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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 21:14:27 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> /* this is the only header you need */
72 #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
73 73
74 /* what follows is a fully working example program */ 74</pre>
75
76</div>
77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt;
80
75 ev_io stdin_watcher; 81 ev_io stdin_watcher;
76 ev_timer timeout_watcher; 82 ev_timer timeout_watcher;
77 83
78 /* called when data readable on stdin */ 84 /* called when data readable on stdin */
79 static void 85 static void
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111 } 117 }
112 118
113</pre> 119</pre>
114 120
115</div> 121</div>
116<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 122<h1 id="DESCRIPTION">DESCRIPTION</h1>
117<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>
118<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
119file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
120these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
121<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
122(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
… …
125watchers</i>, which are relatively small C structures you initialise with the 134watchers</i>, which are relatively small C structures you initialise with the
126details 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
127watcher.</p> 136watcher.</p>
128 137
129</div> 138</div>
130<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
131<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
132<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
133kqueue mechanisms for file descriptor events, relative timers, absolute 142BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
134timers with customised rescheduling, signal events, process status change 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
135events (related to SIGCHLD), and event watchers dealing with the event 144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
136loop 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
137fast (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
138it to libevent for example).</p> 153for example).</p>
139 154
140</div> 155</div>
141<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
142<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
143<p>Libev is very configurable. In this manual the default configuration 158<p>Libev is very configurable. In this manual the default configuration will
144will be described, which supports multiple event loops. For more info 159be described, which supports multiple event loops. For more info about
145about various configuration options please have a look at the file 160various configuration options please have a look at <strong>EMBED</strong> section in
146<cite>README.embed</cite> in the libev distribution. If libev was configured without 161this manual. If libev was configured without support for multiple event
147support for multiple event loops, then all functions taking an initial 162loops, then all functions taking an initial argument of name <code>loop</code>
148argument 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>
149will not have this argument.</p>
150 164
151</div> 165</div>
152<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
153<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
154<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
155(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
156the 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
157called <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
158to 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
159it, you should treat it as such.</p> 173it, you should treat it as such.</p>
160 174
161</div> 175</div>
162<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 176<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
163<div id="GLOBAL_FUNCTIONS_CONTENT"> 177<div id="GLOBAL_FUNCTIONS_CONTENT">
164<p>These functions can be called anytime, even before initialising the 178<p>These functions can be called anytime, even before initialising the
165library in any way.</p> 179library in any way.</p>
166<dl> 180<dl>
167 <dt>ev_tstamp ev_time ()</dt> 181 <dt>ev_tstamp ev_time ()</dt>
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180version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
181 <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,
182as this indicates an incompatible change. Minor versions are usually 196as this indicates an incompatible change. Minor versions are usually
183compatible to older versions, so a larger minor version alone is usually 197compatible to older versions, so a larger minor version alone is usually
184not a problem.</p> 198not a problem.</p>
185 <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
186version:</p> 200version.</p>
187<pre> assert ((&quot;libev version mismatch&quot;, 201<pre> assert ((&quot;libev version mismatch&quot;,
188 ev_version_major () == EV_VERSION_MAJOR 202 ev_version_major () == EV_VERSION_MAJOR
189 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 203 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
190 204
191</pre> 205</pre>
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219might be supported on the current system, you would need to look at 233might be supported on the current system, you would need to look at
220<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 234<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
221recommended ones.</p> 235recommended ones.</p>
222 <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>
223 </dd> 237 </dd>
224 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
225 <dd> 239 <dd>
226 <p>Sets the allocation function to use (the prototype and semantics are 240 <p>Sets the allocation function to use (the prototype is similar - the
227identical to the realloc C function). It is used to allocate and free 241semantics is identical - to the realloc C function). It is used to
228memory (no surprises here). If it returns zero when memory needs to be 242allocate and free memory (no surprises here). If it returns zero when
229allocated, the library might abort or take some potentially destructive 243memory needs to be allocated, the library might abort or take some
230action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
231 <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,
232free 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,
233or 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>
234 <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
235retries: better than mine).</p> 250retries).</p>
236<pre> static void * 251<pre> static void *
237 persistent_realloc (void *ptr, size_t size) 252 persistent_realloc (void *ptr, size_t size)
238 { 253 {
239 for (;;) 254 for (;;)
240 { 255 {
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259indicating the system call or subsystem causing the problem. If this 274indicating the system call or subsystem causing the problem. If this
260callback 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
261matter what, when it returns. That is, libev will generally retry the 276matter what, when it returns. That is, libev will generally retry the
262requested 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
263(such as abort).</p> 278(such as abort).</p>
264 <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>
265<pre> static void 280<pre> static void
266 fatal_error (const char *msg) 281 fatal_error (const char *msg)
267 { 282 {
268 perror (msg); 283 perror (msg);
269 abort (); 284 abort ();
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275</pre> 290</pre>
276 </dd> 291 </dd>
277</dl> 292</dl>
278 293
279</div> 294</div>
280<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>
281<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 296<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
282<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
283types 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
284events, and dynamically created loops which do not.</p> 299events, and dynamically created loops which do not.</p>
285<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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314<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
315override 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
316useful 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
317around bugs.</p> 332around bugs.</p>
318 </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>
319 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
320 <dd> 352 <dd>
321 <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
322libev 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,
323but 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
… …
405 <dd> 437 <dd>
406 <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
407always distinct from the default loop. Unlike the default loop, it cannot 439always distinct from the default loop. Unlike the default loop, it cannot
408handle 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
409undefined behaviour (or a failed assertion if assertions are enabled).</p> 441undefined behaviour (or a failed assertion if assertions are enabled).</p>
410 <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>
411<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);
412 if (!epoller) 444 if (!epoller)
413 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;);
414 446
415</pre> 447</pre>
… …
451 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
452 <dd> 484 <dd>
453 <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
454<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
455after 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>
456 </dd> 497 </dd>
457 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
458 <dd> 499 <dd>
459 <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
460use.</p> 501use.</p>
… …
488one 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
489external event in conjunction with something not expressible using other 530external event in conjunction with something not expressible using other
490libev 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
491usually a better approach for this kind of thing.</p> 532usually a better approach for this kind of thing.</p>
492 <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.
493<pre> * If there are no active watchers (reference count is zero), return. 535 * If there are no active watchers (reference count is zero), return.
494 - Queue prepare watchers and then call all outstanding watchers. 536 - Queue all prepare watchers and then call all outstanding watchers.
495 - If we have been forked, recreate the kernel state. 537 - If we have been forked, recreate the kernel state.
496 - Update the kernel state with all outstanding changes. 538 - Update the kernel state with all outstanding changes.
497 - Update the &quot;event loop time&quot;. 539 - Update the &quot;event loop time&quot;.
498 - Calculate for how long to block. 540 - Calculate for how long to block.
499 - Block the process, waiting for any events. 541 - Block the process, waiting for any events.
… …
508 be handled here by queueing them when their watcher gets executed. 550 be handled here by queueing them when their watcher gets executed.
509 - 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
510 were used, return, otherwise continue with step *. 552 were used, return, otherwise continue with step *.
511 553
512</pre> 554</pre>
513 <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
514anymore.</p> 556anymore.</p>
515<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
516 ... 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..)
517 ev_loop (my_loop, 0); 559 ev_loop (my_loop, 0);
518 ... jobs done. yeah! 560 ... jobs done. yeah!
… …
537example, 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
538visible 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
539no 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
540way 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
541libraries. 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>
542 <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>
543running when nothing else is active.</p> 585running when nothing else is active.</p>
544<pre> struct dv_signal exitsig; 586<pre> struct ev_signal exitsig;
545 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 587 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
546 ev_signal_start (myloop, &amp;exitsig); 588 ev_signal_start (loop, &amp;exitsig);
547 evf_unref (myloop); 589 evf_unref (loop);
548 590
549</pre> 591</pre>
550 <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>
551<pre> ev_ref (myloop); 593<pre> ev_ref (loop);
552 ev_signal_stop (myloop, &amp;exitsig); 594 ev_signal_stop (loop, &amp;exitsig);
553 595
554</pre> 596</pre>
555 </dd> 597 </dd>
556</dl> 598</dl>
557 599
558 600
559 601
560 602
561 603
562</div> 604</div>
563<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>
564<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 606<div id="ANATOMY_OF_A_WATCHER_CONTENT">
565<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
566interest 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
567become 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>
568<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)
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728 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 770 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
729 <dd> 771 <dd>
730 <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
731events 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
732is 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
733<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
734libev (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>
735 </dd> 778 </dd>
736 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 779 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
737 <dd> 780 <dd>
738 <p>Returns the callback currently set on the watcher.</p> 781 <p>Returns the callback currently set on the watcher.</p>
739 </dd> 782 </dd>
740 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 783 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
741 <dd> 784 <dd>
742 <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
743(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>
744 </dd> 821 </dd>
745</dl> 822</dl>
746 823
747 824
748 825
… …
773 struct my_io *w = (struct my_io *)w_; 850 struct my_io *w = (struct my_io *)w_;
774 ... 851 ...
775 } 852 }
776 853
777</pre> 854</pre>
778<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
779have 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 }
780 865
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;
781 870
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 }
782 877
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 }
783 884
784 885
886
887
888</pre>
889
785</div> 890</div>
786<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 891<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
787<div id="WATCHER_TYPES_CONTENT"> 892<div id="WATCHER_TYPES_CONTENT">
788<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
789information given in the last section. Any initialisation/set macros, 894information given in the last section. Any initialisation/set macros,
790functions and members specific to the watcher type are explained.</p> 895functions and members specific to the watcher type are explained.</p>
791<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,
… …
831this situation even with a relatively standard program structure. Thus 936this situation even with a relatively standard program structure. Thus
832it 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
833<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>
834<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
835play 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
836wether 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
837such 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
838its own, so its quite safe to use).</p> 943its own, so its quite safe to use).</p>
839<dl> 944<dl>
840 <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>
841 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 946 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
851 <dt>int events [read-only]</dt> 956 <dt>int events [read-only]</dt>
852 <dd> 957 <dd>
853 <p>The events being watched.</p> 958 <p>The events being watched.</p>
854 </dd> 959 </dd>
855</dl> 960</dl>
856<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
857readable, but only once. Since it is likely line-buffered, you could 962readable, but only once. Since it is likely line-buffered, you could
858attempt to read a whole line in the callback:</p> 963attempt to read a whole line in the callback.</p>
859<pre> static void 964<pre> static void
860 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)
861 { 966 {
862 ev_io_stop (loop, w); 967 ev_io_stop (loop, w);
863 .. 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
… …
912 </dd> 1017 </dd>
913 <dt>ev_timer_again (loop)</dt> 1018 <dt>ev_timer_again (loop)</dt>
914 <dd> 1019 <dd>
915 <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
916repeating. The exact semantics are:</p> 1021repeating. The exact semantics are:</p>
1022 <p>If the timer is pending, its pending status is cleared.</p>
917 <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>
918 <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
919value), 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>
920 <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
921example: 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
922idle 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
923say, 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
924this 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
925<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
926you 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
927socket, 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
928need be.</p> 1034automatically restart it if need be.</p>
929 <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>
930and 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>
931<pre> ev_timer_init (timer, callback, 0., 5.); 1037<pre> ev_timer_init (timer, callback, 0., 5.);
932 ev_timer_again (loop, timer); 1038 ev_timer_again (loop, timer);
933 ... 1039 ...
934 timer-&gt;again = 17.; 1040 timer-&gt;again = 17.;
935 ev_timer_again (loop, timer); 1041 ev_timer_again (loop, timer);
936 ... 1042 ...
937 timer-&gt;again = 10.; 1043 timer-&gt;again = 10.;
938 ev_timer_again (loop, timer); 1044 ev_timer_again (loop, timer);
939 1045
940</pre> 1046</pre>
941 <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
942to modify its timeout value.</p> 1048you want to modify its timeout value.</p>
943 </dd> 1049 </dd>
944 <dt>ev_tstamp repeat [read-write]</dt> 1050 <dt>ev_tstamp repeat [read-write]</dt>
945 <dd> 1051 <dd>
946 <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
947or <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),
948which is also when any modifications are taken into account.</p> 1054which is also when any modifications are taken into account.</p>
949 </dd> 1055 </dd>
950</dl> 1056</dl>
951<p>Example: create a timer that fires after 60 seconds.</p> 1057<p>Example: Create a timer that fires after 60 seconds.</p>
952<pre> static void 1058<pre> static void
953 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)
954 { 1060 {
955 .. one minute over, w is actually stopped right here 1061 .. one minute over, w is actually stopped right here
956 } 1062 }
… …
958 struct ev_timer mytimer; 1064 struct ev_timer mytimer;
959 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1065 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
960 ev_timer_start (loop, &amp;mytimer); 1066 ev_timer_start (loop, &amp;mytimer);
961 1067
962</pre> 1068</pre>
963<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
964inactivity.</p> 1070inactivity.</p>
965<pre> static void 1071<pre> static void
966 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)
967 { 1073 {
968 .. ten seconds without any activity 1074 .. ten seconds without any activity
… …
1084 <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
1085switched 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
1086the 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>
1087 </dd> 1193 </dd>
1088</dl> 1194</dl>
1089<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
1090system clock is divisible by 3600. The callback invocation times have 1196system clock is divisible by 3600. The callback invocation times have
1091potentially a lot of jittering, but good long-term stability.</p> 1197potentially a lot of jittering, but good long-term stability.</p>
1092<pre> static void 1198<pre> static void
1093 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)
1094 { 1200 {
… …
1098 struct ev_periodic hourly_tick; 1204 struct ev_periodic hourly_tick;
1099 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1205 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
1100 ev_periodic_start (loop, &amp;hourly_tick); 1206 ev_periodic_start (loop, &amp;hourly_tick);
1101 1207
1102</pre> 1208</pre>
1103<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>
1104<pre> #include &lt;math.h&gt; 1210<pre> #include &lt;math.h&gt;
1105 1211
1106 static ev_tstamp 1212 static ev_tstamp
1107 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1213 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1108 { 1214 {
… …
1110 } 1216 }
1111 1217
1112 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);
1113 1219
1114</pre> 1220</pre>
1115<p>Example: call a callback every hour, starting now:</p> 1221<p>Example: Call a callback every hour, starting now:</p>
1116<pre> struct ev_periodic hourly_tick; 1222<pre> struct ev_periodic hourly_tick;
1117 ev_periodic_init (&amp;hourly_tick, clock_cb, 1223 ev_periodic_init (&amp;hourly_tick, clock_cb,
1118 fmod (ev_now (loop), 3600.), 3600., 0); 1224 fmod (ev_now (loop), 3600.), 3600., 0);
1119 ev_periodic_start (loop, &amp;hourly_tick); 1225 ev_periodic_start (loop, &amp;hourly_tick);
1120 1226
… …
1181 <dd> 1287 <dd>
1182 <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
1183<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>
1184 </dd> 1290 </dd>
1185</dl> 1291</dl>
1186<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1292<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1187<pre> static void 1293<pre> static void
1188 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)
1189 { 1295 {
1190 ev_unloop (loop, EVUNLOOP_ALL); 1296 ev_unloop (loop, EVUNLOOP_ALL);
1191 } 1297 }
… …
1208<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
1209not 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
1210not 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
1211otherwise 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
1212the 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>
1213<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
1214calls <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
1215can specify a recommended polling interval for this case. If you specify 1323can specify a recommended polling interval for this case. If you specify
1216a 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,
1217unspecified 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
1218five seconds, although this might change dynamically). Libev will also 1326five seconds, although this might change dynamically). Libev will also
1219impose 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
1220usually overkill.</p> 1328usually overkill.</p>
1221<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,
1222as even with OS-supported change notifications, this can be 1330as even with OS-supported change notifications, this can be
1223resource-intensive.</p> 1331resource-intensive.</p>
1224<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
1225if 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>
1226<dl> 1339<dl>
1227 <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>
1228 <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>
1229 <dd> 1342 <dd>
1230 <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
… …
1293</pre> 1406</pre>
1294 1407
1295</div> 1408</div>
1296<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>
1297<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">
1298<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
1299(prepare, check and other idle watchers do not count). That is, as long 1412priority are pending (prepare, check and other idle watchers do not
1300as your process is busy handling sockets or timeouts (or even signals, 1413count).</p>
1301imagine) 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
1302watchers 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
1303until stopped, that is, or your process receives more events and becomes 1418iteration - until stopped, that is, or your process receives more events
1304busy.</p> 1419and becomes busy again with higher priority stuff.</p>
1305<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
1306active, the process will not block when waiting for new events.</p> 1421active, the process will not block when waiting for new events.</p>
1307<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
1308effect 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
1309&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
… …
1314 <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
1315kind. 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,
1316believe me.</p> 1431believe me.</p>
1317 </dd> 1432 </dd>
1318</dl> 1433</dl>
1319<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
1320callback, free it. Alos, use no error checking, as usual.</p> 1435callback, free it. Also, use no error checking, as usual.</p>
1321<pre> static void 1436<pre> static void
1322 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)
1323 { 1438 {
1324 free (w); 1439 free (w);
1325 // now do something you wanted to do when the program has 1440 // now do something you wanted to do when the program has
… …
1369are 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
1370with 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
1371of 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
1372loop from blocking if lower-priority coroutines are active, thus mapping 1487loop from blocking if lower-priority coroutines are active, thus mapping
1373low-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>
1374<dl> 1498<dl>
1375 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1499 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1376 <dt>ev_check_init (ev_check *, callback)</dt> 1500 <dt>ev_check_init (ev_check *, callback)</dt>
1377 <dd> 1501 <dd>
1378 <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
1379parameters 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>
1380macros, but using them is utterly, utterly and completely pointless.</p> 1504macros, but using them is utterly, utterly and completely pointless.</p>
1381 </dd> 1505 </dd>
1382</dl> 1506</dl>
1383<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
1384and 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,
1385in 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
1386pseudo-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>
1387<pre> static ev_io iow [nfd]; 1518<pre> static ev_io iow [nfd];
1388 static ev_timer tw; 1519 static ev_timer tw;
1389 1520
1390 static void 1521 static void
1391 io_cb (ev_loop *loop, ev_io *w, int revents) 1522 io_cb (ev_loop *loop, ev_io *w, int revents)
1392 { 1523 {
1393 // set the relevant poll flags
1394 // could also call adns_processreadable etc. here
1395 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1396 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1397 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1398 } 1524 }
1399 1525
1400 // create io watchers for each fd and a timer before blocking 1526 // create io watchers for each fd and a timer before blocking
1401 static void 1527 static void
1402 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1528 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1403 { 1529 {
1404 int timeout = 3600000;truct pollfd fds [nfd]; 1530 int timeout = 3600000;
1531 struct pollfd fds [nfd];
1405 // actual code will need to loop here and realloc etc. 1532 // actual code will need to loop here and realloc etc.
1406 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 ()));
1407 1534
1408 /* 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 */
1409 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1536 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1410 ev_timer_start (loop, &amp;tw); 1537 ev_timer_start (loop, &amp;tw);
1411 1538
1412 // create on ev_io per pollfd 1539 // create one ev_io per pollfd
1413 for (int i = 0; i &lt; nfd; ++i) 1540 for (int i = 0; i &lt; nfd; ++i)
1414 { 1541 {
1415 ev_io_init (iow + i, io_cb, fds [i].fd, 1542 ev_io_init (iow + i, io_cb, fds [i].fd,
1416 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1543 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1417 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1544 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1418 1545
1419 fds [i].revents = 0; 1546 fds [i].revents = 0;
1420 iow [i].data = fds + i;
1421 ev_io_start (loop, iow + i); 1547 ev_io_start (loop, iow + i);
1422 } 1548 }
1423 } 1549 }
1424 1550
1425 // stop all watchers after blocking 1551 // stop all watchers after blocking
… …
1427 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1553 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1428 { 1554 {
1429 ev_timer_stop (loop, &amp;tw); 1555 ev_timer_stop (loop, &amp;tw);
1430 1556
1431 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
1432 ev_io_stop (loop, iow + i); 1567 ev_io_stop (loop, iow + i);
1568 }
1433 1569
1434 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;
1435 } 1629 }
1436 1630
1437 1631
1438 1632
1439 1633
… …
1550 1744
1551 1745
1552 1746
1553 1747
1554</div> 1748</div>
1555<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1749<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1556<div id="OTHER_FUNCTIONS_CONTENT"> 1750<div id="OTHER_FUNCTIONS_CONTENT">
1557<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>
1558<dl> 1752<dl>
1559 <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>
1560 <dd> 1754 <dd>
… …
1607 1801
1608 1802
1609 1803
1610 1804
1611</div> 1805</div>
1612<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1806<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1613<div id="LIBEVENT_EMULATION_CONTENT"> 1807<div id="LIBEVENT_EMULATION_CONTENT">
1614<p>Libev offers a compatibility emulation layer for libevent. It cannot 1808<p>Libev offers a compatibility emulation layer for libevent. It cannot
1615emulate the internals of libevent, so here are some usage hints:</p> 1809emulate the internals of libevent, so here are some usage hints:</p>
1616<dl> 1810<dl>
1617 <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>
… …
1627 <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
1628to use the libev header file and library.</dt> 1822to use the libev header file and library.</dt>
1629</dl> 1823</dl>
1630 1824
1631</div> 1825</div>
1632<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1826<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1633<div id="C_SUPPORT_CONTENT"> 1827<div id="C_SUPPORT_CONTENT">
1634<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
1635you 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
1636the callback model to a model using method callbacks on objects.</p> 1830the callback model to a model using method callbacks on objects.</p>
1637<p>To use it,</p> 1831<p>To use it,</p>
1638<pre> #include &lt;ev++.h&gt; 1832<pre> #include &lt;ev++.h&gt;
1639 1833
1640</pre> 1834</pre>
1641<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
1642and puts all of its definitions (many of them macros) into the global 1836of them macros) into the global namespace. All C++ specific things are
1643namespace. 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
1644<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>
1645<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>
1646<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>
1647<dl> 1849<dl>
1648 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1850 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1649 <dd> 1851 <dd>
1650 <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.
… …
1661which 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
1662defines by many implementations.</p> 1864defines by many implementations.</p>
1663 <p>All of those classes have these methods:</p> 1865 <p>All of those classes have these methods:</p>
1664 <p> 1866 <p>
1665 <dl> 1867 <dl>
1666 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1868 <dt>ev::TYPE::TYPE ()</dt>
1667 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1869 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1668 <dt>ev::TYPE::~TYPE</dt> 1870 <dt>ev::TYPE::~TYPE</dt>
1669 <dd> 1871 <dd>
1670 <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
1671the event handler callback to call in this class. The constructor calls 1873with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1672<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
1673before starting it. If you do not specify a loop then the constructor 1875<code>set</code> method before starting it.</p>
1674automatically 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>
1675 <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>
1676 </dd> 1917 </dd>
1677 <dt>w-&gt;set (struct ev_loop *)</dt> 1918 <dt>w-&gt;set (struct ev_loop *)</dt>
1678 <dd> 1919 <dd>
1679 <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
1680do this when the watcher is inactive (and not pending either).</p> 1921do this when the watcher is inactive (and not pending either).</p>
1681 </dd> 1922 </dd>
1682 <dt>w-&gt;set ([args])</dt> 1923 <dt>w-&gt;set ([args])</dt>
1683 <dd> 1924 <dd>
1684 <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
1685called at least once. Unlike the C counterpart, an active watcher gets 1926called at least once. Unlike the C counterpart, an active watcher gets
1686automatically stopped and restarted.</p> 1927automatically stopped and restarted when reconfiguring it with this
1928method.</p>
1687 </dd> 1929 </dd>
1688 <dt>w-&gt;start ()</dt> 1930 <dt>w-&gt;start ()</dt>
1689 <dd> 1931 <dd>
1690 <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
1691constructor already takes the loop.</p> 1933constructor already stores the event loop.</p>
1692 </dd> 1934 </dd>
1693 <dt>w-&gt;stop ()</dt> 1935 <dt>w-&gt;stop ()</dt>
1694 <dd> 1936 <dd>
1695 <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>
1696 </dd> 1938 </dd>
… …
1720 1962
1721 myclass (); 1963 myclass ();
1722 } 1964 }
1723 1965
1724 myclass::myclass (int fd) 1966 myclass::myclass (int fd)
1725 : io (this, &amp;myclass::io_cb),
1726 idle (this, &amp;myclass::idle_cb)
1727 { 1967 {
1968 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1969 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1970
1728 io.start (fd, ev::READ); 1971 io.start (fd, ev::READ);
1729 } 1972 }
1730 1973
1731 1974
1732 1975
1733 1976
1734</pre> 1977</pre>
1735 1978
1736</div> 1979</div>
1737<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p> 1980<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1738<div id="MACRO_MAGIC_CONTENT"> 1981<div id="MACRO_MAGIC_CONTENT">
1739<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
1740<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1983<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1741callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1984callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1742<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
1743following macros are defined:</p> 1986following macros are defined:</p>
1744<dl> 1987<dl>
1745 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1988 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1774 <dd> 2017 <dd>
1775 <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
1776loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2019loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1777 </dd> 2020 </dd>
1778</dl> 2021</dl>
1779<p>Example: Declare and initialise a check watcher, working regardless of 2022<p>Example: Declare and initialise a check watcher, utilising the above
1780wether multiple loops are supported or not.</p> 2023macros so it will work regardless of whether multiple loops are supported
2024or not.</p>
1781<pre> static void 2025<pre> static void
1782 check_cb (EV_P_ ev_timer *w, int revents) 2026 check_cb (EV_P_ ev_timer *w, int revents)
1783 { 2027 {
1784 ev_check_stop (EV_A_ w); 2028 ev_check_stop (EV_A_ w);
1785 } 2029 }
… …
1787 ev_check check; 2031 ev_check check;
1788 ev_check_init (&amp;check, check_cb); 2032 ev_check_init (&amp;check, check_cb);
1789 ev_check_start (EV_DEFAULT_ &amp;check); 2033 ev_check_start (EV_DEFAULT_ &amp;check);
1790 ev_loop (EV_DEFAULT_ 0); 2034 ev_loop (EV_DEFAULT_ 0);
1791 2035
1792
1793
1794
1795</pre> 2036</pre>
1796 2037
1797</div> 2038</div>
1798<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 2039<h1 id="EMBEDDING">EMBEDDING</h1>
1799<div id="EMBEDDING_CONTENT"> 2040<div id="EMBEDDING_CONTENT">
1800<p>Libev can (and often is) directly embedded into host 2041<p>Libev can (and often is) directly embedded into host
1801applications. Examples of applications that embed it include the Deliantra 2042applications. Examples of applications that embed it include the Deliantra
1802Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2043Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1803and rxvt-unicode.</p> 2044and rxvt-unicode.</p>
… …
1840 ev_vars.h 2081 ev_vars.h
1841 ev_wrap.h 2082 ev_wrap.h
1842 2083
1843 ev_win32.c required on win32 platforms only 2084 ev_win32.c required on win32 platforms only
1844 2085
1845 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)
1846 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)
1847 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)
1848 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)
1849 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)
1850 2091
… …
1977 </dd> 2218 </dd>
1978 <dt>EV_USE_DEVPOLL</dt> 2219 <dt>EV_USE_DEVPOLL</dt>
1979 <dd> 2220 <dd>
1980 <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>
1981 </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>
1982 <dt>EV_H</dt> 2229 <dt>EV_H</dt>
1983 <dd> 2230 <dd>
1984 <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
1985undefined 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
1986can 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>
… …
2009will 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
2010additional independent event loops. Otherwise there will be no support 2257additional independent event loops. Otherwise there will be no support
2011for multiple event loops and there is no first event loop pointer 2258for multiple event loops and there is no first event loop pointer
2012argument. Instead, all functions act on the single default loop.</p> 2259argument. Instead, all functions act on the single default loop.</p>
2013 </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>
2014 <dt>EV_PERIODIC_ENABLE</dt> 2275 <dt>EV_PERIODIC_ENABLE</dt>
2015 <dd> 2276 <dd>
2016 <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
2017defined 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
2018code.</p> 2279code.</p>
2019 </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>
2020 <dt>EV_EMBED_ENABLE</dt> 2287 <dt>EV_EMBED_ENABLE</dt>
2021 <dd> 2288 <dd>
2022 <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
2023defined to be <code>0</code>, then they are not.</p> 2290defined to be <code>0</code>, then they are not.</p>
2024 </dd> 2291 </dd>
… …
2041 <dt>EV_PID_HASHSIZE</dt> 2308 <dt>EV_PID_HASHSIZE</dt>
2042 <dd> 2309 <dd>
2043 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2310 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2044pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more 2311pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2045than enough. If you need to manage thousands of children you might want to 2312than enough. If you need to manage thousands of children you might want to
2046increase this value.</p> 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>
2047 </dd> 2322 </dd>
2048 <dt>EV_COMMON</dt> 2323 <dt>EV_COMMON</dt>
2049 <dd> 2324 <dd>
2050 <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
2051this 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
… …
2078the <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
2079interface) 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
2080will 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
2081file.</p> 2356file.</p>
2082 <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
2083that 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
2084<pre> #define EV_USE_POLL 0 2360 #define EV_USE_POLL 0
2085 #define EV_MULTIPLICITY 0 2361 #define EV_MULTIPLICITY 0
2086 #define EV_PERIODICS 0 2362 #define EV_PERIODIC_ENABLE 0
2363 #define EV_STAT_ENABLE 0
2364 #define EV_FORK_ENABLE 0
2087 #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
2088 2368
2089 #include &quot;ev++.h&quot; 2369 #include &quot;ev++.h&quot;
2090 2370
2091</pre> 2371</pre>
2092 <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>
… …
2097 2377
2098 2378
2099</pre> 2379</pre>
2100 2380
2101</div> 2381</div>
2102<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2382<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2103<div id="COMPLEXITIES_CONTENT"> 2383<div id="COMPLEXITIES_CONTENT">
2104 <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
2105libev will be explained. For complexity discussions about backends see the 2385libev will be explained. For complexity discussions about backends see the
2106documentation 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>
2107 <p> 2392 <p>
2108 <dl> 2393 <dl>
2109 <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>
2110 <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>
2111 <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.
2112 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2408=item Stopping check/prepare/idle watchers: O(1)</p>
2409 </dd>
2113 <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>
2114 <dt>Finding the next timer per loop iteration: O(1)</dt> 2416 <dt>Finding the next timer per loop iteration: O(1)</dt>
2115 <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>
2116 <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>
2117 </dl> 2429 </dl>
2118 </p> 2430 </p>
2119 2431
2120 2432
2121 2433
2122 2434
2123 2435
2124</div> 2436</div>
2125<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2437<h1 id="AUTHOR">AUTHOR</h1>
2126<div id="AUTHOR_CONTENT"> 2438<div id="AUTHOR_CONTENT">
2127 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2439 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
2128 2440
2129</div> 2441</div>
2130</div></body> 2442</div></body>

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