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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 09:58:27 2007" />	9	<meta name="created" content="Sat Dec 8 15:27:35 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> * If there are no active watchers (reference count is zero), return.
		535	- Queue prepare watchers and then call all outstanding watchers.
		536	- If we have been forked, recreate the kernel state.
		537	- Update the kernel state with all outstanding changes.
		538	- Update the "event loop time".
		539	- Calculate for how long to block.
		540	- Block the process, waiting for any events.
		541	- Queue all outstanding I/O (fd) events.
		542	- Update the "event loop time" and do time jump handling.
		543	- Queue all outstanding timers.
		544	- Queue all outstanding periodics.
		545	- If no events are pending now, queue all idle watchers.
		546	- Queue all check watchers.
		547	- Call all queued watchers in reverse order (i.e. check watchers first).
		548	Signals and child watchers are implemented as I/O watchers, and will
		549	be handled here by queueing them when their watcher gets executed.
		550	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		551	were used, return, otherwise continue with step *.
		552
		553	</pre>
		554	<p>Example: Queue some jobs and then loop until no events are outsanding
		555	anymore.</p>
		556	<pre> ... queue jobs here, make sure they register event watchers as long
		557	... as they still have work to do (even an idle watcher will do..)
		558	ev_loop (my_loop, 0);
		559	... jobs done. yeah!
		560
		561	</pre>
269	</dd>	562	</dd>
270	<dt>ev_unloop (loop, how)</dt>	563	<dt>ev_unloop (loop, how)</dt>
271	<dd>	564	<dd>
272	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it	565	<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	566	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	567	<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>	568	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276	</dd>	569	</dd>
277	<dt>ev_ref (loop)</dt>	570	<dt>ev_ref (loop)</dt>
278	<dt>ev_unref (loop)</dt>	571	<dt>ev_unref (loop)</dt>
279	<dd>	572	<dd>
…		…
285	example, libev itself uses this for its internal signal pipe: It is not	578	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	579	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	580	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	581	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>	582	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		583	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		584	running when nothing else is active.</p>
		585	<pre> struct ev_signal exitsig;
		586	ev_signal_init (&exitsig, sig_cb, SIGINT);
		587	ev_signal_start (loop, &exitsig);
		588	evf_unref (loop);
		589
		590	</pre>
		591	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		592	<pre> ev_ref (loop);
		593	ev_signal_stop (loop, &exitsig);
		594
		595	</pre>
290	</dd>	596	</dd>
291	</dl>	597	</dl>
292		598
		599
		600
		601
		602
293	</div>	603	</div>
294	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	604	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
295	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	605	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
296	<p>A watcher is a structure that you create and register to record your	606	<p>A watcher is a structure that you create and register to record your
297	interest in some event. For instance, if you want to wait for STDIN to	607	interest in some event. For instance, if you want to wait for STDIN to
298	become readable, you would create an <code>ev_io</code> watcher for that:</p>	608	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)	609	<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	636	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	637	*)</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>	638	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	639	<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	640	must not touch the values stored in it. Most specifically you must never
331	reinitialise it or call its set method.</p>	641	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	642	<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	643	registered watcher structure as second, and a bitset of received events as
338	third argument.</p>	644	third argument.</p>
339	<p>The received events usually include a single bit per event type received	645	<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	646	(you can receive multiple events at the same time). The possible bit masks
…		…
360	</dd>	666	</dd>
361	<dt><code>EV_CHILD</code></dt>	667	<dt><code>EV_CHILD</code></dt>
362	<dd>	668	<dd>
363	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>	669	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
364	</dd>	670	</dd>
		671	<dt><code>EV_STAT</code></dt>
		672	<dd>
		673	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		674	</dd>
365	<dt><code>EV_IDLE</code></dt>	675	<dt><code>EV_IDLE</code></dt>
366	<dd>	676	<dd>
367	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>	677	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
368	</dd>	678	</dd>
369	<dt><code>EV_PREPARE</code></dt>	679	<dt><code>EV_PREPARE</code></dt>
…		…
374	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	684	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
375	received events. Callbacks of both watcher types can start and stop as	685	received events. Callbacks of both watcher types can start and stop as
376	many watchers as they want, and all of them will be taken into account	686	many watchers as they want, and all of them will be taken into account
377	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep	687	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
378	<code>ev_loop</code> from blocking).</p>	688	<code>ev_loop</code> from blocking).</p>
		689	</dd>
		690	<dt><code>EV_EMBED</code></dt>
		691	<dd>
		692	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		693	</dd>
		694	<dt><code>EV_FORK</code></dt>
		695	<dd>
		696	<p>The event loop has been resumed in the child process after fork (see
		697	<code>ev_fork</code>).</p>
379	</dd>	698	</dd>
380	<dt><code>EV_ERROR</code></dt>	699	<dt><code>EV_ERROR</code></dt>
381	<dd>	700	<dd>
382	<p>An unspecified error has occured, the watcher has been stopped. This might	701	<p>An unspecified error has occured, the watcher has been stopped. This might
383	happen because the watcher could not be properly started because libev	702	happen because the watcher could not be properly started because libev
…		…
391	programs, though, so beware.</p>	710	programs, though, so beware.</p>
392	</dd>	711	</dd>
393	</dl>	712	</dl>
394		713
395	</div>	714	</div>
		715	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		716	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		717	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		718	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		719	<dl>
		720	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		721	<dd>
		722	<p>This macro initialises the generic portion of a watcher. The contents
		723	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		724	the generic parts of the watcher are initialised, you <i>need</i> to call
		725	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		726	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		727	which rolls both calls into one.</p>
		728	<p>You can reinitialise a watcher at any time as long as it has been stopped
		729	(or never started) and there are no pending events outstanding.</p>
		730	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		731	int revents)</code>.</p>
		732	</dd>
		733	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		734	<dd>
		735	<p>This macro initialises the type-specific parts of a watcher. You need to
		736	call <code>ev_init</code> at least once before you call this macro, but you can
		737	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		738	macro on a watcher that is active (it can be pending, however, which is a
		739	difference to the <code>ev_init</code> macro).</p>
		740	<p>Although some watcher types do not have type-specific arguments
		741	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		742	</dd>
		743	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		744	<dd>
		745	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		746	calls into a single call. This is the most convinient method to initialise
		747	a watcher. The same limitations apply, of course.</p>
		748	</dd>
		749	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		750	<dd>
		751	<p>Starts (activates) the given watcher. Only active watchers will receive
		752	events. If the watcher is already active nothing will happen.</p>
		753	</dd>
		754	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		755	<dd>
		756	<p>Stops the given watcher again (if active) and clears the pending
		757	status. It is possible that stopped watchers are pending (for example,
		758	non-repeating timers are being stopped when they become pending), but
		759	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		760	you want to free or reuse the memory used by the watcher it is therefore a
		761	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		762	</dd>
		763	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		764	<dd>
		765	<p>Returns a true value iff the watcher is active (i.e. it has been started
		766	and not yet been stopped). As long as a watcher is active you must not modify
		767	it.</p>
		768	</dd>
		769	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		770	<dd>
		771	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		772	events but its callback has not yet been invoked). As long as a watcher
		773	is pending (but not active) you must not call an init function on it (but
		774	<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
		775	make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
		776	it).</p>
		777	</dd>
		778	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		779	<dd>
		780	<p>Returns the callback currently set on the watcher.</p>
		781	</dd>
		782	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		783	<dd>
		784	<p>Change the callback. You can change the callback at virtually any time
		785	(modulo threads).</p>
		786	</dd>
		787	<dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
		788	<dt>int ev_priority (ev_TYPE *watcher)</dt>
		789	<dd>
		790	<p>Set and query the priority of the watcher. The priority is a small
		791	integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
		792	(default: <code>-2</code>). Pending watchers with higher priority will be invoked
		793	before watchers with lower priority, but priority will not keep watchers
		794	from being executed (except for <code>ev_idle</code> watchers).</p>
		795	<p>This means that priorities are <i>only</i> used for ordering callback
		796	invocation after new events have been received. This is useful, for
		797	example, to reduce latency after idling, or more often, to bind two
		798	watchers on the same event and make sure one is called first.</p>
		799	<p>If you need to suppress invocation when higher priority events are pending
		800	you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
		801	<p>You <i>must not</i> change the priority of a watcher as long as it is active or
		802	pending.</p>
		803	<p>The default priority used by watchers when no priority has been set is
		804	always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
		805	<p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
		806	fine, as long as you do not mind that the priority value you query might
		807	or might not have been adjusted to be within valid range.</p>
		808	</dd>
		809	<dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
		810	<dd>
		811	<p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
		812	<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
		813	can deal with that fact.</p>
		814	</dd>
		815	<dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
		816	<dd>
		817	<p>If the watcher is pending, this function returns clears its pending status
		818	and returns its <code>revents</code> bitset (as if its callback was invoked). If the
		819	watcher isn't pending it does nothing and returns <code>0</code>.</p>
		820	</dd>
		821	</dl>
		822
		823
		824
		825
		826
		827	</div>
396	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	828	<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">	829	<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	830	<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	831	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	832	to associate arbitrary data with your watcher. If you need more data and
…		…
417	struct my_io w = (struct my_io )w_;	849	struct my_io w = (struct my_io )w_;
418	...	850	...
419	}	851	}
420		852
421	</pre>	853	</pre>
422	<p>More interesting and less C-conformant ways of catsing your callback type	854	<p>More interesting and less C-conformant ways of casting your callback type
423	have been omitted....</p>	855	instead have been omitted.</p>
		856	<p>Another common scenario is having some data structure with multiple
		857	watchers:</p>
		858	<pre> struct my_biggy
		859	{
		860	int some_data;
		861	ev_timer t1;
		862	ev_timer t2;
		863	}
424		864
		865	</pre>
		866	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		867	you need to use <code>offsetof</code>:</p>
		868	<pre> #include <stddef.h>
425		869
		870	static void
		871	t1_cb (EV_P_ struct ev_timer *w, int revents)
		872	{
		873	struct my_biggy big = (struct my_biggy *
		874	(((char *)w) - offsetof (struct my_biggy, t1));
		875	}
426		876
		877	static void
		878	t2_cb (EV_P_ struct ev_timer *w, int revents)
		879	{
		880	struct my_biggy big = (struct my_biggy *
		881	(((char *)w) - offsetof (struct my_biggy, t2));
		882	}
427		883
428		884
		885
		886
		887	</pre>
		888
429	</div>	889	</div>
430	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	890	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
431	<div id="WATCHER_TYPES_CONTENT">	891	<div id="WATCHER_TYPES_CONTENT">
432	<p>This section describes each watcher in detail, but will not repeat	892	<p>This section describes each watcher in detail, but will not repeat
433	information given in the last section.</p>	893	information given in the last section. Any initialisation/set macros,
		894	functions and members specific to the watcher type are explained.</p>
		895	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		896	while the watcher is active, you can look at the member and expect some
		897	sensible content, but you must not modify it (you can modify it while the
		898	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		899	means you can expect it to have some sensible content while the watcher
		900	is active, but you can also modify it. Modifying it may not do something
		901	sensible or take immediate effect (or do anything at all), but libev will
		902	not crash or malfunction in any way.</p>
434		903
		904
		905
		906
		907
435	</div>	908	</div>
436	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	909	<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">	910	<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	911	<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	912	in each iteration of the event loop, or, more precisely, when reading
440	level-triggering because you keep receiving events as long as the	913	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	914	some data. This behaviour is called level-triggering because you keep
442	act on the event and neither want to receive future events).</p>	915	receiving events as long as the condition persists. Remember you can stop
		916	the watcher if you don't want to act on the event and neither want to
		917	receive future events.</p>
443	<p>In general you can register as many read and/or write event watchers oer	918	<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	919	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	920	descriptors to non-blocking mode is also usually a good idea (but not
446	required if you know what you are doing).</p>	921	required if you know what you are doing).</p>
447	<p>You have to be careful with dup'ed file descriptors, though. Some backends	922	<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	923	(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	924	descriptors correctly if you register interest in two or more fds pointing
450	to the same file/socket etc. description.</p>	925	to the same underlying file/socket/etc. description (that is, they share
		926	the same underlying "file open").</p>
451	<p>If you must do this, then force the use of a known-to-be-good backend	927	<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	928	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453	EVMETHOD_POLL).</p>	929	<code>EVBACKEND_POLL</code>).</p>
		930	<p>Another thing you have to watch out for is that it is quite easy to
		931	receive "spurious" readyness notifications, that is your callback might
		932	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		933	because there is no data. Not only are some backends known to create a
		934	lot of those (for example solaris ports), it is very easy to get into
		935	this situation even with a relatively standard program structure. Thus
		936	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		937	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		938	<p>If you cannot run the fd in non-blocking mode (for example you should not
		939	play around with an Xlib connection), then you have to seperately re-test
		940	whether a file descriptor is really ready with a known-to-be good interface
		941	such as poll (fortunately in our Xlib example, Xlib already does this on
		942	its own, so its quite safe to use).</p>
454	<dl>	943	<dl>
455	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	944	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	945	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
457	<dd>	946	<dd>
458	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	947	<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 \|	948	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>	949	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		950	</dd>
		951	<dt>int fd [read-only]</dt>
		952	<dd>
		953	<p>The file descriptor being watched.</p>
		954	</dd>
		955	<dt>int events [read-only]</dt>
		956	<dd>
		957	<p>The events being watched.</p>
461	</dd>	958	</dd>
462	</dl>	959	</dl>
		960	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		961	readable, but only once. Since it is likely line-buffered, you could
		962	attempt to read a whole line in the callback.</p>
		963	<pre> static void
		964	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		965	{
		966	ev_io_stop (loop, w);
		967	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		968	}
463		969
		970	...
		971	struct ev_loop *loop = ev_default_init (0);
		972	struct ev_io stdin_readable;
		973	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		974	ev_io_start (loop, &stdin_readable);
		975	ev_loop (loop, 0);
		976
		977
		978
		979
		980	</pre>
		981
464	</div>	982	</div>
465	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	983	<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">	984	<div id="code_ev_timer_code_relative_and_opti-2">
467	<p>Timer watchers are simple relative timers that generate an event after a	985	<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>	986	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	987	<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	988	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	989	time, it will still time out after (roughly) and hour. "Roughly" because
472	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	990	detecting time jumps is hard, and some inaccuracies are unavoidable (the
473	monotonic clock option helps a lot here).</p>	991	monotonic clock option helps a lot here).</p>
474	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>	992	<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	993	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	994	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	995	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>	996	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.);	997	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
480		998
481	</pre>	999	</pre>
		1000	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		1001	but if multiple timers become ready during the same loop iteration then
		1002	order of execution is undefined.</p>
482	<dl>	1003	<dl>
483	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	1004	<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>	1005	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485	<dd>	1006	<dd>
486	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	1007	<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	1009	timer will automatically be configured to trigger again <code>repeat</code> seconds
489	later, again, and again, until stopped manually.</p>	1010	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	1011	<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	1012	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	1013	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	1014	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>	1015	timer will not fire more than once per event loop iteration.</p>
495	</dd>	1016	</dd>
496	<dt>ev_timer_again (loop)</dt>	1017	<dt>ev_timer_again (loop)</dt>
497	<dd>	1018	<dd>
498	<p>This will act as if the timer timed out and restart it again if it is	1019	<p>This will act as if the timer timed out and restart it again if it is
499	repeating. The exact semantics are:</p>	1020	repeating. The exact semantics are:</p>
		1021	<p>If the timer is pending, its pending status is cleared.</p>
500	<p>If the timer is started but nonrepeating, stop it.</p>	1022	<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	1023	<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>	1024	<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	1025	<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	1026	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	1027	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	1028	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	1029	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	1030	<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	1031	you go into an idle state where you do not expect data to travel on the
		1032	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>	1033	automatically restart it if need be.</p>
		1034	<p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
		1035	altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
		1036	<pre> ev_timer_init (timer, callback, 0., 5.);
		1037	ev_timer_again (loop, timer);
		1038	...
		1039	timer->again = 17.;
		1040	ev_timer_again (loop, timer);
		1041	...
		1042	timer->again = 10.;
		1043	ev_timer_again (loop, timer);
		1044
		1045	</pre>
		1046	<p>This is more slightly efficient then stopping/starting the timer each time
		1047	you want to modify its timeout value.</p>
		1048	</dd>
		1049	<dt>ev_tstamp repeat [read-write]</dt>
		1050	<dd>
		1051	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		1052	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		1053	which is also when any modifications are taken into account.</p>
511	</dd>	1054	</dd>
512	</dl>	1055	</dl>
		1056	<p>Example: Create a timer that fires after 60 seconds.</p>
		1057	<pre> static void
		1058	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1059	{
		1060	.. one minute over, w is actually stopped right here
		1061	}
513		1062
		1063	struct ev_timer mytimer;
		1064	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1065	ev_timer_start (loop, &mytimer);
		1066
		1067	</pre>
		1068	<p>Example: Create a timeout timer that times out after 10 seconds of
		1069	inactivity.</p>
		1070	<pre> static void
		1071	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1072	{
		1073	.. ten seconds without any activity
		1074	}
		1075
		1076	struct ev_timer mytimer;
		1077	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1078	ev_timer_again (&mytimer); /* start timer */
		1079	ev_loop (loop, 0);
		1080
		1081	// and in some piece of code that gets executed on any "activity":
		1082	// reset the timeout to start ticking again at 10 seconds
		1083	ev_timer_again (&mytimer);
		1084
		1085
		1086
		1087
		1088	</pre>
		1089
514	</div>	1090	</div>
515	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	1091	<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">	1092	<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	1093	<p>Periodic watchers are also timers of a kind, but they are very versatile
518	(and unfortunately a bit complex).</p>	1094	(and unfortunately a bit complex).</p>
519	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)	1095	<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	1096	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	1097	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 ()	1098	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	1099	+ 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	1100	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	1101	roughly 10 seconds later and of course not if you reset your system time
526	again).</p>	1102	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 eahc midnight, local time.</p>
		1105	<p>As with timers, the callback is guarenteed to be invoked only when the
		1106	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1107	during the same loop iteration then order of execution is undefined.</p>
529	<dl>	1108	<dl>
530	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1109	<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>	1110	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532	<dd>	1111	<dd>
533	<p>Lots of arguments, lets sort it out... There are basically three modes of	1112	<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>	1113	operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539	<p>	1114	<p>
540	<dl>	1115	<dl>
541	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1116	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542	<dd>	1117	<dd>
543	<p>In this configuration the watcher triggers an event at the wallclock time	1118	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
567	<dd>	1142	<dd>
568	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	1143	<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	1144	ignored. Instead, each time the periodic watcher gets scheduled, the
570	reschedule callback will be called with the watcher as first, and the	1145	reschedule callback will be called with the watcher as first, and the
571	current time as second argument.</p>	1146	current time as second argument.</p>
572	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1147	<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	1148	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>	1149	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	1150	starting a prepare watcher).</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,	1151	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
578	ev_tstamp now)</code>, e.g.:</p>	1152	ev_tstamp now)</code>, e.g.:</p>
579	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1153	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580	{	1154	{
581	return now + 60.;	1155	return now + 60.;
…		…
584	</pre>	1158	</pre>
585	<p>It must return the next time to trigger, based on the passed time value	1159	<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	1160	(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	1161	will usually be called just before the callback will be triggered, but
588	might be called at other times, too.</p>	1162	might be called at other times, too.</p>
		1163	<p>NOTE: <i>This callback must always return a time that is later than the
		1164	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	1165	<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	1166	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	1167	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>	1168	you do this is, again, up to you (but it is not trivial, which is the main
		1169	reason I omitted it as an example).</p>
593	</dd>	1170	</dd>
594	</dl>	1171	</dl>
595	</p>	1172	</p>
596	</dd>	1173	</dd>
597	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1174	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
599	<p>Simply stops and restarts the periodic watcher again. This is only useful	1176	<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	1177	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	1178	a different time than the last time it was called (e.g. in a crond like
602	program when the crontabs have changed).</p>	1179	program when the crontabs have changed).</p>
603	</dd>	1180	</dd>
		1181	<dt>ev_tstamp interval [read-write]</dt>
		1182	<dd>
		1183	<p>The current interval value. Can be modified any time, but changes only
		1184	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1185	called.</p>
		1186	</dd>
		1187	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1188	<dd>
		1189	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1190	switched off. Can be changed any time, but changes only take effect when
		1191	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1192	</dd>
604	</dl>	1193	</dl>
		1194	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1195	system clock is divisible by 3600. The callback invocation times have
		1196	potentially a lot of jittering, but good long-term stability.</p>
		1197	<pre> static void
		1198	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1199	{
		1200	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1201	}
605		1202
		1203	struct ev_periodic hourly_tick;
		1204	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1205	ev_periodic_start (loop, &hourly_tick);
		1206
		1207	</pre>
		1208	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1209	<pre> #include <math.h>
		1210
		1211	static ev_tstamp
		1212	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1213	{
		1214	return fmod (now, 3600.) + 3600.;
		1215	}
		1216
		1217	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1218
		1219	</pre>
		1220	<p>Example: Call a callback every hour, starting now:</p>
		1221	<pre> struct ev_periodic hourly_tick;
		1222	ev_periodic_init (&hourly_tick, clock_cb,
		1223	fmod (ev_now (loop), 3600.), 3600., 0);
		1224	ev_periodic_start (loop, &hourly_tick);
		1225
		1226
		1227
		1228
		1229	</pre>
		1230
606	</div>	1231	</div>
607	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	1232	<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">	1233	<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	1234	<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	1235	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	1236	will try it's best to deliver signals synchronously, i.e. as part of the
612	normal event processing, like any other event.</p>	1237	normal event processing, like any other event.</p>
…		…
621	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1246	<dt>ev_signal_set (ev_signal *, int signum)</dt>
622	<dd>	1247	<dd>
623	<p>Configures the watcher to trigger on the given signal number (usually one	1248	<p>Configures the watcher to trigger on the given signal number (usually one
624	of the <code>SIGxxx</code> constants).</p>	1249	of the <code>SIGxxx</code> constants).</p>
625	</dd>	1250	</dd>
		1251	<dt>int signum [read-only]</dt>
		1252	<dd>
		1253	<p>The signal the watcher watches out for.</p>
		1254	</dd>
626	</dl>	1255	</dl>
627		1256
		1257
		1258
		1259
		1260
628	</div>	1261	</div>
629	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	1262	<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">	1263	<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	1264	<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>	1265	some child status changes (most typically when a child of yours dies).</p>
633	<dl>	1266	<dl>
634	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1267	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
635	<dt>ev_child_set (ev_child *, int pid)</dt>	1268	<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	1272	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	1273	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	1274	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642	process causing the status change.</p>	1275	process causing the status change.</p>
643	</dd>	1276	</dd>
		1277	<dt>int pid [read-only]</dt>
		1278	<dd>
		1279	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1280	</dd>
		1281	<dt>int rpid [read-write]</dt>
		1282	<dd>
		1283	<p>The process id that detected a status change.</p>
		1284	</dd>
		1285	<dt>int rstatus [read-write]</dt>
		1286	<dd>
		1287	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1288	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
		1289	</dd>
644	</dl>	1290	</dl>
		1291	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1292	<pre> static void
		1293	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1294	{
		1295	ev_unloop (loop, EVUNLOOP_ALL);
		1296	}
645		1297
		1298	struct ev_signal signal_watcher;
		1299	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1300	ev_signal_start (loop, &sigint_cb);
		1301
		1302
		1303
		1304
		1305	</pre>
		1306
646	</div>	1307	</div>
		1308	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1309	<div id="code_ev_stat_code_did_the_file_attri-2">
		1310	<p>This watches a filesystem path for attribute changes. That is, it calls
		1311	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1312	compared to the last time, invoking the callback if it did.</p>
		1313	<p>The path does not need to exist: changing from "path exists" to "path does
		1314	not exist" is a status change like any other. The condition "path does
		1315	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1316	otherwise always forced to be at least one) and all the other fields of
		1317	the stat buffer having unspecified contents.</p>
		1318	<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
		1319	relative and your working directory changes, the behaviour is undefined.</p>
		1320	<p>Since there is no standard to do this, the portable implementation simply
		1321	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1322	can specify a recommended polling interval for this case. If you specify
		1323	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1324	unspecified default</i> value will be used (which you can expect to be around
		1325	five seconds, although this might change dynamically). Libev will also
		1326	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1327	usually overkill.</p>
		1328	<p>This watcher type is not meant for massive numbers of stat watchers,
		1329	as even with OS-supported change notifications, this can be
		1330	resource-intensive.</p>
		1331	<p>At the time of this writing, only the Linux inotify interface is
		1332	implemented (implementing kqueue support is left as an exercise for the
		1333	reader). Inotify will be used to give hints only and should not change the
		1334	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1335	to fall back to regular polling again even with inotify, but changes are
		1336	usually detected immediately, and if the file exists there will be no
		1337	polling.</p>
		1338	<dl>
		1339	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1340	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1341	<dd>
		1342	<p>Configures the watcher to wait for status changes of the given
		1343	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1344	be detected and should normally be specified as <code>0</code> to let libev choose
		1345	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1346	path for as long as the watcher is active.</p>
		1347	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1348	relative to the attributes at the time the watcher was started (or the
		1349	last change was detected).</p>
		1350	</dd>
		1351	<dt>ev_stat_stat (ev_stat *)</dt>
		1352	<dd>
		1353	<p>Updates the stat buffer immediately with new values. If you change the
		1354	watched path in your callback, you could call this fucntion to avoid
		1355	detecting this change (while introducing a race condition). Can also be
		1356	useful simply to find out the new values.</p>
		1357	</dd>
		1358	<dt>ev_statdata attr [read-only]</dt>
		1359	<dd>
		1360	<p>The most-recently detected attributes of the file. Although the type is of
		1361	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1362	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1363	was some error while <code>stat</code>ing the file.</p>
		1364	</dd>
		1365	<dt>ev_statdata prev [read-only]</dt>
		1366	<dd>
		1367	<p>The previous attributes of the file. The callback gets invoked whenever
		1368	<code>prev</code> != <code>attr</code>.</p>
		1369	</dd>
		1370	<dt>ev_tstamp interval [read-only]</dt>
		1371	<dd>
		1372	<p>The specified interval.</p>
		1373	</dd>
		1374	<dt>const char *path [read-only]</dt>
		1375	<dd>
		1376	<p>The filesystem path that is being watched.</p>
		1377	</dd>
		1378	</dl>
		1379	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1380	<pre> static void
		1381	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1382	{
		1383	/* /etc/passwd changed in some way */
		1384	if (w->attr.st_nlink)
		1385	{
		1386	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1387	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1388	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1389	}
		1390	else
		1391	/* you shalt not abuse printf for puts */
		1392	puts ("wow, /etc/passwd is not there, expect problems. "
		1393	"if this is windows, they already arrived\n");
		1394	}
		1395
		1396	...
		1397	ev_stat passwd;
		1398
		1399	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1400	ev_stat_start (loop, &passwd);
		1401
		1402
		1403
		1404
		1405	</pre>
		1406
		1407	</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>	1408	<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">	1409	<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	1410	<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	1411	priority are pending (prepare, check and other idle watchers do not
651	as your process is busy handling sockets or timeouts (or even signals,	1412	count).</p>
652	imagine) it will not be triggered. But when your process is idle all idle	1413	<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 -	1414	(or even signals, imagine) of the same or higher priority it will not be
		1415	triggered. But when your process is idle (or only lower-priority watchers
		1416	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	1417	iteration - until stopped, that is, or your process receives more events
655	busy.</p>	1418	and becomes busy again with higher priority stuff.</p>
656	<p>The most noteworthy effect is that as long as any idle watchers are	1419	<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>	1420	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	1421	<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	1422	effect on its own sometimes), idle watchers are a good place to do
660	"pseudo-background processing", or delay processing stuff to after the	1423	"pseudo-background processing", or delay processing stuff to after the
…		…
665	<p>Initialises and configures the idle watcher - it has no parameters of any	1428	<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,	1429	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667	believe me.</p>	1430	believe me.</p>
668	</dd>	1431	</dd>
669	</dl>	1432	</dl>
		1433	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1434	callback, free it. Also, use no error checking, as usual.</p>
		1435	<pre> static void
		1436	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1437	{
		1438	free (w);
		1439	// now do something you wanted to do when the program has
		1440	// no longer asnything immediate to do.
		1441	}
670		1442
		1443	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1444	ev_idle_init (idle_watcher, idle_cb);
		1445	ev_idle_start (loop, idle_cb);
		1446
		1447
		1448
		1449
		1450	</pre>
		1451
671	</div>	1452	</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>	1453	<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">	1454	<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:	1455	<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	1456	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.</p>	1457	afterwards.</p>
		1458	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1459	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1460	watchers. Other loops than the current one are fine, however. The
		1461	rationale behind this is that you do not need to check for recursion in
		1462	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1463	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1464	called in pairs bracketing the blocking call.</p>
677	<p>Their main purpose is to integrate other event mechanisms into libev. This	1465	<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	1466	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>	1467	variable changes, implement your own watchers, integrate net-snmp or a
		1468	coroutine library and lots more. They are also occasionally useful if
		1469	you cache some data and want to flush it before blocking (for example,
		1470	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1471	watcher).</p>
680	<p>This is done by examining in each prepare call which file descriptors need	1472	<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	1473	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	1474	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	1475	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	1476	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	1477	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,	1478	callbacks will never actually be called (but must be valid nevertheless,
687	because you never know, you know?).</p>	1479	because you never know, you know?).</p>
688	<p>As another example, the Perl Coro module uses these hooks to integrate	1480	<p>As another example, the Perl Coro module uses these hooks to integrate
689	coroutines into libev programs, by yielding to other active coroutines	1481	coroutines into libev programs, by yielding to other active coroutines
690	during each prepare and only letting the process block if no coroutines	1482	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	1483	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,	1484	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	1485	of lower priority, but only once, using idle watchers to keep the event
694	coroutines exist, thus mapping low-priority coroutines to idle/background	1486	loop from blocking if lower-priority coroutines are active, thus mapping
695	tasks).</p>	1487	low-priority coroutines to idle/background tasks).</p>
696	<dl>	1488	<dl>
697	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1489	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
698	<dt>ev_check_init (ev_check *, callback)</dt>	1490	<dt>ev_check_init (ev_check *, callback)</dt>
699	<dd>	1491	<dd>
700	<p>Initialises and configures the prepare or check watcher - they have no	1492	<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>	1493	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>	1494	macros, but using them is utterly, utterly and completely pointless.</p>
703	</dd>	1495	</dd>
704	</dl>	1496	</dl>
		1497	<p>Example: To include a library such as adns, you would add IO watchers
		1498	and a timeout watcher in a prepare handler, as required by libadns, and
		1499	in a check watcher, destroy them and call into libadns. What follows is
		1500	pseudo-code only of course:</p>
		1501	<pre> static ev_io iow [nfd];
		1502	static ev_timer tw;
705		1503
		1504	static void
		1505	io_cb (ev_loop loop, ev_io w, int revents)
		1506	{
		1507	// set the relevant poll flags
		1508	// could also call adns_processreadable etc. here
		1509	struct pollfd fd = (struct pollfd )w->data;
		1510	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1511	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1512	}
		1513
		1514	// create io watchers for each fd and a timer before blocking
		1515	static void
		1516	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1517	{
		1518	int timeout = 3600000;
		1519	struct pollfd fds [nfd];
		1520	// actual code will need to loop here and realloc etc.
		1521	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1522
		1523	/* the callback is illegal, but won't be called as we stop during check */
		1524	ev_timer_init (&tw, 0, timeout * 1e-3);
		1525	ev_timer_start (loop, &tw);
		1526
		1527	// create on ev_io per pollfd
		1528	for (int i = 0; i < nfd; ++i)
		1529	{
		1530	ev_io_init (iow + i, io_cb, fds [i].fd,
		1531	((fds [i].events & POLLIN ? EV_READ : 0)
		1532	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1533
		1534	fds [i].revents = 0;
		1535	iow [i].data = fds + i;
		1536	ev_io_start (loop, iow + i);
		1537	}
		1538	}
		1539
		1540	// stop all watchers after blocking
		1541	static void
		1542	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1543	{
		1544	ev_timer_stop (loop, &tw);
		1545
		1546	for (int i = 0; i < nfd; ++i)
		1547	ev_io_stop (loop, iow + i);
		1548
		1549	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1550	}
		1551
		1552
		1553
		1554
		1555	</pre>
		1556
706	</div>	1557	</div>
707	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1558	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1559	<div id="code_ev_embed_code_when_one_backend_-2">
		1560	<p>This is a rather advanced watcher type that lets you embed one event loop
		1561	into another (currently only <code>ev_io</code> events are supported in the embedded
		1562	loop, other types of watchers might be handled in a delayed or incorrect
		1563	fashion and must not be used).</p>
		1564	<p>There are primarily two reasons you would want that: work around bugs and
		1565	prioritise I/O.</p>
		1566	<p>As an example for a bug workaround, the kqueue backend might only support
		1567	sockets on some platform, so it is unusable as generic backend, but you
		1568	still want to make use of it because you have many sockets and it scales
		1569	so nicely. In this case, you would create a kqueue-based loop and embed it
		1570	into your default loop (which might use e.g. poll). Overall operation will
		1571	be a bit slower because first libev has to poll and then call kevent, but
		1572	at least you can use both at what they are best.</p>
		1573	<p>As for prioritising I/O: rarely you have the case where some fds have
		1574	to be watched and handled very quickly (with low latency), and even
		1575	priorities and idle watchers might have too much overhead. In this case
		1576	you would put all the high priority stuff in one loop and all the rest in
		1577	a second one, and embed the second one in the first.</p>
		1578	<p>As long as the watcher is active, the callback will be invoked every time
		1579	there might be events pending in the embedded loop. The callback must then
		1580	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1581	their callbacks (you could also start an idle watcher to give the embedded
		1582	loop strictly lower priority for example). You can also set the callback
		1583	to <code>0</code>, in which case the embed watcher will automatically execute the
		1584	embedded loop sweep.</p>
		1585	<p>As long as the watcher is started it will automatically handle events. The
		1586	callback will be invoked whenever some events have been handled. You can
		1587	set the callback to <code>0</code> to avoid having to specify one if you are not
		1588	interested in that.</p>
		1589	<p>Also, there have not currently been made special provisions for forking:
		1590	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1591	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1592	yourself.</p>
		1593	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1594	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1595	portable one.</p>
		1596	<p>So when you want to use this feature you will always have to be prepared
		1597	that you cannot get an embeddable loop. The recommended way to get around
		1598	this is to have a separate variables for your embeddable loop, try to
		1599	create it, and if that fails, use the normal loop for everything:</p>
		1600	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1601	struct ev_loop *loop_lo = 0;
		1602	struct ev_embed embed;
		1603
		1604	// see if there is a chance of getting one that works
		1605	// (remember that a flags value of 0 means autodetection)
		1606	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1607	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1608	: 0;
		1609
		1610	// if we got one, then embed it, otherwise default to loop_hi
		1611	if (loop_lo)
		1612	{
		1613	ev_embed_init (&embed, 0, loop_lo);
		1614	ev_embed_start (loop_hi, &embed);
		1615	}
		1616	else
		1617	loop_lo = loop_hi;
		1618
		1619	</pre>
		1620	<dl>
		1621	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1622	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1623	<dd>
		1624	<p>Configures the watcher to embed the given loop, which must be
		1625	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1626	invoked automatically, otherwise it is the responsibility of the callback
		1627	to invoke it (it will continue to be called until the sweep has been done,
		1628	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1629	</dd>
		1630	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1631	<dd>
		1632	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1633	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1634	apropriate way for embedded loops.</p>
		1635	</dd>
		1636	<dt>struct ev_loop *loop [read-only]</dt>
		1637	<dd>
		1638	<p>The embedded event loop.</p>
		1639	</dd>
		1640	</dl>
		1641
		1642
		1643
		1644
		1645
		1646	</div>
		1647	<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>
		1648	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1649	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1650	whoever is a good citizen cared to tell libev about it by calling
		1651	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1652	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1653	and only in the child after the fork. If whoever good citizen calling
		1654	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1655	handlers will be invoked, too, of course.</p>
		1656	<dl>
		1657	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1658	<dd>
		1659	<p>Initialises and configures the fork watcher - it has no parameters of any
		1660	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1661	believe me.</p>
		1662	</dd>
		1663	</dl>
		1664
		1665
		1666
		1667
		1668
		1669	</div>
		1670	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
708	<div id="OTHER_FUNCTIONS_CONTENT">	1671	<div id="OTHER_FUNCTIONS_CONTENT">
709	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1672	<p>There are some other functions of possible interest. Described. Here. Now.</p>
710	<dl>	1673	<dl>
711	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1674	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712	<dd>	1675	<dd>
713	<p>This function combines a simple timer and an I/O watcher, calls your	1676	<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	1677	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	1678	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	1679	or timeout without having to allocate/configure/start/stop/free one or
717	more watchers yourself.</p>	1680	more watchers yourself.</p>
718	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events	1681	<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	1682	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>	1683	<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	1684	<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	1685	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	1686	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724	dubious value.</p>	1687	dubious value.</p>
725	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets	1688	<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	1689	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>	1690	<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>	1691	value passed to <code>ev_once</code>:</p>
729	<pre> static void stdin_ready (int revents, void *arg)	1692	<pre> static void stdin_ready (int revents, void *arg)
730	{	1693	{
731	if (revents & EV_TIMEOUT)	1694	if (revents & EV_TIMEOUT)
…		…
736		1699
737	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1700	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738		1701
739	</pre>	1702	</pre>
740	</dd>	1703	</dd>
741	<dt>ev_feed_event (loop, watcher, int events)</dt>	1704	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
742	<dd>	1705	<dd>
743	<p>Feeds the given event set into the event loop, as if the specified event	1706	<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	1707	had happened for the specified watcher (which must be a pointer to an
745	initialised but not necessarily started event watcher).</p>	1708	initialised but not necessarily started event watcher).</p>
746	</dd>	1709	</dd>
747	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1710	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
748	<dd>	1711	<dd>
749	<p>Feed an event on the given fd, as if a file descriptor backend detected	1712	<p>Feed an event on the given fd, as if a file descriptor backend detected
750	the given events it.</p>	1713	the given events it.</p>
751	</dd>	1714	</dd>
752	<dt>ev_feed_signal_event (loop, int signum)</dt>	1715	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
753	<dd>	1716	<dd>
754	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1717	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1718	loop!).</p>
755	</dd>	1719	</dd>
756	</dl>	1720	</dl>
757		1721
		1722
		1723
		1724
		1725
758	</div>	1726	</div>
759	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1727	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1728	<div id="LIBEVENT_EMULATION_CONTENT">
		1729	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1730	emulate the internals of libevent, so here are some usage hints:</p>
		1731	<dl>
		1732	<dt>* Use it by including <event.h>, as usual.</dt>
		1733	<dt>* The following members are fully supported: ev_base, ev_callback,
		1734	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1735	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1736	maintained by libev, it does not work exactly the same way as in libevent (consider
		1737	it a private API).</dt>
		1738	<dt>* Priorities are not currently supported. Initialising priorities
		1739	will fail and all watchers will have the same priority, even though there
		1740	is an ev_pri field.</dt>
		1741	<dt>* Other members are not supported.</dt>
		1742	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1743	to use the libev header file and library.</dt>
		1744	</dl>
		1745
		1746	</div>
		1747	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1748	<div id="C_SUPPORT_CONTENT">
		1749	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1750	you to use some convinience methods to start/stop watchers and also change
		1751	the callback model to a model using method callbacks on objects.</p>
		1752	<p>To use it,</p>
		1753	<pre> #include <ev++.h>
		1754
		1755	</pre>
		1756	<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
		1757	of them macros) into the global namespace. All C++ specific things are
		1758	put into the <code>ev</code> namespace. It should support all the same embedding
		1759	options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
		1760	<p>Care has been taken to keep the overhead low. The only data member the C++
		1761	classes add (compared to plain C-style watchers) is the event loop pointer
		1762	that the watcher is associated with (or no additional members at all if
		1763	you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
		1764	<p>Currently, functions, and static and non-static member functions can be
		1765	used as callbacks. Other types should be easy to add as long as they only
		1766	need one additional pointer for context. If you need support for other
		1767	types of functors please contact the author (preferably after implementing
		1768	it).</p>
		1769	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1770	<dl>
		1771	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1772	<dd>
		1773	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1774	macros from <cite>ev.h</cite>.</p>
		1775	</dd>
		1776	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1777	<dd>
		1778	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1779	</dd>
		1780	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1781	<dd>
		1782	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1783	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1784	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1785	defines by many implementations.</p>
		1786	<p>All of those classes have these methods:</p>
		1787	<p>
		1788	<dl>
		1789	<dt>ev::TYPE::TYPE ()</dt>
		1790	<dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
		1791	<dt>ev::TYPE::~TYPE</dt>
		1792	<dd>
		1793	<p>The constructor (optionally) takes an event loop to associate the watcher
		1794	with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
		1795	<p>The constructor calls <code>ev_init</code> for you, which means you have to call the
		1796	<code>set</code> method before starting it.</p>
		1797	<p>It will not set a callback, however: You have to call the templated <code>set</code>
		1798	method to set a callback before you can start the watcher.</p>
		1799	<p>(The reason why you have to use a method is a limitation in C++ which does
		1800	not allow explicit template arguments for constructors).</p>
		1801	<p>The destructor automatically stops the watcher if it is active.</p>
		1802	</dd>
		1803	<dt>w->set<class, &class::method> (object *)</dt>
		1804	<dd>
		1805	<p>This method sets the callback method to call. The method has to have a
		1806	signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as
		1807	first argument and the <code>revents</code> as second. The object must be given as
		1808	parameter and is stored in the <code>data</code> member of the watcher.</p>
		1809	<p>This method synthesizes efficient thunking code to call your method from
		1810	the C callback that libev requires. If your compiler can inline your
		1811	callback (i.e. it is visible to it at the place of the <code>set</code> call and
		1812	your compiler is good :), then the method will be fully inlined into the
		1813	thunking function, making it as fast as a direct C callback.</p>
		1814	<p>Example: simple class declaration and watcher initialisation</p>
		1815	<pre> struct myclass
		1816	{
		1817	void io_cb (ev::io &w, int revents) { }
		1818	}
		1819
		1820	myclass obj;
		1821	ev::io iow;
		1822	iow.set <myclass, &myclass::io_cb> (&obj);
		1823
		1824	</pre>
		1825	</dd>
		1826	<dt>w->set<function> (void *data = 0)</dt>
		1827	<dd>
		1828	<p>Also sets a callback, but uses a static method or plain function as
		1829	callback. The optional <code>data</code> argument will be stored in the watcher's
		1830	<code>data</code> member and is free for you to use.</p>
		1831	<p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p>
		1832	<p>See the method-<code>set</code> above for more details.</p>
		1833	<p>Example:</p>
		1834	<pre> static void io_cb (ev::io &w, int revents) { }
		1835	iow.set <io_cb> ();
		1836
		1837	</pre>
		1838	</dd>
		1839	<dt>w->set (struct ev_loop *)</dt>
		1840	<dd>
		1841	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1842	do this when the watcher is inactive (and not pending either).</p>
		1843	</dd>
		1844	<dt>w->set ([args])</dt>
		1845	<dd>
		1846	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1847	called at least once. Unlike the C counterpart, an active watcher gets
		1848	automatically stopped and restarted when reconfiguring it with this
		1849	method.</p>
		1850	</dd>
		1851	<dt>w->start ()</dt>
		1852	<dd>
		1853	<p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
		1854	constructor already stores the event loop.</p>
		1855	</dd>
		1856	<dt>w->stop ()</dt>
		1857	<dd>
		1858	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1859	</dd>
		1860	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1861	<dd>
		1862	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1863	<code>ev_TYPE_again</code> function.</p>
		1864	</dd>
		1865	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1866	<dd>
		1867	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1868	</dd>
		1869	<dt>w->update () <code>ev::stat</code> only</dt>
		1870	<dd>
		1871	<p>Invokes <code>ev_stat_stat</code>.</p>
		1872	</dd>
		1873	</dl>
		1874	</p>
		1875	</dd>
		1876	</dl>
		1877	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1878	the constructor.</p>
		1879	<pre> class myclass
		1880	{
		1881	ev_io io; void io_cb (ev::io &w, int revents);
		1882	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1883
		1884	myclass ();
		1885	}
		1886
		1887	myclass::myclass (int fd)
		1888	{
		1889	io .set <myclass, &myclass::io_cb > (this);
		1890	idle.set <myclass, &myclass::idle_cb> (this);
		1891
		1892	io.start (fd, ev::READ);
		1893	}
		1894
		1895
		1896
		1897
		1898	</pre>
		1899
		1900	</div>
		1901	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		1902	<div id="MACRO_MAGIC_CONTENT">
		1903	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1904	<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
		1905	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1906	<p>To make it easier to write programs that cope with either variant, the
		1907	following macros are defined:</p>
		1908	<dl>
		1909	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		1910	<dd>
		1911	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		1912	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		1913	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		1914	<pre> ev_unref (EV_A);
		1915	ev_timer_add (EV_A_ watcher);
		1916	ev_loop (EV_A_ 0);
		1917
		1918	</pre>
		1919	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		1920	which is often provided by the following macro.</p>
		1921	</dd>
		1922	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		1923	<dd>
		1924	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		1925	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		1926	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		1927	<pre> // this is how ev_unref is being declared
		1928	static void ev_unref (EV_P);
		1929
		1930	// this is how you can declare your typical callback
		1931	static void cb (EV_P_ ev_timer *w, int revents)
		1932
		1933	</pre>
		1934	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		1935	suitable for use with <code>EV_A</code>.</p>
		1936	</dd>
		1937	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		1938	<dd>
		1939	<p>Similar to the other two macros, this gives you the value of the default
		1940	loop, if multiple loops are supported ("ev loop default").</p>
		1941	</dd>
		1942	</dl>
		1943	<p>Example: Declare and initialise a check watcher, utilising the above
		1944	macros so it will work regardless of whether multiple loops are supported
		1945	or not.</p>
		1946	<pre> static void
		1947	check_cb (EV_P_ ev_timer *w, int revents)
		1948	{
		1949	ev_check_stop (EV_A_ w);
		1950	}
		1951
		1952	ev_check check;
		1953	ev_check_init (&check, check_cb);
		1954	ev_check_start (EV_DEFAULT_ &check);
		1955	ev_loop (EV_DEFAULT_ 0);
		1956
		1957	</pre>
		1958
		1959	</div>
		1960	<h1 id="EMBEDDING">EMBEDDING</h1>
		1961	<div id="EMBEDDING_CONTENT">
		1962	<p>Libev can (and often is) directly embedded into host
		1963	applications. Examples of applications that embed it include the Deliantra
		1964	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1965	and rxvt-unicode.</p>
		1966	<p>The goal is to enable you to just copy the neecssary files into your
		1967	source directory without having to change even a single line in them, so
		1968	you can easily upgrade by simply copying (or having a checked-out copy of
		1969	libev somewhere in your source tree).</p>
		1970
		1971	</div>
		1972	<h2 id="FILESETS">FILESETS</h2>
		1973	<div id="FILESETS_CONTENT">
		1974	<p>Depending on what features you need you need to include one or more sets of files
		1975	in your app.</p>
		1976
		1977	</div>
		1978	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1979	<div id="CORE_EVENT_LOOP_CONTENT">
		1980	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1981	configuration (no autoconf):</p>
		1982	<pre> #define EV_STANDALONE 1
		1983	#include "ev.c"
		1984
		1985	</pre>
		1986	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1987	single C source file only to provide the function implementations. To use
		1988	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1989	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1990	where you can put other configuration options):</p>
		1991	<pre> #define EV_STANDALONE 1
		1992	#include "ev.h"
		1993
		1994	</pre>
		1995	<p>Both header files and implementation files can be compiled with a C++
		1996	compiler (at least, thats a stated goal, and breakage will be treated
		1997	as a bug).</p>
		1998	<p>You need the following files in your source tree, or in a directory
		1999	in your include path (e.g. in libev/ when using -Ilibev):</p>
		2000	<pre> ev.h
		2001	ev.c
		2002	ev_vars.h
		2003	ev_wrap.h
		2004
		2005	ev_win32.c required on win32 platforms only
		2006
		2007	ev_select.c only when select backend is enabled (which is enabled by default)
		2008	ev_poll.c only when poll backend is enabled (disabled by default)
		2009	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2010	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2011	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2012
		2013	</pre>
		2014	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		2015	to compile this single file.</p>
		2016
		2017	</div>
		2018	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		2019	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		2020	<p>To include the libevent compatibility API, also include:</p>
		2021	<pre> #include "event.c"
		2022
		2023	</pre>
		2024	<p>in the file including <cite>ev.c</cite>, and:</p>
		2025	<pre> #include "event.h"
		2026
		2027	</pre>
		2028	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		2029	<p>You need the following additional files for this:</p>
		2030	<pre> event.h
		2031	event.c
		2032
		2033	</pre>
		2034
		2035	</div>
		2036	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		2037	<div id="AUTOCONF_SUPPORT_CONTENT">
		2038	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		2039	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		2040	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		2041	include <cite>config.h</cite> and configure itself accordingly.</p>
		2042	<p>For this of course you need the m4 file:</p>
		2043	<pre> libev.m4
		2044
		2045	</pre>
		2046
		2047	</div>
		2048	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		2049	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		2050	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		2051	before including any of its files. The default is not to build for multiplicity
		2052	and only include the select backend.</p>
		2053	<dl>
		2054	<dt>EV_STANDALONE</dt>
		2055	<dd>
		2056	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		2057	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		2058	implementations for some libevent functions (such as logging, which is not
		2059	supported). It will also not define any of the structs usually found in
		2060	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		2061	</dd>
		2062	<dt>EV_USE_MONOTONIC</dt>
		2063	<dd>
		2064	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2065	monotonic clock option at both compiletime and runtime. Otherwise no use
		2066	of the monotonic clock option will be attempted. If you enable this, you
		2067	usually have to link against librt or something similar. Enabling it when
		2068	the functionality isn't available is safe, though, althoguh you have
		2069	to make sure you link against any libraries where the <code>clock_gettime</code>
		2070	function is hiding in (often <cite>-lrt</cite>).</p>
		2071	</dd>
		2072	<dt>EV_USE_REALTIME</dt>
		2073	<dd>
		2074	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		2075	realtime clock option at compiletime (and assume its availability at
		2076	runtime if successful). Otherwise no use of the realtime clock option will
		2077	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		2078	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		2079	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		2080	</dd>
		2081	<dt>EV_USE_SELECT</dt>
		2082	<dd>
		2083	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		2084	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		2085	other method takes over, select will be it. Otherwise the select backend
		2086	will not be compiled in.</p>
		2087	</dd>
		2088	<dt>EV_SELECT_USE_FD_SET</dt>
		2089	<dd>
		2090	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		2091	structure. This is useful if libev doesn't compile due to a missing
		2092	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		2093	exotic systems. This usually limits the range of file descriptors to some
		2094	low limit such as 1024 or might have other limitations (winsocket only
		2095	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		2096	influence the size of the <code>fd_set</code> used.</p>
		2097	</dd>
		2098	<dt>EV_SELECT_IS_WINSOCKET</dt>
		2099	<dd>
		2100	<p>When defined to <code>1</code>, the select backend will assume that
		2101	select/socket/connect etc. don't understand file descriptors but
		2102	wants osf handles on win32 (this is the case when the select to
		2103	be used is the winsock select). This means that it will call
		2104	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		2105	it is assumed that all these functions actually work on fds, even
		2106	on win32. Should not be defined on non-win32 platforms.</p>
		2107	</dd>
		2108	<dt>EV_USE_POLL</dt>
		2109	<dd>
		2110	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		2111	backend. Otherwise it will be enabled on non-win32 platforms. It
		2112	takes precedence over select.</p>
		2113	</dd>
		2114	<dt>EV_USE_EPOLL</dt>
		2115	<dd>
		2116	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		2117	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2118	otherwise another method will be used as fallback. This is the
		2119	preferred backend for GNU/Linux systems.</p>
		2120	</dd>
		2121	<dt>EV_USE_KQUEUE</dt>
		2122	<dd>
		2123	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2124	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2125	otherwise another method will be used as fallback. This is the preferred
		2126	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2127	supports some types of fds correctly (the only platform we found that
		2128	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2129	not be used unless explicitly requested. The best way to use it is to find
		2130	out whether kqueue supports your type of fd properly and use an embedded
		2131	kqueue loop.</p>
		2132	</dd>
		2133	<dt>EV_USE_PORT</dt>
		2134	<dd>
		2135	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2136	10 port style backend. Its availability will be detected at runtime,
		2137	otherwise another method will be used as fallback. This is the preferred
		2138	backend for Solaris 10 systems.</p>
		2139	</dd>
		2140	<dt>EV_USE_DEVPOLL</dt>
		2141	<dd>
		2142	<p>reserved for future expansion, works like the USE symbols above.</p>
		2143	</dd>
		2144	<dt>EV_USE_INOTIFY</dt>
		2145	<dd>
		2146	<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
		2147	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2148	be detected at runtime.</p>
		2149	</dd>
		2150	<dt>EV_H</dt>
		2151	<dd>
		2152	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2153	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2154	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2155	</dd>
		2156	<dt>EV_CONFIG_H</dt>
		2157	<dd>
		2158	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2159	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2160	<code>EV_H</code>, above.</p>
		2161	</dd>
		2162	<dt>EV_EVENT_H</dt>
		2163	<dd>
		2164	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2165	of how the <cite>event.h</cite> header can be found.</p>
		2166	</dd>
		2167	<dt>EV_PROTOTYPES</dt>
		2168	<dd>
		2169	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2170	prototypes, but still define all the structs and other symbols. This is
		2171	occasionally useful if you want to provide your own wrapper functions
		2172	around libev functions.</p>
		2173	</dd>
		2174	<dt>EV_MULTIPLICITY</dt>
		2175	<dd>
		2176	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2177	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2178	additional independent event loops. Otherwise there will be no support
		2179	for multiple event loops and there is no first event loop pointer
		2180	argument. Instead, all functions act on the single default loop.</p>
		2181	</dd>
		2182	<dt>EV_MINPRI</dt>
		2183	<dt>EV_MAXPRI</dt>
		2184	<dd>
		2185	<p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
		2186	<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
		2187	provide for more priorities by overriding those symbols (usually defined
		2188	to be <code>-2</code> and <code>2</code>, respectively).</p>
		2189	<p>When doing priority-based operations, libev usually has to linearly search
		2190	all the priorities, so having many of them (hundreds) uses a lot of space
		2191	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2192	fine.</p>
		2193	<p>If your embedding app does not need any priorities, defining these both to
		2194	<code>0</code> will save some memory and cpu.</p>
		2195	</dd>
		2196	<dt>EV_PERIODIC_ENABLE</dt>
		2197	<dd>
		2198	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2199	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2200	code.</p>
		2201	</dd>
		2202	<dt>EV_IDLE_ENABLE</dt>
		2203	<dd>
		2204	<p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
		2205	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2206	code.</p>
		2207	</dd>
		2208	<dt>EV_EMBED_ENABLE</dt>
		2209	<dd>
		2210	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2211	defined to be <code>0</code>, then they are not.</p>
		2212	</dd>
		2213	<dt>EV_STAT_ENABLE</dt>
		2214	<dd>
		2215	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2216	defined to be <code>0</code>, then they are not.</p>
		2217	</dd>
		2218	<dt>EV_FORK_ENABLE</dt>
		2219	<dd>
		2220	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2221	defined to be <code>0</code>, then they are not.</p>
		2222	</dd>
		2223	<dt>EV_MINIMAL</dt>
		2224	<dd>
		2225	<p>If you need to shave off some kilobytes of code at the expense of some
		2226	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2227	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2228	</dd>
		2229	<dt>EV_PID_HASHSIZE</dt>
		2230	<dd>
		2231	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2232	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2233	than enough. If you need to manage thousands of children you might want to
		2234	increase this value (<i>must</i> be a power of two).</p>
		2235	</dd>
		2236	<dt>EV_INOTIFY_HASHSIZE</dt>
		2237	<dd>
		2238	<p><code>ev_staz</code> watchers use a small hash table to distribute workload by
		2239	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2240	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2241	watchers you might want to increase this value (<i>must</i> be a power of
		2242	two).</p>
		2243	</dd>
		2244	<dt>EV_COMMON</dt>
		2245	<dd>
		2246	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2247	this macro to a something else you can include more and other types of
		2248	members. You have to define it each time you include one of the files,
		2249	though, and it must be identical each time.</p>
		2250	<p>For example, the perl EV module uses something like this:</p>
		2251	<pre> #define EV_COMMON \
		2252	SV self; / contains this struct */ \
		2253	SV cb_sv, fh /* note no trailing ";" */
		2254
		2255	</pre>
		2256	</dd>
		2257	<dt>EV_CB_DECLARE (type)</dt>
		2258	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2259	<dt>ev_set_cb (ev, cb)</dt>
		2260	<dd>
		2261	<p>Can be used to change the callback member declaration in each watcher,
		2262	and the way callbacks are invoked and set. Must expand to a struct member
		2263	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2264	their default definitions. One possible use for overriding these is to
		2265	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2266	method calls instead of plain function calls in C++.</p>
		2267
		2268	</div>
		2269	<h2 id="EXAMPLES">EXAMPLES</h2>
		2270	<div id="EXAMPLES_CONTENT">
		2271	<p>For a real-world example of a program the includes libev
		2272	verbatim, you can have a look at the EV perl module
		2273	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2274	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2275	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2276	will be compiled. It is pretty complex because it provides its own header
		2277	file.</p>
		2278	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2279	that everybody includes and which overrides some configure choices:</p>
		2280	<pre> #define EV_MINIMAL 1
		2281	#define EV_USE_POLL 0
		2282	#define EV_MULTIPLICITY 0
		2283	#define EV_PERIODIC_ENABLE 0
		2284	#define EV_STAT_ENABLE 0
		2285	#define EV_FORK_ENABLE 0
		2286	#define EV_CONFIG_H <config.h>
		2287	#define EV_MINPRI 0
		2288	#define EV_MAXPRI 0
		2289
		2290	#include "ev++.h"
		2291
		2292	</pre>
		2293	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2294	<pre> #include "ev_cpp.h"
		2295	#include "ev.c"
		2296
		2297
		2298
		2299
		2300	</pre>
		2301
		2302	</div>
		2303	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2304	<div id="COMPLEXITIES_CONTENT">
		2305	<p>In this section the complexities of (many of) the algorithms used inside
		2306	libev will be explained. For complexity discussions about backends see the
		2307	documentation for <code>ev_default_init</code>.</p>
		2308	<p>All of the following are about amortised time: If an array needs to be
		2309	extended, libev needs to realloc and move the whole array, but this
		2310	happens asymptotically never with higher number of elements, so O(1) might
		2311	mean it might do a lengthy realloc operation in rare cases, but on average
		2312	it is much faster and asymptotically approaches constant time.</p>
		2313	<p>
		2314	<dl>
		2315	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2316	<dd>
		2317	<p>This means that, when you have a watcher that triggers in one hour and
		2318	there are 100 watchers that would trigger before that then inserting will
		2319	have to skip those 100 watchers.</p>
		2320	</dd>
		2321	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2322	<dd>
		2323	<p>That means that for changing a timer costs less than removing/adding them
		2324	as only the relative motion in the event queue has to be paid for.</p>
		2325	</dd>
		2326	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2327	<dd>
		2328	<p>These just add the watcher into an array or at the head of a list.
		2329	=item Stopping check/prepare/idle watchers: O(1)</p>
		2330	</dd>
		2331	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
		2332	<dd>
		2333	<p>These watchers are stored in lists then need to be walked to find the
		2334	correct watcher to remove. The lists are usually short (you don't usually
		2335	have many watchers waiting for the same fd or signal).</p>
		2336	</dd>
		2337	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2338	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2339	<dd>
		2340	<p>A change means an I/O watcher gets started or stopped, which requires
		2341	libev to recalculate its status (and possibly tell the kernel).</p>
		2342	</dd>
		2343	<dt>Activating one watcher: O(1)</dt>
		2344	<dt>Priority handling: O(number_of_priorities)</dt>
		2345	<dd>
		2346	<p>Priorities are implemented by allocating some space for each
		2347	priority. When doing priority-based operations, libev usually has to
		2348	linearly search all the priorities.</p>
		2349	</dd>
		2350	</dl>
		2351	</p>
		2352
		2353
		2354
		2355
		2356
		2357	</div>
		2358	<h1 id="AUTHOR">AUTHOR</h1>
760	<div id="AUTHOR_CONTENT">	2359	<div id="AUTHOR_CONTENT">
761	<p>Marc Lehmann <libev@schmorp.de>.</p>	2360	<p>Marc Lehmann <libev@schmorp.de>.</p>
762		2361
763	</div>	2362	</div>
764	</div></body>	2363	</div></body>
765	</html>	2364	</html>

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Revision 1.70 by root, Sat Dec 8 14:27:39 2007 UTC