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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>" />
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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>
		33	<ul><li><a href="#The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</a></li>
		34	<li><a href="#Watcher_Specific_Functions">Watcher-Specific Functions</a></li>
		35	</ul>
		36	</li>
30	<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li>	37	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a>
		38	<ul><li><a href="#Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</a></li>
		39	</ul>
		40	</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>	41	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a>
		42	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</a></li>
		43	</ul>
		44	</li>
32	<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li>	45	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a>
33	<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li>	46	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</a></li>
		47	</ul>
		48	</li>
		49	<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a>
		50	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</a></li>
		51	</ul>
		52	</li>
		53	<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a>
		54	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</a></li>
		55	</ul>
		56	</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>	57	<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>
35	<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li>	58	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</a></li>
		59	</ul>
		60	</li>
		61	<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>
		62	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</a></li>
		63	</ul>
		64	</li>
		65	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a>
		66	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</a></li>
		67	</ul>
		68	</li>
		69	<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>
		70	<ul><li><a href="#Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</a></li>
		71	</ul>
		72	</li>
36	</ul>	73	</ul>
37	</li>	74	</li>
38	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	75	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		76	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		77	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		78	<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
		79	<li><a href="#EMBEDDING">EMBEDDING</a>
		80	<ul><li><a href="#FILESETS">FILESETS</a>
		81	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		82	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		83	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		84	</ul>
		85	</li>
		86	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		87	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		88	</ul>
		89	</li>
		90	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
39	<li><a href="#AUTHOR">AUTHOR</a>	91	<li><a href="#AUTHOR">AUTHOR</a>
40	</li>	92	</li>
41	</ul><hr />	93	</ul><hr />
42	<!-- INDEX END -->	94	<!-- INDEX END -->
43		95
44	<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>	96	<h1 id="NAME">NAME</h1>
45	<div id="NAME_CONTENT">	97	<div id="NAME_CONTENT">
46	<p>libev - a high performance full-featured event loop written in C</p>	98	<p>libev - a high performance full-featured event loop written in C</p>
47		99
48	</div>	100	</div>
49	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>	101	<h1 id="SYNOPSIS">SYNOPSIS</h1>
50	<div id="SYNOPSIS_CONTENT">	102	<div id="SYNOPSIS_CONTENT">
51	<pre> #include <ev.h>	103	<pre> #include <ev.h>
52		104
53	</pre>	105	</pre>
54		106
55	</div>	107	</div>
56	<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>	108	<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
		109	<div id="EXAMPLE_PROGRAM_CONTENT">
		110	<pre> #include <ev.h>
		111
		112	ev_io stdin_watcher;
		113	ev_timer timeout_watcher;
		114
		115	/* called when data readable on stdin */
		116	static void
		117	stdin_cb (EV_P_ struct ev_io *w, int revents)
		118	{
		119	/* puts ("stdin ready"); */
		120	ev_io_stop (EV_A_ w); /* just a syntax example */
		121	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		122	}
		123
		124	static void
		125	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		126	{
		127	/* puts ("timeout"); */
		128	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		129	}
		130
		131	int
		132	main (void)
		133	{
		134	struct ev_loop *loop = ev_default_loop (0);
		135
		136	/* initialise an io watcher, then start it */
		137	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		138	ev_io_start (loop, &stdin_watcher);
		139
		140	/* simple non-repeating 5.5 second timeout */
		141	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		142	ev_timer_start (loop, &timeout_watcher);
		143
		144	/* loop till timeout or data ready */
		145	ev_loop (loop, 0);
		146
		147	return 0;
		148	}
		149
		150	</pre>
		151
		152	</div>
		153	<h1 id="DESCRIPTION">DESCRIPTION</h1>
57	<div id="DESCRIPTION_CONTENT">	154	<div id="DESCRIPTION_CONTENT">
		155	<p>The newest version of this document is also available as a html-formatted
		156	web page you might find easier to navigate when reading it for the first
		157	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	158	<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	159	file descriptor being readable or a timeout occuring), and it will manage
60	these event sources and provide your program with events.</p>	160	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	161	<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	162	(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	165	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	166	details of the event, and then hand it over to libev by <i>starting</i> the
67	watcher.</p>	167	watcher.</p>
68		168
69	</div>	169	</div>
70	<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>	170	<h1 id="FEATURES">FEATURES</h1>
71	<div id="FEATURES_CONTENT">	171	<div id="FEATURES_CONTENT">
72	<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific	172	<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	173	BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
74	timers with customised rescheduling, signal events, process status change	174	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	175	(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	176	with customised rescheduling (<code>ev_periodic</code>), synchronous signals
77	fast (see a <b>http://libev.schmorp.de/bench.html</b> (<cite>benchmark</cite>) comparing it	177	(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
78	to libevent).</p>	178	watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
		179	<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
		180	file watchers (<code>ev_stat</code>) and even limited support for fork events
		181	(<code>ev_fork</code>).</p>
		182	<p>It also is quite fast (see this
		183	<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
		184	for example).</p>
79		185
80	</div>	186	</div>
81	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	187	<h1 id="CONVENTIONS">CONVENTIONS</h1>
82	<div id="CONVENTIONS_CONTENT">	188	<div id="CONVENTIONS_CONTENT">
83	<p>Libev is very configurable. In this manual the default configuration	189	<p>Libev is very configurable. In this manual the default configuration will
84	will be described, which supports multiple event loops. For more info	190	be described, which supports multiple event loops. For more info about
85	about various configuraiton options please have a look at the file	191	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	192	this manual. If libev was configured without support for multiple event
87	support for multiple event loops, then all functions taking an initial	193	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>)	194	(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
89	will not have this argument.</p>
90		195
91	</div>	196	</div>
92	<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	197	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
93	<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT">	198	<div id="TIME_REPRESENTATION_CONTENT">
94	<p>Libev represents time as a single floating point number, representing the	199	<p>Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	200	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	201	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	202	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
98	to the double type in C.</p>	203	to the <code>double</code> type in C, and when you need to do any calculations on
		204	it, you should treat it as such.</p>
		205
		206	</div>
		207	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
		208	<div id="GLOBAL_FUNCTIONS_CONTENT">
		209	<p>These functions can be called anytime, even before initialising the
		210	library in any way.</p>
99	<dl>	211	<dl>
100	<dt>ev_tstamp ev_time ()</dt>	212	<dt>ev_tstamp ev_time ()</dt>
101	<dd>	213	<dd>
102	<p>Returns the current time as libev would use it.</p>	214	<p>Returns the current time as libev would use it. Please note that the
		215	<code>ev_now</code> function is usually faster and also often returns the timestamp
		216	you actually want to know.</p>
103	</dd>	217	</dd>
104	<dt>int ev_version_major ()</dt>	218	<dt>int ev_version_major ()</dt>
105	<dt>int ev_version_minor ()</dt>	219	<dt>int ev_version_minor ()</dt>
106	<dd>	220	<dd>
107	<p>You can find out the major and minor version numbers of the library	221	<p>You can find out the major and minor ABI version numbers of the library
108	you linked against by calling the functions <code>ev_version_major</code> and	222	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	223	<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	224	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>	225	version of the library your program was compiled against.</p>
		226	<p>These version numbers refer to the ABI version of the library, not the
		227	release version.</p>
112	<p>Usually, its a good idea to terminate if the major versions mismatch,	228	<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	229	as this indicates an incompatible change. Minor versions are usually
114	compatible to older versions, so a larger minor version alone is usually	230	compatible to older versions, so a larger minor version alone is usually
115	not a problem.</p>	231	not a problem.</p>
		232	<p>Example: Make sure we haven't accidentally been linked against the wrong
		233	version.</p>
		234	<pre> assert (("libev version mismatch",
		235	ev_version_major () == EV_VERSION_MAJOR
		236	&& ev_version_minor () >= EV_VERSION_MINOR));
		237
		238	</pre>
		239	</dd>
		240	<dt>unsigned int ev_supported_backends ()</dt>
		241	<dd>
		242	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		243	value) compiled into this binary of libev (independent of their
		244	availability on the system you are running on). See <code>ev_default_loop</code> for
		245	a description of the set values.</p>
		246	<p>Example: make sure we have the epoll method, because yeah this is cool and
		247	a must have and can we have a torrent of it please!!!11</p>
		248	<pre> assert (("sorry, no epoll, no sex",
		249	ev_supported_backends () & EVBACKEND_EPOLL));
		250
		251	</pre>
		252	</dd>
		253	<dt>unsigned int ev_recommended_backends ()</dt>
		254	<dd>
		255	<p>Return the set of all backends compiled into this binary of libev and also
		256	recommended for this platform. This set is often smaller than the one
		257	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		258	most BSDs and will not be autodetected unless you explicitly request it
		259	(assuming you know what you are doing). This is the set of backends that
		260	libev will probe for if you specify no backends explicitly.</p>
		261	</dd>
		262	<dt>unsigned int ev_embeddable_backends ()</dt>
		263	<dd>
		264	<p>Returns the set of backends that are embeddable in other event loops. This
		265	is the theoretical, all-platform, value. To find which backends
		266	might be supported on the current system, you would need to look at
		267	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		268	recommended ones.</p>
		269	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
116	</dd>	270	</dd>
117	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	271	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
118	<dd>	272	<dd>
119	<p>Sets the allocation function to use (the prototype is similar to the	273	<p>Sets the allocation function to use (the prototype is similar - the
120	realloc function). It is used to allocate and free memory (no surprises	274	semantics is identical - to the realloc C function). It is used to
121	here). If it returns zero when memory needs to be allocated, the library	275	allocate and free memory (no surprises here). If it returns zero when
122	might abort or take some potentially destructive action. The default is	276	memory needs to be allocated, the library might abort or take some
123	your system realloc function.</p>	277	potentially destructive action. The default is your system realloc
		278	function.</p>
124	<p>You could override this function in high-availability programs to, say,	279	<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,	280	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>	281	or even to sleep a while and retry until some memory is available.</p>
		282	<p>Example: Replace the libev allocator with one that waits a bit and then
		283	retries).</p>
		284	<pre> static void *
		285	persistent_realloc (void *ptr, size_t size)
		286	{
		287	for (;;)
		288	{
		289	void *newptr = realloc (ptr, size);
		290
		291	if (newptr)
		292	return newptr;
		293
		294	sleep (60);
		295	}
		296	}
		297
		298	...
		299	ev_set_allocator (persistent_realloc);
		300
		301	</pre>
127	</dd>	302	</dd>
128	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	303	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
129	<dd>	304	<dd>
130	<p>Set the callback function to call on a retryable syscall error (such	305	<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	306	as failed select, poll, epoll_wait). The message is a printable string
132	indicating the system call or subsystem causing the problem. If this	307	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	308	callback is set, then libev will expect it to remedy the sitution, no
134	matter what, when it returns. That is, libev will geenrally retry the	309	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	310	requested operation, or, if the condition doesn't go away, do bad stuff
136	(such as abort).</p>	311	(such as abort).</p>
		312	<p>Example: This is basically the same thing that libev does internally, too.</p>
		313	<pre> static void
		314	fatal_error (const char *msg)
		315	{
		316	perror (msg);
		317	abort ();
		318	}
		319
		320	...
		321	ev_set_syserr_cb (fatal_error);
		322
		323	</pre>
137	</dd>	324	</dd>
138	</dl>	325	</dl>
139		326
140	</div>	327	</div>
141	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	328	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
142	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	329	<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	330	<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	331	types of such loops, the <i>default</i> loop, which supports signals and child
145	events, and dynamically created loops which do not.</p>	332	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	333	<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	334	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 lockign	335	create, you also create another event loop. Libev itself does no locking
149	whatsoever, so if you mix calls to different event loops, make sure you	336	whatsoever, so if you mix calls to the same event loop in different
150	lock (this is usually a bad idea, though, even if done right).</p>	337	threads, make sure you lock (this is usually a bad idea, though, even if
		338	done correctly, because it's hideous and inefficient).</p>
151	<dl>	339	<dl>
152	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	340	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
153	<dd>	341	<dd>
154	<p>This will initialise the default event loop if it hasn't been initialised	342	<p>This will initialise the default event loop if it hasn't been initialised
155	yet and return it. If the default loop could not be initialised, returns	343	yet and return it. If the default loop could not be initialised, returns
156	false. If it already was initialised it simply returns it (and ignores the	344	false. If it already was initialised it simply returns it (and ignores the
157	flags).</p>	345	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
158	<p>If you don't know what event loop to use, use the one returned from this	346	<p>If you don't know what event loop to use, use the one returned from this
159	function.</p>	347	function.</p>
160	<p>The flags argument can be used to specify special behaviour or specific	348	<p>The flags argument can be used to specify special behaviour or specific
161	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p>	349	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
162	<p>It supports the following flags:</p>	350	<p>The following flags are supported:</p>
163	<p>	351	<p>
164	<dl>	352	<dl>
165	<dt>EVFLAG_AUTO</dt>	353	<dt><code>EVFLAG_AUTO</code></dt>
166	<dd>	354	<dd>
167	<p>The default flags value. Use this if you have no clue (its the right	355	<p>The default flags value. Use this if you have no clue (it's the right
168	thing, believe me).</p>	356	thing, believe me).</p>
169	</dd>	357	</dd>
170	<dt>EVFLAG_NOENV</dt>	358	<dt><code>EVFLAG_NOENV</code></dt>
171	<dd>
172	<p>If this flag bit is ored into the flag value then libev will <i>not</i> look
173	at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
174	environment variable will override the flags completely. This is useful
175	to try out specific backends to tets their performance, or to work around
176	bugs.</p>
177	</dd>	359	<dd>
178	<dt>EVMETHOD_SELECT portable select backend</dt>	360	<p>If this flag bit is ored into the flag value (or the program runs setuid
179	<dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt>	361	or setgid) then libev will <i>not</i> look at the environment variable
180	<dt>EVMETHOD_EPOLL linux only</dt>	362	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181	<dt>EVMETHOD_KQUEUE some bsds only</dt>	363	override the flags completely if it is found in the environment. This is
182	<dt>EVMETHOD_DEVPOLL solaris 8 only</dt>	364	useful to try out specific backends to test their performance, or to work
183	<dt>EVMETHOD_PORT solaris 10 only</dt>	365	around bugs.</p>
184	<dd>	366	</dd>
185	<p>If one or more of these are ored into the flags value, then only these	367	<dt><code>EVFLAG_FORKCHECK</code></dt>
186	backends will be tried (in the reverse order as given here). If one are	368	<dd>
187	specified, any backend will do.</p>	369	<p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
		370	a fork, you can also make libev check for a fork in each iteration by
		371	enabling this flag.</p>
		372	<p>This works by calling <code>getpid ()</code> on every iteration of the loop,
		373	and thus this might slow down your event loop if you do a lot of loop
		374	iterations and little real work, but is usually not noticeable (on my
		375	Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
		376	without a syscall and thus <i>very</i> fast, but my Linux system also has
		377	<code>pthread_atfork</code> which is even faster).</p>
		378	<p>The big advantage of this flag is that you can forget about fork (and
		379	forget about forgetting to tell libev about forking) when you use this
		380	flag.</p>
		381	<p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
		382	environment variable.</p>
		383	</dd>
		384	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
		385	<dd>
		386	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
		387	libev tries to roll its own fd_set with no limits on the number of fds,
		388	but if that fails, expect a fairly low limit on the number of fds when
		389	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		390	the fastest backend for a low number of fds.</p>
		391	</dd>
		392	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		393	<dd>
		394	<p>And this is your standard poll(2) backend. It's more complicated than
		395	select, but handles sparse fds better and has no artificial limit on the
		396	number of fds you can use (except it will slow down considerably with a
		397	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		398	</dd>
		399	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		400	<dd>
		401	<p>For few fds, this backend is a bit little slower than poll and select,
		402	but it scales phenomenally better. While poll and select usually scale like
		403	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		404	either O(1) or O(active_fds).</p>
		405	<p>While stopping and starting an I/O watcher in the same iteration will
		406	result in some caching, there is still a syscall per such incident
		407	(because the fd could point to a different file description now), so its
		408	best to avoid that. Also, dup()ed file descriptors might not work very
		409	well if you register events for both fds.</p>
		410	<p>Please note that epoll sometimes generates spurious notifications, so you
		411	need to use non-blocking I/O or other means to avoid blocking when no data
		412	(or space) is available.</p>
		413	</dd>
		414	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		415	<dd>
		416	<p>Kqueue deserves special mention, as at the time of this writing, it
		417	was broken on all BSDs except NetBSD (usually it doesn't work with
		418	anything but sockets and pipes, except on Darwin, where of course its
		419	completely useless). For this reason its not being "autodetected"
		420	unless you explicitly specify it explicitly in the flags (i.e. using
		421	<code>EVBACKEND_KQUEUE</code>).</p>
		422	<p>It scales in the same way as the epoll backend, but the interface to the
		423	kernel is more efficient (which says nothing about its actual speed, of
		424	course). While starting and stopping an I/O watcher does not cause an
		425	extra syscall as with epoll, it still adds up to four event changes per
		426	incident, so its best to avoid that.</p>
		427	</dd>
		428	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		429	<dd>
		430	<p>This is not implemented yet (and might never be).</p>
		431	</dd>
		432	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		433	<dd>
		434	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		435	it's really slow, but it still scales very well (O(active_fds)).</p>
		436	<p>Please note that solaris ports can result in a lot of spurious
		437	notifications, so you need to use non-blocking I/O or other means to avoid
		438	blocking when no data (or space) is available.</p>
		439	</dd>
		440	<dt><code>EVBACKEND_ALL</code></dt>
		441	<dd>
		442	<p>Try all backends (even potentially broken ones that wouldn't be tried
		443	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		444	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
188	</dd>	445	</dd>
189	</dl>	446	</dl>
190	</p>	447	</p>
		448	<p>If one or more of these are ored into the flags value, then only these
		449	backends will be tried (in the reverse order as given here). If none are
		450	specified, most compiled-in backend will be tried, usually in reverse
		451	order of their flag values :)</p>
		452	<p>The most typical usage is like this:</p>
		453	<pre> if (!ev_default_loop (0))
		454	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		455
		456	</pre>
		457	<p>Restrict libev to the select and poll backends, and do not allow
		458	environment settings to be taken into account:</p>
		459	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		460
		461	</pre>
		462	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		463	available (warning, breaks stuff, best use only with your own private
		464	event loop and only if you know the OS supports your types of fds):</p>
		465	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		466
		467	</pre>
191	</dd>	468	</dd>
192	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	469	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
193	<dd>	470	<dd>
194	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	471	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
195	always distinct from the default loop. Unlike the default loop, it cannot	472	always distinct from the default loop. Unlike the default loop, it cannot
196	handle signal and child watchers, and attempts to do so will be greeted by	473	handle signal and child watchers, and attempts to do so will be greeted by
197	undefined behaviour (or a failed assertion if assertions are enabled).</p>	474	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		475	<p>Example: Try to create a event loop that uses epoll and nothing else.</p>
		476	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		477	if (!epoller)
		478	fatal ("no epoll found here, maybe it hides under your chair");
		479
		480	</pre>
198	</dd>	481	</dd>
199	<dt>ev_default_destroy ()</dt>	482	<dt>ev_default_destroy ()</dt>
200	<dd>	483	<dd>
201	<p>Destroys the default loop again (frees all memory and kernel state	484	<p>Destroys the default loop again (frees all memory and kernel state
202	etc.). This stops all registered event watchers (by not touching them in	485	etc.). None of the active event watchers will be stopped in the normal
203	any way whatsoever, although you cnanot rely on this :).</p>	486	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		487	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		488	calling this function, or cope with the fact afterwards (which is usually
		489	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		490	for example).</p>
204	</dd>	491	</dd>
205	<dt>ev_loop_destroy (loop)</dt>	492	<dt>ev_loop_destroy (loop)</dt>
206	<dd>	493	<dd>
207	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	494	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
208	earlier call to <code>ev_loop_new</code>.</p>	495	earlier call to <code>ev_loop_new</code>.</p>
…		…
211	<dd>	498	<dd>
212	<p>This function reinitialises the kernel state for backends that have	499	<p>This function reinitialises the kernel state for backends that have
213	one. Despite the name, you can call it anytime, but it makes most sense	500	one. Despite the name, you can call it anytime, but it makes most sense
214	after forking, in either the parent or child process (or both, but that	501	after forking, in either the parent or child process (or both, but that
215	again makes little sense).</p>	502	again makes little sense).</p>
216	<p>You <i>must</i> call this function after forking if and only if you want to	503	<p>You <i>must</i> call this function in the child process after forking if and
217	use the event library in both processes. If you just fork+exec, you don't	504	only if you want to use the event library in both processes. If you just
218	have to call it.</p>	505	fork+exec, you don't have to call it.</p>
219	<p>The function itself is quite fast and its usually not a problem to call	506	<p>The function itself is quite fast and it's usually not a problem to call
220	it just in case after a fork. To make this easy, the function will fit in	507	it just in case after a fork. To make this easy, the function will fit in
221	quite nicely into a call to <code>pthread_atfork</code>:</p>	508	quite nicely into a call to <code>pthread_atfork</code>:</p>
222	<pre> pthread_atfork (0, 0, ev_default_fork);	509	<pre> pthread_atfork (0, 0, ev_default_fork);
223		510
224	</pre>	511	</pre>
		512	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		513	without calling this function, so if you force one of those backends you
		514	do not need to care.</p>
225	</dd>	515	</dd>
226	<dt>ev_loop_fork (loop)</dt>	516	<dt>ev_loop_fork (loop)</dt>
227	<dd>	517	<dd>
228	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	518	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
229	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	519	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
230	after fork, and how you do this is entirely your own problem.</p>	520	after fork, and how you do this is entirely your own problem.</p>
231	</dd>	521	</dd>
232	<dt>unsigned int ev_method (loop)</dt>	522	<dt>unsigned int ev_loop_count (loop)</dt>
		523	<dd>
		524	<p>Returns the count of loop iterations for the loop, which is identical to
		525	the number of times libev did poll for new events. It starts at <code>0</code> and
		526	happily wraps around with enough iterations.</p>
		527	<p>This value can sometimes be useful as a generation counter of sorts (it
		528	"ticks" the number of loop iterations), as it roughly corresponds with
		529	<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
233	<dd>	530	</dd>
		531	<dt>unsigned int ev_backend (loop)</dt>
		532	<dd>
234	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	533	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
235	use.</p>	534	use.</p>
236	</dd>	535	</dd>
237	<dt>ev_tstamp = ev_now (loop)</dt>	536	<dt>ev_tstamp ev_now (loop)</dt>
238	<dd>	537	<dd>
239	<p>Returns the current "event loop time", which is the time the event loop	538	<p>Returns the current "event loop time", which is the time the event loop
240	got events and started processing them. This timestamp does not change	539	received events and started processing them. This timestamp does not
241	as long as callbacks are being processed, and this is also the base time	540	change as long as callbacks are being processed, and this is also the base
242	used for relative timers. You can treat it as the timestamp of the event	541	time used for relative timers. You can treat it as the timestamp of the
243	occuring (or more correctly, the mainloop finding out about it).</p>	542	event occuring (or more correctly, libev finding out about it).</p>
244	</dd>	543	</dd>
245	<dt>ev_loop (loop, int flags)</dt>	544	<dt>ev_loop (loop, int flags)</dt>
246	<dd>	545	<dd>
247	<p>Finally, this is it, the event handler. This function usually is called	546	<p>Finally, this is it, the event handler. This function usually is called
248	after you initialised all your watchers and you want to start handling	547	after you initialised all your watchers and you want to start handling
249	events.</p>	548	events.</p>
250	<p>If the flags argument is specified as 0, it will not return until either	549	<p>If the flags argument is specified as <code>0</code>, it will not return until
251	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	550	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		551	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		552	relying on all watchers to be stopped when deciding when a program has
		553	finished (especially in interactive programs), but having a program that
		554	automatically loops as long as it has to and no longer by virtue of
		555	relying on its watchers stopping correctly is a thing of beauty.</p>
252	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	556	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
253	those events and any outstanding ones, but will not block your process in	557	those events and any outstanding ones, but will not block your process in
254	case there are no events.</p>	558	case there are no events and will return after one iteration of the loop.</p>
255	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	559	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
256	neccessary) and will handle those and any outstanding ones. It will block	560	neccessary) and will handle those and any outstanding ones. It will block
257	your process until at least one new event arrives.</p>	561	your process until at least one new event arrives, and will return after
258	<p>This flags value could be used to implement alternative looping	562	one iteration of the loop. This is useful if you are waiting for some
259	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	563	external event in conjunction with something not expressible using other
260	more generic mechanism.</p>	564	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
		565	usually a better approach for this kind of thing.</p>
		566	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		567	<pre> - Before the first iteration, call any pending watchers.
		568	* If there are no active watchers (reference count is zero), return.
		569	- Queue all prepare watchers and then call all outstanding watchers.
		570	- If we have been forked, recreate the kernel state.
		571	- Update the kernel state with all outstanding changes.
		572	- Update the "event loop time".
		573	- Calculate for how long to block.
		574	- Block the process, waiting for any events.
		575	- Queue all outstanding I/O (fd) events.
		576	- Update the "event loop time" and do time jump handling.
		577	- Queue all outstanding timers.
		578	- Queue all outstanding periodics.
		579	- If no events are pending now, queue all idle watchers.
		580	- Queue all check watchers.
		581	- Call all queued watchers in reverse order (i.e. check watchers first).
		582	Signals and child watchers are implemented as I/O watchers, and will
		583	be handled here by queueing them when their watcher gets executed.
		584	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		585	were used, return, otherwise continue with step *.
		586
		587	</pre>
		588	<p>Example: Queue some jobs and then loop until no events are outsanding
		589	anymore.</p>
		590	<pre> ... queue jobs here, make sure they register event watchers as long
		591	... as they still have work to do (even an idle watcher will do..)
		592	ev_loop (my_loop, 0);
		593	... jobs done. yeah!
		594
		595	</pre>
261	</dd>	596	</dd>
262	<dt>ev_unloop (loop, how)</dt>	597	<dt>ev_unloop (loop, how)</dt>
263	<dd>	598	<dd>
264	<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument	599	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
		600	has processed all outstanding events). The <code>how</code> argument must be either
265	must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code>	601	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
266	call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code>	602	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
267	calls return.</p>
268	</dd>	603	</dd>
269	<dt>ev_ref (loop)</dt>	604	<dt>ev_ref (loop)</dt>
270	<dt>ev_unref (loop)</dt>	605	<dt>ev_unref (loop)</dt>
271	<dd>	606	<dd>
272	<p>Ref/unref can be used to add or remove a refcount on the event loop: Every	607	<p>Ref/unref can be used to add or remove a reference count on the event
273	watcher keeps one reference. If you have a long-runing watcher you never	608	loop: Every watcher keeps one reference, and as long as the reference
274	unregister that should not keep ev_loop from running, ev_unref() after	609	count is nonzero, <code>ev_loop</code> will not return on its own. If you have
275	starting, and ev_ref() before stopping it. Libev itself uses this for	610	a watcher you never unregister that should not keep <code>ev_loop</code> from
276	example for its internal signal pipe: It is not visible to you as a user	611	returning, ev_unref() after starting, and ev_ref() before stopping it. For
277	and should not keep <code>ev_loop</code> from exiting if the work is done. It is	612	example, libev itself uses this for its internal signal pipe: It is not
278	also an excellent way to do this for generic recurring timers or from	613	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
279	within third-party libraries. Just remember to unref after start and ref	614	no event watchers registered by it are active. It is also an excellent
280	before stop.</p>	615	way to do this for generic recurring timers or from within third-party
		616	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		617	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		618	running when nothing else is active.</p>
		619	<pre> struct ev_signal exitsig;
		620	ev_signal_init (&exitsig, sig_cb, SIGINT);
		621	ev_signal_start (loop, &exitsig);
		622	evf_unref (loop);
		623
		624	</pre>
		625	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		626	<pre> ev_ref (loop);
		627	ev_signal_stop (loop, &exitsig);
		628
		629	</pre>
281	</dd>	630	</dd>
282	</dl>	631	</dl>
283		632
		633
		634
		635
		636
284	</div>	637	</div>
285	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	638	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
286	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	639	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
287	<p>A watcher is a structure that you create and register to record your	640	<p>A watcher is a structure that you create and register to record your
288	interest in some event. For instance, if you want to wait for STDIN to	641	interest in some event. For instance, if you want to wait for STDIN to
289	become readable, you would create an ev_io watcher for that:</p>	642	become readable, you would create an <code>ev_io</code> watcher for that:</p>
290	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	643	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
291	{	644	{
292	ev_io_stop (w);	645	ev_io_stop (w);
293	ev_unloop (loop, EVUNLOOP_ALL);	646	ev_unloop (loop, EVUNLOOP_ALL);
294	}	647	}
…		…
317	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	670	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
318	*)</code>), and you can stop watching for events at any time by calling the	671	*)</code>), and you can stop watching for events at any time by calling the
319	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	672	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
320	<p>As long as your watcher is active (has been started but not stopped) you	673	<p>As long as your watcher is active (has been started but not stopped) you
321	must not touch the values stored in it. Most specifically you must never	674	must not touch the values stored in it. Most specifically you must never
322	reinitialise it or call its set method.</p>	675	reinitialise it or call its <code>set</code> macro.</p>
323	<p>You cna check whether an event is active by calling the <code>ev_is_active
324	(watcher *)</code> macro. To see whether an event is outstanding (but the
325	callback for it has not been called yet) you cna use the <code>ev_is_pending
326	(watcher *)</code> macro.</p>
327	<p>Each and every callback receives the event loop pointer as first, the	676	<p>Each and every callback receives the event loop pointer as first, the
328	registered watcher structure as second, and a bitset of received events as	677	registered watcher structure as second, and a bitset of received events as
329	third argument.</p>	678	third argument.</p>
330	<p>The rceeived events usually include a single bit per event type received	679	<p>The received events usually include a single bit per event type received
331	(you can receive multiple events at the same time). The possible bit masks	680	(you can receive multiple events at the same time). The possible bit masks
332	are:</p>	681	are:</p>
333	<dl>	682	<dl>
334	<dt>EV_READ</dt>	683	<dt><code>EV_READ</code></dt>
335	<dt>EV_WRITE</dt>	684	<dt><code>EV_WRITE</code></dt>
336	<dd>	685	<dd>
337	<p>The file descriptor in the ev_io watcher has become readable and/or	686	<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
338	writable.</p>	687	writable.</p>
339	</dd>	688	</dd>
340	<dt>EV_TIMEOUT</dt>	689	<dt><code>EV_TIMEOUT</code></dt>
341	<dd>
342	<p>The ev_timer watcher has timed out.</p>
343	</dd>	690	<dd>
344	<dt>EV_PERIODIC</dt>	691	<p>The <code>ev_timer</code> watcher has timed out.</p>
345	<dd>	692	</dd>
346	<p>The ev_periodic watcher has timed out.</p>	693	<dt><code>EV_PERIODIC</code></dt>
347	</dd>	694	<dd>
348	<dt>EV_SIGNAL</dt>	695	<p>The <code>ev_periodic</code> watcher has timed out.</p>
349	<dd>	696	</dd>
		697	<dt><code>EV_SIGNAL</code></dt>
		698	<dd>
350	<p>The signal specified in the ev_signal watcher has been received by a thread.</p>	699	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
351	</dd>
352	<dt>EV_CHILD</dt>
353	<dd>	700	</dd>
		701	<dt><code>EV_CHILD</code></dt>
		702	<dd>
354	<p>The pid specified in the ev_child watcher has received a status change.</p>	703	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
355	</dd>
356	<dt>EV_IDLE</dt>
357	<dd>	704	</dd>
		705	<dt><code>EV_STAT</code></dt>
		706	<dd>
		707	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		708	</dd>
		709	<dt><code>EV_IDLE</code></dt>
		710	<dd>
358	<p>The ev_idle watcher has determined that you have nothing better to do.</p>	711	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
359	</dd>
360	<dt>EV_PREPARE</dt>
361	<dt>EV_CHECK</dt>
362	<dd>	712	</dd>
		713	<dt><code>EV_PREPARE</code></dt>
		714	<dt><code>EV_CHECK</code></dt>
		715	<dd>
363	<p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts	716	<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
364	to gather new events, and all ev_check watchers are invoked just after	717	to gather new events, and all <code>ev_check</code> watchers are invoked just after
365	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	718	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
366	received events. Callbacks of both watcher types can start and stop as	719	received events. Callbacks of both watcher types can start and stop as
367	many watchers as they want, and all of them will be taken into account	720	many watchers as they want, and all of them will be taken into account
368	(for example, a ev_prepare watcher might start an idle watcher to keep	721	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
369	<code>ev_loop</code> from blocking).</p>	722	<code>ev_loop</code> from blocking).</p>
370	</dd>	723	</dd>
371	<dt>EV_ERROR</dt>	724	<dt><code>EV_EMBED</code></dt>
		725	<dd>
		726	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		727	</dd>
		728	<dt><code>EV_FORK</code></dt>
		729	<dd>
		730	<p>The event loop has been resumed in the child process after fork (see
		731	<code>ev_fork</code>).</p>
		732	</dd>
		733	<dt><code>EV_ERROR</code></dt>
372	<dd>	734	<dd>
373	<p>An unspecified error has occured, the watcher has been stopped. This might	735	<p>An unspecified error has occured, the watcher has been stopped. This might
374	happen because the watcher could not be properly started because libev	736	happen because the watcher could not be properly started because libev
375	ran out of memory, a file descriptor was found to be closed or any other	737	ran out of memory, a file descriptor was found to be closed or any other
376	problem. You best act on it by reporting the problem and somehow coping	738	problem. You best act on it by reporting the problem and somehow coping
…		…
382	programs, though, so beware.</p>	744	programs, though, so beware.</p>
383	</dd>	745	</dd>
384	</dl>	746	</dl>
385		747
386	</div>	748	</div>
		749	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		750	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		751	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		752	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		753	<dl>
		754	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		755	<dd>
		756	<p>This macro initialises the generic portion of a watcher. The contents
		757	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		758	the generic parts of the watcher are initialised, you <i>need</i> to call
		759	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		760	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		761	which rolls both calls into one.</p>
		762	<p>You can reinitialise a watcher at any time as long as it has been stopped
		763	(or never started) and there are no pending events outstanding.</p>
		764	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		765	int revents)</code>.</p>
		766	</dd>
		767	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		768	<dd>
		769	<p>This macro initialises the type-specific parts of a watcher. You need to
		770	call <code>ev_init</code> at least once before you call this macro, but you can
		771	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		772	macro on a watcher that is active (it can be pending, however, which is a
		773	difference to the <code>ev_init</code> macro).</p>
		774	<p>Although some watcher types do not have type-specific arguments
		775	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		776	</dd>
		777	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		778	<dd>
		779	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		780	calls into a single call. This is the most convinient method to initialise
		781	a watcher. The same limitations apply, of course.</p>
		782	</dd>
		783	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		784	<dd>
		785	<p>Starts (activates) the given watcher. Only active watchers will receive
		786	events. If the watcher is already active nothing will happen.</p>
		787	</dd>
		788	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		789	<dd>
		790	<p>Stops the given watcher again (if active) and clears the pending
		791	status. It is possible that stopped watchers are pending (for example,
		792	non-repeating timers are being stopped when they become pending), but
		793	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		794	you want to free or reuse the memory used by the watcher it is therefore a
		795	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		796	</dd>
		797	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		798	<dd>
		799	<p>Returns a true value iff the watcher is active (i.e. it has been started
		800	and not yet been stopped). As long as a watcher is active you must not modify
		801	it.</p>
		802	</dd>
		803	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		804	<dd>
		805	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		806	events but its callback has not yet been invoked). As long as a watcher
		807	is pending (but not active) you must not call an init function on it (but
		808	<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
		809	make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
		810	it).</p>
		811	</dd>
		812	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		813	<dd>
		814	<p>Returns the callback currently set on the watcher.</p>
		815	</dd>
		816	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		817	<dd>
		818	<p>Change the callback. You can change the callback at virtually any time
		819	(modulo threads).</p>
		820	</dd>
		821	<dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
		822	<dt>int ev_priority (ev_TYPE *watcher)</dt>
		823	<dd>
		824	<p>Set and query the priority of the watcher. The priority is a small
		825	integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
		826	(default: <code>-2</code>). Pending watchers with higher priority will be invoked
		827	before watchers with lower priority, but priority will not keep watchers
		828	from being executed (except for <code>ev_idle</code> watchers).</p>
		829	<p>This means that priorities are <i>only</i> used for ordering callback
		830	invocation after new events have been received. This is useful, for
		831	example, to reduce latency after idling, or more often, to bind two
		832	watchers on the same event and make sure one is called first.</p>
		833	<p>If you need to suppress invocation when higher priority events are pending
		834	you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
		835	<p>You <i>must not</i> change the priority of a watcher as long as it is active or
		836	pending.</p>
		837	<p>The default priority used by watchers when no priority has been set is
		838	always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
		839	<p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
		840	fine, as long as you do not mind that the priority value you query might
		841	or might not have been adjusted to be within valid range.</p>
		842	</dd>
		843	<dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
		844	<dd>
		845	<p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
		846	<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
		847	can deal with that fact.</p>
		848	</dd>
		849	<dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
		850	<dd>
		851	<p>If the watcher is pending, this function returns clears its pending status
		852	and returns its <code>revents</code> bitset (as if its callback was invoked). If the
		853	watcher isn't pending it does nothing and returns <code>0</code>.</p>
		854	</dd>
		855	</dl>
		856
		857
		858
		859
		860
		861	</div>
387	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	862	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
388	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	863	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
389	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	864	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
390	and read at any time, libev will completely ignore it. This cna be used	865	and read at any time, libev will completely ignore it. This can be used
391	to associate arbitrary data with your watcher. If you need more data and	866	to associate arbitrary data with your watcher. If you need more data and
392	don't want to allocate memory and store a pointer to it in that data	867	don't want to allocate memory and store a pointer to it in that data
393	member, you can also "subclass" the watcher type and provide your own	868	member, you can also "subclass" the watcher type and provide your own
394	data:</p>	869	data:</p>
395	<pre> struct my_io	870	<pre> struct my_io
…		…
408	struct my_io w = (struct my_io )w_;	883	struct my_io w = (struct my_io )w_;
409	...	884	...
410	}	885	}
411		886
412	</pre>	887	</pre>
413	<p>More interesting and less C-conformant ways of catsing your callback type	888	<p>More interesting and less C-conformant ways of casting your callback type
414	have been omitted....</p>	889	instead have been omitted.</p>
		890	<p>Another common scenario is having some data structure with multiple
		891	watchers:</p>
		892	<pre> struct my_biggy
		893	{
		894	int some_data;
		895	ev_timer t1;
		896	ev_timer t2;
		897	}
415		898
		899	</pre>
		900	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		901	you need to use <code>offsetof</code>:</p>
		902	<pre> #include <stddef.h>
416		903
		904	static void
		905	t1_cb (EV_P_ struct ev_timer *w, int revents)
		906	{
		907	struct my_biggy big = (struct my_biggy *
		908	(((char *)w) - offsetof (struct my_biggy, t1));
		909	}
417		910
		911	static void
		912	t2_cb (EV_P_ struct ev_timer *w, int revents)
		913	{
		914	struct my_biggy big = (struct my_biggy *
		915	(((char *)w) - offsetof (struct my_biggy, t2));
		916	}
418		917
419		918
		919
		920
		921	</pre>
		922
420	</div>	923	</div>
421	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	924	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
422	<div id="WATCHER_TYPES_CONTENT">	925	<div id="WATCHER_TYPES_CONTENT">
423	<p>This section describes each watcher in detail, but will not repeat	926	<p>This section describes each watcher in detail, but will not repeat
424	information given in the last section.</p>	927	information given in the last section. Any initialisation/set macros,
		928	functions and members specific to the watcher type are explained.</p>
		929	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		930	while the watcher is active, you can look at the member and expect some
		931	sensible content, but you must not modify it (you can modify it while the
		932	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		933	means you can expect it to have some sensible content while the watcher
		934	is active, but you can also modify it. Modifying it may not do something
		935	sensible or take immediate effect (or do anything at all), but libev will
		936	not crash or malfunction in any way.</p>
425		937
		938
		939
		940
		941
426	</div>	942	</div>
427	<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2>	943	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
428	<div id="struct_ev_io_is_my_file_descriptor_r-2">	944	<div id="code_ev_io_code_is_this_file_descrip-2">
429	<p>I/O watchers check whether a file descriptor is readable or writable	945	<p>I/O watchers check whether a file descriptor is readable or writable
430	in each iteration of the event loop (This behaviour is called	946	in each iteration of the event loop, or, more precisely, when reading
431	level-triggering because you keep receiving events as long as the	947	would not block the process and writing would at least be able to write
432	condition persists. Remember you cna stop the watcher if you don't want to	948	some data. This behaviour is called level-triggering because you keep
433	act on the event and neither want to receive future events).</p>	949	receiving events as long as the condition persists. Remember you can stop
		950	the watcher if you don't want to act on the event and neither want to
		951	receive future events.</p>
		952	<p>In general you can register as many read and/or write event watchers per
		953	fd as you want (as long as you don't confuse yourself). Setting all file
		954	descriptors to non-blocking mode is also usually a good idea (but not
		955	required if you know what you are doing).</p>
		956	<p>You have to be careful with dup'ed file descriptors, though. Some backends
		957	(the linux epoll backend is a notable example) cannot handle dup'ed file
		958	descriptors correctly if you register interest in two or more fds pointing
		959	to the same underlying file/socket/etc. description (that is, they share
		960	the same underlying "file open").</p>
		961	<p>If you must do this, then force the use of a known-to-be-good backend
		962	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
		963	<code>EVBACKEND_POLL</code>).</p>
		964	<p>Another thing you have to watch out for is that it is quite easy to
		965	receive "spurious" readyness notifications, that is your callback might
		966	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		967	because there is no data. Not only are some backends known to create a
		968	lot of those (for example solaris ports), it is very easy to get into
		969	this situation even with a relatively standard program structure. Thus
		970	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		971	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		972	<p>If you cannot run the fd in non-blocking mode (for example you should not
		973	play around with an Xlib connection), then you have to seperately re-test
		974	whether a file descriptor is really ready with a known-to-be good interface
		975	such as poll (fortunately in our Xlib example, Xlib already does this on
		976	its own, so its quite safe to use).</p>
		977
		978	</div>
		979	<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
		980	<div id="The_special_problem_of_disappearing_-2">
		981	<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
		982	descriptor (either by calling <code>close</code> explicitly or by any other means,
		983	such as <code>dup</code>). The reason is that you register interest in some file
		984	descriptor, but when it goes away, the operating system will silently drop
		985	this interest. If another file descriptor with the same number then is
		986	registered with libev, there is no efficient way to see that this is, in
		987	fact, a different file descriptor.</p>
		988	<p>To avoid having to explicitly tell libev about such cases, libev follows
		989	the following policy: Each time <code>ev_io_set</code> is being called, libev
		990	will assume that this is potentially a new file descriptor, otherwise
		991	it is assumed that the file descriptor stays the same. That means that
		992	you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
		993	descriptor even if the file descriptor number itself did not change.</p>
		994	<p>This is how one would do it normally anyway, the important point is that
		995	the libev application should not optimise around libev but should leave
		996	optimisations to libev.</p>
		997
		998
		999
		1000
		1001
		1002	</div>
		1003	<h3 id="Watcher_Specific_Functions">Watcher-Specific Functions</h3>
		1004	<div id="Watcher_Specific_Functions_CONTENT">
434	<dl>	1005	<dl>
435	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	1006	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
436	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	1007	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
437	<dd>	1008	<dd>
438	<p>Configures an ev_io watcher. The fd is the file descriptor to rceeive	1009	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
439	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	1010	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
440	EV_WRITE</code> to receive the given events.</p>	1011	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		1012	</dd>
		1013	<dt>int fd [read-only]</dt>
		1014	<dd>
		1015	<p>The file descriptor being watched.</p>
		1016	</dd>
		1017	<dt>int events [read-only]</dt>
		1018	<dd>
		1019	<p>The events being watched.</p>
441	</dd>	1020	</dd>
442	</dl>	1021	</dl>
		1022	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		1023	readable, but only once. Since it is likely line-buffered, you could
		1024	attempt to read a whole line in the callback.</p>
		1025	<pre> static void
		1026	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		1027	{
		1028	ev_io_stop (loop, w);
		1029	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1030	}
443		1031
		1032	...
		1033	struct ev_loop *loop = ev_default_init (0);
		1034	struct ev_io stdin_readable;
		1035	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1036	ev_io_start (loop, &stdin_readable);
		1037	ev_loop (loop, 0);
		1038
		1039
		1040
		1041
		1042	</pre>
		1043
444	</div>	1044	</div>
445	<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2>	1045	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
446	<div id="struct_ev_timer_relative_and_optiona-2">	1046	<div id="code_ev_timer_code_relative_and_opti-2">
447	<p>Timer watchers are simple relative timers that generate an event after a	1047	<p>Timer watchers are simple relative timers that generate an event after a
448	given time, and optionally repeating in regular intervals after that.</p>	1048	given time, and optionally repeating in regular intervals after that.</p>
449	<p>The timers are based on real time, that is, if you register an event that	1049	<p>The timers are based on real time, that is, if you register an event that
450	times out after an hour and youreset your system clock to last years	1050	times out after an hour and you reset your system clock to last years
451	time, it will still time out after (roughly) and hour. "Roughly" because	1051	time, it will still time out after (roughly) and hour. "Roughly" because
452	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1052	detecting time jumps is hard, and some inaccuracies are unavoidable (the
453	monotonic clock option helps a lot here).</p>	1053	monotonic clock option helps a lot here).</p>
		1054	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
		1055	time. This is usually the right thing as this timestamp refers to the time
		1056	of the event triggering whatever timeout you are modifying/starting. If
		1057	you suspect event processing to be delayed and you <i>need</i> to base the timeout
		1058	on the current time, use something like this to adjust for this:</p>
		1059	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1060
		1061	</pre>
		1062	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		1063	but if multiple timers become ready during the same loop iteration then
		1064	order of execution is undefined.</p>
		1065
		1066	</div>
		1067	<h3 id="Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</h3>
		1068	<div id="Watcher_Specific_Functions_and_Data_-2">
454	<dl>	1069	<dl>
455	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	1070	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
456	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	1071	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
457	<dd>	1072	<dd>
458	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	1073	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
460	timer will automatically be configured to trigger again <code>repeat</code> seconds	1075	timer will automatically be configured to trigger again <code>repeat</code> seconds
461	later, again, and again, until stopped manually.</p>	1076	later, again, and again, until stopped manually.</p>
462	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	1077	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
463	configure a timer to trigger every 10 seconds, then it will trigger at	1078	configure a timer to trigger every 10 seconds, then it will trigger at
464	exactly 10 second intervals. If, however, your program cannot keep up with	1079	exactly 10 second intervals. If, however, your program cannot keep up with
465	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1080	the timer (because it takes longer than those 10 seconds to do stuff) the
466	timer will not fire more than once per event loop iteration.</p>	1081	timer will not fire more than once per event loop iteration.</p>
467	</dd>	1082	</dd>
468	<dt>ev_timer_again (loop)</dt>	1083	<dt>ev_timer_again (loop)</dt>
469	<dd>	1084	<dd>
470	<p>This will act as if the timer timed out and restart it again if it is	1085	<p>This will act as if the timer timed out and restart it again if it is
471	repeating. The exact semantics are:</p>	1086	repeating. The exact semantics are:</p>
		1087	<p>If the timer is pending, its pending status is cleared.</p>
472	<p>If the timer is started but nonrepeating, stop it.</p>	1088	<p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
473	<p>If the timer is repeating, either start it if necessary (with the repeat	1089	<p>If the timer is repeating, either start it if necessary (with the
474	value), or reset the running timer to the repeat value.</p>	1090	<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
475	<p>This sounds a bit complicated, but here is a useful and typical	1091	<p>This sounds a bit complicated, but here is a useful and typical
476	example: Imagine you have a tcp connection and you want a so-called idle	1092	example: Imagine you have a tcp connection and you want a so-called idle
477	timeout, that is, you want to be called when there have been, say, 60	1093	timeout, that is, you want to be called when there have been, say, 60
478	seconds of inactivity on the socket. The easiest way to do this is to	1094	seconds of inactivity on the socket. The easiest way to do this is to
479	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	1095	configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
480	time you successfully read or write some data. If you go into an idle	1096	<code>ev_timer_again</code> each time you successfully read or write some data. If
481	state where you do not expect data to travel on the socket, you can stop	1097	you go into an idle state where you do not expect data to travel on the
		1098	socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
482	the timer, and again will automatically restart it if need be.</p>	1099	automatically restart it if need be.</p>
		1100	<p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
		1101	altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
		1102	<pre> ev_timer_init (timer, callback, 0., 5.);
		1103	ev_timer_again (loop, timer);
		1104	...
		1105	timer->again = 17.;
		1106	ev_timer_again (loop, timer);
		1107	...
		1108	timer->again = 10.;
		1109	ev_timer_again (loop, timer);
		1110
		1111	</pre>
		1112	<p>This is more slightly efficient then stopping/starting the timer each time
		1113	you want to modify its timeout value.</p>
		1114	</dd>
		1115	<dt>ev_tstamp repeat [read-write]</dt>
		1116	<dd>
		1117	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		1118	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		1119	which is also when any modifications are taken into account.</p>
483	</dd>	1120	</dd>
484	</dl>	1121	</dl>
		1122	<p>Example: Create a timer that fires after 60 seconds.</p>
		1123	<pre> static void
		1124	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1125	{
		1126	.. one minute over, w is actually stopped right here
		1127	}
485		1128
		1129	struct ev_timer mytimer;
		1130	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1131	ev_timer_start (loop, &mytimer);
		1132
		1133	</pre>
		1134	<p>Example: Create a timeout timer that times out after 10 seconds of
		1135	inactivity.</p>
		1136	<pre> static void
		1137	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1138	{
		1139	.. ten seconds without any activity
		1140	}
		1141
		1142	struct ev_timer mytimer;
		1143	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1144	ev_timer_again (&mytimer); /* start timer */
		1145	ev_loop (loop, 0);
		1146
		1147	// and in some piece of code that gets executed on any "activity":
		1148	// reset the timeout to start ticking again at 10 seconds
		1149	ev_timer_again (&mytimer);
		1150
		1151
		1152
		1153
		1154	</pre>
		1155
486	</div>	1156	</div>
487	<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2>	1157	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
488	<div id="ev_periodic_to_cron_or_not_to_cron_i-2">	1158	<div id="code_ev_periodic_code_to_cron_or_not-2">
489	<p>Periodic watchers are also timers of a kind, but they are very versatile	1159	<p>Periodic watchers are also timers of a kind, but they are very versatile
490	(and unfortunately a bit complex).</p>	1160	(and unfortunately a bit complex).</p>
491	<p>Unlike ev_timer's, they are not based on real time (or relative time)	1161	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
492	but on wallclock time (absolute time). You can tell a periodic watcher	1162	but on wallclock time (absolute time). You can tell a periodic watcher
493	to trigger "at" some specific point in time. For example, if you tell a	1163	to trigger "at" some specific point in time. For example, if you tell a
494	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1164	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
495	+ 10.>) and then reset your system clock to the last year, then it will	1165	+ 10.</code>) and then reset your system clock to the last year, then it will
496	take a year to trigger the event (unlike an ev_timer, which would trigger	1166	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
497	roughly 10 seconds later and of course not if you reset your system time	1167	roughly 10 seconds later).</p>
498	again).</p>
499	<p>They can also be used to implement vastly more complex timers, such as	1168	<p>They can also be used to implement vastly more complex timers, such as
500	triggering an event on eahc midnight, local time.</p>	1169	triggering an event on each midnight, local time or other, complicated,
		1170	rules.</p>
		1171	<p>As with timers, the callback is guarenteed to be invoked only when the
		1172	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1173	during the same loop iteration then order of execution is undefined.</p>
		1174
		1175	</div>
		1176	<h3 id="Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</h3>
		1177	<div id="Watcher_Specific_Functions_and_Data_-2">
501	<dl>	1178	<dl>
502	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1179	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
503	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	1180	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
504	<dd>	1181	<dd>
505	<p>Lots of arguments, lets sort it out... There are basically three modes of	1182	<p>Lots of arguments, lets sort it out... There are basically three modes of
506	operation, and we will explain them from simplest to complex:</p>	1183	operation, and we will explain them from simplest to complex:</p>
507
508
509
510
511	<p>	1184	<p>
512	<dl>	1185	<dl>
513	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1186	<dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
514	<dd>	1187	<dd>
515	<p>In this configuration the watcher triggers an event at the wallclock time	1188	<p>In this configuration the watcher triggers an event at the wallclock time
516	<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,	1189	<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
517	that is, if it is to be run at January 1st 2011 then it will run when the	1190	that is, if it is to be run at January 1st 2011 then it will run when the
518	system time reaches or surpasses this time.</p>	1191	system time reaches or surpasses this time.</p>
519	</dd>	1192	</dd>
520	<dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt>	1193	<dt>* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)</dt>
521	<dd>	1194	<dd>
522	<p>In this mode the watcher will always be scheduled to time out at the next	1195	<p>In this mode the watcher will always be scheduled to time out at the next
523	<code>at + N * interval</code> time (for some integer N) and then repeat, regardless	1196	<code>at + N * interval</code> time (for some integer N, which can also be negative)
524	of any time jumps.</p>	1197	and then repeat, regardless of any time jumps.</p>
525	<p>This can be used to create timers that do not drift with respect to system	1198	<p>This can be used to create timers that do not drift with respect to system
526	time:</p>	1199	time:</p>
527	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	1200	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
528		1201
529	</pre>	1202	</pre>
530	<p>This doesn't mean there will always be 3600 seconds in between triggers,	1203	<p>This doesn't mean there will always be 3600 seconds in between triggers,
531	but only that the the callback will be called when the system time shows a	1204	but only that the the callback will be called when the system time shows a
532	full hour (UTC), or more correct, when the system time is evenly divisible	1205	full hour (UTC), or more correctly, when the system time is evenly divisible
533	by 3600.</p>	1206	by 3600.</p>
534	<p>Another way to think about it (for the mathematically inclined) is that	1207	<p>Another way to think about it (for the mathematically inclined) is that
535	ev_periodic will try to run the callback in this mode at the next possible	1208	<code>ev_periodic</code> will try to run the callback in this mode at the next possible
536	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	1209	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
		1210	<p>For numerical stability it is preferable that the <code>at</code> value is near
		1211	<code>ev_now ()</code> (the current time), but there is no range requirement for
		1212	this value.</p>
537	</dd>	1213	</dd>
538	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	1214	<dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
539	<dd>	1215	<dd>
540	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	1216	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
541	ignored. Instead, each time the periodic watcher gets scheduled, the	1217	ignored. Instead, each time the periodic watcher gets scheduled, the
542	reschedule callback will be called with the watcher as first, and the	1218	reschedule callback will be called with the watcher as first, and the
543	current time as second argument.</p>	1219	current time as second argument.</p>
544	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1220	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
545	periodic watcher, ever, or make any event loop modificstions</i>. If you need	1221	ever, or make any event loop modifications</i>. If you need to stop it,
546	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p>	1222	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
		1223	starting an <code>ev_prepare</code> watcher, which is legal).</p>
547	<p>Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1224	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
548	ev_tstamp now)>, e.g.:</p>	1225	ev_tstamp now)</code>, e.g.:</p>
549	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1226	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
550	{	1227	{
551	return now + 60.;	1228	return now + 60.;
552	}	1229	}
553		1230
554	</pre>	1231	</pre>
555	<p>It must return the next time to trigger, based on the passed time value	1232	<p>It must return the next time to trigger, based on the passed time value
556	(that is, the lowest time value larger than to the second argument). It	1233	(that is, the lowest time value larger than to the second argument). It
557	will usually be called just before the callback will be triggered, but	1234	will usually be called just before the callback will be triggered, but
558	might be called at other times, too.</p>	1235	might be called at other times, too.</p>
		1236	<p>NOTE: <i>This callback must always return a time that is later than the
		1237	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
559	<p>This can be used to create very complex timers, such as a timer that	1238	<p>This can be used to create very complex timers, such as a timer that
560	triggers on each midnight, local time. To do this, you would calculate the	1239	triggers on each midnight, local time. To do this, you would calculate the
561	next midnight after <code>now</code> and return the timestamp value for this. How you do this	1240	next midnight after <code>now</code> and return the timestamp value for this. How
562	is, again, up to you (but it is not trivial).</p>	1241	you do this is, again, up to you (but it is not trivial, which is the main
		1242	reason I omitted it as an example).</p>
563	</dd>	1243	</dd>
564	</dl>	1244	</dl>
565	</p>	1245	</p>
566	</dd>	1246	</dd>
567	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1247	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
569	<p>Simply stops and restarts the periodic watcher again. This is only useful	1249	<p>Simply stops and restarts the periodic watcher again. This is only useful
570	when you changed some parameters or the reschedule callback would return	1250	when you changed some parameters or the reschedule callback would return
571	a different time than the last time it was called (e.g. in a crond like	1251	a different time than the last time it was called (e.g. in a crond like
572	program when the crontabs have changed).</p>	1252	program when the crontabs have changed).</p>
573	</dd>	1253	</dd>
		1254	<dt>ev_tstamp offset [read-write]</dt>
		1255	<dd>
		1256	<p>When repeating, this contains the offset value, otherwise this is the
		1257	absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
		1258	<p>Can be modified any time, but changes only take effect when the periodic
		1259	timer fires or <code>ev_periodic_again</code> is being called.</p>
		1260	</dd>
		1261	<dt>ev_tstamp interval [read-write]</dt>
		1262	<dd>
		1263	<p>The current interval value. Can be modified any time, but changes only
		1264	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1265	called.</p>
		1266	</dd>
		1267	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1268	<dd>
		1269	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1270	switched off. Can be changed any time, but changes only take effect when
		1271	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1272	</dd>
574	</dl>	1273	</dl>
		1274	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1275	system clock is divisible by 3600. The callback invocation times have
		1276	potentially a lot of jittering, but good long-term stability.</p>
		1277	<pre> static void
		1278	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1279	{
		1280	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1281	}
575		1282
		1283	struct ev_periodic hourly_tick;
		1284	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1285	ev_periodic_start (loop, &hourly_tick);
		1286
		1287	</pre>
		1288	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1289	<pre> #include <math.h>
		1290
		1291	static ev_tstamp
		1292	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1293	{
		1294	return fmod (now, 3600.) + 3600.;
		1295	}
		1296
		1297	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1298
		1299	</pre>
		1300	<p>Example: Call a callback every hour, starting now:</p>
		1301	<pre> struct ev_periodic hourly_tick;
		1302	ev_periodic_init (&hourly_tick, clock_cb,
		1303	fmod (ev_now (loop), 3600.), 3600., 0);
		1304	ev_periodic_start (loop, &hourly_tick);
		1305
		1306
		1307
		1308
		1309	</pre>
		1310
576	</div>	1311	</div>
577	<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>	1312	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
578	<div id="ev_signal_signal_me_when_a_signal_ge-2">	1313	<div id="code_ev_signal_code_signal_me_when_a-2">
579	<p>Signal watchers will trigger an event when the process receives a specific	1314	<p>Signal watchers will trigger an event when the process receives a specific
580	signal one or more times. Even though signals are very asynchronous, libev	1315	signal one or more times. Even though signals are very asynchronous, libev
581	will try its best to deliver signals synchronously, i.e. as part of the	1316	will try it's best to deliver signals synchronously, i.e. as part of the
582	normal event processing, like any other event.</p>	1317	normal event processing, like any other event.</p>
583	<p>You cna configure as many watchers as you like per signal. Only when the	1318	<p>You can configure as many watchers as you like per signal. Only when the
584	first watcher gets started will libev actually register a signal watcher	1319	first watcher gets started will libev actually register a signal watcher
585	with the kernel (thus it coexists with your own signal handlers as long	1320	with the kernel (thus it coexists with your own signal handlers as long
586	as you don't register any with libev). Similarly, when the last signal	1321	as you don't register any with libev). Similarly, when the last signal
587	watcher for a signal is stopped libev will reset the signal handler to	1322	watcher for a signal is stopped libev will reset the signal handler to
588	SIG_DFL (regardless of what it was set to before).</p>	1323	SIG_DFL (regardless of what it was set to before).</p>
		1324
		1325	</div>
		1326	<h3 id="Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</h3>
		1327	<div id="Watcher_Specific_Functions_and_Data_-2-2">
589	<dl>	1328	<dl>
590	<dt>ev_signal_init (ev_signal *, callback, int signum)</dt>	1329	<dt>ev_signal_init (ev_signal *, callback, int signum)</dt>
591	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1330	<dt>ev_signal_set (ev_signal *, int signum)</dt>
592	<dd>	1331	<dd>
593	<p>Configures the watcher to trigger on the given signal number (usually one	1332	<p>Configures the watcher to trigger on the given signal number (usually one
594	of the <code>SIGxxx</code> constants).</p>	1333	of the <code>SIGxxx</code> constants).</p>
595	</dd>	1334	</dd>
		1335	<dt>int signum [read-only]</dt>
		1336	<dd>
		1337	<p>The signal the watcher watches out for.</p>
		1338	</dd>
596	</dl>	1339	</dl>
597		1340
		1341
		1342
		1343
		1344
598	</div>	1345	</div>
599	<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2>	1346	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
600	<div id="ev_child_wait_for_pid_status_changes-2">	1347	<div id="code_ev_child_code_watch_out_for_pro-2">
601	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1348	<p>Child watchers trigger when your process receives a SIGCHLD in response to
602	some child status changes (most typically when a child of yours dies).</p>	1349	some child status changes (most typically when a child of yours dies).</p>
		1350
		1351	</div>
		1352	<h3 id="Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</h3>
		1353	<div id="Watcher_Specific_Functions_and_Data_-2-3">
603	<dl>	1354	<dl>
604	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1355	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
605	<dt>ev_child_set (ev_child *, int pid)</dt>	1356	<dt>ev_child_set (ev_child *, int pid)</dt>
606	<dd>	1357	<dd>
607	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or	1358	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
608	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look	1359	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
609	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1360	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
610	the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member	1361	the status word (use the macros from <code>sys/wait.h</code> and see your systems
		1362	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
611	contains the pid of the process causing the status change.</p>	1363	process causing the status change.</p>
		1364	</dd>
		1365	<dt>int pid [read-only]</dt>
		1366	<dd>
		1367	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1368	</dd>
		1369	<dt>int rpid [read-write]</dt>
		1370	<dd>
		1371	<p>The process id that detected a status change.</p>
		1372	</dd>
		1373	<dt>int rstatus [read-write]</dt>
		1374	<dd>
		1375	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1376	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
612	</dd>	1377	</dd>
613	</dl>	1378	</dl>
		1379	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1380	<pre> static void
		1381	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1382	{
		1383	ev_unloop (loop, EVUNLOOP_ALL);
		1384	}
614		1385
		1386	struct ev_signal signal_watcher;
		1387	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1388	ev_signal_start (loop, &sigint_cb);
		1389
		1390
		1391
		1392
		1393	</pre>
		1394
615	</div>	1395	</div>
		1396	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1397	<div id="code_ev_stat_code_did_the_file_attri-2">
		1398	<p>This watches a filesystem path for attribute changes. That is, it calls
		1399	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1400	compared to the last time, invoking the callback if it did.</p>
		1401	<p>The path does not need to exist: changing from "path exists" to "path does
		1402	not exist" is a status change like any other. The condition "path does
		1403	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1404	otherwise always forced to be at least one) and all the other fields of
		1405	the stat buffer having unspecified contents.</p>
		1406	<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
		1407	relative and your working directory changes, the behaviour is undefined.</p>
		1408	<p>Since there is no standard to do this, the portable implementation simply
		1409	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1410	can specify a recommended polling interval for this case. If you specify
		1411	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1412	unspecified default</i> value will be used (which you can expect to be around
		1413	five seconds, although this might change dynamically). Libev will also
		1414	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1415	usually overkill.</p>
		1416	<p>This watcher type is not meant for massive numbers of stat watchers,
		1417	as even with OS-supported change notifications, this can be
		1418	resource-intensive.</p>
		1419	<p>At the time of this writing, only the Linux inotify interface is
		1420	implemented (implementing kqueue support is left as an exercise for the
		1421	reader). Inotify will be used to give hints only and should not change the
		1422	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1423	to fall back to regular polling again even with inotify, but changes are
		1424	usually detected immediately, and if the file exists there will be no
		1425	polling.</p>
		1426
		1427	</div>
		1428	<h3 id="Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</h3>
		1429	<div id="Watcher_Specific_Functions_and_Data_-2-4">
		1430	<dl>
		1431	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1432	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1433	<dd>
		1434	<p>Configures the watcher to wait for status changes of the given
		1435	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1436	be detected and should normally be specified as <code>0</code> to let libev choose
		1437	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1438	path for as long as the watcher is active.</p>
		1439	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1440	relative to the attributes at the time the watcher was started (or the
		1441	last change was detected).</p>
		1442	</dd>
		1443	<dt>ev_stat_stat (ev_stat *)</dt>
		1444	<dd>
		1445	<p>Updates the stat buffer immediately with new values. If you change the
		1446	watched path in your callback, you could call this fucntion to avoid
		1447	detecting this change (while introducing a race condition). Can also be
		1448	useful simply to find out the new values.</p>
		1449	</dd>
		1450	<dt>ev_statdata attr [read-only]</dt>
		1451	<dd>
		1452	<p>The most-recently detected attributes of the file. Although the type is of
		1453	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1454	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1455	was some error while <code>stat</code>ing the file.</p>
		1456	</dd>
		1457	<dt>ev_statdata prev [read-only]</dt>
		1458	<dd>
		1459	<p>The previous attributes of the file. The callback gets invoked whenever
		1460	<code>prev</code> != <code>attr</code>.</p>
		1461	</dd>
		1462	<dt>ev_tstamp interval [read-only]</dt>
		1463	<dd>
		1464	<p>The specified interval.</p>
		1465	</dd>
		1466	<dt>const char *path [read-only]</dt>
		1467	<dd>
		1468	<p>The filesystem path that is being watched.</p>
		1469	</dd>
		1470	</dl>
		1471	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1472	<pre> static void
		1473	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1474	{
		1475	/* /etc/passwd changed in some way */
		1476	if (w->attr.st_nlink)
		1477	{
		1478	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1479	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1480	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1481	}
		1482	else
		1483	/* you shalt not abuse printf for puts */
		1484	puts ("wow, /etc/passwd is not there, expect problems. "
		1485	"if this is windows, they already arrived\n");
		1486	}
		1487
		1488	...
		1489	ev_stat passwd;
		1490
		1491	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1492	ev_stat_start (loop, &passwd);
		1493
		1494
		1495
		1496
		1497	</pre>
		1498
		1499	</div>
616	<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2>	1500	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
617	<div id="ev_idle_when_you_ve_got_nothing_bett-2">	1501	<div id="code_ev_idle_code_when_you_ve_got_no-2">
618	<p>Idle watchers trigger events when there are no other I/O or timer (or	1502	<p>Idle watchers trigger events when no other events of the same or higher
619	periodic) events pending. That is, as long as your process is busy	1503	priority are pending (prepare, check and other idle watchers do not
620	handling sockets or timeouts it will not be called. But when your process	1504	count).</p>
621	is idle all idle watchers are being called again and again - until	1505	<p>That is, as long as your process is busy handling sockets or timeouts
		1506	(or even signals, imagine) of the same or higher priority it will not be
		1507	triggered. But when your process is idle (or only lower-priority watchers
		1508	are pending), the idle watchers are being called once per event loop
622	stopped, that is, or your process receives more events.</p>	1509	iteration - until stopped, that is, or your process receives more events
		1510	and becomes busy again with higher priority stuff.</p>
623	<p>The most noteworthy effect is that as long as any idle watchers are	1511	<p>The most noteworthy effect is that as long as any idle watchers are
624	active, the process will not block when waiting for new events.</p>	1512	active, the process will not block when waiting for new events.</p>
625	<p>Apart from keeping your process non-blocking (which is a useful	1513	<p>Apart from keeping your process non-blocking (which is a useful
626	effect on its own sometimes), idle watchers are a good place to do	1514	effect on its own sometimes), idle watchers are a good place to do
627	"pseudo-background processing", or delay processing stuff to after the	1515	"pseudo-background processing", or delay processing stuff to after the
628	event loop has handled all outstanding events.</p>	1516	event loop has handled all outstanding events.</p>
		1517
		1518	</div>
		1519	<h3 id="Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</h3>
		1520	<div id="Watcher_Specific_Functions_and_Data_-2-5">
629	<dl>	1521	<dl>
630	<dt>ev_idle_init (ev_signal *, callback)</dt>	1522	<dt>ev_idle_init (ev_signal *, callback)</dt>
631	<dd>	1523	<dd>
632	<p>Initialises and configures the idle watcher - it has no parameters of any	1524	<p>Initialises and configures the idle watcher - it has no parameters of any
633	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1525	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
634	believe me.</p>	1526	believe me.</p>
635	</dd>	1527	</dd>
636	</dl>	1528	</dl>
		1529	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1530	callback, free it. Also, use no error checking, as usual.</p>
		1531	<pre> static void
		1532	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1533	{
		1534	free (w);
		1535	// now do something you wanted to do when the program has
		1536	// no longer asnything immediate to do.
		1537	}
637		1538
		1539	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1540	ev_idle_init (idle_watcher, idle_cb);
		1541	ev_idle_start (loop, idle_cb);
		1542
		1543
		1544
		1545
		1546	</pre>
		1547
638	</div>	1548	</div>
639	<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>	1549	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
640	<div id="prepare_and_check_your_hooks_into_th-2">	1550	<div id="code_ev_prepare_code_and_code_ev_che-2">
641	<p>Prepare and check watchers usually (but not always) are used in	1551	<p>Prepare and check watchers are usually (but not always) used in tandem:
642	tandom. Prepare watchers get invoked before the process blocks and check	1552	prepare watchers get invoked before the process blocks and check watchers
643	watchers afterwards.</p>	1553	afterwards.</p>
		1554	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1555	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1556	watchers. Other loops than the current one are fine, however. The
		1557	rationale behind this is that you do not need to check for recursion in
		1558	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1559	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1560	called in pairs bracketing the blocking call.</p>
644	<p>Their main purpose is to integrate other event mechanisms into libev. This	1561	<p>Their main purpose is to integrate other event mechanisms into libev and
645	could be used, for example, to track variable changes, implement your own	1562	their use is somewhat advanced. This could be used, for example, to track
646	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1563	variable changes, implement your own watchers, integrate net-snmp or a
		1564	coroutine library and lots more. They are also occasionally useful if
		1565	you cache some data and want to flush it before blocking (for example,
		1566	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1567	watcher).</p>
647	<p>This is done by examining in each prepare call which file descriptors need	1568	<p>This is done by examining in each prepare call which file descriptors need
648	to be watched by the other library, registering ev_io watchers for them	1569	to be watched by the other library, registering <code>ev_io</code> watchers for
649	and starting an ev_timer watcher for any timeouts (many libraries provide	1570	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
650	just this functionality). Then, in the check watcher you check for any	1571	provide just this functionality). Then, in the check watcher you check for
651	events that occured (by making your callbacks set soem flags for example)	1572	any events that occured (by checking the pending status of all watchers
652	and call back into the library.</p>	1573	and stopping them) and call back into the library. The I/O and timer
		1574	callbacks will never actually be called (but must be valid nevertheless,
		1575	because you never know, you know?).</p>
653	<p>As another example, the perl Coro module uses these hooks to integrate	1576	<p>As another example, the Perl Coro module uses these hooks to integrate
654	coroutines into libev programs, by yielding to other active coroutines	1577	coroutines into libev programs, by yielding to other active coroutines
655	during each prepare and only letting the process block if no coroutines	1578	during each prepare and only letting the process block if no coroutines
656	are ready to run.</p>	1579	are ready to run (it's actually more complicated: it only runs coroutines
		1580	with priority higher than or equal to the event loop and one coroutine
		1581	of lower priority, but only once, using idle watchers to keep the event
		1582	loop from blocking if lower-priority coroutines are active, thus mapping
		1583	low-priority coroutines to idle/background tasks).</p>
		1584	<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
		1585	priority, to ensure that they are being run before any other watchers
		1586	after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
		1587	too) should not activate ("feed") events into libev. While libev fully
		1588	supports this, they will be called before other <code>ev_check</code> watchers did
		1589	their job. As <code>ev_check</code> watchers are often used to embed other event
		1590	loops those other event loops might be in an unusable state until their
		1591	<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
		1592	others).</p>
		1593
		1594	</div>
		1595	<h3 id="Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</h3>
		1596	<div id="Watcher_Specific_Functions_and_Data_-2-6">
657	<dl>	1597	<dl>
658	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1598	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
659	<dt>ev_check_init (ev_check *, callback)</dt>	1599	<dt>ev_check_init (ev_check *, callback)</dt>
660	<dd>	1600	<dd>
661	<p>Initialises and configures the prepare or check watcher - they have no	1601	<p>Initialises and configures the prepare or check watcher - they have no
662	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1602	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
663	macros, but using them is utterly, utterly pointless.</p>	1603	macros, but using them is utterly, utterly and completely pointless.</p>
664	</dd>	1604	</dd>
665	</dl>	1605	</dl>
		1606	<p>There are a number of principal ways to embed other event loops or modules
		1607	into libev. Here are some ideas on how to include libadns into libev
		1608	(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
		1609	use for an actually working example. Another Perl module named <code>EV::Glib</code>
		1610	embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
		1611	into the Glib event loop).</p>
		1612	<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1613	and in a check watcher, destroy them and call into libadns. What follows
		1614	is pseudo-code only of course. This requires you to either use a low
		1615	priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
		1616	the callbacks for the IO/timeout watchers might not have been called yet.</p>
		1617	<pre> static ev_io iow [nfd];
		1618	static ev_timer tw;
666		1619
		1620	static void
		1621	io_cb (ev_loop loop, ev_io w, int revents)
		1622	{
		1623	}
		1624
		1625	// create io watchers for each fd and a timer before blocking
		1626	static void
		1627	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1628	{
		1629	int timeout = 3600000;
		1630	struct pollfd fds [nfd];
		1631	// actual code will need to loop here and realloc etc.
		1632	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1633
		1634	/* the callback is illegal, but won't be called as we stop during check */
		1635	ev_timer_init (&tw, 0, timeout * 1e-3);
		1636	ev_timer_start (loop, &tw);
		1637
		1638	// create one ev_io per pollfd
		1639	for (int i = 0; i < nfd; ++i)
		1640	{
		1641	ev_io_init (iow + i, io_cb, fds [i].fd,
		1642	((fds [i].events & POLLIN ? EV_READ : 0)
		1643	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1644
		1645	fds [i].revents = 0;
		1646	ev_io_start (loop, iow + i);
		1647	}
		1648	}
		1649
		1650	// stop all watchers after blocking
		1651	static void
		1652	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1653	{
		1654	ev_timer_stop (loop, &tw);
		1655
		1656	for (int i = 0; i < nfd; ++i)
		1657	{
		1658	// set the relevant poll flags
		1659	// could also call adns_processreadable etc. here
		1660	struct pollfd *fd = fds + i;
		1661	int revents = ev_clear_pending (iow + i);
		1662	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1663	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1664
		1665	// now stop the watcher
		1666	ev_io_stop (loop, iow + i);
		1667	}
		1668
		1669	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1670	}
		1671
		1672	</pre>
		1673	<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
		1674	in the prepare watcher and would dispose of the check watcher.</p>
		1675	<p>Method 3: If the module to be embedded supports explicit event
		1676	notification (adns does), you can also make use of the actual watcher
		1677	callbacks, and only destroy/create the watchers in the prepare watcher.</p>
		1678	<pre> static void
		1679	timer_cb (EV_P_ ev_timer *w, int revents)
		1680	{
		1681	adns_state ads = (adns_state)w->data;
		1682	update_now (EV_A);
		1683
		1684	adns_processtimeouts (ads, &tv_now);
		1685	}
		1686
		1687	static void
		1688	io_cb (EV_P_ ev_io *w, int revents)
		1689	{
		1690	adns_state ads = (adns_state)w->data;
		1691	update_now (EV_A);
		1692
		1693	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1694	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1695	}
		1696
		1697	// do not ever call adns_afterpoll
		1698
		1699	</pre>
		1700	<p>Method 4: Do not use a prepare or check watcher because the module you
		1701	want to embed is too inflexible to support it. Instead, youc na override
		1702	their poll function. The drawback with this solution is that the main
		1703	loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
		1704	this.</p>
		1705	<pre> static gint
		1706	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1707	{
		1708	int got_events = 0;
		1709
		1710	for (n = 0; n < nfds; ++n)
		1711	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1712
		1713	if (timeout >= 0)
		1714	// create/start timer
		1715
		1716	// poll
		1717	ev_loop (EV_A_ 0);
		1718
		1719	// stop timer again
		1720	if (timeout >= 0)
		1721	ev_timer_stop (EV_A_ &to);
		1722
		1723	// stop io watchers again - their callbacks should have set
		1724	for (n = 0; n < nfds; ++n)
		1725	ev_io_stop (EV_A_ iow [n]);
		1726
		1727	return got_events;
		1728	}
		1729
		1730
		1731
		1732
		1733	</pre>
		1734
667	</div>	1735	</div>
668	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1736	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1737	<div id="code_ev_embed_code_when_one_backend_-2">
		1738	<p>This is a rather advanced watcher type that lets you embed one event loop
		1739	into another (currently only <code>ev_io</code> events are supported in the embedded
		1740	loop, other types of watchers might be handled in a delayed or incorrect
		1741	fashion and must not be used).</p>
		1742	<p>There are primarily two reasons you would want that: work around bugs and
		1743	prioritise I/O.</p>
		1744	<p>As an example for a bug workaround, the kqueue backend might only support
		1745	sockets on some platform, so it is unusable as generic backend, but you
		1746	still want to make use of it because you have many sockets and it scales
		1747	so nicely. In this case, you would create a kqueue-based loop and embed it
		1748	into your default loop (which might use e.g. poll). Overall operation will
		1749	be a bit slower because first libev has to poll and then call kevent, but
		1750	at least you can use both at what they are best.</p>
		1751	<p>As for prioritising I/O: rarely you have the case where some fds have
		1752	to be watched and handled very quickly (with low latency), and even
		1753	priorities and idle watchers might have too much overhead. In this case
		1754	you would put all the high priority stuff in one loop and all the rest in
		1755	a second one, and embed the second one in the first.</p>
		1756	<p>As long as the watcher is active, the callback will be invoked every time
		1757	there might be events pending in the embedded loop. The callback must then
		1758	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1759	their callbacks (you could also start an idle watcher to give the embedded
		1760	loop strictly lower priority for example). You can also set the callback
		1761	to <code>0</code>, in which case the embed watcher will automatically execute the
		1762	embedded loop sweep.</p>
		1763	<p>As long as the watcher is started it will automatically handle events. The
		1764	callback will be invoked whenever some events have been handled. You can
		1765	set the callback to <code>0</code> to avoid having to specify one if you are not
		1766	interested in that.</p>
		1767	<p>Also, there have not currently been made special provisions for forking:
		1768	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1769	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1770	yourself.</p>
		1771	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1772	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1773	portable one.</p>
		1774	<p>So when you want to use this feature you will always have to be prepared
		1775	that you cannot get an embeddable loop. The recommended way to get around
		1776	this is to have a separate variables for your embeddable loop, try to
		1777	create it, and if that fails, use the normal loop for everything:</p>
		1778	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1779	struct ev_loop *loop_lo = 0;
		1780	struct ev_embed embed;
		1781
		1782	// see if there is a chance of getting one that works
		1783	// (remember that a flags value of 0 means autodetection)
		1784	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1785	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1786	: 0;
		1787
		1788	// if we got one, then embed it, otherwise default to loop_hi
		1789	if (loop_lo)
		1790	{
		1791	ev_embed_init (&embed, 0, loop_lo);
		1792	ev_embed_start (loop_hi, &embed);
		1793	}
		1794	else
		1795	loop_lo = loop_hi;
		1796
		1797	</pre>
		1798
		1799	</div>
		1800	<h3 id="Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</h3>
		1801	<div id="Watcher_Specific_Functions_and_Data_-2-7">
		1802	<dl>
		1803	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1804	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1805	<dd>
		1806	<p>Configures the watcher to embed the given loop, which must be
		1807	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1808	invoked automatically, otherwise it is the responsibility of the callback
		1809	to invoke it (it will continue to be called until the sweep has been done,
		1810	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1811	</dd>
		1812	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1813	<dd>
		1814	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1815	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1816	apropriate way for embedded loops.</p>
		1817	</dd>
		1818	<dt>struct ev_loop *loop [read-only]</dt>
		1819	<dd>
		1820	<p>The embedded event loop.</p>
		1821	</dd>
		1822	</dl>
		1823
		1824
		1825
		1826
		1827
		1828	</div>
		1829	<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>
		1830	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1831	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1832	whoever is a good citizen cared to tell libev about it by calling
		1833	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1834	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1835	and only in the child after the fork. If whoever good citizen calling
		1836	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1837	handlers will be invoked, too, of course.</p>
		1838
		1839	</div>
		1840	<h3 id="Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</h3>
		1841	<div id="Watcher_Specific_Functions_and_Data_-2-8">
		1842	<dl>
		1843	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1844	<dd>
		1845	<p>Initialises and configures the fork watcher - it has no parameters of any
		1846	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1847	believe me.</p>
		1848	</dd>
		1849	</dl>
		1850
		1851
		1852
		1853
		1854
		1855	</div>
		1856	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
669	<div id="OTHER_FUNCTIONS_CONTENT">	1857	<div id="OTHER_FUNCTIONS_CONTENT">
670	<p>There are some other fucntions of possible interest. Described. Here. Now.</p>	1858	<p>There are some other functions of possible interest. Described. Here. Now.</p>
671	<dl>	1859	<dl>
672	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1860	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
673	<dd>	1861	<dd>
674	<p>This function combines a simple timer and an I/O watcher, calls your	1862	<p>This function combines a simple timer and an I/O watcher, calls your
675	callback on whichever event happens first and automatically stop both	1863	callback on whichever event happens first and automatically stop both
676	watchers. This is useful if you want to wait for a single event on an fd	1864	watchers. This is useful if you want to wait for a single event on an fd
677	or timeout without havign to allocate/configure/start/stop/free one or	1865	or timeout without having to allocate/configure/start/stop/free one or
678	more watchers yourself.</p>	1866	more watchers yourself.</p>
679	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is	1867	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
680	ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set	1868	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
681	will be craeted and started.</p>	1869	<code>events</code> set will be craeted and started.</p>
682	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1870	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
683	started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat	1871	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
684	= 0) will be started.</p>	1872	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
		1873	dubious value.</p>
685	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and	1874	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
686	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1875	passed an <code>revents</code> set like normal event callbacks (a combination of
687	EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p>	1876	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
		1877	value passed to <code>ev_once</code>:</p>
688	<pre> static void stdin_ready (int revents, void *arg)	1878	<pre> static void stdin_ready (int revents, void *arg)
689	{	1879	{
690	if (revents & EV_TIMEOUT)	1880	if (revents & EV_TIMEOUT)
691	/* doh, nothing entered */	1881	/* doh, nothing entered */;
692	else if (revents & EV_READ)	1882	else if (revents & EV_READ)
693	/* stdin might have data for us, joy! */	1883	/* stdin might have data for us, joy! */;
694	}	1884	}
695		1885
696	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1886	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
697		1887
698	</pre>	1888	</pre>
699	</dd>	1889	</dd>
700	<dt>ev_feed_event (loop, watcher, int events)</dt>	1890	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
701	<dd>	1891	<dd>
702	<p>Feeds the given event set into the event loop, as if the specified event	1892	<p>Feeds the given event set into the event loop, as if the specified event
703	has happened for the specified watcher (which must be a pointer to an	1893	had happened for the specified watcher (which must be a pointer to an
704	initialised but not necessarily active event watcher).</p>	1894	initialised but not necessarily started event watcher).</p>
705	</dd>	1895	</dd>
706	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1896	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
707	<dd>	1897	<dd>
708	<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>	1898	<p>Feed an event on the given fd, as if a file descriptor backend detected
		1899	the given events it.</p>
709	</dd>	1900	</dd>
710	<dt>ev_feed_signal_event (loop, int signum)</dt>	1901	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
711	<dd>	1902	<dd>
712	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1903	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1904	loop!).</p>
713	</dd>	1905	</dd>
714	</dl>	1906	</dl>
715		1907
		1908
		1909
		1910
		1911
716	</div>	1912	</div>
717	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1913	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1914	<div id="LIBEVENT_EMULATION_CONTENT">
		1915	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1916	emulate the internals of libevent, so here are some usage hints:</p>
		1917	<dl>
		1918	<dt>* Use it by including <event.h>, as usual.</dt>
		1919	<dt>* The following members are fully supported: ev_base, ev_callback,
		1920	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1921	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1922	maintained by libev, it does not work exactly the same way as in libevent (consider
		1923	it a private API).</dt>
		1924	<dt>* Priorities are not currently supported. Initialising priorities
		1925	will fail and all watchers will have the same priority, even though there
		1926	is an ev_pri field.</dt>
		1927	<dt>* Other members are not supported.</dt>
		1928	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1929	to use the libev header file and library.</dt>
		1930	</dl>
		1931
		1932	</div>
		1933	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1934	<div id="C_SUPPORT_CONTENT">
		1935	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1936	you to use some convinience methods to start/stop watchers and also change
		1937	the callback model to a model using method callbacks on objects.</p>
		1938	<p>To use it,</p>
		1939	<pre> #include <ev++.h>
		1940
		1941	</pre>
		1942	<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
		1943	of them macros) into the global namespace. All C++ specific things are
		1944	put into the <code>ev</code> namespace. It should support all the same embedding
		1945	options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
		1946	<p>Care has been taken to keep the overhead low. The only data member the C++
		1947	classes add (compared to plain C-style watchers) is the event loop pointer
		1948	that the watcher is associated with (or no additional members at all if
		1949	you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
		1950	<p>Currently, functions, and static and non-static member functions can be
		1951	used as callbacks. Other types should be easy to add as long as they only
		1952	need one additional pointer for context. If you need support for other
		1953	types of functors please contact the author (preferably after implementing
		1954	it).</p>
		1955	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1956	<dl>
		1957	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1958	<dd>
		1959	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1960	macros from <cite>ev.h</cite>.</p>
		1961	</dd>
		1962	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1963	<dd>
		1964	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1965	</dd>
		1966	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1967	<dd>
		1968	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1969	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1970	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1971	defines by many implementations.</p>
		1972	<p>All of those classes have these methods:</p>
		1973	<p>
		1974	<dl>
		1975	<dt>ev::TYPE::TYPE ()</dt>
		1976	<dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
		1977	<dt>ev::TYPE::~TYPE</dt>
		1978	<dd>
		1979	<p>The constructor (optionally) takes an event loop to associate the watcher
		1980	with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
		1981	<p>The constructor calls <code>ev_init</code> for you, which means you have to call the
		1982	<code>set</code> method before starting it.</p>
		1983	<p>It will not set a callback, however: You have to call the templated <code>set</code>
		1984	method to set a callback before you can start the watcher.</p>
		1985	<p>(The reason why you have to use a method is a limitation in C++ which does
		1986	not allow explicit template arguments for constructors).</p>
		1987	<p>The destructor automatically stops the watcher if it is active.</p>
		1988	</dd>
		1989	<dt>w->set<class, &class::method> (object *)</dt>
		1990	<dd>
		1991	<p>This method sets the callback method to call. The method has to have a
		1992	signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as
		1993	first argument and the <code>revents</code> as second. The object must be given as
		1994	parameter and is stored in the <code>data</code> member of the watcher.</p>
		1995	<p>This method synthesizes efficient thunking code to call your method from
		1996	the C callback that libev requires. If your compiler can inline your
		1997	callback (i.e. it is visible to it at the place of the <code>set</code> call and
		1998	your compiler is good :), then the method will be fully inlined into the
		1999	thunking function, making it as fast as a direct C callback.</p>
		2000	<p>Example: simple class declaration and watcher initialisation</p>
		2001	<pre> struct myclass
		2002	{
		2003	void io_cb (ev::io &w, int revents) { }
		2004	}
		2005
		2006	myclass obj;
		2007	ev::io iow;
		2008	iow.set <myclass, &myclass::io_cb> (&obj);
		2009
		2010	</pre>
		2011	</dd>
		2012	<dt>w->set<function> (void *data = 0)</dt>
		2013	<dd>
		2014	<p>Also sets a callback, but uses a static method or plain function as
		2015	callback. The optional <code>data</code> argument will be stored in the watcher's
		2016	<code>data</code> member and is free for you to use.</p>
		2017	<p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p>
		2018	<p>See the method-<code>set</code> above for more details.</p>
		2019	<p>Example:</p>
		2020	<pre> static void io_cb (ev::io &w, int revents) { }
		2021	iow.set <io_cb> ();
		2022
		2023	</pre>
		2024	</dd>
		2025	<dt>w->set (struct ev_loop *)</dt>
		2026	<dd>
		2027	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		2028	do this when the watcher is inactive (and not pending either).</p>
		2029	</dd>
		2030	<dt>w->set ([args])</dt>
		2031	<dd>
		2032	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		2033	called at least once. Unlike the C counterpart, an active watcher gets
		2034	automatically stopped and restarted when reconfiguring it with this
		2035	method.</p>
		2036	</dd>
		2037	<dt>w->start ()</dt>
		2038	<dd>
		2039	<p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
		2040	constructor already stores the event loop.</p>
		2041	</dd>
		2042	<dt>w->stop ()</dt>
		2043	<dd>
		2044	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		2045	</dd>
		2046	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		2047	<dd>
		2048	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		2049	<code>ev_TYPE_again</code> function.</p>
		2050	</dd>
		2051	<dt>w->sweep () <code>ev::embed</code> only</dt>
		2052	<dd>
		2053	<p>Invokes <code>ev_embed_sweep</code>.</p>
		2054	</dd>
		2055	<dt>w->update () <code>ev::stat</code> only</dt>
		2056	<dd>
		2057	<p>Invokes <code>ev_stat_stat</code>.</p>
		2058	</dd>
		2059	</dl>
		2060	</p>
		2061	</dd>
		2062	</dl>
		2063	<p>Example: Define a class with an IO and idle watcher, start one of them in
		2064	the constructor.</p>
		2065	<pre> class myclass
		2066	{
		2067	ev_io io; void io_cb (ev::io &w, int revents);
		2068	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2069
		2070	myclass ();
		2071	}
		2072
		2073	myclass::myclass (int fd)
		2074	{
		2075	io .set <myclass, &myclass::io_cb > (this);
		2076	idle.set <myclass, &myclass::idle_cb> (this);
		2077
		2078	io.start (fd, ev::READ);
		2079	}
		2080
		2081
		2082
		2083
		2084	</pre>
		2085
		2086	</div>
		2087	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		2088	<div id="MACRO_MAGIC_CONTENT">
		2089	<p>Libev can be compiled with a variety of options, the most fundemantal is
		2090	<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
		2091	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		2092	<p>To make it easier to write programs that cope with either variant, the
		2093	following macros are defined:</p>
		2094	<dl>
		2095	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		2096	<dd>
		2097	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		2098	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		2099	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		2100	<pre> ev_unref (EV_A);
		2101	ev_timer_add (EV_A_ watcher);
		2102	ev_loop (EV_A_ 0);
		2103
		2104	</pre>
		2105	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		2106	which is often provided by the following macro.</p>
		2107	</dd>
		2108	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		2109	<dd>
		2110	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		2111	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		2112	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		2113	<pre> // this is how ev_unref is being declared
		2114	static void ev_unref (EV_P);
		2115
		2116	// this is how you can declare your typical callback
		2117	static void cb (EV_P_ ev_timer *w, int revents)
		2118
		2119	</pre>
		2120	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		2121	suitable for use with <code>EV_A</code>.</p>
		2122	</dd>
		2123	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		2124	<dd>
		2125	<p>Similar to the other two macros, this gives you the value of the default
		2126	loop, if multiple loops are supported ("ev loop default").</p>
		2127	</dd>
		2128	</dl>
		2129	<p>Example: Declare and initialise a check watcher, utilising the above
		2130	macros so it will work regardless of whether multiple loops are supported
		2131	or not.</p>
		2132	<pre> static void
		2133	check_cb (EV_P_ ev_timer *w, int revents)
		2134	{
		2135	ev_check_stop (EV_A_ w);
		2136	}
		2137
		2138	ev_check check;
		2139	ev_check_init (&check, check_cb);
		2140	ev_check_start (EV_DEFAULT_ &check);
		2141	ev_loop (EV_DEFAULT_ 0);
		2142
		2143	</pre>
		2144
		2145	</div>
		2146	<h1 id="EMBEDDING">EMBEDDING</h1>
		2147	<div id="EMBEDDING_CONTENT">
		2148	<p>Libev can (and often is) directly embedded into host
		2149	applications. Examples of applications that embed it include the Deliantra
		2150	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2151	and rxvt-unicode.</p>
		2152	<p>The goal is to enable you to just copy the neecssary files into your
		2153	source directory without having to change even a single line in them, so
		2154	you can easily upgrade by simply copying (or having a checked-out copy of
		2155	libev somewhere in your source tree).</p>
		2156
		2157	</div>
		2158	<h2 id="FILESETS">FILESETS</h2>
		2159	<div id="FILESETS_CONTENT">
		2160	<p>Depending on what features you need you need to include one or more sets of files
		2161	in your app.</p>
		2162
		2163	</div>
		2164	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		2165	<div id="CORE_EVENT_LOOP_CONTENT">
		2166	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		2167	configuration (no autoconf):</p>
		2168	<pre> #define EV_STANDALONE 1
		2169	#include "ev.c"
		2170
		2171	</pre>
		2172	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		2173	single C source file only to provide the function implementations. To use
		2174	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		2175	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		2176	where you can put other configuration options):</p>
		2177	<pre> #define EV_STANDALONE 1
		2178	#include "ev.h"
		2179
		2180	</pre>
		2181	<p>Both header files and implementation files can be compiled with a C++
		2182	compiler (at least, thats a stated goal, and breakage will be treated
		2183	as a bug).</p>
		2184	<p>You need the following files in your source tree, or in a directory
		2185	in your include path (e.g. in libev/ when using -Ilibev):</p>
		2186	<pre> ev.h
		2187	ev.c
		2188	ev_vars.h
		2189	ev_wrap.h
		2190
		2191	ev_win32.c required on win32 platforms only
		2192
		2193	ev_select.c only when select backend is enabled (which is enabled by default)
		2194	ev_poll.c only when poll backend is enabled (disabled by default)
		2195	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2196	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2197	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2198
		2199	</pre>
		2200	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		2201	to compile this single file.</p>
		2202
		2203	</div>
		2204	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		2205	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		2206	<p>To include the libevent compatibility API, also include:</p>
		2207	<pre> #include "event.c"
		2208
		2209	</pre>
		2210	<p>in the file including <cite>ev.c</cite>, and:</p>
		2211	<pre> #include "event.h"
		2212
		2213	</pre>
		2214	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		2215	<p>You need the following additional files for this:</p>
		2216	<pre> event.h
		2217	event.c
		2218
		2219	</pre>
		2220
		2221	</div>
		2222	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		2223	<div id="AUTOCONF_SUPPORT_CONTENT">
		2224	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		2225	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		2226	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		2227	include <cite>config.h</cite> and configure itself accordingly.</p>
		2228	<p>For this of course you need the m4 file:</p>
		2229	<pre> libev.m4
		2230
		2231	</pre>
		2232
		2233	</div>
		2234	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		2235	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		2236	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		2237	before including any of its files. The default is not to build for multiplicity
		2238	and only include the select backend.</p>
		2239	<dl>
		2240	<dt>EV_STANDALONE</dt>
		2241	<dd>
		2242	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		2243	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		2244	implementations for some libevent functions (such as logging, which is not
		2245	supported). It will also not define any of the structs usually found in
		2246	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		2247	</dd>
		2248	<dt>EV_USE_MONOTONIC</dt>
		2249	<dd>
		2250	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2251	monotonic clock option at both compiletime and runtime. Otherwise no use
		2252	of the monotonic clock option will be attempted. If you enable this, you
		2253	usually have to link against librt or something similar. Enabling it when
		2254	the functionality isn't available is safe, though, althoguh you have
		2255	to make sure you link against any libraries where the <code>clock_gettime</code>
		2256	function is hiding in (often <cite>-lrt</cite>).</p>
		2257	</dd>
		2258	<dt>EV_USE_REALTIME</dt>
		2259	<dd>
		2260	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2261	realtime clock option at compiletime (and assume its availability at
		2262	runtime if successful). Otherwise no use of the realtime clock option will
		2263	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		2264	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		2265	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		2266	</dd>
		2267	<dt>EV_USE_SELECT</dt>
		2268	<dd>
		2269	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		2270	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		2271	other method takes over, select will be it. Otherwise the select backend
		2272	will not be compiled in.</p>
		2273	</dd>
		2274	<dt>EV_SELECT_USE_FD_SET</dt>
		2275	<dd>
		2276	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		2277	structure. This is useful if libev doesn't compile due to a missing
		2278	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		2279	exotic systems. This usually limits the range of file descriptors to some
		2280	low limit such as 1024 or might have other limitations (winsocket only
		2281	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		2282	influence the size of the <code>fd_set</code> used.</p>
		2283	</dd>
		2284	<dt>EV_SELECT_IS_WINSOCKET</dt>
		2285	<dd>
		2286	<p>When defined to <code>1</code>, the select backend will assume that
		2287	select/socket/connect etc. don't understand file descriptors but
		2288	wants osf handles on win32 (this is the case when the select to
		2289	be used is the winsock select). This means that it will call
		2290	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		2291	it is assumed that all these functions actually work on fds, even
		2292	on win32. Should not be defined on non-win32 platforms.</p>
		2293	</dd>
		2294	<dt>EV_USE_POLL</dt>
		2295	<dd>
		2296	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		2297	backend. Otherwise it will be enabled on non-win32 platforms. It
		2298	takes precedence over select.</p>
		2299	</dd>
		2300	<dt>EV_USE_EPOLL</dt>
		2301	<dd>
		2302	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		2303	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2304	otherwise another method will be used as fallback. This is the
		2305	preferred backend for GNU/Linux systems.</p>
		2306	</dd>
		2307	<dt>EV_USE_KQUEUE</dt>
		2308	<dd>
		2309	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2310	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2311	otherwise another method will be used as fallback. This is the preferred
		2312	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2313	supports some types of fds correctly (the only platform we found that
		2314	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2315	not be used unless explicitly requested. The best way to use it is to find
		2316	out whether kqueue supports your type of fd properly and use an embedded
		2317	kqueue loop.</p>
		2318	</dd>
		2319	<dt>EV_USE_PORT</dt>
		2320	<dd>
		2321	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2322	10 port style backend. Its availability will be detected at runtime,
		2323	otherwise another method will be used as fallback. This is the preferred
		2324	backend for Solaris 10 systems.</p>
		2325	</dd>
		2326	<dt>EV_USE_DEVPOLL</dt>
		2327	<dd>
		2328	<p>reserved for future expansion, works like the USE symbols above.</p>
		2329	</dd>
		2330	<dt>EV_USE_INOTIFY</dt>
		2331	<dd>
		2332	<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
		2333	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2334	be detected at runtime.</p>
		2335	</dd>
		2336	<dt>EV_H</dt>
		2337	<dd>
		2338	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2339	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2340	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2341	</dd>
		2342	<dt>EV_CONFIG_H</dt>
		2343	<dd>
		2344	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2345	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2346	<code>EV_H</code>, above.</p>
		2347	</dd>
		2348	<dt>EV_EVENT_H</dt>
		2349	<dd>
		2350	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2351	of how the <cite>event.h</cite> header can be found.</p>
		2352	</dd>
		2353	<dt>EV_PROTOTYPES</dt>
		2354	<dd>
		2355	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2356	prototypes, but still define all the structs and other symbols. This is
		2357	occasionally useful if you want to provide your own wrapper functions
		2358	around libev functions.</p>
		2359	</dd>
		2360	<dt>EV_MULTIPLICITY</dt>
		2361	<dd>
		2362	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2363	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2364	additional independent event loops. Otherwise there will be no support
		2365	for multiple event loops and there is no first event loop pointer
		2366	argument. Instead, all functions act on the single default loop.</p>
		2367	</dd>
		2368	<dt>EV_MINPRI</dt>
		2369	<dt>EV_MAXPRI</dt>
		2370	<dd>
		2371	<p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
		2372	<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
		2373	provide for more priorities by overriding those symbols (usually defined
		2374	to be <code>-2</code> and <code>2</code>, respectively).</p>
		2375	<p>When doing priority-based operations, libev usually has to linearly search
		2376	all the priorities, so having many of them (hundreds) uses a lot of space
		2377	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2378	fine.</p>
		2379	<p>If your embedding app does not need any priorities, defining these both to
		2380	<code>0</code> will save some memory and cpu.</p>
		2381	</dd>
		2382	<dt>EV_PERIODIC_ENABLE</dt>
		2383	<dd>
		2384	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2385	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2386	code.</p>
		2387	</dd>
		2388	<dt>EV_IDLE_ENABLE</dt>
		2389	<dd>
		2390	<p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
		2391	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2392	code.</p>
		2393	</dd>
		2394	<dt>EV_EMBED_ENABLE</dt>
		2395	<dd>
		2396	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2397	defined to be <code>0</code>, then they are not.</p>
		2398	</dd>
		2399	<dt>EV_STAT_ENABLE</dt>
		2400	<dd>
		2401	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2402	defined to be <code>0</code>, then they are not.</p>
		2403	</dd>
		2404	<dt>EV_FORK_ENABLE</dt>
		2405	<dd>
		2406	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2407	defined to be <code>0</code>, then they are not.</p>
		2408	</dd>
		2409	<dt>EV_MINIMAL</dt>
		2410	<dd>
		2411	<p>If you need to shave off some kilobytes of code at the expense of some
		2412	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2413	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2414	</dd>
		2415	<dt>EV_PID_HASHSIZE</dt>
		2416	<dd>
		2417	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2418	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2419	than enough. If you need to manage thousands of children you might want to
		2420	increase this value (<i>must</i> be a power of two).</p>
		2421	</dd>
		2422	<dt>EV_INOTIFY_HASHSIZE</dt>
		2423	<dd>
		2424	<p><code>ev_staz</code> watchers use a small hash table to distribute workload by
		2425	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2426	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2427	watchers you might want to increase this value (<i>must</i> be a power of
		2428	two).</p>
		2429	</dd>
		2430	<dt>EV_COMMON</dt>
		2431	<dd>
		2432	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2433	this macro to a something else you can include more and other types of
		2434	members. You have to define it each time you include one of the files,
		2435	though, and it must be identical each time.</p>
		2436	<p>For example, the perl EV module uses something like this:</p>
		2437	<pre> #define EV_COMMON \
		2438	SV self; / contains this struct */ \
		2439	SV cb_sv, fh /* note no trailing ";" */
		2440
		2441	</pre>
		2442	</dd>
		2443	<dt>EV_CB_DECLARE (type)</dt>
		2444	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2445	<dt>ev_set_cb (ev, cb)</dt>
		2446	<dd>
		2447	<p>Can be used to change the callback member declaration in each watcher,
		2448	and the way callbacks are invoked and set. Must expand to a struct member
		2449	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2450	their default definitions. One possible use for overriding these is to
		2451	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2452	method calls instead of plain function calls in C++.</p>
		2453
		2454	</div>
		2455	<h2 id="EXAMPLES">EXAMPLES</h2>
		2456	<div id="EXAMPLES_CONTENT">
		2457	<p>For a real-world example of a program the includes libev
		2458	verbatim, you can have a look at the EV perl module
		2459	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2460	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2461	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2462	will be compiled. It is pretty complex because it provides its own header
		2463	file.</p>
		2464	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2465	that everybody includes and which overrides some configure choices:</p>
		2466	<pre> #define EV_MINIMAL 1
		2467	#define EV_USE_POLL 0
		2468	#define EV_MULTIPLICITY 0
		2469	#define EV_PERIODIC_ENABLE 0
		2470	#define EV_STAT_ENABLE 0
		2471	#define EV_FORK_ENABLE 0
		2472	#define EV_CONFIG_H <config.h>
		2473	#define EV_MINPRI 0
		2474	#define EV_MAXPRI 0
		2475
		2476	#include "ev++.h"
		2477
		2478	</pre>
		2479	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2480	<pre> #include "ev_cpp.h"
		2481	#include "ev.c"
		2482
		2483
		2484
		2485
		2486	</pre>
		2487
		2488	</div>
		2489	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2490	<div id="COMPLEXITIES_CONTENT">
		2491	<p>In this section the complexities of (many of) the algorithms used inside
		2492	libev will be explained. For complexity discussions about backends see the
		2493	documentation for <code>ev_default_init</code>.</p>
		2494	<p>All of the following are about amortised time: If an array needs to be
		2495	extended, libev needs to realloc and move the whole array, but this
		2496	happens asymptotically never with higher number of elements, so O(1) might
		2497	mean it might do a lengthy realloc operation in rare cases, but on average
		2498	it is much faster and asymptotically approaches constant time.</p>
		2499	<p>
		2500	<dl>
		2501	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2502	<dd>
		2503	<p>This means that, when you have a watcher that triggers in one hour and
		2504	there are 100 watchers that would trigger before that then inserting will
		2505	have to skip those 100 watchers.</p>
		2506	</dd>
		2507	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2508	<dd>
		2509	<p>That means that for changing a timer costs less than removing/adding them
		2510	as only the relative motion in the event queue has to be paid for.</p>
		2511	</dd>
		2512	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2513	<dd>
		2514	<p>These just add the watcher into an array or at the head of a list.
		2515	=item Stopping check/prepare/idle watchers: O(1)</p>
		2516	</dd>
		2517	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
		2518	<dd>
		2519	<p>These watchers are stored in lists then need to be walked to find the
		2520	correct watcher to remove. The lists are usually short (you don't usually
		2521	have many watchers waiting for the same fd or signal).</p>
		2522	</dd>
		2523	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2524	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2525	<dd>
		2526	<p>A change means an I/O watcher gets started or stopped, which requires
		2527	libev to recalculate its status (and possibly tell the kernel).</p>
		2528	</dd>
		2529	<dt>Activating one watcher: O(1)</dt>
		2530	<dt>Priority handling: O(number_of_priorities)</dt>
		2531	<dd>
		2532	<p>Priorities are implemented by allocating some space for each
		2533	priority. When doing priority-based operations, libev usually has to
		2534	linearly search all the priorities.</p>
		2535	</dd>
		2536	</dl>
		2537	</p>
		2538
		2539
		2540
		2541
		2542
		2543	</div>
		2544	<h1 id="AUTHOR">AUTHOR</h1>
718	<div id="AUTHOR_CONTENT">	2545	<div id="AUTHOR_CONTENT">
719	<p>Marc Lehmann <libev@schmorp.de>.</p>	2546	<p>Marc Lehmann <libev@schmorp.de>.</p>
720		2547
721	</div>	2548	</div>
722	</div></body>	2549	</div></body>
723	</html>	2550	</html>

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Revision 1.79 by root, Wed Dec 12 17:55:30 2007 UTC