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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="Tue Nov 27 11:59:06 2007" /> 9 <meta name="created" content="Sat Dec 8 23:11:11 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>
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59<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
60</li> 61</li>
61</ul><hr /> 62</ul><hr />
62<!-- INDEX END --> 63<!-- INDEX END -->
63 64
64<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
65<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
66<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>
67 68
68</div> 69</div>
69<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
70<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
71<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
72 73
73</pre> 74</pre>
74 75
75</div> 76</div>
76<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>
77<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>
78<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
79file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
80these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
81<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
82(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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85watchers</i>, which are relatively small C structures you initialise with the 134watchers</i>, which are relatively small C structures you initialise with the
86details 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
87watcher.</p> 136watcher.</p>
88 137
89</div> 138</div>
90<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
91<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
92<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
93kqueue mechanisms for file descriptor events, relative timers, absolute 142BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
94timers with customised rescheduling, signal events, process status change 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
95events (related to SIGCHLD), and event watchers dealing with the event 144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
96loop 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
97fast (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
98it to libevent for example).</p> 153for example).</p>
99 154
100</div> 155</div>
101<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
102<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
103<p>Libev is very configurable. In this manual the default configuration 158<p>Libev is very configurable. In this manual the default configuration will
104will be described, which supports multiple event loops. For more info 159be described, which supports multiple event loops. For more info about
105about various configuration options please have a look at the file 160various configuration options please have a look at <strong>EMBED</strong> section in
106<cite>README.embed</cite> in the libev distribution. If libev was configured without 161this manual. If libev was configured without support for multiple event
107support for multiple event loops, then all functions taking an initial 162loops, then all functions taking an initial argument of name <code>loop</code>
108argument 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>
109will not have this argument.</p>
110 164
111</div> 165</div>
112<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
113<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
114<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
115(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
116the 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
117called <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
118to 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
119it, you should treat it as such.</p> 173it, you should treat it as such.</p>
120 174
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
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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 ();
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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
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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
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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>
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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>
… …
448one iteration of the loop. This is useful if you are waiting for some 529one iteration of the loop. This is useful if you are waiting for some
449external event in conjunction with something not expressible using other 530external event in conjunction with something not expressible using other
450libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 531libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
451usually a better approach for this kind of thing.</p> 532usually a better approach for this kind of thing.</p>
452 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 533 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
534<pre> - Before the first iteration, call any pending watchers.
453<pre> * If there are no active watchers (reference count is zero), return. 535 * If there are no active watchers (reference count is zero), return.
454 - Queue prepare watchers and then call all outstanding watchers. 536 - Queue all prepare watchers and then call all outstanding watchers.
455 - If we have been forked, recreate the kernel state. 537 - If we have been forked, recreate the kernel state.
456 - Update the kernel state with all outstanding changes. 538 - Update the kernel state with all outstanding changes.
457 - Update the &quot;event loop time&quot;. 539 - Update the &quot;event loop time&quot;.
458 - Calculate for how long to block. 540 - Calculate for how long to block.
459 - Block the process, waiting for any events. 541 - Block the process, waiting for any events.
… …
468 be handled here by queueing them when their watcher gets executed. 550 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 551 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *. 552 were used, return, otherwise continue with step *.
471 553
472</pre> 554</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding 555 <p>Example: Queue some jobs and then loop until no events are outsanding
474anymore.</p> 556anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long 557<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..) 558 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0); 559 ev_loop (my_loop, 0);
478 ... jobs done. yeah! 560 ... jobs done. yeah!
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497example, libev itself uses this for its internal signal pipe: It is not 579example, 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 580visible 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 581no 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 582way 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> 583libraries. 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> 584 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p> 585running when nothing else is active.</p>
504<pre> struct dv_signal exitsig; 586<pre> struct ev_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 587 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig); 588 ev_signal_start (loop, &amp;exitsig);
507 evf_unref (myloop); 589 evf_unref (loop);
508 590
509</pre> 591</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p> 592 <p>Example: For some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop); 593<pre> ev_ref (loop);
512 ev_signal_stop (myloop, &amp;exitsig); 594 ev_signal_stop (loop, &amp;exitsig);
513 595
514</pre> 596</pre>
515 </dd> 597 </dd>
516</dl> 598</dl>
517 599
518 600
519 601
520 602
521 603
522</div> 604</div>
523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 605<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
524<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 606<div id="ANATOMY_OF_A_WATCHER_CONTENT">
525<p>A watcher is a structure that you create and register to record your 607<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 608interest 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> 609become 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) 610<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
688 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 770 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
689 <dd> 771 <dd>
690 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 772 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
691events but its callback has not yet been invoked). As long as a watcher 773events but its callback has not yet been invoked). As long as a watcher
692is pending (but not active) you must not call an init function on it (but 774is pending (but not active) you must not call an init function on it (but
693<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 775<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
694libev (e.g. you cnanot <code>free ()</code> it).</p> 776make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
777it).</p>
695 </dd> 778 </dd>
696 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 779 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
697 <dd> 780 <dd>
698 <p>Returns the callback currently set on the watcher.</p> 781 <p>Returns the callback currently set on the watcher.</p>
699 </dd> 782 </dd>
700 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 783 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
701 <dd> 784 <dd>
702 <p>Change the callback. You can change the callback at virtually any time 785 <p>Change the callback. You can change the callback at virtually any time
703(modulo threads).</p> 786(modulo threads).</p>
787 </dd>
788 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
789 <dt>int ev_priority (ev_TYPE *watcher)</dt>
790 <dd>
791 <p>Set and query the priority of the watcher. The priority is a small
792integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
793(default: <code>-2</code>). Pending watchers with higher priority will be invoked
794before watchers with lower priority, but priority will not keep watchers
795from being executed (except for <code>ev_idle</code> watchers).</p>
796 <p>This means that priorities are <i>only</i> used for ordering callback
797invocation after new events have been received. This is useful, for
798example, to reduce latency after idling, or more often, to bind two
799watchers on the same event and make sure one is called first.</p>
800 <p>If you need to suppress invocation when higher priority events are pending
801you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
802 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
803pending.</p>
804 <p>The default priority used by watchers when no priority has been set is
805always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
806 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
807fine, as long as you do not mind that the priority value you query might
808or might not have been adjusted to be within valid range.</p>
809 </dd>
810 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
811 <dd>
812 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
813<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
814can deal with that fact.</p>
815 </dd>
816 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
817 <dd>
818 <p>If the watcher is pending, this function returns clears its pending status
819and returns its <code>revents</code> bitset (as if its callback was invoked). If the
820watcher isn't pending it does nothing and returns <code>0</code>.</p>
704 </dd> 821 </dd>
705</dl> 822</dl>
706 823
707 824
708 825
… …
733 struct my_io *w = (struct my_io *)w_; 850 struct my_io *w = (struct my_io *)w_;
734 ... 851 ...
735 } 852 }
736 853
737</pre> 854</pre>
738<p>More interesting and less C-conformant ways of catsing your callback type 855<p>More interesting and less C-conformant ways of casting your callback type
739have been omitted....</p> 856instead have been omitted.</p>
857<p>Another common scenario is having some data structure with multiple
858watchers:</p>
859<pre> struct my_biggy
860 {
861 int some_data;
862 ev_timer t1;
863 ev_timer t2;
864 }
740 865
866</pre>
867<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
868you need to use <code>offsetof</code>:</p>
869<pre> #include &lt;stddef.h&gt;
741 870
871 static void
872 t1_cb (EV_P_ struct ev_timer *w, int revents)
873 {
874 struct my_biggy big = (struct my_biggy *
875 (((char *)w) - offsetof (struct my_biggy, t1));
876 }
742 877
878 static void
879 t2_cb (EV_P_ struct ev_timer *w, int revents)
880 {
881 struct my_biggy big = (struct my_biggy *
882 (((char *)w) - offsetof (struct my_biggy, t2));
883 }
743 884
744 885
886
887
888</pre>
889
745</div> 890</div>
746<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 891<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
747<div id="WATCHER_TYPES_CONTENT"> 892<div id="WATCHER_TYPES_CONTENT">
748<p>This section describes each watcher in detail, but will not repeat 893<p>This section describes each watcher in detail, but will not repeat
749information given in the last section. Any initialisation/set macros, 894information given in the last section. Any initialisation/set macros,
750functions and members specific to the watcher type are explained.</p> 895functions and members specific to the watcher type are explained.</p>
751<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, 896<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
… …
791this situation even with a relatively standard program structure. Thus 936this situation even with a relatively standard program structure. Thus
792it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 937it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
793<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 938<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
794<p>If you cannot run the fd in non-blocking mode (for example you should not 939<p>If you cannot run the fd in non-blocking mode (for example you should not
795play around with an Xlib connection), then you have to seperately re-test 940play around with an Xlib connection), then you have to seperately re-test
796wether a file descriptor is really ready with a known-to-be good interface 941whether a file descriptor is really ready with a known-to-be good interface
797such as poll (fortunately in our Xlib example, Xlib already does this on 942such as poll (fortunately in our Xlib example, Xlib already does this on
798its own, so its quite safe to use).</p> 943its own, so its quite safe to use).</p>
799<dl> 944<dl>
800 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 945 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
801 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 946 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
811 <dt>int events [read-only]</dt> 956 <dt>int events [read-only]</dt>
812 <dd> 957 <dd>
813 <p>The events being watched.</p> 958 <p>The events being watched.</p>
814 </dd> 959 </dd>
815</dl> 960</dl>
816<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 961<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
817readable, but only once. Since it is likely line-buffered, you could 962readable, but only once. Since it is likely line-buffered, you could
818attempt to read a whole line in the callback:</p> 963attempt to read a whole line in the callback.</p>
819<pre> static void 964<pre> static void
820 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 965 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
821 { 966 {
822 ev_io_stop (loop, w); 967 ev_io_stop (loop, w);
823 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 968 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
872 </dd> 1017 </dd>
873 <dt>ev_timer_again (loop)</dt> 1018 <dt>ev_timer_again (loop)</dt>
874 <dd> 1019 <dd>
875 <p>This will act as if the timer timed out and restart it again if it is 1020 <p>This will act as if the timer timed out and restart it again if it is
876repeating. The exact semantics are:</p> 1021repeating. The exact semantics are:</p>
1022 <p>If the timer is pending, its pending status is cleared.</p>
877 <p>If the timer is started but nonrepeating, stop it.</p> 1023 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
878 <p>If the timer is repeating, either start it if necessary (with the repeat 1024 <p>If the timer is repeating, either start it if necessary (with the
879value), or reset the running timer to the repeat value.</p> 1025<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
880 <p>This sounds a bit complicated, but here is a useful and typical 1026 <p>This sounds a bit complicated, but here is a useful and typical
881example: Imagine you have a tcp connection and you want a so-called 1027example: Imagine you have a tcp connection and you want a so-called idle
882idle timeout, that is, you want to be called when there have been, 1028timeout, that is, you want to be called when there have been, say, 60
883say, 60 seconds of inactivity on the socket. The easiest way to do 1029seconds of inactivity on the socket. The easiest way to do this is to
884this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling 1030configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
885<code>ev_timer_again</code> each time you successfully read or write some data. If 1031<code>ev_timer_again</code> each time you successfully read or write some data. If
886you go into an idle state where you do not expect data to travel on the 1032you go into an idle state where you do not expect data to travel on the
887socket, you can stop the timer, and again will automatically restart it if 1033socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
888need be.</p> 1034automatically restart it if need be.</p>
889 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1035 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
890and only ever use the <code>repeat</code> value:</p> 1036altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
891<pre> ev_timer_init (timer, callback, 0., 5.); 1037<pre> ev_timer_init (timer, callback, 0., 5.);
892 ev_timer_again (loop, timer); 1038 ev_timer_again (loop, timer);
893 ... 1039 ...
894 timer-&gt;again = 17.; 1040 timer-&gt;again = 17.;
895 ev_timer_again (loop, timer); 1041 ev_timer_again (loop, timer);
896 ... 1042 ...
897 timer-&gt;again = 10.; 1043 timer-&gt;again = 10.;
898 ev_timer_again (loop, timer); 1044 ev_timer_again (loop, timer);
899 1045
900</pre> 1046</pre>
901 <p>This is more efficient then stopping/starting the timer eahc time you want 1047 <p>This is more slightly efficient then stopping/starting the timer each time
902to modify its timeout value.</p> 1048you want to modify its timeout value.</p>
903 </dd> 1049 </dd>
904 <dt>ev_tstamp repeat [read-write]</dt> 1050 <dt>ev_tstamp repeat [read-write]</dt>
905 <dd> 1051 <dd>
906 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1052 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
907or <code>ev_timer_again</code> is called and determines the next timeout (if any), 1053or <code>ev_timer_again</code> is called and determines the next timeout (if any),
908which is also when any modifications are taken into account.</p> 1054which is also when any modifications are taken into account.</p>
909 </dd> 1055 </dd>
910</dl> 1056</dl>
911<p>Example: create a timer that fires after 60 seconds.</p> 1057<p>Example: Create a timer that fires after 60 seconds.</p>
912<pre> static void 1058<pre> static void
913 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1059 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
914 { 1060 {
915 .. one minute over, w is actually stopped right here 1061 .. one minute over, w is actually stopped right here
916 } 1062 }
… …
918 struct ev_timer mytimer; 1064 struct ev_timer mytimer;
919 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1065 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
920 ev_timer_start (loop, &amp;mytimer); 1066 ev_timer_start (loop, &amp;mytimer);
921 1067
922</pre> 1068</pre>
923<p>Example: create a timeout timer that times out after 10 seconds of 1069<p>Example: Create a timeout timer that times out after 10 seconds of
924inactivity.</p> 1070inactivity.</p>
925<pre> static void 1071<pre> static void
926 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1072 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
927 { 1073 {
928 .. ten seconds without any activity 1074 .. ten seconds without any activity
… …
1044 <p>The current reschedule callback, or <code>0</code>, if this functionality is 1190 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1045switched off. Can be changed any time, but changes only take effect when 1191switched off. Can be changed any time, but changes only take effect when
1046the periodic timer fires or <code>ev_periodic_again</code> is being called.</p> 1192the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1047 </dd> 1193 </dd>
1048</dl> 1194</dl>
1049<p>Example: call a callback every hour, or, more precisely, whenever the 1195<p>Example: Call a callback every hour, or, more precisely, whenever the
1050system clock is divisible by 3600. The callback invocation times have 1196system clock is divisible by 3600. The callback invocation times have
1051potentially a lot of jittering, but good long-term stability.</p> 1197potentially a lot of jittering, but good long-term stability.</p>
1052<pre> static void 1198<pre> static void
1053 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1199 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1054 { 1200 {
… …
1058 struct ev_periodic hourly_tick; 1204 struct ev_periodic hourly_tick;
1059 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1205 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
1060 ev_periodic_start (loop, &amp;hourly_tick); 1206 ev_periodic_start (loop, &amp;hourly_tick);
1061 1207
1062</pre> 1208</pre>
1063<p>Example: the same as above, but use a reschedule callback to do it:</p> 1209<p>Example: The same as above, but use a reschedule callback to do it:</p>
1064<pre> #include &lt;math.h&gt; 1210<pre> #include &lt;math.h&gt;
1065 1211
1066 static ev_tstamp 1212 static ev_tstamp
1067 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1213 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1068 { 1214 {
… …
1070 } 1216 }
1071 1217
1072 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1218 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1073 1219
1074</pre> 1220</pre>
1075<p>Example: call a callback every hour, starting now:</p> 1221<p>Example: Call a callback every hour, starting now:</p>
1076<pre> struct ev_periodic hourly_tick; 1222<pre> struct ev_periodic hourly_tick;
1077 ev_periodic_init (&amp;hourly_tick, clock_cb, 1223 ev_periodic_init (&amp;hourly_tick, clock_cb,
1078 fmod (ev_now (loop), 3600.), 3600., 0); 1224 fmod (ev_now (loop), 3600.), 3600., 0);
1079 ev_periodic_start (loop, &amp;hourly_tick); 1225 ev_periodic_start (loop, &amp;hourly_tick);
1080 1226
… …
1141 <dd> 1287 <dd>
1142 <p>The process exit/trace status caused by <code>rpid</code> (see your systems 1288 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1143<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p> 1289<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1144 </dd> 1290 </dd>
1145</dl> 1291</dl>
1146<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1292<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1147<pre> static void 1293<pre> static void
1148 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1294 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1149 { 1295 {
1150 ev_unloop (loop, EVUNLOOP_ALL); 1296 ev_unloop (loop, EVUNLOOP_ALL);
1151 } 1297 }
… …
1168<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1314<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1169not exist&quot; is a status change like any other. The condition &quot;path does 1315not exist&quot; is a status change like any other. The condition &quot;path does
1170not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is 1316not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1171otherwise always forced to be at least one) and all the other fields of 1317otherwise always forced to be at least one) and all the other fields of
1172the stat buffer having unspecified contents.</p> 1318the stat buffer having unspecified contents.</p>
1319<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1320relative and your working directory changes, the behaviour is undefined.</p>
1173<p>Since there is no standard to do this, the portable implementation simply 1321<p>Since there is no standard to do this, the portable implementation simply
1174calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You 1322calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1175can specify a recommended polling interval for this case. If you specify 1323can specify a recommended polling interval for this case. If you specify
1176a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1324a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1177unspecified default</i> value will be used (which you can expect to be around 1325unspecified default</i> value will be used (which you can expect to be around
1178five seconds, although this might change dynamically). Libev will also 1326five seconds, although this might change dynamically). Libev will also
1179impose a minimum interval which is currently around <code>0.1</code>, but thats 1327impose a minimum interval which is currently around <code>0.1</code>, but thats
1180usually overkill.</p> 1328usually overkill.</p>
1181<p>This watcher type is not meant for massive numbers of stat watchers, 1329<p>This watcher type is not meant for massive numbers of stat watchers,
1182as even with OS-supported change notifications, this can be 1330as even with OS-supported change notifications, this can be
1183resource-intensive.</p> 1331resource-intensive.</p>
1184<p>At the time of this writing, no specific OS backends are implemented, but 1332<p>At the time of this writing, only the Linux inotify interface is
1185if demand increases, at least a kqueue and inotify backend will be added.</p> 1333implemented (implementing kqueue support is left as an exercise for the
1334reader). Inotify will be used to give hints only and should not change the
1335semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1336to fall back to regular polling again even with inotify, but changes are
1337usually detected immediately, and if the file exists there will be no
1338polling.</p>
1186<dl> 1339<dl>
1187 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1340 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1188 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> 1341 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1189 <dd> 1342 <dd>
1190 <p>Configures the watcher to wait for status changes of the given 1343 <p>Configures the watcher to wait for status changes of the given
… …
1253</pre> 1406</pre>
1254 1407
1255</div> 1408</div>
1256<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1409<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1257<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1410<div id="code_ev_idle_code_when_you_ve_got_no-2">
1258<p>Idle watchers trigger events when there are no other events are pending 1411<p>Idle watchers trigger events when no other events of the same or higher
1259(prepare, check and other idle watchers do not count). That is, as long 1412priority are pending (prepare, check and other idle watchers do not
1260as your process is busy handling sockets or timeouts (or even signals, 1413count).</p>
1261imagine) it will not be triggered. But when your process is idle all idle 1414<p>That is, as long as your process is busy handling sockets or timeouts
1262watchers are being called again and again, once per event loop iteration - 1415(or even signals, imagine) of the same or higher priority it will not be
1416triggered. But when your process is idle (or only lower-priority watchers
1417are pending), the idle watchers are being called once per event loop
1263until stopped, that is, or your process receives more events and becomes 1418iteration - until stopped, that is, or your process receives more events
1264busy.</p> 1419and becomes busy again with higher priority stuff.</p>
1265<p>The most noteworthy effect is that as long as any idle watchers are 1420<p>The most noteworthy effect is that as long as any idle watchers are
1266active, the process will not block when waiting for new events.</p> 1421active, the process will not block when waiting for new events.</p>
1267<p>Apart from keeping your process non-blocking (which is a useful 1422<p>Apart from keeping your process non-blocking (which is a useful
1268effect on its own sometimes), idle watchers are a good place to do 1423effect on its own sometimes), idle watchers are a good place to do
1269&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1424&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1274 <p>Initialises and configures the idle watcher - it has no parameters of any 1429 <p>Initialises and configures the idle watcher - it has no parameters of any
1275kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1430kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1276believe me.</p> 1431believe me.</p>
1277 </dd> 1432 </dd>
1278</dl> 1433</dl>
1279<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1434<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1280callback, free it. Alos, use no error checking, as usual.</p> 1435callback, free it. Also, use no error checking, as usual.</p>
1281<pre> static void 1436<pre> static void
1282 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1437 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1283 { 1438 {
1284 free (w); 1439 free (w);
1285 // now do something you wanted to do when the program has 1440 // now do something you wanted to do when the program has
… …
1329are ready to run (it's actually more complicated: it only runs coroutines 1484are ready to run (it's actually more complicated: it only runs coroutines
1330with priority higher than or equal to the event loop and one coroutine 1485with priority higher than or equal to the event loop and one coroutine
1331of lower priority, but only once, using idle watchers to keep the event 1486of lower priority, but only once, using idle watchers to keep the event
1332loop from blocking if lower-priority coroutines are active, thus mapping 1487loop from blocking if lower-priority coroutines are active, thus mapping
1333low-priority coroutines to idle/background tasks).</p> 1488low-priority coroutines to idle/background tasks).</p>
1489<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1490priority, to ensure that they are being run before any other watchers
1491after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1492too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1493supports this, they will be called before other <code>ev_check</code> watchers did
1494their job. As <code>ev_check</code> watchers are often used to embed other event
1495loops those other event loops might be in an unusable state until their
1496<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1497others).</p>
1334<dl> 1498<dl>
1335 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1499 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1336 <dt>ev_check_init (ev_check *, callback)</dt> 1500 <dt>ev_check_init (ev_check *, callback)</dt>
1337 <dd> 1501 <dd>
1338 <p>Initialises and configures the prepare or check watcher - they have no 1502 <p>Initialises and configures the prepare or check watcher - they have no
1339parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1503parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1340macros, but using them is utterly, utterly and completely pointless.</p> 1504macros, but using them is utterly, utterly and completely pointless.</p>
1341 </dd> 1505 </dd>
1342</dl> 1506</dl>
1343<p>Example: To include a library such as adns, you would add IO watchers 1507<p>There are a number of principal ways to embed other event loops or modules
1344and a timeout watcher in a prepare handler, as required by libadns, and 1508into libev. Here are some ideas on how to include libadns into libev
1509(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1510use for an actually working example. Another Perl module named <code>EV::Glib</code>
1511embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1512into the Glib event loop).</p>
1513<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1345in a check watcher, destroy them and call into libadns. What follows is 1514and in a check watcher, destroy them and call into libadns. What follows
1346pseudo-code only of course:</p> 1515is pseudo-code only of course. This requires you to either use a low
1516priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1517the callbacks for the IO/timeout watchers might not have been called yet.</p>
1347<pre> static ev_io iow [nfd]; 1518<pre> static ev_io iow [nfd];
1348 static ev_timer tw; 1519 static ev_timer tw;
1349 1520
1350 static void 1521 static void
1351 io_cb (ev_loop *loop, ev_io *w, int revents) 1522 io_cb (ev_loop *loop, ev_io *w, int revents)
1352 { 1523 {
1353 // set the relevant poll flags
1354 // could also call adns_processreadable etc. here
1355 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1356 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1357 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1358 } 1524 }
1359 1525
1360 // create io watchers for each fd and a timer before blocking 1526 // create io watchers for each fd and a timer before blocking
1361 static void 1527 static void
1362 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1528 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1363 { 1529 {
1364 int timeout = 3600000;truct pollfd fds [nfd]; 1530 int timeout = 3600000;
1531 struct pollfd fds [nfd];
1365 // actual code will need to loop here and realloc etc. 1532 // actual code will need to loop here and realloc etc.
1366 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1533 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1367 1534
1368 /* the callback is illegal, but won't be called as we stop during check */ 1535 /* the callback is illegal, but won't be called as we stop during check */
1369 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1536 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1370 ev_timer_start (loop, &amp;tw); 1537 ev_timer_start (loop, &amp;tw);
1371 1538
1372 // create on ev_io per pollfd 1539 // create one ev_io per pollfd
1373 for (int i = 0; i &lt; nfd; ++i) 1540 for (int i = 0; i &lt; nfd; ++i)
1374 { 1541 {
1375 ev_io_init (iow + i, io_cb, fds [i].fd, 1542 ev_io_init (iow + i, io_cb, fds [i].fd,
1376 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1543 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1377 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1544 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1378 1545
1379 fds [i].revents = 0; 1546 fds [i].revents = 0;
1380 iow [i].data = fds + i;
1381 ev_io_start (loop, iow + i); 1547 ev_io_start (loop, iow + i);
1382 } 1548 }
1383 } 1549 }
1384 1550
1385 // stop all watchers after blocking 1551 // stop all watchers after blocking
… …
1387 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1553 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1388 { 1554 {
1389 ev_timer_stop (loop, &amp;tw); 1555 ev_timer_stop (loop, &amp;tw);
1390 1556
1391 for (int i = 0; i &lt; nfd; ++i) 1557 for (int i = 0; i &lt; nfd; ++i)
1558 {
1559 // set the relevant poll flags
1560 // could also call adns_processreadable etc. here
1561 struct pollfd *fd = fds + i;
1562 int revents = ev_clear_pending (iow + i);
1563 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1564 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1565
1566 // now stop the watcher
1392 ev_io_stop (loop, iow + i); 1567 ev_io_stop (loop, iow + i);
1568 }
1393 1569
1394 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1570 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1571 }
1572
1573</pre>
1574<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1575in the prepare watcher and would dispose of the check watcher.</p>
1576<p>Method 3: If the module to be embedded supports explicit event
1577notification (adns does), you can also make use of the actual watcher
1578callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1579<pre> static void
1580 timer_cb (EV_P_ ev_timer *w, int revents)
1581 {
1582 adns_state ads = (adns_state)w-&gt;data;
1583 update_now (EV_A);
1584
1585 adns_processtimeouts (ads, &amp;tv_now);
1586 }
1587
1588 static void
1589 io_cb (EV_P_ ev_io *w, int revents)
1590 {
1591 adns_state ads = (adns_state)w-&gt;data;
1592 update_now (EV_A);
1593
1594 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1595 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1596 }
1597
1598 // do not ever call adns_afterpoll
1599
1600</pre>
1601<p>Method 4: Do not use a prepare or check watcher because the module you
1602want to embed is too inflexible to support it. Instead, youc na override
1603their poll function. The drawback with this solution is that the main
1604loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1605this.</p>
1606<pre> static gint
1607 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1608 {
1609 int got_events = 0;
1610
1611 for (n = 0; n &lt; nfds; ++n)
1612 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1613
1614 if (timeout &gt;= 0)
1615 // create/start timer
1616
1617 // poll
1618 ev_loop (EV_A_ 0);
1619
1620 // stop timer again
1621 if (timeout &gt;= 0)
1622 ev_timer_stop (EV_A_ &amp;to);
1623
1624 // stop io watchers again - their callbacks should have set
1625 for (n = 0; n &lt; nfds; ++n)
1626 ev_io_stop (EV_A_ iow [n]);
1627
1628 return got_events;
1395 } 1629 }
1396 1630
1397 1631
1398 1632
1399 1633
… …
1510 1744
1511 1745
1512 1746
1513 1747
1514</div> 1748</div>
1515<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1749<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1516<div id="OTHER_FUNCTIONS_CONTENT"> 1750<div id="OTHER_FUNCTIONS_CONTENT">
1517<p>There are some other functions of possible interest. Described. Here. Now.</p> 1751<p>There are some other functions of possible interest. Described. Here. Now.</p>
1518<dl> 1752<dl>
1519 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1753 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1520 <dd> 1754 <dd>
… …
1567 1801
1568 1802
1569 1803
1570 1804
1571</div> 1805</div>
1572<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1806<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1573<div id="LIBEVENT_EMULATION_CONTENT"> 1807<div id="LIBEVENT_EMULATION_CONTENT">
1574<p>Libev offers a compatibility emulation layer for libevent. It cannot 1808<p>Libev offers a compatibility emulation layer for libevent. It cannot
1575emulate the internals of libevent, so here are some usage hints:</p> 1809emulate the internals of libevent, so here are some usage hints:</p>
1576<dl> 1810<dl>
1577 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1811 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1587 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1821 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1588to use the libev header file and library.</dt> 1822to use the libev header file and library.</dt>
1589</dl> 1823</dl>
1590 1824
1591</div> 1825</div>
1592<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1826<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1593<div id="C_SUPPORT_CONTENT"> 1827<div id="C_SUPPORT_CONTENT">
1594<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1828<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1595you to use some convinience methods to start/stop watchers and also change 1829you to use some convinience methods to start/stop watchers and also change
1596the callback model to a model using method callbacks on objects.</p> 1830the callback model to a model using method callbacks on objects.</p>
1597<p>To use it,</p> 1831<p>To use it,</p>
1598<pre> #include &lt;ev++.h&gt; 1832<pre> #include &lt;ev++.h&gt;
1599 1833
1600</pre> 1834</pre>
1601<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1835<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1602and puts all of its definitions (many of them macros) into the global 1836of them macros) into the global namespace. All C++ specific things are
1603namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1837put into the <code>ev</code> namespace. It should support all the same embedding
1604<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1838options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1605<code>EV_MULTIPLICITY</code>.</p> 1839<p>Care has been taken to keep the overhead low. The only data member the C++
1840classes add (compared to plain C-style watchers) is the event loop pointer
1841that the watcher is associated with (or no additional members at all if
1842you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1843<p>Currently, functions, and static and non-static member functions can be
1844used as callbacks. Other types should be easy to add as long as they only
1845need one additional pointer for context. If you need support for other
1846types of functors please contact the author (preferably after implementing
1847it).</p>
1606<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1848<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1607<dl> 1849<dl>
1608 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1850 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1609 <dd> 1851 <dd>
1610 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1852 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1621which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1863which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1622defines by many implementations.</p> 1864defines by many implementations.</p>
1623 <p>All of those classes have these methods:</p> 1865 <p>All of those classes have these methods:</p>
1624 <p> 1866 <p>
1625 <dl> 1867 <dl>
1626 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1868 <dt>ev::TYPE::TYPE ()</dt>
1627 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1869 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1628 <dt>ev::TYPE::~TYPE</dt> 1870 <dt>ev::TYPE::~TYPE</dt>
1629 <dd> 1871 <dd>
1630 <p>The constructor takes a pointer to an object and a method pointer to 1872 <p>The constructor (optionally) takes an event loop to associate the watcher
1631the event handler callback to call in this class. The constructor calls 1873with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1632<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1874 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1633before starting it. If you do not specify a loop then the constructor 1875<code>set</code> method before starting it.</p>
1634automatically associates the default loop with this watcher.</p> 1876 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1877method to set a callback before you can start the watcher.</p>
1878 <p>(The reason why you have to use a method is a limitation in C++ which does
1879not allow explicit template arguments for constructors).</p>
1635 <p>The destructor automatically stops the watcher if it is active.</p> 1880 <p>The destructor automatically stops the watcher if it is active.</p>
1881 </dd>
1882 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1883 <dd>
1884 <p>This method sets the callback method to call. The method has to have a
1885signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1886first argument and the <code>revents</code> as second. The object must be given as
1887parameter and is stored in the <code>data</code> member of the watcher.</p>
1888 <p>This method synthesizes efficient thunking code to call your method from
1889the C callback that libev requires. If your compiler can inline your
1890callback (i.e. it is visible to it at the place of the <code>set</code> call and
1891your compiler is good :), then the method will be fully inlined into the
1892thunking function, making it as fast as a direct C callback.</p>
1893 <p>Example: simple class declaration and watcher initialisation</p>
1894<pre> struct myclass
1895 {
1896 void io_cb (ev::io &amp;w, int revents) { }
1897 }
1898
1899 myclass obj;
1900 ev::io iow;
1901 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1902
1903</pre>
1904 </dd>
1905 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1906 <dd>
1907 <p>Also sets a callback, but uses a static method or plain function as
1908callback. The optional <code>data</code> argument will be stored in the watcher's
1909<code>data</code> member and is free for you to use.</p>
1910 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1911 <p>See the method-<code>set</code> above for more details.</p>
1912 <p>Example:</p>
1913<pre> static void io_cb (ev::io &amp;w, int revents) { }
1914 iow.set &lt;io_cb&gt; ();
1915
1916</pre>
1636 </dd> 1917 </dd>
1637 <dt>w-&gt;set (struct ev_loop *)</dt> 1918 <dt>w-&gt;set (struct ev_loop *)</dt>
1638 <dd> 1919 <dd>
1639 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1920 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1640do this when the watcher is inactive (and not pending either).</p> 1921do this when the watcher is inactive (and not pending either).</p>
1641 </dd> 1922 </dd>
1642 <dt>w-&gt;set ([args])</dt> 1923 <dt>w-&gt;set ([args])</dt>
1643 <dd> 1924 <dd>
1644 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1925 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1645called at least once. Unlike the C counterpart, an active watcher gets 1926called at least once. Unlike the C counterpart, an active watcher gets
1646automatically stopped and restarted.</p> 1927automatically stopped and restarted when reconfiguring it with this
1928method.</p>
1647 </dd> 1929 </dd>
1648 <dt>w-&gt;start ()</dt> 1930 <dt>w-&gt;start ()</dt>
1649 <dd> 1931 <dd>
1650 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1932 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1651constructor already takes the loop.</p> 1933constructor already stores the event loop.</p>
1652 </dd> 1934 </dd>
1653 <dt>w-&gt;stop ()</dt> 1935 <dt>w-&gt;stop ()</dt>
1654 <dd> 1936 <dd>
1655 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1937 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1656 </dd> 1938 </dd>
… …
1680 1962
1681 myclass (); 1963 myclass ();
1682 } 1964 }
1683 1965
1684 myclass::myclass (int fd) 1966 myclass::myclass (int fd)
1685 : io (this, &amp;myclass::io_cb),
1686 idle (this, &amp;myclass::idle_cb)
1687 { 1967 {
1968 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1969 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1970
1688 io.start (fd, ev::READ); 1971 io.start (fd, ev::READ);
1689 } 1972 }
1690 1973
1691 1974
1692 1975
1693 1976
1694</pre> 1977</pre>
1695 1978
1696</div> 1979</div>
1697<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p> 1980<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1698<div id="MACRO_MAGIC_CONTENT"> 1981<div id="MACRO_MAGIC_CONTENT">
1699<p>Libev can be compiled with a variety of options, the most fundemantal is 1982<p>Libev can be compiled with a variety of options, the most fundemantal is
1700<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1983<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1701callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1984callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1702<p>To make it easier to write programs that cope with either variant, the 1985<p>To make it easier to write programs that cope with either variant, the
1703following macros are defined:</p> 1986following macros are defined:</p>
1704<dl> 1987<dl>
1705 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1988 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1734 <dd> 2017 <dd>
1735 <p>Similar to the other two macros, this gives you the value of the default 2018 <p>Similar to the other two macros, this gives you the value of the default
1736loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2019loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1737 </dd> 2020 </dd>
1738</dl> 2021</dl>
1739<p>Example: Declare and initialise a check watcher, working regardless of 2022<p>Example: Declare and initialise a check watcher, utilising the above
1740wether multiple loops are supported or not.</p> 2023macros so it will work regardless of whether multiple loops are supported
2024or not.</p>
1741<pre> static void 2025<pre> static void
1742 check_cb (EV_P_ ev_timer *w, int revents) 2026 check_cb (EV_P_ ev_timer *w, int revents)
1743 { 2027 {
1744 ev_check_stop (EV_A_ w); 2028 ev_check_stop (EV_A_ w);
1745 } 2029 }
… …
1747 ev_check check; 2031 ev_check check;
1748 ev_check_init (&amp;check, check_cb); 2032 ev_check_init (&amp;check, check_cb);
1749 ev_check_start (EV_DEFAULT_ &amp;check); 2033 ev_check_start (EV_DEFAULT_ &amp;check);
1750 ev_loop (EV_DEFAULT_ 0); 2034 ev_loop (EV_DEFAULT_ 0);
1751 2035
1752
1753
1754
1755</pre> 2036</pre>
1756 2037
1757</div> 2038</div>
1758<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 2039<h1 id="EMBEDDING">EMBEDDING</h1>
1759<div id="EMBEDDING_CONTENT"> 2040<div id="EMBEDDING_CONTENT">
1760<p>Libev can (and often is) directly embedded into host 2041<p>Libev can (and often is) directly embedded into host
1761applications. Examples of applications that embed it include the Deliantra 2042applications. Examples of applications that embed it include the Deliantra
1762Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2043Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1763and rxvt-unicode.</p> 2044and rxvt-unicode.</p>
… …
1800 ev_vars.h 2081 ev_vars.h
1801 ev_wrap.h 2082 ev_wrap.h
1802 2083
1803 ev_win32.c required on win32 platforms only 2084 ev_win32.c required on win32 platforms only
1804 2085
1805 ev_select.c only when select backend is enabled (which is by default) 2086 ev_select.c only when select backend is enabled (which is enabled by default)
1806 ev_poll.c only when poll backend is enabled (disabled by default) 2087 ev_poll.c only when poll backend is enabled (disabled by default)
1807 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2088 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1808 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2089 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1809 ev_port.c only when the solaris port backend is enabled (disabled by default) 2090 ev_port.c only when the solaris port backend is enabled (disabled by default)
1810 2091
… …
1937 </dd> 2218 </dd>
1938 <dt>EV_USE_DEVPOLL</dt> 2219 <dt>EV_USE_DEVPOLL</dt>
1939 <dd> 2220 <dd>
1940 <p>reserved for future expansion, works like the USE symbols above.</p> 2221 <p>reserved for future expansion, works like the USE symbols above.</p>
1941 </dd> 2222 </dd>
2223 <dt>EV_USE_INOTIFY</dt>
2224 <dd>
2225 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2226interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2227be detected at runtime.</p>
2228 </dd>
1942 <dt>EV_H</dt> 2229 <dt>EV_H</dt>
1943 <dd> 2230 <dd>
1944 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2231 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1945undefined 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 2232undefined 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
1946can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2233can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1969will have the <code>struct ev_loop *</code> as first argument, and you can create 2256will have the <code>struct ev_loop *</code> as first argument, and you can create
1970additional independent event loops. Otherwise there will be no support 2257additional independent event loops. Otherwise there will be no support
1971for multiple event loops and there is no first event loop pointer 2258for multiple event loops and there is no first event loop pointer
1972argument. Instead, all functions act on the single default loop.</p> 2259argument. Instead, all functions act on the single default loop.</p>
1973 </dd> 2260 </dd>
2261 <dt>EV_MINPRI</dt>
2262 <dt>EV_MAXPRI</dt>
2263 <dd>
2264 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2265<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2266provide for more priorities by overriding those symbols (usually defined
2267to be <code>-2</code> and <code>2</code>, respectively).</p>
2268 <p>When doing priority-based operations, libev usually has to linearly search
2269all the priorities, so having many of them (hundreds) uses a lot of space
2270and time, so using the defaults of five priorities (-2 .. +2) is usually
2271fine.</p>
2272 <p>If your embedding app does not need any priorities, defining these both to
2273<code>0</code> will save some memory and cpu.</p>
2274 </dd>
1974 <dt>EV_PERIODIC_ENABLE</dt> 2275 <dt>EV_PERIODIC_ENABLE</dt>
1975 <dd> 2276 <dd>
1976 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2277 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1977defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2278defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1978code.</p> 2279code.</p>
1979 </dd> 2280 </dd>
2281 <dt>EV_IDLE_ENABLE</dt>
2282 <dd>
2283 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2284defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2285code.</p>
2286 </dd>
1980 <dt>EV_EMBED_ENABLE</dt> 2287 <dt>EV_EMBED_ENABLE</dt>
1981 <dd> 2288 <dd>
1982 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2289 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
1983defined to be <code>0</code>, then they are not.</p> 2290defined to be <code>0</code>, then they are not.</p>
1984 </dd> 2291 </dd>
… …
1995 <dt>EV_MINIMAL</dt> 2302 <dt>EV_MINIMAL</dt>
1996 <dd> 2303 <dd>
1997 <p>If you need to shave off some kilobytes of code at the expense of some 2304 <p>If you need to shave off some kilobytes of code at the expense of some
1998speed, define this symbol to <code>1</code>. Currently only used for gcc to override 2305speed, define this symbol to <code>1</code>. Currently only used for gcc to override
1999some inlining decisions, saves roughly 30% codesize of amd64.</p> 2306some inlining decisions, saves roughly 30% codesize of amd64.</p>
2307 </dd>
2308 <dt>EV_PID_HASHSIZE</dt>
2309 <dd>
2310 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2311pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2312than enough. If you need to manage thousands of children you might want to
2313increase this value (<i>must</i> be a power of two).</p>
2314 </dd>
2315 <dt>EV_INOTIFY_HASHSIZE</dt>
2316 <dd>
2317 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2318inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2319usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2320watchers you might want to increase this value (<i>must</i> be a power of
2321two).</p>
2000 </dd> 2322 </dd>
2001 <dt>EV_COMMON</dt> 2323 <dt>EV_COMMON</dt>
2002 <dd> 2324 <dd>
2003 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2325 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2004this macro to a something else you can include more and other types of 2326this macro to a something else you can include more and other types of
… …
2031the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2353the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2032interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2354interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2033will be compiled. It is pretty complex because it provides its own header 2355will be compiled. It is pretty complex because it provides its own header
2034file.</p> 2356file.</p>
2035 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2357 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2036that everybody includes and which overrides some autoconf choices:</p> 2358that everybody includes and which overrides some configure choices:</p>
2359<pre> #define EV_MINIMAL 1
2037<pre> #define EV_USE_POLL 0 2360 #define EV_USE_POLL 0
2038 #define EV_MULTIPLICITY 0 2361 #define EV_MULTIPLICITY 0
2039 #define EV_PERIODICS 0 2362 #define EV_PERIODIC_ENABLE 0
2363 #define EV_STAT_ENABLE 0
2364 #define EV_FORK_ENABLE 0
2040 #define EV_CONFIG_H &lt;config.h&gt; 2365 #define EV_CONFIG_H &lt;config.h&gt;
2366 #define EV_MINPRI 0
2367 #define EV_MAXPRI 0
2041 2368
2042 #include &quot;ev++.h&quot; 2369 #include &quot;ev++.h&quot;
2043 2370
2044</pre> 2371</pre>
2045 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2372 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2050 2377
2051 2378
2052</pre> 2379</pre>
2053 2380
2054</div> 2381</div>
2055<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2382<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2056<div id="COMPLEXITIES_CONTENT"> 2383<div id="COMPLEXITIES_CONTENT">
2057 <p>In this section the complexities of (many of) the algorithms used inside 2384 <p>In this section the complexities of (many of) the algorithms used inside
2058libev will be explained. For complexity discussions about backends see the 2385libev will be explained. For complexity discussions about backends see the
2059documentation for <code>ev_default_init</code>.</p> 2386documentation for <code>ev_default_init</code>.</p>
2387 <p>All of the following are about amortised time: If an array needs to be
2388extended, libev needs to realloc and move the whole array, but this
2389happens asymptotically never with higher number of elements, so O(1) might
2390mean it might do a lengthy realloc operation in rare cases, but on average
2391it is much faster and asymptotically approaches constant time.</p>
2060 <p> 2392 <p>
2061 <dl> 2393 <dl>
2062 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2394 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2395 <dd>
2396 <p>This means that, when you have a watcher that triggers in one hour and
2397there are 100 watchers that would trigger before that then inserting will
2398have to skip those 100 watchers.</p>
2399 </dd>
2063 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2400 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2401 <dd>
2402 <p>That means that for changing a timer costs less than removing/adding them
2403as only the relative motion in the event queue has to be paid for.</p>
2404 </dd>
2064 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2405 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2406 <dd>
2407 <p>These just add the watcher into an array or at the head of a list.
2065 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2408=item Stopping check/prepare/idle watchers: O(1)</p>
2409 </dd>
2066 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2410 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2411 <dd>
2412 <p>These watchers are stored in lists then need to be walked to find the
2413correct watcher to remove. The lists are usually short (you don't usually
2414have many watchers waiting for the same fd or signal).</p>
2415 </dd>
2067 <dt>Finding the next timer per loop iteration: O(1)</dt> 2416 <dt>Finding the next timer per loop iteration: O(1)</dt>
2068 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2417 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2418 <dd>
2419 <p>A change means an I/O watcher gets started or stopped, which requires
2420libev to recalculate its status (and possibly tell the kernel).</p>
2421 </dd>
2069 <dt>Activating one watcher: O(1)</dt> 2422 <dt>Activating one watcher: O(1)</dt>
2423 <dt>Priority handling: O(number_of_priorities)</dt>
2424 <dd>
2425 <p>Priorities are implemented by allocating some space for each
2426priority. When doing priority-based operations, libev usually has to
2427linearly search all the priorities.</p>
2428 </dd>
2070 </dl> 2429 </dl>
2071 </p> 2430 </p>
2072 2431
2073 2432
2074 2433
2075 2434
2076 2435
2077</div> 2436</div>
2078<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2437<h1 id="AUTHOR">AUTHOR</h1>
2079<div id="AUTHOR_CONTENT"> 2438<div id="AUTHOR_CONTENT">
2080 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2439 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
2081 2440
2082</div> 2441</div>
2083</div></body> 2442</div></body>

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