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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></li>
30	<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li>	33	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
31	<li><a href="#ev_periodic">ev_periodic</a></li>	34	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
32	<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li>	35	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
33	<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li>	36	<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
		37	<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
34	<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li>	38	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
35	<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li>	39	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
		40	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
		41	<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
36	</ul>	42	</ul>
37	</li>	43	</li>
38	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	44	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		45	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		46	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		47	<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
		48	<li><a href="#EMBEDDING">EMBEDDING</a>
		49	<ul><li><a href="#FILESETS">FILESETS</a>
		50	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		51	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		52	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		53	</ul>
		54	</li>
		55	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		56	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		57	</ul>
		58	</li>
		59	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
39	<li><a href="#AUTHOR">AUTHOR</a>	60	<li><a href="#AUTHOR">AUTHOR</a>
40	</li>	61	</li>
41	</ul><hr />	62	</ul><hr />
42	<!-- INDEX END -->	63	<!-- INDEX END -->
43		64
44	<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>	65	<h1 id="NAME">NAME</h1>
45	<div id="NAME_CONTENT">	66	<div id="NAME_CONTENT">
46	<p>libev - a high performance full-featured event loop written in C</p>	67	<p>libev - a high performance full-featured event loop written in C</p>
47		68
48	</div>	69	</div>
49	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>	70	<h1 id="SYNOPSIS">SYNOPSIS</h1>
50	<div id="SYNOPSIS_CONTENT">	71	<div id="SYNOPSIS_CONTENT">
51	<pre> #include <ev.h>	72	<pre> #include <ev.h>
52		73
53	</pre>	74	</pre>
54		75
55	</div>	76	</div>
56	<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>	77	<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
		78	<div id="EXAMPLE_PROGRAM_CONTENT">
		79	<pre> #include <ev.h>
		80
		81	ev_io stdin_watcher;
		82	ev_timer timeout_watcher;
		83
		84	/* called when data readable on stdin */
		85	static void
		86	stdin_cb (EV_P_ struct ev_io *w, int revents)
		87	{
		88	/* puts ("stdin ready"); */
		89	ev_io_stop (EV_A_ w); /* just a syntax example */
		90	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		91	}
		92
		93	static void
		94	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		95	{
		96	/* puts ("timeout"); */
		97	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		98	}
		99
		100	int
		101	main (void)
		102	{
		103	struct ev_loop *loop = ev_default_loop (0);
		104
		105	/* initialise an io watcher, then start it */
		106	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		107	ev_io_start (loop, &stdin_watcher);
		108
		109	/* simple non-repeating 5.5 second timeout */
		110	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		111	ev_timer_start (loop, &timeout_watcher);
		112
		113	/* loop till timeout or data ready */
		114	ev_loop (loop, 0);
		115
		116	return 0;
		117	}
		118
		119	</pre>
		120
		121	</div>
		122	<h1 id="DESCRIPTION">DESCRIPTION</h1>
57	<div id="DESCRIPTION_CONTENT">	123	<div id="DESCRIPTION_CONTENT">
58	<p>Libev is an event loop: you register interest in certain events (such as a	124	<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	125	file descriptor being readable or a timeout occuring), and it will manage
60	these event sources and provide your program events.</p>	126	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	127	<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	128	(or thread) by executing the <i>event loop</i> handler, and will then
63	communicate events via a callback mechanism.</p>	129	communicate events via a callback mechanism.</p>
64	<p>You register interest in certain events by registering so-called <i>event	130	<p>You register interest in certain events by registering so-called <i>event
65	watchers</i>, which are relatively small C structures you initialise with the	131	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	132	details of the event, and then hand it over to libev by <i>starting</i> the
67	watcher.</p>	133	watcher.</p>
68		134
69	</div>	135	</div>
70	<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>	136	<h1 id="FEATURES">FEATURES</h1>
71	<div id="FEATURES_CONTENT">	137	<div id="FEATURES_CONTENT">
72	<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific	138	<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	139	BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
74	timers with customised rescheduling, signal events, process status change	140	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	141	(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
76	loop mechanism itself (idle, prepare and check watchers).</p>	142	with customised rescheduling (<code>ev_periodic</code>), synchronous signals
		143	(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
		144	watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
		145	<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
		146	file watchers (<code>ev_stat</code>) and even limited support for fork events
		147	(<code>ev_fork</code>).</p>
		148	<p>It also is quite fast (see this
		149	<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
		150	for example).</p>
77		151
78	</div>	152	</div>
79	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	153	<h1 id="CONVENTIONS">CONVENTIONS</h1>
80	<div id="CONVENTIONS_CONTENT">	154	<div id="CONVENTIONS_CONTENT">
81	<p>Libev is very configurable. In this manual the default configuration	155	<p>Libev is very configurable. In this manual the default configuration will
82	will be described, which supports multiple event loops. For more info	156	be described, which supports multiple event loops. For more info about
83	about various configuraiton options please have a look at the file	157	various configuration options please have a look at <strong>EMBED</strong> section in
84	<cite>README.embed</cite> in the libev distribution. If libev was configured without	158	this manual. If libev was configured without support for multiple event
85	support for multiple event loops, then all functions taking an initial	159	loops, then all functions taking an initial argument of name <code>loop</code>
86	argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)	160	(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
87	will not have this argument.</p>
88		161
89	</div>	162	</div>
90	<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	163	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
91	<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT">	164	<div id="TIME_REPRESENTATION_CONTENT">
92	<p>Libev represents time as a single floating point number. This type is	165	<p>Libev represents time as a single floating point number, representing the
		166	(fractional) number of seconds since the (POSIX) epoch (somewhere near
		167	the beginning of 1970, details are complicated, don't ask). This type is
93	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	168	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
94	to the double type in C.</p>	169	to the <code>double</code> type in C, and when you need to do any calculations on
		170	it, you should treat it as such.</p>
		171
		172	</div>
		173	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
		174	<div id="GLOBAL_FUNCTIONS_CONTENT">
		175	<p>These functions can be called anytime, even before initialising the
		176	library in any way.</p>
95	<dl>	177	<dl>
96	<dt>ev_tstamp ev_time ()</dt>	178	<dt>ev_tstamp ev_time ()</dt>
97	<dd>	179	<dd>
98	<p>Returns the current time as libev would use it.</p>	180	<p>Returns the current time as libev would use it. Please note that the
		181	<code>ev_now</code> function is usually faster and also often returns the timestamp
		182	you actually want to know.</p>
99	</dd>	183	</dd>
100	<dt>int ev_version_major ()</dt>	184	<dt>int ev_version_major ()</dt>
101	<dt>int ev_version_minor ()</dt>	185	<dt>int ev_version_minor ()</dt>
102	<dd>	186	<dd>
103	<p>You can find out the major and minor version numbers of the library	187	<p>You can find out the major and minor version numbers of the library
104	you linked against by calling the functions <code>ev_version_major</code> and	188	you linked against by calling the functions <code>ev_version_major</code> and
105	<code>ev_version_minor</code>. If you want, you can compare against the global	189	<code>ev_version_minor</code>. If you want, you can compare against the global
106	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the	190	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
107	version of the library your program was compiled against.</p>	191	version of the library your program was compiled against.</p>
108	<p>Usually, its a good idea to terminate if the major versions mismatch,	192	<p>Usually, it's a good idea to terminate if the major versions mismatch,
109	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
110	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
111	not a problem.</p>	195	not a problem.</p>
		196	<p>Example: Make sure we haven't accidentally been linked against the wrong
		197	version.</p>
		198	<pre> assert (("libev version mismatch",
		199	ev_version_major () == EV_VERSION_MAJOR
		200	&& ev_version_minor () >= EV_VERSION_MINOR));
		201
		202	</pre>
		203	</dd>
		204	<dt>unsigned int ev_supported_backends ()</dt>
		205	<dd>
		206	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		207	value) compiled into this binary of libev (independent of their
		208	availability on the system you are running on). See <code>ev_default_loop</code> for
		209	a description of the set values.</p>
		210	<p>Example: make sure we have the epoll method, because yeah this is cool and
		211	a must have and can we have a torrent of it please!!!11</p>
		212	<pre> assert (("sorry, no epoll, no sex",
		213	ev_supported_backends () & EVBACKEND_EPOLL));
		214
		215	</pre>
		216	</dd>
		217	<dt>unsigned int ev_recommended_backends ()</dt>
		218	<dd>
		219	<p>Return the set of all backends compiled into this binary of libev and also
		220	recommended for this platform. This set is often smaller than the one
		221	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		222	most BSDs and will not be autodetected unless you explicitly request it
		223	(assuming you know what you are doing). This is the set of backends that
		224	libev will probe for if you specify no backends explicitly.</p>
		225	</dd>
		226	<dt>unsigned int ev_embeddable_backends ()</dt>
		227	<dd>
		228	<p>Returns the set of backends that are embeddable in other event loops. This
		229	is the theoretical, all-platform, value. To find which backends
		230	might be supported on the current system, you would need to look at
		231	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		232	recommended ones.</p>
		233	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
112	</dd>	234	</dd>
113	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	235	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
114	<dd>	236	<dd>
115	<p>Sets the allocation function to use (the prototype is similar to the	237	<p>Sets the allocation function to use (the prototype is similar - the
116	realloc function). It is used to allocate and free memory (no surprises	238	semantics is identical - to the realloc C function). It is used to
117	here). If it returns zero when memory needs to be allocated, the library	239	allocate and free memory (no surprises here). If it returns zero when
118	might abort or take some potentially destructive action. The default is	240	memory needs to be allocated, the library might abort or take some
119	your system realloc function.</p>	241	potentially destructive action. The default is your system realloc
		242	function.</p>
120	<p>You could override this function in high-availability programs to, say,	243	<p>You could override this function in high-availability programs to, say,
121	free some memory if it cannot allocate memory, to use a special allocator,	244	free some memory if it cannot allocate memory, to use a special allocator,
122	or even to sleep a while and retry until some memory is available.</p>	245	or even to sleep a while and retry until some memory is available.</p>
		246	<p>Example: Replace the libev allocator with one that waits a bit and then
		247	retries).</p>
		248	<pre> static void *
		249	persistent_realloc (void *ptr, size_t size)
		250	{
		251	for (;;)
		252	{
		253	void *newptr = realloc (ptr, size);
		254
		255	if (newptr)
		256	return newptr;
		257
		258	sleep (60);
		259	}
		260	}
		261
		262	...
		263	ev_set_allocator (persistent_realloc);
		264
		265	</pre>
123	</dd>	266	</dd>
124	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	267	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
125	<dd>	268	<dd>
126	<p>Set the callback function to call on a retryable syscall error (such	269	<p>Set the callback function to call on a retryable syscall error (such
127	as failed select, poll, epoll_wait). The message is a printable string	270	as failed select, poll, epoll_wait). The message is a printable string
128	indicating the system call or subsystem causing the problem. If this	271	indicating the system call or subsystem causing the problem. If this
129	callback is set, then libev will expect it to remedy the sitution, no	272	callback is set, then libev will expect it to remedy the sitution, no
130	matter what, when it returns. That is, libev will geenrally retry the	273	matter what, when it returns. That is, libev will generally retry the
131	requested operation, or, if the condition doesn't go away, do bad stuff	274	requested operation, or, if the condition doesn't go away, do bad stuff
132	(such as abort).</p>	275	(such as abort).</p>
		276	<p>Example: This is basically the same thing that libev does internally, too.</p>
		277	<pre> static void
		278	fatal_error (const char *msg)
		279	{
		280	perror (msg);
		281	abort ();
		282	}
		283
		284	...
		285	ev_set_syserr_cb (fatal_error);
		286
		287	</pre>
133	</dd>	288	</dd>
134	</dl>	289	</dl>
135		290
136	</div>	291	</div>
137	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	292	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
138	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	293	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
139	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two	294	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
140	types of such loops, the <i>default</i> loop, which supports signals and child	295	types of such loops, the <i>default</i> loop, which supports signals and child
141	events, and dynamically created loops which do not.</p>	296	events, and dynamically created loops which do not.</p>
142	<p>If you use threads, a common model is to run the default event loop	297	<p>If you use threads, a common model is to run the default event loop
143	in your main thread (or in a separate thrad) and for each thread you	298	in your main thread (or in a separate thread) and for each thread you
144	create, you also create another event loop. Libev itself does no lockign	299	create, you also create another event loop. Libev itself does no locking
145	whatsoever, so if you mix calls to different event loops, make sure you	300	whatsoever, so if you mix calls to the same event loop in different
146	lock (this is usually a bad idea, though, even if done right).</p>	301	threads, make sure you lock (this is usually a bad idea, though, even if
		302	done correctly, because it's hideous and inefficient).</p>
147	<dl>	303	<dl>
148	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	304	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
149	<dd>	305	<dd>
150	<p>This will initialise the default event loop if it hasn't been initialised	306	<p>This will initialise the default event loop if it hasn't been initialised
151	yet and return it. If the default loop could not be initialised, returns	307	yet and return it. If the default loop could not be initialised, returns
152	false. If it already was initialised it simply returns it (and ignores the	308	false. If it already was initialised it simply returns it (and ignores the
153	flags).</p>	309	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
154	<p>If you don't know what event loop to use, use the one returned from this	310	<p>If you don't know what event loop to use, use the one returned from this
155	function.</p>	311	function.</p>
156	<p>The flags argument can be used to specify special behaviour or specific	312	<p>The flags argument can be used to specify special behaviour or specific
157	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p>	313	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
158	<p>It supports the following flags:</p>	314	<p>The following flags are supported:</p>
159	<p>	315	<p>
160	<dl>	316	<dl>
161	<dt>EVFLAG_AUTO</dt>	317	<dt><code>EVFLAG_AUTO</code></dt>
162	<dd>	318	<dd>
163	<p>The default flags value. Use this if you have no clue (its the right	319	<p>The default flags value. Use this if you have no clue (it's the right
164	thing, believe me).</p>	320	thing, believe me).</p>
165	</dd>	321	</dd>
166	<dt>EVFLAG_NOENV</dt>	322	<dt><code>EVFLAG_NOENV</code></dt>
167	<dd>	323	<dd>
168	<p>If this flag bit is ored into the flag value then libev will <i>not</i> look	324	<p>If this flag bit is ored into the flag value (or the program runs setuid
169	at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this	325	or setgid) then libev will <i>not</i> look at the environment variable
170	environment variable will override the flags completely. This is useful	326	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
		327	override the flags completely if it is found in the environment. This is
171	to try out specific backends to tets their performance, or to work around	328	useful to try out specific backends to test their performance, or to work
172	bugs.</p>	329	around bugs.</p>
173	</dd>	330	</dd>
174	<dt>EVMETHOD_SELECT portable select backend</dt>	331	<dt><code>EVFLAG_FORKCHECK</code></dt>
175	<dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt>
176	<dt>EVMETHOD_EPOLL linux only</dt>
177	<dt>EVMETHOD_KQUEUE some bsds only</dt>
178	<dt>EVMETHOD_DEVPOLL solaris 8 only</dt>
179	<dt>EVMETHOD_PORT solaris 10 only</dt>
180	<dd>	332	<dd>
181	<p>If one or more of these are ored into the flags value, then only these	333	<p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
182	backends will be tried (in the reverse order as given here). If one are	334	a fork, you can also make libev check for a fork in each iteration by
183	specified, any backend will do.</p>	335	enabling this flag.</p>
		336	<p>This works by calling <code>getpid ()</code> on every iteration of the loop,
		337	and thus this might slow down your event loop if you do a lot of loop
		338	iterations and little real work, but is usually not noticeable (on my
		339	Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
		340	without a syscall and thus <i>very</i> fast, but my Linux system also has
		341	<code>pthread_atfork</code> which is even faster).</p>
		342	<p>The big advantage of this flag is that you can forget about fork (and
		343	forget about forgetting to tell libev about forking) when you use this
		344	flag.</p>
		345	<p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
		346	environment variable.</p>
		347	</dd>
		348	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
		349	<dd>
		350	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
		351	libev tries to roll its own fd_set with no limits on the number of fds,
		352	but if that fails, expect a fairly low limit on the number of fds when
		353	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		354	the fastest backend for a low number of fds.</p>
		355	</dd>
		356	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		357	<dd>
		358	<p>And this is your standard poll(2) backend. It's more complicated than
		359	select, but handles sparse fds better and has no artificial limit on the
		360	number of fds you can use (except it will slow down considerably with a
		361	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		362	</dd>
		363	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		364	<dd>
		365	<p>For few fds, this backend is a bit little slower than poll and select,
		366	but it scales phenomenally better. While poll and select usually scale like
		367	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		368	either O(1) or O(active_fds).</p>
		369	<p>While stopping and starting an I/O watcher in the same iteration will
		370	result in some caching, there is still a syscall per such incident
		371	(because the fd could point to a different file description now), so its
		372	best to avoid that. Also, dup()ed file descriptors might not work very
		373	well if you register events for both fds.</p>
		374	<p>Please note that epoll sometimes generates spurious notifications, so you
		375	need to use non-blocking I/O or other means to avoid blocking when no data
		376	(or space) is available.</p>
		377	</dd>
		378	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		379	<dd>
		380	<p>Kqueue deserves special mention, as at the time of this writing, it
		381	was broken on all BSDs except NetBSD (usually it doesn't work with
		382	anything but sockets and pipes, except on Darwin, where of course its
		383	completely useless). For this reason its not being "autodetected"
		384	unless you explicitly specify it explicitly in the flags (i.e. using
		385	<code>EVBACKEND_KQUEUE</code>).</p>
		386	<p>It scales in the same way as the epoll backend, but the interface to the
		387	kernel is more efficient (which says nothing about its actual speed, of
		388	course). While starting and stopping an I/O watcher does not cause an
		389	extra syscall as with epoll, it still adds up to four event changes per
		390	incident, so its best to avoid that.</p>
		391	</dd>
		392	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		393	<dd>
		394	<p>This is not implemented yet (and might never be).</p>
		395	</dd>
		396	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		397	<dd>
		398	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		399	it's really slow, but it still scales very well (O(active_fds)).</p>
		400	<p>Please note that solaris ports can result in a lot of spurious
		401	notifications, so you need to use non-blocking I/O or other means to avoid
		402	blocking when no data (or space) is available.</p>
		403	</dd>
		404	<dt><code>EVBACKEND_ALL</code></dt>
		405	<dd>
		406	<p>Try all backends (even potentially broken ones that wouldn't be tried
		407	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		408	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
184	</dd>	409	</dd>
185	</dl>	410	</dl>
186	</p>	411	</p>
		412	<p>If one or more of these are ored into the flags value, then only these
		413	backends will be tried (in the reverse order as given here). If none are
		414	specified, most compiled-in backend will be tried, usually in reverse
		415	order of their flag values :)</p>
		416	<p>The most typical usage is like this:</p>
		417	<pre> if (!ev_default_loop (0))
		418	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		419
		420	</pre>
		421	<p>Restrict libev to the select and poll backends, and do not allow
		422	environment settings to be taken into account:</p>
		423	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		424
		425	</pre>
		426	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		427	available (warning, breaks stuff, best use only with your own private
		428	event loop and only if you know the OS supports your types of fds):</p>
		429	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		430
		431	</pre>
187	</dd>	432	</dd>
188	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	433	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
189	<dd>	434	<dd>
190	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	435	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
191	always distinct from the default loop. Unlike the default loop, it cannot	436	always distinct from the default loop. Unlike the default loop, it cannot
192	handle signal and child watchers, and attempts to do so will be greeted by	437	handle signal and child watchers, and attempts to do so will be greeted by
193	undefined behaviour (or a failed assertion if assertions are enabled).</p>	438	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		439	<p>Example: Try to create a event loop that uses epoll and nothing else.</p>
		440	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		441	if (!epoller)
		442	fatal ("no epoll found here, maybe it hides under your chair");
		443
		444	</pre>
194	</dd>	445	</dd>
195	<dt>ev_default_destroy ()</dt>	446	<dt>ev_default_destroy ()</dt>
196	<dd>	447	<dd>
197	<p>Destroys the default loop again (frees all memory and kernel state	448	<p>Destroys the default loop again (frees all memory and kernel state
198	etc.). This stops all registered event watchers (by not touching them in	449	etc.). None of the active event watchers will be stopped in the normal
199	any way whatsoever, although you cnanot rely on this :).</p>	450	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		451	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		452	calling this function, or cope with the fact afterwards (which is usually
		453	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		454	for example).</p>
200	</dd>	455	</dd>
201	<dt>ev_loop_destroy (loop)</dt>	456	<dt>ev_loop_destroy (loop)</dt>
202	<dd>	457	<dd>
203	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	458	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
204	earlier call to <code>ev_loop_new</code>.</p>	459	earlier call to <code>ev_loop_new</code>.</p>
…		…
207	<dd>	462	<dd>
208	<p>This function reinitialises the kernel state for backends that have	463	<p>This function reinitialises the kernel state for backends that have
209	one. Despite the name, you can call it anytime, but it makes most sense	464	one. Despite the name, you can call it anytime, but it makes most sense
210	after forking, in either the parent or child process (or both, but that	465	after forking, in either the parent or child process (or both, but that
211	again makes little sense).</p>	466	again makes little sense).</p>
212	<p>You <i>must</i> call this function after forking if and only if you want to	467	<p>You <i>must</i> call this function in the child process after forking if and
213	use the event library in both processes. If you just fork+exec, you don't	468	only if you want to use the event library in both processes. If you just
214	have to call it.</p>	469	fork+exec, you don't have to call it.</p>
215	<p>The function itself is quite fast and its usually not a problem to call	470	<p>The function itself is quite fast and it's usually not a problem to call
216	it just in case after a fork. To make this easy, the function will fit in	471	it just in case after a fork. To make this easy, the function will fit in
217	quite nicely into a call to <code>pthread_atfork</code>:</p>	472	quite nicely into a call to <code>pthread_atfork</code>:</p>
218	<pre> pthread_atfork (0, 0, ev_default_fork);	473	<pre> pthread_atfork (0, 0, ev_default_fork);
219		474
220	</pre>	475	</pre>
		476	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		477	without calling this function, so if you force one of those backends you
		478	do not need to care.</p>
221	</dd>	479	</dd>
222	<dt>ev_loop_fork (loop)</dt>	480	<dt>ev_loop_fork (loop)</dt>
223	<dd>	481	<dd>
224	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	482	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
225	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	483	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
226	after fork, and how you do this is entirely your own problem.</p>	484	after fork, and how you do this is entirely your own problem.</p>
227	</dd>	485	</dd>
228	<dt>unsigned int ev_method (loop)</dt>	486	<dt>unsigned int ev_loop_count (loop)</dt>
		487	<dd>
		488	<p>Returns the count of loop iterations for the loop, which is identical to
		489	the number of times libev did poll for new events. It starts at <code>0</code> and
		490	happily wraps around with enough iterations.</p>
		491	<p>This value can sometimes be useful as a generation counter of sorts (it
		492	"ticks" the number of loop iterations), as it roughly corresponds with
		493	<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
229	<dd>	494	</dd>
		495	<dt>unsigned int ev_backend (loop)</dt>
		496	<dd>
230	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	497	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
231	use.</p>	498	use.</p>
232	</dd>	499	</dd>
233	<dt>ev_tstamp = ev_now (loop)</dt>	500	<dt>ev_tstamp ev_now (loop)</dt>
234	<dd>	501	<dd>
235	<p>Returns the current "event loop time", which is the time the event loop	502	<p>Returns the current "event loop time", which is the time the event loop
236	got events and started processing them. This timestamp does not change	503	received events and started processing them. This timestamp does not
237	as long as callbacks are being processed, and this is also the base time	504	change as long as callbacks are being processed, and this is also the base
238	used for relative timers. You can treat it as the timestamp of the event	505	time used for relative timers. You can treat it as the timestamp of the
239	occuring (or more correctly, the mainloop finding out about it).</p>	506	event occuring (or more correctly, libev finding out about it).</p>
240	</dd>	507	</dd>
241	<dt>ev_loop (loop, int flags)</dt>	508	<dt>ev_loop (loop, int flags)</dt>
242	<dd>	509	<dd>
243	<p>Finally, this is it, the event handler. This function usually is called	510	<p>Finally, this is it, the event handler. This function usually is called
244	after you initialised all your watchers and you want to start handling	511	after you initialised all your watchers and you want to start handling
245	events.</p>	512	events.</p>
246	<p>If the flags argument is specified as 0, it will not return until either	513	<p>If the flags argument is specified as <code>0</code>, it will not return until
247	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	514	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		515	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		516	relying on all watchers to be stopped when deciding when a program has
		517	finished (especially in interactive programs), but having a program that
		518	automatically loops as long as it has to and no longer by virtue of
		519	relying on its watchers stopping correctly is a thing of beauty.</p>
248	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	520	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
249	those events and any outstanding ones, but will not block your process in	521	those events and any outstanding ones, but will not block your process in
250	case there are no events.</p>	522	case there are no events and will return after one iteration of the loop.</p>
251	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	523	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
252	neccessary) and will handle those and any outstanding ones. It will block	524	neccessary) and will handle those and any outstanding ones. It will block
253	your process until at least one new event arrives.</p>	525	your process until at least one new event arrives, and will return after
254	<p>This flags value could be used to implement alternative looping	526	one iteration of the loop. This is useful if you are waiting for some
255	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	527	external event in conjunction with something not expressible using other
256	more generic mechanism.</p>	528	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
		529	usually a better approach for this kind of thing.</p>
		530	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		531	<pre> * If there are no active watchers (reference count is zero), return.
		532	- Queue prepare watchers and then call all outstanding watchers.
		533	- If we have been forked, recreate the kernel state.
		534	- Update the kernel state with all outstanding changes.
		535	- Update the "event loop time".
		536	- Calculate for how long to block.
		537	- Block the process, waiting for any events.
		538	- Queue all outstanding I/O (fd) events.
		539	- Update the "event loop time" and do time jump handling.
		540	- Queue all outstanding timers.
		541	- Queue all outstanding periodics.
		542	- If no events are pending now, queue all idle watchers.
		543	- Queue all check watchers.
		544	- Call all queued watchers in reverse order (i.e. check watchers first).
		545	Signals and child watchers are implemented as I/O watchers, and will
		546	be handled here by queueing them when their watcher gets executed.
		547	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		548	were used, return, otherwise continue with step *.
		549
		550	</pre>
		551	<p>Example: Queue some jobs and then loop until no events are outsanding
		552	anymore.</p>
		553	<pre> ... queue jobs here, make sure they register event watchers as long
		554	... as they still have work to do (even an idle watcher will do..)
		555	ev_loop (my_loop, 0);
		556	... jobs done. yeah!
		557
		558	</pre>
257	</dd>	559	</dd>
258	<dt>ev_unloop (loop, how)</dt>	560	<dt>ev_unloop (loop, how)</dt>
259	<dd>	561	<dd>
260	<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument	562	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
		563	has processed all outstanding events). The <code>how</code> argument must be either
261	must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code>	564	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
262	call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code>	565	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
263	calls return.</p>
264	</dd>	566	</dd>
265	<dt>ev_ref (loop)</dt>	567	<dt>ev_ref (loop)</dt>
266	<dt>ev_unref (loop)</dt>	568	<dt>ev_unref (loop)</dt>
267	<dd>	569	<dd>
268	<p>Ref/unref can be used to add or remove a refcount on the event loop: Every	570	<p>Ref/unref can be used to add or remove a reference count on the event
269	watcher keeps one reference. If you have a long-runing watcher you never	571	loop: Every watcher keeps one reference, and as long as the reference
270	unregister that should not keep ev_loop from running, ev_unref() after	572	count is nonzero, <code>ev_loop</code> will not return on its own. If you have
271	starting, and ev_ref() before stopping it. Libev itself uses this for	573	a watcher you never unregister that should not keep <code>ev_loop</code> from
272	example for its internal signal pipe: It is not visible to you as a user	574	returning, ev_unref() after starting, and ev_ref() before stopping it. For
273	and should not keep <code>ev_loop</code> from exiting if the work is done. It is	575	example, libev itself uses this for its internal signal pipe: It is not
274	also an excellent way to do this for generic recurring timers or from	576	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
275	within third-party libraries. Just remember to unref after start and ref	577	no event watchers registered by it are active. It is also an excellent
276	before stop.</p>	578	way to do this for generic recurring timers or from within third-party
		579	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		580	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		581	running when nothing else is active.</p>
		582	<pre> struct ev_signal exitsig;
		583	ev_signal_init (&exitsig, sig_cb, SIGINT);
		584	ev_signal_start (loop, &exitsig);
		585	evf_unref (loop);
		586
		587	</pre>
		588	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		589	<pre> ev_ref (loop);
		590	ev_signal_stop (loop, &exitsig);
		591
		592	</pre>
277	</dd>	593	</dd>
278	</dl>	594	</dl>
279		595
		596
		597
		598
		599
280	</div>	600	</div>
281	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	601	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
282	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	602	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
283	<p>A watcher is a structure that you create and register to record your	603	<p>A watcher is a structure that you create and register to record your
284	interest in some event. For instance, if you want to wait for STDIN to	604	interest in some event. For instance, if you want to wait for STDIN to
285	become readable, you would create an ev_io watcher for that:</p>	605	become readable, you would create an <code>ev_io</code> watcher for that:</p>
286	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	606	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
287	{	607	{
288	ev_io_stop (w);	608	ev_io_stop (w);
289	ev_unloop (loop, EVUNLOOP_ALL);	609	ev_unloop (loop, EVUNLOOP_ALL);
290	}	610	}
…		…
313	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	633	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
314	*)</code>), and you can stop watching for events at any time by calling the	634	*)</code>), and you can stop watching for events at any time by calling the
315	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	635	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
316	<p>As long as your watcher is active (has been started but not stopped) you	636	<p>As long as your watcher is active (has been started but not stopped) you
317	must not touch the values stored in it. Most specifically you must never	637	must not touch the values stored in it. Most specifically you must never
318	reinitialise it or call its set method.</p>	638	reinitialise it or call its <code>set</code> macro.</p>
319	<p>You cna check wether an event is active by calling the <code>ev_is_active
320	(watcher *)</code> macro. To see wether an event is outstanding (but the
321	callback for it has not been called yet) you cna use the <code>ev_is_pending
322	(watcher *)</code> macro.</p>
323	<p>Each and every callback receives the event loop pointer as first, the	639	<p>Each and every callback receives the event loop pointer as first, the
324	registered watcher structure as second, and a bitset of received events as	640	registered watcher structure as second, and a bitset of received events as
325	third argument.</p>	641	third argument.</p>
326	<p>The rceeived events usually include a single bit per event type received	642	<p>The received events usually include a single bit per event type received
327	(you can receive multiple events at the same time). The possible bit masks	643	(you can receive multiple events at the same time). The possible bit masks
328	are:</p>	644	are:</p>
329	<dl>	645	<dl>
330	<dt>EV_READ</dt>	646	<dt><code>EV_READ</code></dt>
331	<dt>EV_WRITE</dt>	647	<dt><code>EV_WRITE</code></dt>
332	<dd>	648	<dd>
333	<p>The file descriptor in the ev_io watcher has become readable and/or	649	<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
334	writable.</p>	650	writable.</p>
335	</dd>	651	</dd>
336	<dt>EV_TIMEOUT</dt>	652	<dt><code>EV_TIMEOUT</code></dt>
337	<dd>
338	<p>The ev_timer watcher has timed out.</p>
339	</dd>	653	<dd>
340	<dt>EV_PERIODIC</dt>	654	<p>The <code>ev_timer</code> watcher has timed out.</p>
341	<dd>	655	</dd>
342	<p>The ev_periodic watcher has timed out.</p>	656	<dt><code>EV_PERIODIC</code></dt>
343	</dd>	657	<dd>
344	<dt>EV_SIGNAL</dt>	658	<p>The <code>ev_periodic</code> watcher has timed out.</p>
345	<dd>	659	</dd>
		660	<dt><code>EV_SIGNAL</code></dt>
		661	<dd>
346	<p>The signal specified in the ev_signal watcher has been received by a thread.</p>	662	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
347	</dd>
348	<dt>EV_CHILD</dt>
349	<dd>	663	</dd>
		664	<dt><code>EV_CHILD</code></dt>
		665	<dd>
350	<p>The pid specified in the ev_child watcher has received a status change.</p>	666	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
351	</dd>
352	<dt>EV_IDLE</dt>
353	<dd>	667	</dd>
		668	<dt><code>EV_STAT</code></dt>
		669	<dd>
		670	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		671	</dd>
		672	<dt><code>EV_IDLE</code></dt>
		673	<dd>
354	<p>The ev_idle watcher has determined that you have nothing better to do.</p>	674	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
355	</dd>
356	<dt>EV_PREPARE</dt>
357	<dt>EV_CHECK</dt>
358	<dd>	675	</dd>
		676	<dt><code>EV_PREPARE</code></dt>
		677	<dt><code>EV_CHECK</code></dt>
		678	<dd>
359	<p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts	679	<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
360	to gather new events, and all ev_check watchers are invoked just after	680	to gather new events, and all <code>ev_check</code> watchers are invoked just after
361	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	681	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
362	received events. Callbacks of both watcher types can start and stop as	682	received events. Callbacks of both watcher types can start and stop as
363	many watchers as they want, and all of them will be taken into account	683	many watchers as they want, and all of them will be taken into account
364	(for example, a ev_prepare watcher might start an idle watcher to keep	684	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
365	<code>ev_loop</code> from blocking).</p>	685	<code>ev_loop</code> from blocking).</p>
366	</dd>	686	</dd>
367	<dt>EV_ERROR</dt>	687	<dt><code>EV_EMBED</code></dt>
		688	<dd>
		689	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		690	</dd>
		691	<dt><code>EV_FORK</code></dt>
		692	<dd>
		693	<p>The event loop has been resumed in the child process after fork (see
		694	<code>ev_fork</code>).</p>
		695	</dd>
		696	<dt><code>EV_ERROR</code></dt>
368	<dd>	697	<dd>
369	<p>An unspecified error has occured, the watcher has been stopped. This might	698	<p>An unspecified error has occured, the watcher has been stopped. This might
370	happen because the watcher could not be properly started because libev	699	happen because the watcher could not be properly started because libev
371	ran out of memory, a file descriptor was found to be closed or any other	700	ran out of memory, a file descriptor was found to be closed or any other
372	problem. You best act on it by reporting the problem and somehow coping	701	problem. You best act on it by reporting the problem and somehow coping
…		…
378	programs, though, so beware.</p>	707	programs, though, so beware.</p>
379	</dd>	708	</dd>
380	</dl>	709	</dl>
381		710
382	</div>	711	</div>
		712	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		713	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		714	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		715	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		716	<dl>
		717	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		718	<dd>
		719	<p>This macro initialises the generic portion of a watcher. The contents
		720	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		721	the generic parts of the watcher are initialised, you <i>need</i> to call
		722	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		723	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		724	which rolls both calls into one.</p>
		725	<p>You can reinitialise a watcher at any time as long as it has been stopped
		726	(or never started) and there are no pending events outstanding.</p>
		727	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		728	int revents)</code>.</p>
		729	</dd>
		730	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		731	<dd>
		732	<p>This macro initialises the type-specific parts of a watcher. You need to
		733	call <code>ev_init</code> at least once before you call this macro, but you can
		734	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		735	macro on a watcher that is active (it can be pending, however, which is a
		736	difference to the <code>ev_init</code> macro).</p>
		737	<p>Although some watcher types do not have type-specific arguments
		738	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		739	</dd>
		740	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		741	<dd>
		742	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		743	calls into a single call. This is the most convinient method to initialise
		744	a watcher. The same limitations apply, of course.</p>
		745	</dd>
		746	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		747	<dd>
		748	<p>Starts (activates) the given watcher. Only active watchers will receive
		749	events. If the watcher is already active nothing will happen.</p>
		750	</dd>
		751	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		752	<dd>
		753	<p>Stops the given watcher again (if active) and clears the pending
		754	status. It is possible that stopped watchers are pending (for example,
		755	non-repeating timers are being stopped when they become pending), but
		756	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		757	you want to free or reuse the memory used by the watcher it is therefore a
		758	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		759	</dd>
		760	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		761	<dd>
		762	<p>Returns a true value iff the watcher is active (i.e. it has been started
		763	and not yet been stopped). As long as a watcher is active you must not modify
		764	it.</p>
		765	</dd>
		766	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		767	<dd>
		768	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		769	events but its callback has not yet been invoked). As long as a watcher
		770	is pending (but not active) you must not call an init function on it (but
		771	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		772	libev (e.g. you cnanot <code>free ()</code> it).</p>
		773	</dd>
		774	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		775	<dd>
		776	<p>Returns the callback currently set on the watcher.</p>
		777	</dd>
		778	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		779	<dd>
		780	<p>Change the callback. You can change the callback at virtually any time
		781	(modulo threads).</p>
		782	</dd>
		783	<dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
		784	<dt>int ev_priority (ev_TYPE *watcher)</dt>
		785	<dd>
		786	<p>Set and query the priority of the watcher. The priority is a small
		787	integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
		788	(default: <code>-2</code>). Pending watchers with higher priority will be invoked
		789	before watchers with lower priority, but priority will not keep watchers
		790	from being executed (except for <code>ev_idle</code> watchers).</p>
		791	<p>This means that priorities are <i>only</i> used for ordering callback
		792	invocation after new events have been received. This is useful, for
		793	example, to reduce latency after idling, or more often, to bind two
		794	watchers on the same event and make sure one is called first.</p>
		795	<p>If you need to suppress invocation when higher priority events are pending
		796	you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
		797	<p>The default priority used by watchers when no priority has been set is
		798	always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
		799	<p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
		800	fine, as long as you do not mind that the priority value you query might
		801	or might not have been adjusted to be within valid range.</p>
		802	</dd>
		803	</dl>
		804
		805
		806
		807
		808
		809	</div>
383	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	810	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
384	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	811	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
385	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	812	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
386	and read at any time, libev will completely ignore it. This cna be used	813	and read at any time, libev will completely ignore it. This can be used
387	to associate arbitrary data with your watcher. If you need more data and	814	to associate arbitrary data with your watcher. If you need more data and
388	don't want to allocate memory and store a pointer to it in that data	815	don't want to allocate memory and store a pointer to it in that data
389	member, you can also "subclass" the watcher type and provide your own	816	member, you can also "subclass" the watcher type and provide your own
390	data:</p>	817	data:</p>
391	<pre> struct my_io	818	<pre> struct my_io
…		…
404	struct my_io w = (struct my_io )w_;	831	struct my_io w = (struct my_io )w_;
405	...	832	...
406	}	833	}
407		834
408	</pre>	835	</pre>
409	<p>More interesting and less C-conformant ways of catsing your callback type	836	<p>More interesting and less C-conformant ways of casting your callback type
410	have been omitted....</p>	837	instead have been omitted.</p>
		838	<p>Another common scenario is having some data structure with multiple
		839	watchers:</p>
		840	<pre> struct my_biggy
		841	{
		842	int some_data;
		843	ev_timer t1;
		844	ev_timer t2;
		845	}
411		846
		847	</pre>
		848	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		849	you need to use <code>offsetof</code>:</p>
		850	<pre> #include <stddef.h>
412		851
		852	static void
		853	t1_cb (EV_P_ struct ev_timer *w, int revents)
		854	{
		855	struct my_biggy big = (struct my_biggy *
		856	(((char *)w) - offsetof (struct my_biggy, t1));
		857	}
413		858
		859	static void
		860	t2_cb (EV_P_ struct ev_timer *w, int revents)
		861	{
		862	struct my_biggy big = (struct my_biggy *
		863	(((char *)w) - offsetof (struct my_biggy, t2));
		864	}
414		865
415		866
		867
		868
		869	</pre>
		870
416	</div>	871	</div>
417	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	872	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
418	<div id="WATCHER_TYPES_CONTENT">	873	<div id="WATCHER_TYPES_CONTENT">
419	<p>This section describes each watcher in detail, but will not repeat	874	<p>This section describes each watcher in detail, but will not repeat
420	information given in the last section.</p>	875	information given in the last section. Any initialisation/set macros,
		876	functions and members specific to the watcher type are explained.</p>
		877	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		878	while the watcher is active, you can look at the member and expect some
		879	sensible content, but you must not modify it (you can modify it while the
		880	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		881	means you can expect it to have some sensible content while the watcher
		882	is active, but you can also modify it. Modifying it may not do something
		883	sensible or take immediate effect (or do anything at all), but libev will
		884	not crash or malfunction in any way.</p>
421		885
		886
		887
		888
		889
422	</div>	890	</div>
423	<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2>	891	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
424	<div id="struct_ev_io_is_my_file_descriptor_r-2">	892	<div id="code_ev_io_code_is_this_file_descrip-2">
425	<p>I/O watchers check wether a file descriptor is readable or writable	893	<p>I/O watchers check whether a file descriptor is readable or writable
426	in each iteration of the event loop (This behaviour is called	894	in each iteration of the event loop, or, more precisely, when reading
427	level-triggering because you keep receiving events as long as the	895	would not block the process and writing would at least be able to write
428	condition persists. Remember you cna stop the watcher if you don't want to	896	some data. This behaviour is called level-triggering because you keep
429	act on the event and neither want to receive future events).</p>	897	receiving events as long as the condition persists. Remember you can stop
		898	the watcher if you don't want to act on the event and neither want to
		899	receive future events.</p>
		900	<p>In general you can register as many read and/or write event watchers per
		901	fd as you want (as long as you don't confuse yourself). Setting all file
		902	descriptors to non-blocking mode is also usually a good idea (but not
		903	required if you know what you are doing).</p>
		904	<p>You have to be careful with dup'ed file descriptors, though. Some backends
		905	(the linux epoll backend is a notable example) cannot handle dup'ed file
		906	descriptors correctly if you register interest in two or more fds pointing
		907	to the same underlying file/socket/etc. description (that is, they share
		908	the same underlying "file open").</p>
		909	<p>If you must do this, then force the use of a known-to-be-good backend
		910	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
		911	<code>EVBACKEND_POLL</code>).</p>
		912	<p>Another thing you have to watch out for is that it is quite easy to
		913	receive "spurious" readyness notifications, that is your callback might
		914	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		915	because there is no data. Not only are some backends known to create a
		916	lot of those (for example solaris ports), it is very easy to get into
		917	this situation even with a relatively standard program structure. Thus
		918	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		919	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		920	<p>If you cannot run the fd in non-blocking mode (for example you should not
		921	play around with an Xlib connection), then you have to seperately re-test
		922	wether a file descriptor is really ready with a known-to-be good interface
		923	such as poll (fortunately in our Xlib example, Xlib already does this on
		924	its own, so its quite safe to use).</p>
430	<dl>	925	<dl>
431	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	926	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
432	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	927	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
433	<dd>	928	<dd>
434	<p>Configures an ev_io watcher. The fd is the file descriptor to rceeive	929	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
435	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	930	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
436	EV_WRITE</code> to receive the given events.</p>	931	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		932	</dd>
		933	<dt>int fd [read-only]</dt>
		934	<dd>
		935	<p>The file descriptor being watched.</p>
		936	</dd>
		937	<dt>int events [read-only]</dt>
		938	<dd>
		939	<p>The events being watched.</p>
437	</dd>	940	</dd>
438	</dl>	941	</dl>
		942	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		943	readable, but only once. Since it is likely line-buffered, you could
		944	attempt to read a whole line in the callback.</p>
		945	<pre> static void
		946	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		947	{
		948	ev_io_stop (loop, w);
		949	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		950	}
439		951
		952	...
		953	struct ev_loop *loop = ev_default_init (0);
		954	struct ev_io stdin_readable;
		955	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		956	ev_io_start (loop, &stdin_readable);
		957	ev_loop (loop, 0);
		958
		959
		960
		961
		962	</pre>
		963
440	</div>	964	</div>
441	<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2>	965	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
442	<div id="struct_ev_timer_relative_and_optiona-2">	966	<div id="code_ev_timer_code_relative_and_opti-2">
443	<p>Timer watchers are simple relative timers that generate an event after a	967	<p>Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.</p>	968	given time, and optionally repeating in regular intervals after that.</p>
445	<p>The timers are based on real time, that is, if you register an event that	969	<p>The timers are based on real time, that is, if you register an event that
446	times out after an hour and youreset your system clock to last years	970	times out after an hour and you reset your system clock to last years
447	time, it will still time out after (roughly) and hour. "Roughly" because	971	time, it will still time out after (roughly) and hour. "Roughly" because
448	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	972	detecting time jumps is hard, and some inaccuracies are unavoidable (the
449	monotonic clock option helps a lot here).</p>	973	monotonic clock option helps a lot here).</p>
		974	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
		975	time. This is usually the right thing as this timestamp refers to the time
		976	of the event triggering whatever timeout you are modifying/starting. If
		977	you suspect event processing to be delayed and you <i>need</i> to base the timeout
		978	on the current time, use something like this to adjust for this:</p>
		979	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		980
		981	</pre>
		982	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		983	but if multiple timers become ready during the same loop iteration then
		984	order of execution is undefined.</p>
450	<dl>	985	<dl>
451	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	986	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
452	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	987	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
453	<dd>	988	<dd>
454	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	989	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
456	timer will automatically be configured to trigger again <code>repeat</code> seconds	991	timer will automatically be configured to trigger again <code>repeat</code> seconds
457	later, again, and again, until stopped manually.</p>	992	later, again, and again, until stopped manually.</p>
458	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	993	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
459	configure a timer to trigger every 10 seconds, then it will trigger at	994	configure a timer to trigger every 10 seconds, then it will trigger at
460	exactly 10 second intervals. If, however, your program cannot keep up with	995	exactly 10 second intervals. If, however, your program cannot keep up with
461	the timer (ecause it takes longer than those 10 seconds to do stuff) the	996	the timer (because it takes longer than those 10 seconds to do stuff) the
462	timer will not fire more than once per event loop iteration.</p>	997	timer will not fire more than once per event loop iteration.</p>
463	</dd>	998	</dd>
464	<dt>ev_timer_again (loop)</dt>	999	<dt>ev_timer_again (loop)</dt>
465	<dd>	1000	<dd>
466	<p>This will act as if the timer timed out and restart it again if it is	1001	<p>This will act as if the timer timed out and restart it again if it is
467	repeating. The exact semantics are:</p>	1002	repeating. The exact semantics are:</p>
		1003	<p>If the timer is pending, its pending status is cleared.</p>
468	<p>If the timer is started but nonrepeating, stop it.</p>	1004	<p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
469	<p>If the timer is repeating, either start it if necessary (with the repeat	1005	<p>If the timer is repeating, either start it if necessary (with the
470	value), or reset the running timer to the repeat value.</p>	1006	<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
471	<p>This sounds a bit complicated, but here is a useful and typical	1007	<p>This sounds a bit complicated, but here is a useful and typical
472	example: Imagine you have a tcp connection and you want a so-called idle	1008	example: Imagine you have a tcp connection and you want a so-called idle
473	timeout, that is, you want to be called when there have been, say, 60	1009	timeout, that is, you want to be called when there have been, say, 60
474	seconds of inactivity on the socket. The easiest way to do this is to	1010	seconds of inactivity on the socket. The easiest way to do this is to
475	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	1011	configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
476	time you successfully read or write some data. If you go into an idle	1012	<code>ev_timer_again</code> each time you successfully read or write some data. If
477	state where you do not expect data to travel on the socket, you can stop	1013	you go into an idle state where you do not expect data to travel on the
		1014	socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
478	the timer, and again will automatically restart it if need be.</p>	1015	automatically restart it if need be.</p>
		1016	<p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
		1017	altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
		1018	<pre> ev_timer_init (timer, callback, 0., 5.);
		1019	ev_timer_again (loop, timer);
		1020	...
		1021	timer->again = 17.;
		1022	ev_timer_again (loop, timer);
		1023	...
		1024	timer->again = 10.;
		1025	ev_timer_again (loop, timer);
		1026
		1027	</pre>
		1028	<p>This is more slightly efficient then stopping/starting the timer each time
		1029	you want to modify its timeout value.</p>
		1030	</dd>
		1031	<dt>ev_tstamp repeat [read-write]</dt>
		1032	<dd>
		1033	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		1034	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		1035	which is also when any modifications are taken into account.</p>
479	</dd>	1036	</dd>
480	</dl>	1037	</dl>
		1038	<p>Example: Create a timer that fires after 60 seconds.</p>
		1039	<pre> static void
		1040	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1041	{
		1042	.. one minute over, w is actually stopped right here
		1043	}
481		1044
		1045	struct ev_timer mytimer;
		1046	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1047	ev_timer_start (loop, &mytimer);
		1048
		1049	</pre>
		1050	<p>Example: Create a timeout timer that times out after 10 seconds of
		1051	inactivity.</p>
		1052	<pre> static void
		1053	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1054	{
		1055	.. ten seconds without any activity
		1056	}
		1057
		1058	struct ev_timer mytimer;
		1059	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1060	ev_timer_again (&mytimer); /* start timer */
		1061	ev_loop (loop, 0);
		1062
		1063	// and in some piece of code that gets executed on any "activity":
		1064	// reset the timeout to start ticking again at 10 seconds
		1065	ev_timer_again (&mytimer);
		1066
		1067
		1068
		1069
		1070	</pre>
		1071
482	</div>	1072	</div>
483	<h2 id="ev_periodic">ev_periodic</h2>	1073	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
484	<div id="ev_periodic_CONTENT">	1074	<div id="code_ev_periodic_code_to_cron_or_not-2">
485	<p>Periodic watchers are also timers of a kind, but they are very versatile	1075	<p>Periodic watchers are also timers of a kind, but they are very versatile
486	(and unfortunately a bit complex).</p>	1076	(and unfortunately a bit complex).</p>
487	<p>Unlike ev_timer's, they are not based on real time (or relative time)	1077	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
488	but on wallclock time (absolute time). You can tell a periodic watcher	1078	but on wallclock time (absolute time). You can tell a periodic watcher
489	to trigger "at" some specific point in time. For example, if you tell a	1079	to trigger "at" some specific point in time. For example, if you tell a
490	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1080	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
491	+ 10.>) and then reset your system clock to the last year, then it will	1081	+ 10.</code>) and then reset your system clock to the last year, then it will
492	take a year to trigger the event (unlike an ev_timer, which would trigger	1082	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
493	roughly 10 seconds later and of course not if you reset your system time	1083	roughly 10 seconds later and of course not if you reset your system time
494	again).</p>	1084	again).</p>
495	<p>They can also be used to implement vastly more complex timers, such as	1085	<p>They can also be used to implement vastly more complex timers, such as
496	triggering an event on eahc midnight, local time.</p>	1086	triggering an event on eahc midnight, local time.</p>
		1087	<p>As with timers, the callback is guarenteed to be invoked only when the
		1088	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1089	during the same loop iteration then order of execution is undefined.</p>
497	<dl>	1090	<dl>
498	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1091	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
499	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	1092	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
500	<dd>	1093	<dd>
501	<p>Lots of arguments, lets sort it out... There are basically three modes of	1094	<p>Lots of arguments, lets sort it out... There are basically three modes of
502	operation, and we will explain them from simplest to complex:</p>	1095	operation, and we will explain them from simplest to complex:</p>
503
504
505
506
507	<p>	1096	<p>
508	<dl>	1097	<dl>
509	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1098	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
510	<dd>	1099	<dd>
511	<p>In this configuration the watcher triggers an event at the wallclock time	1100	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
523	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	1112	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
524		1113
525	</pre>	1114	</pre>
526	<p>This doesn't mean there will always be 3600 seconds in between triggers,	1115	<p>This doesn't mean there will always be 3600 seconds in between triggers,
527	but only that the the callback will be called when the system time shows a	1116	but only that the the callback will be called when the system time shows a
528	full hour (UTC), or more correct, when the system time is evenly divisible	1117	full hour (UTC), or more correctly, when the system time is evenly divisible
529	by 3600.</p>	1118	by 3600.</p>
530	<p>Another way to think about it (for the mathematically inclined) is that	1119	<p>Another way to think about it (for the mathematically inclined) is that
531	ev_periodic will try to run the callback in this mode at the next possible	1120	<code>ev_periodic</code> will try to run the callback in this mode at the next possible
532	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	1121	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
533	</dd>	1122	</dd>
534	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	1123	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>
535	<dd>	1124	<dd>
536	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	1125	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
537	ignored. Instead, each time the periodic watcher gets scheduled, the	1126	ignored. Instead, each time the periodic watcher gets scheduled, the
538	reschedule callback will be called with the watcher as first, and the	1127	reschedule callback will be called with the watcher as first, and the
539	current time as second argument.</p>	1128	current time as second argument.</p>
540	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1129	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
541	periodic watcher, ever, or make any event loop modificstions</i>. If you need	1130	ever, or make any event loop modifications</i>. If you need to stop it,
542	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p>	1131	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
		1132	starting a prepare watcher).</p>
543	<p>Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1133	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
544	ev_tstamp now)>, e.g.:</p>	1134	ev_tstamp now)</code>, e.g.:</p>
545	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1135	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
546	{	1136	{
547	return now + 60.;	1137	return now + 60.;
548	}	1138	}
549		1139
550	</pre>	1140	</pre>
551	<p>It must return the next time to trigger, based on the passed time value	1141	<p>It must return the next time to trigger, based on the passed time value
552	(that is, the lowest time value larger than to the second argument). It	1142	(that is, the lowest time value larger than to the second argument). It
553	will usually be called just before the callback will be triggered, but	1143	will usually be called just before the callback will be triggered, but
554	might be called at other times, too.</p>	1144	might be called at other times, too.</p>
		1145	<p>NOTE: <i>This callback must always return a time that is later than the
		1146	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
555	<p>This can be used to create very complex timers, such as a timer that	1147	<p>This can be used to create very complex timers, such as a timer that
556	triggers on each midnight, local time. To do this, you would calculate the	1148	triggers on each midnight, local time. To do this, you would calculate the
557	next midnight after <code>now</code> and return the timestamp value for this. How you do this	1149	next midnight after <code>now</code> and return the timestamp value for this. How
558	is, again, up to you (but it is not trivial).</p>	1150	you do this is, again, up to you (but it is not trivial, which is the main
		1151	reason I omitted it as an example).</p>
559	</dd>	1152	</dd>
560	</dl>	1153	</dl>
561	</p>	1154	</p>
562	</dd>	1155	</dd>
563	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1156	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
565	<p>Simply stops and restarts the periodic watcher again. This is only useful	1158	<p>Simply stops and restarts the periodic watcher again. This is only useful
566	when you changed some parameters or the reschedule callback would return	1159	when you changed some parameters or the reschedule callback would return
567	a different time than the last time it was called (e.g. in a crond like	1160	a different time than the last time it was called (e.g. in a crond like
568	program when the crontabs have changed).</p>	1161	program when the crontabs have changed).</p>
569	</dd>	1162	</dd>
		1163	<dt>ev_tstamp interval [read-write]</dt>
		1164	<dd>
		1165	<p>The current interval value. Can be modified any time, but changes only
		1166	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1167	called.</p>
		1168	</dd>
		1169	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1170	<dd>
		1171	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1172	switched off. Can be changed any time, but changes only take effect when
		1173	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1174	</dd>
570	</dl>	1175	</dl>
		1176	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1177	system clock is divisible by 3600. The callback invocation times have
		1178	potentially a lot of jittering, but good long-term stability.</p>
		1179	<pre> static void
		1180	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1181	{
		1182	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1183	}
571		1184
		1185	struct ev_periodic hourly_tick;
		1186	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1187	ev_periodic_start (loop, &hourly_tick);
		1188
		1189	</pre>
		1190	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1191	<pre> #include <math.h>
		1192
		1193	static ev_tstamp
		1194	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1195	{
		1196	return fmod (now, 3600.) + 3600.;
		1197	}
		1198
		1199	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1200
		1201	</pre>
		1202	<p>Example: Call a callback every hour, starting now:</p>
		1203	<pre> struct ev_periodic hourly_tick;
		1204	ev_periodic_init (&hourly_tick, clock_cb,
		1205	fmod (ev_now (loop), 3600.), 3600., 0);
		1206	ev_periodic_start (loop, &hourly_tick);
		1207
		1208
		1209
		1210
		1211	</pre>
		1212
572	</div>	1213	</div>
573	<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>	1214	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
574	<div id="ev_signal_signal_me_when_a_signal_ge-2">	1215	<div id="code_ev_signal_code_signal_me_when_a-2">
575	<p>Signal watchers will trigger an event when the process receives a specific	1216	<p>Signal watchers will trigger an event when the process receives a specific
576	signal one or more times. Even though signals are very asynchronous, libev	1217	signal one or more times. Even though signals are very asynchronous, libev
577	will try its best to deliver signals synchronously, i.e. as part of the	1218	will try it's best to deliver signals synchronously, i.e. as part of the
578	normal event processing, like any other event.</p>	1219	normal event processing, like any other event.</p>
579	<p>You cna configure as many watchers as you like per signal. Only when the	1220	<p>You can configure as many watchers as you like per signal. Only when the
580	first watcher gets started will libev actually register a signal watcher	1221	first watcher gets started will libev actually register a signal watcher
581	with the kernel (thus it coexists with your own signal handlers as long	1222	with the kernel (thus it coexists with your own signal handlers as long
582	as you don't register any with libev). Similarly, when the last signal	1223	as you don't register any with libev). Similarly, when the last signal
583	watcher for a signal is stopped libev will reset the signal handler to	1224	watcher for a signal is stopped libev will reset the signal handler to
584	SIG_DFL (regardless of what it was set to before).</p>	1225	SIG_DFL (regardless of what it was set to before).</p>
…		…
587	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1228	<dt>ev_signal_set (ev_signal *, int signum)</dt>
588	<dd>	1229	<dd>
589	<p>Configures the watcher to trigger on the given signal number (usually one	1230	<p>Configures the watcher to trigger on the given signal number (usually one
590	of the <code>SIGxxx</code> constants).</p>	1231	of the <code>SIGxxx</code> constants).</p>
591	</dd>	1232	</dd>
		1233	<dt>int signum [read-only]</dt>
		1234	<dd>
		1235	<p>The signal the watcher watches out for.</p>
		1236	</dd>
592	</dl>	1237	</dl>
593		1238
		1239
		1240
		1241
		1242
594	</div>	1243	</div>
595	<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2>	1244	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
596	<div id="ev_child_wait_for_pid_status_changes-2">	1245	<div id="code_ev_child_code_watch_out_for_pro-2">
597	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1246	<p>Child watchers trigger when your process receives a SIGCHLD in response to
598	some child status changes (most typically when a child of yours dies).</p>	1247	some child status changes (most typically when a child of yours dies).</p>
599	<dl>	1248	<dl>
600	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1249	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
601	<dt>ev_child_set (ev_child *, int pid)</dt>	1250	<dt>ev_child_set (ev_child *, int pid)</dt>
602	<dd>	1251	<dd>
603	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or	1252	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
604	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look	1253	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
605	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1254	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
606	the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member	1255	the status word (use the macros from <code>sys/wait.h</code> and see your systems
		1256	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
607	contains the pid of the process causing the status change.</p>	1257	process causing the status change.</p>
		1258	</dd>
		1259	<dt>int pid [read-only]</dt>
		1260	<dd>
		1261	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1262	</dd>
		1263	<dt>int rpid [read-write]</dt>
		1264	<dd>
		1265	<p>The process id that detected a status change.</p>
		1266	</dd>
		1267	<dt>int rstatus [read-write]</dt>
		1268	<dd>
		1269	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1270	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
608	</dd>	1271	</dd>
609	</dl>	1272	</dl>
		1273	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1274	<pre> static void
		1275	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1276	{
		1277	ev_unloop (loop, EVUNLOOP_ALL);
		1278	}
610		1279
		1280	struct ev_signal signal_watcher;
		1281	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1282	ev_signal_start (loop, &sigint_cb);
		1283
		1284
		1285
		1286
		1287	</pre>
		1288
611	</div>	1289	</div>
		1290	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1291	<div id="code_ev_stat_code_did_the_file_attri-2">
		1292	<p>This watches a filesystem path for attribute changes. That is, it calls
		1293	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1294	compared to the last time, invoking the callback if it did.</p>
		1295	<p>The path does not need to exist: changing from "path exists" to "path does
		1296	not exist" is a status change like any other. The condition "path does
		1297	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1298	otherwise always forced to be at least one) and all the other fields of
		1299	the stat buffer having unspecified contents.</p>
		1300	<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
		1301	relative and your working directory changes, the behaviour is undefined.</p>
		1302	<p>Since there is no standard to do this, the portable implementation simply
		1303	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1304	can specify a recommended polling interval for this case. If you specify
		1305	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1306	unspecified default</i> value will be used (which you can expect to be around
		1307	five seconds, although this might change dynamically). Libev will also
		1308	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1309	usually overkill.</p>
		1310	<p>This watcher type is not meant for massive numbers of stat watchers,
		1311	as even with OS-supported change notifications, this can be
		1312	resource-intensive.</p>
		1313	<p>At the time of this writing, only the Linux inotify interface is
		1314	implemented (implementing kqueue support is left as an exercise for the
		1315	reader). Inotify will be used to give hints only and should not change the
		1316	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1317	to fall back to regular polling again even with inotify, but changes are
		1318	usually detected immediately, and if the file exists there will be no
		1319	polling.</p>
		1320	<dl>
		1321	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1322	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1323	<dd>
		1324	<p>Configures the watcher to wait for status changes of the given
		1325	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1326	be detected and should normally be specified as <code>0</code> to let libev choose
		1327	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1328	path for as long as the watcher is active.</p>
		1329	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1330	relative to the attributes at the time the watcher was started (or the
		1331	last change was detected).</p>
		1332	</dd>
		1333	<dt>ev_stat_stat (ev_stat *)</dt>
		1334	<dd>
		1335	<p>Updates the stat buffer immediately with new values. If you change the
		1336	watched path in your callback, you could call this fucntion to avoid
		1337	detecting this change (while introducing a race condition). Can also be
		1338	useful simply to find out the new values.</p>
		1339	</dd>
		1340	<dt>ev_statdata attr [read-only]</dt>
		1341	<dd>
		1342	<p>The most-recently detected attributes of the file. Although the type is of
		1343	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1344	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1345	was some error while <code>stat</code>ing the file.</p>
		1346	</dd>
		1347	<dt>ev_statdata prev [read-only]</dt>
		1348	<dd>
		1349	<p>The previous attributes of the file. The callback gets invoked whenever
		1350	<code>prev</code> != <code>attr</code>.</p>
		1351	</dd>
		1352	<dt>ev_tstamp interval [read-only]</dt>
		1353	<dd>
		1354	<p>The specified interval.</p>
		1355	</dd>
		1356	<dt>const char *path [read-only]</dt>
		1357	<dd>
		1358	<p>The filesystem path that is being watched.</p>
		1359	</dd>
		1360	</dl>
		1361	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1362	<pre> static void
		1363	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1364	{
		1365	/* /etc/passwd changed in some way */
		1366	if (w->attr.st_nlink)
		1367	{
		1368	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1369	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1370	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1371	}
		1372	else
		1373	/* you shalt not abuse printf for puts */
		1374	puts ("wow, /etc/passwd is not there, expect problems. "
		1375	"if this is windows, they already arrived\n");
		1376	}
		1377
		1378	...
		1379	ev_stat passwd;
		1380
		1381	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1382	ev_stat_start (loop, &passwd);
		1383
		1384
		1385
		1386
		1387	</pre>
		1388
		1389	</div>
612	<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2>	1390	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
613	<div id="ev_idle_when_you_ve_got_nothing_bett-2">	1391	<div id="code_ev_idle_code_when_you_ve_got_no-2">
614	<p>Idle watchers trigger events when there are no other I/O or timer (or	1392	<p>Idle watchers trigger events when no other events of the same or higher
615	periodic) events pending. That is, as long as your process is busy	1393	priority are pending (prepare, check and other idle watchers do not
616	handling sockets or timeouts it will not be called. But when your process	1394	count).</p>
617	is idle all idle watchers are being called again and again - until	1395	<p>That is, as long as your process is busy handling sockets or timeouts
		1396	(or even signals, imagine) of the same or higher priority it will not be
		1397	triggered. But when your process is idle (or only lower-priority watchers
		1398	are pending), the idle watchers are being called once per event loop
618	stopped, that is, or your process receives more events.</p>	1399	iteration - until stopped, that is, or your process receives more events
		1400	and becomes busy again with higher priority stuff.</p>
619	<p>The most noteworthy effect is that as long as any idle watchers are	1401	<p>The most noteworthy effect is that as long as any idle watchers are
620	active, the process will not block when waiting for new events.</p>	1402	active, the process will not block when waiting for new events.</p>
621	<p>Apart from keeping your process non-blocking (which is a useful	1403	<p>Apart from keeping your process non-blocking (which is a useful
622	effect on its own sometimes), idle watchers are a good place to do	1404	effect on its own sometimes), idle watchers are a good place to do
623	"pseudo-background processing", or delay processing stuff to after the	1405	"pseudo-background processing", or delay processing stuff to after the
…		…
628	<p>Initialises and configures the idle watcher - it has no parameters of any	1410	<p>Initialises and configures the idle watcher - it has no parameters of any
629	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1411	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
630	believe me.</p>	1412	believe me.</p>
631	</dd>	1413	</dd>
632	</dl>	1414	</dl>
		1415	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1416	callback, free it. Also, use no error checking, as usual.</p>
		1417	<pre> static void
		1418	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1419	{
		1420	free (w);
		1421	// now do something you wanted to do when the program has
		1422	// no longer asnything immediate to do.
		1423	}
633		1424
		1425	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1426	ev_idle_init (idle_watcher, idle_cb);
		1427	ev_idle_start (loop, idle_cb);
		1428
		1429
		1430
		1431
		1432	</pre>
		1433
634	</div>	1434	</div>
635	<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>	1435	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
636	<div id="prepare_and_check_your_hooks_into_th-2">	1436	<div id="code_ev_prepare_code_and_code_ev_che-2">
637	<p>Prepare and check watchers usually (but not always) are used in	1437	<p>Prepare and check watchers are usually (but not always) used in tandem:
638	tandom. Prepare watchers get invoked before the process blocks and check	1438	prepare watchers get invoked before the process blocks and check watchers
639	watchers afterwards.</p>	1439	afterwards.</p>
		1440	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1441	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1442	watchers. Other loops than the current one are fine, however. The
		1443	rationale behind this is that you do not need to check for recursion in
		1444	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1445	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1446	called in pairs bracketing the blocking call.</p>
640	<p>Their main purpose is to integrate other event mechanisms into libev. This	1447	<p>Their main purpose is to integrate other event mechanisms into libev and
641	could be used, for example, to track variable changes, implement your own	1448	their use is somewhat advanced. This could be used, for example, to track
642	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1449	variable changes, implement your own watchers, integrate net-snmp or a
		1450	coroutine library and lots more. They are also occasionally useful if
		1451	you cache some data and want to flush it before blocking (for example,
		1452	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1453	watcher).</p>
643	<p>This is done by examining in each prepare call which file descriptors need	1454	<p>This is done by examining in each prepare call which file descriptors need
644	to be watched by the other library, registering ev_io watchers for them	1455	to be watched by the other library, registering <code>ev_io</code> watchers for
645	and starting an ev_timer watcher for any timeouts (many libraries provide	1456	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
646	just this functionality). Then, in the check watcher you check for any	1457	provide just this functionality). Then, in the check watcher you check for
647	events that occured (by making your callbacks set soem flags for example)	1458	any events that occured (by checking the pending status of all watchers
648	and call back into the library.</p>	1459	and stopping them) and call back into the library. The I/O and timer
		1460	callbacks will never actually be called (but must be valid nevertheless,
		1461	because you never know, you know?).</p>
649	<p>As another example, the perl Coro module uses these hooks to integrate	1462	<p>As another example, the Perl Coro module uses these hooks to integrate
650	coroutines into libev programs, by yielding to other active coroutines	1463	coroutines into libev programs, by yielding to other active coroutines
651	during each prepare and only letting the process block if no coroutines	1464	during each prepare and only letting the process block if no coroutines
652	are ready to run.</p>	1465	are ready to run (it's actually more complicated: it only runs coroutines
		1466	with priority higher than or equal to the event loop and one coroutine
		1467	of lower priority, but only once, using idle watchers to keep the event
		1468	loop from blocking if lower-priority coroutines are active, thus mapping
		1469	low-priority coroutines to idle/background tasks).</p>
653	<dl>	1470	<dl>
654	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1471	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
655	<dt>ev_check_init (ev_check *, callback)</dt>	1472	<dt>ev_check_init (ev_check *, callback)</dt>
656	<dd>	1473	<dd>
657	<p>Initialises and configures the prepare or check watcher - they have no	1474	<p>Initialises and configures the prepare or check watcher - they have no
658	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1475	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
659	macros, but using them is utterly, utterly pointless.</p>	1476	macros, but using them is utterly, utterly and completely pointless.</p>
660	</dd>	1477	</dd>
661	</dl>	1478	</dl>
		1479	<p>Example: To include a library such as adns, you would add IO watchers
		1480	and a timeout watcher in a prepare handler, as required by libadns, and
		1481	in a check watcher, destroy them and call into libadns. What follows is
		1482	pseudo-code only of course:</p>
		1483	<pre> static ev_io iow [nfd];
		1484	static ev_timer tw;
662		1485
		1486	static void
		1487	io_cb (ev_loop loop, ev_io w, int revents)
		1488	{
		1489	// set the relevant poll flags
		1490	// could also call adns_processreadable etc. here
		1491	struct pollfd fd = (struct pollfd )w->data;
		1492	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1493	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1494	}
		1495
		1496	// create io watchers for each fd and a timer before blocking
		1497	static void
		1498	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1499	{
		1500	int timeout = 3600000;
		1501	struct pollfd fds [nfd];
		1502	// actual code will need to loop here and realloc etc.
		1503	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1504
		1505	/* the callback is illegal, but won't be called as we stop during check */
		1506	ev_timer_init (&tw, 0, timeout * 1e-3);
		1507	ev_timer_start (loop, &tw);
		1508
		1509	// create on ev_io per pollfd
		1510	for (int i = 0; i < nfd; ++i)
		1511	{
		1512	ev_io_init (iow + i, io_cb, fds [i].fd,
		1513	((fds [i].events & POLLIN ? EV_READ : 0)
		1514	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1515
		1516	fds [i].revents = 0;
		1517	iow [i].data = fds + i;
		1518	ev_io_start (loop, iow + i);
		1519	}
		1520	}
		1521
		1522	// stop all watchers after blocking
		1523	static void
		1524	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1525	{
		1526	ev_timer_stop (loop, &tw);
		1527
		1528	for (int i = 0; i < nfd; ++i)
		1529	ev_io_stop (loop, iow + i);
		1530
		1531	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1532	}
		1533
		1534
		1535
		1536
		1537	</pre>
		1538
663	</div>	1539	</div>
664	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1540	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1541	<div id="code_ev_embed_code_when_one_backend_-2">
		1542	<p>This is a rather advanced watcher type that lets you embed one event loop
		1543	into another (currently only <code>ev_io</code> events are supported in the embedded
		1544	loop, other types of watchers might be handled in a delayed or incorrect
		1545	fashion and must not be used).</p>
		1546	<p>There are primarily two reasons you would want that: work around bugs and
		1547	prioritise I/O.</p>
		1548	<p>As an example for a bug workaround, the kqueue backend might only support
		1549	sockets on some platform, so it is unusable as generic backend, but you
		1550	still want to make use of it because you have many sockets and it scales
		1551	so nicely. In this case, you would create a kqueue-based loop and embed it
		1552	into your default loop (which might use e.g. poll). Overall operation will
		1553	be a bit slower because first libev has to poll and then call kevent, but
		1554	at least you can use both at what they are best.</p>
		1555	<p>As for prioritising I/O: rarely you have the case where some fds have
		1556	to be watched and handled very quickly (with low latency), and even
		1557	priorities and idle watchers might have too much overhead. In this case
		1558	you would put all the high priority stuff in one loop and all the rest in
		1559	a second one, and embed the second one in the first.</p>
		1560	<p>As long as the watcher is active, the callback will be invoked every time
		1561	there might be events pending in the embedded loop. The callback must then
		1562	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1563	their callbacks (you could also start an idle watcher to give the embedded
		1564	loop strictly lower priority for example). You can also set the callback
		1565	to <code>0</code>, in which case the embed watcher will automatically execute the
		1566	embedded loop sweep.</p>
		1567	<p>As long as the watcher is started it will automatically handle events. The
		1568	callback will be invoked whenever some events have been handled. You can
		1569	set the callback to <code>0</code> to avoid having to specify one if you are not
		1570	interested in that.</p>
		1571	<p>Also, there have not currently been made special provisions for forking:
		1572	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1573	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1574	yourself.</p>
		1575	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1576	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1577	portable one.</p>
		1578	<p>So when you want to use this feature you will always have to be prepared
		1579	that you cannot get an embeddable loop. The recommended way to get around
		1580	this is to have a separate variables for your embeddable loop, try to
		1581	create it, and if that fails, use the normal loop for everything:</p>
		1582	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1583	struct ev_loop *loop_lo = 0;
		1584	struct ev_embed embed;
		1585
		1586	// see if there is a chance of getting one that works
		1587	// (remember that a flags value of 0 means autodetection)
		1588	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1589	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1590	: 0;
		1591
		1592	// if we got one, then embed it, otherwise default to loop_hi
		1593	if (loop_lo)
		1594	{
		1595	ev_embed_init (&embed, 0, loop_lo);
		1596	ev_embed_start (loop_hi, &embed);
		1597	}
		1598	else
		1599	loop_lo = loop_hi;
		1600
		1601	</pre>
		1602	<dl>
		1603	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1604	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1605	<dd>
		1606	<p>Configures the watcher to embed the given loop, which must be
		1607	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1608	invoked automatically, otherwise it is the responsibility of the callback
		1609	to invoke it (it will continue to be called until the sweep has been done,
		1610	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1611	</dd>
		1612	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1613	<dd>
		1614	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1615	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1616	apropriate way for embedded loops.</p>
		1617	</dd>
		1618	<dt>struct ev_loop *loop [read-only]</dt>
		1619	<dd>
		1620	<p>The embedded event loop.</p>
		1621	</dd>
		1622	</dl>
		1623
		1624
		1625
		1626
		1627
		1628	</div>
		1629	<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>
		1630	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1631	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1632	whoever is a good citizen cared to tell libev about it by calling
		1633	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1634	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1635	and only in the child after the fork. If whoever good citizen calling
		1636	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1637	handlers will be invoked, too, of course.</p>
		1638	<dl>
		1639	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1640	<dd>
		1641	<p>Initialises and configures the fork watcher - it has no parameters of any
		1642	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1643	believe me.</p>
		1644	</dd>
		1645	</dl>
		1646
		1647
		1648
		1649
		1650
		1651	</div>
		1652	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
665	<div id="OTHER_FUNCTIONS_CONTENT">	1653	<div id="OTHER_FUNCTIONS_CONTENT">
666	<p>There are some other fucntions of possible interest. Described. Here. Now.</p>	1654	<p>There are some other functions of possible interest. Described. Here. Now.</p>
667	<dl>	1655	<dl>
668	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1656	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
669	<dd>	1657	<dd>
670	<p>This function combines a simple timer and an I/O watcher, calls your	1658	<p>This function combines a simple timer and an I/O watcher, calls your
671	callback on whichever event happens first and automatically stop both	1659	callback on whichever event happens first and automatically stop both
672	watchers. This is useful if you want to wait for a single event on an fd	1660	watchers. This is useful if you want to wait for a single event on an fd
673	or timeout without havign to allocate/configure/start/stop/free one or	1661	or timeout without having to allocate/configure/start/stop/free one or
674	more watchers yourself.</p>	1662	more watchers yourself.</p>
675	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is	1663	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
676	ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set	1664	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
677	will be craeted and started.</p>	1665	<code>events</code> set will be craeted and started.</p>
678	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1666	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
679	started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat	1667	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
680	= 0) will be started.</p>	1668	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
		1669	dubious value.</p>
681	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and	1670	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
682	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1671	passed an <code>revents</code> set like normal event callbacks (a combination of
683	EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p>	1672	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
		1673	value passed to <code>ev_once</code>:</p>
684	<pre> static void stdin_ready (int revents, void *arg)	1674	<pre> static void stdin_ready (int revents, void *arg)
685	{	1675	{
686	if (revents & EV_TIMEOUT)	1676	if (revents & EV_TIMEOUT)
687	/* doh, nothing entered */	1677	/* doh, nothing entered */;
688	else if (revents & EV_READ)	1678	else if (revents & EV_READ)
689	/* stdin might have data for us, joy! */	1679	/* stdin might have data for us, joy! */;
690	}	1680	}
691		1681
692	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1682	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
693		1683
694	</pre>	1684	</pre>
695	</dd>	1685	</dd>
696	<dt>ev_feed_event (loop, watcher, int events)</dt>	1686	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
697	<dd>	1687	<dd>
698	<p>Feeds the given event set into the event loop, as if the specified event	1688	<p>Feeds the given event set into the event loop, as if the specified event
699	has happened for the specified watcher (which must be a pointer to an	1689	had happened for the specified watcher (which must be a pointer to an
700	initialised but not necessarily active event watcher).</p>	1690	initialised but not necessarily started event watcher).</p>
701	</dd>	1691	</dd>
702	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1692	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
703	<dd>	1693	<dd>
704	<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>	1694	<p>Feed an event on the given fd, as if a file descriptor backend detected
		1695	the given events it.</p>
705	</dd>	1696	</dd>
706	<dt>ev_feed_signal_event (loop, int signum)</dt>	1697	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
707	<dd>	1698	<dd>
708	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1699	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1700	loop!).</p>
709	</dd>	1701	</dd>
710	</dl>	1702	</dl>
711		1703
		1704
		1705
		1706
		1707
712	</div>	1708	</div>
713	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1709	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1710	<div id="LIBEVENT_EMULATION_CONTENT">
		1711	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1712	emulate the internals of libevent, so here are some usage hints:</p>
		1713	<dl>
		1714	<dt>* Use it by including <event.h>, as usual.</dt>
		1715	<dt>* The following members are fully supported: ev_base, ev_callback,
		1716	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1717	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1718	maintained by libev, it does not work exactly the same way as in libevent (consider
		1719	it a private API).</dt>
		1720	<dt>* Priorities are not currently supported. Initialising priorities
		1721	will fail and all watchers will have the same priority, even though there
		1722	is an ev_pri field.</dt>
		1723	<dt>* Other members are not supported.</dt>
		1724	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1725	to use the libev header file and library.</dt>
		1726	</dl>
		1727
		1728	</div>
		1729	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1730	<div id="C_SUPPORT_CONTENT">
		1731	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1732	you to use some convinience methods to start/stop watchers and also change
		1733	the callback model to a model using method callbacks on objects.</p>
		1734	<p>To use it,</p>
		1735	<pre> #include <ev++.h>
		1736
		1737	</pre>
		1738	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1739	and puts all of its definitions (many of them macros) into the global
		1740	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1741	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1742	<code>EV_MULTIPLICITY</code>.</p>
		1743	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1744	<dl>
		1745	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1746	<dd>
		1747	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1748	macros from <cite>ev.h</cite>.</p>
		1749	</dd>
		1750	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1751	<dd>
		1752	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1753	</dd>
		1754	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1755	<dd>
		1756	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1757	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1758	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1759	defines by many implementations.</p>
		1760	<p>All of those classes have these methods:</p>
		1761	<p>
		1762	<dl>
		1763	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1764	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1765	<dt>ev::TYPE::~TYPE</dt>
		1766	<dd>
		1767	<p>The constructor takes a pointer to an object and a method pointer to
		1768	the event handler callback to call in this class. The constructor calls
		1769	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1770	before starting it. If you do not specify a loop then the constructor
		1771	automatically associates the default loop with this watcher.</p>
		1772	<p>The destructor automatically stops the watcher if it is active.</p>
		1773	</dd>
		1774	<dt>w->set (struct ev_loop *)</dt>
		1775	<dd>
		1776	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1777	do this when the watcher is inactive (and not pending either).</p>
		1778	</dd>
		1779	<dt>w->set ([args])</dt>
		1780	<dd>
		1781	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1782	called at least once. Unlike the C counterpart, an active watcher gets
		1783	automatically stopped and restarted.</p>
		1784	</dd>
		1785	<dt>w->start ()</dt>
		1786	<dd>
		1787	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1788	constructor already takes the loop.</p>
		1789	</dd>
		1790	<dt>w->stop ()</dt>
		1791	<dd>
		1792	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1793	</dd>
		1794	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1795	<dd>
		1796	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1797	<code>ev_TYPE_again</code> function.</p>
		1798	</dd>
		1799	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1800	<dd>
		1801	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1802	</dd>
		1803	<dt>w->update () <code>ev::stat</code> only</dt>
		1804	<dd>
		1805	<p>Invokes <code>ev_stat_stat</code>.</p>
		1806	</dd>
		1807	</dl>
		1808	</p>
		1809	</dd>
		1810	</dl>
		1811	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1812	the constructor.</p>
		1813	<pre> class myclass
		1814	{
		1815	ev_io io; void io_cb (ev::io &w, int revents);
		1816	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1817
		1818	myclass ();
		1819	}
		1820
		1821	myclass::myclass (int fd)
		1822	: io (this, &myclass::io_cb),
		1823	idle (this, &myclass::idle_cb)
		1824	{
		1825	io.start (fd, ev::READ);
		1826	}
		1827
		1828
		1829
		1830
		1831	</pre>
		1832
		1833	</div>
		1834	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		1835	<div id="MACRO_MAGIC_CONTENT">
		1836	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1837	<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
		1838	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1839	<p>To make it easier to write programs that cope with either variant, the
		1840	following macros are defined:</p>
		1841	<dl>
		1842	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		1843	<dd>
		1844	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		1845	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		1846	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		1847	<pre> ev_unref (EV_A);
		1848	ev_timer_add (EV_A_ watcher);
		1849	ev_loop (EV_A_ 0);
		1850
		1851	</pre>
		1852	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		1853	which is often provided by the following macro.</p>
		1854	</dd>
		1855	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		1856	<dd>
		1857	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		1858	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		1859	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		1860	<pre> // this is how ev_unref is being declared
		1861	static void ev_unref (EV_P);
		1862
		1863	// this is how you can declare your typical callback
		1864	static void cb (EV_P_ ev_timer *w, int revents)
		1865
		1866	</pre>
		1867	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		1868	suitable for use with <code>EV_A</code>.</p>
		1869	</dd>
		1870	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		1871	<dd>
		1872	<p>Similar to the other two macros, this gives you the value of the default
		1873	loop, if multiple loops are supported ("ev loop default").</p>
		1874	</dd>
		1875	</dl>
		1876	<p>Example: Declare and initialise a check watcher, utilising the above
		1877	macros so it will work regardless of wether multiple loops are supported
		1878	or not.</p>
		1879	<pre> static void
		1880	check_cb (EV_P_ ev_timer *w, int revents)
		1881	{
		1882	ev_check_stop (EV_A_ w);
		1883	}
		1884
		1885	ev_check check;
		1886	ev_check_init (&check, check_cb);
		1887	ev_check_start (EV_DEFAULT_ &check);
		1888	ev_loop (EV_DEFAULT_ 0);
		1889
		1890	</pre>
		1891
		1892	</div>
		1893	<h1 id="EMBEDDING">EMBEDDING</h1>
		1894	<div id="EMBEDDING_CONTENT">
		1895	<p>Libev can (and often is) directly embedded into host
		1896	applications. Examples of applications that embed it include the Deliantra
		1897	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1898	and rxvt-unicode.</p>
		1899	<p>The goal is to enable you to just copy the neecssary files into your
		1900	source directory without having to change even a single line in them, so
		1901	you can easily upgrade by simply copying (or having a checked-out copy of
		1902	libev somewhere in your source tree).</p>
		1903
		1904	</div>
		1905	<h2 id="FILESETS">FILESETS</h2>
		1906	<div id="FILESETS_CONTENT">
		1907	<p>Depending on what features you need you need to include one or more sets of files
		1908	in your app.</p>
		1909
		1910	</div>
		1911	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1912	<div id="CORE_EVENT_LOOP_CONTENT">
		1913	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1914	configuration (no autoconf):</p>
		1915	<pre> #define EV_STANDALONE 1
		1916	#include "ev.c"
		1917
		1918	</pre>
		1919	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1920	single C source file only to provide the function implementations. To use
		1921	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1922	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1923	where you can put other configuration options):</p>
		1924	<pre> #define EV_STANDALONE 1
		1925	#include "ev.h"
		1926
		1927	</pre>
		1928	<p>Both header files and implementation files can be compiled with a C++
		1929	compiler (at least, thats a stated goal, and breakage will be treated
		1930	as a bug).</p>
		1931	<p>You need the following files in your source tree, or in a directory
		1932	in your include path (e.g. in libev/ when using -Ilibev):</p>
		1933	<pre> ev.h
		1934	ev.c
		1935	ev_vars.h
		1936	ev_wrap.h
		1937
		1938	ev_win32.c required on win32 platforms only
		1939
		1940	ev_select.c only when select backend is enabled (which is enabled by default)
		1941	ev_poll.c only when poll backend is enabled (disabled by default)
		1942	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1943	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1944	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1945
		1946	</pre>
		1947	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		1948	to compile this single file.</p>
		1949
		1950	</div>
		1951	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		1952	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		1953	<p>To include the libevent compatibility API, also include:</p>
		1954	<pre> #include "event.c"
		1955
		1956	</pre>
		1957	<p>in the file including <cite>ev.c</cite>, and:</p>
		1958	<pre> #include "event.h"
		1959
		1960	</pre>
		1961	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		1962	<p>You need the following additional files for this:</p>
		1963	<pre> event.h
		1964	event.c
		1965
		1966	</pre>
		1967
		1968	</div>
		1969	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		1970	<div id="AUTOCONF_SUPPORT_CONTENT">
		1971	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		1972	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		1973	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		1974	include <cite>config.h</cite> and configure itself accordingly.</p>
		1975	<p>For this of course you need the m4 file:</p>
		1976	<pre> libev.m4
		1977
		1978	</pre>
		1979
		1980	</div>
		1981	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		1982	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		1983	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		1984	before including any of its files. The default is not to build for multiplicity
		1985	and only include the select backend.</p>
		1986	<dl>
		1987	<dt>EV_STANDALONE</dt>
		1988	<dd>
		1989	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		1990	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		1991	implementations for some libevent functions (such as logging, which is not
		1992	supported). It will also not define any of the structs usually found in
		1993	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		1994	</dd>
		1995	<dt>EV_USE_MONOTONIC</dt>
		1996	<dd>
		1997	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1998	monotonic clock option at both compiletime and runtime. Otherwise no use
		1999	of the monotonic clock option will be attempted. If you enable this, you
		2000	usually have to link against librt or something similar. Enabling it when
		2001	the functionality isn't available is safe, though, althoguh you have
		2002	to make sure you link against any libraries where the <code>clock_gettime</code>
		2003	function is hiding in (often <cite>-lrt</cite>).</p>
		2004	</dd>
		2005	<dt>EV_USE_REALTIME</dt>
		2006	<dd>
		2007	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2008	realtime clock option at compiletime (and assume its availability at
		2009	runtime if successful). Otherwise no use of the realtime clock option will
		2010	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		2011	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		2012	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		2013	</dd>
		2014	<dt>EV_USE_SELECT</dt>
		2015	<dd>
		2016	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		2017	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		2018	other method takes over, select will be it. Otherwise the select backend
		2019	will not be compiled in.</p>
		2020	</dd>
		2021	<dt>EV_SELECT_USE_FD_SET</dt>
		2022	<dd>
		2023	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		2024	structure. This is useful if libev doesn't compile due to a missing
		2025	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		2026	exotic systems. This usually limits the range of file descriptors to some
		2027	low limit such as 1024 or might have other limitations (winsocket only
		2028	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		2029	influence the size of the <code>fd_set</code> used.</p>
		2030	</dd>
		2031	<dt>EV_SELECT_IS_WINSOCKET</dt>
		2032	<dd>
		2033	<p>When defined to <code>1</code>, the select backend will assume that
		2034	select/socket/connect etc. don't understand file descriptors but
		2035	wants osf handles on win32 (this is the case when the select to
		2036	be used is the winsock select). This means that it will call
		2037	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		2038	it is assumed that all these functions actually work on fds, even
		2039	on win32. Should not be defined on non-win32 platforms.</p>
		2040	</dd>
		2041	<dt>EV_USE_POLL</dt>
		2042	<dd>
		2043	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		2044	backend. Otherwise it will be enabled on non-win32 platforms. It
		2045	takes precedence over select.</p>
		2046	</dd>
		2047	<dt>EV_USE_EPOLL</dt>
		2048	<dd>
		2049	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		2050	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2051	otherwise another method will be used as fallback. This is the
		2052	preferred backend for GNU/Linux systems.</p>
		2053	</dd>
		2054	<dt>EV_USE_KQUEUE</dt>
		2055	<dd>
		2056	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2057	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2058	otherwise another method will be used as fallback. This is the preferred
		2059	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2060	supports some types of fds correctly (the only platform we found that
		2061	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2062	not be used unless explicitly requested. The best way to use it is to find
		2063	out whether kqueue supports your type of fd properly and use an embedded
		2064	kqueue loop.</p>
		2065	</dd>
		2066	<dt>EV_USE_PORT</dt>
		2067	<dd>
		2068	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2069	10 port style backend. Its availability will be detected at runtime,
		2070	otherwise another method will be used as fallback. This is the preferred
		2071	backend for Solaris 10 systems.</p>
		2072	</dd>
		2073	<dt>EV_USE_DEVPOLL</dt>
		2074	<dd>
		2075	<p>reserved for future expansion, works like the USE symbols above.</p>
		2076	</dd>
		2077	<dt>EV_USE_INOTIFY</dt>
		2078	<dd>
		2079	<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
		2080	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2081	be detected at runtime.</p>
		2082	</dd>
		2083	<dt>EV_H</dt>
		2084	<dd>
		2085	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2086	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2087	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2088	</dd>
		2089	<dt>EV_CONFIG_H</dt>
		2090	<dd>
		2091	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2092	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2093	<code>EV_H</code>, above.</p>
		2094	</dd>
		2095	<dt>EV_EVENT_H</dt>
		2096	<dd>
		2097	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2098	of how the <cite>event.h</cite> header can be found.</p>
		2099	</dd>
		2100	<dt>EV_PROTOTYPES</dt>
		2101	<dd>
		2102	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2103	prototypes, but still define all the structs and other symbols. This is
		2104	occasionally useful if you want to provide your own wrapper functions
		2105	around libev functions.</p>
		2106	</dd>
		2107	<dt>EV_MULTIPLICITY</dt>
		2108	<dd>
		2109	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2110	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2111	additional independent event loops. Otherwise there will be no support
		2112	for multiple event loops and there is no first event loop pointer
		2113	argument. Instead, all functions act on the single default loop.</p>
		2114	</dd>
		2115	<dt>EV_PERIODIC_ENABLE</dt>
		2116	<dd>
		2117	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2118	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2119	code.</p>
		2120	</dd>
		2121	<dt>EV_IDLE_ENABLE</dt>
		2122	<dd>
		2123	<p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
		2124	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2125	code.</p>
		2126	</dd>
		2127	<dt>EV_EMBED_ENABLE</dt>
		2128	<dd>
		2129	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2130	defined to be <code>0</code>, then they are not.</p>
		2131	</dd>
		2132	<dt>EV_STAT_ENABLE</dt>
		2133	<dd>
		2134	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2135	defined to be <code>0</code>, then they are not.</p>
		2136	</dd>
		2137	<dt>EV_FORK_ENABLE</dt>
		2138	<dd>
		2139	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2140	defined to be <code>0</code>, then they are not.</p>
		2141	</dd>
		2142	<dt>EV_MINIMAL</dt>
		2143	<dd>
		2144	<p>If you need to shave off some kilobytes of code at the expense of some
		2145	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2146	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2147	</dd>
		2148	<dt>EV_PID_HASHSIZE</dt>
		2149	<dd>
		2150	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2151	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2152	than enough. If you need to manage thousands of children you might want to
		2153	increase this value (<i>must</i> be a power of two).</p>
		2154	</dd>
		2155	<dt>EV_INOTIFY_HASHSIZE</dt>
		2156	<dd>
		2157	<p><code>ev_staz</code> watchers use a small hash table to distribute workload by
		2158	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2159	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2160	watchers you might want to increase this value (<i>must</i> be a power of
		2161	two).</p>
		2162	</dd>
		2163	<dt>EV_COMMON</dt>
		2164	<dd>
		2165	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2166	this macro to a something else you can include more and other types of
		2167	members. You have to define it each time you include one of the files,
		2168	though, and it must be identical each time.</p>
		2169	<p>For example, the perl EV module uses something like this:</p>
		2170	<pre> #define EV_COMMON \
		2171	SV self; / contains this struct */ \
		2172	SV cb_sv, fh /* note no trailing ";" */
		2173
		2174	</pre>
		2175	</dd>
		2176	<dt>EV_CB_DECLARE (type)</dt>
		2177	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2178	<dt>ev_set_cb (ev, cb)</dt>
		2179	<dd>
		2180	<p>Can be used to change the callback member declaration in each watcher,
		2181	and the way callbacks are invoked and set. Must expand to a struct member
		2182	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2183	their default definitions. One possible use for overriding these is to
		2184	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2185	method calls instead of plain function calls in C++.</p>
		2186
		2187	</div>
		2188	<h2 id="EXAMPLES">EXAMPLES</h2>
		2189	<div id="EXAMPLES_CONTENT">
		2190	<p>For a real-world example of a program the includes libev
		2191	verbatim, you can have a look at the EV perl module
		2192	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2193	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2194	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2195	will be compiled. It is pretty complex because it provides its own header
		2196	file.</p>
		2197	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2198	that everybody includes and which overrides some configure choices:</p>
		2199	<pre> #define EV_MINIMAL 1
		2200	#define EV_USE_POLL 0
		2201	#define EV_MULTIPLICITY 0
		2202	#define EV_PERIODIC_ENABLE 0
		2203	#define EV_STAT_ENABLE 0
		2204	#define EV_FORK_ENABLE 0
		2205	#define EV_CONFIG_H <config.h>
		2206	#define EV_MINPRI 0
		2207	#define EV_MAXPRI 0
		2208
		2209	#include "ev++.h"
		2210
		2211	</pre>
		2212	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2213	<pre> #include "ev_cpp.h"
		2214	#include "ev.c"
		2215
		2216
		2217
		2218
		2219	</pre>
		2220
		2221	</div>
		2222	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2223	<div id="COMPLEXITIES_CONTENT">
		2224	<p>In this section the complexities of (many of) the algorithms used inside
		2225	libev will be explained. For complexity discussions about backends see the
		2226	documentation for <code>ev_default_init</code>.</p>
		2227	<p>
		2228	<dl>
		2229	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2230	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2231	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2232	<dt>Stopping check/prepare/idle watchers: O(1)</dt>
		2233	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
		2234	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2235	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2236	<dt>Activating one watcher: O(1)</dt>
		2237	</dl>
		2238	</p>
		2239
		2240
		2241
		2242
		2243
		2244	</div>
		2245	<h1 id="AUTHOR">AUTHOR</h1>
714	<div id="AUTHOR_CONTENT">	2246	<div id="AUTHOR_CONTENT">
715	<p>Marc Lehmann <libev@schmorp.de>.</p>	2247	<p>Marc Lehmann <libev@schmorp.de>.</p>
716		2248
717	</div>	2249	</div>
718	</div></body>	2250	</div></body>
719	</html>	2251	</html>

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