</p> 1211process causing the status change.</p>
1064 </dd> 1212 </dd>
1213 <dt>int pid [read-only]</dt>
1214 <dd>
1215 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1216 </dd>
1217 <dt>int rpid [read-write]</dt>
1218 <dd>
1219 <p>The process id that detected a status change.</p>
1220 </dd>
1221 <dt>int rstatus [read-write]</dt>
1222 <dd>
1223 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1224<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1225 </dd>
1065</dl> 1226</dl>
1066<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1227<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1067<pre> static void 1228<pre> static void
1068 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1229 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1069 { 1230 {
1070 ev_unloop (loop, EVUNLOOP_ALL); 1231 ev_unloop (loop, EVUNLOOP_ALL);
1071 } 1232 }
1072 1233
1073 struct ev_signal signal_watcher; 1234 struct ev_signal signal_watcher;
1074 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT); 1235 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1075 ev_signal_start (loop, &amp;sigint_cb); 1236 ev_signal_start (loop, &amp;sigint_cb);
1237
1238
1239
1240
1241</pre>
1242
1243</div>
1244<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1245<div id="code_ev_stat_code_did_the_file_attri-2">
1246<p>This watches a filesystem path for attribute changes. That is, it calls
1247<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1248compared to the last time, invoking the callback if it did.</p>
1249<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1250not exist&quot; is a status change like any other. The condition &quot;path does
1251not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1252otherwise always forced to be at least one) and all the other fields of
1253the stat buffer having unspecified contents.</p>
1254<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1255relative and your working directory changes, the behaviour is undefined.</p>
1256<p>Since there is no standard to do this, the portable implementation simply
1257calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1258can specify a recommended polling interval for this case. If you specify
1259a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1260unspecified default</i> value will be used (which you can expect to be around
1261five seconds, although this might change dynamically). Libev will also
1262impose a minimum interval which is currently around <code>0.1</code>, but thats
1263usually overkill.</p>
1264<p>This watcher type is not meant for massive numbers of stat watchers,
1265as even with OS-supported change notifications, this can be
1266resource-intensive.</p>
1267<p>At the time of this writing, only the Linux inotify interface is
1268implemented (implementing kqueue support is left as an exercise for the
1269reader). Inotify will be used to give hints only and should not change the
1270semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1271to fall back to regular polling again even with inotify, but changes are
1272usually detected immediately, and if the file exists there will be no
1273polling.</p>
1274<dl>
1275 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1276 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1277 <dd>
1278 <p>Configures the watcher to wait for status changes of the given
1279<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1280be detected and should normally be specified as <code>0</code> to let libev choose
1281a suitable value. The memory pointed to by <code>path</code> must point to the same
1282path for as long as the watcher is active.</p>
1283 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1284relative to the attributes at the time the watcher was started (or the
1285last change was detected).</p>
1286 </dd>
1287 <dt>ev_stat_stat (ev_stat *)</dt>
1288 <dd>
1289 <p>Updates the stat buffer immediately with new values. If you change the
1290watched path in your callback, you could call this fucntion to avoid
1291detecting this change (while introducing a race condition). Can also be
1292useful simply to find out the new values.</p>
1293 </dd>
1294 <dt>ev_statdata attr [read-only]</dt>
1295 <dd>
1296 <p>The most-recently detected attributes of the file. Although the type is of
1297<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1298suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1299was some error while <code>stat</code>ing the file.</p>
1300 </dd>
1301 <dt>ev_statdata prev [read-only]</dt>
1302 <dd>
1303 <p>The previous attributes of the file. The callback gets invoked whenever
1304<code>prev</code> != <code>attr</code>.</p>
1305 </dd>
1306 <dt>ev_tstamp interval [read-only]</dt>
1307 <dd>
1308 <p>The specified interval.</p>
1309 </dd>
1310 <dt>const char *path [read-only]</dt>
1311 <dd>
1312 <p>The filesystem path that is being watched.</p>
1313 </dd>
1314</dl>
1315<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1316<pre> static void
1317 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1318 {
1319 /* /etc/passwd changed in some way */
1320 if (w-&gt;attr.st_nlink)
1321 {
1322 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1323 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1324 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1325 }
1326 else
1327 /* you shalt not abuse printf for puts */
1328 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1329 &quot;if this is windows, they already arrived\n&quot;);
1330 }
1331
1332 ...
1333 ev_stat passwd;
1334
1335 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1336 ev_stat_start (loop, &amp;passwd);
1076 1337
1077 1338
1078 1339
1079 1340
1080</pre> 1341</pre>
… …
1101 <p>Initialises and configures the idle watcher - it has no parameters of any 1362 <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, 1363kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1103believe me.</p> 1364believe me.</p>
1104 </dd> 1365 </dd>
1105</dl> 1366</dl>
1106<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1367<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> 1368callback, free it. Also, use no error checking, as usual.</p>
1108<pre> static void 1369<pre> static void
1109 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1370 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1110 { 1371 {
1111 free (w); 1372 free (w);
1112 // now do something you wanted to do when the program has 1373 // now do something you wanted to do when the program has
… …
1176 1437
1177 static void 1438 static void
1178 io_cb (ev_loop *loop, ev_io *w, int revents) 1439 io_cb (ev_loop *loop, ev_io *w, int revents)
1179 { 1440 {
1180 // set the relevant poll flags 1441 // set the relevant poll flags
1442 // could also call adns_processreadable etc. here
1181 struct pollfd *fd = (struct pollfd *)w-&gt;data; 1443 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1182 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN; 1444 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1183 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT; 1445 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1184 } 1446 }
1185 1447
… …
1302 <dd> 1564 <dd>
1303 <p>Make a single, non-blocking sweep over the embedded loop. This works 1565 <p>Make a single, non-blocking sweep over the embedded loop. This works
1304similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1566similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1305apropriate way for embedded loops.</p> 1567apropriate way for embedded loops.</p>
1306 </dd> 1568 </dd>
1569 <dt>struct ev_loop *loop [read-only]</dt>
1570 <dd>
1571 <p>The embedded event loop.</p>
1572 </dd>
1307</dl> 1573</dl>
1308 1574
1309 1575
1310 1576
1311 1577
1312 1578
1313</div> 1579</div>
1314<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1580<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>
1581<div id="code_ev_fork_code_the_audacity_to_re-2">
1582<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1583whoever is a good citizen cared to tell libev about it by calling
1584<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1585event loop blocks next and before <code>ev_check</code> watchers are being called,
1586and only in the child after the fork. If whoever good citizen calling
1587<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1588handlers will be invoked, too, of course.</p>
1589<dl>
1590 <dt>ev_fork_init (ev_signal *, callback)</dt>
1591 <dd>
1592 <p>Initialises and configures the fork watcher - it has no parameters of any
1593kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1594believe me.</p>
1595 </dd>
1596</dl>
1597
1598
1599
1600
1601
1602</div>
1603<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1315<div id="OTHER_FUNCTIONS_CONTENT"> 1604<div id="OTHER_FUNCTIONS_CONTENT">
1316<p>There are some other functions of possible interest. Described. Here. Now.</p> 1605<p>There are some other functions of possible interest. Described. Here. Now.</p>
1317<dl> 1606<dl>
1318 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1607 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1319 <dd> 1608 <dd>
… …
1366 1655
1367 1656
1368 1657
1369 1658
1370</div> 1659</div>
1371<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1660<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1372<div id="LIBEVENT_EMULATION_CONTENT"> 1661<div id="LIBEVENT_EMULATION_CONTENT">
1373<p>Libev offers a compatibility emulation layer for libevent. It cannot 1662<p>Libev offers a compatibility emulation layer for libevent. It cannot
1374emulate the internals of libevent, so here are some usage hints:</p> 1663emulate the internals of libevent, so here are some usage hints:</p>
1375<dl> 1664<dl>
1376 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1665 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1386 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1675 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1387to use the libev header file and library.</dt> 1676to use the libev header file and library.</dt>
1388</dl> 1677</dl>
1389 1678
1390</div> 1679</div>
1391<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1680<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1392<div id="C_SUPPORT_CONTENT"> 1681<div id="C_SUPPORT_CONTENT">
1393<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1682<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1394you to use some convinience methods to start/stop watchers and also change 1683you to use some convinience methods to start/stop watchers and also change
1395the callback model to a model using method callbacks on objects.</p> 1684the callback model to a model using method callbacks on objects.</p>
1396<p>To use it,</p> 1685<p>To use it,</p>
… …
1460 </dd> 1749 </dd>
1461 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1750 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1462 <dd> 1751 <dd>
1463 <p>Invokes <code>ev_embed_sweep</code>.</p> 1752 <p>Invokes <code>ev_embed_sweep</code>.</p>
1464 </dd> 1753 </dd>
1754 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1755 <dd>
1756 <p>Invokes <code>ev_stat_stat</code>.</p>
1757 </dd>
1465 </dl> 1758 </dl>
1466 </p> 1759 </p>
1467 </dd> 1760 </dd>
1468</dl> 1761</dl>
1469<p>Example: Define a class with an IO and idle watcher, start one of them in 1762<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1481 idle (this, &amp;myclass::idle_cb) 1774 idle (this, &amp;myclass::idle_cb)
1482 { 1775 {
1483 io.start (fd, ev::READ); 1776 io.start (fd, ev::READ);
1484 } 1777 }
1485 1778
1486</pre>
1487 1779
1780
1781
1782</pre>
1783
1488</div> 1784</div>
1489<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1785<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1786<div id="MACRO_MAGIC_CONTENT">
1787<p>Libev can be compiled with a variety of options, the most fundemantal is
1788<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1789callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1790<p>To make it easier to write programs that cope with either variant, the
1791following macros are defined:</p>
1792<dl>
1793 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1794 <dd>
1795 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1796loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1797<code>EV_A_</code> is used when other arguments are following. Example:</p>
1798<pre> ev_unref (EV_A);
1799 ev_timer_add (EV_A_ watcher);
1800 ev_loop (EV_A_ 0);
1801
1802</pre>
1803 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1804which is often provided by the following macro.</p>
1805 </dd>
1806 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1807 <dd>
1808 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1809loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1810<code>EV_P_</code> is used when other parameters are following. Example:</p>
1811<pre> // this is how ev_unref is being declared
1812 static void ev_unref (EV_P);
1813
1814 // this is how you can declare your typical callback
1815 static void cb (EV_P_ ev_timer *w, int revents)
1816
1817</pre>
1818 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1819suitable for use with <code>EV_A</code>.</p>
1820 </dd>
1821 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1822 <dd>
1823 <p>Similar to the other two macros, this gives you the value of the default
1824loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1825 </dd>
1826</dl>
1827<p>Example: Declare and initialise a check watcher, working regardless of
1828wether multiple loops are supported or not.</p>
1829<pre> static void
1830 check_cb (EV_P_ ev_timer *w, int revents)
1831 {
1832 ev_check_stop (EV_A_ w);
1833 }
1834
1835 ev_check check;
1836 ev_check_init (&amp;check, check_cb);
1837 ev_check_start (EV_DEFAULT_ &amp;check);
1838 ev_loop (EV_DEFAULT_ 0);
1839
1840
1841
1842
1843</pre>
1844
1845</div>
1846<h1 id="EMBEDDING">EMBEDDING</h1>
1490<div id="EMBEDDING_CONTENT"> 1847<div id="EMBEDDING_CONTENT">
1491<p>Libev can (and often is) directly embedded into host 1848<p>Libev can (and often is) directly embedded into host
1492applications. Examples of applications that embed it include the Deliantra 1849applications. Examples of applications that embed it include the Deliantra
1493Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1850Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1494and rxvt-unicode.</p> 1851and rxvt-unicode.</p>
… …
1668 </dd> 2025 </dd>
1669 <dt>EV_USE_DEVPOLL</dt> 2026 <dt>EV_USE_DEVPOLL</dt>
1670 <dd> 2027 <dd>
1671 <p>reserved for future expansion, works like the USE symbols above.</p> 2028 <p>reserved for future expansion, works like the USE symbols above.</p>
1672 </dd> 2029 </dd>
2030 <dt>EV_USE_INOTIFY</dt>
2031 <dd>
2032 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2033interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2034be detected at runtime.</p>
2035 </dd>
1673 <dt>EV_H</dt> 2036 <dt>EV_H</dt>
1674 <dd> 2037 <dd>
1675 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2038 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1676undefined 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 2039undefined 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
1677can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2040can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1700will have the <code>struct ev_loop *</code> as first argument, and you can create 2063will have the <code>struct ev_loop *</code> as first argument, and you can create
1701additional independent event loops. Otherwise there will be no support 2064additional independent event loops. Otherwise there will be no support
1702for multiple event loops and there is no first event loop pointer 2065for multiple event loops and there is no first event loop pointer
1703argument. Instead, all functions act on the single default loop.</p> 2066argument. Instead, all functions act on the single default loop.</p>
1704 </dd> 2067 </dd>
1705 <dt>EV_PERIODICS</dt> 2068 <dt>EV_PERIODIC_ENABLE</dt>
1706 <dd> 2069 <dd>
1707 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2070 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1708otherwise not. This saves a few kb of code.</p> 2071defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2072code.</p>
2073 </dd>
2074 <dt>EV_EMBED_ENABLE</dt>
2075 <dd>
2076 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2077defined to be <code>0</code>, then they are not.</p>
2078 </dd>
2079 <dt>EV_STAT_ENABLE</dt>
2080 <dd>
2081 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2082defined to be <code>0</code>, then they are not.</p>
2083 </dd>
2084 <dt>EV_FORK_ENABLE</dt>
2085 <dd>
2086 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2087defined to be <code>0</code>, then they are not.</p>
2088 </dd>
2089 <dt>EV_MINIMAL</dt>
2090 <dd>
2091 <p>If you need to shave off some kilobytes of code at the expense of some
2092speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2093some inlining decisions, saves roughly 30% codesize of amd64.</p>
2094 </dd>
2095 <dt>EV_PID_HASHSIZE</dt>
2096 <dd>
2097 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2098pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2099than enough. If you need to manage thousands of children you might want to
2100increase this value (<i>must</i> be a power of two).</p>
2101 </dd>
2102 <dt>EV_INOTIFY_HASHSIZE</dt>
2103 <dd>
2104 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2105inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2106usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2107watchers you might want to increase this value (<i>must</i> be a power of
2108two).</p>
1709 </dd> 2109 </dd>
1710 <dt>EV_COMMON</dt> 2110 <dt>EV_COMMON</dt>
1711 <dd> 2111 <dd>
1712 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2112 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1713this macro to a something else you can include more and other types of 2113this macro to a something else you can include more and other types of
… …
1753</pre> 2153</pre>
1754 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2154 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1755<pre> #include &quot;ev_cpp.h&quot; 2155<pre> #include &quot;ev_cpp.h&quot;
1756 #include &quot;ev.c&quot; 2156 #include &quot;ev.c&quot;
1757 2157
1758</pre>
1759 2158
2159
2160
2161</pre>
2162
1760</div> 2163</div>
1761<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2164<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2165<div id="COMPLEXITIES_CONTENT">
2166 <p>In this section the complexities of (many of) the algorithms used inside
2167libev will be explained. For complexity discussions about backends see the
2168documentation for <code>ev_default_init</code>.</p>
2169 <p>
2170 <dl>
2171 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2172 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2173 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2174 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2175 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2176 <dt>Finding the next timer per loop iteration: O(1)</dt>
2177 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2178 <dt>Activating one watcher: O(1)</dt>
2179 </dl>
2180 </p>
2181
2182
2183
2184
2185
2186</div>
2187<h1 id="AUTHOR">AUTHOR</h1>
1762<div id="AUTHOR_CONTENT"> 2188<div id="AUTHOR_CONTENT">
1763 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2189 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1764 2190
1765</div> 2191</div>
1766</div></body> 2192</div></body>

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