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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Sat Nov 24 17:31:33 2007" /> 9 <meta name="created" content="Fri Dec 7 21:19:14 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">
124<p>The newest version of this document is also available as a html-formatted
125web page you might find easier to navigate when reading it for the first
126time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
74<p>Libev is an event loop: you register interest in certain events (such as a 127<p>Libev is an event loop: you register interest in certain events (such as a
75file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
76these event sources and provide your program with events.</p> 129these 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 130<p>To do this, it must take more or less complete control over your process
78(or thread) by executing the <i>event loop</i> handler, and will then 131(or thread) by executing the <i>event loop</i> handler, and will then
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81watchers</i>, which are relatively small C structures you initialise with the 134watchers</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 135details of the event, and then hand it over to libev by <i>starting</i> the
83watcher.</p> 136watcher.</p>
84 137
85</div> 138</div>
86<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
87<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
88<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 141<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
89kqueue mechanisms for file descriptor events, relative timers, absolute 142BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
90timers with customised rescheduling, signal events, process status change 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
91events (related to SIGCHLD), and event watchers dealing with the event 144(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 145with customised rescheduling (<code>ev_periodic</code>), synchronous signals
146(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
147watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
148<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
149file watchers (<code>ev_stat</code>) and even limited support for fork events
150(<code>ev_fork</code>).</p>
151<p>It also is quite fast (see this
93fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 152<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
94it to libevent for example).</p> 153for example).</p>
95 154
96</div> 155</div>
97<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
98<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
99<p>Libev is very configurable. In this manual the default configuration 158<p>Libev is very configurable. In this manual the default configuration will
100will be described, which supports multiple event loops. For more info 159be described, which supports multiple event loops. For more info about
101about various configuration options please have a look at the file 160various 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 161this manual. If libev was configured without support for multiple event
103support for multiple event loops, then all functions taking an initial 162loops, 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>) 163(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
105will not have this argument.</p>
106 164
107</div> 165</div>
108<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
109<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
110<p>Libev represents time as a single floating point number, representing the 168<p>Libev represents time as a single floating point number, representing the
111(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
112the beginning of 1970, details are complicated, don't ask). This type is 170the beginning of 1970, details are complicated, don't ask). This type is
113called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 171called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
114to the <code>double</code> type in C, and when you need to do any calculations on 172to the <code>double</code> type in C, and when you need to do any calculations on
115it, you should treat it as such.</p> 173it, you should treat it as such.</p>
116 174
117
118
119
120
121</div> 175</div>
122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 176<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
123<div id="GLOBAL_FUNCTIONS_CONTENT"> 177<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the 178<p>These functions can be called anytime, even before initialising the
125library in any way.</p> 179library in any way.</p>
126<dl> 180<dl>
127 <dt>ev_tstamp ev_time ()</dt> 181 <dt>ev_tstamp ev_time ()</dt>
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140version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
141 <p>Usually, it's a good idea to terminate if the major versions mismatch, 195 <p>Usually, it's a good idea to terminate if the major versions mismatch,
142as this indicates an incompatible change. Minor versions are usually 196as this indicates an incompatible change. Minor versions are usually
143compatible to older versions, so a larger minor version alone is usually 197compatible to older versions, so a larger minor version alone is usually
144not a problem.</p> 198not a problem.</p>
145 <p>Example: make sure we haven't accidentally been linked against the wrong 199 <p>Example: Make sure we haven't accidentally been linked against the wrong
146version:</p> 200version.</p>
147<pre> assert ((&quot;libev version mismatch&quot;, 201<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR 202 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 203 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150 204
151</pre> 205</pre>
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181recommended ones.</p> 235recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 236 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
183 </dd> 237 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
185 <dd> 239 <dd>
186 <p>Sets the allocation function to use (the prototype is similar to the 240 <p>Sets the allocation function to use (the prototype is similar - the
187realloc C function, the semantics are identical). It is used to allocate 241semantics is identical - to the realloc C function). It is used to
188and free memory (no surprises here). If it returns zero when memory 242allocate and free memory (no surprises here). If it returns zero when
189needs to be allocated, the library might abort or take some potentially 243memory needs to be allocated, the library might abort or take some
190destructive action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
191 <p>You could override this function in high-availability programs to, say, 246 <p>You could override this function in high-availability programs to, say,
192free some memory if it cannot allocate memory, to use a special allocator, 247free some memory if it cannot allocate memory, to use a special allocator,
193or even to sleep a while and retry until some memory is available.</p> 248or even to sleep a while and retry until some memory is available.</p>
194 <p>Example: replace the libev allocator with one that waits a bit and then 249 <p>Example: Replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p> 250retries).</p>
196<pre> static void * 251<pre> static void *
197 persistent_realloc (void *ptr, long size) 252 persistent_realloc (void *ptr, size_t size)
198 { 253 {
199 for (;;) 254 for (;;)
200 { 255 {
201 void *newptr = realloc (ptr, size); 256 void *newptr = realloc (ptr, size);
202 257
… …
219indicating the system call or subsystem causing the problem. If this 274indicating the system call or subsystem causing the problem. If this
220callback is set, then libev will expect it to remedy the sitution, no 275callback is set, then libev will expect it to remedy the sitution, no
221matter what, when it returns. That is, libev will generally retry the 276matter what, when it returns. That is, libev will generally retry the
222requested operation, or, if the condition doesn't go away, do bad stuff 277requested operation, or, if the condition doesn't go away, do bad stuff
223(such as abort).</p> 278(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p> 279 <p>Example: This is basically the same thing that libev does internally, too.</p>
225<pre> static void 280<pre> static void
226 fatal_error (const char *msg) 281 fatal_error (const char *msg)
227 { 282 {
228 perror (msg); 283 perror (msg);
229 abort (); 284 abort ();
… …
235</pre> 290</pre>
236 </dd> 291 </dd>
237</dl> 292</dl>
238 293
239</div> 294</div>
240<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 295<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
241<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 296<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 297<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 298types of such loops, the <i>default</i> loop, which supports signals and child
244events, and dynamically created loops which do not.</p> 299events, and dynamically created loops which do not.</p>
245<p>If you use threads, a common model is to run the default event loop 300<p>If you use threads, a common model is to run the default event loop
… …
274<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
275override the flags completely if it is found in the environment. This is 330override the flags completely if it is found in the environment. This is
276useful to try out specific backends to test their performance, or to work 331useful to try out specific backends to test their performance, or to work
277around bugs.</p> 332around bugs.</p>
278 </dd> 333 </dd>
334 <dt><code>EVFLAG_FORKCHECK</code></dt>
335 <dd>
336 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
337a fork, you can also make libev check for a fork in each iteration by
338enabling this flag.</p>
339 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
340and thus this might slow down your event loop if you do a lot of loop
341iterations and little real work, but is usually not noticeable (on my
342Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
343without a syscall and thus <i>very</i> fast, but my Linux system also has
344<code>pthread_atfork</code> which is even faster).</p>
345 <p>The big advantage of this flag is that you can forget about fork (and
346forget about forgetting to tell libev about forking) when you use this
347flag.</p>
348 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
349environment variable.</p>
350 </dd>
279 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
280 <dd> 352 <dd>
281 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 353 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
282libev tries to roll its own fd_set with no limits on the number of fds, 354libev tries to roll its own fd_set with no limits on the number of fds,
283but if that fails, expect a fairly low limit on the number of fds when 355but if that fails, expect a fairly low limit on the number of fds when
… …
365 <dd> 437 <dd>
366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 438 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
367always distinct from the default loop. Unlike the default loop, it cannot 439always 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 440handle signal and child watchers, and attempts to do so will be greeted by
369undefined behaviour (or a failed assertion if assertions are enabled).</p> 441undefined 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> 442 <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); 443<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller) 444 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 445 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374 446
375</pre> 447</pre>
… …
411 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
412 <dd> 484 <dd>
413 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 485 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
414<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 486<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
415after fork, and how you do this is entirely your own problem.</p> 487after fork, and how you do this is entirely your own problem.</p>
488 </dd>
489 <dt>unsigned int ev_loop_count (loop)</dt>
490 <dd>
491 <p>Returns the count of loop iterations for the loop, which is identical to
492the number of times libev did poll for new events. It starts at <code>0</code> and
493happily wraps around with enough iterations.</p>
494 <p>This value can sometimes be useful as a generation counter of sorts (it
495&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
496<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
416 </dd> 497 </dd>
417 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
418 <dd> 499 <dd>
419 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 500 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
420use.</p> 501use.</p>
… …
468 be handled here by queueing them when their watcher gets executed. 549 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 550 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *. 551 were used, return, otherwise continue with step *.
471 552
472</pre> 553</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding 554 <p>Example: Queue some jobs and then loop until no events are outsanding
474anymore.</p> 555anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long 556<pre> ... queue jobs here, make sure they register event watchers as long
476 ... as they still have work to do (even an idle watcher will do..) 557 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0); 558 ev_loop (my_loop, 0);
478 ... jobs done. yeah! 559 ... jobs done. yeah!
… …
497example, libev itself uses this for its internal signal pipe: It is not 578example, libev itself uses this for its internal signal pipe: It is not
498visible to the libev user and should not keep <code>ev_loop</code> from exiting if 579visible to the libev user and should not keep <code>ev_loop</code> from exiting if
499no event watchers registered by it are active. It is also an excellent 580no event watchers registered by it are active. It is also an excellent
500way to do this for generic recurring timers or from within third-party 581way to do this for generic recurring timers or from within third-party
501libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 582libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
502 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 583 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p> 584running when nothing else is active.</p>
504<pre> struct dv_signal exitsig; 585<pre> struct ev_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 586 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig); 587 ev_signal_start (loop, &amp;exitsig);
507 evf_unref (myloop); 588 evf_unref (loop);
508 589
509</pre> 590</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p> 591 <p>Example: For some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop); 592<pre> ev_ref (loop);
512 ev_signal_stop (myloop, &amp;exitsig); 593 ev_signal_stop (loop, &amp;exitsig);
513 594
514</pre> 595</pre>
515 </dd> 596 </dd>
516</dl> 597</dl>
517 598
518 599
519 600
520 601
521 602
522</div> 603</div>
523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 604<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
524<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 605<div id="ANATOMY_OF_A_WATCHER_CONTENT">
525<p>A watcher is a structure that you create and register to record your 606<p>A watcher is a structure that you create and register to record your
526interest in some event. For instance, if you want to wait for STDIN to 607interest in some event. For instance, if you want to wait for STDIN to
527become readable, you would create an <code>ev_io</code> watcher for that:</p> 608become readable, you would create an <code>ev_io</code> watcher for that:</p>
528<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 609<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
585 </dd> 666 </dd>
586 <dt><code>EV_CHILD</code></dt> 667 <dt><code>EV_CHILD</code></dt>
587 <dd> 668 <dd>
588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 669 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
589 </dd> 670 </dd>
671 <dt><code>EV_STAT</code></dt>
672 <dd>
673 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
674 </dd>
590 <dt><code>EV_IDLE</code></dt> 675 <dt><code>EV_IDLE</code></dt>
591 <dd> 676 <dd>
592 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 677 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
593 </dd> 678 </dd>
594 <dt><code>EV_PREPARE</code></dt> 679 <dt><code>EV_PREPARE</code></dt>
… …
599<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 684<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
600received events. Callbacks of both watcher types can start and stop as 685received 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 686many 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 687(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
603<code>ev_loop</code> from blocking).</p> 688<code>ev_loop</code> from blocking).</p>
689 </dd>
690 <dt><code>EV_EMBED</code></dt>
691 <dd>
692 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
693 </dd>
694 <dt><code>EV_FORK</code></dt>
695 <dd>
696 <p>The event loop has been resumed in the child process after fork (see
697<code>ev_fork</code>).</p>
604 </dd> 698 </dd>
605 <dt><code>EV_ERROR</code></dt> 699 <dt><code>EV_ERROR</code></dt>
606 <dd> 700 <dd>
607 <p>An unspecified error has occured, the watcher has been stopped. This might 701 <p>An unspecified error has occured, the watcher has been stopped. This might
608happen because the watcher could not be properly started because libev 702happen because the watcher could not be properly started because libev
… …
678events but its callback has not yet been invoked). As long as a watcher 772events 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 773is 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 774<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> 775libev (e.g. you cnanot <code>free ()</code> it).</p>
682 </dd> 776 </dd>
683 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 777 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
684 <dd> 778 <dd>
685 <p>Returns the callback currently set on the watcher.</p> 779 <p>Returns the callback currently set on the watcher.</p>
686 </dd> 780 </dd>
687 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 781 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
688 <dd> 782 <dd>
689 <p>Change the callback. You can change the callback at virtually any time 783 <p>Change the callback. You can change the callback at virtually any time
690(modulo threads).</p> 784(modulo threads).</p>
785 </dd>
786 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
787 <dt>int ev_priority (ev_TYPE *watcher)</dt>
788 <dd>
789 <p>Set and query the priority of the watcher. The priority is a small
790integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
791(default: <code>-2</code>). Pending watchers with higher priority will be invoked
792before watchers with lower priority, but priority will not keep watchers
793from being executed (except for <code>ev_idle</code> watchers).</p>
794 <p>This means that priorities are <i>only</i> used for ordering callback
795invocation after new events have been received. This is useful, for
796example, to reduce latency after idling, or more often, to bind two
797watchers on the same event and make sure one is called first.</p>
798 <p>If you need to suppress invocation when higher priority events are pending
799you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
800 <p>The default priority used by watchers when no priority has been set is
801always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
802 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
803fine, as long as you do not mind that the priority value you query might
804or might not have been adjusted to be within valid range.</p>
691 </dd> 805 </dd>
692</dl> 806</dl>
693 807
694 808
695 809
… …
720 struct my_io *w = (struct my_io *)w_; 834 struct my_io *w = (struct my_io *)w_;
721 ... 835 ...
722 } 836 }
723 837
724</pre> 838</pre>
725<p>More interesting and less C-conformant ways of catsing your callback type 839<p>More interesting and less C-conformant ways of casting your callback type
726have been omitted....</p> 840instead have been omitted.</p>
841<p>Another common scenario is having some data structure with multiple
842watchers:</p>
843<pre> struct my_biggy
844 {
845 int some_data;
846 ev_timer t1;
847 ev_timer t2;
848 }
727 849
850</pre>
851<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
852you need to use <code>offsetof</code>:</p>
853<pre> #include &lt;stddef.h&gt;
728 854
855 static void
856 t1_cb (EV_P_ struct ev_timer *w, int revents)
857 {
858 struct my_biggy big = (struct my_biggy *
859 (((char *)w) - offsetof (struct my_biggy, t1));
860 }
729 861
862 static void
863 t2_cb (EV_P_ struct ev_timer *w, int revents)
864 {
865 struct my_biggy big = (struct my_biggy *
866 (((char *)w) - offsetof (struct my_biggy, t2));
867 }
730 868
731 869
870
871
872</pre>
873
732</div> 874</div>
733<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 875<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
734<div id="WATCHER_TYPES_CONTENT"> 876<div id="WATCHER_TYPES_CONTENT">
735<p>This section describes each watcher in detail, but will not repeat 877<p>This section describes each watcher in detail, but will not repeat
736information given in the last section.</p> 878information given in the last section. Any initialisation/set macros,
879functions and members specific to the watcher type are explained.</p>
880<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
881while the watcher is active, you can look at the member and expect some
882sensible content, but you must not modify it (you can modify it while the
883watcher is stopped to your hearts content), or <i>[read-write]</i>, which
884means you can expect it to have some sensible content while the watcher
885is active, but you can also modify it. Modifying it may not do something
886sensible or take immediate effect (or do anything at all), but libev will
887not crash or malfunction in any way.</p>
737 888
738 889
739 890
740 891
741 892
… …
769this situation even with a relatively standard program structure. Thus 920this situation even with a relatively standard program structure. Thus
770it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 921it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
771<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 922<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
772<p>If you cannot run the fd in non-blocking mode (for example you should not 923<p>If you cannot run the fd in non-blocking mode (for example you should not
773play around with an Xlib connection), then you have to seperately re-test 924play around with an Xlib connection), then you have to seperately re-test
774wether a file descriptor is really ready with a known-to-be good interface 925whether a file descriptor is really ready with a known-to-be good interface
775such as poll (fortunately in our Xlib example, Xlib already does this on 926such as poll (fortunately in our Xlib example, Xlib already does this on
776its own, so its quite safe to use).</p> 927its own, so its quite safe to use).</p>
777<dl> 928<dl>
778 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 929 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
779 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 930 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
780 <dd> 931 <dd>
781 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 932 <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 933rceeive 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> 934<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
784 </dd> 935 </dd>
936 <dt>int fd [read-only]</dt>
937 <dd>
938 <p>The file descriptor being watched.</p>
939 </dd>
940 <dt>int events [read-only]</dt>
941 <dd>
942 <p>The events being watched.</p>
943 </dd>
785</dl> 944</dl>
786<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 945<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 946readable, but only once. Since it is likely line-buffered, you could
788attempt to read a whole line in the callback:</p> 947attempt to read a whole line in the callback.</p>
789<pre> static void 948<pre> static void
790 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 949 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
791 { 950 {
792 ev_io_stop (loop, w); 951 ev_io_stop (loop, w);
793 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 952 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
842 </dd> 1001 </dd>
843 <dt>ev_timer_again (loop)</dt> 1002 <dt>ev_timer_again (loop)</dt>
844 <dd> 1003 <dd>
845 <p>This will act as if the timer timed out and restart it again if it is 1004 <p>This will act as if the timer timed out and restart it again if it is
846repeating. The exact semantics are:</p> 1005repeating. The exact semantics are:</p>
1006 <p>If the timer is pending, its pending status is cleared.</p>
847 <p>If the timer is started but nonrepeating, stop it.</p> 1007 <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 1008 <p>If the timer is repeating, either start it if necessary (with the
849value), or reset the running timer to the repeat value.</p> 1009<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 1010 <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 1011example: 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 1012timeout, 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 1013seconds 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 1014configure 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 1015<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 1016you go into an idle state where you do not expect data to travel on the
1017socket, 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> 1018automatically restart it if need be.</p>
1019 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
1020altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
1021<pre> ev_timer_init (timer, callback, 0., 5.);
1022 ev_timer_again (loop, timer);
1023 ...
1024 timer-&gt;again = 17.;
1025 ev_timer_again (loop, timer);
1026 ...
1027 timer-&gt;again = 10.;
1028 ev_timer_again (loop, timer);
1029
1030</pre>
1031 <p>This is more slightly efficient then stopping/starting the timer each time
1032you want to modify its timeout value.</p>
1033 </dd>
1034 <dt>ev_tstamp repeat [read-write]</dt>
1035 <dd>
1036 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
1037or <code>ev_timer_again</code> is called and determines the next timeout (if any),
1038which is also when any modifications are taken into account.</p>
858 </dd> 1039 </dd>
859</dl> 1040</dl>
860<p>Example: create a timer that fires after 60 seconds.</p> 1041<p>Example: Create a timer that fires after 60 seconds.</p>
861<pre> static void 1042<pre> static void
862 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1043 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
863 { 1044 {
864 .. one minute over, w is actually stopped right here 1045 .. one minute over, w is actually stopped right here
865 } 1046 }
… …
867 struct ev_timer mytimer; 1048 struct ev_timer mytimer;
868 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1049 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
869 ev_timer_start (loop, &amp;mytimer); 1050 ev_timer_start (loop, &amp;mytimer);
870 1051
871</pre> 1052</pre>
872<p>Example: create a timeout timer that times out after 10 seconds of 1053<p>Example: Create a timeout timer that times out after 10 seconds of
873inactivity.</p> 1054inactivity.</p>
874<pre> static void 1055<pre> static void
875 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1056 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
876 { 1057 {
877 .. ten seconds without any activity 1058 .. ten seconds without any activity
… …
980 <p>Simply stops and restarts the periodic watcher again. This is only useful 1161 <p>Simply stops and restarts the periodic watcher again. This is only useful
981when you changed some parameters or the reschedule callback would return 1162when 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 1163a different time than the last time it was called (e.g. in a crond like
983program when the crontabs have changed).</p> 1164program when the crontabs have changed).</p>
984 </dd> 1165 </dd>
1166 <dt>ev_tstamp interval [read-write]</dt>
1167 <dd>
1168 <p>The current interval value. Can be modified any time, but changes only
1169take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1170called.</p>
1171 </dd>
1172 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1173 <dd>
1174 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1175switched off. Can be changed any time, but changes only take effect when
1176the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1177 </dd>
985</dl> 1178</dl>
986<p>Example: call a callback every hour, or, more precisely, whenever the 1179<p>Example: Call a callback every hour, or, more precisely, whenever the
987system clock is divisible by 3600. The callback invocation times have 1180system clock is divisible by 3600. The callback invocation times have
988potentially a lot of jittering, but good long-term stability.</p> 1181potentially a lot of jittering, but good long-term stability.</p>
989<pre> static void 1182<pre> static void
990 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1183 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
991 { 1184 {
… …
995 struct ev_periodic hourly_tick; 1188 struct ev_periodic hourly_tick;
996 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1189 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
997 ev_periodic_start (loop, &amp;hourly_tick); 1190 ev_periodic_start (loop, &amp;hourly_tick);
998 1191
999</pre> 1192</pre>
1000<p>Example: the same as above, but use a reschedule callback to do it:</p> 1193<p>Example: The same as above, but use a reschedule callback to do it:</p>
1001<pre> #include &lt;math.h&gt; 1194<pre> #include &lt;math.h&gt;
1002 1195
1003 static ev_tstamp 1196 static ev_tstamp
1004 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1197 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1005 { 1198 {
… …
1007 } 1200 }
1008 1201
1009 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1202 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1010 1203
1011</pre> 1204</pre>
1012<p>Example: call a callback every hour, starting now:</p> 1205<p>Example: Call a callback every hour, starting now:</p>
1013<pre> struct ev_periodic hourly_tick; 1206<pre> struct ev_periodic hourly_tick;
1014 ev_periodic_init (&amp;hourly_tick, clock_cb, 1207 ev_periodic_init (&amp;hourly_tick, clock_cb,
1015 fmod (ev_now (loop), 3600.), 3600., 0); 1208 fmod (ev_now (loop), 3600.), 3600., 0);
1016 ev_periodic_start (loop, &amp;hourly_tick); 1209 ev_periodic_start (loop, &amp;hourly_tick);
1017 1210
… …
1038 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1231 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1039 <dd> 1232 <dd>
1040 <p>Configures the watcher to trigger on the given signal number (usually one 1233 <p>Configures the watcher to trigger on the given signal number (usually one
1041of the <code>SIGxxx</code> constants).</p> 1234of the <code>SIGxxx</code> constants).</p>
1042 </dd> 1235 </dd>
1236 <dt>int signum [read-only]</dt>
1237 <dd>
1238 <p>The signal the watcher watches out for.</p>
1239 </dd>
1043</dl> 1240</dl>
1044 1241
1045 1242
1046 1243
1047 1244
… …
1060at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1257at 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 1258the 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 1259<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1063process causing the status change.</p> 1260process causing the status change.</p>
1064 </dd> 1261 </dd>
1262 <dt>int pid [read-only]</dt>
1263 <dd>
1264 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1265 </dd>
1266 <dt>int rpid [read-write]</dt>
1267 <dd>
1268 <p>The process id that detected a status change.</p>
1269 </dd>
1270 <dt>int rstatus [read-write]</dt>
1271 <dd>
1272 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1273<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1274 </dd>
1065</dl> 1275</dl>
1066<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1276<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1067<pre> static void 1277<pre> static void
1068 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1278 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1069 { 1279 {
1070 ev_unloop (loop, EVUNLOOP_ALL); 1280 ev_unloop (loop, EVUNLOOP_ALL);
1071 } 1281 }
… …
1078 1288
1079 1289
1080</pre> 1290</pre>
1081 1291
1082</div> 1292</div>
1293<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1294<div id="code_ev_stat_code_did_the_file_attri-2">
1295<p>This watches a filesystem path for attribute changes. That is, it calls
1296<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1297compared to the last time, invoking the callback if it did.</p>
1298<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1299not exist&quot; is a status change like any other. The condition &quot;path does
1300not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1301otherwise always forced to be at least one) and all the other fields of
1302the stat buffer having unspecified contents.</p>
1303<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1304relative and your working directory changes, the behaviour is undefined.</p>
1305<p>Since there is no standard to do this, the portable implementation simply
1306calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1307can specify a recommended polling interval for this case. If you specify
1308a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1309unspecified default</i> value will be used (which you can expect to be around
1310five seconds, although this might change dynamically). Libev will also
1311impose a minimum interval which is currently around <code>0.1</code>, but thats
1312usually overkill.</p>
1313<p>This watcher type is not meant for massive numbers of stat watchers,
1314as even with OS-supported change notifications, this can be
1315resource-intensive.</p>
1316<p>At the time of this writing, only the Linux inotify interface is
1317implemented (implementing kqueue support is left as an exercise for the
1318reader). Inotify will be used to give hints only and should not change the
1319semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1320to fall back to regular polling again even with inotify, but changes are
1321usually detected immediately, and if the file exists there will be no
1322polling.</p>
1323<dl>
1324 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1325 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1326 <dd>
1327 <p>Configures the watcher to wait for status changes of the given
1328<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1329be detected and should normally be specified as <code>0</code> to let libev choose
1330a suitable value. The memory pointed to by <code>path</code> must point to the same
1331path for as long as the watcher is active.</p>
1332 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1333relative to the attributes at the time the watcher was started (or the
1334last change was detected).</p>
1335 </dd>
1336 <dt>ev_stat_stat (ev_stat *)</dt>
1337 <dd>
1338 <p>Updates the stat buffer immediately with new values. If you change the
1339watched path in your callback, you could call this fucntion to avoid
1340detecting this change (while introducing a race condition). Can also be
1341useful simply to find out the new values.</p>
1342 </dd>
1343 <dt>ev_statdata attr [read-only]</dt>
1344 <dd>
1345 <p>The most-recently detected attributes of the file. Although the type is of
1346<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1347suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1348was some error while <code>stat</code>ing the file.</p>
1349 </dd>
1350 <dt>ev_statdata prev [read-only]</dt>
1351 <dd>
1352 <p>The previous attributes of the file. The callback gets invoked whenever
1353<code>prev</code> != <code>attr</code>.</p>
1354 </dd>
1355 <dt>ev_tstamp interval [read-only]</dt>
1356 <dd>
1357 <p>The specified interval.</p>
1358 </dd>
1359 <dt>const char *path [read-only]</dt>
1360 <dd>
1361 <p>The filesystem path that is being watched.</p>
1362 </dd>
1363</dl>
1364<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1365<pre> static void
1366 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1367 {
1368 /* /etc/passwd changed in some way */
1369 if (w-&gt;attr.st_nlink)
1370 {
1371 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1372 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1373 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1374 }
1375 else
1376 /* you shalt not abuse printf for puts */
1377 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1378 &quot;if this is windows, they already arrived\n&quot;);
1379 }
1380
1381 ...
1382 ev_stat passwd;
1383
1384 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1385 ev_stat_start (loop, &amp;passwd);
1386
1387
1388
1389
1390</pre>
1391
1392</div>
1083<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1393<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1084<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1394<div id="code_ev_idle_code_when_you_ve_got_no-2">
1085<p>Idle watchers trigger events when there are no other events are pending 1395<p>Idle watchers trigger events when no other events of the same or higher
1086(prepare, check and other idle watchers do not count). That is, as long 1396priority are pending (prepare, check and other idle watchers do not
1087as your process is busy handling sockets or timeouts (or even signals, 1397count).</p>
1088imagine) it will not be triggered. But when your process is idle all idle 1398<p>That is, as long as your process is busy handling sockets or timeouts
1089watchers are being called again and again, once per event loop iteration - 1399(or even signals, imagine) of the same or higher priority it will not be
1400triggered. But when your process is idle (or only lower-priority watchers
1401are pending), the idle watchers are being called once per event loop
1090until stopped, that is, or your process receives more events and becomes 1402iteration - until stopped, that is, or your process receives more events
1091busy.</p> 1403and becomes busy again with higher priority stuff.</p>
1092<p>The most noteworthy effect is that as long as any idle watchers are 1404<p>The most noteworthy effect is that as long as any idle watchers are
1093active, the process will not block when waiting for new events.</p> 1405active, the process will not block when waiting for new events.</p>
1094<p>Apart from keeping your process non-blocking (which is a useful 1406<p>Apart from keeping your process non-blocking (which is a useful
1095effect on its own sometimes), idle watchers are a good place to do 1407effect on its own sometimes), idle watchers are a good place to do
1096&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1408&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1101 <p>Initialises and configures the idle watcher - it has no parameters of any 1413 <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, 1414kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1103believe me.</p> 1415believe me.</p>
1104 </dd> 1416 </dd>
1105</dl> 1417</dl>
1106<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1418<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> 1419callback, free it. Also, use no error checking, as usual.</p>
1108<pre> static void 1420<pre> static void
1109 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1421 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1110 { 1422 {
1111 free (w); 1423 free (w);
1112 // now do something you wanted to do when the program has 1424 // now do something you wanted to do when the program has
… …
1126<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2> 1438<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1127<div id="code_ev_prepare_code_and_code_ev_che-2"> 1439<div id="code_ev_prepare_code_and_code_ev_che-2">
1128<p>Prepare and check watchers are usually (but not always) used in tandem: 1440<p>Prepare and check watchers are usually (but not always) used in tandem:
1129prepare watchers get invoked before the process blocks and check watchers 1441prepare watchers get invoked before the process blocks and check watchers
1130afterwards.</p> 1442afterwards.</p>
1443<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1444the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1445watchers. Other loops than the current one are fine, however. The
1446rationale behind this is that you do not need to check for recursion in
1447those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1448<code>ev_check</code> so if you have one watcher of each kind they will always be
1449called in pairs bracketing the blocking call.</p>
1131<p>Their main purpose is to integrate other event mechanisms into libev and 1450<p>Their main purpose is to integrate other event mechanisms into libev and
1132their use is somewhat advanced. This could be used, for example, to track 1451their use is somewhat advanced. This could be used, for example, to track
1133variable changes, implement your own watchers, integrate net-snmp or a 1452variable changes, implement your own watchers, integrate net-snmp or a
1134coroutine library and lots more.</p> 1453coroutine library and lots more. They are also occasionally useful if
1454you cache some data and want to flush it before blocking (for example,
1455in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1456watcher).</p>
1135<p>This is done by examining in each prepare call which file descriptors need 1457<p>This is done by examining in each prepare call which file descriptors need
1136to be watched by the other library, registering <code>ev_io</code> watchers for 1458to be watched by the other library, registering <code>ev_io</code> watchers for
1137them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1459them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1138provide just this functionality). Then, in the check watcher you check for 1460provide just this functionality). Then, in the check watcher you check for
1139any events that occured (by checking the pending status of all watchers 1461any events that occured (by checking the pending status of all watchers
… …
1155 <p>Initialises and configures the prepare or check watcher - they have no 1477 <p>Initialises and configures the prepare or check watcher - they have no
1156parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1478parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1157macros, but using them is utterly, utterly and completely pointless.</p> 1479macros, but using them is utterly, utterly and completely pointless.</p>
1158 </dd> 1480 </dd>
1159</dl> 1481</dl>
1160<p>Example: *TODO*.</p> 1482<p>Example: To include a library such as adns, you would add IO watchers
1483and a timeout watcher in a prepare handler, as required by libadns, and
1484in a check watcher, destroy them and call into libadns. What follows is
1485pseudo-code only of course:</p>
1486<pre> static ev_io iow [nfd];
1487 static ev_timer tw;
1161 1488
1489 static void
1490 io_cb (ev_loop *loop, ev_io *w, int revents)
1491 {
1492 // set the relevant poll flags
1493 // could also call adns_processreadable etc. here
1494 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1495 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1496 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1497 }
1162 1498
1499 // create io watchers for each fd and a timer before blocking
1500 static void
1501 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1502 {
1503 int timeout = 3600000;
1504 struct pollfd fds [nfd];
1505 // actual code will need to loop here and realloc etc.
1506 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1163 1507
1508 /* the callback is illegal, but won't be called as we stop during check */
1509 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1510 ev_timer_start (loop, &amp;tw);
1164 1511
1512 // create on ev_io per pollfd
1513 for (int i = 0; i &lt; nfd; ++i)
1514 {
1515 ev_io_init (iow + i, io_cb, fds [i].fd,
1516 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1517 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1518
1519 fds [i].revents = 0;
1520 iow [i].data = fds + i;
1521 ev_io_start (loop, iow + i);
1522 }
1523 }
1524
1525 // stop all watchers after blocking
1526 static void
1527 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1528 {
1529 ev_timer_stop (loop, &amp;tw);
1530
1531 for (int i = 0; i &lt; nfd; ++i)
1532 ev_io_stop (loop, iow + i);
1533
1534 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1535 }
1536
1537
1538
1539
1540</pre>
1165 1541
1166</div> 1542</div>
1167<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2> 1543<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1168<div id="code_ev_embed_code_when_one_backend_-2"> 1544<div id="code_ev_embed_code_when_one_backend_-2">
1169<p>This is a rather advanced watcher type that lets you embed one event loop 1545<p>This is a rather advanced watcher type that lets you embed one event loop
… …
1240 <dd> 1616 <dd>
1241 <p>Make a single, non-blocking sweep over the embedded loop. This works 1617 <p>Make a single, non-blocking sweep over the embedded loop. This works
1242similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1618similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1243apropriate way for embedded loops.</p> 1619apropriate way for embedded loops.</p>
1244 </dd> 1620 </dd>
1621 <dt>struct ev_loop *loop [read-only]</dt>
1622 <dd>
1623 <p>The embedded event loop.</p>
1624 </dd>
1245</dl> 1625</dl>
1246 1626
1247 1627
1248 1628
1249 1629
1250 1630
1251</div> 1631</div>
1252<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1632<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>
1633<div id="code_ev_fork_code_the_audacity_to_re-2">
1634<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1635whoever is a good citizen cared to tell libev about it by calling
1636<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1637event loop blocks next and before <code>ev_check</code> watchers are being called,
1638and only in the child after the fork. If whoever good citizen calling
1639<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1640handlers will be invoked, too, of course.</p>
1641<dl>
1642 <dt>ev_fork_init (ev_signal *, callback)</dt>
1643 <dd>
1644 <p>Initialises and configures the fork watcher - it has no parameters of any
1645kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1646believe me.</p>
1647 </dd>
1648</dl>
1649
1650
1651
1652
1653
1654</div>
1655<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1253<div id="OTHER_FUNCTIONS_CONTENT"> 1656<div id="OTHER_FUNCTIONS_CONTENT">
1254<p>There are some other functions of possible interest. Described. Here. Now.</p> 1657<p>There are some other functions of possible interest. Described. Here. Now.</p>
1255<dl> 1658<dl>
1256 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1659 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1257 <dd> 1660 <dd>
… …
1304 1707
1305 1708
1306 1709
1307 1710
1308</div> 1711</div>
1309<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1712<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1310<div id="LIBEVENT_EMULATION_CONTENT"> 1713<div id="LIBEVENT_EMULATION_CONTENT">
1311<p>Libev offers a compatibility emulation layer for libevent. It cannot 1714<p>Libev offers a compatibility emulation layer for libevent. It cannot
1312emulate the internals of libevent, so here are some usage hints:</p> 1715emulate the internals of libevent, so here are some usage hints:</p>
1313<dl> 1716<dl>
1314 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1717 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1324 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1727 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1325to use the libev header file and library.</dt> 1728to use the libev header file and library.</dt>
1326</dl> 1729</dl>
1327 1730
1328</div> 1731</div>
1329<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1732<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1330<div id="C_SUPPORT_CONTENT"> 1733<div id="C_SUPPORT_CONTENT">
1331<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1734<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1332you to use some convinience methods to start/stop watchers and also change 1735you to use some convinience methods to start/stop watchers and also change
1333the callback model to a model using method callbacks on objects.</p> 1736the callback model to a model using method callbacks on objects.</p>
1334<p>To use it,</p> 1737<p>To use it,</p>
1335<pre> #include &lt;ev++.h&gt; 1738<pre> #include &lt;ev++.h&gt;
1336 1739
1337</pre> 1740</pre>
1338<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1741<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1339and puts all of its definitions (many of them macros) into the global 1742of them macros) into the global namespace. All C++ specific things are
1340namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1743put into the <code>ev</code> namespace. It should support all the same embedding
1341<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1744options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1342<code>EV_MULTIPLICITY</code>.</p> 1745<p>Care has been taken to keep the overhead low. The only data member the C++
1746classes add (compared to plain C-style watchers) is the event loop pointer
1747that the watcher is associated with (or no additional members at all if
1748you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1749<p>Currently, functions, and static and non-static member functions can be
1750used as callbacks. Other types should be easy to add as long as they only
1751need one additional pointer for context. If you need support for other
1752types of functors please contact the author (preferably after implementing
1753it).</p>
1343<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1754<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1344<dl> 1755<dl>
1345 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1756 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1346 <dd> 1757 <dd>
1347 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1758 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1358which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1769which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1359defines by many implementations.</p> 1770defines by many implementations.</p>
1360 <p>All of those classes have these methods:</p> 1771 <p>All of those classes have these methods:</p>
1361 <p> 1772 <p>
1362 <dl> 1773 <dl>
1363 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1774 <dt>ev::TYPE::TYPE ()</dt>
1364 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1775 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1365 <dt>ev::TYPE::~TYPE</dt> 1776 <dt>ev::TYPE::~TYPE</dt>
1366 <dd> 1777 <dd>
1367 <p>The constructor takes a pointer to an object and a method pointer to 1778 <p>The constructor (optionally) takes an event loop to associate the watcher
1368the event handler callback to call in this class. The constructor calls 1779with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1369<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1780 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1370before starting it. If you do not specify a loop then the constructor 1781<code>set</code> method before starting it.</p>
1371automatically associates the default loop with this watcher.</p> 1782 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1783method to set a callback before you can start the watcher.</p>
1784 <p>(The reason why you have to use a method is a limitation in C++ which does
1785not allow explicit template arguments for constructors).</p>
1372 <p>The destructor automatically stops the watcher if it is active.</p> 1786 <p>The destructor automatically stops the watcher if it is active.</p>
1787 </dd>
1788 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1789 <dd>
1790 <p>This method sets the callback method to call. The method has to have a
1791signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1792first argument and the <code>revents</code> as second. The object must be given as
1793parameter and is stored in the <code>data</code> member of the watcher.</p>
1794 <p>This method synthesizes efficient thunking code to call your method from
1795the C callback that libev requires. If your compiler can inline your
1796callback (i.e. it is visible to it at the place of the <code>set</code> call and
1797your compiler is good :), then the method will be fully inlined into the
1798thunking function, making it as fast as a direct C callback.</p>
1799 <p>Example: simple class declaration and watcher initialisation</p>
1800<pre> struct myclass
1801 {
1802 void io_cb (ev::io &amp;w, int revents) { }
1803 }
1804
1805 myclass obj;
1806 ev::io iow;
1807 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1808
1809</pre>
1810 </dd>
1811 <dt>w-&gt;set (void (*function)(watcher &amp;w, int), void *data = 0)</dt>
1812 <dd>
1813 <p>Also sets a callback, but uses a static method or plain function as
1814callback. The optional <code>data</code> argument will be stored in the watcher's
1815<code>data</code> member and is free for you to use.</p>
1816 <p>See the method-<code>set</code> above for more details.</p>
1373 </dd> 1817 </dd>
1374 <dt>w-&gt;set (struct ev_loop *)</dt> 1818 <dt>w-&gt;set (struct ev_loop *)</dt>
1375 <dd> 1819 <dd>
1376 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1820 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1377do this when the watcher is inactive (and not pending either).</p> 1821do this when the watcher is inactive (and not pending either).</p>
1378 </dd> 1822 </dd>
1379 <dt>w-&gt;set ([args])</dt> 1823 <dt>w-&gt;set ([args])</dt>
1380 <dd> 1824 <dd>
1381 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1825 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1382called at least once. Unlike the C counterpart, an active watcher gets 1826called at least once. Unlike the C counterpart, an active watcher gets
1383automatically stopped and restarted.</p> 1827automatically stopped and restarted when reconfiguring it with this
1828method.</p>
1384 </dd> 1829 </dd>
1385 <dt>w-&gt;start ()</dt> 1830 <dt>w-&gt;start ()</dt>
1386 <dd> 1831 <dd>
1387 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1832 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1388constructor already takes the loop.</p> 1833constructor already stores the event loop.</p>
1389 </dd> 1834 </dd>
1390 <dt>w-&gt;stop ()</dt> 1835 <dt>w-&gt;stop ()</dt>
1391 <dd> 1836 <dd>
1392 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1837 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1393 </dd> 1838 </dd>
… …
1397<code>ev_TYPE_again</code> function.</p> 1842<code>ev_TYPE_again</code> function.</p>
1398 </dd> 1843 </dd>
1399 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1844 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1400 <dd> 1845 <dd>
1401 <p>Invokes <code>ev_embed_sweep</code>.</p> 1846 <p>Invokes <code>ev_embed_sweep</code>.</p>
1847 </dd>
1848 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1849 <dd>
1850 <p>Invokes <code>ev_stat_stat</code>.</p>
1402 </dd> 1851 </dd>
1403 </dl> 1852 </dl>
1404 </p> 1853 </p>
1405 </dd> 1854 </dd>
1406</dl> 1855</dl>
… …
1413 1862
1414 myclass (); 1863 myclass ();
1415 } 1864 }
1416 1865
1417 myclass::myclass (int fd) 1866 myclass::myclass (int fd)
1418 : io (this, &amp;myclass::io_cb),
1419 idle (this, &amp;myclass::idle_cb)
1420 { 1867 {
1868 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1869 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1870
1421 io.start (fd, ev::READ); 1871 io.start (fd, ev::READ);
1422 } 1872 }
1423 1873
1424</pre>
1425 1874
1875
1876
1877</pre>
1878
1426</div> 1879</div>
1427<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1880<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1881<div id="MACRO_MAGIC_CONTENT">
1882<p>Libev can be compiled with a variety of options, the most fundemantal is
1883<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1884callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1885<p>To make it easier to write programs that cope with either variant, the
1886following macros are defined:</p>
1887<dl>
1888 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1889 <dd>
1890 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1891loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1892<code>EV_A_</code> is used when other arguments are following. Example:</p>
1893<pre> ev_unref (EV_A);
1894 ev_timer_add (EV_A_ watcher);
1895 ev_loop (EV_A_ 0);
1896
1897</pre>
1898 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1899which is often provided by the following macro.</p>
1900 </dd>
1901 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1902 <dd>
1903 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1904loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1905<code>EV_P_</code> is used when other parameters are following. Example:</p>
1906<pre> // this is how ev_unref is being declared
1907 static void ev_unref (EV_P);
1908
1909 // this is how you can declare your typical callback
1910 static void cb (EV_P_ ev_timer *w, int revents)
1911
1912</pre>
1913 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1914suitable for use with <code>EV_A</code>.</p>
1915 </dd>
1916 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1917 <dd>
1918 <p>Similar to the other two macros, this gives you the value of the default
1919loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1920 </dd>
1921</dl>
1922<p>Example: Declare and initialise a check watcher, utilising the above
1923macros so it will work regardless of whether multiple loops are supported
1924or not.</p>
1925<pre> static void
1926 check_cb (EV_P_ ev_timer *w, int revents)
1927 {
1928 ev_check_stop (EV_A_ w);
1929 }
1930
1931 ev_check check;
1932 ev_check_init (&amp;check, check_cb);
1933 ev_check_start (EV_DEFAULT_ &amp;check);
1934 ev_loop (EV_DEFAULT_ 0);
1935
1936</pre>
1937
1938</div>
1939<h1 id="EMBEDDING">EMBEDDING</h1>
1428<div id="EMBEDDING_CONTENT"> 1940<div id="EMBEDDING_CONTENT">
1429<p>Libev can (and often is) directly embedded into host 1941<p>Libev can (and often is) directly embedded into host
1430applications. Examples of applications that embed it include the Deliantra 1942applications. Examples of applications that embed it include the Deliantra
1431Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1943Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1432and rxvt-unicode.</p> 1944and rxvt-unicode.</p>
… …
1469 ev_vars.h 1981 ev_vars.h
1470 ev_wrap.h 1982 ev_wrap.h
1471 1983
1472 ev_win32.c required on win32 platforms only 1984 ev_win32.c required on win32 platforms only
1473 1985
1474 ev_select.c only when select backend is enabled (which is is by default) 1986 ev_select.c only when select backend is enabled (which is enabled by default)
1475 ev_poll.c only when poll backend is enabled (disabled by default) 1987 ev_poll.c only when poll backend is enabled (disabled by default)
1476 ev_epoll.c only when the epoll backend is enabled (disabled by default) 1988 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1477 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 1989 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1478 ev_port.c only when the solaris port backend is enabled (disabled by default) 1990 ev_port.c only when the solaris port backend is enabled (disabled by default)
1479 1991
1480</pre> 1992</pre>
1481<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need 1993<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1482to compile a single file.</p> 1994to compile this single file.</p>
1483 1995
1484</div> 1996</div>
1485<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3> 1997<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1486<div id="LIBEVENT_COMPATIBILITY_API_CONTENT"> 1998<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1487<p>To include the libevent compatibility API, also include:</p> 1999<p>To include the libevent compatibility API, also include:</p>
… …
1502</div> 2014</div>
1503<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3> 2015<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1504<div id="AUTOCONF_SUPPORT_CONTENT"> 2016<div id="AUTOCONF_SUPPORT_CONTENT">
1505<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in 2017<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1506whatever way you want, you can also <code>m4_include([libev.m4])</code> in your 2018whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1507<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> off. <cite>ev.c</cite> will then include 2019<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1508<cite>config.h</cite> and configure itself accordingly.</p> 2020include <cite>config.h</cite> and configure itself accordingly.</p>
1509<p>For this of course you need the m4 file:</p> 2021<p>For this of course you need the m4 file:</p>
1510<pre> libev.m4 2022<pre> libev.m4
1511 2023
1512</pre> 2024</pre>
1513 2025
… …
1606 </dd> 2118 </dd>
1607 <dt>EV_USE_DEVPOLL</dt> 2119 <dt>EV_USE_DEVPOLL</dt>
1608 <dd> 2120 <dd>
1609 <p>reserved for future expansion, works like the USE symbols above.</p> 2121 <p>reserved for future expansion, works like the USE symbols above.</p>
1610 </dd> 2122 </dd>
2123 <dt>EV_USE_INOTIFY</dt>
2124 <dd>
2125 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2126interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2127be detected at runtime.</p>
2128 </dd>
1611 <dt>EV_H</dt> 2129 <dt>EV_H</dt>
1612 <dd> 2130 <dd>
1613 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2131 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1614undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This 2132undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
1615can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2133can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1638will have the <code>struct ev_loop *</code> as first argument, and you can create 2156will have the <code>struct ev_loop *</code> as first argument, and you can create
1639additional independent event loops. Otherwise there will be no support 2157additional independent event loops. Otherwise there will be no support
1640for multiple event loops and there is no first event loop pointer 2158for multiple event loops and there is no first event loop pointer
1641argument. Instead, all functions act on the single default loop.</p> 2159argument. Instead, all functions act on the single default loop.</p>
1642 </dd> 2160 </dd>
1643 <dt>EV_PERIODICS</dt> 2161 <dt>EV_MINPRI</dt>
2162 <dt>EV_MAXPRI</dt>
2163 <dd>
2164 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2165<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2166provide for more priorities by overriding those symbols (usually defined
2167to be <code>-2</code> and <code>2</code>, respectively).</p>
2168 <p>When doing priority-based operations, libev usually has to linearly search
2169all the priorities, so having many of them (hundreds) uses a lot of space
2170and time, so using the defaults of five priorities (-2 .. +2) is usually
2171fine.</p>
2172 <p>If your embedding app does not need any priorities, defining these both to
2173<code>0</code> will save some memory and cpu.</p>
1644 <dd> 2174 </dd>
2175 <dt>EV_PERIODIC_ENABLE</dt>
2176 <dd>
1645 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2177 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1646otherwise not. This saves a few kb of code.</p> 2178defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2179code.</p>
2180 </dd>
2181 <dt>EV_IDLE_ENABLE</dt>
2182 <dd>
2183 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2184defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2185code.</p>
2186 </dd>
2187 <dt>EV_EMBED_ENABLE</dt>
2188 <dd>
2189 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2190defined to be <code>0</code>, then they are not.</p>
2191 </dd>
2192 <dt>EV_STAT_ENABLE</dt>
2193 <dd>
2194 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2195defined to be <code>0</code>, then they are not.</p>
2196 </dd>
2197 <dt>EV_FORK_ENABLE</dt>
2198 <dd>
2199 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2200defined to be <code>0</code>, then they are not.</p>
2201 </dd>
2202 <dt>EV_MINIMAL</dt>
2203 <dd>
2204 <p>If you need to shave off some kilobytes of code at the expense of some
2205speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2206some inlining decisions, saves roughly 30% codesize of amd64.</p>
2207 </dd>
2208 <dt>EV_PID_HASHSIZE</dt>
2209 <dd>
2210 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2211pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2212than enough. If you need to manage thousands of children you might want to
2213increase this value (<i>must</i> be a power of two).</p>
2214 </dd>
2215 <dt>EV_INOTIFY_HASHSIZE</dt>
2216 <dd>
2217 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2218inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2219usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2220watchers you might want to increase this value (<i>must</i> be a power of
2221two).</p>
1647 </dd> 2222 </dd>
1648 <dt>EV_COMMON</dt> 2223 <dt>EV_COMMON</dt>
1649 <dd> 2224 <dd>
1650 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2225 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1651this macro to a something else you can include more and other types of 2226this macro to a something else you can include more and other types of
… …
1656 SV *self; /* contains this struct */ \ 2231 SV *self; /* contains this struct */ \
1657 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */ 2232 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
1658 2233
1659</pre> 2234</pre>
1660 </dd> 2235 </dd>
1661 <dt>EV_CB_DECLARE(type)</dt> 2236 <dt>EV_CB_DECLARE (type)</dt>
1662 <dt>EV_CB_INVOKE(watcher,revents)</dt> 2237 <dt>EV_CB_INVOKE (watcher, revents)</dt>
1663 <dt>ev_set_cb(ev,cb)</dt> 2238 <dt>ev_set_cb (ev, cb)</dt>
1664 <dd> 2239 <dd>
1665 <p>Can be used to change the callback member declaration in each watcher, 2240 <p>Can be used to change the callback member declaration in each watcher,
1666and the way callbacks are invoked and set. Must expand to a struct member 2241and the way callbacks are invoked and set. Must expand to a struct member
1667definition and a statement, respectively. See the <cite>ev.v</cite> header file for 2242definition and a statement, respectively. See the <cite>ev.v</cite> header file for
1668their default definitions. One possible use for overriding these is to 2243their default definitions. One possible use for overriding these is to
1669avoid the ev_loop pointer as first argument in all cases, or to use method 2244avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
1670calls instead of plain function calls in C++.</p> 2245method calls instead of plain function calls in C++.</p>
1671 2246
1672</div> 2247</div>
1673<h2 id="EXAMPLES">EXAMPLES</h2> 2248<h2 id="EXAMPLES">EXAMPLES</h2>
1674<div id="EXAMPLES_CONTENT"> 2249<div id="EXAMPLES_CONTENT">
1675 <p>For a real-world example of a program the includes libev 2250 <p>For a real-world example of a program the includes libev
… …
1678the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2253the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1679interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2254interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1680will be compiled. It is pretty complex because it provides its own header 2255will be compiled. It is pretty complex because it provides its own header
1681file.</p> 2256file.</p>
1682 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2257 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1683that everybody includes and which overrides some autoconf choices:</p> 2258that everybody includes and which overrides some configure choices:</p>
2259<pre> #define EV_MINIMAL 1
1684<pre> #define EV_USE_POLL 0 2260 #define EV_USE_POLL 0
1685 #define EV_MULTIPLICITY 0 2261 #define EV_MULTIPLICITY 0
1686 #define EV_PERIODICS 0 2262 #define EV_PERIODIC_ENABLE 0
2263 #define EV_STAT_ENABLE 0
2264 #define EV_FORK_ENABLE 0
1687 #define EV_CONFIG_H &lt;config.h&gt; 2265 #define EV_CONFIG_H &lt;config.h&gt;
2266 #define EV_MINPRI 0
2267 #define EV_MAXPRI 0
1688 2268
1689 #include &quot;ev++.h&quot; 2269 #include &quot;ev++.h&quot;
1690 2270
1691</pre> 2271</pre>
1692 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2272 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1693<pre> #include &quot;ev_cpp.h&quot; 2273<pre> #include &quot;ev_cpp.h&quot;
1694 #include &quot;ev.c&quot; 2274 #include &quot;ev.c&quot;
1695 2275
1696</pre>
1697 2276
2277
2278
2279</pre>
2280
1698</div> 2281</div>
1699<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2282<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2283<div id="COMPLEXITIES_CONTENT">
2284 <p>In this section the complexities of (many of) the algorithms used inside
2285libev will be explained. For complexity discussions about backends see the
2286documentation for <code>ev_default_init</code>.</p>
2287 <p>All of the following are about amortised time: If an array needs to be
2288extended, libev needs to realloc and move the whole array, but this
2289happens asymptotically never with higher number of elements, so O(1) might
2290mean it might do a lengthy realloc operation in rare cases, but on average
2291it is much faster and asymptotically approaches constant time.</p>
2292 <p>
2293 <dl>
2294 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2295 <dd>
2296 <p>This means that, when you have a watcher that triggers in one hour and
2297there are 100 watchers that would trigger before that then inserting will
2298have to skip those 100 watchers.</p>
2299 </dd>
2300 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2301 <dd>
2302 <p>That means that for changing a timer costs less than removing/adding them
2303as only the relative motion in the event queue has to be paid for.</p>
2304 </dd>
2305 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2306 <dd>
2307 <p>These just add the watcher into an array or at the head of a list.
2308=item Stopping check/prepare/idle watchers: O(1)</p>
2309 </dd>
2310 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2311 <dd>
2312 <p>These watchers are stored in lists then need to be walked to find the
2313correct watcher to remove. The lists are usually short (you don't usually
2314have many watchers waiting for the same fd or signal).</p>
2315 </dd>
2316 <dt>Finding the next timer per loop iteration: O(1)</dt>
2317 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2318 <dd>
2319 <p>A change means an I/O watcher gets started or stopped, which requires
2320libev to recalculate its status (and possibly tell the kernel).</p>
2321 </dd>
2322 <dt>Activating one watcher: O(1)</dt>
2323 <dt>Priority handling: O(number_of_priorities)</dt>
2324 <dd>
2325 <p>Priorities are implemented by allocating some space for each
2326priority. When doing priority-based operations, libev usually has to
2327linearly search all the priorities.</p>
2328 </dd>
2329 </dl>
2330 </p>
2331
2332
2333
2334
2335
2336</div>
2337<h1 id="AUTHOR">AUTHOR</h1>
1700<div id="AUTHOR_CONTENT"> 2338<div id="AUTHOR_CONTENT">
1701 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2339 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1702 2340
1703</div> 2341</div>
1704</div></body> 2342</div></body>

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