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Revision 1.157 by root, Tue May 20 23:49:41 2008 UTC vs.
Revision 1.210 by root, Thu Oct 30 08:09:30 2008 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	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	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	68	web page you might find easier to navigate when reading it for the first
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	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	107	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	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	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	116	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	117	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	118	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	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	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	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	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	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	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	203	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	204	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	205	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	206	(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.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	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	222	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	223	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	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	250	}
230		251
231	...	252	...
232	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
233		254
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		256
236	Set the callback function to call on a retryable syscall error (such	257	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	258	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	259	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	260	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	261	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	262	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	263	(such as abort).
243		264
244	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
255		276
256	=back	277	=back
257		278
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		280
260	An event loop is described by a C<struct ev_loop *>. The library knows two	281	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	282	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
263		288
264	=over 4	289	=over 4
265		290
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		292
…		…
273	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
274	function.	299	function.
275		300
276	Note that this function is I<not> thread-safe, so if you want to use it	301	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,	302	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
279		304
280	The default loop is the only loop that can handle C<ev_signal> and	305	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	306	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	307	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	308	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	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	310	C<ev_default_init>.
286		311
287	The flags argument can be used to specify special behaviour or specific	312	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	321	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	322	thing, believe me).
298		323
299	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
300		325
301	If this flag bit is ored into the flag value (or the program runs setuid	326	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	327	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	329	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	330	useful to try out specific backends to test their performance, or to work
306	around bugs.	331	around bugs.
…		…
313		338
314	This works by calling C<getpid ()> on every iteration of the loop,	339	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	340	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	341	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	342	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	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
320		345
321	The big advantage of this flag is that you can forget about fork (and	346	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	347	forget about forgetting to tell libev about forking) when you use this
323	flag.	348	flag.
324		349
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	351	environment variable.
327		352
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		354
330	This is your standard select(2) backend. Not I<completely> standard, as	355	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	357	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	358	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.	359	usually the fastest backend for a low number of (low-numbered :) fds.
335		360
336	To get good performance out of this backend you need a high amount of	361	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	362	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	363	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	364	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	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
342		371
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		373
345	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	375	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	376	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,	377	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	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	379	performance tips.
351		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		385
354	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	390
359	cases and requiring a syscall per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
361		407
362	While stopping, setting and starting an I/O watcher in the same iteration	408	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	409	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	410	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	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
367		413	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		414
372	Best performance from this backend is achieved by not unregistering all	415	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.	416	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	417	i.e. keep at least one watcher active per fd at all times. Stopping and
		418	starting a watcher (without re-setting it) also usually doesn't cause
		419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
375		422
376	While nominally embeddeble in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	424	all kernel versions tested so far.
		425
		426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		427	C<EVBACKEND_POLL>.
378		428
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		430
381	Kqueue deserves special mention, as at the time of this writing, it	431	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	432	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	433	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"	434	it's completely useless). Unlike epoll, however, whose brokenness
		435	is by design, these kqueue bugs can (and eventually will) be fixed
		436	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	437	"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)	438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	439	system like NetBSD.
388		440
389	You still can embed kqueue into a normal poll or select backend and use it	441	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	442	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.	443	the target platform). See C<ev_embed> watchers for more info.
392		444
393	It scales in the same way as the epoll backend, but the interface to the	445	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	446	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	447	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	448	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	449	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
399		452
400	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
401		454
402	While nominally embeddable in other event loops, this doesn't work	455	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	456	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	457	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	458	(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	459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	460	using it only for sockets.
		461
		462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		464	C<NOTE_EOF>.
408		465
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	466	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		467
411	This is not implemented yet (and might never be, unless you send me an	468	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	469	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	473	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		474
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	475	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)).	476	it's really slow, but it still scales very well (O(active_fds)).
420		477
421	Please note that solaris event ports can deliver a lot of spurious	478	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	479	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	480	blocking when no data (or space) is available.
424		481
425	While this backend scales well, it requires one system call per active	482	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	483	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	485	might perform better.
429		486
430	On the positive side, ignoring the spurious readiness notifications, this	487	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	488	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	489	in all tests and is fully embeddable, which is a rare feat among the
		490	OS-specific backends (I vastly prefer correctness over speed hacks).
		491
		492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		493	C<EVBACKEND_POLL>.
433		494
434	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
435		496
436	Try all backends (even potentially broken ones that wouldn't be tried	497	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	498	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		500
440	It is definitely not recommended to use this flag.	501	It is definitely not recommended to use this flag.
441		502
442	=back	503	=back
443		504
444	If one or more of these are ored into the flags value, then only these	505	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	506	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.	507	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		508
448	The most typical usage is like this:	509	Example: This is the most typical usage.
449		510
450	if (!ev_default_loop (0))	511	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		513
453	Restrict libev to the select and poll backends, and do not allow	514	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	515	environment settings to be taken into account:
455		516
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		518
458	Use whatever libev has to offer, but make sure that kqueue is used if	519	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	520	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):	521	private event loop and only if you know the OS supports your types of
		522	fds):
461		523
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		525
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	526	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		527
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	528	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	529	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	534	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	535	default loop in the "main" or "initial" thread.
474		536
475	Example: Try to create a event loop that uses epoll and nothing else.	537	Example: Try to create a event loop that uses epoll and nothing else.
476		538
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	540	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	541	fatal ("no epoll found here, maybe it hides under your chair");
480		542
481	=item ev_default_destroy ()	543	=item ev_default_destroy ()
482		544
483	Destroys the default loop again (frees all memory and kernel state	545	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	546	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	547	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>	548	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	549	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	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	551	for example).
490		552
491	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
494		556
495	In general it is not advisable to call this function except in the	557	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	558	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	559	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		585
524	=item ev_loop_fork (loop)	586	=item ev_loop_fork (loop)
525		587
526	Like C<ev_default_fork>, but acts on an event loop created by	588	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	589	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.	590	after fork that you want to re-use in the child, and how you do this is
		591	entirely your own problem.
529		592
530	=item int ev_is_default_loop (loop)	593	=item int ev_is_default_loop (loop)
531		594
532	Returns true when the given loop actually is the default loop, false otherwise.	595	Returns true when the given loop is, in fact, the default loop, and false
		596	otherwise.
533		597
534	=item unsigned int ev_loop_count (loop)	598	=item unsigned int ev_loop_count (loop)
535		599
536	Returns the count of loop iterations for the loop, which is identical to	600	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	601	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	616	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	617	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	618	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).	619	event occurring (or more correctly, libev finding out about it).
556		620
		621	=item ev_now_update (loop)
		622
		623	Establishes the current time by querying the kernel, updating the time
		624	returned by C<ev_now ()> in the progress. This is a costly operation and
		625	is usually done automatically within C<ev_loop ()>.
		626
		627	This function is rarely useful, but when some event callback runs for a
		628	very long time without entering the event loop, updating libev's idea of
		629	the current time is a good idea.
		630
		631	See also "The special problem of time updates" in the C<ev_timer> section.
		632
557	=item ev_loop (loop, int flags)	633	=item ev_loop (loop, int flags)
558		634
559	Finally, this is it, the event handler. This function usually is called	635	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	636	after you initialised all your watchers and you want to start handling
561	events.	637	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	639	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.	640	either no event watchers are active anymore or C<ev_unloop> was called.
565		641
566	Please note that an explicit C<ev_unloop> is usually better than	642	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	643	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	644	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	645	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.	646	of relying on its watchers stopping correctly, that is truly a thing of
		647	beauty.
571		648
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	649	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	650	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.	651	process in case there are no events and will return after one iteration of
		652	the loop.
575		653
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	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	655	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	656	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	657	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	658	user-registered callback will be called), and will return after one
		659	iteration of the loop.
		660
		661	This is useful if you are waiting for some external event in conjunction
		662	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	663	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.	664	usually a better approach for this kind of thing.
583		665
584	Here are the gory details of what C<ev_loop> does:	666	Here are the gory details of what C<ev_loop> does:
585		667
586	- Before the first iteration, call any pending watchers.	668	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	669	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	670	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	671	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	672	- If we have been forked, detach and recreate the kernel state
		673	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	674	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	675	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	676	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	677	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	678	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	679	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	680	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	681	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	683	- Queue all expired timers.
601	- Queue all outstanding periodics.	684	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	685	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	686	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	687	- 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	688	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	689	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	690	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	695	anymore.
613		696
614	... queue jobs here, make sure they register event watchers as long	697	... 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..)	698	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	699	ev_loop (my_loop, 0);
617	... jobs done. yeah!	700	... jobs done or somebody called unloop. yeah!
618		701
619	=item ev_unloop (loop, how)	702	=item ev_unloop (loop, how)
620		703
621	Can be used to make a call to C<ev_loop> return early (but only after it	704	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	705	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	706	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.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		708
626	This "unloop state" will be cleared when entering C<ev_loop> again.	709	This "unloop state" will be cleared when entering C<ev_loop> again.
627		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
628	=item ev_ref (loop)	713	=item ev_ref (loop)
629		714
630	=item ev_unref (loop)	715	=item ev_unref (loop)
631		716
632	Ref/unref can be used to add or remove a reference count on the event	717	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	718	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	719	count is nonzero, C<ev_loop> will not return on its own.
		720
635	a watcher you never unregister that should not keep C<ev_loop> from	721	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	722	from returning, call ev_unref() after starting, and ev_ref() before
		723	stopping it.
		724
637	example, libev itself uses this for its internal signal pipe: It is not	725	As an example, libev itself uses this for its internal signal pipe: It is
638	visible to the libev user and should not keep C<ev_loop> from exiting if	726	not visible to the libev user and should not keep C<ev_loop> from exiting
639	no event watchers registered by it are active. It is also an excellent	727	if no event watchers registered by it are active. It is also an excellent
640	way to do this for generic recurring timers or from within third-party	728	way to do this for generic recurring timers or from within third-party
641	libraries. Just remember to I<unref after start> and I<ref before stop>	729	libraries. Just remember to I<unref after start> and I<ref before stop>
642	(but only if the watcher wasn't active before, or was active before,	730	(but only if the watcher wasn't active before, or was active before,
643	respectively).	731	respectively).
644		732
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	734	running when nothing else is active.
647		735
648	struct ev_signal exitsig;	736	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	739	evf_unref (loop);
652		740
653	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
654		742
655	ev_ref (loop);	743	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	744	ev_signal_stop (loop, &exitsig);
657		745
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	746	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		747
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	748	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		749
662	These advanced functions influence the time that libev will spend waiting	750	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	751	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.	752	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		753	latency.
665		754
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	755	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	756	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	757	to increase efficiency of loop iterations (or to increase power-saving
		758	opportunities).
669		759
670	The background is that sometimes your program runs just fast enough to	760	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	761	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	762	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	763	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	764	overhead for the actual polling but can deliver many events at once.
675		765
676	By setting a higher I<io collect interval> you allow libev to spend more	766	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,	767	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	769	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.	770	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		771
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	772	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	773	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	774	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	775	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	776	value will not introduce any overhead in libev.
687		777
688	Many (busy) programs can usually benefit by setting the io collect	778	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	779	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	780	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>,	781	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.	782	as this approaches the timing granularity of most systems.
		783
		784	Setting the I<timeout collect interval> can improve the opportunity for
		785	saving power, as the program will "bundle" timer callback invocations that
		786	are "near" in time together, by delaying some, thus reducing the number of
		787	times the process sleeps and wakes up again. Another useful technique to
		788	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		789	they fire on, say, one-second boundaries only.
		790
		791	=item ev_loop_verify (loop)
		792
		793	This function only does something when C<EV_VERIFY> support has been
		794	compiled in, which is the default for non-minimal builds. It tries to go
		795	through all internal structures and checks them for validity. If anything
		796	is found to be inconsistent, it will print an error message to standard
		797	error and call C<abort ()>.
		798
		799	This can be used to catch bugs inside libev itself: under normal
		800	circumstances, this function will never abort as of course libev keeps its
		801	data structures consistent.
693		802
694	=back	803	=back
695		804
696		805
697	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
698		811
699	A watcher is a structure that you create and register to record your	812	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	813	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:	814	become readable, you would create an C<ev_io> watcher for that:
702		815
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	817	{
705	ev_io_stop (w);	818	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
707	}	820	}
708		821
709	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
710	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
711	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
714	ev_loop (loop, 0);	830	ev_loop (loop, 0);
715		831
716	As you can see, you are responsible for allocating the memory for your	832	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,	833	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		838
720	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	840	(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	841	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	842	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	843	is readable and/or writable).
725		844
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	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	846	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	847	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
730		849
731	To make the watcher actually watch out for events, you have to start it	850	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	851	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	852	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		854
736	As long as your watcher is active (has been started but not stopped) you	855	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	856	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
739		858
740	Each and every callback receives the event loop pointer as first, the	859	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	860	registered watcher structure as second, and a bitset of received events as
742	third argument.	861	third argument.
743		862
…		…
803		922
804	The given async watcher has been asynchronously notified (see C<ev_async>).	923	The given async watcher has been asynchronously notified (see C<ev_async>).
805		924
806	=item C<EV_ERROR>	925	=item C<EV_ERROR>
807		926
808	An unspecified error has occured, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	928	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	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
811	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
813		936
814	Libev will usually signal a few "dummy" events together with an error,	937	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	938	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	939	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	940	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	941	programs, though, as the fd could already be closed and reused for another
		942	thing, so beware.
819		943
820	=back	944	=back
821		945
822	=head2 GENERIC WATCHER FUNCTIONS	946	=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		947
827	=over 4	948	=over 4
828		949
829	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
830		951
…		…
836	which rolls both calls into one.	957	which rolls both calls into one.
837		958
838	You can reinitialise a watcher at any time as long as it has been stopped	959	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.	960	(or never started) and there are no pending events outstanding.
840		961
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	963	int revents)>.
		964
		965	Example: Initialise an C<ev_io> watcher in two steps.
		966
		967	ev_io w;
		968	ev_init (&w, my_cb);
		969	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		970
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	971	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		972
846	This macro initialises the type-specific parts of a watcher. You need to	973	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	974	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	977	difference to the C<ev_init> macro).
851		978
852	Although some watcher types do not have type-specific arguments	979	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.	980	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		981
		982	See C<ev_init>, above, for an example.
		983
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	984	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		985
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	986	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	987	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	988	a watcher. The same limitations apply, of course.
		989
		990	Example: Initialise and set an C<ev_io> watcher in one step.
		991
		992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		993
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		995
863	Starts (activates) the given watcher. Only active watchers will receive	996	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	997	events. If the watcher is already active nothing will happen.
865		998
		999	Example: Start the C<ev_io> watcher that is being abused as example in this
		1000	whole section.
		1001
		1002	ev_io_start (EV_DEFAULT_UC, &w);
		1003
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		1005
868	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
869	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1010	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	1011	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	1012	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.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1014
875	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
876		1016
877	Returns a true value iff the watcher is active (i.e. it has been started	1017	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	1018	and not yet been stopped). As long as a watcher is active you must not modify
…		…
920	The default priority used by watchers when no priority has been set is	1060	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 :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
922		1062
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
924	fine, as long as you do not mind that the priority value you query might	1064	fine, as long as you do not mind that the priority value you query might
925	or might not have been adjusted to be within valid range.	1065	or might not have been clamped to the valid range.
926		1066
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1068
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	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	1070	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1071	can deal with that fact, as both are simply passed through to the
		1072	callback.
932		1073
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1074	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1075
935	If the watcher is pending, this function returns clears its pending status	1076	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	1077	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>.	1078	watcher isn't pending it does nothing and returns C<0>.
938		1079
		1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1081	callback to be invoked, which can be accomplished with this function.
		1082
939	=back	1083	=back
940		1084
941		1085
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1087
944	Each watcher has, by default, a member C<void *data> that you can change	1088	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	1089	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	1090	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	1091	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	1092	member, you can also "subclass" the watcher type and provide your own
949	data:	1093	data:
950		1094
951	struct my_io	1095	struct my_io
952	{	1096	{
953	struct ev_io io;	1097	ev_io io;
954	int otherfd;	1098	int otherfd;
955	void *somedata;	1099	void *somedata;
956	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
957	}	1101	};
		1102
		1103	...
		1104	struct my_io w;
		1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1106
959	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1108	can cast it back to your own type:
961		1109
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1111	{
964	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
965	...	1113	...
966	}	1114	}
967		1115
968	More interesting and less C-conformant ways of casting your callback type	1116	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1117	instead have been omitted.
970		1118
971	Another common scenario is having some data structure with multiple	1119	Another common scenario is to use some data structure with multiple
972	watchers:	1120	embedded watchers:
973		1121
974	struct my_biggy	1122	struct my_biggy
975	{	1123	{
976	int some_data;	1124	int some_data;
977	ev_timer t1;	1125	ev_timer t1;
978	ev_timer t2;	1126	ev_timer t2;
979	}	1127	}
980		1128
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1129	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1130	complicated: Either you store the address of your C<my_biggy> struct
		1131	in the C<data> member of the watcher (for woozies), or you need to use
		1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
983		1134
984	#include <stddef.h>	1135	#include <stddef.h>
985		1136
986	static void	1137	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1139	{
989	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1142	}
992		1143
993	static void	1144	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1146	{
996	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1149	}
999		1150
1000		1151
1001	=head1 WATCHER TYPES	1152	=head1 WATCHER TYPES
1002		1153
1003	This section describes each watcher in detail, but will not repeat	1154	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	1178	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	1179	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	1180	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1181	required if you know what you are doing).
1031		1182
1032	If you must do this, then force the use of a known-to-be-good backend	1183	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	1184	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1186
1036	Another thing you have to watch out for is that it is quite easy to	1187	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1188	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	1189	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	1190	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	1191	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	1192	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	1193	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.	1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1195
1045	If you cannot run the fd in non-blocking mode (for example you should not	1196	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	1197	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	1198	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	1199	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1200	does this on its own, so its quite safe to use). Some people additionally
		1201	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1202	indefinitely.
		1203
		1204	But really, best use non-blocking mode.
1050		1205
1051	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1052		1207
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1208	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,	1209	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	1210	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	1211	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	1212	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	1213	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1214	fact, a different file descriptor.
1060		1215
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1093		1248
1094	=head3 The special problem of SIGPIPE	1249	=head3 The special problem of SIGPIPE
1095		1250
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1251	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	1252	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	1253	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1254	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1255
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1256	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	1257	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).	1258	somewhere, as that would have given you a big clue).
1105		1259
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1266
1113	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1114		1268
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1269	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	1270	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.	1271	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1272
1119	=item int fd [read-only]	1273	=item int fd [read-only]
1120		1274
1121	The file descriptor being watched.	1275	The file descriptor being watched.
1122		1276
…		…
1130		1284
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	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	1286	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1134		1288
1135	static void	1289	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1291	{
1138	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1294	}
1141		1295
1142	...	1296	...
1143	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1148		1302
1149		1303
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1304	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1305
1152	Timer watchers are simple relative timers that generate an event after a	1306	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1154		1308
1155	The timers are based on real time, that is, if you register an event that	1309	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 january last	1310	times out after an hour and you reset your system clock to January last
1157	year, it will still time out after (roughly) and hour. "Roughly" because	1311	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
		1314
		1315	The callback is guaranteed to be invoked only I<after> its timeout has
		1316	passed, but if multiple timers become ready during the same loop iteration
		1317	then order of execution is undefined.
		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
		1493
		1494	=head3 The special problem of time updates
		1495
		1496	Establishing the current time is a costly operation (it usually takes at
		1497	least two system calls): EV therefore updates its idea of the current
		1498	time only before and after C<ev_loop> collects new events, which causes a
		1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1500	lots of events in one iteration.
1160		1501
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1502	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	1503	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	1504	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	1505	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:	1506	timeout on the current time, use something like this to adjust for this:
1166		1507
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1508	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1509
1169	The callback is guarenteed to be invoked only after its timeout has passed,	1510	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	1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1512	()>.
1172		1513
1173	=head3 Watcher-Specific Functions and Data Members	1514	=head3 Watcher-Specific Functions and Data Members
1174		1515
1175	=over 4	1516	=over 4
1176		1517
…		…
1195	This will act as if the timer timed out and restart it again if it is	1536	This will act as if the timer timed out and restart it again if it is
1196	repeating. The exact semantics are:	1537	repeating. The exact semantics are:
1197		1538
1198	If the timer is pending, its pending status is cleared.	1539	If the timer is pending, its pending status is cleared.
1199		1540
1200	If the timer is started but nonrepeating, stop it (as if it timed out).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1201		1542
1202	If the timer is repeating, either start it if necessary (with the	1543	If the timer is repeating, either start it if necessary (with the
1203	C<repeat> value), or reset the running timer to the C<repeat> value.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1204		1545
1205	This sounds a bit complicated, but here is a useful and typical	1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1206	example: Imagine you have a tcp connection and you want a so-called idle	1547	usage example.
1207	timeout, that is, you want to be called when there have been, say, 60
1208	seconds of inactivity on the socket. The easiest way to do this is to
1209	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1210	C<ev_timer_again> each time you successfully read or write some data. If
1211	you go into an idle state where you do not expect data to travel on the
1212	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1213	automatically restart it if need be.
1214
1215	That means you can ignore the C<after> value and C<ev_timer_start>
1216	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1217
1218	ev_timer_init (timer, callback, 0., 5.);
1219	ev_timer_again (loop, timer);
1220	...
1221	timer->again = 17.;
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 10.;
1225	ev_timer_again (loop, timer);
1226
1227	This is more slightly efficient then stopping/starting the timer each time
1228	you want to modify its timeout value.
1229		1548
1230	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1231		1550
1232	The current C<repeat> value. Will be used each time the watcher times out	1551	The current C<repeat> value. Will be used each time the watcher times out
1233	or C<ev_timer_again> is called and determines the next timeout (if any),	1552	or C<ev_timer_again> is called, and determines the next timeout (if any),
1234	which is also when any modifications are taken into account.	1553	which is also when any modifications are taken into account.
1235		1554
1236	=back	1555	=back
1237		1556
1238	=head3 Examples	1557	=head3 Examples
1239		1558
1240	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1241		1560
1242	static void	1561	static void
1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1244	{	1563	{
1245	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1246	}	1565	}
1247		1566
1248	struct ev_timer mytimer;	1567	ev_timer mytimer;
1249	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1250	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1251		1570
1252	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1253	inactivity.	1572	inactivity.
1254		1573
1255	static void	1574	static void
1256	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1257	{	1576	{
1258	.. ten seconds without any activity	1577	.. ten seconds without any activity
1259	}	1578	}
1260		1579
1261	struct ev_timer mytimer;	1580	ev_timer mytimer;
1262	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1263	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1264	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1265		1584
1266	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
1267	// reset the timeout to start ticking again at 10 seconds	1586	// reset the timeout to start ticking again at 10 seconds
1268	ev_timer_again (&mytimer);	1587	ev_timer_again (&mytimer);
1269		1588
1270		1589
1271	=head2 C<ev_periodic> - to cron or not to cron?	1590	=head2 C<ev_periodic> - to cron or not to cron?
1272		1591
1273	Periodic watchers are also timers of a kind, but they are very versatile	1592	Periodic watchers are also timers of a kind, but they are very versatile
1274	(and unfortunately a bit complex).	1593	(and unfortunately a bit complex).
1275		1594
1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1595	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1277	but on wallclock time (absolute time). You can tell a periodic watcher	1596	but on wall clock time (absolute time). You can tell a periodic watcher
1278	to trigger after some specific point in time. For example, if you tell a	1597	to trigger after some specific point in time. For example, if you tell a
1279	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1598	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1280	+ 10.>, that is, an absolute time not a delay) and then reset your system	1599	+ 10.>, that is, an absolute time not a delay) and then reset your system
1281	clock to january of the previous year, then it will take more than year	1600	clock to January of the previous year, then it will take more than year
1282	to trigger the event (unlike an C<ev_timer>, which would still trigger	1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1283	roughly 10 seconds later as it uses a relative timeout).	1602	roughly 10 seconds later as it uses a relative timeout).
1284		1603
1285	C<ev_periodic>s can also be used to implement vastly more complex timers,	1604	C<ev_periodic>s can also be used to implement vastly more complex timers,
1286	such as triggering an event on each "midnight, local time", or other	1605	such as triggering an event on each "midnight, local time", or other
1287	complicated, rules.	1606	complicated rules.
1288		1607
1289	As with timers, the callback is guarenteed to be invoked only when the	1608	As with timers, the callback is guaranteed to be invoked only when the
1290	time (C<at>) has passed, but if multiple periodic timers become ready	1609	time (C<at>) has passed, but if multiple periodic timers become ready
1291	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1292		1611
1293	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1294		1613
1295	=over 4	1614	=over 4
1296		1615
1297	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1298		1617
1299	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1300		1619
1301	Lots of arguments, lets sort it out... There are basically three modes of	1620	Lots of arguments, lets sort it out... There are basically three modes of
1302	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1303		1622
1304	=over 4	1623	=over 4
1305		1624
1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1307		1626
1308	In this configuration the watcher triggers an event after the wallclock	1627	In this configuration the watcher triggers an event after the wall clock
1309	time C<at> has passed and doesn't repeat. It will not adjust when a time	1628	time C<at> has passed. It will not repeat and will not adjust when a time
1310	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1311	run when the system time reaches or surpasses this time.	1630	only run when the system clock reaches or surpasses this time.
1312		1631
1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1314		1633
1315	In this mode the watcher will always be scheduled to time out at the next	1634	In this mode the watcher will always be scheduled to time out at the next
1316	C<at + N * interval> time (for some integer N, which can also be negative)	1635	C<at + N * interval> time (for some integer N, which can also be negative)
1317	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1318		1637
1319	This can be used to create timers that do not drift with respect to system	1638	This can be used to create timers that do not drift with respect to the
1320	time, for example, here is a C<ev_periodic> that triggers each hour, on	1639	system clock, for example, here is a C<ev_periodic> that triggers each
1321	the hour:	1640	hour, on the hour:
1322		1641
1323	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1324		1643
1325	This doesn't mean there will always be 3600 seconds in between triggers,	1644	This doesn't mean there will always be 3600 seconds in between triggers,
1326	but only that the the callback will be called when the system time shows a	1645	but only that the callback will be called when the system time shows a
1327	full hour (UTC), or more correctly, when the system time is evenly divisible	1646	full hour (UTC), or more correctly, when the system time is evenly divisible
1328	by 3600.	1647	by 3600.
1329		1648
1330	Another way to think about it (for the mathematically inclined) is that	1649	Another way to think about it (for the mathematically inclined) is that
1331	C<ev_periodic> will try to run the callback in this mode at the next possible	1650	C<ev_periodic> will try to run the callback in this mode at the next possible
1332	time where C<time = at (mod interval)>, regardless of any time jumps.	1651	time where C<time = at (mod interval)>, regardless of any time jumps.
1333		1652
1334	For numerical stability it is preferable that the C<at> value is near	1653	For numerical stability it is preferable that the C<at> value is near
1335	C<ev_now ()> (the current time), but there is no range requirement for	1654	C<ev_now ()> (the current time), but there is no range requirement for
1336	this value, and in fact is often specified as zero.	1655	this value, and in fact is often specified as zero.
		1656
		1657	Note also that there is an upper limit to how often a timer can fire (CPU
		1658	speed for example), so if C<interval> is very small then timing stability
		1659	will of course deteriorate. Libev itself tries to be exact to be about one
		1660	millisecond (if the OS supports it and the machine is fast enough).
1337		1661
1338	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1339		1663
1340	In this mode the values for C<interval> and C<at> are both being	1664	In this mode the values for C<interval> and C<at> are both being
1341	ignored. Instead, each time the periodic watcher gets scheduled, the	1665	ignored. Instead, each time the periodic watcher gets scheduled, the
…		…
1347		1671
1348	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1349	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1350	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1351		1675
1352	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1353	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1354		1678
		1679	static ev_tstamp
1355	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1356	{	1681	{
1357	return now + 60.;	1682	return now + 60.;
1358	}	1683	}
1359		1684
1360	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
…		…
1397		1722
1398	The current interval value. Can be modified any time, but changes only	1723	The current interval value. Can be modified any time, but changes only
1399	take effect when the periodic timer fires or C<ev_periodic_again> is being	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1400	called.	1725	called.
1401		1726
1402	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1403		1728
1404	The current reschedule callback, or C<0>, if this functionality is	1729	The current reschedule callback, or C<0>, if this functionality is
1405	switched off. Can be changed any time, but changes only take effect when	1730	switched off. Can be changed any time, but changes only take effect when
1406	the periodic timer fires or C<ev_periodic_again> is being called.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1407		1732
1408	=back	1733	=back
1409		1734
1410	=head3 Examples	1735	=head3 Examples
1411		1736
1412	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1413	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1414	potentially a lot of jittering, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1415		1740
1416	static void	1741	static void
1417	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1418	{	1743	{
1419	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1420	}	1745	}
1421		1746
1422	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1423	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1424	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1425		1750
1426	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1427		1752
1428	#include <math.h>	1753	#include <math.h>
1429		1754
1430	static ev_tstamp	1755	static ev_tstamp
1431	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1432	{	1757	{
1433	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1434	}	1759	}
1435		1760
1436	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1437		1762
1438	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1439		1764
1440	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1441	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1442	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1443	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1444		1769
1445		1770
1446	=head2 C<ev_signal> - signal me when a signal gets signalled!	1771	=head2 C<ev_signal> - signal me when a signal gets signalled!
1447		1772
1448	Signal watchers will trigger an event when the process receives a specific	1773	Signal watchers will trigger an event when the process receives a specific
1449	signal one or more times. Even though signals are very asynchronous, libev	1774	signal one or more times. Even though signals are very asynchronous, libev
1450	will try it's best to deliver signals synchronously, i.e. as part of the	1775	will try it's best to deliver signals synchronously, i.e. as part of the
1451	normal event processing, like any other event.	1776	normal event processing, like any other event.
1452		1777
		1778	If you want signals asynchronously, just use C<sigaction> as you would
		1779	do without libev and forget about sharing the signal. You can even use
		1780	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1781
1453	You can configure as many watchers as you like per signal. Only when the	1782	You can configure as many watchers as you like per signal. Only when the
1454	first watcher gets started will libev actually register a signal watcher	1783	first watcher gets started will libev actually register a signal handler
1455	with the kernel (thus it coexists with your own signal handlers as long	1784	with the kernel (thus it coexists with your own signal handlers as long as
1456	as you don't register any with libev). Similarly, when the last signal	1785	you don't register any with libev for the same signal). Similarly, when
1457	watcher for a signal is stopped libev will reset the signal handler to	1786	the last signal watcher for a signal is stopped, libev will reset the
1458	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
1459		1788
1460	If possible and supported, libev will install its handlers with	1789	If possible and supported, libev will install its handlers with
1461	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1462	interrupted. If you have a problem with syscalls getting interrupted by	1791	interrupted. If you have a problem with system calls getting interrupted by
1463	signals you can block all signals in an C<ev_check> watcher and unblock	1792	signals you can block all signals in an C<ev_check> watcher and unblock
1464	them in an C<ev_prepare> watcher.	1793	them in an C<ev_prepare> watcher.
1465		1794
1466	=head3 Watcher-Specific Functions and Data Members	1795	=head3 Watcher-Specific Functions and Data Members
1467		1796
…		…
1480		1809
1481	=back	1810	=back
1482		1811
1483	=head3 Examples	1812	=head3 Examples
1484		1813
1485	Example: Try to exit cleanly on SIGINT and SIGTERM.	1814	Example: Try to exit cleanly on SIGINT.
1486		1815
1487	static void	1816	static void
1488	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1489	{	1818	{
1490	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1491	}	1820	}
1492		1821
1493	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1494	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1495	ev_signal_start (loop, &sigint_cb);	1824	ev_signal_start (loop, &signal_watcher);
1496		1825
1497		1826
1498	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1499		1828
1500	Child watchers trigger when your process receives a SIGCHLD in response to	1829	Child watchers trigger when your process receives a SIGCHLD in response to
1501	some child status changes (most typically when a child of yours dies). It	1830	some child status changes (most typically when a child of yours dies or
1502	is permissible to install a child watcher I<after> the child has been	1831	exits). It is permissible to install a child watcher I<after> the child
1503	forked (which implies it might have already exited), as long as the event	1832	has been forked (which implies it might have already exited), as long
1504	loop isn't entered (or is continued from a watcher).	1833	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1834	forking and then immediately registering a watcher for the child is fine,
		1835	but forking and registering a watcher a few event loop iterations later is
		1836	not.
1505		1837
1506	Only the default event loop is capable of handling signals, and therefore	1838	Only the default event loop is capable of handling signals, and therefore
1507	you can only rgeister child watchers in the default event loop.	1839	you can only register child watchers in the default event loop.
1508		1840
1509	=head3 Process Interaction	1841	=head3 Process Interaction
1510		1842
1511	Libev grabs C<SIGCHLD> as soon as the default event loop is	1843	Libev grabs C<SIGCHLD> as soon as the default event loop is
1512	initialised. This is necessary to guarantee proper behaviour even if	1844	initialised. This is necessary to guarantee proper behaviour even if
1513	the first child watcher is started after the child exits. The occurance	1845	the first child watcher is started after the child exits. The occurrence
1514	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1515	synchronously as part of the event loop processing. Libev always reaps all	1847	synchronously as part of the event loop processing. Libev always reaps all
1516	children, even ones not watched.	1848	children, even ones not watched.
1517		1849
1518	=head3 Overriding the Built-In Processing	1850	=head3 Overriding the Built-In Processing
…		…
1522	handler, you can override it easily by installing your own handler for	1854	handler, you can override it easily by installing your own handler for
1523	C<SIGCHLD> after initialising the default loop, and making sure the	1855	C<SIGCHLD> after initialising the default loop, and making sure the
1524	default loop never gets destroyed. You are encouraged, however, to use an	1856	default loop never gets destroyed. You are encouraged, however, to use an
1525	event-based approach to child reaping and thus use libev's support for	1857	event-based approach to child reaping and thus use libev's support for
1526	that, so other libev users can use C<ev_child> watchers freely.	1858	that, so other libev users can use C<ev_child> watchers freely.
		1859
		1860	=head3 Stopping the Child Watcher
		1861
		1862	Currently, the child watcher never gets stopped, even when the
		1863	child terminates, so normally one needs to stop the watcher in the
		1864	callback. Future versions of libev might stop the watcher automatically
		1865	when a child exit is detected.
1527		1866
1528	=head3 Watcher-Specific Functions and Data Members	1867	=head3 Watcher-Specific Functions and Data Members
1529		1868
1530	=over 4	1869	=over 4
1531		1870
…		…
1560	=head3 Examples	1899	=head3 Examples
1561		1900
1562	Example: C<fork()> a new process and install a child handler to wait for	1901	Example: C<fork()> a new process and install a child handler to wait for
1563	its completion.	1902	its completion.
1564		1903
1565	ev_child cw;	1904	ev_child cw;
1566		1905
1567	static void	1906	static void
1568	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1569	{	1908	{
1570	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1571	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1572	}	1911	}
1573		1912
1574	pid_t pid = fork ();	1913	pid_t pid = fork ();
1575		1914
1576	if (pid < 0)	1915	if (pid < 0)
1577	// error	1916	// error
1578	else if (pid == 0)	1917	else if (pid == 0)
1579	{	1918	{
1580	// the forked child executes here	1919	// the forked child executes here
1581	exit (1);	1920	exit (1);
1582	}	1921	}
1583	else	1922	else
1584	{	1923	{
1585	ev_child_init (&cw, child_cb, pid, 0);	1924	ev_child_init (&cw, child_cb, pid, 0);
1586	ev_child_start (EV_DEFAULT_ &cw);	1925	ev_child_start (EV_DEFAULT_ &cw);
1587	}	1926	}
1588		1927
1589		1928
1590	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1591		1930
1592	This watches a filesystem path for attribute changes. That is, it calls	1931	This watches a file system path for attribute changes. That is, it calls
1593	C<stat> regularly (or when the OS says it changed) and sees if it changed	1932	C<stat> on that path in regular intervals (or when the OS says it changed)
1594	compared to the last time, invoking the callback if it did.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1595		1935
1596	The path does not need to exist: changing from "path exists" to "path does	1936	The path does not need to exist: changing from "path exists" to "path does
1597	not exist" is a status change like any other. The condition "path does	1937	not exist" is a status change like any other. The condition "path does
1598	not exist" is signified by the C<st_nlink> field being zero (which is	1938	not exist" is signified by the C<st_nlink> field being zero (which is
1599	otherwise always forced to be at least one) and all the other fields of	1939	otherwise always forced to be at least one) and all the other fields of
1600	the stat buffer having unspecified contents.	1940	the stat buffer having unspecified contents.
1601		1941
1602	The path I<should> be absolute and I<must not> end in a slash. If it is	1942	The path I<must not> end in a slash or contain special components such as
		1943	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1603	relative and your working directory changes, the behaviour is undefined.	1944	your working directory changes, then the behaviour is undefined.
1604		1945
1605	Since there is no standard to do this, the portable implementation simply	1946	Since there is no portable change notification interface available, the
1606	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1947	portable implementation simply calls C<stat(2)> regularly on the path
1607	can specify a recommended polling interval for this case. If you specify	1948	to see if it changed somehow. You can specify a recommended polling
1608	a polling interval of C<0> (highly recommended!) then a I<suitable,	1949	interval for this case. If you specify a polling interval of C<0> (highly
1609	unspecified default> value will be used (which you can expect to be around	1950	recommended!) then a I<suitable, unspecified default> value will be used
1610	five seconds, although this might change dynamically). Libev will also	1951	(which you can expect to be around five seconds, although this might
1611	impose a minimum interval which is currently around C<0.1>, but thats	1952	change dynamically). Libev will also impose a minimum interval which is
1612	usually overkill.	1953	currently around C<0.1>, but that's usually overkill.
1613		1954
1614	This watcher type is not meant for massive numbers of stat watchers,	1955	This watcher type is not meant for massive numbers of stat watchers,
1615	as even with OS-supported change notifications, this can be	1956	as even with OS-supported change notifications, this can be
1616	resource-intensive.	1957	resource-intensive.
1617		1958
1618	At the time of this writing, only the Linux inotify interface is	1959	At the time of this writing, the only OS-specific interface implemented
1619	implemented (implementing kqueue support is left as an exercise for the	1960	is the Linux inotify interface (implementing kqueue support is left as
1620	reader, note, however, that the author sees no way of implementing ev_stat	1961	an exercise for the reader. Note, however, that the author sees no way
1621	semantics with kqueue). Inotify will be used to give hints only and should	1962	of implementing C<ev_stat> semantics with kqueue).
1622	not change the semantics of C<ev_stat> watchers, which means that libev
1623	sometimes needs to fall back to regular polling again even with inotify,
1624	but changes are usually detected immediately, and if the file exists there
1625	will be no polling.
1626		1963
1627	=head3 ABI Issues (Largefile Support)	1964	=head3 ABI Issues (Largefile Support)
1628		1965
1629	Libev by default (unless the user overrides this) uses the default	1966	Libev by default (unless the user overrides this) uses the default
1630	compilation environment, which means that on systems with optionally	1967	compilation environment, which means that on systems with large file
1631	disabled large file support, you get the 32 bit version of the stat	1968	support disabled by default, you get the 32 bit version of the stat
1632	structure. When using the library from programs that change the ABI to	1969	structure. When using the library from programs that change the ABI to
1633	use 64 bit file offsets the programs will fail. In that case you have to	1970	use 64 bit file offsets the programs will fail. In that case you have to
1634	compile libev with the same flags to get binary compatibility. This is	1971	compile libev with the same flags to get binary compatibility. This is
1635	obviously the case with any flags that change the ABI, but the problem is	1972	obviously the case with any flags that change the ABI, but the problem is
1636	most noticably with ev_stat and largefile support.	1973	most noticeably displayed with ev_stat and large file support.
1637		1974
1638	=head3 Inotify	1975	The solution for this is to lobby your distribution maker to make large
		1976	file interfaces available by default (as e.g. FreeBSD does) and not
		1977	optional. Libev cannot simply switch on large file support because it has
		1978	to exchange stat structures with application programs compiled using the
		1979	default compilation environment.
1639		1980
		1981	=head3 Inotify and Kqueue
		1982
1640	When C<inotify (7)> support has been compiled into libev (generally only	1983	When C<inotify (7)> support has been compiled into libev (generally
		1984	only available with Linux 2.6.25 or above due to bugs in earlier
1641	available on Linux) and present at runtime, it will be used to speed up	1985	implementations) and present at runtime, it will be used to speed up
1642	change detection where possible. The inotify descriptor will be created lazily	1986	change detection where possible. The inotify descriptor will be created
1643	when the first C<ev_stat> watcher is being started.	1987	lazily when the first C<ev_stat> watcher is being started.
1644		1988
1645	Inotify presence does not change the semantics of C<ev_stat> watchers	1989	Inotify presence does not change the semantics of C<ev_stat> watchers
1646	except that changes might be detected earlier, and in some cases, to avoid	1990	except that changes might be detected earlier, and in some cases, to avoid
1647	making regular C<stat> calls. Even in the presence of inotify support	1991	making regular C<stat> calls. Even in the presence of inotify support
1648	there are many cases where libev has to resort to regular C<stat> polling.	1992	there are many cases where libev has to resort to regular C<stat> polling,
		1993	but as long as the path exists, libev usually gets away without polling.
1649		1994
1650	(There is no support for kqueue, as apparently it cannot be used to	1995	There is no support for kqueue, as apparently it cannot be used to
1651	implement this functionality, due to the requirement of having a file	1996	implement this functionality, due to the requirement of having a file
1652	descriptor open on the object at all times).	1997	descriptor open on the object at all times, and detecting renames, unlinks
		1998	etc. is difficult.
1653		1999
1654	=head3 The special problem of stat time resolution	2000	=head3 The special problem of stat time resolution
1655		2001
1656	The C<stat ()> syscall only supports full-second resolution portably, and	2002	The C<stat ()> system call only supports full-second resolution portably,
1657	even on systems where the resolution is higher, many filesystems still	2003	and even on systems where the resolution is higher, most file systems
1658	only support whole seconds.	2004	still only support whole seconds.
1659		2005
1660	That means that, if the time is the only thing that changes, you can	2006	That means that, if the time is the only thing that changes, you can
1661	easily miss updates: on the first update, C<ev_stat> detects a change and	2007	easily miss updates: on the first update, C<ev_stat> detects a change and
1662	calls your callback, which does something. When there is another update	2008	calls your callback, which does something. When there is another update
1663	within the same second, C<ev_stat> will be unable to detect it as the stat	2009	within the same second, C<ev_stat> will be unable to detect unless the
1664	data does not change.	2010	stat data does change in other ways (e.g. file size).
1665		2011
1666	The solution to this is to delay acting on a change for slightly more	2012	The solution to this is to delay acting on a change for slightly more
1667	than a second (or till slightly after the next full second boundary), using	2013	than a second (or till slightly after the next full second boundary), using
1668	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2014	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1669	ev_timer_again (loop, w)>).	2015	ev_timer_again (loop, w)>).
…		…
1689	C<path>. The C<interval> is a hint on how quickly a change is expected to	2035	C<path>. The C<interval> is a hint on how quickly a change is expected to
1690	be detected and should normally be specified as C<0> to let libev choose	2036	be detected and should normally be specified as C<0> to let libev choose
1691	a suitable value. The memory pointed to by C<path> must point to the same	2037	a suitable value. The memory pointed to by C<path> must point to the same
1692	path for as long as the watcher is active.	2038	path for as long as the watcher is active.
1693		2039
1694	The callback will receive C<EV_STAT> when a change was detected, relative	2040	The callback will receive an C<EV_STAT> event when a change was detected,
1695	to the attributes at the time the watcher was started (or the last change	2041	relative to the attributes at the time the watcher was started (or the
1696	was detected).	2042	last change was detected).
1697		2043
1698	=item ev_stat_stat (loop, ev_stat *)	2044	=item ev_stat_stat (loop, ev_stat *)
1699		2045
1700	Updates the stat buffer immediately with new values. If you change the	2046	Updates the stat buffer immediately with new values. If you change the
1701	watched path in your callback, you could call this function to avoid	2047	watched path in your callback, you could call this function to avoid
…		…
1722		2068
1723	The specified interval.	2069	The specified interval.
1724		2070
1725	=item const char *path [read-only]	2071	=item const char *path [read-only]
1726		2072
1727	The filesystem path that is being watched.	2073	The file system path that is being watched.
1728		2074
1729	=back	2075	=back
1730		2076
1731	=head3 Examples	2077	=head3 Examples
1732		2078
1733	Example: Watch C</etc/passwd> for attribute changes.	2079	Example: Watch C</etc/passwd> for attribute changes.
1734		2080
1735	static void	2081	static void
1736	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2082	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1737	{	2083	{
1738	/* /etc/passwd changed in some way */	2084	/* /etc/passwd changed in some way */
1739	if (w->attr.st_nlink)	2085	if (w->attr.st_nlink)
1740	{	2086	{
1741	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2087	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1742	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2088	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1743	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2089	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1744	}	2090	}
1745	else	2091	else
1746	/* you shalt not abuse printf for puts */	2092	/* you shalt not abuse printf for puts */
1747	puts ("wow, /etc/passwd is not there, expect problems. "	2093	puts ("wow, /etc/passwd is not there, expect problems. "
1748	"if this is windows, they already arrived\n");	2094	"if this is windows, they already arrived\n");
1749	}	2095	}
1750		2096
1751	...	2097	...
1752	ev_stat passwd;	2098	ev_stat passwd;
1753		2099
1754	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2100	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1755	ev_stat_start (loop, &passwd);	2101	ev_stat_start (loop, &passwd);
1756		2102
1757	Example: Like above, but additionally use a one-second delay so we do not	2103	Example: Like above, but additionally use a one-second delay so we do not
1758	miss updates (however, frequent updates will delay processing, too, so	2104	miss updates (however, frequent updates will delay processing, too, so
1759	one might do the work both on C<ev_stat> callback invocation I<and> on	2105	one might do the work both on C<ev_stat> callback invocation I<and> on
1760	C<ev_timer> callback invocation).	2106	C<ev_timer> callback invocation).
1761		2107
1762	static ev_stat passwd;	2108	static ev_stat passwd;
1763	static ev_timer timer;	2109	static ev_timer timer;
1764		2110
1765	static void	2111	static void
1766	timer_cb (EV_P_ ev_timer *w, int revents)	2112	timer_cb (EV_P_ ev_timer *w, int revents)
1767	{	2113	{
1768	ev_timer_stop (EV_A_ w);	2114	ev_timer_stop (EV_A_ w);
1769		2115
1770	/* now it's one second after the most recent passwd change */	2116	/* now it's one second after the most recent passwd change */
1771	}	2117	}
1772		2118
1773	static void	2119	static void
1774	stat_cb (EV_P_ ev_stat *w, int revents)	2120	stat_cb (EV_P_ ev_stat *w, int revents)
1775	{	2121	{
1776	/* reset the one-second timer */	2122	/* reset the one-second timer */
1777	ev_timer_again (EV_A_ &timer);	2123	ev_timer_again (EV_A_ &timer);
1778	}	2124	}
1779		2125
1780	...	2126	...
1781	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2127	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1782	ev_stat_start (loop, &passwd);	2128	ev_stat_start (loop, &passwd);
1783	ev_timer_init (&timer, timer_cb, 0., 1.02);	2129	ev_timer_init (&timer, timer_cb, 0., 1.02);
1784		2130
1785		2131
1786	=head2 C<ev_idle> - when you've got nothing better to do...	2132	=head2 C<ev_idle> - when you've got nothing better to do...
1787		2133
1788	Idle watchers trigger events when no other events of the same or higher	2134	Idle watchers trigger events when no other events of the same or higher
1789	priority are pending (prepare, check and other idle watchers do not	2135	priority are pending (prepare, check and other idle watchers do not count
1790	count).	2136	as receiving "events").
1791		2137
1792	That is, as long as your process is busy handling sockets or timeouts	2138	That is, as long as your process is busy handling sockets or timeouts
1793	(or even signals, imagine) of the same or higher priority it will not be	2139	(or even signals, imagine) of the same or higher priority it will not be
1794	triggered. But when your process is idle (or only lower-priority watchers	2140	triggered. But when your process is idle (or only lower-priority watchers
1795	are pending), the idle watchers are being called once per event loop	2141	are pending), the idle watchers are being called once per event loop
…		…
1819	=head3 Examples	2165	=head3 Examples
1820		2166
1821	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2167	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1822	callback, free it. Also, use no error checking, as usual.	2168	callback, free it. Also, use no error checking, as usual.
1823		2169
1824	static void	2170	static void
1825	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2171	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1826	{	2172	{
1827	free (w);	2173	free (w);
1828	// now do something you wanted to do when the program has	2174	// now do something you wanted to do when the program has
1829	// no longer anything immediate to do.	2175	// no longer anything immediate to do.
1830	}	2176	}
1831		2177
1832	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2178	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1833	ev_idle_init (idle_watcher, idle_cb);	2179	ev_idle_init (idle_watcher, idle_cb);
1834	ev_idle_start (loop, idle_cb);	2180	ev_idle_start (loop, idle_cb);
1835		2181
1836		2182
1837	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2183	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1838		2184
1839	Prepare and check watchers are usually (but not always) used in tandem:	2185	Prepare and check watchers are usually (but not always) used in pairs:
1840	prepare watchers get invoked before the process blocks and check watchers	2186	prepare watchers get invoked before the process blocks and check watchers
1841	afterwards.	2187	afterwards.
1842		2188
1843	You I<must not> call C<ev_loop> or similar functions that enter	2189	You I<must not> call C<ev_loop> or similar functions that enter
1844	the current event loop from either C<ev_prepare> or C<ev_check>	2190	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1847	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2193	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1848	C<ev_check> so if you have one watcher of each kind they will always be	2194	C<ev_check> so if you have one watcher of each kind they will always be
1849	called in pairs bracketing the blocking call.	2195	called in pairs bracketing the blocking call.
1850		2196
1851	Their main purpose is to integrate other event mechanisms into libev and	2197	Their main purpose is to integrate other event mechanisms into libev and
1852	their use is somewhat advanced. This could be used, for example, to track	2198	their use is somewhat advanced. They could be used, for example, to track
1853	variable changes, implement your own watchers, integrate net-snmp or a	2199	variable changes, implement your own watchers, integrate net-snmp or a
1854	coroutine library and lots more. They are also occasionally useful if	2200	coroutine library and lots more. They are also occasionally useful if
1855	you cache some data and want to flush it before blocking (for example,	2201	you cache some data and want to flush it before blocking (for example,
1856	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2202	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1857	watcher).	2203	watcher).
1858		2204
1859	This is done by examining in each prepare call which file descriptors need	2205	This is done by examining in each prepare call which file descriptors
1860	to be watched by the other library, registering C<ev_io> watchers for	2206	need to be watched by the other library, registering C<ev_io> watchers
1861	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2207	for them and starting an C<ev_timer> watcher for any timeouts (many
1862	provide just this functionality). Then, in the check watcher you check for	2208	libraries provide exactly this functionality). Then, in the check watcher,
1863	any events that occured (by checking the pending status of all watchers	2209	you check for any events that occurred (by checking the pending status
1864	and stopping them) and call back into the library. The I/O and timer	2210	of all watchers and stopping them) and call back into the library. The
1865	callbacks will never actually be called (but must be valid nevertheless,	2211	I/O and timer callbacks will never actually be called (but must be valid
1866	because you never know, you know?).	2212	nevertheless, because you never know, you know?).
1867		2213
1868	As another example, the Perl Coro module uses these hooks to integrate	2214	As another example, the Perl Coro module uses these hooks to integrate
1869	coroutines into libev programs, by yielding to other active coroutines	2215	coroutines into libev programs, by yielding to other active coroutines
1870	during each prepare and only letting the process block if no coroutines	2216	during each prepare and only letting the process block if no coroutines
1871	are ready to run (it's actually more complicated: it only runs coroutines	2217	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1874	loop from blocking if lower-priority coroutines are active, thus mapping	2220	loop from blocking if lower-priority coroutines are active, thus mapping
1875	low-priority coroutines to idle/background tasks).	2221	low-priority coroutines to idle/background tasks).
1876		2222
1877	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2223	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1878	priority, to ensure that they are being run before any other watchers	2224	priority, to ensure that they are being run before any other watchers
		2225	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2226
1879	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2227	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1880	too) should not activate ("feed") events into libev. While libev fully	2228	activate ("feed") events into libev. While libev fully supports this, they
1881	supports this, they might get executed before other C<ev_check> watchers	2229	might get executed before other C<ev_check> watchers did their job. As
1882	did their job. As C<ev_check> watchers are often used to embed other	2230	C<ev_check> watchers are often used to embed other (non-libev) event
1883	(non-libev) event loops those other event loops might be in an unusable	2231	loops those other event loops might be in an unusable state until their
1884	state until their C<ev_check> watcher ran (always remind yourself to	2232	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1885	coexist peacefully with others).	2233	others).
1886		2234
1887	=head3 Watcher-Specific Functions and Data Members	2235	=head3 Watcher-Specific Functions and Data Members
1888		2236
1889	=over 4	2237	=over 4
1890		2238
…		…
1892		2240
1893	=item ev_check_init (ev_check *, callback)	2241	=item ev_check_init (ev_check *, callback)
1894		2242
1895	Initialises and configures the prepare or check watcher - they have no	2243	Initialises and configures the prepare or check watcher - they have no
1896	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2244	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1897	macros, but using them is utterly, utterly and completely pointless.	2245	macros, but using them is utterly, utterly, utterly and completely
		2246	pointless.
1898		2247
1899	=back	2248	=back
1900		2249
1901	=head3 Examples	2250	=head3 Examples
1902		2251
…		…
1911	and in a check watcher, destroy them and call into libadns. What follows	2260	and in a check watcher, destroy them and call into libadns. What follows
1912	is pseudo-code only of course. This requires you to either use a low	2261	is pseudo-code only of course. This requires you to either use a low
1913	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2262	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1914	the callbacks for the IO/timeout watchers might not have been called yet.	2263	the callbacks for the IO/timeout watchers might not have been called yet.
1915		2264
1916	static ev_io iow [nfd];	2265	static ev_io iow [nfd];
1917	static ev_timer tw;	2266	static ev_timer tw;
1918		2267
1919	static void	2268	static void
1920	io_cb (ev_loop *loop, ev_io *w, int revents)	2269	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1921	{	2270	{
1922	}	2271	}
1923		2272
1924	// create io watchers for each fd and a timer before blocking	2273	// create io watchers for each fd and a timer before blocking
1925	static void	2274	static void
1926	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2275	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1927	{	2276	{
1928	int timeout = 3600000;	2277	int timeout = 3600000;
1929	struct pollfd fds [nfd];	2278	struct pollfd fds [nfd];
1930	// actual code will need to loop here and realloc etc.	2279	// actual code will need to loop here and realloc etc.
1931	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2280	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1932		2281
1933	/* the callback is illegal, but won't be called as we stop during check */	2282	/* the callback is illegal, but won't be called as we stop during check */
1934	ev_timer_init (&tw, 0, timeout * 1e-3);	2283	ev_timer_init (&tw, 0, timeout * 1e-3);
1935	ev_timer_start (loop, &tw);	2284	ev_timer_start (loop, &tw);
1936		2285
1937	// create one ev_io per pollfd	2286	// create one ev_io per pollfd
1938	for (int i = 0; i < nfd; ++i)	2287	for (int i = 0; i < nfd; ++i)
1939	{	2288	{
1940	ev_io_init (iow + i, io_cb, fds [i].fd,	2289	ev_io_init (iow + i, io_cb, fds [i].fd,
1941	((fds [i].events & POLLIN ? EV_READ : 0)	2290	((fds [i].events & POLLIN ? EV_READ : 0)
1942	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2291	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1943		2292
1944	fds [i].revents = 0;	2293	fds [i].revents = 0;
1945	ev_io_start (loop, iow + i);	2294	ev_io_start (loop, iow + i);
1946	}	2295	}
1947	}	2296	}
1948		2297
1949	// stop all watchers after blocking	2298	// stop all watchers after blocking
1950	static void	2299	static void
1951	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2300	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1952	{	2301	{
1953	ev_timer_stop (loop, &tw);	2302	ev_timer_stop (loop, &tw);
1954		2303
1955	for (int i = 0; i < nfd; ++i)	2304	for (int i = 0; i < nfd; ++i)
1956	{	2305	{
1957	// set the relevant poll flags	2306	// set the relevant poll flags
1958	// could also call adns_processreadable etc. here	2307	// could also call adns_processreadable etc. here
1959	struct pollfd *fd = fds + i;	2308	struct pollfd *fd = fds + i;
1960	int revents = ev_clear_pending (iow + i);	2309	int revents = ev_clear_pending (iow + i);
1961	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2310	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1962	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2311	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1963		2312
1964	// now stop the watcher	2313	// now stop the watcher
1965	ev_io_stop (loop, iow + i);	2314	ev_io_stop (loop, iow + i);
1966	}	2315	}
1967		2316
1968	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2317	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1969	}	2318	}
1970		2319
1971	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2320	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1972	in the prepare watcher and would dispose of the check watcher.	2321	in the prepare watcher and would dispose of the check watcher.
1973		2322
1974	Method 3: If the module to be embedded supports explicit event	2323	Method 3: If the module to be embedded supports explicit event
1975	notification (adns does), you can also make use of the actual watcher	2324	notification (libadns does), you can also make use of the actual watcher
1976	callbacks, and only destroy/create the watchers in the prepare watcher.	2325	callbacks, and only destroy/create the watchers in the prepare watcher.
1977		2326
1978	static void	2327	static void
1979	timer_cb (EV_P_ ev_timer *w, int revents)	2328	timer_cb (EV_P_ ev_timer *w, int revents)
1980	{	2329	{
1981	adns_state ads = (adns_state)w->data;	2330	adns_state ads = (adns_state)w->data;
1982	update_now (EV_A);	2331	update_now (EV_A);
1983		2332
1984	adns_processtimeouts (ads, &tv_now);	2333	adns_processtimeouts (ads, &tv_now);
1985	}	2334	}
1986		2335
1987	static void	2336	static void
1988	io_cb (EV_P_ ev_io *w, int revents)	2337	io_cb (EV_P_ ev_io *w, int revents)
1989	{	2338	{
1990	adns_state ads = (adns_state)w->data;	2339	adns_state ads = (adns_state)w->data;
1991	update_now (EV_A);	2340	update_now (EV_A);
1992		2341
1993	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2342	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1994	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2343	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1995	}	2344	}
1996		2345
1997	// do not ever call adns_afterpoll	2346	// do not ever call adns_afterpoll
1998		2347
1999	Method 4: Do not use a prepare or check watcher because the module you	2348	Method 4: Do not use a prepare or check watcher because the module you
2000	want to embed is too inflexible to support it. Instead, youc na override	2349	want to embed is not flexible enough to support it. Instead, you can
2001	their poll function. The drawback with this solution is that the main	2350	override their poll function. The drawback with this solution is that the
2002	loop is now no longer controllable by EV. The C<Glib::EV> module does	2351	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2003	this.	2352	this approach, effectively embedding EV as a client into the horrible
		2353	libglib event loop.
2004		2354
2005	static gint	2355	static gint
2006	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2356	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2007	{	2357	{
2008	int got_events = 0;	2358	int got_events = 0;
2009		2359
2010	for (n = 0; n < nfds; ++n)	2360	for (n = 0; n < nfds; ++n)
2011	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2361	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2012		2362
2013	if (timeout >= 0)	2363	if (timeout >= 0)
2014	// create/start timer	2364	// create/start timer
2015		2365
2016	// poll	2366	// poll
2017	ev_loop (EV_A_ 0);	2367	ev_loop (EV_A_ 0);
2018		2368
2019	// stop timer again	2369	// stop timer again
2020	if (timeout >= 0)	2370	if (timeout >= 0)
2021	ev_timer_stop (EV_A_ &to);	2371	ev_timer_stop (EV_A_ &to);
2022		2372
2023	// stop io watchers again - their callbacks should have set	2373	// stop io watchers again - their callbacks should have set
2024	for (n = 0; n < nfds; ++n)	2374	for (n = 0; n < nfds; ++n)
2025	ev_io_stop (EV_A_ iow [n]);	2375	ev_io_stop (EV_A_ iow [n]);
2026		2376
2027	return got_events;	2377	return got_events;
2028	}	2378	}
2029		2379
2030		2380
2031	=head2 C<ev_embed> - when one backend isn't enough...	2381	=head2 C<ev_embed> - when one backend isn't enough...
2032		2382
2033	This is a rather advanced watcher type that lets you embed one event loop	2383	This is a rather advanced watcher type that lets you embed one event loop
…		…
2039	prioritise I/O.	2389	prioritise I/O.
2040		2390
2041	As an example for a bug workaround, the kqueue backend might only support	2391	As an example for a bug workaround, the kqueue backend might only support
2042	sockets on some platform, so it is unusable as generic backend, but you	2392	sockets on some platform, so it is unusable as generic backend, but you
2043	still want to make use of it because you have many sockets and it scales	2393	still want to make use of it because you have many sockets and it scales
2044	so nicely. In this case, you would create a kqueue-based loop and embed it	2394	so nicely. In this case, you would create a kqueue-based loop and embed
2045	into your default loop (which might use e.g. poll). Overall operation will	2395	it into your default loop (which might use e.g. poll). Overall operation
2046	be a bit slower because first libev has to poll and then call kevent, but	2396	will be a bit slower because first libev has to call C<poll> and then
2047	at least you can use both at what they are best.	2397	C<kevent>, but at least you can use both mechanisms for what they are
		2398	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2048		2399
2049	As for prioritising I/O: rarely you have the case where some fds have	2400	As for prioritising I/O: under rare circumstances you have the case where
2050	to be watched and handled very quickly (with low latency), and even	2401	some fds have to be watched and handled very quickly (with low latency),
2051	priorities and idle watchers might have too much overhead. In this case	2402	and even priorities and idle watchers might have too much overhead. In
2052	you would put all the high priority stuff in one loop and all the rest in	2403	this case you would put all the high priority stuff in one loop and all
2053	a second one, and embed the second one in the first.	2404	the rest in a second one, and embed the second one in the first.
2054		2405
2055	As long as the watcher is active, the callback will be invoked every time	2406	As long as the watcher is active, the callback will be invoked every time
2056	there might be events pending in the embedded loop. The callback must then	2407	there might be events pending in the embedded loop. The callback must then
2057	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2408	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2058	their callbacks (you could also start an idle watcher to give the embedded	2409	their callbacks (you could also start an idle watcher to give the embedded
…		…
2066	interested in that.	2417	interested in that.
2067		2418
2068	Also, there have not currently been made special provisions for forking:	2419	Also, there have not currently been made special provisions for forking:
2069	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2420	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2070	but you will also have to stop and restart any C<ev_embed> watchers	2421	but you will also have to stop and restart any C<ev_embed> watchers
2071	yourself.	2422	yourself - but you can use a fork watcher to handle this automatically,
		2423	and future versions of libev might do just that.
2072		2424
2073	Unfortunately, not all backends are embeddable, only the ones returned by	2425	Unfortunately, not all backends are embeddable: only the ones returned by
2074	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2426	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2075	portable one.	2427	portable one.
2076		2428
2077	So when you want to use this feature you will always have to be prepared	2429	So when you want to use this feature you will always have to be prepared
2078	that you cannot get an embeddable loop. The recommended way to get around	2430	that you cannot get an embeddable loop. The recommended way to get around
2079	this is to have a separate variables for your embeddable loop, try to	2431	this is to have a separate variables for your embeddable loop, try to
2080	create it, and if that fails, use the normal loop for everything.	2432	create it, and if that fails, use the normal loop for everything.
2081		2433
		2434	=head3 C<ev_embed> and fork
		2435
		2436	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2437	automatically be applied to the embedded loop as well, so no special
		2438	fork handling is required in that case. When the watcher is not running,
		2439	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2440	as applicable.
		2441
2082	=head3 Watcher-Specific Functions and Data Members	2442	=head3 Watcher-Specific Functions and Data Members
2083		2443
2084	=over 4	2444	=over 4
2085		2445
2086	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2446	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2089		2449
2090	Configures the watcher to embed the given loop, which must be	2450	Configures the watcher to embed the given loop, which must be
2091	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2451	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2092	invoked automatically, otherwise it is the responsibility of the callback	2452	invoked automatically, otherwise it is the responsibility of the callback
2093	to invoke it (it will continue to be called until the sweep has been done,	2453	to invoke it (it will continue to be called until the sweep has been done,
2094	if you do not want thta, you need to temporarily stop the embed watcher).	2454	if you do not want that, you need to temporarily stop the embed watcher).
2095		2455
2096	=item ev_embed_sweep (loop, ev_embed *)	2456	=item ev_embed_sweep (loop, ev_embed *)
2097		2457
2098	Make a single, non-blocking sweep over the embedded loop. This works	2458	Make a single, non-blocking sweep over the embedded loop. This works
2099	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2459	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2100	apropriate way for embedded loops.	2460	appropriate way for embedded loops.
2101		2461
2102	=item struct ev_loop *other [read-only]	2462	=item struct ev_loop *other [read-only]
2103		2463
2104	The embedded event loop.	2464	The embedded event loop.
2105		2465
…		…
2107		2467
2108	=head3 Examples	2468	=head3 Examples
2109		2469
2110	Example: Try to get an embeddable event loop and embed it into the default	2470	Example: Try to get an embeddable event loop and embed it into the default
2111	event loop. If that is not possible, use the default loop. The default	2471	event loop. If that is not possible, use the default loop. The default
2112	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2472	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2113	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2473	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2114	used).	2474	used).
2115		2475
2116	struct ev_loop *loop_hi = ev_default_init (0);	2476	struct ev_loop *loop_hi = ev_default_init (0);
2117	struct ev_loop *loop_lo = 0;	2477	struct ev_loop *loop_lo = 0;
2118	struct ev_embed embed;	2478	ev_embed embed;
2119		2479
2120	// see if there is a chance of getting one that works	2480	// see if there is a chance of getting one that works
2121	// (remember that a flags value of 0 means autodetection)	2481	// (remember that a flags value of 0 means autodetection)
2122	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2482	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2123	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2483	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2124	: 0;	2484	: 0;
2125		2485
2126	// if we got one, then embed it, otherwise default to loop_hi	2486	// if we got one, then embed it, otherwise default to loop_hi
2127	if (loop_lo)	2487	if (loop_lo)
2128	{	2488	{
2129	ev_embed_init (&embed, 0, loop_lo);	2489	ev_embed_init (&embed, 0, loop_lo);
2130	ev_embed_start (loop_hi, &embed);	2490	ev_embed_start (loop_hi, &embed);
2131	}	2491	}
2132	else	2492	else
2133	loop_lo = loop_hi;	2493	loop_lo = loop_hi;
2134		2494
2135	Example: Check if kqueue is available but not recommended and create	2495	Example: Check if kqueue is available but not recommended and create
2136	a kqueue backend for use with sockets (which usually work with any	2496	a kqueue backend for use with sockets (which usually work with any
2137	kqueue implementation). Store the kqueue/socket-only event loop in	2497	kqueue implementation). Store the kqueue/socket-only event loop in
2138	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2498	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2139		2499
2140	struct ev_loop *loop = ev_default_init (0);	2500	struct ev_loop *loop = ev_default_init (0);
2141	struct ev_loop *loop_socket = 0;	2501	struct ev_loop *loop_socket = 0;
2142	struct ev_embed embed;	2502	ev_embed embed;
2143		2503
2144	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2504	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2145	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2505	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2146	{	2506	{
2147	ev_embed_init (&embed, 0, loop_socket);	2507	ev_embed_init (&embed, 0, loop_socket);
2148	ev_embed_start (loop, &embed);	2508	ev_embed_start (loop, &embed);
2149	}	2509	}
2150		2510
2151	if (!loop_socket)	2511	if (!loop_socket)
2152	loop_socket = loop;	2512	loop_socket = loop;
2153		2513
2154	// now use loop_socket for all sockets, and loop for everything else	2514	// now use loop_socket for all sockets, and loop for everything else
2155		2515
2156		2516
2157	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2517	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2158		2518
2159	Fork watchers are called when a C<fork ()> was detected (usually because	2519	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2203	is that the author does not know of a simple (or any) algorithm for a	2563	is that the author does not know of a simple (or any) algorithm for a
2204	multiple-writer-single-reader queue that works in all cases and doesn't	2564	multiple-writer-single-reader queue that works in all cases and doesn't
2205	need elaborate support such as pthreads.	2565	need elaborate support such as pthreads.
2206		2566
2207	That means that if you want to queue data, you have to provide your own	2567	That means that if you want to queue data, you have to provide your own
2208	queue. But at least I can tell you would implement locking around your	2568	queue. But at least I can tell you how to implement locking around your
2209	queue:	2569	queue:
2210		2570
2211	=over 4	2571	=over 4
2212		2572
2213	=item queueing from a signal handler context	2573	=item queueing from a signal handler context
2214		2574
2215	To implement race-free queueing, you simply add to the queue in the signal	2575	To implement race-free queueing, you simply add to the queue in the signal
2216	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2576	handler but you block the signal handler in the watcher callback. Here is
2217	some fictitiuous SIGUSR1 handler:	2577	an example that does that for some fictitious SIGUSR1 handler:
2218		2578
2219	static ev_async mysig;	2579	static ev_async mysig;
2220		2580
2221	static void	2581	static void
2222	sigusr1_handler (void)	2582	sigusr1_handler (void)
…		…
2288	=over 4	2648	=over 4
2289		2649
2290	=item ev_async_init (ev_async *, callback)	2650	=item ev_async_init (ev_async *, callback)
2291		2651
2292	Initialises and configures the async watcher - it has no parameters of any	2652	Initialises and configures the async watcher - it has no parameters of any
2293	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2653	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2294	believe me.	2654	trust me.
2295		2655
2296	=item ev_async_send (loop, ev_async *)	2656	=item ev_async_send (loop, ev_async *)
2297		2657
2298	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2658	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2299	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2659	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2300	C<ev_feed_event>, this call is safe to do in other threads, signal or	2660	C<ev_feed_event>, this call is safe to do from other threads, signal or
2301	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2661	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2302	section below on what exactly this means).	2662	section below on what exactly this means).
2303		2663
2304	This call incurs the overhead of a syscall only once per loop iteration,	2664	This call incurs the overhead of a system call only once per loop iteration,
2305	so while the overhead might be noticable, it doesn't apply to repeated	2665	so while the overhead might be noticeable, it doesn't apply to repeated
2306	calls to C<ev_async_send>.	2666	calls to C<ev_async_send>.
2307		2667
2308	=item bool = ev_async_pending (ev_async *)	2668	=item bool = ev_async_pending (ev_async *)
2309		2669
2310	Returns a non-zero value when C<ev_async_send> has been called on the	2670	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2312	event loop.	2672	event loop.
2313		2673
2314	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2674	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2315	the loop iterates next and checks for the watcher to have become active,	2675	the loop iterates next and checks for the watcher to have become active,
2316	it will reset the flag again. C<ev_async_pending> can be used to very	2676	it will reset the flag again. C<ev_async_pending> can be used to very
2317	quickly check wether invoking the loop might be a good idea.	2677	quickly check whether invoking the loop might be a good idea.
2318		2678
2319	Not that this does I<not> check wether the watcher itself is pending, only	2679	Not that this does I<not> check whether the watcher itself is pending, only
2320	wether it has been requested to make this watcher pending.	2680	whether it has been requested to make this watcher pending.
2321		2681
2322	=back	2682	=back
2323		2683
2324		2684
2325	=head1 OTHER FUNCTIONS	2685	=head1 OTHER FUNCTIONS
…		…
2329	=over 4	2689	=over 4
2330		2690
2331	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2691	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2332		2692
2333	This function combines a simple timer and an I/O watcher, calls your	2693	This function combines a simple timer and an I/O watcher, calls your
2334	callback on whichever event happens first and automatically stop both	2694	callback on whichever event happens first and automatically stops both
2335	watchers. This is useful if you want to wait for a single event on an fd	2695	watchers. This is useful if you want to wait for a single event on an fd
2336	or timeout without having to allocate/configure/start/stop/free one or	2696	or timeout without having to allocate/configure/start/stop/free one or
2337	more watchers yourself.	2697	more watchers yourself.
2338		2698
2339	If C<fd> is less than 0, then no I/O watcher will be started and events	2699	If C<fd> is less than 0, then no I/O watcher will be started and the
2340	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2700	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2341	C<events> set will be craeted and started.	2701	the given C<fd> and C<events> set will be created and started.
2342		2702
2343	If C<timeout> is less than 0, then no timeout watcher will be	2703	If C<timeout> is less than 0, then no timeout watcher will be
2344	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2704	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2345	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2705	repeat = 0) will be started. C<0> is a valid timeout.
2346	dubious value.
2347		2706
2348	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2707	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2349	passed an C<revents> set like normal event callbacks (a combination of	2708	passed an C<revents> set like normal event callbacks (a combination of
2350	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2709	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2351	value passed to C<ev_once>:	2710	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2711	a timeout and an io event at the same time - you probably should give io
		2712	events precedence.
2352		2713
		2714	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2715
2353	static void stdin_ready (int revents, void *arg)	2716	static void stdin_ready (int revents, void *arg)
2354	{	2717	{
2355	if (revents & EV_TIMEOUT)
2356	/* doh, nothing entered */;
2357	else if (revents & EV_READ)	2718	if (revents & EV_READ)
2358	/* stdin might have data for us, joy! */;	2719	/* stdin might have data for us, joy! */;
		2720	else if (revents & EV_TIMEOUT)
		2721	/* doh, nothing entered */;
2359	}	2722	}
2360		2723
2361	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2724	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2362		2725
2363	=item ev_feed_event (ev_loop *, watcher *, int revents)	2726	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2364		2727
2365	Feeds the given event set into the event loop, as if the specified event	2728	Feeds the given event set into the event loop, as if the specified event
2366	had happened for the specified watcher (which must be a pointer to an	2729	had happened for the specified watcher (which must be a pointer to an
2367	initialised but not necessarily started event watcher).	2730	initialised but not necessarily started event watcher).
2368		2731
2369	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2732	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2370		2733
2371	Feed an event on the given fd, as if a file descriptor backend detected	2734	Feed an event on the given fd, as if a file descriptor backend detected
2372	the given events it.	2735	the given events it.
2373		2736
2374	=item ev_feed_signal_event (ev_loop *loop, int signum)	2737	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2375		2738
2376	Feed an event as if the given signal occured (C<loop> must be the default	2739	Feed an event as if the given signal occurred (C<loop> must be the default
2377	loop!).	2740	loop!).
2378		2741
2379	=back	2742	=back
2380		2743
2381		2744
…		…
2410	=back	2773	=back
2411		2774
2412	=head1 C++ SUPPORT	2775	=head1 C++ SUPPORT
2413		2776
2414	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2777	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2415	you to use some convinience methods to start/stop watchers and also change	2778	you to use some convenience methods to start/stop watchers and also change
2416	the callback model to a model using method callbacks on objects.	2779	the callback model to a model using method callbacks on objects.
2417		2780
2418	To use it,	2781	To use it,
2419		2782
2420	#include <ev++.h>	2783	#include <ev++.h>
2421		2784
2422	This automatically includes F<ev.h> and puts all of its definitions (many	2785	This automatically includes F<ev.h> and puts all of its definitions (many
2423	of them macros) into the global namespace. All C++ specific things are	2786	of them macros) into the global namespace. All C++ specific things are
2424	put into the C<ev> namespace. It should support all the same embedding	2787	put into the C<ev> namespace. It should support all the same embedding
2425	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2788	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2492	your compiler is good :), then the method will be fully inlined into the	2855	your compiler is good :), then the method will be fully inlined into the
2493	thunking function, making it as fast as a direct C callback.	2856	thunking function, making it as fast as a direct C callback.
2494		2857
2495	Example: simple class declaration and watcher initialisation	2858	Example: simple class declaration and watcher initialisation
2496		2859
2497	struct myclass	2860	struct myclass
2498	{	2861	{
2499	void io_cb (ev::io &w, int revents) { }	2862	void io_cb (ev::io &w, int revents) { }
2500	}	2863	}
2501		2864
2502	myclass obj;	2865	myclass obj;
2503	ev::io iow;	2866	ev::io iow;
2504	iow.set <myclass, &myclass::io_cb> (&obj);	2867	iow.set <myclass, &myclass::io_cb> (&obj);
2505		2868
2506	=item w->set<function> (void *data = 0)	2869	=item w->set<function> (void *data = 0)
2507		2870
2508	Also sets a callback, but uses a static method or plain function as	2871	Also sets a callback, but uses a static method or plain function as
2509	callback. The optional C<data> argument will be stored in the watcher's	2872	callback. The optional C<data> argument will be stored in the watcher's
…		…
2511		2874
2512	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2875	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2513		2876
2514	See the method-C<set> above for more details.	2877	See the method-C<set> above for more details.
2515		2878
2516	Example:	2879	Example: Use a plain function as callback.
2517		2880
2518	static void io_cb (ev::io &w, int revents) { }	2881	static void io_cb (ev::io &w, int revents) { }
2519	iow.set <io_cb> ();	2882	iow.set <io_cb> ();
2520		2883
2521	=item w->set (struct ev_loop *)	2884	=item w->set (struct ev_loop *)
2522		2885
2523	Associates a different C<struct ev_loop> with this watcher. You can only	2886	Associates a different C<struct ev_loop> with this watcher. You can only
2524	do this when the watcher is inactive (and not pending either).	2887	do this when the watcher is inactive (and not pending either).
2525		2888
2526	=item w->set ([args])	2889	=item w->set ([arguments])
2527		2890
2528	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2891	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2529	called at least once. Unlike the C counterpart, an active watcher gets	2892	called at least once. Unlike the C counterpart, an active watcher gets
2530	automatically stopped and restarted when reconfiguring it with this	2893	automatically stopped and restarted when reconfiguring it with this
2531	method.	2894	method.
2532		2895
2533	=item w->start ()	2896	=item w->start ()
…		…
2557	=back	2920	=back
2558		2921
2559	Example: Define a class with an IO and idle watcher, start one of them in	2922	Example: Define a class with an IO and idle watcher, start one of them in
2560	the constructor.	2923	the constructor.
2561		2924
2562	class myclass	2925	class myclass
2563	{	2926	{
2564	ev::io io; void io_cb (ev::io &w, int revents);	2927	ev::io io ; void io_cb (ev::io &w, int revents);
2565	ev:idle idle void idle_cb (ev::idle &w, int revents);	2928	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2566		2929
2567	myclass (int fd)	2930	myclass (int fd)
2568	{	2931	{
2569	io .set <myclass, &myclass::io_cb > (this);	2932	io .set <myclass, &myclass::io_cb > (this);
2570	idle.set <myclass, &myclass::idle_cb> (this);	2933	idle.set <myclass, &myclass::idle_cb> (this);
2571		2934
2572	io.start (fd, ev::READ);	2935	io.start (fd, ev::READ);
2573	}	2936	}
2574	};	2937	};
2575		2938
2576		2939
2577	=head1 OTHER LANGUAGE BINDINGS	2940	=head1 OTHER LANGUAGE BINDINGS
2578		2941
2579	Libev does not offer other language bindings itself, but bindings for a	2942	Libev does not offer other language bindings itself, but bindings for a
2580	numbe rof languages exist in the form of third-party packages. If you know	2943	number of languages exist in the form of third-party packages. If you know
2581	any interesting language binding in addition to the ones listed here, drop	2944	any interesting language binding in addition to the ones listed here, drop
2582	me a note.	2945	me a note.
2583		2946
2584	=over 4	2947	=over 4
2585		2948
2586	=item Perl	2949	=item Perl
2587		2950
2588	The EV module implements the full libev API and is actually used to test	2951	The EV module implements the full libev API and is actually used to test
2589	libev. EV is developed together with libev. Apart from the EV core module,	2952	libev. EV is developed together with libev. Apart from the EV core module,
2590	there are additional modules that implement libev-compatible interfaces	2953	there are additional modules that implement libev-compatible interfaces
2591	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2954	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2592	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2955	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2956	and C<EV::Glib>).
2593		2957
2594	It can be found and installed via CPAN, its homepage is found at	2958	It can be found and installed via CPAN, its homepage is at
2595	L<http://software.schmorp.de/pkg/EV>.	2959	L<http://software.schmorp.de/pkg/EV>.
2596		2960
		2961	=item Python
		2962
		2963	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2964	seems to be quite complete and well-documented. Note, however, that the
		2965	patch they require for libev is outright dangerous as it breaks the ABI
		2966	for everybody else, and therefore, should never be applied in an installed
		2967	libev (if python requires an incompatible ABI then it needs to embed
		2968	libev).
		2969
2597	=item Ruby	2970	=item Ruby
2598		2971
2599	Tony Arcieri has written a ruby extension that offers access to a subset	2972	Tony Arcieri has written a ruby extension that offers access to a subset
2600	of the libev API and adds filehandle abstractions, asynchronous DNS and	2973	of the libev API and adds file handle abstractions, asynchronous DNS and
2601	more on top of it. It can be found via gem servers. Its homepage is at	2974	more on top of it. It can be found via gem servers. Its homepage is at
2602	L<http://rev.rubyforge.org/>.	2975	L<http://rev.rubyforge.org/>.
2603		2976
2604	=item D	2977	=item D
2605		2978
2606	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2979	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2607	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2980	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2981
		2982	=item Ocaml
		2983
		2984	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2985	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2608		2986
2609	=back	2987	=back
2610		2988
2611		2989
2612	=head1 MACRO MAGIC	2990	=head1 MACRO MAGIC
2613		2991
2614	Libev can be compiled with a variety of options, the most fundamantal	2992	Libev can be compiled with a variety of options, the most fundamental
2615	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2993	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2616	functions and callbacks have an initial C<struct ev_loop *> argument.	2994	functions and callbacks have an initial C<struct ev_loop *> argument.
2617		2995
2618	To make it easier to write programs that cope with either variant, the	2996	To make it easier to write programs that cope with either variant, the
2619	following macros are defined:	2997	following macros are defined:
…		…
2624		3002
2625	This provides the loop I<argument> for functions, if one is required ("ev	3003	This provides the loop I<argument> for functions, if one is required ("ev
2626	loop argument"). The C<EV_A> form is used when this is the sole argument,	3004	loop argument"). The C<EV_A> form is used when this is the sole argument,
2627	C<EV_A_> is used when other arguments are following. Example:	3005	C<EV_A_> is used when other arguments are following. Example:
2628		3006
2629	ev_unref (EV_A);	3007	ev_unref (EV_A);
2630	ev_timer_add (EV_A_ watcher);	3008	ev_timer_add (EV_A_ watcher);
2631	ev_loop (EV_A_ 0);	3009	ev_loop (EV_A_ 0);
2632		3010
2633	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3011	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2634	which is often provided by the following macro.	3012	which is often provided by the following macro.
2635		3013
2636	=item C<EV_P>, C<EV_P_>	3014	=item C<EV_P>, C<EV_P_>
2637		3015
2638	This provides the loop I<parameter> for functions, if one is required ("ev	3016	This provides the loop I<parameter> for functions, if one is required ("ev
2639	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3017	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2640	C<EV_P_> is used when other parameters are following. Example:	3018	C<EV_P_> is used when other parameters are following. Example:
2641		3019
2642	// this is how ev_unref is being declared	3020	// this is how ev_unref is being declared
2643	static void ev_unref (EV_P);	3021	static void ev_unref (EV_P);
2644		3022
2645	// this is how you can declare your typical callback	3023	// this is how you can declare your typical callback
2646	static void cb (EV_P_ ev_timer *w, int revents)	3024	static void cb (EV_P_ ev_timer *w, int revents)
2647		3025
2648	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3026	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2649	suitable for use with C<EV_A>.	3027	suitable for use with C<EV_A>.
2650		3028
2651	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3029	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2667		3045
2668	Example: Declare and initialise a check watcher, utilising the above	3046	Example: Declare and initialise a check watcher, utilising the above
2669	macros so it will work regardless of whether multiple loops are supported	3047	macros so it will work regardless of whether multiple loops are supported
2670	or not.	3048	or not.
2671		3049
2672	static void	3050	static void
2673	check_cb (EV_P_ ev_timer *w, int revents)	3051	check_cb (EV_P_ ev_timer *w, int revents)
2674	{	3052	{
2675	ev_check_stop (EV_A_ w);	3053	ev_check_stop (EV_A_ w);
2676	}	3054	}
2677		3055
2678	ev_check check;	3056	ev_check check;
2679	ev_check_init (&check, check_cb);	3057	ev_check_init (&check, check_cb);
2680	ev_check_start (EV_DEFAULT_ &check);	3058	ev_check_start (EV_DEFAULT_ &check);
2681	ev_loop (EV_DEFAULT_ 0);	3059	ev_loop (EV_DEFAULT_ 0);
2682		3060
2683	=head1 EMBEDDING	3061	=head1 EMBEDDING
2684		3062
2685	Libev can (and often is) directly embedded into host	3063	Libev can (and often is) directly embedded into host
2686	applications. Examples of applications that embed it include the Deliantra	3064	applications. Examples of applications that embed it include the Deliantra
…		…
2693	libev somewhere in your source tree).	3071	libev somewhere in your source tree).
2694		3072
2695	=head2 FILESETS	3073	=head2 FILESETS
2696		3074
2697	Depending on what features you need you need to include one or more sets of files	3075	Depending on what features you need you need to include one or more sets of files
2698	in your app.	3076	in your application.
2699		3077
2700	=head3 CORE EVENT LOOP	3078	=head3 CORE EVENT LOOP
2701		3079
2702	To include only the libev core (all the C<ev_*> functions), with manual	3080	To include only the libev core (all the C<ev_*> functions), with manual
2703	configuration (no autoconf):	3081	configuration (no autoconf):
2704		3082
2705	#define EV_STANDALONE 1	3083	#define EV_STANDALONE 1
2706	#include "ev.c"	3084	#include "ev.c"
2707		3085
2708	This will automatically include F<ev.h>, too, and should be done in a	3086	This will automatically include F<ev.h>, too, and should be done in a
2709	single C source file only to provide the function implementations. To use	3087	single C source file only to provide the function implementations. To use
2710	it, do the same for F<ev.h> in all files wishing to use this API (best	3088	it, do the same for F<ev.h> in all files wishing to use this API (best
2711	done by writing a wrapper around F<ev.h> that you can include instead and	3089	done by writing a wrapper around F<ev.h> that you can include instead and
2712	where you can put other configuration options):	3090	where you can put other configuration options):
2713		3091
2714	#define EV_STANDALONE 1	3092	#define EV_STANDALONE 1
2715	#include "ev.h"	3093	#include "ev.h"
2716		3094
2717	Both header files and implementation files can be compiled with a C++	3095	Both header files and implementation files can be compiled with a C++
2718	compiler (at least, thats a stated goal, and breakage will be treated	3096	compiler (at least, that's a stated goal, and breakage will be treated
2719	as a bug).	3097	as a bug).
2720		3098
2721	You need the following files in your source tree, or in a directory	3099	You need the following files in your source tree, or in a directory
2722	in your include path (e.g. in libev/ when using -Ilibev):	3100	in your include path (e.g. in libev/ when using -Ilibev):
2723		3101
2724	ev.h	3102	ev.h
2725	ev.c	3103	ev.c
2726	ev_vars.h	3104	ev_vars.h
2727	ev_wrap.h	3105	ev_wrap.h
2728		3106
2729	ev_win32.c required on win32 platforms only	3107	ev_win32.c required on win32 platforms only
2730		3108
2731	ev_select.c only when select backend is enabled (which is enabled by default)	3109	ev_select.c only when select backend is enabled (which is enabled by default)
2732	ev_poll.c only when poll backend is enabled (disabled by default)	3110	ev_poll.c only when poll backend is enabled (disabled by default)
2733	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3111	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2734	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3112	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2735	ev_port.c only when the solaris port backend is enabled (disabled by default)	3113	ev_port.c only when the solaris port backend is enabled (disabled by default)
2736		3114
2737	F<ev.c> includes the backend files directly when enabled, so you only need	3115	F<ev.c> includes the backend files directly when enabled, so you only need
2738	to compile this single file.	3116	to compile this single file.
2739		3117
2740	=head3 LIBEVENT COMPATIBILITY API	3118	=head3 LIBEVENT COMPATIBILITY API
2741		3119
2742	To include the libevent compatibility API, also include:	3120	To include the libevent compatibility API, also include:
2743		3121
2744	#include "event.c"	3122	#include "event.c"
2745		3123
2746	in the file including F<ev.c>, and:	3124	in the file including F<ev.c>, and:
2747		3125
2748	#include "event.h"	3126	#include "event.h"
2749		3127
2750	in the files that want to use the libevent API. This also includes F<ev.h>.	3128	in the files that want to use the libevent API. This also includes F<ev.h>.
2751		3129
2752	You need the following additional files for this:	3130	You need the following additional files for this:
2753		3131
2754	event.h	3132	event.h
2755	event.c	3133	event.c
2756		3134
2757	=head3 AUTOCONF SUPPORT	3135	=head3 AUTOCONF SUPPORT
2758		3136
2759	Instead of using C<EV_STANDALONE=1> and providing your config in	3137	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2760	whatever way you want, you can also C<m4_include([libev.m4])> in your	3138	whatever way you want, you can also C<m4_include([libev.m4])> in your
2761	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3139	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2762	include F<config.h> and configure itself accordingly.	3140	include F<config.h> and configure itself accordingly.
2763		3141
2764	For this of course you need the m4 file:	3142	For this of course you need the m4 file:
2765		3143
2766	libev.m4	3144	libev.m4
2767		3145
2768	=head2 PREPROCESSOR SYMBOLS/MACROS	3146	=head2 PREPROCESSOR SYMBOLS/MACROS
2769		3147
2770	Libev can be configured via a variety of preprocessor symbols you have to	3148	Libev can be configured via a variety of preprocessor symbols you have to
2771	define before including any of its files. The default in the absense of	3149	define before including any of its files. The default in the absence of
2772	autoconf is noted for every option.	3150	autoconf is documented for every option.
2773		3151
2774	=over 4	3152	=over 4
2775		3153
2776	=item EV_STANDALONE	3154	=item EV_STANDALONE
2777		3155
…		…
2782	F<event.h> that are not directly supported by the libev core alone.	3160	F<event.h> that are not directly supported by the libev core alone.
2783		3161
2784	=item EV_USE_MONOTONIC	3162	=item EV_USE_MONOTONIC
2785		3163
2786	If defined to be C<1>, libev will try to detect the availability of the	3164	If defined to be C<1>, libev will try to detect the availability of the
2787	monotonic clock option at both compiletime and runtime. Otherwise no use	3165	monotonic clock option at both compile time and runtime. Otherwise no use
2788	of the monotonic clock option will be attempted. If you enable this, you	3166	of the monotonic clock option will be attempted. If you enable this, you
2789	usually have to link against librt or something similar. Enabling it when	3167	usually have to link against librt or something similar. Enabling it when
2790	the functionality isn't available is safe, though, although you have	3168	the functionality isn't available is safe, though, although you have
2791	to make sure you link against any libraries where the C<clock_gettime>	3169	to make sure you link against any libraries where the C<clock_gettime>
2792	function is hiding in (often F<-lrt>).	3170	function is hiding in (often F<-lrt>).
2793		3171
2794	=item EV_USE_REALTIME	3172	=item EV_USE_REALTIME
2795		3173
2796	If defined to be C<1>, libev will try to detect the availability of the	3174	If defined to be C<1>, libev will try to detect the availability of the
2797	realtime clock option at compiletime (and assume its availability at	3175	real-time clock option at compile time (and assume its availability at
2798	runtime if successful). Otherwise no use of the realtime clock option will	3176	runtime if successful). Otherwise no use of the real-time clock option will
2799	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3177	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2800	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3178	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2801	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3179	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2802		3180
2803	=item EV_USE_NANOSLEEP	3181	=item EV_USE_NANOSLEEP
…		…
2814	2.7 or newer, otherwise disabled.	3192	2.7 or newer, otherwise disabled.
2815		3193
2816	=item EV_USE_SELECT	3194	=item EV_USE_SELECT
2817		3195
2818	If undefined or defined to be C<1>, libev will compile in support for the	3196	If undefined or defined to be C<1>, libev will compile in support for the
2819	C<select>(2) backend. No attempt at autodetection will be done: if no	3197	C<select>(2) backend. No attempt at auto-detection will be done: if no
2820	other method takes over, select will be it. Otherwise the select backend	3198	other method takes over, select will be it. Otherwise the select backend
2821	will not be compiled in.	3199	will not be compiled in.
2822		3200
2823	=item EV_SELECT_USE_FD_SET	3201	=item EV_SELECT_USE_FD_SET
2824		3202
2825	If defined to C<1>, then the select backend will use the system C<fd_set>	3203	If defined to C<1>, then the select backend will use the system C<fd_set>
2826	structure. This is useful if libev doesn't compile due to a missing	3204	structure. This is useful if libev doesn't compile due to a missing
2827	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3205	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2828	exotic systems. This usually limits the range of file descriptors to some	3206	exotic systems. This usually limits the range of file descriptors to some
2829	low limit such as 1024 or might have other limitations (winsocket only	3207	low limit such as 1024 or might have other limitations (winsocket only
2830	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3208	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2831	influence the size of the C<fd_set> used.	3209	influence the size of the C<fd_set> used.
2832		3210
…		…
2881	otherwise another method will be used as fallback. This is the preferred	3259	otherwise another method will be used as fallback. This is the preferred
2882	backend for Solaris 10 systems.	3260	backend for Solaris 10 systems.
2883		3261
2884	=item EV_USE_DEVPOLL	3262	=item EV_USE_DEVPOLL
2885		3263
2886	reserved for future expansion, works like the USE symbols above.	3264	Reserved for future expansion, works like the USE symbols above.
2887		3265
2888	=item EV_USE_INOTIFY	3266	=item EV_USE_INOTIFY
2889		3267
2890	If defined to be C<1>, libev will compile in support for the Linux inotify	3268	If defined to be C<1>, libev will compile in support for the Linux inotify
2891	interface to speed up C<ev_stat> watchers. Its actual availability will	3269	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2898	access is atomic with respect to other threads or signal contexts. No such	3276	access is atomic with respect to other threads or signal contexts. No such
2899	type is easily found in the C language, so you can provide your own type	3277	type is easily found in the C language, so you can provide your own type
2900	that you know is safe for your purposes. It is used both for signal handler "locking"	3278	that you know is safe for your purposes. It is used both for signal handler "locking"
2901	as well as for signal and thread safety in C<ev_async> watchers.	3279	as well as for signal and thread safety in C<ev_async> watchers.
2902		3280
2903	In the absense of this define, libev will use C<sig_atomic_t volatile>	3281	In the absence of this define, libev will use C<sig_atomic_t volatile>
2904	(from F<signal.h>), which is usually good enough on most platforms.	3282	(from F<signal.h>), which is usually good enough on most platforms.
2905		3283
2906	=item EV_H	3284	=item EV_H
2907		3285
2908	The name of the F<ev.h> header file used to include it. The default if	3286	The name of the F<ev.h> header file used to include it. The default if
…		…
2947	When doing priority-based operations, libev usually has to linearly search	3325	When doing priority-based operations, libev usually has to linearly search
2948	all the priorities, so having many of them (hundreds) uses a lot of space	3326	all the priorities, so having many of them (hundreds) uses a lot of space
2949	and time, so using the defaults of five priorities (-2 .. +2) is usually	3327	and time, so using the defaults of five priorities (-2 .. +2) is usually
2950	fine.	3328	fine.
2951		3329
2952	If your embedding app does not need any priorities, defining these both to	3330	If your embedding application does not need any priorities, defining these
2953	C<0> will save some memory and cpu.	3331	both to C<0> will save some memory and CPU.
2954		3332
2955	=item EV_PERIODIC_ENABLE	3333	=item EV_PERIODIC_ENABLE
2956		3334
2957	If undefined or defined to be C<1>, then periodic timers are supported. If	3335	If undefined or defined to be C<1>, then periodic timers are supported. If
2958	defined to be C<0>, then they are not. Disabling them saves a few kB of	3336	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2965	code.	3343	code.
2966		3344
2967	=item EV_EMBED_ENABLE	3345	=item EV_EMBED_ENABLE
2968		3346
2969	If undefined or defined to be C<1>, then embed watchers are supported. If	3347	If undefined or defined to be C<1>, then embed watchers are supported. If
2970	defined to be C<0>, then they are not.	3348	defined to be C<0>, then they are not. Embed watchers rely on most other
		3349	watcher types, which therefore must not be disabled.
2971		3350
2972	=item EV_STAT_ENABLE	3351	=item EV_STAT_ENABLE
2973		3352
2974	If undefined or defined to be C<1>, then stat watchers are supported. If	3353	If undefined or defined to be C<1>, then stat watchers are supported. If
2975	defined to be C<0>, then they are not.	3354	defined to be C<0>, then they are not.
…		…
2986		3365
2987	=item EV_MINIMAL	3366	=item EV_MINIMAL
2988		3367
2989	If you need to shave off some kilobytes of code at the expense of some	3368	If you need to shave off some kilobytes of code at the expense of some
2990	speed, define this symbol to C<1>. Currently this is used to override some	3369	speed, define this symbol to C<1>. Currently this is used to override some
2991	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3370	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2992	much smaller 2-heap for timer management over the default 4-heap.	3371	much smaller 2-heap for timer management over the default 4-heap.
2993		3372
2994	=item EV_PID_HASHSIZE	3373	=item EV_PID_HASHSIZE
2995		3374
2996	C<ev_child> watchers use a small hash table to distribute workload by	3375	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3007	two).	3386	two).
3008		3387
3009	=item EV_USE_4HEAP	3388	=item EV_USE_4HEAP
3010		3389
3011	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3390	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3012	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3391	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3013	to C<1>. The 4-heap uses more complicated (longer) code but has	3392	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3014	noticably faster performance with many (thousands) of watchers.	3393	faster performance with many (thousands) of watchers.
3015		3394
3016	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3395	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3017	(disabled).	3396	(disabled).
3018		3397
3019	=item EV_HEAP_CACHE_AT	3398	=item EV_HEAP_CACHE_AT
3020		3399
3021	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3400	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3022	timer and periodics heap, libev can cache the timestamp (I<at>) within	3401	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3023	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3402	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3024	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3403	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3025	but avoids random read accesses on heap changes. This improves performance	3404	but avoids random read accesses on heap changes. This improves performance
3026	noticably with with many (hundreds) of watchers.	3405	noticeably with many (hundreds) of watchers.
3027		3406
3028	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3407	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3029	(disabled).	3408	(disabled).
		3409
		3410	=item EV_VERIFY
		3411
		3412	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3413	be done: If set to C<0>, no internal verification code will be compiled
		3414	in. If set to C<1>, then verification code will be compiled in, but not
		3415	called. If set to C<2>, then the internal verification code will be
		3416	called once per loop, which can slow down libev. If set to C<3>, then the
		3417	verification code will be called very frequently, which will slow down
		3418	libev considerably.
		3419
		3420	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3421	C<0>.
3030		3422
3031	=item EV_COMMON	3423	=item EV_COMMON
3032		3424
3033	By default, all watchers have a C<void *data> member. By redefining	3425	By default, all watchers have a C<void *data> member. By redefining
3034	this macro to a something else you can include more and other types of	3426	this macro to a something else you can include more and other types of
3035	members. You have to define it each time you include one of the files,	3427	members. You have to define it each time you include one of the files,
3036	though, and it must be identical each time.	3428	though, and it must be identical each time.
3037		3429
3038	For example, the perl EV module uses something like this:	3430	For example, the perl EV module uses something like this:
3039		3431
3040	#define EV_COMMON \	3432	#define EV_COMMON \
3041	SV *self; /* contains this struct */ \	3433	SV *self; /* contains this struct */ \
3042	SV *cb_sv, *fh /* note no trailing ";" */	3434	SV *cb_sv, *fh /* note no trailing ";" */
3043		3435
3044	=item EV_CB_DECLARE (type)	3436	=item EV_CB_DECLARE (type)
3045		3437
3046	=item EV_CB_INVOKE (watcher, revents)	3438	=item EV_CB_INVOKE (watcher, revents)
3047		3439
…		…
3052	definition and a statement, respectively. See the F<ev.h> header file for	3444	definition and a statement, respectively. See the F<ev.h> header file for
3053	their default definitions. One possible use for overriding these is to	3445	their default definitions. One possible use for overriding these is to
3054	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3446	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3055	method calls instead of plain function calls in C++.	3447	method calls instead of plain function calls in C++.
3056		3448
		3449	=back
		3450
3057	=head2 EXPORTED API SYMBOLS	3451	=head2 EXPORTED API SYMBOLS
3058		3452
3059	If you need to re-export the API (e.g. via a dll) and you need a list of	3453	If you need to re-export the API (e.g. via a DLL) and you need a list of
3060	exported symbols, you can use the provided F<Symbol.*> files which list	3454	exported symbols, you can use the provided F<Symbol.*> files which list
3061	all public symbols, one per line:	3455	all public symbols, one per line:
3062		3456
3063	Symbols.ev for libev proper	3457	Symbols.ev for libev proper
3064	Symbols.event for the libevent emulation	3458	Symbols.event for the libevent emulation
3065		3459
3066	This can also be used to rename all public symbols to avoid clashes with	3460	This can also be used to rename all public symbols to avoid clashes with
3067	multiple versions of libev linked together (which is obviously bad in	3461	multiple versions of libev linked together (which is obviously bad in
3068	itself, but sometimes it is inconvinient to avoid this).	3462	itself, but sometimes it is inconvenient to avoid this).
3069		3463
3070	A sed command like this will create wrapper C<#define>'s that you need to	3464	A sed command like this will create wrapper C<#define>'s that you need to
3071	include before including F<ev.h>:	3465	include before including F<ev.h>:
3072		3466
3073	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3467	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3090	file.	3484	file.
3091		3485
3092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3486	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3093	that everybody includes and which overrides some configure choices:	3487	that everybody includes and which overrides some configure choices:
3094		3488
3095	#define EV_MINIMAL 1	3489	#define EV_MINIMAL 1
3096	#define EV_USE_POLL 0	3490	#define EV_USE_POLL 0
3097	#define EV_MULTIPLICITY 0	3491	#define EV_MULTIPLICITY 0
3098	#define EV_PERIODIC_ENABLE 0	3492	#define EV_PERIODIC_ENABLE 0
3099	#define EV_STAT_ENABLE 0	3493	#define EV_STAT_ENABLE 0
3100	#define EV_FORK_ENABLE 0	3494	#define EV_FORK_ENABLE 0
3101	#define EV_CONFIG_H <config.h>	3495	#define EV_CONFIG_H <config.h>
3102	#define EV_MINPRI 0	3496	#define EV_MINPRI 0
3103	#define EV_MAXPRI 0	3497	#define EV_MAXPRI 0
3104		3498
3105	#include "ev++.h"	3499	#include "ev++.h"
3106		3500
3107	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3501	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3108		3502
3109	#include "ev_cpp.h"	3503	#include "ev_cpp.h"
3110	#include "ev.c"	3504	#include "ev.c"
3111		3505
		3506	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3112		3507
3113	=head1 THREADS AND COROUTINES	3508	=head2 THREADS AND COROUTINES
3114		3509
3115	=head2 THREADS	3510	=head3 THREADS
3116		3511
3117	Libev itself is completely threadsafe, but it uses no locking. This	3512	All libev functions are reentrant and thread-safe unless explicitly
		3513	documented otherwise, but libev implements no locking itself. This means
3118	means that you can use as many loops as you want in parallel, as long as	3514	that you can use as many loops as you want in parallel, as long as there
3119	only one thread ever calls into one libev function with the same loop	3515	are no concurrent calls into any libev function with the same loop
3120	parameter.	3516	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3517	of course): libev guarantees that different event loops share no data
		3518	structures that need any locking.
3121		3519
3122	Or put differently: calls with different loop parameters can be done in	3520	Or to put it differently: calls with different loop parameters can be done
3123	parallel from multiple threads, calls with the same loop parameter must be	3521	concurrently from multiple threads, calls with the same loop parameter
3124	done serially (but can be done from different threads, as long as only one	3522	must be done serially (but can be done from different threads, as long as
3125	thread ever is inside a call at any point in time, e.g. by using a mutex	3523	only one thread ever is inside a call at any point in time, e.g. by using
3126	per loop).	3524	a mutex per loop).
3127		3525
3128	If you want to know which design is best for your problem, then I cannot	3526	Specifically to support threads (and signal handlers), libev implements
		3527	so-called C<ev_async> watchers, which allow some limited form of
		3528	concurrency on the same event loop, namely waking it up "from the
		3529	outside".
		3530
		3531	If you want to know which design (one loop, locking, or multiple loops
		3532	without or something else still) is best for your problem, then I cannot
3129	help you but by giving some generic advice:	3533	help you, but here is some generic advice:
3130		3534
3131	=over 4	3535	=over 4
3132		3536
3133	=item * most applications have a main thread: use the default libev loop	3537	=item * most applications have a main thread: use the default libev loop
3134	in that thread, or create a seperate thread running only the default loop.	3538	in that thread, or create a separate thread running only the default loop.
3135		3539
3136	This helps integrating other libraries or software modules that use libev	3540	This helps integrating other libraries or software modules that use libev
3137	themselves and don't care/know about threading.	3541	themselves and don't care/know about threading.
3138		3542
3139	=item * one loop per thread is usually a good model.	3543	=item * one loop per thread is usually a good model.
3140		3544
3141	Doing this is almost never wrong, sometimes a better-performance model	3545	Doing this is almost never wrong, sometimes a better-performance model
3142	exists, but it is always a good start.	3546	exists, but it is always a good start.
3143		3547
3144	=item * other models exist, such as the leader/follower pattern, where one	3548	=item * other models exist, such as the leader/follower pattern, where one
3145	loop is handed through multiple threads in a kind of round-robbin fashion.	3549	loop is handed through multiple threads in a kind of round-robin fashion.
3146		3550
3147	Chosing a model is hard - look around, learn, know that usually you cna do	3551	Choosing a model is hard - look around, learn, know that usually you can do
3148	better than you currently do :-)	3552	better than you currently do :-)
3149		3553
3150	=item * often you need to talk to some other thread which blocks in the	3554	=item * often you need to talk to some other thread which blocks in the
		3555	event loop.
		3556
3151	event loop - C<ev_async> watchers can be used to wake them up from other	3557	C<ev_async> watchers can be used to wake them up from other threads safely
3152	threads safely (or from signal contexts...).	3558	(or from signal contexts...).
		3559
		3560	An example use would be to communicate signals or other events that only
		3561	work in the default loop by registering the signal watcher with the
		3562	default loop and triggering an C<ev_async> watcher from the default loop
		3563	watcher callback into the event loop interested in the signal.
3153		3564
3154	=back	3565	=back
3155		3566
3156	=head2 COROUTINES	3567	=head3 COROUTINES
3157		3568
3158	Libev is much more accomodating to coroutines ("cooperative threads"):	3569	Libev is very accommodating to coroutines ("cooperative threads"):
3159	libev fully supports nesting calls to it's functions from different	3570	libev fully supports nesting calls to its functions from different
3160	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3571	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3161	different coroutines and switch freely between both coroutines running the	3572	different coroutines, and switch freely between both coroutines running the
3162	loop, as long as you don't confuse yourself). The only exception is that	3573	loop, as long as you don't confuse yourself). The only exception is that
3163	you must not do this from C<ev_periodic> reschedule callbacks.	3574	you must not do this from C<ev_periodic> reschedule callbacks.
3164		3575
3165	Care has been invested into making sure that libev does not keep local	3576	Care has been taken to ensure that libev does not keep local state inside
3166	state inside C<ev_loop>, and other calls do not usually allow coroutine	3577	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3167	switches.	3578	they do not call any callbacks.
3168		3579
		3580	=head2 COMPILER WARNINGS
3169		3581
3170	=head1 COMPLEXITIES	3582	Depending on your compiler and compiler settings, you might get no or a
		3583	lot of warnings when compiling libev code. Some people are apparently
		3584	scared by this.
3171		3585
3172	In this section the complexities of (many of) the algorithms used inside	3586	However, these are unavoidable for many reasons. For one, each compiler
3173	libev will be explained. For complexity discussions about backends see the	3587	has different warnings, and each user has different tastes regarding
3174	documentation for C<ev_default_init>.	3588	warning options. "Warn-free" code therefore cannot be a goal except when
		3589	targeting a specific compiler and compiler-version.
3175		3590
3176	All of the following are about amortised time: If an array needs to be	3591	Another reason is that some compiler warnings require elaborate
3177	extended, libev needs to realloc and move the whole array, but this	3592	workarounds, or other changes to the code that make it less clear and less
3178	happens asymptotically never with higher number of elements, so O(1) might	3593	maintainable.
3179	mean it might do a lengthy realloc operation in rare cases, but on average
3180	it is much faster and asymptotically approaches constant time.
3181		3594
3182	=over 4	3595	And of course, some compiler warnings are just plain stupid, or simply
		3596	wrong (because they don't actually warn about the condition their message
		3597	seems to warn about). For example, certain older gcc versions had some
		3598	warnings that resulted an extreme number of false positives. These have
		3599	been fixed, but some people still insist on making code warn-free with
		3600	such buggy versions.
3183		3601
3184	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3602	While libev is written to generate as few warnings as possible,
		3603	"warn-free" code is not a goal, and it is recommended not to build libev
		3604	with any compiler warnings enabled unless you are prepared to cope with
		3605	them (e.g. by ignoring them). Remember that warnings are just that:
		3606	warnings, not errors, or proof of bugs.
3185		3607
3186	This means that, when you have a watcher that triggers in one hour and
3187	there are 100 watchers that would trigger before that then inserting will
3188	have to skip roughly seven (C<ld 100>) of these watchers.
3189		3608
3190	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3609	=head2 VALGRIND
3191		3610
3192	That means that changing a timer costs less than removing/adding them	3611	Valgrind has a special section here because it is a popular tool that is
3193	as only the relative motion in the event queue has to be paid for.	3612	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3194		3613
3195	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3614	If you think you found a bug (memory leak, uninitialised data access etc.)
		3615	in libev, then check twice: If valgrind reports something like:
3196		3616
3197	These just add the watcher into an array or at the head of a list.	3617	==2274== definitely lost: 0 bytes in 0 blocks.
		3618	==2274== possibly lost: 0 bytes in 0 blocks.
		3619	==2274== still reachable: 256 bytes in 1 blocks.
3198		3620
3199	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3621	Then there is no memory leak, just as memory accounted to global variables
		3622	is not a memleak - the memory is still being referenced, and didn't leak.
3200		3623
3201	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3624	Similarly, under some circumstances, valgrind might report kernel bugs
		3625	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3626	although an acceptable workaround has been found here), or it might be
		3627	confused.
3202		3628
3203	These watchers are stored in lists then need to be walked to find the	3629	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3204	correct watcher to remove. The lists are usually short (you don't usually	3630	make it into some kind of religion.
3205	have many watchers waiting for the same fd or signal).
3206		3631
3207	=item Finding the next timer in each loop iteration: O(1)	3632	If you are unsure about something, feel free to contact the mailing list
		3633	with the full valgrind report and an explanation on why you think this
		3634	is a bug in libev (best check the archives, too :). However, don't be
		3635	annoyed when you get a brisk "this is no bug" answer and take the chance
		3636	of learning how to interpret valgrind properly.
3208		3637
3209	By virtue of using a binary or 4-heap, the next timer is always found at a	3638	If you need, for some reason, empty reports from valgrind for your project
3210	fixed position in the storage array.	3639	I suggest using suppression lists.
3211		3640
3212	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3213		3641
3214	A change means an I/O watcher gets started or stopped, which requires	3642	=head1 PORTABILITY NOTES
3215	libev to recalculate its status (and possibly tell the kernel, depending
3216	on backend and wether C<ev_io_set> was used).
3217		3643
3218	=item Activating one watcher (putting it into the pending state): O(1)	3644	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3219
3220	=item Priority handling: O(number_of_priorities)
3221
3222	Priorities are implemented by allocating some space for each
3223	priority. When doing priority-based operations, libev usually has to
3224	linearly search all the priorities, but starting/stopping and activating
3225	watchers becomes O(1) w.r.t. priority handling.
3226
3227	=item Sending an ev_async: O(1)
3228
3229	=item Processing ev_async_send: O(number_of_async_watchers)
3230
3231	=item Processing signals: O(max_signal_number)
3232
3233	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3234	calls in the current loop iteration. Checking for async and signal events
3235	involves iterating over all running async watchers or all signal numbers.
3236
3237	=back
3238
3239
3240	=head1 Win32 platform limitations and workarounds
3241		3645
3242	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3646	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3243	requires, and its I/O model is fundamentally incompatible with the POSIX	3647	requires, and its I/O model is fundamentally incompatible with the POSIX
3244	model. Libev still offers limited functionality on this platform in	3648	model. Libev still offers limited functionality on this platform in
3245	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3649	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3252	way (note also that glib is the slowest event library known to man).	3656	way (note also that glib is the slowest event library known to man).
3253		3657
3254	There is no supported compilation method available on windows except	3658	There is no supported compilation method available on windows except
3255	embedding it into other applications.	3659	embedding it into other applications.
3256		3660
		3661	Not a libev limitation but worth mentioning: windows apparently doesn't
		3662	accept large writes: instead of resulting in a partial write, windows will
		3663	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3664	so make sure you only write small amounts into your sockets (less than a
		3665	megabyte seems safe, but this apparently depends on the amount of memory
		3666	available).
		3667
3257	Due to the many, low, and arbitrary limits on the win32 platform and	3668	Due to the many, low, and arbitrary limits on the win32 platform and
3258	the abysmal performance of winsockets, using a large number of sockets	3669	the abysmal performance of winsockets, using a large number of sockets
3259	is not recommended (and not reasonable). If your program needs to use	3670	is not recommended (and not reasonable). If your program needs to use
3260	more than a hundred or so sockets, then likely it needs to use a totally	3671	more than a hundred or so sockets, then likely it needs to use a totally
3261	different implementation for windows, as libev offers the POSIX readiness	3672	different implementation for windows, as libev offers the POSIX readiness
3262	notification model, which cannot be implemented efficiently on windows	3673	notification model, which cannot be implemented efficiently on windows
3263	(microsoft monopoly games).	3674	(Microsoft monopoly games).
		3675
		3676	A typical way to use libev under windows is to embed it (see the embedding
		3677	section for details) and use the following F<evwrap.h> header file instead
		3678	of F<ev.h>:
		3679
		3680	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3681	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3682
		3683	#include "ev.h"
		3684
		3685	And compile the following F<evwrap.c> file into your project (make sure
		3686	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3687
		3688	#include "evwrap.h"
		3689	#include "ev.c"
3264		3690
3265	=over 4	3691	=over 4
3266		3692
3267	=item The winsocket select function	3693	=item The winsocket select function
3268		3694
3269	The winsocket C<select> function doesn't follow POSIX in that it requires	3695	The winsocket C<select> function doesn't follow POSIX in that it
3270	socket I<handles> and not socket I<file descriptors>. This makes select	3696	requires socket I<handles> and not socket I<file descriptors> (it is
3271	very inefficient, and also requires a mapping from file descriptors	3697	also extremely buggy). This makes select very inefficient, and also
3272	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3698	requires a mapping from file descriptors to socket handles (the Microsoft
3273	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3699	C runtime provides the function C<_open_osfhandle> for this). See the
3274	symbols for more info.	3700	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3701	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3275		3702
3276	The configuration for a "naked" win32 using the microsoft runtime	3703	The configuration for a "naked" win32 using the Microsoft runtime
3277	libraries and raw winsocket select is:	3704	libraries and raw winsocket select is:
3278		3705
3279	#define EV_USE_SELECT 1	3706	#define EV_USE_SELECT 1
3280	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3707	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3281		3708
3282	Note that winsockets handling of fd sets is O(n), so you can easily get a	3709	Note that winsockets handling of fd sets is O(n), so you can easily get a
3283	complexity in the O(n²) range when using win32.	3710	complexity in the O(n²) range when using win32.
3284		3711
3285	=item Limited number of file descriptors	3712	=item Limited number of file descriptors
3286		3713
3287	Windows has numerous arbitrary (and low) limits on things.	3714	Windows has numerous arbitrary (and low) limits on things.
3288		3715
3289	Early versions of winsocket's select only supported waiting for a maximum	3716	Early versions of winsocket's select only supported waiting for a maximum
3290	of C<64> handles (probably owning to the fact that all windows kernels	3717	of C<64> handles (probably owning to the fact that all windows kernels
3291	can only wait for C<64> things at the same time internally; microsoft	3718	can only wait for C<64> things at the same time internally; Microsoft
3292	recommends spawning a chain of threads and wait for 63 handles and the	3719	recommends spawning a chain of threads and wait for 63 handles and the
3293	previous thread in each. Great).	3720	previous thread in each. Great).
3294		3721
3295	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3722	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3296	to some high number (e.g. C<2048>) before compiling the winsocket select	3723	to some high number (e.g. C<2048>) before compiling the winsocket select
3297	call (which might be in libev or elsewhere, for example, perl does its own	3724	call (which might be in libev or elsewhere, for example, perl does its own
3298	select emulation on windows).	3725	select emulation on windows).
3299		3726
3300	Another limit is the number of file descriptors in the microsoft runtime	3727	Another limit is the number of file descriptors in the Microsoft runtime
3301	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3728	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3302	or something like this inside microsoft). You can increase this by calling	3729	or something like this inside Microsoft). You can increase this by calling
3303	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3730	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3304	arbitrary limit), but is broken in many versions of the microsoft runtime	3731	arbitrary limit), but is broken in many versions of the Microsoft runtime
3305	libraries.	3732	libraries.
3306		3733
3307	This might get you to about C<512> or C<2048> sockets (depending on	3734	This might get you to about C<512> or C<2048> sockets (depending on
3308	windows version and/or the phase of the moon). To get more, you need to	3735	windows version and/or the phase of the moon). To get more, you need to
3309	wrap all I/O functions and provide your own fd management, but the cost of	3736	wrap all I/O functions and provide your own fd management, but the cost of
3310	calling select (O(n²)) will likely make this unworkable.	3737	calling select (O(n²)) will likely make this unworkable.
3311		3738
3312	=back	3739	=back
3313		3740
3314
3315	=head1 PORTABILITY REQUIREMENTS	3741	=head2 PORTABILITY REQUIREMENTS
3316		3742
3317	In addition to a working ISO-C implementation, libev relies on a few	3743	In addition to a working ISO-C implementation and of course the
3318	additional extensions:	3744	backend-specific APIs, libev relies on a few additional extensions:
3319		3745
3320	=over 4	3746	=over 4
3321		3747
		3748	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3749	calling conventions regardless of C<ev_watcher_type *>.
		3750
		3751	Libev assumes not only that all watcher pointers have the same internal
		3752	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3753	assumes that the same (machine) code can be used to call any watcher
		3754	callback: The watcher callbacks have different type signatures, but libev
		3755	calls them using an C<ev_watcher *> internally.
		3756
3322	=item C<sig_atomic_t volatile> must be thread-atomic as well	3757	=item C<sig_atomic_t volatile> must be thread-atomic as well
3323		3758
3324	The type C<sig_atomic_t volatile> (or whatever is defined as	3759	The type C<sig_atomic_t volatile> (or whatever is defined as
3325	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3760	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3326	threads. This is not part of the specification for C<sig_atomic_t>, but is	3761	threads. This is not part of the specification for C<sig_atomic_t>, but is
3327	believed to be sufficiently portable.	3762	believed to be sufficiently portable.
3328		3763
3329	=item C<sigprocmask> must work in a threaded environment	3764	=item C<sigprocmask> must work in a threaded environment
3330		3765
…		…
3339	except the initial one, and run the default loop in the initial thread as	3774	except the initial one, and run the default loop in the initial thread as
3340	well.	3775	well.
3341		3776
3342	=item C<long> must be large enough for common memory allocation sizes	3777	=item C<long> must be large enough for common memory allocation sizes
3343		3778
3344	To improve portability and simplify using libev, libev uses C<long>	3779	To improve portability and simplify its API, libev uses C<long> internally
3345	internally instead of C<size_t> when allocating its data structures. On	3780	instead of C<size_t> when allocating its data structures. On non-POSIX
3346	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3781	systems (Microsoft...) this might be unexpectedly low, but is still at
3347	is still at least 31 bits everywhere, which is enough for hundreds of	3782	least 31 bits everywhere, which is enough for hundreds of millions of
3348	millions of watchers.	3783	watchers.
3349		3784
3350	=item C<double> must hold a time value in seconds with enough accuracy	3785	=item C<double> must hold a time value in seconds with enough accuracy
3351		3786
3352	The type C<double> is used to represent timestamps. It is required to	3787	The type C<double> is used to represent timestamps. It is required to
3353	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3788	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3357	=back	3792	=back
3358		3793
3359	If you know of other additional requirements drop me a note.	3794	If you know of other additional requirements drop me a note.
3360		3795
3361		3796
3362	=head1 VALGRIND	3797	=head1 ALGORITHMIC COMPLEXITIES
3363		3798
3364	Valgrind has a special section here because it is a popular tool that is	3799	In this section the complexities of (many of) the algorithms used inside
3365	highly useful, but valgrind reports are very hard to interpret.	3800	libev will be documented. For complexity discussions about backends see
		3801	the documentation for C<ev_default_init>.
3366		3802
3367	If you think you found a bug (memory leak, uninitialised data access etc.)	3803	All of the following are about amortised time: If an array needs to be
3368	in libev, then check twice: If valgrind reports something like:	3804	extended, libev needs to realloc and move the whole array, but this
		3805	happens asymptotically rarer with higher number of elements, so O(1) might
		3806	mean that libev does a lengthy realloc operation in rare cases, but on
		3807	average it is much faster and asymptotically approaches constant time.
3369		3808
3370	==2274== definitely lost: 0 bytes in 0 blocks.	3809	=over 4
3371	==2274== possibly lost: 0 bytes in 0 blocks.
3372	==2274== still reachable: 256 bytes in 1 blocks.
3373		3810
3374	then there is no memory leak. Similarly, under some circumstances,	3811	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3375	valgrind might report kernel bugs as if it were a bug in libev, or it
3376	might be confused (it is a very good tool, but only a tool).
3377		3812
3378	If you are unsure about something, feel free to contact the mailing list	3813	This means that, when you have a watcher that triggers in one hour and
3379	with the full valgrind report and an explanation on why you think this is	3814	there are 100 watchers that would trigger before that, then inserting will
3380	a bug in libev. However, don't be annoyed when you get a brisk "this is	3815	have to skip roughly seven (C<ld 100>) of these watchers.
3381	no bug" answer and take the chance of learning how to interpret valgrind
3382	properly.
3383		3816
3384	If you need, for some reason, empty reports from valgrind for your project	3817	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3385	I suggest using suppression lists.	3818
		3819	That means that changing a timer costs less than removing/adding them,
		3820	as only the relative motion in the event queue has to be paid for.
		3821
		3822	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3823
		3824	These just add the watcher into an array or at the head of a list.
		3825
		3826	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3827
		3828	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3829
		3830	These watchers are stored in lists, so they need to be walked to find the
		3831	correct watcher to remove. The lists are usually short (you don't usually
		3832	have many watchers waiting for the same fd or signal: one is typical, two
		3833	is rare).
		3834
		3835	=item Finding the next timer in each loop iteration: O(1)
		3836
		3837	By virtue of using a binary or 4-heap, the next timer is always found at a
		3838	fixed position in the storage array.
		3839
		3840	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3841
		3842	A change means an I/O watcher gets started or stopped, which requires
		3843	libev to recalculate its status (and possibly tell the kernel, depending
		3844	on backend and whether C<ev_io_set> was used).
		3845
		3846	=item Activating one watcher (putting it into the pending state): O(1)
		3847
		3848	=item Priority handling: O(number_of_priorities)
		3849
		3850	Priorities are implemented by allocating some space for each
		3851	priority. When doing priority-based operations, libev usually has to
		3852	linearly search all the priorities, but starting/stopping and activating
		3853	watchers becomes O(1) with respect to priority handling.
		3854
		3855	=item Sending an ev_async: O(1)
		3856
		3857	=item Processing ev_async_send: O(number_of_async_watchers)
		3858
		3859	=item Processing signals: O(max_signal_number)
		3860
		3861	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3862	calls in the current loop iteration. Checking for async and signal events
		3863	involves iterating over all running async watchers or all signal numbers.
		3864
		3865	=back
3386		3866
3387		3867
3388	=head1 AUTHOR	3868	=head1 AUTHOR
3389		3869
3390	Marc Lehmann <libev@schmorp.de>.	3870	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3391		3871

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