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

Comparing libev/ev.pod (file contents):
Revision 1.8 by root, Mon Nov 12 08:20:02 2007 UTC vs.
Revision 1.29 by root, Thu Nov 22 12:28:28 2007 UTC

…		…
39	F<README.embed> in the libev distribution. If libev was configured without	39	F<README.embed> in the libev distribution. If libev was configured without
40	support for multiple event loops, then all functions taking an initial	40	support for multiple event loops, then all functions taking an initial
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	41	argument of name C<loop> (which is always of type C<struct ev_loop *>)
42	will not have this argument.	42	will not have this argument.
43		43
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	44	=head1 TIME REPRESENTATION
45		45
46	Libev represents time as a single floating point number, representing the	46	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	48	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	49	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	50	to the double type in C.
51		51
		52	=head1 GLOBAL FUNCTIONS
		53
		54	These functions can be called anytime, even before initialising the
		55	library in any way.
		56
52	=over 4	57	=over 4
53		58
54	=item ev_tstamp ev_time ()	59	=item ev_tstamp ev_time ()
55		60
56	Returns the current time as libev would use it.	61	Returns the current time as libev would use it. Please note that the
		62	C<ev_now> function is usually faster and also often returns the timestamp
		63	you actually want to know.
57		64
58	=item int ev_version_major ()	65	=item int ev_version_major ()
59		66
60	=item int ev_version_minor ()	67	=item int ev_version_minor ()
61		68
…		…
63	you linked against by calling the functions C<ev_version_major> and	70	you linked against by calling the functions C<ev_version_major> and
64	C<ev_version_minor>. If you want, you can compare against the global	71	C<ev_version_minor>. If you want, you can compare against the global
65	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	72	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66	version of the library your program was compiled against.	73	version of the library your program was compiled against.
67		74
68	Usually, its a good idea to terminate if the major versions mismatch,	75	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	76	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	77	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	78	not a problem.
72		79
73	=item ev_set_allocator (void (cb)(void *ptr, long size))	80	=item ev_set_allocator (void (cb)(void *ptr, long size))
…		…
99	An event loop is described by a C<struct ev_loop *>. The library knows two	106	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	107	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	108	events, and dynamically created loops which do not.
102		109
103	If you use threads, a common model is to run the default event loop	110	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you	111	in your main thread (or in a separate thread) and for each thread you
105	create, you also create another event loop. Libev itself does no locking	112	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	113	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	114	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because its hideous and inefficient).	115	done correctly, because it's hideous and inefficient).
109		116
110	=over 4	117	=over 4
111		118
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	119	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		120
…		…
124		131
125	It supports the following flags:	132	It supports the following flags:
126		133
127	=over 4	134	=over 4
128		135
129	=item EVFLAG_AUTO	136	=item C<EVFLAG_AUTO>
130		137
131	The default flags value. Use this if you have no clue (its the right	138	The default flags value. Use this if you have no clue (it's the right
132	thing, believe me).	139	thing, believe me).
133		140
134	=item EVFLAG_NOENV	141	=item C<EVFLAG_NOENV>
135		142
136	If this flag bit is ored into the flag value (or the program runs setuid	143	If this flag bit is ored into the flag value (or the program runs setuid
137	or setgid) then libev will I<not> look at the environment variable	144	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	146	override the flags completely if it is found in the environment. This is
140	useful to try out specific backends to test their performance, or to work	147	useful to try out specific backends to test their performance, or to work
141	around bugs.	148	around bugs.
142		149
143	=item EVMETHOD_SELECT portable select backend	150	=item C<EVMETHOD_SELECT> (value 1, portable select backend)
144		151
		152	This is your standard select(2) backend. Not I<completely> standard, as
		153	libev tries to roll its own fd_set with no limits on the number of fds,
		154	but if that fails, expect a fairly low limit on the number of fds when
		155	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		156	the fastest backend for a low number of fds.
		157
145	=item EVMETHOD_POLL poll backend (everywhere except windows)	158	=item C<EVMETHOD_POLL> (value 2, poll backend, available everywhere except on windows)
146		159
147	=item EVMETHOD_EPOLL linux only	160	And this is your standard poll(2) backend. It's more complicated than
		161	select, but handles sparse fds better and has no artificial limit on the
		162	number of fds you can use (except it will slow down considerably with a
		163	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
148		164
149	=item EVMETHOD_KQUEUE some bsds only	165	=item C<EVMETHOD_EPOLL> (value 4, Linux)
150		166
151	=item EVMETHOD_DEVPOLL solaris 8 only	167	For few fds, this backend is a bit little slower than poll and select,
		168	but it scales phenomenally better. While poll and select usually scale like
		169	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		170	either O(1) or O(active_fds).
152		171
153	=item EVMETHOD_PORT solaris 10 only	172	While stopping and starting an I/O watcher in the same iteration will
		173	result in some caching, there is still a syscall per such incident
		174	(because the fd could point to a different file description now), so its
		175	best to avoid that. Also, dup()ed file descriptors might not work very
		176	well if you register events for both fds.
		177
		178	=item C<EVMETHOD_KQUEUE> (value 8, most BSD clones)
		179
		180	Kqueue deserves special mention, as at the time of this writing, it
		181	was broken on all BSDs except NetBSD (usually it doesn't work with
		182	anything but sockets and pipes, except on Darwin, where of course its
		183	completely useless). For this reason its not being "autodetected" unless
		184	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).
		185
		186	It scales in the same way as the epoll backend, but the interface to the
		187	kernel is more efficient (which says nothing about its actual speed, of
		188	course). While starting and stopping an I/O watcher does not cause an
		189	extra syscall as with epoll, it still adds up to four event changes per
		190	incident, so its best to avoid that.
		191
		192	=item C<EVMETHOD_DEVPOLL> (value 16, Solaris 8)
		193
		194	This is not implemented yet (and might never be).
		195
		196	=item C<EVMETHOD_PORT> (value 32, Solaris 10)
		197
		198	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		199	it's really slow, but it still scales very well (O(active_fds)).
		200
		201	=item C<EVMETHOD_ALL>
		202
		203	Try all backends (even potentially broken ones that wouldn't be tried
		204	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		205	C<EVMETHOD_ALL & ~EVMETHOD_KQUEUE>.
		206
		207	=back
154		208
155	If one or more of these are ored into the flags value, then only these	209	If one or more of these are ored into the flags value, then only these
156	backends will be tried (in the reverse order as given here). If one are	210	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	211	specified, most compiled-in backend will be tried, usually in reverse
158		212	order of their flag values :)
159	=back
160		213
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	214	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		215
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	216	Similar to C<ev_default_loop>, but always creates a new event loop that is
164	always distinct from the default loop. Unlike the default loop, it cannot	217	always distinct from the default loop. Unlike the default loop, it cannot
…		…
167		220
168	=item ev_default_destroy ()	221	=item ev_default_destroy ()
169		222
170	Destroys the default loop again (frees all memory and kernel state	223	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	224	etc.). This stops all registered event watchers (by not touching them in
172	any way whatsoever, although you cnanot rely on this :).	225	any way whatsoever, although you cannot rely on this :).
173		226
174	=item ev_loop_destroy (loop)	227	=item ev_loop_destroy (loop)
175		228
176	Like C<ev_default_destroy>, but destroys an event loop created by an	229	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	230	earlier call to C<ev_loop_new>.
…		…
185		238
186	You I<must> call this function after forking if and only if you want to	239	You I<must> call this function after forking if and only if you want to
187	use the event library in both processes. If you just fork+exec, you don't	240	use the event library in both processes. If you just fork+exec, you don't
188	have to call it.	241	have to call it.
189		242
190	The function itself is quite fast and its usually not a problem to call	243	The function itself is quite fast and it's usually not a problem to call
191	it just in case after a fork. To make this easy, the function will fit in	244	it just in case after a fork. To make this easy, the function will fit in
192	quite nicely into a call to C<pthread_atfork>:	245	quite nicely into a call to C<pthread_atfork>:
193		246
194	pthread_atfork (0, 0, ev_default_fork);	247	pthread_atfork (0, 0, ev_default_fork);
195		248
…		…
202	=item unsigned int ev_method (loop)	255	=item unsigned int ev_method (loop)
203		256
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	257	Returns one of the C<EVMETHOD_*> flags indicating the event backend in
205	use.	258	use.
206		259
207	=item ev_tstamp = ev_now (loop)	260	=item ev_tstamp ev_now (loop)
208		261
209	Returns the current "event loop time", which is the time the event loop	262	Returns the current "event loop time", which is the time the event loop
210	got events and started processing them. This timestamp does not change	263	got events and started processing them. This timestamp does not change
211	as long as callbacks are being processed, and this is also the base time	264	as long as callbacks are being processed, and this is also the base time
212	used for relative timers. You can treat it as the timestamp of the event	265	used for relative timers. You can treat it as the timestamp of the event
…		…
221	If the flags argument is specified as 0, it will not return until either	274	If the flags argument is specified as 0, it will not return until either
222	no event watchers are active anymore or C<ev_unloop> was called.	275	no event watchers are active anymore or C<ev_unloop> was called.
223		276
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	277	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
225	those events and any outstanding ones, but will not block your process in	278	those events and any outstanding ones, but will not block your process in
226	case there are no events.	279	case there are no events and will return after one iteration of the loop.
227		280
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	281	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
229	neccessary) and will handle those and any outstanding ones. It will block	282	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	283	your process until at least one new event arrives, and will return after
		284	one iteration of the loop.
231		285
232	This flags value could be used to implement alternative looping	286	This flags value could be used to implement alternative looping
233	constructs, but the C<prepare> and C<check> watchers provide a better and	287	constructs, but the C<prepare> and C<check> watchers provide a better and
234	more generic mechanism.	288	more generic mechanism.
235		289
		290	Here are the gory details of what ev_loop does:
		291
		292	1. If there are no active watchers (reference count is zero), return.
		293	2. Queue and immediately call all prepare watchers.
		294	3. If we have been forked, recreate the kernel state.
		295	4. Update the kernel state with all outstanding changes.
		296	5. Update the "event loop time".
		297	6. Calculate for how long to block.
		298	7. Block the process, waiting for events.
		299	8. Update the "event loop time" and do time jump handling.
		300	9. Queue all outstanding timers.
		301	10. Queue all outstanding periodics.
		302	11. If no events are pending now, queue all idle watchers.
		303	12. Queue all check watchers.
		304	13. Call all queued watchers in reverse order (i.e. check watchers first).
		305	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		306	was used, return, otherwise continue with step #1.
		307
236	=item ev_unloop (loop, how)	308	=item ev_unloop (loop, how)
237		309
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	310	Can be used to make a call to C<ev_loop> return early (but only after it
		311	has processed all outstanding events). The C<how> argument must be either
239	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	312	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
240	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	313	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.
242		314
243	=item ev_ref (loop)	315	=item ev_ref (loop)
244		316
245	=item ev_unref (loop)	317	=item ev_unref (loop)
246		318
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	319	Ref/unref can be used to add or remove a reference count on the event
248	watcher keeps one reference. If you have a long-runing watcher you never	320	loop: Every watcher keeps one reference, and as long as the reference
249	unregister that should not keep ev_loop from running, ev_unref() after	321	count is nonzero, C<ev_loop> will not return on its own. If you have
250	starting, and ev_ref() before stopping it. Libev itself uses this for	322	a watcher you never unregister that should not keep C<ev_loop> from
251	example for its internal signal pipe: It is not visible to you as a user	323	returning, ev_unref() after starting, and ev_ref() before stopping it. For
252	and should not keep C<ev_loop> from exiting if the work is done. It is	324	example, libev itself uses this for its internal signal pipe: It is not
253	also an excellent way to do this for generic recurring timers or from	325	visible to the libev user and should not keep C<ev_loop> from exiting if
254	within third-party libraries. Just remember to unref after start and ref	326	no event watchers registered by it are active. It is also an excellent
255	before stop.	327	way to do this for generic recurring timers or from within third-party
		328	libraries. Just remember to I<unref after start> and I<ref before stop>.
256		329
257	=back	330	=back
258		331
259	=head1 ANATOMY OF A WATCHER	332	=head1 ANATOMY OF A WATCHER
260		333
261	A watcher is a structure that you create and register to record your	334	A watcher is a structure that you create and register to record your
262	interest in some event. For instance, if you want to wait for STDIN to	335	interest in some event. For instance, if you want to wait for STDIN to
263	become readable, you would create an ev_io watcher for that:	336	become readable, you would create an C<ev_io> watcher for that:
264		337
265	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	338	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
266	{	339	{
267	ev_io_stop (w);	340	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	341	ev_unloop (loop, EVUNLOOP_ALL);
…		…
297		370
298	As long as your watcher is active (has been started but not stopped) you	371	As long as your watcher is active (has been started but not stopped) you
299	must not touch the values stored in it. Most specifically you must never	372	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	373	reinitialise it or call its set method.
301		374
302	You cna check whether an event is active by calling the C<ev_is_active	375	You can check whether an event is active by calling the C<ev_is_active
303	(watcher *)> macro. To see whether an event is outstanding (but the	376	(watcher *)> macro. To see whether an event is outstanding (but the
304	callback for it has not been called yet) you cna use the C<ev_is_pending	377	callback for it has not been called yet) you can use the C<ev_is_pending
305	(watcher *)> macro.	378	(watcher *)> macro.
306		379
307	Each and every callback receives the event loop pointer as first, the	380	Each and every callback receives the event loop pointer as first, the
308	registered watcher structure as second, and a bitset of received events as	381	registered watcher structure as second, and a bitset of received events as
309	third argument.	382	third argument.
310		383
311	The rceeived events usually include a single bit per event type received	384	The received events usually include a single bit per event type received
312	(you can receive multiple events at the same time). The possible bit masks	385	(you can receive multiple events at the same time). The possible bit masks
313	are:	386	are:
314		387
315	=over 4	388	=over 4
316		389
317	=item EV_READ	390	=item C<EV_READ>
318		391
319	=item EV_WRITE	392	=item C<EV_WRITE>
320		393
321	The file descriptor in the ev_io watcher has become readable and/or	394	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	395	writable.
323		396
324	=item EV_TIMEOUT	397	=item C<EV_TIMEOUT>
325		398
326	The ev_timer watcher has timed out.	399	The C<ev_timer> watcher has timed out.
327		400
328	=item EV_PERIODIC	401	=item C<EV_PERIODIC>
329		402
330	The ev_periodic watcher has timed out.	403	The C<ev_periodic> watcher has timed out.
331		404
332	=item EV_SIGNAL	405	=item C<EV_SIGNAL>
333		406
334	The signal specified in the ev_signal watcher has been received by a thread.	407	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		408
336	=item EV_CHILD	409	=item C<EV_CHILD>
337		410
338	The pid specified in the ev_child watcher has received a status change.	411	The pid specified in the C<ev_child> watcher has received a status change.
339		412
340	=item EV_IDLE	413	=item C<EV_IDLE>
341		414
342	The ev_idle watcher has determined that you have nothing better to do.	415	The C<ev_idle> watcher has determined that you have nothing better to do.
343		416
344	=item EV_PREPARE	417	=item C<EV_PREPARE>
345		418
346	=item EV_CHECK	419	=item C<EV_CHECK>
347		420
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	421	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
349	to gather new events, and all ev_check watchers are invoked just after	422	to gather new events, and all C<ev_check> watchers are invoked just after
350	C<ev_loop> has gathered them, but before it invokes any callbacks for any	423	C<ev_loop> has gathered them, but before it invokes any callbacks for any
351	received events. Callbacks of both watcher types can start and stop as	424	received events. Callbacks of both watcher types can start and stop as
352	many watchers as they want, and all of them will be taken into account	425	many watchers as they want, and all of them will be taken into account
353	(for example, a ev_prepare watcher might start an idle watcher to keep	426	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	427	C<ev_loop> from blocking).
355		428
356	=item EV_ERROR	429	=item C<EV_ERROR>
357		430
358	An unspecified error has occured, the watcher has been stopped. This might	431	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	432	happen because the watcher could not be properly started because libev
360	ran out of memory, a file descriptor was found to be closed or any other	433	ran out of memory, a file descriptor was found to be closed or any other
361	problem. You best act on it by reporting the problem and somehow coping	434	problem. You best act on it by reporting the problem and somehow coping
…		…
370	=back	443	=back
371		444
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	445	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		446
374	Each watcher has, by default, a member C<void *data> that you can change	447	Each watcher has, by default, a member C<void *data> that you can change
375	and read at any time, libev will completely ignore it. This cna be used	448	and read at any time, libev will completely ignore it. This can be used
376	to associate arbitrary data with your watcher. If you need more data and	449	to associate arbitrary data with your watcher. If you need more data and
377	don't want to allocate memory and store a pointer to it in that data	450	don't want to allocate memory and store a pointer to it in that data
378	member, you can also "subclass" the watcher type and provide your own	451	member, you can also "subclass" the watcher type and provide your own
379	data:	452	data:
380		453
…		…
402	=head1 WATCHER TYPES	475	=head1 WATCHER TYPES
403		476
404	This section describes each watcher in detail, but will not repeat	477	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	478	information given in the last section.
406		479
407	=head2 struct ev_io - is my file descriptor readable or writable	480	=head2 C<ev_io> - is this file descriptor readable or writable
408		481
409	I/O watchers check whether a file descriptor is readable or writable	482	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	483	in each iteration of the event loop (This behaviour is called
411	level-triggering because you keep receiving events as long as the	484	level-triggering because you keep receiving events as long as the
412	condition persists. Remember you cna stop the watcher if you don't want to	485	condition persists. Remember you can stop the watcher if you don't want to
413	act on the event and neither want to receive future events).	486	act on the event and neither want to receive future events).
414		487
415	In general you can register as many read and/or write event watchers oer	488	In general you can register as many read and/or write event watchers per
416	fd as you want (as long as you don't confuse yourself). Setting all file	489	fd as you want (as long as you don't confuse yourself). Setting all file
417	descriptors to non-blocking mode is also usually a good idea (but not	490	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	491	required if you know what you are doing).
419		492
420	You have to be careful with dup'ed file descriptors, though. Some backends	493	You have to be careful with dup'ed file descriptors, though. Some backends
421	(the linux epoll backend is a notable example) cannot handle dup'ed file	494	(the linux epoll backend is a notable example) cannot handle dup'ed file
422	descriptors correctly if you register interest in two or more fds pointing	495	descriptors correctly if you register interest in two or more fds pointing
423	to the same file/socket etc. description.	496	to the same underlying file/socket etc. description (that is, they share
		497	the same underlying "file open").
424		498
425	If you must do this, then force the use of a known-to-be-good backend	499	If you must do this, then force the use of a known-to-be-good backend
426	(at the time of this writing, this includes only EVMETHOD_SELECT and	500	(at the time of this writing, this includes only EVMETHOD_SELECT and
427	EVMETHOD_POLL).	501	EVMETHOD_POLL).
428		502
…		…
430		504
431	=item ev_io_init (ev_io *, callback, int fd, int events)	505	=item ev_io_init (ev_io *, callback, int fd, int events)
432		506
433	=item ev_io_set (ev_io *, int fd, int events)	507	=item ev_io_set (ev_io *, int fd, int events)
434		508
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	509	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
436	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|	510	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|
437	EV_WRITE> to receive the given events.	511	EV_WRITE> to receive the given events.
438		512
439	=back	513	=back
440		514
441	=head2 struct ev_timer - relative and optionally recurring timeouts	515	=head2 C<ev_timer> - relative and optionally recurring timeouts
442		516
443	Timer watchers are simple relative timers that generate an event after a	517	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	518	given time, and optionally repeating in regular intervals after that.
445		519
446	The timers are based on real time, that is, if you register an event that	520	The timers are based on real time, that is, if you register an event that
447	times out after an hour and youreset your system clock to last years	521	times out after an hour and you reset your system clock to last years
448	time, it will still time out after (roughly) and hour. "Roughly" because	522	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	523	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	524	monotonic clock option helps a lot here).
		525
		526	The relative timeouts are calculated relative to the C<ev_now ()>
		527	time. This is usually the right thing as this timestamp refers to the time
		528	of the event triggering whatever timeout you are modifying/starting. If
		529	you suspect event processing to be delayed and you I<need> to base the timeout
		530	on the current time, use something like this to adjust for this:
		531
		532	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		533
		534	The callback is guarenteed to be invoked only when its timeout has passed,
		535	but if multiple timers become ready during the same loop iteration then
		536	order of execution is undefined.
451		537
452	=over 4	538	=over 4
453		539
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	540	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		541
…		…
461	later, again, and again, until stopped manually.	547	later, again, and again, until stopped manually.
462		548
463	The timer itself will do a best-effort at avoiding drift, that is, if you	549	The timer itself will do a best-effort at avoiding drift, that is, if you
464	configure a timer to trigger every 10 seconds, then it will trigger at	550	configure a timer to trigger every 10 seconds, then it will trigger at
465	exactly 10 second intervals. If, however, your program cannot keep up with	551	exactly 10 second intervals. If, however, your program cannot keep up with
466	the timer (ecause it takes longer than those 10 seconds to do stuff) the	552	the timer (because it takes longer than those 10 seconds to do stuff) the
467	timer will not fire more than once per event loop iteration.	553	timer will not fire more than once per event loop iteration.
468		554
469	=item ev_timer_again (loop)	555	=item ev_timer_again (loop)
470		556
471	This will act as if the timer timed out and restart it again if it is	557	This will act as if the timer timed out and restart it again if it is
…		…
478		564
479	This sounds a bit complicated, but here is a useful and typical	565	This sounds a bit complicated, but here is a useful and typical
480	example: Imagine you have a tcp connection and you want a so-called idle	566	example: Imagine you have a tcp connection and you want a so-called idle
481	timeout, that is, you want to be called when there have been, say, 60	567	timeout, that is, you want to be called when there have been, say, 60
482	seconds of inactivity on the socket. The easiest way to do this is to	568	seconds of inactivity on the socket. The easiest way to do this is to
483	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	569	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
484	time you successfully read or write some data. If you go into an idle	570	time you successfully read or write some data. If you go into an idle
485	state where you do not expect data to travel on the socket, you can stop	571	state where you do not expect data to travel on the socket, you can stop
486	the timer, and again will automatically restart it if need be.	572	the timer, and again will automatically restart it if need be.
487		573
488	=back	574	=back
489		575
490	=head2 ev_periodic - to cron or not to cron it	576	=head2 C<ev_periodic> - to cron or not to cron
491		577
492	Periodic watchers are also timers of a kind, but they are very versatile	578	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	579	(and unfortunately a bit complex).
494		580
495	Unlike ev_timer's, they are not based on real time (or relative time)	581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
496	but on wallclock time (absolute time). You can tell a periodic watcher	582	but on wallclock time (absolute time). You can tell a periodic watcher
497	to trigger "at" some specific point in time. For example, if you tell a	583	to trigger "at" some specific point in time. For example, if you tell a
498	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	584	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
499	+ 10.>) and then reset your system clock to the last year, then it will	585	+ 10.>) and then reset your system clock to the last year, then it will
500	take a year to trigger the event (unlike an ev_timer, which would trigger	586	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
501	roughly 10 seconds later and of course not if you reset your system time	587	roughly 10 seconds later and of course not if you reset your system time
502	again).	588	again).
503		589
504	They can also be used to implement vastly more complex timers, such as	590	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	591	triggering an event on eahc midnight, local time.
506		592
		593	As with timers, the callback is guarenteed to be invoked only when the
		594	time (C<at>) has been passed, but if multiple periodic timers become ready
		595	during the same loop iteration then order of execution is undefined.
		596
507	=over 4	597	=over 4
508		598
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		600
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		602
513	Lots of arguments, lets sort it out... There are basically three modes of	603	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	604	operation, and we will explain them from simplest to complex:
515
516		605
517	=over 4	606	=over 4
518		607
519	=item * absolute timer (interval = reschedule_cb = 0)	608	=item * absolute timer (interval = reschedule_cb = 0)
520		609
…		…
534		623
535	ev_periodic_set (&periodic, 0., 3600., 0);	624	ev_periodic_set (&periodic, 0., 3600., 0);
536		625
537	This doesn't mean there will always be 3600 seconds in between triggers,	626	This doesn't mean there will always be 3600 seconds in between triggers,
538	but only that the the callback will be called when the system time shows a	627	but only that the the callback will be called when the system time shows a
539	full hour (UTC), or more correct, when the system time is evenly divisible	628	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	629	by 3600.
541		630
542	Another way to think about it (for the mathematically inclined) is that	631	Another way to think about it (for the mathematically inclined) is that
543	ev_periodic will try to run the callback in this mode at the next possible	632	C<ev_periodic> will try to run the callback in this mode at the next possible
544	time where C<time = at (mod interval)>, regardless of any time jumps.	633	time where C<time = at (mod interval)>, regardless of any time jumps.
545		634
546	=item * manual reschedule mode (reschedule_cb = callback)	635	=item * manual reschedule mode (reschedule_cb = callback)
547		636
548	In this mode the values for C<interval> and C<at> are both being	637	In this mode the values for C<interval> and C<at> are both being
549	ignored. Instead, each time the periodic watcher gets scheduled, the	638	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	639	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	640	current time as second argument.
552		641
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	642	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
554	periodic watcher, ever, or make any event loop modificstions>. If you need	643	ever, or make any event loop modifications>. If you need to stop it,
555	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	644	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		645	starting a prepare watcher).
556		646
557	Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	647	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
558	ev_tstamp now)>, e.g.:	648	ev_tstamp now)>, e.g.:
559		649
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	650	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	651	{
562	return now + 60.;	652	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	655	It must return the next time to trigger, based on the passed time value
566	(that is, the lowest time value larger than to the second argument). It	656	(that is, the lowest time value larger than to the second argument). It
567	will usually be called just before the callback will be triggered, but	657	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	658	might be called at other times, too.
569		659
		660	NOTE: I<< This callback must always return a time that is later than the
		661	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		662
570	This can be used to create very complex timers, such as a timer that	663	This can be used to create very complex timers, such as a timer that
571	triggers on each midnight, local time. To do this, you would calculate the	664	triggers on each midnight, local time. To do this, you would calculate the
572	next midnight after C<now> and return the timestamp value for this. How you do this	665	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	666	you do this is, again, up to you (but it is not trivial, which is the main
		667	reason I omitted it as an example).
574		668
575	=back	669	=back
576		670
577	=item ev_periodic_again (loop, ev_periodic *)	671	=item ev_periodic_again (loop, ev_periodic *)
578		672
…		…
581	a different time than the last time it was called (e.g. in a crond like	675	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	676	program when the crontabs have changed).
583		677
584	=back	678	=back
585		679
586	=head2 ev_signal - signal me when a signal gets signalled	680	=head2 C<ev_signal> - signal me when a signal gets signalled
587		681
588	Signal watchers will trigger an event when the process receives a specific	682	Signal watchers will trigger an event when the process receives a specific
589	signal one or more times. Even though signals are very asynchronous, libev	683	signal one or more times. Even though signals are very asynchronous, libev
590	will try its best to deliver signals synchronously, i.e. as part of the	684	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	685	normal event processing, like any other event.
592		686
593	You cna configure as many watchers as you like per signal. Only when the	687	You can configure as many watchers as you like per signal. Only when the
594	first watcher gets started will libev actually register a signal watcher	688	first watcher gets started will libev actually register a signal watcher
595	with the kernel (thus it coexists with your own signal handlers as long	689	with the kernel (thus it coexists with your own signal handlers as long
596	as you don't register any with libev). Similarly, when the last signal	690	as you don't register any with libev). Similarly, when the last signal
597	watcher for a signal is stopped libev will reset the signal handler to	691	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	692	SIG_DFL (regardless of what it was set to before).
…		…
606	Configures the watcher to trigger on the given signal number (usually one	700	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	701	of the C<SIGxxx> constants).
608		702
609	=back	703	=back
610		704
611	=head2 ev_child - wait for pid status changes	705	=head2 C<ev_child> - wait for pid status changes
612		706
613	Child watchers trigger when your process receives a SIGCHLD in response to	707	Child watchers trigger when your process receives a SIGCHLD in response to
614	some child status changes (most typically when a child of yours dies).	708	some child status changes (most typically when a child of yours dies).
615		709
616	=over 4	710	=over 4
…		…
620	=item ev_child_set (ev_child *, int pid)	714	=item ev_child_set (ev_child *, int pid)
621		715
622	Configures the watcher to wait for status changes of process C<pid> (or	716	Configures the watcher to wait for status changes of process C<pid> (or
623	I<any> process if C<pid> is specified as C<0>). The callback can look	717	I<any> process if C<pid> is specified as C<0>). The callback can look
624	at the C<rstatus> member of the C<ev_child> watcher structure to see	718	at the C<rstatus> member of the C<ev_child> watcher structure to see
625	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	719	the status word (use the macros from C<sys/wait.h> and see your systems
626	contains the pid of the process causing the status change.	720	C<waitpid> documentation). The C<rpid> member contains the pid of the
		721	process causing the status change.
627		722
628	=back	723	=back
629		724
630	=head2 ev_idle - when you've got nothing better to do	725	=head2 C<ev_idle> - when you've got nothing better to do
631		726
632	Idle watchers trigger events when there are no other I/O or timer (or	727	Idle watchers trigger events when there are no other events are pending
633	periodic) events pending. That is, as long as your process is busy	728	(prepare, check and other idle watchers do not count). That is, as long
634	handling sockets or timeouts it will not be called. But when your process	729	as your process is busy handling sockets or timeouts (or even signals,
635	is idle all idle watchers are being called again and again - until	730	imagine) it will not be triggered. But when your process is idle all idle
		731	watchers are being called again and again, once per event loop iteration -
636	stopped, that is, or your process receives more events.	732	until stopped, that is, or your process receives more events and becomes
		733	busy.
637		734
638	The most noteworthy effect is that as long as any idle watchers are	735	The most noteworthy effect is that as long as any idle watchers are
639	active, the process will not block when waiting for new events.	736	active, the process will not block when waiting for new events.
640		737
641	Apart from keeping your process non-blocking (which is a useful	738	Apart from keeping your process non-blocking (which is a useful
…		…
651	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	748	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	749	believe me.
653		750
654	=back	751	=back
655		752
656	=head2 prepare and check - your hooks into the event loop	753	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
657		754
658	Prepare and check watchers usually (but not always) are used in	755	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	756	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	757	afterwards.
661		758
662	Their main purpose is to integrate other event mechanisms into libev. This	759	Their main purpose is to integrate other event mechanisms into libev. This
663	could be used, for example, to track variable changes, implement your own	760	could be used, for example, to track variable changes, implement your own
664	watchers, integrate net-snmp or a coroutine library and lots more.	761	watchers, integrate net-snmp or a coroutine library and lots more.
665		762
666	This is done by examining in each prepare call which file descriptors need	763	This is done by examining in each prepare call which file descriptors need
667	to be watched by the other library, registering ev_io watchers for them	764	to be watched by the other library, registering C<ev_io> watchers for
668	and starting an ev_timer watcher for any timeouts (many libraries provide	765	them and starting an C<ev_timer> watcher for any timeouts (many libraries
669	just this functionality). Then, in the check watcher you check for any	766	provide just this functionality). Then, in the check watcher you check for
670	events that occured (by making your callbacks set soem flags for example)	767	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	768	and stopping them) and call back into the library. The I/O and timer
		769	callbacks will never actually be called (but must be valid nevertheless,
		770	because you never know, you know?).
672		771
673	As another example, the perl Coro module uses these hooks to integrate	772	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	773	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	774	during each prepare and only letting the process block if no coroutines
676	are ready to run.	775	are ready to run (it's actually more complicated: it only runs coroutines
		776	with priority higher than or equal to the event loop and one coroutine
		777	of lower priority, but only once, using idle watchers to keep the event
		778	loop from blocking if lower-priority coroutines are active, thus mapping
		779	low-priority coroutines to idle/background tasks).
677		780
678	=over 4	781	=over 4
679		782
680	=item ev_prepare_init (ev_prepare *, callback)	783	=item ev_prepare_init (ev_prepare *, callback)
681		784
682	=item ev_check_init (ev_check *, callback)	785	=item ev_check_init (ev_check *, callback)
683		786
684	Initialises and configures the prepare or check watcher - they have no	787	Initialises and configures the prepare or check watcher - they have no
685	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	788	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	789	macros, but using them is utterly, utterly and completely pointless.
687		790
688	=back	791	=back
689		792
690	=head1 OTHER FUNCTIONS	793	=head1 OTHER FUNCTIONS
691		794
692	There are some other fucntions of possible interest. Described. Here. Now.	795	There are some other functions of possible interest. Described. Here. Now.
693		796
694	=over 4	797	=over 4
695		798
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	799	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		800
698	This function combines a simple timer and an I/O watcher, calls your	801	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	802	callback on whichever event happens first and automatically stop both
700	watchers. This is useful if you want to wait for a single event on an fd	803	watchers. This is useful if you want to wait for a single event on an fd
701	or timeout without havign to allocate/configure/start/stop/free one or	804	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	805	more watchers yourself.
703		806
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	807	If C<fd> is less than 0, then no I/O watcher will be started and events
705	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	808	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	809	C<events> set will be craeted and started.
707		810
708	If C<timeout> is less than 0, then no timeout watcher will be	811	If C<timeout> is less than 0, then no timeout watcher will be
709	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	812	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	813	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		814	dubious value.
711		815
712	The callback has the type C<void (cb)(int revents, void arg)> and	816	The callback has the type C<void (cb)(int revents, void arg)> and gets
713	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	817	passed an C<revents> set like normal event callbacks (a combination of
714	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	818	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		819	value passed to C<ev_once>:
715		820
716	static void stdin_ready (int revents, void *arg)	821	static void stdin_ready (int revents, void *arg)
717	{	822	{
718	if (revents & EV_TIMEOUT)	823	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	824	/* doh, nothing entered */;
720	else if (revents & EV_READ)	825	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	826	/* stdin might have data for us, joy! */;
722	}	827	}
723		828
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	829	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		830
726	=item ev_feed_event (loop, watcher, int events)	831	=item ev_feed_event (loop, watcher, int events)
727		832
728	Feeds the given event set into the event loop, as if the specified event	833	Feeds the given event set into the event loop, as if the specified event
729	has happened for the specified watcher (which must be a pointer to an	834	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	835	initialised but not necessarily started event watcher).
731		836
732	=item ev_feed_fd_event (loop, int fd, int revents)	837	=item ev_feed_fd_event (loop, int fd, int revents)
733		838
734	Feed an event on the given fd, as if a file descriptor backend detected it.	839	Feed an event on the given fd, as if a file descriptor backend detected
		840	the given events it.
735		841
736	=item ev_feed_signal_event (loop, int signum)	842	=item ev_feed_signal_event (loop, int signum)
737		843
738	Feed an event as if the given signal occured (loop must be the default loop!).	844	Feed an event as if the given signal occured (loop must be the default loop!).
739		845
740	=back	846	=back
741		847
		848	=head1 LIBEVENT EMULATION
		849
		850	Libev offers a compatibility emulation layer for libevent. It cannot
		851	emulate the internals of libevent, so here are some usage hints:
		852
		853	=over 4
		854
		855	=item * Use it by including <event.h>, as usual.
		856
		857	=item * The following members are fully supported: ev_base, ev_callback,
		858	ev_arg, ev_fd, ev_res, ev_events.
		859
		860	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		861	maintained by libev, it does not work exactly the same way as in libevent (consider
		862	it a private API).
		863
		864	=item * Priorities are not currently supported. Initialising priorities
		865	will fail and all watchers will have the same priority, even though there
		866	is an ev_pri field.
		867
		868	=item * Other members are not supported.
		869
		870	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		871	to use the libev header file and library.
		872
		873	=back
		874
		875	=head1 C++ SUPPORT
		876
		877	TBD.
		878
742	=head1 AUTHOR	879	=head1 AUTHOR
743		880
744	Marc Lehmann <libev@schmorp.de>.	881	Marc Lehmann <libev@schmorp.de>.
745		882

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Comparing libev/ev.pod (file contents): Revision 1.8 by root, Mon Nov 12 08:20:02 2007 UTC vs. Revision 1.29 by root, Thu Nov 22 12:28:28 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.8 by root, Mon Nov 12 08:20:02 2007 UTC vs.
Revision 1.29 by root, Thu Nov 22 12:28:28 2007 UTC