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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Sat Nov 24 08:13:46 2007" /> 9 <meta name="created" content="Tue Nov 27 21:26:46 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
15<h3 id="TOP">Index</h3> 15<h3 id="TOP">Index</h3>
16 16
17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 20<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 21<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 22<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 23<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 24<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 25<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 26<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
26<ul><li><a href="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</a></li> 27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
27<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
28</ul> 29</ul>
29</li> 30</li>
30<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
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 recurring timeouts</a></li> 33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
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_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
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>
48<li><a href="#EMBEDDING">EMBEDDING</a>
49<ul><li><a href="#FILESETS">FILESETS</a>
50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
53</ul>
54</li>
55<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
56<li><a href="#EXAMPLES">EXAMPLES</a></li>
57</ul>
58</li>
59<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
44<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
45</li> 61</li>
46</ul><hr /> 62</ul><hr />
47<!-- INDEX END --> 63<!-- INDEX END -->
48 64
… …
52 68
53</div> 69</div>
54<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>
55<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
56<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
73
74</pre>
75
76</div>
77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1><p><a href="#TOP" class="toplink">Top</a></p>
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 }
57 118
58</pre> 119</pre>
59 120
60</div> 121</div>
61<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 122<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
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72watcher.</p> 133watcher.</p>
73 134
74</div> 135</div>
75<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>
76<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
77<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
78kqueue mechanisms for file descriptor events, relative timers, absolute 139bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms
79timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>),
80events (related to SIGCHLD), and event watchers dealing with the event 141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous
81loop mechanism itself (idle, prepare and check watchers). It also is quite 142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and
143event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
144<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
145file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this
82fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
83it to libevent for example).</p> 149for example).</p>
84 150
85</div> 151</div>
86<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 152<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
87<div id="CONVENTIONS_CONTENT"> 153<div id="CONVENTIONS_CONTENT">
88<p>Libev is very configurable. In this manual the default configuration 154<p>Libev is very configurable. In this manual the default configuration will
89will be described, which supports multiple event loops. For more info 155be described, which supports multiple event loops. For more info about
90about various configuration options please have a look at the file 156various configuration options please have a look at <strong>EMBED</strong> section in
91<cite>README.embed</cite> in the libev distribution. If libev was configured without 157this manual. If libev was configured without support for multiple event
92support for multiple event loops, then all functions taking an initial 158loops, then all functions taking an initial argument of name <code>loop</code>
93argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 159(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
94will not have this argument.</p>
95 160
96</div> 161</div>
97<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 162<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
98<div id="TIME_REPRESENTATION_CONTENT"> 163<div id="TIME_REPRESENTATION_CONTENT">
99<p>Libev represents time as a single floating point number, representing the 164<p>Libev represents time as a single floating point number, representing the
100(fractional) number of seconds since the (POSIX) epoch (somewhere near 165(fractional) number of seconds since the (POSIX) epoch (somewhere near
101the beginning of 1970, details are complicated, don't ask). This type is 166the beginning of 1970, details are complicated, don't ask). This type is
102called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 167called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
103to the <code>double</code> type in C, and when you need to do any calculations on 168to the <code>double</code> type in C, and when you need to do any calculations on
104it, you should treat it as such.</p> 169it, you should treat it as such.</p>
105
106
107
108
109 170
110</div> 171</div>
111<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 172<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
112<div id="GLOBAL_FUNCTIONS_CONTENT"> 173<div id="GLOBAL_FUNCTIONS_CONTENT">
113<p>These functions can be called anytime, even before initialising the 174<p>These functions can be called anytime, even before initialising the
… …
129version of the library your program was compiled against.</p> 190version of the library your program was compiled against.</p>
130 <p>Usually, it's a good idea to terminate if the major versions mismatch, 191 <p>Usually, it's a good idea to terminate if the major versions mismatch,
131as this indicates an incompatible change. Minor versions are usually 192as this indicates an incompatible change. Minor versions are usually
132compatible to older versions, so a larger minor version alone is usually 193compatible to older versions, so a larger minor version alone is usually
133not a problem.</p> 194not a problem.</p>
134 <p>Example: make sure we haven't accidentally been linked against the wrong 195 <p>Example: Make sure we haven't accidentally been linked against the wrong
135version:</p> 196version.</p>
136<pre> assert ((&quot;libev version mismatch&quot;, 197<pre> assert ((&quot;libev version mismatch&quot;,
137 ev_version_major () == EV_VERSION_MAJOR 198 ev_version_major () == EV_VERSION_MAJOR
138 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 199 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
139 200
140</pre> 201</pre>
… …
168might be supported on the current system, you would need to look at 229might be supported on the current system, you would need to look at
169<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
170recommended ones.</p> 231recommended ones.</p>
171 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 232 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
172 </dd> 233 </dd>
173 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
174 <dd> 235 <dd>
175 <p>Sets the allocation function to use (the prototype is similar to the 236 <p>Sets the allocation function to use (the prototype and semantics are
176realloc C function, the semantics are identical). It is used to allocate 237identical to the realloc C function). It is used to allocate and free
177and free memory (no surprises here). If it returns zero when memory 238memory (no surprises here). If it returns zero when memory needs to be
178needs to be allocated, the library might abort or take some potentially 239allocated, the library might abort or take some potentially destructive
179destructive action. The default is your system realloc function.</p> 240action. The default is your system realloc function.</p>
180 <p>You could override this function in high-availability programs to, say, 241 <p>You could override this function in high-availability programs to, say,
181free some memory if it cannot allocate memory, to use a special allocator, 242free some memory if it cannot allocate memory, to use a special allocator,
182or even to sleep a while and retry until some memory is available.</p> 243or even to sleep a while and retry until some memory is available.</p>
183 <p>Example: replace the libev allocator with one that waits a bit and then 244 <p>Example: Replace the libev allocator with one that waits a bit and then
184retries: better than mine).</p> 245retries).</p>
185<pre> static void * 246<pre> static void *
186 persistent_realloc (void *ptr, long size) 247 persistent_realloc (void *ptr, size_t size)
187 { 248 {
188 for (;;) 249 for (;;)
189 { 250 {
190 void *newptr = realloc (ptr, size); 251 void *newptr = realloc (ptr, size);
191 252
… …
208indicating the system call or subsystem causing the problem. If this 269indicating the system call or subsystem causing the problem. If this
209callback is set, then libev will expect it to remedy the sitution, no 270callback is set, then libev will expect it to remedy the sitution, no
210matter what, when it returns. That is, libev will generally retry the 271matter what, when it returns. That is, libev will generally retry the
211requested operation, or, if the condition doesn't go away, do bad stuff 272requested operation, or, if the condition doesn't go away, do bad stuff
212(such as abort).</p> 273(such as abort).</p>
213 <p>Example: do the same thing as libev does internally:</p> 274 <p>Example: This is basically the same thing that libev does internally, too.</p>
214<pre> static void 275<pre> static void
215 fatal_error (const char *msg) 276 fatal_error (const char *msg)
216 { 277 {
217 perror (msg); 278 perror (msg);
218 abort (); 279 abort ();
… …
354 <dd> 415 <dd>
355 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 416 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
356always distinct from the default loop. Unlike the default loop, it cannot 417always distinct from the default loop. Unlike the default loop, it cannot
357handle signal and child watchers, and attempts to do so will be greeted by 418handle signal and child watchers, and attempts to do so will be greeted by
358undefined behaviour (or a failed assertion if assertions are enabled).</p> 419undefined behaviour (or a failed assertion if assertions are enabled).</p>
359 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 420 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
360<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 421<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
361 if (!epoller) 422 if (!epoller)
362 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 423 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
363 424
364</pre> 425</pre>
365 </dd> 426 </dd>
366 <dt>ev_default_destroy ()</dt> 427 <dt>ev_default_destroy ()</dt>
367 <dd> 428 <dd>
368 <p>Destroys the default loop again (frees all memory and kernel state 429 <p>Destroys the default loop again (frees all memory and kernel state
369etc.). This stops all registered event watchers (by not touching them in 430etc.). None of the active event watchers will be stopped in the normal
370any way whatsoever, although you cannot rely on this :).</p> 431sense, so e.g. <code>ev_is_active</code> might still return true. It is your
432responsibility to either stop all watchers cleanly yoursef <i>before</i>
433calling this function, or cope with the fact afterwards (which is usually
434the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
435for example).</p>
371 </dd> 436 </dd>
372 <dt>ev_loop_destroy (loop)</dt> 437 <dt>ev_loop_destroy (loop)</dt>
373 <dd> 438 <dd>
374 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 439 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
375earlier call to <code>ev_loop_new</code>.</p> 440earlier call to <code>ev_loop_new</code>.</p>
… …
453 be handled here by queueing them when their watcher gets executed. 518 be handled here by queueing them when their watcher gets executed.
454 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 519 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
455 were used, return, otherwise continue with step *. 520 were used, return, otherwise continue with step *.
456 521
457</pre> 522</pre>
458 <p>Example: queue some jobs and then loop until no events are outsanding 523 <p>Example: Queue some jobs and then loop until no events are outsanding
459anymore.</p> 524anymore.</p>
460<pre> ... queue jobs here, make sure they register event watchers as long 525<pre> ... queue jobs here, make sure they register event watchers as long
461 ... as they still have work to do (even an idle watcher will do..) 526 ... as they still have work to do (even an idle watcher will do..)
462 ev_loop (my_loop, 0); 527 ev_loop (my_loop, 0);
463 ... jobs done. yeah! 528 ... jobs done. yeah!
… …
482example, libev itself uses this for its internal signal pipe: It is not 547example, libev itself uses this for its internal signal pipe: It is not
483visible to the libev user and should not keep <code>ev_loop</code> from exiting if 548visible to the libev user and should not keep <code>ev_loop</code> from exiting if
484no event watchers registered by it are active. It is also an excellent 549no event watchers registered by it are active. It is also an excellent
485way to do this for generic recurring timers or from within third-party 550way to do this for generic recurring timers or from within third-party
486libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 551libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
487 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 552 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
488running when nothing else is active.</p> 553running when nothing else is active.</p>
489<pre> struct dv_signal exitsig; 554<pre> struct ev_signal exitsig;
490 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 555 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
491 ev_signal_start (myloop, &amp;exitsig); 556 ev_signal_start (loop, &amp;exitsig);
492 evf_unref (myloop); 557 evf_unref (loop);
493 558
494</pre> 559</pre>
495 <p>Example: for some weird reason, unregister the above signal handler again.</p> 560 <p>Example: For some weird reason, unregister the above signal handler again.</p>
496<pre> ev_ref (myloop); 561<pre> ev_ref (loop);
497 ev_signal_stop (myloop, &amp;exitsig); 562 ev_signal_stop (loop, &amp;exitsig);
498 563
499</pre> 564</pre>
500 </dd> 565 </dd>
501</dl> 566</dl>
567
568
569
570
502 571
503</div> 572</div>
504<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 573<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
505<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 574<div id="ANATOMY_OF_A_WATCHER_CONTENT">
506<p>A watcher is a structure that you create and register to record your 575<p>A watcher is a structure that you create and register to record your
… …
566 </dd> 635 </dd>
567 <dt><code>EV_CHILD</code></dt> 636 <dt><code>EV_CHILD</code></dt>
568 <dd> 637 <dd>
569 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 638 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
570 </dd> 639 </dd>
640 <dt><code>EV_STAT</code></dt>
641 <dd>
642 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
643 </dd>
571 <dt><code>EV_IDLE</code></dt> 644 <dt><code>EV_IDLE</code></dt>
572 <dd> 645 <dd>
573 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 646 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
574 </dd> 647 </dd>
575 <dt><code>EV_PREPARE</code></dt> 648 <dt><code>EV_PREPARE</code></dt>
… …
580<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 653<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
581received events. Callbacks of both watcher types can start and stop as 654received events. Callbacks of both watcher types can start and stop as
582many watchers as they want, and all of them will be taken into account 655many watchers as they want, and all of them will be taken into account
583(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 656(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
584<code>ev_loop</code> from blocking).</p> 657<code>ev_loop</code> from blocking).</p>
658 </dd>
659 <dt><code>EV_EMBED</code></dt>
660 <dd>
661 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
662 </dd>
663 <dt><code>EV_FORK</code></dt>
664 <dd>
665 <p>The event loop has been resumed in the child process after fork (see
666<code>ev_fork</code>).</p>
585 </dd> 667 </dd>
586 <dt><code>EV_ERROR</code></dt> 668 <dt><code>EV_ERROR</code></dt>
587 <dd> 669 <dd>
588 <p>An unspecified error has occured, the watcher has been stopped. This might 670 <p>An unspecified error has occured, the watcher has been stopped. This might
589happen because the watcher could not be properly started because libev 671happen because the watcher could not be properly started because libev
… …
597programs, though, so beware.</p> 679programs, though, so beware.</p>
598 </dd> 680 </dd>
599</dl> 681</dl>
600 682
601</div> 683</div>
602<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2> 684<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
603<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2"> 685<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
604<p>In the following description, <code>TYPE</code> stands for the watcher type, 686<p>In the following description, <code>TYPE</code> stands for the watcher type,
605e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> 687e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
606<dl> 688<dl>
607 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> 689 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
608 <dd> 690 <dd>
… …
612the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the 694the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
613type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro 695type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
614which rolls both calls into one.</p> 696which rolls both calls into one.</p>
615 <p>You can reinitialise a watcher at any time as long as it has been stopped 697 <p>You can reinitialise a watcher at any time as long as it has been stopped
616(or never started) and there are no pending events outstanding.</p> 698(or never started) and there are no pending events outstanding.</p>
617 <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, 699 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
618int revents)</code>.</p> 700int revents)</code>.</p>
619 </dd> 701 </dd>
620 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> 702 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
621 <dd> 703 <dd>
622 <p>This macro initialises the type-specific parts of a watcher. You need to 704 <p>This macro initialises the type-specific parts of a watcher. You need to
… …
712 794
713</div> 795</div>
714<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
715<div id="WATCHER_TYPES_CONTENT"> 797<div id="WATCHER_TYPES_CONTENT">
716<p>This section describes each watcher in detail, but will not repeat 798<p>This section describes each watcher in detail, but will not repeat
717information given in the last section.</p> 799information given in the last section. Any initialisation/set macros,
800functions and members specific to the watcher type are explained.</p>
801<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
802while the watcher is active, you can look at the member and expect some
803sensible content, but you must not modify it (you can modify it while the
804watcher is stopped to your hearts content), or <i>[read-write]</i>, which
805means you can expect it to have some sensible content while the watcher
806is active, but you can also modify it. Modifying it may not do something
807sensible or take immediate effect (or do anything at all), but libev will
808not crash or malfunction in any way.</p>
718 809
719 810
720 811
721 812
722 813
723</div> 814</div>
724<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 815<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
725<div id="code_ev_io_code_is_this_file_descrip-2"> 816<div id="code_ev_io_code_is_this_file_descrip-2">
726<p>I/O watchers check whether a file descriptor is readable or writable 817<p>I/O watchers check whether a file descriptor is readable or writable
727in each iteration of the event loop (This behaviour is called 818in each iteration of the event loop, or, more precisely, when reading
728level-triggering because you keep receiving events as long as the 819would not block the process and writing would at least be able to write
729condition persists. Remember you can stop the watcher if you don't want to 820some data. This behaviour is called level-triggering because you keep
730act on the event and neither want to receive future events).</p> 821receiving events as long as the condition persists. Remember you can stop
822the watcher if you don't want to act on the event and neither want to
823receive future events.</p>
731<p>In general you can register as many read and/or write event watchers per 824<p>In general you can register as many read and/or write event watchers per
732fd as you want (as long as you don't confuse yourself). Setting all file 825fd as you want (as long as you don't confuse yourself). Setting all file
733descriptors to non-blocking mode is also usually a good idea (but not 826descriptors to non-blocking mode is also usually a good idea (but not
734required if you know what you are doing).</p> 827required if you know what you are doing).</p>
735<p>You have to be careful with dup'ed file descriptors, though. Some backends 828<p>You have to be careful with dup'ed file descriptors, though. Some backends
736(the linux epoll backend is a notable example) cannot handle dup'ed file 829(the linux epoll backend is a notable example) cannot handle dup'ed file
737descriptors correctly if you register interest in two or more fds pointing 830descriptors correctly if you register interest in two or more fds pointing
738to the same underlying file/socket etc. description (that is, they share 831to the same underlying file/socket/etc. description (that is, they share
739the same underlying &quot;file open&quot;).</p> 832the same underlying &quot;file open&quot;).</p>
740<p>If you must do this, then force the use of a known-to-be-good backend 833<p>If you must do this, then force the use of a known-to-be-good backend
741(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 834(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
742<code>EVBACKEND_POLL</code>).</p> 835<code>EVBACKEND_POLL</code>).</p>
836<p>Another thing you have to watch out for is that it is quite easy to
837receive &quot;spurious&quot; readyness notifications, that is your callback might
838be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
839because there is no data. Not only are some backends known to create a
840lot of those (for example solaris ports), it is very easy to get into
841this situation even with a relatively standard program structure. Thus
842it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
843<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
844<p>If you cannot run the fd in non-blocking mode (for example you should not
845play around with an Xlib connection), then you have to seperately re-test
846wether a file descriptor is really ready with a known-to-be good interface
847such as poll (fortunately in our Xlib example, Xlib already does this on
848its own, so its quite safe to use).</p>
743<dl> 849<dl>
744 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 850 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
745 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 851 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
746 <dd> 852 <dd>
747 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 853 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
748events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 854rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
749EV_WRITE</code> to receive the given events.</p> 855<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
750 <p>Please note that most of the more scalable backend mechanisms (for example 856 </dd>
751epoll and solaris ports) can result in spurious readyness notifications 857 <dt>int fd [read-only]</dt>
752for file descriptors, so you practically need to use non-blocking I/O (and 858 <dd>
753treat callback invocation as hint only), or retest separately with a safe 859 <p>The file descriptor being watched.</p>
754interface before doing I/O (XLib can do this), or force the use of either 860 </dd>
755<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 861 <dt>int events [read-only]</dt>
756problem. Also note that it is quite easy to have your callback invoked 862 <dd>
757when the readyness condition is no longer valid even when employing 863 <p>The events being watched.</p>
758typical ways of handling events, so its a good idea to use non-blocking
759I/O unconditionally.</p>
760 </dd> 864 </dd>
761</dl> 865</dl>
762<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 866<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
763readable, but only once. Since it is likely line-buffered, you could 867readable, but only once. Since it is likely line-buffered, you could
764attempt to read a whole line in the callback:</p> 868attempt to read a whole line in the callback.</p>
765<pre> static void 869<pre> static void
766 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 870 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
767 { 871 {
768 ev_io_stop (loop, w); 872 ev_io_stop (loop, w);
769 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 873 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
780 884
781 885
782</pre> 886</pre>
783 887
784</div> 888</div>
785<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 889<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
786<div id="code_ev_timer_code_relative_and_opti-2"> 890<div id="code_ev_timer_code_relative_and_opti-2">
787<p>Timer watchers are simple relative timers that generate an event after a 891<p>Timer watchers are simple relative timers that generate an event after a
788given time, and optionally repeating in regular intervals after that.</p> 892given time, and optionally repeating in regular intervals after that.</p>
789<p>The timers are based on real time, that is, if you register an event that 893<p>The timers are based on real time, that is, if you register an event that
790times out after an hour and you reset your system clock to last years 894times out after an hour and you reset your system clock to last years
… …
822repeating. The exact semantics are:</p> 926repeating. The exact semantics are:</p>
823 <p>If the timer is started but nonrepeating, stop it.</p> 927 <p>If the timer is started but nonrepeating, stop it.</p>
824 <p>If the timer is repeating, either start it if necessary (with the repeat 928 <p>If the timer is repeating, either start it if necessary (with the repeat
825value), or reset the running timer to the repeat value.</p> 929value), or reset the running timer to the repeat value.</p>
826 <p>This sounds a bit complicated, but here is a useful and typical 930 <p>This sounds a bit complicated, but here is a useful and typical
827example: Imagine you have a tcp connection and you want a so-called idle 931example: Imagine you have a tcp connection and you want a so-called
828timeout, that is, you want to be called when there have been, say, 60 932idle timeout, that is, you want to be called when there have been,
829seconds of inactivity on the socket. The easiest way to do this is to 933say, 60 seconds of inactivity on the socket. The easiest way to do
830configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 934this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
831time you successfully read or write some data. If you go into an idle 935<code>ev_timer_again</code> each time you successfully read or write some data. If
832state where you do not expect data to travel on the socket, you can stop 936you go into an idle state where you do not expect data to travel on the
833the timer, and again will automatically restart it if need be.</p> 937socket, you can stop the timer, and again will automatically restart it if
938need be.</p>
939 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
940and only ever use the <code>repeat</code> value:</p>
941<pre> ev_timer_init (timer, callback, 0., 5.);
942 ev_timer_again (loop, timer);
943 ...
944 timer-&gt;again = 17.;
945 ev_timer_again (loop, timer);
946 ...
947 timer-&gt;again = 10.;
948 ev_timer_again (loop, timer);
949
950</pre>
951 <p>This is more efficient then stopping/starting the timer eahc time you want
952to modify its timeout value.</p>
953 </dd>
954 <dt>ev_tstamp repeat [read-write]</dt>
955 <dd>
956 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
957or <code>ev_timer_again</code> is called and determines the next timeout (if any),
958which is also when any modifications are taken into account.</p>
834 </dd> 959 </dd>
835</dl> 960</dl>
836<p>Example: create a timer that fires after 60 seconds.</p> 961<p>Example: Create a timer that fires after 60 seconds.</p>
837<pre> static void 962<pre> static void
838 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 963 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839 { 964 {
840 .. one minute over, w is actually stopped right here 965 .. one minute over, w is actually stopped right here
841 } 966 }
… …
843 struct ev_timer mytimer; 968 struct ev_timer mytimer;
844 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 969 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
845 ev_timer_start (loop, &amp;mytimer); 970 ev_timer_start (loop, &amp;mytimer);
846 971
847</pre> 972</pre>
848<p>Example: create a timeout timer that times out after 10 seconds of 973<p>Example: Create a timeout timer that times out after 10 seconds of
849inactivity.</p> 974inactivity.</p>
850<pre> static void 975<pre> static void
851 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 976 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
852 { 977 {
853 .. ten seconds without any activity 978 .. ten seconds without any activity
… …
866 991
867 992
868</pre> 993</pre>
869 994
870</div> 995</div>
871<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 996<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
872<div id="code_ev_periodic_code_to_cron_or_not-2"> 997<div id="code_ev_periodic_code_to_cron_or_not-2">
873<p>Periodic watchers are also timers of a kind, but they are very versatile 998<p>Periodic watchers are also timers of a kind, but they are very versatile
874(and unfortunately a bit complex).</p> 999(and unfortunately a bit complex).</p>
875<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1000<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
876but on wallclock time (absolute time). You can tell a periodic watcher 1001but on wallclock time (absolute time). You can tell a periodic watcher
877to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1002to trigger &quot;at&quot; some specific point in time. For example, if you tell a
878periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 1003periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
879+ 10.&gt;) and then reset your system clock to the last year, then it will 1004+ 10.</code>) and then reset your system clock to the last year, then it will
880take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1005take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
881roughly 10 seconds later and of course not if you reset your system time 1006roughly 10 seconds later and of course not if you reset your system time
882again).</p> 1007again).</p>
883<p>They can also be used to implement vastly more complex timers, such as 1008<p>They can also be used to implement vastly more complex timers, such as
884triggering an event on eahc midnight, local time.</p> 1009triggering an event on eahc midnight, local time.</p>
… …
956 <p>Simply stops and restarts the periodic watcher again. This is only useful 1081 <p>Simply stops and restarts the periodic watcher again. This is only useful
957when you changed some parameters or the reschedule callback would return 1082when you changed some parameters or the reschedule callback would return
958a different time than the last time it was called (e.g. in a crond like 1083a different time than the last time it was called (e.g. in a crond like
959program when the crontabs have changed).</p> 1084program when the crontabs have changed).</p>
960 </dd> 1085 </dd>
1086 <dt>ev_tstamp interval [read-write]</dt>
1087 <dd>
1088 <p>The current interval value. Can be modified any time, but changes only
1089take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1090called.</p>
1091 </dd>
1092 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1093 <dd>
1094 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1095switched off. Can be changed any time, but changes only take effect when
1096the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1097 </dd>
961</dl> 1098</dl>
962<p>Example: call a callback every hour, or, more precisely, whenever the 1099<p>Example: Call a callback every hour, or, more precisely, whenever the
963system clock is divisible by 3600. The callback invocation times have 1100system clock is divisible by 3600. The callback invocation times have
964potentially a lot of jittering, but good long-term stability.</p> 1101potentially a lot of jittering, but good long-term stability.</p>
965<pre> static void 1102<pre> static void
966 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1103 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
967 { 1104 {
… …
971 struct ev_periodic hourly_tick; 1108 struct ev_periodic hourly_tick;
972 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1109 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
973 ev_periodic_start (loop, &amp;hourly_tick); 1110 ev_periodic_start (loop, &amp;hourly_tick);
974 1111
975</pre> 1112</pre>
976<p>Example: the same as above, but use a reschedule callback to do it:</p> 1113<p>Example: The same as above, but use a reschedule callback to do it:</p>
977<pre> #include &lt;math.h&gt; 1114<pre> #include &lt;math.h&gt;
978 1115
979 static ev_tstamp 1116 static ev_tstamp
980 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1117 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
981 { 1118 {
… …
983 } 1120 }
984 1121
985 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1122 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
986 1123
987</pre> 1124</pre>
988<p>Example: call a callback every hour, starting now:</p> 1125<p>Example: Call a callback every hour, starting now:</p>
989<pre> struct ev_periodic hourly_tick; 1126<pre> struct ev_periodic hourly_tick;
990 ev_periodic_init (&amp;hourly_tick, clock_cb, 1127 ev_periodic_init (&amp;hourly_tick, clock_cb,
991 fmod (ev_now (loop), 3600.), 3600., 0); 1128 fmod (ev_now (loop), 3600.), 3600., 0);
992 ev_periodic_start (loop, &amp;hourly_tick); 1129 ev_periodic_start (loop, &amp;hourly_tick);
993 1130
… …
995 1132
996 1133
997</pre> 1134</pre>
998 1135
999</div> 1136</div>
1000<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1137<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
1001<div id="code_ev_signal_code_signal_me_when_a-2"> 1138<div id="code_ev_signal_code_signal_me_when_a-2">
1002<p>Signal watchers will trigger an event when the process receives a specific 1139<p>Signal watchers will trigger an event when the process receives a specific
1003signal one or more times. Even though signals are very asynchronous, libev 1140signal one or more times. Even though signals are very asynchronous, libev
1004will try it's best to deliver signals synchronously, i.e. as part of the 1141will try it's best to deliver signals synchronously, i.e. as part of the
1005normal event processing, like any other event.</p> 1142normal event processing, like any other event.</p>
… …
1014 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1151 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1015 <dd> 1152 <dd>
1016 <p>Configures the watcher to trigger on the given signal number (usually one 1153 <p>Configures the watcher to trigger on the given signal number (usually one
1017of the <code>SIGxxx</code> constants).</p> 1154of the <code>SIGxxx</code> constants).</p>
1018 </dd> 1155 </dd>
1156 <dt>int signum [read-only]</dt>
1157 <dd>
1158 <p>The signal the watcher watches out for.</p>
1159 </dd>
1019</dl> 1160</dl>
1020 1161
1021 1162
1022 1163
1023 1164
1024 1165
1025</div> 1166</div>
1026<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1167<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1027<div id="code_ev_child_code_wait_for_pid_stat-2"> 1168<div id="code_ev_child_code_watch_out_for_pro-2">
1028<p>Child watchers trigger when your process receives a SIGCHLD in response to 1169<p>Child watchers trigger when your process receives a SIGCHLD in response to
1029some child status changes (most typically when a child of yours dies).</p> 1170some child status changes (most typically when a child of yours dies).</p>
1030<dl> 1171<dl>
1031 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1172 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1032 <dt>ev_child_set (ev_child *, int pid)</dt> 1173 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
1036at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1177at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1037the status word (use the macros from <code>sys/wait.h</code> and see your systems 1178the status word (use the macros from <code>sys/wait.h</code> and see your systems
1038<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1179<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1039process causing the status change.</p> 1180process causing the status change.</p>
1040 </dd> 1181 </dd>
1182 <dt>int pid [read-only]</dt>
1183 <dd>
1184 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1185 </dd>
1186 <dt>int rpid [read-write]</dt>
1187 <dd>
1188 <p>The process id that detected a status change.</p>
1189 </dd>
1190 <dt>int rstatus [read-write]</dt>
1191 <dd>
1192 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1193<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1194 </dd>
1041</dl> 1195</dl>
1042<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1196<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1043<pre> static void 1197<pre> static void
1044 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1198 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1045 { 1199 {
1046 ev_unloop (loop, EVUNLOOP_ALL); 1200 ev_unloop (loop, EVUNLOOP_ALL);
1047 } 1201 }
… …
1054 1208
1055 1209
1056</pre> 1210</pre>
1057 1211
1058</div> 1212</div>
1213<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1214<div id="code_ev_stat_code_did_the_file_attri-2">
1215<p>This watches a filesystem path for attribute changes. That is, it calls
1216<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1217compared to the last time, invoking the callback if it did.</p>
1218<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1219not exist&quot; is a status change like any other. The condition &quot;path does
1220not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1221otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p>
1223<p>Since there is no standard to do this, the portable implementation simply
1224calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
1225can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1227unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be
1233resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but
1235if demand increases, at least a kqueue and inotify backend will be added.</p>
1236<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1238 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd>
1240 <p>Configures the watcher to wait for status changes of the given
1241<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1242be detected and should normally be specified as <code>0</code> to let libev choose
1243a suitable value. The memory pointed to by <code>path</code> must point to the same
1244path for as long as the watcher is active.</p>
1245 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1246relative to the attributes at the time the watcher was started (or the
1247last change was detected).</p>
1248 </dd>
1249 <dt>ev_stat_stat (ev_stat *)</dt>
1250 <dd>
1251 <p>Updates the stat buffer immediately with new values. If you change the
1252watched path in your callback, you could call this fucntion to avoid
1253detecting this change (while introducing a race condition). Can also be
1254useful simply to find out the new values.</p>
1255 </dd>
1256 <dt>ev_statdata attr [read-only]</dt>
1257 <dd>
1258 <p>The most-recently detected attributes of the file. Although the type is of
1259<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1260suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1261was some error while <code>stat</code>ing the file.</p>
1262 </dd>
1263 <dt>ev_statdata prev [read-only]</dt>
1264 <dd>
1265 <p>The previous attributes of the file. The callback gets invoked whenever
1266<code>prev</code> != <code>attr</code>.</p>
1267 </dd>
1268 <dt>ev_tstamp interval [read-only]</dt>
1269 <dd>
1270 <p>The specified interval.</p>
1271 </dd>
1272 <dt>const char *path [read-only]</dt>
1273 <dd>
1274 <p>The filesystem path that is being watched.</p>
1275 </dd>
1276</dl>
1277<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1278<pre> static void
1279 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1280 {
1281 /* /etc/passwd changed in some way */
1282 if (w-&gt;attr.st_nlink)
1283 {
1284 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1285 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1286 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1287 }
1288 else
1289 /* you shalt not abuse printf for puts */
1290 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1291 &quot;if this is windows, they already arrived\n&quot;);
1292 }
1293
1294 ...
1295 ev_stat passwd;
1296
1297 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1298 ev_stat_start (loop, &amp;passwd);
1299
1300
1301
1302
1303</pre>
1304
1305</div>
1059<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1306<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1060<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1307<div id="code_ev_idle_code_when_you_ve_got_no-2">
1061<p>Idle watchers trigger events when there are no other events are pending 1308<p>Idle watchers trigger events when there are no other events are pending
1062(prepare, check and other idle watchers do not count). That is, as long 1309(prepare, check and other idle watchers do not count). That is, as long
1063as your process is busy handling sockets or timeouts (or even signals, 1310as your process is busy handling sockets or timeouts (or even signals,
1064imagine) it will not be triggered. But when your process is idle all idle 1311imagine) it will not be triggered. But when your process is idle all idle
… …
1077 <p>Initialises and configures the idle watcher - it has no parameters of any 1324 <p>Initialises and configures the idle watcher - it has no parameters of any
1078kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1325kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1079believe me.</p> 1326believe me.</p>
1080 </dd> 1327 </dd>
1081</dl> 1328</dl>
1082<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1329<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1083callback, free it. Alos, use no error checking, as usual.</p> 1330callback, free it. Also, use no error checking, as usual.</p>
1084<pre> static void 1331<pre> static void
1085 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1332 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1086 { 1333 {
1087 free (w); 1334 free (w);
1088 // now do something you wanted to do when the program has 1335 // now do something you wanted to do when the program has
… …
1097 1344
1098 1345
1099</pre> 1346</pre>
1100 1347
1101</div> 1348</div>
1102<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1349<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1103<div id="code_ev_prepare_code_and_code_ev_che-2"> 1350<div id="code_ev_prepare_code_and_code_ev_che-2">
1104<p>Prepare and check watchers are usually (but not always) used in tandem: 1351<p>Prepare and check watchers are usually (but not always) used in tandem:
1105prepare watchers get invoked before the process blocks and check watchers 1352prepare watchers get invoked before the process blocks and check watchers
1106afterwards.</p> 1353afterwards.</p>
1354<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1355the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1356watchers. Other loops than the current one are fine, however. The
1357rationale behind this is that you do not need to check for recursion in
1358those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1359<code>ev_check</code> so if you have one watcher of each kind they will always be
1360called in pairs bracketing the blocking call.</p>
1107<p>Their main purpose is to integrate other event mechanisms into libev and 1361<p>Their main purpose is to integrate other event mechanisms into libev and
1108their use is somewhat advanced. This could be used, for example, to track 1362their use is somewhat advanced. This could be used, for example, to track
1109variable changes, implement your own watchers, integrate net-snmp or a 1363variable changes, implement your own watchers, integrate net-snmp or a
1110coroutine library and lots more.</p> 1364coroutine library and lots more. They are also occasionally useful if
1365you cache some data and want to flush it before blocking (for example,
1366in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1367watcher).</p>
1111<p>This is done by examining in each prepare call which file descriptors need 1368<p>This is done by examining in each prepare call which file descriptors need
1112to be watched by the other library, registering <code>ev_io</code> watchers for 1369to be watched by the other library, registering <code>ev_io</code> watchers for
1113them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1370them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1114provide just this functionality). Then, in the check watcher you check for 1371provide just this functionality). Then, in the check watcher you check for
1115any events that occured (by checking the pending status of all watchers 1372any events that occured (by checking the pending status of all watchers
… …
1131 <p>Initialises and configures the prepare or check watcher - they have no 1388 <p>Initialises and configures the prepare or check watcher - they have no
1132parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1389parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1133macros, but using them is utterly, utterly and completely pointless.</p> 1390macros, but using them is utterly, utterly and completely pointless.</p>
1134 </dd> 1391 </dd>
1135</dl> 1392</dl>
1136<p>Example: *TODO*.</p> 1393<p>Example: To include a library such as adns, you would add IO watchers
1394and a timeout watcher in a prepare handler, as required by libadns, and
1395in a check watcher, destroy them and call into libadns. What follows is
1396pseudo-code only of course:</p>
1397<pre> static ev_io iow [nfd];
1398 static ev_timer tw;
1137 1399
1400 static void
1401 io_cb (ev_loop *loop, ev_io *w, int revents)
1402 {
1403 // set the relevant poll flags
1404 // could also call adns_processreadable etc. here
1405 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1406 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1407 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1408 }
1138 1409
1410 // create io watchers for each fd and a timer before blocking
1411 static void
1412 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1413 {
1414 int timeout = 3600000;truct pollfd fds [nfd];
1415 // actual code will need to loop here and realloc etc.
1416 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1139 1417
1418 /* the callback is illegal, but won't be called as we stop during check */
1419 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1420 ev_timer_start (loop, &amp;tw);
1140 1421
1422 // create on ev_io per pollfd
1423 for (int i = 0; i &lt; nfd; ++i)
1424 {
1425 ev_io_init (iow + i, io_cb, fds [i].fd,
1426 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1427 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1141 1428
1429 fds [i].revents = 0;
1430 iow [i].data = fds + i;
1431 ev_io_start (loop, iow + i);
1432 }
1433 }
1434
1435 // stop all watchers after blocking
1436 static void
1437 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1438 {
1439 ev_timer_stop (loop, &amp;tw);
1440
1441 for (int i = 0; i &lt; nfd; ++i)
1442 ev_io_stop (loop, iow + i);
1443
1444 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1445 }
1446
1447
1448
1449
1450</pre>
1451
1142</div> 1452</div>
1143<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1453<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1144<div id="code_ev_embed_code_when_one_backend_-2"> 1454<div id="code_ev_embed_code_when_one_backend_-2">
1145<p>This is a rather advanced watcher type that lets you embed one event loop 1455<p>This is a rather advanced watcher type that lets you embed one event loop
1146into another (currently only <code>ev_io</code> events are supported in the embedded 1456into another (currently only <code>ev_io</code> events are supported in the embedded
1147loop, other types of watchers might be handled in a delayed or incorrect 1457loop, other types of watchers might be handled in a delayed or incorrect
1148fashion and must not be used).</p> 1458fashion and must not be used).</p>
… …
1216 <dd> 1526 <dd>
1217 <p>Make a single, non-blocking sweep over the embedded loop. This works 1527 <p>Make a single, non-blocking sweep over the embedded loop. This works
1218similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1528similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1219apropriate way for embedded loops.</p> 1529apropriate way for embedded loops.</p>
1220 </dd> 1530 </dd>
1531 <dt>struct ev_loop *loop [read-only]</dt>
1532 <dd>
1533 <p>The embedded event loop.</p>
1534 </dd>
1535</dl>
1536
1537
1538
1539
1540
1541</div>
1542<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>
1543<div id="code_ev_fork_code_the_audacity_to_re-2">
1544<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1545whoever is a good citizen cared to tell libev about it by calling
1546<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1547event loop blocks next and before <code>ev_check</code> watchers are being called,
1548and only in the child after the fork. If whoever good citizen calling
1549<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1550handlers will be invoked, too, of course.</p>
1551<dl>
1552 <dt>ev_fork_init (ev_signal *, callback)</dt>
1553 <dd>
1554 <p>Initialises and configures the fork watcher - it has no parameters of any
1555kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1556believe me.</p>
1557 </dd>
1221</dl> 1558</dl>
1222 1559
1223 1560
1224 1561
1225 1562
… …
1302</dl> 1639</dl>
1303 1640
1304</div> 1641</div>
1305<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1642<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
1306<div id="C_SUPPORT_CONTENT"> 1643<div id="C_SUPPORT_CONTENT">
1307<p>TBD.</p> 1644<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1645you to use some convinience methods to start/stop watchers and also change
1646the callback model to a model using method callbacks on objects.</p>
1647<p>To use it,</p>
1648<pre> #include &lt;ev++.h&gt;
1649
1650</pre>
1651<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1652and puts all of its definitions (many of them macros) into the global
1653namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1654<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1655<code>EV_MULTIPLICITY</code>.</p>
1656<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1657<dl>
1658 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1659 <dd>
1660 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1661macros from <cite>ev.h</cite>.</p>
1662 </dd>
1663 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1664 <dd>
1665 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1666 </dd>
1667 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1668 <dd>
1669 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1670the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1671which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1672defines by many implementations.</p>
1673 <p>All of those classes have these methods:</p>
1674 <p>
1675 <dl>
1676 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1677 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1678 <dt>ev::TYPE::~TYPE</dt>
1679 <dd>
1680 <p>The constructor takes a pointer to an object and a method pointer to
1681the event handler callback to call in this class. The constructor calls
1682<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1683before starting it. If you do not specify a loop then the constructor
1684automatically associates the default loop with this watcher.</p>
1685 <p>The destructor automatically stops the watcher if it is active.</p>
1686 </dd>
1687 <dt>w-&gt;set (struct ev_loop *)</dt>
1688 <dd>
1689 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1690do this when the watcher is inactive (and not pending either).</p>
1691 </dd>
1692 <dt>w-&gt;set ([args])</dt>
1693 <dd>
1694 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1695called at least once. Unlike the C counterpart, an active watcher gets
1696automatically stopped and restarted.</p>
1697 </dd>
1698 <dt>w-&gt;start ()</dt>
1699 <dd>
1700 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1701constructor already takes the loop.</p>
1702 </dd>
1703 <dt>w-&gt;stop ()</dt>
1704 <dd>
1705 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1706 </dd>
1707 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1708 <dd>
1709 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1710<code>ev_TYPE_again</code> function.</p>
1711 </dd>
1712 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1713 <dd>
1714 <p>Invokes <code>ev_embed_sweep</code>.</p>
1715 </dd>
1716 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1717 <dd>
1718 <p>Invokes <code>ev_stat_stat</code>.</p>
1719 </dd>
1720 </dl>
1721 </p>
1722 </dd>
1723</dl>
1724<p>Example: Define a class with an IO and idle watcher, start one of them in
1725the constructor.</p>
1726<pre> class myclass
1727 {
1728 ev_io io; void io_cb (ev::io &amp;w, int revents);
1729 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1730
1731 myclass ();
1732 }
1733
1734 myclass::myclass (int fd)
1735 : io (this, &amp;myclass::io_cb),
1736 idle (this, &amp;myclass::idle_cb)
1737 {
1738 io.start (fd, ev::READ);
1739 }
1740
1741
1742
1743
1744</pre>
1745
1746</div>
1747<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p>
1748<div id="MACRO_MAGIC_CONTENT">
1749<p>Libev can be compiled with a variety of options, the most fundemantal is
1750<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1751callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1752<p>To make it easier to write programs that cope with either variant, the
1753following macros are defined:</p>
1754<dl>
1755 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1756 <dd>
1757 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1758loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1759<code>EV_A_</code> is used when other arguments are following. Example:</p>
1760<pre> ev_unref (EV_A);
1761 ev_timer_add (EV_A_ watcher);
1762 ev_loop (EV_A_ 0);
1763
1764</pre>
1765 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1766which is often provided by the following macro.</p>
1767 </dd>
1768 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1769 <dd>
1770 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1771loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1772<code>EV_P_</code> is used when other parameters are following. Example:</p>
1773<pre> // this is how ev_unref is being declared
1774 static void ev_unref (EV_P);
1775
1776 // this is how you can declare your typical callback
1777 static void cb (EV_P_ ev_timer *w, int revents)
1778
1779</pre>
1780 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1781suitable for use with <code>EV_A</code>.</p>
1782 </dd>
1783 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1784 <dd>
1785 <p>Similar to the other two macros, this gives you the value of the default
1786loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1787 </dd>
1788</dl>
1789<p>Example: Declare and initialise a check watcher, working regardless of
1790wether multiple loops are supported or not.</p>
1791<pre> static void
1792 check_cb (EV_P_ ev_timer *w, int revents)
1793 {
1794 ev_check_stop (EV_A_ w);
1795 }
1796
1797 ev_check check;
1798 ev_check_init (&amp;check, check_cb);
1799 ev_check_start (EV_DEFAULT_ &amp;check);
1800 ev_loop (EV_DEFAULT_ 0);
1801
1802
1803
1804
1805</pre>
1806
1807</div>
1808<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
1809<div id="EMBEDDING_CONTENT">
1810<p>Libev can (and often is) directly embedded into host
1811applications. Examples of applications that embed it include the Deliantra
1812Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1813and rxvt-unicode.</p>
1814<p>The goal is to enable you to just copy the neecssary files into your
1815source directory without having to change even a single line in them, so
1816you can easily upgrade by simply copying (or having a checked-out copy of
1817libev somewhere in your source tree).</p>
1818
1819</div>
1820<h2 id="FILESETS">FILESETS</h2>
1821<div id="FILESETS_CONTENT">
1822<p>Depending on what features you need you need to include one or more sets of files
1823in your app.</p>
1824
1825</div>
1826<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1827<div id="CORE_EVENT_LOOP_CONTENT">
1828<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1829configuration (no autoconf):</p>
1830<pre> #define EV_STANDALONE 1
1831 #include &quot;ev.c&quot;
1832
1833</pre>
1834<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1835single C source file only to provide the function implementations. To use
1836it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1837done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1838where you can put other configuration options):</p>
1839<pre> #define EV_STANDALONE 1
1840 #include &quot;ev.h&quot;
1841
1842</pre>
1843<p>Both header files and implementation files can be compiled with a C++
1844compiler (at least, thats a stated goal, and breakage will be treated
1845as a bug).</p>
1846<p>You need the following files in your source tree, or in a directory
1847in your include path (e.g. in libev/ when using -Ilibev):</p>
1848<pre> ev.h
1849 ev.c
1850 ev_vars.h
1851 ev_wrap.h
1852
1853 ev_win32.c required on win32 platforms only
1854
1855 ev_select.c only when select backend is enabled (which is by default)
1856 ev_poll.c only when poll backend is enabled (disabled by default)
1857 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1858 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1859 ev_port.c only when the solaris port backend is enabled (disabled by default)
1860
1861</pre>
1862<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1863to compile this single file.</p>
1864
1865</div>
1866<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1867<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1868<p>To include the libevent compatibility API, also include:</p>
1869<pre> #include &quot;event.c&quot;
1870
1871</pre>
1872<p>in the file including <cite>ev.c</cite>, and:</p>
1873<pre> #include &quot;event.h&quot;
1874
1875</pre>
1876<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1877<p>You need the following additional files for this:</p>
1878<pre> event.h
1879 event.c
1880
1881</pre>
1882
1883</div>
1884<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1885<div id="AUTOCONF_SUPPORT_CONTENT">
1886<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1887whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1888<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1889include <cite>config.h</cite> and configure itself accordingly.</p>
1890<p>For this of course you need the m4 file:</p>
1891<pre> libev.m4
1892
1893</pre>
1894
1895</div>
1896<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1897<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1898<p>Libev can be configured via a variety of preprocessor symbols you have to define
1899before including any of its files. The default is not to build for multiplicity
1900and only include the select backend.</p>
1901<dl>
1902 <dt>EV_STANDALONE</dt>
1903 <dd>
1904 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1905keeps libev from including <cite>config.h</cite>, and it also defines dummy
1906implementations for some libevent functions (such as logging, which is not
1907supported). It will also not define any of the structs usually found in
1908<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1909 </dd>
1910 <dt>EV_USE_MONOTONIC</dt>
1911 <dd>
1912 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1913monotonic clock option at both compiletime and runtime. Otherwise no use
1914of the monotonic clock option will be attempted. If you enable this, you
1915usually have to link against librt or something similar. Enabling it when
1916the functionality isn't available is safe, though, althoguh you have
1917to make sure you link against any libraries where the <code>clock_gettime</code>
1918function is hiding in (often <cite>-lrt</cite>).</p>
1919 </dd>
1920 <dt>EV_USE_REALTIME</dt>
1921 <dd>
1922 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1923realtime clock option at compiletime (and assume its availability at
1924runtime if successful). Otherwise no use of the realtime clock option will
1925be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1926(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1927in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1928 </dd>
1929 <dt>EV_USE_SELECT</dt>
1930 <dd>
1931 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1932<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1933other method takes over, select will be it. Otherwise the select backend
1934will not be compiled in.</p>
1935 </dd>
1936 <dt>EV_SELECT_USE_FD_SET</dt>
1937 <dd>
1938 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1939structure. This is useful if libev doesn't compile due to a missing
1940<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1941exotic systems. This usually limits the range of file descriptors to some
1942low limit such as 1024 or might have other limitations (winsocket only
1943allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1944influence the size of the <code>fd_set</code> used.</p>
1945 </dd>
1946 <dt>EV_SELECT_IS_WINSOCKET</dt>
1947 <dd>
1948 <p>When defined to <code>1</code>, the select backend will assume that
1949select/socket/connect etc. don't understand file descriptors but
1950wants osf handles on win32 (this is the case when the select to
1951be used is the winsock select). This means that it will call
1952<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1953it is assumed that all these functions actually work on fds, even
1954on win32. Should not be defined on non-win32 platforms.</p>
1955 </dd>
1956 <dt>EV_USE_POLL</dt>
1957 <dd>
1958 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1959backend. Otherwise it will be enabled on non-win32 platforms. It
1960takes precedence over select.</p>
1961 </dd>
1962 <dt>EV_USE_EPOLL</dt>
1963 <dd>
1964 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1965<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1966otherwise another method will be used as fallback. This is the
1967preferred backend for GNU/Linux systems.</p>
1968 </dd>
1969 <dt>EV_USE_KQUEUE</dt>
1970 <dd>
1971 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
1972<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
1973otherwise another method will be used as fallback. This is the preferred
1974backend for BSD and BSD-like systems, although on most BSDs kqueue only
1975supports some types of fds correctly (the only platform we found that
1976supports ptys for example was NetBSD), so kqueue might be compiled in, but
1977not be used unless explicitly requested. The best way to use it is to find
1978out whether kqueue supports your type of fd properly and use an embedded
1979kqueue loop.</p>
1980 </dd>
1981 <dt>EV_USE_PORT</dt>
1982 <dd>
1983 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
198410 port style backend. Its availability will be detected at runtime,
1985otherwise another method will be used as fallback. This is the preferred
1986backend for Solaris 10 systems.</p>
1987 </dd>
1988 <dt>EV_USE_DEVPOLL</dt>
1989 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd>
1992 <dt>EV_H</dt>
1993 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1995undefined 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
1996can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
1997 </dd>
1998 <dt>EV_CONFIG_H</dt>
1999 <dd>
2000 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2001<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2002<code>EV_H</code>, above.</p>
2003 </dd>
2004 <dt>EV_EVENT_H</dt>
2005 <dd>
2006 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2007of how the <cite>event.h</cite> header can be found.</p>
2008 </dd>
2009 <dt>EV_PROTOTYPES</dt>
2010 <dd>
2011 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2012prototypes, but still define all the structs and other symbols. This is
2013occasionally useful if you want to provide your own wrapper functions
2014around libev functions.</p>
2015 </dd>
2016 <dt>EV_MULTIPLICITY</dt>
2017 <dd>
2018 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2019will have the <code>struct ev_loop *</code> as first argument, and you can create
2020additional independent event loops. Otherwise there will be no support
2021for multiple event loops and there is no first event loop pointer
2022argument. Instead, all functions act on the single default loop.</p>
2023 </dd>
2024 <dt>EV_PERIODIC_ENABLE</dt>
2025 <dd>
2026 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2027defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2028code.</p>
2029 </dd>
2030 <dt>EV_EMBED_ENABLE</dt>
2031 <dd>
2032 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2033defined to be <code>0</code>, then they are not.</p>
2034 </dd>
2035 <dt>EV_STAT_ENABLE</dt>
2036 <dd>
2037 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2038defined to be <code>0</code>, then they are not.</p>
2039 </dd>
2040 <dt>EV_FORK_ENABLE</dt>
2041 <dd>
2042 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2043defined to be <code>0</code>, then they are not.</p>
2044 </dd>
2045 <dt>EV_MINIMAL</dt>
2046 <dd>
2047 <p>If you need to shave off some kilobytes of code at the expense of some
2048speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2049some inlining decisions, saves roughly 30% codesize of amd64.</p>
2050 </dd>
2051 <dt>EV_PID_HASHSIZE</dt>
2052 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2054pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2055than enough. If you need to manage thousands of children you might want to
2056increase this value.</p>
2057 </dd>
2058 <dt>EV_COMMON</dt>
2059 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2061this macro to a something else you can include more and other types of
2062members. You have to define it each time you include one of the files,
2063though, and it must be identical each time.</p>
2064 <p>For example, the perl EV module uses something like this:</p>
2065<pre> #define EV_COMMON \
2066 SV *self; /* contains this struct */ \
2067 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2068
2069</pre>
2070 </dd>
2071 <dt>EV_CB_DECLARE (type)</dt>
2072 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2073 <dt>ev_set_cb (ev, cb)</dt>
2074 <dd>
2075 <p>Can be used to change the callback member declaration in each watcher,
2076and the way callbacks are invoked and set. Must expand to a struct member
2077definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2078their default definitions. One possible use for overriding these is to
2079avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2080method calls instead of plain function calls in C++.</p>
2081
2082</div>
2083<h2 id="EXAMPLES">EXAMPLES</h2>
2084<div id="EXAMPLES_CONTENT">
2085 <p>For a real-world example of a program the includes libev
2086verbatim, you can have a look at the EV perl module
2087(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2088the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2089interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2090will be compiled. It is pretty complex because it provides its own header
2091file.</p>
2092 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2093that everybody includes and which overrides some autoconf choices:</p>
2094<pre> #define EV_USE_POLL 0
2095 #define EV_MULTIPLICITY 0
2096 #define EV_PERIODICS 0
2097 #define EV_CONFIG_H &lt;config.h&gt;
2098
2099 #include &quot;ev++.h&quot;
2100
2101</pre>
2102 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2103<pre> #include &quot;ev_cpp.h&quot;
2104 #include &quot;ev.c&quot;
2105
2106
2107
2108
2109</pre>
2110
2111</div>
2112<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
2113<div id="COMPLEXITIES_CONTENT">
2114 <p>In this section the complexities of (many of) the algorithms used inside
2115libev will be explained. For complexity discussions about backends see the
2116documentation for <code>ev_default_init</code>.</p>
2117 <p>
2118 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2120 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2121 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2122 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2123 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
2124 <dt>Finding the next timer per loop iteration: O(1)</dt>
2125 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2126 <dt>Activating one watcher: O(1)</dt>
2127 </dl>
2128 </p>
2129
2130
2131
2132
1308 2133
1309</div> 2134</div>
1310<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2135<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
1311<div id="AUTHOR_CONTENT"> 2136<div id="AUTHOR_CONTENT">
1312<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2137 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1313 2138
1314</div> 2139</div>
1315</div></body> 2140</div></body>
1316</html> 2141</html>

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