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

Comparing libev/ev.pod (file contents):
Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC vs.
Revision 1.242 by root, Thu Jun 18 18:16:54 2009 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floatingpoint value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
		135
		136	=head1 ERROR HANDLING
		137
		138	Libev knows three classes of errors: operating system errors, usage errors
		139	and internal errors (bugs).
		140
		141	When libev catches an operating system error it cannot handle (for example
		142	a system call indicating a condition libev cannot fix), it calls the callback
		143	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		144	abort. The default is to print a diagnostic message and to call C<abort
		145	()>.
		146
		147	When libev detects a usage error such as a negative timer interval, then
		148	it will print a diagnostic message and abort (via the C<assert> mechanism,
		149	so C<NDEBUG> will disable this checking): these are programming errors in
		150	the libev caller and need to be fixed there.
		151
		152	Libev also has a few internal error-checking C<assert>ions, and also has
		153	extensive consistency checking code. These do not trigger under normal
		154	circumstances, as they indicate either a bug in libev or worse.
		155
121		156
122	=head1 GLOBAL FUNCTIONS	157	=head1 GLOBAL FUNCTIONS
123		158
124	These functions can be called anytime, even before initialising the	159	These functions can be called anytime, even before initialising the
125	library in any way.	160	library in any way.
…		…
134		169
135	=item ev_sleep (ev_tstamp interval)	170	=item ev_sleep (ev_tstamp interval)
136		171
137	Sleep for the given interval: The current thread will be blocked until	172	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	173	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	174	this is a sub-second-resolution C<sleep ()>.
140		175
141	=item int ev_version_major ()	176	=item int ev_version_major ()
142		177
143	=item int ev_version_minor ()	178	=item int ev_version_minor ()
144		179
…		…
157	not a problem.	192	not a problem.
158		193
159	Example: Make sure we haven't accidentally been linked against the wrong	194	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	195	version.
161		196
162	assert (("libev version mismatch",	197	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	198	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	199	&& ev_version_minor () >= EV_VERSION_MINOR));
165		200
166	=item unsigned int ev_supported_backends ()	201	=item unsigned int ev_supported_backends ()
167		202
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	203	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	204	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	206	a description of the set values.
172		207
173	Example: make sure we have the epoll method, because yeah this is cool and	208	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	209	a must have and can we have a torrent of it please!!!11
175		210
176	assert (("sorry, no epoll, no sex",	211	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	212	ev_supported_backends () & EVBACKEND_EPOLL));
178		213
179	=item unsigned int ev_recommended_backends ()	214	=item unsigned int ev_recommended_backends ()
180		215
181	Return the set of all backends compiled into this binary of libev and also	216	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	217	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	218	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	219	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	220	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	221	libev will probe for if you specify no backends explicitly.
187		222
188	=item unsigned int ev_embeddable_backends ()	223	=item unsigned int ev_embeddable_backends ()
189		224
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	229	recommended ones.
195		230
196	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
197		232
198	=item ev_set_allocator (void (cb)(void *ptr, long size))	233	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
199		234
200	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	237	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	264	}
230		265
231	...	266	...
232	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
233		268
234	=item ev_set_syserr_cb (void (cb)(const char msg));	269	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]
235		270
236	Set the callback function to call on a retryable syscall error (such	271	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	272	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	274	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	275	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	276	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	277	(such as abort).
243		278
244	Example: This is basically the same thing that libev does internally, too.	279	Example: This is basically the same thing that libev does internally, too.
…		…
255		290
256	=back	291	=back
257		292
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		294
260	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
261	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
263		302
264	=over 4	303	=over 4
265		304
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		306
…		…
273	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
274	function.	313	function.
275		314
276	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
279		318
280	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	324	C<ev_default_init>.
286		325
287	The flags argument can be used to specify special behaviour or specific	326	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	335	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	336	thing, believe me).
298		337
299	=item C<EVFLAG_NOENV>	338	=item C<EVFLAG_NOENV>
300		339
301	If this flag bit is ored into the flag value (or the program runs setuid	340	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	341	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	343	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	344	useful to try out specific backends to test their performance, or to work
306	around bugs.	345	around bugs.
…		…
313		352
314	This works by calling C<getpid ()> on every iteration of the loop,	353	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	354	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	355	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	357	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
320		359
321	The big advantage of this flag is that you can forget about fork (and	360	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	361	forget about forgetting to tell libev about forking) when you use this
323	flag.	362	flag.
324		363
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	365	environment variable.
327		366
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		368
330	This is your standard select(2) backend. Not I<completely> standard, as	369	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	371	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	372	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	373	usually the fastest backend for a low number of (low-numbered :) fds.
335		374
336	To get good performance out of this backend you need a high amount of	375	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	376	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	380	readiness notifications you get per iteration.
		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
342		385
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		387
345	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	393	performance tips.
351		394
		395	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.
		397
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		399
354	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	404
359	cases and requiring a syscall per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
361		421
362	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	423	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
367		427	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		428
372	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
375		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
		440
376	While nominally embeddeble in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
378		446
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		448
381	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	457	system like NetBSD.
388		458
389	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
392		462
393	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
399		470
400	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
401		472
402	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
408		483
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		485
411	This is not implemented yet (and might never be, unless you send me an	486	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		492
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	494	it's really slow, but it still scales very well (O(active_fds)).
420		495
421	Please note that solaris event ports can deliver a lot of spurious	496	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	497	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	498	blocking when no data (or space) is available.
424		499
425	While this backend scales well, it requires one system call per active	500	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	501	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	503	might perform better.
429		504
430	On the positive side, ignoring the spurious readyness notifications, this	505	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
433		512
434	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
435		514
436	Try all backends (even potentially broken ones that wouldn't be tried	515	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		518
440	It is definitely not recommended to use this flag.	519	It is definitely not recommended to use this flag.
441		520
442	=back	521	=back
443		522
444	If one or more of these are ored into the flags value, then only these	523	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		526
448	The most typical usage is like this:	527	Example: This is the most typical usage.
449		528
450	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		531
453	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	533	environment settings to be taken into account:
455		534
456	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
457		536
458	Use whatever libev has to offer, but make sure that kqueue is used if	537	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
461		541
462	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
463		543
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		545
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	546	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	547	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	552	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	553	default loop in the "main" or "initial" thread.
474		554
475	Example: Try to create a event loop that uses epoll and nothing else.	555	Example: Try to create a event loop that uses epoll and nothing else.
476		556
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
478	if (!epoller)	558	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	559	fatal ("no epoll found here, maybe it hides under your chair");
480		560
481	=item ev_default_destroy ()	561	=item ev_default_destroy ()
482		562
483	Destroys the default loop again (frees all memory and kernel state	563	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	564	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	565	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	569	for example).
490		570
491	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
494		574
495	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
496	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
497	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		603
524	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
525		605
526	Like C<ev_default_fork>, but acts on an event loop created by	606	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
529		610
530	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
531		612
532	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
533		615
534	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
535		617
536	Returns the count of loop iterations for the loop, which is identical to	618	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	619	the number of times libev did poll for new events. It starts at C<0> and
…		…
552	received events and started processing them. This timestamp does not	634	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	635	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	636	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	637	event occurring (or more correctly, libev finding out about it).
556		638
		639	=item ev_now_update (loop)
		640
		641	Establishes the current time by querying the kernel, updating the time
		642	returned by C<ev_now ()> in the progress. This is a costly operation and
		643	is usually done automatically within C<ev_loop ()>.
		644
		645	This function is rarely useful, but when some event callback runs for a
		646	very long time without entering the event loop, updating libev's idea of
		647	the current time is a good idea.
		648
		649	See also L<The special problem of time updates> in the C<ev_timer> section.
		650
		651	=item ev_suspend (loop)
		652
		653	=item ev_resume (loop)
		654
		655	These two functions suspend and resume a loop, for use when the loop is
		656	not used for a while and timeouts should not be processed.
		657
		658	A typical use case would be an interactive program such as a game: When
		659	the user presses C<^Z> to suspend the game and resumes it an hour later it
		660	would be best to handle timeouts as if no time had actually passed while
		661	the program was suspended. This can be achieved by calling C<ev_suspend>
		662	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		663	C<ev_resume> directly afterwards to resume timer processing.
		664
		665	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		667	will be rescheduled (that is, they will lose any events that would have
		668	occured while suspended).
		669
		670	After calling C<ev_suspend> you B<must not> call I<any> function on the
		671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		672	without a previous call to C<ev_suspend>.
		673
		674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		675	event loop time (see C<ev_now_update>).
		676
557	=item ev_loop (loop, int flags)	677	=item ev_loop (loop, int flags)
558		678
559	Finally, this is it, the event handler. This function usually is called	679	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	680	after you initialised all your watchers and you want to start handling
561	events.	681	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	683	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	684	either no event watchers are active anymore or C<ev_unloop> was called.
565		685
566	Please note that an explicit C<ev_unloop> is usually better than	686	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	687	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	688	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	689	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	690	of relying on its watchers stopping correctly, that is truly a thing of
		691	beauty.
571		692
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	693	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	694	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	695	process in case there are no events and will return after one iteration of
		696	the loop.
575		697
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	698	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	699	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	700	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	701	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	702	user-registered callback will be called), and will return after one
		703	iteration of the loop.
		704
		705	This is useful if you are waiting for some external event in conjunction
		706	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	707	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	708	usually a better approach for this kind of thing.
583		709
584	Here are the gory details of what C<ev_loop> does:	710	Here are the gory details of what C<ev_loop> does:
585		711
586	- Before the first iteration, call any pending watchers.	712	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	713	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	714	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	715	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	716	- If we have been forked, detach and recreate the kernel state
		717	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	718	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	719	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	720	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	721	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	722	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	723	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	724	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	725	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	727	- Queue all expired timers.
601	- Queue all outstanding periodics.	728	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	729	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	730	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	731	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	732	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	733	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	734	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	739	anymore.
613		740
614	... queue jobs here, make sure they register event watchers as long	741	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	742	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	743	ev_loop (my_loop, 0);
617	... jobs done. yeah!	744	... jobs done or somebody called unloop. yeah!
618		745
619	=item ev_unloop (loop, how)	746	=item ev_unloop (loop, how)
620		747
621	Can be used to make a call to C<ev_loop> return early (but only after it	748	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	749	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		752
626	This "unloop state" will be cleared when entering C<ev_loop> again.	753	This "unloop state" will be cleared when entering C<ev_loop> again.
627		754
		755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		756
628	=item ev_ref (loop)	757	=item ev_ref (loop)
629		758
630	=item ev_unref (loop)	759	=item ev_unref (loop)
631		760
632	Ref/unref can be used to add or remove a reference count on the event	761	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	762	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	763	count is nonzero, C<ev_loop> will not return on its own.
		764
635	a watcher you never unregister that should not keep C<ev_loop> from	765	If you have a watcher you never unregister that should not keep C<ev_loop>
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	766	from returning, call ev_unref() after starting, and ev_ref() before
		767	stopping it.
		768
637	example, libev itself uses this for its internal signal pipe: It is not	769	As an example, libev itself uses this for its internal signal pipe: It
638	visible to the libev user and should not keep C<ev_loop> from exiting if	770	is not visible to the libev user and should not keep C<ev_loop> from
639	no event watchers registered by it are active. It is also an excellent	771	exiting if no event watchers registered by it are active. It is also an
640	way to do this for generic recurring timers or from within third-party	772	excellent way to do this for generic recurring timers or from within
641	libraries. Just remember to I<unref after start> and I<ref before stop>	773	third-party libraries. Just remember to I<unref after start> and I<ref
642	(but only if the watcher wasn't active before, or was active before,	774	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	775	before, respectively. Note also that libev might stop watchers itself
		776	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		777	in the callback).
644		778
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	780	running when nothing else is active.
647		781
648	struct ev_signal exitsig;	782	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	783	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	784	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	785	evf_unref (loop);
652		786
653	Example: For some weird reason, unregister the above signal handler again.	787	Example: For some weird reason, unregister the above signal handler again.
654		788
655	ev_ref (loop);	789	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	790	ev_signal_stop (loop, &exitsig);
657		791
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	792	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		793
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	794	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		795
662	These advanced functions influence the time that libev will spend waiting	796	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	797	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	798	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		799	latency.
665		800
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	801	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	802	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	803	to increase efficiency of loop iterations (or to increase power-saving
		804	opportunities).
669		805
670	The background is that sometimes your program runs just fast enough to	806	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	807	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	808	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	809	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	810	overhead for the actual polling but can deliver many events at once.
675		811
676	By setting a higher I<io collect interval> you allow libev to spend more	812	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	813	time collecting I/O events, so you can handle more events per iteration,
…		…
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	815	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	816	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		817
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	818	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	819	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	820	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	821	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	822	value will not introduce any overhead in libev.
687		823
688	Many (busy) programs can usually benefit by setting the io collect	824	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	825	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	826	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	827	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	828	as this approaches the timing granularity of most systems.
		829
		830	Setting the I<timeout collect interval> can improve the opportunity for
		831	saving power, as the program will "bundle" timer callback invocations that
		832	are "near" in time together, by delaying some, thus reducing the number of
		833	times the process sleeps and wakes up again. Another useful technique to
		834	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		835	they fire on, say, one-second boundaries only.
		836
		837	=item ev_loop_verify (loop)
		838
		839	This function only does something when C<EV_VERIFY> support has been
		840	compiled in, which is the default for non-minimal builds. It tries to go
		841	through all internal structures and checks them for validity. If anything
		842	is found to be inconsistent, it will print an error message to standard
		843	error and call C<abort ()>.
		844
		845	This can be used to catch bugs inside libev itself: under normal
		846	circumstances, this function will never abort as of course libev keeps its
		847	data structures consistent.
693		848
694	=back	849	=back
695		850
696		851
697	=head1 ANATOMY OF A WATCHER	852	=head1 ANATOMY OF A WATCHER
		853
		854	In the following description, uppercase C<TYPE> in names stands for the
		855	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		856	watchers and C<ev_io_start> for I/O watchers.
698		857
699	A watcher is a structure that you create and register to record your	858	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	859	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	860	become readable, you would create an C<ev_io> watcher for that:
702		861
703	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	862	static void my_cb (struct ev_loop loop, ev_io w, int revents)
704	{	863	{
705	ev_io_stop (w);	864	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	865	ev_unloop (loop, EVUNLOOP_ALL);
707	}	866	}
708		867
709	struct ev_loop *loop = ev_default_loop (0);	868	struct ev_loop *loop = ev_default_loop (0);
		869
710	struct ev_io stdin_watcher;	870	ev_io stdin_watcher;
		871
711	ev_init (&stdin_watcher, my_cb);	872	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	873	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	874	ev_io_start (loop, &stdin_watcher);
		875
714	ev_loop (loop, 0);	876	ev_loop (loop, 0);
715		877
716	As you can see, you are responsible for allocating the memory for your	878	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	879	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	880	stack).
		881
		882	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		883	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		884
720	Each watcher structure must be initialised by a call to C<ev_init	885	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	886	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	887	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	888	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	889	is readable and/or writable).
725		890
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	891	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	892	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	893	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	894	ev_TYPE_init (watcher *, callback, ...) >>.
730		895
731	To make the watcher actually watch out for events, you have to start it	896	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	897	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	898	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	899	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		900
736	As long as your watcher is active (has been started but not stopped) you	901	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	902	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	903	reinitialise it or call its C<ev_TYPE_set> macro.
739		904
740	Each and every callback receives the event loop pointer as first, the	905	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	906	registered watcher structure as second, and a bitset of received events as
742	third argument.	907	third argument.
743		908
…		…
801		966
802	=item C<EV_ASYNC>	967	=item C<EV_ASYNC>
803		968
804	The given async watcher has been asynchronously notified (see C<ev_async>).	969	The given async watcher has been asynchronously notified (see C<ev_async>).
805		970
		971	=item C<EV_CUSTOM>
		972
		973	Not ever sent (or otherwise used) by libev itself, but can be freely used
		974	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		975
806	=item C<EV_ERROR>	976	=item C<EV_ERROR>
807		977
808	An unspecified error has occured, the watcher has been stopped. This might	978	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	979	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	980	ran out of memory, a file descriptor was found to be closed or any other
		981	problem. Libev considers these application bugs.
		982
811	problem. You best act on it by reporting the problem and somehow coping	983	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	984	watcher being stopped. Note that well-written programs should not receive
		985	an error ever, so when your watcher receives it, this usually indicates a
		986	bug in your program.
813		987
814	Libev will usually signal a few "dummy" events together with an error,	988	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	989	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	990	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	991	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	992	programs, though, as the fd could already be closed and reused for another
		993	thing, so beware.
819		994
820	=back	995	=back
821		996
822	=head2 GENERIC WATCHER FUNCTIONS	997	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		998
827	=over 4	999	=over 4
828		1000
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1001	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1002
…		…
836	which rolls both calls into one.	1008	which rolls both calls into one.
837		1009
838	You can reinitialise a watcher at any time as long as it has been stopped	1010	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	1011	(or never started) and there are no pending events outstanding.
840		1012
841	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	1013	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
842	int revents)>.	1014	int revents)>.
		1015
		1016	Example: Initialise an C<ev_io> watcher in two steps.
		1017
		1018	ev_io w;
		1019	ev_init (&w, my_cb);
		1020	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		1021
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1022	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		1023
846	This macro initialises the type-specific parts of a watcher. You need to	1024	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	1025	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	1028	difference to the C<ev_init> macro).
851		1029
852	Although some watcher types do not have type-specific arguments	1030	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1031	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1032
		1033	See C<ev_init>, above, for an example.
		1034
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1035	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1036
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1037	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	1038	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1039	a watcher. The same limitations apply, of course.
		1040
		1041	Example: Initialise and set an C<ev_io> watcher in one step.
		1042
		1043	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		1044
861	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)	1045	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)
862		1046
863	Starts (activates) the given watcher. Only active watchers will receive	1047	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1048	events. If the watcher is already active nothing will happen.
865		1049
		1050	Example: Start the C<ev_io> watcher that is being abused as example in this
		1051	whole section.
		1052
		1053	ev_io_start (EV_DEFAULT_UC, &w);
		1054
866	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1055	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
867		1056
868	Stops the given watcher again (if active) and clears the pending	1057	Stops the given watcher if active, and clears the pending status (whether
		1058	the watcher was active or not).
		1059
869	status. It is possible that stopped watchers are pending (for example,	1060	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1061	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1062	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	1063	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	1064	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1065
875	=item bool ev_is_active (ev_TYPE *watcher)	1066	=item bool ev_is_active (ev_TYPE *watcher)
876		1067
877	Returns a true value iff the watcher is active (i.e. it has been started	1068	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1069	and not yet been stopped). As long as a watcher is active you must not modify
…		…
904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1095	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1096	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1097	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1098	from being executed (except for C<ev_idle> watchers).
908		1099
909	This means that priorities are I<only> used for ordering callback
910	invocation after new events have been received. This is useful, for
911	example, to reduce latency after idling, or more often, to bind two
912	watchers on the same event and make sure one is called first.
913
914	If you need to suppress invocation when higher priority events are pending	1100	If you need to suppress invocation when higher priority events are pending
915	you need to look at C<ev_idle> watchers, which provide this functionality.	1101	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1102
917	You I<must not> change the priority of a watcher as long as it is active or	1103	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1104	pending.
919		1105
		1106	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1107	fine, as long as you do not mind that the priority value you query might
		1108	or might not have been clamped to the valid range.
		1109
920	The default priority used by watchers when no priority has been set is	1110	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1111	always C<0>, which is supposed to not be too high and not be too low :).
922		1112
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1113	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
924	fine, as long as you do not mind that the priority value you query might	1114	priorities.
925	or might not have been adjusted to be within valid range.
926		1115
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1116	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1117
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1118	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1119	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1120	can deal with that fact, as both are simply passed through to the
		1121	callback.
932		1122
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1123	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1124
935	If the watcher is pending, this function returns clears its pending status	1125	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1126	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1127	watcher isn't pending it does nothing and returns C<0>.
938		1128
		1129	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1130	callback to be invoked, which can be accomplished with this function.
		1131
939	=back	1132	=back
940		1133
941		1134
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1135	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1136
944	Each watcher has, by default, a member C<void *data> that you can change	1137	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1138	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1139	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1140	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1141	member, you can also "subclass" the watcher type and provide your own
949	data:	1142	data:
950		1143
951	struct my_io	1144	struct my_io
952	{	1145	{
953	struct ev_io io;	1146	ev_io io;
954	int otherfd;	1147	int otherfd;
955	void *somedata;	1148	void *somedata;
956	struct whatever *mostinteresting;	1149	struct whatever *mostinteresting;
957	}	1150	};
		1151
		1152	...
		1153	struct my_io w;
		1154	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1155
959	And since your callback will be called with a pointer to the watcher, you	1156	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1157	can cast it back to your own type:
961		1158
962	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1159	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
963	{	1160	{
964	struct my_io w = (struct my_io )w_;	1161	struct my_io w = (struct my_io )w_;
965	...	1162	...
966	}	1163	}
967		1164
968	More interesting and less C-conformant ways of casting your callback type	1165	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1166	instead have been omitted.
970		1167
971	Another common scenario is having some data structure with multiple	1168	Another common scenario is to use some data structure with multiple
972	watchers:	1169	embedded watchers:
973		1170
974	struct my_biggy	1171	struct my_biggy
975	{	1172	{
976	int some_data;	1173	int some_data;
977	ev_timer t1;	1174	ev_timer t1;
978	ev_timer t2;	1175	ev_timer t2;
979	}	1176	}
980		1177
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1178	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1179	complicated: Either you store the address of your C<my_biggy> struct
		1180	in the C<data> member of the watcher (for woozies), or you need to use
		1181	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1182	programmers):
983		1183
984	#include <stddef.h>	1184	#include <stddef.h>
985		1185
986	static void	1186	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1187	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1188	{
989	struct my_biggy big = (struct my_biggy *	1189	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1190	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1191	}
992		1192
993	static void	1193	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1194	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1195	{
996	struct my_biggy big = (struct my_biggy *	1196	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1197	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1198	}
		1199
		1200	=head2 WATCHER PRIORITY MODELS
		1201
		1202	Many event loops support I<watcher priorities>, which are usually small
		1203	integers that influence the ordering of event callback invocation
		1204	between watchers in some way, all else being equal.
		1205
		1206	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1207	description for the more technical details such as the actual priority
		1208	range.
		1209
		1210	There are two common ways how these these priorities are being interpreted
		1211	by event loops:
		1212
		1213	In the more common lock-out model, higher priorities "lock out" invocation
		1214	of lower priority watchers, which means as long as higher priority
		1215	watchers receive events, lower priority watchers are not being invoked.
		1216
		1217	The less common only-for-ordering model uses priorities solely to order
		1218	callback invocation within a single event loop iteration: Higher priority
		1219	watchers are invoked before lower priority ones, but they all get invoked
		1220	before polling for new events.
		1221
		1222	Libev uses the second (only-for-ordering) model for all its watchers
		1223	except for idle watchers (which use the lock-out model).
		1224
		1225	The rationale behind this is that implementing the lock-out model for
		1226	watchers is not well supported by most kernel interfaces, and most event
		1227	libraries will just poll for the same events again and again as long as
		1228	their callbacks have not been executed, which is very inefficient in the
		1229	common case of one high-priority watcher locking out a mass of lower
		1230	priority ones.
		1231
		1232	Static (ordering) priorities are most useful when you have two or more
		1233	watchers handling the same resource: a typical usage example is having an
		1234	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1235	timeouts. Under load, data might be received while the program handles
		1236	other jobs, but since timers normally get invoked first, the timeout
		1237	handler will be executed before checking for data. In that case, giving
		1238	the timer a lower priority than the I/O watcher ensures that I/O will be
		1239	handled first even under adverse conditions (which is usually, but not
		1240	always, what you want).
		1241
		1242	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1243	will only be executed when no same or higher priority watchers have
		1244	received events, they can be used to implement the "lock-out" model when
		1245	required.
		1246
		1247	For example, to emulate how many other event libraries handle priorities,
		1248	you can associate an C<ev_idle> watcher to each such watcher, and in
		1249	the normal watcher callback, you just start the idle watcher. The real
		1250	processing is done in the idle watcher callback. This causes libev to
		1251	continously poll and process kernel event data for the watcher, but when
		1252	the lock-out case is known to be rare (which in turn is rare :), this is
		1253	workable.
		1254
		1255	Usually, however, the lock-out model implemented that way will perform
		1256	miserably under the type of load it was designed to handle. In that case,
		1257	it might be preferable to stop the real watcher before starting the
		1258	idle watcher, so the kernel will not have to process the event in case
		1259	the actual processing will be delayed for considerable time.
		1260
		1261	Here is an example of an I/O watcher that should run at a strictly lower
		1262	priority than the default, and which should only process data when no
		1263	other events are pending:
		1264
		1265	ev_idle idle; // actual processing watcher
		1266	ev_io io; // actual event watcher
		1267
		1268	static void
		1269	io_cb (EV_P_ ev_io *w, int revents)
		1270	{
		1271	// stop the I/O watcher, we received the event, but
		1272	// are not yet ready to handle it.
		1273	ev_io_stop (EV_A_ w);
		1274
		1275	// start the idle watcher to ahndle the actual event.
		1276	// it will not be executed as long as other watchers
		1277	// with the default priority are receiving events.
		1278	ev_idle_start (EV_A_ &idle);
		1279	}
		1280
		1281	static void
		1282	idle_cb (EV_P_ ev_idle *w, int revents)
		1283	{
		1284	// actual processing
		1285	read (STDIN_FILENO, ...);
		1286
		1287	// have to start the I/O watcher again, as
		1288	// we have handled the event
		1289	ev_io_start (EV_P_ &io);
		1290	}
		1291
		1292	// initialisation
		1293	ev_idle_init (&idle, idle_cb);
		1294	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1295	ev_io_start (EV_DEFAULT_ &io);
		1296
		1297	In the "real" world, it might also be beneficial to start a timer, so that
		1298	low-priority connections can not be locked out forever under load. This
		1299	enables your program to keep a lower latency for important connections
		1300	during short periods of high load, while not completely locking out less
		1301	important ones.
999		1302
1000		1303
1001	=head1 WATCHER TYPES	1304	=head1 WATCHER TYPES
1002		1305
1003	This section describes each watcher in detail, but will not repeat	1306	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1330	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1331	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1332	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1333	required if you know what you are doing).
1031		1334
1032	If you must do this, then force the use of a known-to-be-good backend	1335	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1336	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1337	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1338	descriptors for which non-blocking operation makes no sense (such as
		1339	files) - libev doesn't guarentee any specific behaviour in that case.
1035		1340
1036	Another thing you have to watch out for is that it is quite easy to	1341	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1342	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1343	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1344	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1345	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1346	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1347	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1348	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1349
1045	If you cannot run the fd in non-blocking mode (for example you should not	1350	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1351	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1352	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1353	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1354	does this on its own, so its quite safe to use). Some people additionally
		1355	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1356	indefinitely.
		1357
		1358	But really, best use non-blocking mode.
1050		1359
1051	=head3 The special problem of disappearing file descriptors	1360	=head3 The special problem of disappearing file descriptors
1052		1361
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1362	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1363	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1364	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1365	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1366	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1367	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1368	fact, a different file descriptor.
1060		1369
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1400	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1401	C<EVBACKEND_POLL>.
1093		1402
1094	=head3 The special problem of SIGPIPE	1403	=head3 The special problem of SIGPIPE
1095		1404
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1405	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1406	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1407	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1408	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1409
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1410	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1411	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1412	somewhere, as that would have given you a big clue).
1105		1413
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1419	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1420
1113	=item ev_io_set (ev_io *, int fd, int events)	1421	=item ev_io_set (ev_io *, int fd, int events)
1114		1422
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1423	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1424	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ \| EV_WRITE> to receive the given events.	1425	C<EV_READ \| EV_WRITE>, to express the desire to receive the given events.
1118		1426
1119	=item int fd [read-only]	1427	=item int fd [read-only]
1120		1428
1121	The file descriptor being watched.	1429	The file descriptor being watched.
1122		1430
…		…
1130		1438
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1439	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1440	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1441	attempt to read a whole line in the callback.
1134		1442
1135	static void	1443	static void
1136	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1444	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1137	{	1445	{
1138	ev_io_stop (loop, w);	1446	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1447	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1448	}
1141		1449
1142	...	1450	...
1143	struct ev_loop *loop = ev_default_init (0);	1451	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1452	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1453	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1454	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1455	ev_loop (loop, 0);
1148		1456
1149		1457
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1458	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1459
1152	Timer watchers are simple relative timers that generate an event after a	1460	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1461	given time, and optionally repeating in regular intervals after that.
1154		1462
1155	The timers are based on real time, that is, if you register an event that	1463	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1464	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1465	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1466	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1467	monotonic clock option helps a lot here).
		1468
		1469	The callback is guaranteed to be invoked only I<after> its timeout has
		1470	passed (not I<at>, so on systems with very low-resolution clocks this
		1471	might introduce a small delay). If multiple timers become ready during the
		1472	same loop iteration then the ones with earlier time-out values are invoked
		1473	before ones with later time-out values (but this is no longer true when a
		1474	callback calls C<ev_loop> recursively).
		1475
		1476	=head3 Be smart about timeouts
		1477
		1478	Many real-world problems involve some kind of timeout, usually for error
		1479	recovery. A typical example is an HTTP request - if the other side hangs,
		1480	you want to raise some error after a while.
		1481
		1482	What follows are some ways to handle this problem, from obvious and
		1483	inefficient to smart and efficient.
		1484
		1485	In the following, a 60 second activity timeout is assumed - a timeout that
		1486	gets reset to 60 seconds each time there is activity (e.g. each time some
		1487	data or other life sign was received).
		1488
		1489	=over 4
		1490
		1491	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1492
		1493	This is the most obvious, but not the most simple way: In the beginning,
		1494	start the watcher:
		1495
		1496	ev_timer_init (timer, callback, 60., 0.);
		1497	ev_timer_start (loop, timer);
		1498
		1499	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1500	and start it again:
		1501
		1502	ev_timer_stop (loop, timer);
		1503	ev_timer_set (timer, 60., 0.);
		1504	ev_timer_start (loop, timer);
		1505
		1506	This is relatively simple to implement, but means that each time there is
		1507	some activity, libev will first have to remove the timer from its internal
		1508	data structure and then add it again. Libev tries to be fast, but it's
		1509	still not a constant-time operation.
		1510
		1511	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1512
		1513	This is the easiest way, and involves using C<ev_timer_again> instead of
		1514	C<ev_timer_start>.
		1515
		1516	To implement this, configure an C<ev_timer> with a C<repeat> value
		1517	of C<60> and then call C<ev_timer_again> at start and each time you
		1518	successfully read or write some data. If you go into an idle state where
		1519	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1520	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1521
		1522	That means you can ignore both the C<ev_timer_start> function and the
		1523	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1524	member and C<ev_timer_again>.
		1525
		1526	At start:
		1527
		1528	ev_timer_init (timer, callback);
		1529	timer->repeat = 60.;
		1530	ev_timer_again (loop, timer);
		1531
		1532	Each time there is some activity:
		1533
		1534	ev_timer_again (loop, timer);
		1535
		1536	It is even possible to change the time-out on the fly, regardless of
		1537	whether the watcher is active or not:
		1538
		1539	timer->repeat = 30.;
		1540	ev_timer_again (loop, timer);
		1541
		1542	This is slightly more efficient then stopping/starting the timer each time
		1543	you want to modify its timeout value, as libev does not have to completely
		1544	remove and re-insert the timer from/into its internal data structure.
		1545
		1546	It is, however, even simpler than the "obvious" way to do it.
		1547
		1548	=item 3. Let the timer time out, but then re-arm it as required.
		1549
		1550	This method is more tricky, but usually most efficient: Most timeouts are
		1551	relatively long compared to the intervals between other activity - in
		1552	our example, within 60 seconds, there are usually many I/O events with
		1553	associated activity resets.
		1554
		1555	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1556	but remember the time of last activity, and check for a real timeout only
		1557	within the callback:
		1558
		1559	ev_tstamp last_activity; // time of last activity
		1560
		1561	static void
		1562	callback (EV_P_ ev_timer *w, int revents)
		1563	{
		1564	ev_tstamp now = ev_now (EV_A);
		1565	ev_tstamp timeout = last_activity + 60.;
		1566
		1567	// if last_activity + 60. is older than now, we did time out
		1568	if (timeout < now)
		1569	{
		1570	// timeout occured, take action
		1571	}
		1572	else
		1573	{
		1574	// callback was invoked, but there was some activity, re-arm
		1575	// the watcher to fire in last_activity + 60, which is
		1576	// guaranteed to be in the future, so "again" is positive:
		1577	w->repeat = timeout - now;
		1578	ev_timer_again (EV_A_ w);
		1579	}
		1580	}
		1581
		1582	To summarise the callback: first calculate the real timeout (defined
		1583	as "60 seconds after the last activity"), then check if that time has
		1584	been reached, which means something I<did>, in fact, time out. Otherwise
		1585	the callback was invoked too early (C<timeout> is in the future), so
		1586	re-schedule the timer to fire at that future time, to see if maybe we have
		1587	a timeout then.
		1588
		1589	Note how C<ev_timer_again> is used, taking advantage of the
		1590	C<ev_timer_again> optimisation when the timer is already running.
		1591
		1592	This scheme causes more callback invocations (about one every 60 seconds
		1593	minus half the average time between activity), but virtually no calls to
		1594	libev to change the timeout.
		1595
		1596	To start the timer, simply initialise the watcher and set C<last_activity>
		1597	to the current time (meaning we just have some activity :), then call the
		1598	callback, which will "do the right thing" and start the timer:
		1599
		1600	ev_timer_init (timer, callback);
		1601	last_activity = ev_now (loop);
		1602	callback (loop, timer, EV_TIMEOUT);
		1603
		1604	And when there is some activity, simply store the current time in
		1605	C<last_activity>, no libev calls at all:
		1606
		1607	last_actiivty = ev_now (loop);
		1608
		1609	This technique is slightly more complex, but in most cases where the
		1610	time-out is unlikely to be triggered, much more efficient.
		1611
		1612	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1613	callback :) - just change the timeout and invoke the callback, which will
		1614	fix things for you.
		1615
		1616	=item 4. Wee, just use a double-linked list for your timeouts.
		1617
		1618	If there is not one request, but many thousands (millions...), all
		1619	employing some kind of timeout with the same timeout value, then one can
		1620	do even better:
		1621
		1622	When starting the timeout, calculate the timeout value and put the timeout
		1623	at the I<end> of the list.
		1624
		1625	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1626	the list is expected to fire (for example, using the technique #3).
		1627
		1628	When there is some activity, remove the timer from the list, recalculate
		1629	the timeout, append it to the end of the list again, and make sure to
		1630	update the C<ev_timer> if it was taken from the beginning of the list.
		1631
		1632	This way, one can manage an unlimited number of timeouts in O(1) time for
		1633	starting, stopping and updating the timers, at the expense of a major
		1634	complication, and having to use a constant timeout. The constant timeout
		1635	ensures that the list stays sorted.
		1636
		1637	=back
		1638
		1639	So which method the best?
		1640
		1641	Method #2 is a simple no-brain-required solution that is adequate in most
		1642	situations. Method #3 requires a bit more thinking, but handles many cases
		1643	better, and isn't very complicated either. In most case, choosing either
		1644	one is fine, with #3 being better in typical situations.
		1645
		1646	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1647	rather complicated, but extremely efficient, something that really pays
		1648	off after the first million or so of active timers, i.e. it's usually
		1649	overkill :)
		1650
		1651	=head3 The special problem of time updates
		1652
		1653	Establishing the current time is a costly operation (it usually takes at
		1654	least two system calls): EV therefore updates its idea of the current
		1655	time only before and after C<ev_loop> collects new events, which causes a
		1656	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1657	lots of events in one iteration.
1160		1658
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1659	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1660	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1661	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1662	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1663	timeout on the current time, use something like this to adjust for this:
1166		1664
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1665	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1666
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1667	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1668	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1669	()>.
1172		1670
1173	=head3 Watcher-Specific Functions and Data Members	1671	=head3 Watcher-Specific Functions and Data Members
1174		1672
1175	=over 4	1673	=over 4
1176		1674
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1675	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1676
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1677	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1678
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1679	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1680	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1681	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1682	configured to trigger again C<repeat> seconds later, again, and again,
		1683	until stopped manually.
1185		1684
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1685	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1686	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1687	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1688	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1689	do stuff) the timer will not fire more than once per event loop iteration.
1191		1690
1192	=item ev_timer_again (loop, ev_timer *)	1691	=item ev_timer_again (loop, ev_timer *)
1193		1692
1194	This will act as if the timer timed out and restart it again if it is	1693	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1694	repeating. The exact semantics are:
1196		1695
1197	If the timer is pending, its pending status is cleared.	1696	If the timer is pending, its pending status is cleared.
1198		1697
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1698	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1699
1201	If the timer is repeating, either start it if necessary (with the	1700	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	1701	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1702
1204	This sounds a bit complicated, but here is a useful and typical	1703	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1205	example: Imagine you have a tcp connection and you want a so-called idle	1704	usage example.
1206	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the
1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1212	automatically restart it if need be.
1213
1214	That means you can ignore the C<after> value and C<ev_timer_start>
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216
1217	ev_timer_init (timer, callback, 0., 5.);
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 17.;
1221	ev_timer_again (loop, timer);
1222	...
1223	timer->again = 10.;
1224	ev_timer_again (loop, timer);
1225
1226	This is more slightly efficient then stopping/starting the timer each time
1227	you want to modify its timeout value.
1228		1705
1229	=item ev_tstamp repeat [read-write]	1706	=item ev_tstamp repeat [read-write]
1230		1707
1231	The current C<repeat> value. Will be used each time the watcher times out	1708	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	1709	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	1710	which is also when any modifications are taken into account.
1234		1711
1235	=back	1712	=back
1236		1713
1237	=head3 Examples	1714	=head3 Examples
1238		1715
1239	Example: Create a timer that fires after 60 seconds.	1716	Example: Create a timer that fires after 60 seconds.
1240		1717
1241	static void	1718	static void
1242	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1719	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1243	{	1720	{
1244	.. one minute over, w is actually stopped right here	1721	.. one minute over, w is actually stopped right here
1245	}	1722	}
1246		1723
1247	struct ev_timer mytimer;	1724	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1725	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1726	ev_timer_start (loop, &mytimer);
1250		1727
1251	Example: Create a timeout timer that times out after 10 seconds of	1728	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1729	inactivity.
1253		1730
1254	static void	1731	static void
1255	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1732	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1256	{	1733	{
1257	.. ten seconds without any activity	1734	.. ten seconds without any activity
1258	}	1735	}
1259		1736
1260	struct ev_timer mytimer;	1737	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1738	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1739	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1740	ev_loop (loop, 0);
1264		1741
1265	// and in some piece of code that gets executed on any "activity":	1742	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1743	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1744	ev_timer_again (&mytimer);
1268		1745
1269		1746
1270	=head2 C<ev_periodic> - to cron or not to cron?	1747	=head2 C<ev_periodic> - to cron or not to cron?
1271		1748
1272	Periodic watchers are also timers of a kind, but they are very versatile	1749	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1750	(and unfortunately a bit complex).
1274		1751
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1752	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1753	relative time, the physical time that passes) but on wall clock time
1277	to trigger "at" some specific point in time. For example, if you tell a	1754	(absolute time, the thing you can read on your calender or clock). The
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1755	difference is that wall clock time can run faster or slower than real
1279	+ 10.>) and then reset your system clock to the last year, then it will	1756	time, and time jumps are not uncommon (e.g. when you adjust your
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1757	wrist-watch).
1281	roughly 10 seconds later).
1282		1758
1283	They can also be used to implement vastly more complex timers, such as	1759	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	1760	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	1761	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1762	not a delay) and then reset your system clock to January of the previous
		1763	year, then it will take a year or more to trigger the event (unlike an
		1764	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1765	it, as it uses a relative timeout).
1286		1766
		1767	C<ev_periodic> watchers can also be used to implement vastly more complex
		1768	timers, such as triggering an event on each "midnight, local time", or
		1769	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1770	those cannot react to time jumps.
		1771
1287	As with timers, the callback is guarenteed to be invoked only when the	1772	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1773	point in time where it is supposed to trigger has passed. If multiple
1289	during the same loop iteration then order of execution is undefined.	1774	timers become ready during the same loop iteration then the ones with
		1775	earlier time-out values are invoked before ones with later time-out values
		1776	(but this is no longer true when a callback calls C<ev_loop> recursively).
1290		1777
1291	=head3 Watcher-Specific Functions and Data Members	1778	=head3 Watcher-Specific Functions and Data Members
1292		1779
1293	=over 4	1780	=over 4
1294		1781
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1782	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		1783
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1784	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1785
1299	Lots of arguments, lets sort it out... There are basically three modes of	1786	Lots of arguments, let's sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1787	operation, and we will explain them from simplest to most complex:
1301		1788
1302	=over 4	1789	=over 4
1303		1790
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1791	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		1792
1306	In this configuration the watcher triggers an event at the wallclock time	1793	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1794	time C<offset> has passed. It will not repeat and will not adjust when a
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1795	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1309	system time reaches or surpasses this time.	1796	will be stopped and invoked when the system clock reaches or surpasses
		1797	this point in time.
1310		1798
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1799	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		1800
1313	In this mode the watcher will always be scheduled to time out at the next	1801	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1802	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	1803	negative) and then repeat, regardless of any time jumps. The C<offset>
		1804	argument is merely an offset into the C<interval> periods.
1316		1805
1317	This can be used to create timers that do not drift with respect to system	1806	This can be used to create timers that do not drift with respect to the
1318	time:	1807	system clock, for example, here is an C<ev_periodic> that triggers each
		1808	hour, on the hour (with respect to UTC):
1319		1809
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1810	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1811
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1812	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1813	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	1814	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1815	by 3600.
1326		1816
1327	Another way to think about it (for the mathematically inclined) is that	1817	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1818	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1819	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		1820
1331	For numerical stability it is preferable that the C<at> value is near	1821	For numerical stability it is preferable that the C<offset> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1822	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1823	this value, and in fact is often specified as zero.
1334		1824
		1825	Note also that there is an upper limit to how often a timer can fire (CPU
		1826	speed for example), so if C<interval> is very small then timing stability
		1827	will of course deteriorate. Libev itself tries to be exact to be about one
		1828	millisecond (if the OS supports it and the machine is fast enough).
		1829
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1830	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		1831
1337	In this mode the values for C<interval> and C<at> are both being	1832	In this mode the values for C<interval> and C<offset> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1833	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1834	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1835	current time as second argument.
1341		1836
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1837	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1343	ever, or make any event loop modifications>. If you need to stop it,	1838	or make ANY other event loop modifications whatsoever, unless explicitly
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1839	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1840
		1841	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1842	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1843	only event loop modification you are allowed to do).
		1844
1347	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1845	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1846	*w, ev_tstamp now)>, e.g.:
1349		1847
		1848	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1849	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1850	{
1352	return now + 60.;	1851	return now + 60.;
1353	}	1852	}
1354		1853
1355	It must return the next time to trigger, based on the passed time value	1854	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	1855	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	1856	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1857	might be called at other times, too.
1359		1858
1360	NOTE: I<< This callback must always return a time that is later than the	1859	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1860	equal to the passed C<now> value >>.
1362		1861
1363	This can be used to create very complex timers, such as a timer that	1862	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	1863	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	1864	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	1865	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	1866	reason I omitted it as an example).
1368		1867
1369	=back	1868	=back
…		…
1373	Simply stops and restarts the periodic watcher again. This is only useful	1872	Simply stops and restarts the periodic watcher again. This is only useful
1374	when you changed some parameters or the reschedule callback would return	1873	when you changed some parameters or the reschedule callback would return
1375	a different time than the last time it was called (e.g. in a crond like	1874	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	1875	program when the crontabs have changed).
1377		1876
		1877	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1878
		1879	When active, returns the absolute time that the watcher is supposed
		1880	to trigger next. This is not the same as the C<offset> argument to
		1881	C<ev_periodic_set>, but indeed works even in interval and manual
		1882	rescheduling modes.
		1883
1378	=item ev_tstamp offset [read-write]	1884	=item ev_tstamp offset [read-write]
1379		1885
1380	When repeating, this contains the offset value, otherwise this is the	1886	When repeating, this contains the offset value, otherwise this is the
1381	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1887	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1888	although libev might modify this value for better numerical stability).
1382		1889
1383	Can be modified any time, but changes only take effect when the periodic	1890	Can be modified any time, but changes only take effect when the periodic
1384	timer fires or C<ev_periodic_again> is being called.	1891	timer fires or C<ev_periodic_again> is being called.
1385		1892
1386	=item ev_tstamp interval [read-write]	1893	=item ev_tstamp interval [read-write]
1387		1894
1388	The current interval value. Can be modified any time, but changes only	1895	The current interval value. Can be modified any time, but changes only
1389	take effect when the periodic timer fires or C<ev_periodic_again> is being	1896	take effect when the periodic timer fires or C<ev_periodic_again> is being
1390	called.	1897	called.
1391		1898
1392	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1899	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1393		1900
1394	The current reschedule callback, or C<0>, if this functionality is	1901	The current reschedule callback, or C<0>, if this functionality is
1395	switched off. Can be changed any time, but changes only take effect when	1902	switched off. Can be changed any time, but changes only take effect when
1396	the periodic timer fires or C<ev_periodic_again> is being called.	1903	the periodic timer fires or C<ev_periodic_again> is being called.
1397		1904
1398	=item ev_tstamp at [read-only]
1399
1400	When active, contains the absolute time that the watcher is supposed to
1401	trigger next.
1402
1403	=back	1905	=back
1404		1906
1405	=head3 Examples	1907	=head3 Examples
1406		1908
1407	Example: Call a callback every hour, or, more precisely, whenever the	1909	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1910	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1911	potentially a lot of jitter, but good long-term stability.
1410		1912
1411	static void	1913	static void
1412	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1914	clock_cb (struct ev_loop loop, ev_io w, int revents)
1413	{	1915	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1916	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1917	}
1416		1918
1417	struct ev_periodic hourly_tick;	1919	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1920	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1921	ev_periodic_start (loop, &hourly_tick);
1420		1922
1421	Example: The same as above, but use a reschedule callback to do it:	1923	Example: The same as above, but use a reschedule callback to do it:
1422		1924
1423	#include <math.h>	1925	#include <math.h>
1424		1926
1425	static ev_tstamp	1927	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1928	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	1929	{
1428	return fmod (now, 3600.) + 3600.;	1930	return now + (3600. - fmod (now, 3600.));
1429	}	1931	}
1430		1932
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1933	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1934
1433	Example: Call a callback every hour, starting now:	1935	Example: Call a callback every hour, starting now:
1434		1936
1435	struct ev_periodic hourly_tick;	1937	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1938	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1939	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1940	ev_periodic_start (loop, &hourly_tick);
1439		1941
1440		1942
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1943	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1944
1443	Signal watchers will trigger an event when the process receives a specific	1945	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	1946	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	1947	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1948	normal event processing, like any other event.
1447		1949
		1950	If you want signals asynchronously, just use C<sigaction> as you would
		1951	do without libev and forget about sharing the signal. You can even use
		1952	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1953
1448	You can configure as many watchers as you like per signal. Only when the	1954	You can configure as many watchers as you like per signal. Only when the
1449	first watcher gets started will libev actually register a signal watcher	1955	first watcher gets started will libev actually register a signal handler
1450	with the kernel (thus it coexists with your own signal handlers as long	1956	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	1957	you don't register any with libev for the same signal). Similarly, when
1452	watcher for a signal is stopped libev will reset the signal handler to	1958	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1959	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1960
1455	If possible and supported, libev will install its handlers with	1961	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1962	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1963	interrupted. If you have a problem with system calls getting interrupted by
1458	signals you can block all signals in an C<ev_check> watcher and unblock	1964	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1965	them in an C<ev_prepare> watcher.
1460		1966
1461	=head3 Watcher-Specific Functions and Data Members	1967	=head3 Watcher-Specific Functions and Data Members
1462		1968
…		…
1475		1981
1476	=back	1982	=back
1477		1983
1478	=head3 Examples	1984	=head3 Examples
1479		1985
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	1986	Example: Try to exit cleanly on SIGINT.
1481		1987
1482	static void	1988	static void
1483	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1989	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1484	{	1990	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	1991	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	1992	}
1487		1993
1488	struct ev_signal signal_watcher;	1994	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1995	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	1996	ev_signal_start (loop, &signal_watcher);
1491		1997
1492		1998
1493	=head2 C<ev_child> - watch out for process status changes	1999	=head2 C<ev_child> - watch out for process status changes
1494		2000
1495	Child watchers trigger when your process receives a SIGCHLD in response to	2001	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	2002	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	2003	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	2004	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2005	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2006	forking and then immediately registering a watcher for the child is fine,
		2007	but forking and registering a watcher a few event loop iterations later is
		2008	not.
1500		2009
1501	Only the default event loop is capable of handling signals, and therefore	2010	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2011	you can only register child watchers in the default event loop.
1503		2012
1504	=head3 Process Interaction	2013	=head3 Process Interaction
1505		2014
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2015	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2016	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	2017	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2018	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2019	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2020	children, even ones not watched.
1512		2021
1513	=head3 Overriding the Built-In Processing	2022	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2026	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2027	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2028	default loop never gets destroyed. You are encouraged, however, to use an
1520	event-based approach to child reaping and thus use libev's support for	2029	event-based approach to child reaping and thus use libev's support for
1521	that, so other libev users can use C<ev_child> watchers freely.	2030	that, so other libev users can use C<ev_child> watchers freely.
		2031
		2032	=head3 Stopping the Child Watcher
		2033
		2034	Currently, the child watcher never gets stopped, even when the
		2035	child terminates, so normally one needs to stop the watcher in the
		2036	callback. Future versions of libev might stop the watcher automatically
		2037	when a child exit is detected.
1522		2038
1523	=head3 Watcher-Specific Functions and Data Members	2039	=head3 Watcher-Specific Functions and Data Members
1524		2040
1525	=over 4	2041	=over 4
1526		2042
…		…
1555	=head3 Examples	2071	=head3 Examples
1556		2072
1557	Example: C<fork()> a new process and install a child handler to wait for	2073	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2074	its completion.
1559		2075
1560	ev_child cw;	2076	ev_child cw;
1561		2077
1562	static void	2078	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2079	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2080	{
1565	ev_child_stop (EV_A_ w);	2081	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2082	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2083	}
1568		2084
1569	pid_t pid = fork ();	2085	pid_t pid = fork ();
1570		2086
1571	if (pid < 0)	2087	if (pid < 0)
1572	// error	2088	// error
1573	else if (pid == 0)	2089	else if (pid == 0)
1574	{	2090	{
1575	// the forked child executes here	2091	// the forked child executes here
1576	exit (1);	2092	exit (1);
1577	}	2093	}
1578	else	2094	else
1579	{	2095	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2096	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2097	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2098	}
1583		2099
1584		2100
1585	=head2 C<ev_stat> - did the file attributes just change?	2101	=head2 C<ev_stat> - did the file attributes just change?
1586		2102
1587	This watches a filesystem path for attribute changes. That is, it calls	2103	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	2104	C<stat> on that path in regular intervals (or when the OS says it changed)
1589	compared to the last time, invoking the callback if it did.	2105	and sees if it changed compared to the last time, invoking the callback if
		2106	it did.
1590		2107
1591	The path does not need to exist: changing from "path exists" to "path does	2108	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	2109	not exist" is a status change like any other. The condition "path does not
1593	not exist" is signified by the C<st_nlink> field being zero (which is	2110	exist" (or more correctly "path cannot be stat'ed") is signified by the
1594	otherwise always forced to be at least one) and all the other fields of	2111	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2112	least one) and all the other fields of the stat buffer having unspecified
		2113	contents.
1596		2114
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2115	The path I<must not> end in a slash or contain special components such as
		2116	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1598	relative and your working directory changes, the behaviour is undefined.	2117	your working directory changes, then the behaviour is undefined.
1599		2118
1600	Since there is no standard to do this, the portable implementation simply	2119	Since there is no portable change notification interface available, the
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2120	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2121	to see if it changed somehow. You can specify a recommended polling
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	2122	interval for this case. If you specify a polling interval of C<0> (highly
1604	unspecified default> value will be used (which you can expect to be around	2123	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2124	(which you can expect to be around five seconds, although this might
1606	impose a minimum interval which is currently around C<0.1>, but thats	2125	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2126	currently around C<0.1>, but that's usually overkill.
1608		2127
1609	This watcher type is not meant for massive numbers of stat watchers,	2128	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2129	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2130	resource-intensive.
1612		2131
1613	At the time of this writing, only the Linux inotify interface is	2132	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2133	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader). Inotify will be used to give hints only and should not change the	2134	exercise for the reader. Note, however, that the author sees no way of
1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2135	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	to fall back to regular polling again even with inotify, but changes are
1618	usually detected immediately, and if the file exists there will be no
1619	polling.
1620		2136
1621	=head3 ABI Issues (Largefile Support)	2137	=head3 ABI Issues (Largefile Support)
1622		2138
1623	Libev by default (unless the user overrides this) uses the default	2139	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	2140	compilation environment, which means that on systems with large file
1625	disabled large file support, you get the 32 bit version of the stat	2141	support disabled by default, you get the 32 bit version of the stat
1626	structure. When using the library from programs that change the ABI to	2142	structure. When using the library from programs that change the ABI to
1627	use 64 bit file offsets the programs will fail. In that case you have to	2143	use 64 bit file offsets the programs will fail. In that case you have to
1628	compile libev with the same flags to get binary compatibility. This is	2144	compile libev with the same flags to get binary compatibility. This is
1629	obviously the case with any flags that change the ABI, but the problem is	2145	obviously the case with any flags that change the ABI, but the problem is
1630	most noticably with ev_stat and largefile support.	2146	most noticeably displayed with ev_stat and large file support.
1631		2147
1632	=head3 Inotify	2148	The solution for this is to lobby your distribution maker to make large
		2149	file interfaces available by default (as e.g. FreeBSD does) and not
		2150	optional. Libev cannot simply switch on large file support because it has
		2151	to exchange stat structures with application programs compiled using the
		2152	default compilation environment.
1633		2153
		2154	=head3 Inotify and Kqueue
		2155
1634	When C<inotify (7)> support has been compiled into libev (generally only	2156	When C<inotify (7)> support has been compiled into libev and present at
1635	available on Linux) and present at runtime, it will be used to speed up	2157	runtime, it will be used to speed up change detection where possible. The
1636	change detection where possible. The inotify descriptor will be created lazily	2158	inotify descriptor will be created lazily when the first C<ev_stat>
1637	when the first C<ev_stat> watcher is being started.	2159	watcher is being started.
1638		2160
1639	Inotify presence does not change the semantics of C<ev_stat> watchers	2161	Inotify presence does not change the semantics of C<ev_stat> watchers
1640	except that changes might be detected earlier, and in some cases, to avoid	2162	except that changes might be detected earlier, and in some cases, to avoid
1641	making regular C<stat> calls. Even in the presence of inotify support	2163	making regular C<stat> calls. Even in the presence of inotify support
1642	there are many cases where libev has to resort to regular C<stat> polling.	2164	there are many cases where libev has to resort to regular C<stat> polling,
		2165	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2166	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2167	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2168	xfs are fully working) libev usually gets away without polling.
1643		2169
1644	(There is no support for kqueue, as apparently it cannot be used to	2170	There is no support for kqueue, as apparently it cannot be used to
1645	implement this functionality, due to the requirement of having a file	2171	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	2172	descriptor open on the object at all times, and detecting renames, unlinks
		2173	etc. is difficult.
		2174
		2175	=head3 C<stat ()> is a synchronous operation
		2176
		2177	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2178	the process. The exception are C<ev_stat> watchers - those call C<stat
		2179	()>, which is a synchronous operation.
		2180
		2181	For local paths, this usually doesn't matter: unless the system is very
		2182	busy or the intervals between stat's are large, a stat call will be fast,
		2183	as the path data is usually in memory already (except when starting the
		2184	watcher).
		2185
		2186	For networked file systems, calling C<stat ()> can block an indefinite
		2187	time due to network issues, and even under good conditions, a stat call
		2188	often takes multiple milliseconds.
		2189
		2190	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2191	paths, although this is fully supported by libev.
1647		2192
1648	=head3 The special problem of stat time resolution	2193	=head3 The special problem of stat time resolution
1649		2194
1650	The C<stat ()> syscall only supports full-second resolution portably, and	2195	The C<stat ()> system call only supports full-second resolution portably,
1651	even on systems where the resolution is higher, many filesystems still	2196	and even on systems where the resolution is higher, most file systems
1652	only support whole seconds.	2197	still only support whole seconds.
1653		2198
1654	That means that, if the time is the only thing that changes, you might	2199	That means that, if the time is the only thing that changes, you can
1655	miss updates: on the first update, C<ev_stat> detects a change and calls	2200	easily miss updates: on the first update, C<ev_stat> detects a change and
1656	your callback, which does something. When there is another update within	2201	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	2202	within the same second, C<ev_stat> will be unable to detect unless the
		2203	stat data does change in other ways (e.g. file size).
1658		2204
1659	The solution to this is to delay acting on a change for a second (or till	2205	The solution to this is to delay acting on a change for slightly more
1660	the next second boundary), using a roughly one-second delay C<ev_timer>	2206	than a second (or till slightly after the next full second boundary), using
1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2207	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1662	is added to work around small timing inconsistencies of some operating	2208	ev_timer_again (loop, w)>).
1663	systems.	2209
		2210	The C<.02> offset is added to work around small timing inconsistencies
		2211	of some operating systems (where the second counter of the current time
		2212	might be be delayed. One such system is the Linux kernel, where a call to
		2213	C<gettimeofday> might return a timestamp with a full second later than
		2214	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2215	update file times then there will be a small window where the kernel uses
		2216	the previous second to update file times but libev might already execute
		2217	the timer callback).
1664		2218
1665	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1666		2220
1667	=over 4	2221	=over 4
1668		2222
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	2228	C<path>. The C<interval> is a hint on how quickly a change is expected to
1675	be detected and should normally be specified as C<0> to let libev choose	2229	be detected and should normally be specified as C<0> to let libev choose
1676	a suitable value. The memory pointed to by C<path> must point to the same	2230	a suitable value. The memory pointed to by C<path> must point to the same
1677	path for as long as the watcher is active.	2231	path for as long as the watcher is active.
1678		2232
1679	The callback will be receive C<EV_STAT> when a change was detected,	2233	The callback will receive an C<EV_STAT> event when a change was detected,
1680	relative to the attributes at the time the watcher was started (or the	2234	relative to the attributes at the time the watcher was started (or the
1681	last change was detected).	2235	last change was detected).
1682		2236
1683	=item ev_stat_stat (loop, ev_stat *)	2237	=item ev_stat_stat (loop, ev_stat *)
1684		2238
1685	Updates the stat buffer immediately with new values. If you change the	2239	Updates the stat buffer immediately with new values. If you change the
1686	watched path in your callback, you could call this fucntion to avoid	2240	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	2241	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	2242	the only one changing the path). Can also be useful simply to find out the
		2243	new values.
1689		2244
1690	=item ev_statdata attr [read-only]	2245	=item ev_statdata attr [read-only]
1691		2246
1692	The most-recently detected attributes of the file. Although the type is of	2247	The most-recently detected attributes of the file. Although the type is
1693	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2248	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1694	suitable for your system. If the C<st_nlink> member is C<0>, then there	2249	suitable for your system, but you can only rely on the POSIX-standardised
		2250	members to be present. If the C<st_nlink> member is C<0>, then there was
1695	was some error while C<stat>ing the file.	2251	some error while C<stat>ing the file.
1696		2252
1697	=item ev_statdata prev [read-only]	2253	=item ev_statdata prev [read-only]
1698		2254
1699	The previous attributes of the file. The callback gets invoked whenever	2255	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	2256	C<prev> != C<attr>, or, more precisely, one or more of these members
		2257	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2258	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		2259
1702	=item ev_tstamp interval [read-only]	2260	=item ev_tstamp interval [read-only]
1703		2261
1704	The specified interval.	2262	The specified interval.
1705		2263
1706	=item const char *path [read-only]	2264	=item const char *path [read-only]
1707		2265
1708	The filesystem path that is being watched.	2266	The file system path that is being watched.
1709		2267
1710	=back	2268	=back
1711		2269
1712	=head3 Examples	2270	=head3 Examples
1713		2271
1714	Example: Watch C</etc/passwd> for attribute changes.	2272	Example: Watch C</etc/passwd> for attribute changes.
1715		2273
1716	static void	2274	static void
1717	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	2275	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
1718	{	2276	{
1719	/* /etc/passwd changed in some way */	2277	/* /etc/passwd changed in some way */
1720	if (w->attr.st_nlink)	2278	if (w->attr.st_nlink)
1721	{	2279	{
1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2280	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2281	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2282	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1725	}	2283	}
1726	else	2284	else
1727	/* you shalt not abuse printf for puts */	2285	/* you shalt not abuse printf for puts */
1728	puts ("wow, /etc/passwd is not there, expect problems. "	2286	puts ("wow, /etc/passwd is not there, expect problems. "
1729	"if this is windows, they already arrived\n");	2287	"if this is windows, they already arrived\n");
1730	}	2288	}
1731		2289
1732	...	2290	...
1733	ev_stat passwd;	2291	ev_stat passwd;
1734		2292
1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2293	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2294	ev_stat_start (loop, &passwd);
1737		2295
1738	Example: Like above, but additionally use a one-second delay so we do not	2296	Example: Like above, but additionally use a one-second delay so we do not
1739	miss updates (however, frequent updates will delay processing, too, so	2297	miss updates (however, frequent updates will delay processing, too, so
1740	one might do the work both on C<ev_stat> callback invocation I<and> on	2298	one might do the work both on C<ev_stat> callback invocation I<and> on
1741	C<ev_timer> callback invocation).	2299	C<ev_timer> callback invocation).
1742		2300
1743	static ev_stat passwd;	2301	static ev_stat passwd;
1744	static ev_timer timer;	2302	static ev_timer timer;
1745		2303
1746	static void	2304	static void
1747	timer_cb (EV_P_ ev_timer *w, int revents)	2305	timer_cb (EV_P_ ev_timer *w, int revents)
1748	{	2306	{
1749	ev_timer_stop (EV_A_ w);	2307	ev_timer_stop (EV_A_ w);
1750		2308
1751	/* now it's one second after the most recent passwd change */	2309	/* now it's one second after the most recent passwd change */
1752	}	2310	}
1753		2311
1754	static void	2312	static void
1755	stat_cb (EV_P_ ev_stat *w, int revents)	2313	stat_cb (EV_P_ ev_stat *w, int revents)
1756	{	2314	{
1757	/* reset the one-second timer */	2315	/* reset the one-second timer */
1758	ev_timer_again (EV_A_ &timer);	2316	ev_timer_again (EV_A_ &timer);
1759	}	2317	}
1760		2318
1761	...	2319	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2320	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	2321	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	2322	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		2323
1766		2324
1767	=head2 C<ev_idle> - when you've got nothing better to do...	2325	=head2 C<ev_idle> - when you've got nothing better to do...
1768		2326
1769	Idle watchers trigger events when no other events of the same or higher	2327	Idle watchers trigger events when no other events of the same or higher
1770	priority are pending (prepare, check and other idle watchers do not	2328	priority are pending (prepare, check and other idle watchers do not count
1771	count).	2329	as receiving "events").
1772		2330
1773	That is, as long as your process is busy handling sockets or timeouts	2331	That is, as long as your process is busy handling sockets or timeouts
1774	(or even signals, imagine) of the same or higher priority it will not be	2332	(or even signals, imagine) of the same or higher priority it will not be
1775	triggered. But when your process is idle (or only lower-priority watchers	2333	triggered. But when your process is idle (or only lower-priority watchers
1776	are pending), the idle watchers are being called once per event loop	2334	are pending), the idle watchers are being called once per event loop
…		…
1787		2345
1788	=head3 Watcher-Specific Functions and Data Members	2346	=head3 Watcher-Specific Functions and Data Members
1789		2347
1790	=over 4	2348	=over 4
1791		2349
1792	=item ev_idle_init (ev_signal *, callback)	2350	=item ev_idle_init (ev_idle *, callback)
1793		2351
1794	Initialises and configures the idle watcher - it has no parameters of any	2352	Initialises and configures the idle watcher - it has no parameters of any
1795	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2353	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1796	believe me.	2354	believe me.
1797		2355
…		…
1800	=head3 Examples	2358	=head3 Examples
1801		2359
1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2360	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1803	callback, free it. Also, use no error checking, as usual.	2361	callback, free it. Also, use no error checking, as usual.
1804		2362
1805	static void	2363	static void
1806	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2364	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1807	{	2365	{
1808	free (w);	2366	free (w);
1809	// now do something you wanted to do when the program has	2367	// now do something you wanted to do when the program has
1810	// no longer anything immediate to do.	2368	// no longer anything immediate to do.
1811	}	2369	}
1812		2370
1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2371	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1814	ev_idle_init (idle_watcher, idle_cb);	2372	ev_idle_init (idle_watcher, idle_cb);
1815	ev_idle_start (loop, idle_cb);	2373	ev_idle_start (loop, idle_watcher);
1816		2374
1817		2375
1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2376	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1819		2377
1820	Prepare and check watchers are usually (but not always) used in tandem:	2378	Prepare and check watchers are usually (but not always) used in pairs:
1821	prepare watchers get invoked before the process blocks and check watchers	2379	prepare watchers get invoked before the process blocks and check watchers
1822	afterwards.	2380	afterwards.
1823		2381
1824	You I<must not> call C<ev_loop> or similar functions that enter	2382	You I<must not> call C<ev_loop> or similar functions that enter
1825	the current event loop from either C<ev_prepare> or C<ev_check>	2383	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1828	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2386	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1829	C<ev_check> so if you have one watcher of each kind they will always be	2387	C<ev_check> so if you have one watcher of each kind they will always be
1830	called in pairs bracketing the blocking call.	2388	called in pairs bracketing the blocking call.
1831		2389
1832	Their main purpose is to integrate other event mechanisms into libev and	2390	Their main purpose is to integrate other event mechanisms into libev and
1833	their use is somewhat advanced. This could be used, for example, to track	2391	their use is somewhat advanced. They could be used, for example, to track
1834	variable changes, implement your own watchers, integrate net-snmp or a	2392	variable changes, implement your own watchers, integrate net-snmp or a
1835	coroutine library and lots more. They are also occasionally useful if	2393	coroutine library and lots more. They are also occasionally useful if
1836	you cache some data and want to flush it before blocking (for example,	2394	you cache some data and want to flush it before blocking (for example,
1837	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2395	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1838	watcher).	2396	watcher).
1839		2397
1840	This is done by examining in each prepare call which file descriptors need	2398	This is done by examining in each prepare call which file descriptors
1841	to be watched by the other library, registering C<ev_io> watchers for	2399	need to be watched by the other library, registering C<ev_io> watchers
1842	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2400	for them and starting an C<ev_timer> watcher for any timeouts (many
1843	provide just this functionality). Then, in the check watcher you check for	2401	libraries provide exactly this functionality). Then, in the check watcher,
1844	any events that occured (by checking the pending status of all watchers	2402	you check for any events that occurred (by checking the pending status
1845	and stopping them) and call back into the library. The I/O and timer	2403	of all watchers and stopping them) and call back into the library. The
1846	callbacks will never actually be called (but must be valid nevertheless,	2404	I/O and timer callbacks will never actually be called (but must be valid
1847	because you never know, you know?).	2405	nevertheless, because you never know, you know?).
1848		2406
1849	As another example, the Perl Coro module uses these hooks to integrate	2407	As another example, the Perl Coro module uses these hooks to integrate
1850	coroutines into libev programs, by yielding to other active coroutines	2408	coroutines into libev programs, by yielding to other active coroutines
1851	during each prepare and only letting the process block if no coroutines	2409	during each prepare and only letting the process block if no coroutines
1852	are ready to run (it's actually more complicated: it only runs coroutines	2410	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1855	loop from blocking if lower-priority coroutines are active, thus mapping	2413	loop from blocking if lower-priority coroutines are active, thus mapping
1856	low-priority coroutines to idle/background tasks).	2414	low-priority coroutines to idle/background tasks).
1857		2415
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2416	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1859	priority, to ensure that they are being run before any other watchers	2417	priority, to ensure that they are being run before any other watchers
		2418	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2419
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2420	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1861	too) should not activate ("feed") events into libev. While libev fully	2421	activate ("feed") events into libev. While libev fully supports this, they
1862	supports this, they will be called before other C<ev_check> watchers	2422	might get executed before other C<ev_check> watchers did their job. As
1863	did their job. As C<ev_check> watchers are often used to embed other	2423	C<ev_check> watchers are often used to embed other (non-libev) event
1864	(non-libev) event loops those other event loops might be in an unusable	2424	loops those other event loops might be in an unusable state until their
1865	state until their C<ev_check> watcher ran (always remind yourself to	2425	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1866	coexist peacefully with others).	2426	others).
1867		2427
1868	=head3 Watcher-Specific Functions and Data Members	2428	=head3 Watcher-Specific Functions and Data Members
1869		2429
1870	=over 4	2430	=over 4
1871		2431
…		…
1873		2433
1874	=item ev_check_init (ev_check *, callback)	2434	=item ev_check_init (ev_check *, callback)
1875		2435
1876	Initialises and configures the prepare or check watcher - they have no	2436	Initialises and configures the prepare or check watcher - they have no
1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2437	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1878	macros, but using them is utterly, utterly and completely pointless.	2438	macros, but using them is utterly, utterly, utterly and completely
		2439	pointless.
1879		2440
1880	=back	2441	=back
1881		2442
1882	=head3 Examples	2443	=head3 Examples
1883		2444
1884	There are a number of principal ways to embed other event loops or modules	2445	There are a number of principal ways to embed other event loops or modules
1885	into libev. Here are some ideas on how to include libadns into libev	2446	into libev. Here are some ideas on how to include libadns into libev
1886	(there is a Perl module named C<EV::ADNS> that does this, which you could	2447	(there is a Perl module named C<EV::ADNS> that does this, which you could
1887	use for an actually working example. Another Perl module named C<EV::Glib>	2448	use as a working example. Another Perl module named C<EV::Glib> embeds a
1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2449	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	2450	Glib event loop).
1890		2451
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2452	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1892	and in a check watcher, destroy them and call into libadns. What follows	2453	and in a check watcher, destroy them and call into libadns. What follows
1893	is pseudo-code only of course. This requires you to either use a low	2454	is pseudo-code only of course. This requires you to either use a low
1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2455	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1895	the callbacks for the IO/timeout watchers might not have been called yet.	2456	the callbacks for the IO/timeout watchers might not have been called yet.
1896		2457
1897	static ev_io iow [nfd];	2458	static ev_io iow [nfd];
1898	static ev_timer tw;	2459	static ev_timer tw;
1899		2460
1900	static void	2461	static void
1901	io_cb (ev_loop loop, ev_io w, int revents)	2462	io_cb (struct ev_loop loop, ev_io w, int revents)
1902	{	2463	{
1903	}	2464	}
1904		2465
1905	// create io watchers for each fd and a timer before blocking	2466	// create io watchers for each fd and a timer before blocking
1906	static void	2467	static void
1907	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2468	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
1908	{	2469	{
1909	int timeout = 3600000;	2470	int timeout = 3600000;
1910	struct pollfd fds [nfd];	2471	struct pollfd fds [nfd];
1911	// actual code will need to loop here and realloc etc.	2472	// actual code will need to loop here and realloc etc.
1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2473	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1913		2474
1914	/* the callback is illegal, but won't be called as we stop during check */	2475	/* the callback is illegal, but won't be called as we stop during check */
1915	ev_timer_init (&tw, 0, timeout * 1e-3);	2476	ev_timer_init (&tw, 0, timeout * 1e-3);
1916	ev_timer_start (loop, &tw);	2477	ev_timer_start (loop, &tw);
1917		2478
1918	// create one ev_io per pollfd	2479	// create one ev_io per pollfd
1919	for (int i = 0; i < nfd; ++i)	2480	for (int i = 0; i < nfd; ++i)
1920	{	2481	{
1921	ev_io_init (iow + i, io_cb, fds [i].fd,	2482	ev_io_init (iow + i, io_cb, fds [i].fd,
1922	((fds [i].events & POLLIN ? EV_READ : 0)	2483	((fds [i].events & POLLIN ? EV_READ : 0)
1923	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2484	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1924		2485
1925	fds [i].revents = 0;	2486	fds [i].revents = 0;
1926	ev_io_start (loop, iow + i);	2487	ev_io_start (loop, iow + i);
1927	}	2488	}
1928	}	2489	}
1929		2490
1930	// stop all watchers after blocking	2491	// stop all watchers after blocking
1931	static void	2492	static void
1932	adns_check_cb (ev_loop loop, ev_check w, int revents)	2493	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
1933	{	2494	{
1934	ev_timer_stop (loop, &tw);	2495	ev_timer_stop (loop, &tw);
1935		2496
1936	for (int i = 0; i < nfd; ++i)	2497	for (int i = 0; i < nfd; ++i)
1937	{	2498	{
1938	// set the relevant poll flags	2499	// set the relevant poll flags
1939	// could also call adns_processreadable etc. here	2500	// could also call adns_processreadable etc. here
1940	struct pollfd *fd = fds + i;	2501	struct pollfd *fd = fds + i;
1941	int revents = ev_clear_pending (iow + i);	2502	int revents = ev_clear_pending (iow + i);
1942	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;	2503	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1943	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;	2504	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1944		2505
1945	// now stop the watcher	2506	// now stop the watcher
1946	ev_io_stop (loop, iow + i);	2507	ev_io_stop (loop, iow + i);
1947	}	2508	}
1948		2509
1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2510	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1950	}	2511	}
1951		2512
1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2513	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1953	in the prepare watcher and would dispose of the check watcher.	2514	in the prepare watcher and would dispose of the check watcher.
1954		2515
1955	Method 3: If the module to be embedded supports explicit event	2516	Method 3: If the module to be embedded supports explicit event
1956	notification (adns does), you can also make use of the actual watcher	2517	notification (libadns does), you can also make use of the actual watcher
1957	callbacks, and only destroy/create the watchers in the prepare watcher.	2518	callbacks, and only destroy/create the watchers in the prepare watcher.
1958		2519
1959	static void	2520	static void
1960	timer_cb (EV_P_ ev_timer *w, int revents)	2521	timer_cb (EV_P_ ev_timer *w, int revents)
1961	{	2522	{
1962	adns_state ads = (adns_state)w->data;	2523	adns_state ads = (adns_state)w->data;
1963	update_now (EV_A);	2524	update_now (EV_A);
1964		2525
1965	adns_processtimeouts (ads, &tv_now);	2526	adns_processtimeouts (ads, &tv_now);
1966	}	2527	}
1967		2528
1968	static void	2529	static void
1969	io_cb (EV_P_ ev_io *w, int revents)	2530	io_cb (EV_P_ ev_io *w, int revents)
1970	{	2531	{
1971	adns_state ads = (adns_state)w->data;	2532	adns_state ads = (adns_state)w->data;
1972	update_now (EV_A);	2533	update_now (EV_A);
1973		2534
1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2535	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2536	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1976	}	2537	}
1977		2538
1978	// do not ever call adns_afterpoll	2539	// do not ever call adns_afterpoll
1979		2540
1980	Method 4: Do not use a prepare or check watcher because the module you	2541	Method 4: Do not use a prepare or check watcher because the module you
1981	want to embed is too inflexible to support it. Instead, youc na override	2542	want to embed is not flexible enough to support it. Instead, you can
1982	their poll function. The drawback with this solution is that the main	2543	override their poll function. The drawback with this solution is that the
1983	loop is now no longer controllable by EV. The C<Glib::EV> module does	2544	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1984	this.	2545	this approach, effectively embedding EV as a client into the horrible
		2546	libglib event loop.
1985		2547
1986	static gint	2548	static gint
1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2549	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1988	{	2550	{
1989	int got_events = 0;	2551	int got_events = 0;
1990		2552
1991	for (n = 0; n < nfds; ++n)	2553	for (n = 0; n < nfds; ++n)
1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2554	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1993		2555
1994	if (timeout >= 0)	2556	if (timeout >= 0)
1995	// create/start timer	2557	// create/start timer
1996		2558
1997	// poll	2559	// poll
1998	ev_loop (EV_A_ 0);	2560	ev_loop (EV_A_ 0);
1999		2561
2000	// stop timer again	2562	// stop timer again
2001	if (timeout >= 0)	2563	if (timeout >= 0)
2002	ev_timer_stop (EV_A_ &to);	2564	ev_timer_stop (EV_A_ &to);
2003		2565
2004	// stop io watchers again - their callbacks should have set	2566	// stop io watchers again - their callbacks should have set
2005	for (n = 0; n < nfds; ++n)	2567	for (n = 0; n < nfds; ++n)
2006	ev_io_stop (EV_A_ iow [n]);	2568	ev_io_stop (EV_A_ iow [n]);
2007		2569
2008	return got_events;	2570	return got_events;
2009	}	2571	}
2010		2572
2011		2573
2012	=head2 C<ev_embed> - when one backend isn't enough...	2574	=head2 C<ev_embed> - when one backend isn't enough...
2013		2575
2014	This is a rather advanced watcher type that lets you embed one event loop	2576	This is a rather advanced watcher type that lets you embed one event loop
…		…
2020	prioritise I/O.	2582	prioritise I/O.
2021		2583
2022	As an example for a bug workaround, the kqueue backend might only support	2584	As an example for a bug workaround, the kqueue backend might only support
2023	sockets on some platform, so it is unusable as generic backend, but you	2585	sockets on some platform, so it is unusable as generic backend, but you
2024	still want to make use of it because you have many sockets and it scales	2586	still want to make use of it because you have many sockets and it scales
2025	so nicely. In this case, you would create a kqueue-based loop and embed it	2587	so nicely. In this case, you would create a kqueue-based loop and embed
2026	into your default loop (which might use e.g. poll). Overall operation will	2588	it into your default loop (which might use e.g. poll). Overall operation
2027	be a bit slower because first libev has to poll and then call kevent, but	2589	will be a bit slower because first libev has to call C<poll> and then
2028	at least you can use both at what they are best.	2590	C<kevent>, but at least you can use both mechanisms for what they are
		2591	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2029		2592
2030	As for prioritising I/O: rarely you have the case where some fds have	2593	As for prioritising I/O: under rare circumstances you have the case where
2031	to be watched and handled very quickly (with low latency), and even	2594	some fds have to be watched and handled very quickly (with low latency),
2032	priorities and idle watchers might have too much overhead. In this case	2595	and even priorities and idle watchers might have too much overhead. In
2033	you would put all the high priority stuff in one loop and all the rest in	2596	this case you would put all the high priority stuff in one loop and all
2034	a second one, and embed the second one in the first.	2597	the rest in a second one, and embed the second one in the first.
2035		2598
2036	As long as the watcher is active, the callback will be invoked every time	2599	As long as the watcher is active, the callback will be invoked every
2037	there might be events pending in the embedded loop. The callback must then	2600	time there might be events pending in the embedded loop. The callback
2038	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2601	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2039	their callbacks (you could also start an idle watcher to give the embedded	2602	sweep and invoke their callbacks (the callback doesn't need to invoke the
2040	loop strictly lower priority for example). You can also set the callback	2603	C<ev_embed_sweep> function directly, it could also start an idle watcher
2041	to C<0>, in which case the embed watcher will automatically execute the	2604	to give the embedded loop strictly lower priority for example).
2042	embedded loop sweep.
2043		2605
2044	As long as the watcher is started it will automatically handle events. The	2606	You can also set the callback to C<0>, in which case the embed watcher
2045	callback will be invoked whenever some events have been handled. You can	2607	will automatically execute the embedded loop sweep whenever necessary.
2046	set the callback to C<0> to avoid having to specify one if you are not
2047	interested in that.
2048		2608
2049	Also, there have not currently been made special provisions for forking:	2609	Fork detection will be handled transparently while the C<ev_embed> watcher
2050	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2610	is active, i.e., the embedded loop will automatically be forked when the
2051	but you will also have to stop and restart any C<ev_embed> watchers	2611	embedding loop forks. In other cases, the user is responsible for calling
2052	yourself.	2612	C<ev_loop_fork> on the embedded loop.
2053		2613
2054	Unfortunately, not all backends are embeddable, only the ones returned by	2614	Unfortunately, not all backends are embeddable: only the ones returned by
2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2615	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2056	portable one.	2616	portable one.
2057		2617
2058	So when you want to use this feature you will always have to be prepared	2618	So when you want to use this feature you will always have to be prepared
2059	that you cannot get an embeddable loop. The recommended way to get around	2619	that you cannot get an embeddable loop. The recommended way to get around
2060	this is to have a separate variables for your embeddable loop, try to	2620	this is to have a separate variables for your embeddable loop, try to
2061	create it, and if that fails, use the normal loop for everything.	2621	create it, and if that fails, use the normal loop for everything.
2062		2622
		2623	=head3 C<ev_embed> and fork
		2624
		2625	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2626	automatically be applied to the embedded loop as well, so no special
		2627	fork handling is required in that case. When the watcher is not running,
		2628	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2629	as applicable.
		2630
2063	=head3 Watcher-Specific Functions and Data Members	2631	=head3 Watcher-Specific Functions and Data Members
2064		2632
2065	=over 4	2633	=over 4
2066		2634
2067	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2635	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
…		…
2070		2638
2071	Configures the watcher to embed the given loop, which must be	2639	Configures the watcher to embed the given loop, which must be
2072	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2640	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2073	invoked automatically, otherwise it is the responsibility of the callback	2641	invoked automatically, otherwise it is the responsibility of the callback
2074	to invoke it (it will continue to be called until the sweep has been done,	2642	to invoke it (it will continue to be called until the sweep has been done,
2075	if you do not want thta, you need to temporarily stop the embed watcher).	2643	if you do not want that, you need to temporarily stop the embed watcher).
2076		2644
2077	=item ev_embed_sweep (loop, ev_embed *)	2645	=item ev_embed_sweep (loop, ev_embed *)
2078		2646
2079	Make a single, non-blocking sweep over the embedded loop. This works	2647	Make a single, non-blocking sweep over the embedded loop. This works
2080	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2648	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2081	apropriate way for embedded loops.	2649	appropriate way for embedded loops.
2082		2650
2083	=item struct ev_loop *other [read-only]	2651	=item struct ev_loop *other [read-only]
2084		2652
2085	The embedded event loop.	2653	The embedded event loop.
2086		2654
…		…
2088		2656
2089	=head3 Examples	2657	=head3 Examples
2090		2658
2091	Example: Try to get an embeddable event loop and embed it into the default	2659	Example: Try to get an embeddable event loop and embed it into the default
2092	event loop. If that is not possible, use the default loop. The default	2660	event loop. If that is not possible, use the default loop. The default
2093	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2661	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2662	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2095	used).	2663	used).
2096		2664
2097	struct ev_loop *loop_hi = ev_default_init (0);	2665	struct ev_loop *loop_hi = ev_default_init (0);
2098	struct ev_loop *loop_lo = 0;	2666	struct ev_loop *loop_lo = 0;
2099	struct ev_embed embed;	2667	ev_embed embed;
2100		2668
2101	// see if there is a chance of getting one that works	2669	// see if there is a chance of getting one that works
2102	// (remember that a flags value of 0 means autodetection)	2670	// (remember that a flags value of 0 means autodetection)
2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2671	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2672	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2105	: 0;	2673	: 0;
2106		2674
2107	// if we got one, then embed it, otherwise default to loop_hi	2675	// if we got one, then embed it, otherwise default to loop_hi
2108	if (loop_lo)	2676	if (loop_lo)
2109	{	2677	{
2110	ev_embed_init (&embed, 0, loop_lo);	2678	ev_embed_init (&embed, 0, loop_lo);
2111	ev_embed_start (loop_hi, &embed);	2679	ev_embed_start (loop_hi, &embed);
2112	}	2680	}
2113	else	2681	else
2114	loop_lo = loop_hi;	2682	loop_lo = loop_hi;
2115		2683
2116	Example: Check if kqueue is available but not recommended and create	2684	Example: Check if kqueue is available but not recommended and create
2117	a kqueue backend for use with sockets (which usually work with any	2685	a kqueue backend for use with sockets (which usually work with any
2118	kqueue implementation). Store the kqueue/socket-only event loop in	2686	kqueue implementation). Store the kqueue/socket-only event loop in
2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2687	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2120		2688
2121	struct ev_loop *loop = ev_default_init (0);	2689	struct ev_loop *loop = ev_default_init (0);
2122	struct ev_loop *loop_socket = 0;	2690	struct ev_loop *loop_socket = 0;
2123	struct ev_embed embed;	2691	ev_embed embed;
2124		2692
2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2693	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2694	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2127	{	2695	{
2128	ev_embed_init (&embed, 0, loop_socket);	2696	ev_embed_init (&embed, 0, loop_socket);
2129	ev_embed_start (loop, &embed);	2697	ev_embed_start (loop, &embed);
2130	}	2698	}
2131		2699
2132	if (!loop_socket)	2700	if (!loop_socket)
2133	loop_socket = loop;	2701	loop_socket = loop;
2134		2702
2135	// now use loop_socket for all sockets, and loop for everything else	2703	// now use loop_socket for all sockets, and loop for everything else
2136		2704
2137		2705
2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2706	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2139		2707
2140	Fork watchers are called when a C<fork ()> was detected (usually because	2708	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2143	event loop blocks next and before C<ev_check> watchers are being called,	2711	event loop blocks next and before C<ev_check> watchers are being called,
2144	and only in the child after the fork. If whoever good citizen calling	2712	and only in the child after the fork. If whoever good citizen calling
2145	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2713	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2146	handlers will be invoked, too, of course.	2714	handlers will be invoked, too, of course.
2147		2715
		2716	=head3 The special problem of life after fork - how is it possible?
		2717
		2718	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2719	up/change the process environment, followed by a call to C<exec()>. This
		2720	sequence should be handled by libev without any problems.
		2721
		2722	This changes when the application actually wants to do event handling
		2723	in the child, or both parent in child, in effect "continuing" after the
		2724	fork.
		2725
		2726	The default mode of operation (for libev, with application help to detect
		2727	forks) is to duplicate all the state in the child, as would be expected
		2728	when I<either> the parent I<or> the child process continues.
		2729
		2730	When both processes want to continue using libev, then this is usually the
		2731	wrong result. In that case, usually one process (typically the parent) is
		2732	supposed to continue with all watchers in place as before, while the other
		2733	process typically wants to start fresh, i.e. without any active watchers.
		2734
		2735	The cleanest and most efficient way to achieve that with libev is to
		2736	simply create a new event loop, which of course will be "empty", and
		2737	use that for new watchers. This has the advantage of not touching more
		2738	memory than necessary, and thus avoiding the copy-on-write, and the
		2739	disadvantage of having to use multiple event loops (which do not support
		2740	signal watchers).
		2741
		2742	When this is not possible, or you want to use the default loop for
		2743	other reasons, then in the process that wants to start "fresh", call
		2744	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2745	the default loop will "orphan" (not stop) all registered watchers, so you
		2746	have to be careful not to execute code that modifies those watchers. Note
		2747	also that in that case, you have to re-register any signal watchers.
		2748
2148	=head3 Watcher-Specific Functions and Data Members	2749	=head3 Watcher-Specific Functions and Data Members
2149		2750
2150	=over 4	2751	=over 4
2151		2752
2152	=item ev_fork_init (ev_signal *, callback)	2753	=item ev_fork_init (ev_signal *, callback)
…		…
2184	is that the author does not know of a simple (or any) algorithm for a	2785	is that the author does not know of a simple (or any) algorithm for a
2185	multiple-writer-single-reader queue that works in all cases and doesn't	2786	multiple-writer-single-reader queue that works in all cases and doesn't
2186	need elaborate support such as pthreads.	2787	need elaborate support such as pthreads.
2187		2788
2188	That means that if you want to queue data, you have to provide your own	2789	That means that if you want to queue data, you have to provide your own
2189	queue. But at least I can tell you would implement locking around your	2790	queue. But at least I can tell you how to implement locking around your
2190	queue:	2791	queue:
2191		2792
2192	=over 4	2793	=over 4
2193		2794
2194	=item queueing from a signal handler context	2795	=item queueing from a signal handler context
2195		2796
2196	To implement race-free queueing, you simply add to the queue in the signal	2797	To implement race-free queueing, you simply add to the queue in the signal
2197	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2798	handler but you block the signal handler in the watcher callback. Here is
2198	some fictitiuous SIGUSR1 handler:	2799	an example that does that for some fictitious SIGUSR1 handler:
2199		2800
2200	static ev_async mysig;	2801	static ev_async mysig;
2201		2802
2202	static void	2803	static void
2203	sigusr1_handler (void)	2804	sigusr1_handler (void)
…		…
2269	=over 4	2870	=over 4
2270		2871
2271	=item ev_async_init (ev_async *, callback)	2872	=item ev_async_init (ev_async *, callback)
2272		2873
2273	Initialises and configures the async watcher - it has no parameters of any	2874	Initialises and configures the async watcher - it has no parameters of any
2274	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2875	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2275	believe me.	2876	trust me.
2276		2877
2277	=item ev_async_send (loop, ev_async *)	2878	=item ev_async_send (loop, ev_async *)
2278		2879
2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2880	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2280	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2881	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2281	C<ev_feed_event>, this call is safe to do in other threads, signal or	2882	C<ev_feed_event>, this call is safe to do from other threads, signal or
2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2883	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2283	section below on what exactly this means).	2884	section below on what exactly this means).
2284		2885
		2886	Note that, as with other watchers in libev, multiple events might get
		2887	compressed into a single callback invocation (another way to look at this
		2888	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2889	reset when the event loop detects that).
		2890
2285	This call incurs the overhead of a syscall only once per loop iteration,	2891	This call incurs the overhead of a system call only once per event loop
2286	so while the overhead might be noticable, it doesn't apply to repeated	2892	iteration, so while the overhead might be noticeable, it doesn't apply to
2287	calls to C<ev_async_send>.	2893	repeated calls to C<ev_async_send> for the same event loop.
2288		2894
2289	=item bool = ev_async_pending (ev_async *)	2895	=item bool = ev_async_pending (ev_async *)
2290		2896
2291	Returns a non-zero value when C<ev_async_send> has been called on the	2897	Returns a non-zero value when C<ev_async_send> has been called on the
2292	watcher but the event has not yet been processed (or even noted) by the	2898	watcher but the event has not yet been processed (or even noted) by the
2293	event loop.	2899	event loop.
2294		2900
2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2901	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2296	the loop iterates next and checks for the watcher to have become active,	2902	the loop iterates next and checks for the watcher to have become active,
2297	it will reset the flag again. C<ev_async_pending> can be used to very	2903	it will reset the flag again. C<ev_async_pending> can be used to very
2298	quickly check wether invoking the loop might be a good idea.	2904	quickly check whether invoking the loop might be a good idea.
2299		2905
2300	Not that this does I<not> check wether the watcher itself is pending, only	2906	Not that this does I<not> check whether the watcher itself is pending,
2301	wether it has been requested to make this watcher pending.	2907	only whether it has been requested to make this watcher pending: there
		2908	is a time window between the event loop checking and resetting the async
		2909	notification, and the callback being invoked.
2302		2910
2303	=back	2911	=back
2304		2912
2305		2913
2306	=head1 OTHER FUNCTIONS	2914	=head1 OTHER FUNCTIONS
…		…
2310	=over 4	2918	=over 4
2311		2919
2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2920	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2313		2921
2314	This function combines a simple timer and an I/O watcher, calls your	2922	This function combines a simple timer and an I/O watcher, calls your
2315	callback on whichever event happens first and automatically stop both	2923	callback on whichever event happens first and automatically stops both
2316	watchers. This is useful if you want to wait for a single event on an fd	2924	watchers. This is useful if you want to wait for a single event on an fd
2317	or timeout without having to allocate/configure/start/stop/free one or	2925	or timeout without having to allocate/configure/start/stop/free one or
2318	more watchers yourself.	2926	more watchers yourself.
2319		2927
2320	If C<fd> is less than 0, then no I/O watcher will be started and events	2928	If C<fd> is less than 0, then no I/O watcher will be started and the
2321	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2929	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2322	C<events> set will be craeted and started.	2930	the given C<fd> and C<events> set will be created and started.
2323		2931
2324	If C<timeout> is less than 0, then no timeout watcher will be	2932	If C<timeout> is less than 0, then no timeout watcher will be
2325	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2933	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2326	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2934	repeat = 0) will be started. C<0> is a valid timeout.
2327	dubious value.
2328		2935
2329	The callback has the type C<void (cb)(int revents, void arg)> and gets	2936	The callback has the type C<void (cb)(int revents, void arg)> and gets
2330	passed an C<revents> set like normal event callbacks (a combination of	2937	passed an C<revents> set like normal event callbacks (a combination of
2331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2938	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2332	value passed to C<ev_once>:	2939	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2940	a timeout and an io event at the same time - you probably should give io
		2941	events precedence.
2333		2942
		2943	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2944
2334	static void stdin_ready (int revents, void *arg)	2945	static void stdin_ready (int revents, void *arg)
2335	{	2946	{
2336	if (revents & EV_TIMEOUT)
2337	/* doh, nothing entered */;
2338	else if (revents & EV_READ)	2947	if (revents & EV_READ)
2339	/* stdin might have data for us, joy! */;	2948	/* stdin might have data for us, joy! */;
		2949	else if (revents & EV_TIMEOUT)
		2950	/* doh, nothing entered */;
2340	}	2951	}
2341		2952
2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2953	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2343		2954
2344	=item ev_feed_event (ev_loop , watcher , int revents)	2955	=item ev_feed_event (struct ev_loop , watcher , int revents)
2345		2956
2346	Feeds the given event set into the event loop, as if the specified event	2957	Feeds the given event set into the event loop, as if the specified event
2347	had happened for the specified watcher (which must be a pointer to an	2958	had happened for the specified watcher (which must be a pointer to an
2348	initialised but not necessarily started event watcher).	2959	initialised but not necessarily started event watcher).
2349		2960
2350	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2961	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2351		2962
2352	Feed an event on the given fd, as if a file descriptor backend detected	2963	Feed an event on the given fd, as if a file descriptor backend detected
2353	the given events it.	2964	the given events it.
2354		2965
2355	=item ev_feed_signal_event (ev_loop *loop, int signum)	2966	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2356		2967
2357	Feed an event as if the given signal occured (C<loop> must be the default	2968	Feed an event as if the given signal occurred (C<loop> must be the default
2358	loop!).	2969	loop!).
2359		2970
2360	=back	2971	=back
2361		2972
2362		2973
…		…
2391	=back	3002	=back
2392		3003
2393	=head1 C++ SUPPORT	3004	=head1 C++ SUPPORT
2394		3005
2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3006	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2396	you to use some convinience methods to start/stop watchers and also change	3007	you to use some convenience methods to start/stop watchers and also change
2397	the callback model to a model using method callbacks on objects.	3008	the callback model to a model using method callbacks on objects.
2398		3009
2399	To use it,	3010	To use it,
2400		3011
2401	#include <ev++.h>	3012	#include <ev++.h>
2402		3013
2403	This automatically includes F<ev.h> and puts all of its definitions (many	3014	This automatically includes F<ev.h> and puts all of its definitions (many
2404	of them macros) into the global namespace. All C++ specific things are	3015	of them macros) into the global namespace. All C++ specific things are
2405	put into the C<ev> namespace. It should support all the same embedding	3016	put into the C<ev> namespace. It should support all the same embedding
2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3017	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2473	your compiler is good :), then the method will be fully inlined into the	3084	your compiler is good :), then the method will be fully inlined into the
2474	thunking function, making it as fast as a direct C callback.	3085	thunking function, making it as fast as a direct C callback.
2475		3086
2476	Example: simple class declaration and watcher initialisation	3087	Example: simple class declaration and watcher initialisation
2477		3088
2478	struct myclass	3089	struct myclass
2479	{	3090	{
2480	void io_cb (ev::io &w, int revents) { }	3091	void io_cb (ev::io &w, int revents) { }
2481	}	3092	}
2482		3093
2483	myclass obj;	3094	myclass obj;
2484	ev::io iow;	3095	ev::io iow;
2485	iow.set <myclass, &myclass::io_cb> (&obj);	3096	iow.set <myclass, &myclass::io_cb> (&obj);
		3097
		3098	=item w->set (object *)
		3099
		3100	This is an B<experimental> feature that might go away in a future version.
		3101
		3102	This is a variation of a method callback - leaving out the method to call
		3103	will default the method to C<operator ()>, which makes it possible to use
		3104	functor objects without having to manually specify the C<operator ()> all
		3105	the time. Incidentally, you can then also leave out the template argument
		3106	list.
		3107
		3108	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3109	int revents)>.
		3110
		3111	See the method-C<set> above for more details.
		3112
		3113	Example: use a functor object as callback.
		3114
		3115	struct myfunctor
		3116	{
		3117	void operator() (ev::io &w, int revents)
		3118	{
		3119	...
		3120	}
		3121	}
		3122
		3123	myfunctor f;
		3124
		3125	ev::io w;
		3126	w.set (&f);
2486		3127
2487	=item w->set<function> (void *data = 0)	3128	=item w->set<function> (void *data = 0)
2488		3129
2489	Also sets a callback, but uses a static method or plain function as	3130	Also sets a callback, but uses a static method or plain function as
2490	callback. The optional C<data> argument will be stored in the watcher's	3131	callback. The optional C<data> argument will be stored in the watcher's
…		…
2492		3133
2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3134	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2494		3135
2495	See the method-C<set> above for more details.	3136	See the method-C<set> above for more details.
2496		3137
2497	Example:	3138	Example: Use a plain function as callback.
2498		3139
2499	static void io_cb (ev::io &w, int revents) { }	3140	static void io_cb (ev::io &w, int revents) { }
2500	iow.set <io_cb> ();	3141	iow.set <io_cb> ();
2501		3142
2502	=item w->set (struct ev_loop *)	3143	=item w->set (struct ev_loop *)
2503		3144
2504	Associates a different C<struct ev_loop> with this watcher. You can only	3145	Associates a different C<struct ev_loop> with this watcher. You can only
2505	do this when the watcher is inactive (and not pending either).	3146	do this when the watcher is inactive (and not pending either).
2506		3147
2507	=item w->set ([args])	3148	=item w->set ([arguments])
2508		3149
2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3150	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2510	called at least once. Unlike the C counterpart, an active watcher gets	3151	called at least once. Unlike the C counterpart, an active watcher gets
2511	automatically stopped and restarted when reconfiguring it with this	3152	automatically stopped and restarted when reconfiguring it with this
2512	method.	3153	method.
2513		3154
2514	=item w->start ()	3155	=item w->start ()
…		…
2538	=back	3179	=back
2539		3180
2540	Example: Define a class with an IO and idle watcher, start one of them in	3181	Example: Define a class with an IO and idle watcher, start one of them in
2541	the constructor.	3182	the constructor.
2542		3183
2543	class myclass	3184	class myclass
2544	{	3185	{
2545	ev::io io; void io_cb (ev::io &w, int revents);	3186	ev::io io ; void io_cb (ev::io &w, int revents);
2546	ev:idle idle void idle_cb (ev::idle &w, int revents);	3187	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2547		3188
2548	myclass (int fd)	3189	myclass (int fd)
2549	{	3190	{
2550	io .set <myclass, &myclass::io_cb > (this);	3191	io .set <myclass, &myclass::io_cb > (this);
2551	idle.set <myclass, &myclass::idle_cb> (this);	3192	idle.set <myclass, &myclass::idle_cb> (this);
2552		3193
2553	io.start (fd, ev::READ);	3194	io.start (fd, ev::READ);
2554	}	3195	}
2555	};	3196	};
2556		3197
2557		3198
2558	=head1 OTHER LANGUAGE BINDINGS	3199	=head1 OTHER LANGUAGE BINDINGS
2559		3200
2560	Libev does not offer other language bindings itself, but bindings for a	3201	Libev does not offer other language bindings itself, but bindings for a
2561	numbe rof languages exist in the form of third-party packages. If you know	3202	number of languages exist in the form of third-party packages. If you know
2562	any interesting language binding in addition to the ones listed here, drop	3203	any interesting language binding in addition to the ones listed here, drop
2563	me a note.	3204	me a note.
2564		3205
2565	=over 4	3206	=over 4
2566		3207
2567	=item Perl	3208	=item Perl
2568		3209
2569	The EV module implements the full libev API and is actually used to test	3210	The EV module implements the full libev API and is actually used to test
2570	libev. EV is developed together with libev. Apart from the EV core module,	3211	libev. EV is developed together with libev. Apart from the EV core module,
2571	there are additional modules that implement libev-compatible interfaces	3212	there are additional modules that implement libev-compatible interfaces
2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3213	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3214	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3215	and C<EV::Glib>).
2574		3216
2575	It can be found and installed via CPAN, its homepage is found at	3217	It can be found and installed via CPAN, its homepage is at
2576	L<http://software.schmorp.de/pkg/EV>.	3218	L<http://software.schmorp.de/pkg/EV>.
2577		3219
		3220	=item Python
		3221
		3222	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3223	seems to be quite complete and well-documented.
		3224
2578	=item Ruby	3225	=item Ruby
2579		3226
2580	Tony Arcieri has written a ruby extension that offers access to a subset	3227	Tony Arcieri has written a ruby extension that offers access to a subset
2581	of the libev API and adds filehandle abstractions, asynchronous DNS and	3228	of the libev API and adds file handle abstractions, asynchronous DNS and
2582	more on top of it. It can be found via gem servers. Its homepage is at	3229	more on top of it. It can be found via gem servers. Its homepage is at
2583	L<http://rev.rubyforge.org/>.	3230	L<http://rev.rubyforge.org/>.
2584		3231
		3232	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3233	makes rev work even on mingw.
		3234
		3235	=item Haskell
		3236
		3237	A haskell binding to libev is available at
		3238	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3239
2585	=item D	3240	=item D
2586		3241
2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3242	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3243	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3244
		3245	=item Ocaml
		3246
		3247	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3248	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2589		3249
2590	=back	3250	=back
2591		3251
2592		3252
2593	=head1 MACRO MAGIC	3253	=head1 MACRO MAGIC
2594		3254
2595	Libev can be compiled with a variety of options, the most fundamantal	3255	Libev can be compiled with a variety of options, the most fundamental
2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3256	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2597	functions and callbacks have an initial C<struct ev_loop *> argument.	3257	functions and callbacks have an initial C<struct ev_loop *> argument.
2598		3258
2599	To make it easier to write programs that cope with either variant, the	3259	To make it easier to write programs that cope with either variant, the
2600	following macros are defined:	3260	following macros are defined:
…		…
2605		3265
2606	This provides the loop I<argument> for functions, if one is required ("ev	3266	This provides the loop I<argument> for functions, if one is required ("ev
2607	loop argument"). The C<EV_A> form is used when this is the sole argument,	3267	loop argument"). The C<EV_A> form is used when this is the sole argument,
2608	C<EV_A_> is used when other arguments are following. Example:	3268	C<EV_A_> is used when other arguments are following. Example:
2609		3269
2610	ev_unref (EV_A);	3270	ev_unref (EV_A);
2611	ev_timer_add (EV_A_ watcher);	3271	ev_timer_add (EV_A_ watcher);
2612	ev_loop (EV_A_ 0);	3272	ev_loop (EV_A_ 0);
2613		3273
2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3274	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2615	which is often provided by the following macro.	3275	which is often provided by the following macro.
2616		3276
2617	=item C<EV_P>, C<EV_P_>	3277	=item C<EV_P>, C<EV_P_>
2618		3278
2619	This provides the loop I<parameter> for functions, if one is required ("ev	3279	This provides the loop I<parameter> for functions, if one is required ("ev
2620	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3280	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2621	C<EV_P_> is used when other parameters are following. Example:	3281	C<EV_P_> is used when other parameters are following. Example:
2622		3282
2623	// this is how ev_unref is being declared	3283	// this is how ev_unref is being declared
2624	static void ev_unref (EV_P);	3284	static void ev_unref (EV_P);
2625		3285
2626	// this is how you can declare your typical callback	3286	// this is how you can declare your typical callback
2627	static void cb (EV_P_ ev_timer *w, int revents)	3287	static void cb (EV_P_ ev_timer *w, int revents)
2628		3288
2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3289	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2630	suitable for use with C<EV_A>.	3290	suitable for use with C<EV_A>.
2631		3291
2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3292	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2648		3308
2649	Example: Declare and initialise a check watcher, utilising the above	3309	Example: Declare and initialise a check watcher, utilising the above
2650	macros so it will work regardless of whether multiple loops are supported	3310	macros so it will work regardless of whether multiple loops are supported
2651	or not.	3311	or not.
2652		3312
2653	static void	3313	static void
2654	check_cb (EV_P_ ev_timer *w, int revents)	3314	check_cb (EV_P_ ev_timer *w, int revents)
2655	{	3315	{
2656	ev_check_stop (EV_A_ w);	3316	ev_check_stop (EV_A_ w);
2657	}	3317	}
2658		3318
2659	ev_check check;	3319	ev_check check;
2660	ev_check_init (&check, check_cb);	3320	ev_check_init (&check, check_cb);
2661	ev_check_start (EV_DEFAULT_ &check);	3321	ev_check_start (EV_DEFAULT_ &check);
2662	ev_loop (EV_DEFAULT_ 0);	3322	ev_loop (EV_DEFAULT_ 0);
2663		3323
2664	=head1 EMBEDDING	3324	=head1 EMBEDDING
2665		3325
2666	Libev can (and often is) directly embedded into host	3326	Libev can (and often is) directly embedded into host
2667	applications. Examples of applications that embed it include the Deliantra	3327	applications. Examples of applications that embed it include the Deliantra
…		…
2674	libev somewhere in your source tree).	3334	libev somewhere in your source tree).
2675		3335
2676	=head2 FILESETS	3336	=head2 FILESETS
2677		3337
2678	Depending on what features you need you need to include one or more sets of files	3338	Depending on what features you need you need to include one or more sets of files
2679	in your app.	3339	in your application.
2680		3340
2681	=head3 CORE EVENT LOOP	3341	=head3 CORE EVENT LOOP
2682		3342
2683	To include only the libev core (all the C<ev_*> functions), with manual	3343	To include only the libev core (all the C<ev_*> functions), with manual
2684	configuration (no autoconf):	3344	configuration (no autoconf):
2685		3345
2686	#define EV_STANDALONE 1	3346	#define EV_STANDALONE 1
2687	#include "ev.c"	3347	#include "ev.c"
2688		3348
2689	This will automatically include F<ev.h>, too, and should be done in a	3349	This will automatically include F<ev.h>, too, and should be done in a
2690	single C source file only to provide the function implementations. To use	3350	single C source file only to provide the function implementations. To use
2691	it, do the same for F<ev.h> in all files wishing to use this API (best	3351	it, do the same for F<ev.h> in all files wishing to use this API (best
2692	done by writing a wrapper around F<ev.h> that you can include instead and	3352	done by writing a wrapper around F<ev.h> that you can include instead and
2693	where you can put other configuration options):	3353	where you can put other configuration options):
2694		3354
2695	#define EV_STANDALONE 1	3355	#define EV_STANDALONE 1
2696	#include "ev.h"	3356	#include "ev.h"
2697		3357
2698	Both header files and implementation files can be compiled with a C++	3358	Both header files and implementation files can be compiled with a C++
2699	compiler (at least, thats a stated goal, and breakage will be treated	3359	compiler (at least, that's a stated goal, and breakage will be treated
2700	as a bug).	3360	as a bug).
2701		3361
2702	You need the following files in your source tree, or in a directory	3362	You need the following files in your source tree, or in a directory
2703	in your include path (e.g. in libev/ when using -Ilibev):	3363	in your include path (e.g. in libev/ when using -Ilibev):
2704		3364
2705	ev.h	3365	ev.h
2706	ev.c	3366	ev.c
2707	ev_vars.h	3367	ev_vars.h
2708	ev_wrap.h	3368	ev_wrap.h
2709		3369
2710	ev_win32.c required on win32 platforms only	3370	ev_win32.c required on win32 platforms only
2711		3371
2712	ev_select.c only when select backend is enabled (which is enabled by default)	3372	ev_select.c only when select backend is enabled (which is enabled by default)
2713	ev_poll.c only when poll backend is enabled (disabled by default)	3373	ev_poll.c only when poll backend is enabled (disabled by default)
2714	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3374	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2715	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3375	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2716	ev_port.c only when the solaris port backend is enabled (disabled by default)	3376	ev_port.c only when the solaris port backend is enabled (disabled by default)
2717		3377
2718	F<ev.c> includes the backend files directly when enabled, so you only need	3378	F<ev.c> includes the backend files directly when enabled, so you only need
2719	to compile this single file.	3379	to compile this single file.
2720		3380
2721	=head3 LIBEVENT COMPATIBILITY API	3381	=head3 LIBEVENT COMPATIBILITY API
2722		3382
2723	To include the libevent compatibility API, also include:	3383	To include the libevent compatibility API, also include:
2724		3384
2725	#include "event.c"	3385	#include "event.c"
2726		3386
2727	in the file including F<ev.c>, and:	3387	in the file including F<ev.c>, and:
2728		3388
2729	#include "event.h"	3389	#include "event.h"
2730		3390
2731	in the files that want to use the libevent API. This also includes F<ev.h>.	3391	in the files that want to use the libevent API. This also includes F<ev.h>.
2732		3392
2733	You need the following additional files for this:	3393	You need the following additional files for this:
2734		3394
2735	event.h	3395	event.h
2736	event.c	3396	event.c
2737		3397
2738	=head3 AUTOCONF SUPPORT	3398	=head3 AUTOCONF SUPPORT
2739		3399
2740	Instead of using C<EV_STANDALONE=1> and providing your config in	3400	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2741	whatever way you want, you can also C<m4_include([libev.m4])> in your	3401	whatever way you want, you can also C<m4_include([libev.m4])> in your
2742	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3402	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2743	include F<config.h> and configure itself accordingly.	3403	include F<config.h> and configure itself accordingly.
2744		3404
2745	For this of course you need the m4 file:	3405	For this of course you need the m4 file:
2746		3406
2747	libev.m4	3407	libev.m4
2748		3408
2749	=head2 PREPROCESSOR SYMBOLS/MACROS	3409	=head2 PREPROCESSOR SYMBOLS/MACROS
2750		3410
2751	Libev can be configured via a variety of preprocessor symbols you have to	3411	Libev can be configured via a variety of preprocessor symbols you have to
2752	define before including any of its files. The default in the absense of	3412	define before including any of its files. The default in the absence of
2753	autoconf is noted for every option.	3413	autoconf is documented for every option.
2754		3414
2755	=over 4	3415	=over 4
2756		3416
2757	=item EV_STANDALONE	3417	=item EV_STANDALONE
2758		3418
…		…
2760	keeps libev from including F<config.h>, and it also defines dummy	3420	keeps libev from including F<config.h>, and it also defines dummy
2761	implementations for some libevent functions (such as logging, which is not	3421	implementations for some libevent functions (such as logging, which is not
2762	supported). It will also not define any of the structs usually found in	3422	supported). It will also not define any of the structs usually found in
2763	F<event.h> that are not directly supported by the libev core alone.	3423	F<event.h> that are not directly supported by the libev core alone.
2764		3424
		3425	In stanbdalone mode, libev will still try to automatically deduce the
		3426	configuration, but has to be more conservative.
		3427
2765	=item EV_USE_MONOTONIC	3428	=item EV_USE_MONOTONIC
2766		3429
2767	If defined to be C<1>, libev will try to detect the availability of the	3430	If defined to be C<1>, libev will try to detect the availability of the
2768	monotonic clock option at both compiletime and runtime. Otherwise no use	3431	monotonic clock option at both compile time and runtime. Otherwise no
2769	of the monotonic clock option will be attempted. If you enable this, you	3432	use of the monotonic clock option will be attempted. If you enable this,
2770	usually have to link against librt or something similar. Enabling it when	3433	you usually have to link against librt or something similar. Enabling it
2771	the functionality isn't available is safe, though, although you have	3434	when the functionality isn't available is safe, though, although you have
2772	to make sure you link against any libraries where the C<clock_gettime>	3435	to make sure you link against any libraries where the C<clock_gettime>
2773	function is hiding in (often F<-lrt>).	3436	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2774		3437
2775	=item EV_USE_REALTIME	3438	=item EV_USE_REALTIME
2776		3439
2777	If defined to be C<1>, libev will try to detect the availability of the	3440	If defined to be C<1>, libev will try to detect the availability of the
2778	realtime clock option at compiletime (and assume its availability at	3441	real-time clock option at compile time (and assume its availability
2779	runtime if successful). Otherwise no use of the realtime clock option will	3442	at runtime if successful). Otherwise no use of the real-time clock
2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3443	option will be attempted. This effectively replaces C<gettimeofday>
2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3444	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3445	correctness. See the note about libraries in the description of
		3446	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3447	C<EV_USE_CLOCK_SYSCALL>.
		3448
		3449	=item EV_USE_CLOCK_SYSCALL
		3450
		3451	If defined to be C<1>, libev will try to use a direct syscall instead
		3452	of calling the system-provided C<clock_gettime> function. This option
		3453	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3454	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3455	programs needlessly. Using a direct syscall is slightly slower (in
		3456	theory), because no optimised vdso implementation can be used, but avoids
		3457	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3458	higher, as it simplifies linking (no need for C<-lrt>).
2783		3459
2784	=item EV_USE_NANOSLEEP	3460	=item EV_USE_NANOSLEEP
2785		3461
2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3462	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2787	and will use it for delays. Otherwise it will use C<select ()>.	3463	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2795	2.7 or newer, otherwise disabled.	3471	2.7 or newer, otherwise disabled.
2796		3472
2797	=item EV_USE_SELECT	3473	=item EV_USE_SELECT
2798		3474
2799	If undefined or defined to be C<1>, libev will compile in support for the	3475	If undefined or defined to be C<1>, libev will compile in support for the
2800	C<select>(2) backend. No attempt at autodetection will be done: if no	3476	C<select>(2) backend. No attempt at auto-detection will be done: if no
2801	other method takes over, select will be it. Otherwise the select backend	3477	other method takes over, select will be it. Otherwise the select backend
2802	will not be compiled in.	3478	will not be compiled in.
2803		3479
2804	=item EV_SELECT_USE_FD_SET	3480	=item EV_SELECT_USE_FD_SET
2805		3481
2806	If defined to C<1>, then the select backend will use the system C<fd_set>	3482	If defined to C<1>, then the select backend will use the system C<fd_set>
2807	structure. This is useful if libev doesn't compile due to a missing	3483	structure. This is useful if libev doesn't compile due to a missing
2808	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3484	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2809	exotic systems. This usually limits the range of file descriptors to some	3485	on exotic systems. This usually limits the range of file descriptors to
2810	low limit such as 1024 or might have other limitations (winsocket only	3486	some low limit such as 1024 or might have other limitations (winsocket
2811	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3487	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2812	influence the size of the C<fd_set> used.	3488	configures the maximum size of the C<fd_set>.
2813		3489
2814	=item EV_SELECT_IS_WINSOCKET	3490	=item EV_SELECT_IS_WINSOCKET
2815		3491
2816	When defined to C<1>, the select backend will assume that	3492	When defined to C<1>, the select backend will assume that
2817	select/socket/connect etc. don't understand file descriptors but	3493	select/socket/connect etc. don't understand file descriptors but
…		…
2862	otherwise another method will be used as fallback. This is the preferred	3538	otherwise another method will be used as fallback. This is the preferred
2863	backend for Solaris 10 systems.	3539	backend for Solaris 10 systems.
2864		3540
2865	=item EV_USE_DEVPOLL	3541	=item EV_USE_DEVPOLL
2866		3542
2867	reserved for future expansion, works like the USE symbols above.	3543	Reserved for future expansion, works like the USE symbols above.
2868		3544
2869	=item EV_USE_INOTIFY	3545	=item EV_USE_INOTIFY
2870		3546
2871	If defined to be C<1>, libev will compile in support for the Linux inotify	3547	If defined to be C<1>, libev will compile in support for the Linux inotify
2872	interface to speed up C<ev_stat> watchers. Its actual availability will	3548	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2879	access is atomic with respect to other threads or signal contexts. No such	3555	access is atomic with respect to other threads or signal contexts. No such
2880	type is easily found in the C language, so you can provide your own type	3556	type is easily found in the C language, so you can provide your own type
2881	that you know is safe for your purposes. It is used both for signal handler "locking"	3557	that you know is safe for your purposes. It is used both for signal handler "locking"
2882	as well as for signal and thread safety in C<ev_async> watchers.	3558	as well as for signal and thread safety in C<ev_async> watchers.
2883		3559
2884	In the absense of this define, libev will use C<sig_atomic_t volatile>	3560	In the absence of this define, libev will use C<sig_atomic_t volatile>
2885	(from F<signal.h>), which is usually good enough on most platforms.	3561	(from F<signal.h>), which is usually good enough on most platforms.
2886		3562
2887	=item EV_H	3563	=item EV_H
2888		3564
2889	The name of the F<ev.h> header file used to include it. The default if	3565	The name of the F<ev.h> header file used to include it. The default if
…		…
2928	When doing priority-based operations, libev usually has to linearly search	3604	When doing priority-based operations, libev usually has to linearly search
2929	all the priorities, so having many of them (hundreds) uses a lot of space	3605	all the priorities, so having many of them (hundreds) uses a lot of space
2930	and time, so using the defaults of five priorities (-2 .. +2) is usually	3606	and time, so using the defaults of five priorities (-2 .. +2) is usually
2931	fine.	3607	fine.
2932		3608
2933	If your embedding app does not need any priorities, defining these both to	3609	If your embedding application does not need any priorities, defining these
2934	C<0> will save some memory and cpu.	3610	both to C<0> will save some memory and CPU.
2935		3611
2936	=item EV_PERIODIC_ENABLE	3612	=item EV_PERIODIC_ENABLE
2937		3613
2938	If undefined or defined to be C<1>, then periodic timers are supported. If	3614	If undefined or defined to be C<1>, then periodic timers are supported. If
2939	defined to be C<0>, then they are not. Disabling them saves a few kB of	3615	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2946	code.	3622	code.
2947		3623
2948	=item EV_EMBED_ENABLE	3624	=item EV_EMBED_ENABLE
2949		3625
2950	If undefined or defined to be C<1>, then embed watchers are supported. If	3626	If undefined or defined to be C<1>, then embed watchers are supported. If
2951	defined to be C<0>, then they are not.	3627	defined to be C<0>, then they are not. Embed watchers rely on most other
		3628	watcher types, which therefore must not be disabled.
2952		3629
2953	=item EV_STAT_ENABLE	3630	=item EV_STAT_ENABLE
2954		3631
2955	If undefined or defined to be C<1>, then stat watchers are supported. If	3632	If undefined or defined to be C<1>, then stat watchers are supported. If
2956	defined to be C<0>, then they are not.	3633	defined to be C<0>, then they are not.
…		…
2966	defined to be C<0>, then they are not.	3643	defined to be C<0>, then they are not.
2967		3644
2968	=item EV_MINIMAL	3645	=item EV_MINIMAL
2969		3646
2970	If you need to shave off some kilobytes of code at the expense of some	3647	If you need to shave off some kilobytes of code at the expense of some
2971	speed, define this symbol to C<1>. Currently only used for gcc to override	3648	speed, define this symbol to C<1>. Currently this is used to override some
2972	some inlining decisions, saves roughly 30% codesize of amd64.	3649	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3650	much smaller 2-heap for timer management over the default 4-heap.
2973		3651
2974	=item EV_PID_HASHSIZE	3652	=item EV_PID_HASHSIZE
2975		3653
2976	C<ev_child> watchers use a small hash table to distribute workload by	3654	C<ev_child> watchers use a small hash table to distribute workload by
2977	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3655	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3662	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2985	usually more than enough. If you need to manage thousands of C<ev_stat>	3663	usually more than enough. If you need to manage thousands of C<ev_stat>
2986	watchers you might want to increase this value (I<must> be a power of	3664	watchers you might want to increase this value (I<must> be a power of
2987	two).	3665	two).
2988		3666
		3667	=item EV_USE_4HEAP
		3668
		3669	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3670	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3671	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3672	faster performance with many (thousands) of watchers.
		3673
		3674	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3675	(disabled).
		3676
		3677	=item EV_HEAP_CACHE_AT
		3678
		3679	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3680	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3681	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3682	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3683	but avoids random read accesses on heap changes. This improves performance
		3684	noticeably with many (hundreds) of watchers.
		3685
		3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3687	(disabled).
		3688
		3689	=item EV_VERIFY
		3690
		3691	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3692	be done: If set to C<0>, no internal verification code will be compiled
		3693	in. If set to C<1>, then verification code will be compiled in, but not
		3694	called. If set to C<2>, then the internal verification code will be
		3695	called once per loop, which can slow down libev. If set to C<3>, then the
		3696	verification code will be called very frequently, which will slow down
		3697	libev considerably.
		3698
		3699	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3700	C<0>.
		3701
2989	=item EV_COMMON	3702	=item EV_COMMON
2990		3703
2991	By default, all watchers have a C<void *data> member. By redefining	3704	By default, all watchers have a C<void *data> member. By redefining
2992	this macro to a something else you can include more and other types of	3705	this macro to a something else you can include more and other types of
2993	members. You have to define it each time you include one of the files,	3706	members. You have to define it each time you include one of the files,
2994	though, and it must be identical each time.	3707	though, and it must be identical each time.
2995		3708
2996	For example, the perl EV module uses something like this:	3709	For example, the perl EV module uses something like this:
2997		3710
2998	#define EV_COMMON \	3711	#define EV_COMMON \
2999	SV self; / contains this struct */ \	3712	SV self; / contains this struct */ \
3000	SV cb_sv, fh /* note no trailing ";" */	3713	SV cb_sv, fh /* note no trailing ";" */
3001		3714
3002	=item EV_CB_DECLARE (type)	3715	=item EV_CB_DECLARE (type)
3003		3716
3004	=item EV_CB_INVOKE (watcher, revents)	3717	=item EV_CB_INVOKE (watcher, revents)
3005		3718
…		…
3010	definition and a statement, respectively. See the F<ev.h> header file for	3723	definition and a statement, respectively. See the F<ev.h> header file for
3011	their default definitions. One possible use for overriding these is to	3724	their default definitions. One possible use for overriding these is to
3012	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3725	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3013	method calls instead of plain function calls in C++.	3726	method calls instead of plain function calls in C++.
3014		3727
		3728	=back
		3729
3015	=head2 EXPORTED API SYMBOLS	3730	=head2 EXPORTED API SYMBOLS
3016		3731
3017	If you need to re-export the API (e.g. via a dll) and you need a list of	3732	If you need to re-export the API (e.g. via a DLL) and you need a list of
3018	exported symbols, you can use the provided F<Symbol.*> files which list	3733	exported symbols, you can use the provided F<Symbol.*> files which list
3019	all public symbols, one per line:	3734	all public symbols, one per line:
3020		3735
3021	Symbols.ev for libev proper	3736	Symbols.ev for libev proper
3022	Symbols.event for the libevent emulation	3737	Symbols.event for the libevent emulation
3023		3738
3024	This can also be used to rename all public symbols to avoid clashes with	3739	This can also be used to rename all public symbols to avoid clashes with
3025	multiple versions of libev linked together (which is obviously bad in	3740	multiple versions of libev linked together (which is obviously bad in
3026	itself, but sometimes it is inconvinient to avoid this).	3741	itself, but sometimes it is inconvenient to avoid this).
3027		3742
3028	A sed command like this will create wrapper C<#define>'s that you need to	3743	A sed command like this will create wrapper C<#define>'s that you need to
3029	include before including F<ev.h>:	3744	include before including F<ev.h>:
3030		3745
3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3746	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3048	file.	3763	file.
3049		3764
3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3765	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3051	that everybody includes and which overrides some configure choices:	3766	that everybody includes and which overrides some configure choices:
3052		3767
3053	#define EV_MINIMAL 1	3768	#define EV_MINIMAL 1
3054	#define EV_USE_POLL 0	3769	#define EV_USE_POLL 0
3055	#define EV_MULTIPLICITY 0	3770	#define EV_MULTIPLICITY 0
3056	#define EV_PERIODIC_ENABLE 0	3771	#define EV_PERIODIC_ENABLE 0
3057	#define EV_STAT_ENABLE 0	3772	#define EV_STAT_ENABLE 0
3058	#define EV_FORK_ENABLE 0	3773	#define EV_FORK_ENABLE 0
3059	#define EV_CONFIG_H <config.h>	3774	#define EV_CONFIG_H <config.h>
3060	#define EV_MINPRI 0	3775	#define EV_MINPRI 0
3061	#define EV_MAXPRI 0	3776	#define EV_MAXPRI 0
3062		3777
3063	#include "ev++.h"	3778	#include "ev++.h"
3064		3779
3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3780	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3066		3781
3067	#include "ev_cpp.h"	3782	#include "ev_cpp.h"
3068	#include "ev.c"	3783	#include "ev.c"
3069		3784
		3785	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3070		3786
3071	=head1 THREADS AND COROUTINES	3787	=head2 THREADS AND COROUTINES
3072		3788
3073	=head2 THREADS	3789	=head3 THREADS
3074		3790
3075	Libev itself is completely threadsafe, but it uses no locking. This	3791	All libev functions are reentrant and thread-safe unless explicitly
		3792	documented otherwise, but libev implements no locking itself. This means
3076	means that you can use as many loops as you want in parallel, as long as	3793	that you can use as many loops as you want in parallel, as long as there
3077	only one thread ever calls into one libev function with the same loop	3794	are no concurrent calls into any libev function with the same loop
3078	parameter.	3795	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3796	of course): libev guarantees that different event loops share no data
		3797	structures that need any locking.
3079		3798
3080	Or put differently: calls with different loop parameters can be done in	3799	Or to put it differently: calls with different loop parameters can be done
3081	parallel from multiple threads, calls with the same loop parameter must be	3800	concurrently from multiple threads, calls with the same loop parameter
3082	done serially (but can be done from different threads, as long as only one	3801	must be done serially (but can be done from different threads, as long as
3083	thread ever is inside a call at any point in time, e.g. by using a mutex	3802	only one thread ever is inside a call at any point in time, e.g. by using
3084	per loop).	3803	a mutex per loop).
3085		3804
3086	If you want to know which design is best for your problem, then I cannot	3805	Specifically to support threads (and signal handlers), libev implements
		3806	so-called C<ev_async> watchers, which allow some limited form of
		3807	concurrency on the same event loop, namely waking it up "from the
		3808	outside".
		3809
		3810	If you want to know which design (one loop, locking, or multiple loops
		3811	without or something else still) is best for your problem, then I cannot
3087	help you but by giving some generic advice:	3812	help you, but here is some generic advice:
3088		3813
3089	=over 4	3814	=over 4
3090		3815
3091	=item * most applications have a main thread: use the default libev loop	3816	=item * most applications have a main thread: use the default libev loop
3092	in that thread, or create a seperate thread running only the default loop.	3817	in that thread, or create a separate thread running only the default loop.
3093		3818
3094	This helps integrating other libraries or software modules that use libev	3819	This helps integrating other libraries or software modules that use libev
3095	themselves and don't care/know about threading.	3820	themselves and don't care/know about threading.
3096		3821
3097	=item * one loop per thread is usually a good model.	3822	=item * one loop per thread is usually a good model.
3098		3823
3099	Doing this is almost never wrong, sometimes a better-performance model	3824	Doing this is almost never wrong, sometimes a better-performance model
3100	exists, but it is always a good start.	3825	exists, but it is always a good start.
3101		3826
3102	=item * other models exist, such as the leader/follower pattern, where one	3827	=item * other models exist, such as the leader/follower pattern, where one
3103	loop is handed through multiple threads in a kind of round-robbin fashion.	3828	loop is handed through multiple threads in a kind of round-robin fashion.
3104		3829
3105	Chosing a model is hard - look around, learn, know that usually you cna do	3830	Choosing a model is hard - look around, learn, know that usually you can do
3106	better than you currently do :-)	3831	better than you currently do :-)
3107		3832
3108	=item * often you need to talk to some other thread which blocks in the	3833	=item * often you need to talk to some other thread which blocks in the
		3834	event loop.
		3835
3109	event loop - C<ev_async> watchers can be used to wake them up from other	3836	C<ev_async> watchers can be used to wake them up from other threads safely
3110	threads safely (or from signal contexts...).	3837	(or from signal contexts...).
		3838
		3839	An example use would be to communicate signals or other events that only
		3840	work in the default loop by registering the signal watcher with the
		3841	default loop and triggering an C<ev_async> watcher from the default loop
		3842	watcher callback into the event loop interested in the signal.
3111		3843
3112	=back	3844	=back
3113		3845
3114	=head2 COROUTINES	3846	=head3 COROUTINES
3115		3847
3116	Libev is much more accomodating to coroutines ("cooperative threads"):	3848	Libev is very accommodating to coroutines ("cooperative threads"):
3117	libev fully supports nesting calls to it's functions from different	3849	libev fully supports nesting calls to its functions from different
3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3850	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3119	different coroutines and switch freely between both coroutines running the	3851	different coroutines, and switch freely between both coroutines running the
3120	loop, as long as you don't confuse yourself). The only exception is that	3852	loop, as long as you don't confuse yourself). The only exception is that
3121	you must not do this from C<ev_periodic> reschedule callbacks.	3853	you must not do this from C<ev_periodic> reschedule callbacks.
3122		3854
3123	Care has been invested into making sure that libev does not keep local	3855	Care has been taken to ensure that libev does not keep local state inside
3124	state inside C<ev_loop>, and other calls do not usually allow coroutine	3856	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3125	switches.	3857	they do not call any callbacks.
3126		3858
		3859	=head2 COMPILER WARNINGS
3127		3860
3128	=head1 COMPLEXITIES	3861	Depending on your compiler and compiler settings, you might get no or a
		3862	lot of warnings when compiling libev code. Some people are apparently
		3863	scared by this.
3129		3864
3130	In this section the complexities of (many of) the algorithms used inside	3865	However, these are unavoidable for many reasons. For one, each compiler
3131	libev will be explained. For complexity discussions about backends see the	3866	has different warnings, and each user has different tastes regarding
3132	documentation for C<ev_default_init>.	3867	warning options. "Warn-free" code therefore cannot be a goal except when
		3868	targeting a specific compiler and compiler-version.
3133		3869
3134	All of the following are about amortised time: If an array needs to be	3870	Another reason is that some compiler warnings require elaborate
3135	extended, libev needs to realloc and move the whole array, but this	3871	workarounds, or other changes to the code that make it less clear and less
3136	happens asymptotically never with higher number of elements, so O(1) might	3872	maintainable.
3137	mean it might do a lengthy realloc operation in rare cases, but on average
3138	it is much faster and asymptotically approaches constant time.
3139		3873
3140	=over 4	3874	And of course, some compiler warnings are just plain stupid, or simply
		3875	wrong (because they don't actually warn about the condition their message
		3876	seems to warn about). For example, certain older gcc versions had some
		3877	warnings that resulted an extreme number of false positives. These have
		3878	been fixed, but some people still insist on making code warn-free with
		3879	such buggy versions.
3141		3880
3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3881	While libev is written to generate as few warnings as possible,
		3882	"warn-free" code is not a goal, and it is recommended not to build libev
		3883	with any compiler warnings enabled unless you are prepared to cope with
		3884	them (e.g. by ignoring them). Remember that warnings are just that:
		3885	warnings, not errors, or proof of bugs.
3143		3886
3144	This means that, when you have a watcher that triggers in one hour and
3145	there are 100 watchers that would trigger before that then inserting will
3146	have to skip roughly seven (C<ld 100>) of these watchers.
3147		3887
3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3888	=head2 VALGRIND
3149		3889
3150	That means that changing a timer costs less than removing/adding them	3890	Valgrind has a special section here because it is a popular tool that is
3151	as only the relative motion in the event queue has to be paid for.	3891	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3152		3892
3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3893	If you think you found a bug (memory leak, uninitialised data access etc.)
		3894	in libev, then check twice: If valgrind reports something like:
3154		3895
3155	These just add the watcher into an array or at the head of a list.	3896	==2274== definitely lost: 0 bytes in 0 blocks.
		3897	==2274== possibly lost: 0 bytes in 0 blocks.
		3898	==2274== still reachable: 256 bytes in 1 blocks.
3156		3899
3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3900	Then there is no memory leak, just as memory accounted to global variables
		3901	is not a memleak - the memory is still being referenced, and didn't leak.
3158		3902
3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3903	Similarly, under some circumstances, valgrind might report kernel bugs
		3904	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3905	although an acceptable workaround has been found here), or it might be
		3906	confused.
3160		3907
3161	These watchers are stored in lists then need to be walked to find the	3908	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3162	correct watcher to remove. The lists are usually short (you don't usually	3909	make it into some kind of religion.
3163	have many watchers waiting for the same fd or signal).
3164		3910
3165	=item Finding the next timer in each loop iteration: O(1)	3911	If you are unsure about something, feel free to contact the mailing list
		3912	with the full valgrind report and an explanation on why you think this
		3913	is a bug in libev (best check the archives, too :). However, don't be
		3914	annoyed when you get a brisk "this is no bug" answer and take the chance
		3915	of learning how to interpret valgrind properly.
3166		3916
3167	By virtue of using a binary heap, the next timer is always found at the	3917	If you need, for some reason, empty reports from valgrind for your project
3168	beginning of the storage array.	3918	I suggest using suppression lists.
3169		3919
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		3920
3172	A change means an I/O watcher gets started or stopped, which requires	3921	=head1 PORTABILITY NOTES
3173	libev to recalculate its status (and possibly tell the kernel, depending
3174	on backend and wether C<ev_io_set> was used).
3175		3922
3176	=item Activating one watcher (putting it into the pending state): O(1)	3923	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3177
3178	=item Priority handling: O(number_of_priorities)
3179
3180	Priorities are implemented by allocating some space for each
3181	priority. When doing priority-based operations, libev usually has to
3182	linearly search all the priorities, but starting/stopping and activating
3183	watchers becomes O(1) w.r.t. priority handling.
3184
3185	=item Sending an ev_async: O(1)
3186
3187	=item Processing ev_async_send: O(number_of_async_watchers)
3188
3189	=item Processing signals: O(max_signal_number)
3190
3191	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3192	calls in the current loop iteration. Checking for async and signal events
3193	involves iterating over all running async watchers or all signal numbers.
3194
3195	=back
3196
3197
3198	=head1 Win32 platform limitations and workarounds
3199		3924
3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3925	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3201	requires, and its I/O model is fundamentally incompatible with the POSIX	3926	requires, and its I/O model is fundamentally incompatible with the POSIX
3202	model. Libev still offers limited functionality on this platform in	3927	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3928	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	3929	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	3930	e.g. cygwin.
3206		3931
		3932	Lifting these limitations would basically require the full
		3933	re-implementation of the I/O system. If you are into these kinds of
		3934	things, then note that glib does exactly that for you in a very portable
		3935	way (note also that glib is the slowest event library known to man).
		3936
3207	There is no supported compilation method available on windows except	3937	There is no supported compilation method available on windows except
3208	embedding it into other applications.	3938	embedding it into other applications.
3209		3939
		3940	Sensible signal handling is officially unsupported by Microsoft - libev
		3941	tries its best, but under most conditions, signals will simply not work.
		3942
		3943	Not a libev limitation but worth mentioning: windows apparently doesn't
		3944	accept large writes: instead of resulting in a partial write, windows will
		3945	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3946	so make sure you only write small amounts into your sockets (less than a
		3947	megabyte seems safe, but this apparently depends on the amount of memory
		3948	available).
		3949
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	3950	Due to the many, low, and arbitrary limits on the win32 platform and
3211	abysmal performance of winsockets, using a large number of sockets is not	3951	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	3952	is not recommended (and not reasonable). If your program needs to use
3213	a hundred or so sockets, then likely it needs to use a totally different	3953	more than a hundred or so sockets, then likely it needs to use a totally
3214	implementation for windows, as libev offers the POSIX model, which cannot	3954	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	3955	notification model, which cannot be implemented efficiently on windows
		3956	(due to Microsoft monopoly games).
		3957
		3958	A typical way to use libev under windows is to embed it (see the embedding
		3959	section for details) and use the following F<evwrap.h> header file instead
		3960	of F<ev.h>:
		3961
		3962	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3963	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3964
		3965	#include "ev.h"
		3966
		3967	And compile the following F<evwrap.c> file into your project (make sure
		3968	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3969
		3970	#include "evwrap.h"
		3971	#include "ev.c"
3216		3972
3217	=over 4	3973	=over 4
3218		3974
3219	=item The winsocket select function	3975	=item The winsocket select function
3220		3976
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	3977	The winsocket C<select> function doesn't follow POSIX in that it
3222	socket I<handles> and not socket I<file descriptors>. This makes select	3978	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	3979	also extremely buggy). This makes select very inefficient, and also
3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3980	requires a mapping from file descriptors to socket handles (the Microsoft
3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3981	C runtime provides the function C<_open_osfhandle> for this). See the
3226	symbols for more info.	3982	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3983	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		3984
3228	The configuration for a "naked" win32 using the microsoft runtime	3985	The configuration for a "naked" win32 using the Microsoft runtime
3229	libraries and raw winsocket select is:	3986	libraries and raw winsocket select is:
3230		3987
3231	#define EV_USE_SELECT 1	3988	#define EV_USE_SELECT 1
3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3989	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3233		3990
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	3991	Note that winsockets handling of fd sets is O(n), so you can easily get a
3235	complexity in the O(n²) range when using win32.	3992	complexity in the O(n²) range when using win32.
3236		3993
3237	=item Limited number of file descriptors	3994	=item Limited number of file descriptors
3238		3995
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	3996	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	3997
		3998	Early versions of winsocket's select only supported waiting for a maximum
3241	(probably owning to the fact that all windows kernels can only wait for	3999	of C<64> handles (probably owning to the fact that all windows kernels
3242	C<64> things at the same time internally; microsoft recommends spawning a	4000	can only wait for C<64> things at the same time internally; Microsoft
3243	chain of threads and wait for 63 handles and the previous thread in each).	4001	recommends spawning a chain of threads and wait for 63 handles and the
		4002	previous thread in each. Sounds great!).
3244		4003
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4004	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3246	to some high number (e.g. C<2048>) before compiling the winsocket select	4005	to some high number (e.g. C<2048>) before compiling the winsocket select
3247	call (which might be in libev or elsewhere, for example, perl does its own	4006	call (which might be in libev or elsewhere, for example, perl and many
3248	select emulation on windows).	4007	other interpreters do their own select emulation on windows).
3249		4008
3250	Another limit is the number of file descriptors in the microsoft runtime	4009	Another limit is the number of file descriptors in the Microsoft runtime
3251	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4010	libraries, which by default is C<64> (there must be a hidden I<64>
3252	or something like this inside microsoft). You can increase this by calling	4011	fetish or something like this inside Microsoft). You can increase this
3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4012	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3254	arbitrary limit), but is broken in many versions of the microsoft runtime	4013	(another arbitrary limit), but is broken in many versions of the Microsoft
3255	libraries.
3256
3257	This might get you to about C<512> or C<2048> sockets (depending on	4014	runtime libraries. This might get you to about C<512> or C<2048> sockets
3258	windows version and/or the phase of the moon). To get more, you need to	4015	(depending on windows version and/or the phase of the moon). To get more,
3259	wrap all I/O functions and provide your own fd management, but the cost of	4016	you need to wrap all I/O functions and provide your own fd management, but
3260	calling select (O(n²)) will likely make this unworkable.	4017	the cost of calling select (O(n²)) will likely make this unworkable.
3261		4018
3262	=back	4019	=back
3263		4020
3264
3265	=head1 PORTABILITY REQUIREMENTS	4021	=head2 PORTABILITY REQUIREMENTS
3266		4022
3267	In addition to a working ISO-C implementation, libev relies on a few	4023	In addition to a working ISO-C implementation and of course the
3268	additional extensions:	4024	backend-specific APIs, libev relies on a few additional extensions:
3269		4025
3270	=over 4	4026	=over 4
3271		4027
		4028	=item C<void ()(ev_watcher_type , int revents)> must have compatible
		4029	calling conventions regardless of C<ev_watcher_type *>.
		4030
		4031	Libev assumes not only that all watcher pointers have the same internal
		4032	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4033	assumes that the same (machine) code can be used to call any watcher
		4034	callback: The watcher callbacks have different type signatures, but libev
		4035	calls them using an C<ev_watcher *> internally.
		4036
3272	=item C<sig_atomic_t volatile> must be thread-atomic as well	4037	=item C<sig_atomic_t volatile> must be thread-atomic as well
3273		4038
3274	The type C<sig_atomic_t volatile> (or whatever is defined as	4039	The type C<sig_atomic_t volatile> (or whatever is defined as
3275	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4040	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3276	threads. This is not part of the specification for C<sig_atomic_t>, but is	4041	threads. This is not part of the specification for C<sig_atomic_t>, but is
3277	believed to be sufficiently portable.	4042	believed to be sufficiently portable.
3278		4043
3279	=item C<sigprocmask> must work in a threaded environment	4044	=item C<sigprocmask> must work in a threaded environment
3280		4045
…		…
3287		4052
3288	The most portable way to handle signals is to block signals in all threads	4053	The most portable way to handle signals is to block signals in all threads
3289	except the initial one, and run the default loop in the initial thread as	4054	except the initial one, and run the default loop in the initial thread as
3290	well.	4055	well.
3291		4056
		4057	=item C<long> must be large enough for common memory allocation sizes
		4058
		4059	To improve portability and simplify its API, libev uses C<long> internally
		4060	instead of C<size_t> when allocating its data structures. On non-POSIX
		4061	systems (Microsoft...) this might be unexpectedly low, but is still at
		4062	least 31 bits everywhere, which is enough for hundreds of millions of
		4063	watchers.
		4064
		4065	=item C<double> must hold a time value in seconds with enough accuracy
		4066
		4067	The type C<double> is used to represent timestamps. It is required to
		4068	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4069	enough for at least into the year 4000. This requirement is fulfilled by
		4070	implementations implementing IEEE 754 (basically all existing ones).
		4071
3292	=back	4072	=back
3293		4073
3294	If you know of other additional requirements drop me a note.	4074	If you know of other additional requirements drop me a note.
3295		4075
3296		4076
		4077	=head1 ALGORITHMIC COMPLEXITIES
		4078
		4079	In this section the complexities of (many of) the algorithms used inside
		4080	libev will be documented. For complexity discussions about backends see
		4081	the documentation for C<ev_default_init>.
		4082
		4083	All of the following are about amortised time: If an array needs to be
		4084	extended, libev needs to realloc and move the whole array, but this
		4085	happens asymptotically rarer with higher number of elements, so O(1) might
		4086	mean that libev does a lengthy realloc operation in rare cases, but on
		4087	average it is much faster and asymptotically approaches constant time.
		4088
		4089	=over 4
		4090
		4091	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4092
		4093	This means that, when you have a watcher that triggers in one hour and
		4094	there are 100 watchers that would trigger before that, then inserting will
		4095	have to skip roughly seven (C<ld 100>) of these watchers.
		4096
		4097	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4098
		4099	That means that changing a timer costs less than removing/adding them,
		4100	as only the relative motion in the event queue has to be paid for.
		4101
		4102	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4103
		4104	These just add the watcher into an array or at the head of a list.
		4105
		4106	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4107
		4108	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4109
		4110	These watchers are stored in lists, so they need to be walked to find the
		4111	correct watcher to remove. The lists are usually short (you don't usually
		4112	have many watchers waiting for the same fd or signal: one is typical, two
		4113	is rare).
		4114
		4115	=item Finding the next timer in each loop iteration: O(1)
		4116
		4117	By virtue of using a binary or 4-heap, the next timer is always found at a
		4118	fixed position in the storage array.
		4119
		4120	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4121
		4122	A change means an I/O watcher gets started or stopped, which requires
		4123	libev to recalculate its status (and possibly tell the kernel, depending
		4124	on backend and whether C<ev_io_set> was used).
		4125
		4126	=item Activating one watcher (putting it into the pending state): O(1)
		4127
		4128	=item Priority handling: O(number_of_priorities)
		4129
		4130	Priorities are implemented by allocating some space for each
		4131	priority. When doing priority-based operations, libev usually has to
		4132	linearly search all the priorities, but starting/stopping and activating
		4133	watchers becomes O(1) with respect to priority handling.
		4134
		4135	=item Sending an ev_async: O(1)
		4136
		4137	=item Processing ev_async_send: O(number_of_async_watchers)
		4138
		4139	=item Processing signals: O(max_signal_number)
		4140
		4141	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4142	calls in the current loop iteration. Checking for async and signal events
		4143	involves iterating over all running async watchers or all signal numbers.
		4144
		4145	=back
		4146
		4147
		4148	=head1 GLOSSARY
		4149
		4150	=over 4
		4151
		4152	=item active
		4153
		4154	A watcher is active as long as it has been started (has been attached to
		4155	an event loop) but not yet stopped (disassociated from the event loop).
		4156
		4157	=item application
		4158
		4159	In this document, an application is whatever is using libev.
		4160
		4161	=item callback
		4162
		4163	The address of a function that is called when some event has been
		4164	detected. Callbacks are being passed the event loop, the watcher that
		4165	received the event, and the actual event bitset.
		4166
		4167	=item callback invocation
		4168
		4169	The act of calling the callback associated with a watcher.
		4170
		4171	=item event
		4172
		4173	A change of state of some external event, such as data now being available
		4174	for reading on a file descriptor, time having passed or simply not having
		4175	any other events happening anymore.
		4176
		4177	In libev, events are represented as single bits (such as C<EV_READ> or
		4178	C<EV_TIMEOUT>).
		4179
		4180	=item event library
		4181
		4182	A software package implementing an event model and loop.
		4183
		4184	=item event loop
		4185
		4186	An entity that handles and processes external events and converts them
		4187	into callback invocations.
		4188
		4189	=item event model
		4190
		4191	The model used to describe how an event loop handles and processes
		4192	watchers and events.
		4193
		4194	=item pending
		4195
		4196	A watcher is pending as soon as the corresponding event has been detected,
		4197	and stops being pending as soon as the watcher will be invoked or its
		4198	pending status is explicitly cleared by the application.
		4199
		4200	A watcher can be pending, but not active. Stopping a watcher also clears
		4201	its pending status.
		4202
		4203	=item real time
		4204
		4205	The physical time that is observed. It is apparently strictly monotonic :)
		4206
		4207	=item wall-clock time
		4208
		4209	The time and date as shown on clocks. Unlike real time, it can actually
		4210	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4211	clock.
		4212
		4213	=item watcher
		4214
		4215	A data structure that describes interest in certain events. Watchers need
		4216	to be started (attached to an event loop) before they can receive events.
		4217
		4218	=item watcher invocation
		4219
		4220	The act of calling the callback associated with a watcher.
		4221
		4222	=back
		4223
3297	=head1 AUTHOR	4224	=head1 AUTHOR
3298		4225
3299	Marc Lehmann <libev@schmorp.de>.	4226	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3300		4227

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Revision 1.242 by root, Thu Jun 18 18:16:54 2009 UTC