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Revision 1.152 by root, Wed May 7 14:45:17 2008 UTC vs.
Revision 1.173 by root, Thu Aug 7 19:24:56 2008 UTC

2 2
3libev - a high performance full-featured event loop written in C 3libev - a high performance full-featured event loop written in C
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 #include <ev.h> 7 #include <ev.h>
8 8
9=head2 EXAMPLE PROGRAM 9=head2 EXAMPLE PROGRAM
10 10
11 // a single header file is required 11 // a single header file is required
12 #include <ev.h> 12 #include <ev.h>
13 13
14 // every watcher type has its own typedef'd struct 14 // every watcher type has its own typedef'd struct
15 // with the name ev_<type> 15 // with the name ev_<type>
16 ev_io stdin_watcher; 16 ev_io stdin_watcher;
17 ev_timer timeout_watcher; 17 ev_timer timeout_watcher;
18 18
19 // all watcher callbacks have a similar signature 19 // all watcher callbacks have a similar signature
20 // this callback is called when data is readable on stdin 20 // this callback is called when data is readable on stdin
21 static void 21 static void
22 stdin_cb (EV_P_ struct ev_io *w, int revents) 22 stdin_cb (EV_P_ struct ev_io *w, int revents)
23 { 23 {
24 puts ("stdin ready"); 24 puts ("stdin ready");
25 // for one-shot events, one must manually stop the watcher 25 // for one-shot events, one must manually stop the watcher
26 // with its corresponding stop function. 26 // with its corresponding stop function.
27 ev_io_stop (EV_A_ w); 27 ev_io_stop (EV_A_ w);
28 28
29 // this causes all nested ev_loop's to stop iterating 29 // this causes all nested ev_loop's to stop iterating
30 ev_unloop (EV_A_ EVUNLOOP_ALL); 30 ev_unloop (EV_A_ EVUNLOOP_ALL);
31 } 31 }
32 32
33 // another callback, this time for a time-out 33 // another callback, this time for a time-out
34 static void 34 static void
35 timeout_cb (EV_P_ struct ev_timer *w, int revents) 35 timeout_cb (EV_P_ struct ev_timer *w, int revents)
36 { 36 {
37 puts ("timeout"); 37 puts ("timeout");
38 // this causes the innermost ev_loop to stop iterating 38 // this causes the innermost ev_loop to stop iterating
39 ev_unloop (EV_A_ EVUNLOOP_ONE); 39 ev_unloop (EV_A_ EVUNLOOP_ONE);
40 } 40 }
41 41
42 int 42 int
43 main (void) 43 main (void)
44 { 44 {
45 // use the default event loop unless you have special needs 45 // use the default event loop unless you have special needs
46 struct ev_loop *loop = ev_default_loop (0); 46 struct ev_loop *loop = ev_default_loop (0);
47 47
48 // initialise an io watcher, then start it 48 // initialise an io watcher, then start it
49 // this one will watch for stdin to become readable 49 // this one will watch for stdin to become readable
50 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); 50 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51 ev_io_start (loop, &stdin_watcher); 51 ev_io_start (loop, &stdin_watcher);
52 52
53 // initialise a timer watcher, then start it 53 // initialise a timer watcher, then start it
54 // simple non-repeating 5.5 second timeout 54 // simple non-repeating 5.5 second timeout
55 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); 55 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56 ev_timer_start (loop, &timeout_watcher); 56 ev_timer_start (loop, &timeout_watcher);
57 57
58 // now wait for events to arrive 58 // now wait for events to arrive
59 ev_loop (loop, 0); 59 ev_loop (loop, 0);
60 60
61 // unloop was called, so exit 61 // unloop was called, so exit
62 return 0; 62 return 0;
63 } 63 }
64 64
65=head1 DESCRIPTION 65=head1 DESCRIPTION
66 66
67The newest version of this document is also available as an html-formatted 67The newest version of this document is also available as an html-formatted
68web page you might find easier to navigate when reading it for the first 68web page you might find easier to navigate when reading it for the first
69time: L<http://cvs.schmorp.de/libev/ev.html>. 69time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70 70
71Libev is an event loop: you register interest in certain events (such as a 71Libev is an event loop: you register interest in certain events (such as a
72file descriptor being readable or a timeout occurring), and it will manage 72file descriptor being readable or a timeout occurring), and it will manage
73these event sources and provide your program with events. 73these event sources and provide your program with events.
74 74
113Libev represents time as a single floating point number, representing the 113Libev represents time as a single floating point number, representing the
114(fractional) number of seconds since the (POSIX) epoch (somewhere near 114(fractional) number of seconds since the (POSIX) epoch (somewhere near
115the beginning of 1970, details are complicated, don't ask). This type is 115the beginning of 1970, details are complicated, don't ask). This type is
116called C<ev_tstamp>, which is what you should use too. It usually aliases 116called C<ev_tstamp>, which is what you should use too. It usually aliases
117to the C<double> type in C, and when you need to do any calculations on 117to the C<double> type in C, and when you need to do any calculations on
118it, you should treat it as some floatingpoint value. Unlike the name 118it, you should treat it as some floating point value. Unlike the name
119component C<stamp> might indicate, it is also used for time differences 119component C<stamp> might indicate, it is also used for time differences
120throughout libev. 120throughout libev.
121
122=head1 ERROR HANDLING
123
124Libev knows three classes of errors: operating system errors, usage errors
125and internal errors (bugs).
126
127When libev catches an operating system error it cannot handle (for example
128a system call indicating a condition libev cannot fix), it calls the callback
129set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
130abort. The default is to print a diagnostic message and to call C<abort
131()>.
132
133When libev detects a usage error such as a negative timer interval, then
134it will print a diagnostic message and abort (via the C<assert> mechanism,
135so C<NDEBUG> will disable this checking): these are programming errors in
136the libev caller and need to be fixed there.
137
138Libev also has a few internal error-checking C<assert>ions, and also has
139extensive consistency checking code. These do not trigger under normal
140circumstances, as they indicate either a bug in libev or worse.
141
121 142
122=head1 GLOBAL FUNCTIONS 143=head1 GLOBAL FUNCTIONS
123 144
124These functions can be called anytime, even before initialising the 145These functions can be called anytime, even before initialising the
125library in any way. 146library in any way.
134 155
135=item ev_sleep (ev_tstamp interval) 156=item ev_sleep (ev_tstamp interval)
136 157
137Sleep for the given interval: The current thread will be blocked until 158Sleep for the given interval: The current thread will be blocked until
138either it is interrupted or the given time interval has passed. Basically 159either it is interrupted or the given time interval has passed. Basically
139this is a subsecond-resolution C<sleep ()>. 160this is a sub-second-resolution C<sleep ()>.
140 161
141=item int ev_version_major () 162=item int ev_version_major ()
142 163
143=item int ev_version_minor () 164=item int ev_version_minor ()
144 165
157not a problem. 178not a problem.
158 179
159Example: Make sure we haven't accidentally been linked against the wrong 180Example: Make sure we haven't accidentally been linked against the wrong
160version. 181version.
161 182
162 assert (("libev version mismatch", 183 assert (("libev version mismatch",
163 ev_version_major () == EV_VERSION_MAJOR 184 ev_version_major () == EV_VERSION_MAJOR
164 && ev_version_minor () >= EV_VERSION_MINOR)); 185 && ev_version_minor () >= EV_VERSION_MINOR));
165 186
166=item unsigned int ev_supported_backends () 187=item unsigned int ev_supported_backends ()
167 188
168Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> 189Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169value) compiled into this binary of libev (independent of their 190value) compiled into this binary of libev (independent of their
171a description of the set values. 192a description of the set values.
172 193
173Example: make sure we have the epoll method, because yeah this is cool and 194Example: make sure we have the epoll method, because yeah this is cool and
174a must have and can we have a torrent of it please!!!11 195a must have and can we have a torrent of it please!!!11
175 196
176 assert (("sorry, no epoll, no sex", 197 assert (("sorry, no epoll, no sex",
177 ev_supported_backends () & EVBACKEND_EPOLL)); 198 ev_supported_backends () & EVBACKEND_EPOLL));
178 199
179=item unsigned int ev_recommended_backends () 200=item unsigned int ev_recommended_backends ()
180 201
181Return the set of all backends compiled into this binary of libev and also 202Return the set of all backends compiled into this binary of libev and also
182recommended for this platform. This set is often smaller than the one 203recommended for this platform. This set is often smaller than the one
183returned by C<ev_supported_backends>, as for example kqueue is broken on 204returned by C<ev_supported_backends>, as for example kqueue is broken on
184most BSDs and will not be autodetected unless you explicitly request it 205most BSDs and will not be auto-detected unless you explicitly request it
185(assuming you know what you are doing). This is the set of backends that 206(assuming you know what you are doing). This is the set of backends that
186libev will probe for if you specify no backends explicitly. 207libev will probe for if you specify no backends explicitly.
187 208
188=item unsigned int ev_embeddable_backends () 209=item unsigned int ev_embeddable_backends ()
189 210
231 ... 252 ...
232 ev_set_allocator (persistent_realloc); 253 ev_set_allocator (persistent_realloc);
233 254
234=item ev_set_syserr_cb (void (*cb)(const char *msg)); 255=item ev_set_syserr_cb (void (*cb)(const char *msg));
235 256
236Set the callback function to call on a retryable syscall error (such 257Set the callback function to call on a retryable system call error (such
237as failed select, poll, epoll_wait). The message is a printable string 258as failed select, poll, epoll_wait). The message is a printable string
238indicating the system call or subsystem causing the problem. If this 259indicating the system call or subsystem causing the problem. If this
239callback is set, then libev will expect it to remedy the sitution, no 260callback is set, then libev will expect it to remedy the situation, no
240matter what, when it returns. That is, libev will generally retry the 261matter what, when it returns. That is, libev will generally retry the
241requested operation, or, if the condition doesn't go away, do bad stuff 262requested operation, or, if the condition doesn't go away, do bad stuff
242(such as abort). 263(such as abort).
243 264
244Example: This is basically the same thing that libev does internally, too. 265Example: This is basically the same thing that libev does internally, too.
277from multiple threads, you have to lock (note also that this is unlikely, 298from multiple threads, you have to lock (note also that this is unlikely,
278as loops cannot bes hared easily between threads anyway). 299as loops cannot bes hared easily between threads anyway).
279 300
280The default loop is the only loop that can handle C<ev_signal> and 301The default loop is the only loop that can handle C<ev_signal> and
281C<ev_child> watchers, and to do this, it always registers a handler 302C<ev_child> watchers, and to do this, it always registers a handler
282for C<SIGCHLD>. If this is a problem for your app you can either 303for C<SIGCHLD>. If this is a problem for your application you can either
283create a dynamic loop with C<ev_loop_new> that doesn't do that, or you 304create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284can simply overwrite the C<SIGCHLD> signal handler I<after> calling 305can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285C<ev_default_init>. 306C<ev_default_init>.
286 307
287The flags argument can be used to specify special behaviour or specific 308The flags argument can be used to specify special behaviour or specific
296The default flags value. Use this if you have no clue (it's the right 317The default flags value. Use this if you have no clue (it's the right
297thing, believe me). 318thing, believe me).
298 319
299=item C<EVFLAG_NOENV> 320=item C<EVFLAG_NOENV>
300 321
301If this flag bit is ored into the flag value (or the program runs setuid 322If this flag bit is or'ed into the flag value (or the program runs setuid
302or setgid) then libev will I<not> look at the environment variable 323or setgid) then libev will I<not> look at the environment variable
303C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will 324C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304override the flags completely if it is found in the environment. This is 325override the flags completely if it is found in the environment. This is
305useful to try out specific backends to test their performance, or to work 326useful to try out specific backends to test their performance, or to work
306around bugs. 327around bugs.
313 334
314This works by calling C<getpid ()> on every iteration of the loop, 335This works by calling C<getpid ()> on every iteration of the loop,
315and thus this might slow down your event loop if you do a lot of loop 336and thus this might slow down your event loop if you do a lot of loop
316iterations and little real work, but is usually not noticeable (on my 337iterations and little real work, but is usually not noticeable (on my
317GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence 338GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318without a syscall and thus I<very> fast, but my GNU/Linux system also has 339without a system call and thus I<very> fast, but my GNU/Linux system also has
319C<pthread_atfork> which is even faster). 340C<pthread_atfork> which is even faster).
320 341
321The big advantage of this flag is that you can forget about fork (and 342The big advantage of this flag is that you can forget about fork (and
322forget about forgetting to tell libev about forking) when you use this 343forget about forgetting to tell libev about forking) when you use this
323flag. 344flag.
324 345
325This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS> 346This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326environment variable. 347environment variable.
327 348
328=item C<EVBACKEND_SELECT> (value 1, portable select backend) 349=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329 350
330This is your standard select(2) backend. Not I<completely> standard, as 351This is your standard select(2) backend. Not I<completely> standard, as
332but if that fails, expect a fairly low limit on the number of fds when 353but if that fails, expect a fairly low limit on the number of fds when
333using this backend. It doesn't scale too well (O(highest_fd)), but its 354using this backend. It doesn't scale too well (O(highest_fd)), but its
334usually the fastest backend for a low number of (low-numbered :) fds. 355usually the fastest backend for a low number of (low-numbered :) fds.
335 356
336To get good performance out of this backend you need a high amount of 357To get good performance out of this backend you need a high amount of
337parallelity (most of the file descriptors should be busy). If you are 358parallelism (most of the file descriptors should be busy). If you are
338writing a server, you should C<accept ()> in a loop to accept as many 359writing a server, you should C<accept ()> in a loop to accept as many
339connections as possible during one iteration. You might also want to have 360connections as possible during one iteration. You might also want to have
340a look at C<ev_set_io_collect_interval ()> to increase the amount of 361a look at C<ev_set_io_collect_interval ()> to increase the amount of
341readyness notifications you get per iteration. 362readiness notifications you get per iteration.
342 363
343=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) 364=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344 365
345And this is your standard poll(2) backend. It's more complicated 366And this is your standard poll(2) backend. It's more complicated
346than select, but handles sparse fds better and has no artificial 367than select, but handles sparse fds better and has no artificial
354For few fds, this backend is a bit little slower than poll and select, 375For few fds, this backend is a bit little slower than poll and select,
355but it scales phenomenally better. While poll and select usually scale 376but it scales phenomenally better. While poll and select usually scale
356like O(total_fds) where n is the total number of fds (or the highest fd), 377like O(total_fds) where n is the total number of fds (or the highest fd),
357epoll scales either O(1) or O(active_fds). The epoll design has a number 378epoll scales either O(1) or O(active_fds). The epoll design has a number
358of shortcomings, such as silently dropping events in some hard-to-detect 379of shortcomings, such as silently dropping events in some hard-to-detect
359cases and requiring a syscall per fd change, no fork support and bad 380cases and requiring a system call per fd change, no fork support and bad
360support for dup. 381support for dup.
361 382
362While stopping, setting and starting an I/O watcher in the same iteration 383While stopping, setting and starting an I/O watcher in the same iteration
363will result in some caching, there is still a syscall per such incident 384will result in some caching, there is still a system call per such incident
364(because the fd could point to a different file description now), so its 385(because the fd could point to a different file description now), so its
365best to avoid that. Also, C<dup ()>'ed file descriptors might not work 386best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366very well if you register events for both fds. 387very well if you register events for both fds.
367 388
368Please note that epoll sometimes generates spurious notifications, so you 389Please note that epoll sometimes generates spurious notifications, so you
371 392
372Best performance from this backend is achieved by not unregistering all 393Best performance from this backend is achieved by not unregistering all
373watchers for a file descriptor until it has been closed, if possible, i.e. 394watchers for a file descriptor until it has been closed, if possible, i.e.
374keep at least one watcher active per fd at all times. 395keep at least one watcher active per fd at all times.
375 396
376While nominally embeddeble in other event loops, this feature is broken in 397While nominally embeddable in other event loops, this feature is broken in
377all kernel versions tested so far. 398all kernel versions tested so far.
378 399
379=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 400=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380 401
381Kqueue deserves special mention, as at the time of this writing, it 402Kqueue deserves special mention, as at the time of this writing, it
382was broken on all BSDs except NetBSD (usually it doesn't work reliably 403was broken on all BSDs except NetBSD (usually it doesn't work reliably
383with anything but sockets and pipes, except on Darwin, where of course 404with anything but sockets and pipes, except on Darwin, where of course
384it's completely useless). For this reason it's not being "autodetected" 405it's completely useless). For this reason it's not being "auto-detected"
385unless you explicitly specify it explicitly in the flags (i.e. using 406unless you explicitly specify it explicitly in the flags (i.e. using
386C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) 407C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387system like NetBSD. 408system like NetBSD.
388 409
389You still can embed kqueue into a normal poll or select backend and use it 410You still can embed kqueue into a normal poll or select backend and use it
391the target platform). See C<ev_embed> watchers for more info. 412the target platform). See C<ev_embed> watchers for more info.
392 413
393It scales in the same way as the epoll backend, but the interface to the 414It scales in the same way as the epoll backend, but the interface to the
394kernel is more efficient (which says nothing about its actual speed, of 415kernel is more efficient (which says nothing about its actual speed, of
395course). While stopping, setting and starting an I/O watcher does never 416course). While stopping, setting and starting an I/O watcher does never
396cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to 417cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397two event changes per incident, support for C<fork ()> is very bad and it 418two event changes per incident, support for C<fork ()> is very bad and it
398drops fds silently in similarly hard-to-detect cases. 419drops fds silently in similarly hard-to-detect cases.
399 420
400This backend usually performs well under most conditions. 421This backend usually performs well under most conditions.
401 422
416=item C<EVBACKEND_PORT> (value 32, Solaris 10) 437=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417 438
418This uses the Solaris 10 event port mechanism. As with everything on Solaris, 439This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419it's really slow, but it still scales very well (O(active_fds)). 440it's really slow, but it still scales very well (O(active_fds)).
420 441
421Please note that solaris event ports can deliver a lot of spurious 442Please note that Solaris event ports can deliver a lot of spurious
422notifications, so you need to use non-blocking I/O or other means to avoid 443notifications, so you need to use non-blocking I/O or other means to avoid
423blocking when no data (or space) is available. 444blocking when no data (or space) is available.
424 445
425While this backend scales well, it requires one system call per active 446While this backend scales well, it requires one system call per active
426file descriptor per loop iteration. For small and medium numbers of file 447file descriptor per loop iteration. For small and medium numbers of file
427descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend 448descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428might perform better. 449might perform better.
429 450
430On the positive side, ignoring the spurious readyness notifications, this 451On the positive side, ignoring the spurious readiness notifications, this
431backend actually performed to specification in all tests and is fully 452backend actually performed to specification in all tests and is fully
432embeddable, which is a rare feat among the OS-specific backends. 453embeddable, which is a rare feat among the OS-specific backends.
433 454
434=item C<EVBACKEND_ALL> 455=item C<EVBACKEND_ALL>
435 456
439 460
440It is definitely not recommended to use this flag. 461It is definitely not recommended to use this flag.
441 462
442=back 463=back
443 464
444If one or more of these are ored into the flags value, then only these 465If one or more of these are or'ed into the flags value, then only these
445backends will be tried (in the reverse order as listed here). If none are 466backends will be tried (in the reverse order as listed here). If none are
446specified, all backends in C<ev_recommended_backends ()> will be tried. 467specified, all backends in C<ev_recommended_backends ()> will be tried.
447 468
448The most typical usage is like this: 469The most typical usage is like this:
449 470
450 if (!ev_default_loop (0)) 471 if (!ev_default_loop (0))
451 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 472 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452 473
453Restrict libev to the select and poll backends, and do not allow 474Restrict libev to the select and poll backends, and do not allow
454environment settings to be taken into account: 475environment settings to be taken into account:
455 476
456 ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); 477 ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457 478
458Use whatever libev has to offer, but make sure that kqueue is used if 479Use whatever libev has to offer, but make sure that kqueue is used if
459available (warning, breaks stuff, best use only with your own private 480available (warning, breaks stuff, best use only with your own private
460event loop and only if you know the OS supports your types of fds): 481event loop and only if you know the OS supports your types of fds):
461 482
462 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); 483 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463 484
464=item struct ev_loop *ev_loop_new (unsigned int flags) 485=item struct ev_loop *ev_loop_new (unsigned int flags)
465 486
466Similar to C<ev_default_loop>, but always creates a new event loop that is 487Similar to C<ev_default_loop>, but always creates a new event loop that is
467always distinct from the default loop. Unlike the default loop, it cannot 488always distinct from the default loop. Unlike the default loop, it cannot
472libev with threads is indeed to create one loop per thread, and using the 493libev with threads is indeed to create one loop per thread, and using the
473default loop in the "main" or "initial" thread. 494default loop in the "main" or "initial" thread.
474 495
475Example: Try to create a event loop that uses epoll and nothing else. 496Example: Try to create a event loop that uses epoll and nothing else.
476 497
477 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 498 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478 if (!epoller) 499 if (!epoller)
479 fatal ("no epoll found here, maybe it hides under your chair"); 500 fatal ("no epoll found here, maybe it hides under your chair");
480 501
481=item ev_default_destroy () 502=item ev_default_destroy ()
482 503
483Destroys the default loop again (frees all memory and kernel state 504Destroys the default loop again (frees all memory and kernel state
484etc.). None of the active event watchers will be stopped in the normal 505etc.). None of the active event watchers will be stopped in the normal
485sense, so e.g. C<ev_is_active> might still return true. It is your 506sense, so e.g. C<ev_is_active> might still return true. It is your
486responsibility to either stop all watchers cleanly yoursef I<before> 507responsibility to either stop all watchers cleanly yourself I<before>
487calling this function, or cope with the fact afterwards (which is usually 508calling this function, or cope with the fact afterwards (which is usually
488the easiest thing, you can just ignore the watchers and/or C<free ()> them 509the easiest thing, you can just ignore the watchers and/or C<free ()> them
489for example). 510for example).
490 511
491Note that certain global state, such as signal state, will not be freed by 512Note that certain global state, such as signal state, will not be freed by
572A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle 593A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573those events and any outstanding ones, but will not block your process in 594those events and any outstanding ones, but will not block your process in
574case there are no events and will return after one iteration of the loop. 595case there are no events and will return after one iteration of the loop.
575 596
576A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if 597A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577neccessary) and will handle those and any outstanding ones. It will block 598necessary) and will handle those and any outstanding ones. It will block
578your process until at least one new event arrives, and will return after 599your process until at least one new event arrives, and will return after
579one iteration of the loop. This is useful if you are waiting for some 600one iteration of the loop. This is useful if you are waiting for some
580external event in conjunction with something not expressible using other 601external event in conjunction with something not expressible using other
581libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is 602libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
582usually a better approach for this kind of thing. 603usually a better approach for this kind of thing.
583 604
584Here are the gory details of what C<ev_loop> does: 605Here are the gory details of what C<ev_loop> does:
585 606
586 - Before the first iteration, call any pending watchers. 607 - Before the first iteration, call any pending watchers.
587 * If EVFLAG_FORKCHECK was used, check for a fork. 608 * If EVFLAG_FORKCHECK was used, check for a fork.
588 - If a fork was detected, queue and call all fork watchers. 609 - If a fork was detected (by any means), queue and call all fork watchers.
589 - Queue and call all prepare watchers. 610 - Queue and call all prepare watchers.
590 - If we have been forked, recreate the kernel state. 611 - If we have been forked, detach and recreate the kernel state
612 as to not disturb the other process.
591 - Update the kernel state with all outstanding changes. 613 - Update the kernel state with all outstanding changes.
592 - Update the "event loop time". 614 - Update the "event loop time" (ev_now ()).
593 - Calculate for how long to sleep or block, if at all 615 - Calculate for how long to sleep or block, if at all
594 (active idle watchers, EVLOOP_NONBLOCK or not having 616 (active idle watchers, EVLOOP_NONBLOCK or not having
595 any active watchers at all will result in not sleeping). 617 any active watchers at all will result in not sleeping).
596 - Sleep if the I/O and timer collect interval say so. 618 - Sleep if the I/O and timer collect interval say so.
597 - Block the process, waiting for any events. 619 - Block the process, waiting for any events.
598 - Queue all outstanding I/O (fd) events. 620 - Queue all outstanding I/O (fd) events.
599 - Update the "event loop time" and do time jump handling. 621 - Update the "event loop time" (ev_now ()), and do time jump adjustments.
600 - Queue all outstanding timers. 622 - Queue all outstanding timers.
601 - Queue all outstanding periodics. 623 - Queue all outstanding periodics.
602 - If no events are pending now, queue all idle watchers. 624 - Unless any events are pending now, queue all idle watchers.
603 - Queue all check watchers. 625 - Queue all check watchers.
604 - Call all queued watchers in reverse order (i.e. check watchers first). 626 - Call all queued watchers in reverse order (i.e. check watchers first).
605 Signals and child watchers are implemented as I/O watchers, and will 627 Signals and child watchers are implemented as I/O watchers, and will
606 be handled here by queueing them when their watcher gets executed. 628 be handled here by queueing them when their watcher gets executed.
607 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 629 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
612anymore. 634anymore.
613 635
614 ... queue jobs here, make sure they register event watchers as long 636 ... queue jobs here, make sure they register event watchers as long
615 ... as they still have work to do (even an idle watcher will do..) 637 ... as they still have work to do (even an idle watcher will do..)
616 ev_loop (my_loop, 0); 638 ev_loop (my_loop, 0);
617 ... jobs done. yeah! 639 ... jobs done or somebody called unloop. yeah!
618 640
619=item ev_unloop (loop, how) 641=item ev_unloop (loop, how)
620 642
621Can be used to make a call to C<ev_loop> return early (but only after it 643Can be used to make a call to C<ev_loop> return early (but only after it
622has processed all outstanding events). The C<how> argument must be either 644has processed all outstanding events). The C<how> argument must be either
643respectively). 665respectively).
644 666
645Example: Create a signal watcher, but keep it from keeping C<ev_loop> 667Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646running when nothing else is active. 668running when nothing else is active.
647 669
648 struct ev_signal exitsig; 670 struct ev_signal exitsig;
649 ev_signal_init (&exitsig, sig_cb, SIGINT); 671 ev_signal_init (&exitsig, sig_cb, SIGINT);
650 ev_signal_start (loop, &exitsig); 672 ev_signal_start (loop, &exitsig);
651 evf_unref (loop); 673 evf_unref (loop);
652 674
653Example: For some weird reason, unregister the above signal handler again. 675Example: For some weird reason, unregister the above signal handler again.
654 676
655 ev_ref (loop); 677 ev_ref (loop);
656 ev_signal_stop (loop, &exitsig); 678 ev_signal_stop (loop, &exitsig);
657 679
658=item ev_set_io_collect_interval (loop, ev_tstamp interval) 680=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659 681
660=item ev_set_timeout_collect_interval (loop, ev_tstamp interval) 682=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661 683
662These advanced functions influence the time that libev will spend waiting 684These advanced functions influence the time that libev will spend waiting
663for events. Both are by default C<0>, meaning that libev will try to 685for events. Both time intervals are by default C<0>, meaning that libev
664invoke timer/periodic callbacks and I/O callbacks with minimum latency. 686will try to invoke timer/periodic callbacks and I/O callbacks with minimum
687latency.
665 688
666Setting these to a higher value (the C<interval> I<must> be >= C<0>) 689Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667allows libev to delay invocation of I/O and timer/periodic callbacks to 690allows libev to delay invocation of I/O and timer/periodic callbacks
668increase efficiency of loop iterations. 691to increase efficiency of loop iterations (or to increase power-saving
692opportunities).
669 693
670The background is that sometimes your program runs just fast enough to 694The background is that sometimes your program runs just fast enough to
671handle one (or very few) event(s) per loop iteration. While this makes 695handle one (or very few) event(s) per loop iteration. While this makes
672the program responsive, it also wastes a lot of CPU time to poll for new 696the program responsive, it also wastes a lot of CPU time to poll for new
673events, especially with backends like C<select ()> which have a high 697events, especially with backends like C<select ()> which have a high
683to spend more time collecting timeouts, at the expense of increased 707to spend more time collecting timeouts, at the expense of increased
684latency (the watcher callback will be called later). C<ev_io> watchers 708latency (the watcher callback will be called later). C<ev_io> watchers
685will not be affected. Setting this to a non-null value will not introduce 709will not be affected. Setting this to a non-null value will not introduce
686any overhead in libev. 710any overhead in libev.
687 711
688Many (busy) programs can usually benefit by setting the io collect 712Many (busy) programs can usually benefit by setting the I/O collect
689interval to a value near C<0.1> or so, which is often enough for 713interval to a value near C<0.1> or so, which is often enough for
690interactive servers (of course not for games), likewise for timeouts. It 714interactive servers (of course not for games), likewise for timeouts. It
691usually doesn't make much sense to set it to a lower value than C<0.01>, 715usually doesn't make much sense to set it to a lower value than C<0.01>,
692as this approsaches the timing granularity of most systems. 716as this approaches the timing granularity of most systems.
717
718Setting the I<timeout collect interval> can improve the opportunity for
719saving power, as the program will "bundle" timer callback invocations that
720are "near" in time together, by delaying some, thus reducing the number of
721times the process sleeps and wakes up again. Another useful technique to
722reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
723they fire on, say, one-second boundaries only.
724
725=item ev_loop_verify (loop)
726
727This function only does something when C<EV_VERIFY> support has been
728compiled in. It tries to go through all internal structures and checks
729them for validity. If anything is found to be inconsistent, it will print
730an error message to standard error and call C<abort ()>.
731
732This can be used to catch bugs inside libev itself: under normal
733circumstances, this function will never abort as of course libev keeps its
734data structures consistent.
693 735
694=back 736=back
695 737
696 738
697=head1 ANATOMY OF A WATCHER 739=head1 ANATOMY OF A WATCHER
698 740
699A watcher is a structure that you create and register to record your 741A watcher is a structure that you create and register to record your
700interest in some event. For instance, if you want to wait for STDIN to 742interest in some event. For instance, if you want to wait for STDIN to
701become readable, you would create an C<ev_io> watcher for that: 743become readable, you would create an C<ev_io> watcher for that:
702 744
703 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 745 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
704 { 746 {
705 ev_io_stop (w); 747 ev_io_stop (w);
706 ev_unloop (loop, EVUNLOOP_ALL); 748 ev_unloop (loop, EVUNLOOP_ALL);
707 } 749 }
708 750
709 struct ev_loop *loop = ev_default_loop (0); 751 struct ev_loop *loop = ev_default_loop (0);
710 struct ev_io stdin_watcher; 752 struct ev_io stdin_watcher;
711 ev_init (&stdin_watcher, my_cb); 753 ev_init (&stdin_watcher, my_cb);
712 ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); 754 ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713 ev_io_start (loop, &stdin_watcher); 755 ev_io_start (loop, &stdin_watcher);
714 ev_loop (loop, 0); 756 ev_loop (loop, 0);
715 757
716As you can see, you are responsible for allocating the memory for your 758As you can see, you are responsible for allocating the memory for your
717watcher structures (and it is usually a bad idea to do this on the stack, 759watcher structures (and it is usually a bad idea to do this on the stack,
718although this can sometimes be quite valid). 760although this can sometimes be quite valid).
719 761
720Each watcher structure must be initialised by a call to C<ev_init 762Each watcher structure must be initialised by a call to C<ev_init
721(watcher *, callback)>, which expects a callback to be provided. This 763(watcher *, callback)>, which expects a callback to be provided. This
722callback gets invoked each time the event occurs (or, in the case of io 764callback gets invoked each time the event occurs (or, in the case of I/O
723watchers, each time the event loop detects that the file descriptor given 765watchers, each time the event loop detects that the file descriptor given
724is readable and/or writable). 766is readable and/or writable).
725 767
726Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro 768Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
727with arguments specific to this watcher type. There is also a macro 769with arguments specific to this watcher type. There is also a macro
803 845
804The given async watcher has been asynchronously notified (see C<ev_async>). 846The given async watcher has been asynchronously notified (see C<ev_async>).
805 847
806=item C<EV_ERROR> 848=item C<EV_ERROR>
807 849
808An unspecified error has occured, the watcher has been stopped. This might 850An unspecified error has occurred, the watcher has been stopped. This might
809happen because the watcher could not be properly started because libev 851happen because the watcher could not be properly started because libev
810ran out of memory, a file descriptor was found to be closed or any other 852ran out of memory, a file descriptor was found to be closed or any other
811problem. You best act on it by reporting the problem and somehow coping 853problem. You best act on it by reporting the problem and somehow coping
812with the watcher being stopped. 854with the watcher being stopped.
813 855
814Libev will usually signal a few "dummy" events together with an error, 856Libev will usually signal a few "dummy" events together with an error,
815for example it might indicate that a fd is readable or writable, and if 857for example it might indicate that a fd is readable or writable, and if
816your callbacks is well-written it can just attempt the operation and cope 858your callbacks is well-written it can just attempt the operation and cope
817with the error from read() or write(). This will not work in multithreaded 859with the error from read() or write(). This will not work in multi-threaded
818programs, though, so beware. 860programs, though, so beware.
819 861
820=back 862=back
821 863
822=head2 GENERIC WATCHER FUNCTIONS 864=head2 GENERIC WATCHER FUNCTIONS
852Although some watcher types do not have type-specific arguments 894Although some watcher types do not have type-specific arguments
853(e.g. C<ev_prepare>) you still need to call its C<set> macro. 895(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854 896
855=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) 897=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856 898
857This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro 899This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858calls into a single call. This is the most convinient method to initialise 900calls into a single call. This is the most convenient method to initialise
859a watcher. The same limitations apply, of course. 901a watcher. The same limitations apply, of course.
860 902
861=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) 903=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862 904
863Starts (activates) the given watcher. Only active watchers will receive 905Starts (activates) the given watcher. Only active watchers will receive
946to associate arbitrary data with your watcher. If you need more data and 988to associate arbitrary data with your watcher. If you need more data and
947don't want to allocate memory and store a pointer to it in that data 989don't want to allocate memory and store a pointer to it in that data
948member, you can also "subclass" the watcher type and provide your own 990member, you can also "subclass" the watcher type and provide your own
949data: 991data:
950 992
951 struct my_io 993 struct my_io
952 { 994 {
953 struct ev_io io; 995 struct ev_io io;
954 int otherfd; 996 int otherfd;
955 void *somedata; 997 void *somedata;
956 struct whatever *mostinteresting; 998 struct whatever *mostinteresting;
957 } 999 }
958 1000
959And since your callback will be called with a pointer to the watcher, you 1001And since your callback will be called with a pointer to the watcher, you
960can cast it back to your own type: 1002can cast it back to your own type:
961 1003
962 static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) 1004 static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
963 { 1005 {
964 struct my_io *w = (struct my_io *)w_; 1006 struct my_io *w = (struct my_io *)w_;
965 ... 1007 ...
966 } 1008 }
967 1009
968More interesting and less C-conformant ways of casting your callback type 1010More interesting and less C-conformant ways of casting your callback type
969instead have been omitted. 1011instead have been omitted.
970 1012
971Another common scenario is having some data structure with multiple 1013Another common scenario is having some data structure with multiple
972watchers: 1014watchers:
973 1015
974 struct my_biggy 1016 struct my_biggy
975 { 1017 {
976 int some_data; 1018 int some_data;
977 ev_timer t1; 1019 ev_timer t1;
978 ev_timer t2; 1020 ev_timer t2;
979 } 1021 }
980 1022
981In this case getting the pointer to C<my_biggy> is a bit more complicated, 1023In this case getting the pointer to C<my_biggy> is a bit more complicated,
982you need to use C<offsetof>: 1024you need to use C<offsetof>:
983 1025
984 #include <stddef.h> 1026 #include <stddef.h>
985 1027
986 static void 1028 static void
987 t1_cb (EV_P_ struct ev_timer *w, int revents) 1029 t1_cb (EV_P_ struct ev_timer *w, int revents)
988 { 1030 {
989 struct my_biggy big = (struct my_biggy * 1031 struct my_biggy big = (struct my_biggy *
990 (((char *)w) - offsetof (struct my_biggy, t1)); 1032 (((char *)w) - offsetof (struct my_biggy, t1));
991 } 1033 }
992 1034
993 static void 1035 static void
994 t2_cb (EV_P_ struct ev_timer *w, int revents) 1036 t2_cb (EV_P_ struct ev_timer *w, int revents)
995 { 1037 {
996 struct my_biggy big = (struct my_biggy * 1038 struct my_biggy big = (struct my_biggy *
997 (((char *)w) - offsetof (struct my_biggy, t2)); 1039 (((char *)w) - offsetof (struct my_biggy, t2));
998 } 1040 }
999 1041
1000 1042
1001=head1 WATCHER TYPES 1043=head1 WATCHER TYPES
1002 1044
1003This section describes each watcher in detail, but will not repeat 1045This section describes each watcher in detail, but will not repeat
1032If you must do this, then force the use of a known-to-be-good backend 1074If you must do this, then force the use of a known-to-be-good backend
1033(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1075(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1034C<EVBACKEND_POLL>). 1076C<EVBACKEND_POLL>).
1035 1077
1036Another thing you have to watch out for is that it is quite easy to 1078Another thing you have to watch out for is that it is quite easy to
1037receive "spurious" readyness notifications, that is your callback might 1079receive "spurious" readiness notifications, that is your callback might
1038be called with C<EV_READ> but a subsequent C<read>(2) will actually block 1080be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039because there is no data. Not only are some backends known to create a 1081because there is no data. Not only are some backends known to create a
1040lot of those (for example solaris ports), it is very easy to get into 1082lot of those (for example Solaris ports), it is very easy to get into
1041this situation even with a relatively standard program structure. Thus 1083this situation even with a relatively standard program structure. Thus
1042it is best to always use non-blocking I/O: An extra C<read>(2) returning 1084it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043C<EAGAIN> is far preferable to a program hanging until some data arrives. 1085C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044 1086
1045If you cannot run the fd in non-blocking mode (for example you should not 1087If you cannot run the fd in non-blocking mode (for example you should not
1046play around with an Xlib connection), then you have to seperately re-test 1088play around with an Xlib connection), then you have to separately re-test
1047whether a file descriptor is really ready with a known-to-be good interface 1089whether a file descriptor is really ready with a known-to-be good interface
1048such as poll (fortunately in our Xlib example, Xlib already does this on 1090such as poll (fortunately in our Xlib example, Xlib already does this on
1049its own, so its quite safe to use). 1091its own, so its quite safe to use).
1050 1092
1051=head3 The special problem of disappearing file descriptors 1093=head3 The special problem of disappearing file descriptors
1111=item ev_io_init (ev_io *, callback, int fd, int events) 1153=item ev_io_init (ev_io *, callback, int fd, int events)
1112 1154
1113=item ev_io_set (ev_io *, int fd, int events) 1155=item ev_io_set (ev_io *, int fd, int events)
1114 1156
1115Configures an C<ev_io> watcher. The C<fd> is the file descriptor to 1157Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or 1158receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1117C<EV_READ | EV_WRITE> to receive the given events. 1159C<EV_READ | EV_WRITE> to receive the given events.
1118 1160
1119=item int fd [read-only] 1161=item int fd [read-only]
1120 1162
1121The file descriptor being watched. 1163The file descriptor being watched.
1130 1172
1131Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1173Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132readable, but only once. Since it is likely line-buffered, you could 1174readable, but only once. Since it is likely line-buffered, you could
1133attempt to read a whole line in the callback. 1175attempt to read a whole line in the callback.
1134 1176
1135 static void 1177 static void
1136 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1178 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1137 { 1179 {
1138 ev_io_stop (loop, w); 1180 ev_io_stop (loop, w);
1139 .. read from stdin here (or from w->fd) and haqndle any I/O errors 1181 .. read from stdin here (or from w->fd) and haqndle any I/O errors
1140 } 1182 }
1141 1183
1142 ... 1184 ...
1143 struct ev_loop *loop = ev_default_init (0); 1185 struct ev_loop *loop = ev_default_init (0);
1144 struct ev_io stdin_readable; 1186 struct ev_io stdin_readable;
1145 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1187 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146 ev_io_start (loop, &stdin_readable); 1188 ev_io_start (loop, &stdin_readable);
1147 ev_loop (loop, 0); 1189 ev_loop (loop, 0);
1148 1190
1149 1191
1150=head2 C<ev_timer> - relative and optionally repeating timeouts 1192=head2 C<ev_timer> - relative and optionally repeating timeouts
1151 1193
1152Timer watchers are simple relative timers that generate an event after a 1194Timer watchers are simple relative timers that generate an event after a
1153given time, and optionally repeating in regular intervals after that. 1195given time, and optionally repeating in regular intervals after that.
1154 1196
1155The timers are based on real time, that is, if you register an event that 1197The timers are based on real time, that is, if you register an event that
1156times out after an hour and you reset your system clock to last years 1198times out after an hour and you reset your system clock to January last
1157time, it will still time out after (roughly) and hour. "Roughly" because 1199year, it will still time out after (roughly) and hour. "Roughly" because
1158detecting time jumps is hard, and some inaccuracies are unavoidable (the 1200detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159monotonic clock option helps a lot here). 1201monotonic clock option helps a lot here).
1160 1202
1161The relative timeouts are calculated relative to the C<ev_now ()> 1203The relative timeouts are calculated relative to the C<ev_now ()>
1162time. This is usually the right thing as this timestamp refers to the time 1204time. This is usually the right thing as this timestamp refers to the time
1164you suspect event processing to be delayed and you I<need> to base the timeout 1206you suspect event processing to be delayed and you I<need> to base the timeout
1165on the current time, use something like this to adjust for this: 1207on the current time, use something like this to adjust for this:
1166 1208
1167 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1209 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168 1210
1169The callback is guarenteed to be invoked only when its timeout has passed, 1211The callback is guaranteed to be invoked only after its timeout has passed,
1170but if multiple timers become ready during the same loop iteration then 1212but if multiple timers become ready during the same loop iteration then
1171order of execution is undefined. 1213order of execution is undefined.
1172 1214
1173=head3 Watcher-Specific Functions and Data Members 1215=head3 Watcher-Specific Functions and Data Members
1174 1216
1176 1218
1177=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1219=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178 1220
1179=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) 1221=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180 1222
1181Configure the timer to trigger after C<after> seconds. If C<repeat> is 1223Configure the timer to trigger after C<after> seconds. If C<repeat>
1182C<0.>, then it will automatically be stopped. If it is positive, then the 1224is C<0.>, then it will automatically be stopped once the timeout is
1183timer will automatically be configured to trigger again C<repeat> seconds 1225reached. If it is positive, then the timer will automatically be
1184later, again, and again, until stopped manually. 1226configured to trigger again C<repeat> seconds later, again, and again,
1227until stopped manually.
1185 1228
1186The timer itself will do a best-effort at avoiding drift, that is, if you 1229The timer itself will do a best-effort at avoiding drift, that is, if
1187configure a timer to trigger every 10 seconds, then it will trigger at 1230you configure a timer to trigger every 10 seconds, then it will normally
1188exactly 10 second intervals. If, however, your program cannot keep up with 1231trigger at exactly 10 second intervals. If, however, your program cannot
1189the timer (because it takes longer than those 10 seconds to do stuff) the 1232keep up with the timer (because it takes longer than those 10 seconds to
1190timer will not fire more than once per event loop iteration. 1233do stuff) the timer will not fire more than once per event loop iteration.
1191 1234
1192=item ev_timer_again (loop, ev_timer *) 1235=item ev_timer_again (loop, ev_timer *)
1193 1236
1194This will act as if the timer timed out and restart it again if it is 1237This will act as if the timer timed out and restart it again if it is
1195repeating. The exact semantics are: 1238repeating. The exact semantics are:
1196 1239
1197If the timer is pending, its pending status is cleared. 1240If the timer is pending, its pending status is cleared.
1198 1241
1199If the timer is started but nonrepeating, stop it (as if it timed out). 1242If the timer is started but non-repeating, stop it (as if it timed out).
1200 1243
1201If the timer is repeating, either start it if necessary (with the 1244If the timer is repeating, either start it if necessary (with the
1202C<repeat> value), or reset the running timer to the C<repeat> value. 1245C<repeat> value), or reset the running timer to the C<repeat> value.
1203 1246
1204This sounds a bit complicated, but here is a useful and typical 1247This sounds a bit complicated, but here is a useful and typical
1205example: Imagine you have a tcp connection and you want a so-called idle 1248example: Imagine you have a TCP connection and you want a so-called idle
1206timeout, that is, you want to be called when there have been, say, 60 1249timeout, that is, you want to be called when there have been, say, 60
1207seconds of inactivity on the socket. The easiest way to do this is to 1250seconds of inactivity on the socket. The easiest way to do this is to
1208configure an C<ev_timer> with a C<repeat> value of C<60> and then call 1251configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209C<ev_timer_again> each time you successfully read or write some data. If 1252C<ev_timer_again> each time you successfully read or write some data. If
1210you go into an idle state where you do not expect data to travel on the 1253you go into an idle state where you do not expect data to travel on the
1236 1279
1237=head3 Examples 1280=head3 Examples
1238 1281
1239Example: Create a timer that fires after 60 seconds. 1282Example: Create a timer that fires after 60 seconds.
1240 1283
1241 static void 1284 static void
1242 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1285 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1243 { 1286 {
1244 .. one minute over, w is actually stopped right here 1287 .. one minute over, w is actually stopped right here
1245 } 1288 }
1246 1289
1247 struct ev_timer mytimer; 1290 struct ev_timer mytimer;
1248 ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1291 ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249 ev_timer_start (loop, &mytimer); 1292 ev_timer_start (loop, &mytimer);
1250 1293
1251Example: Create a timeout timer that times out after 10 seconds of 1294Example: Create a timeout timer that times out after 10 seconds of
1252inactivity. 1295inactivity.
1253 1296
1254 static void 1297 static void
1255 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1298 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1256 { 1299 {
1257 .. ten seconds without any activity 1300 .. ten seconds without any activity
1258 } 1301 }
1259 1302
1260 struct ev_timer mytimer; 1303 struct ev_timer mytimer;
1261 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ 1304 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262 ev_timer_again (&mytimer); /* start timer */ 1305 ev_timer_again (&mytimer); /* start timer */
1263 ev_loop (loop, 0); 1306 ev_loop (loop, 0);
1264 1307
1265 // and in some piece of code that gets executed on any "activity": 1308 // and in some piece of code that gets executed on any "activity":
1266 // reset the timeout to start ticking again at 10 seconds 1309 // reset the timeout to start ticking again at 10 seconds
1267 ev_timer_again (&mytimer); 1310 ev_timer_again (&mytimer);
1268 1311
1269 1312
1270=head2 C<ev_periodic> - to cron or not to cron? 1313=head2 C<ev_periodic> - to cron or not to cron?
1271 1314
1272Periodic watchers are also timers of a kind, but they are very versatile 1315Periodic watchers are also timers of a kind, but they are very versatile
1273(and unfortunately a bit complex). 1316(and unfortunately a bit complex).
1274 1317
1275Unlike C<ev_timer>'s, they are not based on real time (or relative time) 1318Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1276but on wallclock time (absolute time). You can tell a periodic watcher 1319but on wall clock time (absolute time). You can tell a periodic watcher
1277to trigger "at" some specific point in time. For example, if you tell a 1320to trigger after some specific point in time. For example, if you tell a
1278periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () 1321periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1279+ 10.>) and then reset your system clock to the last year, then it will 1322+ 10.>, that is, an absolute time not a delay) and then reset your system
1323clock to January of the previous year, then it will take more than year
1280take a year to trigger the event (unlike an C<ev_timer>, which would trigger 1324to trigger the event (unlike an C<ev_timer>, which would still trigger
1281roughly 10 seconds later). 1325roughly 10 seconds later as it uses a relative timeout).
1282 1326
1283They can also be used to implement vastly more complex timers, such as 1327C<ev_periodic>s can also be used to implement vastly more complex timers,
1284triggering an event on each midnight, local time or other, complicated, 1328such as triggering an event on each "midnight, local time", or other
1285rules. 1329complicated, rules.
1286 1330
1287As with timers, the callback is guarenteed to be invoked only when the 1331As with timers, the callback is guaranteed to be invoked only when the
1288time (C<at>) has been passed, but if multiple periodic timers become ready 1332time (C<at>) has passed, but if multiple periodic timers become ready
1289during the same loop iteration then order of execution is undefined. 1333during the same loop iteration then order of execution is undefined.
1290 1334
1291=head3 Watcher-Specific Functions and Data Members 1335=head3 Watcher-Specific Functions and Data Members
1292 1336
1293=over 4 1337=over 4
1301 1345
1302=over 4 1346=over 4
1303 1347
1304=item * absolute timer (at = time, interval = reschedule_cb = 0) 1348=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305 1349
1306In this configuration the watcher triggers an event at the wallclock time 1350In this configuration the watcher triggers an event after the wall clock
1307C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1351time C<at> has passed and doesn't repeat. It will not adjust when a time
1308that is, if it is to be run at January 1st 2011 then it will run when the 1352jump occurs, that is, if it is to be run at January 1st 2011 then it will
1309system time reaches or surpasses this time. 1353run when the system time reaches or surpasses this time.
1310 1354
1311=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) 1355=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312 1356
1313In this mode the watcher will always be scheduled to time out at the next 1357In this mode the watcher will always be scheduled to time out at the next
1314C<at + N * interval> time (for some integer N, which can also be negative) 1358C<at + N * interval> time (for some integer N, which can also be negative)
1315and then repeat, regardless of any time jumps. 1359and then repeat, regardless of any time jumps.
1316 1360
1317This can be used to create timers that do not drift with respect to system 1361This can be used to create timers that do not drift with respect to system
1318time: 1362time, for example, here is a C<ev_periodic> that triggers each hour, on
1363the hour:
1319 1364
1320 ev_periodic_set (&periodic, 0., 3600., 0); 1365 ev_periodic_set (&periodic, 0., 3600., 0);
1321 1366
1322This doesn't mean there will always be 3600 seconds in between triggers, 1367This doesn't mean there will always be 3600 seconds in between triggers,
1323but only that the the callback will be called when the system time shows a 1368but only that the callback will be called when the system time shows a
1324full hour (UTC), or more correctly, when the system time is evenly divisible 1369full hour (UTC), or more correctly, when the system time is evenly divisible
1325by 3600. 1370by 3600.
1326 1371
1327Another way to think about it (for the mathematically inclined) is that 1372Another way to think about it (for the mathematically inclined) is that
1328C<ev_periodic> will try to run the callback in this mode at the next possible 1373C<ev_periodic> will try to run the callback in this mode at the next possible
1329time where C<time = at (mod interval)>, regardless of any time jumps. 1374time where C<time = at (mod interval)>, regardless of any time jumps.
1330 1375
1331For numerical stability it is preferable that the C<at> value is near 1376For numerical stability it is preferable that the C<at> value is near
1332C<ev_now ()> (the current time), but there is no range requirement for 1377C<ev_now ()> (the current time), but there is no range requirement for
1333this value. 1378this value, and in fact is often specified as zero.
1379
1380Note also that there is an upper limit to how often a timer can fire (CPU
1381speed for example), so if C<interval> is very small then timing stability
1382will of course deteriorate. Libev itself tries to be exact to be about one
1383millisecond (if the OS supports it and the machine is fast enough).
1334 1384
1335=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) 1385=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336 1386
1337In this mode the values for C<interval> and C<at> are both being 1387In this mode the values for C<interval> and C<at> are both being
1338ignored. Instead, each time the periodic watcher gets scheduled, the 1388ignored. Instead, each time the periodic watcher gets scheduled, the
1339reschedule callback will be called with the watcher as first, and the 1389reschedule callback will be called with the watcher as first, and the
1340current time as second argument. 1390current time as second argument.
1341 1391
1342NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, 1392NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1343ever, or make any event loop modifications>. If you need to stop it, 1393ever, or make ANY event loop modifications whatsoever>.
1344return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1345starting an C<ev_prepare> watcher, which is legal).
1346 1394
1395If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1396it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1397only event loop modification you are allowed to do).
1398
1347Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1399The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1348ev_tstamp now)>, e.g.: 1400*w, ev_tstamp now)>, e.g.:
1349 1401
1350 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1402 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1351 { 1403 {
1352 return now + 60.; 1404 return now + 60.;
1353 } 1405 }
1355It must return the next time to trigger, based on the passed time value 1407It must return the next time to trigger, based on the passed time value
1356(that is, the lowest time value larger than to the second argument). It 1408(that is, the lowest time value larger than to the second argument). It
1357will usually be called just before the callback will be triggered, but 1409will usually be called just before the callback will be triggered, but
1358might be called at other times, too. 1410might be called at other times, too.
1359 1411
1360NOTE: I<< This callback must always return a time that is later than the 1412NOTE: I<< This callback must always return a time that is higher than or
1361passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. 1413equal to the passed C<now> value >>.
1362 1414
1363This can be used to create very complex timers, such as a timer that 1415This can be used to create very complex timers, such as a timer that
1364triggers on each midnight, local time. To do this, you would calculate the 1416triggers on "next midnight, local time". To do this, you would calculate the
1365next midnight after C<now> and return the timestamp value for this. How 1417next midnight after C<now> and return the timestamp value for this. How
1366you do this is, again, up to you (but it is not trivial, which is the main 1418you do this is, again, up to you (but it is not trivial, which is the main
1367reason I omitted it as an example). 1419reason I omitted it as an example).
1368 1420
1369=back 1421=back
1404 1456
1405=head3 Examples 1457=head3 Examples
1406 1458
1407Example: Call a callback every hour, or, more precisely, whenever the 1459Example: Call a callback every hour, or, more precisely, whenever the
1408system clock is divisible by 3600. The callback invocation times have 1460system clock is divisible by 3600. The callback invocation times have
1409potentially a lot of jittering, but good long-term stability. 1461potentially a lot of jitter, but good long-term stability.
1410 1462
1411 static void 1463 static void
1412 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1464 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1413 { 1465 {
1414 ... its now a full hour (UTC, or TAI or whatever your clock follows) 1466 ... its now a full hour (UTC, or TAI or whatever your clock follows)
1415 } 1467 }
1416 1468
1417 struct ev_periodic hourly_tick; 1469 struct ev_periodic hourly_tick;
1418 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1470 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419 ev_periodic_start (loop, &hourly_tick); 1471 ev_periodic_start (loop, &hourly_tick);
1420 1472
1421Example: The same as above, but use a reschedule callback to do it: 1473Example: The same as above, but use a reschedule callback to do it:
1422 1474
1423 #include <math.h> 1475 #include <math.h>
1424 1476
1425 static ev_tstamp 1477 static ev_tstamp
1426 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1478 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1427 { 1479 {
1428 return fmod (now, 3600.) + 3600.; 1480 return fmod (now, 3600.) + 3600.;
1429 } 1481 }
1430 1482
1431 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1483 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432 1484
1433Example: Call a callback every hour, starting now: 1485Example: Call a callback every hour, starting now:
1434 1486
1435 struct ev_periodic hourly_tick; 1487 struct ev_periodic hourly_tick;
1436 ev_periodic_init (&hourly_tick, clock_cb, 1488 ev_periodic_init (&hourly_tick, clock_cb,
1437 fmod (ev_now (loop), 3600.), 3600., 0); 1489 fmod (ev_now (loop), 3600.), 3600., 0);
1438 ev_periodic_start (loop, &hourly_tick); 1490 ev_periodic_start (loop, &hourly_tick);
1439 1491
1440 1492
1441=head2 C<ev_signal> - signal me when a signal gets signalled! 1493=head2 C<ev_signal> - signal me when a signal gets signalled!
1442 1494
1443Signal watchers will trigger an event when the process receives a specific 1495Signal watchers will trigger an event when the process receives a specific
1451as you don't register any with libev). Similarly, when the last signal 1503as you don't register any with libev). Similarly, when the last signal
1452watcher for a signal is stopped libev will reset the signal handler to 1504watcher for a signal is stopped libev will reset the signal handler to
1453SIG_DFL (regardless of what it was set to before). 1505SIG_DFL (regardless of what it was set to before).
1454 1506
1455If possible and supported, libev will install its handlers with 1507If possible and supported, libev will install its handlers with
1456C<SA_RESTART> behaviour enabled, so syscalls should not be unduly 1508C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457interrupted. If you have a problem with syscalls getting interrupted by 1509interrupted. If you have a problem with system calls getting interrupted by
1458signals you can block all signals in an C<ev_check> watcher and unblock 1510signals you can block all signals in an C<ev_check> watcher and unblock
1459them in an C<ev_prepare> watcher. 1511them in an C<ev_prepare> watcher.
1460 1512
1461=head3 Watcher-Specific Functions and Data Members 1513=head3 Watcher-Specific Functions and Data Members
1462 1514
1477 1529
1478=head3 Examples 1530=head3 Examples
1479 1531
1480Example: Try to exit cleanly on SIGINT and SIGTERM. 1532Example: Try to exit cleanly on SIGINT and SIGTERM.
1481 1533
1482 static void 1534 static void
1483 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1535 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1484 { 1536 {
1485 ev_unloop (loop, EVUNLOOP_ALL); 1537 ev_unloop (loop, EVUNLOOP_ALL);
1486 } 1538 }
1487 1539
1488 struct ev_signal signal_watcher; 1540 struct ev_signal signal_watcher;
1489 ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1541 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490 ev_signal_start (loop, &sigint_cb); 1542 ev_signal_start (loop, &sigint_cb);
1491 1543
1492 1544
1493=head2 C<ev_child> - watch out for process status changes 1545=head2 C<ev_child> - watch out for process status changes
1494 1546
1495Child watchers trigger when your process receives a SIGCHLD in response to 1547Child watchers trigger when your process receives a SIGCHLD in response to
1497is permissible to install a child watcher I<after> the child has been 1549is permissible to install a child watcher I<after> the child has been
1498forked (which implies it might have already exited), as long as the event 1550forked (which implies it might have already exited), as long as the event
1499loop isn't entered (or is continued from a watcher). 1551loop isn't entered (or is continued from a watcher).
1500 1552
1501Only the default event loop is capable of handling signals, and therefore 1553Only the default event loop is capable of handling signals, and therefore
1502you can only rgeister child watchers in the default event loop. 1554you can only register child watchers in the default event loop.
1503 1555
1504=head3 Process Interaction 1556=head3 Process Interaction
1505 1557
1506Libev grabs C<SIGCHLD> as soon as the default event loop is 1558Libev grabs C<SIGCHLD> as soon as the default event loop is
1507initialised. This is necessary to guarantee proper behaviour even if 1559initialised. This is necessary to guarantee proper behaviour even if
1508the first child watcher is started after the child exits. The occurance 1560the first child watcher is started after the child exits. The occurrence
1509of C<SIGCHLD> is recorded asynchronously, but child reaping is done 1561of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510synchronously as part of the event loop processing. Libev always reaps all 1562synchronously as part of the event loop processing. Libev always reaps all
1511children, even ones not watched. 1563children, even ones not watched.
1512 1564
1513=head3 Overriding the Built-In Processing 1565=head3 Overriding the Built-In Processing
1517handler, you can override it easily by installing your own handler for 1569handler, you can override it easily by installing your own handler for
1518C<SIGCHLD> after initialising the default loop, and making sure the 1570C<SIGCHLD> after initialising the default loop, and making sure the
1519default loop never gets destroyed. You are encouraged, however, to use an 1571default loop never gets destroyed. You are encouraged, however, to use an
1520event-based approach to child reaping and thus use libev's support for 1572event-based approach to child reaping and thus use libev's support for
1521that, so other libev users can use C<ev_child> watchers freely. 1573that, so other libev users can use C<ev_child> watchers freely.
1574
1575=head3 Stopping the Child Watcher
1576
1577Currently, the child watcher never gets stopped, even when the
1578child terminates, so normally one needs to stop the watcher in the
1579callback. Future versions of libev might stop the watcher automatically
1580when a child exit is detected.
1522 1581
1523=head3 Watcher-Specific Functions and Data Members 1582=head3 Watcher-Specific Functions and Data Members
1524 1583
1525=over 4 1584=over 4
1526 1585
1555=head3 Examples 1614=head3 Examples
1556 1615
1557Example: C<fork()> a new process and install a child handler to wait for 1616Example: C<fork()> a new process and install a child handler to wait for
1558its completion. 1617its completion.
1559 1618
1560 ev_child cw; 1619 ev_child cw;
1561 1620
1562 static void 1621 static void
1563 child_cb (EV_P_ struct ev_child *w, int revents) 1622 child_cb (EV_P_ struct ev_child *w, int revents)
1564 { 1623 {
1565 ev_child_stop (EV_A_ w); 1624 ev_child_stop (EV_A_ w);
1566 printf ("process %d exited with status %x\n", w->rpid, w->rstatus); 1625 printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567 } 1626 }
1568 1627
1569 pid_t pid = fork (); 1628 pid_t pid = fork ();
1570 1629
1571 if (pid < 0) 1630 if (pid < 0)
1572 // error 1631 // error
1573 else if (pid == 0) 1632 else if (pid == 0)
1574 { 1633 {
1575 // the forked child executes here 1634 // the forked child executes here
1576 exit (1); 1635 exit (1);
1577 } 1636 }
1578 else 1637 else
1579 { 1638 {
1580 ev_child_init (&cw, child_cb, pid, 0); 1639 ev_child_init (&cw, child_cb, pid, 0);
1581 ev_child_start (EV_DEFAULT_ &cw); 1640 ev_child_start (EV_DEFAULT_ &cw);
1582 } 1641 }
1583 1642
1584 1643
1585=head2 C<ev_stat> - did the file attributes just change? 1644=head2 C<ev_stat> - did the file attributes just change?
1586 1645
1587This watches a filesystem path for attribute changes. That is, it calls 1646This watches a file system path for attribute changes. That is, it calls
1588C<stat> regularly (or when the OS says it changed) and sees if it changed 1647C<stat> regularly (or when the OS says it changed) and sees if it changed
1589compared to the last time, invoking the callback if it did. 1648compared to the last time, invoking the callback if it did.
1590 1649
1591The path does not need to exist: changing from "path exists" to "path does 1650The path does not need to exist: changing from "path exists" to "path does
1592not exist" is a status change like any other. The condition "path does 1651not exist" is a status change like any other. The condition "path does
1620will be no polling. 1679will be no polling.
1621 1680
1622=head3 ABI Issues (Largefile Support) 1681=head3 ABI Issues (Largefile Support)
1623 1682
1624Libev by default (unless the user overrides this) uses the default 1683Libev by default (unless the user overrides this) uses the default
1625compilation environment, which means that on systems with optionally 1684compilation environment, which means that on systems with large file
1626disabled large file support, you get the 32 bit version of the stat 1685support disabled by default, you get the 32 bit version of the stat
1627structure. When using the library from programs that change the ABI to 1686structure. When using the library from programs that change the ABI to
1628use 64 bit file offsets the programs will fail. In that case you have to 1687use 64 bit file offsets the programs will fail. In that case you have to
1629compile libev with the same flags to get binary compatibility. This is 1688compile libev with the same flags to get binary compatibility. This is
1630obviously the case with any flags that change the ABI, but the problem is 1689obviously the case with any flags that change the ABI, but the problem is
1631most noticably with ev_stat and largefile support. 1690most noticeably disabled with ev_stat and large file support.
1691
1692The solution for this is to lobby your distribution maker to make large
1693file interfaces available by default (as e.g. FreeBSD does) and not
1694optional. Libev cannot simply switch on large file support because it has
1695to exchange stat structures with application programs compiled using the
1696default compilation environment.
1632 1697
1633=head3 Inotify 1698=head3 Inotify
1634 1699
1635When C<inotify (7)> support has been compiled into libev (generally only 1700When C<inotify (7)> support has been compiled into libev (generally only
1636available on Linux) and present at runtime, it will be used to speed up 1701available on Linux) and present at runtime, it will be used to speed up
1646implement this functionality, due to the requirement of having a file 1711implement this functionality, due to the requirement of having a file
1647descriptor open on the object at all times). 1712descriptor open on the object at all times).
1648 1713
1649=head3 The special problem of stat time resolution 1714=head3 The special problem of stat time resolution
1650 1715
1651The C<stat ()> syscall only supports full-second resolution portably, and 1716The C<stat ()> system call only supports full-second resolution portably, and
1652even on systems where the resolution is higher, many filesystems still 1717even on systems where the resolution is higher, many file systems still
1653only support whole seconds. 1718only support whole seconds.
1654 1719
1655That means that, if the time is the only thing that changes, you can 1720That means that, if the time is the only thing that changes, you can
1656easily miss updates: on the first update, C<ev_stat> detects a change and 1721easily miss updates: on the first update, C<ev_stat> detects a change and
1657calls your callback, which does something. When there is another update 1722calls your callback, which does something. When there is another update
1658within the same second, C<ev_stat> will be unable to detect it as the stat 1723within the same second, C<ev_stat> will be unable to detect it as the stat
1659data does not change. 1724data does not change.
1660 1725
1661The solution to this is to delay acting on a change for slightly more 1726The solution to this is to delay acting on a change for slightly more
1662than second (or till slightly after the next full second boundary), using 1727than a second (or till slightly after the next full second boundary), using
1663a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); 1728a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664ev_timer_again (loop, w)>). 1729ev_timer_again (loop, w)>).
1665 1730
1666The C<.02> offset is added to work around small timing inconsistencies 1731The C<.02> offset is added to work around small timing inconsistencies
1667of some operating systems (where the second counter of the current time 1732of some operating systems (where the second counter of the current time
1717 1782
1718The specified interval. 1783The specified interval.
1719 1784
1720=item const char *path [read-only] 1785=item const char *path [read-only]
1721 1786
1722The filesystem path that is being watched. 1787The file system path that is being watched.
1723 1788
1724=back 1789=back
1725 1790
1726=head3 Examples 1791=head3 Examples
1727 1792
1728Example: Watch C</etc/passwd> for attribute changes. 1793Example: Watch C</etc/passwd> for attribute changes.
1729 1794
1730 static void 1795 static void
1731 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1796 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732 { 1797 {
1733 /* /etc/passwd changed in some way */ 1798 /* /etc/passwd changed in some way */
1734 if (w->attr.st_nlink) 1799 if (w->attr.st_nlink)
1735 { 1800 {
1736 printf ("passwd current size %ld\n", (long)w->attr.st_size); 1801 printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737 printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); 1802 printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738 printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); 1803 printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739 } 1804 }
1740 else 1805 else
1741 /* you shalt not abuse printf for puts */ 1806 /* you shalt not abuse printf for puts */
1742 puts ("wow, /etc/passwd is not there, expect problems. " 1807 puts ("wow, /etc/passwd is not there, expect problems. "
1743 "if this is windows, they already arrived\n"); 1808 "if this is windows, they already arrived\n");
1744 } 1809 }
1745 1810
1746 ... 1811 ...
1747 ev_stat passwd; 1812 ev_stat passwd;
1748 1813
1749 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); 1814 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750 ev_stat_start (loop, &passwd); 1815 ev_stat_start (loop, &passwd);
1751 1816
1752Example: Like above, but additionally use a one-second delay so we do not 1817Example: Like above, but additionally use a one-second delay so we do not
1753miss updates (however, frequent updates will delay processing, too, so 1818miss updates (however, frequent updates will delay processing, too, so
1754one might do the work both on C<ev_stat> callback invocation I<and> on 1819one might do the work both on C<ev_stat> callback invocation I<and> on
1755C<ev_timer> callback invocation). 1820C<ev_timer> callback invocation).
1756 1821
1757 static ev_stat passwd; 1822 static ev_stat passwd;
1758 static ev_timer timer; 1823 static ev_timer timer;
1759 1824
1760 static void 1825 static void
1761 timer_cb (EV_P_ ev_timer *w, int revents) 1826 timer_cb (EV_P_ ev_timer *w, int revents)
1762 { 1827 {
1763 ev_timer_stop (EV_A_ w); 1828 ev_timer_stop (EV_A_ w);
1764 1829
1765 /* now it's one second after the most recent passwd change */ 1830 /* now it's one second after the most recent passwd change */
1766 } 1831 }
1767 1832
1768 static void 1833 static void
1769 stat_cb (EV_P_ ev_stat *w, int revents) 1834 stat_cb (EV_P_ ev_stat *w, int revents)
1770 { 1835 {
1771 /* reset the one-second timer */ 1836 /* reset the one-second timer */
1772 ev_timer_again (EV_A_ &timer); 1837 ev_timer_again (EV_A_ &timer);
1773 } 1838 }
1774 1839
1775 ... 1840 ...
1776 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); 1841 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777 ev_stat_start (loop, &passwd); 1842 ev_stat_start (loop, &passwd);
1778 ev_timer_init (&timer, timer_cb, 0., 1.02); 1843 ev_timer_init (&timer, timer_cb, 0., 1.02);
1779 1844
1780 1845
1781=head2 C<ev_idle> - when you've got nothing better to do... 1846=head2 C<ev_idle> - when you've got nothing better to do...
1782 1847
1783Idle watchers trigger events when no other events of the same or higher 1848Idle watchers trigger events when no other events of the same or higher
1814=head3 Examples 1879=head3 Examples
1815 1880
1816Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1881Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817callback, free it. Also, use no error checking, as usual. 1882callback, free it. Also, use no error checking, as usual.
1818 1883
1819 static void 1884 static void
1820 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1885 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1821 { 1886 {
1822 free (w); 1887 free (w);
1823 // now do something you wanted to do when the program has 1888 // now do something you wanted to do when the program has
1824 // no longer anything immediate to do. 1889 // no longer anything immediate to do.
1825 } 1890 }
1826 1891
1827 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1892 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1828 ev_idle_init (idle_watcher, idle_cb); 1893 ev_idle_init (idle_watcher, idle_cb);
1829 ev_idle_start (loop, idle_cb); 1894 ev_idle_start (loop, idle_cb);
1830 1895
1831 1896
1832=head2 C<ev_prepare> and C<ev_check> - customise your event loop! 1897=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833 1898
1834Prepare and check watchers are usually (but not always) used in tandem: 1899Prepare and check watchers are usually (but not always) used in tandem:
1853 1918
1854This is done by examining in each prepare call which file descriptors need 1919This is done by examining in each prepare call which file descriptors need
1855to be watched by the other library, registering C<ev_io> watchers for 1920to be watched by the other library, registering C<ev_io> watchers for
1856them and starting an C<ev_timer> watcher for any timeouts (many libraries 1921them and starting an C<ev_timer> watcher for any timeouts (many libraries
1857provide just this functionality). Then, in the check watcher you check for 1922provide just this functionality). Then, in the check watcher you check for
1858any events that occured (by checking the pending status of all watchers 1923any events that occurred (by checking the pending status of all watchers
1859and stopping them) and call back into the library. The I/O and timer 1924and stopping them) and call back into the library. The I/O and timer
1860callbacks will never actually be called (but must be valid nevertheless, 1925callbacks will never actually be called (but must be valid nevertheless,
1861because you never know, you know?). 1926because you never know, you know?).
1862 1927
1863As another example, the Perl Coro module uses these hooks to integrate 1928As another example, the Perl Coro module uses these hooks to integrate
1906and in a check watcher, destroy them and call into libadns. What follows 1971and in a check watcher, destroy them and call into libadns. What follows
1907is pseudo-code only of course. This requires you to either use a low 1972is pseudo-code only of course. This requires you to either use a low
1908priority for the check watcher or use C<ev_clear_pending> explicitly, as 1973priority for the check watcher or use C<ev_clear_pending> explicitly, as
1909the callbacks for the IO/timeout watchers might not have been called yet. 1974the callbacks for the IO/timeout watchers might not have been called yet.
1910 1975
1911 static ev_io iow [nfd]; 1976 static ev_io iow [nfd];
1912 static ev_timer tw; 1977 static ev_timer tw;
1913 1978
1914 static void 1979 static void
1915 io_cb (ev_loop *loop, ev_io *w, int revents) 1980 io_cb (ev_loop *loop, ev_io *w, int revents)
1916 { 1981 {
1917 } 1982 }
1918 1983
1919 // create io watchers for each fd and a timer before blocking 1984 // create io watchers for each fd and a timer before blocking
1920 static void 1985 static void
1921 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1986 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1922 { 1987 {
1923 int timeout = 3600000; 1988 int timeout = 3600000;
1924 struct pollfd fds [nfd]; 1989 struct pollfd fds [nfd];
1925 // actual code will need to loop here and realloc etc. 1990 // actual code will need to loop here and realloc etc.
1926 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 1991 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927 1992
1928 /* the callback is illegal, but won't be called as we stop during check */ 1993 /* the callback is illegal, but won't be called as we stop during check */
1929 ev_timer_init (&tw, 0, timeout * 1e-3); 1994 ev_timer_init (&tw, 0, timeout * 1e-3);
1930 ev_timer_start (loop, &tw); 1995 ev_timer_start (loop, &tw);
1931 1996
1932 // create one ev_io per pollfd 1997 // create one ev_io per pollfd
1933 for (int i = 0; i < nfd; ++i) 1998 for (int i = 0; i < nfd; ++i)
1934 { 1999 {
1935 ev_io_init (iow + i, io_cb, fds [i].fd, 2000 ev_io_init (iow + i, io_cb, fds [i].fd,
1936 ((fds [i].events & POLLIN ? EV_READ : 0) 2001 ((fds [i].events & POLLIN ? EV_READ : 0)
1937 | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 2002 | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938 2003
1939 fds [i].revents = 0; 2004 fds [i].revents = 0;
1940 ev_io_start (loop, iow + i); 2005 ev_io_start (loop, iow + i);
1941 } 2006 }
1942 } 2007 }
1943 2008
1944 // stop all watchers after blocking 2009 // stop all watchers after blocking
1945 static void 2010 static void
1946 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 2011 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1947 { 2012 {
1948 ev_timer_stop (loop, &tw); 2013 ev_timer_stop (loop, &tw);
1949 2014
1950 for (int i = 0; i < nfd; ++i) 2015 for (int i = 0; i < nfd; ++i)
1951 { 2016 {
1952 // set the relevant poll flags 2017 // set the relevant poll flags
1953 // could also call adns_processreadable etc. here 2018 // could also call adns_processreadable etc. here
1954 struct pollfd *fd = fds + i; 2019 struct pollfd *fd = fds + i;
1955 int revents = ev_clear_pending (iow + i); 2020 int revents = ev_clear_pending (iow + i);
1956 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; 2021 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; 2022 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958 2023
1959 // now stop the watcher 2024 // now stop the watcher
1960 ev_io_stop (loop, iow + i); 2025 ev_io_stop (loop, iow + i);
1961 } 2026 }
1962 2027
1963 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 2028 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964 } 2029 }
1965 2030
1966Method 2: This would be just like method 1, but you run C<adns_afterpoll> 2031Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1967in the prepare watcher and would dispose of the check watcher. 2032in the prepare watcher and would dispose of the check watcher.
1968 2033
1969Method 3: If the module to be embedded supports explicit event 2034Method 3: If the module to be embedded supports explicit event
1970notification (adns does), you can also make use of the actual watcher 2035notification (libadns does), you can also make use of the actual watcher
1971callbacks, and only destroy/create the watchers in the prepare watcher. 2036callbacks, and only destroy/create the watchers in the prepare watcher.
1972 2037
1973 static void 2038 static void
1974 timer_cb (EV_P_ ev_timer *w, int revents) 2039 timer_cb (EV_P_ ev_timer *w, int revents)
1975 { 2040 {
1976 adns_state ads = (adns_state)w->data; 2041 adns_state ads = (adns_state)w->data;
1977 update_now (EV_A); 2042 update_now (EV_A);
1978 2043
1979 adns_processtimeouts (ads, &tv_now); 2044 adns_processtimeouts (ads, &tv_now);
1980 } 2045 }
1981 2046
1982 static void 2047 static void
1983 io_cb (EV_P_ ev_io *w, int revents) 2048 io_cb (EV_P_ ev_io *w, int revents)
1984 { 2049 {
1985 adns_state ads = (adns_state)w->data; 2050 adns_state ads = (adns_state)w->data;
1986 update_now (EV_A); 2051 update_now (EV_A);
1987 2052
1988 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); 2053 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); 2054 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990 } 2055 }
1991 2056
1992 // do not ever call adns_afterpoll 2057 // do not ever call adns_afterpoll
1993 2058
1994Method 4: Do not use a prepare or check watcher because the module you 2059Method 4: Do not use a prepare or check watcher because the module you
1995want to embed is too inflexible to support it. Instead, youc na override 2060want to embed is too inflexible to support it. Instead, you can override
1996their poll function. The drawback with this solution is that the main 2061their poll function. The drawback with this solution is that the main
1997loop is now no longer controllable by EV. The C<Glib::EV> module does 2062loop is now no longer controllable by EV. The C<Glib::EV> module does
1998this. 2063this.
1999 2064
2000 static gint 2065 static gint
2001 event_poll_func (GPollFD *fds, guint nfds, gint timeout) 2066 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002 { 2067 {
2003 int got_events = 0; 2068 int got_events = 0;
2004 2069
2005 for (n = 0; n < nfds; ++n) 2070 for (n = 0; n < nfds; ++n)
2006 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events 2071 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007 2072
2008 if (timeout >= 0) 2073 if (timeout >= 0)
2009 // create/start timer 2074 // create/start timer
2010 2075
2011 // poll 2076 // poll
2012 ev_loop (EV_A_ 0); 2077 ev_loop (EV_A_ 0);
2013 2078
2014 // stop timer again 2079 // stop timer again
2015 if (timeout >= 0) 2080 if (timeout >= 0)
2016 ev_timer_stop (EV_A_ &to); 2081 ev_timer_stop (EV_A_ &to);
2017 2082
2018 // stop io watchers again - their callbacks should have set 2083 // stop io watchers again - their callbacks should have set
2019 for (n = 0; n < nfds; ++n) 2084 for (n = 0; n < nfds; ++n)
2020 ev_io_stop (EV_A_ iow [n]); 2085 ev_io_stop (EV_A_ iow [n]);
2021 2086
2022 return got_events; 2087 return got_events;
2023 } 2088 }
2024 2089
2025 2090
2026=head2 C<ev_embed> - when one backend isn't enough... 2091=head2 C<ev_embed> - when one backend isn't enough...
2027 2092
2028This is a rather advanced watcher type that lets you embed one event loop 2093This is a rather advanced watcher type that lets you embed one event loop
2084 2149
2085Configures the watcher to embed the given loop, which must be 2150Configures the watcher to embed the given loop, which must be
2086embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be 2151embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087invoked automatically, otherwise it is the responsibility of the callback 2152invoked automatically, otherwise it is the responsibility of the callback
2088to invoke it (it will continue to be called until the sweep has been done, 2153to invoke it (it will continue to be called until the sweep has been done,
2089if you do not want thta, you need to temporarily stop the embed watcher). 2154if you do not want that, you need to temporarily stop the embed watcher).
2090 2155
2091=item ev_embed_sweep (loop, ev_embed *) 2156=item ev_embed_sweep (loop, ev_embed *)
2092 2157
2093Make a single, non-blocking sweep over the embedded loop. This works 2158Make a single, non-blocking sweep over the embedded loop. This works
2094similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most 2159similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095apropriate way for embedded loops. 2160appropriate way for embedded loops.
2096 2161
2097=item struct ev_loop *other [read-only] 2162=item struct ev_loop *other [read-only]
2098 2163
2099The embedded event loop. 2164The embedded event loop.
2100 2165
2102 2167
2103=head3 Examples 2168=head3 Examples
2104 2169
2105Example: Try to get an embeddable event loop and embed it into the default 2170Example: Try to get an embeddable event loop and embed it into the default
2106event loop. If that is not possible, use the default loop. The default 2171event loop. If that is not possible, use the default loop. The default
2107loop is stored in C<loop_hi>, while the mebeddable loop is stored in 2172loop is stored in C<loop_hi>, while the embeddable loop is stored in
2108C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be 2173C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109used). 2174used).
2110 2175
2111 struct ev_loop *loop_hi = ev_default_init (0); 2176 struct ev_loop *loop_hi = ev_default_init (0);
2112 struct ev_loop *loop_lo = 0; 2177 struct ev_loop *loop_lo = 0;
2113 struct ev_embed embed; 2178 struct ev_embed embed;
2114 2179
2115 // see if there is a chance of getting one that works 2180 // see if there is a chance of getting one that works
2116 // (remember that a flags value of 0 means autodetection) 2181 // (remember that a flags value of 0 means autodetection)
2117 loop_lo = ev_embeddable_backends () & ev_recommended_backends () 2182 loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) 2183 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119 : 0; 2184 : 0;
2120 2185
2121 // if we got one, then embed it, otherwise default to loop_hi 2186 // if we got one, then embed it, otherwise default to loop_hi
2122 if (loop_lo) 2187 if (loop_lo)
2123 { 2188 {
2124 ev_embed_init (&embed, 0, loop_lo); 2189 ev_embed_init (&embed, 0, loop_lo);
2125 ev_embed_start (loop_hi, &embed); 2190 ev_embed_start (loop_hi, &embed);
2126 } 2191 }
2127 else 2192 else
2128 loop_lo = loop_hi; 2193 loop_lo = loop_hi;
2129 2194
2130Example: Check if kqueue is available but not recommended and create 2195Example: Check if kqueue is available but not recommended and create
2131a kqueue backend for use with sockets (which usually work with any 2196a kqueue backend for use with sockets (which usually work with any
2132kqueue implementation). Store the kqueue/socket-only event loop in 2197kqueue implementation). Store the kqueue/socket-only event loop in
2133C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). 2198C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134 2199
2135 struct ev_loop *loop = ev_default_init (0); 2200 struct ev_loop *loop = ev_default_init (0);
2136 struct ev_loop *loop_socket = 0; 2201 struct ev_loop *loop_socket = 0;
2137 struct ev_embed embed; 2202 struct ev_embed embed;
2138 2203
2139 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) 2204 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) 2205 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141 { 2206 {
2142 ev_embed_init (&embed, 0, loop_socket); 2207 ev_embed_init (&embed, 0, loop_socket);
2143 ev_embed_start (loop, &embed); 2208 ev_embed_start (loop, &embed);
2144 } 2209 }
2145 2210
2146 if (!loop_socket) 2211 if (!loop_socket)
2147 loop_socket = loop; 2212 loop_socket = loop;
2148 2213
2149 // now use loop_socket for all sockets, and loop for everything else 2214 // now use loop_socket for all sockets, and loop for everything else
2150 2215
2151 2216
2152=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2217=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153 2218
2154Fork watchers are called when a C<fork ()> was detected (usually because 2219Fork watchers are called when a C<fork ()> was detected (usually because
2207 2272
2208=item queueing from a signal handler context 2273=item queueing from a signal handler context
2209 2274
2210To implement race-free queueing, you simply add to the queue in the signal 2275To implement race-free queueing, you simply add to the queue in the signal
2211handler but you block the signal handler in the watcher callback. Here is an example that does that for 2276handler but you block the signal handler in the watcher callback. Here is an example that does that for
2212some fictitiuous SIGUSR1 handler: 2277some fictitious SIGUSR1 handler:
2213 2278
2214 static ev_async mysig; 2279 static ev_async mysig;
2215 2280
2216 static void 2281 static void
2217 sigusr1_handler (void) 2282 sigusr1_handler (void)
2291=item ev_async_send (loop, ev_async *) 2356=item ev_async_send (loop, ev_async *)
2292 2357
2293Sends/signals/activates the given C<ev_async> watcher, that is, feeds 2358Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294an C<EV_ASYNC> event on the watcher into the event loop. Unlike 2359an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2295C<ev_feed_event>, this call is safe to do in other threads, signal or 2360C<ev_feed_event>, this call is safe to do in other threads, signal or
2296similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding 2361similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297section below on what exactly this means). 2362section below on what exactly this means).
2298 2363
2299This call incurs the overhead of a syscall only once per loop iteration, 2364This call incurs the overhead of a system call only once per loop iteration,
2300so while the overhead might be noticable, it doesn't apply to repeated 2365so while the overhead might be noticeable, it doesn't apply to repeated
2301calls to C<ev_async_send>. 2366calls to C<ev_async_send>.
2302 2367
2303=item bool = ev_async_pending (ev_async *) 2368=item bool = ev_async_pending (ev_async *)
2304 2369
2305Returns a non-zero value when C<ev_async_send> has been called on the 2370Returns a non-zero value when C<ev_async_send> has been called on the
2307event loop. 2372event loop.
2308 2373
2309C<ev_async_send> sets a flag in the watcher and wakes up the loop. When 2374C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2310the loop iterates next and checks for the watcher to have become active, 2375the loop iterates next and checks for the watcher to have become active,
2311it will reset the flag again. C<ev_async_pending> can be used to very 2376it will reset the flag again. C<ev_async_pending> can be used to very
2312quickly check wether invoking the loop might be a good idea. 2377quickly check whether invoking the loop might be a good idea.
2313 2378
2314Not that this does I<not> check wether the watcher itself is pending, only 2379Not that this does I<not> check whether the watcher itself is pending, only
2315wether it has been requested to make this watcher pending. 2380whether it has been requested to make this watcher pending.
2316 2381
2317=back 2382=back
2318 2383
2319 2384
2320=head1 OTHER FUNCTIONS 2385=head1 OTHER FUNCTIONS
2331or timeout without having to allocate/configure/start/stop/free one or 2396or timeout without having to allocate/configure/start/stop/free one or
2332more watchers yourself. 2397more watchers yourself.
2333 2398
2334If C<fd> is less than 0, then no I/O watcher will be started and events 2399If C<fd> is less than 0, then no I/O watcher will be started and events
2335is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and 2400is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2336C<events> set will be craeted and started. 2401C<events> set will be created and started.
2337 2402
2338If C<timeout> is less than 0, then no timeout watcher will be 2403If C<timeout> is less than 0, then no timeout watcher will be
2339started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 2404started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2340repeat = 0) will be started. While C<0> is a valid timeout, it is of 2405repeat = 0) will be started. While C<0> is a valid timeout, it is of
2341dubious value. 2406dubious value.
2343The callback has the type C<void (*cb)(int revents, void *arg)> and gets 2408The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2344passed an C<revents> set like normal event callbacks (a combination of 2409passed an C<revents> set like normal event callbacks (a combination of
2345C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> 2410C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346value passed to C<ev_once>: 2411value passed to C<ev_once>:
2347 2412
2348 static void stdin_ready (int revents, void *arg) 2413 static void stdin_ready (int revents, void *arg)
2349 { 2414 {
2350 if (revents & EV_TIMEOUT) 2415 if (revents & EV_TIMEOUT)
2351 /* doh, nothing entered */; 2416 /* doh, nothing entered */;
2352 else if (revents & EV_READ) 2417 else if (revents & EV_READ)
2353 /* stdin might have data for us, joy! */; 2418 /* stdin might have data for us, joy! */;
2354 } 2419 }
2355 2420
2356 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2421 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357 2422
2358=item ev_feed_event (ev_loop *, watcher *, int revents) 2423=item ev_feed_event (ev_loop *, watcher *, int revents)
2359 2424
2360Feeds the given event set into the event loop, as if the specified event 2425Feeds the given event set into the event loop, as if the specified event
2361had happened for the specified watcher (which must be a pointer to an 2426had happened for the specified watcher (which must be a pointer to an
2366Feed an event on the given fd, as if a file descriptor backend detected 2431Feed an event on the given fd, as if a file descriptor backend detected
2367the given events it. 2432the given events it.
2368 2433
2369=item ev_feed_signal_event (ev_loop *loop, int signum) 2434=item ev_feed_signal_event (ev_loop *loop, int signum)
2370 2435
2371Feed an event as if the given signal occured (C<loop> must be the default 2436Feed an event as if the given signal occurred (C<loop> must be the default
2372loop!). 2437loop!).
2373 2438
2374=back 2439=back
2375 2440
2376 2441
2405=back 2470=back
2406 2471
2407=head1 C++ SUPPORT 2472=head1 C++ SUPPORT
2408 2473
2409Libev comes with some simplistic wrapper classes for C++ that mainly allow 2474Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410you to use some convinience methods to start/stop watchers and also change 2475you to use some convenience methods to start/stop watchers and also change
2411the callback model to a model using method callbacks on objects. 2476the callback model to a model using method callbacks on objects.
2412 2477
2413To use it, 2478To use it,
2414 2479
2415 #include <ev++.h> 2480 #include <ev++.h>
2416 2481
2417This automatically includes F<ev.h> and puts all of its definitions (many 2482This automatically includes F<ev.h> and puts all of its definitions (many
2418of them macros) into the global namespace. All C++ specific things are 2483of them macros) into the global namespace. All C++ specific things are
2419put into the C<ev> namespace. It should support all the same embedding 2484put into the C<ev> namespace. It should support all the same embedding
2420options as F<ev.h>, most notably C<EV_MULTIPLICITY>. 2485options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
2487your compiler is good :), then the method will be fully inlined into the 2552your compiler is good :), then the method will be fully inlined into the
2488thunking function, making it as fast as a direct C callback. 2553thunking function, making it as fast as a direct C callback.
2489 2554
2490Example: simple class declaration and watcher initialisation 2555Example: simple class declaration and watcher initialisation
2491 2556
2492 struct myclass 2557 struct myclass
2493 { 2558 {
2494 void io_cb (ev::io &w, int revents) { } 2559 void io_cb (ev::io &w, int revents) { }
2495 } 2560 }
2496 2561
2497 myclass obj; 2562 myclass obj;
2498 ev::io iow; 2563 ev::io iow;
2499 iow.set <myclass, &myclass::io_cb> (&obj); 2564 iow.set <myclass, &myclass::io_cb> (&obj);
2500 2565
2501=item w->set<function> (void *data = 0) 2566=item w->set<function> (void *data = 0)
2502 2567
2503Also sets a callback, but uses a static method or plain function as 2568Also sets a callback, but uses a static method or plain function as
2504callback. The optional C<data> argument will be stored in the watcher's 2569callback. The optional C<data> argument will be stored in the watcher's
2508 2573
2509See the method-C<set> above for more details. 2574See the method-C<set> above for more details.
2510 2575
2511Example: 2576Example:
2512 2577
2513 static void io_cb (ev::io &w, int revents) { } 2578 static void io_cb (ev::io &w, int revents) { }
2514 iow.set <io_cb> (); 2579 iow.set <io_cb> ();
2515 2580
2516=item w->set (struct ev_loop *) 2581=item w->set (struct ev_loop *)
2517 2582
2518Associates a different C<struct ev_loop> with this watcher. You can only 2583Associates a different C<struct ev_loop> with this watcher. You can only
2519do this when the watcher is inactive (and not pending either). 2584do this when the watcher is inactive (and not pending either).
2520 2585
2521=item w->set ([args]) 2586=item w->set ([arguments])
2522 2587
2523Basically the same as C<ev_TYPE_set>, with the same args. Must be 2588Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2524called at least once. Unlike the C counterpart, an active watcher gets 2589called at least once. Unlike the C counterpart, an active watcher gets
2525automatically stopped and restarted when reconfiguring it with this 2590automatically stopped and restarted when reconfiguring it with this
2526method. 2591method.
2527 2592
2528=item w->start () 2593=item w->start ()
2552=back 2617=back
2553 2618
2554Example: Define a class with an IO and idle watcher, start one of them in 2619Example: Define a class with an IO and idle watcher, start one of them in
2555the constructor. 2620the constructor.
2556 2621
2557 class myclass 2622 class myclass
2558 { 2623 {
2559 ev::io io; void io_cb (ev::io &w, int revents); 2624 ev::io io; void io_cb (ev::io &w, int revents);
2560 ev:idle idle void idle_cb (ev::idle &w, int revents); 2625 ev:idle idle void idle_cb (ev::idle &w, int revents);
2561 2626
2562 myclass (int fd) 2627 myclass (int fd)
2563 { 2628 {
2564 io .set <myclass, &myclass::io_cb > (this); 2629 io .set <myclass, &myclass::io_cb > (this);
2565 idle.set <myclass, &myclass::idle_cb> (this); 2630 idle.set <myclass, &myclass::idle_cb> (this);
2566 2631
2567 io.start (fd, ev::READ); 2632 io.start (fd, ev::READ);
2568 } 2633 }
2569 }; 2634 };
2570 2635
2571 2636
2572=head1 OTHER LANGUAGE BINDINGS 2637=head1 OTHER LANGUAGE BINDINGS
2573 2638
2574Libev does not offer other language bindings itself, but bindings for a 2639Libev does not offer other language bindings itself, but bindings for a
2575numbe rof languages exist in the form of third-party packages. If you know 2640number of languages exist in the form of third-party packages. If you know
2576any interesting language binding in addition to the ones listed here, drop 2641any interesting language binding in addition to the ones listed here, drop
2577me a note. 2642me a note.
2578 2643
2579=over 4 2644=over 4
2580 2645
2584libev. EV is developed together with libev. Apart from the EV core module, 2649libev. EV is developed together with libev. Apart from the EV core module,
2585there are additional modules that implement libev-compatible interfaces 2650there are additional modules that implement libev-compatible interfaces
2586to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the 2651to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
2587C<libglib> event core (C<Glib::EV> and C<EV::Glib>). 2652C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
2588 2653
2589It can be found and installed via CPAN, its homepage is found at 2654It can be found and installed via CPAN, its homepage is at
2590L<http://software.schmorp.de/pkg/EV>. 2655L<http://software.schmorp.de/pkg/EV>.
2591 2656
2657=item Python
2658
2659Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2660seems to be quite complete and well-documented. Note, however, that the
2661patch they require for libev is outright dangerous as it breaks the ABI
2662for everybody else, and therefore, should never be applied in an installed
2663libev (if python requires an incompatible ABI then it needs to embed
2664libev).
2665
2592=item Ruby 2666=item Ruby
2593 2667
2594Tony Arcieri has written a ruby extension that offers access to a subset 2668Tony Arcieri has written a ruby extension that offers access to a subset
2595of the libev API and adds filehandle abstractions, asynchronous DNS and 2669of the libev API and adds file handle abstractions, asynchronous DNS and
2596more on top of it. It can be found via gem servers. Its homepage is at 2670more on top of it. It can be found via gem servers. Its homepage is at
2597L<http://rev.rubyforge.org/>. 2671L<http://rev.rubyforge.org/>.
2598 2672
2599=item D 2673=item D
2600 2674
2601Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to 2675Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2602be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. 2676be found at L<http://proj.llucax.com.ar/wiki/evd>.
2603 2677
2604=back 2678=back
2605 2679
2606 2680
2607=head1 MACRO MAGIC 2681=head1 MACRO MAGIC
2608 2682
2609Libev can be compiled with a variety of options, the most fundamantal 2683Libev can be compiled with a variety of options, the most fundamental
2610of which is C<EV_MULTIPLICITY>. This option determines whether (most) 2684of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611functions and callbacks have an initial C<struct ev_loop *> argument. 2685functions and callbacks have an initial C<struct ev_loop *> argument.
2612 2686
2613To make it easier to write programs that cope with either variant, the 2687To make it easier to write programs that cope with either variant, the
2614following macros are defined: 2688following macros are defined:
2619 2693
2620This provides the loop I<argument> for functions, if one is required ("ev 2694This provides the loop I<argument> for functions, if one is required ("ev
2621loop argument"). The C<EV_A> form is used when this is the sole argument, 2695loop argument"). The C<EV_A> form is used when this is the sole argument,
2622C<EV_A_> is used when other arguments are following. Example: 2696C<EV_A_> is used when other arguments are following. Example:
2623 2697
2624 ev_unref (EV_A); 2698 ev_unref (EV_A);
2625 ev_timer_add (EV_A_ watcher); 2699 ev_timer_add (EV_A_ watcher);
2626 ev_loop (EV_A_ 0); 2700 ev_loop (EV_A_ 0);
2627 2701
2628It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, 2702It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629which is often provided by the following macro. 2703which is often provided by the following macro.
2630 2704
2631=item C<EV_P>, C<EV_P_> 2705=item C<EV_P>, C<EV_P_>
2632 2706
2633This provides the loop I<parameter> for functions, if one is required ("ev 2707This provides the loop I<parameter> for functions, if one is required ("ev
2634loop parameter"). The C<EV_P> form is used when this is the sole parameter, 2708loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2635C<EV_P_> is used when other parameters are following. Example: 2709C<EV_P_> is used when other parameters are following. Example:
2636 2710
2637 // this is how ev_unref is being declared 2711 // this is how ev_unref is being declared
2638 static void ev_unref (EV_P); 2712 static void ev_unref (EV_P);
2639 2713
2640 // this is how you can declare your typical callback 2714 // this is how you can declare your typical callback
2641 static void cb (EV_P_ ev_timer *w, int revents) 2715 static void cb (EV_P_ ev_timer *w, int revents)
2642 2716
2643It declares a parameter C<loop> of type C<struct ev_loop *>, quite 2717It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644suitable for use with C<EV_A>. 2718suitable for use with C<EV_A>.
2645 2719
2646=item C<EV_DEFAULT>, C<EV_DEFAULT_> 2720=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2662 2736
2663Example: Declare and initialise a check watcher, utilising the above 2737Example: Declare and initialise a check watcher, utilising the above
2664macros so it will work regardless of whether multiple loops are supported 2738macros so it will work regardless of whether multiple loops are supported
2665or not. 2739or not.
2666 2740
2667 static void 2741 static void
2668 check_cb (EV_P_ ev_timer *w, int revents) 2742 check_cb (EV_P_ ev_timer *w, int revents)
2669 { 2743 {
2670 ev_check_stop (EV_A_ w); 2744 ev_check_stop (EV_A_ w);
2671 } 2745 }
2672 2746
2673 ev_check check; 2747 ev_check check;
2674 ev_check_init (&check, check_cb); 2748 ev_check_init (&check, check_cb);
2675 ev_check_start (EV_DEFAULT_ &check); 2749 ev_check_start (EV_DEFAULT_ &check);
2676 ev_loop (EV_DEFAULT_ 0); 2750 ev_loop (EV_DEFAULT_ 0);
2677 2751
2678=head1 EMBEDDING 2752=head1 EMBEDDING
2679 2753
2680Libev can (and often is) directly embedded into host 2754Libev can (and often is) directly embedded into host
2681applications. Examples of applications that embed it include the Deliantra 2755applications. Examples of applications that embed it include the Deliantra
2688libev somewhere in your source tree). 2762libev somewhere in your source tree).
2689 2763
2690=head2 FILESETS 2764=head2 FILESETS
2691 2765
2692Depending on what features you need you need to include one or more sets of files 2766Depending on what features you need you need to include one or more sets of files
2693in your app. 2767in your application.
2694 2768
2695=head3 CORE EVENT LOOP 2769=head3 CORE EVENT LOOP
2696 2770
2697To include only the libev core (all the C<ev_*> functions), with manual 2771To include only the libev core (all the C<ev_*> functions), with manual
2698configuration (no autoconf): 2772configuration (no autoconf):
2699 2773
2700 #define EV_STANDALONE 1 2774 #define EV_STANDALONE 1
2701 #include "ev.c" 2775 #include "ev.c"
2702 2776
2703This will automatically include F<ev.h>, too, and should be done in a 2777This will automatically include F<ev.h>, too, and should be done in a
2704single C source file only to provide the function implementations. To use 2778single C source file only to provide the function implementations. To use
2705it, do the same for F<ev.h> in all files wishing to use this API (best 2779it, do the same for F<ev.h> in all files wishing to use this API (best
2706done by writing a wrapper around F<ev.h> that you can include instead and 2780done by writing a wrapper around F<ev.h> that you can include instead and
2707where you can put other configuration options): 2781where you can put other configuration options):
2708 2782
2709 #define EV_STANDALONE 1 2783 #define EV_STANDALONE 1
2710 #include "ev.h" 2784 #include "ev.h"
2711 2785
2712Both header files and implementation files can be compiled with a C++ 2786Both header files and implementation files can be compiled with a C++
2713compiler (at least, thats a stated goal, and breakage will be treated 2787compiler (at least, thats a stated goal, and breakage will be treated
2714as a bug). 2788as a bug).
2715 2789
2716You need the following files in your source tree, or in a directory 2790You need the following files in your source tree, or in a directory
2717in your include path (e.g. in libev/ when using -Ilibev): 2791in your include path (e.g. in libev/ when using -Ilibev):
2718 2792
2719 ev.h 2793 ev.h
2720 ev.c 2794 ev.c
2721 ev_vars.h 2795 ev_vars.h
2722 ev_wrap.h 2796 ev_wrap.h
2723 2797
2724 ev_win32.c required on win32 platforms only 2798 ev_win32.c required on win32 platforms only
2725 2799
2726 ev_select.c only when select backend is enabled (which is enabled by default) 2800 ev_select.c only when select backend is enabled (which is enabled by default)
2727 ev_poll.c only when poll backend is enabled (disabled by default) 2801 ev_poll.c only when poll backend is enabled (disabled by default)
2728 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2802 ev_epoll.c only when the epoll backend is enabled (disabled by default)
2729 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2803 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2730 ev_port.c only when the solaris port backend is enabled (disabled by default) 2804 ev_port.c only when the solaris port backend is enabled (disabled by default)
2731 2805
2732F<ev.c> includes the backend files directly when enabled, so you only need 2806F<ev.c> includes the backend files directly when enabled, so you only need
2733to compile this single file. 2807to compile this single file.
2734 2808
2735=head3 LIBEVENT COMPATIBILITY API 2809=head3 LIBEVENT COMPATIBILITY API
2736 2810
2737To include the libevent compatibility API, also include: 2811To include the libevent compatibility API, also include:
2738 2812
2739 #include "event.c" 2813 #include "event.c"
2740 2814
2741in the file including F<ev.c>, and: 2815in the file including F<ev.c>, and:
2742 2816
2743 #include "event.h" 2817 #include "event.h"
2744 2818
2745in the files that want to use the libevent API. This also includes F<ev.h>. 2819in the files that want to use the libevent API. This also includes F<ev.h>.
2746 2820
2747You need the following additional files for this: 2821You need the following additional files for this:
2748 2822
2749 event.h 2823 event.h
2750 event.c 2824 event.c
2751 2825
2752=head3 AUTOCONF SUPPORT 2826=head3 AUTOCONF SUPPORT
2753 2827
2754Instead of using C<EV_STANDALONE=1> and providing your config in 2828Instead of using C<EV_STANDALONE=1> and providing your configuration in
2755whatever way you want, you can also C<m4_include([libev.m4])> in your 2829whatever way you want, you can also C<m4_include([libev.m4])> in your
2756F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then 2830F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757include F<config.h> and configure itself accordingly. 2831include F<config.h> and configure itself accordingly.
2758 2832
2759For this of course you need the m4 file: 2833For this of course you need the m4 file:
2760 2834
2761 libev.m4 2835 libev.m4
2762 2836
2763=head2 PREPROCESSOR SYMBOLS/MACROS 2837=head2 PREPROCESSOR SYMBOLS/MACROS
2764 2838
2765Libev can be configured via a variety of preprocessor symbols you have to 2839Libev can be configured via a variety of preprocessor symbols you have to
2766define before including any of its files. The default in the absense of 2840define before including any of its files. The default in the absence of
2767autoconf is noted for every option. 2841autoconf is noted for every option.
2768 2842
2769=over 4 2843=over 4
2770 2844
2771=item EV_STANDALONE 2845=item EV_STANDALONE
2777F<event.h> that are not directly supported by the libev core alone. 2851F<event.h> that are not directly supported by the libev core alone.
2778 2852
2779=item EV_USE_MONOTONIC 2853=item EV_USE_MONOTONIC
2780 2854
2781If defined to be C<1>, libev will try to detect the availability of the 2855If defined to be C<1>, libev will try to detect the availability of the
2782monotonic clock option at both compiletime and runtime. Otherwise no use 2856monotonic clock option at both compile time and runtime. Otherwise no use
2783of the monotonic clock option will be attempted. If you enable this, you 2857of the monotonic clock option will be attempted. If you enable this, you
2784usually have to link against librt or something similar. Enabling it when 2858usually have to link against librt or something similar. Enabling it when
2785the functionality isn't available is safe, though, although you have 2859the functionality isn't available is safe, though, although you have
2786to make sure you link against any libraries where the C<clock_gettime> 2860to make sure you link against any libraries where the C<clock_gettime>
2787function is hiding in (often F<-lrt>). 2861function is hiding in (often F<-lrt>).
2788 2862
2789=item EV_USE_REALTIME 2863=item EV_USE_REALTIME
2790 2864
2791If defined to be C<1>, libev will try to detect the availability of the 2865If defined to be C<1>, libev will try to detect the availability of the
2792realtime clock option at compiletime (and assume its availability at 2866real-time clock option at compile time (and assume its availability at
2793runtime if successful). Otherwise no use of the realtime clock option will 2867runtime if successful). Otherwise no use of the real-time clock option will
2794be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2868be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2795(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the 2869(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2796note about libraries in the description of C<EV_USE_MONOTONIC>, though. 2870note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2797 2871
2798=item EV_USE_NANOSLEEP 2872=item EV_USE_NANOSLEEP
28092.7 or newer, otherwise disabled. 28832.7 or newer, otherwise disabled.
2810 2884
2811=item EV_USE_SELECT 2885=item EV_USE_SELECT
2812 2886
2813If undefined or defined to be C<1>, libev will compile in support for the 2887If undefined or defined to be C<1>, libev will compile in support for the
2814C<select>(2) backend. No attempt at autodetection will be done: if no 2888C<select>(2) backend. No attempt at auto-detection will be done: if no
2815other method takes over, select will be it. Otherwise the select backend 2889other method takes over, select will be it. Otherwise the select backend
2816will not be compiled in. 2890will not be compiled in.
2817 2891
2818=item EV_SELECT_USE_FD_SET 2892=item EV_SELECT_USE_FD_SET
2819 2893
2820If defined to C<1>, then the select backend will use the system C<fd_set> 2894If defined to C<1>, then the select backend will use the system C<fd_set>
2821structure. This is useful if libev doesn't compile due to a missing 2895structure. This is useful if libev doesn't compile due to a missing
2822C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on 2896C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2823exotic systems. This usually limits the range of file descriptors to some 2897exotic systems. This usually limits the range of file descriptors to some
2824low limit such as 1024 or might have other limitations (winsocket only 2898low limit such as 1024 or might have other limitations (winsocket only
2825allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might 2899allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2826influence the size of the C<fd_set> used. 2900influence the size of the C<fd_set> used.
2827 2901
2876otherwise another method will be used as fallback. This is the preferred 2950otherwise another method will be used as fallback. This is the preferred
2877backend for Solaris 10 systems. 2951backend for Solaris 10 systems.
2878 2952
2879=item EV_USE_DEVPOLL 2953=item EV_USE_DEVPOLL
2880 2954
2881reserved for future expansion, works like the USE symbols above. 2955Reserved for future expansion, works like the USE symbols above.
2882 2956
2883=item EV_USE_INOTIFY 2957=item EV_USE_INOTIFY
2884 2958
2885If defined to be C<1>, libev will compile in support for the Linux inotify 2959If defined to be C<1>, libev will compile in support for the Linux inotify
2886interface to speed up C<ev_stat> watchers. Its actual availability will 2960interface to speed up C<ev_stat> watchers. Its actual availability will
2893access is atomic with respect to other threads or signal contexts. No such 2967access is atomic with respect to other threads or signal contexts. No such
2894type is easily found in the C language, so you can provide your own type 2968type is easily found in the C language, so you can provide your own type
2895that you know is safe for your purposes. It is used both for signal handler "locking" 2969that you know is safe for your purposes. It is used both for signal handler "locking"
2896as well as for signal and thread safety in C<ev_async> watchers. 2970as well as for signal and thread safety in C<ev_async> watchers.
2897 2971
2898In the absense of this define, libev will use C<sig_atomic_t volatile> 2972In the absence of this define, libev will use C<sig_atomic_t volatile>
2899(from F<signal.h>), which is usually good enough on most platforms. 2973(from F<signal.h>), which is usually good enough on most platforms.
2900 2974
2901=item EV_H 2975=item EV_H
2902 2976
2903The name of the F<ev.h> header file used to include it. The default if 2977The name of the F<ev.h> header file used to include it. The default if
2942When doing priority-based operations, libev usually has to linearly search 3016When doing priority-based operations, libev usually has to linearly search
2943all the priorities, so having many of them (hundreds) uses a lot of space 3017all the priorities, so having many of them (hundreds) uses a lot of space
2944and time, so using the defaults of five priorities (-2 .. +2) is usually 3018and time, so using the defaults of five priorities (-2 .. +2) is usually
2945fine. 3019fine.
2946 3020
2947If your embedding app does not need any priorities, defining these both to 3021If your embedding application does not need any priorities, defining these both to
2948C<0> will save some memory and cpu. 3022C<0> will save some memory and CPU.
2949 3023
2950=item EV_PERIODIC_ENABLE 3024=item EV_PERIODIC_ENABLE
2951 3025
2952If undefined or defined to be C<1>, then periodic timers are supported. If 3026If undefined or defined to be C<1>, then periodic timers are supported. If
2953defined to be C<0>, then they are not. Disabling them saves a few kB of 3027defined to be C<0>, then they are not. Disabling them saves a few kB of
2981 3055
2982=item EV_MINIMAL 3056=item EV_MINIMAL
2983 3057
2984If you need to shave off some kilobytes of code at the expense of some 3058If you need to shave off some kilobytes of code at the expense of some
2985speed, define this symbol to C<1>. Currently this is used to override some 3059speed, define this symbol to C<1>. Currently this is used to override some
2986inlining decisions, saves roughly 30% codesize of amd64. It also selects a 3060inlining decisions, saves roughly 30% code size on amd64. It also selects a
2987much smaller 2-heap for timer management over the default 4-heap. 3061much smaller 2-heap for timer management over the default 4-heap.
2988 3062
2989=item EV_PID_HASHSIZE 3063=item EV_PID_HASHSIZE
2990 3064
2991C<ev_child> watchers use a small hash table to distribute workload by 3065C<ev_child> watchers use a small hash table to distribute workload by
2999inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 3073inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
3000usually more than enough. If you need to manage thousands of C<ev_stat> 3074usually more than enough. If you need to manage thousands of C<ev_stat>
3001watchers you might want to increase this value (I<must> be a power of 3075watchers you might want to increase this value (I<must> be a power of
3002two). 3076two).
3003 3077
3078=item EV_USE_4HEAP
3079
3080Heaps are not very cache-efficient. To improve the cache-efficiency of the
3081timer and periodics heap, libev uses a 4-heap when this symbol is defined
3082to C<1>. The 4-heap uses more complicated (longer) code but has
3083noticeably faster performance with many (thousands) of watchers.
3084
3085The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3086(disabled).
3087
3088=item EV_HEAP_CACHE_AT
3089
3090Heaps are not very cache-efficient. To improve the cache-efficiency of the
3091timer and periodics heap, libev can cache the timestamp (I<at>) within
3092the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3093which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3094but avoids random read accesses on heap changes. This improves performance
3095noticeably with with many (hundreds) of watchers.
3096
3097The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3098(disabled).
3099
3100=item EV_VERIFY
3101
3102Controls how much internal verification (see C<ev_loop_verify ()>) will
3103be done: If set to C<0>, no internal verification code will be compiled
3104in. If set to C<1>, then verification code will be compiled in, but not
3105called. If set to C<2>, then the internal verification code will be
3106called once per loop, which can slow down libev. If set to C<3>, then the
3107verification code will be called very frequently, which will slow down
3108libev considerably.
3109
3110The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3111C<0.>
3112
3004=item EV_COMMON 3113=item EV_COMMON
3005 3114
3006By default, all watchers have a C<void *data> member. By redefining 3115By default, all watchers have a C<void *data> member. By redefining
3007this macro to a something else you can include more and other types of 3116this macro to a something else you can include more and other types of
3008members. You have to define it each time you include one of the files, 3117members. You have to define it each time you include one of the files,
3009though, and it must be identical each time. 3118though, and it must be identical each time.
3010 3119
3011For example, the perl EV module uses something like this: 3120For example, the perl EV module uses something like this:
3012 3121
3013 #define EV_COMMON \ 3122 #define EV_COMMON \
3014 SV *self; /* contains this struct */ \ 3123 SV *self; /* contains this struct */ \
3015 SV *cb_sv, *fh /* note no trailing ";" */ 3124 SV *cb_sv, *fh /* note no trailing ";" */
3016 3125
3017=item EV_CB_DECLARE (type) 3126=item EV_CB_DECLARE (type)
3018 3127
3019=item EV_CB_INVOKE (watcher, revents) 3128=item EV_CB_INVOKE (watcher, revents)
3020 3129
3027avoid the C<struct ev_loop *> as first argument in all cases, or to use 3136avoid the C<struct ev_loop *> as first argument in all cases, or to use
3028method calls instead of plain function calls in C++. 3137method calls instead of plain function calls in C++.
3029 3138
3030=head2 EXPORTED API SYMBOLS 3139=head2 EXPORTED API SYMBOLS
3031 3140
3032If you need to re-export the API (e.g. via a dll) and you need a list of 3141If you need to re-export the API (e.g. via a DLL) and you need a list of
3033exported symbols, you can use the provided F<Symbol.*> files which list 3142exported symbols, you can use the provided F<Symbol.*> files which list
3034all public symbols, one per line: 3143all public symbols, one per line:
3035 3144
3036 Symbols.ev for libev proper 3145 Symbols.ev for libev proper
3037 Symbols.event for the libevent emulation 3146 Symbols.event for the libevent emulation
3038 3147
3039This can also be used to rename all public symbols to avoid clashes with 3148This can also be used to rename all public symbols to avoid clashes with
3040multiple versions of libev linked together (which is obviously bad in 3149multiple versions of libev linked together (which is obviously bad in
3041itself, but sometimes it is inconvinient to avoid this). 3150itself, but sometimes it is inconvenient to avoid this).
3042 3151
3043A sed command like this will create wrapper C<#define>'s that you need to 3152A sed command like this will create wrapper C<#define>'s that you need to
3044include before including F<ev.h>: 3153include before including F<ev.h>:
3045 3154
3046 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h 3155 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
3063file. 3172file.
3064 3173
3065The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 3174The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3066that everybody includes and which overrides some configure choices: 3175that everybody includes and which overrides some configure choices:
3067 3176
3068 #define EV_MINIMAL 1 3177 #define EV_MINIMAL 1
3069 #define EV_USE_POLL 0 3178 #define EV_USE_POLL 0
3070 #define EV_MULTIPLICITY 0 3179 #define EV_MULTIPLICITY 0
3071 #define EV_PERIODIC_ENABLE 0 3180 #define EV_PERIODIC_ENABLE 0
3072 #define EV_STAT_ENABLE 0 3181 #define EV_STAT_ENABLE 0
3073 #define EV_FORK_ENABLE 0 3182 #define EV_FORK_ENABLE 0
3074 #define EV_CONFIG_H <config.h> 3183 #define EV_CONFIG_H <config.h>
3075 #define EV_MINPRI 0 3184 #define EV_MINPRI 0
3076 #define EV_MAXPRI 0 3185 #define EV_MAXPRI 0
3077 3186
3078 #include "ev++.h" 3187 #include "ev++.h"
3079 3188
3080And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 3189And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3081 3190
3082 #include "ev_cpp.h" 3191 #include "ev_cpp.h"
3083 #include "ev.c" 3192 #include "ev.c"
3084 3193
3085 3194
3086=head1 THREADS AND COROUTINES 3195=head1 THREADS AND COROUTINES
3087 3196
3088=head2 THREADS 3197=head2 THREADS
3089 3198
3090Libev itself is completely threadsafe, but it uses no locking. This 3199Libev itself is completely thread-safe, but it uses no locking. This
3091means that you can use as many loops as you want in parallel, as long as 3200means that you can use as many loops as you want in parallel, as long as
3092only one thread ever calls into one libev function with the same loop 3201only one thread ever calls into one libev function with the same loop
3093parameter. 3202parameter.
3094 3203
3095Or put differently: calls with different loop parameters can be done in 3204Or put differently: calls with different loop parameters can be done in
3096parallel from multiple threads, calls with the same loop parameter must be 3205parallel from multiple threads, calls with the same loop parameter must be
3097done serially (but can be done from different threads, as long as only one 3206done serially (but can be done from different threads, as long as only one
3098thread ever is inside a call at any point in time, e.g. by using a mutex 3207thread ever is inside a call at any point in time, e.g. by using a mutex
3099per loop). 3208per loop).
3100 3209
3101If you want to know which design is best for your problem, then I cannot 3210If you want to know which design (one loop, locking, or multiple loops
3102help you but by giving some generic advice: 3211without or something else still) is best for your problem, then I cannot
3212help you. I can give some generic advice however:
3103 3213
3104=over 4 3214=over 4
3105 3215
3106=item * most applications have a main thread: use the default libev loop 3216=item * most applications have a main thread: use the default libev loop
3107in that thread, or create a seperate thread running only the default loop. 3217in that thread, or create a separate thread running only the default loop.
3108 3218
3109This helps integrating other libraries or software modules that use libev 3219This helps integrating other libraries or software modules that use libev
3110themselves and don't care/know about threading. 3220themselves and don't care/know about threading.
3111 3221
3112=item * one loop per thread is usually a good model. 3222=item * one loop per thread is usually a good model.
3113 3223
3114Doing this is almost never wrong, sometimes a better-performance model 3224Doing this is almost never wrong, sometimes a better-performance model
3115exists, but it is always a good start. 3225exists, but it is always a good start.
3116 3226
3117=item * other models exist, such as the leader/follower pattern, where one 3227=item * other models exist, such as the leader/follower pattern, where one
3118loop is handed through multiple threads in a kind of round-robbin fashion. 3228loop is handed through multiple threads in a kind of round-robin fashion.
3119 3229
3120Chosing a model is hard - look around, learn, know that usually you cna do 3230Choosing a model is hard - look around, learn, know that usually you can do
3121better than you currently do :-) 3231better than you currently do :-)
3122 3232
3123=item * often you need to talk to some other thread which blocks in the 3233=item * often you need to talk to some other thread which blocks in the
3124event loop - C<ev_async> watchers can be used to wake them up from other 3234event loop - C<ev_async> watchers can be used to wake them up from other
3125threads safely (or from signal contexts...). 3235threads safely (or from signal contexts...).
3126 3236
3127=back 3237=back
3128 3238
3129=head2 COROUTINES 3239=head2 COROUTINES
3130 3240
3131Libev is much more accomodating to coroutines ("cooperative threads"): 3241Libev is much more accommodating to coroutines ("cooperative threads"):
3132libev fully supports nesting calls to it's functions from different 3242libev fully supports nesting calls to it's functions from different
3133coroutines (e.g. you can call C<ev_loop> on the same loop from two 3243coroutines (e.g. you can call C<ev_loop> on the same loop from two
3134different coroutines and switch freely between both coroutines running the 3244different coroutines and switch freely between both coroutines running the
3135loop, as long as you don't confuse yourself). The only exception is that 3245loop, as long as you don't confuse yourself). The only exception is that
3136you must not do this from C<ev_periodic> reschedule callbacks. 3246you must not do this from C<ev_periodic> reschedule callbacks.
3184 3294
3185=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 3295=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3186 3296
3187A change means an I/O watcher gets started or stopped, which requires 3297A change means an I/O watcher gets started or stopped, which requires
3188libev to recalculate its status (and possibly tell the kernel, depending 3298libev to recalculate its status (and possibly tell the kernel, depending
3189on backend and wether C<ev_io_set> was used). 3299on backend and whether C<ev_io_set> was used).
3190 3300
3191=item Activating one watcher (putting it into the pending state): O(1) 3301=item Activating one watcher (putting it into the pending state): O(1)
3192 3302
3193=item Priority handling: O(number_of_priorities) 3303=item Priority handling: O(number_of_priorities)
3194 3304
3201 3311
3202=item Processing ev_async_send: O(number_of_async_watchers) 3312=item Processing ev_async_send: O(number_of_async_watchers)
3203 3313
3204=item Processing signals: O(max_signal_number) 3314=item Processing signals: O(max_signal_number)
3205 3315
3206Sending involves a syscall I<iff> there were no other C<ev_async_send> 3316Sending involves a system call I<iff> there were no other C<ev_async_send>
3207calls in the current loop iteration. Checking for async and signal events 3317calls in the current loop iteration. Checking for async and signal events
3208involves iterating over all running async watchers or all signal numbers. 3318involves iterating over all running async watchers or all signal numbers.
3209 3319
3210=back 3320=back
3211 3321
3212 3322
3213=head1 Win32 platform limitations and workarounds 3323=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3214 3324
3215Win32 doesn't support any of the standards (e.g. POSIX) that libev 3325Win32 doesn't support any of the standards (e.g. POSIX) that libev
3216requires, and its I/O model is fundamentally incompatible with the POSIX 3326requires, and its I/O model is fundamentally incompatible with the POSIX
3217model. Libev still offers limited functionality on this platform in 3327model. Libev still offers limited functionality on this platform in
3218the form of the C<EVBACKEND_SELECT> backend, and only supports socket 3328the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3225way (note also that glib is the slowest event library known to man). 3335way (note also that glib is the slowest event library known to man).
3226 3336
3227There is no supported compilation method available on windows except 3337There is no supported compilation method available on windows except
3228embedding it into other applications. 3338embedding it into other applications.
3229 3339
3340Not a libev limitation but worth mentioning: windows apparently doesn't
3341accept large writes: instead of resulting in a partial write, windows will
3342either accept everything or return C<ENOBUFS> if the buffer is too large,
3343so make sure you only write small amounts into your sockets (less than a
3344megabyte seems safe, but thsi apparently depends on the amount of memory
3345available).
3346
3230Due to the many, low, and arbitrary limits on the win32 platform and 3347Due to the many, low, and arbitrary limits on the win32 platform and
3231the abysmal performance of winsockets, using a large number of sockets 3348the abysmal performance of winsockets, using a large number of sockets
3232is not recommended (and not reasonable). If your program needs to use 3349is not recommended (and not reasonable). If your program needs to use
3233more than a hundred or so sockets, then likely it needs to use a totally 3350more than a hundred or so sockets, then likely it needs to use a totally
3234different implementation for windows, as libev offers the POSIX readyness 3351different implementation for windows, as libev offers the POSIX readiness
3235notification model, which cannot be implemented efficiently on windows 3352notification model, which cannot be implemented efficiently on windows
3236(microsoft monopoly games). 3353(Microsoft monopoly games).
3354
3355A typical way to use libev under windows is to embed it (see the embedding
3356section for details) and use the following F<evwrap.h> header file instead
3357of F<ev.h>:
3358
3359 #define EV_STANDALONE /* keeps ev from requiring config.h */
3360 #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3361
3362 #include "ev.h"
3363
3364And compile the following F<evwrap.c> file into your project (make sure
3365you do I<not> compile the F<ev.c> or any other embedded soruce files!):
3366
3367 #include "evwrap.h"
3368 #include "ev.c"
3237 3369
3238=over 4 3370=over 4
3239 3371
3240=item The winsocket select function 3372=item The winsocket select function
3241 3373
3242The winsocket C<select> function doesn't follow POSIX in that it requires 3374The winsocket C<select> function doesn't follow POSIX in that it
3243socket I<handles> and not socket I<file descriptors>. This makes select 3375requires socket I<handles> and not socket I<file descriptors> (it is
3244very inefficient, and also requires a mapping from file descriptors 3376also extremely buggy). This makes select very inefficient, and also
3245to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, 3377requires a mapping from file descriptors to socket handles (the Microsoft
3246C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor 3378C runtime provides the function C<_open_osfhandle> for this). See the
3247symbols for more info. 3379discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3380C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3248 3381
3249The configuration for a "naked" win32 using the microsoft runtime 3382The configuration for a "naked" win32 using the Microsoft runtime
3250libraries and raw winsocket select is: 3383libraries and raw winsocket select is:
3251 3384
3252 #define EV_USE_SELECT 1 3385 #define EV_USE_SELECT 1
3253 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ 3386 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3254 3387
3255Note that winsockets handling of fd sets is O(n), so you can easily get a 3388Note that winsockets handling of fd sets is O(n), so you can easily get a
3256complexity in the O(n²) range when using win32. 3389complexity in the O(n²) range when using win32.
3257 3390
3258=item Limited number of file descriptors 3391=item Limited number of file descriptors
3259 3392
3260Windows has numerous arbitrary (and low) limits on things. 3393Windows has numerous arbitrary (and low) limits on things.
3261 3394
3262Early versions of winsocket's select only supported waiting for a maximum 3395Early versions of winsocket's select only supported waiting for a maximum
3263of C<64> handles (probably owning to the fact that all windows kernels 3396of C<64> handles (probably owning to the fact that all windows kernels
3264can only wait for C<64> things at the same time internally; microsoft 3397can only wait for C<64> things at the same time internally; Microsoft
3265recommends spawning a chain of threads and wait for 63 handles and the 3398recommends spawning a chain of threads and wait for 63 handles and the
3266previous thread in each. Great). 3399previous thread in each. Great).
3267 3400
3268Newer versions support more handles, but you need to define C<FD_SETSIZE> 3401Newer versions support more handles, but you need to define C<FD_SETSIZE>
3269to some high number (e.g. C<2048>) before compiling the winsocket select 3402to some high number (e.g. C<2048>) before compiling the winsocket select
3270call (which might be in libev or elsewhere, for example, perl does its own 3403call (which might be in libev or elsewhere, for example, perl does its own
3271select emulation on windows). 3404select emulation on windows).
3272 3405
3273Another limit is the number of file descriptors in the microsoft runtime 3406Another limit is the number of file descriptors in the Microsoft runtime
3274libraries, which by default is C<64> (there must be a hidden I<64> fetish 3407libraries, which by default is C<64> (there must be a hidden I<64> fetish
3275or something like this inside microsoft). You can increase this by calling 3408or something like this inside Microsoft). You can increase this by calling
3276C<_setmaxstdio>, which can increase this limit to C<2048> (another 3409C<_setmaxstdio>, which can increase this limit to C<2048> (another
3277arbitrary limit), but is broken in many versions of the microsoft runtime 3410arbitrary limit), but is broken in many versions of the Microsoft runtime
3278libraries. 3411libraries.
3279 3412
3280This might get you to about C<512> or C<2048> sockets (depending on 3413This might get you to about C<512> or C<2048> sockets (depending on
3281windows version and/or the phase of the moon). To get more, you need to 3414windows version and/or the phase of the moon). To get more, you need to
3282wrap all I/O functions and provide your own fd management, but the cost of 3415wrap all I/O functions and provide your own fd management, but the cost of
3289 3422
3290In addition to a working ISO-C implementation, libev relies on a few 3423In addition to a working ISO-C implementation, libev relies on a few
3291additional extensions: 3424additional extensions:
3292 3425
3293=over 4 3426=over 4
3427
3428=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3429calling conventions regardless of C<ev_watcher_type *>.
3430
3431Libev assumes not only that all watcher pointers have the same internal
3432structure (guaranteed by POSIX but not by ISO C for example), but it also
3433assumes that the same (machine) code can be used to call any watcher
3434callback: The watcher callbacks have different type signatures, but libev
3435calls them using an C<ev_watcher *> internally.
3294 3436
3295=item C<sig_atomic_t volatile> must be thread-atomic as well 3437=item C<sig_atomic_t volatile> must be thread-atomic as well
3296 3438
3297The type C<sig_atomic_t volatile> (or whatever is defined as 3439The type C<sig_atomic_t volatile> (or whatever is defined as
3298C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different 3440C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
3330=back 3472=back
3331 3473
3332If you know of other additional requirements drop me a note. 3474If you know of other additional requirements drop me a note.
3333 3475
3334 3476
3477=head1 COMPILER WARNINGS
3478
3479Depending on your compiler and compiler settings, you might get no or a
3480lot of warnings when compiling libev code. Some people are apparently
3481scared by this.
3482
3483However, these are unavoidable for many reasons. For one, each compiler
3484has different warnings, and each user has different tastes regarding
3485warning options. "Warn-free" code therefore cannot be a goal except when
3486targeting a specific compiler and compiler-version.
3487
3488Another reason is that some compiler warnings require elaborate
3489workarounds, or other changes to the code that make it less clear and less
3490maintainable.
3491
3492And of course, some compiler warnings are just plain stupid, or simply
3493wrong (because they don't actually warn about the condition their message
3494seems to warn about).
3495
3496While libev is written to generate as few warnings as possible,
3497"warn-free" code is not a goal, and it is recommended not to build libev
3498with any compiler warnings enabled unless you are prepared to cope with
3499them (e.g. by ignoring them). Remember that warnings are just that:
3500warnings, not errors, or proof of bugs.
3501
3502
3503=head1 VALGRIND
3504
3505Valgrind has a special section here because it is a popular tool that is
3506highly useful, but valgrind reports are very hard to interpret.
3507
3508If you think you found a bug (memory leak, uninitialised data access etc.)
3509in libev, then check twice: If valgrind reports something like:
3510
3511 ==2274== definitely lost: 0 bytes in 0 blocks.
3512 ==2274== possibly lost: 0 bytes in 0 blocks.
3513 ==2274== still reachable: 256 bytes in 1 blocks.
3514
3515Then there is no memory leak. Similarly, under some circumstances,
3516valgrind might report kernel bugs as if it were a bug in libev, or it
3517might be confused (it is a very good tool, but only a tool).
3518
3519If you are unsure about something, feel free to contact the mailing list
3520with the full valgrind report and an explanation on why you think this is
3521a bug in libev. However, don't be annoyed when you get a brisk "this is
3522no bug" answer and take the chance of learning how to interpret valgrind
3523properly.
3524
3525If you need, for some reason, empty reports from valgrind for your project
3526I suggest using suppression lists.
3527
3528
3335=head1 AUTHOR 3529=head1 AUTHOR
3336 3530
3337Marc Lehmann <libev@schmorp.de>. 3531Marc Lehmann <libev@schmorp.de>.
3338 3532

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