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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 26 11:20:35 2007" /> 9 <meta name="created" content="Sat Dec 8 16:30:24 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
15<h3 id="TOP">Index</h3> 15<h3 id="TOP">Index</h3>
16 16
17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 20<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 21<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 22<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 23<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 24<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
… …
31<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
33<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> 34<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
34<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li> 35<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
36<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li> 38<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
37<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li> 39<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
39</ul> 42</ul>
40</li> 43</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
47<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
44<li><a href="#EMBEDDING">EMBEDDING</a> 48<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a> 49<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
… …
56<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
57</li> 61</li>
58</ul><hr /> 62</ul><hr />
59<!-- INDEX END --> 63<!-- INDEX END -->
60 64
61<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
62<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
63<p>libev - a high performance full-featured event loop written in C</p> 67<p>libev - a high performance full-featured event loop written in C</p>
64 68
65</div> 69</div>
66<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
67<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
68<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
69 73
70</pre> 74</pre>
71 75
72</div> 76</div>
73<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt;
80
81 ev_io stdin_watcher;
82 ev_timer timeout_watcher;
83
84 /* called when data readable on stdin */
85 static void
86 stdin_cb (EV_P_ struct ev_io *w, int revents)
87 {
88 /* puts (&quot;stdin ready&quot;); */
89 ev_io_stop (EV_A_ w); /* just a syntax example */
90 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
91 }
92
93 static void
94 timeout_cb (EV_P_ struct ev_timer *w, int revents)
95 {
96 /* puts (&quot;timeout&quot;); */
97 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
98 }
99
100 int
101 main (void)
102 {
103 struct ev_loop *loop = ev_default_loop (0);
104
105 /* initialise an io watcher, then start it */
106 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
107 ev_io_start (loop, &amp;stdin_watcher);
108
109 /* simple non-repeating 5.5 second timeout */
110 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
111 ev_timer_start (loop, &amp;timeout_watcher);
112
113 /* loop till timeout or data ready */
114 ev_loop (loop, 0);
115
116 return 0;
117 }
118
119</pre>
120
121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1>
74<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
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>
75<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
76file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
77these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
78<p>To do this, it must take more or less complete control over your process 130<p>To do this, it must take more or less complete control over your process
79(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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82watchers</i>, which are relatively small C structures you initialise with the 134watchers</i>, which are relatively small C structures you initialise with the
83details of the event, and then hand it over to libev by <i>starting</i> the 135details of the event, and then hand it over to libev by <i>starting</i> the
84watcher.</p> 136watcher.</p>
85 137
86</div> 138</div>
87<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
88<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
89<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
90kqueue mechanisms for file descriptor events, relative timers, absolute 142BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
91timers with customised rescheduling, signal events, process status change 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
92events (related to SIGCHLD), and event watchers dealing with the event 144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
93loop mechanism itself (idle, prepare and check watchers). It also is quite 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
94fast (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
95it to libevent for example).</p> 153for example).</p>
96 154
97</div> 155</div>
98<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
99<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
100<p>Libev is very configurable. In this manual the default configuration 158<p>Libev is very configurable. In this manual the default configuration will
101will be described, which supports multiple event loops. For more info 159be described, which supports multiple event loops. For more info about
102about various configuration options please have a look at the file 160various configuration options please have a look at <strong>EMBED</strong> section in
103<cite>README.embed</cite> in the libev distribution. If libev was configured without 161this manual. If libev was configured without support for multiple event
104support for multiple event loops, then all functions taking an initial 162loops, then all functions taking an initial argument of name <code>loop</code>
105argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 163(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
106will not have this argument.</p>
107 164
108</div> 165</div>
109<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
110<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
111<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
112(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
113the 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
114called <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
115to 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
116it, you should treat it as such.</p> 173it, you should treat it as such.</p>
117 174
118
119
120
121
122</div> 175</div>
123<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 176<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
124<div id="GLOBAL_FUNCTIONS_CONTENT"> 177<div id="GLOBAL_FUNCTIONS_CONTENT">
125<p>These functions can be called anytime, even before initialising the 178<p>These functions can be called anytime, even before initialising the
126library in any way.</p> 179library in any way.</p>
127<dl> 180<dl>
128 <dt>ev_tstamp ev_time ()</dt> 181 <dt>ev_tstamp ev_time ()</dt>
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141version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
142 <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,
143as this indicates an incompatible change. Minor versions are usually 196as this indicates an incompatible change. Minor versions are usually
144compatible to older versions, so a larger minor version alone is usually 197compatible to older versions, so a larger minor version alone is usually
145not a problem.</p> 198not a problem.</p>
146 <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
147version:</p> 200version.</p>
148<pre> assert ((&quot;libev version mismatch&quot;, 201<pre> assert ((&quot;libev version mismatch&quot;,
149 ev_version_major () == EV_VERSION_MAJOR 202 ev_version_major () == EV_VERSION_MAJOR
150 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 203 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
151 204
152</pre> 205</pre>
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182recommended ones.</p> 235recommended ones.</p>
183 <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>
184 </dd> 237 </dd>
185 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
186 <dd> 239 <dd>
187 <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
188realloc C function, the semantics are identical). It is used to allocate 241semantics is identical - to the realloc C function). It is used to
189and free memory (no surprises here). If it returns zero when memory 242allocate and free memory (no surprises here). If it returns zero when
190needs to be allocated, the library might abort or take some potentially 243memory needs to be allocated, the library might abort or take some
191destructive action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
192 <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,
193free 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,
194or 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>
195 <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
196retries: better than mine).</p> 250retries).</p>
197<pre> static void * 251<pre> static void *
198 persistent_realloc (void *ptr, long size) 252 persistent_realloc (void *ptr, size_t size)
199 { 253 {
200 for (;;) 254 for (;;)
201 { 255 {
202 void *newptr = realloc (ptr, size); 256 void *newptr = realloc (ptr, size);
203 257
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220indicating the system call or subsystem causing the problem. If this 274indicating the system call or subsystem causing the problem. If this
221callback 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
222matter what, when it returns. That is, libev will generally retry the 276matter what, when it returns. That is, libev will generally retry the
223requested 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
224(such as abort).</p> 278(such as abort).</p>
225 <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>
226<pre> static void 280<pre> static void
227 fatal_error (const char *msg) 281 fatal_error (const char *msg)
228 { 282 {
229 perror (msg); 283 perror (msg);
230 abort (); 284 abort ();
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236</pre> 290</pre>
237 </dd> 291 </dd>
238</dl> 292</dl>
239 293
240</div> 294</div>
241<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>
242<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 296<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
243<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 297<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
244types of such loops, the <i>default</i> loop, which supports signals and child 298types of such loops, the <i>default</i> loop, which supports signals and child
245events, and dynamically created loops which do not.</p> 299events, and dynamically created loops which do not.</p>
246<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
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275<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
276override 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
277useful 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
278around bugs.</p> 332around bugs.</p>
279 </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>
280 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
281 <dd> 352 <dd>
282 <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
283libev 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,
284but 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
… …
366 <dd> 437 <dd>
367 <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
368always distinct from the default loop. Unlike the default loop, it cannot 439always distinct from the default loop. Unlike the default loop, it cannot
369handle signal and child watchers, and attempts to do so will be greeted by 440handle signal and child watchers, and attempts to do so will be greeted by
370undefined behaviour (or a failed assertion if assertions are enabled).</p> 441undefined behaviour (or a failed assertion if assertions are enabled).</p>
371 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 442 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
372<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 443<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
373 if (!epoller) 444 if (!epoller)
374 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;);
375 446
376</pre> 447</pre>
… …
412 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
413 <dd> 484 <dd>
414 <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
415<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
416after 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>
417 </dd> 497 </dd>
418 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
419 <dd> 499 <dd>
420 <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
421use.</p> 501use.</p>
… …
469 be handled here by queueing them when their watcher gets executed. 549 be handled here by queueing them when their watcher gets executed.
470 - 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
471 were used, return, otherwise continue with step *. 551 were used, return, otherwise continue with step *.
472 552
473</pre> 553</pre>
474 <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
475anymore.</p> 555anymore.</p>
476<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
477 ... 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..)
478 ev_loop (my_loop, 0); 558 ev_loop (my_loop, 0);
479 ... jobs done. yeah! 559 ... jobs done. yeah!
… …
498example, 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
499visible 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
500no 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
501way 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
502libraries. 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>
503 <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>
504running when nothing else is active.</p> 584running when nothing else is active.</p>
505<pre> struct dv_signal exitsig; 585<pre> struct ev_signal exitsig;
506 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 586 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
507 ev_signal_start (myloop, &amp;exitsig); 587 ev_signal_start (loop, &amp;exitsig);
508 evf_unref (myloop); 588 evf_unref (loop);
509 589
510</pre> 590</pre>
511 <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>
512<pre> ev_ref (myloop); 592<pre> ev_ref (loop);
513 ev_signal_stop (myloop, &amp;exitsig); 593 ev_signal_stop (loop, &amp;exitsig);
514 594
515</pre> 595</pre>
516 </dd> 596 </dd>
517</dl> 597</dl>
518 598
519 599
520 600
521 601
522 602
523</div> 603</div>
524<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>
525<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 605<div id="ANATOMY_OF_A_WATCHER_CONTENT">
526<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
527interest 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
528become 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>
529<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)
… …
586 </dd> 666 </dd>
587 <dt><code>EV_CHILD</code></dt> 667 <dt><code>EV_CHILD</code></dt>
588 <dd> 668 <dd>
589 <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>
590 </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>
591 <dt><code>EV_IDLE</code></dt> 675 <dt><code>EV_IDLE</code></dt>
592 <dd> 676 <dd>
593 <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>
594 </dd> 678 </dd>
595 <dt><code>EV_PREPARE</code></dt> 679 <dt><code>EV_PREPARE</code></dt>
… …
600<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
601received events. Callbacks of both watcher types can start and stop as 685received events. Callbacks of both watcher types can start and stop as
602many watchers as they want, and all of them will be taken into account 686many watchers as they want, and all of them will be taken into account
603(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 687(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
604<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>
605 </dd> 698 </dd>
606 <dt><code>EV_ERROR</code></dt> 699 <dt><code>EV_ERROR</code></dt>
607 <dd> 700 <dd>
608 <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
609happen because the watcher could not be properly started because libev 702happen because the watcher could not be properly started because libev
… …
676 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 769 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
677 <dd> 770 <dd>
678 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 771 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
679events 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
680is 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
681<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), you must not change its priority, and you must
682libev (e.g. you cnanot <code>free ()</code> it).</p> 775make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
776it).</p>
683 </dd> 777 </dd>
684 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 778 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
685 <dd> 779 <dd>
686 <p>Returns the callback currently set on the watcher.</p> 780 <p>Returns the callback currently set on the watcher.</p>
687 </dd> 781 </dd>
688 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 782 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
689 <dd> 783 <dd>
690 <p>Change the callback. You can change the callback at virtually any time 784 <p>Change the callback. You can change the callback at virtually any time
691(modulo threads).</p> 785(modulo threads).</p>
786 </dd>
787 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
788 <dt>int ev_priority (ev_TYPE *watcher)</dt>
789 <dd>
790 <p>Set and query the priority of the watcher. The priority is a small
791integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
792(default: <code>-2</code>). Pending watchers with higher priority will be invoked
793before watchers with lower priority, but priority will not keep watchers
794from being executed (except for <code>ev_idle</code> watchers).</p>
795 <p>This means that priorities are <i>only</i> used for ordering callback
796invocation after new events have been received. This is useful, for
797example, to reduce latency after idling, or more often, to bind two
798watchers on the same event and make sure one is called first.</p>
799 <p>If you need to suppress invocation when higher priority events are pending
800you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
801 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
802pending.</p>
803 <p>The default priority used by watchers when no priority has been set is
804always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
805 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
806fine, as long as you do not mind that the priority value you query might
807or might not have been adjusted to be within valid range.</p>
808 </dd>
809 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
810 <dd>
811 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
812<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
813can deal with that fact.</p>
814 </dd>
815 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
816 <dd>
817 <p>If the watcher is pending, this function returns clears its pending status
818and returns its <code>revents</code> bitset (as if its callback was invoked). If the
819watcher isn't pending it does nothing and returns <code>0</code>.</p>
692 </dd> 820 </dd>
693</dl> 821</dl>
694 822
695 823
696 824
… …
721 struct my_io *w = (struct my_io *)w_; 849 struct my_io *w = (struct my_io *)w_;
722 ... 850 ...
723 } 851 }
724 852
725</pre> 853</pre>
726<p>More interesting and less C-conformant ways of catsing your callback type 854<p>More interesting and less C-conformant ways of casting your callback type
727have been omitted....</p> 855instead have been omitted.</p>
856<p>Another common scenario is having some data structure with multiple
857watchers:</p>
858<pre> struct my_biggy
859 {
860 int some_data;
861 ev_timer t1;
862 ev_timer t2;
863 }
728 864
865</pre>
866<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
867you need to use <code>offsetof</code>:</p>
868<pre> #include &lt;stddef.h&gt;
729 869
870 static void
871 t1_cb (EV_P_ struct ev_timer *w, int revents)
872 {
873 struct my_biggy big = (struct my_biggy *
874 (((char *)w) - offsetof (struct my_biggy, t1));
875 }
730 876
877 static void
878 t2_cb (EV_P_ struct ev_timer *w, int revents)
879 {
880 struct my_biggy big = (struct my_biggy *
881 (((char *)w) - offsetof (struct my_biggy, t2));
882 }
731 883
732 884
885
886
887</pre>
888
733</div> 889</div>
734<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 890<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
735<div id="WATCHER_TYPES_CONTENT"> 891<div id="WATCHER_TYPES_CONTENT">
736<p>This section describes each watcher in detail, but will not repeat 892<p>This section describes each watcher in detail, but will not repeat
737information given in the last section.</p> 893information given in the last section. Any initialisation/set macros,
894functions and members specific to the watcher type are explained.</p>
895<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
896while the watcher is active, you can look at the member and expect some
897sensible content, but you must not modify it (you can modify it while the
898watcher is stopped to your hearts content), or <i>[read-write]</i>, which
899means you can expect it to have some sensible content while the watcher
900is active, but you can also modify it. Modifying it may not do something
901sensible or take immediate effect (or do anything at all), but libev will
902not crash or malfunction in any way.</p>
738 903
739 904
740 905
741 906
742 907
… …
770this situation even with a relatively standard program structure. Thus 935this situation even with a relatively standard program structure. Thus
771it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 936it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
772<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 937<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
773<p>If you cannot run the fd in non-blocking mode (for example you should not 938<p>If you cannot run the fd in non-blocking mode (for example you should not
774play around with an Xlib connection), then you have to seperately re-test 939play around with an Xlib connection), then you have to seperately re-test
775wether a file descriptor is really ready with a known-to-be good interface 940whether a file descriptor is really ready with a known-to-be good interface
776such as poll (fortunately in our Xlib example, Xlib already does this on 941such as poll (fortunately in our Xlib example, Xlib already does this on
777its own, so its quite safe to use).</p> 942its own, so its quite safe to use).</p>
778<dl> 943<dl>
779 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 944 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
780 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 945 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
781 <dd> 946 <dd>
782 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 947 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
783rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or 948rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
784<code>EV_READ | EV_WRITE</code> to receive the given events.</p> 949<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
785 </dd> 950 </dd>
951 <dt>int fd [read-only]</dt>
952 <dd>
953 <p>The file descriptor being watched.</p>
954 </dd>
955 <dt>int events [read-only]</dt>
956 <dd>
957 <p>The events being watched.</p>
958 </dd>
786</dl> 959</dl>
787<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 960<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
788readable, but only once. Since it is likely line-buffered, you could 961readable, but only once. Since it is likely line-buffered, you could
789attempt to read a whole line in the callback:</p> 962attempt to read a whole line in the callback.</p>
790<pre> static void 963<pre> static void
791 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 964 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
792 { 965 {
793 ev_io_stop (loop, w); 966 ev_io_stop (loop, w);
794 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 967 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
843 </dd> 1016 </dd>
844 <dt>ev_timer_again (loop)</dt> 1017 <dt>ev_timer_again (loop)</dt>
845 <dd> 1018 <dd>
846 <p>This will act as if the timer timed out and restart it again if it is 1019 <p>This will act as if the timer timed out and restart it again if it is
847repeating. The exact semantics are:</p> 1020repeating. The exact semantics are:</p>
1021 <p>If the timer is pending, its pending status is cleared.</p>
848 <p>If the timer is started but nonrepeating, stop it.</p> 1022 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
849 <p>If the timer is repeating, either start it if necessary (with the repeat 1023 <p>If the timer is repeating, either start it if necessary (with the
850value), or reset the running timer to the repeat value.</p> 1024<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
851 <p>This sounds a bit complicated, but here is a useful and typical 1025 <p>This sounds a bit complicated, but here is a useful and typical
852example: Imagine you have a tcp connection and you want a so-called idle 1026example: Imagine you have a tcp connection and you want a so-called idle
853timeout, that is, you want to be called when there have been, say, 60 1027timeout, that is, you want to be called when there have been, say, 60
854seconds of inactivity on the socket. The easiest way to do this is to 1028seconds of inactivity on the socket. The easiest way to do this is to
855configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 1029configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
856time you successfully read or write some data. If you go into an idle 1030<code>ev_timer_again</code> each time you successfully read or write some data. If
857state where you do not expect data to travel on the socket, you can stop 1031you go into an idle state where you do not expect data to travel on the
1032socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
858the timer, and again will automatically restart it if need be.</p> 1033automatically restart it if need be.</p>
1034 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
1035altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
1036<pre> ev_timer_init (timer, callback, 0., 5.);
1037 ev_timer_again (loop, timer);
1038 ...
1039 timer-&gt;again = 17.;
1040 ev_timer_again (loop, timer);
1041 ...
1042 timer-&gt;again = 10.;
1043 ev_timer_again (loop, timer);
1044
1045</pre>
1046 <p>This is more slightly efficient then stopping/starting the timer each time
1047you want to modify its timeout value.</p>
1048 </dd>
1049 <dt>ev_tstamp repeat [read-write]</dt>
1050 <dd>
1051 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
1052or <code>ev_timer_again</code> is called and determines the next timeout (if any),
1053which is also when any modifications are taken into account.</p>
859 </dd> 1054 </dd>
860</dl> 1055</dl>
861<p>Example: create a timer that fires after 60 seconds.</p> 1056<p>Example: Create a timer that fires after 60 seconds.</p>
862<pre> static void 1057<pre> static void
863 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1058 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
864 { 1059 {
865 .. one minute over, w is actually stopped right here 1060 .. one minute over, w is actually stopped right here
866 } 1061 }
… …
868 struct ev_timer mytimer; 1063 struct ev_timer mytimer;
869 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1064 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
870 ev_timer_start (loop, &amp;mytimer); 1065 ev_timer_start (loop, &amp;mytimer);
871 1066
872</pre> 1067</pre>
873<p>Example: create a timeout timer that times out after 10 seconds of 1068<p>Example: Create a timeout timer that times out after 10 seconds of
874inactivity.</p> 1069inactivity.</p>
875<pre> static void 1070<pre> static void
876 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1071 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
877 { 1072 {
878 .. ten seconds without any activity 1073 .. ten seconds without any activity
… …
981 <p>Simply stops and restarts the periodic watcher again. This is only useful 1176 <p>Simply stops and restarts the periodic watcher again. This is only useful
982when you changed some parameters or the reschedule callback would return 1177when you changed some parameters or the reschedule callback would return
983a different time than the last time it was called (e.g. in a crond like 1178a different time than the last time it was called (e.g. in a crond like
984program when the crontabs have changed).</p> 1179program when the crontabs have changed).</p>
985 </dd> 1180 </dd>
1181 <dt>ev_tstamp interval [read-write]</dt>
1182 <dd>
1183 <p>The current interval value. Can be modified any time, but changes only
1184take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1185called.</p>
1186 </dd>
1187 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1188 <dd>
1189 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1190switched off. Can be changed any time, but changes only take effect when
1191the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1192 </dd>
986</dl> 1193</dl>
987<p>Example: call a callback every hour, or, more precisely, whenever the 1194<p>Example: Call a callback every hour, or, more precisely, whenever the
988system clock is divisible by 3600. The callback invocation times have 1195system clock is divisible by 3600. The callback invocation times have
989potentially a lot of jittering, but good long-term stability.</p> 1196potentially a lot of jittering, but good long-term stability.</p>
990<pre> static void 1197<pre> static void
991 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1198 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
992 { 1199 {
… …
996 struct ev_periodic hourly_tick; 1203 struct ev_periodic hourly_tick;
997 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1204 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
998 ev_periodic_start (loop, &amp;hourly_tick); 1205 ev_periodic_start (loop, &amp;hourly_tick);
999 1206
1000</pre> 1207</pre>
1001<p>Example: the same as above, but use a reschedule callback to do it:</p> 1208<p>Example: The same as above, but use a reschedule callback to do it:</p>
1002<pre> #include &lt;math.h&gt; 1209<pre> #include &lt;math.h&gt;
1003 1210
1004 static ev_tstamp 1211 static ev_tstamp
1005 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1212 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1006 { 1213 {
… …
1008 } 1215 }
1009 1216
1010 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1217 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1011 1218
1012</pre> 1219</pre>
1013<p>Example: call a callback every hour, starting now:</p> 1220<p>Example: Call a callback every hour, starting now:</p>
1014<pre> struct ev_periodic hourly_tick; 1221<pre> struct ev_periodic hourly_tick;
1015 ev_periodic_init (&amp;hourly_tick, clock_cb, 1222 ev_periodic_init (&amp;hourly_tick, clock_cb,
1016 fmod (ev_now (loop), 3600.), 3600., 0); 1223 fmod (ev_now (loop), 3600.), 3600., 0);
1017 ev_periodic_start (loop, &amp;hourly_tick); 1224 ev_periodic_start (loop, &amp;hourly_tick);
1018 1225
… …
1039 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1246 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1040 <dd> 1247 <dd>
1041 <p>Configures the watcher to trigger on the given signal number (usually one 1248 <p>Configures the watcher to trigger on the given signal number (usually one
1042of the <code>SIGxxx</code> constants).</p> 1249of the <code>SIGxxx</code> constants).</p>
1043 </dd> 1250 </dd>
1251 <dt>int signum [read-only]</dt>
1252 <dd>
1253 <p>The signal the watcher watches out for.</p>
1254 </dd>
1044</dl> 1255</dl>
1045 1256
1046 1257
1047 1258
1048 1259
… …
1061at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1272at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1062the status word (use the macros from <code>sys/wait.h</code> and see your systems 1273the status word (use the macros from <code>sys/wait.h</code> and see your systems
1063<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1274<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1064process causing the status change.</p> 1275process causing the status change.</p>
1065 </dd> 1276 </dd>
1277 <dt>int pid [read-only]</dt>
1278 <dd>
1279 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1280 </dd>
1281 <dt>int rpid [read-write]</dt>
1282 <dd>
1283 <p>The process id that detected a status change.</p>
1284 </dd>
1285 <dt>int rstatus [read-write]</dt>
1286 <dd>
1287 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1288<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1289 </dd>
1066</dl> 1290</dl>
1067<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1291<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1068<pre> static void 1292<pre> static void
1069 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1293 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1070 { 1294 {
1071 ev_unloop (loop, EVUNLOOP_ALL); 1295 ev_unloop (loop, EVUNLOOP_ALL);
1072 } 1296 }
… …
1079 1303
1080 1304
1081</pre> 1305</pre>
1082 1306
1083</div> 1307</div>
1308<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1309<div id="code_ev_stat_code_did_the_file_attri-2">
1310<p>This watches a filesystem path for attribute changes. That is, it calls
1311<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1312compared to the last time, invoking the callback if it did.</p>
1313<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1314not exist&quot; is a status change like any other. The condition &quot;path does
1315not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1316otherwise always forced to be at least one) and all the other fields of
1317the stat buffer having unspecified contents.</p>
1318<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1319relative and your working directory changes, the behaviour is undefined.</p>
1320<p>Since there is no standard to do this, the portable implementation simply
1321calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1322can specify a recommended polling interval for this case. If you specify
1323a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1324unspecified default</i> value will be used (which you can expect to be around
1325five seconds, although this might change dynamically). Libev will also
1326impose a minimum interval which is currently around <code>0.1</code>, but thats
1327usually overkill.</p>
1328<p>This watcher type is not meant for massive numbers of stat watchers,
1329as even with OS-supported change notifications, this can be
1330resource-intensive.</p>
1331<p>At the time of this writing, only the Linux inotify interface is
1332implemented (implementing kqueue support is left as an exercise for the
1333reader). Inotify will be used to give hints only and should not change the
1334semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1335to fall back to regular polling again even with inotify, but changes are
1336usually detected immediately, and if the file exists there will be no
1337polling.</p>
1338<dl>
1339 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1340 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1341 <dd>
1342 <p>Configures the watcher to wait for status changes of the given
1343<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1344be detected and should normally be specified as <code>0</code> to let libev choose
1345a suitable value. The memory pointed to by <code>path</code> must point to the same
1346path for as long as the watcher is active.</p>
1347 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1348relative to the attributes at the time the watcher was started (or the
1349last change was detected).</p>
1350 </dd>
1351 <dt>ev_stat_stat (ev_stat *)</dt>
1352 <dd>
1353 <p>Updates the stat buffer immediately with new values. If you change the
1354watched path in your callback, you could call this fucntion to avoid
1355detecting this change (while introducing a race condition). Can also be
1356useful simply to find out the new values.</p>
1357 </dd>
1358 <dt>ev_statdata attr [read-only]</dt>
1359 <dd>
1360 <p>The most-recently detected attributes of the file. Although the type is of
1361<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1362suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1363was some error while <code>stat</code>ing the file.</p>
1364 </dd>
1365 <dt>ev_statdata prev [read-only]</dt>
1366 <dd>
1367 <p>The previous attributes of the file. The callback gets invoked whenever
1368<code>prev</code> != <code>attr</code>.</p>
1369 </dd>
1370 <dt>ev_tstamp interval [read-only]</dt>
1371 <dd>
1372 <p>The specified interval.</p>
1373 </dd>
1374 <dt>const char *path [read-only]</dt>
1375 <dd>
1376 <p>The filesystem path that is being watched.</p>
1377 </dd>
1378</dl>
1379<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1380<pre> static void
1381 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1382 {
1383 /* /etc/passwd changed in some way */
1384 if (w-&gt;attr.st_nlink)
1385 {
1386 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1387 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1388 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1389 }
1390 else
1391 /* you shalt not abuse printf for puts */
1392 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1393 &quot;if this is windows, they already arrived\n&quot;);
1394 }
1395
1396 ...
1397 ev_stat passwd;
1398
1399 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1400 ev_stat_start (loop, &amp;passwd);
1401
1402
1403
1404
1405</pre>
1406
1407</div>
1084<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1408<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1085<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1409<div id="code_ev_idle_code_when_you_ve_got_no-2">
1086<p>Idle watchers trigger events when there are no other events are pending 1410<p>Idle watchers trigger events when no other events of the same or higher
1087(prepare, check and other idle watchers do not count). That is, as long 1411priority are pending (prepare, check and other idle watchers do not
1088as your process is busy handling sockets or timeouts (or even signals, 1412count).</p>
1089imagine) it will not be triggered. But when your process is idle all idle 1413<p>That is, as long as your process is busy handling sockets or timeouts
1090watchers are being called again and again, once per event loop iteration - 1414(or even signals, imagine) of the same or higher priority it will not be
1415triggered. But when your process is idle (or only lower-priority watchers
1416are pending), the idle watchers are being called once per event loop
1091until stopped, that is, or your process receives more events and becomes 1417iteration - until stopped, that is, or your process receives more events
1092busy.</p> 1418and becomes busy again with higher priority stuff.</p>
1093<p>The most noteworthy effect is that as long as any idle watchers are 1419<p>The most noteworthy effect is that as long as any idle watchers are
1094active, the process will not block when waiting for new events.</p> 1420active, the process will not block when waiting for new events.</p>
1095<p>Apart from keeping your process non-blocking (which is a useful 1421<p>Apart from keeping your process non-blocking (which is a useful
1096effect on its own sometimes), idle watchers are a good place to do 1422effect on its own sometimes), idle watchers are a good place to do
1097&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1423&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1102 <p>Initialises and configures the idle watcher - it has no parameters of any 1428 <p>Initialises and configures the idle watcher - it has no parameters of any
1103kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1429kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1104believe me.</p> 1430believe me.</p>
1105 </dd> 1431 </dd>
1106</dl> 1432</dl>
1107<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1433<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1108callback, free it. Alos, use no error checking, as usual.</p> 1434callback, free it. Also, use no error checking, as usual.</p>
1109<pre> static void 1435<pre> static void
1110 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1436 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1111 { 1437 {
1112 free (w); 1438 free (w);
1113 // now do something you wanted to do when the program has 1439 // now do something you wanted to do when the program has
… …
1166 <p>Initialises and configures the prepare or check watcher - they have no 1492 <p>Initialises and configures the prepare or check watcher - they have no
1167parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1493parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1168macros, but using them is utterly, utterly and completely pointless.</p> 1494macros, but using them is utterly, utterly and completely pointless.</p>
1169 </dd> 1495 </dd>
1170</dl> 1496</dl>
1171<p>Example: To include a library such as adns, you would add IO watchers 1497<p>There are a number of principal ways to embed other event loops or modules
1172and a timeout watcher in a prepare handler, as required by libadns, and 1498into libev. Here are some ideas on how to include libadns into libev
1499(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1500use for an actually working example. Another Perl module named <code>EV::Glib</code>
1501embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1502into the Glib event loop).</p>
1503<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1173in a check watcher, destroy them and call into libadns. What follows is 1504and in a check watcher, destroy them and call into libadns. What follows
1174pseudo-code only of course:</p> 1505is pseudo-code only of course. This requires you to either use a low
1506priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1507the callbacks for the IO/timeout watchers might not have been called yet.</p>
1175<pre> static ev_io iow [nfd]; 1508<pre> static ev_io iow [nfd];
1176 static ev_timer tw; 1509 static ev_timer tw;
1177 1510
1178 static void 1511 static void
1179 io_cb (ev_loop *loop, ev_io *w, int revents) 1512 io_cb (ev_loop *loop, ev_io *w, int revents)
1180 { 1513 {
1181 // set the relevant poll flags
1182 // could also call adns_processreadable etc. here
1183 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1184 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1185 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1186 } 1514 }
1187 1515
1188 // create io watchers for each fd and a timer before blocking 1516 // create io watchers for each fd and a timer before blocking
1189 static void 1517 static void
1190 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1518 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1191 { 1519 {
1192 int timeout = 3600000;truct pollfd fds [nfd]; 1520 int timeout = 3600000;
1521 struct pollfd fds [nfd];
1193 // actual code will need to loop here and realloc etc. 1522 // actual code will need to loop here and realloc etc.
1194 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1523 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1195 1524
1196 /* the callback is illegal, but won't be called as we stop during check */ 1525 /* the callback is illegal, but won't be called as we stop during check */
1197 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1526 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1198 ev_timer_start (loop, &amp;tw); 1527 ev_timer_start (loop, &amp;tw);
1199 1528
1200 // create on ev_io per pollfd 1529 // create one ev_io per pollfd
1201 for (int i = 0; i &lt; nfd; ++i) 1530 for (int i = 0; i &lt; nfd; ++i)
1202 { 1531 {
1203 ev_io_init (iow + i, io_cb, fds [i].fd, 1532 ev_io_init (iow + i, io_cb, fds [i].fd,
1204 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1533 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1205 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1534 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1206 1535
1207 fds [i].revents = 0; 1536 fds [i].revents = 0;
1208 iow [i].data = fds + i;
1209 ev_io_start (loop, iow + i); 1537 ev_io_start (loop, iow + i);
1210 } 1538 }
1211 } 1539 }
1212 1540
1213 // stop all watchers after blocking 1541 // stop all watchers after blocking
… …
1215 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1543 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1216 { 1544 {
1217 ev_timer_stop (loop, &amp;tw); 1545 ev_timer_stop (loop, &amp;tw);
1218 1546
1219 for (int i = 0; i &lt; nfd; ++i) 1547 for (int i = 0; i &lt; nfd; ++i)
1548 {
1549 // set the relevant poll flags
1550 // could also call adns_processreadable etc. here
1551 struct pollfd *fd = fds + i;
1552 int revents = ev_clear_pending (iow + i);
1553 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1554 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1555
1556 // now stop the watcher
1220 ev_io_stop (loop, iow + i); 1557 ev_io_stop (loop, iow + i);
1558 }
1221 1559
1222 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1560 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1561 }
1562
1563</pre>
1564<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1565in the prepare watcher and would dispose of the check watcher.</p>
1566<p>Method 3: If the module to be embedded supports explicit event
1567notification (adns does), you can also make use of the actual watcher
1568callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1569<pre> static void
1570 timer_cb (EV_P_ ev_timer *w, int revents)
1571 {
1572 adns_state ads = (adns_state)w-&gt;data;
1573 update_now (EV_A);
1574
1575 adns_processtimeouts (ads, &amp;tv_now);
1576 }
1577
1578 static void
1579 io_cb (EV_P_ ev_io *w, int revents)
1580 {
1581 adns_state ads = (adns_state)w-&gt;data;
1582 update_now (EV_A);
1583
1584 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1585 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1586 }
1587
1588 // do not ever call adns_afterpoll
1589
1590</pre>
1591<p>Method 4: Do not use a prepare or check watcher because the module you
1592want to embed is too inflexible to support it. Instead, youc na override
1593their poll function. The drawback with this solution is that the main
1594loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1595this.</p>
1596<pre> static gint
1597 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1598 {
1599 int got_events = 0;
1600
1601 for (n = 0; n &lt; nfds; ++n)
1602 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1603
1604 if (timeout &gt;= 0)
1605 // create/start timer
1606
1607 // poll
1608 ev_loop (EV_A_ 0);
1609
1610 // stop timer again
1611 if (timeout &gt;= 0)
1612 ev_timer_stop (EV_A_ &amp;to);
1613
1614 // stop io watchers again - their callbacks should have set
1615 for (n = 0; n &lt; nfds; ++n)
1616 ev_io_stop (EV_A_ iow [n]);
1617
1618 return got_events;
1223 } 1619 }
1224 1620
1225 1621
1226 1622
1227 1623
… …
1304 <dd> 1700 <dd>
1305 <p>Make a single, non-blocking sweep over the embedded loop. This works 1701 <p>Make a single, non-blocking sweep over the embedded loop. This works
1306similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1702similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1307apropriate way for embedded loops.</p> 1703apropriate way for embedded loops.</p>
1308 </dd> 1704 </dd>
1705 <dt>struct ev_loop *loop [read-only]</dt>
1706 <dd>
1707 <p>The embedded event loop.</p>
1708 </dd>
1309</dl> 1709</dl>
1310 1710
1311 1711
1312 1712
1313 1713
1314 1714
1315</div> 1715</div>
1316<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1716<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>
1717<div id="code_ev_fork_code_the_audacity_to_re-2">
1718<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1719whoever is a good citizen cared to tell libev about it by calling
1720<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1721event loop blocks next and before <code>ev_check</code> watchers are being called,
1722and only in the child after the fork. If whoever good citizen calling
1723<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1724handlers will be invoked, too, of course.</p>
1725<dl>
1726 <dt>ev_fork_init (ev_signal *, callback)</dt>
1727 <dd>
1728 <p>Initialises and configures the fork watcher - it has no parameters of any
1729kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1730believe me.</p>
1731 </dd>
1732</dl>
1733
1734
1735
1736
1737
1738</div>
1739<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1317<div id="OTHER_FUNCTIONS_CONTENT"> 1740<div id="OTHER_FUNCTIONS_CONTENT">
1318<p>There are some other functions of possible interest. Described. Here. Now.</p> 1741<p>There are some other functions of possible interest. Described. Here. Now.</p>
1319<dl> 1742<dl>
1320 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1743 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1321 <dd> 1744 <dd>
… …
1368 1791
1369 1792
1370 1793
1371 1794
1372</div> 1795</div>
1373<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1796<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1374<div id="LIBEVENT_EMULATION_CONTENT"> 1797<div id="LIBEVENT_EMULATION_CONTENT">
1375<p>Libev offers a compatibility emulation layer for libevent. It cannot 1798<p>Libev offers a compatibility emulation layer for libevent. It cannot
1376emulate the internals of libevent, so here are some usage hints:</p> 1799emulate the internals of libevent, so here are some usage hints:</p>
1377<dl> 1800<dl>
1378 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1801 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1388 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1811 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1389to use the libev header file and library.</dt> 1812to use the libev header file and library.</dt>
1390</dl> 1813</dl>
1391 1814
1392</div> 1815</div>
1393<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1816<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1394<div id="C_SUPPORT_CONTENT"> 1817<div id="C_SUPPORT_CONTENT">
1395<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1818<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1396you to use some convinience methods to start/stop watchers and also change 1819you to use some convinience methods to start/stop watchers and also change
1397the callback model to a model using method callbacks on objects.</p> 1820the callback model to a model using method callbacks on objects.</p>
1398<p>To use it,</p> 1821<p>To use it,</p>
1399<pre> #include &lt;ev++.h&gt; 1822<pre> #include &lt;ev++.h&gt;
1400 1823
1401</pre> 1824</pre>
1402<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1825<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1403and puts all of its definitions (many of them macros) into the global 1826of them macros) into the global namespace. All C++ specific things are
1404namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1827put into the <code>ev</code> namespace. It should support all the same embedding
1405<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1828options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1406<code>EV_MULTIPLICITY</code>.</p> 1829<p>Care has been taken to keep the overhead low. The only data member the C++
1830classes add (compared to plain C-style watchers) is the event loop pointer
1831that the watcher is associated with (or no additional members at all if
1832you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1833<p>Currently, functions, and static and non-static member functions can be
1834used as callbacks. Other types should be easy to add as long as they only
1835need one additional pointer for context. If you need support for other
1836types of functors please contact the author (preferably after implementing
1837it).</p>
1407<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1838<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1408<dl> 1839<dl>
1409 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1840 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1410 <dd> 1841 <dd>
1411 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1842 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1422which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1853which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1423defines by many implementations.</p> 1854defines by many implementations.</p>
1424 <p>All of those classes have these methods:</p> 1855 <p>All of those classes have these methods:</p>
1425 <p> 1856 <p>
1426 <dl> 1857 <dl>
1427 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1858 <dt>ev::TYPE::TYPE ()</dt>
1428 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1859 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1429 <dt>ev::TYPE::~TYPE</dt> 1860 <dt>ev::TYPE::~TYPE</dt>
1430 <dd> 1861 <dd>
1431 <p>The constructor takes a pointer to an object and a method pointer to 1862 <p>The constructor (optionally) takes an event loop to associate the watcher
1432the event handler callback to call in this class. The constructor calls 1863with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1433<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1864 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1434before starting it. If you do not specify a loop then the constructor 1865<code>set</code> method before starting it.</p>
1435automatically associates the default loop with this watcher.</p> 1866 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1867method to set a callback before you can start the watcher.</p>
1868 <p>(The reason why you have to use a method is a limitation in C++ which does
1869not allow explicit template arguments for constructors).</p>
1436 <p>The destructor automatically stops the watcher if it is active.</p> 1870 <p>The destructor automatically stops the watcher if it is active.</p>
1871 </dd>
1872 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1873 <dd>
1874 <p>This method sets the callback method to call. The method has to have a
1875signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1876first argument and the <code>revents</code> as second. The object must be given as
1877parameter and is stored in the <code>data</code> member of the watcher.</p>
1878 <p>This method synthesizes efficient thunking code to call your method from
1879the C callback that libev requires. If your compiler can inline your
1880callback (i.e. it is visible to it at the place of the <code>set</code> call and
1881your compiler is good :), then the method will be fully inlined into the
1882thunking function, making it as fast as a direct C callback.</p>
1883 <p>Example: simple class declaration and watcher initialisation</p>
1884<pre> struct myclass
1885 {
1886 void io_cb (ev::io &amp;w, int revents) { }
1887 }
1888
1889 myclass obj;
1890 ev::io iow;
1891 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1892
1893</pre>
1894 </dd>
1895 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1896 <dd>
1897 <p>Also sets a callback, but uses a static method or plain function as
1898callback. The optional <code>data</code> argument will be stored in the watcher's
1899<code>data</code> member and is free for you to use.</p>
1900 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1901 <p>See the method-<code>set</code> above for more details.</p>
1902 <p>Example:</p>
1903<pre> static void io_cb (ev::io &amp;w, int revents) { }
1904 iow.set &lt;io_cb&gt; ();
1905
1906</pre>
1437 </dd> 1907 </dd>
1438 <dt>w-&gt;set (struct ev_loop *)</dt> 1908 <dt>w-&gt;set (struct ev_loop *)</dt>
1439 <dd> 1909 <dd>
1440 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1910 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1441do this when the watcher is inactive (and not pending either).</p> 1911do this when the watcher is inactive (and not pending either).</p>
1442 </dd> 1912 </dd>
1443 <dt>w-&gt;set ([args])</dt> 1913 <dt>w-&gt;set ([args])</dt>
1444 <dd> 1914 <dd>
1445 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1915 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1446called at least once. Unlike the C counterpart, an active watcher gets 1916called at least once. Unlike the C counterpart, an active watcher gets
1447automatically stopped and restarted.</p> 1917automatically stopped and restarted when reconfiguring it with this
1918method.</p>
1448 </dd> 1919 </dd>
1449 <dt>w-&gt;start ()</dt> 1920 <dt>w-&gt;start ()</dt>
1450 <dd> 1921 <dd>
1451 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1922 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1452constructor already takes the loop.</p> 1923constructor already stores the event loop.</p>
1453 </dd> 1924 </dd>
1454 <dt>w-&gt;stop ()</dt> 1925 <dt>w-&gt;stop ()</dt>
1455 <dd> 1926 <dd>
1456 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1927 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1457 </dd> 1928 </dd>
… …
1461<code>ev_TYPE_again</code> function.</p> 1932<code>ev_TYPE_again</code> function.</p>
1462 </dd> 1933 </dd>
1463 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1934 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1464 <dd> 1935 <dd>
1465 <p>Invokes <code>ev_embed_sweep</code>.</p> 1936 <p>Invokes <code>ev_embed_sweep</code>.</p>
1937 </dd>
1938 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1939 <dd>
1940 <p>Invokes <code>ev_stat_stat</code>.</p>
1466 </dd> 1941 </dd>
1467 </dl> 1942 </dl>
1468 </p> 1943 </p>
1469 </dd> 1944 </dd>
1470</dl> 1945</dl>
… …
1477 1952
1478 myclass (); 1953 myclass ();
1479 } 1954 }
1480 1955
1481 myclass::myclass (int fd) 1956 myclass::myclass (int fd)
1482 : io (this, &amp;myclass::io_cb),
1483 idle (this, &amp;myclass::idle_cb)
1484 { 1957 {
1958 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1959 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1960
1485 io.start (fd, ev::READ); 1961 io.start (fd, ev::READ);
1486 } 1962 }
1487 1963
1488</pre>
1489 1964
1965
1966
1967</pre>
1968
1490</div> 1969</div>
1491<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1970<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1971<div id="MACRO_MAGIC_CONTENT">
1972<p>Libev can be compiled with a variety of options, the most fundemantal is
1973<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1974callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1975<p>To make it easier to write programs that cope with either variant, the
1976following macros are defined:</p>
1977<dl>
1978 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1979 <dd>
1980 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1981loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1982<code>EV_A_</code> is used when other arguments are following. Example:</p>
1983<pre> ev_unref (EV_A);
1984 ev_timer_add (EV_A_ watcher);
1985 ev_loop (EV_A_ 0);
1986
1987</pre>
1988 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1989which is often provided by the following macro.</p>
1990 </dd>
1991 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1992 <dd>
1993 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1994loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1995<code>EV_P_</code> is used when other parameters are following. Example:</p>
1996<pre> // this is how ev_unref is being declared
1997 static void ev_unref (EV_P);
1998
1999 // this is how you can declare your typical callback
2000 static void cb (EV_P_ ev_timer *w, int revents)
2001
2002</pre>
2003 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
2004suitable for use with <code>EV_A</code>.</p>
2005 </dd>
2006 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
2007 <dd>
2008 <p>Similar to the other two macros, this gives you the value of the default
2009loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
2010 </dd>
2011</dl>
2012<p>Example: Declare and initialise a check watcher, utilising the above
2013macros so it will work regardless of whether multiple loops are supported
2014or not.</p>
2015<pre> static void
2016 check_cb (EV_P_ ev_timer *w, int revents)
2017 {
2018 ev_check_stop (EV_A_ w);
2019 }
2020
2021 ev_check check;
2022 ev_check_init (&amp;check, check_cb);
2023 ev_check_start (EV_DEFAULT_ &amp;check);
2024 ev_loop (EV_DEFAULT_ 0);
2025
2026</pre>
2027
2028</div>
2029<h1 id="EMBEDDING">EMBEDDING</h1>
1492<div id="EMBEDDING_CONTENT"> 2030<div id="EMBEDDING_CONTENT">
1493<p>Libev can (and often is) directly embedded into host 2031<p>Libev can (and often is) directly embedded into host
1494applications. Examples of applications that embed it include the Deliantra 2032applications. Examples of applications that embed it include the Deliantra
1495Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2033Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1496and rxvt-unicode.</p> 2034and rxvt-unicode.</p>
… …
1533 ev_vars.h 2071 ev_vars.h
1534 ev_wrap.h 2072 ev_wrap.h
1535 2073
1536 ev_win32.c required on win32 platforms only 2074 ev_win32.c required on win32 platforms only
1537 2075
1538 ev_select.c only when select backend is enabled (which is by default) 2076 ev_select.c only when select backend is enabled (which is enabled by default)
1539 ev_poll.c only when poll backend is enabled (disabled by default) 2077 ev_poll.c only when poll backend is enabled (disabled by default)
1540 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2078 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1541 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2079 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1542 ev_port.c only when the solaris port backend is enabled (disabled by default) 2080 ev_port.c only when the solaris port backend is enabled (disabled by default)
1543 2081
… …
1670 </dd> 2208 </dd>
1671 <dt>EV_USE_DEVPOLL</dt> 2209 <dt>EV_USE_DEVPOLL</dt>
1672 <dd> 2210 <dd>
1673 <p>reserved for future expansion, works like the USE symbols above.</p> 2211 <p>reserved for future expansion, works like the USE symbols above.</p>
1674 </dd> 2212 </dd>
2213 <dt>EV_USE_INOTIFY</dt>
2214 <dd>
2215 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2216interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2217be detected at runtime.</p>
2218 </dd>
1675 <dt>EV_H</dt> 2219 <dt>EV_H</dt>
1676 <dd> 2220 <dd>
1677 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2221 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1678undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This 2222undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
1679can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2223can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1702will have the <code>struct ev_loop *</code> as first argument, and you can create 2246will have the <code>struct ev_loop *</code> as first argument, and you can create
1703additional independent event loops. Otherwise there will be no support 2247additional independent event loops. Otherwise there will be no support
1704for multiple event loops and there is no first event loop pointer 2248for multiple event loops and there is no first event loop pointer
1705argument. Instead, all functions act on the single default loop.</p> 2249argument. Instead, all functions act on the single default loop.</p>
1706 </dd> 2250 </dd>
1707 <dt>EV_PERIODICS</dt> 2251 <dt>EV_MINPRI</dt>
2252 <dt>EV_MAXPRI</dt>
2253 <dd>
2254 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2255<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2256provide for more priorities by overriding those symbols (usually defined
2257to be <code>-2</code> and <code>2</code>, respectively).</p>
2258 <p>When doing priority-based operations, libev usually has to linearly search
2259all the priorities, so having many of them (hundreds) uses a lot of space
2260and time, so using the defaults of five priorities (-2 .. +2) is usually
2261fine.</p>
2262 <p>If your embedding app does not need any priorities, defining these both to
2263<code>0</code> will save some memory and cpu.</p>
1708 <dd> 2264 </dd>
2265 <dt>EV_PERIODIC_ENABLE</dt>
2266 <dd>
1709 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2267 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1710otherwise not. This saves a few kb of code.</p> 2268defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2269code.</p>
2270 </dd>
2271 <dt>EV_IDLE_ENABLE</dt>
2272 <dd>
2273 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2274defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2275code.</p>
2276 </dd>
2277 <dt>EV_EMBED_ENABLE</dt>
2278 <dd>
2279 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2280defined to be <code>0</code>, then they are not.</p>
2281 </dd>
2282 <dt>EV_STAT_ENABLE</dt>
2283 <dd>
2284 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2285defined to be <code>0</code>, then they are not.</p>
2286 </dd>
2287 <dt>EV_FORK_ENABLE</dt>
2288 <dd>
2289 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2290defined to be <code>0</code>, then they are not.</p>
2291 </dd>
2292 <dt>EV_MINIMAL</dt>
2293 <dd>
2294 <p>If you need to shave off some kilobytes of code at the expense of some
2295speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2296some inlining decisions, saves roughly 30% codesize of amd64.</p>
2297 </dd>
2298 <dt>EV_PID_HASHSIZE</dt>
2299 <dd>
2300 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2301pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2302than enough. If you need to manage thousands of children you might want to
2303increase this value (<i>must</i> be a power of two).</p>
2304 </dd>
2305 <dt>EV_INOTIFY_HASHSIZE</dt>
2306 <dd>
2307 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2308inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2309usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2310watchers you might want to increase this value (<i>must</i> be a power of
2311two).</p>
1711 </dd> 2312 </dd>
1712 <dt>EV_COMMON</dt> 2313 <dt>EV_COMMON</dt>
1713 <dd> 2314 <dd>
1714 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2315 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1715this macro to a something else you can include more and other types of 2316this macro to a something else you can include more and other types of
… …
1742the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2343the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1743interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2344interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1744will be compiled. It is pretty complex because it provides its own header 2345will be compiled. It is pretty complex because it provides its own header
1745file.</p> 2346file.</p>
1746 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2347 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1747that everybody includes and which overrides some autoconf choices:</p> 2348that everybody includes and which overrides some configure choices:</p>
2349<pre> #define EV_MINIMAL 1
1748<pre> #define EV_USE_POLL 0 2350 #define EV_USE_POLL 0
1749 #define EV_MULTIPLICITY 0 2351 #define EV_MULTIPLICITY 0
1750 #define EV_PERIODICS 0 2352 #define EV_PERIODIC_ENABLE 0
2353 #define EV_STAT_ENABLE 0
2354 #define EV_FORK_ENABLE 0
1751 #define EV_CONFIG_H &lt;config.h&gt; 2355 #define EV_CONFIG_H &lt;config.h&gt;
2356 #define EV_MINPRI 0
2357 #define EV_MAXPRI 0
1752 2358
1753 #include &quot;ev++.h&quot; 2359 #include &quot;ev++.h&quot;
1754 2360
1755</pre> 2361</pre>
1756 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2362 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
1761 2367
1762 2368
1763</pre> 2369</pre>
1764 2370
1765</div> 2371</div>
1766<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2372<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
1767<div id="COMPLEXITIES_CONTENT"> 2373<div id="COMPLEXITIES_CONTENT">
1768 <p>In this section the complexities of (many of) the algorithms used inside 2374 <p>In this section the complexities of (many of) the algorithms used inside
1769libev will be explained. For complexity discussions about backends see the 2375libev will be explained. For complexity discussions about backends see the
1770documentation for <code>ev_default_init</code>.</p> 2376documentation for <code>ev_default_init</code>.</p>
2377 <p>All of the following are about amortised time: If an array needs to be
2378extended, libev needs to realloc and move the whole array, but this
2379happens asymptotically never with higher number of elements, so O(1) might
2380mean it might do a lengthy realloc operation in rare cases, but on average
2381it is much faster and asymptotically approaches constant time.</p>
1771 <p> 2382 <p>
1772 <dl> 2383 <dl>
1773 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2384 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2385 <dd>
2386 <p>This means that, when you have a watcher that triggers in one hour and
2387there are 100 watchers that would trigger before that then inserting will
2388have to skip those 100 watchers.</p>
2389 </dd>
1774 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2390 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2391 <dd>
2392 <p>That means that for changing a timer costs less than removing/adding them
2393as only the relative motion in the event queue has to be paid for.</p>
2394 </dd>
1775 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2395 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2396 <dd>
2397 <p>These just add the watcher into an array or at the head of a list.
1776 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2398=item Stopping check/prepare/idle watchers: O(1)</p>
2399 </dd>
1777 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2400 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2401 <dd>
2402 <p>These watchers are stored in lists then need to be walked to find the
2403correct watcher to remove. The lists are usually short (you don't usually
2404have many watchers waiting for the same fd or signal).</p>
2405 </dd>
1778 <dt>Finding the next timer per loop iteration: O(1)</dt> 2406 <dt>Finding the next timer per loop iteration: O(1)</dt>
1779 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2407 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2408 <dd>
2409 <p>A change means an I/O watcher gets started or stopped, which requires
2410libev to recalculate its status (and possibly tell the kernel).</p>
2411 </dd>
1780 <dt>Activating one watcher: O(1)</dt> 2412 <dt>Activating one watcher: O(1)</dt>
2413 <dt>Priority handling: O(number_of_priorities)</dt>
2414 <dd>
2415 <p>Priorities are implemented by allocating some space for each
2416priority. When doing priority-based operations, libev usually has to
2417linearly search all the priorities.</p>
2418 </dd>
1781 </dl> 2419 </dl>
1782 </p> 2420 </p>
1783 2421
1784 2422
1785 2423
1786 2424
1787 2425
1788</div> 2426</div>
1789<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2427<h1 id="AUTHOR">AUTHOR</h1>
1790<div id="AUTHOR_CONTENT"> 2428<div id="AUTHOR_CONTENT">
1791 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2429 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1792 2430
1793</div> 2431</div>
1794</div></body> 2432</div></body>

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