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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 20:38:24 2007" /> 9 <meta name="created" content="Sun Dec 9 20:45:16 2007" />
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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>
… …
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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131you actually want to know.</p> 185you actually want to know.</p>
132 </dd> 186 </dd>
133 <dt>int ev_version_major ()</dt> 187 <dt>int ev_version_major ()</dt>
134 <dt>int ev_version_minor ()</dt> 188 <dt>int ev_version_minor ()</dt>
135 <dd> 189 <dd>
136 <p>You can find out the major and minor version numbers of the library 190 <p>You can find out the major and minor API/ABI version numbers of the library
137you linked against by calling the functions <code>ev_version_major</code> and 191you linked against by calling the functions <code>ev_version_major</code> and
138<code>ev_version_minor</code>. If you want, you can compare against the global 192<code>ev_version_minor</code>. If you want, you can compare against the global
139symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 193symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
140version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
195 <p>These version numbers refer to the API and ABI version of the library, not
196the release version.</p>
141 <p>Usually, it's a good idea to terminate if the major versions mismatch, 197 <p>Usually, it's a good idea to terminate if the major versions mismatch,
142as this indicates an incompatible change. Minor versions are usually 198as this indicates an incompatible change. Minor versions are usually
143compatible to older versions, so a larger minor version alone is usually 199compatible to older versions, so a larger minor version alone is usually
144not a problem.</p> 200not a problem.</p>
145 <p>Example: make sure we haven't accidentally been linked against the wrong 201 <p>Example: Make sure we haven't accidentally been linked against the wrong
146version:</p> 202version.</p>
147<pre> assert ((&quot;libev version mismatch&quot;, 203<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR 204 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 205 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150 206
151</pre> 207</pre>
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179might be supported on the current system, you would need to look at 235might be supported on the current system, you would need to look at
180<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 236<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
181recommended ones.</p> 237recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 238 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
183 </dd> 239 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 240 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
185 <dd> 241 <dd>
186 <p>Sets the allocation function to use (the prototype and semantics are 242 <p>Sets the allocation function to use (the prototype is similar - the
187identical to the realloc C function). It is used to allocate and free 243semantics is identical - to the realloc C function). It is used to
188memory (no surprises here). If it returns zero when memory needs to be 244allocate and free memory (no surprises here). If it returns zero when
189allocated, the library might abort or take some potentially destructive 245memory needs to be allocated, the library might abort or take some
190action. The default is your system realloc function.</p> 246potentially destructive action. The default is your system realloc
247function.</p>
191 <p>You could override this function in high-availability programs to, say, 248 <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, 249free 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> 250or 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 251 <p>Example: Replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p> 252retries).</p>
196<pre> static void * 253<pre> static void *
197 persistent_realloc (void *ptr, size_t size) 254 persistent_realloc (void *ptr, size_t size)
198 { 255 {
199 for (;;) 256 for (;;)
200 { 257 {
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219indicating the system call or subsystem causing the problem. If this 276indicating the system call or subsystem causing the problem. If this
220callback is set, then libev will expect it to remedy the sitution, no 277callback is set, then libev will expect it to remedy the sitution, no
221matter what, when it returns. That is, libev will generally retry the 278matter what, when it returns. That is, libev will generally retry the
222requested operation, or, if the condition doesn't go away, do bad stuff 279requested operation, or, if the condition doesn't go away, do bad stuff
223(such as abort).</p> 280(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p> 281 <p>Example: This is basically the same thing that libev does internally, too.</p>
225<pre> static void 282<pre> static void
226 fatal_error (const char *msg) 283 fatal_error (const char *msg)
227 { 284 {
228 perror (msg); 285 perror (msg);
229 abort (); 286 abort ();
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235</pre> 292</pre>
236 </dd> 293 </dd>
237</dl> 294</dl>
238 295
239</div> 296</div>
240<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 297<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
241<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 298<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 299<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 300types of such loops, the <i>default</i> loop, which supports signals and child
244events, and dynamically created loops which do not.</p> 301events, and dynamically created loops which do not.</p>
245<p>If you use threads, a common model is to run the default event loop 302<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 331<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
275override the flags completely if it is found in the environment. This is 332override 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 333useful to try out specific backends to test their performance, or to work
277around bugs.</p> 334around bugs.</p>
278 </dd> 335 </dd>
336 <dt><code>EVFLAG_FORKCHECK</code></dt>
337 <dd>
338 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
339a fork, you can also make libev check for a fork in each iteration by
340enabling this flag.</p>
341 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
342and thus this might slow down your event loop if you do a lot of loop
343iterations and little real work, but is usually not noticeable (on my
344Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
345without a syscall and thus <i>very</i> fast, but my Linux system also has
346<code>pthread_atfork</code> which is even faster).</p>
347 <p>The big advantage of this flag is that you can forget about fork (and
348forget about forgetting to tell libev about forking) when you use this
349flag.</p>
350 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
351environment variable.</p>
352 </dd>
279 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 353 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
280 <dd> 354 <dd>
281 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 355 <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, 356libev 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 357but if that fails, expect a fairly low limit on the number of fds when
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365 <dd> 439 <dd>
366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 440 <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 441always 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 442handle signal and child watchers, and attempts to do so will be greeted by
369undefined behaviour (or a failed assertion if assertions are enabled).</p> 443undefined 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> 444 <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); 445<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller) 446 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 447 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374 448
375</pre> 449</pre>
… …
411 <dt>ev_loop_fork (loop)</dt> 485 <dt>ev_loop_fork (loop)</dt>
412 <dd> 486 <dd>
413 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 487 <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 488<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> 489after fork, and how you do this is entirely your own problem.</p>
490 </dd>
491 <dt>unsigned int ev_loop_count (loop)</dt>
492 <dd>
493 <p>Returns the count of loop iterations for the loop, which is identical to
494the number of times libev did poll for new events. It starts at <code>0</code> and
495happily wraps around with enough iterations.</p>
496 <p>This value can sometimes be useful as a generation counter of sorts (it
497&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
498<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
416 </dd> 499 </dd>
417 <dt>unsigned int ev_backend (loop)</dt> 500 <dt>unsigned int ev_backend (loop)</dt>
418 <dd> 501 <dd>
419 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 502 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
420use.</p> 503use.</p>
… …
448one iteration of the loop. This is useful if you are waiting for some 531one iteration of the loop. This is useful if you are waiting for some
449external event in conjunction with something not expressible using other 532external 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 533libev 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> 534usually a better approach for this kind of thing.</p>
452 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 535 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
536<pre> - Before the first iteration, call any pending watchers.
453<pre> * If there are no active watchers (reference count is zero), return. 537 * If there are no active watchers (reference count is zero), return.
454 - Queue prepare watchers and then call all outstanding watchers. 538 - Queue all prepare watchers and then call all outstanding watchers.
455 - If we have been forked, recreate the kernel state. 539 - If we have been forked, recreate the kernel state.
456 - Update the kernel state with all outstanding changes. 540 - Update the kernel state with all outstanding changes.
457 - Update the &quot;event loop time&quot;. 541 - Update the &quot;event loop time&quot;.
458 - Calculate for how long to block. 542 - Calculate for how long to block.
459 - Block the process, waiting for any events. 543 - Block the process, waiting for any events.
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468 be handled here by queueing them when their watcher gets executed. 552 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 553 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *. 554 were used, return, otherwise continue with step *.
471 555
472</pre> 556</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding 557 <p>Example: Queue some jobs and then loop until no events are outsanding
474anymore.</p> 558anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long 559<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..) 560 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0); 561 ev_loop (my_loop, 0);
478 ... jobs done. yeah! 562 ... jobs done. yeah!
… …
497example, libev itself uses this for its internal signal pipe: It is not 581example, 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 582visible 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 583no 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 584way 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> 585libraries. 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> 586 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p> 587running when nothing else is active.</p>
504<pre> struct dv_signal exitsig; 588<pre> struct ev_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 589 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig); 590 ev_signal_start (loop, &amp;exitsig);
507 evf_unref (myloop); 591 evf_unref (loop);
508 592
509</pre> 593</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p> 594 <p>Example: For some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop); 595<pre> ev_ref (loop);
512 ev_signal_stop (myloop, &amp;exitsig); 596 ev_signal_stop (loop, &amp;exitsig);
513 597
514</pre> 598</pre>
515 </dd> 599 </dd>
516</dl> 600</dl>
517 601
518 602
519 603
520 604
521 605
522</div> 606</div>
523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 607<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
524<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 608<div id="ANATOMY_OF_A_WATCHER_CONTENT">
525<p>A watcher is a structure that you create and register to record your 609<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 610interest 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> 611become 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) 612<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> 772 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
689 <dd> 773 <dd>
690 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 774 <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 775events 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 776is 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 777<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> 778make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
779it).</p>
695 </dd> 780 </dd>
696 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 781 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
697 <dd> 782 <dd>
698 <p>Returns the callback currently set on the watcher.</p> 783 <p>Returns the callback currently set on the watcher.</p>
699 </dd> 784 </dd>
700 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 785 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
701 <dd> 786 <dd>
702 <p>Change the callback. You can change the callback at virtually any time 787 <p>Change the callback. You can change the callback at virtually any time
703(modulo threads).</p> 788(modulo threads).</p>
789 </dd>
790 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
791 <dt>int ev_priority (ev_TYPE *watcher)</dt>
792 <dd>
793 <p>Set and query the priority of the watcher. The priority is a small
794integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
795(default: <code>-2</code>). Pending watchers with higher priority will be invoked
796before watchers with lower priority, but priority will not keep watchers
797from being executed (except for <code>ev_idle</code> watchers).</p>
798 <p>This means that priorities are <i>only</i> used for ordering callback
799invocation after new events have been received. This is useful, for
800example, to reduce latency after idling, or more often, to bind two
801watchers on the same event and make sure one is called first.</p>
802 <p>If you need to suppress invocation when higher priority events are pending
803you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
804 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
805pending.</p>
806 <p>The default priority used by watchers when no priority has been set is
807always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
808 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
809fine, as long as you do not mind that the priority value you query might
810or might not have been adjusted to be within valid range.</p>
811 </dd>
812 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
813 <dd>
814 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
815<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
816can deal with that fact.</p>
817 </dd>
818 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
819 <dd>
820 <p>If the watcher is pending, this function returns clears its pending status
821and returns its <code>revents</code> bitset (as if its callback was invoked). If the
822watcher isn't pending it does nothing and returns <code>0</code>.</p>
704 </dd> 823 </dd>
705</dl> 824</dl>
706 825
707 826
708 827
… …
733 struct my_io *w = (struct my_io *)w_; 852 struct my_io *w = (struct my_io *)w_;
734 ... 853 ...
735 } 854 }
736 855
737</pre> 856</pre>
738<p>More interesting and less C-conformant ways of catsing your callback type 857<p>More interesting and less C-conformant ways of casting your callback type
739have been omitted....</p> 858instead have been omitted.</p>
859<p>Another common scenario is having some data structure with multiple
860watchers:</p>
861<pre> struct my_biggy
862 {
863 int some_data;
864 ev_timer t1;
865 ev_timer t2;
866 }
740 867
868</pre>
869<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
870you need to use <code>offsetof</code>:</p>
871<pre> #include &lt;stddef.h&gt;
741 872
873 static void
874 t1_cb (EV_P_ struct ev_timer *w, int revents)
875 {
876 struct my_biggy big = (struct my_biggy *
877 (((char *)w) - offsetof (struct my_biggy, t1));
878 }
742 879
880 static void
881 t2_cb (EV_P_ struct ev_timer *w, int revents)
882 {
883 struct my_biggy big = (struct my_biggy *
884 (((char *)w) - offsetof (struct my_biggy, t2));
885 }
743 886
744 887
888
889
890</pre>
891
745</div> 892</div>
746<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 893<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
747<div id="WATCHER_TYPES_CONTENT"> 894<div id="WATCHER_TYPES_CONTENT">
748<p>This section describes each watcher in detail, but will not repeat 895<p>This section describes each watcher in detail, but will not repeat
749information given in the last section. Any initialisation/set macros, 896information given in the last section. Any initialisation/set macros,
750functions and members specific to the watcher type are explained.</p> 897functions and members specific to the watcher type are explained.</p>
751<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, 898<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
… …
791this situation even with a relatively standard program structure. Thus 938this 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 939it 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> 940<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 941<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 942play 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 943whether 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 944such as poll (fortunately in our Xlib example, Xlib already does this on
798its own, so its quite safe to use).</p> 945its own, so its quite safe to use).</p>
799<dl> 946<dl>
800 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 947 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
801 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 948 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
811 <dt>int events [read-only]</dt> 958 <dt>int events [read-only]</dt>
812 <dd> 959 <dd>
813 <p>The events being watched.</p> 960 <p>The events being watched.</p>
814 </dd> 961 </dd>
815</dl> 962</dl>
816<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 963<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 964readable, but only once. Since it is likely line-buffered, you could
818attempt to read a whole line in the callback:</p> 965attempt to read a whole line in the callback.</p>
819<pre> static void 966<pre> static void
820 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 967 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
821 { 968 {
822 ev_io_stop (loop, w); 969 ev_io_stop (loop, w);
823 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 970 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
872 </dd> 1019 </dd>
873 <dt>ev_timer_again (loop)</dt> 1020 <dt>ev_timer_again (loop)</dt>
874 <dd> 1021 <dd>
875 <p>This will act as if the timer timed out and restart it again if it is 1022 <p>This will act as if the timer timed out and restart it again if it is
876repeating. The exact semantics are:</p> 1023repeating. The exact semantics are:</p>
1024 <p>If the timer is pending, its pending status is cleared.</p>
877 <p>If the timer is started but nonrepeating, stop it.</p> 1025 <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 1026 <p>If the timer is repeating, either start it if necessary (with the
879value), or reset the running timer to the repeat value.</p> 1027<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 1028 <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 1029example: 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, 1030timeout, 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 1031seconds 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 1032configure 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 1033<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 1034you 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 1035socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
888need be.</p> 1036automatically restart it if need be.</p>
889 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1037 <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> 1038altogether 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.); 1039<pre> ev_timer_init (timer, callback, 0., 5.);
892 ev_timer_again (loop, timer); 1040 ev_timer_again (loop, timer);
893 ... 1041 ...
894 timer-&gt;again = 17.; 1042 timer-&gt;again = 17.;
895 ev_timer_again (loop, timer); 1043 ev_timer_again (loop, timer);
896 ... 1044 ...
897 timer-&gt;again = 10.; 1045 timer-&gt;again = 10.;
898 ev_timer_again (loop, timer); 1046 ev_timer_again (loop, timer);
899 1047
900</pre> 1048</pre>
901 <p>This is more efficient then stopping/starting the timer eahc time you want 1049 <p>This is more slightly efficient then stopping/starting the timer each time
902to modify its timeout value.</p> 1050you want to modify its timeout value.</p>
903 </dd> 1051 </dd>
904 <dt>ev_tstamp repeat [read-write]</dt> 1052 <dt>ev_tstamp repeat [read-write]</dt>
905 <dd> 1053 <dd>
906 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1054 <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), 1055or <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> 1056which is also when any modifications are taken into account.</p>
909 </dd> 1057 </dd>
910</dl> 1058</dl>
911<p>Example: create a timer that fires after 60 seconds.</p> 1059<p>Example: Create a timer that fires after 60 seconds.</p>
912<pre> static void 1060<pre> static void
913 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1061 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
914 { 1062 {
915 .. one minute over, w is actually stopped right here 1063 .. one minute over, w is actually stopped right here
916 } 1064 }
… …
918 struct ev_timer mytimer; 1066 struct ev_timer mytimer;
919 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1067 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
920 ev_timer_start (loop, &amp;mytimer); 1068 ev_timer_start (loop, &amp;mytimer);
921 1069
922</pre> 1070</pre>
923<p>Example: create a timeout timer that times out after 10 seconds of 1071<p>Example: Create a timeout timer that times out after 10 seconds of
924inactivity.</p> 1072inactivity.</p>
925<pre> static void 1073<pre> static void
926 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1074 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
927 { 1075 {
928 .. ten seconds without any activity 1076 .. ten seconds without any activity
… …
951but on wallclock time (absolute time). You can tell a periodic watcher 1099but on wallclock time (absolute time). You can tell a periodic watcher
952to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1100to trigger &quot;at&quot; some specific point in time. For example, if you tell a
953periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1101periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
954+ 10.</code>) and then reset your system clock to the last year, then it will 1102+ 10.</code>) and then reset your system clock to the last year, then it will
955take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1103take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
956roughly 10 seconds later and of course not if you reset your system time 1104roughly 10 seconds later).</p>
957again).</p>
958<p>They can also be used to implement vastly more complex timers, such as 1105<p>They can also be used to implement vastly more complex timers, such as
959triggering an event on eahc midnight, local time.</p> 1106triggering an event on each midnight, local time or other, complicated,
1107rules.</p>
960<p>As with timers, the callback is guarenteed to be invoked only when the 1108<p>As with timers, the callback is guarenteed to be invoked only when the
961time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1109time (<code>at</code>) has been passed, but if multiple periodic timers become ready
962during the same loop iteration then order of execution is undefined.</p> 1110during the same loop iteration then order of execution is undefined.</p>
963<dl> 1111<dl>
964 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1112 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
… …
966 <dd> 1114 <dd>
967 <p>Lots of arguments, lets sort it out... There are basically three modes of 1115 <p>Lots of arguments, lets sort it out... There are basically three modes of
968operation, and we will explain them from simplest to complex:</p> 1116operation, and we will explain them from simplest to complex:</p>
969 <p> 1117 <p>
970 <dl> 1118 <dl>
971 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1119 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
972 <dd> 1120 <dd>
973 <p>In this configuration the watcher triggers an event at the wallclock time 1121 <p>In this configuration the watcher triggers an event at the wallclock time
974<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1122<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
975that is, if it is to be run at January 1st 2011 then it will run when the 1123that is, if it is to be run at January 1st 2011 then it will run when the
976system time reaches or surpasses this time.</p> 1124system time reaches or surpasses this time.</p>
977 </dd> 1125 </dd>
978 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1126 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
979 <dd> 1127 <dd>
980 <p>In this mode the watcher will always be scheduled to time out at the next 1128 <p>In this mode the watcher will always be scheduled to time out at the next
981<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1129<code>at + N * interval</code> time (for some integer N, which can also be negative)
982of any time jumps.</p> 1130and then repeat, regardless of any time jumps.</p>
983 <p>This can be used to create timers that do not drift with respect to system 1131 <p>This can be used to create timers that do not drift with respect to system
984time:</p> 1132time:</p>
985<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1133<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
986 1134
987</pre> 1135</pre>
… …
990full hour (UTC), or more correctly, when the system time is evenly divisible 1138full hour (UTC), or more correctly, when the system time is evenly divisible
991by 3600.</p> 1139by 3600.</p>
992 <p>Another way to think about it (for the mathematically inclined) is that 1140 <p>Another way to think about it (for the mathematically inclined) is that
993<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1141<code>ev_periodic</code> will try to run the callback in this mode at the next possible
994time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1142time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1143 <p>For numerical stability it is preferable that the <code>at</code> value is near
1144<code>ev_now ()</code> (the current time), but there is no range requirement for
1145this value.</p>
995 </dd> 1146 </dd>
996 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1147 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
997 <dd> 1148 <dd>
998 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1149 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
999ignored. Instead, each time the periodic watcher gets scheduled, the 1150ignored. Instead, each time the periodic watcher gets scheduled, the
1000reschedule callback will be called with the watcher as first, and the 1151reschedule callback will be called with the watcher as first, and the
1001current time as second argument.</p> 1152current time as second argument.</p>
1002 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1153 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
1003ever, or make any event loop modifications</i>. If you need to stop it, 1154ever, or make any event loop modifications</i>. If you need to stop it,
1004return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1155return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1005starting a prepare watcher).</p> 1156starting an <code>ev_prepare</code> watcher, which is legal).</p>
1006 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1157 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1007ev_tstamp now)</code>, e.g.:</p> 1158ev_tstamp now)</code>, e.g.:</p>
1008<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1159<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1009 { 1160 {
1010 return now + 60.; 1161 return now + 60.;
… …
1031 <p>Simply stops and restarts the periodic watcher again. This is only useful 1182 <p>Simply stops and restarts the periodic watcher again. This is only useful
1032when you changed some parameters or the reschedule callback would return 1183when you changed some parameters or the reschedule callback would return
1033a different time than the last time it was called (e.g. in a crond like 1184a different time than the last time it was called (e.g. in a crond like
1034program when the crontabs have changed).</p> 1185program when the crontabs have changed).</p>
1035 </dd> 1186 </dd>
1187 <dt>ev_tstamp offset [read-write]</dt>
1188 <dd>
1189 <p>When repeating, this contains the offset value, otherwise this is the
1190absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1191 <p>Can be modified any time, but changes only take effect when the periodic
1192timer fires or <code>ev_periodic_again</code> is being called.</p>
1193 </dd>
1036 <dt>ev_tstamp interval [read-write]</dt> 1194 <dt>ev_tstamp interval [read-write]</dt>
1037 <dd> 1195 <dd>
1038 <p>The current interval value. Can be modified any time, but changes only 1196 <p>The current interval value. Can be modified any time, but changes only
1039take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1197take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1040called.</p> 1198called.</p>
… …
1044 <p>The current reschedule callback, or <code>0</code>, if this functionality is 1202 <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 1203switched 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> 1204the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1047 </dd> 1205 </dd>
1048</dl> 1206</dl>
1049<p>Example: call a callback every hour, or, more precisely, whenever the 1207<p>Example: Call a callback every hour, or, more precisely, whenever the
1050system clock is divisible by 3600. The callback invocation times have 1208system clock is divisible by 3600. The callback invocation times have
1051potentially a lot of jittering, but good long-term stability.</p> 1209potentially a lot of jittering, but good long-term stability.</p>
1052<pre> static void 1210<pre> static void
1053 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1211 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1054 { 1212 {
… …
1058 struct ev_periodic hourly_tick; 1216 struct ev_periodic hourly_tick;
1059 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1217 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
1060 ev_periodic_start (loop, &amp;hourly_tick); 1218 ev_periodic_start (loop, &amp;hourly_tick);
1061 1219
1062</pre> 1220</pre>
1063<p>Example: the same as above, but use a reschedule callback to do it:</p> 1221<p>Example: The same as above, but use a reschedule callback to do it:</p>
1064<pre> #include &lt;math.h&gt; 1222<pre> #include &lt;math.h&gt;
1065 1223
1066 static ev_tstamp 1224 static ev_tstamp
1067 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1225 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1068 { 1226 {
… …
1070 } 1228 }
1071 1229
1072 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1230 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1073 1231
1074</pre> 1232</pre>
1075<p>Example: call a callback every hour, starting now:</p> 1233<p>Example: Call a callback every hour, starting now:</p>
1076<pre> struct ev_periodic hourly_tick; 1234<pre> struct ev_periodic hourly_tick;
1077 ev_periodic_init (&amp;hourly_tick, clock_cb, 1235 ev_periodic_init (&amp;hourly_tick, clock_cb,
1078 fmod (ev_now (loop), 3600.), 3600., 0); 1236 fmod (ev_now (loop), 3600.), 3600., 0);
1079 ev_periodic_start (loop, &amp;hourly_tick); 1237 ev_periodic_start (loop, &amp;hourly_tick);
1080 1238
… …
1141 <dd> 1299 <dd>
1142 <p>The process exit/trace status caused by <code>rpid</code> (see your systems 1300 <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> 1301<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1144 </dd> 1302 </dd>
1145</dl> 1303</dl>
1146<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1304<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1147<pre> static void 1305<pre> static void
1148 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1306 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1149 { 1307 {
1150 ev_unloop (loop, EVUNLOOP_ALL); 1308 ev_unloop (loop, EVUNLOOP_ALL);
1151 } 1309 }
… …
1168<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1326<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 1327not 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 1328not 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 1329otherwise always forced to be at least one) and all the other fields of
1172the stat buffer having unspecified contents.</p> 1330the stat buffer having unspecified contents.</p>
1331<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1332relative and your working directory changes, the behaviour is undefined.</p>
1173<p>Since there is no standard to do this, the portable implementation simply 1333<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 1334calls <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 1335can specify a recommended polling interval for this case. If you specify
1176a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1336a 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 1337unspecified default</i> value will be used (which you can expect to be around
1178five seconds, although this might change dynamically). Libev will also 1338five seconds, although this might change dynamically). Libev will also
1179impose a minimum interval which is currently around <code>0.1</code>, but thats 1339impose a minimum interval which is currently around <code>0.1</code>, but thats
1180usually overkill.</p> 1340usually overkill.</p>
1181<p>This watcher type is not meant for massive numbers of stat watchers, 1341<p>This watcher type is not meant for massive numbers of stat watchers,
1182as even with OS-supported change notifications, this can be 1342as even with OS-supported change notifications, this can be
1183resource-intensive.</p> 1343resource-intensive.</p>
1184<p>At the time of this writing, no specific OS backends are implemented, but 1344<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> 1345implemented (implementing kqueue support is left as an exercise for the
1346reader). Inotify will be used to give hints only and should not change the
1347semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1348to fall back to regular polling again even with inotify, but changes are
1349usually detected immediately, and if the file exists there will be no
1350polling.</p>
1186<dl> 1351<dl>
1187 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1352 <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> 1353 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1189 <dd> 1354 <dd>
1190 <p>Configures the watcher to wait for status changes of the given 1355 <p>Configures the watcher to wait for status changes of the given
… …
1253</pre> 1418</pre>
1254 1419
1255</div> 1420</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> 1421<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"> 1422<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 1423<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 1424priority are pending (prepare, check and other idle watchers do not
1260as your process is busy handling sockets or timeouts (or even signals, 1425count).</p>
1261imagine) it will not be triggered. But when your process is idle all idle 1426<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 - 1427(or even signals, imagine) of the same or higher priority it will not be
1428triggered. But when your process is idle (or only lower-priority watchers
1429are pending), the idle watchers are being called once per event loop
1263until stopped, that is, or your process receives more events and becomes 1430iteration - until stopped, that is, or your process receives more events
1264busy.</p> 1431and becomes busy again with higher priority stuff.</p>
1265<p>The most noteworthy effect is that as long as any idle watchers are 1432<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> 1433active, the process will not block when waiting for new events.</p>
1267<p>Apart from keeping your process non-blocking (which is a useful 1434<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 1435effect 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 1436&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 1441 <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, 1442kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1276believe me.</p> 1443believe me.</p>
1277 </dd> 1444 </dd>
1278</dl> 1445</dl>
1279<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1446<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> 1447callback, free it. Also, use no error checking, as usual.</p>
1281<pre> static void 1448<pre> static void
1282 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1449 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1283 { 1450 {
1284 free (w); 1451 free (w);
1285 // now do something you wanted to do when the program has 1452 // now do something you wanted to do when the program has
… …
1329are ready to run (it's actually more complicated: it only runs coroutines 1496are 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 1497with 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 1498of lower priority, but only once, using idle watchers to keep the event
1332loop from blocking if lower-priority coroutines are active, thus mapping 1499loop from blocking if lower-priority coroutines are active, thus mapping
1333low-priority coroutines to idle/background tasks).</p> 1500low-priority coroutines to idle/background tasks).</p>
1501<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1502priority, to ensure that they are being run before any other watchers
1503after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1504too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1505supports this, they will be called before other <code>ev_check</code> watchers did
1506their job. As <code>ev_check</code> watchers are often used to embed other event
1507loops those other event loops might be in an unusable state until their
1508<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1509others).</p>
1334<dl> 1510<dl>
1335 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1511 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1336 <dt>ev_check_init (ev_check *, callback)</dt> 1512 <dt>ev_check_init (ev_check *, callback)</dt>
1337 <dd> 1513 <dd>
1338 <p>Initialises and configures the prepare or check watcher - they have no 1514 <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> 1515parameters 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> 1516macros, but using them is utterly, utterly and completely pointless.</p>
1341 </dd> 1517 </dd>
1342</dl> 1518</dl>
1343<p>Example: To include a library such as adns, you would add IO watchers 1519<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 1520into libev. Here are some ideas on how to include libadns into libev
1521(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1522use for an actually working example. Another Perl module named <code>EV::Glib</code>
1523embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1524into the Glib event loop).</p>
1525<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 1526and in a check watcher, destroy them and call into libadns. What follows
1346pseudo-code only of course:</p> 1527is pseudo-code only of course. This requires you to either use a low
1528priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1529the callbacks for the IO/timeout watchers might not have been called yet.</p>
1347<pre> static ev_io iow [nfd]; 1530<pre> static ev_io iow [nfd];
1348 static ev_timer tw; 1531 static ev_timer tw;
1349 1532
1350 static void 1533 static void
1351 io_cb (ev_loop *loop, ev_io *w, int revents) 1534 io_cb (ev_loop *loop, ev_io *w, int revents)
1352 { 1535 {
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 } 1536 }
1359 1537
1360 // create io watchers for each fd and a timer before blocking 1538 // create io watchers for each fd and a timer before blocking
1361 static void 1539 static void
1362 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1540 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1363 { 1541 {
1364 int timeout = 3600000;truct pollfd fds [nfd]; 1542 int timeout = 3600000;
1543 struct pollfd fds [nfd];
1365 // actual code will need to loop here and realloc etc. 1544 // actual code will need to loop here and realloc etc.
1366 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1545 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1367 1546
1368 /* the callback is illegal, but won't be called as we stop during check */ 1547 /* the callback is illegal, but won't be called as we stop during check */
1369 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1548 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1370 ev_timer_start (loop, &amp;tw); 1549 ev_timer_start (loop, &amp;tw);
1371 1550
1372 // create on ev_io per pollfd 1551 // create one ev_io per pollfd
1373 for (int i = 0; i &lt; nfd; ++i) 1552 for (int i = 0; i &lt; nfd; ++i)
1374 { 1553 {
1375 ev_io_init (iow + i, io_cb, fds [i].fd, 1554 ev_io_init (iow + i, io_cb, fds [i].fd,
1376 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1555 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1377 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1556 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1378 1557
1379 fds [i].revents = 0; 1558 fds [i].revents = 0;
1380 iow [i].data = fds + i;
1381 ev_io_start (loop, iow + i); 1559 ev_io_start (loop, iow + i);
1382 } 1560 }
1383 } 1561 }
1384 1562
1385 // stop all watchers after blocking 1563 // stop all watchers after blocking
… …
1387 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1565 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1388 { 1566 {
1389 ev_timer_stop (loop, &amp;tw); 1567 ev_timer_stop (loop, &amp;tw);
1390 1568
1391 for (int i = 0; i &lt; nfd; ++i) 1569 for (int i = 0; i &lt; nfd; ++i)
1570 {
1571 // set the relevant poll flags
1572 // could also call adns_processreadable etc. here
1573 struct pollfd *fd = fds + i;
1574 int revents = ev_clear_pending (iow + i);
1575 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1576 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1577
1578 // now stop the watcher
1392 ev_io_stop (loop, iow + i); 1579 ev_io_stop (loop, iow + i);
1580 }
1393 1581
1394 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1582 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1583 }
1584
1585</pre>
1586<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1587in the prepare watcher and would dispose of the check watcher.</p>
1588<p>Method 3: If the module to be embedded supports explicit event
1589notification (adns does), you can also make use of the actual watcher
1590callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1591<pre> static void
1592 timer_cb (EV_P_ ev_timer *w, int revents)
1593 {
1594 adns_state ads = (adns_state)w-&gt;data;
1595 update_now (EV_A);
1596
1597 adns_processtimeouts (ads, &amp;tv_now);
1598 }
1599
1600 static void
1601 io_cb (EV_P_ ev_io *w, int revents)
1602 {
1603 adns_state ads = (adns_state)w-&gt;data;
1604 update_now (EV_A);
1605
1606 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1607 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1608 }
1609
1610 // do not ever call adns_afterpoll
1611
1612</pre>
1613<p>Method 4: Do not use a prepare or check watcher because the module you
1614want to embed is too inflexible to support it. Instead, youc na override
1615their poll function. The drawback with this solution is that the main
1616loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1617this.</p>
1618<pre> static gint
1619 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1620 {
1621 int got_events = 0;
1622
1623 for (n = 0; n &lt; nfds; ++n)
1624 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1625
1626 if (timeout &gt;= 0)
1627 // create/start timer
1628
1629 // poll
1630 ev_loop (EV_A_ 0);
1631
1632 // stop timer again
1633 if (timeout &gt;= 0)
1634 ev_timer_stop (EV_A_ &amp;to);
1635
1636 // stop io watchers again - their callbacks should have set
1637 for (n = 0; n &lt; nfds; ++n)
1638 ev_io_stop (EV_A_ iow [n]);
1639
1640 return got_events;
1395 } 1641 }
1396 1642
1397 1643
1398 1644
1399 1645
… …
1510 1756
1511 1757
1512 1758
1513 1759
1514</div> 1760</div>
1515<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1761<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1516<div id="OTHER_FUNCTIONS_CONTENT"> 1762<div id="OTHER_FUNCTIONS_CONTENT">
1517<p>There are some other functions of possible interest. Described. Here. Now.</p> 1763<p>There are some other functions of possible interest. Described. Here. Now.</p>
1518<dl> 1764<dl>
1519 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1765 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1520 <dd> 1766 <dd>
… …
1567 1813
1568 1814
1569 1815
1570 1816
1571</div> 1817</div>
1572<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1818<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1573<div id="LIBEVENT_EMULATION_CONTENT"> 1819<div id="LIBEVENT_EMULATION_CONTENT">
1574<p>Libev offers a compatibility emulation layer for libevent. It cannot 1820<p>Libev offers a compatibility emulation layer for libevent. It cannot
1575emulate the internals of libevent, so here are some usage hints:</p> 1821emulate the internals of libevent, so here are some usage hints:</p>
1576<dl> 1822<dl>
1577 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1823 <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 1833 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1588to use the libev header file and library.</dt> 1834to use the libev header file and library.</dt>
1589</dl> 1835</dl>
1590 1836
1591</div> 1837</div>
1592<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1838<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1593<div id="C_SUPPORT_CONTENT"> 1839<div id="C_SUPPORT_CONTENT">
1594<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1840<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 1841you to use some convinience methods to start/stop watchers and also change
1596the callback model to a model using method callbacks on objects.</p> 1842the callback model to a model using method callbacks on objects.</p>
1597<p>To use it,</p> 1843<p>To use it,</p>
1598<pre> #include &lt;ev++.h&gt; 1844<pre> #include &lt;ev++.h&gt;
1599 1845
1600</pre> 1846</pre>
1601<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1847<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 1848of 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> 1849put 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 1850options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1605<code>EV_MULTIPLICITY</code>.</p> 1851<p>Care has been taken to keep the overhead low. The only data member the C++
1852classes add (compared to plain C-style watchers) is the event loop pointer
1853that the watcher is associated with (or no additional members at all if
1854you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1855<p>Currently, functions, and static and non-static member functions can be
1856used as callbacks. Other types should be easy to add as long as they only
1857need one additional pointer for context. If you need support for other
1858types of functors please contact the author (preferably after implementing
1859it).</p>
1606<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1860<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1607<dl> 1861<dl>
1608 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1862 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1609 <dd> 1863 <dd>
1610 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1864 <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 1875which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1622defines by many implementations.</p> 1876defines by many implementations.</p>
1623 <p>All of those classes have these methods:</p> 1877 <p>All of those classes have these methods:</p>
1624 <p> 1878 <p>
1625 <dl> 1879 <dl>
1626 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1880 <dt>ev::TYPE::TYPE ()</dt>
1627 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1881 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1628 <dt>ev::TYPE::~TYPE</dt> 1882 <dt>ev::TYPE::~TYPE</dt>
1629 <dd> 1883 <dd>
1630 <p>The constructor takes a pointer to an object and a method pointer to 1884 <p>The constructor (optionally) takes an event loop to associate the watcher
1631the event handler callback to call in this class. The constructor calls 1885with. 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 1886 <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 1887<code>set</code> method before starting it.</p>
1634automatically associates the default loop with this watcher.</p> 1888 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1889method to set a callback before you can start the watcher.</p>
1890 <p>(The reason why you have to use a method is a limitation in C++ which does
1891not allow explicit template arguments for constructors).</p>
1635 <p>The destructor automatically stops the watcher if it is active.</p> 1892 <p>The destructor automatically stops the watcher if it is active.</p>
1893 </dd>
1894 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1895 <dd>
1896 <p>This method sets the callback method to call. The method has to have a
1897signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1898first argument and the <code>revents</code> as second. The object must be given as
1899parameter and is stored in the <code>data</code> member of the watcher.</p>
1900 <p>This method synthesizes efficient thunking code to call your method from
1901the C callback that libev requires. If your compiler can inline your
1902callback (i.e. it is visible to it at the place of the <code>set</code> call and
1903your compiler is good :), then the method will be fully inlined into the
1904thunking function, making it as fast as a direct C callback.</p>
1905 <p>Example: simple class declaration and watcher initialisation</p>
1906<pre> struct myclass
1907 {
1908 void io_cb (ev::io &amp;w, int revents) { }
1909 }
1910
1911 myclass obj;
1912 ev::io iow;
1913 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1914
1915</pre>
1916 </dd>
1917 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1918 <dd>
1919 <p>Also sets a callback, but uses a static method or plain function as
1920callback. The optional <code>data</code> argument will be stored in the watcher's
1921<code>data</code> member and is free for you to use.</p>
1922 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1923 <p>See the method-<code>set</code> above for more details.</p>
1924 <p>Example:</p>
1925<pre> static void io_cb (ev::io &amp;w, int revents) { }
1926 iow.set &lt;io_cb&gt; ();
1927
1928</pre>
1636 </dd> 1929 </dd>
1637 <dt>w-&gt;set (struct ev_loop *)</dt> 1930 <dt>w-&gt;set (struct ev_loop *)</dt>
1638 <dd> 1931 <dd>
1639 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1932 <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> 1933do this when the watcher is inactive (and not pending either).</p>
1641 </dd> 1934 </dd>
1642 <dt>w-&gt;set ([args])</dt> 1935 <dt>w-&gt;set ([args])</dt>
1643 <dd> 1936 <dd>
1644 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1937 <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 1938called at least once. Unlike the C counterpart, an active watcher gets
1646automatically stopped and restarted.</p> 1939automatically stopped and restarted when reconfiguring it with this
1940method.</p>
1647 </dd> 1941 </dd>
1648 <dt>w-&gt;start ()</dt> 1942 <dt>w-&gt;start ()</dt>
1649 <dd> 1943 <dd>
1650 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1944 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1651constructor already takes the loop.</p> 1945constructor already stores the event loop.</p>
1652 </dd> 1946 </dd>
1653 <dt>w-&gt;stop ()</dt> 1947 <dt>w-&gt;stop ()</dt>
1654 <dd> 1948 <dd>
1655 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1949 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1656 </dd> 1950 </dd>
… …
1680 1974
1681 myclass (); 1975 myclass ();
1682 } 1976 }
1683 1977
1684 myclass::myclass (int fd) 1978 myclass::myclass (int fd)
1685 : io (this, &amp;myclass::io_cb),
1686 idle (this, &amp;myclass::idle_cb)
1687 { 1979 {
1980 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1981 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1982
1688 io.start (fd, ev::READ); 1983 io.start (fd, ev::READ);
1689 } 1984 }
1690 1985
1691 1986
1692 1987
1693 1988
1694</pre> 1989</pre>
1695 1990
1696</div> 1991</div>
1697<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p> 1992<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1698<div id="MACRO_MAGIC_CONTENT"> 1993<div id="MACRO_MAGIC_CONTENT">
1699<p>Libev can be compiled with a variety of options, the most fundemantal is 1994<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 1995<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1701callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1996callbacks 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 1997<p>To make it easier to write programs that cope with either variant, the
1703following macros are defined:</p> 1998following macros are defined:</p>
1704<dl> 1999<dl>
1705 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 2000 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1734 <dd> 2029 <dd>
1735 <p>Similar to the other two macros, this gives you the value of the default 2030 <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> 2031loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1737 </dd> 2032 </dd>
1738</dl> 2033</dl>
1739<p>Example: Declare and initialise a check watcher, working regardless of 2034<p>Example: Declare and initialise a check watcher, utilising the above
1740wether multiple loops are supported or not.</p> 2035macros so it will work regardless of whether multiple loops are supported
2036or not.</p>
1741<pre> static void 2037<pre> static void
1742 check_cb (EV_P_ ev_timer *w, int revents) 2038 check_cb (EV_P_ ev_timer *w, int revents)
1743 { 2039 {
1744 ev_check_stop (EV_A_ w); 2040 ev_check_stop (EV_A_ w);
1745 } 2041 }
… …
1747 ev_check check; 2043 ev_check check;
1748 ev_check_init (&amp;check, check_cb); 2044 ev_check_init (&amp;check, check_cb);
1749 ev_check_start (EV_DEFAULT_ &amp;check); 2045 ev_check_start (EV_DEFAULT_ &amp;check);
1750 ev_loop (EV_DEFAULT_ 0); 2046 ev_loop (EV_DEFAULT_ 0);
1751 2047
1752
1753
1754
1755</pre> 2048</pre>
1756 2049
1757</div> 2050</div>
1758<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 2051<h1 id="EMBEDDING">EMBEDDING</h1>
1759<div id="EMBEDDING_CONTENT"> 2052<div id="EMBEDDING_CONTENT">
1760<p>Libev can (and often is) directly embedded into host 2053<p>Libev can (and often is) directly embedded into host
1761applications. Examples of applications that embed it include the Deliantra 2054applications. Examples of applications that embed it include the Deliantra
1762Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2055Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1763and rxvt-unicode.</p> 2056and rxvt-unicode.</p>
… …
1800 ev_vars.h 2093 ev_vars.h
1801 ev_wrap.h 2094 ev_wrap.h
1802 2095
1803 ev_win32.c required on win32 platforms only 2096 ev_win32.c required on win32 platforms only
1804 2097
1805 ev_select.c only when select backend is enabled (which is by default) 2098 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) 2099 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) 2100 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) 2101 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) 2102 ev_port.c only when the solaris port backend is enabled (disabled by default)
1810 2103
… …
1937 </dd> 2230 </dd>
1938 <dt>EV_USE_DEVPOLL</dt> 2231 <dt>EV_USE_DEVPOLL</dt>
1939 <dd> 2232 <dd>
1940 <p>reserved for future expansion, works like the USE symbols above.</p> 2233 <p>reserved for future expansion, works like the USE symbols above.</p>
1941 </dd> 2234 </dd>
2235 <dt>EV_USE_INOTIFY</dt>
2236 <dd>
2237 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2238interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2239be detected at runtime.</p>
2240 </dd>
1942 <dt>EV_H</dt> 2241 <dt>EV_H</dt>
1943 <dd> 2242 <dd>
1944 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2243 <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 2244undefined 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> 2245can 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 2268will have the <code>struct ev_loop *</code> as first argument, and you can create
1970additional independent event loops. Otherwise there will be no support 2269additional independent event loops. Otherwise there will be no support
1971for multiple event loops and there is no first event loop pointer 2270for multiple event loops and there is no first event loop pointer
1972argument. Instead, all functions act on the single default loop.</p> 2271argument. Instead, all functions act on the single default loop.</p>
1973 </dd> 2272 </dd>
2273 <dt>EV_MINPRI</dt>
2274 <dt>EV_MAXPRI</dt>
2275 <dd>
2276 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2277<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2278provide for more priorities by overriding those symbols (usually defined
2279to be <code>-2</code> and <code>2</code>, respectively).</p>
2280 <p>When doing priority-based operations, libev usually has to linearly search
2281all the priorities, so having many of them (hundreds) uses a lot of space
2282and time, so using the defaults of five priorities (-2 .. +2) is usually
2283fine.</p>
2284 <p>If your embedding app does not need any priorities, defining these both to
2285<code>0</code> will save some memory and cpu.</p>
2286 </dd>
1974 <dt>EV_PERIODIC_ENABLE</dt> 2287 <dt>EV_PERIODIC_ENABLE</dt>
1975 <dd> 2288 <dd>
1976 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2289 <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 2290defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1978code.</p> 2291code.</p>
1979 </dd> 2292 </dd>
2293 <dt>EV_IDLE_ENABLE</dt>
2294 <dd>
2295 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2296defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2297code.</p>
2298 </dd>
1980 <dt>EV_EMBED_ENABLE</dt> 2299 <dt>EV_EMBED_ENABLE</dt>
1981 <dd> 2300 <dd>
1982 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2301 <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> 2302defined to be <code>0</code>, then they are not.</p>
1984 </dd> 2303 </dd>
… …
2001 <dt>EV_PID_HASHSIZE</dt> 2320 <dt>EV_PID_HASHSIZE</dt>
2002 <dd> 2321 <dd>
2003 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2322 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2004pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more 2323pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2005than enough. If you need to manage thousands of children you might want to 2324than enough. If you need to manage thousands of children you might want to
2006increase this value.</p> 2325increase this value (<i>must</i> be a power of two).</p>
2326 </dd>
2327 <dt>EV_INOTIFY_HASHSIZE</dt>
2328 <dd>
2329 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2330inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2331usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2332watchers you might want to increase this value (<i>must</i> be a power of
2333two).</p>
2007 </dd> 2334 </dd>
2008 <dt>EV_COMMON</dt> 2335 <dt>EV_COMMON</dt>
2009 <dd> 2336 <dd>
2010 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2337 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2011this macro to a something else you can include more and other types of 2338this macro to a something else you can include more and other types of
… …
2038the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2365the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2039interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2366interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2040will be compiled. It is pretty complex because it provides its own header 2367will be compiled. It is pretty complex because it provides its own header
2041file.</p> 2368file.</p>
2042 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2369 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2043that everybody includes and which overrides some autoconf choices:</p> 2370that everybody includes and which overrides some configure choices:</p>
2371<pre> #define EV_MINIMAL 1
2044<pre> #define EV_USE_POLL 0 2372 #define EV_USE_POLL 0
2045 #define EV_MULTIPLICITY 0 2373 #define EV_MULTIPLICITY 0
2046 #define EV_PERIODICS 0 2374 #define EV_PERIODIC_ENABLE 0
2375 #define EV_STAT_ENABLE 0
2376 #define EV_FORK_ENABLE 0
2047 #define EV_CONFIG_H &lt;config.h&gt; 2377 #define EV_CONFIG_H &lt;config.h&gt;
2378 #define EV_MINPRI 0
2379 #define EV_MAXPRI 0
2048 2380
2049 #include &quot;ev++.h&quot; 2381 #include &quot;ev++.h&quot;
2050 2382
2051</pre> 2383</pre>
2052 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2384 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2057 2389
2058 2390
2059</pre> 2391</pre>
2060 2392
2061</div> 2393</div>
2062<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2394<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2063<div id="COMPLEXITIES_CONTENT"> 2395<div id="COMPLEXITIES_CONTENT">
2064 <p>In this section the complexities of (many of) the algorithms used inside 2396 <p>In this section the complexities of (many of) the algorithms used inside
2065libev will be explained. For complexity discussions about backends see the 2397libev will be explained. For complexity discussions about backends see the
2066documentation for <code>ev_default_init</code>.</p> 2398documentation for <code>ev_default_init</code>.</p>
2399 <p>All of the following are about amortised time: If an array needs to be
2400extended, libev needs to realloc and move the whole array, but this
2401happens asymptotically never with higher number of elements, so O(1) might
2402mean it might do a lengthy realloc operation in rare cases, but on average
2403it is much faster and asymptotically approaches constant time.</p>
2067 <p> 2404 <p>
2068 <dl> 2405 <dl>
2069 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2406 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2407 <dd>
2408 <p>This means that, when you have a watcher that triggers in one hour and
2409there are 100 watchers that would trigger before that then inserting will
2410have to skip those 100 watchers.</p>
2411 </dd>
2070 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2412 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2413 <dd>
2414 <p>That means that for changing a timer costs less than removing/adding them
2415as only the relative motion in the event queue has to be paid for.</p>
2416 </dd>
2071 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2417 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2418 <dd>
2419 <p>These just add the watcher into an array or at the head of a list.
2072 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2420=item Stopping check/prepare/idle watchers: O(1)</p>
2421 </dd>
2073 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2422 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2423 <dd>
2424 <p>These watchers are stored in lists then need to be walked to find the
2425correct watcher to remove. The lists are usually short (you don't usually
2426have many watchers waiting for the same fd or signal).</p>
2427 </dd>
2074 <dt>Finding the next timer per loop iteration: O(1)</dt> 2428 <dt>Finding the next timer per loop iteration: O(1)</dt>
2075 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2429 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2430 <dd>
2431 <p>A change means an I/O watcher gets started or stopped, which requires
2432libev to recalculate its status (and possibly tell the kernel).</p>
2433 </dd>
2076 <dt>Activating one watcher: O(1)</dt> 2434 <dt>Activating one watcher: O(1)</dt>
2435 <dt>Priority handling: O(number_of_priorities)</dt>
2436 <dd>
2437 <p>Priorities are implemented by allocating some space for each
2438priority. When doing priority-based operations, libev usually has to
2439linearly search all the priorities.</p>
2440 </dd>
2077 </dl> 2441 </dl>
2078 </p> 2442 </p>
2079 2443
2080 2444
2081 2445
2082 2446
2083 2447
2084</div> 2448</div>
2085<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2449<h1 id="AUTHOR">AUTHOR</h1>
2086<div id="AUTHOR_CONTENT"> 2450<div id="AUTHOR_CONTENT">
2087 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2451 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
2088 2452
2089</div> 2453</div>
2090</div></body> 2454</div></body>

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