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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 09:16:01 2007" />	9	<meta name="created" content="Fri Dec 7 20:07:44 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>
		23	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
22	<li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li>	24	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>	25	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
24	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>	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>
25	<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>
26	</ul>	29	</ul>
27	</li>	30	</li>
28	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>	31	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29	<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li>	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>
30	<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - 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>
31	<li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</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>
32	<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - 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>
33	<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - 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>
34	<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - 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>
35	<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the 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>
36	</ul>	42	</ul>
37	</li>	43	</li>
38	<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>
39	<li><a href="#AUTHOR">AUTHOR</a>	60	<li><a href="#AUTHOR">AUTHOR</a>
40	</li>	61	</li>
41	</ul><hr />	62	</ul><hr />
42	<!-- INDEX END -->	63	<!-- INDEX END -->
43		64
44	<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>	65	<h1 id="NAME">NAME</h1>
45	<div id="NAME_CONTENT">	66	<div id="NAME_CONTENT">
46	<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>
47		68
48	</div>	69	</div>
49	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>	70	<h1 id="SYNOPSIS">SYNOPSIS</h1>
50	<div id="SYNOPSIS_CONTENT">	71	<div id="SYNOPSIS_CONTENT">
51	<pre> #include <ev.h>	72	<pre> #include <ev.h>
52		73
53	</pre>	74	</pre>
54		75
55	</div>	76	</div>
56	<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>
57	<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>
58	<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
59	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
60	these event sources and provide your program with events.</p>	129	these event sources and provide your program with events.</p>
61	<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
62	(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
…		…
65	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
66	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
67	watcher.</p>	136	watcher.</p>
68		137
69	</div>	138	</div>
70	<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>	139	<h1 id="FEATURES">FEATURES</h1>
71	<div id="FEATURES_CONTENT">	140	<div id="FEATURES_CONTENT">
72	<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
73	kqueue mechanisms for file descriptor events, relative timers, absolute	142	BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
74	timers with customised rescheduling, signal events, process status change	143	for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
75	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
76	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
77	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
78	it to libevent for example).</p>	153	for example).</p>
79		154
80	</div>	155	</div>
81	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	156	<h1 id="CONVENTIONS">CONVENTIONS</h1>
82	<div id="CONVENTIONS_CONTENT">	157	<div id="CONVENTIONS_CONTENT">
83	<p>Libev is very configurable. In this manual the default configuration	158	<p>Libev is very configurable. In this manual the default configuration will
84	will be described, which supports multiple event loops. For more info	159	be described, which supports multiple event loops. For more info about
85	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
86	<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
87	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>
88	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>
89	will not have this argument.</p>
90		164
91	</div>	165	</div>
92	<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	166	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
93	<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT">	167	<div id="TIME_REPRESENTATION_CONTENT">
94	<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
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	169	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	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
97	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
98	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>
		174
		175	</div>
		176	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
		177	<div id="GLOBAL_FUNCTIONS_CONTENT">
		178	<p>These functions can be called anytime, even before initialising the
		179	library in any way.</p>
99	<dl>	180	<dl>
100	<dt>ev_tstamp ev_time ()</dt>	181	<dt>ev_tstamp ev_time ()</dt>
101	<dd>	182	<dd>
102	<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>
103	</dd>	186	</dd>
104	<dt>int ev_version_major ()</dt>	187	<dt>int ev_version_major ()</dt>
105	<dt>int ev_version_minor ()</dt>	188	<dt>int ev_version_minor ()</dt>
106	<dd>	189	<dd>
107	<p>You can find out the major and minor version numbers of the library	190	<p>You can find out the major and minor version numbers of the library
108	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
109	<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
110	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
111	version of the library your program was compiled against.</p>	194	version of the library your program was compiled against.</p>
112	<p>Usually, its a good idea to terminate if the major versions mismatch,	195	<p>Usually, it's a good idea to terminate if the major versions mismatch,
113	as this indicates an incompatible change. Minor versions are usually	196	as this indicates an incompatible change. Minor versions are usually
114	compatible to older versions, so a larger minor version alone is usually	197	compatible to older versions, so a larger minor version alone is usually
115	not a problem.</p>	198	not a problem.</p>
		199	<p>Example: Make sure we haven't accidentally been linked against the wrong
		200	version.</p>
		201	<pre> assert (("libev version mismatch",
		202	ev_version_major () == EV_VERSION_MAJOR
		203	&& ev_version_minor () >= EV_VERSION_MINOR));
		204
		205	</pre>
		206	</dd>
		207	<dt>unsigned int ev_supported_backends ()</dt>
		208	<dd>
		209	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		210	value) compiled into this binary of libev (independent of their
		211	availability on the system you are running on). See <code>ev_default_loop</code> for
		212	a description of the set values.</p>
		213	<p>Example: make sure we have the epoll method, because yeah this is cool and
		214	a must have and can we have a torrent of it please!!!11</p>
		215	<pre> assert (("sorry, no epoll, no sex",
		216	ev_supported_backends () & EVBACKEND_EPOLL));
		217
		218	</pre>
		219	</dd>
		220	<dt>unsigned int ev_recommended_backends ()</dt>
		221	<dd>
		222	<p>Return the set of all backends compiled into this binary of libev and also
		223	recommended for this platform. This set is often smaller than the one
		224	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		225	most BSDs and will not be autodetected unless you explicitly request it
		226	(assuming you know what you are doing). This is the set of backends that
		227	libev will probe for if you specify no backends explicitly.</p>
		228	</dd>
		229	<dt>unsigned int ev_embeddable_backends ()</dt>
		230	<dd>
		231	<p>Returns the set of backends that are embeddable in other event loops. This
		232	is the theoretical, all-platform, value. To find which backends
		233	might be supported on the current system, you would need to look at
		234	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		235	recommended ones.</p>
		236	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
116	</dd>	237	</dd>
117	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	238	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
118	<dd>	239	<dd>
119	<p>Sets the allocation function to use (the prototype is similar to the	240	<p>Sets the allocation function to use (the prototype is similar - the
120	realloc C function, the semantics are identical). It is used to allocate	241	semantics is identical - to the realloc C function). It is used to
121	and free memory (no surprises here). If it returns zero when memory	242	allocate and free memory (no surprises here). If it returns zero when
122	needs to be allocated, the library might abort or take some potentially	243	memory needs to be allocated, the library might abort or take some
123	destructive action. The default is your system realloc function.</p>	244	potentially destructive action. The default is your system realloc
		245	function.</p>
124	<p>You could override this function in high-availability programs to, say,	246	<p>You could override this function in high-availability programs to, say,
125	free some memory if it cannot allocate memory, to use a special allocator,	247	free some memory if it cannot allocate memory, to use a special allocator,
126	or even to sleep a while and retry until some memory is available.</p>	248	or even to sleep a while and retry until some memory is available.</p>
		249	<p>Example: Replace the libev allocator with one that waits a bit and then
		250	retries).</p>
		251	<pre> static void *
		252	persistent_realloc (void *ptr, size_t size)
		253	{
		254	for (;;)
		255	{
		256	void *newptr = realloc (ptr, size);
		257
		258	if (newptr)
		259	return newptr;
		260
		261	sleep (60);
		262	}
		263	}
		264
		265	...
		266	ev_set_allocator (persistent_realloc);
		267
		268	</pre>
127	</dd>	269	</dd>
128	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	270	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
129	<dd>	271	<dd>
130	<p>Set the callback function to call on a retryable syscall error (such	272	<p>Set the callback function to call on a retryable syscall error (such
131	as failed select, poll, epoll_wait). The message is a printable string	273	as failed select, poll, epoll_wait). The message is a printable string
132	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
133	callback is set, then libev will expect it to remedy the sitution, no	275	callback is set, then libev will expect it to remedy the sitution, no
134	matter what, when it returns. That is, libev will generally retry the	276	matter what, when it returns. That is, libev will generally retry the
135	requested operation, or, if the condition doesn't go away, do bad stuff	277	requested operation, or, if the condition doesn't go away, do bad stuff
136	(such as abort).</p>	278	(such as abort).</p>
		279	<p>Example: This is basically the same thing that libev does internally, too.</p>
		280	<pre> static void
		281	fatal_error (const char *msg)
		282	{
		283	perror (msg);
		284	abort ();
		285	}
		286
		287	...
		288	ev_set_syserr_cb (fatal_error);
		289
		290	</pre>
137	</dd>	291	</dd>
138	</dl>	292	</dl>
139		293
140	</div>	294	</div>
141	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	295	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
142	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	296	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two	297	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
144	types of such loops, the <i>default</i> loop, which supports signals and child	298	types of such loops, the <i>default</i> loop, which supports signals and child
145	events, and dynamically created loops which do not.</p>	299	events, and dynamically created loops which do not.</p>
146	<p>If you use threads, a common model is to run the default event loop	300	<p>If you use threads, a common model is to run the default event loop
147	in your main thread (or in a separate thrad) and for each thread you	301	in your main thread (or in a separate thread) and for each thread you
148	create, you also create another event loop. Libev itself does no locking	302	create, you also create another event loop. Libev itself does no locking
149	whatsoever, so if you mix calls to the same event loop in different	303	whatsoever, so if you mix calls to the same event loop in different
150	threads, make sure you lock (this is usually a bad idea, though, even if	304	threads, make sure you lock (this is usually a bad idea, though, even if
151	done correctly, because its hideous and inefficient).</p>	305	done correctly, because it's hideous and inefficient).</p>
152	<dl>	306	<dl>
153	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	307	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
154	<dd>	308	<dd>
155	<p>This will initialise the default event loop if it hasn't been initialised	309	<p>This will initialise the default event loop if it hasn't been initialised
156	yet and return it. If the default loop could not be initialised, returns	310	yet and return it. If the default loop could not be initialised, returns
157	false. If it already was initialised it simply returns it (and ignores the	311	false. If it already was initialised it simply returns it (and ignores the
158	flags).</p>	312	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
159	<p>If you don't know what event loop to use, use the one returned from this	313	<p>If you don't know what event loop to use, use the one returned from this
160	function.</p>	314	function.</p>
161	<p>The flags argument can be used to specify special behaviour or specific	315	<p>The flags argument can be used to specify special behaviour or specific
162	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p>	316	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
163	<p>It supports the following flags:</p>	317	<p>The following flags are supported:</p>
164	<p>	318	<p>
165	<dl>	319	<dl>
166	<dt>EVFLAG_AUTO</dt>	320	<dt><code>EVFLAG_AUTO</code></dt>
167	<dd>	321	<dd>
168	<p>The default flags value. Use this if you have no clue (its the right	322	<p>The default flags value. Use this if you have no clue (it's the right
169	thing, believe me).</p>	323	thing, believe me).</p>
170	</dd>	324	</dd>
171	<dt>EVFLAG_NOENV</dt>	325	<dt><code>EVFLAG_NOENV</code></dt>
172	<dd>
173	<p>If this flag bit is ored into the flag value then libev will <i>not</i> look
174	at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
175	environment variable will override the flags completely. This is useful
176	to try out specific backends to tets their performance, or to work around
177	bugs.</p>
178	</dd>	326	<dd>
179	<dt>EVMETHOD_SELECT portable select backend</dt>	327	<p>If this flag bit is ored into the flag value (or the program runs setuid
180	<dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt>	328	or setgid) then libev will <i>not</i> look at the environment variable
181	<dt>EVMETHOD_EPOLL linux only</dt>	329	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
182	<dt>EVMETHOD_KQUEUE some bsds only</dt>	330	override the flags completely if it is found in the environment. This is
183	<dt>EVMETHOD_DEVPOLL solaris 8 only</dt>	331	useful to try out specific backends to test their performance, or to work
184	<dt>EVMETHOD_PORT solaris 10 only</dt>	332	around bugs.</p>
185	<dd>	333	</dd>
186	<p>If one or more of these are ored into the flags value, then only these	334	<dt><code>EVFLAG_FORKCHECK</code></dt>
187	backends will be tried (in the reverse order as given here). If one are	335	<dd>
188	specified, any backend will do.</p>	336	<p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
		337	a fork, you can also make libev check for a fork in each iteration by
		338	enabling this flag.</p>
		339	<p>This works by calling <code>getpid ()</code> on every iteration of the loop,
		340	and thus this might slow down your event loop if you do a lot of loop
		341	iterations and little real work, but is usually not noticeable (on my
		342	Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
		343	without a syscall and thus <i>very</i> fast, but my Linux system also has
		344	<code>pthread_atfork</code> which is even faster).</p>
		345	<p>The big advantage of this flag is that you can forget about fork (and
		346	forget about forgetting to tell libev about forking) when you use this
		347	flag.</p>
		348	<p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
		349	environment variable.</p>
		350	</dd>
		351	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
		352	<dd>
		353	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
		354	libev tries to roll its own fd_set with no limits on the number of fds,
		355	but if that fails, expect a fairly low limit on the number of fds when
		356	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		357	the fastest backend for a low number of fds.</p>
		358	</dd>
		359	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		360	<dd>
		361	<p>And this is your standard poll(2) backend. It's more complicated than
		362	select, but handles sparse fds better and has no artificial limit on the
		363	number of fds you can use (except it will slow down considerably with a
		364	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		365	</dd>
		366	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		367	<dd>
		368	<p>For few fds, this backend is a bit little slower than poll and select,
		369	but it scales phenomenally better. While poll and select usually scale like
		370	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		371	either O(1) or O(active_fds).</p>
		372	<p>While stopping and starting an I/O watcher in the same iteration will
		373	result in some caching, there is still a syscall per such incident
		374	(because the fd could point to a different file description now), so its
		375	best to avoid that. Also, dup()ed file descriptors might not work very
		376	well if you register events for both fds.</p>
		377	<p>Please note that epoll sometimes generates spurious notifications, so you
		378	need to use non-blocking I/O or other means to avoid blocking when no data
		379	(or space) is available.</p>
		380	</dd>
		381	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		382	<dd>
		383	<p>Kqueue deserves special mention, as at the time of this writing, it
		384	was broken on all BSDs except NetBSD (usually it doesn't work with
		385	anything but sockets and pipes, except on Darwin, where of course its
		386	completely useless). For this reason its not being "autodetected"
		387	unless you explicitly specify it explicitly in the flags (i.e. using
		388	<code>EVBACKEND_KQUEUE</code>).</p>
		389	<p>It scales in the same way as the epoll backend, but the interface to the
		390	kernel is more efficient (which says nothing about its actual speed, of
		391	course). While starting and stopping an I/O watcher does not cause an
		392	extra syscall as with epoll, it still adds up to four event changes per
		393	incident, so its best to avoid that.</p>
		394	</dd>
		395	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		396	<dd>
		397	<p>This is not implemented yet (and might never be).</p>
		398	</dd>
		399	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		400	<dd>
		401	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		402	it's really slow, but it still scales very well (O(active_fds)).</p>
		403	<p>Please note that solaris ports can result in a lot of spurious
		404	notifications, so you need to use non-blocking I/O or other means to avoid
		405	blocking when no data (or space) is available.</p>
		406	</dd>
		407	<dt><code>EVBACKEND_ALL</code></dt>
		408	<dd>
		409	<p>Try all backends (even potentially broken ones that wouldn't be tried
		410	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		411	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
189	</dd>	412	</dd>
190	</dl>	413	</dl>
191	</p>	414	</p>
		415	<p>If one or more of these are ored into the flags value, then only these
		416	backends will be tried (in the reverse order as given here). If none are
		417	specified, most compiled-in backend will be tried, usually in reverse
		418	order of their flag values :)</p>
		419	<p>The most typical usage is like this:</p>
		420	<pre> if (!ev_default_loop (0))
		421	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		422
		423	</pre>
		424	<p>Restrict libev to the select and poll backends, and do not allow
		425	environment settings to be taken into account:</p>
		426	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		427
		428	</pre>
		429	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		430	available (warning, breaks stuff, best use only with your own private
		431	event loop and only if you know the OS supports your types of fds):</p>
		432	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		433
		434	</pre>
192	</dd>	435	</dd>
193	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	436	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
194	<dd>	437	<dd>
195	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	438	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
196	always distinct from the default loop. Unlike the default loop, it cannot	439	always distinct from the default loop. Unlike the default loop, it cannot
197	handle signal and child watchers, and attempts to do so will be greeted by	440	handle signal and child watchers, and attempts to do so will be greeted by
198	undefined behaviour (or a failed assertion if assertions are enabled).</p>	441	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		442	<p>Example: Try to create a event loop that uses epoll and nothing else.</p>
		443	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		444	if (!epoller)
		445	fatal ("no epoll found here, maybe it hides under your chair");
		446
		447	</pre>
199	</dd>	448	</dd>
200	<dt>ev_default_destroy ()</dt>	449	<dt>ev_default_destroy ()</dt>
201	<dd>	450	<dd>
202	<p>Destroys the default loop again (frees all memory and kernel state	451	<p>Destroys the default loop again (frees all memory and kernel state
203	etc.). This stops all registered event watchers (by not touching them in	452	etc.). None of the active event watchers will be stopped in the normal
204	any way whatsoever, although you cnanot rely on this :).</p>	453	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		454	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		455	calling this function, or cope with the fact afterwards (which is usually
		456	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		457	for example).</p>
205	</dd>	458	</dd>
206	<dt>ev_loop_destroy (loop)</dt>	459	<dt>ev_loop_destroy (loop)</dt>
207	<dd>	460	<dd>
208	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	461	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
209	earlier call to <code>ev_loop_new</code>.</p>	462	earlier call to <code>ev_loop_new</code>.</p>
…		…
212	<dd>	465	<dd>
213	<p>This function reinitialises the kernel state for backends that have	466	<p>This function reinitialises the kernel state for backends that have
214	one. Despite the name, you can call it anytime, but it makes most sense	467	one. Despite the name, you can call it anytime, but it makes most sense
215	after forking, in either the parent or child process (or both, but that	468	after forking, in either the parent or child process (or both, but that
216	again makes little sense).</p>	469	again makes little sense).</p>
217	<p>You <i>must</i> call this function after forking if and only if you want to	470	<p>You <i>must</i> call this function in the child process after forking if and
218	use the event library in both processes. If you just fork+exec, you don't	471	only if you want to use the event library in both processes. If you just
219	have to call it.</p>	472	fork+exec, you don't have to call it.</p>
220	<p>The function itself is quite fast and its usually not a problem to call	473	<p>The function itself is quite fast and it's usually not a problem to call
221	it just in case after a fork. To make this easy, the function will fit in	474	it just in case after a fork. To make this easy, the function will fit in
222	quite nicely into a call to <code>pthread_atfork</code>:</p>	475	quite nicely into a call to <code>pthread_atfork</code>:</p>
223	<pre> pthread_atfork (0, 0, ev_default_fork);	476	<pre> pthread_atfork (0, 0, ev_default_fork);
224		477
225	</pre>	478	</pre>
		479	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		480	without calling this function, so if you force one of those backends you
		481	do not need to care.</p>
226	</dd>	482	</dd>
227	<dt>ev_loop_fork (loop)</dt>	483	<dt>ev_loop_fork (loop)</dt>
228	<dd>	484	<dd>
229	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	485	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
230	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	486	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
231	after fork, and how you do this is entirely your own problem.</p>	487	after fork, and how you do this is entirely your own problem.</p>
232	</dd>	488	</dd>
233	<dt>unsigned int ev_method (loop)</dt>	489	<dt>unsigned int ev_loop_count (loop)</dt>
		490	<dd>
		491	<p>Returns the count of loop iterations for the loop, which is identical to
		492	the number of times libev did poll for new events. It starts at <code>0</code> and
		493	happily wraps around with enough iterations.</p>
		494	<p>This value can sometimes be useful as a generation counter of sorts (it
		495	"ticks" the number of loop iterations), as it roughly corresponds with
		496	<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
234	<dd>	497	</dd>
		498	<dt>unsigned int ev_backend (loop)</dt>
		499	<dd>
235	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	500	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
236	use.</p>	501	use.</p>
237	</dd>	502	</dd>
238	<dt>ev_tstamp = ev_now (loop)</dt>	503	<dt>ev_tstamp ev_now (loop)</dt>
239	<dd>	504	<dd>
240	<p>Returns the current "event loop time", which is the time the event loop	505	<p>Returns the current "event loop time", which is the time the event loop
241	got events and started processing them. This timestamp does not change	506	received events and started processing them. This timestamp does not
242	as long as callbacks are being processed, and this is also the base time	507	change as long as callbacks are being processed, and this is also the base
243	used for relative timers. You can treat it as the timestamp of the event	508	time used for relative timers. You can treat it as the timestamp of the
244	occuring (or more correctly, the mainloop finding out about it).</p>	509	event occuring (or more correctly, libev finding out about it).</p>
245	</dd>	510	</dd>
246	<dt>ev_loop (loop, int flags)</dt>	511	<dt>ev_loop (loop, int flags)</dt>
247	<dd>	512	<dd>
248	<p>Finally, this is it, the event handler. This function usually is called	513	<p>Finally, this is it, the event handler. This function usually is called
249	after you initialised all your watchers and you want to start handling	514	after you initialised all your watchers and you want to start handling
250	events.</p>	515	events.</p>
251	<p>If the flags argument is specified as 0, it will not return until either	516	<p>If the flags argument is specified as <code>0</code>, it will not return until
252	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	517	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		518	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		519	relying on all watchers to be stopped when deciding when a program has
		520	finished (especially in interactive programs), but having a program that
		521	automatically loops as long as it has to and no longer by virtue of
		522	relying on its watchers stopping correctly is a thing of beauty.</p>
253	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	523	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
254	those events and any outstanding ones, but will not block your process in	524	those events and any outstanding ones, but will not block your process in
255	case there are no events.</p>	525	case there are no events and will return after one iteration of the loop.</p>
256	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	526	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
257	neccessary) and will handle those and any outstanding ones. It will block	527	neccessary) and will handle those and any outstanding ones. It will block
258	your process until at least one new event arrives.</p>	528	your process until at least one new event arrives, and will return after
259	<p>This flags value could be used to implement alternative looping	529	one iteration of the loop. This is useful if you are waiting for some
260	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	530	external event in conjunction with something not expressible using other
261	more generic mechanism.</p>	531	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
		532	usually a better approach for this kind of thing.</p>
		533	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		534	<pre> * If there are no active watchers (reference count is zero), return.
		535	- Queue prepare watchers and then call all outstanding watchers.
		536	- If we have been forked, recreate the kernel state.
		537	- Update the kernel state with all outstanding changes.
		538	- Update the "event loop time".
		539	- Calculate for how long to block.
		540	- Block the process, waiting for any events.
		541	- Queue all outstanding I/O (fd) events.
		542	- Update the "event loop time" and do time jump handling.
		543	- Queue all outstanding timers.
		544	- Queue all outstanding periodics.
		545	- If no events are pending now, queue all idle watchers.
		546	- Queue all check watchers.
		547	- Call all queued watchers in reverse order (i.e. check watchers first).
		548	Signals and child watchers are implemented as I/O watchers, and will
		549	be handled here by queueing them when their watcher gets executed.
		550	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		551	were used, return, otherwise continue with step *.
		552
		553	</pre>
		554	<p>Example: Queue some jobs and then loop until no events are outsanding
		555	anymore.</p>
		556	<pre> ... queue jobs here, make sure they register event watchers as long
		557	... as they still have work to do (even an idle watcher will do..)
		558	ev_loop (my_loop, 0);
		559	... jobs done. yeah!
		560
		561	</pre>
262	</dd>	562	</dd>
263	<dt>ev_unloop (loop, how)</dt>	563	<dt>ev_unloop (loop, how)</dt>
264	<dd>	564	<dd>
265	<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument	565	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
		566	has processed all outstanding events). The <code>how</code> argument must be either
266	must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code>	567	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
267	call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code>	568	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
268	calls return.</p>
269	</dd>	569	</dd>
270	<dt>ev_ref (loop)</dt>	570	<dt>ev_ref (loop)</dt>
271	<dt>ev_unref (loop)</dt>	571	<dt>ev_unref (loop)</dt>
272	<dd>	572	<dd>
273	<p>Ref/unref can be used to add or remove a refcount on the event loop: Every	573	<p>Ref/unref can be used to add or remove a reference count on the event
274	watcher keeps one reference. If you have a long-runing watcher you never	574	loop: Every watcher keeps one reference, and as long as the reference
275	unregister that should not keep ev_loop from running, ev_unref() after	575	count is nonzero, <code>ev_loop</code> will not return on its own. If you have
276	starting, and ev_ref() before stopping it. Libev itself uses this for	576	a watcher you never unregister that should not keep <code>ev_loop</code> from
277	example for its internal signal pipe: It is not visible to you as a user	577	returning, ev_unref() after starting, and ev_ref() before stopping it. For
278	and should not keep <code>ev_loop</code> from exiting if the work is done. It is	578	example, libev itself uses this for its internal signal pipe: It is not
279	also an excellent way to do this for generic recurring timers or from	579	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
280	within third-party libraries. Just remember to unref after start and ref	580	no event watchers registered by it are active. It is also an excellent
281	before stop.</p>	581	way to do this for generic recurring timers or from within third-party
		582	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		583	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		584	running when nothing else is active.</p>
		585	<pre> struct ev_signal exitsig;
		586	ev_signal_init (&exitsig, sig_cb, SIGINT);
		587	ev_signal_start (loop, &exitsig);
		588	evf_unref (loop);
		589
		590	</pre>
		591	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		592	<pre> ev_ref (loop);
		593	ev_signal_stop (loop, &exitsig);
		594
		595	</pre>
282	</dd>	596	</dd>
283	</dl>	597	</dl>
284		598
		599
		600
		601
		602
285	</div>	603	</div>
286	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	604	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
287	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	605	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
288	<p>A watcher is a structure that you create and register to record your	606	<p>A watcher is a structure that you create and register to record your
289	interest in some event. For instance, if you want to wait for STDIN to	607	interest in some event. For instance, if you want to wait for STDIN to
290	become readable, you would create an ev_io watcher for that:</p>	608	become readable, you would create an <code>ev_io</code> watcher for that:</p>
291	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	609	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
292	{	610	{
293	ev_io_stop (w);	611	ev_io_stop (w);
294	ev_unloop (loop, EVUNLOOP_ALL);	612	ev_unloop (loop, EVUNLOOP_ALL);
295	}	613	}
…		…
318	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	636	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
319	*)</code>), and you can stop watching for events at any time by calling the	637	*)</code>), and you can stop watching for events at any time by calling the
320	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	638	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
321	<p>As long as your watcher is active (has been started but not stopped) you	639	<p>As long as your watcher is active (has been started but not stopped) you
322	must not touch the values stored in it. Most specifically you must never	640	must not touch the values stored in it. Most specifically you must never
323	reinitialise it or call its set method.</p>	641	reinitialise it or call its <code>set</code> macro.</p>
324	<p>You cna check whether an event is active by calling the <code>ev_is_active
325	(watcher *)</code> macro. To see whether an event is outstanding (but the
326	callback for it has not been called yet) you cna use the <code>ev_is_pending
327	(watcher *)</code> macro.</p>
328	<p>Each and every callback receives the event loop pointer as first, the	642	<p>Each and every callback receives the event loop pointer as first, the
329	registered watcher structure as second, and a bitset of received events as	643	registered watcher structure as second, and a bitset of received events as
330	third argument.</p>	644	third argument.</p>
331	<p>The rceeived events usually include a single bit per event type received	645	<p>The received events usually include a single bit per event type received
332	(you can receive multiple events at the same time). The possible bit masks	646	(you can receive multiple events at the same time). The possible bit masks
333	are:</p>	647	are:</p>
334	<dl>	648	<dl>
335	<dt>EV_READ</dt>	649	<dt><code>EV_READ</code></dt>
336	<dt>EV_WRITE</dt>	650	<dt><code>EV_WRITE</code></dt>
337	<dd>	651	<dd>
338	<p>The file descriptor in the ev_io watcher has become readable and/or	652	<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
339	writable.</p>	653	writable.</p>
340	</dd>	654	</dd>
341	<dt>EV_TIMEOUT</dt>	655	<dt><code>EV_TIMEOUT</code></dt>
342	<dd>
343	<p>The ev_timer watcher has timed out.</p>
344	</dd>	656	<dd>
345	<dt>EV_PERIODIC</dt>	657	<p>The <code>ev_timer</code> watcher has timed out.</p>
346	<dd>	658	</dd>
347	<p>The ev_periodic watcher has timed out.</p>	659	<dt><code>EV_PERIODIC</code></dt>
348	</dd>	660	<dd>
349	<dt>EV_SIGNAL</dt>	661	<p>The <code>ev_periodic</code> watcher has timed out.</p>
350	<dd>	662	</dd>
		663	<dt><code>EV_SIGNAL</code></dt>
		664	<dd>
351	<p>The signal specified in the ev_signal watcher has been received by a thread.</p>	665	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
352	</dd>
353	<dt>EV_CHILD</dt>
354	<dd>	666	</dd>
		667	<dt><code>EV_CHILD</code></dt>
		668	<dd>
355	<p>The pid specified in the ev_child watcher has received a status change.</p>	669	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
356	</dd>
357	<dt>EV_IDLE</dt>
358	<dd>	670	</dd>
		671	<dt><code>EV_STAT</code></dt>
		672	<dd>
		673	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		674	</dd>
		675	<dt><code>EV_IDLE</code></dt>
		676	<dd>
359	<p>The ev_idle watcher has determined that you have nothing better to do.</p>	677	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
360	</dd>
361	<dt>EV_PREPARE</dt>
362	<dt>EV_CHECK</dt>
363	<dd>	678	</dd>
		679	<dt><code>EV_PREPARE</code></dt>
		680	<dt><code>EV_CHECK</code></dt>
		681	<dd>
364	<p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts	682	<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
365	to gather new events, and all ev_check watchers are invoked just after	683	to gather new events, and all <code>ev_check</code> watchers are invoked just after
366	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	684	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
367	received events. Callbacks of both watcher types can start and stop as	685	received events. Callbacks of both watcher types can start and stop as
368	many watchers as they want, and all of them will be taken into account	686	many watchers as they want, and all of them will be taken into account
369	(for example, a ev_prepare watcher might start an idle watcher to keep	687	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
370	<code>ev_loop</code> from blocking).</p>	688	<code>ev_loop</code> from blocking).</p>
371	</dd>	689	</dd>
372	<dt>EV_ERROR</dt>	690	<dt><code>EV_EMBED</code></dt>
		691	<dd>
		692	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		693	</dd>
		694	<dt><code>EV_FORK</code></dt>
		695	<dd>
		696	<p>The event loop has been resumed in the child process after fork (see
		697	<code>ev_fork</code>).</p>
		698	</dd>
		699	<dt><code>EV_ERROR</code></dt>
373	<dd>	700	<dd>
374	<p>An unspecified error has occured, the watcher has been stopped. This might	701	<p>An unspecified error has occured, the watcher has been stopped. This might
375	happen because the watcher could not be properly started because libev	702	happen because the watcher could not be properly started because libev
376	ran out of memory, a file descriptor was found to be closed or any other	703	ran out of memory, a file descriptor was found to be closed or any other
377	problem. You best act on it by reporting the problem and somehow coping	704	problem. You best act on it by reporting the problem and somehow coping
…		…
383	programs, though, so beware.</p>	710	programs, though, so beware.</p>
384	</dd>	711	</dd>
385	</dl>	712	</dl>
386		713
387	</div>	714	</div>
		715	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		716	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		717	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		718	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		719	<dl>
		720	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		721	<dd>
		722	<p>This macro initialises the generic portion of a watcher. The contents
		723	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		724	the generic parts of the watcher are initialised, you <i>need</i> to call
		725	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		726	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		727	which rolls both calls into one.</p>
		728	<p>You can reinitialise a watcher at any time as long as it has been stopped
		729	(or never started) and there are no pending events outstanding.</p>
		730	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		731	int revents)</code>.</p>
		732	</dd>
		733	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		734	<dd>
		735	<p>This macro initialises the type-specific parts of a watcher. You need to
		736	call <code>ev_init</code> at least once before you call this macro, but you can
		737	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		738	macro on a watcher that is active (it can be pending, however, which is a
		739	difference to the <code>ev_init</code> macro).</p>
		740	<p>Although some watcher types do not have type-specific arguments
		741	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		742	</dd>
		743	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		744	<dd>
		745	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		746	calls into a single call. This is the most convinient method to initialise
		747	a watcher. The same limitations apply, of course.</p>
		748	</dd>
		749	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		750	<dd>
		751	<p>Starts (activates) the given watcher. Only active watchers will receive
		752	events. If the watcher is already active nothing will happen.</p>
		753	</dd>
		754	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		755	<dd>
		756	<p>Stops the given watcher again (if active) and clears the pending
		757	status. It is possible that stopped watchers are pending (for example,
		758	non-repeating timers are being stopped when they become pending), but
		759	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		760	you want to free or reuse the memory used by the watcher it is therefore a
		761	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		762	</dd>
		763	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		764	<dd>
		765	<p>Returns a true value iff the watcher is active (i.e. it has been started
		766	and not yet been stopped). As long as a watcher is active you must not modify
		767	it.</p>
		768	</dd>
		769	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		770	<dd>
		771	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		772	events but its callback has not yet been invoked). As long as a watcher
		773	is pending (but not active) you must not call an init function on it (but
		774	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		775	libev (e.g. you cnanot <code>free ()</code> it).</p>
		776	</dd>
		777	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		778	<dd>
		779	<p>Returns the callback currently set on the watcher.</p>
		780	</dd>
		781	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		782	<dd>
		783	<p>Change the callback. You can change the callback at virtually any time
		784	(modulo threads).</p>
		785	</dd>
		786	<dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
		787	<dt>int ev_priority (ev_TYPE *watcher)</dt>
		788	<dd>
		789	<p>Set and query the priority of the watcher. The priority is a small
		790	integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
		791	(default: <code>-2</code>). Pending watchers with higher priority will be invoked
		792	before watchers with lower priority, but priority will not keep watchers
		793	from being executed (except for <code>ev_idle</code> watchers).</p>
		794	<p>This means that priorities are <i>only</i> used for ordering callback
		795	invocation after new events have been received. This is useful, for
		796	example, to reduce latency after idling, or more often, to bind two
		797	watchers on the same event and make sure one is called first.</p>
		798	<p>If you need to suppress invocation when higher priority events are pending
		799	you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
		800	<p>The default priority used by watchers when no priority has been set is
		801	always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
		802	<p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
		803	fine, as long as you do not mind that the priority value you query might
		804	or might not have been adjusted to be within valid range.</p>
		805	</dd>
		806	</dl>
		807
		808
		809
		810
		811
		812	</div>
388	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	813	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
389	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	814	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
390	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	815	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
391	and read at any time, libev will completely ignore it. This cna be used	816	and read at any time, libev will completely ignore it. This can be used
392	to associate arbitrary data with your watcher. If you need more data and	817	to associate arbitrary data with your watcher. If you need more data and
393	don't want to allocate memory and store a pointer to it in that data	818	don't want to allocate memory and store a pointer to it in that data
394	member, you can also "subclass" the watcher type and provide your own	819	member, you can also "subclass" the watcher type and provide your own
395	data:</p>	820	data:</p>
396	<pre> struct my_io	821	<pre> struct my_io
…		…
409	struct my_io w = (struct my_io )w_;	834	struct my_io w = (struct my_io )w_;
410	...	835	...
411	}	836	}
412		837
413	</pre>	838	</pre>
414	<p>More interesting and less C-conformant ways of catsing your callback type	839	<p>More interesting and less C-conformant ways of casting your callback type
415	have been omitted....</p>	840	instead have been omitted.</p>
		841	<p>Another common scenario is having some data structure with multiple
		842	watchers:</p>
		843	<pre> struct my_biggy
		844	{
		845	int some_data;
		846	ev_timer t1;
		847	ev_timer t2;
		848	}
416		849
		850	</pre>
		851	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		852	you need to use <code>offsetof</code>:</p>
		853	<pre> #include <stddef.h>
417		854
		855	static void
		856	t1_cb (EV_P_ struct ev_timer *w, int revents)
		857	{
		858	struct my_biggy big = (struct my_biggy *
		859	(((char *)w) - offsetof (struct my_biggy, t1));
		860	}
418		861
		862	static void
		863	t2_cb (EV_P_ struct ev_timer *w, int revents)
		864	{
		865	struct my_biggy big = (struct my_biggy *
		866	(((char *)w) - offsetof (struct my_biggy, t2));
		867	}
419		868
420		869
		870
		871
		872	</pre>
		873
421	</div>	874	</div>
422	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	875	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
423	<div id="WATCHER_TYPES_CONTENT">	876	<div id="WATCHER_TYPES_CONTENT">
424	<p>This section describes each watcher in detail, but will not repeat	877	<p>This section describes each watcher in detail, but will not repeat
425	information given in the last section.</p>	878	information given in the last section. Any initialisation/set macros,
		879	functions and members specific to the watcher type are explained.</p>
		880	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		881	while the watcher is active, you can look at the member and expect some
		882	sensible content, but you must not modify it (you can modify it while the
		883	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		884	means you can expect it to have some sensible content while the watcher
		885	is active, but you can also modify it. Modifying it may not do something
		886	sensible or take immediate effect (or do anything at all), but libev will
		887	not crash or malfunction in any way.</p>
426		888
		889
		890
		891
		892
427	</div>	893	</div>
428	<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2>	894	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
429	<div id="struct_ev_io_is_my_file_descriptor_r-2">	895	<div id="code_ev_io_code_is_this_file_descrip-2">
430	<p>I/O watchers check whether a file descriptor is readable or writable	896	<p>I/O watchers check whether a file descriptor is readable or writable
431	in each iteration of the event loop (This behaviour is called	897	in each iteration of the event loop, or, more precisely, when reading
432	level-triggering because you keep receiving events as long as the	898	would not block the process and writing would at least be able to write
433	condition persists. Remember you cna stop the watcher if you don't want to	899	some data. This behaviour is called level-triggering because you keep
434	act on the event and neither want to receive future events).</p>	900	receiving events as long as the condition persists. Remember you can stop
		901	the watcher if you don't want to act on the event and neither want to
		902	receive future events.</p>
		903	<p>In general you can register as many read and/or write event watchers per
		904	fd as you want (as long as you don't confuse yourself). Setting all file
		905	descriptors to non-blocking mode is also usually a good idea (but not
		906	required if you know what you are doing).</p>
		907	<p>You have to be careful with dup'ed file descriptors, though. Some backends
		908	(the linux epoll backend is a notable example) cannot handle dup'ed file
		909	descriptors correctly if you register interest in two or more fds pointing
		910	to the same underlying file/socket/etc. description (that is, they share
		911	the same underlying "file open").</p>
		912	<p>If you must do this, then force the use of a known-to-be-good backend
		913	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
		914	<code>EVBACKEND_POLL</code>).</p>
		915	<p>Another thing you have to watch out for is that it is quite easy to
		916	receive "spurious" readyness notifications, that is your callback might
		917	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		918	because there is no data. Not only are some backends known to create a
		919	lot of those (for example solaris ports), it is very easy to get into
		920	this situation even with a relatively standard program structure. Thus
		921	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		922	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		923	<p>If you cannot run the fd in non-blocking mode (for example you should not
		924	play around with an Xlib connection), then you have to seperately re-test
		925	whether a file descriptor is really ready with a known-to-be good interface
		926	such as poll (fortunately in our Xlib example, Xlib already does this on
		927	its own, so its quite safe to use).</p>
435	<dl>	928	<dl>
436	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	929	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
437	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	930	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
438	<dd>	931	<dd>
439	<p>Configures an ev_io watcher. The fd is the file descriptor to rceeive	932	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
440	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	933	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
441	EV_WRITE</code> to receive the given events.</p>	934	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		935	</dd>
		936	<dt>int fd [read-only]</dt>
		937	<dd>
		938	<p>The file descriptor being watched.</p>
		939	</dd>
		940	<dt>int events [read-only]</dt>
		941	<dd>
		942	<p>The events being watched.</p>
442	</dd>	943	</dd>
443	</dl>	944	</dl>
		945	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		946	readable, but only once. Since it is likely line-buffered, you could
		947	attempt to read a whole line in the callback.</p>
		948	<pre> static void
		949	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		950	{
		951	ev_io_stop (loop, w);
		952	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		953	}
444		954
		955	...
		956	struct ev_loop *loop = ev_default_init (0);
		957	struct ev_io stdin_readable;
		958	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		959	ev_io_start (loop, &stdin_readable);
		960	ev_loop (loop, 0);
		961
		962
		963
		964
		965	</pre>
		966
445	</div>	967	</div>
446	<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2>	968	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
447	<div id="struct_ev_timer_relative_and_optiona-2">	969	<div id="code_ev_timer_code_relative_and_opti-2">
448	<p>Timer watchers are simple relative timers that generate an event after a	970	<p>Timer watchers are simple relative timers that generate an event after a
449	given time, and optionally repeating in regular intervals after that.</p>	971	given time, and optionally repeating in regular intervals after that.</p>
450	<p>The timers are based on real time, that is, if you register an event that	972	<p>The timers are based on real time, that is, if you register an event that
451	times out after an hour and youreset your system clock to last years	973	times out after an hour and you reset your system clock to last years
452	time, it will still time out after (roughly) and hour. "Roughly" because	974	time, it will still time out after (roughly) and hour. "Roughly" because
453	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	975	detecting time jumps is hard, and some inaccuracies are unavoidable (the
454	monotonic clock option helps a lot here).</p>	976	monotonic clock option helps a lot here).</p>
		977	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
		978	time. This is usually the right thing as this timestamp refers to the time
		979	of the event triggering whatever timeout you are modifying/starting. If
		980	you suspect event processing to be delayed and you <i>need</i> to base the timeout
		981	on the current time, use something like this to adjust for this:</p>
		982	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		983
		984	</pre>
		985	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		986	but if multiple timers become ready during the same loop iteration then
		987	order of execution is undefined.</p>
455	<dl>	988	<dl>
456	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	989	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
457	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	990	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
458	<dd>	991	<dd>
459	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	992	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
461	timer will automatically be configured to trigger again <code>repeat</code> seconds	994	timer will automatically be configured to trigger again <code>repeat</code> seconds
462	later, again, and again, until stopped manually.</p>	995	later, again, and again, until stopped manually.</p>
463	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	996	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
464	configure a timer to trigger every 10 seconds, then it will trigger at	997	configure a timer to trigger every 10 seconds, then it will trigger at
465	exactly 10 second intervals. If, however, your program cannot keep up with	998	exactly 10 second intervals. If, however, your program cannot keep up with
466	the timer (ecause it takes longer than those 10 seconds to do stuff) the	999	the timer (because it takes longer than those 10 seconds to do stuff) the
467	timer will not fire more than once per event loop iteration.</p>	1000	timer will not fire more than once per event loop iteration.</p>
468	</dd>	1001	</dd>
469	<dt>ev_timer_again (loop)</dt>	1002	<dt>ev_timer_again (loop)</dt>
470	<dd>	1003	<dd>
471	<p>This will act as if the timer timed out and restart it again if it is	1004	<p>This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:</p>	1005	repeating. The exact semantics are:</p>
		1006	<p>If the timer is pending, its pending status is cleared.</p>
473	<p>If the timer is started but nonrepeating, stop it.</p>	1007	<p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
474	<p>If the timer is repeating, either start it if necessary (with the repeat	1008	<p>If the timer is repeating, either start it if necessary (with the
475	value), or reset the running timer to the repeat value.</p>	1009	<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
476	<p>This sounds a bit complicated, but here is a useful and typical	1010	<p>This sounds a bit complicated, but here is a useful and typical
477	example: Imagine you have a tcp connection and you want a so-called idle	1011	example: Imagine you have a tcp connection and you want a so-called idle
478	timeout, that is, you want to be called when there have been, say, 60	1012	timeout, that is, you want to be called when there have been, say, 60
479	seconds of inactivity on the socket. The easiest way to do this is to	1013	seconds of inactivity on the socket. The easiest way to do this is to
480	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	1014	configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
481	time you successfully read or write some data. If you go into an idle	1015	<code>ev_timer_again</code> each time you successfully read or write some data. If
482	state where you do not expect data to travel on the socket, you can stop	1016	you go into an idle state where you do not expect data to travel on the
		1017	socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
483	the timer, and again will automatically restart it if need be.</p>	1018	automatically restart it if need be.</p>
		1019	<p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
		1020	altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
		1021	<pre> ev_timer_init (timer, callback, 0., 5.);
		1022	ev_timer_again (loop, timer);
		1023	...
		1024	timer->again = 17.;
		1025	ev_timer_again (loop, timer);
		1026	...
		1027	timer->again = 10.;
		1028	ev_timer_again (loop, timer);
		1029
		1030	</pre>
		1031	<p>This is more slightly efficient then stopping/starting the timer each time
		1032	you want to modify its timeout value.</p>
		1033	</dd>
		1034	<dt>ev_tstamp repeat [read-write]</dt>
		1035	<dd>
		1036	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		1037	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		1038	which is also when any modifications are taken into account.</p>
484	</dd>	1039	</dd>
485	</dl>	1040	</dl>
		1041	<p>Example: Create a timer that fires after 60 seconds.</p>
		1042	<pre> static void
		1043	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1044	{
		1045	.. one minute over, w is actually stopped right here
		1046	}
486		1047
		1048	struct ev_timer mytimer;
		1049	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1050	ev_timer_start (loop, &mytimer);
		1051
		1052	</pre>
		1053	<p>Example: Create a timeout timer that times out after 10 seconds of
		1054	inactivity.</p>
		1055	<pre> static void
		1056	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1057	{
		1058	.. ten seconds without any activity
		1059	}
		1060
		1061	struct ev_timer mytimer;
		1062	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1063	ev_timer_again (&mytimer); /* start timer */
		1064	ev_loop (loop, 0);
		1065
		1066	// and in some piece of code that gets executed on any "activity":
		1067	// reset the timeout to start ticking again at 10 seconds
		1068	ev_timer_again (&mytimer);
		1069
		1070
		1071
		1072
		1073	</pre>
		1074
487	</div>	1075	</div>
488	<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2>	1076	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
489	<div id="ev_periodic_to_cron_or_not_to_cron_i-2">	1077	<div id="code_ev_periodic_code_to_cron_or_not-2">
490	<p>Periodic watchers are also timers of a kind, but they are very versatile	1078	<p>Periodic watchers are also timers of a kind, but they are very versatile
491	(and unfortunately a bit complex).</p>	1079	(and unfortunately a bit complex).</p>
492	<p>Unlike ev_timer's, they are not based on real time (or relative time)	1080	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
493	but on wallclock time (absolute time). You can tell a periodic watcher	1081	but on wallclock time (absolute time). You can tell a periodic watcher
494	to trigger "at" some specific point in time. For example, if you tell a	1082	to trigger "at" some specific point in time. For example, if you tell a
495	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1083	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
496	+ 10.>) and then reset your system clock to the last year, then it will	1084	+ 10.</code>) and then reset your system clock to the last year, then it will
497	take a year to trigger the event (unlike an ev_timer, which would trigger	1085	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
498	roughly 10 seconds later and of course not if you reset your system time	1086	roughly 10 seconds later and of course not if you reset your system time
499	again).</p>	1087	again).</p>
500	<p>They can also be used to implement vastly more complex timers, such as	1088	<p>They can also be used to implement vastly more complex timers, such as
501	triggering an event on eahc midnight, local time.</p>	1089	triggering an event on eahc midnight, local time.</p>
		1090	<p>As with timers, the callback is guarenteed to be invoked only when the
		1091	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1092	during the same loop iteration then order of execution is undefined.</p>
502	<dl>	1093	<dl>
503	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1094	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
504	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	1095	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
505	<dd>	1096	<dd>
506	<p>Lots of arguments, lets sort it out... There are basically three modes of	1097	<p>Lots of arguments, lets sort it out... There are basically three modes of
507	operation, and we will explain them from simplest to complex:</p>	1098	operation, and we will explain them from simplest to complex:</p>
508
509
510
511
512	<p>	1099	<p>
513	<dl>	1100	<dl>
514	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1101	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
515	<dd>	1102	<dd>
516	<p>In this configuration the watcher triggers an event at the wallclock time	1103	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
528	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	1115	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
529		1116
530	</pre>	1117	</pre>
531	<p>This doesn't mean there will always be 3600 seconds in between triggers,	1118	<p>This doesn't mean there will always be 3600 seconds in between triggers,
532	but only that the the callback will be called when the system time shows a	1119	but only that the the callback will be called when the system time shows a
533	full hour (UTC), or more correct, when the system time is evenly divisible	1120	full hour (UTC), or more correctly, when the system time is evenly divisible
534	by 3600.</p>	1121	by 3600.</p>
535	<p>Another way to think about it (for the mathematically inclined) is that	1122	<p>Another way to think about it (for the mathematically inclined) is that
536	ev_periodic will try to run the callback in this mode at the next possible	1123	<code>ev_periodic</code> will try to run the callback in this mode at the next possible
537	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	1124	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
538	</dd>	1125	</dd>
539	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	1126	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>
540	<dd>	1127	<dd>
541	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	1128	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
542	ignored. Instead, each time the periodic watcher gets scheduled, the	1129	ignored. Instead, each time the periodic watcher gets scheduled, the
543	reschedule callback will be called with the watcher as first, and the	1130	reschedule callback will be called with the watcher as first, and the
544	current time as second argument.</p>	1131	current time as second argument.</p>
545	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1132	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
546	periodic watcher, ever, or make any event loop modificstions</i>. If you need	1133	ever, or make any event loop modifications</i>. If you need to stop it,
547	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p>	1134	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
		1135	starting a prepare watcher).</p>
548	<p>Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1136	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
549	ev_tstamp now)>, e.g.:</p>	1137	ev_tstamp now)</code>, e.g.:</p>
550	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1138	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
551	{	1139	{
552	return now + 60.;	1140	return now + 60.;
553	}	1141	}
554		1142
555	</pre>	1143	</pre>
556	<p>It must return the next time to trigger, based on the passed time value	1144	<p>It must return the next time to trigger, based on the passed time value
557	(that is, the lowest time value larger than to the second argument). It	1145	(that is, the lowest time value larger than to the second argument). It
558	will usually be called just before the callback will be triggered, but	1146	will usually be called just before the callback will be triggered, but
559	might be called at other times, too.</p>	1147	might be called at other times, too.</p>
		1148	<p>NOTE: <i>This callback must always return a time that is later than the
		1149	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
560	<p>This can be used to create very complex timers, such as a timer that	1150	<p>This can be used to create very complex timers, such as a timer that
561	triggers on each midnight, local time. To do this, you would calculate the	1151	triggers on each midnight, local time. To do this, you would calculate the
562	next midnight after <code>now</code> and return the timestamp value for this. How you do this	1152	next midnight after <code>now</code> and return the timestamp value for this. How
563	is, again, up to you (but it is not trivial).</p>	1153	you do this is, again, up to you (but it is not trivial, which is the main
		1154	reason I omitted it as an example).</p>
564	</dd>	1155	</dd>
565	</dl>	1156	</dl>
566	</p>	1157	</p>
567	</dd>	1158	</dd>
568	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1159	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
570	<p>Simply stops and restarts the periodic watcher again. This is only useful	1161	<p>Simply stops and restarts the periodic watcher again. This is only useful
571	when you changed some parameters or the reschedule callback would return	1162	when you changed some parameters or the reschedule callback would return
572	a different time than the last time it was called (e.g. in a crond like	1163	a different time than the last time it was called (e.g. in a crond like
573	program when the crontabs have changed).</p>	1164	program when the crontabs have changed).</p>
574	</dd>	1165	</dd>
		1166	<dt>ev_tstamp interval [read-write]</dt>
		1167	<dd>
		1168	<p>The current interval value. Can be modified any time, but changes only
		1169	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1170	called.</p>
		1171	</dd>
		1172	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1173	<dd>
		1174	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1175	switched off. Can be changed any time, but changes only take effect when
		1176	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1177	</dd>
575	</dl>	1178	</dl>
		1179	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1180	system clock is divisible by 3600. The callback invocation times have
		1181	potentially a lot of jittering, but good long-term stability.</p>
		1182	<pre> static void
		1183	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1184	{
		1185	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1186	}
576		1187
		1188	struct ev_periodic hourly_tick;
		1189	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1190	ev_periodic_start (loop, &hourly_tick);
		1191
		1192	</pre>
		1193	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1194	<pre> #include <math.h>
		1195
		1196	static ev_tstamp
		1197	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1198	{
		1199	return fmod (now, 3600.) + 3600.;
		1200	}
		1201
		1202	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1203
		1204	</pre>
		1205	<p>Example: Call a callback every hour, starting now:</p>
		1206	<pre> struct ev_periodic hourly_tick;
		1207	ev_periodic_init (&hourly_tick, clock_cb,
		1208	fmod (ev_now (loop), 3600.), 3600., 0);
		1209	ev_periodic_start (loop, &hourly_tick);
		1210
		1211
		1212
		1213
		1214	</pre>
		1215
577	</div>	1216	</div>
578	<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>	1217	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
579	<div id="ev_signal_signal_me_when_a_signal_ge-2">	1218	<div id="code_ev_signal_code_signal_me_when_a-2">
580	<p>Signal watchers will trigger an event when the process receives a specific	1219	<p>Signal watchers will trigger an event when the process receives a specific
581	signal one or more times. Even though signals are very asynchronous, libev	1220	signal one or more times. Even though signals are very asynchronous, libev
582	will try its best to deliver signals synchronously, i.e. as part of the	1221	will try it's best to deliver signals synchronously, i.e. as part of the
583	normal event processing, like any other event.</p>	1222	normal event processing, like any other event.</p>
584	<p>You cna configure as many watchers as you like per signal. Only when the	1223	<p>You can configure as many watchers as you like per signal. Only when the
585	first watcher gets started will libev actually register a signal watcher	1224	first watcher gets started will libev actually register a signal watcher
586	with the kernel (thus it coexists with your own signal handlers as long	1225	with the kernel (thus it coexists with your own signal handlers as long
587	as you don't register any with libev). Similarly, when the last signal	1226	as you don't register any with libev). Similarly, when the last signal
588	watcher for a signal is stopped libev will reset the signal handler to	1227	watcher for a signal is stopped libev will reset the signal handler to
589	SIG_DFL (regardless of what it was set to before).</p>	1228	SIG_DFL (regardless of what it was set to before).</p>
…		…
592	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1231	<dt>ev_signal_set (ev_signal *, int signum)</dt>
593	<dd>	1232	<dd>
594	<p>Configures the watcher to trigger on the given signal number (usually one	1233	<p>Configures the watcher to trigger on the given signal number (usually one
595	of the <code>SIGxxx</code> constants).</p>	1234	of the <code>SIGxxx</code> constants).</p>
596	</dd>	1235	</dd>
		1236	<dt>int signum [read-only]</dt>
		1237	<dd>
		1238	<p>The signal the watcher watches out for.</p>
		1239	</dd>
597	</dl>	1240	</dl>
598		1241
		1242
		1243
		1244
		1245
599	</div>	1246	</div>
600	<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2>	1247	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
601	<div id="ev_child_wait_for_pid_status_changes-2">	1248	<div id="code_ev_child_code_watch_out_for_pro-2">
602	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1249	<p>Child watchers trigger when your process receives a SIGCHLD in response to
603	some child status changes (most typically when a child of yours dies).</p>	1250	some child status changes (most typically when a child of yours dies).</p>
604	<dl>	1251	<dl>
605	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1252	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
606	<dt>ev_child_set (ev_child *, int pid)</dt>	1253	<dt>ev_child_set (ev_child *, int pid)</dt>
607	<dd>	1254	<dd>
608	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or	1255	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
609	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look	1256	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
610	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1257	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
611	the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member	1258	the status word (use the macros from <code>sys/wait.h</code> and see your systems
		1259	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
612	contains the pid of the process causing the status change.</p>	1260	process causing the status change.</p>
		1261	</dd>
		1262	<dt>int pid [read-only]</dt>
		1263	<dd>
		1264	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1265	</dd>
		1266	<dt>int rpid [read-write]</dt>
		1267	<dd>
		1268	<p>The process id that detected a status change.</p>
		1269	</dd>
		1270	<dt>int rstatus [read-write]</dt>
		1271	<dd>
		1272	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1273	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
613	</dd>	1274	</dd>
614	</dl>	1275	</dl>
		1276	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1277	<pre> static void
		1278	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1279	{
		1280	ev_unloop (loop, EVUNLOOP_ALL);
		1281	}
615		1282
		1283	struct ev_signal signal_watcher;
		1284	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1285	ev_signal_start (loop, &sigint_cb);
		1286
		1287
		1288
		1289
		1290	</pre>
		1291
616	</div>	1292	</div>
		1293	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1294	<div id="code_ev_stat_code_did_the_file_attri-2">
		1295	<p>This watches a filesystem path for attribute changes. That is, it calls
		1296	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1297	compared to the last time, invoking the callback if it did.</p>
		1298	<p>The path does not need to exist: changing from "path exists" to "path does
		1299	not exist" is a status change like any other. The condition "path does
		1300	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1301	otherwise always forced to be at least one) and all the other fields of
		1302	the stat buffer having unspecified contents.</p>
		1303	<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
		1304	relative and your working directory changes, the behaviour is undefined.</p>
		1305	<p>Since there is no standard to do this, the portable implementation simply
		1306	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1307	can specify a recommended polling interval for this case. If you specify
		1308	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1309	unspecified default</i> value will be used (which you can expect to be around
		1310	five seconds, although this might change dynamically). Libev will also
		1311	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1312	usually overkill.</p>
		1313	<p>This watcher type is not meant for massive numbers of stat watchers,
		1314	as even with OS-supported change notifications, this can be
		1315	resource-intensive.</p>
		1316	<p>At the time of this writing, only the Linux inotify interface is
		1317	implemented (implementing kqueue support is left as an exercise for the
		1318	reader). Inotify will be used to give hints only and should not change the
		1319	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1320	to fall back to regular polling again even with inotify, but changes are
		1321	usually detected immediately, and if the file exists there will be no
		1322	polling.</p>
		1323	<dl>
		1324	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1325	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1326	<dd>
		1327	<p>Configures the watcher to wait for status changes of the given
		1328	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1329	be detected and should normally be specified as <code>0</code> to let libev choose
		1330	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1331	path for as long as the watcher is active.</p>
		1332	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1333	relative to the attributes at the time the watcher was started (or the
		1334	last change was detected).</p>
		1335	</dd>
		1336	<dt>ev_stat_stat (ev_stat *)</dt>
		1337	<dd>
		1338	<p>Updates the stat buffer immediately with new values. If you change the
		1339	watched path in your callback, you could call this fucntion to avoid
		1340	detecting this change (while introducing a race condition). Can also be
		1341	useful simply to find out the new values.</p>
		1342	</dd>
		1343	<dt>ev_statdata attr [read-only]</dt>
		1344	<dd>
		1345	<p>The most-recently detected attributes of the file. Although the type is of
		1346	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1347	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1348	was some error while <code>stat</code>ing the file.</p>
		1349	</dd>
		1350	<dt>ev_statdata prev [read-only]</dt>
		1351	<dd>
		1352	<p>The previous attributes of the file. The callback gets invoked whenever
		1353	<code>prev</code> != <code>attr</code>.</p>
		1354	</dd>
		1355	<dt>ev_tstamp interval [read-only]</dt>
		1356	<dd>
		1357	<p>The specified interval.</p>
		1358	</dd>
		1359	<dt>const char *path [read-only]</dt>
		1360	<dd>
		1361	<p>The filesystem path that is being watched.</p>
		1362	</dd>
		1363	</dl>
		1364	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1365	<pre> static void
		1366	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1367	{
		1368	/* /etc/passwd changed in some way */
		1369	if (w->attr.st_nlink)
		1370	{
		1371	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1372	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1373	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1374	}
		1375	else
		1376	/* you shalt not abuse printf for puts */
		1377	puts ("wow, /etc/passwd is not there, expect problems. "
		1378	"if this is windows, they already arrived\n");
		1379	}
		1380
		1381	...
		1382	ev_stat passwd;
		1383
		1384	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1385	ev_stat_start (loop, &passwd);
		1386
		1387
		1388
		1389
		1390	</pre>
		1391
		1392	</div>
617	<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2>	1393	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
618	<div id="ev_idle_when_you_ve_got_nothing_bett-2">	1394	<div id="code_ev_idle_code_when_you_ve_got_no-2">
619	<p>Idle watchers trigger events when there are no other I/O or timer (or	1395	<p>Idle watchers trigger events when no other events of the same or higher
620	periodic) events pending. That is, as long as your process is busy	1396	priority are pending (prepare, check and other idle watchers do not
621	handling sockets or timeouts it will not be called. But when your process	1397	count).</p>
622	is idle all idle watchers are being called again and again - until	1398	<p>That is, as long as your process is busy handling sockets or timeouts
		1399	(or even signals, imagine) of the same or higher priority it will not be
		1400	triggered. But when your process is idle (or only lower-priority watchers
		1401	are pending), the idle watchers are being called once per event loop
623	stopped, that is, or your process receives more events.</p>	1402	iteration - until stopped, that is, or your process receives more events
		1403	and becomes busy again with higher priority stuff.</p>
624	<p>The most noteworthy effect is that as long as any idle watchers are	1404	<p>The most noteworthy effect is that as long as any idle watchers are
625	active, the process will not block when waiting for new events.</p>	1405	active, the process will not block when waiting for new events.</p>
626	<p>Apart from keeping your process non-blocking (which is a useful	1406	<p>Apart from keeping your process non-blocking (which is a useful
627	effect on its own sometimes), idle watchers are a good place to do	1407	effect on its own sometimes), idle watchers are a good place to do
628	"pseudo-background processing", or delay processing stuff to after the	1408	"pseudo-background processing", or delay processing stuff to after the
…		…
633	<p>Initialises and configures the idle watcher - it has no parameters of any	1413	<p>Initialises and configures the idle watcher - it has no parameters of any
634	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1414	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
635	believe me.</p>	1415	believe me.</p>
636	</dd>	1416	</dd>
637	</dl>	1417	</dl>
		1418	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1419	callback, free it. Also, use no error checking, as usual.</p>
		1420	<pre> static void
		1421	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1422	{
		1423	free (w);
		1424	// now do something you wanted to do when the program has
		1425	// no longer asnything immediate to do.
		1426	}
638		1427
		1428	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1429	ev_idle_init (idle_watcher, idle_cb);
		1430	ev_idle_start (loop, idle_cb);
		1431
		1432
		1433
		1434
		1435	</pre>
		1436
639	</div>	1437	</div>
640	<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>	1438	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
641	<div id="prepare_and_check_your_hooks_into_th-2">	1439	<div id="code_ev_prepare_code_and_code_ev_che-2">
642	<p>Prepare and check watchers usually (but not always) are used in	1440	<p>Prepare and check watchers are usually (but not always) used in tandem:
643	tandom. Prepare watchers get invoked before the process blocks and check	1441	prepare watchers get invoked before the process blocks and check watchers
644	watchers afterwards.</p>	1442	afterwards.</p>
		1443	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1444	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1445	watchers. Other loops than the current one are fine, however. The
		1446	rationale behind this is that you do not need to check for recursion in
		1447	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1448	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1449	called in pairs bracketing the blocking call.</p>
645	<p>Their main purpose is to integrate other event mechanisms into libev. This	1450	<p>Their main purpose is to integrate other event mechanisms into libev and
646	could be used, for example, to track variable changes, implement your own	1451	their use is somewhat advanced. This could be used, for example, to track
647	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1452	variable changes, implement your own watchers, integrate net-snmp or a
		1453	coroutine library and lots more. They are also occasionally useful if
		1454	you cache some data and want to flush it before blocking (for example,
		1455	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1456	watcher).</p>
648	<p>This is done by examining in each prepare call which file descriptors need	1457	<p>This is done by examining in each prepare call which file descriptors need
649	to be watched by the other library, registering ev_io watchers for them	1458	to be watched by the other library, registering <code>ev_io</code> watchers for
650	and starting an ev_timer watcher for any timeouts (many libraries provide	1459	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
651	just this functionality). Then, in the check watcher you check for any	1460	provide just this functionality). Then, in the check watcher you check for
652	events that occured (by making your callbacks set soem flags for example)	1461	any events that occured (by checking the pending status of all watchers
653	and call back into the library.</p>	1462	and stopping them) and call back into the library. The I/O and timer
		1463	callbacks will never actually be called (but must be valid nevertheless,
		1464	because you never know, you know?).</p>
654	<p>As another example, the perl Coro module uses these hooks to integrate	1465	<p>As another example, the Perl Coro module uses these hooks to integrate
655	coroutines into libev programs, by yielding to other active coroutines	1466	coroutines into libev programs, by yielding to other active coroutines
656	during each prepare and only letting the process block if no coroutines	1467	during each prepare and only letting the process block if no coroutines
657	are ready to run.</p>	1468	are ready to run (it's actually more complicated: it only runs coroutines
		1469	with priority higher than or equal to the event loop and one coroutine
		1470	of lower priority, but only once, using idle watchers to keep the event
		1471	loop from blocking if lower-priority coroutines are active, thus mapping
		1472	low-priority coroutines to idle/background tasks).</p>
658	<dl>	1473	<dl>
659	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1474	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
660	<dt>ev_check_init (ev_check *, callback)</dt>	1475	<dt>ev_check_init (ev_check *, callback)</dt>
661	<dd>	1476	<dd>
662	<p>Initialises and configures the prepare or check watcher - they have no	1477	<p>Initialises and configures the prepare or check watcher - they have no
663	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1478	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
664	macros, but using them is utterly, utterly pointless.</p>	1479	macros, but using them is utterly, utterly and completely pointless.</p>
665	</dd>	1480	</dd>
666	</dl>	1481	</dl>
		1482	<p>Example: To include a library such as adns, you would add IO watchers
		1483	and a timeout watcher in a prepare handler, as required by libadns, and
		1484	in a check watcher, destroy them and call into libadns. What follows is
		1485	pseudo-code only of course:</p>
		1486	<pre> static ev_io iow [nfd];
		1487	static ev_timer tw;
667		1488
		1489	static void
		1490	io_cb (ev_loop loop, ev_io w, int revents)
		1491	{
		1492	// set the relevant poll flags
		1493	// could also call adns_processreadable etc. here
		1494	struct pollfd fd = (struct pollfd )w->data;
		1495	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1496	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1497	}
		1498
		1499	// create io watchers for each fd and a timer before blocking
		1500	static void
		1501	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1502	{
		1503	int timeout = 3600000;
		1504	struct pollfd fds [nfd];
		1505	// actual code will need to loop here and realloc etc.
		1506	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1507
		1508	/* the callback is illegal, but won't be called as we stop during check */
		1509	ev_timer_init (&tw, 0, timeout * 1e-3);
		1510	ev_timer_start (loop, &tw);
		1511
		1512	// create on ev_io per pollfd
		1513	for (int i = 0; i < nfd; ++i)
		1514	{
		1515	ev_io_init (iow + i, io_cb, fds [i].fd,
		1516	((fds [i].events & POLLIN ? EV_READ : 0)
		1517	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1518
		1519	fds [i].revents = 0;
		1520	iow [i].data = fds + i;
		1521	ev_io_start (loop, iow + i);
		1522	}
		1523	}
		1524
		1525	// stop all watchers after blocking
		1526	static void
		1527	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1528	{
		1529	ev_timer_stop (loop, &tw);
		1530
		1531	for (int i = 0; i < nfd; ++i)
		1532	ev_io_stop (loop, iow + i);
		1533
		1534	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1535	}
		1536
		1537
		1538
		1539
		1540	</pre>
		1541
668	</div>	1542	</div>
669	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1543	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1544	<div id="code_ev_embed_code_when_one_backend_-2">
		1545	<p>This is a rather advanced watcher type that lets you embed one event loop
		1546	into another (currently only <code>ev_io</code> events are supported in the embedded
		1547	loop, other types of watchers might be handled in a delayed or incorrect
		1548	fashion and must not be used).</p>
		1549	<p>There are primarily two reasons you would want that: work around bugs and
		1550	prioritise I/O.</p>
		1551	<p>As an example for a bug workaround, the kqueue backend might only support
		1552	sockets on some platform, so it is unusable as generic backend, but you
		1553	still want to make use of it because you have many sockets and it scales
		1554	so nicely. In this case, you would create a kqueue-based loop and embed it
		1555	into your default loop (which might use e.g. poll). Overall operation will
		1556	be a bit slower because first libev has to poll and then call kevent, but
		1557	at least you can use both at what they are best.</p>
		1558	<p>As for prioritising I/O: rarely you have the case where some fds have
		1559	to be watched and handled very quickly (with low latency), and even
		1560	priorities and idle watchers might have too much overhead. In this case
		1561	you would put all the high priority stuff in one loop and all the rest in
		1562	a second one, and embed the second one in the first.</p>
		1563	<p>As long as the watcher is active, the callback will be invoked every time
		1564	there might be events pending in the embedded loop. The callback must then
		1565	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1566	their callbacks (you could also start an idle watcher to give the embedded
		1567	loop strictly lower priority for example). You can also set the callback
		1568	to <code>0</code>, in which case the embed watcher will automatically execute the
		1569	embedded loop sweep.</p>
		1570	<p>As long as the watcher is started it will automatically handle events. The
		1571	callback will be invoked whenever some events have been handled. You can
		1572	set the callback to <code>0</code> to avoid having to specify one if you are not
		1573	interested in that.</p>
		1574	<p>Also, there have not currently been made special provisions for forking:
		1575	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1576	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1577	yourself.</p>
		1578	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1579	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1580	portable one.</p>
		1581	<p>So when you want to use this feature you will always have to be prepared
		1582	that you cannot get an embeddable loop. The recommended way to get around
		1583	this is to have a separate variables for your embeddable loop, try to
		1584	create it, and if that fails, use the normal loop for everything:</p>
		1585	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1586	struct ev_loop *loop_lo = 0;
		1587	struct ev_embed embed;
		1588
		1589	// see if there is a chance of getting one that works
		1590	// (remember that a flags value of 0 means autodetection)
		1591	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1592	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1593	: 0;
		1594
		1595	// if we got one, then embed it, otherwise default to loop_hi
		1596	if (loop_lo)
		1597	{
		1598	ev_embed_init (&embed, 0, loop_lo);
		1599	ev_embed_start (loop_hi, &embed);
		1600	}
		1601	else
		1602	loop_lo = loop_hi;
		1603
		1604	</pre>
		1605	<dl>
		1606	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1607	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1608	<dd>
		1609	<p>Configures the watcher to embed the given loop, which must be
		1610	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1611	invoked automatically, otherwise it is the responsibility of the callback
		1612	to invoke it (it will continue to be called until the sweep has been done,
		1613	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1614	</dd>
		1615	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1616	<dd>
		1617	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1618	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1619	apropriate way for embedded loops.</p>
		1620	</dd>
		1621	<dt>struct ev_loop *loop [read-only]</dt>
		1622	<dd>
		1623	<p>The embedded event loop.</p>
		1624	</dd>
		1625	</dl>
		1626
		1627
		1628
		1629
		1630
		1631	</div>
		1632	<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>
		1633	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1634	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1635	whoever is a good citizen cared to tell libev about it by calling
		1636	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1637	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1638	and only in the child after the fork. If whoever good citizen calling
		1639	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1640	handlers will be invoked, too, of course.</p>
		1641	<dl>
		1642	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1643	<dd>
		1644	<p>Initialises and configures the fork watcher - it has no parameters of any
		1645	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1646	believe me.</p>
		1647	</dd>
		1648	</dl>
		1649
		1650
		1651
		1652
		1653
		1654	</div>
		1655	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
670	<div id="OTHER_FUNCTIONS_CONTENT">	1656	<div id="OTHER_FUNCTIONS_CONTENT">
671	<p>There are some other fucntions of possible interest. Described. Here. Now.</p>	1657	<p>There are some other functions of possible interest. Described. Here. Now.</p>
672	<dl>	1658	<dl>
673	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1659	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
674	<dd>	1660	<dd>
675	<p>This function combines a simple timer and an I/O watcher, calls your	1661	<p>This function combines a simple timer and an I/O watcher, calls your
676	callback on whichever event happens first and automatically stop both	1662	callback on whichever event happens first and automatically stop both
677	watchers. This is useful if you want to wait for a single event on an fd	1663	watchers. This is useful if you want to wait for a single event on an fd
678	or timeout without havign to allocate/configure/start/stop/free one or	1664	or timeout without having to allocate/configure/start/stop/free one or
679	more watchers yourself.</p>	1665	more watchers yourself.</p>
680	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is	1666	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
681	ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set	1667	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
682	will be craeted and started.</p>	1668	<code>events</code> set will be craeted and started.</p>
683	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1669	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
684	started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat	1670	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
685	= 0) will be started.</p>	1671	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
		1672	dubious value.</p>
686	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and	1673	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
687	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1674	passed an <code>revents</code> set like normal event callbacks (a combination of
688	EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p>	1675	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
		1676	value passed to <code>ev_once</code>:</p>
689	<pre> static void stdin_ready (int revents, void *arg)	1677	<pre> static void stdin_ready (int revents, void *arg)
690	{	1678	{
691	if (revents & EV_TIMEOUT)	1679	if (revents & EV_TIMEOUT)
692	/* doh, nothing entered */	1680	/* doh, nothing entered */;
693	else if (revents & EV_READ)	1681	else if (revents & EV_READ)
694	/* stdin might have data for us, joy! */	1682	/* stdin might have data for us, joy! */;
695	}	1683	}
696		1684
697	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1685	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
698		1686
699	</pre>	1687	</pre>
700	</dd>	1688	</dd>
701	<dt>ev_feed_event (loop, watcher, int events)</dt>	1689	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
702	<dd>	1690	<dd>
703	<p>Feeds the given event set into the event loop, as if the specified event	1691	<p>Feeds the given event set into the event loop, as if the specified event
704	has happened for the specified watcher (which must be a pointer to an	1692	had happened for the specified watcher (which must be a pointer to an
705	initialised but not necessarily active event watcher).</p>	1693	initialised but not necessarily started event watcher).</p>
706	</dd>	1694	</dd>
707	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1695	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
708	<dd>	1696	<dd>
709	<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>	1697	<p>Feed an event on the given fd, as if a file descriptor backend detected
		1698	the given events it.</p>
710	</dd>	1699	</dd>
711	<dt>ev_feed_signal_event (loop, int signum)</dt>	1700	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
712	<dd>	1701	<dd>
713	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1702	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1703	loop!).</p>
714	</dd>	1704	</dd>
715	</dl>	1705	</dl>
716		1706
		1707
		1708
		1709
		1710
717	</div>	1711	</div>
718	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1712	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1713	<div id="LIBEVENT_EMULATION_CONTENT">
		1714	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1715	emulate the internals of libevent, so here are some usage hints:</p>
		1716	<dl>
		1717	<dt>* Use it by including <event.h>, as usual.</dt>
		1718	<dt>* The following members are fully supported: ev_base, ev_callback,
		1719	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1720	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1721	maintained by libev, it does not work exactly the same way as in libevent (consider
		1722	it a private API).</dt>
		1723	<dt>* Priorities are not currently supported. Initialising priorities
		1724	will fail and all watchers will have the same priority, even though there
		1725	is an ev_pri field.</dt>
		1726	<dt>* Other members are not supported.</dt>
		1727	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1728	to use the libev header file and library.</dt>
		1729	</dl>
		1730
		1731	</div>
		1732	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1733	<div id="C_SUPPORT_CONTENT">
		1734	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1735	you to use some convinience methods to start/stop watchers and also change
		1736	the callback model to a model using method callbacks on objects.</p>
		1737	<p>To use it,</p>
		1738	<pre> #include <ev++.h>
		1739
		1740	</pre>
		1741	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1742	and puts all of its definitions (many of them macros) into the global
		1743	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1744	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1745	<code>EV_MULTIPLICITY</code>.</p>
		1746	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1747	<dl>
		1748	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1749	<dd>
		1750	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1751	macros from <cite>ev.h</cite>.</p>
		1752	</dd>
		1753	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1754	<dd>
		1755	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1756	</dd>
		1757	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1758	<dd>
		1759	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1760	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1761	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1762	defines by many implementations.</p>
		1763	<p>All of those classes have these methods:</p>
		1764	<p>
		1765	<dl>
		1766	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1767	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1768	<dt>ev::TYPE::~TYPE</dt>
		1769	<dd>
		1770	<p>The constructor takes a pointer to an object and a method pointer to
		1771	the event handler callback to call in this class. The constructor calls
		1772	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1773	before starting it. If you do not specify a loop then the constructor
		1774	automatically associates the default loop with this watcher.</p>
		1775	<p>The destructor automatically stops the watcher if it is active.</p>
		1776	</dd>
		1777	<dt>w->set (struct ev_loop *)</dt>
		1778	<dd>
		1779	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1780	do this when the watcher is inactive (and not pending either).</p>
		1781	</dd>
		1782	<dt>w->set ([args])</dt>
		1783	<dd>
		1784	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1785	called at least once. Unlike the C counterpart, an active watcher gets
		1786	automatically stopped and restarted.</p>
		1787	</dd>
		1788	<dt>w->start ()</dt>
		1789	<dd>
		1790	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1791	constructor already takes the loop.</p>
		1792	</dd>
		1793	<dt>w->stop ()</dt>
		1794	<dd>
		1795	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1796	</dd>
		1797	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1798	<dd>
		1799	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1800	<code>ev_TYPE_again</code> function.</p>
		1801	</dd>
		1802	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1803	<dd>
		1804	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1805	</dd>
		1806	<dt>w->update () <code>ev::stat</code> only</dt>
		1807	<dd>
		1808	<p>Invokes <code>ev_stat_stat</code>.</p>
		1809	</dd>
		1810	</dl>
		1811	</p>
		1812	</dd>
		1813	</dl>
		1814	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1815	the constructor.</p>
		1816	<pre> class myclass
		1817	{
		1818	ev_io io; void io_cb (ev::io &w, int revents);
		1819	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1820
		1821	myclass ();
		1822	}
		1823
		1824	myclass::myclass (int fd)
		1825	: io (this, &myclass::io_cb),
		1826	idle (this, &myclass::idle_cb)
		1827	{
		1828	io.start (fd, ev::READ);
		1829	}
		1830
		1831
		1832
		1833
		1834	</pre>
		1835
		1836	</div>
		1837	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		1838	<div id="MACRO_MAGIC_CONTENT">
		1839	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1840	<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
		1841	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1842	<p>To make it easier to write programs that cope with either variant, the
		1843	following macros are defined:</p>
		1844	<dl>
		1845	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		1846	<dd>
		1847	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		1848	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		1849	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		1850	<pre> ev_unref (EV_A);
		1851	ev_timer_add (EV_A_ watcher);
		1852	ev_loop (EV_A_ 0);
		1853
		1854	</pre>
		1855	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		1856	which is often provided by the following macro.</p>
		1857	</dd>
		1858	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		1859	<dd>
		1860	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		1861	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		1862	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		1863	<pre> // this is how ev_unref is being declared
		1864	static void ev_unref (EV_P);
		1865
		1866	// this is how you can declare your typical callback
		1867	static void cb (EV_P_ ev_timer *w, int revents)
		1868
		1869	</pre>
		1870	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		1871	suitable for use with <code>EV_A</code>.</p>
		1872	</dd>
		1873	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		1874	<dd>
		1875	<p>Similar to the other two macros, this gives you the value of the default
		1876	loop, if multiple loops are supported ("ev loop default").</p>
		1877	</dd>
		1878	</dl>
		1879	<p>Example: Declare and initialise a check watcher, utilising the above
		1880	macros so it will work regardless of whether multiple loops are supported
		1881	or not.</p>
		1882	<pre> static void
		1883	check_cb (EV_P_ ev_timer *w, int revents)
		1884	{
		1885	ev_check_stop (EV_A_ w);
		1886	}
		1887
		1888	ev_check check;
		1889	ev_check_init (&check, check_cb);
		1890	ev_check_start (EV_DEFAULT_ &check);
		1891	ev_loop (EV_DEFAULT_ 0);
		1892
		1893	</pre>
		1894
		1895	</div>
		1896	<h1 id="EMBEDDING">EMBEDDING</h1>
		1897	<div id="EMBEDDING_CONTENT">
		1898	<p>Libev can (and often is) directly embedded into host
		1899	applications. Examples of applications that embed it include the Deliantra
		1900	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1901	and rxvt-unicode.</p>
		1902	<p>The goal is to enable you to just copy the neecssary files into your
		1903	source directory without having to change even a single line in them, so
		1904	you can easily upgrade by simply copying (or having a checked-out copy of
		1905	libev somewhere in your source tree).</p>
		1906
		1907	</div>
		1908	<h2 id="FILESETS">FILESETS</h2>
		1909	<div id="FILESETS_CONTENT">
		1910	<p>Depending on what features you need you need to include one or more sets of files
		1911	in your app.</p>
		1912
		1913	</div>
		1914	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1915	<div id="CORE_EVENT_LOOP_CONTENT">
		1916	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1917	configuration (no autoconf):</p>
		1918	<pre> #define EV_STANDALONE 1
		1919	#include "ev.c"
		1920
		1921	</pre>
		1922	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1923	single C source file only to provide the function implementations. To use
		1924	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1925	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1926	where you can put other configuration options):</p>
		1927	<pre> #define EV_STANDALONE 1
		1928	#include "ev.h"
		1929
		1930	</pre>
		1931	<p>Both header files and implementation files can be compiled with a C++
		1932	compiler (at least, thats a stated goal, and breakage will be treated
		1933	as a bug).</p>
		1934	<p>You need the following files in your source tree, or in a directory
		1935	in your include path (e.g. in libev/ when using -Ilibev):</p>
		1936	<pre> ev.h
		1937	ev.c
		1938	ev_vars.h
		1939	ev_wrap.h
		1940
		1941	ev_win32.c required on win32 platforms only
		1942
		1943	ev_select.c only when select backend is enabled (which is enabled by default)
		1944	ev_poll.c only when poll backend is enabled (disabled by default)
		1945	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1946	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1947	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1948
		1949	</pre>
		1950	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		1951	to compile this single file.</p>
		1952
		1953	</div>
		1954	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		1955	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		1956	<p>To include the libevent compatibility API, also include:</p>
		1957	<pre> #include "event.c"
		1958
		1959	</pre>
		1960	<p>in the file including <cite>ev.c</cite>, and:</p>
		1961	<pre> #include "event.h"
		1962
		1963	</pre>
		1964	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		1965	<p>You need the following additional files for this:</p>
		1966	<pre> event.h
		1967	event.c
		1968
		1969	</pre>
		1970
		1971	</div>
		1972	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		1973	<div id="AUTOCONF_SUPPORT_CONTENT">
		1974	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		1975	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		1976	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		1977	include <cite>config.h</cite> and configure itself accordingly.</p>
		1978	<p>For this of course you need the m4 file:</p>
		1979	<pre> libev.m4
		1980
		1981	</pre>
		1982
		1983	</div>
		1984	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		1985	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		1986	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		1987	before including any of its files. The default is not to build for multiplicity
		1988	and only include the select backend.</p>
		1989	<dl>
		1990	<dt>EV_STANDALONE</dt>
		1991	<dd>
		1992	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		1993	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		1994	implementations for some libevent functions (such as logging, which is not
		1995	supported). It will also not define any of the structs usually found in
		1996	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		1997	</dd>
		1998	<dt>EV_USE_MONOTONIC</dt>
		1999	<dd>
		2000	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2001	monotonic clock option at both compiletime and runtime. Otherwise no use
		2002	of the monotonic clock option will be attempted. If you enable this, you
		2003	usually have to link against librt or something similar. Enabling it when
		2004	the functionality isn't available is safe, though, althoguh you have
		2005	to make sure you link against any libraries where the <code>clock_gettime</code>
		2006	function is hiding in (often <cite>-lrt</cite>).</p>
		2007	</dd>
		2008	<dt>EV_USE_REALTIME</dt>
		2009	<dd>
		2010	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2011	realtime clock option at compiletime (and assume its availability at
		2012	runtime if successful). Otherwise no use of the realtime clock option will
		2013	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		2014	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		2015	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		2016	</dd>
		2017	<dt>EV_USE_SELECT</dt>
		2018	<dd>
		2019	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		2020	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		2021	other method takes over, select will be it. Otherwise the select backend
		2022	will not be compiled in.</p>
		2023	</dd>
		2024	<dt>EV_SELECT_USE_FD_SET</dt>
		2025	<dd>
		2026	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		2027	structure. This is useful if libev doesn't compile due to a missing
		2028	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		2029	exotic systems. This usually limits the range of file descriptors to some
		2030	low limit such as 1024 or might have other limitations (winsocket only
		2031	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		2032	influence the size of the <code>fd_set</code> used.</p>
		2033	</dd>
		2034	<dt>EV_SELECT_IS_WINSOCKET</dt>
		2035	<dd>
		2036	<p>When defined to <code>1</code>, the select backend will assume that
		2037	select/socket/connect etc. don't understand file descriptors but
		2038	wants osf handles on win32 (this is the case when the select to
		2039	be used is the winsock select). This means that it will call
		2040	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		2041	it is assumed that all these functions actually work on fds, even
		2042	on win32. Should not be defined on non-win32 platforms.</p>
		2043	</dd>
		2044	<dt>EV_USE_POLL</dt>
		2045	<dd>
		2046	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		2047	backend. Otherwise it will be enabled on non-win32 platforms. It
		2048	takes precedence over select.</p>
		2049	</dd>
		2050	<dt>EV_USE_EPOLL</dt>
		2051	<dd>
		2052	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		2053	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2054	otherwise another method will be used as fallback. This is the
		2055	preferred backend for GNU/Linux systems.</p>
		2056	</dd>
		2057	<dt>EV_USE_KQUEUE</dt>
		2058	<dd>
		2059	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2060	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2061	otherwise another method will be used as fallback. This is the preferred
		2062	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2063	supports some types of fds correctly (the only platform we found that
		2064	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2065	not be used unless explicitly requested. The best way to use it is to find
		2066	out whether kqueue supports your type of fd properly and use an embedded
		2067	kqueue loop.</p>
		2068	</dd>
		2069	<dt>EV_USE_PORT</dt>
		2070	<dd>
		2071	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2072	10 port style backend. Its availability will be detected at runtime,
		2073	otherwise another method will be used as fallback. This is the preferred
		2074	backend for Solaris 10 systems.</p>
		2075	</dd>
		2076	<dt>EV_USE_DEVPOLL</dt>
		2077	<dd>
		2078	<p>reserved for future expansion, works like the USE symbols above.</p>
		2079	</dd>
		2080	<dt>EV_USE_INOTIFY</dt>
		2081	<dd>
		2082	<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
		2083	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2084	be detected at runtime.</p>
		2085	</dd>
		2086	<dt>EV_H</dt>
		2087	<dd>
		2088	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2089	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2090	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2091	</dd>
		2092	<dt>EV_CONFIG_H</dt>
		2093	<dd>
		2094	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2095	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2096	<code>EV_H</code>, above.</p>
		2097	</dd>
		2098	<dt>EV_EVENT_H</dt>
		2099	<dd>
		2100	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2101	of how the <cite>event.h</cite> header can be found.</p>
		2102	</dd>
		2103	<dt>EV_PROTOTYPES</dt>
		2104	<dd>
		2105	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2106	prototypes, but still define all the structs and other symbols. This is
		2107	occasionally useful if you want to provide your own wrapper functions
		2108	around libev functions.</p>
		2109	</dd>
		2110	<dt>EV_MULTIPLICITY</dt>
		2111	<dd>
		2112	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2113	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2114	additional independent event loops. Otherwise there will be no support
		2115	for multiple event loops and there is no first event loop pointer
		2116	argument. Instead, all functions act on the single default loop.</p>
		2117	</dd>
		2118	<dt>EV_MINPRI</dt>
		2119	<dt>EV_MAXPRI</dt>
		2120	<dd>
		2121	<p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
		2122	<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
		2123	provide for more priorities by overriding those symbols (usually defined
		2124	to be <code>-2</code> and <code>2</code>, respectively).</p>
		2125	<p>When doing priority-based operations, libev usually has to linearly search
		2126	all the priorities, so having many of them (hundreds) uses a lot of space
		2127	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2128	fine.</p>
		2129	<p>If your embedding app does not need any priorities, defining these both to
		2130	<code>0</code> will save some memory and cpu.</p>
		2131	</dd>
		2132	<dt>EV_PERIODIC_ENABLE</dt>
		2133	<dd>
		2134	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2135	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2136	code.</p>
		2137	</dd>
		2138	<dt>EV_IDLE_ENABLE</dt>
		2139	<dd>
		2140	<p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
		2141	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2142	code.</p>
		2143	</dd>
		2144	<dt>EV_EMBED_ENABLE</dt>
		2145	<dd>
		2146	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2147	defined to be <code>0</code>, then they are not.</p>
		2148	</dd>
		2149	<dt>EV_STAT_ENABLE</dt>
		2150	<dd>
		2151	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2152	defined to be <code>0</code>, then they are not.</p>
		2153	</dd>
		2154	<dt>EV_FORK_ENABLE</dt>
		2155	<dd>
		2156	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2157	defined to be <code>0</code>, then they are not.</p>
		2158	</dd>
		2159	<dt>EV_MINIMAL</dt>
		2160	<dd>
		2161	<p>If you need to shave off some kilobytes of code at the expense of some
		2162	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2163	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2164	</dd>
		2165	<dt>EV_PID_HASHSIZE</dt>
		2166	<dd>
		2167	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2168	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2169	than enough. If you need to manage thousands of children you might want to
		2170	increase this value (<i>must</i> be a power of two).</p>
		2171	</dd>
		2172	<dt>EV_INOTIFY_HASHSIZE</dt>
		2173	<dd>
		2174	<p><code>ev_staz</code> watchers use a small hash table to distribute workload by
		2175	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2176	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2177	watchers you might want to increase this value (<i>must</i> be a power of
		2178	two).</p>
		2179	</dd>
		2180	<dt>EV_COMMON</dt>
		2181	<dd>
		2182	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2183	this macro to a something else you can include more and other types of
		2184	members. You have to define it each time you include one of the files,
		2185	though, and it must be identical each time.</p>
		2186	<p>For example, the perl EV module uses something like this:</p>
		2187	<pre> #define EV_COMMON \
		2188	SV self; / contains this struct */ \
		2189	SV cb_sv, fh /* note no trailing ";" */
		2190
		2191	</pre>
		2192	</dd>
		2193	<dt>EV_CB_DECLARE (type)</dt>
		2194	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2195	<dt>ev_set_cb (ev, cb)</dt>
		2196	<dd>
		2197	<p>Can be used to change the callback member declaration in each watcher,
		2198	and the way callbacks are invoked and set. Must expand to a struct member
		2199	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2200	their default definitions. One possible use for overriding these is to
		2201	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2202	method calls instead of plain function calls in C++.</p>
		2203
		2204	</div>
		2205	<h2 id="EXAMPLES">EXAMPLES</h2>
		2206	<div id="EXAMPLES_CONTENT">
		2207	<p>For a real-world example of a program the includes libev
		2208	verbatim, you can have a look at the EV perl module
		2209	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2210	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2211	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2212	will be compiled. It is pretty complex because it provides its own header
		2213	file.</p>
		2214	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2215	that everybody includes and which overrides some configure choices:</p>
		2216	<pre> #define EV_MINIMAL 1
		2217	#define EV_USE_POLL 0
		2218	#define EV_MULTIPLICITY 0
		2219	#define EV_PERIODIC_ENABLE 0
		2220	#define EV_STAT_ENABLE 0
		2221	#define EV_FORK_ENABLE 0
		2222	#define EV_CONFIG_H <config.h>
		2223	#define EV_MINPRI 0
		2224	#define EV_MAXPRI 0
		2225
		2226	#include "ev++.h"
		2227
		2228	</pre>
		2229	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2230	<pre> #include "ev_cpp.h"
		2231	#include "ev.c"
		2232
		2233
		2234
		2235
		2236	</pre>
		2237
		2238	</div>
		2239	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2240	<div id="COMPLEXITIES_CONTENT">
		2241	<p>In this section the complexities of (many of) the algorithms used inside
		2242	libev will be explained. For complexity discussions about backends see the
		2243	documentation for <code>ev_default_init</code>.</p>
		2244	<p>
		2245	<dl>
		2246	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2247	<dd>
		2248	<p>This means that, when you have a watcher that triggers in one hour and
		2249	there are 100 watchers that would trigger before that then inserting will
		2250	have to skip those 100 watchers.</p>
		2251	</dd>
		2252	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2253	<dd>
		2254	<p>That means that for changing a timer costs less than removing/adding them
		2255	as only the relative motion in the event queue has to be paid for.</p>
		2256	</dd>
		2257	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2258	<dd>
		2259	<p>These just add the watcher into an array or at the head of a list. If
		2260	the array needs to be extended libev needs to realloc and move the whole
		2261	array, but this happen asymptotically less and less with more watchers,
		2262	thus amortised O(1).</p>
		2263	</dd>
		2264	<dt>Stopping check/prepare/idle watchers: O(1)</dt>
		2265	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
		2266	<dd>
		2267	<p>These watchers are stored in lists then need to be walked to find the
		2268	correct watcher to remove. The lists are usually short (you don't usually
		2269	have many watchers waiting for the same fd or signal).</p>
		2270	</dd>
		2271	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2272	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2273	<dd>
		2274	<p>A change means an I/O watcher gets started or stopped, which requires
		2275	libev to recalculate its status (and possibly tell the kernel).</p>
		2276	</dd>
		2277	<dt>Activating one watcher: O(1)</dt>
		2278	<dt>Priority handling: O(number_of_priorities)</dt>
		2279	<dd>
		2280	<p>Priorities are implemented by allocating some space for each
		2281	priority. When doing priority-based operations, libev usually has to
		2282	linearly search all the priorities.</p>
		2283	</dd>
		2284	</dl>
		2285	</p>
		2286
		2287
		2288
		2289
		2290
		2291	</div>
		2292	<h1 id="AUTHOR">AUTHOR</h1>
719	<div id="AUTHOR_CONTENT">	2293	<div id="AUTHOR_CONTENT">
720	<p>Marc Lehmann <libev@schmorp.de>.</p>	2294	<p>Marc Lehmann <libev@schmorp.de>.</p>
721		2295
722	</div>	2296	</div>
723	</div></body>	2297	</div></body>
724	</html>	2298	</html>

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Revision 1.66 by root, Fri Dec 7 19:15:39 2007 UTC