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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 12 09:29:10 2007" /> 9 <meta name="created" content="Mon Nov 12 09:57:02 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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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="#DESCRIPTION">DESCRIPTION</a></li> 19<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 20<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 21<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
22<li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 27</ul>
27</li> 28</li>
28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> 30<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>
30<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> 31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
31<li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</a></li> 32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
32<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> 33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
33<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> 34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
34<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> 35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> 36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
36</ul> 37</ul>
37</li> 38</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 40<li><a href="#AUTHOR">AUTHOR</a>
40</li> 41</li>
… …
87support for multiple event loops, then all functions taking an initial 88support for multiple event loops, then all functions taking an initial
88argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 89argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
89will not have this argument.</p> 90will not have this argument.</p>
90 91
91</div> 92</div>
92<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 93<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
93<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> 94<div id="TIME_REPRESENTATION_CONTENT">
94<p>Libev represents time as a single floating point number, representing the 95<p>Libev represents time as a single floating point number, representing the
95(fractional) number of seconds since the (POSIX) epoch (somewhere near 96(fractional) number of seconds since the (POSIX) epoch (somewhere near
96the beginning of 1970, details are complicated, don't ask). This type is 97the beginning of 1970, details are complicated, don't ask). This type is
97called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 98called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
98to the double type in C.</p> 99to the double type in C.</p>
100
101</div>
102<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
103<div id="GLOBAL_FUNCTIONS_CONTENT">
99<dl> 104<dl>
100 <dt>ev_tstamp ev_time ()</dt> 105 <dt>ev_tstamp ev_time ()</dt>
101 <dd> 106 <dd>
102 <p>Returns the current time as libev would use it.</p> 107 <p>Returns the current time as libev would use it.</p>
103 </dd> 108 </dd>
… …
142<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 147<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 148<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
144types of such loops, the <i>default</i> loop, which supports signals and child 149types of such loops, the <i>default</i> loop, which supports signals and child
145events, and dynamically created loops which do not.</p> 150events, and dynamically created loops which do not.</p>
146<p>If you use threads, a common model is to run the default event loop 151<p>If you use threads, a common model is to run the default event loop
147in your main thread (or in a separate thrad) and for each thread you 152in your main thread (or in a separate thread) and for each thread you
148create, you also create another event loop. Libev itself does no locking 153create, you also create another event loop. Libev itself does no locking
149whatsoever, so if you mix calls to the same event loop in different 154whatsoever, so if you mix calls to the same event loop in different
150threads, make sure you lock (this is usually a bad idea, though, even if 155threads, make sure you lock (this is usually a bad idea, though, even if
151done correctly, because it's hideous and inefficient).</p> 156done correctly, because it's hideous and inefficient).</p>
152<dl> 157<dl>
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161 <p>The flags argument can be used to specify special behaviour or specific 166 <p>The flags argument can be used to specify special behaviour or specific
162backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 167backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
163 <p>It supports the following flags:</p> 168 <p>It supports the following flags:</p>
164 <p> 169 <p>
165 <dl> 170 <dl>
166 <dt>EVFLAG_AUTO</dt> 171 <dt><code>EVFLAG_AUTO</code></dt>
167 <dd> 172 <dd>
168 <p>The default flags value. Use this if you have no clue (it's the right 173 <p>The default flags value. Use this if you have no clue (it's the right
169thing, believe me).</p> 174thing, believe me).</p>
170 </dd> 175 </dd>
171 <dt>EVFLAG_NOENV</dt> 176 <dt><code>EVFLAG_NOENV</code></dt>
172 <dd> 177 <dd>
173 <p>If this flag bit is ored into the flag value (or the program runs setuid 178 <p>If this flag bit is ored into the flag value (or the program runs setuid
174or setgid) then libev will <i>not</i> look at the environment variable 179or setgid) then libev will <i>not</i> look at the environment variable
175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 180<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
176override the flags completely if it is found in the environment. This is 181override the flags completely if it is found in the environment. This is
177useful to try out specific backends to test their performance, or to work 182useful to try out specific backends to test their performance, or to work
178around bugs.</p> 183around bugs.</p>
179 </dd> 184 </dd>
180 <dt>EVMETHOD_SELECT (portable select backend)</dt> 185 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>
181 <dt>EVMETHOD_POLL (poll backend, available everywhere except on windows)</dt> 186 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
182 <dt>EVMETHOD_EPOLL (linux only)</dt> 187 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
183 <dt>EVMETHOD_KQUEUE (some bsds only)</dt> 188 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
184 <dt>EVMETHOD_DEVPOLL (solaris 8 only)</dt> 189 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
185 <dt>EVMETHOD_PORT (solaris 10 only)</dt> 190 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
186 <dd> 191 <dd>
187 <p>If one or more of these are ored into the flags value, then only these 192 <p>If one or more of these are ored into the flags value, then only these
188backends will be tried (in the reverse order as given here). If one are 193backends will be tried (in the reverse order as given here). If one are
189specified, any backend will do.</p> 194specified, any backend will do.</p>
190 </dd> 195 </dd>
… …
288</div> 293</div>
289<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 294<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
290<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 295<div id="ANATOMY_OF_A_WATCHER_CONTENT">
291<p>A watcher is a structure that you create and register to record your 296<p>A watcher is a structure that you create and register to record your
292interest in some event. For instance, if you want to wait for STDIN to 297interest in some event. For instance, if you want to wait for STDIN to
293become readable, you would create an ev_io watcher for that:</p> 298become readable, you would create an <code>ev_io</code> watcher for that:</p>
294<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 299<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
295 { 300 {
296 ev_io_stop (w); 301 ev_io_stop (w);
297 ev_unloop (loop, EVUNLOOP_ALL); 302 ev_unloop (loop, EVUNLOOP_ALL);
298 } 303 }
… …
322*)</code>), and you can stop watching for events at any time by calling the 327*)</code>), and you can stop watching for events at any time by calling the
323corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 328corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
324<p>As long as your watcher is active (has been started but not stopped) you 329<p>As long as your watcher is active (has been started but not stopped) you
325must not touch the values stored in it. Most specifically you must never 330must not touch the values stored in it. Most specifically you must never
326reinitialise it or call its set method.</p> 331reinitialise it or call its set method.</p>
327<p>You cna check whether an event is active by calling the <code>ev_is_active 332<p>You can check whether an event is active by calling the <code>ev_is_active
328(watcher *)</code> macro. To see whether an event is outstanding (but the 333(watcher *)</code> macro. To see whether an event is outstanding (but the
329callback for it has not been called yet) you cna use the <code>ev_is_pending 334callback for it has not been called yet) you can use the <code>ev_is_pending
330(watcher *)</code> macro.</p> 335(watcher *)</code> macro.</p>
331<p>Each and every callback receives the event loop pointer as first, the 336<p>Each and every callback receives the event loop pointer as first, the
332registered watcher structure as second, and a bitset of received events as 337registered watcher structure as second, and a bitset of received events as
333third argument.</p> 338third argument.</p>
334<p>The rceeived events usually include a single bit per event type received 339<p>The received events usually include a single bit per event type received
335(you can receive multiple events at the same time). The possible bit masks 340(you can receive multiple events at the same time). The possible bit masks
336are:</p> 341are:</p>
337<dl> 342<dl>
338 <dt>EV_READ</dt> 343 <dt><code>EV_READ</code></dt>
339 <dt>EV_WRITE</dt> 344 <dt><code>EV_WRITE</code></dt>
340 <dd> 345 <dd>
341 <p>The file descriptor in the ev_io watcher has become readable and/or 346 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
342writable.</p> 347writable.</p>
343 </dd> 348 </dd>
344 <dt>EV_TIMEOUT</dt> 349 <dt><code>EV_TIMEOUT</code></dt>
345 <dd>
346 <p>The ev_timer watcher has timed out.</p>
347 </dd> 350 <dd>
348 <dt>EV_PERIODIC</dt> 351 <p>The <code>ev_timer</code> watcher has timed out.</p>
349 <dd> 352 </dd>
350 <p>The ev_periodic watcher has timed out.</p> 353 <dt><code>EV_PERIODIC</code></dt>
351 </dd> 354 <dd>
352 <dt>EV_SIGNAL</dt> 355 <p>The <code>ev_periodic</code> watcher has timed out.</p>
353 <dd> 356 </dd>
357 <dt><code>EV_SIGNAL</code></dt>
358 <dd>
354 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 359 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
355 </dd>
356 <dt>EV_CHILD</dt>
357 <dd> 360 </dd>
361 <dt><code>EV_CHILD</code></dt>
362 <dd>
358 <p>The pid specified in the ev_child watcher has received a status change.</p> 363 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
359 </dd>
360 <dt>EV_IDLE</dt>
361 <dd> 364 </dd>
365 <dt><code>EV_IDLE</code></dt>
366 <dd>
362 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 367 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
363 </dd>
364 <dt>EV_PREPARE</dt>
365 <dt>EV_CHECK</dt>
366 <dd> 368 </dd>
369 <dt><code>EV_PREPARE</code></dt>
370 <dt><code>EV_CHECK</code></dt>
371 <dd>
367 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 372 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
368to gather new events, and all ev_check watchers are invoked just after 373to gather new events, and all <code>ev_check</code> watchers are invoked just after
369<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 374<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
370received events. Callbacks of both watcher types can start and stop as 375received events. Callbacks of both watcher types can start and stop as
371many watchers as they want, and all of them will be taken into account 376many watchers as they want, and all of them will be taken into account
372(for example, a ev_prepare watcher might start an idle watcher to keep 377(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
373<code>ev_loop</code> from blocking).</p> 378<code>ev_loop</code> from blocking).</p>
374 </dd> 379 </dd>
375 <dt>EV_ERROR</dt> 380 <dt><code>EV_ERROR</code></dt>
376 <dd> 381 <dd>
377 <p>An unspecified error has occured, the watcher has been stopped. This might 382 <p>An unspecified error has occured, the watcher has been stopped. This might
378happen because the watcher could not be properly started because libev 383happen because the watcher could not be properly started because libev
379ran out of memory, a file descriptor was found to be closed or any other 384ran out of memory, a file descriptor was found to be closed or any other
380problem. You best act on it by reporting the problem and somehow coping 385problem. You best act on it by reporting the problem and somehow coping
… …
389 394
390</div> 395</div>
391<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 396<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
392<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 397<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
393<p>Each watcher has, by default, a member <code>void *data</code> that you can change 398<p>Each watcher has, by default, a member <code>void *data</code> that you can change
394and read at any time, libev will completely ignore it. This cna be used 399and read at any time, libev will completely ignore it. This can be used
395to associate arbitrary data with your watcher. If you need more data and 400to associate arbitrary data with your watcher. If you need more data and
396don't want to allocate memory and store a pointer to it in that data 401don't want to allocate memory and store a pointer to it in that data
397member, you can also &quot;subclass&quot; the watcher type and provide your own 402member, you can also &quot;subclass&quot; the watcher type and provide your own
398data:</p> 403data:</p>
399<pre> struct my_io 404<pre> struct my_io
… …
426<div id="WATCHER_TYPES_CONTENT"> 431<div id="WATCHER_TYPES_CONTENT">
427<p>This section describes each watcher in detail, but will not repeat 432<p>This section describes each watcher in detail, but will not repeat
428information given in the last section.</p> 433information given in the last section.</p>
429 434
430</div> 435</div>
431<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 436<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
432<div id="struct_ev_io_is_my_file_descriptor_r-2"> 437<div id="code_ev_io_code_is_this_file_descrip-2">
433<p>I/O watchers check whether a file descriptor is readable or writable 438<p>I/O watchers check whether a file descriptor is readable or writable
434in each iteration of the event loop (This behaviour is called 439in each iteration of the event loop (This behaviour is called
435level-triggering because you keep receiving events as long as the 440level-triggering because you keep receiving events as long as the
436condition persists. Remember you cna stop the watcher if you don't want to 441condition persists. Remember you can stop the watcher if you don't want to
437act on the event and neither want to receive future events).</p> 442act on the event and neither want to receive future events).</p>
438<p>In general you can register as many read and/or write event watchers oer 443<p>In general you can register as many read and/or write event watchers oer
439fd as you want (as long as you don't confuse yourself). Setting all file 444fd as you want (as long as you don't confuse yourself). Setting all file
440descriptors to non-blocking mode is also usually a good idea (but not 445descriptors to non-blocking mode is also usually a good idea (but not
441required if you know what you are doing).</p> 446required if you know what you are doing).</p>
… …
448EVMETHOD_POLL).</p> 453EVMETHOD_POLL).</p>
449<dl> 454<dl>
450 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 455 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
451 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 456 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
452 <dd> 457 <dd>
453 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 458 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
454events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 459events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
455EV_WRITE</code> to receive the given events.</p> 460EV_WRITE</code> to receive the given events.</p>
456 </dd> 461 </dd>
457</dl> 462</dl>
458 463
459</div> 464</div>
460<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 465<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
461<div id="struct_ev_timer_relative_and_optiona-2"> 466<div id="code_ev_timer_code_relative_and_opti-2">
462<p>Timer watchers are simple relative timers that generate an event after a 467<p>Timer watchers are simple relative timers that generate an event after a
463given time, and optionally repeating in regular intervals after that.</p> 468given time, and optionally repeating in regular intervals after that.</p>
464<p>The timers are based on real time, that is, if you register an event that 469<p>The timers are based on real time, that is, if you register an event that
465times out after an hour and youreset your system clock to last years 470times out after an hour and youreset your system clock to last years
466time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 471time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
… …
497value), or reset the running timer to the repeat value.</p> 502value), or reset the running timer to the repeat value.</p>
498 <p>This sounds a bit complicated, but here is a useful and typical 503 <p>This sounds a bit complicated, but here is a useful and typical
499example: Imagine you have a tcp connection and you want a so-called idle 504example: Imagine you have a tcp connection and you want a so-called idle
500timeout, that is, you want to be called when there have been, say, 60 505timeout, that is, you want to be called when there have been, say, 60
501seconds of inactivity on the socket. The easiest way to do this is to 506seconds of inactivity on the socket. The easiest way to do this is to
502configure an ev_timer with after=repeat=60 and calling ev_timer_again each 507configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
503time you successfully read or write some data. If you go into an idle 508time you successfully read or write some data. If you go into an idle
504state where you do not expect data to travel on the socket, you can stop 509state where you do not expect data to travel on the socket, you can stop
505the timer, and again will automatically restart it if need be.</p> 510the timer, and again will automatically restart it if need be.</p>
506 </dd> 511 </dd>
507</dl> 512</dl>
508 513
509</div> 514</div>
510<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> 515<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
511<div id="ev_periodic_to_cron_or_not_to_cron_i-2"> 516<div id="code_ev_periodic_code_to_cron_or_not-2">
512<p>Periodic watchers are also timers of a kind, but they are very versatile 517<p>Periodic watchers are also timers of a kind, but they are very versatile
513(and unfortunately a bit complex).</p> 518(and unfortunately a bit complex).</p>
514<p>Unlike ev_timer's, they are not based on real time (or relative time) 519<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
515but on wallclock time (absolute time). You can tell a periodic watcher 520but on wallclock time (absolute time). You can tell a periodic watcher
516to trigger &quot;at&quot; some specific point in time. For example, if you tell a 521to trigger &quot;at&quot; some specific point in time. For example, if you tell a
517periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 522periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
518+ 10.&gt;) and then reset your system clock to the last year, then it will 523+ 10.&gt;) and then reset your system clock to the last year, then it will
519take a year to trigger the event (unlike an ev_timer, which would trigger 524take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
520roughly 10 seconds later and of course not if you reset your system time 525roughly 10 seconds later and of course not if you reset your system time
521again).</p> 526again).</p>
522<p>They can also be used to implement vastly more complex timers, such as 527<p>They can also be used to implement vastly more complex timers, such as
523triggering an event on eahc midnight, local time.</p> 528triggering an event on eahc midnight, local time.</p>
524<dl> 529<dl>
… …
550<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 555<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
551 556
552</pre> 557</pre>
553 <p>This doesn't mean there will always be 3600 seconds in between triggers, 558 <p>This doesn't mean there will always be 3600 seconds in between triggers,
554but only that the the callback will be called when the system time shows a 559but only that the the callback will be called when the system time shows a
555full hour (UTC), or more correct, when the system time is evenly divisible 560full hour (UTC), or more correctly, when the system time is evenly divisible
556by 3600.</p> 561by 3600.</p>
557 <p>Another way to think about it (for the mathematically inclined) is that 562 <p>Another way to think about it (for the mathematically inclined) is that
558ev_periodic will try to run the callback in this mode at the next possible 563<code>ev_periodic</code> will try to run the callback in this mode at the next possible
559time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 564time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
560 </dd> 565 </dd>
561 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 566 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
562 <dd> 567 <dd>
563 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 568 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
564ignored. Instead, each time the periodic watcher gets scheduled, the 569ignored. Instead, each time the periodic watcher gets scheduled, the
565reschedule callback will be called with the watcher as first, and the 570reschedule callback will be called with the watcher as first, and the
566current time as second argument.</p> 571current time as second argument.</p>
567 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 572 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other
568periodic watcher, ever, or make any event loop modificstions</i>. If you need 573periodic watcher, ever, or make any event loop modifications</i>. If you need
569to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 574to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p>
575 <p>Also, <i>this callback must always return a time that is later than the
576passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
570 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 577 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
571ev_tstamp now)&gt;, e.g.:</p> 578ev_tstamp now)</code>, e.g.:</p>
572<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 579<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
573 { 580 {
574 return now + 60.; 581 return now + 60.;
575 } 582 }
576 583
… …
595program when the crontabs have changed).</p> 602program when the crontabs have changed).</p>
596 </dd> 603 </dd>
597</dl> 604</dl>
598 605
599</div> 606</div>
600<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 607<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
601<div id="ev_signal_signal_me_when_a_signal_ge-2"> 608<div id="code_ev_signal_code_signal_me_when_a-2">
602<p>Signal watchers will trigger an event when the process receives a specific 609<p>Signal watchers will trigger an event when the process receives a specific
603signal one or more times. Even though signals are very asynchronous, libev 610signal one or more times. Even though signals are very asynchronous, libev
604will try it's best to deliver signals synchronously, i.e. as part of the 611will try it's best to deliver signals synchronously, i.e. as part of the
605normal event processing, like any other event.</p> 612normal event processing, like any other event.</p>
606<p>You cna configure as many watchers as you like per signal. Only when the 613<p>You can configure as many watchers as you like per signal. Only when the
607first watcher gets started will libev actually register a signal watcher 614first watcher gets started will libev actually register a signal watcher
608with the kernel (thus it coexists with your own signal handlers as long 615with the kernel (thus it coexists with your own signal handlers as long
609as you don't register any with libev). Similarly, when the last signal 616as you don't register any with libev). Similarly, when the last signal
610watcher for a signal is stopped libev will reset the signal handler to 617watcher for a signal is stopped libev will reset the signal handler to
611SIG_DFL (regardless of what it was set to before).</p> 618SIG_DFL (regardless of what it was set to before).</p>
… …
617of the <code>SIGxxx</code> constants).</p> 624of the <code>SIGxxx</code> constants).</p>
618 </dd> 625 </dd>
619</dl> 626</dl>
620 627
621</div> 628</div>
622<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 629<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
623<div id="ev_child_wait_for_pid_status_changes-2"> 630<div id="code_ev_child_code_wait_for_pid_stat-2">
624<p>Child watchers trigger when your process receives a SIGCHLD in response to 631<p>Child watchers trigger when your process receives a SIGCHLD in response to
625some child status changes (most typically when a child of yours dies).</p> 632some child status changes (most typically when a child of yours dies).</p>
626<dl> 633<dl>
627 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 634 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
628 <dt>ev_child_set (ev_child *, int pid)</dt> 635 <dt>ev_child_set (ev_child *, int pid)</dt>
629 <dd> 636 <dd>
630 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 637 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
631<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 638<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
632at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 639at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
633the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 640the status word (use the macros from <code>sys/wait.h</code> and see your systems
641<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
634contains the pid of the process causing the status change.</p> 642process causing the status change.</p>
635 </dd> 643 </dd>
636</dl> 644</dl>
637 645
638</div> 646</div>
639<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 647<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
640<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 648<div id="code_ev_idle_code_when_you_ve_got_no-2">
641<p>Idle watchers trigger events when there are no other I/O or timer (or 649<p>Idle watchers trigger events when there are no other events are pending
642periodic) events pending. That is, as long as your process is busy 650(prepare, check and other idle watchers do not count). That is, as long
643handling sockets or timeouts it will not be called. But when your process 651as your process is busy handling sockets or timeouts (or even signals,
644is idle all idle watchers are being called again and again - until 652imagine) it will not be triggered. But when your process is idle all idle
653watchers are being called again and again, once per event loop iteration -
645stopped, that is, or your process receives more events.</p> 654until stopped, that is, or your process receives more events and becomes
655busy.</p>
646<p>The most noteworthy effect is that as long as any idle watchers are 656<p>The most noteworthy effect is that as long as any idle watchers are
647active, the process will not block when waiting for new events.</p> 657active, the process will not block when waiting for new events.</p>
648<p>Apart from keeping your process non-blocking (which is a useful 658<p>Apart from keeping your process non-blocking (which is a useful
649effect on its own sometimes), idle watchers are a good place to do 659effect on its own sometimes), idle watchers are a good place to do
650&quot;pseudo-background processing&quot;, or delay processing stuff to after the 660&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
657believe me.</p> 667believe me.</p>
658 </dd> 668 </dd>
659</dl> 669</dl>
660 670
661</div> 671</div>
662<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 672<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
663<div id="prepare_and_check_your_hooks_into_th-2"> 673<div id="code_ev_prepare_code_and_code_ev_che-2">
664<p>Prepare and check watchers usually (but not always) are used in 674<p>Prepare and check watchers are usually (but not always) used in tandem:
665tandom. Prepare watchers get invoked before the process blocks and check 675Prepare watchers get invoked before the process blocks and check watchers
666watchers afterwards.</p> 676afterwards.</p>
667<p>Their main purpose is to integrate other event mechanisms into libev. This 677<p>Their main purpose is to integrate other event mechanisms into libev. This
668could be used, for example, to track variable changes, implement your own 678could be used, for example, to track variable changes, implement your own
669watchers, integrate net-snmp or a coroutine library and lots more.</p> 679watchers, integrate net-snmp or a coroutine library and lots more.</p>
670<p>This is done by examining in each prepare call which file descriptors need 680<p>This is done by examining in each prepare call which file descriptors need
671to be watched by the other library, registering ev_io watchers for them 681to be watched by the other library, registering <code>ev_io</code> watchers for
672and starting an ev_timer watcher for any timeouts (many libraries provide 682them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
673just this functionality). Then, in the check watcher you check for any 683provide just this functionality). Then, in the check watcher you check for
674events that occured (by making your callbacks set soem flags for example) 684any events that occured (by checking the pending status of all watchers
675and call back into the library.</p> 685and stopping them) and call back into the library. The I/O and timer
686callbacks will never actually be called (but must be valid neverthelles,
687because you never know, you know?).</p>
676<p>As another example, the perl Coro module uses these hooks to integrate 688<p>As another example, the Perl Coro module uses these hooks to integrate
677coroutines into libev programs, by yielding to other active coroutines 689coroutines into libev programs, by yielding to other active coroutines
678during each prepare and only letting the process block if no coroutines 690during each prepare and only letting the process block if no coroutines
679are ready to run.</p> 691are ready to run (its actually more complicated, it only runs coroutines
692with priority higher than the event loop and one lower priority once,
693using idle watchers to keep the event loop from blocking if lower-priority
694coroutines exist, thus mapping low-priority coroutines to idle/background
695tasks).</p>
680<dl> 696<dl>
681 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 697 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
682 <dt>ev_check_init (ev_check *, callback)</dt> 698 <dt>ev_check_init (ev_check *, callback)</dt>
683 <dd> 699 <dd>
684 <p>Initialises and configures the prepare or check watcher - they have no 700 <p>Initialises and configures the prepare or check watcher - they have no
685parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 701parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
686macros, but using them is utterly, utterly pointless.</p> 702macros, but using them is utterly, utterly and completely pointless.</p>
687 </dd> 703 </dd>
688</dl> 704</dl>
689 705
690</div> 706</div>
691<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 707<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
692<div id="OTHER_FUNCTIONS_CONTENT"> 708<div id="OTHER_FUNCTIONS_CONTENT">
693<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 709<p>There are some other functions of possible interest. Described. Here. Now.</p>
694<dl> 710<dl>
695 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 711 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
696 <dd> 712 <dd>
697 <p>This function combines a simple timer and an I/O watcher, calls your 713 <p>This function combines a simple timer and an I/O watcher, calls your
698callback on whichever event happens first and automatically stop both 714callback on whichever event happens first and automatically stop both
699watchers. This is useful if you want to wait for a single event on an fd 715watchers. This is useful if you want to wait for a single event on an fd
700or timeout without havign to allocate/configure/start/stop/free one or 716or timeout without havign to allocate/configure/start/stop/free one or
701more watchers yourself.</p> 717more watchers yourself.</p>
702 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 718 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
703ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 719is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
704will be craeted and started.</p> 720<code>events</code> set will be craeted and started.</p>
705 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 721 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
706started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 722started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
707= 0) will be started.</p> 723repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724dubious value.</p>
708 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 725 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
709gets passed an events set (normally a combination of EV_ERROR, EV_READ, 726passed an events set like normal event callbacks (with a combination of
710EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 727<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728value passed to <code>ev_once</code>:</p>
711<pre> static void stdin_ready (int revents, void *arg) 729<pre> static void stdin_ready (int revents, void *arg)
712 { 730 {
713 if (revents &amp; EV_TIMEOUT) 731 if (revents &amp; EV_TIMEOUT)
714 /* doh, nothing entered */ 732 /* doh, nothing entered */;
715 else if (revents &amp; EV_READ) 733 else if (revents &amp; EV_READ)
716 /* stdin might have data for us, joy! */ 734 /* stdin might have data for us, joy! */;
717 } 735 }
718 736
719 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 737 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
720 738
721</pre> 739</pre>
722 </dd> 740 </dd>
723 <dt>ev_feed_event (loop, watcher, int events)</dt> 741 <dt>ev_feed_event (loop, watcher, int events)</dt>
724 <dd> 742 <dd>
725 <p>Feeds the given event set into the event loop, as if the specified event 743 <p>Feeds the given event set into the event loop, as if the specified event
726has happened for the specified watcher (which must be a pointer to an 744had happened for the specified watcher (which must be a pointer to an
727initialised but not necessarily active event watcher).</p> 745initialised but not necessarily started event watcher).</p>
728 </dd> 746 </dd>
729 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 747 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
730 <dd> 748 <dd>
731 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 749 <p>Feed an event on the given fd, as if a file descriptor backend detected
750the given events it.</p>
732 </dd> 751 </dd>
733 <dt>ev_feed_signal_event (loop, int signum)</dt> 752 <dt>ev_feed_signal_event (loop, int signum)</dt>
734 <dd> 753 <dd>
735 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 754 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
736 </dd> 755 </dd>

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