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Revision 1.6 by root, Mon Nov 12 08:12:14 2007 UTC vs.
Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC

26Libev supports select, poll, the linux-specific epoll and the bsd-specific 26Libev supports select, poll, the linux-specific epoll and the bsd-specific
27kqueue mechanisms for file descriptor events, relative timers, absolute 27kqueue mechanisms for file descriptor events, relative timers, absolute
28timers with customised rescheduling, signal events, process status change 28timers with customised rescheduling, signal events, process status change
29events (related to SIGCHLD), and event watchers dealing with the event 29events (related to SIGCHLD), and event watchers dealing with the event
30loop mechanism itself (idle, prepare and check watchers). It also is quite 30loop mechanism itself (idle, prepare and check watchers). It also is quite
31fast (see a L<benchmark|http://libev.schmorp.de/bench.html> comparing it 31fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing
32to libevent). 32it to libevent for example).
33 33
34=head1 CONVENTIONS 34=head1 CONVENTIONS
35 35
36Libev is very configurable. In this manual the default configuration 36Libev is very configurable. In this manual the default configuration
37will be described, which supports multiple event loops. For more info 37will be described, which supports multiple event loops. For more info
38about various configuraiton options please have a look at the file 38about various configuration options please have a look at the file
39F<README.embed> in the libev distribution. If libev was configured without 39F<README.embed> in the libev distribution. If libev was configured without
40support for multiple event loops, then all functions taking an initial 40support for multiple event loops, then all functions taking an initial
41argument of name C<loop> (which is always of type C<struct ev_loop *>) 41argument of name C<loop> (which is always of type C<struct ev_loop *>)
42will not have this argument. 42will not have this argument.
43 43
44=head1 TIME AND OTHER GLOBAL FUNCTIONS 44=head1 TIME REPRESENTATION
45 45
46Libev represents time as a single floating point number, representing the 46Libev 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
48the beginning of 1970, details are complicated, don't ask). This type is 48the beginning of 1970, details are complicated, don't ask). This type is
49called C<ev_tstamp>, which is what you should use too. It usually aliases 49called C<ev_tstamp>, which is what you should use too. It usually aliases
50to the double type in C. 50to the C<double> type in C, and when you need to do any calculations on
51it, you should treat it as such.
52
53
54=head1 GLOBAL FUNCTIONS
55
56These functions can be called anytime, even before initialising the
57library in any way.
51 58
52=over 4 59=over 4
53 60
54=item ev_tstamp ev_time () 61=item ev_tstamp ev_time ()
55 62
56Returns the current time as libev would use it. 63Returns the current time as libev would use it. Please note that the
64C<ev_now> function is usually faster and also often returns the timestamp
65you actually want to know.
57 66
58=item int ev_version_major () 67=item int ev_version_major ()
59 68
60=item int ev_version_minor () 69=item int ev_version_minor ()
61 70
63you linked against by calling the functions C<ev_version_major> and 72you linked against by calling the functions C<ev_version_major> and
64C<ev_version_minor>. If you want, you can compare against the global 73C<ev_version_minor>. If you want, you can compare against the global
65symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 74symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66version of the library your program was compiled against. 75version of the library your program was compiled against.
67 76
68Usually, its a good idea to terminate if the major versions mismatch, 77Usually, it's a good idea to terminate if the major versions mismatch,
69as this indicates an incompatible change. Minor versions are usually 78as this indicates an incompatible change. Minor versions are usually
70compatible to older versions, so a larger minor version alone is usually 79compatible to older versions, so a larger minor version alone is usually
71not a problem. 80not a problem.
72 81
82Example: make sure we haven't accidentally been linked against the wrong
83version:
84
85 assert (("libev version mismatch",
86 ev_version_major () == EV_VERSION_MAJOR
87 && ev_version_minor () >= EV_VERSION_MINOR));
88
89=item unsigned int ev_supported_backends ()
90
91Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
92value) compiled into this binary of libev (independent of their
93availability on the system you are running on). See C<ev_default_loop> for
94a description of the set values.
95
96Example: make sure we have the epoll method, because yeah this is cool and
97a must have and can we have a torrent of it please!!!11
98
99 assert (("sorry, no epoll, no sex",
100 ev_supported_backends () & EVBACKEND_EPOLL));
101
102=item unsigned int ev_recommended_backends ()
103
104Return the set of all backends compiled into this binary of libev and also
105recommended for this platform. This set is often smaller than the one
106returned by C<ev_supported_backends>, as for example kqueue is broken on
107most BSDs and will not be autodetected unless you explicitly request it
108(assuming you know what you are doing). This is the set of backends that
109libev will probe for if you specify no backends explicitly.
110
111=item unsigned int ev_embeddable_backends ()
112
113Returns the set of backends that are embeddable in other event loops. This
114is the theoretical, all-platform, value. To find which backends
115might be supported on the current system, you would need to look at
116C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
117recommended ones.
118
119See the description of C<ev_embed> watchers for more info.
120
73=item ev_set_allocator (void *(*cb)(void *ptr, long size)) 121=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74 122
75Sets the allocation function to use (the prototype is similar to the 123Sets the allocation function to use (the prototype is similar to the
76realloc function). It is used to allocate and free memory (no surprises 124realloc C function, the semantics are identical). It is used to allocate
77here). If it returns zero when memory needs to be allocated, the library 125and free memory (no surprises here). If it returns zero when memory
78might abort or take some potentially destructive action. The default is 126needs to be allocated, the library might abort or take some potentially
79your system realloc function. 127destructive action. The default is your system realloc function.
80 128
81You could override this function in high-availability programs to, say, 129You could override this function in high-availability programs to, say,
82free some memory if it cannot allocate memory, to use a special allocator, 130free some memory if it cannot allocate memory, to use a special allocator,
83or even to sleep a while and retry until some memory is available. 131or even to sleep a while and retry until some memory is available.
132
133Example: replace the libev allocator with one that waits a bit and then
134retries: better than mine).
135
136 static void *
137 persistent_realloc (void *ptr, long size)
138 {
139 for (;;)
140 {
141 void *newptr = realloc (ptr, size);
142
143 if (newptr)
144 return newptr;
145
146 sleep (60);
147 }
148 }
149
150 ...
151 ev_set_allocator (persistent_realloc);
84 152
85=item ev_set_syserr_cb (void (*cb)(const char *msg)); 153=item ev_set_syserr_cb (void (*cb)(const char *msg));
86 154
87Set the callback function to call on a retryable syscall error (such 155Set the callback function to call on a retryable syscall error (such
88as failed select, poll, epoll_wait). The message is a printable string 156as failed select, poll, epoll_wait). The message is a printable string
89indicating the system call or subsystem causing the problem. If this 157indicating the system call or subsystem causing the problem. If this
90callback is set, then libev will expect it to remedy the sitution, no 158callback is set, then libev will expect it to remedy the sitution, no
91matter what, when it returns. That is, libev will geenrally retry the 159matter what, when it returns. That is, libev will generally retry the
92requested operation, or, if the condition doesn't go away, do bad stuff 160requested operation, or, if the condition doesn't go away, do bad stuff
93(such as abort). 161(such as abort).
162
163Example: do the same thing as libev does internally:
164
165 static void
166 fatal_error (const char *msg)
167 {
168 perror (msg);
169 abort ();
170 }
171
172 ...
173 ev_set_syserr_cb (fatal_error);
94 174
95=back 175=back
96 176
97=head1 FUNCTIONS CONTROLLING THE EVENT LOOP 177=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98 178
99An event loop is described by a C<struct ev_loop *>. The library knows two 179An event loop is described by a C<struct ev_loop *>. The library knows two
100types of such loops, the I<default> loop, which supports signals and child 180types of such loops, the I<default> loop, which supports signals and child
101events, and dynamically created loops which do not. 181events, and dynamically created loops which do not.
102 182
103If you use threads, a common model is to run the default event loop 183If you use threads, a common model is to run the default event loop
104in your main thread (or in a separate thrad) and for each thread you 184in your main thread (or in a separate thread) and for each thread you
105create, you also create another event loop. Libev itself does no lockign 185create, you also create another event loop. Libev itself does no locking
106whatsoever, so if you mix calls to different event loops, make sure you 186whatsoever, so if you mix calls to the same event loop in different
107lock (this is usually a bad idea, though, even if done right). 187threads, make sure you lock (this is usually a bad idea, though, even if
188done correctly, because it's hideous and inefficient).
108 189
109=over 4 190=over 4
110 191
111=item struct ev_loop *ev_default_loop (unsigned int flags) 192=item struct ev_loop *ev_default_loop (unsigned int flags)
112 193
113This will initialise the default event loop if it hasn't been initialised 194This will initialise the default event loop if it hasn't been initialised
114yet and return it. If the default loop could not be initialised, returns 195yet and return it. If the default loop could not be initialised, returns
115false. If it already was initialised it simply returns it (and ignores the 196false. If it already was initialised it simply returns it (and ignores the
116flags). 197flags. If that is troubling you, check C<ev_backend ()> afterwards).
117 198
118If you don't know what event loop to use, use the one returned from this 199If you don't know what event loop to use, use the one returned from this
119function. 200function.
120 201
121The flags argument can be used to specify special behaviour or specific 202The flags argument can be used to specify special behaviour or specific
122backends to use, and is usually specified as 0 (or EVFLAG_AUTO) 203backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
123 204
124It supports the following flags: 205The following flags are supported:
125 206
126=over 4 207=over 4
127 208
128=item EVFLAG_AUTO 209=item C<EVFLAG_AUTO>
129 210
130The default flags value. Use this if you have no clue (its the right 211The default flags value. Use this if you have no clue (it's the right
131thing, believe me). 212thing, believe me).
132 213
133=item EVFLAG_NOENV 214=item C<EVFLAG_NOENV>
134 215
135If this flag bit is ored into the flag value then libev will I<not> look 216If this flag bit is ored into the flag value (or the program runs setuid
136at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this 217or setgid) then libev will I<not> look at the environment variable
137environment variable will override the flags completely. This is useful 218C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219override the flags completely if it is found in the environment. This is
138to try out specific backends to tets their performance, or to work around 220useful to try out specific backends to test their performance, or to work
139bugs. 221around bugs.
140 222
141=item EVMETHOD_SELECT portable select backend 223=item C<EVBACKEND_SELECT> (value 1, portable select backend)
142 224
143=item EVMETHOD_POLL poll backend (everywhere except windows) 225This is your standard select(2) backend. Not I<completely> standard, as
226libev tries to roll its own fd_set with no limits on the number of fds,
227but if that fails, expect a fairly low limit on the number of fds when
228using this backend. It doesn't scale too well (O(highest_fd)), but its usually
229the fastest backend for a low number of fds.
144 230
145=item EVMETHOD_EPOLL linux only 231=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146 232
147=item EVMETHOD_KQUEUE some bsds only 233And this is your standard poll(2) backend. It's more complicated than
234select, but handles sparse fds better and has no artificial limit on the
235number of fds you can use (except it will slow down considerably with a
236lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
148 237
149=item EVMETHOD_DEVPOLL solaris 8 only 238=item C<EVBACKEND_EPOLL> (value 4, Linux)
150 239
151=item EVMETHOD_PORT solaris 10 only 240For few fds, this backend is a bit little slower than poll and select,
241but it scales phenomenally better. While poll and select usually scale like
242O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
243either O(1) or O(active_fds).
244
245While stopping and starting an I/O watcher in the same iteration will
246result in some caching, there is still a syscall per such incident
247(because the fd could point to a different file description now), so its
248best to avoid that. Also, dup()ed file descriptors might not work very
249well if you register events for both fds.
250
251Please note that epoll sometimes generates spurious notifications, so you
252need to use non-blocking I/O or other means to avoid blocking when no data
253(or space) is available.
254
255=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256
257Kqueue deserves special mention, as at the time of this writing, it
258was broken on all BSDs except NetBSD (usually it doesn't work with
259anything but sockets and pipes, except on Darwin, where of course its
260completely useless). For this reason its not being "autodetected"
261unless you explicitly specify it explicitly in the flags (i.e. using
262C<EVBACKEND_KQUEUE>).
263
264It scales in the same way as the epoll backend, but the interface to the
265kernel is more efficient (which says nothing about its actual speed, of
266course). While starting and stopping an I/O watcher does not cause an
267extra syscall as with epoll, it still adds up to four event changes per
268incident, so its best to avoid that.
269
270=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271
272This is not implemented yet (and might never be).
273
274=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275
276This uses the Solaris 10 port mechanism. As with everything on Solaris,
277it's really slow, but it still scales very well (O(active_fds)).
278
279Please note that solaris ports can result in a lot of spurious
280notifications, so you need to use non-blocking I/O or other means to avoid
281blocking when no data (or space) is available.
282
283=item C<EVBACKEND_ALL>
284
285Try all backends (even potentially broken ones that wouldn't be tried
286with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
287C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
288
289=back
152 290
153If one or more of these are ored into the flags value, then only these 291If one or more of these are ored into the flags value, then only these
154backends will be tried (in the reverse order as given here). If one are 292backends will be tried (in the reverse order as given here). If none are
155specified, any backend will do. 293specified, most compiled-in backend will be tried, usually in reverse
294order of their flag values :)
156 295
157=back 296The most typical usage is like this:
297
298 if (!ev_default_loop (0))
299 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
300
301Restrict libev to the select and poll backends, and do not allow
302environment settings to be taken into account:
303
304 ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
305
306Use whatever libev has to offer, but make sure that kqueue is used if
307available (warning, breaks stuff, best use only with your own private
308event loop and only if you know the OS supports your types of fds):
309
310 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
158 311
159=item struct ev_loop *ev_loop_new (unsigned int flags) 312=item struct ev_loop *ev_loop_new (unsigned int flags)
160 313
161Similar to C<ev_default_loop>, but always creates a new event loop that is 314Similar to C<ev_default_loop>, but always creates a new event loop that is
162always distinct from the default loop. Unlike the default loop, it cannot 315always distinct from the default loop. Unlike the default loop, it cannot
163handle signal and child watchers, and attempts to do so will be greeted by 316handle signal and child watchers, and attempts to do so will be greeted by
164undefined behaviour (or a failed assertion if assertions are enabled). 317undefined behaviour (or a failed assertion if assertions are enabled).
165 318
319Example: try to create a event loop that uses epoll and nothing else.
320
321 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322 if (!epoller)
323 fatal ("no epoll found here, maybe it hides under your chair");
324
166=item ev_default_destroy () 325=item ev_default_destroy ()
167 326
168Destroys the default loop again (frees all memory and kernel state 327Destroys the default loop again (frees all memory and kernel state
169etc.). This stops all registered event watchers (by not touching them in 328etc.). None of the active event watchers will be stopped in the normal
170any way whatsoever, although you cnanot rely on this :). 329sense, so e.g. C<ev_is_active> might still return true. It is your
330responsibility to either stop all watchers cleanly yoursef I<before>
331calling this function, or cope with the fact afterwards (which is usually
332the easiest thing, youc na just ignore the watchers and/or C<free ()> them
333for example).
171 334
172=item ev_loop_destroy (loop) 335=item ev_loop_destroy (loop)
173 336
174Like C<ev_default_destroy>, but destroys an event loop created by an 337Like C<ev_default_destroy>, but destroys an event loop created by an
175earlier call to C<ev_loop_new>. 338earlier call to C<ev_loop_new>.
179This function reinitialises the kernel state for backends that have 342This function reinitialises the kernel state for backends that have
180one. Despite the name, you can call it anytime, but it makes most sense 343one. Despite the name, you can call it anytime, but it makes most sense
181after forking, in either the parent or child process (or both, but that 344after forking, in either the parent or child process (or both, but that
182again makes little sense). 345again makes little sense).
183 346
184You I<must> call this function after forking if and only if you want to 347You I<must> call this function in the child process after forking if and
185use the event library in both processes. If you just fork+exec, you don't 348only if you want to use the event library in both processes. If you just
186have to call it. 349fork+exec, you don't have to call it.
187 350
188The function itself is quite fast and its usually not a problem to call 351The function itself is quite fast and it's usually not a problem to call
189it just in case after a fork. To make this easy, the function will fit in 352it just in case after a fork. To make this easy, the function will fit in
190quite nicely into a call to C<pthread_atfork>: 353quite nicely into a call to C<pthread_atfork>:
191 354
192 pthread_atfork (0, 0, ev_default_fork); 355 pthread_atfork (0, 0, ev_default_fork);
356
357At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
358without calling this function, so if you force one of those backends you
359do not need to care.
193 360
194=item ev_loop_fork (loop) 361=item ev_loop_fork (loop)
195 362
196Like C<ev_default_fork>, but acts on an event loop created by 363Like C<ev_default_fork>, but acts on an event loop created by
197C<ev_loop_new>. Yes, you have to call this on every allocated event loop 364C<ev_loop_new>. Yes, you have to call this on every allocated event loop
198after fork, and how you do this is entirely your own problem. 365after fork, and how you do this is entirely your own problem.
199 366
200=item unsigned int ev_method (loop) 367=item unsigned int ev_backend (loop)
201 368
202Returns one of the C<EVMETHOD_*> flags indicating the event backend in 369Returns one of the C<EVBACKEND_*> flags indicating the event backend in
203use. 370use.
204 371
205=item ev_tstamp = ev_now (loop) 372=item ev_tstamp ev_now (loop)
206 373
207Returns the current "event loop time", which is the time the event loop 374Returns the current "event loop time", which is the time the event loop
208got events and started processing them. This timestamp does not change 375received events and started processing them. This timestamp does not
209as long as callbacks are being processed, and this is also the base time 376change as long as callbacks are being processed, and this is also the base
210used for relative timers. You can treat it as the timestamp of the event 377time used for relative timers. You can treat it as the timestamp of the
211occuring (or more correctly, the mainloop finding out about it). 378event occuring (or more correctly, libev finding out about it).
212 379
213=item ev_loop (loop, int flags) 380=item ev_loop (loop, int flags)
214 381
215Finally, this is it, the event handler. This function usually is called 382Finally, this is it, the event handler. This function usually is called
216after you initialised all your watchers and you want to start handling 383after you initialised all your watchers and you want to start handling
217events. 384events.
218 385
219If the flags argument is specified as 0, it will not return until either 386If the flags argument is specified as C<0>, it will not return until
220no event watchers are active anymore or C<ev_unloop> was called. 387either no event watchers are active anymore or C<ev_unloop> was called.
388
389Please note that an explicit C<ev_unloop> is usually better than
390relying on all watchers to be stopped when deciding when a program has
391finished (especially in interactive programs), but having a program that
392automatically loops as long as it has to and no longer by virtue of
393relying on its watchers stopping correctly is a thing of beauty.
221 394
222A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle 395A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
223those events and any outstanding ones, but will not block your process in 396those events and any outstanding ones, but will not block your process in
224case there are no events. 397case there are no events and will return after one iteration of the loop.
225 398
226A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if 399A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
227neccessary) and will handle those and any outstanding ones. It will block 400neccessary) and will handle those and any outstanding ones. It will block
228your process until at least one new event arrives. 401your process until at least one new event arrives, and will return after
402one iteration of the loop. This is useful if you are waiting for some
403external event in conjunction with something not expressible using other
404libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405usually a better approach for this kind of thing.
229 406
230This flags value could be used to implement alternative looping 407Here are the gory details of what C<ev_loop> does:
231constructs, but the C<prepare> and C<check> watchers provide a better and 408
232more generic mechanism. 409 * If there are no active watchers (reference count is zero), return.
410 - Queue prepare watchers and then call all outstanding watchers.
411 - If we have been forked, recreate the kernel state.
412 - Update the kernel state with all outstanding changes.
413 - Update the "event loop time".
414 - Calculate for how long to block.
415 - Block the process, waiting for any events.
416 - Queue all outstanding I/O (fd) events.
417 - Update the "event loop time" and do time jump handling.
418 - Queue all outstanding timers.
419 - Queue all outstanding periodics.
420 - If no events are pending now, queue all idle watchers.
421 - Queue all check watchers.
422 - Call all queued watchers in reverse order (i.e. check watchers first).
423 Signals and child watchers are implemented as I/O watchers, and will
424 be handled here by queueing them when their watcher gets executed.
425 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426 were used, return, otherwise continue with step *.
427
428Example: queue some jobs and then loop until no events are outsanding
429anymore.
430
431 ... queue jobs here, make sure they register event watchers as long
432 ... as they still have work to do (even an idle watcher will do..)
433 ev_loop (my_loop, 0);
434 ... jobs done. yeah!
233 435
234=item ev_unloop (loop, how) 436=item ev_unloop (loop, how)
235 437
236Can be used to make a call to C<ev_loop> return early. The C<how> argument 438Can be used to make a call to C<ev_loop> return early (but only after it
439has processed all outstanding events). The C<how> argument must be either
237must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> 440C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
238call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> 441C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
239calls return.
240 442
241=item ev_ref (loop) 443=item ev_ref (loop)
242 444
243=item ev_unref (loop) 445=item ev_unref (loop)
244 446
245Ref/unref can be used to add or remove a refcount on the event loop: Every 447Ref/unref can be used to add or remove a reference count on the event
246watcher keeps one reference. If you have a long-runing watcher you never 448loop: Every watcher keeps one reference, and as long as the reference
247unregister that should not keep ev_loop from running, ev_unref() after 449count is nonzero, C<ev_loop> will not return on its own. If you have
248starting, and ev_ref() before stopping it. Libev itself uses this for 450a watcher you never unregister that should not keep C<ev_loop> from
249example for its internal signal pipe: It is not visible to you as a user 451returning, ev_unref() after starting, and ev_ref() before stopping it. For
250and should not keep C<ev_loop> from exiting if the work is done. It is 452example, libev itself uses this for its internal signal pipe: It is not
251also an excellent way to do this for generic recurring timers or from 453visible to the libev user and should not keep C<ev_loop> from exiting if
252within third-party libraries. Just remember to unref after start and ref 454no event watchers registered by it are active. It is also an excellent
253before stop. 455way to do this for generic recurring timers or from within third-party
456libraries. Just remember to I<unref after start> and I<ref before stop>.
457
458Example: create a signal watcher, but keep it from keeping C<ev_loop>
459running when nothing else is active.
460
461 struct dv_signal exitsig;
462 ev_signal_init (&exitsig, sig_cb, SIGINT);
463 ev_signal_start (myloop, &exitsig);
464 evf_unref (myloop);
465
466Example: for some weird reason, unregister the above signal handler again.
467
468 ev_ref (myloop);
469 ev_signal_stop (myloop, &exitsig);
254 470
255=back 471=back
256 472
257=head1 ANATOMY OF A WATCHER 473=head1 ANATOMY OF A WATCHER
258 474
259A watcher is a structure that you create and register to record your 475A watcher is a structure that you create and register to record your
260interest in some event. For instance, if you want to wait for STDIN to 476interest in some event. For instance, if you want to wait for STDIN to
261become readable, you would create an ev_io watcher for that: 477become readable, you would create an C<ev_io> watcher for that:
262 478
263 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 479 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
264 { 480 {
265 ev_io_stop (w); 481 ev_io_stop (w);
266 ev_unloop (loop, EVUNLOOP_ALL); 482 ev_unloop (loop, EVUNLOOP_ALL);
293*) >>), and you can stop watching for events at any time by calling the 509*) >>), and you can stop watching for events at any time by calling the
294corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. 510corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
295 511
296As long as your watcher is active (has been started but not stopped) you 512As long as your watcher is active (has been started but not stopped) you
297must not touch the values stored in it. Most specifically you must never 513must not touch the values stored in it. Most specifically you must never
298reinitialise it or call its set method. 514reinitialise it or call its C<set> macro.
299
300You cna check whether an event is active by calling the C<ev_is_active
301(watcher *)> macro. To see whether an event is outstanding (but the
302callback for it has not been called yet) you cna use the C<ev_is_pending
303(watcher *)> macro.
304 515
305Each and every callback receives the event loop pointer as first, the 516Each and every callback receives the event loop pointer as first, the
306registered watcher structure as second, and a bitset of received events as 517registered watcher structure as second, and a bitset of received events as
307third argument. 518third argument.
308 519
309The rceeived events usually include a single bit per event type received 520The received events usually include a single bit per event type received
310(you can receive multiple events at the same time). The possible bit masks 521(you can receive multiple events at the same time). The possible bit masks
311are: 522are:
312 523
313=over 4 524=over 4
314 525
315=item EV_READ 526=item C<EV_READ>
316 527
317=item EV_WRITE 528=item C<EV_WRITE>
318 529
319The file descriptor in the ev_io watcher has become readable and/or 530The file descriptor in the C<ev_io> watcher has become readable and/or
320writable. 531writable.
321 532
322=item EV_TIMEOUT 533=item C<EV_TIMEOUT>
323 534
324The ev_timer watcher has timed out. 535The C<ev_timer> watcher has timed out.
325 536
326=item EV_PERIODIC 537=item C<EV_PERIODIC>
327 538
328The ev_periodic watcher has timed out. 539The C<ev_periodic> watcher has timed out.
329 540
330=item EV_SIGNAL 541=item C<EV_SIGNAL>
331 542
332The signal specified in the ev_signal watcher has been received by a thread. 543The signal specified in the C<ev_signal> watcher has been received by a thread.
333 544
334=item EV_CHILD 545=item C<EV_CHILD>
335 546
336The pid specified in the ev_child watcher has received a status change. 547The pid specified in the C<ev_child> watcher has received a status change.
337 548
338=item EV_IDLE 549=item C<EV_IDLE>
339 550
340The ev_idle watcher has determined that you have nothing better to do. 551The C<ev_idle> watcher has determined that you have nothing better to do.
341 552
342=item EV_PREPARE 553=item C<EV_PREPARE>
343 554
344=item EV_CHECK 555=item C<EV_CHECK>
345 556
346All ev_prepare watchers are invoked just I<before> C<ev_loop> starts 557All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
347to gather new events, and all ev_check watchers are invoked just after 558to gather new events, and all C<ev_check> watchers are invoked just after
348C<ev_loop> has gathered them, but before it invokes any callbacks for any 559C<ev_loop> has gathered them, but before it invokes any callbacks for any
349received events. Callbacks of both watcher types can start and stop as 560received events. Callbacks of both watcher types can start and stop as
350many watchers as they want, and all of them will be taken into account 561many watchers as they want, and all of them will be taken into account
351(for example, a ev_prepare watcher might start an idle watcher to keep 562(for example, a C<ev_prepare> watcher might start an idle watcher to keep
352C<ev_loop> from blocking). 563C<ev_loop> from blocking).
353 564
354=item EV_ERROR 565=item C<EV_ERROR>
355 566
356An unspecified error has occured, the watcher has been stopped. This might 567An unspecified error has occured, the watcher has been stopped. This might
357happen because the watcher could not be properly started because libev 568happen because the watcher could not be properly started because libev
358ran out of memory, a file descriptor was found to be closed or any other 569ran out of memory, a file descriptor was found to be closed or any other
359problem. You best act on it by reporting the problem and somehow coping 570problem. You best act on it by reporting the problem and somehow coping
365with the error from read() or write(). This will not work in multithreaded 576with the error from read() or write(). This will not work in multithreaded
366programs, though, so beware. 577programs, though, so beware.
367 578
368=back 579=back
369 580
581=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS
582
583In the following description, C<TYPE> stands for the watcher type,
584e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585
586=over 4
587
588=item C<ev_init> (ev_TYPE *watcher, callback)
589
590This macro initialises the generic portion of a watcher. The contents
591of the watcher object can be arbitrary (so C<malloc> will do). Only
592the generic parts of the watcher are initialised, you I<need> to call
593the type-specific C<ev_TYPE_set> macro afterwards to initialise the
594type-specific parts. For each type there is also a C<ev_TYPE_init> macro
595which rolls both calls into one.
596
597You can reinitialise a watcher at any time as long as it has been stopped
598(or never started) and there are no pending events outstanding.
599
600The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601int revents)>.
602
603=item C<ev_TYPE_set> (ev_TYPE *, [args])
604
605This macro initialises the type-specific parts of a watcher. You need to
606call C<ev_init> at least once before you call this macro, but you can
607call C<ev_TYPE_set> any number of times. You must not, however, call this
608macro on a watcher that is active (it can be pending, however, which is a
609difference to the C<ev_init> macro).
610
611Although some watcher types do not have type-specific arguments
612(e.g. C<ev_prepare>) you still need to call its C<set> macro.
613
614=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
615
616This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
617calls into a single call. This is the most convinient method to initialise
618a watcher. The same limitations apply, of course.
619
620=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
621
622Starts (activates) the given watcher. Only active watchers will receive
623events. If the watcher is already active nothing will happen.
624
625=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
626
627Stops the given watcher again (if active) and clears the pending
628status. It is possible that stopped watchers are pending (for example,
629non-repeating timers are being stopped when they become pending), but
630C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
631you want to free or reuse the memory used by the watcher it is therefore a
632good idea to always call its C<ev_TYPE_stop> function.
633
634=item bool ev_is_active (ev_TYPE *watcher)
635
636Returns a true value iff the watcher is active (i.e. it has been started
637and not yet been stopped). As long as a watcher is active you must not modify
638it.
639
640=item bool ev_is_pending (ev_TYPE *watcher)
641
642Returns a true value iff the watcher is pending, (i.e. it has outstanding
643events but its callback has not yet been invoked). As long as a watcher
644is pending (but not active) you must not call an init function on it (but
645C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
646libev (e.g. you cnanot C<free ()> it).
647
648=item callback = ev_cb (ev_TYPE *watcher)
649
650Returns the callback currently set on the watcher.
651
652=item ev_cb_set (ev_TYPE *watcher, callback)
653
654Change the callback. You can change the callback at virtually any time
655(modulo threads).
656
657=back
658
659
370=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 660=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
371 661
372Each watcher has, by default, a member C<void *data> that you can change 662Each watcher has, by default, a member C<void *data> that you can change
373and read at any time, libev will completely ignore it. This cna be used 663and read at any time, libev will completely ignore it. This can be used
374to associate arbitrary data with your watcher. If you need more data and 664to associate arbitrary data with your watcher. If you need more data and
375don't want to allocate memory and store a pointer to it in that data 665don't want to allocate memory and store a pointer to it in that data
376member, you can also "subclass" the watcher type and provide your own 666member, you can also "subclass" the watcher type and provide your own
377data: 667data:
378 668
400=head1 WATCHER TYPES 690=head1 WATCHER TYPES
401 691
402This section describes each watcher in detail, but will not repeat 692This section describes each watcher in detail, but will not repeat
403information given in the last section. 693information given in the last section.
404 694
695
405=head2 struct ev_io - is my file descriptor readable or writable 696=head2 C<ev_io> - is this file descriptor readable or writable
406 697
407I/O watchers check whether a file descriptor is readable or writable 698I/O watchers check whether a file descriptor is readable or writable
408in each iteration of the event loop (This behaviour is called 699in each iteration of the event loop (This behaviour is called
409level-triggering because you keep receiving events as long as the 700level-triggering because you keep receiving events as long as the
410condition persists. Remember you cna stop the watcher if you don't want to 701condition persists. Remember you can stop the watcher if you don't want to
411act on the event and neither want to receive future events). 702act on the event and neither want to receive future events).
412 703
704In general you can register as many read and/or write event watchers per
705fd as you want (as long as you don't confuse yourself). Setting all file
706descriptors to non-blocking mode is also usually a good idea (but not
707required if you know what you are doing).
708
709You have to be careful with dup'ed file descriptors, though. Some backends
710(the linux epoll backend is a notable example) cannot handle dup'ed file
711descriptors correctly if you register interest in two or more fds pointing
712to the same underlying file/socket etc. description (that is, they share
713the same underlying "file open").
714
715If you must do this, then force the use of a known-to-be-good backend
716(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717C<EVBACKEND_POLL>).
718
413=over 4 719=over 4
414 720
415=item ev_io_init (ev_io *, callback, int fd, int events) 721=item ev_io_init (ev_io *, callback, int fd, int events)
416 722
417=item ev_io_set (ev_io *, int fd, int events) 723=item ev_io_set (ev_io *, int fd, int events)
418 724
419Configures an ev_io watcher. The fd is the file descriptor to rceeive 725Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
420events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ | 726events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
421EV_WRITE> to receive the given events. 727EV_WRITE> to receive the given events.
422 728
423=back 729Please note that most of the more scalable backend mechanisms (for example
730epoll and solaris ports) can result in spurious readyness notifications
731for file descriptors, so you practically need to use non-blocking I/O (and
732treat callback invocation as hint only), or retest separately with a safe
733interface before doing I/O (XLib can do this), or force the use of either
734C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
735problem. Also note that it is quite easy to have your callback invoked
736when the readyness condition is no longer valid even when employing
737typical ways of handling events, so its a good idea to use non-blocking
738I/O unconditionally.
424 739
740=back
741
742Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
743readable, but only once. Since it is likely line-buffered, you could
744attempt to read a whole line in the callback:
745
746 static void
747 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748 {
749 ev_io_stop (loop, w);
750 .. read from stdin here (or from w->fd) and haqndle any I/O errors
751 }
752
753 ...
754 struct ev_loop *loop = ev_default_init (0);
755 struct ev_io stdin_readable;
756 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757 ev_io_start (loop, &stdin_readable);
758 ev_loop (loop, 0);
759
760
425=head2 struct ev_timer - relative and optionally recurring timeouts 761=head2 C<ev_timer> - relative and optionally recurring timeouts
426 762
427Timer watchers are simple relative timers that generate an event after a 763Timer watchers are simple relative timers that generate an event after a
428given time, and optionally repeating in regular intervals after that. 764given time, and optionally repeating in regular intervals after that.
429 765
430The timers are based on real time, that is, if you register an event that 766The timers are based on real time, that is, if you register an event that
431times out after an hour and youreset your system clock to last years 767times out after an hour and you reset your system clock to last years
432time, it will still time out after (roughly) and hour. "Roughly" because 768time, it will still time out after (roughly) and hour. "Roughly" because
433detecting time jumps is hard, and soem inaccuracies are unavoidable (the 769detecting time jumps is hard, and some inaccuracies are unavoidable (the
434monotonic clock option helps a lot here). 770monotonic clock option helps a lot here).
771
772The relative timeouts are calculated relative to the C<ev_now ()>
773time. This is usually the right thing as this timestamp refers to the time
774of the event triggering whatever timeout you are modifying/starting. If
775you suspect event processing to be delayed and you I<need> to base the timeout
776on the current time, use something like this to adjust for this:
777
778 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
779
780The callback is guarenteed to be invoked only when its timeout has passed,
781but if multiple timers become ready during the same loop iteration then
782order of execution is undefined.
435 783
436=over 4 784=over 4
437 785
438=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 786=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
439 787
445later, again, and again, until stopped manually. 793later, again, and again, until stopped manually.
446 794
447The timer itself will do a best-effort at avoiding drift, that is, if you 795The timer itself will do a best-effort at avoiding drift, that is, if you
448configure a timer to trigger every 10 seconds, then it will trigger at 796configure a timer to trigger every 10 seconds, then it will trigger at
449exactly 10 second intervals. If, however, your program cannot keep up with 797exactly 10 second intervals. If, however, your program cannot keep up with
450the timer (ecause it takes longer than those 10 seconds to do stuff) the 798the timer (because it takes longer than those 10 seconds to do stuff) the
451timer will not fire more than once per event loop iteration. 799timer will not fire more than once per event loop iteration.
452 800
453=item ev_timer_again (loop) 801=item ev_timer_again (loop)
454 802
455This will act as if the timer timed out and restart it again if it is 803This will act as if the timer timed out and restart it again if it is
462 810
463This sounds a bit complicated, but here is a useful and typical 811This sounds a bit complicated, but here is a useful and typical
464example: Imagine you have a tcp connection and you want a so-called idle 812example: Imagine you have a tcp connection and you want a so-called idle
465timeout, that is, you want to be called when there have been, say, 60 813timeout, that is, you want to be called when there have been, say, 60
466seconds of inactivity on the socket. The easiest way to do this is to 814seconds of inactivity on the socket. The easiest way to do this is to
467configure an ev_timer with after=repeat=60 and calling ev_timer_again each 815configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
468time you successfully read or write some data. If you go into an idle 816time you successfully read or write some data. If you go into an idle
469state where you do not expect data to travel on the socket, you can stop 817state where you do not expect data to travel on the socket, you can stop
470the timer, and again will automatically restart it if need be. 818the timer, and again will automatically restart it if need be.
471 819
472=back 820=back
473 821
822Example: create a timer that fires after 60 seconds.
823
824 static void
825 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826 {
827 .. one minute over, w is actually stopped right here
828 }
829
830 struct ev_timer mytimer;
831 ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832 ev_timer_start (loop, &mytimer);
833
834Example: create a timeout timer that times out after 10 seconds of
835inactivity.
836
837 static void
838 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839 {
840 .. ten seconds without any activity
841 }
842
843 struct ev_timer mytimer;
844 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
845 ev_timer_again (&mytimer); /* start timer */
846 ev_loop (loop, 0);
847
848 // and in some piece of code that gets executed on any "activity":
849 // reset the timeout to start ticking again at 10 seconds
850 ev_timer_again (&mytimer);
851
852
474=head2 ev_periodic - to cron or not to cron it 853=head2 C<ev_periodic> - to cron or not to cron
475 854
476Periodic watchers are also timers of a kind, but they are very versatile 855Periodic watchers are also timers of a kind, but they are very versatile
477(and unfortunately a bit complex). 856(and unfortunately a bit complex).
478 857
479Unlike ev_timer's, they are not based on real time (or relative time) 858Unlike C<ev_timer>'s, they are not based on real time (or relative time)
480but on wallclock time (absolute time). You can tell a periodic watcher 859but on wallclock time (absolute time). You can tell a periodic watcher
481to trigger "at" some specific point in time. For example, if you tell a 860to trigger "at" some specific point in time. For example, if you tell a
482periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 861periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
483+ 10.>) and then reset your system clock to the last year, then it will 862+ 10.>) and then reset your system clock to the last year, then it will
484take a year to trigger the event (unlike an ev_timer, which would trigger 863take a year to trigger the event (unlike an C<ev_timer>, which would trigger
485roughly 10 seconds later and of course not if you reset your system time 864roughly 10 seconds later and of course not if you reset your system time
486again). 865again).
487 866
488They can also be used to implement vastly more complex timers, such as 867They can also be used to implement vastly more complex timers, such as
489triggering an event on eahc midnight, local time. 868triggering an event on eahc midnight, local time.
490 869
870As with timers, the callback is guarenteed to be invoked only when the
871time (C<at>) has been passed, but if multiple periodic timers become ready
872during the same loop iteration then order of execution is undefined.
873
491=over 4 874=over 4
492 875
493=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) 876=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
494 877
495=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) 878=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
496 879
497Lots of arguments, lets sort it out... There are basically three modes of 880Lots of arguments, lets sort it out... There are basically three modes of
498operation, and we will explain them from simplest to complex: 881operation, and we will explain them from simplest to complex:
499
500 882
501=over 4 883=over 4
502 884
503=item * absolute timer (interval = reschedule_cb = 0) 885=item * absolute timer (interval = reschedule_cb = 0)
504 886
518 900
519 ev_periodic_set (&periodic, 0., 3600., 0); 901 ev_periodic_set (&periodic, 0., 3600., 0);
520 902
521This doesn't mean there will always be 3600 seconds in between triggers, 903This doesn't mean there will always be 3600 seconds in between triggers,
522but only that the the callback will be called when the system time shows a 904but only that the the callback will be called when the system time shows a
523full hour (UTC), or more correct, when the system time is evenly divisible 905full hour (UTC), or more correctly, when the system time is evenly divisible
524by 3600. 906by 3600.
525 907
526Another way to think about it (for the mathematically inclined) is that 908Another way to think about it (for the mathematically inclined) is that
527ev_periodic will try to run the callback in this mode at the next possible 909C<ev_periodic> will try to run the callback in this mode at the next possible
528time where C<time = at (mod interval)>, regardless of any time jumps. 910time where C<time = at (mod interval)>, regardless of any time jumps.
529 911
530=item * manual reschedule mode (reschedule_cb = callback) 912=item * manual reschedule mode (reschedule_cb = callback)
531 913
532In this mode the values for C<interval> and C<at> are both being 914In this mode the values for C<interval> and C<at> are both being
533ignored. Instead, each time the periodic watcher gets scheduled, the 915ignored. Instead, each time the periodic watcher gets scheduled, the
534reschedule callback will be called with the watcher as first, and the 916reschedule callback will be called with the watcher as first, and the
535current time as second argument. 917current time as second argument.
536 918
537NOTE: I<This callback MUST NOT stop or destroy the periodic or any other 919NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
538periodic watcher, ever, or make any event loop modificstions>. If you need 920ever, or make any event loop modifications>. If you need to stop it,
539to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards. 921return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922starting a prepare watcher).
540 923
541Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 924Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
542ev_tstamp now)>, e.g.: 925ev_tstamp now)>, e.g.:
543 926
544 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 927 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
545 { 928 {
546 return now + 60.; 929 return now + 60.;
549It must return the next time to trigger, based on the passed time value 932It must return the next time to trigger, based on the passed time value
550(that is, the lowest time value larger than to the second argument). It 933(that is, the lowest time value larger than to the second argument). It
551will usually be called just before the callback will be triggered, but 934will usually be called just before the callback will be triggered, but
552might be called at other times, too. 935might be called at other times, too.
553 936
937NOTE: I<< This callback must always return a time that is later than the
938passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
939
554This can be used to create very complex timers, such as a timer that 940This can be used to create very complex timers, such as a timer that
555triggers on each midnight, local time. To do this, you would calculate the 941triggers on each midnight, local time. To do this, you would calculate the
556next midnight after C<now> and return the timestamp value for this. How you do this 942next midnight after C<now> and return the timestamp value for this. How
557is, again, up to you (but it is not trivial). 943you do this is, again, up to you (but it is not trivial, which is the main
944reason I omitted it as an example).
558 945
559=back 946=back
560 947
561=item ev_periodic_again (loop, ev_periodic *) 948=item ev_periodic_again (loop, ev_periodic *)
562 949
565a different time than the last time it was called (e.g. in a crond like 952a different time than the last time it was called (e.g. in a crond like
566program when the crontabs have changed). 953program when the crontabs have changed).
567 954
568=back 955=back
569 956
957Example: call a callback every hour, or, more precisely, whenever the
958system clock is divisible by 3600. The callback invocation times have
959potentially a lot of jittering, but good long-term stability.
960
961 static void
962 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
963 {
964 ... its now a full hour (UTC, or TAI or whatever your clock follows)
965 }
966
967 struct ev_periodic hourly_tick;
968 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969 ev_periodic_start (loop, &hourly_tick);
970
971Example: the same as above, but use a reschedule callback to do it:
972
973 #include <math.h>
974
975 static ev_tstamp
976 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
977 {
978 return fmod (now, 3600.) + 3600.;
979 }
980
981 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982
983Example: call a callback every hour, starting now:
984
985 struct ev_periodic hourly_tick;
986 ev_periodic_init (&hourly_tick, clock_cb,
987 fmod (ev_now (loop), 3600.), 3600., 0);
988 ev_periodic_start (loop, &hourly_tick);
989
990
570=head2 ev_signal - signal me when a signal gets signalled 991=head2 C<ev_signal> - signal me when a signal gets signalled
571 992
572Signal watchers will trigger an event when the process receives a specific 993Signal watchers will trigger an event when the process receives a specific
573signal one or more times. Even though signals are very asynchronous, libev 994signal one or more times. Even though signals are very asynchronous, libev
574will try its best to deliver signals synchronously, i.e. as part of the 995will try it's best to deliver signals synchronously, i.e. as part of the
575normal event processing, like any other event. 996normal event processing, like any other event.
576 997
577You cna configure as many watchers as you like per signal. Only when the 998You can configure as many watchers as you like per signal. Only when the
578first watcher gets started will libev actually register a signal watcher 999first watcher gets started will libev actually register a signal watcher
579with the kernel (thus it coexists with your own signal handlers as long 1000with the kernel (thus it coexists with your own signal handlers as long
580as you don't register any with libev). Similarly, when the last signal 1001as you don't register any with libev). Similarly, when the last signal
581watcher for a signal is stopped libev will reset the signal handler to 1002watcher for a signal is stopped libev will reset the signal handler to
582SIG_DFL (regardless of what it was set to before). 1003SIG_DFL (regardless of what it was set to before).
590Configures the watcher to trigger on the given signal number (usually one 1011Configures the watcher to trigger on the given signal number (usually one
591of the C<SIGxxx> constants). 1012of the C<SIGxxx> constants).
592 1013
593=back 1014=back
594 1015
1016
595=head2 ev_child - wait for pid status changes 1017=head2 C<ev_child> - wait for pid status changes
596 1018
597Child watchers trigger when your process receives a SIGCHLD in response to 1019Child watchers trigger when your process receives a SIGCHLD in response to
598some child status changes (most typically when a child of yours dies). 1020some child status changes (most typically when a child of yours dies).
599 1021
600=over 4 1022=over 4
604=item ev_child_set (ev_child *, int pid) 1026=item ev_child_set (ev_child *, int pid)
605 1027
606Configures the watcher to wait for status changes of process C<pid> (or 1028Configures the watcher to wait for status changes of process C<pid> (or
607I<any> process if C<pid> is specified as C<0>). The callback can look 1029I<any> process if C<pid> is specified as C<0>). The callback can look
608at the C<rstatus> member of the C<ev_child> watcher structure to see 1030at the C<rstatus> member of the C<ev_child> watcher structure to see
609the status word (use the macros from C<sys/wait.h>). The C<rpid> member 1031the status word (use the macros from C<sys/wait.h> and see your systems
610contains the pid of the process causing the status change. 1032C<waitpid> documentation). The C<rpid> member contains the pid of the
1033process causing the status change.
611 1034
612=back 1035=back
613 1036
1037Example: try to exit cleanly on SIGINT and SIGTERM.
1038
1039 static void
1040 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1041 {
1042 ev_unloop (loop, EVUNLOOP_ALL);
1043 }
1044
1045 struct ev_signal signal_watcher;
1046 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047 ev_signal_start (loop, &sigint_cb);
1048
1049
614=head2 ev_idle - when you've got nothing better to do 1050=head2 C<ev_idle> - when you've got nothing better to do
615 1051
616Idle watchers trigger events when there are no other I/O or timer (or 1052Idle watchers trigger events when there are no other events are pending
617periodic) events pending. That is, as long as your process is busy 1053(prepare, check and other idle watchers do not count). That is, as long
618handling sockets or timeouts it will not be called. But when your process 1054as your process is busy handling sockets or timeouts (or even signals,
619is idle all idle watchers are being called again and again - until 1055imagine) it will not be triggered. But when your process is idle all idle
1056watchers are being called again and again, once per event loop iteration -
620stopped, that is, or your process receives more events. 1057until stopped, that is, or your process receives more events and becomes
1058busy.
621 1059
622The most noteworthy effect is that as long as any idle watchers are 1060The most noteworthy effect is that as long as any idle watchers are
623active, the process will not block when waiting for new events. 1061active, the process will not block when waiting for new events.
624 1062
625Apart from keeping your process non-blocking (which is a useful 1063Apart from keeping your process non-blocking (which is a useful
635kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1073kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
636believe me. 1074believe me.
637 1075
638=back 1076=back
639 1077
640=head2 prepare and check - your hooks into the event loop 1078Example: dynamically allocate an C<ev_idle>, start it, and in the
1079callback, free it. Alos, use no error checking, as usual.
641 1080
1081 static void
1082 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083 {
1084 free (w);
1085 // now do something you wanted to do when the program has
1086 // no longer asnything immediate to do.
1087 }
1088
1089 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090 ev_idle_init (idle_watcher, idle_cb);
1091 ev_idle_start (loop, idle_cb);
1092
1093
1094=head2 C<ev_prepare> and C<ev_check> - customise your event loop
1095
642Prepare and check watchers usually (but not always) are used in 1096Prepare and check watchers are usually (but not always) used in tandem:
643tandom. Prepare watchers get invoked before the process blocks and check 1097prepare watchers get invoked before the process blocks and check watchers
644watchers afterwards. 1098afterwards.
645 1099
646Their main purpose is to integrate other event mechanisms into libev. This 1100Their main purpose is to integrate other event mechanisms into libev and
647could be used, for example, to track variable changes, implement your own 1101their use is somewhat advanced. This could be used, for example, to track
648watchers, integrate net-snmp or a coroutine library and lots more. 1102variable changes, implement your own watchers, integrate net-snmp or a
1103coroutine library and lots more.
649 1104
650This is done by examining in each prepare call which file descriptors need 1105This is done by examining in each prepare call which file descriptors need
651to be watched by the other library, registering ev_io watchers for them 1106to be watched by the other library, registering C<ev_io> watchers for
652and starting an ev_timer watcher for any timeouts (many libraries provide 1107them and starting an C<ev_timer> watcher for any timeouts (many libraries
653just this functionality). Then, in the check watcher you check for any 1108provide just this functionality). Then, in the check watcher you check for
654events that occured (by making your callbacks set soem flags for example) 1109any events that occured (by checking the pending status of all watchers
655and call back into the library. 1110and stopping them) and call back into the library. The I/O and timer
1111callbacks will never actually be called (but must be valid nevertheless,
1112because you never know, you know?).
656 1113
657As another example, the perl Coro module uses these hooks to integrate 1114As another example, the Perl Coro module uses these hooks to integrate
658coroutines into libev programs, by yielding to other active coroutines 1115coroutines into libev programs, by yielding to other active coroutines
659during each prepare and only letting the process block if no coroutines 1116during each prepare and only letting the process block if no coroutines
660are ready to run. 1117are ready to run (it's actually more complicated: it only runs coroutines
1118with priority higher than or equal to the event loop and one coroutine
1119of lower priority, but only once, using idle watchers to keep the event
1120loop from blocking if lower-priority coroutines are active, thus mapping
1121low-priority coroutines to idle/background tasks).
661 1122
662=over 4 1123=over 4
663 1124
664=item ev_prepare_init (ev_prepare *, callback) 1125=item ev_prepare_init (ev_prepare *, callback)
665 1126
666=item ev_check_init (ev_check *, callback) 1127=item ev_check_init (ev_check *, callback)
667 1128
668Initialises and configures the prepare or check watcher - they have no 1129Initialises and configures the prepare or check watcher - they have no
669parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1130parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
670macros, but using them is utterly, utterly pointless. 1131macros, but using them is utterly, utterly and completely pointless.
671 1132
672=back 1133=back
1134
1135Example: *TODO*.
1136
1137
1138=head2 C<ev_embed> - when one backend isn't enough
1139
1140This is a rather advanced watcher type that lets you embed one event loop
1141into another (currently only C<ev_io> events are supported in the embedded
1142loop, other types of watchers might be handled in a delayed or incorrect
1143fashion and must not be used).
1144
1145There are primarily two reasons you would want that: work around bugs and
1146prioritise I/O.
1147
1148As an example for a bug workaround, the kqueue backend might only support
1149sockets on some platform, so it is unusable as generic backend, but you
1150still want to make use of it because you have many sockets and it scales
1151so nicely. In this case, you would create a kqueue-based loop and embed it
1152into your default loop (which might use e.g. poll). Overall operation will
1153be a bit slower because first libev has to poll and then call kevent, but
1154at least you can use both at what they are best.
1155
1156As for prioritising I/O: rarely you have the case where some fds have
1157to be watched and handled very quickly (with low latency), and even
1158priorities and idle watchers might have too much overhead. In this case
1159you would put all the high priority stuff in one loop and all the rest in
1160a second one, and embed the second one in the first.
1161
1162As long as the watcher is active, the callback will be invoked every time
1163there might be events pending in the embedded loop. The callback must then
1164call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1165their callbacks (you could also start an idle watcher to give the embedded
1166loop strictly lower priority for example). You can also set the callback
1167to C<0>, in which case the embed watcher will automatically execute the
1168embedded loop sweep.
1169
1170As long as the watcher is started it will automatically handle events. The
1171callback will be invoked whenever some events have been handled. You can
1172set the callback to C<0> to avoid having to specify one if you are not
1173interested in that.
1174
1175Also, there have not currently been made special provisions for forking:
1176when you fork, you not only have to call C<ev_loop_fork> on both loops,
1177but you will also have to stop and restart any C<ev_embed> watchers
1178yourself.
1179
1180Unfortunately, not all backends are embeddable, only the ones returned by
1181C<ev_embeddable_backends> are, which, unfortunately, does not include any
1182portable one.
1183
1184So when you want to use this feature you will always have to be prepared
1185that you cannot get an embeddable loop. The recommended way to get around
1186this is to have a separate variables for your embeddable loop, try to
1187create it, and if that fails, use the normal loop for everything:
1188
1189 struct ev_loop *loop_hi = ev_default_init (0);
1190 struct ev_loop *loop_lo = 0;
1191 struct ev_embed embed;
1192
1193 // see if there is a chance of getting one that works
1194 // (remember that a flags value of 0 means autodetection)
1195 loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1196 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1197 : 0;
1198
1199 // if we got one, then embed it, otherwise default to loop_hi
1200 if (loop_lo)
1201 {
1202 ev_embed_init (&embed, 0, loop_lo);
1203 ev_embed_start (loop_hi, &embed);
1204 }
1205 else
1206 loop_lo = loop_hi;
1207
1208=over 4
1209
1210=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1211
1212=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1213
1214Configures the watcher to embed the given loop, which must be
1215embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1216invoked automatically, otherwise it is the responsibility of the callback
1217to invoke it (it will continue to be called until the sweep has been done,
1218if you do not want thta, you need to temporarily stop the embed watcher).
1219
1220=item ev_embed_sweep (loop, ev_embed *)
1221
1222Make a single, non-blocking sweep over the embedded loop. This works
1223similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224apropriate way for embedded loops.
1225
1226=back
1227
673 1228
674=head1 OTHER FUNCTIONS 1229=head1 OTHER FUNCTIONS
675 1230
676There are some other fucntions of possible interest. Described. Here. Now. 1231There are some other functions of possible interest. Described. Here. Now.
677 1232
678=over 4 1233=over 4
679 1234
680=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 1235=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
681 1236
682This function combines a simple timer and an I/O watcher, calls your 1237This function combines a simple timer and an I/O watcher, calls your
683callback on whichever event happens first and automatically stop both 1238callback on whichever event happens first and automatically stop both
684watchers. This is useful if you want to wait for a single event on an fd 1239watchers. This is useful if you want to wait for a single event on an fd
685or timeout without havign to allocate/configure/start/stop/free one or 1240or timeout without having to allocate/configure/start/stop/free one or
686more watchers yourself. 1241more watchers yourself.
687 1242
688If C<fd> is less than 0, then no I/O watcher will be started and events is 1243If C<fd> is less than 0, then no I/O watcher will be started and events
689ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set 1244is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
690will be craeted and started. 1245C<events> set will be craeted and started.
691 1246
692If C<timeout> is less than 0, then no timeout watcher will be 1247If C<timeout> is less than 0, then no timeout watcher will be
693started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat 1248started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
694= 0) will be started. 1249repeat = 0) will be started. While C<0> is a valid timeout, it is of
1250dubious value.
695 1251
696The callback has the type C<void (*cb)(int revents, void *arg)> and 1252The callback has the type C<void (*cb)(int revents, void *arg)> and gets
697gets passed an events set (normally a combination of EV_ERROR, EV_READ, 1253passed an C<revents> set like normal event callbacks (a combination of
698EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>: 1254C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1255value passed to C<ev_once>:
699 1256
700 static void stdin_ready (int revents, void *arg) 1257 static void stdin_ready (int revents, void *arg)
701 { 1258 {
702 if (revents & EV_TIMEOUT) 1259 if (revents & EV_TIMEOUT)
703 /* doh, nothing entered */ 1260 /* doh, nothing entered */;
704 else if (revents & EV_READ) 1261 else if (revents & EV_READ)
705 /* stdin might have data for us, joy! */ 1262 /* stdin might have data for us, joy! */;
706 } 1263 }
707 1264
708 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 1265 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
709 1266
710=item ev_feed_event (loop, watcher, int events) 1267=item ev_feed_event (ev_loop *, watcher *, int revents)
711 1268
712Feeds the given event set into the event loop, as if the specified event 1269Feeds the given event set into the event loop, as if the specified event
713has happened for the specified watcher (which must be a pointer to an 1270had happened for the specified watcher (which must be a pointer to an
714initialised but not necessarily active event watcher). 1271initialised but not necessarily started event watcher).
715 1272
716=item ev_feed_fd_event (loop, int fd, int revents) 1273=item ev_feed_fd_event (ev_loop *, int fd, int revents)
717 1274
718Feed an event on the given fd, as if a file descriptor backend detected it. 1275Feed an event on the given fd, as if a file descriptor backend detected
1276the given events it.
719 1277
720=item ev_feed_signal_event (loop, int signum) 1278=item ev_feed_signal_event (ev_loop *loop, int signum)
721 1279
722Feed an event as if the given signal occured (loop must be the default loop!). 1280Feed an event as if the given signal occured (C<loop> must be the default
1281loop!).
723 1282
724=back 1283=back
1284
1285
1286=head1 LIBEVENT EMULATION
1287
1288Libev offers a compatibility emulation layer for libevent. It cannot
1289emulate the internals of libevent, so here are some usage hints:
1290
1291=over 4
1292
1293=item * Use it by including <event.h>, as usual.
1294
1295=item * The following members are fully supported: ev_base, ev_callback,
1296ev_arg, ev_fd, ev_res, ev_events.
1297
1298=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
1299maintained by libev, it does not work exactly the same way as in libevent (consider
1300it a private API).
1301
1302=item * Priorities are not currently supported. Initialising priorities
1303will fail and all watchers will have the same priority, even though there
1304is an ev_pri field.
1305
1306=item * Other members are not supported.
1307
1308=item * The libev emulation is I<not> ABI compatible to libevent, you need
1309to use the libev header file and library.
1310
1311=back
1312
1313=head1 C++ SUPPORT
1314
1315Libev comes with some simplistic wrapper classes for C++ that mainly allow
1316you to use some convinience methods to start/stop watchers and also change
1317the callback model to a model using method callbacks on objects.
1318
1319To use it,
1320
1321 #include <ev++.h>
1322
1323(it is not installed by default). This automatically includes F<ev.h>
1324and puts all of its definitions (many of them macros) into the global
1325namespace. All C++ specific things are put into the C<ev> namespace.
1326
1327It should support all the same embedding options as F<ev.h>, most notably
1328C<EV_MULTIPLICITY>.
1329
1330Here is a list of things available in the C<ev> namespace:
1331
1332=over 4
1333
1334=item C<ev::READ>, C<ev::WRITE> etc.
1335
1336These are just enum values with the same values as the C<EV_READ> etc.
1337macros from F<ev.h>.
1338
1339=item C<ev::tstamp>, C<ev::now>
1340
1341Aliases to the same types/functions as with the C<ev_> prefix.
1342
1343=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
1344
1345For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
1346the same name in the C<ev> namespace, with the exception of C<ev_signal>
1347which is called C<ev::sig> to avoid clashes with the C<signal> macro
1348defines by many implementations.
1349
1350All of those classes have these methods:
1351
1352=over 4
1353
1354=item ev::TYPE::TYPE (object *, object::method *)
1355
1356=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
1357
1358=item ev::TYPE::~TYPE
1359
1360The constructor takes a pointer to an object and a method pointer to
1361the event handler callback to call in this class. The constructor calls
1362C<ev_init> for you, which means you have to call the C<set> method
1363before starting it. If you do not specify a loop then the constructor
1364automatically associates the default loop with this watcher.
1365
1366The destructor automatically stops the watcher if it is active.
1367
1368=item w->set (struct ev_loop *)
1369
1370Associates a different C<struct ev_loop> with this watcher. You can only
1371do this when the watcher is inactive (and not pending either).
1372
1373=item w->set ([args])
1374
1375Basically the same as C<ev_TYPE_set>, with the same args. Must be
1376called at least once. Unlike the C counterpart, an active watcher gets
1377automatically stopped and restarted.
1378
1379=item w->start ()
1380
1381Starts the watcher. Note that there is no C<loop> argument as the
1382constructor already takes the loop.
1383
1384=item w->stop ()
1385
1386Stops the watcher if it is active. Again, no C<loop> argument.
1387
1388=item w->again () C<ev::timer>, C<ev::periodic> only
1389
1390For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1391C<ev_TYPE_again> function.
1392
1393=item w->sweep () C<ev::embed> only
1394
1395Invokes C<ev_embed_sweep>.
1396
1397=back
1398
1399=back
1400
1401Example: Define a class with an IO and idle watcher, start one of them in
1402the constructor.
1403
1404 class myclass
1405 {
1406 ev_io io; void io_cb (ev::io &w, int revents);
1407 ev_idle idle void idle_cb (ev::idle &w, int revents);
1408
1409 myclass ();
1410 }
1411
1412 myclass::myclass (int fd)
1413 : io (this, &myclass::io_cb),
1414 idle (this, &myclass::idle_cb)
1415 {
1416 io.start (fd, ev::READ);
1417 }
725 1418
726=head1 AUTHOR 1419=head1 AUTHOR
727 1420
728Marc Lehmann <libev@schmorp.de>. 1421Marc Lehmann <libev@schmorp.de>.
729 1422

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