[ViewVC] Diff of: cvs/libev/ev.html

Comparing libev/ev.html (file contents):
Revision 1.7 by root, Mon Nov 12 08:16:02 2007 UTC vs.
Revision 1.59 by root, Wed Nov 28 17:32:24 2007 UTC

…		…
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 09:16:01 2007" />	9	<meta name="created" content="Wed Nov 28 18:32:11 2007" />
10	<meta name="generator" content="Pod::Xhtml 1.57" />	10	<meta name="generator" content="Pod::Xhtml 1.57" />
11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>	11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
15	<h3 id="TOP">Index</h3>	15	<h3 id="TOP">Index</h3>
16		16
17	<ul><li><a href="#NAME">NAME</a></li>	17	<ul><li><a href="#NAME">NAME</a></li>
18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>	18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
		19	<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>	20	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20	<li><a href="#FEATURES">FEATURES</a></li>	21	<li><a href="#FEATURES">FEATURES</a></li>
21	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>	22	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
		23	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
22	<li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li>	24	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>	25	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
24	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>	26	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
		27	<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
25	<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>	28	<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26	</ul>	29	</ul>
27	</li>	30	</li>
28	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>	31	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29	<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li>	32	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
30	<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li>	33	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
31	<li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</a></li>	34	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
32	<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li>	35	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
33	<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li>	36	<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
		37	<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
34	<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li>	38	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
35	<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li>	39	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
		40	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
		41	<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
36	</ul>	42	</ul>
37	</li>	43	</li>
38	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	44	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		45	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		46	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		47	<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
		48	<li><a href="#EMBEDDING">EMBEDDING</a>
		49	<ul><li><a href="#FILESETS">FILESETS</a>
		50	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		51	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		52	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		53	</ul>
		54	</li>
		55	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		56	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		57	</ul>
		58	</li>
		59	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
39	<li><a href="#AUTHOR">AUTHOR</a>	60	<li><a href="#AUTHOR">AUTHOR</a>
40	</li>	61	</li>
41	</ul><hr />	62	</ul><hr />
42	<!-- INDEX END -->	63	<!-- INDEX END -->
43		64
44	<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>	65	<h1 id="NAME">NAME</h1>
45	<div id="NAME_CONTENT">	66	<div id="NAME_CONTENT">
46	<p>libev - a high performance full-featured event loop written in C</p>	67	<p>libev - a high performance full-featured event loop written in C</p>
47		68
48	</div>	69	</div>
49	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>	70	<h1 id="SYNOPSIS">SYNOPSIS</h1>
50	<div id="SYNOPSIS_CONTENT">	71	<div id="SYNOPSIS_CONTENT">
51	<pre> #include <ev.h>	72	<pre> #include <ev.h>
52		73
53	</pre>	74	</pre>
54		75
55	</div>	76	</div>
56	<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>	77	<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
		78	<div id="EXAMPLE_PROGRAM_CONTENT">
		79	<pre> #include <ev.h>
		80
		81	ev_io stdin_watcher;
		82	ev_timer timeout_watcher;
		83
		84	/* called when data readable on stdin */
		85	static void
		86	stdin_cb (EV_P_ struct ev_io *w, int revents)
		87	{
		88	/* puts ("stdin ready"); */
		89	ev_io_stop (EV_A_ w); /* just a syntax example */
		90	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		91	}
		92
		93	static void
		94	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		95	{
		96	/* puts ("timeout"); */
		97	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		98	}
		99
		100	int
		101	main (void)
		102	{
		103	struct ev_loop *loop = ev_default_loop (0);
		104
		105	/* initialise an io watcher, then start it */
		106	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		107	ev_io_start (loop, &stdin_watcher);
		108
		109	/* simple non-repeating 5.5 second timeout */
		110	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		111	ev_timer_start (loop, &timeout_watcher);
		112
		113	/* loop till timeout or data ready */
		114	ev_loop (loop, 0);
		115
		116	return 0;
		117	}
		118
		119	</pre>
		120
		121	</div>
		122	<h1 id="DESCRIPTION">DESCRIPTION</h1>
57	<div id="DESCRIPTION_CONTENT">	123	<div id="DESCRIPTION_CONTENT">
58	<p>Libev is an event loop: you register interest in certain events (such as a	124	<p>Libev is an event loop: you register interest in certain events (such as a
59	file descriptor being readable or a timeout occuring), and it will manage	125	file descriptor being readable or a timeout occuring), and it will manage
60	these event sources and provide your program with events.</p>	126	these event sources and provide your program with events.</p>
61	<p>To do this, it must take more or less complete control over your process	127	<p>To do this, it must take more or less complete control over your process
…		…
65	watchers</i>, which are relatively small C structures you initialise with the	131	watchers</i>, which are relatively small C structures you initialise with the
66	details of the event, and then hand it over to libev by <i>starting</i> the	132	details of the event, and then hand it over to libev by <i>starting</i> the
67	watcher.</p>	133	watcher.</p>
68		134
69	</div>	135	</div>
70	<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>	136	<h1 id="FEATURES">FEATURES</h1>
71	<div id="FEATURES_CONTENT">	137	<div id="FEATURES_CONTENT">
72	<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific	138	<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
73	kqueue mechanisms for file descriptor events, relative timers, absolute	139	BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
74	timers with customised rescheduling, signal events, process status change	140	for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
75	events (related to SIGCHLD), and event watchers dealing with the event	141	(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
76	loop mechanism itself (idle, prepare and check watchers). It also is quite	142	with customised rescheduling (<code>ev_periodic</code>), synchronous signals
		143	(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
		144	watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
		145	<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
		146	file watchers (<code>ev_stat</code>) and even limited support for fork events
		147	(<code>ev_fork</code>).</p>
		148	<p>It also is quite fast (see this
77	fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing	149	<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
78	it to libevent for example).</p>	150	for example).</p>
79		151
80	</div>	152	</div>
81	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	153	<h1 id="CONVENTIONS">CONVENTIONS</h1>
82	<div id="CONVENTIONS_CONTENT">	154	<div id="CONVENTIONS_CONTENT">
83	<p>Libev is very configurable. In this manual the default configuration	155	<p>Libev is very configurable. In this manual the default configuration will
84	will be described, which supports multiple event loops. For more info	156	be described, which supports multiple event loops. For more info about
85	about various configuration options please have a look at the file	157	various configuration options please have a look at <strong>EMBED</strong> section in
86	<cite>README.embed</cite> in the libev distribution. If libev was configured without	158	this manual. If libev was configured without support for multiple event
87	support for multiple event loops, then all functions taking an initial	159	loops, then all functions taking an initial argument of name <code>loop</code>
88	argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)	160	(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
89	will not have this argument.</p>
90		161
91	</div>	162	</div>
92	<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	163	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
93	<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT">	164	<div id="TIME_REPRESENTATION_CONTENT">
94	<p>Libev represents time as a single floating point number, representing the	165	<p>Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	166	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	167	the beginning of 1970, details are complicated, don't ask). This type is
97	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	168	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
98	to the double type in C.</p>	169	to the <code>double</code> type in C, and when you need to do any calculations on
		170	it, you should treat it as such.</p>
		171
		172	</div>
		173	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
		174	<div id="GLOBAL_FUNCTIONS_CONTENT">
		175	<p>These functions can be called anytime, even before initialising the
		176	library in any way.</p>
99	<dl>	177	<dl>
100	<dt>ev_tstamp ev_time ()</dt>	178	<dt>ev_tstamp ev_time ()</dt>
101	<dd>	179	<dd>
102	<p>Returns the current time as libev would use it.</p>	180	<p>Returns the current time as libev would use it. Please note that the
		181	<code>ev_now</code> function is usually faster and also often returns the timestamp
		182	you actually want to know.</p>
103	</dd>	183	</dd>
104	<dt>int ev_version_major ()</dt>	184	<dt>int ev_version_major ()</dt>
105	<dt>int ev_version_minor ()</dt>	185	<dt>int ev_version_minor ()</dt>
106	<dd>	186	<dd>
107	<p>You can find out the major and minor version numbers of the library	187	<p>You can find out the major and minor version numbers of the library
108	you linked against by calling the functions <code>ev_version_major</code> and	188	you linked against by calling the functions <code>ev_version_major</code> and
109	<code>ev_version_minor</code>. If you want, you can compare against the global	189	<code>ev_version_minor</code>. If you want, you can compare against the global
110	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the	190	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
111	version of the library your program was compiled against.</p>	191	version of the library your program was compiled against.</p>
112	<p>Usually, its a good idea to terminate if the major versions mismatch,	192	<p>Usually, it's a good idea to terminate if the major versions mismatch,
113	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
114	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
115	not a problem.</p>	195	not a problem.</p>
		196	<p>Example: Make sure we haven't accidentally been linked against the wrong
		197	version.</p>
		198	<pre> assert (("libev version mismatch",
		199	ev_version_major () == EV_VERSION_MAJOR
		200	&& ev_version_minor () >= EV_VERSION_MINOR));
		201
		202	</pre>
		203	</dd>
		204	<dt>unsigned int ev_supported_backends ()</dt>
		205	<dd>
		206	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		207	value) compiled into this binary of libev (independent of their
		208	availability on the system you are running on). See <code>ev_default_loop</code> for
		209	a description of the set values.</p>
		210	<p>Example: make sure we have the epoll method, because yeah this is cool and
		211	a must have and can we have a torrent of it please!!!11</p>
		212	<pre> assert (("sorry, no epoll, no sex",
		213	ev_supported_backends () & EVBACKEND_EPOLL));
		214
		215	</pre>
		216	</dd>
		217	<dt>unsigned int ev_recommended_backends ()</dt>
		218	<dd>
		219	<p>Return the set of all backends compiled into this binary of libev and also
		220	recommended for this platform. This set is often smaller than the one
		221	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		222	most BSDs and will not be autodetected unless you explicitly request it
		223	(assuming you know what you are doing). This is the set of backends that
		224	libev will probe for if you specify no backends explicitly.</p>
		225	</dd>
		226	<dt>unsigned int ev_embeddable_backends ()</dt>
		227	<dd>
		228	<p>Returns the set of backends that are embeddable in other event loops. This
		229	is the theoretical, all-platform, value. To find which backends
		230	might be supported on the current system, you would need to look at
		231	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		232	recommended ones.</p>
		233	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
116	</dd>	234	</dd>
117	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	235	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
118	<dd>	236	<dd>
119	<p>Sets the allocation function to use (the prototype is similar to the	237	<p>Sets the allocation function to use (the prototype is similar - the
120	realloc C function, the semantics are identical). It is used to allocate	238	semantics is identical - to the realloc C function). It is used to
121	and free memory (no surprises here). If it returns zero when memory	239	allocate and free memory (no surprises here). If it returns zero when
122	needs to be allocated, the library might abort or take some potentially	240	memory needs to be allocated, the library might abort or take some
123	destructive action. The default is your system realloc function.</p>	241	potentially destructive action. The default is your system realloc
		242	function.</p>
124	<p>You could override this function in high-availability programs to, say,	243	<p>You could override this function in high-availability programs to, say,
125	free some memory if it cannot allocate memory, to use a special allocator,	244	free some memory if it cannot allocate memory, to use a special allocator,
126	or even to sleep a while and retry until some memory is available.</p>	245	or even to sleep a while and retry until some memory is available.</p>
		246	<p>Example: Replace the libev allocator with one that waits a bit and then
		247	retries).</p>
		248	<pre> static void *
		249	persistent_realloc (void *ptr, size_t size)
		250	{
		251	for (;;)
		252	{
		253	void *newptr = realloc (ptr, size);
		254
		255	if (newptr)
		256	return newptr;
		257
		258	sleep (60);
		259	}
		260	}
		261
		262	...
		263	ev_set_allocator (persistent_realloc);
		264
		265	</pre>
127	</dd>	266	</dd>
128	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	267	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
129	<dd>	268	<dd>
130	<p>Set the callback function to call on a retryable syscall error (such	269	<p>Set the callback function to call on a retryable syscall error (such
131	as failed select, poll, epoll_wait). The message is a printable string	270	as failed select, poll, epoll_wait). The message is a printable string
132	indicating the system call or subsystem causing the problem. If this	271	indicating the system call or subsystem causing the problem. If this
133	callback is set, then libev will expect it to remedy the sitution, no	272	callback is set, then libev will expect it to remedy the sitution, no
134	matter what, when it returns. That is, libev will generally retry the	273	matter what, when it returns. That is, libev will generally retry the
135	requested operation, or, if the condition doesn't go away, do bad stuff	274	requested operation, or, if the condition doesn't go away, do bad stuff
136	(such as abort).</p>	275	(such as abort).</p>
		276	<p>Example: This is basically the same thing that libev does internally, too.</p>
		277	<pre> static void
		278	fatal_error (const char *msg)
		279	{
		280	perror (msg);
		281	abort ();
		282	}
		283
		284	...
		285	ev_set_syserr_cb (fatal_error);
		286
		287	</pre>
137	</dd>	288	</dd>
138	</dl>	289	</dl>
139		290
140	</div>	291	</div>
141	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	292	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
142	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	293	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two	294	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
144	types of such loops, the <i>default</i> loop, which supports signals and child	295	types of such loops, the <i>default</i> loop, which supports signals and child
145	events, and dynamically created loops which do not.</p>	296	events, and dynamically created loops which do not.</p>
146	<p>If you use threads, a common model is to run the default event loop	297	<p>If you use threads, a common model is to run the default event loop
147	in your main thread (or in a separate thrad) and for each thread you	298	in your main thread (or in a separate thread) and for each thread you
148	create, you also create another event loop. Libev itself does no locking	299	create, you also create another event loop. Libev itself does no locking
149	whatsoever, so if you mix calls to the same event loop in different	300	whatsoever, so if you mix calls to the same event loop in different
150	threads, make sure you lock (this is usually a bad idea, though, even if	301	threads, make sure you lock (this is usually a bad idea, though, even if
151	done correctly, because its hideous and inefficient).</p>	302	done correctly, because it's hideous and inefficient).</p>
152	<dl>	303	<dl>
153	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	304	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
154	<dd>	305	<dd>
155	<p>This will initialise the default event loop if it hasn't been initialised	306	<p>This will initialise the default event loop if it hasn't been initialised
156	yet and return it. If the default loop could not be initialised, returns	307	yet and return it. If the default loop could not be initialised, returns
157	false. If it already was initialised it simply returns it (and ignores the	308	false. If it already was initialised it simply returns it (and ignores the
158	flags).</p>	309	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
159	<p>If you don't know what event loop to use, use the one returned from this	310	<p>If you don't know what event loop to use, use the one returned from this
160	function.</p>	311	function.</p>
161	<p>The flags argument can be used to specify special behaviour or specific	312	<p>The flags argument can be used to specify special behaviour or specific
162	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p>	313	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
163	<p>It supports the following flags:</p>	314	<p>The following flags are supported:</p>
164	<p>	315	<p>
165	<dl>	316	<dl>
166	<dt>EVFLAG_AUTO</dt>	317	<dt><code>EVFLAG_AUTO</code></dt>
167	<dd>	318	<dd>
168	<p>The default flags value. Use this if you have no clue (its the right	319	<p>The default flags value. Use this if you have no clue (it's the right
169	thing, believe me).</p>	320	thing, believe me).</p>
170	</dd>	321	</dd>
171	<dt>EVFLAG_NOENV</dt>	322	<dt><code>EVFLAG_NOENV</code></dt>
172	<dd>	323	<dd>
173	<p>If this flag bit is ored into the flag value then libev will <i>not</i> look	324	<p>If this flag bit is ored into the flag value (or the program runs setuid
174	at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this	325	or setgid) then libev will <i>not</i> look at the environment variable
175	environment variable will override the flags completely. This is useful	326	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
		327	override the flags completely if it is found in the environment. This is
176	to try out specific backends to tets their performance, or to work around	328	useful to try out specific backends to test their performance, or to work
177	bugs.</p>	329	around bugs.</p>
178	</dd>	330	</dd>
179	<dt>EVMETHOD_SELECT portable select backend</dt>	331	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
180	<dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt>
181	<dt>EVMETHOD_EPOLL linux only</dt>
182	<dt>EVMETHOD_KQUEUE some bsds only</dt>
183	<dt>EVMETHOD_DEVPOLL solaris 8 only</dt>
184	<dt>EVMETHOD_PORT solaris 10 only</dt>
185	<dd>	332	<dd>
186	<p>If one or more of these are ored into the flags value, then only these	333	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
187	backends will be tried (in the reverse order as given here). If one are	334	libev tries to roll its own fd_set with no limits on the number of fds,
188	specified, any backend will do.</p>	335	but if that fails, expect a fairly low limit on the number of fds when
		336	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		337	the fastest backend for a low number of fds.</p>
		338	</dd>
		339	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		340	<dd>
		341	<p>And this is your standard poll(2) backend. It's more complicated than
		342	select, but handles sparse fds better and has no artificial limit on the
		343	number of fds you can use (except it will slow down considerably with a
		344	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		345	</dd>
		346	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		347	<dd>
		348	<p>For few fds, this backend is a bit little slower than poll and select,
		349	but it scales phenomenally better. While poll and select usually scale like
		350	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		351	either O(1) or O(active_fds).</p>
		352	<p>While stopping and starting an I/O watcher in the same iteration will
		353	result in some caching, there is still a syscall per such incident
		354	(because the fd could point to a different file description now), so its
		355	best to avoid that. Also, dup()ed file descriptors might not work very
		356	well if you register events for both fds.</p>
		357	<p>Please note that epoll sometimes generates spurious notifications, so you
		358	need to use non-blocking I/O or other means to avoid blocking when no data
		359	(or space) is available.</p>
		360	</dd>
		361	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		362	<dd>
		363	<p>Kqueue deserves special mention, as at the time of this writing, it
		364	was broken on all BSDs except NetBSD (usually it doesn't work with
		365	anything but sockets and pipes, except on Darwin, where of course its
		366	completely useless). For this reason its not being "autodetected"
		367	unless you explicitly specify it explicitly in the flags (i.e. using
		368	<code>EVBACKEND_KQUEUE</code>).</p>
		369	<p>It scales in the same way as the epoll backend, but the interface to the
		370	kernel is more efficient (which says nothing about its actual speed, of
		371	course). While starting and stopping an I/O watcher does not cause an
		372	extra syscall as with epoll, it still adds up to four event changes per
		373	incident, so its best to avoid that.</p>
		374	</dd>
		375	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		376	<dd>
		377	<p>This is not implemented yet (and might never be).</p>
		378	</dd>
		379	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		380	<dd>
		381	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		382	it's really slow, but it still scales very well (O(active_fds)).</p>
		383	<p>Please note that solaris ports can result in a lot of spurious
		384	notifications, so you need to use non-blocking I/O or other means to avoid
		385	blocking when no data (or space) is available.</p>
		386	</dd>
		387	<dt><code>EVBACKEND_ALL</code></dt>
		388	<dd>
		389	<p>Try all backends (even potentially broken ones that wouldn't be tried
		390	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		391	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
189	</dd>	392	</dd>
190	</dl>	393	</dl>
191	</p>	394	</p>
		395	<p>If one or more of these are ored into the flags value, then only these
		396	backends will be tried (in the reverse order as given here). If none are
		397	specified, most compiled-in backend will be tried, usually in reverse
		398	order of their flag values :)</p>
		399	<p>The most typical usage is like this:</p>
		400	<pre> if (!ev_default_loop (0))
		401	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		402
		403	</pre>
		404	<p>Restrict libev to the select and poll backends, and do not allow
		405	environment settings to be taken into account:</p>
		406	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		407
		408	</pre>
		409	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		410	available (warning, breaks stuff, best use only with your own private
		411	event loop and only if you know the OS supports your types of fds):</p>
		412	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		413
		414	</pre>
192	</dd>	415	</dd>
193	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	416	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
194	<dd>	417	<dd>
195	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	418	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
196	always distinct from the default loop. Unlike the default loop, it cannot	419	always distinct from the default loop. Unlike the default loop, it cannot
197	handle signal and child watchers, and attempts to do so will be greeted by	420	handle signal and child watchers, and attempts to do so will be greeted by
198	undefined behaviour (or a failed assertion if assertions are enabled).</p>	421	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		422	<p>Example: Try to create a event loop that uses epoll and nothing else.</p>
		423	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		424	if (!epoller)
		425	fatal ("no epoll found here, maybe it hides under your chair");
		426
		427	</pre>
199	</dd>	428	</dd>
200	<dt>ev_default_destroy ()</dt>	429	<dt>ev_default_destroy ()</dt>
201	<dd>	430	<dd>
202	<p>Destroys the default loop again (frees all memory and kernel state	431	<p>Destroys the default loop again (frees all memory and kernel state
203	etc.). This stops all registered event watchers (by not touching them in	432	etc.). None of the active event watchers will be stopped in the normal
204	any way whatsoever, although you cnanot rely on this :).</p>	433	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		434	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		435	calling this function, or cope with the fact afterwards (which is usually
		436	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		437	for example).</p>
205	</dd>	438	</dd>
206	<dt>ev_loop_destroy (loop)</dt>	439	<dt>ev_loop_destroy (loop)</dt>
207	<dd>	440	<dd>
208	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	441	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
209	earlier call to <code>ev_loop_new</code>.</p>	442	earlier call to <code>ev_loop_new</code>.</p>
…		…
212	<dd>	445	<dd>
213	<p>This function reinitialises the kernel state for backends that have	446	<p>This function reinitialises the kernel state for backends that have
214	one. Despite the name, you can call it anytime, but it makes most sense	447	one. Despite the name, you can call it anytime, but it makes most sense
215	after forking, in either the parent or child process (or both, but that	448	after forking, in either the parent or child process (or both, but that
216	again makes little sense).</p>	449	again makes little sense).</p>
217	<p>You <i>must</i> call this function after forking if and only if you want to	450	<p>You <i>must</i> call this function in the child process after forking if and
218	use the event library in both processes. If you just fork+exec, you don't	451	only if you want to use the event library in both processes. If you just
219	have to call it.</p>	452	fork+exec, you don't have to call it.</p>
220	<p>The function itself is quite fast and its usually not a problem to call	453	<p>The function itself is quite fast and it's usually not a problem to call
221	it just in case after a fork. To make this easy, the function will fit in	454	it just in case after a fork. To make this easy, the function will fit in
222	quite nicely into a call to <code>pthread_atfork</code>:</p>	455	quite nicely into a call to <code>pthread_atfork</code>:</p>
223	<pre> pthread_atfork (0, 0, ev_default_fork);	456	<pre> pthread_atfork (0, 0, ev_default_fork);
224		457
225	</pre>	458	</pre>
		459	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		460	without calling this function, so if you force one of those backends you
		461	do not need to care.</p>
226	</dd>	462	</dd>
227	<dt>ev_loop_fork (loop)</dt>	463	<dt>ev_loop_fork (loop)</dt>
228	<dd>	464	<dd>
229	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	465	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
230	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	466	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
231	after fork, and how you do this is entirely your own problem.</p>	467	after fork, and how you do this is entirely your own problem.</p>
232	</dd>	468	</dd>
233	<dt>unsigned int ev_method (loop)</dt>	469	<dt>unsigned int ev_backend (loop)</dt>
234	<dd>	470	<dd>
235	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	471	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
236	use.</p>	472	use.</p>
237	</dd>	473	</dd>
238	<dt>ev_tstamp = ev_now (loop)</dt>	474	<dt>ev_tstamp ev_now (loop)</dt>
239	<dd>	475	<dd>
240	<p>Returns the current "event loop time", which is the time the event loop	476	<p>Returns the current "event loop time", which is the time the event loop
241	got events and started processing them. This timestamp does not change	477	received events and started processing them. This timestamp does not
242	as long as callbacks are being processed, and this is also the base time	478	change as long as callbacks are being processed, and this is also the base
243	used for relative timers. You can treat it as the timestamp of the event	479	time used for relative timers. You can treat it as the timestamp of the
244	occuring (or more correctly, the mainloop finding out about it).</p>	480	event occuring (or more correctly, libev finding out about it).</p>
245	</dd>	481	</dd>
246	<dt>ev_loop (loop, int flags)</dt>	482	<dt>ev_loop (loop, int flags)</dt>
247	<dd>	483	<dd>
248	<p>Finally, this is it, the event handler. This function usually is called	484	<p>Finally, this is it, the event handler. This function usually is called
249	after you initialised all your watchers and you want to start handling	485	after you initialised all your watchers and you want to start handling
250	events.</p>	486	events.</p>
251	<p>If the flags argument is specified as 0, it will not return until either	487	<p>If the flags argument is specified as <code>0</code>, it will not return until
252	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	488	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		489	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		490	relying on all watchers to be stopped when deciding when a program has
		491	finished (especially in interactive programs), but having a program that
		492	automatically loops as long as it has to and no longer by virtue of
		493	relying on its watchers stopping correctly is a thing of beauty.</p>
253	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	494	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
254	those events and any outstanding ones, but will not block your process in	495	those events and any outstanding ones, but will not block your process in
255	case there are no events.</p>	496	case there are no events and will return after one iteration of the loop.</p>
256	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	497	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
257	neccessary) and will handle those and any outstanding ones. It will block	498	neccessary) and will handle those and any outstanding ones. It will block
258	your process until at least one new event arrives.</p>	499	your process until at least one new event arrives, and will return after
259	<p>This flags value could be used to implement alternative looping	500	one iteration of the loop. This is useful if you are waiting for some
260	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	501	external event in conjunction with something not expressible using other
261	more generic mechanism.</p>	502	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
		503	usually a better approach for this kind of thing.</p>
		504	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		505	<pre> * If there are no active watchers (reference count is zero), return.
		506	- Queue prepare watchers and then call all outstanding watchers.
		507	- If we have been forked, recreate the kernel state.
		508	- Update the kernel state with all outstanding changes.
		509	- Update the "event loop time".
		510	- Calculate for how long to block.
		511	- Block the process, waiting for any events.
		512	- Queue all outstanding I/O (fd) events.
		513	- Update the "event loop time" and do time jump handling.
		514	- Queue all outstanding timers.
		515	- Queue all outstanding periodics.
		516	- If no events are pending now, queue all idle watchers.
		517	- Queue all check watchers.
		518	- Call all queued watchers in reverse order (i.e. check watchers first).
		519	Signals and child watchers are implemented as I/O watchers, and will
		520	be handled here by queueing them when their watcher gets executed.
		521	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		522	were used, return, otherwise continue with step *.
		523
		524	</pre>
		525	<p>Example: Queue some jobs and then loop until no events are outsanding
		526	anymore.</p>
		527	<pre> ... queue jobs here, make sure they register event watchers as long
		528	... as they still have work to do (even an idle watcher will do..)
		529	ev_loop (my_loop, 0);
		530	... jobs done. yeah!
		531
		532	</pre>
262	</dd>	533	</dd>
263	<dt>ev_unloop (loop, how)</dt>	534	<dt>ev_unloop (loop, how)</dt>
264	<dd>	535	<dd>
265	<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument	536	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
		537	has processed all outstanding events). The <code>how</code> argument must be either
266	must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code>	538	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
267	call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code>	539	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
268	calls return.</p>
269	</dd>	540	</dd>
270	<dt>ev_ref (loop)</dt>	541	<dt>ev_ref (loop)</dt>
271	<dt>ev_unref (loop)</dt>	542	<dt>ev_unref (loop)</dt>
272	<dd>	543	<dd>
273	<p>Ref/unref can be used to add or remove a refcount on the event loop: Every	544	<p>Ref/unref can be used to add or remove a reference count on the event
274	watcher keeps one reference. If you have a long-runing watcher you never	545	loop: Every watcher keeps one reference, and as long as the reference
275	unregister that should not keep ev_loop from running, ev_unref() after	546	count is nonzero, <code>ev_loop</code> will not return on its own. If you have
276	starting, and ev_ref() before stopping it. Libev itself uses this for	547	a watcher you never unregister that should not keep <code>ev_loop</code> from
277	example for its internal signal pipe: It is not visible to you as a user	548	returning, ev_unref() after starting, and ev_ref() before stopping it. For
278	and should not keep <code>ev_loop</code> from exiting if the work is done. It is	549	example, libev itself uses this for its internal signal pipe: It is not
279	also an excellent way to do this for generic recurring timers or from	550	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
280	within third-party libraries. Just remember to unref after start and ref	551	no event watchers registered by it are active. It is also an excellent
281	before stop.</p>	552	way to do this for generic recurring timers or from within third-party
		553	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		554	<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
		555	running when nothing else is active.</p>
		556	<pre> struct ev_signal exitsig;
		557	ev_signal_init (&exitsig, sig_cb, SIGINT);
		558	ev_signal_start (loop, &exitsig);
		559	evf_unref (loop);
		560
		561	</pre>
		562	<p>Example: For some weird reason, unregister the above signal handler again.</p>
		563	<pre> ev_ref (loop);
		564	ev_signal_stop (loop, &exitsig);
		565
		566	</pre>
282	</dd>	567	</dd>
283	</dl>	568	</dl>
284		569
		570
		571
		572
		573
285	</div>	574	</div>
286	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	575	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
287	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	576	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
288	<p>A watcher is a structure that you create and register to record your	577	<p>A watcher is a structure that you create and register to record your
289	interest in some event. For instance, if you want to wait for STDIN to	578	interest in some event. For instance, if you want to wait for STDIN to
290	become readable, you would create an ev_io watcher for that:</p>	579	become readable, you would create an <code>ev_io</code> watcher for that:</p>
291	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	580	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
292	{	581	{
293	ev_io_stop (w);	582	ev_io_stop (w);
294	ev_unloop (loop, EVUNLOOP_ALL);	583	ev_unloop (loop, EVUNLOOP_ALL);
295	}	584	}
…		…
318	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	607	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
319	*)</code>), and you can stop watching for events at any time by calling the	608	*)</code>), and you can stop watching for events at any time by calling the
320	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	609	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
321	<p>As long as your watcher is active (has been started but not stopped) you	610	<p>As long as your watcher is active (has been started but not stopped) you
322	must not touch the values stored in it. Most specifically you must never	611	must not touch the values stored in it. Most specifically you must never
323	reinitialise it or call its set method.</p>	612	reinitialise it or call its <code>set</code> macro.</p>
324	<p>You cna check whether an event is active by calling the <code>ev_is_active
325	(watcher *)</code> macro. To see whether an event is outstanding (but the
326	callback for it has not been called yet) you cna use the <code>ev_is_pending
327	(watcher *)</code> macro.</p>
328	<p>Each and every callback receives the event loop pointer as first, the	613	<p>Each and every callback receives the event loop pointer as first, the
329	registered watcher structure as second, and a bitset of received events as	614	registered watcher structure as second, and a bitset of received events as
330	third argument.</p>	615	third argument.</p>
331	<p>The rceeived events usually include a single bit per event type received	616	<p>The received events usually include a single bit per event type received
332	(you can receive multiple events at the same time). The possible bit masks	617	(you can receive multiple events at the same time). The possible bit masks
333	are:</p>	618	are:</p>
334	<dl>	619	<dl>
335	<dt>EV_READ</dt>	620	<dt><code>EV_READ</code></dt>
336	<dt>EV_WRITE</dt>	621	<dt><code>EV_WRITE</code></dt>
337	<dd>	622	<dd>
338	<p>The file descriptor in the ev_io watcher has become readable and/or	623	<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
339	writable.</p>	624	writable.</p>
340	</dd>	625	</dd>
341	<dt>EV_TIMEOUT</dt>	626	<dt><code>EV_TIMEOUT</code></dt>
342	<dd>
343	<p>The ev_timer watcher has timed out.</p>
344	</dd>	627	<dd>
345	<dt>EV_PERIODIC</dt>	628	<p>The <code>ev_timer</code> watcher has timed out.</p>
346	<dd>	629	</dd>
347	<p>The ev_periodic watcher has timed out.</p>	630	<dt><code>EV_PERIODIC</code></dt>
348	</dd>	631	<dd>
349	<dt>EV_SIGNAL</dt>	632	<p>The <code>ev_periodic</code> watcher has timed out.</p>
350	<dd>	633	</dd>
		634	<dt><code>EV_SIGNAL</code></dt>
		635	<dd>
351	<p>The signal specified in the ev_signal watcher has been received by a thread.</p>	636	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
352	</dd>
353	<dt>EV_CHILD</dt>
354	<dd>	637	</dd>
		638	<dt><code>EV_CHILD</code></dt>
		639	<dd>
355	<p>The pid specified in the ev_child watcher has received a status change.</p>	640	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
356	</dd>
357	<dt>EV_IDLE</dt>
358	<dd>	641	</dd>
		642	<dt><code>EV_STAT</code></dt>
		643	<dd>
		644	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		645	</dd>
		646	<dt><code>EV_IDLE</code></dt>
		647	<dd>
359	<p>The ev_idle watcher has determined that you have nothing better to do.</p>	648	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
360	</dd>
361	<dt>EV_PREPARE</dt>
362	<dt>EV_CHECK</dt>
363	<dd>	649	</dd>
		650	<dt><code>EV_PREPARE</code></dt>
		651	<dt><code>EV_CHECK</code></dt>
		652	<dd>
364	<p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts	653	<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
365	to gather new events, and all ev_check watchers are invoked just after	654	to gather new events, and all <code>ev_check</code> watchers are invoked just after
366	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	655	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
367	received events. Callbacks of both watcher types can start and stop as	656	received events. Callbacks of both watcher types can start and stop as
368	many watchers as they want, and all of them will be taken into account	657	many watchers as they want, and all of them will be taken into account
369	(for example, a ev_prepare watcher might start an idle watcher to keep	658	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
370	<code>ev_loop</code> from blocking).</p>	659	<code>ev_loop</code> from blocking).</p>
371	</dd>	660	</dd>
372	<dt>EV_ERROR</dt>	661	<dt><code>EV_EMBED</code></dt>
		662	<dd>
		663	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		664	</dd>
		665	<dt><code>EV_FORK</code></dt>
		666	<dd>
		667	<p>The event loop has been resumed in the child process after fork (see
		668	<code>ev_fork</code>).</p>
		669	</dd>
		670	<dt><code>EV_ERROR</code></dt>
373	<dd>	671	<dd>
374	<p>An unspecified error has occured, the watcher has been stopped. This might	672	<p>An unspecified error has occured, the watcher has been stopped. This might
375	happen because the watcher could not be properly started because libev	673	happen because the watcher could not be properly started because libev
376	ran out of memory, a file descriptor was found to be closed or any other	674	ran out of memory, a file descriptor was found to be closed or any other
377	problem. You best act on it by reporting the problem and somehow coping	675	problem. You best act on it by reporting the problem and somehow coping
…		…
383	programs, though, so beware.</p>	681	programs, though, so beware.</p>
384	</dd>	682	</dd>
385	</dl>	683	</dl>
386		684
387	</div>	685	</div>
		686	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		687	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		688	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		689	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		690	<dl>
		691	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		692	<dd>
		693	<p>This macro initialises the generic portion of a watcher. The contents
		694	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		695	the generic parts of the watcher are initialised, you <i>need</i> to call
		696	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		697	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		698	which rolls both calls into one.</p>
		699	<p>You can reinitialise a watcher at any time as long as it has been stopped
		700	(or never started) and there are no pending events outstanding.</p>
		701	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		702	int revents)</code>.</p>
		703	</dd>
		704	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		705	<dd>
		706	<p>This macro initialises the type-specific parts of a watcher. You need to
		707	call <code>ev_init</code> at least once before you call this macro, but you can
		708	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		709	macro on a watcher that is active (it can be pending, however, which is a
		710	difference to the <code>ev_init</code> macro).</p>
		711	<p>Although some watcher types do not have type-specific arguments
		712	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		713	</dd>
		714	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		715	<dd>
		716	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		717	calls into a single call. This is the most convinient method to initialise
		718	a watcher. The same limitations apply, of course.</p>
		719	</dd>
		720	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		721	<dd>
		722	<p>Starts (activates) the given watcher. Only active watchers will receive
		723	events. If the watcher is already active nothing will happen.</p>
		724	</dd>
		725	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		726	<dd>
		727	<p>Stops the given watcher again (if active) and clears the pending
		728	status. It is possible that stopped watchers are pending (for example,
		729	non-repeating timers are being stopped when they become pending), but
		730	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		731	you want to free or reuse the memory used by the watcher it is therefore a
		732	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		733	</dd>
		734	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		735	<dd>
		736	<p>Returns a true value iff the watcher is active (i.e. it has been started
		737	and not yet been stopped). As long as a watcher is active you must not modify
		738	it.</p>
		739	</dd>
		740	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		741	<dd>
		742	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		743	events but its callback has not yet been invoked). As long as a watcher
		744	is pending (but not active) you must not call an init function on it (but
		745	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		746	libev (e.g. you cnanot <code>free ()</code> it).</p>
		747	</dd>
		748	<dt>callback ev_cb (ev_TYPE *watcher)</dt>
		749	<dd>
		750	<p>Returns the callback currently set on the watcher.</p>
		751	</dd>
		752	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		753	<dd>
		754	<p>Change the callback. You can change the callback at virtually any time
		755	(modulo threads).</p>
		756	</dd>
		757	</dl>
		758
		759
		760
		761
		762
		763	</div>
388	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	764	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
389	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	765	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
390	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	766	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
391	and read at any time, libev will completely ignore it. This cna be used	767	and read at any time, libev will completely ignore it. This can be used
392	to associate arbitrary data with your watcher. If you need more data and	768	to associate arbitrary data with your watcher. If you need more data and
393	don't want to allocate memory and store a pointer to it in that data	769	don't want to allocate memory and store a pointer to it in that data
394	member, you can also "subclass" the watcher type and provide your own	770	member, you can also "subclass" the watcher type and provide your own
395	data:</p>	771	data:</p>
396	<pre> struct my_io	772	<pre> struct my_io
…		…
409	struct my_io w = (struct my_io )w_;	785	struct my_io w = (struct my_io )w_;
410	...	786	...
411	}	787	}
412		788
413	</pre>	789	</pre>
414	<p>More interesting and less C-conformant ways of catsing your callback type	790	<p>More interesting and less C-conformant ways of casting your callback type
415	have been omitted....</p>	791	instead have been omitted.</p>
		792	<p>Another common scenario is having some data structure with multiple
		793	watchers:</p>
		794	<pre> struct my_biggy
		795	{
		796	int some_data;
		797	ev_timer t1;
		798	ev_timer t2;
		799	}
416		800
		801	</pre>
		802	<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
		803	you need to use <code>offsetof</code>:</p>
		804	<pre> #include <stddef.h>
417		805
		806	static void
		807	t1_cb (EV_P_ struct ev_timer *w, int revents)
		808	{
		809	struct my_biggy big = (struct my_biggy *
		810	(((char *)w) - offsetof (struct my_biggy, t1));
		811	}
418		812
		813	static void
		814	t2_cb (EV_P_ struct ev_timer *w, int revents)
		815	{
		816	struct my_biggy big = (struct my_biggy *
		817	(((char *)w) - offsetof (struct my_biggy, t2));
		818	}
419		819
420		820
		821
		822
		823	</pre>
		824
421	</div>	825	</div>
422	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	826	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
423	<div id="WATCHER_TYPES_CONTENT">	827	<div id="WATCHER_TYPES_CONTENT">
424	<p>This section describes each watcher in detail, but will not repeat	828	<p>This section describes each watcher in detail, but will not repeat
425	information given in the last section.</p>	829	information given in the last section. Any initialisation/set macros,
		830	functions and members specific to the watcher type are explained.</p>
		831	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		832	while the watcher is active, you can look at the member and expect some
		833	sensible content, but you must not modify it (you can modify it while the
		834	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		835	means you can expect it to have some sensible content while the watcher
		836	is active, but you can also modify it. Modifying it may not do something
		837	sensible or take immediate effect (or do anything at all), but libev will
		838	not crash or malfunction in any way.</p>
426		839
		840
		841
		842
		843
427	</div>	844	</div>
428	<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2>	845	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
429	<div id="struct_ev_io_is_my_file_descriptor_r-2">	846	<div id="code_ev_io_code_is_this_file_descrip-2">
430	<p>I/O watchers check whether a file descriptor is readable or writable	847	<p>I/O watchers check whether a file descriptor is readable or writable
431	in each iteration of the event loop (This behaviour is called	848	in each iteration of the event loop, or, more precisely, when reading
432	level-triggering because you keep receiving events as long as the	849	would not block the process and writing would at least be able to write
433	condition persists. Remember you cna stop the watcher if you don't want to	850	some data. This behaviour is called level-triggering because you keep
434	act on the event and neither want to receive future events).</p>	851	receiving events as long as the condition persists. Remember you can stop
		852	the watcher if you don't want to act on the event and neither want to
		853	receive future events.</p>
		854	<p>In general you can register as many read and/or write event watchers per
		855	fd as you want (as long as you don't confuse yourself). Setting all file
		856	descriptors to non-blocking mode is also usually a good idea (but not
		857	required if you know what you are doing).</p>
		858	<p>You have to be careful with dup'ed file descriptors, though. Some backends
		859	(the linux epoll backend is a notable example) cannot handle dup'ed file
		860	descriptors correctly if you register interest in two or more fds pointing
		861	to the same underlying file/socket/etc. description (that is, they share
		862	the same underlying "file open").</p>
		863	<p>If you must do this, then force the use of a known-to-be-good backend
		864	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
		865	<code>EVBACKEND_POLL</code>).</p>
		866	<p>Another thing you have to watch out for is that it is quite easy to
		867	receive "spurious" readyness notifications, that is your callback might
		868	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		869	because there is no data. Not only are some backends known to create a
		870	lot of those (for example solaris ports), it is very easy to get into
		871	this situation even with a relatively standard program structure. Thus
		872	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		873	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		874	<p>If you cannot run the fd in non-blocking mode (for example you should not
		875	play around with an Xlib connection), then you have to seperately re-test
		876	wether a file descriptor is really ready with a known-to-be good interface
		877	such as poll (fortunately in our Xlib example, Xlib already does this on
		878	its own, so its quite safe to use).</p>
435	<dl>	879	<dl>
436	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	880	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
437	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	881	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
438	<dd>	882	<dd>
439	<p>Configures an ev_io watcher. The fd is the file descriptor to rceeive	883	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
440	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	884	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
441	EV_WRITE</code> to receive the given events.</p>	885	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		886	</dd>
		887	<dt>int fd [read-only]</dt>
		888	<dd>
		889	<p>The file descriptor being watched.</p>
		890	</dd>
		891	<dt>int events [read-only]</dt>
		892	<dd>
		893	<p>The events being watched.</p>
442	</dd>	894	</dd>
443	</dl>	895	</dl>
		896	<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		897	readable, but only once. Since it is likely line-buffered, you could
		898	attempt to read a whole line in the callback.</p>
		899	<pre> static void
		900	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		901	{
		902	ev_io_stop (loop, w);
		903	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		904	}
444		905
		906	...
		907	struct ev_loop *loop = ev_default_init (0);
		908	struct ev_io stdin_readable;
		909	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		910	ev_io_start (loop, &stdin_readable);
		911	ev_loop (loop, 0);
		912
		913
		914
		915
		916	</pre>
		917
445	</div>	918	</div>
446	<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2>	919	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
447	<div id="struct_ev_timer_relative_and_optiona-2">	920	<div id="code_ev_timer_code_relative_and_opti-2">
448	<p>Timer watchers are simple relative timers that generate an event after a	921	<p>Timer watchers are simple relative timers that generate an event after a
449	given time, and optionally repeating in regular intervals after that.</p>	922	given time, and optionally repeating in regular intervals after that.</p>
450	<p>The timers are based on real time, that is, if you register an event that	923	<p>The timers are based on real time, that is, if you register an event that
451	times out after an hour and youreset your system clock to last years	924	times out after an hour and you reset your system clock to last years
452	time, it will still time out after (roughly) and hour. "Roughly" because	925	time, it will still time out after (roughly) and hour. "Roughly" because
453	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	926	detecting time jumps is hard, and some inaccuracies are unavoidable (the
454	monotonic clock option helps a lot here).</p>	927	monotonic clock option helps a lot here).</p>
		928	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
		929	time. This is usually the right thing as this timestamp refers to the time
		930	of the event triggering whatever timeout you are modifying/starting. If
		931	you suspect event processing to be delayed and you <i>need</i> to base the timeout
		932	on the current time, use something like this to adjust for this:</p>
		933	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		934
		935	</pre>
		936	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		937	but if multiple timers become ready during the same loop iteration then
		938	order of execution is undefined.</p>
455	<dl>	939	<dl>
456	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	940	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
457	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	941	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
458	<dd>	942	<dd>
459	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	943	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
461	timer will automatically be configured to trigger again <code>repeat</code> seconds	945	timer will automatically be configured to trigger again <code>repeat</code> seconds
462	later, again, and again, until stopped manually.</p>	946	later, again, and again, until stopped manually.</p>
463	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	947	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
464	configure a timer to trigger every 10 seconds, then it will trigger at	948	configure a timer to trigger every 10 seconds, then it will trigger at
465	exactly 10 second intervals. If, however, your program cannot keep up with	949	exactly 10 second intervals. If, however, your program cannot keep up with
466	the timer (ecause it takes longer than those 10 seconds to do stuff) the	950	the timer (because it takes longer than those 10 seconds to do stuff) the
467	timer will not fire more than once per event loop iteration.</p>	951	timer will not fire more than once per event loop iteration.</p>
468	</dd>	952	</dd>
469	<dt>ev_timer_again (loop)</dt>	953	<dt>ev_timer_again (loop)</dt>
470	<dd>	954	<dd>
471	<p>This will act as if the timer timed out and restart it again if it is	955	<p>This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:</p>	956	repeating. The exact semantics are:</p>
473	<p>If the timer is started but nonrepeating, stop it.</p>	957	<p>If the timer is started but nonrepeating, stop it.</p>
474	<p>If the timer is repeating, either start it if necessary (with the repeat	958	<p>If the timer is repeating, either start it if necessary (with the repeat
475	value), or reset the running timer to the repeat value.</p>	959	value), or reset the running timer to the repeat value.</p>
476	<p>This sounds a bit complicated, but here is a useful and typical	960	<p>This sounds a bit complicated, but here is a useful and typical
477	example: Imagine you have a tcp connection and you want a so-called idle	961	example: Imagine you have a tcp connection and you want a so-called
478	timeout, that is, you want to be called when there have been, say, 60	962	idle timeout, that is, you want to be called when there have been,
479	seconds of inactivity on the socket. The easiest way to do this is to	963	say, 60 seconds of inactivity on the socket. The easiest way to do
480	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	964	this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
481	time you successfully read or write some data. If you go into an idle	965	<code>ev_timer_again</code> each time you successfully read or write some data. If
482	state where you do not expect data to travel on the socket, you can stop	966	you go into an idle state where you do not expect data to travel on the
483	the timer, and again will automatically restart it if need be.</p>	967	socket, you can stop the timer, and again will automatically restart it if
		968	need be.</p>
		969	<p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
		970	and only ever use the <code>repeat</code> value:</p>
		971	<pre> ev_timer_init (timer, callback, 0., 5.);
		972	ev_timer_again (loop, timer);
		973	...
		974	timer->again = 17.;
		975	ev_timer_again (loop, timer);
		976	...
		977	timer->again = 10.;
		978	ev_timer_again (loop, timer);
		979
		980	</pre>
		981	<p>This is more efficient then stopping/starting the timer eahc time you want
		982	to modify its timeout value.</p>
		983	</dd>
		984	<dt>ev_tstamp repeat [read-write]</dt>
		985	<dd>
		986	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		987	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		988	which is also when any modifications are taken into account.</p>
484	</dd>	989	</dd>
485	</dl>	990	</dl>
		991	<p>Example: Create a timer that fires after 60 seconds.</p>
		992	<pre> static void
		993	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		994	{
		995	.. one minute over, w is actually stopped right here
		996	}
486		997
		998	struct ev_timer mytimer;
		999	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1000	ev_timer_start (loop, &mytimer);
		1001
		1002	</pre>
		1003	<p>Example: Create a timeout timer that times out after 10 seconds of
		1004	inactivity.</p>
		1005	<pre> static void
		1006	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		1007	{
		1008	.. ten seconds without any activity
		1009	}
		1010
		1011	struct ev_timer mytimer;
		1012	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1013	ev_timer_again (&mytimer); /* start timer */
		1014	ev_loop (loop, 0);
		1015
		1016	// and in some piece of code that gets executed on any "activity":
		1017	// reset the timeout to start ticking again at 10 seconds
		1018	ev_timer_again (&mytimer);
		1019
		1020
		1021
		1022
		1023	</pre>
		1024
487	</div>	1025	</div>
488	<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2>	1026	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
489	<div id="ev_periodic_to_cron_or_not_to_cron_i-2">	1027	<div id="code_ev_periodic_code_to_cron_or_not-2">
490	<p>Periodic watchers are also timers of a kind, but they are very versatile	1028	<p>Periodic watchers are also timers of a kind, but they are very versatile
491	(and unfortunately a bit complex).</p>	1029	(and unfortunately a bit complex).</p>
492	<p>Unlike ev_timer's, they are not based on real time (or relative time)	1030	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
493	but on wallclock time (absolute time). You can tell a periodic watcher	1031	but on wallclock time (absolute time). You can tell a periodic watcher
494	to trigger "at" some specific point in time. For example, if you tell a	1032	to trigger "at" some specific point in time. For example, if you tell a
495	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1033	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
496	+ 10.>) and then reset your system clock to the last year, then it will	1034	+ 10.</code>) and then reset your system clock to the last year, then it will
497	take a year to trigger the event (unlike an ev_timer, which would trigger	1035	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
498	roughly 10 seconds later and of course not if you reset your system time	1036	roughly 10 seconds later and of course not if you reset your system time
499	again).</p>	1037	again).</p>
500	<p>They can also be used to implement vastly more complex timers, such as	1038	<p>They can also be used to implement vastly more complex timers, such as
501	triggering an event on eahc midnight, local time.</p>	1039	triggering an event on eahc midnight, local time.</p>
		1040	<p>As with timers, the callback is guarenteed to be invoked only when the
		1041	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1042	during the same loop iteration then order of execution is undefined.</p>
502	<dl>	1043	<dl>
503	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1044	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
504	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	1045	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
505	<dd>	1046	<dd>
506	<p>Lots of arguments, lets sort it out... There are basically three modes of	1047	<p>Lots of arguments, lets sort it out... There are basically three modes of
507	operation, and we will explain them from simplest to complex:</p>	1048	operation, and we will explain them from simplest to complex:</p>
508
509
510
511
512	<p>	1049	<p>
513	<dl>	1050	<dl>
514	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1051	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
515	<dd>	1052	<dd>
516	<p>In this configuration the watcher triggers an event at the wallclock time	1053	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
528	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	1065	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
529		1066
530	</pre>	1067	</pre>
531	<p>This doesn't mean there will always be 3600 seconds in between triggers,	1068	<p>This doesn't mean there will always be 3600 seconds in between triggers,
532	but only that the the callback will be called when the system time shows a	1069	but only that the the callback will be called when the system time shows a
533	full hour (UTC), or more correct, when the system time is evenly divisible	1070	full hour (UTC), or more correctly, when the system time is evenly divisible
534	by 3600.</p>	1071	by 3600.</p>
535	<p>Another way to think about it (for the mathematically inclined) is that	1072	<p>Another way to think about it (for the mathematically inclined) is that
536	ev_periodic will try to run the callback in this mode at the next possible	1073	<code>ev_periodic</code> will try to run the callback in this mode at the next possible
537	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	1074	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
538	</dd>	1075	</dd>
539	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	1076	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>
540	<dd>	1077	<dd>
541	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	1078	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
542	ignored. Instead, each time the periodic watcher gets scheduled, the	1079	ignored. Instead, each time the periodic watcher gets scheduled, the
543	reschedule callback will be called with the watcher as first, and the	1080	reschedule callback will be called with the watcher as first, and the
544	current time as second argument.</p>	1081	current time as second argument.</p>
545	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	1082	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
546	periodic watcher, ever, or make any event loop modificstions</i>. If you need	1083	ever, or make any event loop modifications</i>. If you need to stop it,
547	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p>	1084	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
		1085	starting a prepare watcher).</p>
548	<p>Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1086	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
549	ev_tstamp now)>, e.g.:</p>	1087	ev_tstamp now)</code>, e.g.:</p>
550	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1088	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
551	{	1089	{
552	return now + 60.;	1090	return now + 60.;
553	}	1091	}
554		1092
555	</pre>	1093	</pre>
556	<p>It must return the next time to trigger, based on the passed time value	1094	<p>It must return the next time to trigger, based on the passed time value
557	(that is, the lowest time value larger than to the second argument). It	1095	(that is, the lowest time value larger than to the second argument). It
558	will usually be called just before the callback will be triggered, but	1096	will usually be called just before the callback will be triggered, but
559	might be called at other times, too.</p>	1097	might be called at other times, too.</p>
		1098	<p>NOTE: <i>This callback must always return a time that is later than the
		1099	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
560	<p>This can be used to create very complex timers, such as a timer that	1100	<p>This can be used to create very complex timers, such as a timer that
561	triggers on each midnight, local time. To do this, you would calculate the	1101	triggers on each midnight, local time. To do this, you would calculate the
562	next midnight after <code>now</code> and return the timestamp value for this. How you do this	1102	next midnight after <code>now</code> and return the timestamp value for this. How
563	is, again, up to you (but it is not trivial).</p>	1103	you do this is, again, up to you (but it is not trivial, which is the main
		1104	reason I omitted it as an example).</p>
564	</dd>	1105	</dd>
565	</dl>	1106	</dl>
566	</p>	1107	</p>
567	</dd>	1108	</dd>
568	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1109	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
570	<p>Simply stops and restarts the periodic watcher again. This is only useful	1111	<p>Simply stops and restarts the periodic watcher again. This is only useful
571	when you changed some parameters or the reschedule callback would return	1112	when you changed some parameters or the reschedule callback would return
572	a different time than the last time it was called (e.g. in a crond like	1113	a different time than the last time it was called (e.g. in a crond like
573	program when the crontabs have changed).</p>	1114	program when the crontabs have changed).</p>
574	</dd>	1115	</dd>
		1116	<dt>ev_tstamp interval [read-write]</dt>
		1117	<dd>
		1118	<p>The current interval value. Can be modified any time, but changes only
		1119	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1120	called.</p>
		1121	</dd>
		1122	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1123	<dd>
		1124	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1125	switched off. Can be changed any time, but changes only take effect when
		1126	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1127	</dd>
575	</dl>	1128	</dl>
		1129	<p>Example: Call a callback every hour, or, more precisely, whenever the
		1130	system clock is divisible by 3600. The callback invocation times have
		1131	potentially a lot of jittering, but good long-term stability.</p>
		1132	<pre> static void
		1133	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1134	{
		1135	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1136	}
576		1137
		1138	struct ev_periodic hourly_tick;
		1139	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1140	ev_periodic_start (loop, &hourly_tick);
		1141
		1142	</pre>
		1143	<p>Example: The same as above, but use a reschedule callback to do it:</p>
		1144	<pre> #include <math.h>
		1145
		1146	static ev_tstamp
		1147	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1148	{
		1149	return fmod (now, 3600.) + 3600.;
		1150	}
		1151
		1152	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1153
		1154	</pre>
		1155	<p>Example: Call a callback every hour, starting now:</p>
		1156	<pre> struct ev_periodic hourly_tick;
		1157	ev_periodic_init (&hourly_tick, clock_cb,
		1158	fmod (ev_now (loop), 3600.), 3600., 0);
		1159	ev_periodic_start (loop, &hourly_tick);
		1160
		1161
		1162
		1163
		1164	</pre>
		1165
577	</div>	1166	</div>
578	<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>	1167	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
579	<div id="ev_signal_signal_me_when_a_signal_ge-2">	1168	<div id="code_ev_signal_code_signal_me_when_a-2">
580	<p>Signal watchers will trigger an event when the process receives a specific	1169	<p>Signal watchers will trigger an event when the process receives a specific
581	signal one or more times. Even though signals are very asynchronous, libev	1170	signal one or more times. Even though signals are very asynchronous, libev
582	will try its best to deliver signals synchronously, i.e. as part of the	1171	will try it's best to deliver signals synchronously, i.e. as part of the
583	normal event processing, like any other event.</p>	1172	normal event processing, like any other event.</p>
584	<p>You cna configure as many watchers as you like per signal. Only when the	1173	<p>You can configure as many watchers as you like per signal. Only when the
585	first watcher gets started will libev actually register a signal watcher	1174	first watcher gets started will libev actually register a signal watcher
586	with the kernel (thus it coexists with your own signal handlers as long	1175	with the kernel (thus it coexists with your own signal handlers as long
587	as you don't register any with libev). Similarly, when the last signal	1176	as you don't register any with libev). Similarly, when the last signal
588	watcher for a signal is stopped libev will reset the signal handler to	1177	watcher for a signal is stopped libev will reset the signal handler to
589	SIG_DFL (regardless of what it was set to before).</p>	1178	SIG_DFL (regardless of what it was set to before).</p>
…		…
592	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1181	<dt>ev_signal_set (ev_signal *, int signum)</dt>
593	<dd>	1182	<dd>
594	<p>Configures the watcher to trigger on the given signal number (usually one	1183	<p>Configures the watcher to trigger on the given signal number (usually one
595	of the <code>SIGxxx</code> constants).</p>	1184	of the <code>SIGxxx</code> constants).</p>
596	</dd>	1185	</dd>
		1186	<dt>int signum [read-only]</dt>
		1187	<dd>
		1188	<p>The signal the watcher watches out for.</p>
		1189	</dd>
597	</dl>	1190	</dl>
598		1191
		1192
		1193
		1194
		1195
599	</div>	1196	</div>
600	<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2>	1197	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
601	<div id="ev_child_wait_for_pid_status_changes-2">	1198	<div id="code_ev_child_code_watch_out_for_pro-2">
602	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1199	<p>Child watchers trigger when your process receives a SIGCHLD in response to
603	some child status changes (most typically when a child of yours dies).</p>	1200	some child status changes (most typically when a child of yours dies).</p>
604	<dl>	1201	<dl>
605	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1202	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
606	<dt>ev_child_set (ev_child *, int pid)</dt>	1203	<dt>ev_child_set (ev_child *, int pid)</dt>
607	<dd>	1204	<dd>
608	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or	1205	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
609	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look	1206	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
610	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1207	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
611	the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member	1208	the status word (use the macros from <code>sys/wait.h</code> and see your systems
		1209	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
612	contains the pid of the process causing the status change.</p>	1210	process causing the status change.</p>
		1211	</dd>
		1212	<dt>int pid [read-only]</dt>
		1213	<dd>
		1214	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1215	</dd>
		1216	<dt>int rpid [read-write]</dt>
		1217	<dd>
		1218	<p>The process id that detected a status change.</p>
		1219	</dd>
		1220	<dt>int rstatus [read-write]</dt>
		1221	<dd>
		1222	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1223	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
613	</dd>	1224	</dd>
614	</dl>	1225	</dl>
		1226	<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
		1227	<pre> static void
		1228	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1229	{
		1230	ev_unloop (loop, EVUNLOOP_ALL);
		1231	}
615		1232
		1233	struct ev_signal signal_watcher;
		1234	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1235	ev_signal_start (loop, &sigint_cb);
		1236
		1237
		1238
		1239
		1240	</pre>
		1241
616	</div>	1242	</div>
		1243	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1244	<div id="code_ev_stat_code_did_the_file_attri-2">
		1245	<p>This watches a filesystem path for attribute changes. That is, it calls
		1246	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1247	compared to the last time, invoking the callback if it did.</p>
		1248	<p>The path does not need to exist: changing from "path exists" to "path does
		1249	not exist" is a status change like any other. The condition "path does
		1250	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1251	otherwise always forced to be at least one) and all the other fields of
		1252	the stat buffer having unspecified contents.</p>
		1253	<p>Since there is no standard to do this, the portable implementation simply
		1254	calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
		1255	can specify a recommended polling interval for this case. If you specify
		1256	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1257	unspecified default</i> value will be used (which you can expect to be around
		1258	five seconds, although this might change dynamically). Libev will also
		1259	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1260	usually overkill.</p>
		1261	<p>This watcher type is not meant for massive numbers of stat watchers,
		1262	as even with OS-supported change notifications, this can be
		1263	resource-intensive.</p>
		1264	<p>At the time of this writing, only the Linux inotify interface is
		1265	implemented (implementing kqueue support is left as an exercise for the
		1266	reader). Inotify will be used to give hints only and should not change the
		1267	semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
		1268	to fall back to regular polling again even with inotify, but changes are
		1269	usually detected immediately, and if the file exists there will be no
		1270	polling.</p>
		1271	<dl>
		1272	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1273	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1274	<dd>
		1275	<p>Configures the watcher to wait for status changes of the given
		1276	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1277	be detected and should normally be specified as <code>0</code> to let libev choose
		1278	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1279	path for as long as the watcher is active.</p>
		1280	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1281	relative to the attributes at the time the watcher was started (or the
		1282	last change was detected).</p>
		1283	</dd>
		1284	<dt>ev_stat_stat (ev_stat *)</dt>
		1285	<dd>
		1286	<p>Updates the stat buffer immediately with new values. If you change the
		1287	watched path in your callback, you could call this fucntion to avoid
		1288	detecting this change (while introducing a race condition). Can also be
		1289	useful simply to find out the new values.</p>
		1290	</dd>
		1291	<dt>ev_statdata attr [read-only]</dt>
		1292	<dd>
		1293	<p>The most-recently detected attributes of the file. Although the type is of
		1294	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1295	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1296	was some error while <code>stat</code>ing the file.</p>
		1297	</dd>
		1298	<dt>ev_statdata prev [read-only]</dt>
		1299	<dd>
		1300	<p>The previous attributes of the file. The callback gets invoked whenever
		1301	<code>prev</code> != <code>attr</code>.</p>
		1302	</dd>
		1303	<dt>ev_tstamp interval [read-only]</dt>
		1304	<dd>
		1305	<p>The specified interval.</p>
		1306	</dd>
		1307	<dt>const char *path [read-only]</dt>
		1308	<dd>
		1309	<p>The filesystem path that is being watched.</p>
		1310	</dd>
		1311	</dl>
		1312	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1313	<pre> static void
		1314	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1315	{
		1316	/* /etc/passwd changed in some way */
		1317	if (w->attr.st_nlink)
		1318	{
		1319	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1320	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1321	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1322	}
		1323	else
		1324	/* you shalt not abuse printf for puts */
		1325	puts ("wow, /etc/passwd is not there, expect problems. "
		1326	"if this is windows, they already arrived\n");
		1327	}
		1328
		1329	...
		1330	ev_stat passwd;
		1331
		1332	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1333	ev_stat_start (loop, &passwd);
		1334
		1335
		1336
		1337
		1338	</pre>
		1339
		1340	</div>
617	<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2>	1341	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
618	<div id="ev_idle_when_you_ve_got_nothing_bett-2">	1342	<div id="code_ev_idle_code_when_you_ve_got_no-2">
619	<p>Idle watchers trigger events when there are no other I/O or timer (or	1343	<p>Idle watchers trigger events when there are no other events are pending
620	periodic) events pending. That is, as long as your process is busy	1344	(prepare, check and other idle watchers do not count). That is, as long
621	handling sockets or timeouts it will not be called. But when your process	1345	as your process is busy handling sockets or timeouts (or even signals,
622	is idle all idle watchers are being called again and again - until	1346	imagine) it will not be triggered. But when your process is idle all idle
		1347	watchers are being called again and again, once per event loop iteration -
623	stopped, that is, or your process receives more events.</p>	1348	until stopped, that is, or your process receives more events and becomes
		1349	busy.</p>
624	<p>The most noteworthy effect is that as long as any idle watchers are	1350	<p>The most noteworthy effect is that as long as any idle watchers are
625	active, the process will not block when waiting for new events.</p>	1351	active, the process will not block when waiting for new events.</p>
626	<p>Apart from keeping your process non-blocking (which is a useful	1352	<p>Apart from keeping your process non-blocking (which is a useful
627	effect on its own sometimes), idle watchers are a good place to do	1353	effect on its own sometimes), idle watchers are a good place to do
628	"pseudo-background processing", or delay processing stuff to after the	1354	"pseudo-background processing", or delay processing stuff to after the
…		…
633	<p>Initialises and configures the idle watcher - it has no parameters of any	1359	<p>Initialises and configures the idle watcher - it has no parameters of any
634	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1360	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
635	believe me.</p>	1361	believe me.</p>
636	</dd>	1362	</dd>
637	</dl>	1363	</dl>
		1364	<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
		1365	callback, free it. Also, use no error checking, as usual.</p>
		1366	<pre> static void
		1367	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1368	{
		1369	free (w);
		1370	// now do something you wanted to do when the program has
		1371	// no longer asnything immediate to do.
		1372	}
638		1373
		1374	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1375	ev_idle_init (idle_watcher, idle_cb);
		1376	ev_idle_start (loop, idle_cb);
		1377
		1378
		1379
		1380
		1381	</pre>
		1382
639	</div>	1383	</div>
640	<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>	1384	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
641	<div id="prepare_and_check_your_hooks_into_th-2">	1385	<div id="code_ev_prepare_code_and_code_ev_che-2">
642	<p>Prepare and check watchers usually (but not always) are used in	1386	<p>Prepare and check watchers are usually (but not always) used in tandem:
643	tandom. Prepare watchers get invoked before the process blocks and check	1387	prepare watchers get invoked before the process blocks and check watchers
644	watchers afterwards.</p>	1388	afterwards.</p>
		1389	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1390	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1391	watchers. Other loops than the current one are fine, however. The
		1392	rationale behind this is that you do not need to check for recursion in
		1393	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1394	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1395	called in pairs bracketing the blocking call.</p>
645	<p>Their main purpose is to integrate other event mechanisms into libev. This	1396	<p>Their main purpose is to integrate other event mechanisms into libev and
646	could be used, for example, to track variable changes, implement your own	1397	their use is somewhat advanced. This could be used, for example, to track
647	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1398	variable changes, implement your own watchers, integrate net-snmp or a
		1399	coroutine library and lots more. They are also occasionally useful if
		1400	you cache some data and want to flush it before blocking (for example,
		1401	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1402	watcher).</p>
648	<p>This is done by examining in each prepare call which file descriptors need	1403	<p>This is done by examining in each prepare call which file descriptors need
649	to be watched by the other library, registering ev_io watchers for them	1404	to be watched by the other library, registering <code>ev_io</code> watchers for
650	and starting an ev_timer watcher for any timeouts (many libraries provide	1405	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
651	just this functionality). Then, in the check watcher you check for any	1406	provide just this functionality). Then, in the check watcher you check for
652	events that occured (by making your callbacks set soem flags for example)	1407	any events that occured (by checking the pending status of all watchers
653	and call back into the library.</p>	1408	and stopping them) and call back into the library. The I/O and timer
		1409	callbacks will never actually be called (but must be valid nevertheless,
		1410	because you never know, you know?).</p>
654	<p>As another example, the perl Coro module uses these hooks to integrate	1411	<p>As another example, the Perl Coro module uses these hooks to integrate
655	coroutines into libev programs, by yielding to other active coroutines	1412	coroutines into libev programs, by yielding to other active coroutines
656	during each prepare and only letting the process block if no coroutines	1413	during each prepare and only letting the process block if no coroutines
657	are ready to run.</p>	1414	are ready to run (it's actually more complicated: it only runs coroutines
		1415	with priority higher than or equal to the event loop and one coroutine
		1416	of lower priority, but only once, using idle watchers to keep the event
		1417	loop from blocking if lower-priority coroutines are active, thus mapping
		1418	low-priority coroutines to idle/background tasks).</p>
658	<dl>	1419	<dl>
659	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1420	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
660	<dt>ev_check_init (ev_check *, callback)</dt>	1421	<dt>ev_check_init (ev_check *, callback)</dt>
661	<dd>	1422	<dd>
662	<p>Initialises and configures the prepare or check watcher - they have no	1423	<p>Initialises and configures the prepare or check watcher - they have no
663	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1424	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
664	macros, but using them is utterly, utterly pointless.</p>	1425	macros, but using them is utterly, utterly and completely pointless.</p>
665	</dd>	1426	</dd>
666	</dl>	1427	</dl>
		1428	<p>Example: To include a library such as adns, you would add IO watchers
		1429	and a timeout watcher in a prepare handler, as required by libadns, and
		1430	in a check watcher, destroy them and call into libadns. What follows is
		1431	pseudo-code only of course:</p>
		1432	<pre> static ev_io iow [nfd];
		1433	static ev_timer tw;
667		1434
		1435	static void
		1436	io_cb (ev_loop loop, ev_io w, int revents)
		1437	{
		1438	// set the relevant poll flags
		1439	// could also call adns_processreadable etc. here
		1440	struct pollfd fd = (struct pollfd )w->data;
		1441	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1442	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1443	}
		1444
		1445	// create io watchers for each fd and a timer before blocking
		1446	static void
		1447	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1448	{
		1449	int timeout = 3600000;truct pollfd fds [nfd];
		1450	// actual code will need to loop here and realloc etc.
		1451	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1452
		1453	/* the callback is illegal, but won't be called as we stop during check */
		1454	ev_timer_init (&tw, 0, timeout * 1e-3);
		1455	ev_timer_start (loop, &tw);
		1456
		1457	// create on ev_io per pollfd
		1458	for (int i = 0; i < nfd; ++i)
		1459	{
		1460	ev_io_init (iow + i, io_cb, fds [i].fd,
		1461	((fds [i].events & POLLIN ? EV_READ : 0)
		1462	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1463
		1464	fds [i].revents = 0;
		1465	iow [i].data = fds + i;
		1466	ev_io_start (loop, iow + i);
		1467	}
		1468	}
		1469
		1470	// stop all watchers after blocking
		1471	static void
		1472	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1473	{
		1474	ev_timer_stop (loop, &tw);
		1475
		1476	for (int i = 0; i < nfd; ++i)
		1477	ev_io_stop (loop, iow + i);
		1478
		1479	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1480	}
		1481
		1482
		1483
		1484
		1485	</pre>
		1486
668	</div>	1487	</div>
669	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1488	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1489	<div id="code_ev_embed_code_when_one_backend_-2">
		1490	<p>This is a rather advanced watcher type that lets you embed one event loop
		1491	into another (currently only <code>ev_io</code> events are supported in the embedded
		1492	loop, other types of watchers might be handled in a delayed or incorrect
		1493	fashion and must not be used).</p>
		1494	<p>There are primarily two reasons you would want that: work around bugs and
		1495	prioritise I/O.</p>
		1496	<p>As an example for a bug workaround, the kqueue backend might only support
		1497	sockets on some platform, so it is unusable as generic backend, but you
		1498	still want to make use of it because you have many sockets and it scales
		1499	so nicely. In this case, you would create a kqueue-based loop and embed it
		1500	into your default loop (which might use e.g. poll). Overall operation will
		1501	be a bit slower because first libev has to poll and then call kevent, but
		1502	at least you can use both at what they are best.</p>
		1503	<p>As for prioritising I/O: rarely you have the case where some fds have
		1504	to be watched and handled very quickly (with low latency), and even
		1505	priorities and idle watchers might have too much overhead. In this case
		1506	you would put all the high priority stuff in one loop and all the rest in
		1507	a second one, and embed the second one in the first.</p>
		1508	<p>As long as the watcher is active, the callback will be invoked every time
		1509	there might be events pending in the embedded loop. The callback must then
		1510	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1511	their callbacks (you could also start an idle watcher to give the embedded
		1512	loop strictly lower priority for example). You can also set the callback
		1513	to <code>0</code>, in which case the embed watcher will automatically execute the
		1514	embedded loop sweep.</p>
		1515	<p>As long as the watcher is started it will automatically handle events. The
		1516	callback will be invoked whenever some events have been handled. You can
		1517	set the callback to <code>0</code> to avoid having to specify one if you are not
		1518	interested in that.</p>
		1519	<p>Also, there have not currently been made special provisions for forking:
		1520	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1521	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1522	yourself.</p>
		1523	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1524	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1525	portable one.</p>
		1526	<p>So when you want to use this feature you will always have to be prepared
		1527	that you cannot get an embeddable loop. The recommended way to get around
		1528	this is to have a separate variables for your embeddable loop, try to
		1529	create it, and if that fails, use the normal loop for everything:</p>
		1530	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1531	struct ev_loop *loop_lo = 0;
		1532	struct ev_embed embed;
		1533
		1534	// see if there is a chance of getting one that works
		1535	// (remember that a flags value of 0 means autodetection)
		1536	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1537	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1538	: 0;
		1539
		1540	// if we got one, then embed it, otherwise default to loop_hi
		1541	if (loop_lo)
		1542	{
		1543	ev_embed_init (&embed, 0, loop_lo);
		1544	ev_embed_start (loop_hi, &embed);
		1545	}
		1546	else
		1547	loop_lo = loop_hi;
		1548
		1549	</pre>
		1550	<dl>
		1551	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1552	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1553	<dd>
		1554	<p>Configures the watcher to embed the given loop, which must be
		1555	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1556	invoked automatically, otherwise it is the responsibility of the callback
		1557	to invoke it (it will continue to be called until the sweep has been done,
		1558	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1559	</dd>
		1560	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1561	<dd>
		1562	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1563	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1564	apropriate way for embedded loops.</p>
		1565	</dd>
		1566	<dt>struct ev_loop *loop [read-only]</dt>
		1567	<dd>
		1568	<p>The embedded event loop.</p>
		1569	</dd>
		1570	</dl>
		1571
		1572
		1573
		1574
		1575
		1576	</div>
		1577	<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>
		1578	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1579	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1580	whoever is a good citizen cared to tell libev about it by calling
		1581	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1582	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1583	and only in the child after the fork. If whoever good citizen calling
		1584	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1585	handlers will be invoked, too, of course.</p>
		1586	<dl>
		1587	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1588	<dd>
		1589	<p>Initialises and configures the fork watcher - it has no parameters of any
		1590	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1591	believe me.</p>
		1592	</dd>
		1593	</dl>
		1594
		1595
		1596
		1597
		1598
		1599	</div>
		1600	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
670	<div id="OTHER_FUNCTIONS_CONTENT">	1601	<div id="OTHER_FUNCTIONS_CONTENT">
671	<p>There are some other fucntions of possible interest. Described. Here. Now.</p>	1602	<p>There are some other functions of possible interest. Described. Here. Now.</p>
672	<dl>	1603	<dl>
673	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1604	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
674	<dd>	1605	<dd>
675	<p>This function combines a simple timer and an I/O watcher, calls your	1606	<p>This function combines a simple timer and an I/O watcher, calls your
676	callback on whichever event happens first and automatically stop both	1607	callback on whichever event happens first and automatically stop both
677	watchers. This is useful if you want to wait for a single event on an fd	1608	watchers. This is useful if you want to wait for a single event on an fd
678	or timeout without havign to allocate/configure/start/stop/free one or	1609	or timeout without having to allocate/configure/start/stop/free one or
679	more watchers yourself.</p>	1610	more watchers yourself.</p>
680	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is	1611	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
681	ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set	1612	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
682	will be craeted and started.</p>	1613	<code>events</code> set will be craeted and started.</p>
683	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1614	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
684	started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat	1615	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
685	= 0) will be started.</p>	1616	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
		1617	dubious value.</p>
686	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and	1618	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
687	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1619	passed an <code>revents</code> set like normal event callbacks (a combination of
688	EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p>	1620	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
		1621	value passed to <code>ev_once</code>:</p>
689	<pre> static void stdin_ready (int revents, void *arg)	1622	<pre> static void stdin_ready (int revents, void *arg)
690	{	1623	{
691	if (revents & EV_TIMEOUT)	1624	if (revents & EV_TIMEOUT)
692	/* doh, nothing entered */	1625	/* doh, nothing entered */;
693	else if (revents & EV_READ)	1626	else if (revents & EV_READ)
694	/* stdin might have data for us, joy! */	1627	/* stdin might have data for us, joy! */;
695	}	1628	}
696		1629
697	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1630	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
698		1631
699	</pre>	1632	</pre>
700	</dd>	1633	</dd>
701	<dt>ev_feed_event (loop, watcher, int events)</dt>	1634	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
702	<dd>	1635	<dd>
703	<p>Feeds the given event set into the event loop, as if the specified event	1636	<p>Feeds the given event set into the event loop, as if the specified event
704	has happened for the specified watcher (which must be a pointer to an	1637	had happened for the specified watcher (which must be a pointer to an
705	initialised but not necessarily active event watcher).</p>	1638	initialised but not necessarily started event watcher).</p>
706	</dd>	1639	</dd>
707	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1640	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
708	<dd>	1641	<dd>
709	<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>	1642	<p>Feed an event on the given fd, as if a file descriptor backend detected
		1643	the given events it.</p>
710	</dd>	1644	</dd>
711	<dt>ev_feed_signal_event (loop, int signum)</dt>	1645	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
712	<dd>	1646	<dd>
713	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1647	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1648	loop!).</p>
714	</dd>	1649	</dd>
715	</dl>	1650	</dl>
716		1651
		1652
		1653
		1654
		1655
717	</div>	1656	</div>
718	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1657	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
		1658	<div id="LIBEVENT_EMULATION_CONTENT">
		1659	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1660	emulate the internals of libevent, so here are some usage hints:</p>
		1661	<dl>
		1662	<dt>* Use it by including <event.h>, as usual.</dt>
		1663	<dt>* The following members are fully supported: ev_base, ev_callback,
		1664	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1665	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1666	maintained by libev, it does not work exactly the same way as in libevent (consider
		1667	it a private API).</dt>
		1668	<dt>* Priorities are not currently supported. Initialising priorities
		1669	will fail and all watchers will have the same priority, even though there
		1670	is an ev_pri field.</dt>
		1671	<dt>* Other members are not supported.</dt>
		1672	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1673	to use the libev header file and library.</dt>
		1674	</dl>
		1675
		1676	</div>
		1677	<h1 id="C_SUPPORT">C++ SUPPORT</h1>
		1678	<div id="C_SUPPORT_CONTENT">
		1679	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1680	you to use some convinience methods to start/stop watchers and also change
		1681	the callback model to a model using method callbacks on objects.</p>
		1682	<p>To use it,</p>
		1683	<pre> #include <ev++.h>
		1684
		1685	</pre>
		1686	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1687	and puts all of its definitions (many of them macros) into the global
		1688	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1689	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1690	<code>EV_MULTIPLICITY</code>.</p>
		1691	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1692	<dl>
		1693	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1694	<dd>
		1695	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1696	macros from <cite>ev.h</cite>.</p>
		1697	</dd>
		1698	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1699	<dd>
		1700	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1701	</dd>
		1702	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1703	<dd>
		1704	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1705	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1706	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1707	defines by many implementations.</p>
		1708	<p>All of those classes have these methods:</p>
		1709	<p>
		1710	<dl>
		1711	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1712	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1713	<dt>ev::TYPE::~TYPE</dt>
		1714	<dd>
		1715	<p>The constructor takes a pointer to an object and a method pointer to
		1716	the event handler callback to call in this class. The constructor calls
		1717	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1718	before starting it. If you do not specify a loop then the constructor
		1719	automatically associates the default loop with this watcher.</p>
		1720	<p>The destructor automatically stops the watcher if it is active.</p>
		1721	</dd>
		1722	<dt>w->set (struct ev_loop *)</dt>
		1723	<dd>
		1724	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1725	do this when the watcher is inactive (and not pending either).</p>
		1726	</dd>
		1727	<dt>w->set ([args])</dt>
		1728	<dd>
		1729	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1730	called at least once. Unlike the C counterpart, an active watcher gets
		1731	automatically stopped and restarted.</p>
		1732	</dd>
		1733	<dt>w->start ()</dt>
		1734	<dd>
		1735	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1736	constructor already takes the loop.</p>
		1737	</dd>
		1738	<dt>w->stop ()</dt>
		1739	<dd>
		1740	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1741	</dd>
		1742	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1743	<dd>
		1744	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1745	<code>ev_TYPE_again</code> function.</p>
		1746	</dd>
		1747	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1748	<dd>
		1749	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1750	</dd>
		1751	<dt>w->update () <code>ev::stat</code> only</dt>
		1752	<dd>
		1753	<p>Invokes <code>ev_stat_stat</code>.</p>
		1754	</dd>
		1755	</dl>
		1756	</p>
		1757	</dd>
		1758	</dl>
		1759	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1760	the constructor.</p>
		1761	<pre> class myclass
		1762	{
		1763	ev_io io; void io_cb (ev::io &w, int revents);
		1764	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1765
		1766	myclass ();
		1767	}
		1768
		1769	myclass::myclass (int fd)
		1770	: io (this, &myclass::io_cb),
		1771	idle (this, &myclass::idle_cb)
		1772	{
		1773	io.start (fd, ev::READ);
		1774	}
		1775
		1776
		1777
		1778
		1779	</pre>
		1780
		1781	</div>
		1782	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
		1783	<div id="MACRO_MAGIC_CONTENT">
		1784	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1785	<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
		1786	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1787	<p>To make it easier to write programs that cope with either variant, the
		1788	following macros are defined:</p>
		1789	<dl>
		1790	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		1791	<dd>
		1792	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		1793	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		1794	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		1795	<pre> ev_unref (EV_A);
		1796	ev_timer_add (EV_A_ watcher);
		1797	ev_loop (EV_A_ 0);
		1798
		1799	</pre>
		1800	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		1801	which is often provided by the following macro.</p>
		1802	</dd>
		1803	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		1804	<dd>
		1805	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		1806	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		1807	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		1808	<pre> // this is how ev_unref is being declared
		1809	static void ev_unref (EV_P);
		1810
		1811	// this is how you can declare your typical callback
		1812	static void cb (EV_P_ ev_timer *w, int revents)
		1813
		1814	</pre>
		1815	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		1816	suitable for use with <code>EV_A</code>.</p>
		1817	</dd>
		1818	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		1819	<dd>
		1820	<p>Similar to the other two macros, this gives you the value of the default
		1821	loop, if multiple loops are supported ("ev loop default").</p>
		1822	</dd>
		1823	</dl>
		1824	<p>Example: Declare and initialise a check watcher, working regardless of
		1825	wether multiple loops are supported or not.</p>
		1826	<pre> static void
		1827	check_cb (EV_P_ ev_timer *w, int revents)
		1828	{
		1829	ev_check_stop (EV_A_ w);
		1830	}
		1831
		1832	ev_check check;
		1833	ev_check_init (&check, check_cb);
		1834	ev_check_start (EV_DEFAULT_ &check);
		1835	ev_loop (EV_DEFAULT_ 0);
		1836
		1837
		1838
		1839
		1840	</pre>
		1841
		1842	</div>
		1843	<h1 id="EMBEDDING">EMBEDDING</h1>
		1844	<div id="EMBEDDING_CONTENT">
		1845	<p>Libev can (and often is) directly embedded into host
		1846	applications. Examples of applications that embed it include the Deliantra
		1847	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1848	and rxvt-unicode.</p>
		1849	<p>The goal is to enable you to just copy the neecssary files into your
		1850	source directory without having to change even a single line in them, so
		1851	you can easily upgrade by simply copying (or having a checked-out copy of
		1852	libev somewhere in your source tree).</p>
		1853
		1854	</div>
		1855	<h2 id="FILESETS">FILESETS</h2>
		1856	<div id="FILESETS_CONTENT">
		1857	<p>Depending on what features you need you need to include one or more sets of files
		1858	in your app.</p>
		1859
		1860	</div>
		1861	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1862	<div id="CORE_EVENT_LOOP_CONTENT">
		1863	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1864	configuration (no autoconf):</p>
		1865	<pre> #define EV_STANDALONE 1
		1866	#include "ev.c"
		1867
		1868	</pre>
		1869	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1870	single C source file only to provide the function implementations. To use
		1871	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1872	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1873	where you can put other configuration options):</p>
		1874	<pre> #define EV_STANDALONE 1
		1875	#include "ev.h"
		1876
		1877	</pre>
		1878	<p>Both header files and implementation files can be compiled with a C++
		1879	compiler (at least, thats a stated goal, and breakage will be treated
		1880	as a bug).</p>
		1881	<p>You need the following files in your source tree, or in a directory
		1882	in your include path (e.g. in libev/ when using -Ilibev):</p>
		1883	<pre> ev.h
		1884	ev.c
		1885	ev_vars.h
		1886	ev_wrap.h
		1887
		1888	ev_win32.c required on win32 platforms only
		1889
		1890	ev_select.c only when select backend is enabled (which is by default)
		1891	ev_poll.c only when poll backend is enabled (disabled by default)
		1892	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1893	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1894	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1895
		1896	</pre>
		1897	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		1898	to compile this single file.</p>
		1899
		1900	</div>
		1901	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		1902	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		1903	<p>To include the libevent compatibility API, also include:</p>
		1904	<pre> #include "event.c"
		1905
		1906	</pre>
		1907	<p>in the file including <cite>ev.c</cite>, and:</p>
		1908	<pre> #include "event.h"
		1909
		1910	</pre>
		1911	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		1912	<p>You need the following additional files for this:</p>
		1913	<pre> event.h
		1914	event.c
		1915
		1916	</pre>
		1917
		1918	</div>
		1919	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		1920	<div id="AUTOCONF_SUPPORT_CONTENT">
		1921	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		1922	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		1923	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		1924	include <cite>config.h</cite> and configure itself accordingly.</p>
		1925	<p>For this of course you need the m4 file:</p>
		1926	<pre> libev.m4
		1927
		1928	</pre>
		1929
		1930	</div>
		1931	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		1932	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		1933	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		1934	before including any of its files. The default is not to build for multiplicity
		1935	and only include the select backend.</p>
		1936	<dl>
		1937	<dt>EV_STANDALONE</dt>
		1938	<dd>
		1939	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		1940	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		1941	implementations for some libevent functions (such as logging, which is not
		1942	supported). It will also not define any of the structs usually found in
		1943	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		1944	</dd>
		1945	<dt>EV_USE_MONOTONIC</dt>
		1946	<dd>
		1947	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1948	monotonic clock option at both compiletime and runtime. Otherwise no use
		1949	of the monotonic clock option will be attempted. If you enable this, you
		1950	usually have to link against librt or something similar. Enabling it when
		1951	the functionality isn't available is safe, though, althoguh you have
		1952	to make sure you link against any libraries where the <code>clock_gettime</code>
		1953	function is hiding in (often <cite>-lrt</cite>).</p>
		1954	</dd>
		1955	<dt>EV_USE_REALTIME</dt>
		1956	<dd>
		1957	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1958	realtime clock option at compiletime (and assume its availability at
		1959	runtime if successful). Otherwise no use of the realtime clock option will
		1960	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		1961	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		1962	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		1963	</dd>
		1964	<dt>EV_USE_SELECT</dt>
		1965	<dd>
		1966	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		1967	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		1968	other method takes over, select will be it. Otherwise the select backend
		1969	will not be compiled in.</p>
		1970	</dd>
		1971	<dt>EV_SELECT_USE_FD_SET</dt>
		1972	<dd>
		1973	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		1974	structure. This is useful if libev doesn't compile due to a missing
		1975	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		1976	exotic systems. This usually limits the range of file descriptors to some
		1977	low limit such as 1024 or might have other limitations (winsocket only
		1978	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		1979	influence the size of the <code>fd_set</code> used.</p>
		1980	</dd>
		1981	<dt>EV_SELECT_IS_WINSOCKET</dt>
		1982	<dd>
		1983	<p>When defined to <code>1</code>, the select backend will assume that
		1984	select/socket/connect etc. don't understand file descriptors but
		1985	wants osf handles on win32 (this is the case when the select to
		1986	be used is the winsock select). This means that it will call
		1987	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		1988	it is assumed that all these functions actually work on fds, even
		1989	on win32. Should not be defined on non-win32 platforms.</p>
		1990	</dd>
		1991	<dt>EV_USE_POLL</dt>
		1992	<dd>
		1993	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		1994	backend. Otherwise it will be enabled on non-win32 platforms. It
		1995	takes precedence over select.</p>
		1996	</dd>
		1997	<dt>EV_USE_EPOLL</dt>
		1998	<dd>
		1999	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		2000	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		2001	otherwise another method will be used as fallback. This is the
		2002	preferred backend for GNU/Linux systems.</p>
		2003	</dd>
		2004	<dt>EV_USE_KQUEUE</dt>
		2005	<dd>
		2006	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		2007	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		2008	otherwise another method will be used as fallback. This is the preferred
		2009	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2010	supports some types of fds correctly (the only platform we found that
		2011	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2012	not be used unless explicitly requested. The best way to use it is to find
		2013	out whether kqueue supports your type of fd properly and use an embedded
		2014	kqueue loop.</p>
		2015	</dd>
		2016	<dt>EV_USE_PORT</dt>
		2017	<dd>
		2018	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		2019	10 port style backend. Its availability will be detected at runtime,
		2020	otherwise another method will be used as fallback. This is the preferred
		2021	backend for Solaris 10 systems.</p>
		2022	</dd>
		2023	<dt>EV_USE_DEVPOLL</dt>
		2024	<dd>
		2025	<p>reserved for future expansion, works like the USE symbols above.</p>
		2026	</dd>
		2027	<dt>EV_USE_INOTIFY</dt>
		2028	<dd>
		2029	<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
		2030	interface to speed up <code>ev_stat</code> watchers. Its actual availability will
		2031	be detected at runtime.</p>
		2032	</dd>
		2033	<dt>EV_H</dt>
		2034	<dd>
		2035	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		2036	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		2037	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		2038	</dd>
		2039	<dt>EV_CONFIG_H</dt>
		2040	<dd>
		2041	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		2042	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		2043	<code>EV_H</code>, above.</p>
		2044	</dd>
		2045	<dt>EV_EVENT_H</dt>
		2046	<dd>
		2047	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		2048	of how the <cite>event.h</cite> header can be found.</p>
		2049	</dd>
		2050	<dt>EV_PROTOTYPES</dt>
		2051	<dd>
		2052	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2053	prototypes, but still define all the structs and other symbols. This is
		2054	occasionally useful if you want to provide your own wrapper functions
		2055	around libev functions.</p>
		2056	</dd>
		2057	<dt>EV_MULTIPLICITY</dt>
		2058	<dd>
		2059	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2060	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2061	additional independent event loops. Otherwise there will be no support
		2062	for multiple event loops and there is no first event loop pointer
		2063	argument. Instead, all functions act on the single default loop.</p>
		2064	</dd>
		2065	<dt>EV_PERIODIC_ENABLE</dt>
		2066	<dd>
		2067	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2068	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2069	code.</p>
		2070	</dd>
		2071	<dt>EV_EMBED_ENABLE</dt>
		2072	<dd>
		2073	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2074	defined to be <code>0</code>, then they are not.</p>
		2075	</dd>
		2076	<dt>EV_STAT_ENABLE</dt>
		2077	<dd>
		2078	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2079	defined to be <code>0</code>, then they are not.</p>
		2080	</dd>
		2081	<dt>EV_FORK_ENABLE</dt>
		2082	<dd>
		2083	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2084	defined to be <code>0</code>, then they are not.</p>
		2085	</dd>
		2086	<dt>EV_MINIMAL</dt>
		2087	<dd>
		2088	<p>If you need to shave off some kilobytes of code at the expense of some
		2089	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2090	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2091	</dd>
		2092	<dt>EV_PID_HASHSIZE</dt>
		2093	<dd>
		2094	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2095	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2096	than enough. If you need to manage thousands of children you might want to
		2097	increase this value (<i>must</i> be a power of two).</p>
		2098	</dd>
		2099	<dt>EV_INOTIFY_HASHSIZE</dt>
		2100	<dd>
		2101	<p><code>ev_staz</code> watchers use a small hash table to distribute workload by
		2102	inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
		2103	usually more than enough. If you need to manage thousands of <code>ev_stat</code>
		2104	watchers you might want to increase this value (<i>must</i> be a power of
		2105	two).</p>
		2106	</dd>
		2107	<dt>EV_COMMON</dt>
		2108	<dd>
		2109	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2110	this macro to a something else you can include more and other types of
		2111	members. You have to define it each time you include one of the files,
		2112	though, and it must be identical each time.</p>
		2113	<p>For example, the perl EV module uses something like this:</p>
		2114	<pre> #define EV_COMMON \
		2115	SV self; / contains this struct */ \
		2116	SV cb_sv, fh /* note no trailing ";" */
		2117
		2118	</pre>
		2119	</dd>
		2120	<dt>EV_CB_DECLARE (type)</dt>
		2121	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2122	<dt>ev_set_cb (ev, cb)</dt>
		2123	<dd>
		2124	<p>Can be used to change the callback member declaration in each watcher,
		2125	and the way callbacks are invoked and set. Must expand to a struct member
		2126	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2127	their default definitions. One possible use for overriding these is to
		2128	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2129	method calls instead of plain function calls in C++.</p>
		2130
		2131	</div>
		2132	<h2 id="EXAMPLES">EXAMPLES</h2>
		2133	<div id="EXAMPLES_CONTENT">
		2134	<p>For a real-world example of a program the includes libev
		2135	verbatim, you can have a look at the EV perl module
		2136	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2137	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2138	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2139	will be compiled. It is pretty complex because it provides its own header
		2140	file.</p>
		2141	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2142	that everybody includes and which overrides some autoconf choices:</p>
		2143	<pre> #define EV_USE_POLL 0
		2144	#define EV_MULTIPLICITY 0
		2145	#define EV_PERIODICS 0
		2146	#define EV_CONFIG_H <config.h>
		2147
		2148	#include "ev++.h"
		2149
		2150	</pre>
		2151	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2152	<pre> #include "ev_cpp.h"
		2153	#include "ev.c"
		2154
		2155
		2156
		2157
		2158	</pre>
		2159
		2160	</div>
		2161	<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
		2162	<div id="COMPLEXITIES_CONTENT">
		2163	<p>In this section the complexities of (many of) the algorithms used inside
		2164	libev will be explained. For complexity discussions about backends see the
		2165	documentation for <code>ev_default_init</code>.</p>
		2166	<p>
		2167	<dl>
		2168	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2169	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2170	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2171	<dt>Stopping check/prepare/idle watchers: O(1)</dt>
		2172	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
		2173	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2174	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2175	<dt>Activating one watcher: O(1)</dt>
		2176	</dl>
		2177	</p>
		2178
		2179
		2180
		2181
		2182
		2183	</div>
		2184	<h1 id="AUTHOR">AUTHOR</h1>
719	<div id="AUTHOR_CONTENT">	2185	<div id="AUTHOR_CONTENT">
720	<p>Marc Lehmann <libev@schmorp.de>.</p>	2186	<p>Marc Lehmann <libev@schmorp.de>.</p>
721		2187
722	</div>	2188	</div>
723	</div></body>	2189	</div></body>
724	</html>	2190	</html>

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libev/ev.html (file contents): Revision 1.7 by root, Mon Nov 12 08:16:02 2007 UTC vs. Revision 1.59 by root, Wed Nov 28 17:32:24 2007 UTC

Diff Legend

Comparing libev/ev.html (file contents):
Revision 1.7 by root, Mon Nov 12 08:16:02 2007 UTC vs.
Revision 1.59 by root, Wed Nov 28 17:32:24 2007 UTC