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… …
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<http://libev.schmorp.de/bench.html|benchmark> 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 double type in C.
51 51
52=head1 GLOBAL FUNCTIONS
53
54These functions can be called anytime, even before initialising the
55library 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
56Returns the current time as libev would use it. 61Returns the current time as libev would use it.
… …
63you linked against by calling the functions C<ev_version_major> and 68you linked against by calling the functions C<ev_version_major> and
64C<ev_version_minor>. If you want, you can compare against the global 69C<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 70symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66version of the library your program was compiled against. 71version of the library your program was compiled against.
67 72
68Usually, its a good idea to terminate if the major versions mismatch, 73Usually, it's a good idea to terminate if the major versions mismatch,
69as this indicates an incompatible change. Minor versions are usually 74as this indicates an incompatible change. Minor versions are usually
70compatible to older versions, so a larger minor version alone is usually 75compatible to older versions, so a larger minor version alone is usually
71not a problem. 76not a problem.
72 77
73=item ev_set_allocator (void *(*cb)(void *ptr, long size)) 78=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74 79
75Sets the allocation function to use (the prototype is similar to the 80Sets the allocation function to use (the prototype is similar to the
76realloc function). It is used to allocate and free memory (no surprises 81realloc C function, the semantics are identical). It is used to allocate
77here). If it returns zero when memory needs to be allocated, the library 82and free memory (no surprises here). If it returns zero when memory
78might abort or take some potentially destructive action. The default is 83needs to be allocated, the library might abort or take some potentially
79your system realloc function. 84destructive action. The default is your system realloc function.
80 85
81You could override this function in high-availability programs to, say, 86You could override this function in high-availability programs to, say,
82free some memory if it cannot allocate memory, to use a special allocator, 87free 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. 88or even to sleep a while and retry until some memory is available.
84 89
… …
86 91
87Set the callback function to call on a retryable syscall error (such 92Set the callback function to call on a retryable syscall error (such
88as failed select, poll, epoll_wait). The message is a printable string 93as failed select, poll, epoll_wait). The message is a printable string
89indicating the system call or subsystem causing the problem. If this 94indicating the system call or subsystem causing the problem. If this
90callback is set, then libev will expect it to remedy the sitution, no 95callback is set, then libev will expect it to remedy the sitution, no
91matter what, when it returns. That is, libev will geenrally retry the 96matter what, when it returns. That is, libev will generally retry the
92requested operation, or, if the condition doesn't go away, do bad stuff 97requested operation, or, if the condition doesn't go away, do bad stuff
93(such as abort). 98(such as abort).
94 99
95=back 100=back
96 101
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99An event loop is described by a C<struct ev_loop *>. The library knows two 104An 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 105types of such loops, the I<default> loop, which supports signals and child
101events, and dynamically created loops which do not. 106events, and dynamically created loops which do not.
102 107
103If you use threads, a common model is to run the default event loop 108If 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 109in 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 110create, you also create another event loop. Libev itself does no locking
106whatsoever, so if you mix calls to different event loops, make sure you 111whatsoever, so if you mix calls to the same event loop in different
107lock (this is usually a bad idea, though, even if done right). 112threads, make sure you lock (this is usually a bad idea, though, even if
113done correctly, because it's hideous and inefficient).
108 114
109=over 4 115=over 4
110 116
111=item struct ev_loop *ev_default_loop (unsigned int flags) 117=item struct ev_loop *ev_default_loop (unsigned int flags)
112 118
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117 123
118If you don't know what event loop to use, use the one returned from this 124If you don't know what event loop to use, use the one returned from this
119function. 125function.
120 126
121The flags argument can be used to specify special behaviour or specific 127The flags argument can be used to specify special behaviour or specific
122backends to use, and is usually specified as 0 (or EVFLAG_AUTO) 128backends to use, and is usually specified as 0 (or EVFLAG_AUTO).
123 129
124It supports the following flags: 130It supports the following flags:
125 131
126=over 4 132=over 4
127 133
128=item EVFLAG_AUTO 134=item C<EVFLAG_AUTO>
129 135
130The default flags value. Use this if you have no clue (its the right 136The default flags value. Use this if you have no clue (it's the right
131thing, believe me). 137thing, believe me).
132 138
133=item EVFLAG_NOENV 139=item C<EVFLAG_NOENV>
134 140
135If this flag bit is ored into the flag value then libev will I<not> look 141If 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 142or setgid) then libev will I<not> look at the environment variable
137environment variable will override the flags completely. This is useful 143C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
144override 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 145useful to try out specific backends to test their performance, or to work
139bugs. 146around bugs.
140 147
141=item EVMETHOD_SELECT portable select backend 148=item C<EVMETHOD_SELECT> (portable select backend)
142 149
143=item EVMETHOD_POLL poll backend (everywhere except windows) 150=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)
144 151
145=item EVMETHOD_EPOLL linux only 152=item C<EVMETHOD_EPOLL> (linux only)
146 153
147=item EVMETHOD_KQUEUE some bsds only 154=item C<EVMETHOD_KQUEUE> (some bsds only)
148 155
149=item EVMETHOD_DEVPOLL solaris 8 only 156=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
150 157
151=item EVMETHOD_PORT solaris 10 only 158=item C<EVMETHOD_PORT> (solaris 10 only)
152 159
153If one or more of these are ored into the flags value, then only these 160If 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 161backends will be tried (in the reverse order as given here). If one are
155specified, any backend will do. 162specified, any backend will do.
156 163
… …
165 172
166=item ev_default_destroy () 173=item ev_default_destroy ()
167 174
168Destroys the default loop again (frees all memory and kernel state 175Destroys the default loop again (frees all memory and kernel state
169etc.). This stops all registered event watchers (by not touching them in 176etc.). This stops all registered event watchers (by not touching them in
170any way whatsoever, although you cnanot rely on this :). 177any way whatsoever, although you cannot rely on this :).
171 178
172=item ev_loop_destroy (loop) 179=item ev_loop_destroy (loop)
173 180
174Like C<ev_default_destroy>, but destroys an event loop created by an 181Like C<ev_default_destroy>, but destroys an event loop created by an
175earlier call to C<ev_loop_new>. 182earlier call to C<ev_loop_new>.
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183 190
184You I<must> call this function after forking if and only if you want to 191You I<must> call this function after forking if and only if you want to
185use the event library in both processes. If you just fork+exec, you don't 192use the event library in both processes. If you just fork+exec, you don't
186have to call it. 193have to call it.
187 194
188The function itself is quite fast and its usually not a problem to call 195The 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 196it just in case after a fork. To make this easy, the function will fit in
190quite nicely into a call to C<pthread_atfork>: 197quite nicely into a call to C<pthread_atfork>:
191 198
192 pthread_atfork (0, 0, ev_default_fork); 199 pthread_atfork (0, 0, ev_default_fork);
193 200
… …
200=item unsigned int ev_method (loop) 207=item unsigned int ev_method (loop)
201 208
202Returns one of the C<EVMETHOD_*> flags indicating the event backend in 209Returns one of the C<EVMETHOD_*> flags indicating the event backend in
203use. 210use.
204 211
205=item ev_tstamp = ev_now (loop) 212=item ev_tstamp ev_now (loop)
206 213
207Returns the current "event loop time", which is the time the event loop 214Returns the current "event loop time", which is the time the event loop
208got events and started processing them. This timestamp does not change 215got events and started processing them. This timestamp does not change
209as long as callbacks are being processed, and this is also the base time 216as long as callbacks are being processed, and this is also the base time
210used for relative timers. You can treat it as the timestamp of the event 217used for relative timers. You can treat it as the timestamp of the event
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219If the flags argument is specified as 0, it will not return until either 226If the flags argument is specified as 0, it will not return until either
220no event watchers are active anymore or C<ev_unloop> was called. 227no event watchers are active anymore or C<ev_unloop> was called.
221 228
222A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle 229A 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 230those events and any outstanding ones, but will not block your process in
224case there are no events. 231case there are no events and will return after one iteration of the loop.
225 232
226A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if 233A 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 234neccessary) and will handle those and any outstanding ones. It will block
228your process until at least one new event arrives. 235your process until at least one new event arrives, and will return after
236one iteration of the loop.
229 237
230This flags value could be used to implement alternative looping 238This flags value could be used to implement alternative looping
231constructs, but the C<prepare> and C<check> watchers provide a better and 239constructs, but the C<prepare> and C<check> watchers provide a better and
232more generic mechanism. 240more generic mechanism.
233 241
234=item ev_unloop (loop, how) 242=item ev_unloop (loop, how)
235 243
236Can be used to make a call to C<ev_loop> return early. The C<how> argument 244Can be used to make a call to C<ev_loop> return early (but only after it
245has 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> 246C<EVUNLOOP_ONCE>, 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> 247C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
239calls return.
240 248
241=item ev_ref (loop) 249=item ev_ref (loop)
242 250
243=item ev_unref (loop) 251=item ev_unref (loop)
244 252
245Ref/unref can be used to add or remove a refcount on the event loop: Every 253Ref/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 254loop: Every watcher keeps one reference, and as long as the reference
247unregister that should not keep ev_loop from running, ev_unref() after 255count 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 256a 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 257returning, 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 258example, 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 259visible 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 260no event watchers registered by it are active. It is also an excellent
253before stop. 261way to do this for generic recurring timers or from within third-party
262libraries. Just remember to I<unref after start> and I<ref before stop>.
254 263
255=back 264=back
256 265
257=head1 ANATOMY OF A WATCHER 266=head1 ANATOMY OF A WATCHER
258 267
259A watcher is a structure that you create and register to record your 268A 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 269interest in some event. For instance, if you want to wait for STDIN to
261become readable, you would create an ev_io watcher for that: 270become readable, you would create an C<ev_io> watcher for that:
262 271
263 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 272 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
264 { 273 {
265 ev_io_stop (w); 274 ev_io_stop (w);
266 ev_unloop (loop, EVUNLOOP_ALL); 275 ev_unloop (loop, EVUNLOOP_ALL);
… …
295 304
296As long as your watcher is active (has been started but not stopped) you 305As 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 306must not touch the values stored in it. Most specifically you must never
298reinitialise it or call its set method. 307reinitialise it or call its set method.
299 308
300You cna check whether an event is active by calling the C<ev_is_active 309You can 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 310(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 311callback for it has not been called yet) you can use the C<ev_is_pending
303(watcher *)> macro. 312(watcher *)> macro.
304 313
305Each and every callback receives the event loop pointer as first, the 314Each and every callback receives the event loop pointer as first, the
306registered watcher structure as second, and a bitset of received events as 315registered watcher structure as second, and a bitset of received events as
307third argument. 316third argument.
308 317
309The rceeived events usually include a single bit per event type received 318The 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 319(you can receive multiple events at the same time). The possible bit masks
311are: 320are:
312 321
313=over 4 322=over 4
314 323
315=item EV_READ 324=item C<EV_READ>
316 325
317=item EV_WRITE 326=item C<EV_WRITE>
318 327
319The file descriptor in the ev_io watcher has become readable and/or 328The file descriptor in the C<ev_io> watcher has become readable and/or
320writable. 329writable.
321 330
322=item EV_TIMEOUT 331=item C<EV_TIMEOUT>
323 332
324The ev_timer watcher has timed out. 333The C<ev_timer> watcher has timed out.
325 334
326=item EV_PERIODIC 335=item C<EV_PERIODIC>
327 336
328The ev_periodic watcher has timed out. 337The C<ev_periodic> watcher has timed out.
329 338
330=item EV_SIGNAL 339=item C<EV_SIGNAL>
331 340
332The signal specified in the ev_signal watcher has been received by a thread. 341The signal specified in the C<ev_signal> watcher has been received by a thread.
333 342
334=item EV_CHILD 343=item C<EV_CHILD>
335 344
336The pid specified in the ev_child watcher has received a status change. 345The pid specified in the C<ev_child> watcher has received a status change.
337 346
338=item EV_IDLE 347=item C<EV_IDLE>
339 348
340The ev_idle watcher has determined that you have nothing better to do. 349The C<ev_idle> watcher has determined that you have nothing better to do.
341 350
342=item EV_PREPARE 351=item C<EV_PREPARE>
343 352
344=item EV_CHECK 353=item C<EV_CHECK>
345 354
346All ev_prepare watchers are invoked just I<before> C<ev_loop> starts 355All 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 356to 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 357C<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 358received 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 359many 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 360(for example, a C<ev_prepare> watcher might start an idle watcher to keep
352C<ev_loop> from blocking). 361C<ev_loop> from blocking).
353 362
354=item EV_ERROR 363=item C<EV_ERROR>
355 364
356An unspecified error has occured, the watcher has been stopped. This might 365An unspecified error has occured, the watcher has been stopped. This might
357happen because the watcher could not be properly started because libev 366happen 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 367ran 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 368problem. You best act on it by reporting the problem and somehow coping
… …
368=back 377=back
369 378
370=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 379=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
371 380
372Each watcher has, by default, a member C<void *data> that you can change 381Each 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 382and 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 383to 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 384don'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 385member, you can also "subclass" the watcher type and provide your own
377data: 386data:
378 387
… …
400=head1 WATCHER TYPES 409=head1 WATCHER TYPES
401 410
402This section describes each watcher in detail, but will not repeat 411This section describes each watcher in detail, but will not repeat
403information given in the last section. 412information given in the last section.
404 413
405=head2 struct ev_io - is my file descriptor readable or writable 414=head2 C<ev_io> - is this file descriptor readable or writable
406 415
407I/O watchers check whether a file descriptor is readable or writable 416I/O watchers check whether a file descriptor is readable or writable
408in each iteration of the event loop (This behaviour is called 417in each iteration of the event loop (This behaviour is called
409level-triggering because you keep receiving events as long as the 418level-triggering because you keep receiving events as long as the
410condition persists. Remember you cna stop the watcher if you don't want to 419condition persists. Remember you can stop the watcher if you don't want to
411act on the event and neither want to receive future events). 420act on the event and neither want to receive future events).
412 421
422In general you can register as many read and/or write event watchers per
423fd as you want (as long as you don't confuse yourself). Setting all file
424descriptors to non-blocking mode is also usually a good idea (but not
425required if you know what you are doing).
426
427You have to be careful with dup'ed file descriptors, though. Some backends
428(the linux epoll backend is a notable example) cannot handle dup'ed file
429descriptors correctly if you register interest in two or more fds pointing
430to the same file/socket etc. description (that is, they share the same
431underlying "file open").
432
433If you must do this, then force the use of a known-to-be-good backend
434(at the time of this writing, this includes only EVMETHOD_SELECT and
435EVMETHOD_POLL).
436
413=over 4 437=over 4
414 438
415=item ev_io_init (ev_io *, callback, int fd, int events) 439=item ev_io_init (ev_io *, callback, int fd, int events)
416 440
417=item ev_io_set (ev_io *, int fd, int events) 441=item ev_io_set (ev_io *, int fd, int events)
418 442
419Configures an ev_io watcher. The fd is the file descriptor to rceeive 443Configures 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 | 444events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
421EV_WRITE> to receive the given events. 445EV_WRITE> to receive the given events.
422 446
423=back 447=back
424 448
425=head2 struct ev_timer - relative and optionally recurring timeouts 449=head2 C<ev_timer> - relative and optionally recurring timeouts
426 450
427Timer watchers are simple relative timers that generate an event after a 451Timer watchers are simple relative timers that generate an event after a
428given time, and optionally repeating in regular intervals after that. 452given time, and optionally repeating in regular intervals after that.
429 453
430The timers are based on real time, that is, if you register an event that 454The 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 455times 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 456time, it will still time out after (roughly) and hour. "Roughly" because
433detecting time jumps is hard, and soem inaccuracies are unavoidable (the 457detecting time jumps is hard, and soem inaccuracies are unavoidable (the
434monotonic clock option helps a lot here). 458monotonic clock option helps a lot here).
459
460The relative timeouts are calculated relative to the C<ev_now ()>
461time. This is usually the right thing as this timestamp refers to the time
462of the event triggering whatever timeout you are modifying/starting. If
463you suspect event processing to be delayed and you *need* to base the timeout
464on the current time, use something like this to adjust for this:
465
466 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
435 467
436=over 4 468=over 4
437 469
438=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 470=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
439 471
… …
445later, again, and again, until stopped manually. 477later, again, and again, until stopped manually.
446 478
447The timer itself will do a best-effort at avoiding drift, that is, if you 479The 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 480configure a timer to trigger every 10 seconds, then it will trigger at
449exactly 10 second intervals. If, however, your program cannot keep up with 481exactly 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 482the timer (because it takes longer than those 10 seconds to do stuff) the
451timer will not fire more than once per event loop iteration. 483timer will not fire more than once per event loop iteration.
452 484
453=item ev_timer_again (loop) 485=item ev_timer_again (loop)
454 486
455This will act as if the timer timed out and restart it again if it is 487This will act as if the timer timed out and restart it again if it is
… …
462 494
463This sounds a bit complicated, but here is a useful and typical 495This 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 496example: 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 497timeout, 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 498seconds 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 499configure 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 500time 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 501state 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. 502the timer, and again will automatically restart it if need be.
471 503
472=back 504=back
473 505
474=head2 ev_periodic - to cron or not to cron it 506=head2 C<ev_periodic> - to cron or not to cron
475 507
476Periodic watchers are also timers of a kind, but they are very versatile 508Periodic watchers are also timers of a kind, but they are very versatile
477(and unfortunately a bit complex). 509(and unfortunately a bit complex).
478 510
479Unlike ev_timer's, they are not based on real time (or relative time) 511Unlike 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 512but 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 513to 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 () 514periodic 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 515+ 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 516take 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 517roughly 10 seconds later and of course not if you reset your system time
486again). 518again).
487 519
488They can also be used to implement vastly more complex timers, such as 520They can also be used to implement vastly more complex timers, such as
489triggering an event on eahc midnight, local time. 521triggering an event on eahc midnight, local time.
… …
518 550
519 ev_periodic_set (&periodic, 0., 3600., 0); 551 ev_periodic_set (&periodic, 0., 3600., 0);
520 552
521This doesn't mean there will always be 3600 seconds in between triggers, 553This 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 554but 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 555full hour (UTC), or more correctly, when the system time is evenly divisible
524by 3600. 556by 3600.
525 557
526Another way to think about it (for the mathematically inclined) is that 558Another 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 559C<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. 560time where C<time = at (mod interval)>, regardless of any time jumps.
529 561
530=item * manual reschedule mode (reschedule_cb = callback) 562=item * manual reschedule mode (reschedule_cb = callback)
531 563
532In this mode the values for C<interval> and C<at> are both being 564In this mode the values for C<interval> and C<at> are both being
533ignored. Instead, each time the periodic watcher gets scheduled, the 565ignored. Instead, each time the periodic watcher gets scheduled, the
534reschedule callback will be called with the watcher as first, and the 566reschedule callback will be called with the watcher as first, and the
535current time as second argument. 567current time as second argument.
536 568
537NOTE: I<This callback MUST NOT stop or destroy the periodic or any other 569NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
538periodic watcher, ever, or make any event loop modificstions>. If you need 570ever, 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. 571return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
572starting a prepare watcher).
540 573
541Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 574Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
542ev_tstamp now)>, e.g.: 575ev_tstamp now)>, e.g.:
543 576
544 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 577 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
545 { 578 {
546 return now + 60.; 579 return now + 60.;
… …
549It must return the next time to trigger, based on the passed time value 582It 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 583(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 584will usually be called just before the callback will be triggered, but
552might be called at other times, too. 585might be called at other times, too.
553 586
587NOTE: I<< This callback must always return a time that is later than the
588passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
589
554This can be used to create very complex timers, such as a timer that 590This 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 591triggers 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 592next midnight after C<now> and return the timestamp value for this. How
557is, again, up to you (but it is not trivial). 593you do this is, again, up to you (but it is not trivial, which is the main
594reason I omitted it as an example).
558 595
559=back 596=back
560 597
561=item ev_periodic_again (loop, ev_periodic *) 598=item ev_periodic_again (loop, ev_periodic *)
562 599
… …
565a different time than the last time it was called (e.g. in a crond like 602a different time than the last time it was called (e.g. in a crond like
566program when the crontabs have changed). 603program when the crontabs have changed).
567 604
568=back 605=back
569 606
570=head2 ev_signal - signal me when a signal gets signalled 607=head2 C<ev_signal> - signal me when a signal gets signalled
571 608
572Signal watchers will trigger an event when the process receives a specific 609Signal watchers will trigger an event when the process receives a specific
573signal one or more times. Even though signals are very asynchronous, libev 610signal 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 611will try it's best to deliver signals synchronously, i.e. as part of the
575normal event processing, like any other event. 612normal event processing, like any other event.
576 613
577You cna configure as many watchers as you like per signal. Only when the 614You can configure as many watchers as you like per signal. Only when the
578first watcher gets started will libev actually register a signal watcher 615first watcher gets started will libev actually register a signal watcher
579with the kernel (thus it coexists with your own signal handlers as long 616with 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 617as 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 618watcher for a signal is stopped libev will reset the signal handler to
582SIG_DFL (regardless of what it was set to before). 619SIG_DFL (regardless of what it was set to before).
… …
590Configures the watcher to trigger on the given signal number (usually one 627Configures the watcher to trigger on the given signal number (usually one
591of the C<SIGxxx> constants). 628of the C<SIGxxx> constants).
592 629
593=back 630=back
594 631
595=head2 ev_child - wait for pid status changes 632=head2 C<ev_child> - wait for pid status changes
596 633
597Child watchers trigger when your process receives a SIGCHLD in response to 634Child watchers trigger when your process receives a SIGCHLD in response to
598some child status changes (most typically when a child of yours dies). 635some child status changes (most typically when a child of yours dies).
599 636
600=over 4 637=over 4
… …
604=item ev_child_set (ev_child *, int pid) 641=item ev_child_set (ev_child *, int pid)
605 642
606Configures the watcher to wait for status changes of process C<pid> (or 643Configures 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 644I<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 645at 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 646the status word (use the macros from C<sys/wait.h> and see your systems
610contains the pid of the process causing the status change. 647C<waitpid> documentation). The C<rpid> member contains the pid of the
648process causing the status change.
611 649
612=back 650=back
613 651
614=head2 ev_idle - when you've got nothing better to do 652=head2 C<ev_idle> - when you've got nothing better to do
615 653
616Idle watchers trigger events when there are no other I/O or timer (or 654Idle watchers trigger events when there are no other events are pending
617periodic) events pending. That is, as long as your process is busy 655(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 656as your process is busy handling sockets or timeouts (or even signals,
619is idle all idle watchers are being called again and again - until 657imagine) it will not be triggered. But when your process is idle all idle
658watchers are being called again and again, once per event loop iteration -
620stopped, that is, or your process receives more events. 659until stopped, that is, or your process receives more events and becomes
660busy.
621 661
622The most noteworthy effect is that as long as any idle watchers are 662The most noteworthy effect is that as long as any idle watchers are
623active, the process will not block when waiting for new events. 663active, the process will not block when waiting for new events.
624 664
625Apart from keeping your process non-blocking (which is a useful 665Apart 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, 675kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
636believe me. 676believe me.
637 677
638=back 678=back
639 679
640=head2 prepare and check - your hooks into the event loop 680=head2 C<ev_prepare> and C<ev_check> - customise your event loop
641 681
642Prepare and check watchers usually (but not always) are used in 682Prepare and check watchers are usually (but not always) used in tandem:
643tandom. Prepare watchers get invoked before the process blocks and check 683prepare watchers get invoked before the process blocks and check watchers
644watchers afterwards. 684afterwards.
645 685
646Their main purpose is to integrate other event mechanisms into libev. This 686Their main purpose is to integrate other event mechanisms into libev. This
647could be used, for example, to track variable changes, implement your own 687could be used, for example, to track variable changes, implement your own
648watchers, integrate net-snmp or a coroutine library and lots more. 688watchers, integrate net-snmp or a coroutine library and lots more.
649 689
650This is done by examining in each prepare call which file descriptors need 690This 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 691to be watched by the other library, registering C<ev_io> watchers for
652and starting an ev_timer watcher for any timeouts (many libraries provide 692them and starting an C<ev_timer> watcher for any timeouts (many libraries
653just this functionality). Then, in the check watcher you check for any 693provide just this functionality). Then, in the check watcher you check for
654events that occured (by making your callbacks set soem flags for example) 694any events that occured (by checking the pending status of all watchers
655and call back into the library. 695and stopping them) and call back into the library. The I/O and timer
696callbacks will never actually be called (but must be valid nevertheless,
697because you never know, you know?).
656 698
657As another example, the perl Coro module uses these hooks to integrate 699As another example, the Perl Coro module uses these hooks to integrate
658coroutines into libev programs, by yielding to other active coroutines 700coroutines into libev programs, by yielding to other active coroutines
659during each prepare and only letting the process block if no coroutines 701during each prepare and only letting the process block if no coroutines
660are ready to run. 702are ready to run (it's actually more complicated: it only runs coroutines
703with priority higher than or equal to the event loop and one coroutine
704of lower priority, but only once, using idle watchers to keep the event
705loop from blocking if lower-priority coroutines are active, thus mapping
706low-priority coroutines to idle/background tasks).
661 707
662=over 4 708=over 4
663 709
664=item ev_prepare_init (ev_prepare *, callback) 710=item ev_prepare_init (ev_prepare *, callback)
665 711
666=item ev_check_init (ev_check *, callback) 712=item ev_check_init (ev_check *, callback)
667 713
668Initialises and configures the prepare or check watcher - they have no 714Initialises 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> 715parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
670macros, but using them is utterly, utterly pointless. 716macros, but using them is utterly, utterly and completely pointless.
671 717
672=back 718=back
673 719
674=head1 OTHER FUNCTIONS 720=head1 OTHER FUNCTIONS
675 721
676There are some other fucntions of possible interest. Described. Here. Now. 722There are some other functions of possible interest. Described. Here. Now.
677 723
678=over 4 724=over 4
679 725
680=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 726=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
681 727
682This function combines a simple timer and an I/O watcher, calls your 728This function combines a simple timer and an I/O watcher, calls your
683callback on whichever event happens first and automatically stop both 729callback 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 730watchers. 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 731or timeout without having to allocate/configure/start/stop/free one or
686more watchers yourself. 732more watchers yourself.
687 733
688If C<fd> is less than 0, then no I/O watcher will be started and events is 734If 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 735is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
690will be craeted and started. 736C<events> set will be craeted and started.
691 737
692If C<timeout> is less than 0, then no timeout watcher will be 738If C<timeout> is less than 0, then no timeout watcher will be
693started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat 739started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
694= 0) will be started. 740repeat = 0) will be started. While C<0> is a valid timeout, it is of
741dubious value.
695 742
696The callback has the type C<void (*cb)(int revents, void *arg)> and 743The 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, 744passed 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>: 745C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
746value passed to C<ev_once>:
699 747
700 static void stdin_ready (int revents, void *arg) 748 static void stdin_ready (int revents, void *arg)
701 { 749 {
702 if (revents & EV_TIMEOUT) 750 if (revents & EV_TIMEOUT)
703 /* doh, nothing entered */ 751 /* doh, nothing entered */;
704 else if (revents & EV_READ) 752 else if (revents & EV_READ)
705 /* stdin might have data for us, joy! */ 753 /* stdin might have data for us, joy! */;
706 } 754 }
707 755
708 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 756 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
709 757
710=item ev_feed_event (loop, watcher, int events) 758=item ev_feed_event (loop, watcher, int events)
711 759
712Feeds the given event set into the event loop, as if the specified event 760Feeds 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 761had happened for the specified watcher (which must be a pointer to an
714initialised but not necessarily active event watcher). 762initialised but not necessarily started event watcher).
715 763
716=item ev_feed_fd_event (loop, int fd, int revents) 764=item ev_feed_fd_event (loop, int fd, int revents)
717 765
718Feed an event on the given fd, as if a file descriptor backend detected it. 766Feed an event on the given fd, as if a file descriptor backend detected
767the given events it.
719 768
720=item ev_feed_signal_event (loop, int signum) 769=item ev_feed_signal_event (loop, int signum)
721 770
722Feed an event as if the given signal occured (loop must be the default loop!). 771Feed an event as if the given signal occured (loop must be the default loop!).
723 772
724=back 773=back
725 774
775=head1 LIBEVENT EMULATION
776
777TBD.
778
779=head1 C++ SUPPORT
780
781TBD.
782
726=head1 AUTHOR 783=head1 AUTHOR
727 784
728Marc Lehmann <libev@schmorp.de>. 785Marc Lehmann <libev@schmorp.de>.
729 786

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