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4	<head>	4	<head>
5	<title>libev</title>	5	<title>libev</title>
6	<meta name="description" content="Pod documentation for libev" />	6	<meta name="description" content="Pod documentation for libev" />
7	<meta name="inputfile" content="<standard input>" />	7	<meta name="inputfile" content="<standard input>" />
8	<meta name="outputfile" content="<standard output>" />	8	<meta name="outputfile" content="<standard output>" />
9	<meta name="created" content="Mon Nov 12 09:58:24 2007" />	9	<meta name="created" content="Sun Dec 9 20:30:11 2007" />
10	<meta name="generator" content="Pod::Xhtml 1.57" />	10	<meta name="generator" content="Pod::Xhtml 1.57" />
11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>	11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
15	<h3 id="TOP">Index</h3>	15	<h3 id="TOP">Index</h3>
16		16
17	<ul><li><a href="#NAME">NAME</a></li>	17	<ul><li><a href="#NAME">NAME</a></li>
18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>	18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
		19	<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>	20	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20	<li><a href="#FEATURES">FEATURES</a></li>	21	<li><a href="#FEATURES">FEATURES</a></li>
21	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>	22	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>	23	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>	24	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>	25	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>	26	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
		27	<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
26	<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>	28	<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27	</ul>	29	</ul>
28	</li>	30	</li>
29	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>	31	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
30	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>	32	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
31	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>	33	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
32	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>	34	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
33	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>	35	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
34	<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>	36	<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
		37	<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
35	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>	38	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
36	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>	39	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
		40	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
		41	<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
37	</ul>	42	</ul>
38	</li>	43	</li>
39	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	44	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		45	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		46	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		47	<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
		48	<li><a href="#EMBEDDING">EMBEDDING</a>
		49	<ul><li><a href="#FILESETS">FILESETS</a>
		50	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		51	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		52	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		53	</ul>
		54	</li>
		55	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		56	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		57	</ul>
		58	</li>
		59	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
40	<li><a href="#AUTHOR">AUTHOR</a>	60	<li><a href="#AUTHOR">AUTHOR</a>
41	</li>	61	</li>
42	</ul><hr />	62	</ul><hr />
43	<!-- INDEX END -->	63	<!-- INDEX END -->
44		64
45	<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>	65	<h1 id="NAME">NAME</h1>
46	<div id="NAME_CONTENT">	66	<div id="NAME_CONTENT">
47	<p>libev - a high performance full-featured event loop written in C</p>	67	<p>libev - a high performance full-featured event loop written in C</p>
48		68
49	</div>	69	</div>
50	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>	70	<h1 id="SYNOPSIS">SYNOPSIS</h1>
51	<div id="SYNOPSIS_CONTENT">	71	<div id="SYNOPSIS_CONTENT">
52	<pre> #include <ev.h>	72	<pre> #include <ev.h>
53		73
54	</pre>	74	</pre>
55		75
56	</div>	76	</div>
57	<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>	77	<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
		78	<div id="EXAMPLE_PROGRAM_CONTENT">
		79	<pre> #include <ev.h>
		80
		81	ev_io stdin_watcher;
		82	ev_timer timeout_watcher;
		83
		84	/* called when data readable on stdin */
		85	static void
		86	stdin_cb (EV_P_ struct ev_io *w, int revents)
		87	{
		88	/* puts ("stdin ready"); */
		89	ev_io_stop (EV_A_ w); /* just a syntax example */
		90	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		91	}
		92
		93	static void
		94	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		95	{
		96	/* puts ("timeout"); */
		97	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		98	}
		99
		100	int
		101	main (void)
		102	{
		103	struct ev_loop *loop = ev_default_loop (0);
		104
		105	/* initialise an io watcher, then start it */
		106	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		107	ev_io_start (loop, &stdin_watcher);
		108
		109	/* simple non-repeating 5.5 second timeout */
		110	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		111	ev_timer_start (loop, &timeout_watcher);
		112
		113	/* loop till timeout or data ready */
		114	ev_loop (loop, 0);
		115
		116	return 0;
		117	}
		118
		119	</pre>
		120
		121	</div>
		122	<h1 id="DESCRIPTION">DESCRIPTION</h1>
58	<div id="DESCRIPTION_CONTENT">	123	<div id="DESCRIPTION_CONTENT">
		124	<p>The newest version of this document is also available as a html-formatted
		125	web page you might find easier to navigate when reading it for the first
		126	time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
59	<p>Libev is an event loop: you register interest in certain events (such as a	127	<p>Libev is an event loop: you register interest in certain events (such as a
60	file descriptor being readable or a timeout occuring), and it will manage	128	file descriptor being readable or a timeout occuring), and it will manage
61	these event sources and provide your program with events.</p>	129	these event sources and provide your program with events.</p>
62	<p>To do this, it must take more or less complete control over your process	130	<p>To do this, it must take more or less complete control over your process
63	(or thread) by executing the <i>event loop</i> handler, and will then	131	(or thread) by executing the <i>event loop</i> handler, and will then
…		…
66	watchers</i>, which are relatively small C structures you initialise with the	134	watchers</i>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by <i>starting</i> the	135	details of the event, and then hand it over to libev by <i>starting</i> the
68	watcher.</p>	136	watcher.</p>
69		137
70	</div>	138	</div>
71	<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>	139	<h1 id="FEATURES">FEATURES</h1>
72	<div id="FEATURES_CONTENT">	140	<div id="FEATURES_CONTENT">
73	<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific	141	<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
74	kqueue mechanisms for file descriptor events, relative timers, absolute	142	BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
75	timers with customised rescheduling, signal events, process status change	143	for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
76	events (related to SIGCHLD), and event watchers dealing with the event	144	(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
77	loop mechanism itself (idle, prepare and check watchers). It also is quite	145	with customised rescheduling (<code>ev_periodic</code>), synchronous signals
		146	(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
		147	watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
		148	<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
		149	file watchers (<code>ev_stat</code>) and even limited support for fork events
		150	(<code>ev_fork</code>).</p>
		151	<p>It also is quite fast (see this
78	fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing	152	<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
79	it to libevent for example).</p>	153	for example).</p>
80		154
81	</div>	155	</div>
82	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	156	<h1 id="CONVENTIONS">CONVENTIONS</h1>
83	<div id="CONVENTIONS_CONTENT">	157	<div id="CONVENTIONS_CONTENT">
84	<p>Libev is very configurable. In this manual the default configuration	158	<p>Libev is very configurable. In this manual the default configuration will
85	will be described, which supports multiple event loops. For more info	159	be described, which supports multiple event loops. For more info about
86	about various configuration options please have a look at the file	160	various configuration options please have a look at <strong>EMBED</strong> section in
87	<cite>README.embed</cite> in the libev distribution. If libev was configured without	161	this manual. If libev was configured without support for multiple event
88	support for multiple event loops, then all functions taking an initial	162	loops, then all functions taking an initial argument of name <code>loop</code>
89	argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)	163	(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
90	will not have this argument.</p>
91		164
92	</div>	165	</div>
93	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>	166	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
94	<div id="TIME_REPRESENTATION_CONTENT">	167	<div id="TIME_REPRESENTATION_CONTENT">
95	<p>Libev represents time as a single floating point number, representing the	168	<p>Libev represents time as a single floating point number, representing the
96	(fractional) number of seconds since the (POSIX) epoch (somewhere near	169	(fractional) number of seconds since the (POSIX) epoch (somewhere near
97	the beginning of 1970, details are complicated, don't ask). This type is	170	the beginning of 1970, details are complicated, don't ask). This type is
98	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	171	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
99	to the double type in C.</p>	172	to the <code>double</code> type in C, and when you need to do any calculations on
		173	it, you should treat it as such.</p>
100		174
101	</div>	175	</div>
102	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	176	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
103	<div id="GLOBAL_FUNCTIONS_CONTENT">	177	<div id="GLOBAL_FUNCTIONS_CONTENT">
		178	<p>These functions can be called anytime, even before initialising the
		179	library in any way.</p>
104	<dl>	180	<dl>
105	<dt>ev_tstamp ev_time ()</dt>	181	<dt>ev_tstamp ev_time ()</dt>
106	<dd>	182	<dd>
107	<p>Returns the current time as libev would use it.</p>	183	<p>Returns the current time as libev would use it. Please note that the
		184	<code>ev_now</code> function is usually faster and also often returns the timestamp
		185	you actually want to know.</p>
108	</dd>	186	</dd>
109	<dt>int ev_version_major ()</dt>	187	<dt>int ev_version_major ()</dt>
110	<dt>int ev_version_minor ()</dt>	188	<dt>int ev_version_minor ()</dt>
111	<dd>	189	<dd>
112	<p>You can find out the major and minor version numbers of the library	190	<p>You can find out the major and minor version numbers of the library
…		…
116	version of the library your program was compiled against.</p>	194	version of the library your program was compiled against.</p>
117	<p>Usually, it's a good idea to terminate if the major versions mismatch,	195	<p>Usually, it's a good idea to terminate if the major versions mismatch,
118	as this indicates an incompatible change. Minor versions are usually	196	as this indicates an incompatible change. Minor versions are usually
119	compatible to older versions, so a larger minor version alone is usually	197	compatible to older versions, so a larger minor version alone is usually
120	not a problem.</p>	198	not a problem.</p>
		199	<p>Example: Make sure we haven't accidentally been linked against the wrong
		200	version.</p>
		201	<pre> assert (("libev version mismatch",
		202	ev_version_major () == EV_VERSION_MAJOR
		203	&& ev_version_minor () >= EV_VERSION_MINOR));
		204
		205	</pre>
		206	</dd>
		207	<dt>unsigned int ev_supported_backends ()</dt>
		208	<dd>
		209	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		210	value) compiled into this binary of libev (independent of their
		211	availability on the system you are running on). See <code>ev_default_loop</code> for
		212	a description of the set values.</p>
		213	<p>Example: make sure we have the epoll method, because yeah this is cool and
		214	a must have and can we have a torrent of it please!!!11</p>
		215	<pre> assert (("sorry, no epoll, no sex",
		216	ev_supported_backends () & EVBACKEND_EPOLL));
		217
		218	</pre>
		219	</dd>
		220	<dt>unsigned int ev_recommended_backends ()</dt>
		221	<dd>
		222	<p>Return the set of all backends compiled into this binary of libev and also
		223	recommended for this platform. This set is often smaller than the one
		224	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		225	most BSDs and will not be autodetected unless you explicitly request it
		226	(assuming you know what you are doing). This is the set of backends that
		227	libev will probe for if you specify no backends explicitly.</p>
		228	</dd>
		229	<dt>unsigned int ev_embeddable_backends ()</dt>
		230	<dd>
		231	<p>Returns the set of backends that are embeddable in other event loops. This
		232	is the theoretical, all-platform, value. To find which backends
		233	might be supported on the current system, you would need to look at
		234	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		235	recommended ones.</p>
		236	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
121	</dd>	237	</dd>
122	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	238	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
123	<dd>	239	<dd>
124	<p>Sets the allocation function to use (the prototype is similar to the	240	<p>Sets the allocation function to use (the prototype is similar - the
125	realloc C function, the semantics are identical). It is used to allocate	241	semantics is identical - to the realloc C function). It is used to
126	and free memory (no surprises here). If it returns zero when memory	242	allocate and free memory (no surprises here). If it returns zero when
127	needs to be allocated, the library might abort or take some potentially	243	memory needs to be allocated, the library might abort or take some
128	destructive action. The default is your system realloc function.</p>	244	potentially destructive action. The default is your system realloc
		245	function.</p>
129	<p>You could override this function in high-availability programs to, say,	246	<p>You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	247	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.</p>	248	or even to sleep a while and retry until some memory is available.</p>
		249	<p>Example: Replace the libev allocator with one that waits a bit and then
		250	retries).</p>
		251	<pre> static void *
		252	persistent_realloc (void *ptr, size_t size)
		253	{
		254	for (;;)
		255	{
		256	void *newptr = realloc (ptr, size);
		257
		258	if (newptr)
		259	return newptr;
		260
		261	sleep (60);
		262	}
		263	}
		264
		265	...
		266	ev_set_allocator (persistent_realloc);
		267
		268	</pre>
132	</dd>	269	</dd>
133	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	270	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
134	<dd>	271	<dd>
135	<p>Set the callback function to call on a retryable syscall error (such	272	<p>Set the callback function to call on a retryable syscall error (such
136	as failed select, poll, epoll_wait). The message is a printable string	273	as failed select, poll, epoll_wait). The message is a printable string
137	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
138	callback is set, then libev will expect it to remedy the sitution, no	275	callback is set, then libev will expect it to remedy the sitution, no
139	matter what, when it returns. That is, libev will generally retry the	276	matter what, when it returns. That is, libev will generally retry the
140	requested operation, or, if the condition doesn't go away, do bad stuff	277	requested operation, or, if the condition doesn't go away, do bad stuff
141	(such as abort).</p>	278	(such as abort).</p>
		279	<p>Example: This is basically the same thing that libev does internally, too.</p>
		280	<pre> static void
		281	fatal_error (const char *msg)
		282	{
		283	perror (msg);
		284	abort ();
		285	}
		286
		287	...
		288	ev_set_syserr_cb (fatal_error);
		289
		290	</pre>
142	</dd>	291	</dd>
143	</dl>	292	</dl>
144		293
145	</div>	294	</div>
146	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	295	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
147	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	296	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
148	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two	297	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
149	types of such loops, the <i>default</i> loop, which supports signals and child	298	types of such loops, the <i>default</i> loop, which supports signals and child
150	events, and dynamically created loops which do not.</p>	299	events, and dynamically created loops which do not.</p>
151	<p>If you use threads, a common model is to run the default event loop	300	<p>If you use threads, a common model is to run the default event loop
…		…
158	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	307	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159	<dd>	308	<dd>
160	<p>This will initialise the default event loop if it hasn't been initialised	309	<p>This will initialise the default event loop if it hasn't been initialised
161	yet and return it. If the default loop could not be initialised, returns	310	yet and return it. If the default loop could not be initialised, returns
162	false. If it already was initialised it simply returns it (and ignores the	311	false. If it already was initialised it simply returns it (and ignores the
163	flags).</p>	312	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
164	<p>If you don't know what event loop to use, use the one returned from this	313	<p>If you don't know what event loop to use, use the one returned from this
165	function.</p>	314	function.</p>
166	<p>The flags argument can be used to specify special behaviour or specific	315	<p>The flags argument can be used to specify special behaviour or specific
167	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>	316	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
168	<p>It supports the following flags:</p>	317	<p>The following flags are supported:</p>
169	<p>	318	<p>
170	<dl>	319	<dl>
171	<dt><code>EVFLAG_AUTO</code></dt>	320	<dt><code>EVFLAG_AUTO</code></dt>
172	<dd>	321	<dd>
173	<p>The default flags value. Use this if you have no clue (it's the right	322	<p>The default flags value. Use this if you have no clue (it's the right
…		…
180	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will	329	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181	override the flags completely if it is found in the environment. This is	330	override the flags completely if it is found in the environment. This is
182	useful to try out specific backends to test their performance, or to work	331	useful to try out specific backends to test their performance, or to work
183	around bugs.</p>	332	around bugs.</p>
184	</dd>	333	</dd>
185	<dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>	334	<dt><code>EVFLAG_FORKCHECK</code></dt>
186	<dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>	335	<dd>
187	<dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>	336	<p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
188	<dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>	337	a fork, you can also make libev check for a fork in each iteration by
189	<dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>	338	enabling this flag.</p>
190	<dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>	339	<p>This works by calling <code>getpid ()</code> on every iteration of the loop,
		340	and thus this might slow down your event loop if you do a lot of loop
		341	iterations and little real work, but is usually not noticeable (on my
		342	Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
		343	without a syscall and thus <i>very</i> fast, but my Linux system also has
		344	<code>pthread_atfork</code> which is even faster).</p>
		345	<p>The big advantage of this flag is that you can forget about fork (and
		346	forget about forgetting to tell libev about forking) when you use this
		347	flag.</p>
		348	<p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
		349	environment variable.</p>
191	<dd>	350	</dd>
192	<p>If one or more of these are ored into the flags value, then only these	351	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
193	backends will be tried (in the reverse order as given here). If one are	352	<dd>
194	specified, any backend will do.</p>	353	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
		354	libev tries to roll its own fd_set with no limits on the number of fds,
		355	but if that fails, expect a fairly low limit on the number of fds when
		356	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		357	the fastest backend for a low number of fds.</p>
		358	</dd>
		359	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		360	<dd>
		361	<p>And this is your standard poll(2) backend. It's more complicated than
		362	select, but handles sparse fds better and has no artificial limit on the
		363	number of fds you can use (except it will slow down considerably with a
		364	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		365	</dd>
		366	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		367	<dd>
		368	<p>For few fds, this backend is a bit little slower than poll and select,
		369	but it scales phenomenally better. While poll and select usually scale like
		370	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		371	either O(1) or O(active_fds).</p>
		372	<p>While stopping and starting an I/O watcher in the same iteration will
		373	result in some caching, there is still a syscall per such incident
		374	(because the fd could point to a different file description now), so its
		375	best to avoid that. Also, dup()ed file descriptors might not work very
		376	well if you register events for both fds.</p>
		377	<p>Please note that epoll sometimes generates spurious notifications, so you
		378	need to use non-blocking I/O or other means to avoid blocking when no data
		379	(or space) is available.</p>
		380	</dd>
		381	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		382	<dd>
		383	<p>Kqueue deserves special mention, as at the time of this writing, it
		384	was broken on all BSDs except NetBSD (usually it doesn't work with
		385	anything but sockets and pipes, except on Darwin, where of course its
		386	completely useless). For this reason its not being "autodetected"
		387	unless you explicitly specify it explicitly in the flags (i.e. using
		388	<code>EVBACKEND_KQUEUE</code>).</p>
		389	<p>It scales in the same way as the epoll backend, but the interface to the
		390	kernel is more efficient (which says nothing about its actual speed, of
		391	course). While starting and stopping an I/O watcher does not cause an
		392	extra syscall as with epoll, it still adds up to four event changes per
		393	incident, so its best to avoid that.</p>
		394	</dd>
		395	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		396	<dd>
		397	<p>This is not implemented yet (and might never be).</p>
		398	</dd>
		399	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		400	<dd>
		401	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		402	it's really slow, but it still scales very well (O(active_fds)).</p>
		403	<p>Please note that solaris ports can result in a lot of spurious
		404	notifications, so you need to use non-blocking I/O or other means to avoid
		405	blocking when no data (or space) is available.</p>
		406	</dd>
		407	<dt><code>EVBACKEND_ALL</code></dt>
		408	<dd>
		409	<p>Try all backends (even potentially broken ones that wouldn't be tried
		410	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		411	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
195	</dd>	412	</dd>
196	</dl>	413	</dl>
197	</p>	414	</p>
		415	<p>If one or more of these are ored into the flags value, then only these
		416	backends will be tried (in the reverse order as given here). If none are
		417	specified, most compiled-in backend will be tried, usually in reverse
		418	order of their flag values :)</p>
		419	<p>The most typical usage is like this:</p>
		420	<pre> if (!ev_default_loop (0))
		421	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		422
		423	</pre>
		424	<p>Restrict libev to the select and poll backends, and do not allow
		425	environment settings to be taken into account:</p>
		426	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		427
		428	</pre>
		429	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		430	available (warning, breaks stuff, best use only with your own private
		431	event loop and only if you know the OS supports your types of fds):</p>
		432	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		433
		434	</pre>
198	</dd>	435	</dd>
199	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	436	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200	<dd>	437	<dd>
201	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	438	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
202	always distinct from the default loop. Unlike the default loop, it cannot	439	always distinct from the default loop. Unlike the default loop, it cannot
203	handle signal and child watchers, and attempts to do so will be greeted by	440	handle signal and child watchers, and attempts to do so will be greeted by
204	undefined behaviour (or a failed assertion if assertions are enabled).</p>	441	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		442	<p>Example: Try to create a event loop that uses epoll and nothing else.</p>
		443	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		444	if (!epoller)
		445	fatal ("no epoll found here, maybe it hides under your chair");
		446
		447	</pre>
205	</dd>	448	</dd>
206	<dt>ev_default_destroy ()</dt>	449	<dt>ev_default_destroy ()</dt>
207	<dd>	450	<dd>
208	<p>Destroys the default loop again (frees all memory and kernel state	451	<p>Destroys the default loop again (frees all memory and kernel state
209	etc.). This stops all registered event watchers (by not touching them in	452	etc.). None of the active event watchers will be stopped in the normal
210	any way whatsoever, although you cannot rely on this :).</p>	453	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		454	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		455	calling this function, or cope with the fact afterwards (which is usually
		456	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		457	for example).</p>
211	</dd>	458	</dd>
212	<dt>ev_loop_destroy (loop)</dt>	459	<dt>ev_loop_destroy (loop)</dt>
213	<dd>	460	<dd>
214	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	461	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
215	earlier call to <code>ev_loop_new</code>.</p>	462	earlier call to <code>ev_loop_new</code>.</p>
…		…
218	<dd>	465	<dd>
219	<p>This function reinitialises the kernel state for backends that have	466	<p>This function reinitialises the kernel state for backends that have
220	one. Despite the name, you can call it anytime, but it makes most sense	467	one. Despite the name, you can call it anytime, but it makes most sense
221	after forking, in either the parent or child process (or both, but that	468	after forking, in either the parent or child process (or both, but that
222	again makes little sense).</p>	469	again makes little sense).</p>
223	<p>You <i>must</i> call this function after forking if and only if you want to	470	<p>You <i>must</i> call this function in the child process after forking if and
224	use the event library in both processes. If you just fork+exec, you don't	471	only if you want to use the event library in both processes. If you just
225	have to call it.</p>	472	fork+exec, you don't have to call it.</p>
226	<p>The function itself is quite fast and it's usually not a problem to call	473	<p>The function itself is quite fast and it's usually not a problem to call
227	it just in case after a fork. To make this easy, the function will fit in	474	it just in case after a fork. To make this easy, the function will fit in
228	quite nicely into a call to <code>pthread_atfork</code>:</p>	475	quite nicely into a call to <code>pthread_atfork</code>:</p>
229	<pre> pthread_atfork (0, 0, ev_default_fork);	476	<pre> pthread_atfork (0, 0, ev_default_fork);
230		477
231	</pre>	478	</pre>
		479	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		480	without calling this function, so if you force one of those backends you
		481	do not need to care.</p>
232	</dd>	482	</dd>
233	<dt>ev_loop_fork (loop)</dt>	483	<dt>ev_loop_fork (loop)</dt>
234	<dd>	484	<dd>
235	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	485	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
236	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	486	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
237	after fork, and how you do this is entirely your own problem.</p>	487	after fork, and how you do this is entirely your own problem.</p>
238	</dd>	488	</dd>
239	<dt>unsigned int ev_method (loop)</dt>	489	<dt>unsigned int ev_loop_count (loop)</dt>
		490	<dd>
		491	<p>Returns the count of loop iterations for the loop, which is identical to
		492	the number of times libev did poll for new events. It starts at <code>0</code> and
		493	happily wraps around with enough iterations.</p>
		494	<p>This value can sometimes be useful as a generation counter of sorts (it
		495	"ticks" the number of loop iterations), as it roughly corresponds with
		496	<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
240	<dd>	497	</dd>
		498	<dt>unsigned int ev_backend (loop)</dt>
		499	<dd>
241	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	500	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242	use.</p>	501	use.</p>
243	</dd>	502	</dd>
244	<dt>ev_tstamp ev_now (loop)</dt>	503	<dt>ev_tstamp ev_now (loop)</dt>
245	<dd>	504	<dd>
246	<p>Returns the current "event loop time", which is the time the event loop	505	<p>Returns the current "event loop time", which is the time the event loop
247	got events and started processing them. This timestamp does not change	506	received events and started processing them. This timestamp does not
248	as long as callbacks are being processed, and this is also the base time	507	change as long as callbacks are being processed, and this is also the base
249	used for relative timers. You can treat it as the timestamp of the event	508	time used for relative timers. You can treat it as the timestamp of the
250	occuring (or more correctly, the mainloop finding out about it).</p>	509	event occuring (or more correctly, libev finding out about it).</p>
251	</dd>	510	</dd>
252	<dt>ev_loop (loop, int flags)</dt>	511	<dt>ev_loop (loop, int flags)</dt>
253	<dd>	512	<dd>
254	<p>Finally, this is it, the event handler. This function usually is called	513	<p>Finally, this is it, the event handler. This function usually is called
255	after you initialised all your watchers and you want to start handling	514	after you initialised all your watchers and you want to start handling
256	events.</p>	515	events.</p>
257	<p>If the flags argument is specified as 0, it will not return until either	516	<p>If the flags argument is specified as <code>0</code>, it will not return until
258	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	517	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		518	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		519	relying on all watchers to be stopped when deciding when a program has
		520	finished (especially in interactive programs), but having a program that
		521	automatically loops as long as it has to and no longer by virtue of
		522	relying on its watchers stopping correctly is a thing of beauty.</p>
259	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	523	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
260	those events and any outstanding ones, but will not block your process in	524	those events and any outstanding ones, but will not block your process in
261	case there are no events and will return after one iteration of the loop.</p>	525	case there are no events and will return after one iteration of the loop.</p>
262	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	526	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
263	neccessary) and will handle those and any outstanding ones. It will block	527	neccessary) and will handle those and any outstanding ones. It will block
264	your process until at least one new event arrives, and will return after	528	your process until at least one new event arrives, and will return after
265	one iteration of the loop.</p>	529	one iteration of the loop. This is useful if you are waiting for some
266	<p>This flags value could be used to implement alternative looping	530	external event in conjunction with something not expressible using other
267	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	531	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268	more generic mechanism.</p>	532	usually a better approach for this kind of thing.</p>
		533	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		534	<pre> - Before the first iteration, call any pending watchers.
		535	* If there are no active watchers (reference count is zero), return.
		536	- Queue all prepare watchers and then call all outstanding watchers.
		537	- If we have been forked, recreate the kernel state.
		538	- Update the kernel state with all outstanding changes.
		539	- Update the "event loop time".
		540	- Calculate for how long to block.
		541	- Block the process, waiting for any events.
		542	- Queue all outstanding I/O (fd) events.
		543	- Update the "event loop time" and do time jump handling.
		544	- Queue all outstanding timers.
		545	- Queue all outstanding periodics.
		546	- If no events are pending now, queue all idle watchers.
		547	- Queue all check watchers.
		548	- Call all queued watchers in reverse order (i.e. check watchers first).
		549	Signals and child watchers are implemented as I/O watchers, and will
		550	be handled here by queueing them when their watcher gets executed.
		551	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		552	were used, return, otherwise continue with step *.
		553
		554	</pre>
		555	<p>Example: Queue some jobs and then loop until no events are outsanding
		556	anymore.</p>
		557	<pre> ... queue jobs here, make sure they register event watchers as long
		558	... as they still have work to do (even an idle watcher will do..)
		559	ev_loop (my_loop, 0);
		560	... jobs done. yeah!
		561
		562	</pre>
269	</dd>	563	</dd>
270	<dt>ev_unloop (loop, how)</dt>	564	<dt>ev_unloop (loop, how)</dt>
271	<dd>	565	<dd>
272	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it	566	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273	has processed all outstanding events). The <code>how</code> argument must be either	567	has processed all outstanding events). The <code>how</code> argument must be either
274	<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or	568	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
275	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>	569	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276	</dd>	570	</dd>
277	<dt>ev_ref (loop)</dt>	571	<dt>ev_ref (loop)</dt>
278	<dt>ev_unref (loop)</dt>	572	<dt>ev_unref (loop)</dt>
279	<dd>	573	<dd>
…		…
285	example, libev itself uses this for its internal signal pipe: It is not	579	example, libev itself uses this for its internal signal pipe: It is not
286	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	580	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
287	no event watchers registered by it are active. It is also an excellent	581	no event watchers registered by it are active. It is also an excellent
288	way to do this for generic recurring timers or from within third-party	582	way to do this for generic recurring timers or from within third-party
289	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	583	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		584	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		585	running when nothing else is active.</p>
		586	<pre> struct ev_signal exitsig;
		587	ev_signal_init (&exitsig, sig_cb, SIGINT);
		588	ev_signal_start (loop, &exitsig);
		589	evf_unref (loop);
		590
		591	</pre>
		592	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		593	<pre> ev_ref (loop);
		594	ev_signal_stop (loop, &exitsig);
		595
		596	</pre>
290	</dd>	597	</dd>
291	</dl>	598	</dl>
292		599
		600
		601
		602
		603
293	</div>	604	</div>
294	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	605	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
295	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	606	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
296	<p>A watcher is a structure that you create and register to record your	607	<p>A watcher is a structure that you create and register to record your
297	interest in some event. For instance, if you want to wait for STDIN to	608	interest in some event. For instance, if you want to wait for STDIN to
298	become readable, you would create an <code>ev_io</code> watcher for that:</p>	609	become readable, you would create an <code>ev_io</code> watcher for that:</p>
299	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	610	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
326	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	637	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
327	*)</code>), and you can stop watching for events at any time by calling the	638	*)</code>), and you can stop watching for events at any time by calling the
328	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	639	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
329	<p>As long as your watcher is active (has been started but not stopped) you	640	<p>As long as your watcher is active (has been started but not stopped) you
330	must not touch the values stored in it. Most specifically you must never	641	must not touch the values stored in it. Most specifically you must never
331	reinitialise it or call its set method.</p>	642	reinitialise it or call its <code>set</code> macro.</p>
332	<p>You can check whether an event is active by calling the <code>ev_is_active
333	(watcher *)</code> macro. To see whether an event is outstanding (but the
334	callback for it has not been called yet) you can use the <code>ev_is_pending
335	(watcher *)</code> macro.</p>
336	<p>Each and every callback receives the event loop pointer as first, the	643	<p>Each and every callback receives the event loop pointer as first, the
337	registered watcher structure as second, and a bitset of received events as	644	registered watcher structure as second, and a bitset of received events as
338	third argument.</p>	645	third argument.</p>
339	<p>The received events usually include a single bit per event type received	646	<p>The received events usually include a single bit per event type received
340	(you can receive multiple events at the same time). The possible bit masks	647	(you can receive multiple events at the same time). The possible bit masks
…		…
360	</dd>	667	</dd>
361	<dt><code>EV_CHILD</code></dt>	668	<dt><code>EV_CHILD</code></dt>
362	<dd>	669	<dd>
363	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>	670	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
364	</dd>	671	</dd>
		672	<dt><code>EV_STAT</code></dt>
		673	<dd>
		674	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		675	</dd>
365	<dt><code>EV_IDLE</code></dt>	676	<dt><code>EV_IDLE</code></dt>
366	<dd>	677	<dd>
367	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>	678	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
368	</dd>	679	</dd>
369	<dt><code>EV_PREPARE</code></dt>	680	<dt><code>EV_PREPARE</code></dt>
…		…
374	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	685	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
375	received events. Callbacks of both watcher types can start and stop as	686	received events. Callbacks of both watcher types can start and stop as
376	many watchers as they want, and all of them will be taken into account	687	many watchers as they want, and all of them will be taken into account
377	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep	688	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
378	<code>ev_loop</code> from blocking).</p>	689	<code>ev_loop</code> from blocking).</p>
		690	</dd>
		691	<dt><code>EV_EMBED</code></dt>
		692	<dd>
		693	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		694	</dd>
		695	<dt><code>EV_FORK</code></dt>
		696	<dd>
		697	<p>The event loop has been resumed in the child process after fork (see
		698	<code>ev_fork</code>).</p>
379	</dd>	699	</dd>
380	<dt><code>EV_ERROR</code></dt>	700	<dt><code>EV_ERROR</code></dt>
381	<dd>	701	<dd>
382	<p>An unspecified error has occured, the watcher has been stopped. This might	702	<p>An unspecified error has occured, the watcher has been stopped. This might
383	happen because the watcher could not be properly started because libev	703	happen because the watcher could not be properly started because libev
…		…
391	programs, though, so beware.</p>	711	programs, though, so beware.</p>
392	</dd>	712	</dd>
393	</dl>	713	</dl>
394		714
395	</div>	715	</div>
		716	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		717	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		718	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		719	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		720	<dl>
		721	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		722	<dd>
		723	<p>This macro initialises the generic portion of a watcher. The contents
		724	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		725	the generic parts of the watcher are initialised, you <i>need</i> to call
		726	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		727	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		728	which rolls both calls into one.</p>
		729	<p>You can reinitialise a watcher at any time as long as it has been stopped
		730	(or never started) and there are no pending events outstanding.</p>
		731	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		732	int revents)</code>.</p>
		733	</dd>
		734	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		735	<dd>
		736	<p>This macro initialises the type-specific parts of a watcher. You need to
		737	call <code>ev_init</code> at least once before you call this macro, but you can
		738	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		739	macro on a watcher that is active (it can be pending, however, which is a
		740	difference to the <code>ev_init</code> macro).</p>
		741	<p>Although some watcher types do not have type-specific arguments
		742	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		743	</dd>
		744	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		745	<dd>
		746	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		747	calls into a single call. This is the most convinient method to initialise
		748	a watcher. The same limitations apply, of course.</p>
		749	</dd>
		750	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		751	<dd>
		752	<p>Starts (activates) the given watcher. Only active watchers will receive
		753	events. If the watcher is already active nothing will happen.</p>
		754	</dd>
		755	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		756	<dd>
		757	<p>Stops the given watcher again (if active) and clears the pending
		758	status. It is possible that stopped watchers are pending (for example,
		759	non-repeating timers are being stopped when they become pending), but
		760	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		761	you want to free or reuse the memory used by the watcher it is therefore a
		762	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		763	</dd>
		764	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		765	<dd>
		766	<p>Returns a true value iff the watcher is active (i.e. it has been started
		767	and not yet been stopped). As long as a watcher is active you must not modify
		768	it.</p>
		769	</dd>
		770	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		771	<dd>
		772	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		773	events but its callback has not yet been invoked). As long as a watcher
		774	is pending (but not active) you must not call an init function on it (but
		775	<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
		776	make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
		777	it).</p>
		778	</dd>
		779	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		780	<dd>
		781	<p>Returns the callback currently set on the watcher.</p>
		782	</dd>
		783	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		784	<dd>
		785	<p>Change the callback. You can change the callback at virtually any time
		786	(modulo threads).</p>
		787	</dd>
		788	<dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
		789	<dt>int ev_priority (ev_TYPE *watcher)</dt>
		790	<dd>
		791	<p>Set and query the priority of the watcher. The priority is a small
		792	integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
		793	(default: <code>-2</code>). Pending watchers with higher priority will be invoked
		794	before watchers with lower priority, but priority will not keep watchers
		795	from being executed (except for <code>ev_idle</code> watchers).</p>
		796	<p>This means that priorities are <i>only</i> used for ordering callback
		797	invocation after new events have been received. This is useful, for
		798	example, to reduce latency after idling, or more often, to bind two
		799	watchers on the same event and make sure one is called first.</p>
		800	<p>If you need to suppress invocation when higher priority events are pending
		801	you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
		802	<p>You <i>must not</i> change the priority of a watcher as long as it is active or
		803	pending.</p>
		804	<p>The default priority used by watchers when no priority has been set is
		805	always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
		806	<p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
		807	fine, as long as you do not mind that the priority value you query might
		808	or might not have been adjusted to be within valid range.</p>
		809	</dd>
		810	<dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
		811	<dd>
		812	<p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
		813	<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
		814	can deal with that fact.</p>
		815	</dd>
		816	<dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
		817	<dd>
		818	<p>If the watcher is pending, this function returns clears its pending status
		819	and returns its <code>revents</code> bitset (as if its callback was invoked). If the
		820	watcher isn't pending it does nothing and returns <code>0</code>.</p>
		821	</dd>
		822	</dl>
		823
		824
		825
		826
		827
		828	</div>
396	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	829	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
397	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	830	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
398	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	831	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
399	and read at any time, libev will completely ignore it. This can be used	832	and read at any time, libev will completely ignore it. This can be used
400	to associate arbitrary data with your watcher. If you need more data and	833	to associate arbitrary data with your watcher. If you need more data and
…		…
417	struct my_io w = (struct my_io )w_;	850	struct my_io w = (struct my_io )w_;
418	...	851	...
419	}	852	}
420		853
421	</pre>	854	</pre>
422	<p>More interesting and less C-conformant ways of catsing your callback type	855	<p>More interesting and less C-conformant ways of casting your callback type
423	have been omitted....</p>	856	instead have been omitted.</p>
		857	<p>Another common scenario is having some data structure with multiple
		858	watchers:</p>
		859	<pre> struct my_biggy
		860	{
		861	int some_data;
		862	ev_timer t1;
		863	ev_timer t2;
		864	}
424		865
		866	</pre>
		867	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		868	you need to use <code>offsetof</code>:</p>
		869	<pre> #include <stddef.h>
425		870
		871	static void
		872	t1_cb (EV_P_ struct ev_timer *w, int revents)
		873	{
		874	struct my_biggy big = (struct my_biggy *
		875	(((char *)w) - offsetof (struct my_biggy, t1));
		876	}
426		877
		878	static void
		879	t2_cb (EV_P_ struct ev_timer *w, int revents)
		880	{
		881	struct my_biggy big = (struct my_biggy *
		882	(((char *)w) - offsetof (struct my_biggy, t2));
		883	}
427		884
428		885
		886
		887
		888	</pre>
		889
429	</div>	890	</div>
430	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	891	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
431	<div id="WATCHER_TYPES_CONTENT">	892	<div id="WATCHER_TYPES_CONTENT">
432	<p>This section describes each watcher in detail, but will not repeat	893	<p>This section describes each watcher in detail, but will not repeat
433	information given in the last section.</p>	894	information given in the last section. Any initialisation/set macros,
		895	functions and members specific to the watcher type are explained.</p>
		896	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		897	while the watcher is active, you can look at the member and expect some
		898	sensible content, but you must not modify it (you can modify it while the
		899	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		900	means you can expect it to have some sensible content while the watcher
		901	is active, but you can also modify it. Modifying it may not do something
		902	sensible or take immediate effect (or do anything at all), but libev will
		903	not crash or malfunction in any way.</p>
434		904
		905
		906
		907
		908
435	</div>	909	</div>
436	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	910	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
437	<div id="code_ev_io_code_is_this_file_descrip-2">	911	<div id="code_ev_io_code_is_this_file_descrip-2">
438	<p>I/O watchers check whether a file descriptor is readable or writable	912	<p>I/O watchers check whether a file descriptor is readable or writable
439	in each iteration of the event loop (This behaviour is called	913	in each iteration of the event loop, or, more precisely, when reading
440	level-triggering because you keep receiving events as long as the	914	would not block the process and writing would at least be able to write
441	condition persists. Remember you can stop the watcher if you don't want to	915	some data. This behaviour is called level-triggering because you keep
442	act on the event and neither want to receive future events).</p>	916	receiving events as long as the condition persists. Remember you can stop
		917	the watcher if you don't want to act on the event and neither want to
		918	receive future events.</p>
443	<p>In general you can register as many read and/or write event watchers oer	919	<p>In general you can register as many read and/or write event watchers per
444	fd as you want (as long as you don't confuse yourself). Setting all file	920	fd as you want (as long as you don't confuse yourself). Setting all file
445	descriptors to non-blocking mode is also usually a good idea (but not	921	descriptors to non-blocking mode is also usually a good idea (but not
446	required if you know what you are doing).</p>	922	required if you know what you are doing).</p>
447	<p>You have to be careful with dup'ed file descriptors, though. Some backends	923	<p>You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file	924	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing	925	descriptors correctly if you register interest in two or more fds pointing
450	to the same file/socket etc. description.</p>	926	to the same underlying file/socket/etc. description (that is, they share
		927	the same underlying "file open").</p>
451	<p>If you must do this, then force the use of a known-to-be-good backend	928	<p>If you must do this, then force the use of a known-to-be-good backend
452	(at the time of this writing, this includes only EVMETHOD_SELECT and	929	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453	EVMETHOD_POLL).</p>	930	<code>EVBACKEND_POLL</code>).</p>
		931	<p>Another thing you have to watch out for is that it is quite easy to
		932	receive "spurious" readyness notifications, that is your callback might
		933	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		934	because there is no data. Not only are some backends known to create a
		935	lot of those (for example solaris ports), it is very easy to get into
		936	this situation even with a relatively standard program structure. Thus
		937	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		938	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		939	<p>If you cannot run the fd in non-blocking mode (for example you should not
		940	play around with an Xlib connection), then you have to seperately re-test
		941	whether a file descriptor is really ready with a known-to-be good interface
		942	such as poll (fortunately in our Xlib example, Xlib already does this on
		943	its own, so its quite safe to use).</p>
454	<dl>	944	<dl>
455	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	945	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	946	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
457	<dd>	947	<dd>
458	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	948	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
459	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	949	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
460	EV_WRITE</code> to receive the given events.</p>	950	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		951	</dd>
		952	<dt>int fd [read-only]</dt>
		953	<dd>
		954	<p>The file descriptor being watched.</p>
		955	</dd>
		956	<dt>int events [read-only]</dt>
		957	<dd>
		958	<p>The events being watched.</p>
461	</dd>	959	</dd>
462	</dl>	960	</dl>
		961	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		962	readable, but only once. Since it is likely line-buffered, you could
		963	attempt to read a whole line in the callback.</p>
		964	<pre> static void
		965	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		966	{
		967	ev_io_stop (loop, w);
		968	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		969	}
463		970
		971	...
		972	struct ev_loop *loop = ev_default_init (0);
		973	struct ev_io stdin_readable;
		974	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		975	ev_io_start (loop, &stdin_readable);
		976	ev_loop (loop, 0);
		977
		978
		979
		980
		981	</pre>
		982
464	</div>	983	</div>
465	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	984	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
466	<div id="code_ev_timer_code_relative_and_opti-2">	985	<div id="code_ev_timer_code_relative_and_opti-2">
467	<p>Timer watchers are simple relative timers that generate an event after a	986	<p>Timer watchers are simple relative timers that generate an event after a
468	given time, and optionally repeating in regular intervals after that.</p>	987	given time, and optionally repeating in regular intervals after that.</p>
469	<p>The timers are based on real time, that is, if you register an event that	988	<p>The timers are based on real time, that is, if you register an event that
470	times out after an hour and youreset your system clock to last years	989	times out after an hour and you reset your system clock to last years
471	time, it will still time out after (roughly) and hour. "Roughly" because	990	time, it will still time out after (roughly) and hour. "Roughly" because
472	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	991	detecting time jumps is hard, and some inaccuracies are unavoidable (the
473	monotonic clock option helps a lot here).</p>	992	monotonic clock option helps a lot here).</p>
474	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>	993	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475	time. This is usually the right thing as this timestamp refers to the time	994	time. This is usually the right thing as this timestamp refers to the time
476	of the event triggering whatever timeout you are modifying/starting. If	995	of the event triggering whatever timeout you are modifying/starting. If
477	you suspect event processing to be delayed and you need to base the timeout	996	you suspect event processing to be delayed and you <i>need</i> to base the timeout
478	ion the current time, use something like this to adjust for this:</p>	997	on the current time, use something like this to adjust for this:</p>
479	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	998	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
480		999
481	</pre>	1000	</pre>
		1001	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		1002	but if multiple timers become ready during the same loop iteration then
		1003	order of execution is undefined.</p>
482	<dl>	1004	<dl>
483	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	1005	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
484	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	1006	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485	<dd>	1007	<dd>
486	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	1008	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
488	timer will automatically be configured to trigger again <code>repeat</code> seconds	1010	timer will automatically be configured to trigger again <code>repeat</code> seconds
489	later, again, and again, until stopped manually.</p>	1011	later, again, and again, until stopped manually.</p>
490	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	1012	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
491	configure a timer to trigger every 10 seconds, then it will trigger at	1013	configure a timer to trigger every 10 seconds, then it will trigger at
492	exactly 10 second intervals. If, however, your program cannot keep up with	1014	exactly 10 second intervals. If, however, your program cannot keep up with
493	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1015	the timer (because it takes longer than those 10 seconds to do stuff) the
494	timer will not fire more than once per event loop iteration.</p>	1016	timer will not fire more than once per event loop iteration.</p>
495	</dd>	1017	</dd>
496	<dt>ev_timer_again (loop)</dt>	1018	<dt>ev_timer_again (loop)</dt>
497	<dd>	1019	<dd>
498	<p>This will act as if the timer timed out and restart it again if it is	1020	<p>This will act as if the timer timed out and restart it again if it is
499	repeating. The exact semantics are:</p>	1021	repeating. The exact semantics are:</p>
		1022	<p>If the timer is pending, its pending status is cleared.</p>
500	<p>If the timer is started but nonrepeating, stop it.</p>	1023	<p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
501	<p>If the timer is repeating, either start it if necessary (with the repeat	1024	<p>If the timer is repeating, either start it if necessary (with the
502	value), or reset the running timer to the repeat value.</p>	1025	<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
503	<p>This sounds a bit complicated, but here is a useful and typical	1026	<p>This sounds a bit complicated, but here is a useful and typical
504	example: Imagine you have a tcp connection and you want a so-called idle	1027	example: Imagine you have a tcp connection and you want a so-called idle
505	timeout, that is, you want to be called when there have been, say, 60	1028	timeout, that is, you want to be called when there have been, say, 60
506	seconds of inactivity on the socket. The easiest way to do this is to	1029	seconds of inactivity on the socket. The easiest way to do this is to
507	configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each	1030	configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
508	time you successfully read or write some data. If you go into an idle	1031	<code>ev_timer_again</code> each time you successfully read or write some data. If
509	state where you do not expect data to travel on the socket, you can stop	1032	you go into an idle state where you do not expect data to travel on the
		1033	socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
510	the timer, and again will automatically restart it if need be.</p>	1034	automatically restart it if need be.</p>
		1035	<p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
		1036	altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
		1037	<pre> ev_timer_init (timer, callback, 0., 5.);
		1038	ev_timer_again (loop, timer);
		1039	...
		1040	timer->again = 17.;
		1041	ev_timer_again (loop, timer);
		1042	...
		1043	timer->again = 10.;
		1044	ev_timer_again (loop, timer);
		1045
		1046	</pre>
		1047	<p>This is more slightly efficient then stopping/starting the timer each time
		1048	you want to modify its timeout value.</p>
		1049	</dd>
		1050	<dt>ev_tstamp repeat [read-write]</dt>
		1051	<dd>
		1052	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		1053	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		1054	which is also when any modifications are taken into account.</p>
511	</dd>	1055	</dd>
512	</dl>	1056	</dl>
		1057	<p>Example: Create a timer that fires after 60 seconds.</p>
		1058	<pre> static void
		1059	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1060	{
		1061	.. one minute over, w is actually stopped right here
		1062	}
513		1063
		1064	struct ev_timer mytimer;
		1065	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1066	ev_timer_start (loop, &mytimer);
		1067
		1068	</pre>
		1069	<p>Example: Create a timeout timer that times out after 10 seconds of
		1070	inactivity.</p>
		1071	<pre> static void
		1072	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1073	{
		1074	.. ten seconds without any activity
		1075	}
		1076
		1077	struct ev_timer mytimer;
		1078	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1079	ev_timer_again (&mytimer); /* start timer */
		1080	ev_loop (loop, 0);
		1081
		1082	// and in some piece of code that gets executed on any "activity":
		1083	// reset the timeout to start ticking again at 10 seconds
		1084	ev_timer_again (&mytimer);
		1085
		1086
		1087
		1088
		1089	</pre>
		1090
514	</div>	1091	</div>
515	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	1092	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
516	<div id="code_ev_periodic_code_to_cron_or_not-2">	1093	<div id="code_ev_periodic_code_to_cron_or_not-2">
517	<p>Periodic watchers are also timers of a kind, but they are very versatile	1094	<p>Periodic watchers are also timers of a kind, but they are very versatile
518	(and unfortunately a bit complex).</p>	1095	(and unfortunately a bit complex).</p>
519	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)	1096	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
520	but on wallclock time (absolute time). You can tell a periodic watcher	1097	but on wallclock time (absolute time). You can tell a periodic watcher
521	to trigger "at" some specific point in time. For example, if you tell a	1098	to trigger "at" some specific point in time. For example, if you tell a
522	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1099	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
523	+ 10.>) and then reset your system clock to the last year, then it will	1100	+ 10.</code>) and then reset your system clock to the last year, then it will
524	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger	1101	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525	roughly 10 seconds later and of course not if you reset your system time	1102	roughly 10 seconds later).</p>
526	again).</p>
527	<p>They can also be used to implement vastly more complex timers, such as	1103	<p>They can also be used to implement vastly more complex timers, such as
528	triggering an event on eahc midnight, local time.</p>	1104	triggering an event on each midnight, local time or other, complicated,
		1105	rules.</p>
		1106	<p>As with timers, the callback is guarenteed to be invoked only when the
		1107	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1108	during the same loop iteration then order of execution is undefined.</p>
529	<dl>	1109	<dl>
530	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1110	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
531	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	1111	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532	<dd>	1112	<dd>
533	<p>Lots of arguments, lets sort it out... There are basically three modes of	1113	<p>Lots of arguments, lets sort it out... There are basically three modes of
534	operation, and we will explain them from simplest to complex:</p>	1114	operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539	<p>	1115	<p>
540	<dl>	1116	<dl>
541	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1117	<dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
542	<dd>	1118	<dd>
543	<p>In this configuration the watcher triggers an event at the wallclock time	1119	<p>In this configuration the watcher triggers an event at the wallclock time
544	<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,	1120	<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
545	that is, if it is to be run at January 1st 2011 then it will run when the	1121	that is, if it is to be run at January 1st 2011 then it will run when the
546	system time reaches or surpasses this time.</p>	1122	system time reaches or surpasses this time.</p>
547	</dd>	1123	</dd>
548	<dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt>	1124	<dt>* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)</dt>
549	<dd>	1125	<dd>
550	<p>In this mode the watcher will always be scheduled to time out at the next	1126	<p>In this mode the watcher will always be scheduled to time out at the next
551	<code>at + N * interval</code> time (for some integer N) and then repeat, regardless	1127	<code>at + N * interval</code> time (for some integer N, which can also be negative)
552	of any time jumps.</p>	1128	and then repeat, regardless of any time jumps.</p>
553	<p>This can be used to create timers that do not drift with respect to system	1129	<p>This can be used to create timers that do not drift with respect to system
554	time:</p>	1130	time:</p>
555	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	1131	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
556		1132
557	</pre>	1133	</pre>
…		…
560	full hour (UTC), or more correctly, when the system time is evenly divisible	1136	full hour (UTC), or more correctly, when the system time is evenly divisible
561	by 3600.</p>	1137	by 3600.</p>
562	<p>Another way to think about it (for the mathematically inclined) is that	1138	<p>Another way to think about it (for the mathematically inclined) is that
563	<code>ev_periodic</code> will try to run the callback in this mode at the next possible	1139	<code>ev_periodic</code> will try to run the callback in this mode at the next possible
564	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	1140	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
		1141	<p>For numerical stability it is preferable that the <code>at</code> value is near
		1142	<code>ev_now ()</code> (the current time), but there is no range requirement for
		1143	this value.</p>
565	</dd>	1144	</dd>
566	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	1145	<dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
567	<dd>	1146	<dd>
568	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	1147	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
569	ignored. Instead, each time the periodic watcher gets scheduled, the	1148	ignored. Instead, each time the periodic watcher gets scheduled, the
570	reschedule callback will be called with the watcher as first, and the	1149	reschedule callback will be called with the watcher as first, and the
571	current time as second argument.</p>	1150	current time as second argument.</p>
572	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1151	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573	periodic watcher, ever, or make any event loop modifications</i>. If you need	1152	ever, or make any event loop modifications</i>. If you need to stop it,
574	to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p>	1153	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
575	<p>Also, <i>this callback must always return a time that is later than the	1154	starting an <code>ev_prepare</code> watcher, which is legal).</p>
576	passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,	1155	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
578	ev_tstamp now)</code>, e.g.:</p>	1156	ev_tstamp now)</code>, e.g.:</p>
579	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1157	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580	{	1158	{
581	return now + 60.;	1159	return now + 60.;
…		…
584	</pre>	1162	</pre>
585	<p>It must return the next time to trigger, based on the passed time value	1163	<p>It must return the next time to trigger, based on the passed time value
586	(that is, the lowest time value larger than to the second argument). It	1164	(that is, the lowest time value larger than to the second argument). It
587	will usually be called just before the callback will be triggered, but	1165	will usually be called just before the callback will be triggered, but
588	might be called at other times, too.</p>	1166	might be called at other times, too.</p>
		1167	<p>NOTE: <i>This callback must always return a time that is later than the
		1168	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
589	<p>This can be used to create very complex timers, such as a timer that	1169	<p>This can be used to create very complex timers, such as a timer that
590	triggers on each midnight, local time. To do this, you would calculate the	1170	triggers on each midnight, local time. To do this, you would calculate the
591	next midnight after <code>now</code> and return the timestamp value for this. How you do this	1171	next midnight after <code>now</code> and return the timestamp value for this. How
592	is, again, up to you (but it is not trivial).</p>	1172	you do this is, again, up to you (but it is not trivial, which is the main
		1173	reason I omitted it as an example).</p>
593	</dd>	1174	</dd>
594	</dl>	1175	</dl>
595	</p>	1176	</p>
596	</dd>	1177	</dd>
597	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1178	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
599	<p>Simply stops and restarts the periodic watcher again. This is only useful	1180	<p>Simply stops and restarts the periodic watcher again. This is only useful
600	when you changed some parameters or the reschedule callback would return	1181	when you changed some parameters or the reschedule callback would return
601	a different time than the last time it was called (e.g. in a crond like	1182	a different time than the last time it was called (e.g. in a crond like
602	program when the crontabs have changed).</p>	1183	program when the crontabs have changed).</p>
603	</dd>	1184	</dd>
		1185	<dt>ev_tstamp offset [read-write]</dt>
		1186	<dd>
		1187	<p>When repeating, this contains the offset value, otherwise this is the
		1188	absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
		1189	<p>Can be modified any time, but changes only take effect when the periodic
		1190	timer fires or <code>ev_periodic_again</code> is being called.</p>
		1191	</dd>
		1192	<dt>ev_tstamp interval [read-write]</dt>
		1193	<dd>
		1194	<p>The current interval value. Can be modified any time, but changes only
		1195	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1196	called.</p>
		1197	</dd>
		1198	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1199	<dd>
		1200	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1201	switched off. Can be changed any time, but changes only take effect when
		1202	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1203	</dd>
604	</dl>	1204	</dl>
		1205	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1206	system clock is divisible by 3600. The callback invocation times have
		1207	potentially a lot of jittering, but good long-term stability.</p>
		1208	<pre> static void
		1209	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1210	{
		1211	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1212	}
605		1213
		1214	struct ev_periodic hourly_tick;
		1215	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1216	ev_periodic_start (loop, &hourly_tick);
		1217
		1218	</pre>
		1219	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1220	<pre> #include <math.h>
		1221
		1222	static ev_tstamp
		1223	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1224	{
		1225	return fmod (now, 3600.) + 3600.;
		1226	}
		1227
		1228	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1229
		1230	</pre>
		1231	<p>Example: Call a callback every hour, starting now:</p>
		1232	<pre> struct ev_periodic hourly_tick;
		1233	ev_periodic_init (&hourly_tick, clock_cb,
		1234	fmod (ev_now (loop), 3600.), 3600., 0);
		1235	ev_periodic_start (loop, &hourly_tick);
		1236
		1237
		1238
		1239
		1240	</pre>
		1241
606	</div>	1242	</div>
607	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	1243	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
608	<div id="code_ev_signal_code_signal_me_when_a-2">	1244	<div id="code_ev_signal_code_signal_me_when_a-2">
609	<p>Signal watchers will trigger an event when the process receives a specific	1245	<p>Signal watchers will trigger an event when the process receives a specific
610	signal one or more times. Even though signals are very asynchronous, libev	1246	signal one or more times. Even though signals are very asynchronous, libev
611	will try it's best to deliver signals synchronously, i.e. as part of the	1247	will try it's best to deliver signals synchronously, i.e. as part of the
612	normal event processing, like any other event.</p>	1248	normal event processing, like any other event.</p>
…		…
621	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1257	<dt>ev_signal_set (ev_signal *, int signum)</dt>
622	<dd>	1258	<dd>
623	<p>Configures the watcher to trigger on the given signal number (usually one	1259	<p>Configures the watcher to trigger on the given signal number (usually one
624	of the <code>SIGxxx</code> constants).</p>	1260	of the <code>SIGxxx</code> constants).</p>
625	</dd>	1261	</dd>
		1262	<dt>int signum [read-only]</dt>
		1263	<dd>
		1264	<p>The signal the watcher watches out for.</p>
		1265	</dd>
626	</dl>	1266	</dl>
627		1267
		1268
		1269
		1270
		1271
628	</div>	1272	</div>
629	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	1273	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
630	<div id="code_ev_child_code_wait_for_pid_stat-2">	1274	<div id="code_ev_child_code_watch_out_for_pro-2">
631	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1275	<p>Child watchers trigger when your process receives a SIGCHLD in response to
632	some child status changes (most typically when a child of yours dies).</p>	1276	some child status changes (most typically when a child of yours dies).</p>
633	<dl>	1277	<dl>
634	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1278	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
635	<dt>ev_child_set (ev_child *, int pid)</dt>	1279	<dt>ev_child_set (ev_child *, int pid)</dt>
…		…
639	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1283	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
640	the status word (use the macros from <code>sys/wait.h</code> and see your systems	1284	the status word (use the macros from <code>sys/wait.h</code> and see your systems
641	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the	1285	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642	process causing the status change.</p>	1286	process causing the status change.</p>
643	</dd>	1287	</dd>
		1288	<dt>int pid [read-only]</dt>
		1289	<dd>
		1290	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1291	</dd>
		1292	<dt>int rpid [read-write]</dt>
		1293	<dd>
		1294	<p>The process id that detected a status change.</p>
		1295	</dd>
		1296	<dt>int rstatus [read-write]</dt>
		1297	<dd>
		1298	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1299	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
		1300	</dd>
644	</dl>	1301	</dl>
		1302	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1303	<pre> static void
		1304	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1305	{
		1306	ev_unloop (loop, EVUNLOOP_ALL);
		1307	}
645		1308
		1309	struct ev_signal signal_watcher;
		1310	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1311	ev_signal_start (loop, &sigint_cb);
		1312
		1313
		1314
		1315
		1316	</pre>
		1317
646	</div>	1318	</div>
		1319	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1320	<div id="code_ev_stat_code_did_the_file_attri-2">
		1321	<p>This watches a filesystem path for attribute changes. That is, it calls
		1322	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1323	compared to the last time, invoking the callback if it did.</p>
		1324	<p>The path does not need to exist: changing from "path exists" to "path does
		1325	not exist" is a status change like any other. The condition "path does
		1326	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1327	otherwise always forced to be at least one) and all the other fields of
		1328	the stat buffer having unspecified contents.</p>
		1329	<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
		1330	relative and your working directory changes, the behaviour is undefined.</p>
		1331	<p>Since there is no standard to do this, the portable implementation simply
		1332	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1333	can specify a recommended polling interval for this case. If you specify
		1334	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1335	unspecified default</i> value will be used (which you can expect to be around
		1336	five seconds, although this might change dynamically). Libev will also
		1337	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1338	usually overkill.</p>
		1339	<p>This watcher type is not meant for massive numbers of stat watchers,
		1340	as even with OS-supported change notifications, this can be
		1341	resource-intensive.</p>
		1342	<p>At the time of this writing, only the Linux inotify interface is
		1343	implemented (implementing kqueue support is left as an exercise for the
		1344	reader). Inotify will be used to give hints only and should not change the
		1345	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1346	to fall back to regular polling again even with inotify, but changes are
		1347	usually detected immediately, and if the file exists there will be no
		1348	polling.</p>
		1349	<dl>
		1350	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1351	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1352	<dd>
		1353	<p>Configures the watcher to wait for status changes of the given
		1354	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1355	be detected and should normally be specified as <code>0</code> to let libev choose
		1356	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1357	path for as long as the watcher is active.</p>
		1358	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1359	relative to the attributes at the time the watcher was started (or the
		1360	last change was detected).</p>
		1361	</dd>
		1362	<dt>ev_stat_stat (ev_stat *)</dt>
		1363	<dd>
		1364	<p>Updates the stat buffer immediately with new values. If you change the
		1365	watched path in your callback, you could call this fucntion to avoid
		1366	detecting this change (while introducing a race condition). Can also be
		1367	useful simply to find out the new values.</p>
		1368	</dd>
		1369	<dt>ev_statdata attr [read-only]</dt>
		1370	<dd>
		1371	<p>The most-recently detected attributes of the file. Although the type is of
		1372	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1373	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1374	was some error while <code>stat</code>ing the file.</p>
		1375	</dd>
		1376	<dt>ev_statdata prev [read-only]</dt>
		1377	<dd>
		1378	<p>The previous attributes of the file. The callback gets invoked whenever
		1379	<code>prev</code> != <code>attr</code>.</p>
		1380	</dd>
		1381	<dt>ev_tstamp interval [read-only]</dt>
		1382	<dd>
		1383	<p>The specified interval.</p>
		1384	</dd>
		1385	<dt>const char *path [read-only]</dt>
		1386	<dd>
		1387	<p>The filesystem path that is being watched.</p>
		1388	</dd>
		1389	</dl>
		1390	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1391	<pre> static void
		1392	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1393	{
		1394	/* /etc/passwd changed in some way */
		1395	if (w->attr.st_nlink)
		1396	{
		1397	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1398	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1399	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1400	}
		1401	else
		1402	/* you shalt not abuse printf for puts */
		1403	puts ("wow, /etc/passwd is not there, expect problems. "
		1404	"if this is windows, they already arrived\n");
		1405	}
		1406
		1407	...
		1408	ev_stat passwd;
		1409
		1410	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1411	ev_stat_start (loop, &passwd);
		1412
		1413
		1414
		1415
		1416	</pre>
		1417
		1418	</div>
647	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>	1419	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
648	<div id="code_ev_idle_code_when_you_ve_got_no-2">	1420	<div id="code_ev_idle_code_when_you_ve_got_no-2">
649	<p>Idle watchers trigger events when there are no other events are pending	1421	<p>Idle watchers trigger events when no other events of the same or higher
650	(prepare, check and other idle watchers do not count). That is, as long	1422	priority are pending (prepare, check and other idle watchers do not
651	as your process is busy handling sockets or timeouts (or even signals,	1423	count).</p>
652	imagine) it will not be triggered. But when your process is idle all idle	1424	<p>That is, as long as your process is busy handling sockets or timeouts
653	watchers are being called again and again, once per event loop iteration -	1425	(or even signals, imagine) of the same or higher priority it will not be
		1426	triggered. But when your process is idle (or only lower-priority watchers
		1427	are pending), the idle watchers are being called once per event loop
654	until stopped, that is, or your process receives more events and becomes	1428	iteration - until stopped, that is, or your process receives more events
655	busy.</p>	1429	and becomes busy again with higher priority stuff.</p>
656	<p>The most noteworthy effect is that as long as any idle watchers are	1430	<p>The most noteworthy effect is that as long as any idle watchers are
657	active, the process will not block when waiting for new events.</p>	1431	active, the process will not block when waiting for new events.</p>
658	<p>Apart from keeping your process non-blocking (which is a useful	1432	<p>Apart from keeping your process non-blocking (which is a useful
659	effect on its own sometimes), idle watchers are a good place to do	1433	effect on its own sometimes), idle watchers are a good place to do
660	"pseudo-background processing", or delay processing stuff to after the	1434	"pseudo-background processing", or delay processing stuff to after the
…		…
665	<p>Initialises and configures the idle watcher - it has no parameters of any	1439	<p>Initialises and configures the idle watcher - it has no parameters of any
666	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1440	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667	believe me.</p>	1441	believe me.</p>
668	</dd>	1442	</dd>
669	</dl>	1443	</dl>
		1444	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1445	callback, free it. Also, use no error checking, as usual.</p>
		1446	<pre> static void
		1447	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1448	{
		1449	free (w);
		1450	// now do something you wanted to do when the program has
		1451	// no longer asnything immediate to do.
		1452	}
670		1453
		1454	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1455	ev_idle_init (idle_watcher, idle_cb);
		1456	ev_idle_start (loop, idle_cb);
		1457
		1458
		1459
		1460
		1461	</pre>
		1462
671	</div>	1463	</div>
672	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>	1464	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
673	<div id="code_ev_prepare_code_and_code_ev_che-2">	1465	<div id="code_ev_prepare_code_and_code_ev_che-2">
674	<p>Prepare and check watchers are usually (but not always) used in tandem:	1466	<p>Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	1467	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.</p>	1468	afterwards.</p>
		1469	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1470	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1471	watchers. Other loops than the current one are fine, however. The
		1472	rationale behind this is that you do not need to check for recursion in
		1473	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1474	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1475	called in pairs bracketing the blocking call.</p>
677	<p>Their main purpose is to integrate other event mechanisms into libev. This	1476	<p>Their main purpose is to integrate other event mechanisms into libev and
678	could be used, for example, to track variable changes, implement your own	1477	their use is somewhat advanced. This could be used, for example, to track
679	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1478	variable changes, implement your own watchers, integrate net-snmp or a
		1479	coroutine library and lots more. They are also occasionally useful if
		1480	you cache some data and want to flush it before blocking (for example,
		1481	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1482	watcher).</p>
680	<p>This is done by examining in each prepare call which file descriptors need	1483	<p>This is done by examining in each prepare call which file descriptors need
681	to be watched by the other library, registering <code>ev_io</code> watchers for	1484	to be watched by the other library, registering <code>ev_io</code> watchers for
682	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1485	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683	provide just this functionality). Then, in the check watcher you check for	1486	provide just this functionality). Then, in the check watcher you check for
684	any events that occured (by checking the pending status of all watchers	1487	any events that occured (by checking the pending status of all watchers
685	and stopping them) and call back into the library. The I/O and timer	1488	and stopping them) and call back into the library. The I/O and timer
686	callbacks will never actually be called (but must be valid neverthelles,	1489	callbacks will never actually be called (but must be valid nevertheless,
687	because you never know, you know?).</p>	1490	because you never know, you know?).</p>
688	<p>As another example, the Perl Coro module uses these hooks to integrate	1491	<p>As another example, the Perl Coro module uses these hooks to integrate
689	coroutines into libev programs, by yielding to other active coroutines	1492	coroutines into libev programs, by yielding to other active coroutines
690	during each prepare and only letting the process block if no coroutines	1493	during each prepare and only letting the process block if no coroutines
691	are ready to run (its actually more complicated, it only runs coroutines	1494	are ready to run (it's actually more complicated: it only runs coroutines
692	with priority higher than the event loop and one lower priority once,	1495	with priority higher than or equal to the event loop and one coroutine
693	using idle watchers to keep the event loop from blocking if lower-priority	1496	of lower priority, but only once, using idle watchers to keep the event
694	coroutines exist, thus mapping low-priority coroutines to idle/background	1497	loop from blocking if lower-priority coroutines are active, thus mapping
695	tasks).</p>	1498	low-priority coroutines to idle/background tasks).</p>
		1499	<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
		1500	priority, to ensure that they are being run before any other watchers
		1501	after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
		1502	too) should not activate ("feed") events into libev. While libev fully
		1503	supports this, they will be called before other <code>ev_check</code> watchers did
		1504	their job. As <code>ev_check</code> watchers are often used to embed other event
		1505	loops those other event loops might be in an unusable state until their
		1506	<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
		1507	others).</p>
696	<dl>	1508	<dl>
697	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1509	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
698	<dt>ev_check_init (ev_check *, callback)</dt>	1510	<dt>ev_check_init (ev_check *, callback)</dt>
699	<dd>	1511	<dd>
700	<p>Initialises and configures the prepare or check watcher - they have no	1512	<p>Initialises and configures the prepare or check watcher - they have no
701	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1513	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
702	macros, but using them is utterly, utterly and completely pointless.</p>	1514	macros, but using them is utterly, utterly and completely pointless.</p>
703	</dd>	1515	</dd>
704	</dl>	1516	</dl>
		1517	<p>There are a number of principal ways to embed other event loops or modules
		1518	into libev. Here are some ideas on how to include libadns into libev
		1519	(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
		1520	use for an actually working example. Another Perl module named <code>EV::Glib</code>
		1521	embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
		1522	into the Glib event loop).</p>
		1523	<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1524	and in a check watcher, destroy them and call into libadns. What follows
		1525	is pseudo-code only of course. This requires you to either use a low
		1526	priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
		1527	the callbacks for the IO/timeout watchers might not have been called yet.</p>
		1528	<pre> static ev_io iow [nfd];
		1529	static ev_timer tw;
705		1530
		1531	static void
		1532	io_cb (ev_loop loop, ev_io w, int revents)
		1533	{
		1534	}
		1535
		1536	// create io watchers for each fd and a timer before blocking
		1537	static void
		1538	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1539	{
		1540	int timeout = 3600000;
		1541	struct pollfd fds [nfd];
		1542	// actual code will need to loop here and realloc etc.
		1543	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1544
		1545	/* the callback is illegal, but won't be called as we stop during check */
		1546	ev_timer_init (&tw, 0, timeout * 1e-3);
		1547	ev_timer_start (loop, &tw);
		1548
		1549	// create one ev_io per pollfd
		1550	for (int i = 0; i < nfd; ++i)
		1551	{
		1552	ev_io_init (iow + i, io_cb, fds [i].fd,
		1553	((fds [i].events & POLLIN ? EV_READ : 0)
		1554	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1555
		1556	fds [i].revents = 0;
		1557	ev_io_start (loop, iow + i);
		1558	}
		1559	}
		1560
		1561	// stop all watchers after blocking
		1562	static void
		1563	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1564	{
		1565	ev_timer_stop (loop, &tw);
		1566
		1567	for (int i = 0; i < nfd; ++i)
		1568	{
		1569	// set the relevant poll flags
		1570	// could also call adns_processreadable etc. here
		1571	struct pollfd *fd = fds + i;
		1572	int revents = ev_clear_pending (iow + i);
		1573	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1574	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1575
		1576	// now stop the watcher
		1577	ev_io_stop (loop, iow + i);
		1578	}
		1579
		1580	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1581	}
		1582
		1583	</pre>
		1584	<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
		1585	in the prepare watcher and would dispose of the check watcher.</p>
		1586	<p>Method 3: If the module to be embedded supports explicit event
		1587	notification (adns does), you can also make use of the actual watcher
		1588	callbacks, and only destroy/create the watchers in the prepare watcher.</p>
		1589	<pre> static void
		1590	timer_cb (EV_P_ ev_timer *w, int revents)
		1591	{
		1592	adns_state ads = (adns_state)w->data;
		1593	update_now (EV_A);
		1594
		1595	adns_processtimeouts (ads, &tv_now);
		1596	}
		1597
		1598	static void
		1599	io_cb (EV_P_ ev_io *w, int revents)
		1600	{
		1601	adns_state ads = (adns_state)w->data;
		1602	update_now (EV_A);
		1603
		1604	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1605	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1606	}
		1607
		1608	// do not ever call adns_afterpoll
		1609
		1610	</pre>
		1611	<p>Method 4: Do not use a prepare or check watcher because the module you
		1612	want to embed is too inflexible to support it. Instead, youc na override
		1613	their poll function. The drawback with this solution is that the main
		1614	loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
		1615	this.</p>
		1616	<pre> static gint
		1617	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1618	{
		1619	int got_events = 0;
		1620
		1621	for (n = 0; n < nfds; ++n)
		1622	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1623
		1624	if (timeout >= 0)
		1625	// create/start timer
		1626
		1627	// poll
		1628	ev_loop (EV_A_ 0);
		1629
		1630	// stop timer again
		1631	if (timeout >= 0)
		1632	ev_timer_stop (EV_A_ &to);
		1633
		1634	// stop io watchers again - their callbacks should have set
		1635	for (n = 0; n < nfds; ++n)
		1636	ev_io_stop (EV_A_ iow [n]);
		1637
		1638	return got_events;
		1639	}
		1640
		1641
		1642
		1643
		1644	</pre>
		1645
706	</div>	1646	</div>
707	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1647	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1648	<div id="code_ev_embed_code_when_one_backend_-2">
		1649	<p>This is a rather advanced watcher type that lets you embed one event loop
		1650	into another (currently only <code>ev_io</code> events are supported in the embedded
		1651	loop, other types of watchers might be handled in a delayed or incorrect
		1652	fashion and must not be used).</p>
		1653	<p>There are primarily two reasons you would want that: work around bugs and
		1654	prioritise I/O.</p>
		1655	<p>As an example for a bug workaround, the kqueue backend might only support
		1656	sockets on some platform, so it is unusable as generic backend, but you
		1657	still want to make use of it because you have many sockets and it scales
		1658	so nicely. In this case, you would create a kqueue-based loop and embed it
		1659	into your default loop (which might use e.g. poll). Overall operation will
		1660	be a bit slower because first libev has to poll and then call kevent, but
		1661	at least you can use both at what they are best.</p>
		1662	<p>As for prioritising I/O: rarely you have the case where some fds have
		1663	to be watched and handled very quickly (with low latency), and even
		1664	priorities and idle watchers might have too much overhead. In this case
		1665	you would put all the high priority stuff in one loop and all the rest in
		1666	a second one, and embed the second one in the first.</p>
		1667	<p>As long as the watcher is active, the callback will be invoked every time
		1668	there might be events pending in the embedded loop. The callback must then
		1669	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1670	their callbacks (you could also start an idle watcher to give the embedded
		1671	loop strictly lower priority for example). You can also set the callback
		1672	to <code>0</code>, in which case the embed watcher will automatically execute the
		1673	embedded loop sweep.</p>
		1674	<p>As long as the watcher is started it will automatically handle events. The
		1675	callback will be invoked whenever some events have been handled. You can
		1676	set the callback to <code>0</code> to avoid having to specify one if you are not
		1677	interested in that.</p>
		1678	<p>Also, there have not currently been made special provisions for forking:
		1679	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1680	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1681	yourself.</p>
		1682	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1683	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1684	portable one.</p>
		1685	<p>So when you want to use this feature you will always have to be prepared
		1686	that you cannot get an embeddable loop. The recommended way to get around
		1687	this is to have a separate variables for your embeddable loop, try to
		1688	create it, and if that fails, use the normal loop for everything:</p>
		1689	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1690	struct ev_loop *loop_lo = 0;
		1691	struct ev_embed embed;
		1692
		1693	// see if there is a chance of getting one that works
		1694	// (remember that a flags value of 0 means autodetection)
		1695	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1696	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1697	: 0;
		1698
		1699	// if we got one, then embed it, otherwise default to loop_hi
		1700	if (loop_lo)
		1701	{
		1702	ev_embed_init (&embed, 0, loop_lo);
		1703	ev_embed_start (loop_hi, &embed);
		1704	}
		1705	else
		1706	loop_lo = loop_hi;
		1707
		1708	</pre>
		1709	<dl>
		1710	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1711	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1712	<dd>
		1713	<p>Configures the watcher to embed the given loop, which must be
		1714	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1715	invoked automatically, otherwise it is the responsibility of the callback
		1716	to invoke it (it will continue to be called until the sweep has been done,
		1717	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1718	</dd>
		1719	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1720	<dd>
		1721	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1722	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1723	apropriate way for embedded loops.</p>
		1724	</dd>
		1725	<dt>struct ev_loop *loop [read-only]</dt>
		1726	<dd>
		1727	<p>The embedded event loop.</p>
		1728	</dd>
		1729	</dl>
		1730
		1731
		1732
		1733
		1734
		1735	</div>
		1736	<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>
		1737	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1738	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1739	whoever is a good citizen cared to tell libev about it by calling
		1740	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1741	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1742	and only in the child after the fork. If whoever good citizen calling
		1743	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1744	handlers will be invoked, too, of course.</p>
		1745	<dl>
		1746	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1747	<dd>
		1748	<p>Initialises and configures the fork watcher - it has no parameters of any
		1749	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1750	believe me.</p>
		1751	</dd>
		1752	</dl>
		1753
		1754
		1755
		1756
		1757
		1758	</div>
		1759	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
708	<div id="OTHER_FUNCTIONS_CONTENT">	1760	<div id="OTHER_FUNCTIONS_CONTENT">
709	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1761	<p>There are some other functions of possible interest. Described. Here. Now.</p>
710	<dl>	1762	<dl>
711	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1763	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712	<dd>	1764	<dd>
713	<p>This function combines a simple timer and an I/O watcher, calls your	1765	<p>This function combines a simple timer and an I/O watcher, calls your
714	callback on whichever event happens first and automatically stop both	1766	callback on whichever event happens first and automatically stop both
715	watchers. This is useful if you want to wait for a single event on an fd	1767	watchers. This is useful if you want to wait for a single event on an fd
716	or timeout without havign to allocate/configure/start/stop/free one or	1768	or timeout without having to allocate/configure/start/stop/free one or
717	more watchers yourself.</p>	1769	more watchers yourself.</p>
718	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events	1770	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and	1771	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
720	<code>events</code> set will be craeted and started.</p>	1772	<code>events</code> set will be craeted and started.</p>
721	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1773	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and	1774	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of	1775	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724	dubious value.</p>	1776	dubious value.</p>
725	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets	1777	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
726	passed an events set like normal event callbacks (with a combination of	1778	passed an <code>revents</code> set like normal event callbacks (a combination of
727	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>	1779	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728	value passed to <code>ev_once</code>:</p>	1780	value passed to <code>ev_once</code>:</p>
729	<pre> static void stdin_ready (int revents, void *arg)	1781	<pre> static void stdin_ready (int revents, void *arg)
730	{	1782	{
731	if (revents & EV_TIMEOUT)	1783	if (revents & EV_TIMEOUT)
…		…
736		1788
737	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1789	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738		1790
739	</pre>	1791	</pre>
740	</dd>	1792	</dd>
741	<dt>ev_feed_event (loop, watcher, int events)</dt>	1793	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
742	<dd>	1794	<dd>
743	<p>Feeds the given event set into the event loop, as if the specified event	1795	<p>Feeds the given event set into the event loop, as if the specified event
744	had happened for the specified watcher (which must be a pointer to an	1796	had happened for the specified watcher (which must be a pointer to an
745	initialised but not necessarily started event watcher).</p>	1797	initialised but not necessarily started event watcher).</p>
746	</dd>	1798	</dd>
747	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1799	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
748	<dd>	1800	<dd>
749	<p>Feed an event on the given fd, as if a file descriptor backend detected	1801	<p>Feed an event on the given fd, as if a file descriptor backend detected
750	the given events it.</p>	1802	the given events it.</p>
751	</dd>	1803	</dd>
752	<dt>ev_feed_signal_event (loop, int signum)</dt>	1804	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
753	<dd>	1805	<dd>
754	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1806	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1807	loop!).</p>
755	</dd>	1808	</dd>
756	</dl>	1809	</dl>
757		1810
		1811
		1812
		1813
		1814
758	</div>	1815	</div>
759	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1816	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1817	<div id="LIBEVENT_EMULATION_CONTENT">
		1818	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1819	emulate the internals of libevent, so here are some usage hints:</p>
		1820	<dl>
		1821	<dt>* Use it by including <event.h>, as usual.</dt>
		1822	<dt>* The following members are fully supported: ev_base, ev_callback,
		1823	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1824	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1825	maintained by libev, it does not work exactly the same way as in libevent (consider
		1826	it a private API).</dt>
		1827	<dt>* Priorities are not currently supported. Initialising priorities
		1828	will fail and all watchers will have the same priority, even though there
		1829	is an ev_pri field.</dt>
		1830	<dt>* Other members are not supported.</dt>
		1831	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1832	to use the libev header file and library.</dt>
		1833	</dl>
		1834
		1835	</div>
		1836	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1837	<div id="C_SUPPORT_CONTENT">
		1838	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1839	you to use some convinience methods to start/stop watchers and also change
		1840	the callback model to a model using method callbacks on objects.</p>
		1841	<p>To use it,</p>
		1842	<pre> #include <ev++.h>
		1843
		1844	</pre>
		1845	<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
		1846	of them macros) into the global namespace. All C++ specific things are
		1847	put into the <code>ev</code> namespace. It should support all the same embedding
		1848	options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
		1849	<p>Care has been taken to keep the overhead low. The only data member the C++
		1850	classes add (compared to plain C-style watchers) is the event loop pointer
		1851	that the watcher is associated with (or no additional members at all if
		1852	you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
		1853	<p>Currently, functions, and static and non-static member functions can be
		1854	used as callbacks. Other types should be easy to add as long as they only
		1855	need one additional pointer for context. If you need support for other
		1856	types of functors please contact the author (preferably after implementing
		1857	it).</p>
		1858	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1859	<dl>
		1860	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1861	<dd>
		1862	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1863	macros from <cite>ev.h</cite>.</p>
		1864	</dd>
		1865	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1866	<dd>
		1867	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1868	</dd>
		1869	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1870	<dd>
		1871	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1872	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1873	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1874	defines by many implementations.</p>
		1875	<p>All of those classes have these methods:</p>
		1876	<p>
		1877	<dl>
		1878	<dt>ev::TYPE::TYPE ()</dt>
		1879	<dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
		1880	<dt>ev::TYPE::~TYPE</dt>
		1881	<dd>
		1882	<p>The constructor (optionally) takes an event loop to associate the watcher
		1883	with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
		1884	<p>The constructor calls <code>ev_init</code> for you, which means you have to call the
		1885	<code>set</code> method before starting it.</p>
		1886	<p>It will not set a callback, however: You have to call the templated <code>set</code>
		1887	method to set a callback before you can start the watcher.</p>
		1888	<p>(The reason why you have to use a method is a limitation in C++ which does
		1889	not allow explicit template arguments for constructors).</p>
		1890	<p>The destructor automatically stops the watcher if it is active.</p>
		1891	</dd>
		1892	<dt>w->set<class, &class::method> (object *)</dt>
		1893	<dd>
		1894	<p>This method sets the callback method to call. The method has to have a
		1895	signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as
		1896	first argument and the <code>revents</code> as second. The object must be given as
		1897	parameter and is stored in the <code>data</code> member of the watcher.</p>
		1898	<p>This method synthesizes efficient thunking code to call your method from
		1899	the C callback that libev requires. If your compiler can inline your
		1900	callback (i.e. it is visible to it at the place of the <code>set</code> call and
		1901	your compiler is good :), then the method will be fully inlined into the
		1902	thunking function, making it as fast as a direct C callback.</p>
		1903	<p>Example: simple class declaration and watcher initialisation</p>
		1904	<pre> struct myclass
		1905	{
		1906	void io_cb (ev::io &w, int revents) { }
		1907	}
		1908
		1909	myclass obj;
		1910	ev::io iow;
		1911	iow.set <myclass, &myclass::io_cb> (&obj);
		1912
		1913	</pre>
		1914	</dd>
		1915	<dt>w->set<function> (void *data = 0)</dt>
		1916	<dd>
		1917	<p>Also sets a callback, but uses a static method or plain function as
		1918	callback. The optional <code>data</code> argument will be stored in the watcher's
		1919	<code>data</code> member and is free for you to use.</p>
		1920	<p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p>
		1921	<p>See the method-<code>set</code> above for more details.</p>
		1922	<p>Example:</p>
		1923	<pre> static void io_cb (ev::io &w, int revents) { }
		1924	iow.set <io_cb> ();
		1925
		1926	</pre>
		1927	</dd>
		1928	<dt>w->set (struct ev_loop *)</dt>
		1929	<dd>
		1930	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1931	do this when the watcher is inactive (and not pending either).</p>
		1932	</dd>
		1933	<dt>w->set ([args])</dt>
		1934	<dd>
		1935	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1936	called at least once. Unlike the C counterpart, an active watcher gets
		1937	automatically stopped and restarted when reconfiguring it with this
		1938	method.</p>
		1939	</dd>
		1940	<dt>w->start ()</dt>
		1941	<dd>
		1942	<p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
		1943	constructor already stores the event loop.</p>
		1944	</dd>
		1945	<dt>w->stop ()</dt>
		1946	<dd>
		1947	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1948	</dd>
		1949	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1950	<dd>
		1951	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1952	<code>ev_TYPE_again</code> function.</p>
		1953	</dd>
		1954	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1955	<dd>
		1956	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1957	</dd>
		1958	<dt>w->update () <code>ev::stat</code> only</dt>
		1959	<dd>
		1960	<p>Invokes <code>ev_stat_stat</code>.</p>
		1961	</dd>
		1962	</dl>
		1963	</p>
		1964	</dd>
		1965	</dl>
		1966	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1967	the constructor.</p>
		1968	<pre> class myclass
		1969	{
		1970	ev_io io; void io_cb (ev::io &w, int revents);
		1971	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1972
		1973	myclass ();
		1974	}
		1975
		1976	myclass::myclass (int fd)
		1977	{
		1978	io .set <myclass, &myclass::io_cb > (this);
		1979	idle.set <myclass, &myclass::idle_cb> (this);
		1980
		1981	io.start (fd, ev::READ);
		1982	}
		1983
		1984
		1985
		1986
		1987	</pre>
		1988
		1989	</div>
		1990	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		1991	<div id="MACRO_MAGIC_CONTENT">
		1992	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1993	<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
		1994	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1995	<p>To make it easier to write programs that cope with either variant, the
		1996	following macros are defined:</p>
		1997	<dl>
		1998	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		1999	<dd>
		2000	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		2001	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		2002	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		2003	<pre> ev_unref (EV_A);
		2004	ev_timer_add (EV_A_ watcher);
		2005	ev_loop (EV_A_ 0);
		2006
		2007	</pre>
		2008	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		2009	which is often provided by the following macro.</p>
		2010	</dd>
		2011	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		2012	<dd>
		2013	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		2014	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		2015	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		2016	<pre> // this is how ev_unref is being declared
		2017	static void ev_unref (EV_P);
		2018
		2019	// this is how you can declare your typical callback
		2020	static void cb (EV_P_ ev_timer *w, int revents)
		2021
		2022	</pre>
		2023	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		2024	suitable for use with <code>EV_A</code>.</p>
		2025	</dd>
		2026	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		2027	<dd>
		2028	<p>Similar to the other two macros, this gives you the value of the default
		2029	loop, if multiple loops are supported ("ev loop default").</p>
		2030	</dd>
		2031	</dl>
		2032	<p>Example: Declare and initialise a check watcher, utilising the above
		2033	macros so it will work regardless of whether multiple loops are supported
		2034	or not.</p>
		2035	<pre> static void
		2036	check_cb (EV_P_ ev_timer *w, int revents)
		2037	{
		2038	ev_check_stop (EV_A_ w);
		2039	}
		2040
		2041	ev_check check;
		2042	ev_check_init (&check, check_cb);
		2043	ev_check_start (EV_DEFAULT_ &check);
		2044	ev_loop (EV_DEFAULT_ 0);
		2045
		2046	</pre>
		2047
		2048	</div>
		2049	<h1 id="EMBEDDING">EMBEDDING</h1>
		2050	<div id="EMBEDDING_CONTENT">
		2051	<p>Libev can (and often is) directly embedded into host
		2052	applications. Examples of applications that embed it include the Deliantra
		2053	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2054	and rxvt-unicode.</p>
		2055	<p>The goal is to enable you to just copy the neecssary files into your
		2056	source directory without having to change even a single line in them, so
		2057	you can easily upgrade by simply copying (or having a checked-out copy of
		2058	libev somewhere in your source tree).</p>
		2059
		2060	</div>
		2061	<h2 id="FILESETS">FILESETS</h2>
		2062	<div id="FILESETS_CONTENT">
		2063	<p>Depending on what features you need you need to include one or more sets of files
		2064	in your app.</p>
		2065
		2066	</div>
		2067	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		2068	<div id="CORE_EVENT_LOOP_CONTENT">
		2069	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		2070	configuration (no autoconf):</p>
		2071	<pre> #define EV_STANDALONE 1
		2072	#include "ev.c"
		2073
		2074	</pre>
		2075	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		2076	single C source file only to provide the function implementations. To use
		2077	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		2078	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		2079	where you can put other configuration options):</p>
		2080	<pre> #define EV_STANDALONE 1
		2081	#include "ev.h"
		2082
		2083	</pre>
		2084	<p>Both header files and implementation files can be compiled with a C++
		2085	compiler (at least, thats a stated goal, and breakage will be treated
		2086	as a bug).</p>
		2087	<p>You need the following files in your source tree, or in a directory
		2088	in your include path (e.g. in libev/ when using -Ilibev):</p>
		2089	<pre> ev.h
		2090	ev.c
		2091	ev_vars.h
		2092	ev_wrap.h
		2093
		2094	ev_win32.c required on win32 platforms only
		2095
		2096	ev_select.c only when select backend is enabled (which is enabled by default)
		2097	ev_poll.c only when poll backend is enabled (disabled by default)
		2098	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2099	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2100	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2101
		2102	</pre>
		2103	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		2104	to compile this single file.</p>
		2105
		2106	</div>
		2107	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		2108	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		2109	<p>To include the libevent compatibility API, also include:</p>
		2110	<pre> #include "event.c"
		2111
		2112	</pre>
		2113	<p>in the file including <cite>ev.c</cite>, and:</p>
		2114	<pre> #include "event.h"
		2115
		2116	</pre>
		2117	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		2118	<p>You need the following additional files for this:</p>
		2119	<pre> event.h
		2120	event.c
		2121
		2122	</pre>
		2123
		2124	</div>
		2125	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		2126	<div id="AUTOCONF_SUPPORT_CONTENT">
		2127	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		2128	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		2129	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		2130	include <cite>config.h</cite> and configure itself accordingly.</p>
		2131	<p>For this of course you need the m4 file:</p>
		2132	<pre> libev.m4
		2133
		2134	</pre>
		2135
		2136	</div>
		2137	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		2138	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		2139	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		2140	before including any of its files. The default is not to build for multiplicity
		2141	and only include the select backend.</p>
		2142	<dl>
		2143	<dt>EV_STANDALONE</dt>
		2144	<dd>
		2145	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		2146	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		2147	implementations for some libevent functions (such as logging, which is not
		2148	supported). It will also not define any of the structs usually found in
		2149	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		2150	</dd>
		2151	<dt>EV_USE_MONOTONIC</dt>
		2152	<dd>
		2153	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2154	monotonic clock option at both compiletime and runtime. Otherwise no use
		2155	of the monotonic clock option will be attempted. If you enable this, you
		2156	usually have to link against librt or something similar. Enabling it when
		2157	the functionality isn't available is safe, though, althoguh you have
		2158	to make sure you link against any libraries where the <code>clock_gettime</code>
		2159	function is hiding in (often <cite>-lrt</cite>).</p>
		2160	</dd>
		2161	<dt>EV_USE_REALTIME</dt>
		2162	<dd>
		2163	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2164	realtime clock option at compiletime (and assume its availability at
		2165	runtime if successful). Otherwise no use of the realtime clock option will
		2166	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		2167	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		2168	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		2169	</dd>
		2170	<dt>EV_USE_SELECT</dt>
		2171	<dd>
		2172	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		2173	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		2174	other method takes over, select will be it. Otherwise the select backend
		2175	will not be compiled in.</p>
		2176	</dd>
		2177	<dt>EV_SELECT_USE_FD_SET</dt>
		2178	<dd>
		2179	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		2180	structure. This is useful if libev doesn't compile due to a missing
		2181	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		2182	exotic systems. This usually limits the range of file descriptors to some
		2183	low limit such as 1024 or might have other limitations (winsocket only
		2184	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		2185	influence the size of the <code>fd_set</code> used.</p>
		2186	</dd>
		2187	<dt>EV_SELECT_IS_WINSOCKET</dt>
		2188	<dd>
		2189	<p>When defined to <code>1</code>, the select backend will assume that
		2190	select/socket/connect etc. don't understand file descriptors but
		2191	wants osf handles on win32 (this is the case when the select to
		2192	be used is the winsock select). This means that it will call
		2193	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		2194	it is assumed that all these functions actually work on fds, even
		2195	on win32. Should not be defined on non-win32 platforms.</p>
		2196	</dd>
		2197	<dt>EV_USE_POLL</dt>
		2198	<dd>
		2199	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		2200	backend. Otherwise it will be enabled on non-win32 platforms. It
		2201	takes precedence over select.</p>
		2202	</dd>
		2203	<dt>EV_USE_EPOLL</dt>
		2204	<dd>
		2205	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		2206	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2207	otherwise another method will be used as fallback. This is the
		2208	preferred backend for GNU/Linux systems.</p>
		2209	</dd>
		2210	<dt>EV_USE_KQUEUE</dt>
		2211	<dd>
		2212	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2213	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2214	otherwise another method will be used as fallback. This is the preferred
		2215	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2216	supports some types of fds correctly (the only platform we found that
		2217	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2218	not be used unless explicitly requested. The best way to use it is to find
		2219	out whether kqueue supports your type of fd properly and use an embedded
		2220	kqueue loop.</p>
		2221	</dd>
		2222	<dt>EV_USE_PORT</dt>
		2223	<dd>
		2224	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2225	10 port style backend. Its availability will be detected at runtime,
		2226	otherwise another method will be used as fallback. This is the preferred
		2227	backend for Solaris 10 systems.</p>
		2228	</dd>
		2229	<dt>EV_USE_DEVPOLL</dt>
		2230	<dd>
		2231	<p>reserved for future expansion, works like the USE symbols above.</p>
		2232	</dd>
		2233	<dt>EV_USE_INOTIFY</dt>
		2234	<dd>
		2235	<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
		2236	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2237	be detected at runtime.</p>
		2238	</dd>
		2239	<dt>EV_H</dt>
		2240	<dd>
		2241	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2242	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2243	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2244	</dd>
		2245	<dt>EV_CONFIG_H</dt>
		2246	<dd>
		2247	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2248	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2249	<code>EV_H</code>, above.</p>
		2250	</dd>
		2251	<dt>EV_EVENT_H</dt>
		2252	<dd>
		2253	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2254	of how the <cite>event.h</cite> header can be found.</p>
		2255	</dd>
		2256	<dt>EV_PROTOTYPES</dt>
		2257	<dd>
		2258	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2259	prototypes, but still define all the structs and other symbols. This is
		2260	occasionally useful if you want to provide your own wrapper functions
		2261	around libev functions.</p>
		2262	</dd>
		2263	<dt>EV_MULTIPLICITY</dt>
		2264	<dd>
		2265	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2266	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2267	additional independent event loops. Otherwise there will be no support
		2268	for multiple event loops and there is no first event loop pointer
		2269	argument. Instead, all functions act on the single default loop.</p>
		2270	</dd>
		2271	<dt>EV_MINPRI</dt>
		2272	<dt>EV_MAXPRI</dt>
		2273	<dd>
		2274	<p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
		2275	<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
		2276	provide for more priorities by overriding those symbols (usually defined
		2277	to be <code>-2</code> and <code>2</code>, respectively).</p>
		2278	<p>When doing priority-based operations, libev usually has to linearly search
		2279	all the priorities, so having many of them (hundreds) uses a lot of space
		2280	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2281	fine.</p>
		2282	<p>If your embedding app does not need any priorities, defining these both to
		2283	<code>0</code> will save some memory and cpu.</p>
		2284	</dd>
		2285	<dt>EV_PERIODIC_ENABLE</dt>
		2286	<dd>
		2287	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2288	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2289	code.</p>
		2290	</dd>
		2291	<dt>EV_IDLE_ENABLE</dt>
		2292	<dd>
		2293	<p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
		2294	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2295	code.</p>
		2296	</dd>
		2297	<dt>EV_EMBED_ENABLE</dt>
		2298	<dd>
		2299	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2300	defined to be <code>0</code>, then they are not.</p>
		2301	</dd>
		2302	<dt>EV_STAT_ENABLE</dt>
		2303	<dd>
		2304	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2305	defined to be <code>0</code>, then they are not.</p>
		2306	</dd>
		2307	<dt>EV_FORK_ENABLE</dt>
		2308	<dd>
		2309	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2310	defined to be <code>0</code>, then they are not.</p>
		2311	</dd>
		2312	<dt>EV_MINIMAL</dt>
		2313	<dd>
		2314	<p>If you need to shave off some kilobytes of code at the expense of some
		2315	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2316	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2317	</dd>
		2318	<dt>EV_PID_HASHSIZE</dt>
		2319	<dd>
		2320	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2321	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2322	than enough. If you need to manage thousands of children you might want to
		2323	increase this value (<i>must</i> be a power of two).</p>
		2324	</dd>
		2325	<dt>EV_INOTIFY_HASHSIZE</dt>
		2326	<dd>
		2327	<p><code>ev_staz</code> watchers use a small hash table to distribute workload by
		2328	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2329	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2330	watchers you might want to increase this value (<i>must</i> be a power of
		2331	two).</p>
		2332	</dd>
		2333	<dt>EV_COMMON</dt>
		2334	<dd>
		2335	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2336	this macro to a something else you can include more and other types of
		2337	members. You have to define it each time you include one of the files,
		2338	though, and it must be identical each time.</p>
		2339	<p>For example, the perl EV module uses something like this:</p>
		2340	<pre> #define EV_COMMON \
		2341	SV self; / contains this struct */ \
		2342	SV cb_sv, fh /* note no trailing ";" */
		2343
		2344	</pre>
		2345	</dd>
		2346	<dt>EV_CB_DECLARE (type)</dt>
		2347	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2348	<dt>ev_set_cb (ev, cb)</dt>
		2349	<dd>
		2350	<p>Can be used to change the callback member declaration in each watcher,
		2351	and the way callbacks are invoked and set. Must expand to a struct member
		2352	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2353	their default definitions. One possible use for overriding these is to
		2354	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2355	method calls instead of plain function calls in C++.</p>
		2356
		2357	</div>
		2358	<h2 id="EXAMPLES">EXAMPLES</h2>
		2359	<div id="EXAMPLES_CONTENT">
		2360	<p>For a real-world example of a program the includes libev
		2361	verbatim, you can have a look at the EV perl module
		2362	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2363	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2364	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2365	will be compiled. It is pretty complex because it provides its own header
		2366	file.</p>
		2367	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2368	that everybody includes and which overrides some configure choices:</p>
		2369	<pre> #define EV_MINIMAL 1
		2370	#define EV_USE_POLL 0
		2371	#define EV_MULTIPLICITY 0
		2372	#define EV_PERIODIC_ENABLE 0
		2373	#define EV_STAT_ENABLE 0
		2374	#define EV_FORK_ENABLE 0
		2375	#define EV_CONFIG_H <config.h>
		2376	#define EV_MINPRI 0
		2377	#define EV_MAXPRI 0
		2378
		2379	#include "ev++.h"
		2380
		2381	</pre>
		2382	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2383	<pre> #include "ev_cpp.h"
		2384	#include "ev.c"
		2385
		2386
		2387
		2388
		2389	</pre>
		2390
		2391	</div>
		2392	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2393	<div id="COMPLEXITIES_CONTENT">
		2394	<p>In this section the complexities of (many of) the algorithms used inside
		2395	libev will be explained. For complexity discussions about backends see the
		2396	documentation for <code>ev_default_init</code>.</p>
		2397	<p>All of the following are about amortised time: If an array needs to be
		2398	extended, libev needs to realloc and move the whole array, but this
		2399	happens asymptotically never with higher number of elements, so O(1) might
		2400	mean it might do a lengthy realloc operation in rare cases, but on average
		2401	it is much faster and asymptotically approaches constant time.</p>
		2402	<p>
		2403	<dl>
		2404	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2405	<dd>
		2406	<p>This means that, when you have a watcher that triggers in one hour and
		2407	there are 100 watchers that would trigger before that then inserting will
		2408	have to skip those 100 watchers.</p>
		2409	</dd>
		2410	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2411	<dd>
		2412	<p>That means that for changing a timer costs less than removing/adding them
		2413	as only the relative motion in the event queue has to be paid for.</p>
		2414	</dd>
		2415	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2416	<dd>
		2417	<p>These just add the watcher into an array or at the head of a list.
		2418	=item Stopping check/prepare/idle watchers: O(1)</p>
		2419	</dd>
		2420	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
		2421	<dd>
		2422	<p>These watchers are stored in lists then need to be walked to find the
		2423	correct watcher to remove. The lists are usually short (you don't usually
		2424	have many watchers waiting for the same fd or signal).</p>
		2425	</dd>
		2426	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2427	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2428	<dd>
		2429	<p>A change means an I/O watcher gets started or stopped, which requires
		2430	libev to recalculate its status (and possibly tell the kernel).</p>
		2431	</dd>
		2432	<dt>Activating one watcher: O(1)</dt>
		2433	<dt>Priority handling: O(number_of_priorities)</dt>
		2434	<dd>
		2435	<p>Priorities are implemented by allocating some space for each
		2436	priority. When doing priority-based operations, libev usually has to
		2437	linearly search all the priorities.</p>
		2438	</dd>
		2439	</dl>
		2440	</p>
		2441
		2442
		2443
		2444
		2445
		2446	</div>
		2447	<h1 id="AUTHOR">AUTHOR</h1>
760	<div id="AUTHOR_CONTENT">	2448	<div id="AUTHOR_CONTENT">
761	<p>Marc Lehmann <libev@schmorp.de>.</p>	2449	<p>Marc Lehmann <libev@schmorp.de>.</p>
762		2450
763	</div>	2451	</div>
764	</div></body>	2452	</div></body>
765	</html>	2453	</html>

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Revision 1.74 by root, Sun Dec 9 19:42:57 2007 UTC