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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="<standard input>" />	7	<meta name="inputfile" content="<standard input>" />
8	<meta name="outputfile" content="<standard output>" />	8	<meta name="outputfile" content="<standard output>" />
9	<meta name="created" content="Mon Nov 12 09:57:02 2007" />	9	<meta name="created" content="Sun Dec 9 20:45:16 2007" />
10	<meta name="generator" content="Pod::Xhtml 1.57" />	10	<meta name="generator" content="Pod::Xhtml 1.57" />
11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>	11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
15	<h3 id="TOP">Index</h3>	15	<h3 id="TOP">Index</h3>
16		16
17	<ul><li><a href="#NAME">NAME</a></li>	17	<ul><li><a href="#NAME">NAME</a></li>
18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>	18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
		19	<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>	20	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20	<li><a href="#FEATURES">FEATURES</a></li>	21	<li><a href="#FEATURES">FEATURES</a></li>
21	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>	22	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>	23	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>	24	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>	25	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>	26	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
		27	<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
26	<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>	28	<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27	</ul>	29	</ul>
28	</li>	30	</li>
29	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>	31	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
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>	32	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
31	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>	33	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
32	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>	34	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
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>	35	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
34	<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>	36	<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
		37	<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
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>	38	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
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>	39	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
		40	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
		41	<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
37	</ul>	42	</ul>
38	</li>	43	</li>
39	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	44	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		45	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		46	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		47	<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
		48	<li><a href="#EMBEDDING">EMBEDDING</a>
		49	<ul><li><a href="#FILESETS">FILESETS</a>
		50	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		51	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		52	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		53	</ul>
		54	</li>
		55	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		56	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		57	</ul>
		58	</li>
		59	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
40	<li><a href="#AUTHOR">AUTHOR</a>	60	<li><a href="#AUTHOR">AUTHOR</a>
41	</li>	61	</li>
42	</ul><hr />	62	</ul><hr />
43	<!-- INDEX END -->	63	<!-- INDEX END -->
44		64
45	<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>	65	<h1 id="NAME">NAME</h1>
46	<div id="NAME_CONTENT">	66	<div id="NAME_CONTENT">
47	<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>
48		68
49	</div>	69	</div>
50	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>	70	<h1 id="SYNOPSIS">SYNOPSIS</h1>
51	<div id="SYNOPSIS_CONTENT">	71	<div id="SYNOPSIS_CONTENT">
52	<pre> #include <ev.h>	72	<pre> #include <ev.h>
53		73
54	</pre>	74	</pre>
55		75
56	</div>	76	</div>
57	<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 <ev.h>
		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 ("stdin ready"); */
		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 ("timeout"); */
		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 (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		107	ev_io_start (loop, &stdin_watcher);
		108
		109	/* simple non-repeating 5.5 second timeout */
		110	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		111	ev_timer_start (loop, &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>
58	<div id="DESCRIPTION_CONTENT">	123	<div id="DESCRIPTION_CONTENT">
		124	<p>The newest version of this document is also available as a html-formatted
		125	web page you might find easier to navigate when reading it for the first
		126	time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
59	<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
60	file descriptor being readable or a timeout occuring), and it will manage	128	file descriptor being readable or a timeout occuring), and it will manage
61	these event sources and provide your program with events.</p>	129	these event sources and provide your program with events.</p>
62	<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
63	(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
…		…
66	watchers</i>, which are relatively small C structures you initialise with the	134	watchers</i>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by <i>starting</i> the	135	details of the event, and then hand it over to libev by <i>starting</i> the
68	watcher.</p>	136	watcher.</p>
69		137
70	</div>	138	</div>
71	<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>	139	<h1 id="FEATURES">FEATURES</h1>
72	<div id="FEATURES_CONTENT">	140	<div id="FEATURES_CONTENT">
73	<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
74	kqueue mechanisms for file descriptor events, relative timers, absolute	142	BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
75	timers with customised rescheduling, signal events, process status change	143	for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
76	events (related to SIGCHLD), and event watchers dealing with the event	144	(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
77	loop mechanism itself (idle, prepare and check watchers). It also is quite	145	with customised rescheduling (<code>ev_periodic</code>), synchronous signals
		146	(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
		147	watchers 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
		149	file 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
78	fast (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
79	it to libevent for example).</p>	153	for example).</p>
80		154
81	</div>	155	</div>
82	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	156	<h1 id="CONVENTIONS">CONVENTIONS</h1>
83	<div id="CONVENTIONS_CONTENT">	157	<div id="CONVENTIONS_CONTENT">
84	<p>Libev is very configurable. In this manual the default configuration	158	<p>Libev is very configurable. In this manual the default configuration will
85	will be described, which supports multiple event loops. For more info	159	be described, which supports multiple event loops. For more info about
86	about various configuration options please have a look at the file	160	various configuration options please have a look at <strong>EMBED</strong> section in
87	<cite>README.embed</cite> in the libev distribution. If libev was configured without	161	this manual. If libev was configured without support for multiple event
88	support for multiple event loops, then all functions taking an initial	162	loops, then all functions taking an initial argument of name <code>loop</code>
89	argument 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>
90	will not have this argument.</p>
91		164
92	</div>	165	</div>
93	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>	166	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
94	<div id="TIME_REPRESENTATION_CONTENT">	167	<div id="TIME_REPRESENTATION_CONTENT">
95	<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
96	(fractional) number of seconds since the (POSIX) epoch (somewhere near	169	(fractional) number of seconds since the (POSIX) epoch (somewhere near
97	the beginning of 1970, details are complicated, don't ask). This type is	170	the beginning of 1970, details are complicated, don't ask). This type is
98	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	171	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
99	to the double type in C.</p>	172	to the <code>double</code> type in C, and when you need to do any calculations on
		173	it, you should treat it as such.</p>
100		174
101	</div>	175	</div>
102	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	176	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
103	<div id="GLOBAL_FUNCTIONS_CONTENT">	177	<div id="GLOBAL_FUNCTIONS_CONTENT">
		178	<p>These functions can be called anytime, even before initialising the
		179	library in any way.</p>
104	<dl>	180	<dl>
105	<dt>ev_tstamp ev_time ()</dt>	181	<dt>ev_tstamp ev_time ()</dt>
106	<dd>	182	<dd>
107	<p>Returns the current time as libev would use it.</p>	183	<p>Returns the current time as libev would use it. Please note that the
		184	<code>ev_now</code> function is usually faster and also often returns the timestamp
		185	you actually want to know.</p>
108	</dd>	186	</dd>
109	<dt>int ev_version_major ()</dt>	187	<dt>int ev_version_major ()</dt>
110	<dt>int ev_version_minor ()</dt>	188	<dt>int ev_version_minor ()</dt>
111	<dd>	189	<dd>
112	<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
113	you linked against by calling the functions <code>ev_version_major</code> and	191	you linked against by calling the functions <code>ev_version_major</code> and
114	<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
115	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the	193	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
116	version of the library your program was compiled against.</p>	194	version 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
		196	the release version.</p>
117	<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,
118	as this indicates an incompatible change. Minor versions are usually	198	as this indicates an incompatible change. Minor versions are usually
119	compatible to older versions, so a larger minor version alone is usually	199	compatible to older versions, so a larger minor version alone is usually
120	not a problem.</p>	200	not a problem.</p>
		201	<p>Example: Make sure we haven't accidentally been linked against the wrong
		202	version.</p>
		203	<pre> assert (("libev version mismatch",
		204	ev_version_major () == EV_VERSION_MAJOR
		205	&& ev_version_minor () >= EV_VERSION_MINOR));
		206
		207	</pre>
		208	</dd>
		209	<dt>unsigned int ev_supported_backends ()</dt>
		210	<dd>
		211	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		212	value) compiled into this binary of libev (independent of their
		213	availability on the system you are running on). See <code>ev_default_loop</code> for
		214	a description of the set values.</p>
		215	<p>Example: make sure we have the epoll method, because yeah this is cool and
		216	a must have and can we have a torrent of it please!!!11</p>
		217	<pre> assert (("sorry, no epoll, no sex",
		218	ev_supported_backends () & EVBACKEND_EPOLL));
		219
		220	</pre>
		221	</dd>
		222	<dt>unsigned int ev_recommended_backends ()</dt>
		223	<dd>
		224	<p>Return the set of all backends compiled into this binary of libev and also
		225	recommended for this platform. This set is often smaller than the one
		226	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		227	most BSDs and will not be autodetected unless you explicitly request it
		228	(assuming you know what you are doing). This is the set of backends that
		229	libev will probe for if you specify no backends explicitly.</p>
		230	</dd>
		231	<dt>unsigned int ev_embeddable_backends ()</dt>
		232	<dd>
		233	<p>Returns the set of backends that are embeddable in other event loops. This
		234	is the theoretical, all-platform, value. To find which backends
		235	might be supported on the current system, you would need to look at
		236	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		237	recommended ones.</p>
		238	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
121	</dd>	239	</dd>
122	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	240	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
123	<dd>	241	<dd>
124	<p>Sets the allocation function to use (the prototype is similar to the	242	<p>Sets the allocation function to use (the prototype is similar - the
125	realloc C function, the semantics are identical). It is used to allocate	243	semantics is identical - to the realloc C function). It is used to
126	and free memory (no surprises here). If it returns zero when memory	244	allocate and free memory (no surprises here). If it returns zero when
127	needs to be allocated, the library might abort or take some potentially	245	memory needs to be allocated, the library might abort or take some
128	destructive action. The default is your system realloc function.</p>	246	potentially destructive action. The default is your system realloc
		247	function.</p>
129	<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,
130	free some memory if it cannot allocate memory, to use a special allocator,	249	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.</p>	250	or even to sleep a while and retry until some memory is available.</p>
		251	<p>Example: Replace the libev allocator with one that waits a bit and then
		252	retries).</p>
		253	<pre> static void *
		254	persistent_realloc (void *ptr, size_t size)
		255	{
		256	for (;;)
		257	{
		258	void *newptr = realloc (ptr, size);
		259
		260	if (newptr)
		261	return newptr;
		262
		263	sleep (60);
		264	}
		265	}
		266
		267	...
		268	ev_set_allocator (persistent_realloc);
		269
		270	</pre>
132	</dd>	271	</dd>
133	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	272	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
134	<dd>	273	<dd>
135	<p>Set the callback function to call on a retryable syscall error (such	274	<p>Set the callback function to call on a retryable syscall error (such
136	as failed select, poll, epoll_wait). The message is a printable string	275	as failed select, poll, epoll_wait). The message is a printable string
137	indicating the system call or subsystem causing the problem. If this	276	indicating the system call or subsystem causing the problem. If this
138	callback is set, then libev will expect it to remedy the sitution, no	277	callback is set, then libev will expect it to remedy the sitution, no
139	matter what, when it returns. That is, libev will generally retry the	278	matter what, when it returns. That is, libev will generally retry the
140	requested operation, or, if the condition doesn't go away, do bad stuff	279	requested operation, or, if the condition doesn't go away, do bad stuff
141	(such as abort).</p>	280	(such as abort).</p>
		281	<p>Example: This is basically the same thing that libev does internally, too.</p>
		282	<pre> static void
		283	fatal_error (const char *msg)
		284	{
		285	perror (msg);
		286	abort ();
		287	}
		288
		289	...
		290	ev_set_syserr_cb (fatal_error);
		291
		292	</pre>
142	</dd>	293	</dd>
143	</dl>	294	</dl>
144		295
145	</div>	296	</div>
146	<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>
147	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	298	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
148	<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
149	types of such loops, the <i>default</i> loop, which supports signals and child	300	types of such loops, the <i>default</i> loop, which supports signals and child
150	events, and dynamically created loops which do not.</p>	301	events, and dynamically created loops which do not.</p>
151	<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
…		…
158	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	309	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159	<dd>	310	<dd>
160	<p>This will initialise the default event loop if it hasn't been initialised	311	<p>This will initialise the default event loop if it hasn't been initialised
161	yet and return it. If the default loop could not be initialised, returns	312	yet and return it. If the default loop could not be initialised, returns
162	false. If it already was initialised it simply returns it (and ignores the	313	false. If it already was initialised it simply returns it (and ignores the
163	flags).</p>	314	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
164	<p>If you don't know what event loop to use, use the one returned from this	315	<p>If you don't know what event loop to use, use the one returned from this
165	function.</p>	316	function.</p>
166	<p>The flags argument can be used to specify special behaviour or specific	317	<p>The flags argument can be used to specify special behaviour or specific
167	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>	318	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
168	<p>It supports the following flags:</p>	319	<p>The following flags are supported:</p>
169	<p>	320	<p>
170	<dl>	321	<dl>
171	<dt><code>EVFLAG_AUTO</code></dt>	322	<dt><code>EVFLAG_AUTO</code></dt>
172	<dd>	323	<dd>
173	<p>The default flags value. Use this if you have no clue (it's the right	324	<p>The default flags value. Use this if you have no clue (it's the right
…		…
180	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will	331	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181	override the flags completely if it is found in the environment. This is	332	override the flags completely if it is found in the environment. This is
182	useful to try out specific backends to test their performance, or to work	333	useful to try out specific backends to test their performance, or to work
183	around bugs.</p>	334	around bugs.</p>
184	</dd>	335	</dd>
185	<dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>	336	<dt><code>EVFLAG_FORKCHECK</code></dt>
186	<dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>	337	<dd>
187	<dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>	338	<p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
188	<dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>	339	a fork, you can also make libev check for a fork in each iteration by
189	<dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>	340	enabling this flag.</p>
190	<dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>	341	<p>This works by calling <code>getpid ()</code> on every iteration of the loop,
		342	and thus this might slow down your event loop if you do a lot of loop
		343	iterations and little real work, but is usually not noticeable (on my
		344	Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
		345	without 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
		348	forget about forgetting to tell libev about forking) when you use this
		349	flag.</p>
		350	<p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
		351	environment variable.</p>
191	<dd>	352	</dd>
192	<p>If one or more of these are ored into the flags value, then only these	353	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
193	backends will be tried (in the reverse order as given here). If one are	354	<dd>
194	specified, any backend will do.</p>	355	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
		356	libev tries to roll its own fd_set with no limits on the number of fds,
		357	but if that fails, expect a fairly low limit on the number of fds when
		358	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		359	the fastest backend for a low number of fds.</p>
		360	</dd>
		361	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		362	<dd>
		363	<p>And this is your standard poll(2) backend. It's more complicated than
		364	select, but handles sparse fds better and has no artificial limit on the
		365	number of fds you can use (except it will slow down considerably with a
		366	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		367	</dd>
		368	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		369	<dd>
		370	<p>For few fds, this backend is a bit little slower than poll and select,
		371	but it scales phenomenally better. While poll and select usually scale like
		372	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		373	either O(1) or O(active_fds).</p>
		374	<p>While stopping and starting an I/O watcher in the same iteration will
		375	result in some caching, there is still a syscall per such incident
		376	(because the fd could point to a different file description now), so its
		377	best to avoid that. Also, dup()ed file descriptors might not work very
		378	well if you register events for both fds.</p>
		379	<p>Please note that epoll sometimes generates spurious notifications, so you
		380	need to use non-blocking I/O or other means to avoid blocking when no data
		381	(or space) is available.</p>
		382	</dd>
		383	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		384	<dd>
		385	<p>Kqueue deserves special mention, as at the time of this writing, it
		386	was broken on all BSDs except NetBSD (usually it doesn't work with
		387	anything but sockets and pipes, except on Darwin, where of course its
		388	completely useless). For this reason its not being "autodetected"
		389	unless you explicitly specify it explicitly in the flags (i.e. using
		390	<code>EVBACKEND_KQUEUE</code>).</p>
		391	<p>It scales in the same way as the epoll backend, but the interface to the
		392	kernel is more efficient (which says nothing about its actual speed, of
		393	course). While starting and stopping an I/O watcher does not cause an
		394	extra syscall as with epoll, it still adds up to four event changes per
		395	incident, so its best to avoid that.</p>
		396	</dd>
		397	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		398	<dd>
		399	<p>This is not implemented yet (and might never be).</p>
		400	</dd>
		401	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		402	<dd>
		403	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		404	it's really slow, but it still scales very well (O(active_fds)).</p>
		405	<p>Please note that solaris ports can result in a lot of spurious
		406	notifications, so you need to use non-blocking I/O or other means to avoid
		407	blocking when no data (or space) is available.</p>
		408	</dd>
		409	<dt><code>EVBACKEND_ALL</code></dt>
		410	<dd>
		411	<p>Try all backends (even potentially broken ones that wouldn't be tried
		412	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		413	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
195	</dd>	414	</dd>
196	</dl>	415	</dl>
197	</p>	416	</p>
		417	<p>If one or more of these are ored into the flags value, then only these
		418	backends will be tried (in the reverse order as given here). If none are
		419	specified, most compiled-in backend will be tried, usually in reverse
		420	order of their flag values :)</p>
		421	<p>The most typical usage is like this:</p>
		422	<pre> if (!ev_default_loop (0))
		423	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		424
		425	</pre>
		426	<p>Restrict libev to the select and poll backends, and do not allow
		427	environment settings to be taken into account:</p>
		428	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		429
		430	</pre>
		431	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		432	available (warning, breaks stuff, best use only with your own private
		433	event loop and only if you know the OS supports your types of fds):</p>
		434	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		435
		436	</pre>
198	</dd>	437	</dd>
199	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	438	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200	<dd>	439	<dd>
201	<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
202	always distinct from the default loop. Unlike the default loop, it cannot	441	always distinct from the default loop. Unlike the default loop, it cannot
203	handle signal and child watchers, and attempts to do so will be greeted by	442	handle signal and child watchers, and attempts to do so will be greeted by
204	undefined behaviour (or a failed assertion if assertions are enabled).</p>	443	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		444	<p>Example: Try to create a event loop that uses epoll and nothing else.</p>
		445	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		446	if (!epoller)
		447	fatal ("no epoll found here, maybe it hides under your chair");
		448
		449	</pre>
205	</dd>	450	</dd>
206	<dt>ev_default_destroy ()</dt>	451	<dt>ev_default_destroy ()</dt>
207	<dd>	452	<dd>
208	<p>Destroys the default loop again (frees all memory and kernel state	453	<p>Destroys the default loop again (frees all memory and kernel state
209	etc.). This stops all registered event watchers (by not touching them in	454	etc.). None of the active event watchers will be stopped in the normal
210	any way whatsoever, although you cannot rely on this :).</p>	455	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		456	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		457	calling this function, or cope with the fact afterwards (which is usually
		458	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		459	for example).</p>
211	</dd>	460	</dd>
212	<dt>ev_loop_destroy (loop)</dt>	461	<dt>ev_loop_destroy (loop)</dt>
213	<dd>	462	<dd>
214	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	463	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
215	earlier call to <code>ev_loop_new</code>.</p>	464	earlier call to <code>ev_loop_new</code>.</p>
…		…
218	<dd>	467	<dd>
219	<p>This function reinitialises the kernel state for backends that have	468	<p>This function reinitialises the kernel state for backends that have
220	one. Despite the name, you can call it anytime, but it makes most sense	469	one. Despite the name, you can call it anytime, but it makes most sense
221	after forking, in either the parent or child process (or both, but that	470	after forking, in either the parent or child process (or both, but that
222	again makes little sense).</p>	471	again makes little sense).</p>
223	<p>You <i>must</i> call this function after forking if and only if you want to	472	<p>You <i>must</i> call this function in the child process after forking if and
224	use the event library in both processes. If you just fork+exec, you don't	473	only if you want to use the event library in both processes. If you just
225	have to call it.</p>	474	fork+exec, you don't have to call it.</p>
226	<p>The function itself is quite fast and it's usually not a problem to call	475	<p>The function itself is quite fast and it's usually not a problem to call
227	it just in case after a fork. To make this easy, the function will fit in	476	it just in case after a fork. To make this easy, the function will fit in
228	quite nicely into a call to <code>pthread_atfork</code>:</p>	477	quite nicely into a call to <code>pthread_atfork</code>:</p>
229	<pre> pthread_atfork (0, 0, ev_default_fork);	478	<pre> pthread_atfork (0, 0, ev_default_fork);
230		479
231	</pre>	480	</pre>
		481	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		482	without calling this function, so if you force one of those backends you
		483	do not need to care.</p>
232	</dd>	484	</dd>
233	<dt>ev_loop_fork (loop)</dt>	485	<dt>ev_loop_fork (loop)</dt>
234	<dd>	486	<dd>
235	<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
236	<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
237	after fork, and how you do this is entirely your own problem.</p>	489	after fork, and how you do this is entirely your own problem.</p>
238	</dd>	490	</dd>
239	<dt>unsigned int ev_method (loop)</dt>	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
		494	the number of times libev did poll for new events. It starts at <code>0</code> and
		495	happily wraps around with enough iterations.</p>
		496	<p>This value can sometimes be useful as a generation counter of sorts (it
		497	"ticks" the number of loop iterations), as it roughly corresponds with
		498	<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
240	<dd>	499	</dd>
		500	<dt>unsigned int ev_backend (loop)</dt>
		501	<dd>
241	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	502	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242	use.</p>	503	use.</p>
243	</dd>	504	</dd>
244	<dt>ev_tstamp ev_now (loop)</dt>	505	<dt>ev_tstamp ev_now (loop)</dt>
245	<dd>	506	<dd>
246	<p>Returns the current "event loop time", which is the time the event loop	507	<p>Returns the current "event loop time", which is the time the event loop
247	got events and started processing them. This timestamp does not change	508	received events and started processing them. This timestamp does not
248	as long as callbacks are being processed, and this is also the base time	509	change as long as callbacks are being processed, and this is also the base
249	used for relative timers. You can treat it as the timestamp of the event	510	time used for relative timers. You can treat it as the timestamp of the
250	occuring (or more correctly, the mainloop finding out about it).</p>	511	event occuring (or more correctly, libev finding out about it).</p>
251	</dd>	512	</dd>
252	<dt>ev_loop (loop, int flags)</dt>	513	<dt>ev_loop (loop, int flags)</dt>
253	<dd>	514	<dd>
254	<p>Finally, this is it, the event handler. This function usually is called	515	<p>Finally, this is it, the event handler. This function usually is called
255	after you initialised all your watchers and you want to start handling	516	after you initialised all your watchers and you want to start handling
256	events.</p>	517	events.</p>
257	<p>If the flags argument is specified as 0, it will not return until either	518	<p>If the flags argument is specified as <code>0</code>, it will not return until
258	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	519	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		520	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		521	relying on all watchers to be stopped when deciding when a program has
		522	finished (especially in interactive programs), but having a program that
		523	automatically loops as long as it has to and no longer by virtue of
		524	relying on its watchers stopping correctly is a thing of beauty.</p>
259	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	525	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
260	those events and any outstanding ones, but will not block your process in	526	those events and any outstanding ones, but will not block your process in
261	case there are no events and will return after one iteration of the loop.</p>	527	case there are no events and will return after one iteration of the loop.</p>
262	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	528	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
263	neccessary) and will handle those and any outstanding ones. It will block	529	neccessary) and will handle those and any outstanding ones. It will block
264	your process until at least one new event arrives, and will return after	530	your process until at least one new event arrives, and will return after
265	one iteration of the loop.</p>	531	one iteration of the loop. This is useful if you are waiting for some
266	<p>This flags value could be used to implement alternative looping	532	external event in conjunction with something not expressible using other
267	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	533	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268	more generic mechanism.</p>	534	usually a better approach for this kind of thing.</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.
		537	* If there are no active watchers (reference count is zero), return.
		538	- Queue all prepare watchers and then call all outstanding watchers.
		539	- If we have been forked, recreate the kernel state.
		540	- Update the kernel state with all outstanding changes.
		541	- Update the "event loop time".
		542	- Calculate for how long to block.
		543	- Block the process, waiting for any events.
		544	- Queue all outstanding I/O (fd) events.
		545	- Update the "event loop time" and do time jump handling.
		546	- Queue all outstanding timers.
		547	- Queue all outstanding periodics.
		548	- If no events are pending now, queue all idle watchers.
		549	- Queue all check watchers.
		550	- Call all queued watchers in reverse order (i.e. check watchers first).
		551	Signals and child watchers are implemented as I/O watchers, and will
		552	be handled here by queueing them when their watcher gets executed.
		553	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		554	were used, return, otherwise continue with step *.
		555
		556	</pre>
		557	<p>Example: Queue some jobs and then loop until no events are outsanding
		558	anymore.</p>
		559	<pre> ... queue jobs here, make sure they register event watchers as long
		560	... as they still have work to do (even an idle watcher will do..)
		561	ev_loop (my_loop, 0);
		562	... jobs done. yeah!
		563
		564	</pre>
269	</dd>	565	</dd>
270	<dt>ev_unloop (loop, how)</dt>	566	<dt>ev_unloop (loop, how)</dt>
271	<dd>	567	<dd>
272	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it	568	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273	has processed all outstanding events). The <code>how</code> argument must be either	569	has processed all outstanding events). The <code>how</code> argument must be either
274	<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or	570	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
275	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>	571	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276	</dd>	572	</dd>
277	<dt>ev_ref (loop)</dt>	573	<dt>ev_ref (loop)</dt>
278	<dt>ev_unref (loop)</dt>	574	<dt>ev_unref (loop)</dt>
279	<dd>	575	<dd>
…		…
285	example, libev itself uses this for its internal signal pipe: It is not	581	example, libev itself uses this for its internal signal pipe: It is not
286	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	582	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
287	no event watchers registered by it are active. It is also an excellent	583	no event watchers registered by it are active. It is also an excellent
288	way to do this for generic recurring timers or from within third-party	584	way to do this for generic recurring timers or from within third-party
289	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	585	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		586	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		587	running when nothing else is active.</p>
		588	<pre> struct ev_signal exitsig;
		589	ev_signal_init (&exitsig, sig_cb, SIGINT);
		590	ev_signal_start (loop, &exitsig);
		591	evf_unref (loop);
		592
		593	</pre>
		594	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		595	<pre> ev_ref (loop);
		596	ev_signal_stop (loop, &exitsig);
		597
		598	</pre>
290	</dd>	599	</dd>
291	</dl>	600	</dl>
292		601
		602
		603
		604
		605
293	</div>	606	</div>
294	<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>
295	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	608	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
296	<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
297	interest in some event. For instance, if you want to wait for STDIN to	610	interest in some event. For instance, if you want to wait for STDIN to
298	become readable, you would create an <code>ev_io</code> watcher for that:</p>	611	become readable, you would create an <code>ev_io</code> watcher for that:</p>
299	<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)
…		…
326	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	639	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
327	*)</code>), and you can stop watching for events at any time by calling the	640	*)</code>), and you can stop watching for events at any time by calling the
328	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	641	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
329	<p>As long as your watcher is active (has been started but not stopped) you	642	<p>As long as your watcher is active (has been started but not stopped) you
330	must not touch the values stored in it. Most specifically you must never	643	must not touch the values stored in it. Most specifically you must never
331	reinitialise it or call its set method.</p>	644	reinitialise it or call its <code>set</code> macro.</p>
332	<p>You can check whether an event is active by calling the <code>ev_is_active
333	(watcher *)</code> macro. To see whether an event is outstanding (but the
334	callback for it has not been called yet) you can use the <code>ev_is_pending
335	(watcher *)</code> macro.</p>
336	<p>Each and every callback receives the event loop pointer as first, the	645	<p>Each and every callback receives the event loop pointer as first, the
337	registered watcher structure as second, and a bitset of received events as	646	registered watcher structure as second, and a bitset of received events as
338	third argument.</p>	647	third argument.</p>
339	<p>The received events usually include a single bit per event type received	648	<p>The received events usually include a single bit per event type received
340	(you can receive multiple events at the same time). The possible bit masks	649	(you can receive multiple events at the same time). The possible bit masks
…		…
360	</dd>	669	</dd>
361	<dt><code>EV_CHILD</code></dt>	670	<dt><code>EV_CHILD</code></dt>
362	<dd>	671	<dd>
363	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>	672	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
364	</dd>	673	</dd>
		674	<dt><code>EV_STAT</code></dt>
		675	<dd>
		676	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		677	</dd>
365	<dt><code>EV_IDLE</code></dt>	678	<dt><code>EV_IDLE</code></dt>
366	<dd>	679	<dd>
367	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>	680	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
368	</dd>	681	</dd>
369	<dt><code>EV_PREPARE</code></dt>	682	<dt><code>EV_PREPARE</code></dt>
…		…
374	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	687	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
375	received events. Callbacks of both watcher types can start and stop as	688	received events. Callbacks of both watcher types can start and stop as
376	many watchers as they want, and all of them will be taken into account	689	many watchers as they want, and all of them will be taken into account
377	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep	690	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
378	<code>ev_loop</code> from blocking).</p>	691	<code>ev_loop</code> from blocking).</p>
		692	</dd>
		693	<dt><code>EV_EMBED</code></dt>
		694	<dd>
		695	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		696	</dd>
		697	<dt><code>EV_FORK</code></dt>
		698	<dd>
		699	<p>The event loop has been resumed in the child process after fork (see
		700	<code>ev_fork</code>).</p>
379	</dd>	701	</dd>
380	<dt><code>EV_ERROR</code></dt>	702	<dt><code>EV_ERROR</code></dt>
381	<dd>	703	<dd>
382	<p>An unspecified error has occured, the watcher has been stopped. This might	704	<p>An unspecified error has occured, the watcher has been stopped. This might
383	happen because the watcher could not be properly started because libev	705	happen because the watcher could not be properly started because libev
…		…
391	programs, though, so beware.</p>	713	programs, though, so beware.</p>
392	</dd>	714	</dd>
393	</dl>	715	</dl>
394		716
395	</div>	717	</div>
		718	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		719	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		720	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		721	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		722	<dl>
		723	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		724	<dd>
		725	<p>This macro initialises the generic portion of a watcher. The contents
		726	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		727	the generic parts of the watcher are initialised, you <i>need</i> to call
		728	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		729	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		730	which rolls both calls into one.</p>
		731	<p>You can reinitialise a watcher at any time as long as it has been stopped
		732	(or never started) and there are no pending events outstanding.</p>
		733	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		734	int revents)</code>.</p>
		735	</dd>
		736	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		737	<dd>
		738	<p>This macro initialises the type-specific parts of a watcher. You need to
		739	call <code>ev_init</code> at least once before you call this macro, but you can
		740	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		741	macro on a watcher that is active (it can be pending, however, which is a
		742	difference to the <code>ev_init</code> macro).</p>
		743	<p>Although some watcher types do not have type-specific arguments
		744	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		745	</dd>
		746	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		747	<dd>
		748	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		749	calls into a single call. This is the most convinient method to initialise
		750	a watcher. The same limitations apply, of course.</p>
		751	</dd>
		752	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		753	<dd>
		754	<p>Starts (activates) the given watcher. Only active watchers will receive
		755	events. If the watcher is already active nothing will happen.</p>
		756	</dd>
		757	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		758	<dd>
		759	<p>Stops the given watcher again (if active) and clears the pending
		760	status. It is possible that stopped watchers are pending (for example,
		761	non-repeating timers are being stopped when they become pending), but
		762	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		763	you want to free or reuse the memory used by the watcher it is therefore a
		764	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		765	</dd>
		766	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		767	<dd>
		768	<p>Returns a true value iff the watcher is active (i.e. it has been started
		769	and not yet been stopped). As long as a watcher is active you must not modify
		770	it.</p>
		771	</dd>
		772	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		773	<dd>
		774	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		775	events but its callback has not yet been invoked). As long as a watcher
		776	is pending (but not active) you must not call an init function on it (but
		777	<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
		778	make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
		779	it).</p>
		780	</dd>
		781	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		782	<dd>
		783	<p>Returns the callback currently set on the watcher.</p>
		784	</dd>
		785	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		786	<dd>
		787	<p>Change the callback. You can change the callback at virtually any time
		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
		794	integer 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
		796	before watchers with lower priority, but priority will not keep watchers
		797	from being executed (except for <code>ev_idle</code> watchers).</p>
		798	<p>This means that priorities are <i>only</i> used for ordering callback
		799	invocation after new events have been received. This is useful, for
		800	example, to reduce latency after idling, or more often, to bind two
		801	watchers 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
		803	you 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
		805	pending.</p>
		806	<p>The default priority used by watchers when no priority has been set is
		807	always <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
		809	fine, as long as you do not mind that the priority value you query might
		810	or 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
		816	can 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
		821	and returns its <code>revents</code> bitset (as if its callback was invoked). If the
		822	watcher isn't pending it does nothing and returns <code>0</code>.</p>
		823	</dd>
		824	</dl>
		825
		826
		827
		828
		829
		830	</div>
396	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	831	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
397	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	832	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
398	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	833	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
399	and read at any time, libev will completely ignore it. This can be used	834	and read at any time, libev will completely ignore it. This can be used
400	to associate arbitrary data with your watcher. If you need more data and	835	to associate arbitrary data with your watcher. If you need more data and
…		…
417	struct my_io w = (struct my_io )w_;	852	struct my_io w = (struct my_io )w_;
418	...	853	...
419	}	854	}
420		855
421	</pre>	856	</pre>
422	<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
423	have been omitted....</p>	858	instead have been omitted.</p>
		859	<p>Another common scenario is having some data structure with multiple
		860	watchers:</p>
		861	<pre> struct my_biggy
		862	{
		863	int some_data;
		864	ev_timer t1;
		865	ev_timer t2;
		866	}
424		867
		868	</pre>
		869	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		870	you need to use <code>offsetof</code>:</p>
		871	<pre> #include <stddef.h>
425		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	}
426		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	}
427		886
428		887
		888
		889
		890	</pre>
		891
429	</div>	892	</div>
430	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	893	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
431	<div id="WATCHER_TYPES_CONTENT">	894	<div id="WATCHER_TYPES_CONTENT">
432	<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
433	information given in the last section.</p>	896	information given in the last section. Any initialisation/set macros,
		897	functions and members specific to the watcher type are explained.</p>
		898	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		899	while the watcher is active, you can look at the member and expect some
		900	sensible content, but you must not modify it (you can modify it while the
		901	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		902	means you can expect it to have some sensible content while the watcher
		903	is active, but you can also modify it. Modifying it may not do something
		904	sensible or take immediate effect (or do anything at all), but libev will
		905	not crash or malfunction in any way.</p>
434		906
		907
		908
		909
		910
435	</div>	911	</div>
436	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	912	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
437	<div id="code_ev_io_code_is_this_file_descrip-2">	913	<div id="code_ev_io_code_is_this_file_descrip-2">
438	<p>I/O watchers check whether a file descriptor is readable or writable	914	<p>I/O watchers check whether a file descriptor is readable or writable
439	in each iteration of the event loop (This behaviour is called	915	in each iteration of the event loop, or, more precisely, when reading
440	level-triggering because you keep receiving events as long as the	916	would not block the process and writing would at least be able to write
441	condition persists. Remember you can stop the watcher if you don't want to	917	some data. This behaviour is called level-triggering because you keep
442	act on the event and neither want to receive future events).</p>	918	receiving events as long as the condition persists. Remember you can stop
		919	the watcher if you don't want to act on the event and neither want to
		920	receive future events.</p>
443	<p>In general you can register as many read and/or write event watchers oer	921	<p>In general you can register as many read and/or write event watchers per
444	fd as you want (as long as you don't confuse yourself). Setting all file	922	fd as you want (as long as you don't confuse yourself). Setting all file
445	descriptors to non-blocking mode is also usually a good idea (but not	923	descriptors to non-blocking mode is also usually a good idea (but not
446	required if you know what you are doing).</p>	924	required if you know what you are doing).</p>
447	<p>You have to be careful with dup'ed file descriptors, though. Some backends	925	<p>You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file	926	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing	927	descriptors correctly if you register interest in two or more fds pointing
450	to the same file/socket etc. description.</p>	928	to the same underlying file/socket/etc. description (that is, they share
		929	the same underlying "file open").</p>
451	<p>If you must do this, then force the use of a known-to-be-good backend	930	<p>If you must do this, then force the use of a known-to-be-good backend
452	(at the time of this writing, this includes only EVMETHOD_SELECT and	931	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453	EVMETHOD_POLL).</p>	932	<code>EVBACKEND_POLL</code>).</p>
		933	<p>Another thing you have to watch out for is that it is quite easy to
		934	receive "spurious" readyness notifications, that is your callback might
		935	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		936	because there is no data. Not only are some backends known to create a
		937	lot of those (for example solaris ports), it is very easy to get into
		938	this situation even with a relatively standard program structure. Thus
		939	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		940	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		941	<p>If you cannot run the fd in non-blocking mode (for example you should not
		942	play around with an Xlib connection), then you have to seperately re-test
		943	whether a file descriptor is really ready with a known-to-be good interface
		944	such as poll (fortunately in our Xlib example, Xlib already does this on
		945	its own, so its quite safe to use).</p>
454	<dl>	946	<dl>
455	<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>
456	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	948	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
457	<dd>	949	<dd>
458	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	950	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
459	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	951	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
460	EV_WRITE</code> to receive the given events.</p>	952	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		953	</dd>
		954	<dt>int fd [read-only]</dt>
		955	<dd>
		956	<p>The file descriptor being watched.</p>
		957	</dd>
		958	<dt>int events [read-only]</dt>
		959	<dd>
		960	<p>The events being watched.</p>
461	</dd>	961	</dd>
462	</dl>	962	</dl>
		963	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		964	readable, but only once. Since it is likely line-buffered, you could
		965	attempt to read a whole line in the callback.</p>
		966	<pre> static void
		967	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		968	{
		969	ev_io_stop (loop, w);
		970	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		971	}
463		972
		973	...
		974	struct ev_loop *loop = ev_default_init (0);
		975	struct ev_io stdin_readable;
		976	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		977	ev_io_start (loop, &stdin_readable);
		978	ev_loop (loop, 0);
		979
		980
		981
		982
		983	</pre>
		984
464	</div>	985	</div>
465	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	986	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
466	<div id="code_ev_timer_code_relative_and_opti-2">	987	<div id="code_ev_timer_code_relative_and_opti-2">
467	<p>Timer watchers are simple relative timers that generate an event after a	988	<p>Timer watchers are simple relative timers that generate an event after a
468	given time, and optionally repeating in regular intervals after that.</p>	989	given time, and optionally repeating in regular intervals after that.</p>
469	<p>The timers are based on real time, that is, if you register an event that	990	<p>The timers are based on real time, that is, if you register an event that
470	times out after an hour and youreset your system clock to last years	991	times out after an hour and you reset your system clock to last years
471	time, it will still time out after (roughly) and hour. "Roughly" because	992	time, it will still time out after (roughly) and hour. "Roughly" because
472	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	993	detecting time jumps is hard, and some inaccuracies are unavoidable (the
473	monotonic clock option helps a lot here).</p>	994	monotonic clock option helps a lot here).</p>
474	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>	995	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475	time. This is usually the right thing as this timestamp refers to the time	996	time. This is usually the right thing as this timestamp refers to the time
476	of the event triggering whatever timeout you are modifying/starting. If	997	of the event triggering whatever timeout you are modifying/starting. If
477	you suspect event processing to be delayed and you need to base the timeout	998	you suspect event processing to be delayed and you <i>need</i> to base the timeout
478	ion the current time, use something like this to adjust for this:</p>	999	on the current time, use something like this to adjust for this:</p>
479	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1000	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
480		1001
481	</pre>	1002	</pre>
		1003	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		1004	but if multiple timers become ready during the same loop iteration then
		1005	order of execution is undefined.</p>
482	<dl>	1006	<dl>
483	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	1007	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
484	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	1008	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485	<dd>	1009	<dd>
486	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	1010	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
488	timer will automatically be configured to trigger again <code>repeat</code> seconds	1012	timer will automatically be configured to trigger again <code>repeat</code> seconds
489	later, again, and again, until stopped manually.</p>	1013	later, again, and again, until stopped manually.</p>
490	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	1014	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
491	configure a timer to trigger every 10 seconds, then it will trigger at	1015	configure a timer to trigger every 10 seconds, then it will trigger at
492	exactly 10 second intervals. If, however, your program cannot keep up with	1016	exactly 10 second intervals. If, however, your program cannot keep up with
493	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1017	the timer (because it takes longer than those 10 seconds to do stuff) the
494	timer will not fire more than once per event loop iteration.</p>	1018	timer will not fire more than once per event loop iteration.</p>
495	</dd>	1019	</dd>
496	<dt>ev_timer_again (loop)</dt>	1020	<dt>ev_timer_again (loop)</dt>
497	<dd>	1021	<dd>
498	<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
499	repeating. The exact semantics are:</p>	1023	repeating. The exact semantics are:</p>
		1024	<p>If the timer is pending, its pending status is cleared.</p>
500	<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>
501	<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
502	value), 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>
503	<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
504	example: Imagine you have a tcp connection and you want a so-called idle	1029	example: Imagine you have a tcp connection and you want a so-called idle
505	timeout, that is, you want to be called when there have been, say, 60	1030	timeout, that is, you want to be called when there have been, say, 60
506	seconds of inactivity on the socket. The easiest way to do this is to	1031	seconds of inactivity on the socket. The easiest way to do this is to
507	configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each	1032	configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
508	time you successfully read or write some data. If you go into an idle	1033	<code>ev_timer_again</code> each time you successfully read or write some data. If
509	state where you do not expect data to travel on the socket, you can stop	1034	you go into an idle state where you do not expect data to travel on the
		1035	socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
510	the timer, and again will automatically restart it if need be.</p>	1036	automatically restart it if need be.</p>
		1037	<p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
		1038	altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
		1039	<pre> ev_timer_init (timer, callback, 0., 5.);
		1040	ev_timer_again (loop, timer);
		1041	...
		1042	timer->again = 17.;
		1043	ev_timer_again (loop, timer);
		1044	...
		1045	timer->again = 10.;
		1046	ev_timer_again (loop, timer);
		1047
		1048	</pre>
		1049	<p>This is more slightly efficient then stopping/starting the timer each time
		1050	you want to modify its timeout value.</p>
		1051	</dd>
		1052	<dt>ev_tstamp repeat [read-write]</dt>
		1053	<dd>
		1054	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		1055	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		1056	which is also when any modifications are taken into account.</p>
511	</dd>	1057	</dd>
512	</dl>	1058	</dl>
		1059	<p>Example: Create a timer that fires after 60 seconds.</p>
		1060	<pre> static void
		1061	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1062	{
		1063	.. one minute over, w is actually stopped right here
		1064	}
513		1065
		1066	struct ev_timer mytimer;
		1067	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1068	ev_timer_start (loop, &mytimer);
		1069
		1070	</pre>
		1071	<p>Example: Create a timeout timer that times out after 10 seconds of
		1072	inactivity.</p>
		1073	<pre> static void
		1074	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1075	{
		1076	.. ten seconds without any activity
		1077	}
		1078
		1079	struct ev_timer mytimer;
		1080	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1081	ev_timer_again (&mytimer); /* start timer */
		1082	ev_loop (loop, 0);
		1083
		1084	// and in some piece of code that gets executed on any "activity":
		1085	// reset the timeout to start ticking again at 10 seconds
		1086	ev_timer_again (&mytimer);
		1087
		1088
		1089
		1090
		1091	</pre>
		1092
514	</div>	1093	</div>
515	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	1094	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
516	<div id="code_ev_periodic_code_to_cron_or_not-2">	1095	<div id="code_ev_periodic_code_to_cron_or_not-2">
517	<p>Periodic watchers are also timers of a kind, but they are very versatile	1096	<p>Periodic watchers are also timers of a kind, but they are very versatile
518	(and unfortunately a bit complex).</p>	1097	(and unfortunately a bit complex).</p>
519	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)	1098	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
520	but on wallclock time (absolute time). You can tell a periodic watcher	1099	but on wallclock time (absolute time). You can tell a periodic watcher
521	to trigger "at" some specific point in time. For example, if you tell a	1100	to trigger "at" some specific point in time. For example, if you tell a
522	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1101	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
523	+ 10.>) 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
524	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger	1103	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525	roughly 10 seconds later and of course not if you reset your system time	1104	roughly 10 seconds later).</p>
526	again).</p>
527	<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
528	triggering an event on eahc midnight, local time.</p>	1106	triggering an event on each midnight, local time or other, complicated,
		1107	rules.</p>
		1108	<p>As with timers, the callback is guarenteed to be invoked only when the
		1109	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1110	during the same loop iteration then order of execution is undefined.</p>
529	<dl>	1111	<dl>
530	<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>
531	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	1113	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532	<dd>	1114	<dd>
533	<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
534	operation, and we will explain them from simplest to complex:</p>	1116	operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539	<p>	1117	<p>
540	<dl>	1118	<dl>
541	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1119	<dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
542	<dd>	1120	<dd>
543	<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
544	<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,
545	that is, if it is to be run at January 1st 2011 then it will run when the	1123	that is, if it is to be run at January 1st 2011 then it will run when the
546	system time reaches or surpasses this time.</p>	1124	system time reaches or surpasses this time.</p>
547	</dd>	1125	</dd>
548	<dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt>	1126	<dt>* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)</dt>
549	<dd>	1127	<dd>
550	<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
551	<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)
552	of any time jumps.</p>	1130	and then repeat, regardless of any time jumps.</p>
553	<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
554	time:</p>	1132	time:</p>
555	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	1133	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
556		1134
557	</pre>	1135	</pre>
…		…
560	full hour (UTC), or more correctly, when the system time is evenly divisible	1138	full hour (UTC), or more correctly, when the system time is evenly divisible
561	by 3600.</p>	1139	by 3600.</p>
562	<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
563	<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
564	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	1142	time 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
		1145	this value.</p>
565	</dd>	1146	</dd>
566	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	1147	<dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
567	<dd>	1148	<dd>
568	<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
569	ignored. Instead, each time the periodic watcher gets scheduled, the	1150	ignored. Instead, each time the periodic watcher gets scheduled, the
570	reschedule callback will be called with the watcher as first, and the	1151	reschedule callback will be called with the watcher as first, and the
571	current time as second argument.</p>	1152	current time as second argument.</p>
572	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1153	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573	periodic watcher, ever, or make any event loop modifications</i>. If you need	1154	ever, or make any event loop modifications</i>. If you need to stop it,
574	to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p>	1155	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
575	<p>Also, <i>this callback must always return a time that is later than the	1156	starting an <code>ev_prepare</code> watcher, which is legal).</p>
576	passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577	<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,
578	ev_tstamp now)</code>, e.g.:</p>	1158	ev_tstamp now)</code>, e.g.:</p>
579	<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)
580	{	1160	{
581	return now + 60.;	1161	return now + 60.;
…		…
584	</pre>	1164	</pre>
585	<p>It must return the next time to trigger, based on the passed time value	1165	<p>It must return the next time to trigger, based on the passed time value
586	(that is, the lowest time value larger than to the second argument). It	1166	(that is, the lowest time value larger than to the second argument). It
587	will usually be called just before the callback will be triggered, but	1167	will usually be called just before the callback will be triggered, but
588	might be called at other times, too.</p>	1168	might be called at other times, too.</p>
		1169	<p>NOTE: <i>This callback must always return a time that is later than the
		1170	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
589	<p>This can be used to create very complex timers, such as a timer that	1171	<p>This can be used to create very complex timers, such as a timer that
590	triggers on each midnight, local time. To do this, you would calculate the	1172	triggers on each midnight, local time. To do this, you would calculate the
591	next midnight after <code>now</code> and return the timestamp value for this. How you do this	1173	next midnight after <code>now</code> and return the timestamp value for this. How
592	is, again, up to you (but it is not trivial).</p>	1174	you do this is, again, up to you (but it is not trivial, which is the main
		1175	reason I omitted it as an example).</p>
593	</dd>	1176	</dd>
594	</dl>	1177	</dl>
595	</p>	1178	</p>
596	</dd>	1179	</dd>
597	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1180	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
599	<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
600	when you changed some parameters or the reschedule callback would return	1183	when you changed some parameters or the reschedule callback would return
601	a different time than the last time it was called (e.g. in a crond like	1184	a different time than the last time it was called (e.g. in a crond like
602	program when the crontabs have changed).</p>	1185	program when the crontabs have changed).</p>
603	</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
		1190	absolute 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
		1192	timer fires or <code>ev_periodic_again</code> is being called.</p>
		1193	</dd>
		1194	<dt>ev_tstamp interval [read-write]</dt>
		1195	<dd>
		1196	<p>The current interval value. Can be modified any time, but changes only
		1197	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1198	called.</p>
		1199	</dd>
		1200	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1201	<dd>
		1202	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1203	switched off. Can be changed any time, but changes only take effect when
		1204	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1205	</dd>
604	</dl>	1206	</dl>
		1207	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1208	system clock is divisible by 3600. The callback invocation times have
		1209	potentially a lot of jittering, but good long-term stability.</p>
		1210	<pre> static void
		1211	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1212	{
		1213	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1214	}
605		1215
		1216	struct ev_periodic hourly_tick;
		1217	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1218	ev_periodic_start (loop, &hourly_tick);
		1219
		1220	</pre>
		1221	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1222	<pre> #include <math.h>
		1223
		1224	static ev_tstamp
		1225	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1226	{
		1227	return fmod (now, 3600.) + 3600.;
		1228	}
		1229
		1230	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1231
		1232	</pre>
		1233	<p>Example: Call a callback every hour, starting now:</p>
		1234	<pre> struct ev_periodic hourly_tick;
		1235	ev_periodic_init (&hourly_tick, clock_cb,
		1236	fmod (ev_now (loop), 3600.), 3600., 0);
		1237	ev_periodic_start (loop, &hourly_tick);
		1238
		1239
		1240
		1241
		1242	</pre>
		1243
606	</div>	1244	</div>
607	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	1245	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
608	<div id="code_ev_signal_code_signal_me_when_a-2">	1246	<div id="code_ev_signal_code_signal_me_when_a-2">
609	<p>Signal watchers will trigger an event when the process receives a specific	1247	<p>Signal watchers will trigger an event when the process receives a specific
610	signal one or more times. Even though signals are very asynchronous, libev	1248	signal one or more times. Even though signals are very asynchronous, libev
611	will try it's best to deliver signals synchronously, i.e. as part of the	1249	will try it's best to deliver signals synchronously, i.e. as part of the
612	normal event processing, like any other event.</p>	1250	normal event processing, like any other event.</p>
…		…
621	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1259	<dt>ev_signal_set (ev_signal *, int signum)</dt>
622	<dd>	1260	<dd>
623	<p>Configures the watcher to trigger on the given signal number (usually one	1261	<p>Configures the watcher to trigger on the given signal number (usually one
624	of the <code>SIGxxx</code> constants).</p>	1262	of the <code>SIGxxx</code> constants).</p>
625	</dd>	1263	</dd>
		1264	<dt>int signum [read-only]</dt>
		1265	<dd>
		1266	<p>The signal the watcher watches out for.</p>
		1267	</dd>
626	</dl>	1268	</dl>
627		1269
		1270
		1271
		1272
		1273
628	</div>	1274	</div>
629	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	1275	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
630	<div id="code_ev_child_code_wait_for_pid_stat-2">	1276	<div id="code_ev_child_code_watch_out_for_pro-2">
631	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1277	<p>Child watchers trigger when your process receives a SIGCHLD in response to
632	some child status changes (most typically when a child of yours dies).</p>	1278	some child status changes (most typically when a child of yours dies).</p>
633	<dl>	1279	<dl>
634	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1280	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
635	<dt>ev_child_set (ev_child *, int pid)</dt>	1281	<dt>ev_child_set (ev_child *, int pid)</dt>
…		…
639	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1285	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
640	the status word (use the macros from <code>sys/wait.h</code> and see your systems	1286	the 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	1287	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642	process causing the status change.</p>	1288	process causing the status change.</p>
643	</dd>	1289	</dd>
		1290	<dt>int pid [read-only]</dt>
		1291	<dd>
		1292	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1293	</dd>
		1294	<dt>int rpid [read-write]</dt>
		1295	<dd>
		1296	<p>The process id that detected a status change.</p>
		1297	</dd>
		1298	<dt>int rstatus [read-write]</dt>
		1299	<dd>
		1300	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1301	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
		1302	</dd>
644	</dl>	1303	</dl>
		1304	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1305	<pre> static void
		1306	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1307	{
		1308	ev_unloop (loop, EVUNLOOP_ALL);
		1309	}
645		1310
		1311	struct ev_signal signal_watcher;
		1312	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1313	ev_signal_start (loop, &sigint_cb);
		1314
		1315
		1316
		1317
		1318	</pre>
		1319
646	</div>	1320	</div>
		1321	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1322	<div id="code_ev_stat_code_did_the_file_attri-2">
		1323	<p>This watches a filesystem path for attribute changes. That is, it calls
		1324	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1325	compared to the last time, invoking the callback if it did.</p>
		1326	<p>The path does not need to exist: changing from "path exists" to "path does
		1327	not exist" is a status change like any other. The condition "path does
		1328	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1329	otherwise always forced to be at least one) and all the other fields of
		1330	the 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
		1332	relative and your working directory changes, the behaviour is undefined.</p>
		1333	<p>Since there is no standard to do this, the portable implementation simply
		1334	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1335	can specify a recommended polling interval for this case. If you specify
		1336	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1337	unspecified default</i> value will be used (which you can expect to be around
		1338	five seconds, although this might change dynamically). Libev will also
		1339	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1340	usually overkill.</p>
		1341	<p>This watcher type is not meant for massive numbers of stat watchers,
		1342	as even with OS-supported change notifications, this can be
		1343	resource-intensive.</p>
		1344	<p>At the time of this writing, only the Linux inotify interface is
		1345	implemented (implementing kqueue support is left as an exercise for the
		1346	reader). Inotify will be used to give hints only and should not change the
		1347	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1348	to fall back to regular polling again even with inotify, but changes are
		1349	usually detected immediately, and if the file exists there will be no
		1350	polling.</p>
		1351	<dl>
		1352	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1353	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1354	<dd>
		1355	<p>Configures the watcher to wait for status changes of the given
		1356	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1357	be detected and should normally be specified as <code>0</code> to let libev choose
		1358	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1359	path for as long as the watcher is active.</p>
		1360	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1361	relative to the attributes at the time the watcher was started (or the
		1362	last change was detected).</p>
		1363	</dd>
		1364	<dt>ev_stat_stat (ev_stat *)</dt>
		1365	<dd>
		1366	<p>Updates the stat buffer immediately with new values. If you change the
		1367	watched path in your callback, you could call this fucntion to avoid
		1368	detecting this change (while introducing a race condition). Can also be
		1369	useful simply to find out the new values.</p>
		1370	</dd>
		1371	<dt>ev_statdata attr [read-only]</dt>
		1372	<dd>
		1373	<p>The most-recently detected attributes of the file. Although the type is of
		1374	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1375	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1376	was some error while <code>stat</code>ing the file.</p>
		1377	</dd>
		1378	<dt>ev_statdata prev [read-only]</dt>
		1379	<dd>
		1380	<p>The previous attributes of the file. The callback gets invoked whenever
		1381	<code>prev</code> != <code>attr</code>.</p>
		1382	</dd>
		1383	<dt>ev_tstamp interval [read-only]</dt>
		1384	<dd>
		1385	<p>The specified interval.</p>
		1386	</dd>
		1387	<dt>const char *path [read-only]</dt>
		1388	<dd>
		1389	<p>The filesystem path that is being watched.</p>
		1390	</dd>
		1391	</dl>
		1392	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1393	<pre> static void
		1394	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1395	{
		1396	/* /etc/passwd changed in some way */
		1397	if (w->attr.st_nlink)
		1398	{
		1399	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1400	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1401	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1402	}
		1403	else
		1404	/* you shalt not abuse printf for puts */
		1405	puts ("wow, /etc/passwd is not there, expect problems. "
		1406	"if this is windows, they already arrived\n");
		1407	}
		1408
		1409	...
		1410	ev_stat passwd;
		1411
		1412	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1413	ev_stat_start (loop, &passwd);
		1414
		1415
		1416
		1417
		1418	</pre>
		1419
		1420	</div>
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>	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>
648	<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">
649	<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
650	(prepare, check and other idle watchers do not count). That is, as long	1424	priority are pending (prepare, check and other idle watchers do not
651	as your process is busy handling sockets or timeouts (or even signals,	1425	count).</p>
652	imagine) 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
653	watchers 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
		1428	triggered. But when your process is idle (or only lower-priority watchers
		1429	are pending), the idle watchers are being called once per event loop
654	until stopped, that is, or your process receives more events and becomes	1430	iteration - until stopped, that is, or your process receives more events
655	busy.</p>	1431	and becomes busy again with higher priority stuff.</p>
656	<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
657	active, the process will not block when waiting for new events.</p>	1433	active, the process will not block when waiting for new events.</p>
658	<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
659	effect on its own sometimes), idle watchers are a good place to do	1435	effect on its own sometimes), idle watchers are a good place to do
660	"pseudo-background processing", or delay processing stuff to after the	1436	"pseudo-background processing", or delay processing stuff to after the
…		…
665	<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
666	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1442	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667	believe me.</p>	1443	believe me.</p>
668	</dd>	1444	</dd>
669	</dl>	1445	</dl>
		1446	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1447	callback, free it. Also, use no error checking, as usual.</p>
		1448	<pre> static void
		1449	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1450	{
		1451	free (w);
		1452	// now do something you wanted to do when the program has
		1453	// no longer asnything immediate to do.
		1454	}
670		1455
		1456	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1457	ev_idle_init (idle_watcher, idle_cb);
		1458	ev_idle_start (loop, idle_cb);
		1459
		1460
		1461
		1462
		1463	</pre>
		1464
671	</div>	1465	</div>
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>	1466	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
673	<div id="code_ev_prepare_code_and_code_ev_che-2">	1467	<div id="code_ev_prepare_code_and_code_ev_che-2">
674	<p>Prepare and check watchers are usually (but not always) used in tandem:	1468	<p>Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	1469	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.</p>	1470	afterwards.</p>
		1471	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1472	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1473	watchers. Other loops than the current one are fine, however. The
		1474	rationale behind this is that you do not need to check for recursion in
		1475	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1476	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1477	called in pairs bracketing the blocking call.</p>
677	<p>Their main purpose is to integrate other event mechanisms into libev. This	1478	<p>Their main purpose is to integrate other event mechanisms into libev and
678	could be used, for example, to track variable changes, implement your own	1479	their use is somewhat advanced. This could be used, for example, to track
679	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1480	variable changes, implement your own watchers, integrate net-snmp or a
		1481	coroutine library and lots more. They are also occasionally useful if
		1482	you cache some data and want to flush it before blocking (for example,
		1483	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1484	watcher).</p>
680	<p>This is done by examining in each prepare call which file descriptors need	1485	<p>This is done by examining in each prepare call which file descriptors need
681	to be watched by the other library, registering <code>ev_io</code> watchers for	1486	to be watched by the other library, registering <code>ev_io</code> watchers for
682	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1487	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683	provide just this functionality). Then, in the check watcher you check for	1488	provide just this functionality). Then, in the check watcher you check for
684	any events that occured (by checking the pending status of all watchers	1489	any events that occured (by checking the pending status of all watchers
685	and stopping them) and call back into the library. The I/O and timer	1490	and stopping them) and call back into the library. The I/O and timer
686	callbacks will never actually be called (but must be valid neverthelles,	1491	callbacks will never actually be called (but must be valid nevertheless,
687	because you never know, you know?).</p>	1492	because you never know, you know?).</p>
688	<p>As another example, the Perl Coro module uses these hooks to integrate	1493	<p>As another example, the Perl Coro module uses these hooks to integrate
689	coroutines into libev programs, by yielding to other active coroutines	1494	coroutines into libev programs, by yielding to other active coroutines
690	during each prepare and only letting the process block if no coroutines	1495	during each prepare and only letting the process block if no coroutines
691	are ready to run (its actually more complicated, it only runs coroutines	1496	are ready to run (it's actually more complicated: it only runs coroutines
692	with priority higher than the event loop and one lower priority once,	1497	with priority higher than or equal to the event loop and one coroutine
693	using idle watchers to keep the event loop from blocking if lower-priority	1498	of lower priority, but only once, using idle watchers to keep the event
694	coroutines exist, thus mapping low-priority coroutines to idle/background	1499	loop from blocking if lower-priority coroutines are active, thus mapping
695	tasks).</p>	1500	low-priority coroutines to idle/background tasks).</p>
		1501	<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
		1502	priority, to ensure that they are being run before any other watchers
		1503	after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
		1504	too) should not activate ("feed") events into libev. While libev fully
		1505	supports this, they will be called before other <code>ev_check</code> watchers did
		1506	their job. As <code>ev_check</code> watchers are often used to embed other event
		1507	loops 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
		1509	others).</p>
696	<dl>	1510	<dl>
697	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1511	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
698	<dt>ev_check_init (ev_check *, callback)</dt>	1512	<dt>ev_check_init (ev_check *, callback)</dt>
699	<dd>	1513	<dd>
700	<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
701	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1515	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
702	macros, but using them is utterly, utterly and completely pointless.</p>	1516	macros, but using them is utterly, utterly and completely pointless.</p>
703	</dd>	1517	</dd>
704	</dl>	1518	</dl>
		1519	<p>There are a number of principal ways to embed other event loops or modules
		1520	into 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
		1522	use for an actually working example. Another Perl module named <code>EV::Glib</code>
		1523	embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
		1524	into the Glib event loop).</p>
		1525	<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1526	and in a check watcher, destroy them and call into libadns. What follows
		1527	is pseudo-code only of course. This requires you to either use a low
		1528	priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
		1529	the callbacks for the IO/timeout watchers might not have been called yet.</p>
		1530	<pre> static ev_io iow [nfd];
		1531	static ev_timer tw;
705		1532
		1533	static void
		1534	io_cb (ev_loop loop, ev_io w, int revents)
		1535	{
		1536	}
		1537
		1538	// create io watchers for each fd and a timer before blocking
		1539	static void
		1540	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1541	{
		1542	int timeout = 3600000;
		1543	struct pollfd fds [nfd];
		1544	// actual code will need to loop here and realloc etc.
		1545	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1546
		1547	/* the callback is illegal, but won't be called as we stop during check */
		1548	ev_timer_init (&tw, 0, timeout * 1e-3);
		1549	ev_timer_start (loop, &tw);
		1550
		1551	// create one ev_io per pollfd
		1552	for (int i = 0; i < nfd; ++i)
		1553	{
		1554	ev_io_init (iow + i, io_cb, fds [i].fd,
		1555	((fds [i].events & POLLIN ? EV_READ : 0)
		1556	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1557
		1558	fds [i].revents = 0;
		1559	ev_io_start (loop, iow + i);
		1560	}
		1561	}
		1562
		1563	// stop all watchers after blocking
		1564	static void
		1565	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1566	{
		1567	ev_timer_stop (loop, &tw);
		1568
		1569	for (int i = 0; i < 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 & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1576	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1577
		1578	// now stop the watcher
		1579	ev_io_stop (loop, iow + i);
		1580	}
		1581
		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>
		1587	in the prepare watcher and would dispose of the check watcher.</p>
		1588	<p>Method 3: If the module to be embedded supports explicit event
		1589	notification (adns does), you can also make use of the actual watcher
		1590	callbacks, 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->data;
		1595	update_now (EV_A);
		1596
		1597	adns_processtimeouts (ads, &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->data;
		1604	update_now (EV_A);
		1605
		1606	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1607	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &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
		1614	want to embed is too inflexible to support it. Instead, youc na override
		1615	their poll function. The drawback with this solution is that the main
		1616	loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
		1617	this.</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 < nfds; ++n)
		1624	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1625
		1626	if (timeout >= 0)
		1627	// create/start timer
		1628
		1629	// poll
		1630	ev_loop (EV_A_ 0);
		1631
		1632	// stop timer again
		1633	if (timeout >= 0)
		1634	ev_timer_stop (EV_A_ &to);
		1635
		1636	// stop io watchers again - their callbacks should have set
		1637	for (n = 0; n < nfds; ++n)
		1638	ev_io_stop (EV_A_ iow [n]);
		1639
		1640	return got_events;
		1641	}
		1642
		1643
		1644
		1645
		1646	</pre>
		1647
706	</div>	1648	</div>
707	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1649	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1650	<div id="code_ev_embed_code_when_one_backend_-2">
		1651	<p>This is a rather advanced watcher type that lets you embed one event loop
		1652	into another (currently only <code>ev_io</code> events are supported in the embedded
		1653	loop, other types of watchers might be handled in a delayed or incorrect
		1654	fashion and must not be used).</p>
		1655	<p>There are primarily two reasons you would want that: work around bugs and
		1656	prioritise I/O.</p>
		1657	<p>As an example for a bug workaround, the kqueue backend might only support
		1658	sockets on some platform, so it is unusable as generic backend, but you
		1659	still want to make use of it because you have many sockets and it scales
		1660	so nicely. In this case, you would create a kqueue-based loop and embed it
		1661	into your default loop (which might use e.g. poll). Overall operation will
		1662	be a bit slower because first libev has to poll and then call kevent, but
		1663	at least you can use both at what they are best.</p>
		1664	<p>As for prioritising I/O: rarely you have the case where some fds have
		1665	to be watched and handled very quickly (with low latency), and even
		1666	priorities and idle watchers might have too much overhead. In this case
		1667	you would put all the high priority stuff in one loop and all the rest in
		1668	a second one, and embed the second one in the first.</p>
		1669	<p>As long as the watcher is active, the callback will be invoked every time
		1670	there might be events pending in the embedded loop. The callback must then
		1671	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1672	their callbacks (you could also start an idle watcher to give the embedded
		1673	loop strictly lower priority for example). You can also set the callback
		1674	to <code>0</code>, in which case the embed watcher will automatically execute the
		1675	embedded loop sweep.</p>
		1676	<p>As long as the watcher is started it will automatically handle events. The
		1677	callback will be invoked whenever some events have been handled. You can
		1678	set the callback to <code>0</code> to avoid having to specify one if you are not
		1679	interested in that.</p>
		1680	<p>Also, there have not currently been made special provisions for forking:
		1681	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1682	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1683	yourself.</p>
		1684	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1685	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1686	portable one.</p>
		1687	<p>So when you want to use this feature you will always have to be prepared
		1688	that you cannot get an embeddable loop. The recommended way to get around
		1689	this is to have a separate variables for your embeddable loop, try to
		1690	create it, and if that fails, use the normal loop for everything:</p>
		1691	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1692	struct ev_loop *loop_lo = 0;
		1693	struct ev_embed embed;
		1694
		1695	// see if there is a chance of getting one that works
		1696	// (remember that a flags value of 0 means autodetection)
		1697	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1698	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1699	: 0;
		1700
		1701	// if we got one, then embed it, otherwise default to loop_hi
		1702	if (loop_lo)
		1703	{
		1704	ev_embed_init (&embed, 0, loop_lo);
		1705	ev_embed_start (loop_hi, &embed);
		1706	}
		1707	else
		1708	loop_lo = loop_hi;
		1709
		1710	</pre>
		1711	<dl>
		1712	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1713	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1714	<dd>
		1715	<p>Configures the watcher to embed the given loop, which must be
		1716	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1717	invoked automatically, otherwise it is the responsibility of the callback
		1718	to invoke it (it will continue to be called until the sweep has been done,
		1719	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1720	</dd>
		1721	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1722	<dd>
		1723	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1724	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1725	apropriate way for embedded loops.</p>
		1726	</dd>
		1727	<dt>struct ev_loop *loop [read-only]</dt>
		1728	<dd>
		1729	<p>The embedded event loop.</p>
		1730	</dd>
		1731	</dl>
		1732
		1733
		1734
		1735
		1736
		1737	</div>
		1738	<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
		1739	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1740	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1741	whoever is a good citizen cared to tell libev about it by calling
		1742	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1743	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1744	and only in the child after the fork. If whoever good citizen calling
		1745	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1746	handlers will be invoked, too, of course.</p>
		1747	<dl>
		1748	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1749	<dd>
		1750	<p>Initialises and configures the fork watcher - it has no parameters of any
		1751	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1752	believe me.</p>
		1753	</dd>
		1754	</dl>
		1755
		1756
		1757
		1758
		1759
		1760	</div>
		1761	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
708	<div id="OTHER_FUNCTIONS_CONTENT">	1762	<div id="OTHER_FUNCTIONS_CONTENT">
709	<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>
710	<dl>	1764	<dl>
711	<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>
712	<dd>	1766	<dd>
713	<p>This function combines a simple timer and an I/O watcher, calls your	1767	<p>This function combines a simple timer and an I/O watcher, calls your
714	callback on whichever event happens first and automatically stop both	1768	callback on whichever event happens first and automatically stop both
715	watchers. This is useful if you want to wait for a single event on an fd	1769	watchers. This is useful if you want to wait for a single event on an fd
716	or timeout without havign to allocate/configure/start/stop/free one or	1770	or timeout without having to allocate/configure/start/stop/free one or
717	more watchers yourself.</p>	1771	more watchers yourself.</p>
718	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events	1772	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and	1773	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
720	<code>events</code> set will be craeted and started.</p>	1774	<code>events</code> set will be craeted and started.</p>
721	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1775	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and	1776	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of	1777	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724	dubious value.</p>	1778	dubious value.</p>
725	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets	1779	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
726	passed an events set like normal event callbacks (with a combination of	1780	passed an <code>revents</code> set like normal event callbacks (a combination of
727	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>	1781	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728	value passed to <code>ev_once</code>:</p>	1782	value passed to <code>ev_once</code>:</p>
729	<pre> static void stdin_ready (int revents, void *arg)	1783	<pre> static void stdin_ready (int revents, void *arg)
730	{	1784	{
731	if (revents & EV_TIMEOUT)	1785	if (revents & EV_TIMEOUT)
…		…
736		1790
737	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1791	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738		1792
739	</pre>	1793	</pre>
740	</dd>	1794	</dd>
741	<dt>ev_feed_event (loop, watcher, int events)</dt>	1795	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
742	<dd>	1796	<dd>
743	<p>Feeds the given event set into the event loop, as if the specified event	1797	<p>Feeds the given event set into the event loop, as if the specified event
744	had happened for the specified watcher (which must be a pointer to an	1798	had happened for the specified watcher (which must be a pointer to an
745	initialised but not necessarily started event watcher).</p>	1799	initialised but not necessarily started event watcher).</p>
746	</dd>	1800	</dd>
747	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1801	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
748	<dd>	1802	<dd>
749	<p>Feed an event on the given fd, as if a file descriptor backend detected	1803	<p>Feed an event on the given fd, as if a file descriptor backend detected
750	the given events it.</p>	1804	the given events it.</p>
751	</dd>	1805	</dd>
752	<dt>ev_feed_signal_event (loop, int signum)</dt>	1806	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
753	<dd>	1807	<dd>
754	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1808	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1809	loop!).</p>
755	</dd>	1810	</dd>
756	</dl>	1811	</dl>
757		1812
		1813
		1814
		1815
		1816
758	</div>	1817	</div>
759	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1818	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1819	<div id="LIBEVENT_EMULATION_CONTENT">
		1820	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1821	emulate the internals of libevent, so here are some usage hints:</p>
		1822	<dl>
		1823	<dt>* Use it by including <event.h>, as usual.</dt>
		1824	<dt>* The following members are fully supported: ev_base, ev_callback,
		1825	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1826	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1827	maintained by libev, it does not work exactly the same way as in libevent (consider
		1828	it a private API).</dt>
		1829	<dt>* Priorities are not currently supported. Initialising priorities
		1830	will fail and all watchers will have the same priority, even though there
		1831	is an ev_pri field.</dt>
		1832	<dt>* Other members are not supported.</dt>
		1833	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1834	to use the libev header file and library.</dt>
		1835	</dl>
		1836
		1837	</div>
		1838	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1839	<div id="C_SUPPORT_CONTENT">
		1840	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1841	you to use some convinience methods to start/stop watchers and also change
		1842	the callback model to a model using method callbacks on objects.</p>
		1843	<p>To use it,</p>
		1844	<pre> #include <ev++.h>
		1845
		1846	</pre>
		1847	<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
		1848	of them macros) into the global namespace. All C++ specific things are
		1849	put into the <code>ev</code> namespace. It should support all the same embedding
		1850	options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
		1851	<p>Care has been taken to keep the overhead low. The only data member the C++
		1852	classes add (compared to plain C-style watchers) is the event loop pointer
		1853	that the watcher is associated with (or no additional members at all if
		1854	you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
		1855	<p>Currently, functions, and static and non-static member functions can be
		1856	used as callbacks. Other types should be easy to add as long as they only
		1857	need one additional pointer for context. If you need support for other
		1858	types of functors please contact the author (preferably after implementing
		1859	it).</p>
		1860	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1861	<dl>
		1862	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1863	<dd>
		1864	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1865	macros from <cite>ev.h</cite>.</p>
		1866	</dd>
		1867	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1868	<dd>
		1869	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1870	</dd>
		1871	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1872	<dd>
		1873	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1874	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1875	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1876	defines by many implementations.</p>
		1877	<p>All of those classes have these methods:</p>
		1878	<p>
		1879	<dl>
		1880	<dt>ev::TYPE::TYPE ()</dt>
		1881	<dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
		1882	<dt>ev::TYPE::~TYPE</dt>
		1883	<dd>
		1884	<p>The constructor (optionally) takes an event loop to associate the watcher
		1885	with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
		1886	<p>The constructor calls <code>ev_init</code> for you, which means you have to call the
		1887	<code>set</code> method before starting it.</p>
		1888	<p>It will not set a callback, however: You have to call the templated <code>set</code>
		1889	method 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
		1891	not allow explicit template arguments for constructors).</p>
		1892	<p>The destructor automatically stops the watcher if it is active.</p>
		1893	</dd>
		1894	<dt>w->set<class, &class::method> (object *)</dt>
		1895	<dd>
		1896	<p>This method sets the callback method to call. The method has to have a
		1897	signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as
		1898	first argument and the <code>revents</code> as second. The object must be given as
		1899	parameter 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
		1901	the C callback that libev requires. If your compiler can inline your
		1902	callback (i.e. it is visible to it at the place of the <code>set</code> call and
		1903	your compiler is good :), then the method will be fully inlined into the
		1904	thunking 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 &w, int revents) { }
		1909	}
		1910
		1911	myclass obj;
		1912	ev::io iow;
		1913	iow.set <myclass, &myclass::io_cb> (&obj);
		1914
		1915	</pre>
		1916	</dd>
		1917	<dt>w->set<function> (void *data = 0)</dt>
		1918	<dd>
		1919	<p>Also sets a callback, but uses a static method or plain function as
		1920	callback. 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 &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 &w, int revents) { }
		1926	iow.set <io_cb> ();
		1927
		1928	</pre>
		1929	</dd>
		1930	<dt>w->set (struct ev_loop *)</dt>
		1931	<dd>
		1932	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1933	do this when the watcher is inactive (and not pending either).</p>
		1934	</dd>
		1935	<dt>w->set ([args])</dt>
		1936	<dd>
		1937	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1938	called at least once. Unlike the C counterpart, an active watcher gets
		1939	automatically stopped and restarted when reconfiguring it with this
		1940	method.</p>
		1941	</dd>
		1942	<dt>w->start ()</dt>
		1943	<dd>
		1944	<p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
		1945	constructor already stores the event loop.</p>
		1946	</dd>
		1947	<dt>w->stop ()</dt>
		1948	<dd>
		1949	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1950	</dd>
		1951	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1952	<dd>
		1953	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1954	<code>ev_TYPE_again</code> function.</p>
		1955	</dd>
		1956	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1957	<dd>
		1958	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1959	</dd>
		1960	<dt>w->update () <code>ev::stat</code> only</dt>
		1961	<dd>
		1962	<p>Invokes <code>ev_stat_stat</code>.</p>
		1963	</dd>
		1964	</dl>
		1965	</p>
		1966	</dd>
		1967	</dl>
		1968	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1969	the constructor.</p>
		1970	<pre> class myclass
		1971	{
		1972	ev_io io; void io_cb (ev::io &w, int revents);
		1973	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1974
		1975	myclass ();
		1976	}
		1977
		1978	myclass::myclass (int fd)
		1979	{
		1980	io .set <myclass, &myclass::io_cb > (this);
		1981	idle.set <myclass, &myclass::idle_cb> (this);
		1982
		1983	io.start (fd, ev::READ);
		1984	}
		1985
		1986
		1987
		1988
		1989	</pre>
		1990
		1991	</div>
		1992	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		1993	<div id="MACRO_MAGIC_CONTENT">
		1994	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1995	<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
		1996	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1997	<p>To make it easier to write programs that cope with either variant, the
		1998	following macros are defined:</p>
		1999	<dl>
		2000	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		2001	<dd>
		2002	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		2003	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		2004	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		2005	<pre> ev_unref (EV_A);
		2006	ev_timer_add (EV_A_ watcher);
		2007	ev_loop (EV_A_ 0);
		2008
		2009	</pre>
		2010	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		2011	which is often provided by the following macro.</p>
		2012	</dd>
		2013	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		2014	<dd>
		2015	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		2016	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		2017	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		2018	<pre> // this is how ev_unref is being declared
		2019	static void ev_unref (EV_P);
		2020
		2021	// this is how you can declare your typical callback
		2022	static void cb (EV_P_ ev_timer *w, int revents)
		2023
		2024	</pre>
		2025	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		2026	suitable for use with <code>EV_A</code>.</p>
		2027	</dd>
		2028	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		2029	<dd>
		2030	<p>Similar to the other two macros, this gives you the value of the default
		2031	loop, if multiple loops are supported ("ev loop default").</p>
		2032	</dd>
		2033	</dl>
		2034	<p>Example: Declare and initialise a check watcher, utilising the above
		2035	macros so it will work regardless of whether multiple loops are supported
		2036	or not.</p>
		2037	<pre> static void
		2038	check_cb (EV_P_ ev_timer *w, int revents)
		2039	{
		2040	ev_check_stop (EV_A_ w);
		2041	}
		2042
		2043	ev_check check;
		2044	ev_check_init (&check, check_cb);
		2045	ev_check_start (EV_DEFAULT_ &check);
		2046	ev_loop (EV_DEFAULT_ 0);
		2047
		2048	</pre>
		2049
		2050	</div>
		2051	<h1 id="EMBEDDING">EMBEDDING</h1>
		2052	<div id="EMBEDDING_CONTENT">
		2053	<p>Libev can (and often is) directly embedded into host
		2054	applications. Examples of applications that embed it include the Deliantra
		2055	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2056	and rxvt-unicode.</p>
		2057	<p>The goal is to enable you to just copy the neecssary files into your
		2058	source directory without having to change even a single line in them, so
		2059	you can easily upgrade by simply copying (or having a checked-out copy of
		2060	libev somewhere in your source tree).</p>
		2061
		2062	</div>
		2063	<h2 id="FILESETS">FILESETS</h2>
		2064	<div id="FILESETS_CONTENT">
		2065	<p>Depending on what features you need you need to include one or more sets of files
		2066	in your app.</p>
		2067
		2068	</div>
		2069	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		2070	<div id="CORE_EVENT_LOOP_CONTENT">
		2071	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		2072	configuration (no autoconf):</p>
		2073	<pre> #define EV_STANDALONE 1
		2074	#include "ev.c"
		2075
		2076	</pre>
		2077	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		2078	single C source file only to provide the function implementations. To use
		2079	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		2080	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		2081	where you can put other configuration options):</p>
		2082	<pre> #define EV_STANDALONE 1
		2083	#include "ev.h"
		2084
		2085	</pre>
		2086	<p>Both header files and implementation files can be compiled with a C++
		2087	compiler (at least, thats a stated goal, and breakage will be treated
		2088	as a bug).</p>
		2089	<p>You need the following files in your source tree, or in a directory
		2090	in your include path (e.g. in libev/ when using -Ilibev):</p>
		2091	<pre> ev.h
		2092	ev.c
		2093	ev_vars.h
		2094	ev_wrap.h
		2095
		2096	ev_win32.c required on win32 platforms only
		2097
		2098	ev_select.c only when select backend is enabled (which is enabled by default)
		2099	ev_poll.c only when poll backend is enabled (disabled by default)
		2100	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2101	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2102	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2103
		2104	</pre>
		2105	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		2106	to compile this single file.</p>
		2107
		2108	</div>
		2109	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		2110	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		2111	<p>To include the libevent compatibility API, also include:</p>
		2112	<pre> #include "event.c"
		2113
		2114	</pre>
		2115	<p>in the file including <cite>ev.c</cite>, and:</p>
		2116	<pre> #include "event.h"
		2117
		2118	</pre>
		2119	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		2120	<p>You need the following additional files for this:</p>
		2121	<pre> event.h
		2122	event.c
		2123
		2124	</pre>
		2125
		2126	</div>
		2127	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		2128	<div id="AUTOCONF_SUPPORT_CONTENT">
		2129	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		2130	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		2131	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		2132	include <cite>config.h</cite> and configure itself accordingly.</p>
		2133	<p>For this of course you need the m4 file:</p>
		2134	<pre> libev.m4
		2135
		2136	</pre>
		2137
		2138	</div>
		2139	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		2140	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		2141	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		2142	before including any of its files. The default is not to build for multiplicity
		2143	and only include the select backend.</p>
		2144	<dl>
		2145	<dt>EV_STANDALONE</dt>
		2146	<dd>
		2147	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		2148	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		2149	implementations for some libevent functions (such as logging, which is not
		2150	supported). It will also not define any of the structs usually found in
		2151	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		2152	</dd>
		2153	<dt>EV_USE_MONOTONIC</dt>
		2154	<dd>
		2155	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2156	monotonic clock option at both compiletime and runtime. Otherwise no use
		2157	of the monotonic clock option will be attempted. If you enable this, you
		2158	usually have to link against librt or something similar. Enabling it when
		2159	the functionality isn't available is safe, though, althoguh you have
		2160	to make sure you link against any libraries where the <code>clock_gettime</code>
		2161	function is hiding in (often <cite>-lrt</cite>).</p>
		2162	</dd>
		2163	<dt>EV_USE_REALTIME</dt>
		2164	<dd>
		2165	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2166	realtime clock option at compiletime (and assume its availability at
		2167	runtime if successful). Otherwise no use of the realtime clock option will
		2168	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		2169	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		2170	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		2171	</dd>
		2172	<dt>EV_USE_SELECT</dt>
		2173	<dd>
		2174	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		2175	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		2176	other method takes over, select will be it. Otherwise the select backend
		2177	will not be compiled in.</p>
		2178	</dd>
		2179	<dt>EV_SELECT_USE_FD_SET</dt>
		2180	<dd>
		2181	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		2182	structure. This is useful if libev doesn't compile due to a missing
		2183	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		2184	exotic systems. This usually limits the range of file descriptors to some
		2185	low limit such as 1024 or might have other limitations (winsocket only
		2186	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		2187	influence the size of the <code>fd_set</code> used.</p>
		2188	</dd>
		2189	<dt>EV_SELECT_IS_WINSOCKET</dt>
		2190	<dd>
		2191	<p>When defined to <code>1</code>, the select backend will assume that
		2192	select/socket/connect etc. don't understand file descriptors but
		2193	wants osf handles on win32 (this is the case when the select to
		2194	be used is the winsock select). This means that it will call
		2195	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		2196	it is assumed that all these functions actually work on fds, even
		2197	on win32. Should not be defined on non-win32 platforms.</p>
		2198	</dd>
		2199	<dt>EV_USE_POLL</dt>
		2200	<dd>
		2201	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		2202	backend. Otherwise it will be enabled on non-win32 platforms. It
		2203	takes precedence over select.</p>
		2204	</dd>
		2205	<dt>EV_USE_EPOLL</dt>
		2206	<dd>
		2207	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		2208	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2209	otherwise another method will be used as fallback. This is the
		2210	preferred backend for GNU/Linux systems.</p>
		2211	</dd>
		2212	<dt>EV_USE_KQUEUE</dt>
		2213	<dd>
		2214	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2215	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2216	otherwise another method will be used as fallback. This is the preferred
		2217	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2218	supports some types of fds correctly (the only platform we found that
		2219	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2220	not be used unless explicitly requested. The best way to use it is to find
		2221	out whether kqueue supports your type of fd properly and use an embedded
		2222	kqueue loop.</p>
		2223	</dd>
		2224	<dt>EV_USE_PORT</dt>
		2225	<dd>
		2226	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2227	10 port style backend. Its availability will be detected at runtime,
		2228	otherwise another method will be used as fallback. This is the preferred
		2229	backend for Solaris 10 systems.</p>
		2230	</dd>
		2231	<dt>EV_USE_DEVPOLL</dt>
		2232	<dd>
		2233	<p>reserved for future expansion, works like the USE symbols above.</p>
		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
		2238	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2239	be detected at runtime.</p>
		2240	</dd>
		2241	<dt>EV_H</dt>
		2242	<dd>
		2243	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2244	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2245	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2246	</dd>
		2247	<dt>EV_CONFIG_H</dt>
		2248	<dd>
		2249	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2250	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2251	<code>EV_H</code>, above.</p>
		2252	</dd>
		2253	<dt>EV_EVENT_H</dt>
		2254	<dd>
		2255	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2256	of how the <cite>event.h</cite> header can be found.</p>
		2257	</dd>
		2258	<dt>EV_PROTOTYPES</dt>
		2259	<dd>
		2260	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2261	prototypes, but still define all the structs and other symbols. This is
		2262	occasionally useful if you want to provide your own wrapper functions
		2263	around libev functions.</p>
		2264	</dd>
		2265	<dt>EV_MULTIPLICITY</dt>
		2266	<dd>
		2267	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2268	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2269	additional independent event loops. Otherwise there will be no support
		2270	for multiple event loops and there is no first event loop pointer
		2271	argument. Instead, all functions act on the single default loop.</p>
		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
		2278	provide for more priorities by overriding those symbols (usually defined
		2279	to be <code>-2</code> and <code>2</code>, respectively).</p>
		2280	<p>When doing priority-based operations, libev usually has to linearly search
		2281	all the priorities, so having many of them (hundreds) uses a lot of space
		2282	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2283	fine.</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>
		2287	<dt>EV_PERIODIC_ENABLE</dt>
		2288	<dd>
		2289	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2290	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2291	code.</p>
		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
		2296	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2297	code.</p>
		2298	</dd>
		2299	<dt>EV_EMBED_ENABLE</dt>
		2300	<dd>
		2301	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2302	defined to be <code>0</code>, then they are not.</p>
		2303	</dd>
		2304	<dt>EV_STAT_ENABLE</dt>
		2305	<dd>
		2306	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2307	defined to be <code>0</code>, then they are not.</p>
		2308	</dd>
		2309	<dt>EV_FORK_ENABLE</dt>
		2310	<dd>
		2311	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2312	defined to be <code>0</code>, then they are not.</p>
		2313	</dd>
		2314	<dt>EV_MINIMAL</dt>
		2315	<dd>
		2316	<p>If you need to shave off some kilobytes of code at the expense of some
		2317	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2318	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2319	</dd>
		2320	<dt>EV_PID_HASHSIZE</dt>
		2321	<dd>
		2322	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2323	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2324	than enough. If you need to manage thousands of children you might want to
		2325	increase 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
		2330	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2331	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2332	watchers you might want to increase this value (<i>must</i> be a power of
		2333	two).</p>
		2334	</dd>
		2335	<dt>EV_COMMON</dt>
		2336	<dd>
		2337	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2338	this macro to a something else you can include more and other types of
		2339	members. You have to define it each time you include one of the files,
		2340	though, and it must be identical each time.</p>
		2341	<p>For example, the perl EV module uses something like this:</p>
		2342	<pre> #define EV_COMMON \
		2343	SV self; / contains this struct */ \
		2344	SV cb_sv, fh /* note no trailing ";" */
		2345
		2346	</pre>
		2347	</dd>
		2348	<dt>EV_CB_DECLARE (type)</dt>
		2349	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2350	<dt>ev_set_cb (ev, cb)</dt>
		2351	<dd>
		2352	<p>Can be used to change the callback member declaration in each watcher,
		2353	and the way callbacks are invoked and set. Must expand to a struct member
		2354	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2355	their default definitions. One possible use for overriding these is to
		2356	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2357	method calls instead of plain function calls in C++.</p>
		2358
		2359	</div>
		2360	<h2 id="EXAMPLES">EXAMPLES</h2>
		2361	<div id="EXAMPLES_CONTENT">
		2362	<p>For a real-world example of a program the includes libev
		2363	verbatim, you can have a look at the EV perl module
		2364	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2365	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2366	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2367	will be compiled. It is pretty complex because it provides its own header
		2368	file.</p>
		2369	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2370	that everybody includes and which overrides some configure choices:</p>
		2371	<pre> #define EV_MINIMAL 1
		2372	#define EV_USE_POLL 0
		2373	#define EV_MULTIPLICITY 0
		2374	#define EV_PERIODIC_ENABLE 0
		2375	#define EV_STAT_ENABLE 0
		2376	#define EV_FORK_ENABLE 0
		2377	#define EV_CONFIG_H <config.h>
		2378	#define EV_MINPRI 0
		2379	#define EV_MAXPRI 0
		2380
		2381	#include "ev++.h"
		2382
		2383	</pre>
		2384	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2385	<pre> #include "ev_cpp.h"
		2386	#include "ev.c"
		2387
		2388
		2389
		2390
		2391	</pre>
		2392
		2393	</div>
		2394	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2395	<div id="COMPLEXITIES_CONTENT">
		2396	<p>In this section the complexities of (many of) the algorithms used inside
		2397	libev will be explained. For complexity discussions about backends see the
		2398	documentation for <code>ev_default_init</code>.</p>
		2399	<p>All of the following are about amortised time: If an array needs to be
		2400	extended, libev needs to realloc and move the whole array, but this
		2401	happens asymptotically never with higher number of elements, so O(1) might
		2402	mean it might do a lengthy realloc operation in rare cases, but on average
		2403	it is much faster and asymptotically approaches constant time.</p>
		2404	<p>
		2405	<dl>
		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
		2409	there are 100 watchers that would trigger before that then inserting will
		2410	have to skip those 100 watchers.</p>
		2411	</dd>
		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
		2415	as only the relative motion in the event queue has to be paid for.</p>
		2416	</dd>
		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.
		2420	=item Stopping check/prepare/idle watchers: O(1)</p>
		2421	</dd>
		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
		2425	correct watcher to remove. The lists are usually short (you don't usually
		2426	have many watchers waiting for the same fd or signal).</p>
		2427	</dd>
		2428	<dt>Finding the next timer per loop iteration: O(1)</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
		2432	libev to recalculate its status (and possibly tell the kernel).</p>
		2433	</dd>
		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
		2438	priority. When doing priority-based operations, libev usually has to
		2439	linearly search all the priorities.</p>
		2440	</dd>
		2441	</dl>
		2442	</p>
		2443
		2444
		2445
		2446
		2447
		2448	</div>
		2449	<h1 id="AUTHOR">AUTHOR</h1>
760	<div id="AUTHOR_CONTENT">	2450	<div id="AUTHOR_CONTENT">
761	<p>Marc Lehmann <libev@schmorp.de>.</p>	2451	<p>Marc Lehmann <libev@schmorp.de>.</p>
762		2452
763	</div>	2453	</div>
764	</div></body>	2454	</div></body>
765	</html>	2455	</html>

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