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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>
112	</dd>	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>
		234	</dd>
113	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	235	<dt>ev_set_allocator (void (cb)(void *ptr, size_t 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 and semantics are
116	realloc function). It is used to allocate and free memory (no surprises	238	identical to the realloc C function). It is used to allocate and free
117	here). If it returns zero when memory needs to be allocated, the library	239	memory (no surprises here). If it returns zero when memory needs to be
118	might abort or take some potentially destructive action. The default is	240	allocated, the library might abort or take some potentially destructive
119	your system realloc function.</p>	241	action. The default is your system realloc function.</p>
120	<p>You could override this function in high-availability programs to, say,	242	<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,	243	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>	244	or even to sleep a while and retry until some memory is available.</p>
		245	<p>Example: Replace the libev allocator with one that waits a bit and then
		246	retries).</p>
		247	<pre> static void *
		248	persistent_realloc (void *ptr, size_t size)
		249	{
		250	for (;;)
		251	{
		252	void *newptr = realloc (ptr, size);
		253
		254	if (newptr)
		255	return newptr;
		256
		257	sleep (60);
		258	}
		259	}
		260
		261	...
		262	ev_set_allocator (persistent_realloc);
		263
		264	</pre>
123	</dd>	265	</dd>
124	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	266	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
125	<dd>	267	<dd>
126	<p>Set the callback function to call on a retryable syscall error (such	268	<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	269	as failed select, poll, epoll_wait). The message is a printable string
128	indicating the system call or subsystem causing the problem. If this	270	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	271	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	272	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	273	requested operation, or, if the condition doesn't go away, do bad stuff
132	(such as abort).</p>	274	(such as abort).</p>
		275	<p>Example: This is basically the same thing that libev does internally, too.</p>
		276	<pre> static void
		277	fatal_error (const char *msg)
		278	{
		279	perror (msg);
		280	abort ();
		281	}
		282
		283	...
		284	ev_set_syserr_cb (fatal_error);
		285
		286	</pre>
133	</dd>	287	</dd>
134	</dl>	288	</dl>
135		289
136	</div>	290	</div>
137	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	291	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
138	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	292	<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	293	<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	294	types of such loops, the <i>default</i> loop, which supports signals and child
141	events, and dynamically created loops which do not.</p>	295	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	296	<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	297	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	298	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	299	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>	300	threads, make sure you lock (this is usually a bad idea, though, even if
		301	done correctly, because it's hideous and inefficient).</p>
147	<dl>	302	<dl>
148	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	303	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
149	<dd>	304	<dd>
150	<p>This will initialise the default event loop if it hasn't been initialised	305	<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	306	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	307	false. If it already was initialised it simply returns it (and ignores the
153	flags).</p>	308	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	309	<p>If you don't know what event loop to use, use the one returned from this
155	function.</p>	310	function.</p>
156	<p>The flags argument can be used to specify special behaviour or specific	311	<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>	312	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>	313	<p>The following flags are supported:</p>
159	<p>	314	<p>
160	<dl>	315	<dl>
161	<dt>EVFLAG_AUTO</dt>	316	<dt><code>EVFLAG_AUTO</code></dt>
162	<dd>	317	<dd>
163	<p>The default flags value. Use this if you have no clue (its the right	318	<p>The default flags value. Use this if you have no clue (it's the right
164	thing, believe me).</p>	319	thing, believe me).</p>
165	</dd>	320	</dd>
166	<dt>EVFLAG_NOENV</dt>	321	<dt><code>EVFLAG_NOENV</code></dt>
167	<dd>	322	<dd>
168	<p>If this flag bit is ored into the flag value then libev will <i>not</i> look	323	<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	324	or setgid) then libev will <i>not</i> look at the environment variable
170	environment variable will override the flags completely. This is useful	325	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
		326	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	327	useful to try out specific backends to test their performance, or to work
172	bugs.</p>	328	around bugs.</p>
173	</dd>	329	</dd>
174	<dt>EVMETHOD_SELECT portable select backend</dt>	330	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</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>	331	<dd>
181	<p>If one or more of these are ored into the flags value, then only these	332	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
182	backends will be tried (in the reverse order as given here). If one are	333	libev tries to roll its own fd_set with no limits on the number of fds,
183	specified, any backend will do.</p>	334	but if that fails, expect a fairly low limit on the number of fds when
		335	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		336	the fastest backend for a low number of fds.</p>
		337	</dd>
		338	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		339	<dd>
		340	<p>And this is your standard poll(2) backend. It's more complicated than
		341	select, but handles sparse fds better and has no artificial limit on the
		342	number of fds you can use (except it will slow down considerably with a
		343	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		344	</dd>
		345	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		346	<dd>
		347	<p>For few fds, this backend is a bit little slower than poll and select,
		348	but it scales phenomenally better. While poll and select usually scale like
		349	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		350	either O(1) or O(active_fds).</p>
		351	<p>While stopping and starting an I/O watcher in the same iteration will
		352	result in some caching, there is still a syscall per such incident
		353	(because the fd could point to a different file description now), so its
		354	best to avoid that. Also, dup()ed file descriptors might not work very
		355	well if you register events for both fds.</p>
		356	<p>Please note that epoll sometimes generates spurious notifications, so you
		357	need to use non-blocking I/O or other means to avoid blocking when no data
		358	(or space) is available.</p>
		359	</dd>
		360	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		361	<dd>
		362	<p>Kqueue deserves special mention, as at the time of this writing, it
		363	was broken on all BSDs except NetBSD (usually it doesn't work with
		364	anything but sockets and pipes, except on Darwin, where of course its
		365	completely useless). For this reason its not being "autodetected"
		366	unless you explicitly specify it explicitly in the flags (i.e. using
		367	<code>EVBACKEND_KQUEUE</code>).</p>
		368	<p>It scales in the same way as the epoll backend, but the interface to the
		369	kernel is more efficient (which says nothing about its actual speed, of
		370	course). While starting and stopping an I/O watcher does not cause an
		371	extra syscall as with epoll, it still adds up to four event changes per
		372	incident, so its best to avoid that.</p>
		373	</dd>
		374	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		375	<dd>
		376	<p>This is not implemented yet (and might never be).</p>
		377	</dd>
		378	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		379	<dd>
		380	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		381	it's really slow, but it still scales very well (O(active_fds)).</p>
		382	<p>Please note that solaris ports can result in a lot of spurious
		383	notifications, so you need to use non-blocking I/O or other means to avoid
		384	blocking when no data (or space) is available.</p>
		385	</dd>
		386	<dt><code>EVBACKEND_ALL</code></dt>
		387	<dd>
		388	<p>Try all backends (even potentially broken ones that wouldn't be tried
		389	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		390	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
184	</dd>	391	</dd>
185	</dl>	392	</dl>
186	</p>	393	</p>
		394	<p>If one or more of these are ored into the flags value, then only these
		395	backends will be tried (in the reverse order as given here). If none are
		396	specified, most compiled-in backend will be tried, usually in reverse
		397	order of their flag values :)</p>
		398	<p>The most typical usage is like this:</p>
		399	<pre> if (!ev_default_loop (0))
		400	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		401
		402	</pre>
		403	<p>Restrict libev to the select and poll backends, and do not allow
		404	environment settings to be taken into account:</p>
		405	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		406
		407	</pre>
		408	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		409	available (warning, breaks stuff, best use only with your own private
		410	event loop and only if you know the OS supports your types of fds):</p>
		411	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		412
		413	</pre>
187	</dd>	414	</dd>
188	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	415	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
189	<dd>	416	<dd>
190	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	417	<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	418	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	419	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>	420	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		421	<p>Example: Try to create a event loop that uses epoll and nothing else.</p>
		422	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		423	if (!epoller)
		424	fatal ("no epoll found here, maybe it hides under your chair");
		425
		426	</pre>
194	</dd>	427	</dd>
195	<dt>ev_default_destroy ()</dt>	428	<dt>ev_default_destroy ()</dt>
196	<dd>	429	<dd>
197	<p>Destroys the default loop again (frees all memory and kernel state	430	<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	431	etc.). None of the active event watchers will be stopped in the normal
199	any way whatsoever, although you cnanot rely on this :).</p>	432	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		433	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		434	calling this function, or cope with the fact afterwards (which is usually
		435	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		436	for example).</p>
200	</dd>	437	</dd>
201	<dt>ev_loop_destroy (loop)</dt>	438	<dt>ev_loop_destroy (loop)</dt>
202	<dd>	439	<dd>
203	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	440	<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>	441	earlier call to <code>ev_loop_new</code>.</p>
…		…
207	<dd>	444	<dd>
208	<p>This function reinitialises the kernel state for backends that have	445	<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	446	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	447	after forking, in either the parent or child process (or both, but that
211	again makes little sense).</p>	448	again makes little sense).</p>
212	<p>You <i>must</i> call this function after forking if and only if you want to	449	<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	450	only if you want to use the event library in both processes. If you just
214	have to call it.</p>	451	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	452	<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	453	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>	454	quite nicely into a call to <code>pthread_atfork</code>:</p>
218	<pre> pthread_atfork (0, 0, ev_default_fork);	455	<pre> pthread_atfork (0, 0, ev_default_fork);
219		456
220	</pre>	457	</pre>
		458	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		459	without calling this function, so if you force one of those backends you
		460	do not need to care.</p>
221	</dd>	461	</dd>
222	<dt>ev_loop_fork (loop)</dt>	462	<dt>ev_loop_fork (loop)</dt>
223	<dd>	463	<dd>
224	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	464	<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	465	<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>	466	after fork, and how you do this is entirely your own problem.</p>
227	</dd>	467	</dd>
228	<dt>unsigned int ev_method (loop)</dt>	468	<dt>unsigned int ev_backend (loop)</dt>
229	<dd>	469	<dd>
230	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	470	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
231	use.</p>	471	use.</p>
232	</dd>	472	</dd>
233	<dt>ev_tstamp = ev_now (loop)</dt>	473	<dt>ev_tstamp ev_now (loop)</dt>
234	<dd>	474	<dd>
235	<p>Returns the current "event loop time", which is the time the event loop	475	<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	476	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	477	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	478	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>	479	event occuring (or more correctly, libev finding out about it).</p>
240	</dd>	480	</dd>
241	<dt>ev_loop (loop, int flags)</dt>	481	<dt>ev_loop (loop, int flags)</dt>
242	<dd>	482	<dd>
243	<p>Finally, this is it, the event handler. This function usually is called	483	<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	484	after you initialised all your watchers and you want to start handling
245	events.</p>	485	events.</p>
246	<p>If the flags argument is specified as 0, it will not return until either	486	<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>	487	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		488	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		489	relying on all watchers to be stopped when deciding when a program has
		490	finished (especially in interactive programs), but having a program that
		491	automatically loops as long as it has to and no longer by virtue of
		492	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	493	<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	494	those events and any outstanding ones, but will not block your process in
250	case there are no events.</p>	495	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	496	<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	497	neccessary) and will handle those and any outstanding ones. It will block
253	your process until at least one new event arrives.</p>	498	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	499	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	500	external event in conjunction with something not expressible using other
256	more generic mechanism.</p>	501	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
		502	usually a better approach for this kind of thing.</p>
		503	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		504	<pre> * If there are no active watchers (reference count is zero), return.
		505	- Queue prepare watchers and then call all outstanding watchers.
		506	- If we have been forked, recreate the kernel state.
		507	- Update the kernel state with all outstanding changes.
		508	- Update the "event loop time".
		509	- Calculate for how long to block.
		510	- Block the process, waiting for any events.
		511	- Queue all outstanding I/O (fd) events.
		512	- Update the "event loop time" and do time jump handling.
		513	- Queue all outstanding timers.
		514	- Queue all outstanding periodics.
		515	- If no events are pending now, queue all idle watchers.
		516	- Queue all check watchers.
		517	- Call all queued watchers in reverse order (i.e. check watchers first).
		518	Signals and child watchers are implemented as I/O watchers, and will
		519	be handled here by queueing them when their watcher gets executed.
		520	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		521	were used, return, otherwise continue with step *.
		522
		523	</pre>
		524	<p>Example: Queue some jobs and then loop until no events are outsanding
		525	anymore.</p>
		526	<pre> ... queue jobs here, make sure they register event watchers as long
		527	... as they still have work to do (even an idle watcher will do..)
		528	ev_loop (my_loop, 0);
		529	... jobs done. yeah!
		530
		531	</pre>
257	</dd>	532	</dd>
258	<dt>ev_unloop (loop, how)</dt>	533	<dt>ev_unloop (loop, how)</dt>
259	<dd>	534	<dd>
260	<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument	535	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
		536	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>	537	<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>	538	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
263	calls return.</p>
264	</dd>	539	</dd>
265	<dt>ev_ref (loop)</dt>	540	<dt>ev_ref (loop)</dt>
266	<dt>ev_unref (loop)</dt>	541	<dt>ev_unref (loop)</dt>
267	<dd>	542	<dd>
268	<p>Ref/unref can be used to add or remove a refcount on the event loop: Every	543	<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	544	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	545	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	546	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	547	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	548	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	549	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	550	no event watchers registered by it are active. It is also an excellent
276	before stop.</p>	551	way to do this for generic recurring timers or from within third-party
		552	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		553	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		554	running when nothing else is active.</p>
		555	<pre> struct ev_signal exitsig;
		556	ev_signal_init (&exitsig, sig_cb, SIGINT);
		557	ev_signal_start (loop, &exitsig);
		558	evf_unref (loop);
		559
		560	</pre>
		561	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		562	<pre> ev_ref (loop);
		563	ev_signal_stop (loop, &exitsig);
		564
		565	</pre>
277	</dd>	566	</dd>
278	</dl>	567	</dl>
279		568
		569
		570
		571
		572
280	</div>	573	</div>
281	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	574	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
282	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	575	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
283	<p>A watcher is a structure that you create and register to record your	576	<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	577	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>	578	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)	579	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
287	{	580	{
288	ev_io_stop (w);	581	ev_io_stop (w);
289	ev_unloop (loop, EVUNLOOP_ALL);	582	ev_unloop (loop, EVUNLOOP_ALL);
290	}	583	}
…		…
313	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	606	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	607	*)</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>	608	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	609	<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	610	must not touch the values stored in it. Most specifically you must never
318	reinitialise it or call its set method.</p>	611	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	612	<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	613	registered watcher structure as second, and a bitset of received events as
325	third argument.</p>	614	third argument.</p>
326	<p>The rceeived events usually include a single bit per event type received	615	<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	616	(you can receive multiple events at the same time). The possible bit masks
328	are:</p>	617	are:</p>
329	<dl>	618	<dl>
330	<dt>EV_READ</dt>	619	<dt><code>EV_READ</code></dt>
331	<dt>EV_WRITE</dt>	620	<dt><code>EV_WRITE</code></dt>
332	<dd>	621	<dd>
333	<p>The file descriptor in the ev_io watcher has become readable and/or	622	<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
334	writable.</p>	623	writable.</p>
335	</dd>	624	</dd>
336	<dt>EV_TIMEOUT</dt>	625	<dt><code>EV_TIMEOUT</code></dt>
337	<dd>
338	<p>The ev_timer watcher has timed out.</p>
339	</dd>	626	<dd>
340	<dt>EV_PERIODIC</dt>	627	<p>The <code>ev_timer</code> watcher has timed out.</p>
341	<dd>	628	</dd>
342	<p>The ev_periodic watcher has timed out.</p>	629	<dt><code>EV_PERIODIC</code></dt>
343	</dd>	630	<dd>
344	<dt>EV_SIGNAL</dt>	631	<p>The <code>ev_periodic</code> watcher has timed out.</p>
345	<dd>	632	</dd>
		633	<dt><code>EV_SIGNAL</code></dt>
		634	<dd>
346	<p>The signal specified in the ev_signal watcher has been received by a thread.</p>	635	<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>	636	</dd>
		637	<dt><code>EV_CHILD</code></dt>
		638	<dd>
350	<p>The pid specified in the ev_child watcher has received a status change.</p>	639	<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>	640	</dd>
		641	<dt><code>EV_STAT</code></dt>
		642	<dd>
		643	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		644	</dd>
		645	<dt><code>EV_IDLE</code></dt>
		646	<dd>
354	<p>The ev_idle watcher has determined that you have nothing better to do.</p>	647	<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>	648	</dd>
		649	<dt><code>EV_PREPARE</code></dt>
		650	<dt><code>EV_CHECK</code></dt>
		651	<dd>
359	<p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts	652	<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	653	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	654	<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	655	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	656	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	657	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
365	<code>ev_loop</code> from blocking).</p>	658	<code>ev_loop</code> from blocking).</p>
366	</dd>	659	</dd>
367	<dt>EV_ERROR</dt>	660	<dt><code>EV_EMBED</code></dt>
		661	<dd>
		662	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		663	</dd>
		664	<dt><code>EV_FORK</code></dt>
		665	<dd>
		666	<p>The event loop has been resumed in the child process after fork (see
		667	<code>ev_fork</code>).</p>
		668	</dd>
		669	<dt><code>EV_ERROR</code></dt>
368	<dd>	670	<dd>
369	<p>An unspecified error has occured, the watcher has been stopped. This might	671	<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	672	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	673	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	674	problem. You best act on it by reporting the problem and somehow coping
…		…
378	programs, though, so beware.</p>	680	programs, though, so beware.</p>
379	</dd>	681	</dd>
380	</dl>	682	</dl>
381		683
382	</div>	684	</div>
		685	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		686	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		687	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		688	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		689	<dl>
		690	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		691	<dd>
		692	<p>This macro initialises the generic portion of a watcher. The contents
		693	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		694	the generic parts of the watcher are initialised, you <i>need</i> to call
		695	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		696	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		697	which rolls both calls into one.</p>
		698	<p>You can reinitialise a watcher at any time as long as it has been stopped
		699	(or never started) and there are no pending events outstanding.</p>
		700	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		701	int revents)</code>.</p>
		702	</dd>
		703	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		704	<dd>
		705	<p>This macro initialises the type-specific parts of a watcher. You need to
		706	call <code>ev_init</code> at least once before you call this macro, but you can
		707	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		708	macro on a watcher that is active (it can be pending, however, which is a
		709	difference to the <code>ev_init</code> macro).</p>
		710	<p>Although some watcher types do not have type-specific arguments
		711	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		712	</dd>
		713	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		714	<dd>
		715	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		716	calls into a single call. This is the most convinient method to initialise
		717	a watcher. The same limitations apply, of course.</p>
		718	</dd>
		719	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		720	<dd>
		721	<p>Starts (activates) the given watcher. Only active watchers will receive
		722	events. If the watcher is already active nothing will happen.</p>
		723	</dd>
		724	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		725	<dd>
		726	<p>Stops the given watcher again (if active) and clears the pending
		727	status. It is possible that stopped watchers are pending (for example,
		728	non-repeating timers are being stopped when they become pending), but
		729	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		730	you want to free or reuse the memory used by the watcher it is therefore a
		731	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		732	</dd>
		733	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		734	<dd>
		735	<p>Returns a true value iff the watcher is active (i.e. it has been started
		736	and not yet been stopped). As long as a watcher is active you must not modify
		737	it.</p>
		738	</dd>
		739	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		740	<dd>
		741	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		742	events but its callback has not yet been invoked). As long as a watcher
		743	is pending (but not active) you must not call an init function on it (but
		744	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		745	libev (e.g. you cnanot <code>free ()</code> it).</p>
		746	</dd>
		747	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		748	<dd>
		749	<p>Returns the callback currently set on the watcher.</p>
		750	</dd>
		751	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		752	<dd>
		753	<p>Change the callback. You can change the callback at virtually any time
		754	(modulo threads).</p>
		755	</dd>
		756	</dl>
		757
		758
		759
		760
		761
		762	</div>
383	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	763	<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">	764	<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	765	<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	766	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	767	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	768	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	769	member, you can also "subclass" the watcher type and provide your own
390	data:</p>	770	data:</p>
391	<pre> struct my_io	771	<pre> struct my_io
…		…
404	struct my_io w = (struct my_io )w_;	784	struct my_io w = (struct my_io )w_;
405	...	785	...
406	}	786	}
407		787
408	</pre>	788	</pre>
409	<p>More interesting and less C-conformant ways of catsing your callback type	789	<p>More interesting and less C-conformant ways of casting your callback type
410	have been omitted....</p>	790	instead have been omitted.</p>
		791	<p>Another common scenario is having some data structure with multiple
		792	watchers:</p>
		793	<pre> struct my_biggy
		794	{
		795	int some_data;
		796	ev_timer t1;
		797	ev_timer t2;
		798	}
411		799
		800	</pre>
		801	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		802	you need to use <code>offsetof</code>:</p>
		803	<pre> #include <stddef.h>
412		804
		805	static void
		806	t1_cb (EV_P_ struct ev_timer *w, int revents)
		807	{
		808	struct my_biggy big = (struct my_biggy *
		809	(((char *)w) - offsetof (struct my_biggy, t1));
		810	}
413		811
		812	static void
		813	t2_cb (EV_P_ struct ev_timer *w, int revents)
		814	{
		815	struct my_biggy big = (struct my_biggy *
		816	(((char *)w) - offsetof (struct my_biggy, t2));
		817	}
414		818
415		819
		820
		821
		822	</pre>
		823
416	</div>	824	</div>
417	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	825	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
418	<div id="WATCHER_TYPES_CONTENT">	826	<div id="WATCHER_TYPES_CONTENT">
419	<p>This section describes each watcher in detail, but will not repeat	827	<p>This section describes each watcher in detail, but will not repeat
420	information given in the last section.</p>	828	information given in the last section. Any initialisation/set macros,
		829	functions and members specific to the watcher type are explained.</p>
		830	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		831	while the watcher is active, you can look at the member and expect some
		832	sensible content, but you must not modify it (you can modify it while the
		833	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		834	means you can expect it to have some sensible content while the watcher
		835	is active, but you can also modify it. Modifying it may not do something
		836	sensible or take immediate effect (or do anything at all), but libev will
		837	not crash or malfunction in any way.</p>
421		838
		839
		840
		841
		842
422	</div>	843	</div>
423	<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2>	844	<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">	845	<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	846	<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	847	in each iteration of the event loop, or, more precisely, when reading
427	level-triggering because you keep receiving events as long as the	848	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	849	some data. This behaviour is called level-triggering because you keep
429	act on the event and neither want to receive future events).</p>	850	receiving events as long as the condition persists. Remember you can stop
		851	the watcher if you don't want to act on the event and neither want to
		852	receive future events.</p>
		853	<p>In general you can register as many read and/or write event watchers per
		854	fd as you want (as long as you don't confuse yourself). Setting all file
		855	descriptors to non-blocking mode is also usually a good idea (but not
		856	required if you know what you are doing).</p>
		857	<p>You have to be careful with dup'ed file descriptors, though. Some backends
		858	(the linux epoll backend is a notable example) cannot handle dup'ed file
		859	descriptors correctly if you register interest in two or more fds pointing
		860	to the same underlying file/socket/etc. description (that is, they share
		861	the same underlying "file open").</p>
		862	<p>If you must do this, then force the use of a known-to-be-good backend
		863	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
		864	<code>EVBACKEND_POLL</code>).</p>
		865	<p>Another thing you have to watch out for is that it is quite easy to
		866	receive "spurious" readyness notifications, that is your callback might
		867	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		868	because there is no data. Not only are some backends known to create a
		869	lot of those (for example solaris ports), it is very easy to get into
		870	this situation even with a relatively standard program structure. Thus
		871	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		872	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		873	<p>If you cannot run the fd in non-blocking mode (for example you should not
		874	play around with an Xlib connection), then you have to seperately re-test
		875	wether a file descriptor is really ready with a known-to-be good interface
		876	such as poll (fortunately in our Xlib example, Xlib already does this on
		877	its own, so its quite safe to use).</p>
430	<dl>	878	<dl>
431	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	879	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
432	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	880	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
433	<dd>	881	<dd>
434	<p>Configures an ev_io watcher. The fd is the file descriptor to rceeive	882	<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 \|	883	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>	884	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		885	</dd>
		886	<dt>int fd [read-only]</dt>
		887	<dd>
		888	<p>The file descriptor being watched.</p>
		889	</dd>
		890	<dt>int events [read-only]</dt>
		891	<dd>
		892	<p>The events being watched.</p>
437	</dd>	893	</dd>
438	</dl>	894	</dl>
		895	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		896	readable, but only once. Since it is likely line-buffered, you could
		897	attempt to read a whole line in the callback.</p>
		898	<pre> static void
		899	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		900	{
		901	ev_io_stop (loop, w);
		902	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		903	}
439		904
		905	...
		906	struct ev_loop *loop = ev_default_init (0);
		907	struct ev_io stdin_readable;
		908	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		909	ev_io_start (loop, &stdin_readable);
		910	ev_loop (loop, 0);
		911
		912
		913
		914
		915	</pre>
		916
440	</div>	917	</div>
441	<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2>	918	<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">	919	<div id="code_ev_timer_code_relative_and_opti-2">
443	<p>Timer watchers are simple relative timers that generate an event after a	920	<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>	921	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	922	<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	923	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	924	time, it will still time out after (roughly) and hour. "Roughly" because
448	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	925	detecting time jumps is hard, and some inaccuracies are unavoidable (the
449	monotonic clock option helps a lot here).</p>	926	monotonic clock option helps a lot here).</p>
		927	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
		928	time. This is usually the right thing as this timestamp refers to the time
		929	of the event triggering whatever timeout you are modifying/starting. If
		930	you suspect event processing to be delayed and you <i>need</i> to base the timeout
		931	on the current time, use something like this to adjust for this:</p>
		932	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		933
		934	</pre>
		935	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		936	but if multiple timers become ready during the same loop iteration then
		937	order of execution is undefined.</p>
450	<dl>	938	<dl>
451	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	939	<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>	940	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
453	<dd>	941	<dd>
454	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	942	<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	944	timer will automatically be configured to trigger again <code>repeat</code> seconds
457	later, again, and again, until stopped manually.</p>	945	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	946	<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	947	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	948	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	949	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>	950	timer will not fire more than once per event loop iteration.</p>
463	</dd>	951	</dd>
464	<dt>ev_timer_again (loop)</dt>	952	<dt>ev_timer_again (loop)</dt>
465	<dd>	953	<dd>
466	<p>This will act as if the timer timed out and restart it again if it is	954	<p>This will act as if the timer timed out and restart it again if it is
467	repeating. The exact semantics are:</p>	955	repeating. The exact semantics are:</p>
468	<p>If the timer is started but nonrepeating, stop it.</p>	956	<p>If the timer is started but nonrepeating, stop it.</p>
469	<p>If the timer is repeating, either start it if necessary (with the repeat	957	<p>If the timer is repeating, either start it if necessary (with the repeat
470	value), or reset the running timer to the repeat value.</p>	958	value), or reset the running timer to the repeat value.</p>
471	<p>This sounds a bit complicated, but here is a useful and typical	959	<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	960	example: Imagine you have a tcp connection and you want a so-called
473	timeout, that is, you want to be called when there have been, say, 60	961	idle timeout, that is, you want to be called when there have been,
474	seconds of inactivity on the socket. The easiest way to do this is to	962	say, 60 seconds of inactivity on the socket. The easiest way to do
475	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	963	this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
476	time you successfully read or write some data. If you go into an idle	964	<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	965	you go into an idle state where you do not expect data to travel on the
478	the timer, and again will automatically restart it if need be.</p>	966	socket, you can stop the timer, and again will automatically restart it if
		967	need be.</p>
		968	<p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
		969	and only ever use the <code>repeat</code> value:</p>
		970	<pre> ev_timer_init (timer, callback, 0., 5.);
		971	ev_timer_again (loop, timer);
		972	...
		973	timer->again = 17.;
		974	ev_timer_again (loop, timer);
		975	...
		976	timer->again = 10.;
		977	ev_timer_again (loop, timer);
		978
		979	</pre>
		980	<p>This is more efficient then stopping/starting the timer eahc time you want
		981	to modify its timeout value.</p>
		982	</dd>
		983	<dt>ev_tstamp repeat [read-write]</dt>
		984	<dd>
		985	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		986	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		987	which is also when any modifications are taken into account.</p>
479	</dd>	988	</dd>
480	</dl>	989	</dl>
		990	<p>Example: Create a timer that fires after 60 seconds.</p>
		991	<pre> static void
		992	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		993	{
		994	.. one minute over, w is actually stopped right here
		995	}
481		996
		997	struct ev_timer mytimer;
		998	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		999	ev_timer_start (loop, &mytimer);
		1000
		1001	</pre>
		1002	<p>Example: Create a timeout timer that times out after 10 seconds of
		1003	inactivity.</p>
		1004	<pre> static void
		1005	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1006	{
		1007	.. ten seconds without any activity
		1008	}
		1009
		1010	struct ev_timer mytimer;
		1011	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1012	ev_timer_again (&mytimer); /* start timer */
		1013	ev_loop (loop, 0);
		1014
		1015	// and in some piece of code that gets executed on any "activity":
		1016	// reset the timeout to start ticking again at 10 seconds
		1017	ev_timer_again (&mytimer);
		1018
		1019
		1020
		1021
		1022	</pre>
		1023
482	</div>	1024	</div>
483	<h2 id="ev_periodic">ev_periodic</h2>	1025	<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">	1026	<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	1027	<p>Periodic watchers are also timers of a kind, but they are very versatile
486	(and unfortunately a bit complex).</p>	1028	(and unfortunately a bit complex).</p>
487	<p>Unlike ev_timer's, they are not based on real time (or relative time)	1029	<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	1030	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	1031	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 ()	1032	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	1033	+ 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	1034	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	1035	roughly 10 seconds later and of course not if you reset your system time
494	again).</p>	1036	again).</p>
495	<p>They can also be used to implement vastly more complex timers, such as	1037	<p>They can also be used to implement vastly more complex timers, such as
496	triggering an event on eahc midnight, local time.</p>	1038	triggering an event on eahc midnight, local time.</p>
		1039	<p>As with timers, the callback is guarenteed to be invoked only when the
		1040	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1041	during the same loop iteration then order of execution is undefined.</p>
497	<dl>	1042	<dl>
498	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1043	<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>	1044	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
500	<dd>	1045	<dd>
501	<p>Lots of arguments, lets sort it out... There are basically three modes of	1046	<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>	1047	operation, and we will explain them from simplest to complex:</p>
503
504
505
506
507	<p>	1048	<p>
508	<dl>	1049	<dl>
509	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1050	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
510	<dd>	1051	<dd>
511	<p>In this configuration the watcher triggers an event at the wallclock time	1052	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
523	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	1064	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
524		1065
525	</pre>	1066	</pre>
526	<p>This doesn't mean there will always be 3600 seconds in between triggers,	1067	<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	1068	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	1069	full hour (UTC), or more correctly, when the system time is evenly divisible
529	by 3600.</p>	1070	by 3600.</p>
530	<p>Another way to think about it (for the mathematically inclined) is that	1071	<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	1072	<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>	1073	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
533	</dd>	1074	</dd>
534	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	1075	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>
535	<dd>	1076	<dd>
536	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	1077	<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	1078	ignored. Instead, each time the periodic watcher gets scheduled, the
538	reschedule callback will be called with the watcher as first, and the	1079	reschedule callback will be called with the watcher as first, and the
539	current time as second argument.</p>	1080	current time as second argument.</p>
540	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1081	<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	1082	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>	1083	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
		1084	starting a prepare watcher).</p>
543	<p>Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1085	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
544	ev_tstamp now)>, e.g.:</p>	1086	ev_tstamp now)</code>, e.g.:</p>
545	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1087	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
546	{	1088	{
547	return now + 60.;	1089	return now + 60.;
548	}	1090	}
549		1091
550	</pre>	1092	</pre>
551	<p>It must return the next time to trigger, based on the passed time value	1093	<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	1094	(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	1095	will usually be called just before the callback will be triggered, but
554	might be called at other times, too.</p>	1096	might be called at other times, too.</p>
		1097	<p>NOTE: <i>This callback must always return a time that is later than the
		1098	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	1099	<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	1100	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	1101	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>	1102	you do this is, again, up to you (but it is not trivial, which is the main
		1103	reason I omitted it as an example).</p>
559	</dd>	1104	</dd>
560	</dl>	1105	</dl>
561	</p>	1106	</p>
562	</dd>	1107	</dd>
563	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1108	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
565	<p>Simply stops and restarts the periodic watcher again. This is only useful	1110	<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	1111	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	1112	a different time than the last time it was called (e.g. in a crond like
568	program when the crontabs have changed).</p>	1113	program when the crontabs have changed).</p>
569	</dd>	1114	</dd>
		1115	<dt>ev_tstamp interval [read-write]</dt>
		1116	<dd>
		1117	<p>The current interval value. Can be modified any time, but changes only
		1118	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1119	called.</p>
		1120	</dd>
		1121	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1122	<dd>
		1123	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1124	switched off. Can be changed any time, but changes only take effect when
		1125	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1126	</dd>
570	</dl>	1127	</dl>
		1128	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1129	system clock is divisible by 3600. The callback invocation times have
		1130	potentially a lot of jittering, but good long-term stability.</p>
		1131	<pre> static void
		1132	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1133	{
		1134	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1135	}
571		1136
		1137	struct ev_periodic hourly_tick;
		1138	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1139	ev_periodic_start (loop, &hourly_tick);
		1140
		1141	</pre>
		1142	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1143	<pre> #include <math.h>
		1144
		1145	static ev_tstamp
		1146	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1147	{
		1148	return fmod (now, 3600.) + 3600.;
		1149	}
		1150
		1151	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1152
		1153	</pre>
		1154	<p>Example: Call a callback every hour, starting now:</p>
		1155	<pre> struct ev_periodic hourly_tick;
		1156	ev_periodic_init (&hourly_tick, clock_cb,
		1157	fmod (ev_now (loop), 3600.), 3600., 0);
		1158	ev_periodic_start (loop, &hourly_tick);
		1159
		1160
		1161
		1162
		1163	</pre>
		1164
572	</div>	1165	</div>
573	<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>	1166	<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">	1167	<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	1168	<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	1169	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	1170	will try it's best to deliver signals synchronously, i.e. as part of the
578	normal event processing, like any other event.</p>	1171	normal event processing, like any other event.</p>
579	<p>You cna configure as many watchers as you like per signal. Only when the	1172	<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	1173	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	1174	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	1175	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	1176	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>	1177	SIG_DFL (regardless of what it was set to before).</p>
…		…
587	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1180	<dt>ev_signal_set (ev_signal *, int signum)</dt>
588	<dd>	1181	<dd>
589	<p>Configures the watcher to trigger on the given signal number (usually one	1182	<p>Configures the watcher to trigger on the given signal number (usually one
590	of the <code>SIGxxx</code> constants).</p>	1183	of the <code>SIGxxx</code> constants).</p>
591	</dd>	1184	</dd>
		1185	<dt>int signum [read-only]</dt>
		1186	<dd>
		1187	<p>The signal the watcher watches out for.</p>
		1188	</dd>
592	</dl>	1189	</dl>
593		1190
		1191
		1192
		1193
		1194
594	</div>	1195	</div>
595	<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2>	1196	<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">	1197	<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	1198	<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>	1199	some child status changes (most typically when a child of yours dies).</p>
599	<dl>	1200	<dl>
600	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1201	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
601	<dt>ev_child_set (ev_child *, int pid)</dt>	1202	<dt>ev_child_set (ev_child *, int pid)</dt>
602	<dd>	1203	<dd>
603	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or	1204	<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	1205	<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	1206	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	1207	the status word (use the macros from <code>sys/wait.h</code> and see your systems
		1208	<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>	1209	process causing the status change.</p>
		1210	</dd>
		1211	<dt>int pid [read-only]</dt>
		1212	<dd>
		1213	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1214	</dd>
		1215	<dt>int rpid [read-write]</dt>
		1216	<dd>
		1217	<p>The process id that detected a status change.</p>
		1218	</dd>
		1219	<dt>int rstatus [read-write]</dt>
		1220	<dd>
		1221	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1222	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
608	</dd>	1223	</dd>
609	</dl>	1224	</dl>
		1225	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1226	<pre> static void
		1227	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1228	{
		1229	ev_unloop (loop, EVUNLOOP_ALL);
		1230	}
610		1231
		1232	struct ev_signal signal_watcher;
		1233	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1234	ev_signal_start (loop, &sigint_cb);
		1235
		1236
		1237
		1238
		1239	</pre>
		1240
611	</div>	1241	</div>
		1242	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1243	<div id="code_ev_stat_code_did_the_file_attri-2">
		1244	<p>This watches a filesystem path for attribute changes. That is, it calls
		1245	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1246	compared to the last time, invoking the callback if it did.</p>
		1247	<p>The path does not need to exist: changing from "path exists" to "path does
		1248	not exist" is a status change like any other. The condition "path does
		1249	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1250	otherwise always forced to be at least one) and all the other fields of
		1251	the stat buffer having unspecified contents.</p>
		1252	<p>Since there is no standard to do this, the portable implementation simply
		1253	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1254	can specify a recommended polling interval for this case. If you specify
		1255	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1256	unspecified default</i> value will be used (which you can expect to be around
		1257	five seconds, although this might change dynamically). Libev will also
		1258	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1259	usually overkill.</p>
		1260	<p>This watcher type is not meant for massive numbers of stat watchers,
		1261	as even with OS-supported change notifications, this can be
		1262	resource-intensive.</p>
		1263	<p>At the time of this writing, only the Linux inotify interface is
		1264	implemented (implementing kqueue support is left as an exercise for the
		1265	reader). Inotify will be used to give hints only and should not change the
		1266	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1267	to fall back to regular polling again even with inotify, but changes are
		1268	usually detected immediately, and if the file exists there will be no
		1269	polling.</p>
		1270	<dl>
		1271	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1272	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1273	<dd>
		1274	<p>Configures the watcher to wait for status changes of the given
		1275	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1276	be detected and should normally be specified as <code>0</code> to let libev choose
		1277	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1278	path for as long as the watcher is active.</p>
		1279	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1280	relative to the attributes at the time the watcher was started (or the
		1281	last change was detected).</p>
		1282	</dd>
		1283	<dt>ev_stat_stat (ev_stat *)</dt>
		1284	<dd>
		1285	<p>Updates the stat buffer immediately with new values. If you change the
		1286	watched path in your callback, you could call this fucntion to avoid
		1287	detecting this change (while introducing a race condition). Can also be
		1288	useful simply to find out the new values.</p>
		1289	</dd>
		1290	<dt>ev_statdata attr [read-only]</dt>
		1291	<dd>
		1292	<p>The most-recently detected attributes of the file. Although the type is of
		1293	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1294	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1295	was some error while <code>stat</code>ing the file.</p>
		1296	</dd>
		1297	<dt>ev_statdata prev [read-only]</dt>
		1298	<dd>
		1299	<p>The previous attributes of the file. The callback gets invoked whenever
		1300	<code>prev</code> != <code>attr</code>.</p>
		1301	</dd>
		1302	<dt>ev_tstamp interval [read-only]</dt>
		1303	<dd>
		1304	<p>The specified interval.</p>
		1305	</dd>
		1306	<dt>const char *path [read-only]</dt>
		1307	<dd>
		1308	<p>The filesystem path that is being watched.</p>
		1309	</dd>
		1310	</dl>
		1311	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1312	<pre> static void
		1313	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1314	{
		1315	/* /etc/passwd changed in some way */
		1316	if (w->attr.st_nlink)
		1317	{
		1318	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1319	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1320	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1321	}
		1322	else
		1323	/* you shalt not abuse printf for puts */
		1324	puts ("wow, /etc/passwd is not there, expect problems. "
		1325	"if this is windows, they already arrived\n");
		1326	}
		1327
		1328	...
		1329	ev_stat passwd;
		1330
		1331	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1332	ev_stat_start (loop, &passwd);
		1333
		1334
		1335
		1336
		1337	</pre>
		1338
		1339	</div>
612	<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2>	1340	<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">	1341	<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	1342	<p>Idle watchers trigger events when there are no other events are pending
615	periodic) events pending. That is, as long as your process is busy	1343	(prepare, check and other idle watchers do not count). That is, as long
616	handling sockets or timeouts it will not be called. But when your process	1344	as your process is busy handling sockets or timeouts (or even signals,
617	is idle all idle watchers are being called again and again - until	1345	imagine) it will not be triggered. But when your process is idle all idle
		1346	watchers are being called again and again, once per event loop iteration -
618	stopped, that is, or your process receives more events.</p>	1347	until stopped, that is, or your process receives more events and becomes
		1348	busy.</p>
619	<p>The most noteworthy effect is that as long as any idle watchers are	1349	<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>	1350	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	1351	<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	1352	effect on its own sometimes), idle watchers are a good place to do
623	"pseudo-background processing", or delay processing stuff to after the	1353	"pseudo-background processing", or delay processing stuff to after the
…		…
628	<p>Initialises and configures the idle watcher - it has no parameters of any	1358	<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,	1359	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
630	believe me.</p>	1360	believe me.</p>
631	</dd>	1361	</dd>
632	</dl>	1362	</dl>
		1363	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1364	callback, free it. Also, use no error checking, as usual.</p>
		1365	<pre> static void
		1366	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1367	{
		1368	free (w);
		1369	// now do something you wanted to do when the program has
		1370	// no longer asnything immediate to do.
		1371	}
633		1372
		1373	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1374	ev_idle_init (idle_watcher, idle_cb);
		1375	ev_idle_start (loop, idle_cb);
		1376
		1377
		1378
		1379
		1380	</pre>
		1381
634	</div>	1382	</div>
635	<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>	1383	<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">	1384	<div id="code_ev_prepare_code_and_code_ev_che-2">
637	<p>Prepare and check watchers usually (but not always) are used in	1385	<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	1386	prepare watchers get invoked before the process blocks and check watchers
639	watchers afterwards.</p>	1387	afterwards.</p>
		1388	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1389	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1390	watchers. Other loops than the current one are fine, however. The
		1391	rationale behind this is that you do not need to check for recursion in
		1392	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1393	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1394	called in pairs bracketing the blocking call.</p>
640	<p>Their main purpose is to integrate other event mechanisms into libev. This	1395	<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	1396	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>	1397	variable changes, implement your own watchers, integrate net-snmp or a
		1398	coroutine library and lots more. They are also occasionally useful if
		1399	you cache some data and want to flush it before blocking (for example,
		1400	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1401	watcher).</p>
643	<p>This is done by examining in each prepare call which file descriptors need	1402	<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	1403	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	1404	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	1405	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)	1406	any events that occured (by checking the pending status of all watchers
648	and call back into the library.</p>	1407	and stopping them) and call back into the library. The I/O and timer
		1408	callbacks will never actually be called (but must be valid nevertheless,
		1409	because you never know, you know?).</p>
649	<p>As another example, the perl Coro module uses these hooks to integrate	1410	<p>As another example, the Perl Coro module uses these hooks to integrate
650	coroutines into libev programs, by yielding to other active coroutines	1411	coroutines into libev programs, by yielding to other active coroutines
651	during each prepare and only letting the process block if no coroutines	1412	during each prepare and only letting the process block if no coroutines
652	are ready to run.</p>	1413	are ready to run (it's actually more complicated: it only runs coroutines
		1414	with priority higher than or equal to the event loop and one coroutine
		1415	of lower priority, but only once, using idle watchers to keep the event
		1416	loop from blocking if lower-priority coroutines are active, thus mapping
		1417	low-priority coroutines to idle/background tasks).</p>
653	<dl>	1418	<dl>
654	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1419	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
655	<dt>ev_check_init (ev_check *, callback)</dt>	1420	<dt>ev_check_init (ev_check *, callback)</dt>
656	<dd>	1421	<dd>
657	<p>Initialises and configures the prepare or check watcher - they have no	1422	<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>	1423	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>	1424	macros, but using them is utterly, utterly and completely pointless.</p>
660	</dd>	1425	</dd>
661	</dl>	1426	</dl>
		1427	<p>Example: To include a library such as adns, you would add IO watchers
		1428	and a timeout watcher in a prepare handler, as required by libadns, and
		1429	in a check watcher, destroy them and call into libadns. What follows is
		1430	pseudo-code only of course:</p>
		1431	<pre> static ev_io iow [nfd];
		1432	static ev_timer tw;
662		1433
		1434	static void
		1435	io_cb (ev_loop loop, ev_io w, int revents)
		1436	{
		1437	// set the relevant poll flags
		1438	// could also call adns_processreadable etc. here
		1439	struct pollfd fd = (struct pollfd )w->data;
		1440	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1441	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1442	}
		1443
		1444	// create io watchers for each fd and a timer before blocking
		1445	static void
		1446	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1447	{
		1448	int timeout = 3600000;truct pollfd fds [nfd];
		1449	// actual code will need to loop here and realloc etc.
		1450	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1451
		1452	/* the callback is illegal, but won't be called as we stop during check */
		1453	ev_timer_init (&tw, 0, timeout * 1e-3);
		1454	ev_timer_start (loop, &tw);
		1455
		1456	// create on ev_io per pollfd
		1457	for (int i = 0; i < nfd; ++i)
		1458	{
		1459	ev_io_init (iow + i, io_cb, fds [i].fd,
		1460	((fds [i].events & POLLIN ? EV_READ : 0)
		1461	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1462
		1463	fds [i].revents = 0;
		1464	iow [i].data = fds + i;
		1465	ev_io_start (loop, iow + i);
		1466	}
		1467	}
		1468
		1469	// stop all watchers after blocking
		1470	static void
		1471	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1472	{
		1473	ev_timer_stop (loop, &tw);
		1474
		1475	for (int i = 0; i < nfd; ++i)
		1476	ev_io_stop (loop, iow + i);
		1477
		1478	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1479	}
		1480
		1481
		1482
		1483
		1484	</pre>
		1485
663	</div>	1486	</div>
664	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1487	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1488	<div id="code_ev_embed_code_when_one_backend_-2">
		1489	<p>This is a rather advanced watcher type that lets you embed one event loop
		1490	into another (currently only <code>ev_io</code> events are supported in the embedded
		1491	loop, other types of watchers might be handled in a delayed or incorrect
		1492	fashion and must not be used).</p>
		1493	<p>There are primarily two reasons you would want that: work around bugs and
		1494	prioritise I/O.</p>
		1495	<p>As an example for a bug workaround, the kqueue backend might only support
		1496	sockets on some platform, so it is unusable as generic backend, but you
		1497	still want to make use of it because you have many sockets and it scales
		1498	so nicely. In this case, you would create a kqueue-based loop and embed it
		1499	into your default loop (which might use e.g. poll). Overall operation will
		1500	be a bit slower because first libev has to poll and then call kevent, but
		1501	at least you can use both at what they are best.</p>
		1502	<p>As for prioritising I/O: rarely you have the case where some fds have
		1503	to be watched and handled very quickly (with low latency), and even
		1504	priorities and idle watchers might have too much overhead. In this case
		1505	you would put all the high priority stuff in one loop and all the rest in
		1506	a second one, and embed the second one in the first.</p>
		1507	<p>As long as the watcher is active, the callback will be invoked every time
		1508	there might be events pending in the embedded loop. The callback must then
		1509	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1510	their callbacks (you could also start an idle watcher to give the embedded
		1511	loop strictly lower priority for example). You can also set the callback
		1512	to <code>0</code>, in which case the embed watcher will automatically execute the
		1513	embedded loop sweep.</p>
		1514	<p>As long as the watcher is started it will automatically handle events. The
		1515	callback will be invoked whenever some events have been handled. You can
		1516	set the callback to <code>0</code> to avoid having to specify one if you are not
		1517	interested in that.</p>
		1518	<p>Also, there have not currently been made special provisions for forking:
		1519	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1520	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1521	yourself.</p>
		1522	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1523	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1524	portable one.</p>
		1525	<p>So when you want to use this feature you will always have to be prepared
		1526	that you cannot get an embeddable loop. The recommended way to get around
		1527	this is to have a separate variables for your embeddable loop, try to
		1528	create it, and if that fails, use the normal loop for everything:</p>
		1529	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1530	struct ev_loop *loop_lo = 0;
		1531	struct ev_embed embed;
		1532
		1533	// see if there is a chance of getting one that works
		1534	// (remember that a flags value of 0 means autodetection)
		1535	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1536	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1537	: 0;
		1538
		1539	// if we got one, then embed it, otherwise default to loop_hi
		1540	if (loop_lo)
		1541	{
		1542	ev_embed_init (&embed, 0, loop_lo);
		1543	ev_embed_start (loop_hi, &embed);
		1544	}
		1545	else
		1546	loop_lo = loop_hi;
		1547
		1548	</pre>
		1549	<dl>
		1550	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1551	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1552	<dd>
		1553	<p>Configures the watcher to embed the given loop, which must be
		1554	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1555	invoked automatically, otherwise it is the responsibility of the callback
		1556	to invoke it (it will continue to be called until the sweep has been done,
		1557	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1558	</dd>
		1559	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1560	<dd>
		1561	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1562	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1563	apropriate way for embedded loops.</p>
		1564	</dd>
		1565	<dt>struct ev_loop *loop [read-only]</dt>
		1566	<dd>
		1567	<p>The embedded event loop.</p>
		1568	</dd>
		1569	</dl>
		1570
		1571
		1572
		1573
		1574
		1575	</div>
		1576	<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>
		1577	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1578	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1579	whoever is a good citizen cared to tell libev about it by calling
		1580	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1581	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1582	and only in the child after the fork. If whoever good citizen calling
		1583	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1584	handlers will be invoked, too, of course.</p>
		1585	<dl>
		1586	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1587	<dd>
		1588	<p>Initialises and configures the fork watcher - it has no parameters of any
		1589	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1590	believe me.</p>
		1591	</dd>
		1592	</dl>
		1593
		1594
		1595
		1596
		1597
		1598	</div>
		1599	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
665	<div id="OTHER_FUNCTIONS_CONTENT">	1600	<div id="OTHER_FUNCTIONS_CONTENT">
666	<p>There are some other fucntions of possible interest. Described. Here. Now.</p>	1601	<p>There are some other functions of possible interest. Described. Here. Now.</p>
667	<dl>	1602	<dl>
668	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1603	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
669	<dd>	1604	<dd>
670	<p>This function combines a simple timer and an I/O watcher, calls your	1605	<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	1606	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	1607	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	1608	or timeout without having to allocate/configure/start/stop/free one or
674	more watchers yourself.</p>	1609	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	1610	<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	1611	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
677	will be craeted and started.</p>	1612	<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	1613	<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	1614	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
680	= 0) will be started.</p>	1615	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
		1616	dubious value.</p>
681	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and	1617	<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,	1618	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>	1619	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
		1620	value passed to <code>ev_once</code>:</p>
684	<pre> static void stdin_ready (int revents, void *arg)	1621	<pre> static void stdin_ready (int revents, void *arg)
685	{	1622	{
686	if (revents & EV_TIMEOUT)	1623	if (revents & EV_TIMEOUT)
687	/* doh, nothing entered */	1624	/* doh, nothing entered */;
688	else if (revents & EV_READ)	1625	else if (revents & EV_READ)
689	/* stdin might have data for us, joy! */	1626	/* stdin might have data for us, joy! */;
690	}	1627	}
691		1628
692	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1629	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
693		1630
694	</pre>	1631	</pre>
695	</dd>	1632	</dd>
696	<dt>ev_feed_event (loop, watcher, int events)</dt>	1633	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
697	<dd>	1634	<dd>
698	<p>Feeds the given event set into the event loop, as if the specified event	1635	<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	1636	had happened for the specified watcher (which must be a pointer to an
700	initialised but not necessarily active event watcher).</p>	1637	initialised but not necessarily started event watcher).</p>
701	</dd>	1638	</dd>
702	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1639	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
703	<dd>	1640	<dd>
704	<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>	1641	<p>Feed an event on the given fd, as if a file descriptor backend detected
		1642	the given events it.</p>
705	</dd>	1643	</dd>
706	<dt>ev_feed_signal_event (loop, int signum)</dt>	1644	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
707	<dd>	1645	<dd>
708	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1646	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1647	loop!).</p>
709	</dd>	1648	</dd>
710	</dl>	1649	</dl>
711		1650
		1651
		1652
		1653
		1654
712	</div>	1655	</div>
713	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1656	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1657	<div id="LIBEVENT_EMULATION_CONTENT">
		1658	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1659	emulate the internals of libevent, so here are some usage hints:</p>
		1660	<dl>
		1661	<dt>* Use it by including <event.h>, as usual.</dt>
		1662	<dt>* The following members are fully supported: ev_base, ev_callback,
		1663	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1664	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1665	maintained by libev, it does not work exactly the same way as in libevent (consider
		1666	it a private API).</dt>
		1667	<dt>* Priorities are not currently supported. Initialising priorities
		1668	will fail and all watchers will have the same priority, even though there
		1669	is an ev_pri field.</dt>
		1670	<dt>* Other members are not supported.</dt>
		1671	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1672	to use the libev header file and library.</dt>
		1673	</dl>
		1674
		1675	</div>
		1676	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1677	<div id="C_SUPPORT_CONTENT">
		1678	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1679	you to use some convinience methods to start/stop watchers and also change
		1680	the callback model to a model using method callbacks on objects.</p>
		1681	<p>To use it,</p>
		1682	<pre> #include <ev++.h>
		1683
		1684	</pre>
		1685	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1686	and puts all of its definitions (many of them macros) into the global
		1687	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1688	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1689	<code>EV_MULTIPLICITY</code>.</p>
		1690	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1691	<dl>
		1692	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1693	<dd>
		1694	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1695	macros from <cite>ev.h</cite>.</p>
		1696	</dd>
		1697	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1698	<dd>
		1699	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1700	</dd>
		1701	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1702	<dd>
		1703	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1704	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1705	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1706	defines by many implementations.</p>
		1707	<p>All of those classes have these methods:</p>
		1708	<p>
		1709	<dl>
		1710	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1711	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1712	<dt>ev::TYPE::~TYPE</dt>
		1713	<dd>
		1714	<p>The constructor takes a pointer to an object and a method pointer to
		1715	the event handler callback to call in this class. The constructor calls
		1716	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1717	before starting it. If you do not specify a loop then the constructor
		1718	automatically associates the default loop with this watcher.</p>
		1719	<p>The destructor automatically stops the watcher if it is active.</p>
		1720	</dd>
		1721	<dt>w->set (struct ev_loop *)</dt>
		1722	<dd>
		1723	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1724	do this when the watcher is inactive (and not pending either).</p>
		1725	</dd>
		1726	<dt>w->set ([args])</dt>
		1727	<dd>
		1728	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1729	called at least once. Unlike the C counterpart, an active watcher gets
		1730	automatically stopped and restarted.</p>
		1731	</dd>
		1732	<dt>w->start ()</dt>
		1733	<dd>
		1734	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1735	constructor already takes the loop.</p>
		1736	</dd>
		1737	<dt>w->stop ()</dt>
		1738	<dd>
		1739	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1740	</dd>
		1741	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1742	<dd>
		1743	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1744	<code>ev_TYPE_again</code> function.</p>
		1745	</dd>
		1746	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1747	<dd>
		1748	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1749	</dd>
		1750	<dt>w->update () <code>ev::stat</code> only</dt>
		1751	<dd>
		1752	<p>Invokes <code>ev_stat_stat</code>.</p>
		1753	</dd>
		1754	</dl>
		1755	</p>
		1756	</dd>
		1757	</dl>
		1758	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1759	the constructor.</p>
		1760	<pre> class myclass
		1761	{
		1762	ev_io io; void io_cb (ev::io &w, int revents);
		1763	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1764
		1765	myclass ();
		1766	}
		1767
		1768	myclass::myclass (int fd)
		1769	: io (this, &myclass::io_cb),
		1770	idle (this, &myclass::idle_cb)
		1771	{
		1772	io.start (fd, ev::READ);
		1773	}
		1774
		1775
		1776
		1777
		1778	</pre>
		1779
		1780	</div>
		1781	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		1782	<div id="MACRO_MAGIC_CONTENT">
		1783	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1784	<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
		1785	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1786	<p>To make it easier to write programs that cope with either variant, the
		1787	following macros are defined:</p>
		1788	<dl>
		1789	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		1790	<dd>
		1791	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		1792	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		1793	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		1794	<pre> ev_unref (EV_A);
		1795	ev_timer_add (EV_A_ watcher);
		1796	ev_loop (EV_A_ 0);
		1797
		1798	</pre>
		1799	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		1800	which is often provided by the following macro.</p>
		1801	</dd>
		1802	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		1803	<dd>
		1804	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		1805	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		1806	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		1807	<pre> // this is how ev_unref is being declared
		1808	static void ev_unref (EV_P);
		1809
		1810	// this is how you can declare your typical callback
		1811	static void cb (EV_P_ ev_timer *w, int revents)
		1812
		1813	</pre>
		1814	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		1815	suitable for use with <code>EV_A</code>.</p>
		1816	</dd>
		1817	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		1818	<dd>
		1819	<p>Similar to the other two macros, this gives you the value of the default
		1820	loop, if multiple loops are supported ("ev loop default").</p>
		1821	</dd>
		1822	</dl>
		1823	<p>Example: Declare and initialise a check watcher, working regardless of
		1824	wether multiple loops are supported or not.</p>
		1825	<pre> static void
		1826	check_cb (EV_P_ ev_timer *w, int revents)
		1827	{
		1828	ev_check_stop (EV_A_ w);
		1829	}
		1830
		1831	ev_check check;
		1832	ev_check_init (&check, check_cb);
		1833	ev_check_start (EV_DEFAULT_ &check);
		1834	ev_loop (EV_DEFAULT_ 0);
		1835
		1836
		1837
		1838
		1839	</pre>
		1840
		1841	</div>
		1842	<h1 id="EMBEDDING">EMBEDDING</h1>
		1843	<div id="EMBEDDING_CONTENT">
		1844	<p>Libev can (and often is) directly embedded into host
		1845	applications. Examples of applications that embed it include the Deliantra
		1846	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1847	and rxvt-unicode.</p>
		1848	<p>The goal is to enable you to just copy the neecssary files into your
		1849	source directory without having to change even a single line in them, so
		1850	you can easily upgrade by simply copying (or having a checked-out copy of
		1851	libev somewhere in your source tree).</p>
		1852
		1853	</div>
		1854	<h2 id="FILESETS">FILESETS</h2>
		1855	<div id="FILESETS_CONTENT">
		1856	<p>Depending on what features you need you need to include one or more sets of files
		1857	in your app.</p>
		1858
		1859	</div>
		1860	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1861	<div id="CORE_EVENT_LOOP_CONTENT">
		1862	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1863	configuration (no autoconf):</p>
		1864	<pre> #define EV_STANDALONE 1
		1865	#include "ev.c"
		1866
		1867	</pre>
		1868	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1869	single C source file only to provide the function implementations. To use
		1870	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1871	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1872	where you can put other configuration options):</p>
		1873	<pre> #define EV_STANDALONE 1
		1874	#include "ev.h"
		1875
		1876	</pre>
		1877	<p>Both header files and implementation files can be compiled with a C++
		1878	compiler (at least, thats a stated goal, and breakage will be treated
		1879	as a bug).</p>
		1880	<p>You need the following files in your source tree, or in a directory
		1881	in your include path (e.g. in libev/ when using -Ilibev):</p>
		1882	<pre> ev.h
		1883	ev.c
		1884	ev_vars.h
		1885	ev_wrap.h
		1886
		1887	ev_win32.c required on win32 platforms only
		1888
		1889	ev_select.c only when select backend is enabled (which is by default)
		1890	ev_poll.c only when poll backend is enabled (disabled by default)
		1891	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1892	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1893	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1894
		1895	</pre>
		1896	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		1897	to compile this single file.</p>
		1898
		1899	</div>
		1900	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		1901	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		1902	<p>To include the libevent compatibility API, also include:</p>
		1903	<pre> #include "event.c"
		1904
		1905	</pre>
		1906	<p>in the file including <cite>ev.c</cite>, and:</p>
		1907	<pre> #include "event.h"
		1908
		1909	</pre>
		1910	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		1911	<p>You need the following additional files for this:</p>
		1912	<pre> event.h
		1913	event.c
		1914
		1915	</pre>
		1916
		1917	</div>
		1918	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		1919	<div id="AUTOCONF_SUPPORT_CONTENT">
		1920	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		1921	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		1922	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		1923	include <cite>config.h</cite> and configure itself accordingly.</p>
		1924	<p>For this of course you need the m4 file:</p>
		1925	<pre> libev.m4
		1926
		1927	</pre>
		1928
		1929	</div>
		1930	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		1931	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		1932	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		1933	before including any of its files. The default is not to build for multiplicity
		1934	and only include the select backend.</p>
		1935	<dl>
		1936	<dt>EV_STANDALONE</dt>
		1937	<dd>
		1938	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		1939	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		1940	implementations for some libevent functions (such as logging, which is not
		1941	supported). It will also not define any of the structs usually found in
		1942	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		1943	</dd>
		1944	<dt>EV_USE_MONOTONIC</dt>
		1945	<dd>
		1946	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1947	monotonic clock option at both compiletime and runtime. Otherwise no use
		1948	of the monotonic clock option will be attempted. If you enable this, you
		1949	usually have to link against librt or something similar. Enabling it when
		1950	the functionality isn't available is safe, though, althoguh you have
		1951	to make sure you link against any libraries where the <code>clock_gettime</code>
		1952	function is hiding in (often <cite>-lrt</cite>).</p>
		1953	</dd>
		1954	<dt>EV_USE_REALTIME</dt>
		1955	<dd>
		1956	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1957	realtime clock option at compiletime (and assume its availability at
		1958	runtime if successful). Otherwise no use of the realtime clock option will
		1959	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		1960	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		1961	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		1962	</dd>
		1963	<dt>EV_USE_SELECT</dt>
		1964	<dd>
		1965	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		1966	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		1967	other method takes over, select will be it. Otherwise the select backend
		1968	will not be compiled in.</p>
		1969	</dd>
		1970	<dt>EV_SELECT_USE_FD_SET</dt>
		1971	<dd>
		1972	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		1973	structure. This is useful if libev doesn't compile due to a missing
		1974	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		1975	exotic systems. This usually limits the range of file descriptors to some
		1976	low limit such as 1024 or might have other limitations (winsocket only
		1977	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		1978	influence the size of the <code>fd_set</code> used.</p>
		1979	</dd>
		1980	<dt>EV_SELECT_IS_WINSOCKET</dt>
		1981	<dd>
		1982	<p>When defined to <code>1</code>, the select backend will assume that
		1983	select/socket/connect etc. don't understand file descriptors but
		1984	wants osf handles on win32 (this is the case when the select to
		1985	be used is the winsock select). This means that it will call
		1986	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		1987	it is assumed that all these functions actually work on fds, even
		1988	on win32. Should not be defined on non-win32 platforms.</p>
		1989	</dd>
		1990	<dt>EV_USE_POLL</dt>
		1991	<dd>
		1992	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		1993	backend. Otherwise it will be enabled on non-win32 platforms. It
		1994	takes precedence over select.</p>
		1995	</dd>
		1996	<dt>EV_USE_EPOLL</dt>
		1997	<dd>
		1998	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		1999	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2000	otherwise another method will be used as fallback. This is the
		2001	preferred backend for GNU/Linux systems.</p>
		2002	</dd>
		2003	<dt>EV_USE_KQUEUE</dt>
		2004	<dd>
		2005	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2006	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2007	otherwise another method will be used as fallback. This is the preferred
		2008	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2009	supports some types of fds correctly (the only platform we found that
		2010	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2011	not be used unless explicitly requested. The best way to use it is to find
		2012	out whether kqueue supports your type of fd properly and use an embedded
		2013	kqueue loop.</p>
		2014	</dd>
		2015	<dt>EV_USE_PORT</dt>
		2016	<dd>
		2017	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2018	10 port style backend. Its availability will be detected at runtime,
		2019	otherwise another method will be used as fallback. This is the preferred
		2020	backend for Solaris 10 systems.</p>
		2021	</dd>
		2022	<dt>EV_USE_DEVPOLL</dt>
		2023	<dd>
		2024	<p>reserved for future expansion, works like the USE symbols above.</p>
		2025	</dd>
		2026	<dt>EV_USE_INOTIFY</dt>
		2027	<dd>
		2028	<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
		2029	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2030	be detected at runtime.</p>
		2031	</dd>
		2032	<dt>EV_H</dt>
		2033	<dd>
		2034	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2035	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2036	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2037	</dd>
		2038	<dt>EV_CONFIG_H</dt>
		2039	<dd>
		2040	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2041	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2042	<code>EV_H</code>, above.</p>
		2043	</dd>
		2044	<dt>EV_EVENT_H</dt>
		2045	<dd>
		2046	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2047	of how the <cite>event.h</cite> header can be found.</p>
		2048	</dd>
		2049	<dt>EV_PROTOTYPES</dt>
		2050	<dd>
		2051	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2052	prototypes, but still define all the structs and other symbols. This is
		2053	occasionally useful if you want to provide your own wrapper functions
		2054	around libev functions.</p>
		2055	</dd>
		2056	<dt>EV_MULTIPLICITY</dt>
		2057	<dd>
		2058	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2059	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2060	additional independent event loops. Otherwise there will be no support
		2061	for multiple event loops and there is no first event loop pointer
		2062	argument. Instead, all functions act on the single default loop.</p>
		2063	</dd>
		2064	<dt>EV_PERIODIC_ENABLE</dt>
		2065	<dd>
		2066	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2067	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2068	code.</p>
		2069	</dd>
		2070	<dt>EV_EMBED_ENABLE</dt>
		2071	<dd>
		2072	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2073	defined to be <code>0</code>, then they are not.</p>
		2074	</dd>
		2075	<dt>EV_STAT_ENABLE</dt>
		2076	<dd>
		2077	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2078	defined to be <code>0</code>, then they are not.</p>
		2079	</dd>
		2080	<dt>EV_FORK_ENABLE</dt>
		2081	<dd>
		2082	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2083	defined to be <code>0</code>, then they are not.</p>
		2084	</dd>
		2085	<dt>EV_MINIMAL</dt>
		2086	<dd>
		2087	<p>If you need to shave off some kilobytes of code at the expense of some
		2088	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2089	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2090	</dd>
		2091	<dt>EV_PID_HASHSIZE</dt>
		2092	<dd>
		2093	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2094	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2095	than enough. If you need to manage thousands of children you might want to
		2096	increase this value (<i>must</i> be a power of two).</p>
		2097	</dd>
		2098	<dt>EV_INOTIFY_HASHSIZE</dt>
		2099	<dd>
		2100	<p><code>ev_staz</code> watchers use a small hash table to distribute workload by
		2101	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2102	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2103	watchers you might want to increase this value (<i>must</i> be a power of
		2104	two).</p>
		2105	</dd>
		2106	<dt>EV_COMMON</dt>
		2107	<dd>
		2108	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2109	this macro to a something else you can include more and other types of
		2110	members. You have to define it each time you include one of the files,
		2111	though, and it must be identical each time.</p>
		2112	<p>For example, the perl EV module uses something like this:</p>
		2113	<pre> #define EV_COMMON \
		2114	SV self; / contains this struct */ \
		2115	SV cb_sv, fh /* note no trailing ";" */
		2116
		2117	</pre>
		2118	</dd>
		2119	<dt>EV_CB_DECLARE (type)</dt>
		2120	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2121	<dt>ev_set_cb (ev, cb)</dt>
		2122	<dd>
		2123	<p>Can be used to change the callback member declaration in each watcher,
		2124	and the way callbacks are invoked and set. Must expand to a struct member
		2125	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2126	their default definitions. One possible use for overriding these is to
		2127	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2128	method calls instead of plain function calls in C++.</p>
		2129
		2130	</div>
		2131	<h2 id="EXAMPLES">EXAMPLES</h2>
		2132	<div id="EXAMPLES_CONTENT">
		2133	<p>For a real-world example of a program the includes libev
		2134	verbatim, you can have a look at the EV perl module
		2135	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2136	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2137	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2138	will be compiled. It is pretty complex because it provides its own header
		2139	file.</p>
		2140	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2141	that everybody includes and which overrides some autoconf choices:</p>
		2142	<pre> #define EV_USE_POLL 0
		2143	#define EV_MULTIPLICITY 0
		2144	#define EV_PERIODICS 0
		2145	#define EV_CONFIG_H <config.h>
		2146
		2147	#include "ev++.h"
		2148
		2149	</pre>
		2150	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2151	<pre> #include "ev_cpp.h"
		2152	#include "ev.c"
		2153
		2154
		2155
		2156
		2157	</pre>
		2158
		2159	</div>
		2160	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2161	<div id="COMPLEXITIES_CONTENT">
		2162	<p>In this section the complexities of (many of) the algorithms used inside
		2163	libev will be explained. For complexity discussions about backends see the
		2164	documentation for <code>ev_default_init</code>.</p>
		2165	<p>
		2166	<dl>
		2167	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2168	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2169	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2170	<dt>Stopping check/prepare/idle watchers: O(1)</dt>
		2171	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
		2172	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2173	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2174	<dt>Activating one watcher: O(1)</dt>
		2175	</dl>
		2176	</p>
		2177
		2178
		2179
		2180
		2181
		2182	</div>
		2183	<h1 id="AUTHOR">AUTHOR</h1>
714	<div id="AUTHOR_CONTENT">	2184	<div id="AUTHOR_CONTENT">
715	<p>Marc Lehmann <libev@schmorp.de>.</p>	2185	<p>Marc Lehmann <libev@schmorp.de>.</p>
716		2186
717	</div>	2187	</div>
718	</div></body>	2188	</div></body>
719	</html>	2189	</html>

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Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC