[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 1.236 by root, Thu Apr 16 07:56:05 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 the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	129	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	131	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	132	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 "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>).
1035		1338
1036	Another thing you have to watch out for is that it is quite easy to	1339	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	1340	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	1341	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	1342	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	1343	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	1344	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	1345	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.	1346	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1347
1045	If you cannot run the fd in non-blocking mode (for example you should not	1348	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	1349	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	1350	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	1351	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1352	does this on its own, so its quite safe to use). Some people additionally
		1353	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1354	indefinitely.
		1355
		1356	But really, best use non-blocking mode.
1050		1357
1051	=head3 The special problem of disappearing file descriptors	1358	=head3 The special problem of disappearing file descriptors
1052		1359
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1360	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,	1361	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	1362	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	1363	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	1364	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	1365	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1366	fact, a different file descriptor.
1060		1367
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1398	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1399	C<EVBACKEND_POLL>.
1093		1400
1094	=head3 The special problem of SIGPIPE	1401	=head3 The special problem of SIGPIPE
1095		1402
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1403	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	1404	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	1405	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1406	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1407
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1408	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	1409	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).	1410	somewhere, as that would have given you a big clue).
1105		1411
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1417	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1418
1113	=item ev_io_set (ev_io *, int fd, int events)	1419	=item ev_io_set (ev_io *, int fd, int events)
1114		1420
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1421	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	1422	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.	1423	C<EV_READ \| EV_WRITE>, to express the desire to receive the given events.
1118		1424
1119	=item int fd [read-only]	1425	=item int fd [read-only]
1120		1426
1121	The file descriptor being watched.	1427	The file descriptor being watched.
1122		1428
…		…
1130		1436
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1437	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	1438	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1439	attempt to read a whole line in the callback.
1134		1440
1135	static void	1441	static void
1136	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1442	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1137	{	1443	{
1138	ev_io_stop (loop, w);	1444	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1445	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1446	}
1141		1447
1142	...	1448	...
1143	struct ev_loop *loop = ev_default_init (0);	1449	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1450	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1451	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1452	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1453	ev_loop (loop, 0);
1148		1454
1149		1455
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1456	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1457
1152	Timer watchers are simple relative timers that generate an event after a	1458	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1459	given time, and optionally repeating in regular intervals after that.
1154		1460
1155	The timers are based on real time, that is, if you register an event that	1461	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	1462	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	1463	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1464	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1465	monotonic clock option helps a lot here).
		1466
		1467	The callback is guaranteed to be invoked only I<after> its timeout has
		1468	passed. If multiple timers become ready during the same loop iteration
		1469	then the ones with earlier time-out values are invoked before ones with
		1470	later time-out values (but this is no longer true when a callback calls
		1471	C<ev_loop> recursively).
		1472
		1473	=head3 Be smart about timeouts
		1474
		1475	Many real-world problems involve some kind of timeout, usually for error
		1476	recovery. A typical example is an HTTP request - if the other side hangs,
		1477	you want to raise some error after a while.
		1478
		1479	What follows are some ways to handle this problem, from obvious and
		1480	inefficient to smart and efficient.
		1481
		1482	In the following, a 60 second activity timeout is assumed - a timeout that
		1483	gets reset to 60 seconds each time there is activity (e.g. each time some
		1484	data or other life sign was received).
		1485
		1486	=over 4
		1487
		1488	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1489
		1490	This is the most obvious, but not the most simple way: In the beginning,
		1491	start the watcher:
		1492
		1493	ev_timer_init (timer, callback, 60., 0.);
		1494	ev_timer_start (loop, timer);
		1495
		1496	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1497	and start it again:
		1498
		1499	ev_timer_stop (loop, timer);
		1500	ev_timer_set (timer, 60., 0.);
		1501	ev_timer_start (loop, timer);
		1502
		1503	This is relatively simple to implement, but means that each time there is
		1504	some activity, libev will first have to remove the timer from its internal
		1505	data structure and then add it again. Libev tries to be fast, but it's
		1506	still not a constant-time operation.
		1507
		1508	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1509
		1510	This is the easiest way, and involves using C<ev_timer_again> instead of
		1511	C<ev_timer_start>.
		1512
		1513	To implement this, configure an C<ev_timer> with a C<repeat> value
		1514	of C<60> and then call C<ev_timer_again> at start and each time you
		1515	successfully read or write some data. If you go into an idle state where
		1516	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1517	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1518
		1519	That means you can ignore both the C<ev_timer_start> function and the
		1520	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1521	member and C<ev_timer_again>.
		1522
		1523	At start:
		1524
		1525	ev_timer_init (timer, callback);
		1526	timer->repeat = 60.;
		1527	ev_timer_again (loop, timer);
		1528
		1529	Each time there is some activity:
		1530
		1531	ev_timer_again (loop, timer);
		1532
		1533	It is even possible to change the time-out on the fly, regardless of
		1534	whether the watcher is active or not:
		1535
		1536	timer->repeat = 30.;
		1537	ev_timer_again (loop, timer);
		1538
		1539	This is slightly more efficient then stopping/starting the timer each time
		1540	you want to modify its timeout value, as libev does not have to completely
		1541	remove and re-insert the timer from/into its internal data structure.
		1542
		1543	It is, however, even simpler than the "obvious" way to do it.
		1544
		1545	=item 3. Let the timer time out, but then re-arm it as required.
		1546
		1547	This method is more tricky, but usually most efficient: Most timeouts are
		1548	relatively long compared to the intervals between other activity - in
		1549	our example, within 60 seconds, there are usually many I/O events with
		1550	associated activity resets.
		1551
		1552	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1553	but remember the time of last activity, and check for a real timeout only
		1554	within the callback:
		1555
		1556	ev_tstamp last_activity; // time of last activity
		1557
		1558	static void
		1559	callback (EV_P_ ev_timer *w, int revents)
		1560	{
		1561	ev_tstamp now = ev_now (EV_A);
		1562	ev_tstamp timeout = last_activity + 60.;
		1563
		1564	// if last_activity + 60. is older than now, we did time out
		1565	if (timeout < now)
		1566	{
		1567	// timeout occured, take action
		1568	}
		1569	else
		1570	{
		1571	// callback was invoked, but there was some activity, re-arm
		1572	// the watcher to fire in last_activity + 60, which is
		1573	// guaranteed to be in the future, so "again" is positive:
		1574	w->repeat = timeout - now;
		1575	ev_timer_again (EV_A_ w);
		1576	}
		1577	}
		1578
		1579	To summarise the callback: first calculate the real timeout (defined
		1580	as "60 seconds after the last activity"), then check if that time has
		1581	been reached, which means something I<did>, in fact, time out. Otherwise
		1582	the callback was invoked too early (C<timeout> is in the future), so
		1583	re-schedule the timer to fire at that future time, to see if maybe we have
		1584	a timeout then.
		1585
		1586	Note how C<ev_timer_again> is used, taking advantage of the
		1587	C<ev_timer_again> optimisation when the timer is already running.
		1588
		1589	This scheme causes more callback invocations (about one every 60 seconds
		1590	minus half the average time between activity), but virtually no calls to
		1591	libev to change the timeout.
		1592
		1593	To start the timer, simply initialise the watcher and set C<last_activity>
		1594	to the current time (meaning we just have some activity :), then call the
		1595	callback, which will "do the right thing" and start the timer:
		1596
		1597	ev_timer_init (timer, callback);
		1598	last_activity = ev_now (loop);
		1599	callback (loop, timer, EV_TIMEOUT);
		1600
		1601	And when there is some activity, simply store the current time in
		1602	C<last_activity>, no libev calls at all:
		1603
		1604	last_actiivty = ev_now (loop);
		1605
		1606	This technique is slightly more complex, but in most cases where the
		1607	time-out is unlikely to be triggered, much more efficient.
		1608
		1609	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1610	callback :) - just change the timeout and invoke the callback, which will
		1611	fix things for you.
		1612
		1613	=item 4. Wee, just use a double-linked list for your timeouts.
		1614
		1615	If there is not one request, but many thousands (millions...), all
		1616	employing some kind of timeout with the same timeout value, then one can
		1617	do even better:
		1618
		1619	When starting the timeout, calculate the timeout value and put the timeout
		1620	at the I<end> of the list.
		1621
		1622	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1623	the list is expected to fire (for example, using the technique #3).
		1624
		1625	When there is some activity, remove the timer from the list, recalculate
		1626	the timeout, append it to the end of the list again, and make sure to
		1627	update the C<ev_timer> if it was taken from the beginning of the list.
		1628
		1629	This way, one can manage an unlimited number of timeouts in O(1) time for
		1630	starting, stopping and updating the timers, at the expense of a major
		1631	complication, and having to use a constant timeout. The constant timeout
		1632	ensures that the list stays sorted.
		1633
		1634	=back
		1635
		1636	So which method the best?
		1637
		1638	Method #2 is a simple no-brain-required solution that is adequate in most
		1639	situations. Method #3 requires a bit more thinking, but handles many cases
		1640	better, and isn't very complicated either. In most case, choosing either
		1641	one is fine, with #3 being better in typical situations.
		1642
		1643	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1644	rather complicated, but extremely efficient, something that really pays
		1645	off after the first million or so of active timers, i.e. it's usually
		1646	overkill :)
		1647
		1648	=head3 The special problem of time updates
		1649
		1650	Establishing the current time is a costly operation (it usually takes at
		1651	least two system calls): EV therefore updates its idea of the current
		1652	time only before and after C<ev_loop> collects new events, which causes a
		1653	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1654	lots of events in one iteration.
1160		1655
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1656	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	1657	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	1658	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	1659	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:	1660	timeout on the current time, use something like this to adjust for this:
1166		1661
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1662	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1663
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1664	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	1665	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1666	()>.
1172		1667
1173	=head3 Watcher-Specific Functions and Data Members	1668	=head3 Watcher-Specific Functions and Data Members
1174		1669
1175	=over 4	1670	=over 4
1176		1671
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1672	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1673
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1674	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1675
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1676	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	1677	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	1678	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1679	configured to trigger again C<repeat> seconds later, again, and again,
		1680	until stopped manually.
1185		1681
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1682	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	1683	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	1684	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	1685	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.	1686	do stuff) the timer will not fire more than once per event loop iteration.
1191		1687
1192	=item ev_timer_again (loop, ev_timer *)	1688	=item ev_timer_again (loop, ev_timer *)
1193		1689
1194	This will act as if the timer timed out and restart it again if it is	1690	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1691	repeating. The exact semantics are:
1196		1692
1197	If the timer is pending, its pending status is cleared.	1693	If the timer is pending, its pending status is cleared.
1198		1694
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1695	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1696
1201	If the timer is repeating, either start it if necessary (with the	1697	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.	1698	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1699
1204	This sounds a bit complicated, but here is a useful and typical	1700	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	1701	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		1702
1229	=item ev_tstamp repeat [read-write]	1703	=item ev_tstamp repeat [read-write]
1230		1704
1231	The current C<repeat> value. Will be used each time the watcher times out	1705	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),	1706	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.	1707	which is also when any modifications are taken into account.
1234		1708
1235	=back	1709	=back
1236		1710
1237	=head3 Examples	1711	=head3 Examples
1238		1712
1239	Example: Create a timer that fires after 60 seconds.	1713	Example: Create a timer that fires after 60 seconds.
1240		1714
1241	static void	1715	static void
1242	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1716	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1243	{	1717	{
1244	.. one minute over, w is actually stopped right here	1718	.. one minute over, w is actually stopped right here
1245	}	1719	}
1246		1720
1247	struct ev_timer mytimer;	1721	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1722	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1723	ev_timer_start (loop, &mytimer);
1250		1724
1251	Example: Create a timeout timer that times out after 10 seconds of	1725	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1726	inactivity.
1253		1727
1254	static void	1728	static void
1255	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1729	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1256	{	1730	{
1257	.. ten seconds without any activity	1731	.. ten seconds without any activity
1258	}	1732	}
1259		1733
1260	struct ev_timer mytimer;	1734	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1735	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1736	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1737	ev_loop (loop, 0);
1264		1738
1265	// and in some piece of code that gets executed on any "activity":	1739	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1740	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1741	ev_timer_again (&mytimer);
1268		1742
1269		1743
1270	=head2 C<ev_periodic> - to cron or not to cron?	1744	=head2 C<ev_periodic> - to cron or not to cron?
1271		1745
1272	Periodic watchers are also timers of a kind, but they are very versatile	1746	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1747	(and unfortunately a bit complex).
1274		1748
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1749	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	1750	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	1751	(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 ()	1752	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	1753	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	1754	wrist-watch).
1281	roughly 10 seconds later).
1282		1755
1283	They can also be used to implement vastly more complex timers, such as	1756	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	1757	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	1758	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1759	not a delay) and then reset your system clock to January of the previous
		1760	year, then it will take a year or more to trigger the event (unlike an
		1761	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1762	it, as it uses a relative timeout).
1286		1763
		1764	C<ev_periodic> watchers can also be used to implement vastly more complex
		1765	timers, such as triggering an event on each "midnight, local time", or
		1766	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1767	those cannot react to time jumps.
		1768
1287	As with timers, the callback is guarenteed to be invoked only when the	1769	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	1770	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.	1771	timers become ready during the same loop iteration then the ones with
		1772	earlier time-out values are invoked before ones with later time-out values
		1773	(but this is no longer true when a callback calls C<ev_loop> recursively).
1290		1774
1291	=head3 Watcher-Specific Functions and Data Members	1775	=head3 Watcher-Specific Functions and Data Members
1292		1776
1293	=over 4	1777	=over 4
1294		1778
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1779	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		1780
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1781	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1782
1299	Lots of arguments, lets sort it out... There are basically three modes of	1783	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:	1784	operation, and we will explain them from simplest to most complex:
1301		1785
1302	=over 4	1786	=over 4
1303		1787
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1788	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		1789
1306	In this configuration the watcher triggers an event at the wallclock time	1790	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,	1791	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	1792	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.	1793	will be stopped and invoked when the system clock reaches or surpasses
		1794	this point in time.
1310		1795
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1796	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		1797
1313	In this mode the watcher will always be scheduled to time out at the next	1798	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)	1799	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	1800	negative) and then repeat, regardless of any time jumps. The C<offset>
		1801	argument is merely an offset into the C<interval> periods.
1316		1802
1317	This can be used to create timers that do not drift with respect to system	1803	This can be used to create timers that do not drift with respect to the
1318	time:	1804	system clock, for example, here is an C<ev_periodic> that triggers each
		1805	hour, on the hour (with respect to UTC):
1319		1806
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1807	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1808
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1809	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	1810	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	1811	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1812	by 3600.
1326		1813
1327	Another way to think about it (for the mathematically inclined) is that	1814	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	1815	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.	1816	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		1817
1331	For numerical stability it is preferable that the C<at> value is near	1818	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	1819	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1820	this value, and in fact is often specified as zero.
1334		1821
		1822	Note also that there is an upper limit to how often a timer can fire (CPU
		1823	speed for example), so if C<interval> is very small then timing stability
		1824	will of course deteriorate. Libev itself tries to be exact to be about one
		1825	millisecond (if the OS supports it and the machine is fast enough).
		1826
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1827	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		1828
1337	In this mode the values for C<interval> and C<at> are both being	1829	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	1830	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1831	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1832	current time as second argument.
1341		1833
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1834	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,	1835	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	1836	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1837
		1838	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1839	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1840	only event loop modification you are allowed to do).
		1841
1347	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1842	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1843	*w, ev_tstamp now)>, e.g.:
1349		1844
		1845	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1846	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1847	{
1352	return now + 60.;	1848	return now + 60.;
1353	}	1849	}
1354		1850
1355	It must return the next time to trigger, based on the passed time value	1851	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	1852	(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	1853	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1854	might be called at other times, too.
1359		1855
1360	NOTE: I<< This callback must always return a time that is later than the	1856	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.	1857	equal to the passed C<now> value >>.
1362		1858
1363	This can be used to create very complex timers, such as a timer that	1859	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	1860	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	1861	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	1862	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).	1863	reason I omitted it as an example).
1368		1864
1369	=back	1865	=back
…		…
1373	Simply stops and restarts the periodic watcher again. This is only useful	1869	Simply stops and restarts the periodic watcher again. This is only useful
1374	when you changed some parameters or the reschedule callback would return	1870	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	1871	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	1872	program when the crontabs have changed).
1377		1873
		1874	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1875
		1876	When active, returns the absolute time that the watcher is supposed
		1877	to trigger next. This is not the same as the C<offset> argument to
		1878	C<ev_periodic_set>, but indeed works even in interval and manual
		1879	rescheduling modes.
		1880
1378	=item ev_tstamp offset [read-write]	1881	=item ev_tstamp offset [read-write]
1379		1882
1380	When repeating, this contains the offset value, otherwise this is the	1883	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>).	1884	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1885	although libev might modify this value for better numerical stability).
1382		1886
1383	Can be modified any time, but changes only take effect when the periodic	1887	Can be modified any time, but changes only take effect when the periodic
1384	timer fires or C<ev_periodic_again> is being called.	1888	timer fires or C<ev_periodic_again> is being called.
1385		1889
1386	=item ev_tstamp interval [read-write]	1890	=item ev_tstamp interval [read-write]
1387		1891
1388	The current interval value. Can be modified any time, but changes only	1892	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	1893	take effect when the periodic timer fires or C<ev_periodic_again> is being
1390	called.	1894	called.
1391		1895
1392	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1896	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1393		1897
1394	The current reschedule callback, or C<0>, if this functionality is	1898	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	1899	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.	1900	the periodic timer fires or C<ev_periodic_again> is being called.
1397		1901
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	1902	=back
1404		1903
1405	=head3 Examples	1904	=head3 Examples
1406		1905
1407	Example: Call a callback every hour, or, more precisely, whenever the	1906	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1907	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1908	potentially a lot of jitter, but good long-term stability.
1410		1909
1411	static void	1910	static void
1412	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1911	clock_cb (struct ev_loop loop, ev_io w, int revents)
1413	{	1912	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1913	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1914	}
1416		1915
1417	struct ev_periodic hourly_tick;	1916	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1917	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1918	ev_periodic_start (loop, &hourly_tick);
1420		1919
1421	Example: The same as above, but use a reschedule callback to do it:	1920	Example: The same as above, but use a reschedule callback to do it:
1422		1921
1423	#include <math.h>	1922	#include <math.h>
1424		1923
1425	static ev_tstamp	1924	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1925	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	1926	{
1428	return fmod (now, 3600.) + 3600.;	1927	return now + (3600. - fmod (now, 3600.));
1429	}	1928	}
1430		1929
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1930	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1931
1433	Example: Call a callback every hour, starting now:	1932	Example: Call a callback every hour, starting now:
1434		1933
1435	struct ev_periodic hourly_tick;	1934	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1935	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1936	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1937	ev_periodic_start (loop, &hourly_tick);
1439		1938
1440		1939
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1940	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1941
1443	Signal watchers will trigger an event when the process receives a specific	1942	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	1943	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	1944	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1945	normal event processing, like any other event.
1447		1946
		1947	If you want signals asynchronously, just use C<sigaction> as you would
		1948	do without libev and forget about sharing the signal. You can even use
		1949	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1950
1448	You can configure as many watchers as you like per signal. Only when the	1951	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	1952	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	1953	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	1954	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	1955	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1956	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1957
1455	If possible and supported, libev will install its handlers with	1958	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1959	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1960	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	1961	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1962	them in an C<ev_prepare> watcher.
1460		1963
1461	=head3 Watcher-Specific Functions and Data Members	1964	=head3 Watcher-Specific Functions and Data Members
1462		1965
…		…
1475		1978
1476	=back	1979	=back
1477		1980
1478	=head3 Examples	1981	=head3 Examples
1479		1982
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	1983	Example: Try to exit cleanly on SIGINT.
1481		1984
1482	static void	1985	static void
1483	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1986	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1484	{	1987	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	1988	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	1989	}
1487		1990
1488	struct ev_signal signal_watcher;	1991	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1992	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	1993	ev_signal_start (loop, &signal_watcher);
1491		1994
1492		1995
1493	=head2 C<ev_child> - watch out for process status changes	1996	=head2 C<ev_child> - watch out for process status changes
1494		1997
1495	Child watchers trigger when your process receives a SIGCHLD in response to	1998	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	1999	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	2000	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	2001	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2002	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2003	forking and then immediately registering a watcher for the child is fine,
		2004	but forking and registering a watcher a few event loop iterations later is
		2005	not.
1500		2006
1501	Only the default event loop is capable of handling signals, and therefore	2007	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2008	you can only register child watchers in the default event loop.
1503		2009
1504	=head3 Process Interaction	2010	=head3 Process Interaction
1505		2011
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2012	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2013	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	2014	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2015	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2016	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2017	children, even ones not watched.
1512		2018
1513	=head3 Overriding the Built-In Processing	2019	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2023	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2024	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2025	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	2026	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.	2027	that, so other libev users can use C<ev_child> watchers freely.
		2028
		2029	=head3 Stopping the Child Watcher
		2030
		2031	Currently, the child watcher never gets stopped, even when the
		2032	child terminates, so normally one needs to stop the watcher in the
		2033	callback. Future versions of libev might stop the watcher automatically
		2034	when a child exit is detected.
1522		2035
1523	=head3 Watcher-Specific Functions and Data Members	2036	=head3 Watcher-Specific Functions and Data Members
1524		2037
1525	=over 4	2038	=over 4
1526		2039
…		…
1555	=head3 Examples	2068	=head3 Examples
1556		2069
1557	Example: C<fork()> a new process and install a child handler to wait for	2070	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2071	its completion.
1559		2072
1560	ev_child cw;	2073	ev_child cw;
1561		2074
1562	static void	2075	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2076	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2077	{
1565	ev_child_stop (EV_A_ w);	2078	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2079	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2080	}
1568		2081
1569	pid_t pid = fork ();	2082	pid_t pid = fork ();
1570		2083
1571	if (pid < 0)	2084	if (pid < 0)
1572	// error	2085	// error
1573	else if (pid == 0)	2086	else if (pid == 0)
1574	{	2087	{
1575	// the forked child executes here	2088	// the forked child executes here
1576	exit (1);	2089	exit (1);
1577	}	2090	}
1578	else	2091	else
1579	{	2092	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2093	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2094	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2095	}
1583		2096
1584		2097
1585	=head2 C<ev_stat> - did the file attributes just change?	2098	=head2 C<ev_stat> - did the file attributes just change?
1586		2099
1587	This watches a filesystem path for attribute changes. That is, it calls	2100	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	2101	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.	2102	and sees if it changed compared to the last time, invoking the callback if
		2103	it did.
1590		2104
1591	The path does not need to exist: changing from "path exists" to "path does	2105	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	2106	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	2107	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	2108	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2109	least one) and all the other fields of the stat buffer having unspecified
		2110	contents.
1596		2111
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2112	The path I<must not> end in a slash or contain special components such as
		2113	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.	2114	your working directory changes, then the behaviour is undefined.
1599		2115
1600	Since there is no standard to do this, the portable implementation simply	2116	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	2117	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2118	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,	2119	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	2120	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2121	(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	2122	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2123	currently around C<0.1>, but that's usually overkill.
1608		2124
1609	This watcher type is not meant for massive numbers of stat watchers,	2125	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2126	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2127	resource-intensive.
1612		2128
1613	At the time of this writing, only the Linux inotify interface is	2129	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2130	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	2131	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	2132	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		2133
1621	=head3 ABI Issues (Largefile Support)	2134	=head3 ABI Issues (Largefile Support)
1622		2135
1623	Libev by default (unless the user overrides this) uses the default	2136	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	2137	compilation environment, which means that on systems with large file
1625	disabled large file support, you get the 32 bit version of the stat	2138	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	2139	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	2140	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	2141	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	2142	obviously the case with any flags that change the ABI, but the problem is
1630	most noticably with ev_stat and largefile support.	2143	most noticeably displayed with ev_stat and large file support.
1631		2144
1632	=head3 Inotify	2145	The solution for this is to lobby your distribution maker to make large
		2146	file interfaces available by default (as e.g. FreeBSD does) and not
		2147	optional. Libev cannot simply switch on large file support because it has
		2148	to exchange stat structures with application programs compiled using the
		2149	default compilation environment.
1633		2150
		2151	=head3 Inotify and Kqueue
		2152
1634	When C<inotify (7)> support has been compiled into libev (generally only	2153	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	2154	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	2155	inotify descriptor will be created lazily when the first C<ev_stat>
1637	when the first C<ev_stat> watcher is being started.	2156	watcher is being started.
1638		2157
1639	Inotify presence does not change the semantics of C<ev_stat> watchers	2158	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	2159	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	2160	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.	2161	there are many cases where libev has to resort to regular C<stat> polling,
		2162	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2163	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2164	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2165	xfs are fully working) libev usually gets away without polling.
1643		2166
1644	(There is no support for kqueue, as apparently it cannot be used to	2167	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	2168	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	2169	descriptor open on the object at all times, and detecting renames, unlinks
		2170	etc. is difficult.
		2171
		2172	=head3 C<stat ()> is a synchronous operation
		2173
		2174	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2175	the process. The exception are C<ev_stat> watchers - those call C<stat
		2176	()>, which is a synchronous operation.
		2177
		2178	For local paths, this usually doesn't matter: unless the system is very
		2179	busy or the intervals between stat's are large, a stat call will be fast,
		2180	as the path data is usually in memory already (except when starting the
		2181	watcher).
		2182
		2183	For networked file systems, calling C<stat ()> can block an indefinite
		2184	time due to network issues, and even under good conditions, a stat call
		2185	often takes multiple milliseconds.
		2186
		2187	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2188	paths, although this is fully supported by libev.
1647		2189
1648	=head3 The special problem of stat time resolution	2190	=head3 The special problem of stat time resolution
1649		2191
1650	The C<stat ()> syscall only supports full-second resolution portably, and	2192	The C<stat ()> system call only supports full-second resolution portably,
1651	even on systems where the resolution is higher, many filesystems still	2193	and even on systems where the resolution is higher, most file systems
1652	only support whole seconds.	2194	still only support whole seconds.
1653		2195
1654	That means that, if the time is the only thing that changes, you might	2196	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	2197	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	2198	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	2199	within the same second, C<ev_stat> will be unable to detect unless the
		2200	stat data does change in other ways (e.g. file size).
1658		2201
1659	The solution to this is to delay acting on a change for a second (or till	2202	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>	2203	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>	2204	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	2205	ev_timer_again (loop, w)>).
1663	systems.	2206
		2207	The C<.02> offset is added to work around small timing inconsistencies
		2208	of some operating systems (where the second counter of the current time
		2209	might be be delayed. One such system is the Linux kernel, where a call to
		2210	C<gettimeofday> might return a timestamp with a full second later than
		2211	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2212	update file times then there will be a small window where the kernel uses
		2213	the previous second to update file times but libev might already execute
		2214	the timer callback).
1664		2215
1665	=head3 Watcher-Specific Functions and Data Members	2216	=head3 Watcher-Specific Functions and Data Members
1666		2217
1667	=over 4	2218	=over 4
1668		2219
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	2225	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	2226	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	2227	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.	2228	path for as long as the watcher is active.
1678		2229
1679	The callback will be receive C<EV_STAT> when a change was detected,	2230	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	2231	relative to the attributes at the time the watcher was started (or the
1681	last change was detected).	2232	last change was detected).
1682		2233
1683	=item ev_stat_stat (loop, ev_stat *)	2234	=item ev_stat_stat (loop, ev_stat *)
1684		2235
1685	Updates the stat buffer immediately with new values. If you change the	2236	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	2237	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	2238	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	2239	the only one changing the path). Can also be useful simply to find out the
		2240	new values.
1689		2241
1690	=item ev_statdata attr [read-only]	2242	=item ev_statdata attr [read-only]
1691		2243
1692	The most-recently detected attributes of the file. Although the type is of	2244	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	2245	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	2246	suitable for your system, but you can only rely on the POSIX-standardised
		2247	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.	2248	some error while C<stat>ing the file.
1696		2249
1697	=item ev_statdata prev [read-only]	2250	=item ev_statdata prev [read-only]
1698		2251
1699	The previous attributes of the file. The callback gets invoked whenever	2252	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	2253	C<prev> != C<attr>, or, more precisely, one or more of these members
		2254	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2255	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		2256
1702	=item ev_tstamp interval [read-only]	2257	=item ev_tstamp interval [read-only]
1703		2258
1704	The specified interval.	2259	The specified interval.
1705		2260
1706	=item const char *path [read-only]	2261	=item const char *path [read-only]
1707		2262
1708	The filesystem path that is being watched.	2263	The file system path that is being watched.
1709		2264
1710	=back	2265	=back
1711		2266
1712	=head3 Examples	2267	=head3 Examples
1713		2268
1714	Example: Watch C</etc/passwd> for attribute changes.	2269	Example: Watch C</etc/passwd> for attribute changes.
1715		2270
1716	static void	2271	static void
1717	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	2272	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
1718	{	2273	{
1719	/* /etc/passwd changed in some way */	2274	/* /etc/passwd changed in some way */
1720	if (w->attr.st_nlink)	2275	if (w->attr.st_nlink)
1721	{	2276	{
1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2277	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2278	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2279	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1725	}	2280	}
1726	else	2281	else
1727	/* you shalt not abuse printf for puts */	2282	/* you shalt not abuse printf for puts */
1728	puts ("wow, /etc/passwd is not there, expect problems. "	2283	puts ("wow, /etc/passwd is not there, expect problems. "
1729	"if this is windows, they already arrived\n");	2284	"if this is windows, they already arrived\n");
1730	}	2285	}
1731		2286
1732	...	2287	...
1733	ev_stat passwd;	2288	ev_stat passwd;
1734		2289
1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2290	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2291	ev_stat_start (loop, &passwd);
1737		2292
1738	Example: Like above, but additionally use a one-second delay so we do not	2293	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	2294	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	2295	one might do the work both on C<ev_stat> callback invocation I<and> on
1741	C<ev_timer> callback invocation).	2296	C<ev_timer> callback invocation).
1742		2297
1743	static ev_stat passwd;	2298	static ev_stat passwd;
1744	static ev_timer timer;	2299	static ev_timer timer;
1745		2300
1746	static void	2301	static void
1747	timer_cb (EV_P_ ev_timer *w, int revents)	2302	timer_cb (EV_P_ ev_timer *w, int revents)
1748	{	2303	{
1749	ev_timer_stop (EV_A_ w);	2304	ev_timer_stop (EV_A_ w);
1750		2305
1751	/* now it's one second after the most recent passwd change */	2306	/* now it's one second after the most recent passwd change */
1752	}	2307	}
1753		2308
1754	static void	2309	static void
1755	stat_cb (EV_P_ ev_stat *w, int revents)	2310	stat_cb (EV_P_ ev_stat *w, int revents)
1756	{	2311	{
1757	/* reset the one-second timer */	2312	/* reset the one-second timer */
1758	ev_timer_again (EV_A_ &timer);	2313	ev_timer_again (EV_A_ &timer);
1759	}	2314	}
1760		2315
1761	...	2316	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2317	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	2318	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	2319	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		2320
1766		2321
1767	=head2 C<ev_idle> - when you've got nothing better to do...	2322	=head2 C<ev_idle> - when you've got nothing better to do...
1768		2323
1769	Idle watchers trigger events when no other events of the same or higher	2324	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	2325	priority are pending (prepare, check and other idle watchers do not count
1771	count).	2326	as receiving "events").
1772		2327
1773	That is, as long as your process is busy handling sockets or timeouts	2328	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	2329	(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	2330	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	2331	are pending), the idle watchers are being called once per event loop
…		…
1787		2342
1788	=head3 Watcher-Specific Functions and Data Members	2343	=head3 Watcher-Specific Functions and Data Members
1789		2344
1790	=over 4	2345	=over 4
1791		2346
1792	=item ev_idle_init (ev_signal *, callback)	2347	=item ev_idle_init (ev_idle *, callback)
1793		2348
1794	Initialises and configures the idle watcher - it has no parameters of any	2349	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,	2350	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1796	believe me.	2351	believe me.
1797		2352
…		…
1800	=head3 Examples	2355	=head3 Examples
1801		2356
1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2357	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1803	callback, free it. Also, use no error checking, as usual.	2358	callback, free it. Also, use no error checking, as usual.
1804		2359
1805	static void	2360	static void
1806	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2361	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1807	{	2362	{
1808	free (w);	2363	free (w);
1809	// now do something you wanted to do when the program has	2364	// now do something you wanted to do when the program has
1810	// no longer anything immediate to do.	2365	// no longer anything immediate to do.
1811	}	2366	}
1812		2367
1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2368	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1814	ev_idle_init (idle_watcher, idle_cb);	2369	ev_idle_init (idle_watcher, idle_cb);
1815	ev_idle_start (loop, idle_cb);	2370	ev_idle_start (loop, idle_cb);
1816		2371
1817		2372
1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2373	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1819		2374
1820	Prepare and check watchers are usually (but not always) used in tandem:	2375	Prepare and check watchers are usually (but not always) used in pairs:
1821	prepare watchers get invoked before the process blocks and check watchers	2376	prepare watchers get invoked before the process blocks and check watchers
1822	afterwards.	2377	afterwards.
1823		2378
1824	You I<must not> call C<ev_loop> or similar functions that enter	2379	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>	2380	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,	2383	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	2384	C<ev_check> so if you have one watcher of each kind they will always be
1830	called in pairs bracketing the blocking call.	2385	called in pairs bracketing the blocking call.
1831		2386
1832	Their main purpose is to integrate other event mechanisms into libev and	2387	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	2388	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	2389	variable changes, implement your own watchers, integrate net-snmp or a
1835	coroutine library and lots more. They are also occasionally useful if	2390	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,	2391	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>	2392	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1838	watcher).	2393	watcher).
1839		2394
1840	This is done by examining in each prepare call which file descriptors need	2395	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	2396	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	2397	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	2398	libraries provide exactly this functionality). Then, in the check watcher,
1844	any events that occured (by checking the pending status of all watchers	2399	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	2400	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,	2401	I/O and timer callbacks will never actually be called (but must be valid
1847	because you never know, you know?).	2402	nevertheless, because you never know, you know?).
1848		2403
1849	As another example, the Perl Coro module uses these hooks to integrate	2404	As another example, the Perl Coro module uses these hooks to integrate
1850	coroutines into libev programs, by yielding to other active coroutines	2405	coroutines into libev programs, by yielding to other active coroutines
1851	during each prepare and only letting the process block if no coroutines	2406	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	2407	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	2410	loop from blocking if lower-priority coroutines are active, thus mapping
1856	low-priority coroutines to idle/background tasks).	2411	low-priority coroutines to idle/background tasks).
1857		2412
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2413	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	2414	priority, to ensure that they are being run before any other watchers
		2415	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2416
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2417	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	2418	activate ("feed") events into libev. While libev fully supports this, they
1862	supports this, they will be called before other C<ev_check> watchers	2419	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	2420	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	2421	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	2422	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1866	coexist peacefully with others).	2423	others).
1867		2424
1868	=head3 Watcher-Specific Functions and Data Members	2425	=head3 Watcher-Specific Functions and Data Members
1869		2426
1870	=over 4	2427	=over 4
1871		2428
…		…
1873		2430
1874	=item ev_check_init (ev_check *, callback)	2431	=item ev_check_init (ev_check *, callback)
1875		2432
1876	Initialises and configures the prepare or check watcher - they have no	2433	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>	2434	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.	2435	macros, but using them is utterly, utterly, utterly and completely
		2436	pointless.
1879		2437
1880	=back	2438	=back
1881		2439
1882	=head3 Examples	2440	=head3 Examples
1883		2441
1884	There are a number of principal ways to embed other event loops or modules	2442	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	2443	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	2444	(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>	2445	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	2446	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	2447	Glib event loop).
1890		2448
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2449	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	2450	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	2451	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	2452	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.	2453	the callbacks for the IO/timeout watchers might not have been called yet.
1896		2454
1897	static ev_io iow [nfd];	2455	static ev_io iow [nfd];
1898	static ev_timer tw;	2456	static ev_timer tw;
1899		2457
1900	static void	2458	static void
1901	io_cb (ev_loop loop, ev_io w, int revents)	2459	io_cb (struct ev_loop loop, ev_io w, int revents)
1902	{	2460	{
1903	}	2461	}
1904		2462
1905	// create io watchers for each fd and a timer before blocking	2463	// create io watchers for each fd and a timer before blocking
1906	static void	2464	static void
1907	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2465	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
1908	{	2466	{
1909	int timeout = 3600000;	2467	int timeout = 3600000;
1910	struct pollfd fds [nfd];	2468	struct pollfd fds [nfd];
1911	// actual code will need to loop here and realloc etc.	2469	// actual code will need to loop here and realloc etc.
1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2470	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1913		2471
1914	/* the callback is illegal, but won't be called as we stop during check */	2472	/* the callback is illegal, but won't be called as we stop during check */
1915	ev_timer_init (&tw, 0, timeout * 1e-3);	2473	ev_timer_init (&tw, 0, timeout * 1e-3);
1916	ev_timer_start (loop, &tw);	2474	ev_timer_start (loop, &tw);
1917		2475
1918	// create one ev_io per pollfd	2476	// create one ev_io per pollfd
1919	for (int i = 0; i < nfd; ++i)	2477	for (int i = 0; i < nfd; ++i)
1920	{	2478	{
1921	ev_io_init (iow + i, io_cb, fds [i].fd,	2479	ev_io_init (iow + i, io_cb, fds [i].fd,
1922	((fds [i].events & POLLIN ? EV_READ : 0)	2480	((fds [i].events & POLLIN ? EV_READ : 0)
1923	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2481	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1924		2482
1925	fds [i].revents = 0;	2483	fds [i].revents = 0;
1926	ev_io_start (loop, iow + i);	2484	ev_io_start (loop, iow + i);
1927	}	2485	}
1928	}	2486	}
1929		2487
1930	// stop all watchers after blocking	2488	// stop all watchers after blocking
1931	static void	2489	static void
1932	adns_check_cb (ev_loop loop, ev_check w, int revents)	2490	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
1933	{	2491	{
1934	ev_timer_stop (loop, &tw);	2492	ev_timer_stop (loop, &tw);
1935		2493
1936	for (int i = 0; i < nfd; ++i)	2494	for (int i = 0; i < nfd; ++i)
1937	{	2495	{
1938	// set the relevant poll flags	2496	// set the relevant poll flags
1939	// could also call adns_processreadable etc. here	2497	// could also call adns_processreadable etc. here
1940	struct pollfd *fd = fds + i;	2498	struct pollfd *fd = fds + i;
1941	int revents = ev_clear_pending (iow + i);	2499	int revents = ev_clear_pending (iow + i);
1942	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;	2500	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1943	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;	2501	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1944		2502
1945	// now stop the watcher	2503	// now stop the watcher
1946	ev_io_stop (loop, iow + i);	2504	ev_io_stop (loop, iow + i);
1947	}	2505	}
1948		2506
1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2507	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1950	}	2508	}
1951		2509
1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2510	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.	2511	in the prepare watcher and would dispose of the check watcher.
1954		2512
1955	Method 3: If the module to be embedded supports explicit event	2513	Method 3: If the module to be embedded supports explicit event
1956	notification (adns does), you can also make use of the actual watcher	2514	notification (libadns does), you can also make use of the actual watcher
1957	callbacks, and only destroy/create the watchers in the prepare watcher.	2515	callbacks, and only destroy/create the watchers in the prepare watcher.
1958		2516
1959	static void	2517	static void
1960	timer_cb (EV_P_ ev_timer *w, int revents)	2518	timer_cb (EV_P_ ev_timer *w, int revents)
1961	{	2519	{
1962	adns_state ads = (adns_state)w->data;	2520	adns_state ads = (adns_state)w->data;
1963	update_now (EV_A);	2521	update_now (EV_A);
1964		2522
1965	adns_processtimeouts (ads, &tv_now);	2523	adns_processtimeouts (ads, &tv_now);
1966	}	2524	}
1967		2525
1968	static void	2526	static void
1969	io_cb (EV_P_ ev_io *w, int revents)	2527	io_cb (EV_P_ ev_io *w, int revents)
1970	{	2528	{
1971	adns_state ads = (adns_state)w->data;	2529	adns_state ads = (adns_state)w->data;
1972	update_now (EV_A);	2530	update_now (EV_A);
1973		2531
1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2532	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2533	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1976	}	2534	}
1977		2535
1978	// do not ever call adns_afterpoll	2536	// do not ever call adns_afterpoll
1979		2537
1980	Method 4: Do not use a prepare or check watcher because the module you	2538	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	2539	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	2540	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	2541	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1984	this.	2542	this approach, effectively embedding EV as a client into the horrible
		2543	libglib event loop.
1985		2544
1986	static gint	2545	static gint
1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2546	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1988	{	2547	{
1989	int got_events = 0;	2548	int got_events = 0;
1990		2549
1991	for (n = 0; n < nfds; ++n)	2550	for (n = 0; n < nfds; ++n)
1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2551	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1993		2552
1994	if (timeout >= 0)	2553	if (timeout >= 0)
1995	// create/start timer	2554	// create/start timer
1996		2555
1997	// poll	2556	// poll
1998	ev_loop (EV_A_ 0);	2557	ev_loop (EV_A_ 0);
1999		2558
2000	// stop timer again	2559	// stop timer again
2001	if (timeout >= 0)	2560	if (timeout >= 0)
2002	ev_timer_stop (EV_A_ &to);	2561	ev_timer_stop (EV_A_ &to);
2003		2562
2004	// stop io watchers again - their callbacks should have set	2563	// stop io watchers again - their callbacks should have set
2005	for (n = 0; n < nfds; ++n)	2564	for (n = 0; n < nfds; ++n)
2006	ev_io_stop (EV_A_ iow [n]);	2565	ev_io_stop (EV_A_ iow [n]);
2007		2566
2008	return got_events;	2567	return got_events;
2009	}	2568	}
2010		2569
2011		2570
2012	=head2 C<ev_embed> - when one backend isn't enough...	2571	=head2 C<ev_embed> - when one backend isn't enough...
2013		2572
2014	This is a rather advanced watcher type that lets you embed one event loop	2573	This is a rather advanced watcher type that lets you embed one event loop
…		…
2020	prioritise I/O.	2579	prioritise I/O.
2021		2580
2022	As an example for a bug workaround, the kqueue backend might only support	2581	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	2582	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	2583	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	2584	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	2585	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	2586	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.	2587	C<kevent>, but at least you can use both mechanisms for what they are
		2588	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2029		2589
2030	As for prioritising I/O: rarely you have the case where some fds have	2590	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	2591	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	2592	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	2593	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.	2594	the rest in a second one, and embed the second one in the first.
2035		2595
2036	As long as the watcher is active, the callback will be invoked every time	2596	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	2597	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	2598	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	2599	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	2600	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	2601	to give the embedded loop strictly lower priority for example).
2042	embedded loop sweep.
2043		2602
2044	As long as the watcher is started it will automatically handle events. The	2603	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	2604	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		2605
2049	Also, there have not currently been made special provisions for forking:	2606	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,	2607	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	2608	embedding loop forks. In other cases, the user is responsible for calling
2052	yourself.	2609	C<ev_loop_fork> on the embedded loop.
2053		2610
2054	Unfortunately, not all backends are embeddable, only the ones returned by	2611	Unfortunately, not all backends are embeddable: only the ones returned by
2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2612	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2056	portable one.	2613	portable one.
2057		2614
2058	So when you want to use this feature you will always have to be prepared	2615	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	2616	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	2617	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.	2618	create it, and if that fails, use the normal loop for everything.
2062		2619
		2620	=head3 C<ev_embed> and fork
		2621
		2622	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2623	automatically be applied to the embedded loop as well, so no special
		2624	fork handling is required in that case. When the watcher is not running,
		2625	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2626	as applicable.
		2627
2063	=head3 Watcher-Specific Functions and Data Members	2628	=head3 Watcher-Specific Functions and Data Members
2064		2629
2065	=over 4	2630	=over 4
2066		2631
2067	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2632	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
…		…
2070		2635
2071	Configures the watcher to embed the given loop, which must be	2636	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	2637	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	2638	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,	2639	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).	2640	if you do not want that, you need to temporarily stop the embed watcher).
2076		2641
2077	=item ev_embed_sweep (loop, ev_embed *)	2642	=item ev_embed_sweep (loop, ev_embed *)
2078		2643
2079	Make a single, non-blocking sweep over the embedded loop. This works	2644	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	2645	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2081	apropriate way for embedded loops.	2646	appropriate way for embedded loops.
2082		2647
2083	=item struct ev_loop *other [read-only]	2648	=item struct ev_loop *other [read-only]
2084		2649
2085	The embedded event loop.	2650	The embedded event loop.
2086		2651
…		…
2088		2653
2089	=head3 Examples	2654	=head3 Examples
2090		2655
2091	Example: Try to get an embeddable event loop and embed it into the default	2656	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	2657	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	2658	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	2659	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2095	used).	2660	used).
2096		2661
2097	struct ev_loop *loop_hi = ev_default_init (0);	2662	struct ev_loop *loop_hi = ev_default_init (0);
2098	struct ev_loop *loop_lo = 0;	2663	struct ev_loop *loop_lo = 0;
2099	struct ev_embed embed;	2664	ev_embed embed;
2100		2665
2101	// see if there is a chance of getting one that works	2666	// see if there is a chance of getting one that works
2102	// (remember that a flags value of 0 means autodetection)	2667	// (remember that a flags value of 0 means autodetection)
2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2668	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2669	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2105	: 0;	2670	: 0;
2106		2671
2107	// if we got one, then embed it, otherwise default to loop_hi	2672	// if we got one, then embed it, otherwise default to loop_hi
2108	if (loop_lo)	2673	if (loop_lo)
2109	{	2674	{
2110	ev_embed_init (&embed, 0, loop_lo);	2675	ev_embed_init (&embed, 0, loop_lo);
2111	ev_embed_start (loop_hi, &embed);	2676	ev_embed_start (loop_hi, &embed);
2112	}	2677	}
2113	else	2678	else
2114	loop_lo = loop_hi;	2679	loop_lo = loop_hi;
2115		2680
2116	Example: Check if kqueue is available but not recommended and create	2681	Example: Check if kqueue is available but not recommended and create
2117	a kqueue backend for use with sockets (which usually work with any	2682	a kqueue backend for use with sockets (which usually work with any
2118	kqueue implementation). Store the kqueue/socket-only event loop in	2683	kqueue implementation). Store the kqueue/socket-only event loop in
2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2684	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2120		2685
2121	struct ev_loop *loop = ev_default_init (0);	2686	struct ev_loop *loop = ev_default_init (0);
2122	struct ev_loop *loop_socket = 0;	2687	struct ev_loop *loop_socket = 0;
2123	struct ev_embed embed;	2688	ev_embed embed;
2124		2689
2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2690	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2691	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2127	{	2692	{
2128	ev_embed_init (&embed, 0, loop_socket);	2693	ev_embed_init (&embed, 0, loop_socket);
2129	ev_embed_start (loop, &embed);	2694	ev_embed_start (loop, &embed);
2130	}	2695	}
2131		2696
2132	if (!loop_socket)	2697	if (!loop_socket)
2133	loop_socket = loop;	2698	loop_socket = loop;
2134		2699
2135	// now use loop_socket for all sockets, and loop for everything else	2700	// now use loop_socket for all sockets, and loop for everything else
2136		2701
2137		2702
2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2703	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2139		2704
2140	Fork watchers are called when a C<fork ()> was detected (usually because	2705	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2184	is that the author does not know of a simple (or any) algorithm for a	2749	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	2750	multiple-writer-single-reader queue that works in all cases and doesn't
2186	need elaborate support such as pthreads.	2751	need elaborate support such as pthreads.
2187		2752
2188	That means that if you want to queue data, you have to provide your own	2753	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	2754	queue. But at least I can tell you how to implement locking around your
2190	queue:	2755	queue:
2191		2756
2192	=over 4	2757	=over 4
2193		2758
2194	=item queueing from a signal handler context	2759	=item queueing from a signal handler context
2195		2760
2196	To implement race-free queueing, you simply add to the queue in the signal	2761	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	2762	handler but you block the signal handler in the watcher callback. Here is
2198	some fictitiuous SIGUSR1 handler:	2763	an example that does that for some fictitious SIGUSR1 handler:
2199		2764
2200	static ev_async mysig;	2765	static ev_async mysig;
2201		2766
2202	static void	2767	static void
2203	sigusr1_handler (void)	2768	sigusr1_handler (void)
…		…
2269	=over 4	2834	=over 4
2270		2835
2271	=item ev_async_init (ev_async *, callback)	2836	=item ev_async_init (ev_async *, callback)
2272		2837
2273	Initialises and configures the async watcher - it has no parameters of any	2838	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,	2839	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2275	believe me.	2840	trust me.
2276		2841
2277	=item ev_async_send (loop, ev_async *)	2842	=item ev_async_send (loop, ev_async *)
2278		2843
2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2844	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	2845	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	2846	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	2847	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2283	section below on what exactly this means).	2848	section below on what exactly this means).
2284		2849
		2850	Note that, as with other watchers in libev, multiple events might get
		2851	compressed into a single callback invocation (another way to look at this
		2852	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2853	reset when the event loop detects that).
		2854
2285	This call incurs the overhead of a syscall only once per loop iteration,	2855	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	2856	iteration, so while the overhead might be noticeable, it doesn't apply to
2287	calls to C<ev_async_send>.	2857	repeated calls to C<ev_async_send> for the same event loop.
2288		2858
2289	=item bool = ev_async_pending (ev_async *)	2859	=item bool = ev_async_pending (ev_async *)
2290		2860
2291	Returns a non-zero value when C<ev_async_send> has been called on the	2861	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	2862	watcher but the event has not yet been processed (or even noted) by the
2293	event loop.	2863	event loop.
2294		2864
2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2865	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,	2866	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	2867	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.	2868	quickly check whether invoking the loop might be a good idea.
2299		2869
2300	Not that this does I<not> check wether the watcher itself is pending, only	2870	Not that this does I<not> check whether the watcher itself is pending,
2301	wether it has been requested to make this watcher pending.	2871	only whether it has been requested to make this watcher pending: there
		2872	is a time window between the event loop checking and resetting the async
		2873	notification, and the callback being invoked.
2302		2874
2303	=back	2875	=back
2304		2876
2305		2877
2306	=head1 OTHER FUNCTIONS	2878	=head1 OTHER FUNCTIONS
…		…
2310	=over 4	2882	=over 4
2311		2883
2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2884	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2313		2885
2314	This function combines a simple timer and an I/O watcher, calls your	2886	This function combines a simple timer and an I/O watcher, calls your
2315	callback on whichever event happens first and automatically stop both	2887	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	2888	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	2889	or timeout without having to allocate/configure/start/stop/free one or
2318	more watchers yourself.	2890	more watchers yourself.
2319		2891
2320	If C<fd> is less than 0, then no I/O watcher will be started and events	2892	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	2893	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2322	C<events> set will be craeted and started.	2894	the given C<fd> and C<events> set will be created and started.
2323		2895
2324	If C<timeout> is less than 0, then no timeout watcher will be	2896	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	2897	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	2898	repeat = 0) will be started. C<0> is a valid timeout.
2327	dubious value.
2328		2899
2329	The callback has the type C<void (cb)(int revents, void arg)> and gets	2900	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	2901	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>	2902	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2332	value passed to C<ev_once>:	2903	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2904	a timeout and an io event at the same time - you probably should give io
		2905	events precedence.
2333		2906
		2907	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2908
2334	static void stdin_ready (int revents, void *arg)	2909	static void stdin_ready (int revents, void *arg)
2335	{	2910	{
2336	if (revents & EV_TIMEOUT)
2337	/* doh, nothing entered */;
2338	else if (revents & EV_READ)	2911	if (revents & EV_READ)
2339	/* stdin might have data for us, joy! */;	2912	/* stdin might have data for us, joy! */;
		2913	else if (revents & EV_TIMEOUT)
		2914	/* doh, nothing entered */;
2340	}	2915	}
2341		2916
2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2917	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2343		2918
2344	=item ev_feed_event (ev_loop , watcher , int revents)	2919	=item ev_feed_event (struct ev_loop , watcher , int revents)
2345		2920
2346	Feeds the given event set into the event loop, as if the specified event	2921	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	2922	had happened for the specified watcher (which must be a pointer to an
2348	initialised but not necessarily started event watcher).	2923	initialised but not necessarily started event watcher).
2349		2924
2350	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2925	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2351		2926
2352	Feed an event on the given fd, as if a file descriptor backend detected	2927	Feed an event on the given fd, as if a file descriptor backend detected
2353	the given events it.	2928	the given events it.
2354		2929
2355	=item ev_feed_signal_event (ev_loop *loop, int signum)	2930	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2356		2931
2357	Feed an event as if the given signal occured (C<loop> must be the default	2932	Feed an event as if the given signal occurred (C<loop> must be the default
2358	loop!).	2933	loop!).
2359		2934
2360	=back	2935	=back
2361		2936
2362		2937
…		…
2391	=back	2966	=back
2392		2967
2393	=head1 C++ SUPPORT	2968	=head1 C++ SUPPORT
2394		2969
2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2970	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	2971	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.	2972	the callback model to a model using method callbacks on objects.
2398		2973
2399	To use it,	2974	To use it,
2400		2975
2401	#include <ev++.h>	2976	#include <ev++.h>
2402		2977
2403	This automatically includes F<ev.h> and puts all of its definitions (many	2978	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	2979	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	2980	put into the C<ev> namespace. It should support all the same embedding
2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2981	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2473	your compiler is good :), then the method will be fully inlined into the	3048	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.	3049	thunking function, making it as fast as a direct C callback.
2475		3050
2476	Example: simple class declaration and watcher initialisation	3051	Example: simple class declaration and watcher initialisation
2477		3052
2478	struct myclass	3053	struct myclass
2479	{	3054	{
2480	void io_cb (ev::io &w, int revents) { }	3055	void io_cb (ev::io &w, int revents) { }
2481	}	3056	}
2482		3057
2483	myclass obj;	3058	myclass obj;
2484	ev::io iow;	3059	ev::io iow;
2485	iow.set <myclass, &myclass::io_cb> (&obj);	3060	iow.set <myclass, &myclass::io_cb> (&obj);
		3061
		3062	=item w->set (object *)
		3063
		3064	This is an B<experimental> feature that might go away in a future version.
		3065
		3066	This is a variation of a method callback - leaving out the method to call
		3067	will default the method to C<operator ()>, which makes it possible to use
		3068	functor objects without having to manually specify the C<operator ()> all
		3069	the time. Incidentally, you can then also leave out the template argument
		3070	list.
		3071
		3072	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3073	int revents)>.
		3074
		3075	See the method-C<set> above for more details.
		3076
		3077	Example: use a functor object as callback.
		3078
		3079	struct myfunctor
		3080	{
		3081	void operator() (ev::io &w, int revents)
		3082	{
		3083	...
		3084	}
		3085	}
		3086
		3087	myfunctor f;
		3088
		3089	ev::io w;
		3090	w.set (&f);
2486		3091
2487	=item w->set<function> (void *data = 0)	3092	=item w->set<function> (void *data = 0)
2488		3093
2489	Also sets a callback, but uses a static method or plain function as	3094	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	3095	callback. The optional C<data> argument will be stored in the watcher's
…		…
2492		3097
2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3098	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2494		3099
2495	See the method-C<set> above for more details.	3100	See the method-C<set> above for more details.
2496		3101
2497	Example:	3102	Example: Use a plain function as callback.
2498		3103
2499	static void io_cb (ev::io &w, int revents) { }	3104	static void io_cb (ev::io &w, int revents) { }
2500	iow.set <io_cb> ();	3105	iow.set <io_cb> ();
2501		3106
2502	=item w->set (struct ev_loop *)	3107	=item w->set (struct ev_loop *)
2503		3108
2504	Associates a different C<struct ev_loop> with this watcher. You can only	3109	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).	3110	do this when the watcher is inactive (and not pending either).
2506		3111
2507	=item w->set ([args])	3112	=item w->set ([arguments])
2508		3113
2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3114	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	3115	called at least once. Unlike the C counterpart, an active watcher gets
2511	automatically stopped and restarted when reconfiguring it with this	3116	automatically stopped and restarted when reconfiguring it with this
2512	method.	3117	method.
2513		3118
2514	=item w->start ()	3119	=item w->start ()
…		…
2538	=back	3143	=back
2539		3144
2540	Example: Define a class with an IO and idle watcher, start one of them in	3145	Example: Define a class with an IO and idle watcher, start one of them in
2541	the constructor.	3146	the constructor.
2542		3147
2543	class myclass	3148	class myclass
2544	{	3149	{
2545	ev::io io; void io_cb (ev::io &w, int revents);	3150	ev::io io ; void io_cb (ev::io &w, int revents);
2546	ev:idle idle void idle_cb (ev::idle &w, int revents);	3151	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2547		3152
2548	myclass (int fd)	3153	myclass (int fd)
2549	{	3154	{
2550	io .set <myclass, &myclass::io_cb > (this);	3155	io .set <myclass, &myclass::io_cb > (this);
2551	idle.set <myclass, &myclass::idle_cb> (this);	3156	idle.set <myclass, &myclass::idle_cb> (this);
2552		3157
2553	io.start (fd, ev::READ);	3158	io.start (fd, ev::READ);
2554	}	3159	}
2555	};	3160	};
2556		3161
2557		3162
2558	=head1 OTHER LANGUAGE BINDINGS	3163	=head1 OTHER LANGUAGE BINDINGS
2559		3164
2560	Libev does not offer other language bindings itself, but bindings for a	3165	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	3166	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	3167	any interesting language binding in addition to the ones listed here, drop
2563	me a note.	3168	me a note.
2564		3169
2565	=over 4	3170	=over 4
2566		3171
2567	=item Perl	3172	=item Perl
2568		3173
2569	The EV module implements the full libev API and is actually used to test	3174	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,	3175	libev. EV is developed together with libev. Apart from the EV core module,
2571	there are additional modules that implement libev-compatible interfaces	3176	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	3177	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>).	3178	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3179	and C<EV::Glib>).
2574		3180
2575	It can be found and installed via CPAN, its homepage is found at	3181	It can be found and installed via CPAN, its homepage is at
2576	L<http://software.schmorp.de/pkg/EV>.	3182	L<http://software.schmorp.de/pkg/EV>.
2577		3183
		3184	=item Python
		3185
		3186	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3187	seems to be quite complete and well-documented.
		3188
2578	=item Ruby	3189	=item Ruby
2579		3190
2580	Tony Arcieri has written a ruby extension that offers access to a subset	3191	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	3192	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	3193	more on top of it. It can be found via gem servers. Its homepage is at
2583	L<http://rev.rubyforge.org/>.	3194	L<http://rev.rubyforge.org/>.
2584		3195
		3196	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3197	makes rev work even on mingw.
		3198
		3199	=item Haskell
		3200
		3201	A haskell binding to libev is available at
		3202	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3203
2585	=item D	3204	=item D
2586		3205
2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3206	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>.	3207	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3208
		3209	=item Ocaml
		3210
		3211	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3212	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2589		3213
2590	=back	3214	=back
2591		3215
2592		3216
2593	=head1 MACRO MAGIC	3217	=head1 MACRO MAGIC
2594		3218
2595	Libev can be compiled with a variety of options, the most fundamantal	3219	Libev can be compiled with a variety of options, the most fundamental
2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3220	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2597	functions and callbacks have an initial C<struct ev_loop *> argument.	3221	functions and callbacks have an initial C<struct ev_loop *> argument.
2598		3222
2599	To make it easier to write programs that cope with either variant, the	3223	To make it easier to write programs that cope with either variant, the
2600	following macros are defined:	3224	following macros are defined:
…		…
2605		3229
2606	This provides the loop I<argument> for functions, if one is required ("ev	3230	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,	3231	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:	3232	C<EV_A_> is used when other arguments are following. Example:
2609		3233
2610	ev_unref (EV_A);	3234	ev_unref (EV_A);
2611	ev_timer_add (EV_A_ watcher);	3235	ev_timer_add (EV_A_ watcher);
2612	ev_loop (EV_A_ 0);	3236	ev_loop (EV_A_ 0);
2613		3237
2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3238	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2615	which is often provided by the following macro.	3239	which is often provided by the following macro.
2616		3240
2617	=item C<EV_P>, C<EV_P_>	3241	=item C<EV_P>, C<EV_P_>
2618		3242
2619	This provides the loop I<parameter> for functions, if one is required ("ev	3243	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,	3244	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:	3245	C<EV_P_> is used when other parameters are following. Example:
2622		3246
2623	// this is how ev_unref is being declared	3247	// this is how ev_unref is being declared
2624	static void ev_unref (EV_P);	3248	static void ev_unref (EV_P);
2625		3249
2626	// this is how you can declare your typical callback	3250	// this is how you can declare your typical callback
2627	static void cb (EV_P_ ev_timer *w, int revents)	3251	static void cb (EV_P_ ev_timer *w, int revents)
2628		3252
2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3253	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2630	suitable for use with C<EV_A>.	3254	suitable for use with C<EV_A>.
2631		3255
2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3256	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2648		3272
2649	Example: Declare and initialise a check watcher, utilising the above	3273	Example: Declare and initialise a check watcher, utilising the above
2650	macros so it will work regardless of whether multiple loops are supported	3274	macros so it will work regardless of whether multiple loops are supported
2651	or not.	3275	or not.
2652		3276
2653	static void	3277	static void
2654	check_cb (EV_P_ ev_timer *w, int revents)	3278	check_cb (EV_P_ ev_timer *w, int revents)
2655	{	3279	{
2656	ev_check_stop (EV_A_ w);	3280	ev_check_stop (EV_A_ w);
2657	}	3281	}
2658		3282
2659	ev_check check;	3283	ev_check check;
2660	ev_check_init (&check, check_cb);	3284	ev_check_init (&check, check_cb);
2661	ev_check_start (EV_DEFAULT_ &check);	3285	ev_check_start (EV_DEFAULT_ &check);
2662	ev_loop (EV_DEFAULT_ 0);	3286	ev_loop (EV_DEFAULT_ 0);
2663		3287
2664	=head1 EMBEDDING	3288	=head1 EMBEDDING
2665		3289
2666	Libev can (and often is) directly embedded into host	3290	Libev can (and often is) directly embedded into host
2667	applications. Examples of applications that embed it include the Deliantra	3291	applications. Examples of applications that embed it include the Deliantra
…		…
2674	libev somewhere in your source tree).	3298	libev somewhere in your source tree).
2675		3299
2676	=head2 FILESETS	3300	=head2 FILESETS
2677		3301
2678	Depending on what features you need you need to include one or more sets of files	3302	Depending on what features you need you need to include one or more sets of files
2679	in your app.	3303	in your application.
2680		3304
2681	=head3 CORE EVENT LOOP	3305	=head3 CORE EVENT LOOP
2682		3306
2683	To include only the libev core (all the C<ev_*> functions), with manual	3307	To include only the libev core (all the C<ev_*> functions), with manual
2684	configuration (no autoconf):	3308	configuration (no autoconf):
2685		3309
2686	#define EV_STANDALONE 1	3310	#define EV_STANDALONE 1
2687	#include "ev.c"	3311	#include "ev.c"
2688		3312
2689	This will automatically include F<ev.h>, too, and should be done in a	3313	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	3314	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	3315	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	3316	done by writing a wrapper around F<ev.h> that you can include instead and
2693	where you can put other configuration options):	3317	where you can put other configuration options):
2694		3318
2695	#define EV_STANDALONE 1	3319	#define EV_STANDALONE 1
2696	#include "ev.h"	3320	#include "ev.h"
2697		3321
2698	Both header files and implementation files can be compiled with a C++	3322	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	3323	compiler (at least, that's a stated goal, and breakage will be treated
2700	as a bug).	3324	as a bug).
2701		3325
2702	You need the following files in your source tree, or in a directory	3326	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):	3327	in your include path (e.g. in libev/ when using -Ilibev):
2704		3328
2705	ev.h	3329	ev.h
2706	ev.c	3330	ev.c
2707	ev_vars.h	3331	ev_vars.h
2708	ev_wrap.h	3332	ev_wrap.h
2709		3333
2710	ev_win32.c required on win32 platforms only	3334	ev_win32.c required on win32 platforms only
2711		3335
2712	ev_select.c only when select backend is enabled (which is enabled by default)	3336	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)	3337	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)	3338	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)	3339	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)	3340	ev_port.c only when the solaris port backend is enabled (disabled by default)
2717		3341
2718	F<ev.c> includes the backend files directly when enabled, so you only need	3342	F<ev.c> includes the backend files directly when enabled, so you only need
2719	to compile this single file.	3343	to compile this single file.
2720		3344
2721	=head3 LIBEVENT COMPATIBILITY API	3345	=head3 LIBEVENT COMPATIBILITY API
2722		3346
2723	To include the libevent compatibility API, also include:	3347	To include the libevent compatibility API, also include:
2724		3348
2725	#include "event.c"	3349	#include "event.c"
2726		3350
2727	in the file including F<ev.c>, and:	3351	in the file including F<ev.c>, and:
2728		3352
2729	#include "event.h"	3353	#include "event.h"
2730		3354
2731	in the files that want to use the libevent API. This also includes F<ev.h>.	3355	in the files that want to use the libevent API. This also includes F<ev.h>.
2732		3356
2733	You need the following additional files for this:	3357	You need the following additional files for this:
2734		3358
2735	event.h	3359	event.h
2736	event.c	3360	event.c
2737		3361
2738	=head3 AUTOCONF SUPPORT	3362	=head3 AUTOCONF SUPPORT
2739		3363
2740	Instead of using C<EV_STANDALONE=1> and providing your config in	3364	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	3365	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	3366	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2743	include F<config.h> and configure itself accordingly.	3367	include F<config.h> and configure itself accordingly.
2744		3368
2745	For this of course you need the m4 file:	3369	For this of course you need the m4 file:
2746		3370
2747	libev.m4	3371	libev.m4
2748		3372
2749	=head2 PREPROCESSOR SYMBOLS/MACROS	3373	=head2 PREPROCESSOR SYMBOLS/MACROS
2750		3374
2751	Libev can be configured via a variety of preprocessor symbols you have to	3375	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	3376	define before including any of its files. The default in the absence of
2753	autoconf is noted for every option.	3377	autoconf is documented for every option.
2754		3378
2755	=over 4	3379	=over 4
2756		3380
2757	=item EV_STANDALONE	3381	=item EV_STANDALONE
2758		3382
…		…
2760	keeps libev from including F<config.h>, and it also defines dummy	3384	keeps libev from including F<config.h>, and it also defines dummy
2761	implementations for some libevent functions (such as logging, which is not	3385	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	3386	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.	3387	F<event.h> that are not directly supported by the libev core alone.
2764		3388
		3389	In stanbdalone mode, libev will still try to automatically deduce the
		3390	configuration, but has to be more conservative.
		3391
2765	=item EV_USE_MONOTONIC	3392	=item EV_USE_MONOTONIC
2766		3393
2767	If defined to be C<1>, libev will try to detect the availability of the	3394	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	3395	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	3396	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	3397	you usually have to link against librt or something similar. Enabling it
2771	the functionality isn't available is safe, though, although you have	3398	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>	3399	to make sure you link against any libraries where the C<clock_gettime>
2773	function is hiding in (often F<-lrt>).	3400	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2774		3401
2775	=item EV_USE_REALTIME	3402	=item EV_USE_REALTIME
2776		3403
2777	If defined to be C<1>, libev will try to detect the availability of the	3404	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	3405	real-time clock option at compile time (and assume its availability
2779	runtime if successful). Otherwise no use of the realtime clock option will	3406	at runtime if successful). Otherwise no use of the real-time clock
2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3407	option will be attempted. This effectively replaces C<gettimeofday>
2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3408	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3409	correctness. See the note about libraries in the description of
		3410	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3411	C<EV_USE_CLOCK_SYSCALL>.
		3412
		3413	=item EV_USE_CLOCK_SYSCALL
		3414
		3415	If defined to be C<1>, libev will try to use a direct syscall instead
		3416	of calling the system-provided C<clock_gettime> function. This option
		3417	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3418	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3419	programs needlessly. Using a direct syscall is slightly slower (in
		3420	theory), because no optimised vdso implementation can be used, but avoids
		3421	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3422	higher, as it simplifies linking (no need for C<-lrt>).
2783		3423
2784	=item EV_USE_NANOSLEEP	3424	=item EV_USE_NANOSLEEP
2785		3425
2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3426	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 ()>.	3427	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2795	2.7 or newer, otherwise disabled.	3435	2.7 or newer, otherwise disabled.
2796		3436
2797	=item EV_USE_SELECT	3437	=item EV_USE_SELECT
2798		3438
2799	If undefined or defined to be C<1>, libev will compile in support for the	3439	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	3440	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	3441	other method takes over, select will be it. Otherwise the select backend
2802	will not be compiled in.	3442	will not be compiled in.
2803		3443
2804	=item EV_SELECT_USE_FD_SET	3444	=item EV_SELECT_USE_FD_SET
2805		3445
2806	If defined to C<1>, then the select backend will use the system C<fd_set>	3446	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	3447	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	3448	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	3449	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	3450	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	3451	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2812	influence the size of the C<fd_set> used.	3452	configures the maximum size of the C<fd_set>.
2813		3453
2814	=item EV_SELECT_IS_WINSOCKET	3454	=item EV_SELECT_IS_WINSOCKET
2815		3455
2816	When defined to C<1>, the select backend will assume that	3456	When defined to C<1>, the select backend will assume that
2817	select/socket/connect etc. don't understand file descriptors but	3457	select/socket/connect etc. don't understand file descriptors but
…		…
2862	otherwise another method will be used as fallback. This is the preferred	3502	otherwise another method will be used as fallback. This is the preferred
2863	backend for Solaris 10 systems.	3503	backend for Solaris 10 systems.
2864		3504
2865	=item EV_USE_DEVPOLL	3505	=item EV_USE_DEVPOLL
2866		3506
2867	reserved for future expansion, works like the USE symbols above.	3507	Reserved for future expansion, works like the USE symbols above.
2868		3508
2869	=item EV_USE_INOTIFY	3509	=item EV_USE_INOTIFY
2870		3510
2871	If defined to be C<1>, libev will compile in support for the Linux inotify	3511	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	3512	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	3519	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	3520	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"	3521	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.	3522	as well as for signal and thread safety in C<ev_async> watchers.
2883		3523
2884	In the absense of this define, libev will use C<sig_atomic_t volatile>	3524	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.	3525	(from F<signal.h>), which is usually good enough on most platforms.
2886		3526
2887	=item EV_H	3527	=item EV_H
2888		3528
2889	The name of the F<ev.h> header file used to include it. The default if	3529	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	3568	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	3569	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	3570	and time, so using the defaults of five priorities (-2 .. +2) is usually
2931	fine.	3571	fine.
2932		3572
2933	If your embedding app does not need any priorities, defining these both to	3573	If your embedding application does not need any priorities, defining these
2934	C<0> will save some memory and cpu.	3574	both to C<0> will save some memory and CPU.
2935		3575
2936	=item EV_PERIODIC_ENABLE	3576	=item EV_PERIODIC_ENABLE
2937		3577
2938	If undefined or defined to be C<1>, then periodic timers are supported. If	3578	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	3579	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2946	code.	3586	code.
2947		3587
2948	=item EV_EMBED_ENABLE	3588	=item EV_EMBED_ENABLE
2949		3589
2950	If undefined or defined to be C<1>, then embed watchers are supported. If	3590	If undefined or defined to be C<1>, then embed watchers are supported. If
2951	defined to be C<0>, then they are not.	3591	defined to be C<0>, then they are not. Embed watchers rely on most other
		3592	watcher types, which therefore must not be disabled.
2952		3593
2953	=item EV_STAT_ENABLE	3594	=item EV_STAT_ENABLE
2954		3595
2955	If undefined or defined to be C<1>, then stat watchers are supported. If	3596	If undefined or defined to be C<1>, then stat watchers are supported. If
2956	defined to be C<0>, then they are not.	3597	defined to be C<0>, then they are not.
…		…
2966	defined to be C<0>, then they are not.	3607	defined to be C<0>, then they are not.
2967		3608
2968	=item EV_MINIMAL	3609	=item EV_MINIMAL
2969		3610
2970	If you need to shave off some kilobytes of code at the expense of some	3611	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	3612	speed, define this symbol to C<1>. Currently this is used to override some
2972	some inlining decisions, saves roughly 30% codesize of amd64.	3613	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3614	much smaller 2-heap for timer management over the default 4-heap.
2973		3615
2974	=item EV_PID_HASHSIZE	3616	=item EV_PID_HASHSIZE
2975		3617
2976	C<ev_child> watchers use a small hash table to distribute workload by	3618	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	3619	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>),	3626	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>	3627	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	3628	watchers you might want to increase this value (I<must> be a power of
2987	two).	3629	two).
2988		3630
		3631	=item EV_USE_4HEAP
		3632
		3633	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3634	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3635	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3636	faster performance with many (thousands) of watchers.
		3637
		3638	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3639	(disabled).
		3640
		3641	=item EV_HEAP_CACHE_AT
		3642
		3643	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3644	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3645	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3646	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3647	but avoids random read accesses on heap changes. This improves performance
		3648	noticeably with many (hundreds) of watchers.
		3649
		3650	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3651	(disabled).
		3652
		3653	=item EV_VERIFY
		3654
		3655	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3656	be done: If set to C<0>, no internal verification code will be compiled
		3657	in. If set to C<1>, then verification code will be compiled in, but not
		3658	called. If set to C<2>, then the internal verification code will be
		3659	called once per loop, which can slow down libev. If set to C<3>, then the
		3660	verification code will be called very frequently, which will slow down
		3661	libev considerably.
		3662
		3663	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3664	C<0>.
		3665
2989	=item EV_COMMON	3666	=item EV_COMMON
2990		3667
2991	By default, all watchers have a C<void *data> member. By redefining	3668	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	3669	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,	3670	members. You have to define it each time you include one of the files,
2994	though, and it must be identical each time.	3671	though, and it must be identical each time.
2995		3672
2996	For example, the perl EV module uses something like this:	3673	For example, the perl EV module uses something like this:
2997		3674
2998	#define EV_COMMON \	3675	#define EV_COMMON \
2999	SV self; / contains this struct */ \	3676	SV self; / contains this struct */ \
3000	SV cb_sv, fh /* note no trailing ";" */	3677	SV cb_sv, fh /* note no trailing ";" */
3001		3678
3002	=item EV_CB_DECLARE (type)	3679	=item EV_CB_DECLARE (type)
3003		3680
3004	=item EV_CB_INVOKE (watcher, revents)	3681	=item EV_CB_INVOKE (watcher, revents)
3005		3682
…		…
3010	definition and a statement, respectively. See the F<ev.h> header file for	3687	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	3688	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	3689	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++.	3690	method calls instead of plain function calls in C++.
3014		3691
		3692	=back
		3693
3015	=head2 EXPORTED API SYMBOLS	3694	=head2 EXPORTED API SYMBOLS
3016		3695
3017	If you need to re-export the API (e.g. via a dll) and you need a list of	3696	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	3697	exported symbols, you can use the provided F<Symbol.*> files which list
3019	all public symbols, one per line:	3698	all public symbols, one per line:
3020		3699
3021	Symbols.ev for libev proper	3700	Symbols.ev for libev proper
3022	Symbols.event for the libevent emulation	3701	Symbols.event for the libevent emulation
3023		3702
3024	This can also be used to rename all public symbols to avoid clashes with	3703	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	3704	multiple versions of libev linked together (which is obviously bad in
3026	itself, but sometimes it is inconvinient to avoid this).	3705	itself, but sometimes it is inconvenient to avoid this).
3027		3706
3028	A sed command like this will create wrapper C<#define>'s that you need to	3707	A sed command like this will create wrapper C<#define>'s that you need to
3029	include before including F<ev.h>:	3708	include before including F<ev.h>:
3030		3709
3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3710	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3048	file.	3727	file.
3049		3728
3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3729	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:	3730	that everybody includes and which overrides some configure choices:
3052		3731
3053	#define EV_MINIMAL 1	3732	#define EV_MINIMAL 1
3054	#define EV_USE_POLL 0	3733	#define EV_USE_POLL 0
3055	#define EV_MULTIPLICITY 0	3734	#define EV_MULTIPLICITY 0
3056	#define EV_PERIODIC_ENABLE 0	3735	#define EV_PERIODIC_ENABLE 0
3057	#define EV_STAT_ENABLE 0	3736	#define EV_STAT_ENABLE 0
3058	#define EV_FORK_ENABLE 0	3737	#define EV_FORK_ENABLE 0
3059	#define EV_CONFIG_H <config.h>	3738	#define EV_CONFIG_H <config.h>
3060	#define EV_MINPRI 0	3739	#define EV_MINPRI 0
3061	#define EV_MAXPRI 0	3740	#define EV_MAXPRI 0
3062		3741
3063	#include "ev++.h"	3742	#include "ev++.h"
3064		3743
3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3744	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3066		3745
3067	#include "ev_cpp.h"	3746	#include "ev_cpp.h"
3068	#include "ev.c"	3747	#include "ev.c"
3069		3748
		3749	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3070		3750
3071	=head1 THREADS AND COROUTINES	3751	=head2 THREADS AND COROUTINES
3072		3752
3073	=head2 THREADS	3753	=head3 THREADS
3074		3754
3075	Libev itself is completely threadsafe, but it uses no locking. This	3755	All libev functions are reentrant and thread-safe unless explicitly
		3756	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	3757	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	3758	are no concurrent calls into any libev function with the same loop
3078	parameter.	3759	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3760	of course): libev guarantees that different event loops share no data
		3761	structures that need any locking.
3079		3762
3080	Or put differently: calls with different loop parameters can be done in	3763	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	3764	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	3765	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	3766	only one thread ever is inside a call at any point in time, e.g. by using
3084	per loop).	3767	a mutex per loop).
3085		3768
3086	If you want to know which design is best for your problem, then I cannot	3769	Specifically to support threads (and signal handlers), libev implements
		3770	so-called C<ev_async> watchers, which allow some limited form of
		3771	concurrency on the same event loop, namely waking it up "from the
		3772	outside".
		3773
		3774	If you want to know which design (one loop, locking, or multiple loops
		3775	without or something else still) is best for your problem, then I cannot
3087	help you but by giving some generic advice:	3776	help you, but here is some generic advice:
3088		3777
3089	=over 4	3778	=over 4
3090		3779
3091	=item * most applications have a main thread: use the default libev loop	3780	=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.	3781	in that thread, or create a separate thread running only the default loop.
3093		3782
3094	This helps integrating other libraries or software modules that use libev	3783	This helps integrating other libraries or software modules that use libev
3095	themselves and don't care/know about threading.	3784	themselves and don't care/know about threading.
3096		3785
3097	=item * one loop per thread is usually a good model.	3786	=item * one loop per thread is usually a good model.
3098		3787
3099	Doing this is almost never wrong, sometimes a better-performance model	3788	Doing this is almost never wrong, sometimes a better-performance model
3100	exists, but it is always a good start.	3789	exists, but it is always a good start.
3101		3790
3102	=item * other models exist, such as the leader/follower pattern, where one	3791	=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.	3792	loop is handed through multiple threads in a kind of round-robin fashion.
3104		3793
3105	Chosing a model is hard - look around, learn, know that usually you cna do	3794	Choosing a model is hard - look around, learn, know that usually you can do
3106	better than you currently do :-)	3795	better than you currently do :-)
3107		3796
3108	=item * often you need to talk to some other thread which blocks in the	3797	=item * often you need to talk to some other thread which blocks in the
		3798	event loop.
		3799
3109	event loop - C<ev_async> watchers can be used to wake them up from other	3800	C<ev_async> watchers can be used to wake them up from other threads safely
3110	threads safely (or from signal contexts...).	3801	(or from signal contexts...).
		3802
		3803	An example use would be to communicate signals or other events that only
		3804	work in the default loop by registering the signal watcher with the
		3805	default loop and triggering an C<ev_async> watcher from the default loop
		3806	watcher callback into the event loop interested in the signal.
3111		3807
3112	=back	3808	=back
3113		3809
3114	=head2 COROUTINES	3810	=head3 COROUTINES
3115		3811
3116	Libev is much more accomodating to coroutines ("cooperative threads"):	3812	Libev is very accommodating to coroutines ("cooperative threads"):
3117	libev fully supports nesting calls to it's functions from different	3813	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	3814	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	3815	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	3816	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.	3817	you must not do this from C<ev_periodic> reschedule callbacks.
3122		3818
3123	Care has been invested into making sure that libev does not keep local	3819	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	3820	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3125	switches.	3821	they do not call any callbacks.
3126		3822
		3823	=head2 COMPILER WARNINGS
3127		3824
3128	=head1 COMPLEXITIES	3825	Depending on your compiler and compiler settings, you might get no or a
		3826	lot of warnings when compiling libev code. Some people are apparently
		3827	scared by this.
3129		3828
3130	In this section the complexities of (many of) the algorithms used inside	3829	However, these are unavoidable for many reasons. For one, each compiler
3131	libev will be explained. For complexity discussions about backends see the	3830	has different warnings, and each user has different tastes regarding
3132	documentation for C<ev_default_init>.	3831	warning options. "Warn-free" code therefore cannot be a goal except when
		3832	targeting a specific compiler and compiler-version.
3133		3833
3134	All of the following are about amortised time: If an array needs to be	3834	Another reason is that some compiler warnings require elaborate
3135	extended, libev needs to realloc and move the whole array, but this	3835	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	3836	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		3837
3140	=over 4	3838	And of course, some compiler warnings are just plain stupid, or simply
		3839	wrong (because they don't actually warn about the condition their message
		3840	seems to warn about). For example, certain older gcc versions had some
		3841	warnings that resulted an extreme number of false positives. These have
		3842	been fixed, but some people still insist on making code warn-free with
		3843	such buggy versions.
3141		3844
3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3845	While libev is written to generate as few warnings as possible,
		3846	"warn-free" code is not a goal, and it is recommended not to build libev
		3847	with any compiler warnings enabled unless you are prepared to cope with
		3848	them (e.g. by ignoring them). Remember that warnings are just that:
		3849	warnings, not errors, or proof of bugs.
3143		3850
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		3851
3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3852	=head2 VALGRIND
3149		3853
3150	That means that changing a timer costs less than removing/adding them	3854	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.	3855	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3152		3856
3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3857	If you think you found a bug (memory leak, uninitialised data access etc.)
		3858	in libev, then check twice: If valgrind reports something like:
3154		3859
3155	These just add the watcher into an array or at the head of a list.	3860	==2274== definitely lost: 0 bytes in 0 blocks.
		3861	==2274== possibly lost: 0 bytes in 0 blocks.
		3862	==2274== still reachable: 256 bytes in 1 blocks.
3156		3863
3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3864	Then there is no memory leak, just as memory accounted to global variables
		3865	is not a memleak - the memory is still being referenced, and didn't leak.
3158		3866
3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3867	Similarly, under some circumstances, valgrind might report kernel bugs
		3868	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3869	although an acceptable workaround has been found here), or it might be
		3870	confused.
3160		3871
3161	These watchers are stored in lists then need to be walked to find the	3872	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	3873	make it into some kind of religion.
3163	have many watchers waiting for the same fd or signal).
3164		3874
3165	=item Finding the next timer in each loop iteration: O(1)	3875	If you are unsure about something, feel free to contact the mailing list
		3876	with the full valgrind report and an explanation on why you think this
		3877	is a bug in libev (best check the archives, too :). However, don't be
		3878	annoyed when you get a brisk "this is no bug" answer and take the chance
		3879	of learning how to interpret valgrind properly.
3166		3880
3167	By virtue of using a binary heap, the next timer is always found at the	3881	If you need, for some reason, empty reports from valgrind for your project
3168	beginning of the storage array.	3882	I suggest using suppression lists.
3169		3883
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		3884
3172	A change means an I/O watcher gets started or stopped, which requires	3885	=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		3886
3176	=item Activating one watcher (putting it into the pending state): O(1)	3887	=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		3888
3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3889	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	3890	requires, and its I/O model is fundamentally incompatible with the POSIX
3202	model. Libev still offers limited functionality on this platform in	3891	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3892	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	3893	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	3894	e.g. cygwin.
3206		3895
		3896	Lifting these limitations would basically require the full
		3897	re-implementation of the I/O system. If you are into these kinds of
		3898	things, then note that glib does exactly that for you in a very portable
		3899	way (note also that glib is the slowest event library known to man).
		3900
3207	There is no supported compilation method available on windows except	3901	There is no supported compilation method available on windows except
3208	embedding it into other applications.	3902	embedding it into other applications.
3209		3903
		3904	Not a libev limitation but worth mentioning: windows apparently doesn't
		3905	accept large writes: instead of resulting in a partial write, windows will
		3906	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3907	so make sure you only write small amounts into your sockets (less than a
		3908	megabyte seems safe, but this apparently depends on the amount of memory
		3909	available).
		3910
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	3911	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	3912	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	3913	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	3914	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	3915	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	3916	notification model, which cannot be implemented efficiently on windows
		3917	(Microsoft monopoly games).
		3918
		3919	A typical way to use libev under windows is to embed it (see the embedding
		3920	section for details) and use the following F<evwrap.h> header file instead
		3921	of F<ev.h>:
		3922
		3923	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3924	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3925
		3926	#include "ev.h"
		3927
		3928	And compile the following F<evwrap.c> file into your project (make sure
		3929	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3930
		3931	#include "evwrap.h"
		3932	#include "ev.c"
3216		3933
3217	=over 4	3934	=over 4
3218		3935
3219	=item The winsocket select function	3936	=item The winsocket select function
3220		3937
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	3938	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	3939	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	3940	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>,	3941	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	3942	C runtime provides the function C<_open_osfhandle> for this). See the
3226	symbols for more info.	3943	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3944	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		3945
3228	The configuration for a "naked" win32 using the microsoft runtime	3946	The configuration for a "naked" win32 using the Microsoft runtime
3229	libraries and raw winsocket select is:	3947	libraries and raw winsocket select is:
3230		3948
3231	#define EV_USE_SELECT 1	3949	#define EV_USE_SELECT 1
3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3950	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3233		3951
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	3952	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.	3953	complexity in the O(n²) range when using win32.
3236		3954
3237	=item Limited number of file descriptors	3955	=item Limited number of file descriptors
3238		3956
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	3957	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	3958
		3959	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	3960	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	3961	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).	3962	recommends spawning a chain of threads and wait for 63 handles and the
		3963	previous thread in each. Great).
3244		3964
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3965	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	3966	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	3967	call (which might be in libev or elsewhere, for example, perl does its own
3248	select emulation on windows).	3968	select emulation on windows).
3249		3969
3250	Another limit is the number of file descriptors in the microsoft runtime	3970	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	3971	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3252	or something like this inside microsoft). You can increase this by calling	3972	or something like this inside Microsoft). You can increase this by calling
3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3973	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3254	arbitrary limit), but is broken in many versions of the microsoft runtime	3974	arbitrary limit), but is broken in many versions of the Microsoft runtime
3255	libraries.	3975	libraries.
3256		3976
3257	This might get you to about C<512> or C<2048> sockets (depending on	3977	This might get you to about C<512> or C<2048> sockets (depending on
3258	windows version and/or the phase of the moon). To get more, you need to	3978	windows version and/or the phase of the moon). To get more, you need to
3259	wrap all I/O functions and provide your own fd management, but the cost of	3979	wrap all I/O functions and provide your own fd management, but the cost of
3260	calling select (O(n²)) will likely make this unworkable.	3980	calling select (O(n²)) will likely make this unworkable.
3261		3981
3262	=back	3982	=back
3263		3983
3264
3265	=head1 PORTABILITY REQUIREMENTS	3984	=head2 PORTABILITY REQUIREMENTS
3266		3985
3267	In addition to a working ISO-C implementation, libev relies on a few	3986	In addition to a working ISO-C implementation and of course the
3268	additional extensions:	3987	backend-specific APIs, libev relies on a few additional extensions:
3269		3988
3270	=over 4	3989	=over 4
3271		3990
		3991	=item C<void ()(ev_watcher_type , int revents)> must have compatible
		3992	calling conventions regardless of C<ev_watcher_type *>.
		3993
		3994	Libev assumes not only that all watcher pointers have the same internal
		3995	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3996	assumes that the same (machine) code can be used to call any watcher
		3997	callback: The watcher callbacks have different type signatures, but libev
		3998	calls them using an C<ev_watcher *> internally.
		3999
3272	=item C<sig_atomic_t volatile> must be thread-atomic as well	4000	=item C<sig_atomic_t volatile> must be thread-atomic as well
3273		4001
3274	The type C<sig_atomic_t volatile> (or whatever is defined as	4002	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	4003	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	4004	threads. This is not part of the specification for C<sig_atomic_t>, but is
3277	believed to be sufficiently portable.	4005	believed to be sufficiently portable.
3278		4006
3279	=item C<sigprocmask> must work in a threaded environment	4007	=item C<sigprocmask> must work in a threaded environment
3280		4008
…		…
3287		4015
3288	The most portable way to handle signals is to block signals in all threads	4016	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	4017	except the initial one, and run the default loop in the initial thread as
3290	well.	4018	well.
3291		4019
		4020	=item C<long> must be large enough for common memory allocation sizes
		4021
		4022	To improve portability and simplify its API, libev uses C<long> internally
		4023	instead of C<size_t> when allocating its data structures. On non-POSIX
		4024	systems (Microsoft...) this might be unexpectedly low, but is still at
		4025	least 31 bits everywhere, which is enough for hundreds of millions of
		4026	watchers.
		4027
		4028	=item C<double> must hold a time value in seconds with enough accuracy
		4029
		4030	The type C<double> is used to represent timestamps. It is required to
		4031	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4032	enough for at least into the year 4000. This requirement is fulfilled by
		4033	implementations implementing IEEE 754 (basically all existing ones).
		4034
3292	=back	4035	=back
3293		4036
3294	If you know of other additional requirements drop me a note.	4037	If you know of other additional requirements drop me a note.
3295		4038
3296		4039
		4040	=head1 ALGORITHMIC COMPLEXITIES
		4041
		4042	In this section the complexities of (many of) the algorithms used inside
		4043	libev will be documented. For complexity discussions about backends see
		4044	the documentation for C<ev_default_init>.
		4045
		4046	All of the following are about amortised time: If an array needs to be
		4047	extended, libev needs to realloc and move the whole array, but this
		4048	happens asymptotically rarer with higher number of elements, so O(1) might
		4049	mean that libev does a lengthy realloc operation in rare cases, but on
		4050	average it is much faster and asymptotically approaches constant time.
		4051
		4052	=over 4
		4053
		4054	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4055
		4056	This means that, when you have a watcher that triggers in one hour and
		4057	there are 100 watchers that would trigger before that, then inserting will
		4058	have to skip roughly seven (C<ld 100>) of these watchers.
		4059
		4060	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4061
		4062	That means that changing a timer costs less than removing/adding them,
		4063	as only the relative motion in the event queue has to be paid for.
		4064
		4065	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4066
		4067	These just add the watcher into an array or at the head of a list.
		4068
		4069	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4070
		4071	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4072
		4073	These watchers are stored in lists, so they need to be walked to find the
		4074	correct watcher to remove. The lists are usually short (you don't usually
		4075	have many watchers waiting for the same fd or signal: one is typical, two
		4076	is rare).
		4077
		4078	=item Finding the next timer in each loop iteration: O(1)
		4079
		4080	By virtue of using a binary or 4-heap, the next timer is always found at a
		4081	fixed position in the storage array.
		4082
		4083	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4084
		4085	A change means an I/O watcher gets started or stopped, which requires
		4086	libev to recalculate its status (and possibly tell the kernel, depending
		4087	on backend and whether C<ev_io_set> was used).
		4088
		4089	=item Activating one watcher (putting it into the pending state): O(1)
		4090
		4091	=item Priority handling: O(number_of_priorities)
		4092
		4093	Priorities are implemented by allocating some space for each
		4094	priority. When doing priority-based operations, libev usually has to
		4095	linearly search all the priorities, but starting/stopping and activating
		4096	watchers becomes O(1) with respect to priority handling.
		4097
		4098	=item Sending an ev_async: O(1)
		4099
		4100	=item Processing ev_async_send: O(number_of_async_watchers)
		4101
		4102	=item Processing signals: O(max_signal_number)
		4103
		4104	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4105	calls in the current loop iteration. Checking for async and signal events
		4106	involves iterating over all running async watchers or all signal numbers.
		4107
		4108	=back
		4109
		4110
		4111	=head1 GLOSSARY
		4112
		4113	=over 4
		4114
		4115	=item active
		4116
		4117	A watcher is active as long as it has been started (has been attached to
		4118	an event loop) but not yet stopped (disassociated from the event loop).
		4119
		4120	=item application
		4121
		4122	In this document, an application is whatever is using libev.
		4123
		4124	=item callback
		4125
		4126	The address of a function that is called when some event has been
		4127	detected. Callbacks are being passed the event loop, the watcher that
		4128	received the event, and the actual event bitset.
		4129
		4130	=item callback invocation
		4131
		4132	The act of calling the callback associated with a watcher.
		4133
		4134	=item event
		4135
		4136	A change of state of some external event, such as data now being available
		4137	for reading on a file descriptor, time having passed or simply not having
		4138	any other events happening anymore.
		4139
		4140	In libev, events are represented as single bits (such as C<EV_READ> or
		4141	C<EV_TIMEOUT>).
		4142
		4143	=item event library
		4144
		4145	A software package implementing an event model and loop.
		4146
		4147	=item event loop
		4148
		4149	An entity that handles and processes external events and converts them
		4150	into callback invocations.
		4151
		4152	=item event model
		4153
		4154	The model used to describe how an event loop handles and processes
		4155	watchers and events.
		4156
		4157	=item pending
		4158
		4159	A watcher is pending as soon as the corresponding event has been detected,
		4160	and stops being pending as soon as the watcher will be invoked or its
		4161	pending status is explicitly cleared by the application.
		4162
		4163	A watcher can be pending, but not active. Stopping a watcher also clears
		4164	its pending status.
		4165
		4166	=item real time
		4167
		4168	The physical time that is observed. It is apparently strictly monotonic :)
		4169
		4170	=item wall-clock time
		4171
		4172	The time and date as shown on clocks. Unlike real time, it can actually
		4173	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4174	clock.
		4175
		4176	=item watcher
		4177
		4178	A data structure that describes interest in certain events. Watchers need
		4179	to be started (attached to an event loop) before they can receive events.
		4180
		4181	=item watcher invocation
		4182
		4183	The act of calling the callback associated with a watcher.
		4184
		4185	=back
		4186
3297	=head1 AUTHOR	4187	=head1 AUTHOR
3298		4188
3299	Marc Lehmann <libev@schmorp.de>.	4189	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3300		4190

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Comparing libev/ev.pod (file contents):
Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC vs.
Revision 1.236 by root, Thu Apr 16 07:56:05 2009 UTC