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Revision 1.150 by root, Tue May 6 23:34:16 2008 UTC vs.
Revision 1.172 by root, Wed Aug 6 07:01:25 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
1555=head3 Examples 1607=head3 Examples
1556 1608
1557Example: C<fork()> a new process and install a child handler to wait for 1609Example: C<fork()> a new process and install a child handler to wait for
1558its completion. 1610its completion.
1559 1611
1560 ev_child cw; 1612 ev_child cw;
1561 1613
1562 static void 1614 static void
1563 child_cb (EV_P_ struct ev_child *w, int revents) 1615 child_cb (EV_P_ struct ev_child *w, int revents)
1564 { 1616 {
1565 ev_child_stop (EV_A_ w); 1617 ev_child_stop (EV_A_ w);
1566 printf ("process %d exited with status %x\n", w->rpid, w->rstatus); 1618 printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567 } 1619 }
1568 1620
1569 pid_t pid = fork (); 1621 pid_t pid = fork ();
1570 1622
1571 if (pid < 0) 1623 if (pid < 0)
1572 // error 1624 // error
1573 else if (pid == 0) 1625 else if (pid == 0)
1574 { 1626 {
1575 // the forked child executes here 1627 // the forked child executes here
1576 exit (1); 1628 exit (1);
1577 } 1629 }
1578 else 1630 else
1579 { 1631 {
1580 ev_child_init (&cw, child_cb, pid, 0); 1632 ev_child_init (&cw, child_cb, pid, 0);
1581 ev_child_start (EV_DEFAULT_ &cw); 1633 ev_child_start (EV_DEFAULT_ &cw);
1582 } 1634 }
1583 1635
1584 1636
1585=head2 C<ev_stat> - did the file attributes just change? 1637=head2 C<ev_stat> - did the file attributes just change?
1586 1638
1587This watches a filesystem path for attribute changes. That is, it calls 1639This 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 1640C<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. 1641compared to the last time, invoking the callback if it did.
1590 1642
1591The path does not need to exist: changing from "path exists" to "path does 1643The 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 1644not exist" is a status change like any other. The condition "path does
1620will be no polling. 1672will be no polling.
1621 1673
1622=head3 ABI Issues (Largefile Support) 1674=head3 ABI Issues (Largefile Support)
1623 1675
1624Libev by default (unless the user overrides this) uses the default 1676Libev by default (unless the user overrides this) uses the default
1625compilation environment, which means that on systems with optionally 1677compilation environment, which means that on systems with large file
1626disabled large file support, you get the 32 bit version of the stat 1678support disabled by default, you get the 32 bit version of the stat
1627structure. When using the library from programs that change the ABI to 1679structure. 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 1680use 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 1681compile 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 1682obviously the case with any flags that change the ABI, but the problem is
1631most noticably with ev_stat and largefile support. 1683most noticeably disabled with ev_stat and large file support.
1684
1685The solution for this is to lobby your distribution maker to make large
1686file interfaces available by default (as e.g. FreeBSD does) and not
1687optional. Libev cannot simply switch on large file support because it has
1688to exchange stat structures with application programs compiled using the
1689default compilation environment.
1632 1690
1633=head3 Inotify 1691=head3 Inotify
1634 1692
1635When C<inotify (7)> support has been compiled into libev (generally only 1693When 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 1694available on Linux) and present at runtime, it will be used to speed up
1646implement this functionality, due to the requirement of having a file 1704implement this functionality, due to the requirement of having a file
1647descriptor open on the object at all times). 1705descriptor open on the object at all times).
1648 1706
1649=head3 The special problem of stat time resolution 1707=head3 The special problem of stat time resolution
1650 1708
1651The C<stat ()> syscall only supports full-second resolution portably, and 1709The C<stat ()> system call only supports full-second resolution portably, and
1652even on systems where the resolution is higher, many filesystems still 1710even on systems where the resolution is higher, many file systems still
1653only support whole seconds. 1711only support whole seconds.
1654 1712
1655That means that, if the time is the only thing that changes, you can 1713That 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 1714easily miss updates: on the first update, C<ev_stat> detects a change and
1657calls your callback, which does something. When there is another update 1715calls 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 1716within the same second, C<ev_stat> will be unable to detect it as the stat
1659data does not change. 1717data does not change.
1660 1718
1661The solution to this is to delay acting on a change for slightly more 1719The 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 1720than 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); 1721a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664ev_timer_again (loop, w)>). 1722ev_timer_again (loop, w)>).
1665 1723
1666The C<.02> offset is added to work around small timing inconsistencies 1724The C<.02> offset is added to work around small timing inconsistencies
1667of some operating systems (where the second counter of the current time 1725of some operating systems (where the second counter of the current time
1717 1775
1718The specified interval. 1776The specified interval.
1719 1777
1720=item const char *path [read-only] 1778=item const char *path [read-only]
1721 1779
1722The filesystem path that is being watched. 1780The file system path that is being watched.
1723 1781
1724=back 1782=back
1725 1783
1726=head3 Examples 1784=head3 Examples
1727 1785
1728Example: Watch C</etc/passwd> for attribute changes. 1786Example: Watch C</etc/passwd> for attribute changes.
1729 1787
1730 static void 1788 static void
1731 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1789 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732 { 1790 {
1733 /* /etc/passwd changed in some way */ 1791 /* /etc/passwd changed in some way */
1734 if (w->attr.st_nlink) 1792 if (w->attr.st_nlink)
1735 { 1793 {
1736 printf ("passwd current size %ld\n", (long)w->attr.st_size); 1794 printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737 printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); 1795 printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738 printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); 1796 printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739 } 1797 }
1740 else 1798 else
1741 /* you shalt not abuse printf for puts */ 1799 /* you shalt not abuse printf for puts */
1742 puts ("wow, /etc/passwd is not there, expect problems. " 1800 puts ("wow, /etc/passwd is not there, expect problems. "
1743 "if this is windows, they already arrived\n"); 1801 "if this is windows, they already arrived\n");
1744 } 1802 }
1745 1803
1746 ... 1804 ...
1747 ev_stat passwd; 1805 ev_stat passwd;
1748 1806
1749 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); 1807 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750 ev_stat_start (loop, &passwd); 1808 ev_stat_start (loop, &passwd);
1751 1809
1752Example: Like above, but additionally use a one-second delay so we do not 1810Example: Like above, but additionally use a one-second delay so we do not
1753miss updates (however, frequent updates will delay processing, too, so 1811miss updates (however, frequent updates will delay processing, too, so
1754one might do the work both on C<ev_stat> callback invocation I<and> on 1812one might do the work both on C<ev_stat> callback invocation I<and> on
1755C<ev_timer> callback invocation). 1813C<ev_timer> callback invocation).
1756 1814
1757 static ev_stat passwd; 1815 static ev_stat passwd;
1758 static ev_timer timer; 1816 static ev_timer timer;
1759 1817
1760 static void 1818 static void
1761 timer_cb (EV_P_ ev_timer *w, int revents) 1819 timer_cb (EV_P_ ev_timer *w, int revents)
1762 { 1820 {
1763 ev_timer_stop (EV_A_ w); 1821 ev_timer_stop (EV_A_ w);
1764 1822
1765 /* now it's one second after the most recent passwd change */ 1823 /* now it's one second after the most recent passwd change */
1766 } 1824 }
1767 1825
1768 static void 1826 static void
1769 stat_cb (EV_P_ ev_stat *w, int revents) 1827 stat_cb (EV_P_ ev_stat *w, int revents)
1770 { 1828 {
1771 /* reset the one-second timer */ 1829 /* reset the one-second timer */
1772 ev_timer_again (EV_A_ &timer); 1830 ev_timer_again (EV_A_ &timer);
1773 } 1831 }
1774 1832
1775 ... 1833 ...
1776 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); 1834 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777 ev_stat_start (loop, &passwd); 1835 ev_stat_start (loop, &passwd);
1778 ev_timer_init (&timer, timer_cb, 0., 1.02); 1836 ev_timer_init (&timer, timer_cb, 0., 1.02);
1779 1837
1780 1838
1781=head2 C<ev_idle> - when you've got nothing better to do... 1839=head2 C<ev_idle> - when you've got nothing better to do...
1782 1840
1783Idle watchers trigger events when no other events of the same or higher 1841Idle watchers trigger events when no other events of the same or higher
1814=head3 Examples 1872=head3 Examples
1815 1873
1816Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1874Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817callback, free it. Also, use no error checking, as usual. 1875callback, free it. Also, use no error checking, as usual.
1818 1876
1819 static void 1877 static void
1820 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1878 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1821 { 1879 {
1822 free (w); 1880 free (w);
1823 // now do something you wanted to do when the program has 1881 // now do something you wanted to do when the program has
1824 // no longer anything immediate to do. 1882 // no longer anything immediate to do.
1825 } 1883 }
1826 1884
1827 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1885 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1828 ev_idle_init (idle_watcher, idle_cb); 1886 ev_idle_init (idle_watcher, idle_cb);
1829 ev_idle_start (loop, idle_cb); 1887 ev_idle_start (loop, idle_cb);
1830 1888
1831 1889
1832=head2 C<ev_prepare> and C<ev_check> - customise your event loop! 1890=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833 1891
1834Prepare and check watchers are usually (but not always) used in tandem: 1892Prepare and check watchers are usually (but not always) used in tandem:
1853 1911
1854This is done by examining in each prepare call which file descriptors need 1912This 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 1913to 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 1914them and starting an C<ev_timer> watcher for any timeouts (many libraries
1857provide just this functionality). Then, in the check watcher you check for 1915provide just this functionality). Then, in the check watcher you check for
1858any events that occured (by checking the pending status of all watchers 1916any 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 1917and stopping them) and call back into the library. The I/O and timer
1860callbacks will never actually be called (but must be valid nevertheless, 1918callbacks will never actually be called (but must be valid nevertheless,
1861because you never know, you know?). 1919because you never know, you know?).
1862 1920
1863As another example, the Perl Coro module uses these hooks to integrate 1921As another example, the Perl Coro module uses these hooks to integrate
1906and in a check watcher, destroy them and call into libadns. What follows 1964and 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 1965is 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 1966priority 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. 1967the callbacks for the IO/timeout watchers might not have been called yet.
1910 1968
1911 static ev_io iow [nfd]; 1969 static ev_io iow [nfd];
1912 static ev_timer tw; 1970 static ev_timer tw;
1913 1971
1914 static void 1972 static void
1915 io_cb (ev_loop *loop, ev_io *w, int revents) 1973 io_cb (ev_loop *loop, ev_io *w, int revents)
1916 { 1974 {
1917 } 1975 }
1918 1976
1919 // create io watchers for each fd and a timer before blocking 1977 // create io watchers for each fd and a timer before blocking
1920 static void 1978 static void
1921 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1979 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1922 { 1980 {
1923 int timeout = 3600000; 1981 int timeout = 3600000;
1924 struct pollfd fds [nfd]; 1982 struct pollfd fds [nfd];
1925 // actual code will need to loop here and realloc etc. 1983 // actual code will need to loop here and realloc etc.
1926 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 1984 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927 1985
1928 /* the callback is illegal, but won't be called as we stop during check */ 1986 /* the callback is illegal, but won't be called as we stop during check */
1929 ev_timer_init (&tw, 0, timeout * 1e-3); 1987 ev_timer_init (&tw, 0, timeout * 1e-3);
1930 ev_timer_start (loop, &tw); 1988 ev_timer_start (loop, &tw);
1931 1989
1932 // create one ev_io per pollfd 1990 // create one ev_io per pollfd
1933 for (int i = 0; i < nfd; ++i) 1991 for (int i = 0; i < nfd; ++i)
1934 { 1992 {
1935 ev_io_init (iow + i, io_cb, fds [i].fd, 1993 ev_io_init (iow + i, io_cb, fds [i].fd,
1936 ((fds [i].events & POLLIN ? EV_READ : 0) 1994 ((fds [i].events & POLLIN ? EV_READ : 0)
1937 | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1995 | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938 1996
1939 fds [i].revents = 0; 1997 fds [i].revents = 0;
1940 ev_io_start (loop, iow + i); 1998 ev_io_start (loop, iow + i);
1941 } 1999 }
1942 } 2000 }
1943 2001
1944 // stop all watchers after blocking 2002 // stop all watchers after blocking
1945 static void 2003 static void
1946 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 2004 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1947 { 2005 {
1948 ev_timer_stop (loop, &tw); 2006 ev_timer_stop (loop, &tw);
1949 2007
1950 for (int i = 0; i < nfd; ++i) 2008 for (int i = 0; i < nfd; ++i)
1951 { 2009 {
1952 // set the relevant poll flags 2010 // set the relevant poll flags
1953 // could also call adns_processreadable etc. here 2011 // could also call adns_processreadable etc. here
1954 struct pollfd *fd = fds + i; 2012 struct pollfd *fd = fds + i;
1955 int revents = ev_clear_pending (iow + i); 2013 int revents = ev_clear_pending (iow + i);
1956 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; 2014 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; 2015 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958 2016
1959 // now stop the watcher 2017 // now stop the watcher
1960 ev_io_stop (loop, iow + i); 2018 ev_io_stop (loop, iow + i);
1961 } 2019 }
1962 2020
1963 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 2021 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964 } 2022 }
1965 2023
1966Method 2: This would be just like method 1, but you run C<adns_afterpoll> 2024Method 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. 2025in the prepare watcher and would dispose of the check watcher.
1968 2026
1969Method 3: If the module to be embedded supports explicit event 2027Method 3: If the module to be embedded supports explicit event
1970notification (adns does), you can also make use of the actual watcher 2028notification (libadns does), you can also make use of the actual watcher
1971callbacks, and only destroy/create the watchers in the prepare watcher. 2029callbacks, and only destroy/create the watchers in the prepare watcher.
1972 2030
1973 static void 2031 static void
1974 timer_cb (EV_P_ ev_timer *w, int revents) 2032 timer_cb (EV_P_ ev_timer *w, int revents)
1975 { 2033 {
1976 adns_state ads = (adns_state)w->data; 2034 adns_state ads = (adns_state)w->data;
1977 update_now (EV_A); 2035 update_now (EV_A);
1978 2036
1979 adns_processtimeouts (ads, &tv_now); 2037 adns_processtimeouts (ads, &tv_now);
1980 } 2038 }
1981 2039
1982 static void 2040 static void
1983 io_cb (EV_P_ ev_io *w, int revents) 2041 io_cb (EV_P_ ev_io *w, int revents)
1984 { 2042 {
1985 adns_state ads = (adns_state)w->data; 2043 adns_state ads = (adns_state)w->data;
1986 update_now (EV_A); 2044 update_now (EV_A);
1987 2045
1988 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); 2046 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); 2047 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990 } 2048 }
1991 2049
1992 // do not ever call adns_afterpoll 2050 // do not ever call adns_afterpoll
1993 2051
1994Method 4: Do not use a prepare or check watcher because the module you 2052Method 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 2053want to embed is too inflexible to support it. Instead, you can override
1996their poll function. The drawback with this solution is that the main 2054their 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 2055loop is now no longer controllable by EV. The C<Glib::EV> module does
1998this. 2056this.
1999 2057
2000 static gint 2058 static gint
2001 event_poll_func (GPollFD *fds, guint nfds, gint timeout) 2059 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002 { 2060 {
2003 int got_events = 0; 2061 int got_events = 0;
2004 2062
2005 for (n = 0; n < nfds; ++n) 2063 for (n = 0; n < nfds; ++n)
2006 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events 2064 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007 2065
2008 if (timeout >= 0) 2066 if (timeout >= 0)
2009 // create/start timer 2067 // create/start timer
2010 2068
2011 // poll 2069 // poll
2012 ev_loop (EV_A_ 0); 2070 ev_loop (EV_A_ 0);
2013 2071
2014 // stop timer again 2072 // stop timer again
2015 if (timeout >= 0) 2073 if (timeout >= 0)
2016 ev_timer_stop (EV_A_ &to); 2074 ev_timer_stop (EV_A_ &to);
2017 2075
2018 // stop io watchers again - their callbacks should have set 2076 // stop io watchers again - their callbacks should have set
2019 for (n = 0; n < nfds; ++n) 2077 for (n = 0; n < nfds; ++n)
2020 ev_io_stop (EV_A_ iow [n]); 2078 ev_io_stop (EV_A_ iow [n]);
2021 2079
2022 return got_events; 2080 return got_events;
2023 } 2081 }
2024 2082
2025 2083
2026=head2 C<ev_embed> - when one backend isn't enough... 2084=head2 C<ev_embed> - when one backend isn't enough...
2027 2085
2028This is a rather advanced watcher type that lets you embed one event loop 2086This is a rather advanced watcher type that lets you embed one event loop
2084 2142
2085Configures the watcher to embed the given loop, which must be 2143Configures the watcher to embed the given loop, which must be
2086embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be 2144embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087invoked automatically, otherwise it is the responsibility of the callback 2145invoked automatically, otherwise it is the responsibility of the callback
2088to invoke it (it will continue to be called until the sweep has been done, 2146to 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). 2147if you do not want that, you need to temporarily stop the embed watcher).
2090 2148
2091=item ev_embed_sweep (loop, ev_embed *) 2149=item ev_embed_sweep (loop, ev_embed *)
2092 2150
2093Make a single, non-blocking sweep over the embedded loop. This works 2151Make a single, non-blocking sweep over the embedded loop. This works
2094similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most 2152similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095apropriate way for embedded loops. 2153appropriate way for embedded loops.
2096 2154
2097=item struct ev_loop *other [read-only] 2155=item struct ev_loop *other [read-only]
2098 2156
2099The embedded event loop. 2157The embedded event loop.
2100 2158
2102 2160
2103=head3 Examples 2161=head3 Examples
2104 2162
2105Example: Try to get an embeddable event loop and embed it into the default 2163Example: 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 2164event 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 2165loop 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 2166C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109used). 2167used).
2110 2168
2111 struct ev_loop *loop_hi = ev_default_init (0); 2169 struct ev_loop *loop_hi = ev_default_init (0);
2112 struct ev_loop *loop_lo = 0; 2170 struct ev_loop *loop_lo = 0;
2113 struct ev_embed embed; 2171 struct ev_embed embed;
2114 2172
2115 // see if there is a chance of getting one that works 2173 // see if there is a chance of getting one that works
2116 // (remember that a flags value of 0 means autodetection) 2174 // (remember that a flags value of 0 means autodetection)
2117 loop_lo = ev_embeddable_backends () & ev_recommended_backends () 2175 loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) 2176 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119 : 0; 2177 : 0;
2120 2178
2121 // if we got one, then embed it, otherwise default to loop_hi 2179 // if we got one, then embed it, otherwise default to loop_hi
2122 if (loop_lo) 2180 if (loop_lo)
2123 { 2181 {
2124 ev_embed_init (&embed, 0, loop_lo); 2182 ev_embed_init (&embed, 0, loop_lo);
2125 ev_embed_start (loop_hi, &embed); 2183 ev_embed_start (loop_hi, &embed);
2126 } 2184 }
2127 else 2185 else
2128 loop_lo = loop_hi; 2186 loop_lo = loop_hi;
2129 2187
2130Example: Check if kqueue is available but not recommended and create 2188Example: Check if kqueue is available but not recommended and create
2131a kqueue backend for use with sockets (which usually work with any 2189a kqueue backend for use with sockets (which usually work with any
2132kqueue implementation). Store the kqueue/socket-only event loop in 2190kqueue implementation). Store the kqueue/socket-only event loop in
2133C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). 2191C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134 2192
2135 struct ev_loop *loop = ev_default_init (0); 2193 struct ev_loop *loop = ev_default_init (0);
2136 struct ev_loop *loop_socket = 0; 2194 struct ev_loop *loop_socket = 0;
2137 struct ev_embed embed; 2195 struct ev_embed embed;
2138 2196
2139 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) 2197 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) 2198 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141 { 2199 {
2142 ev_embed_init (&embed, 0, loop_socket); 2200 ev_embed_init (&embed, 0, loop_socket);
2143 ev_embed_start (loop, &embed); 2201 ev_embed_start (loop, &embed);
2144 } 2202 }
2145 2203
2146 if (!loop_socket) 2204 if (!loop_socket)
2147 loop_socket = loop; 2205 loop_socket = loop;
2148 2206
2149 // now use loop_socket for all sockets, and loop for everything else 2207 // now use loop_socket for all sockets, and loop for everything else
2150 2208
2151 2209
2152=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2210=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153 2211
2154Fork watchers are called when a C<fork ()> was detected (usually because 2212Fork watchers are called when a C<fork ()> was detected (usually because
2207 2265
2208=item queueing from a signal handler context 2266=item queueing from a signal handler context
2209 2267
2210To implement race-free queueing, you simply add to the queue in the signal 2268To 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 2269handler but you block the signal handler in the watcher callback. Here is an example that does that for
2212some fictitiuous SIGUSR1 handler: 2270some fictitious SIGUSR1 handler:
2213 2271
2214 static ev_async mysig; 2272 static ev_async mysig;
2215 2273
2216 static void 2274 static void
2217 sigusr1_handler (void) 2275 sigusr1_handler (void)
2291=item ev_async_send (loop, ev_async *) 2349=item ev_async_send (loop, ev_async *)
2292 2350
2293Sends/signals/activates the given C<ev_async> watcher, that is, feeds 2351Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294an C<EV_ASYNC> event on the watcher into the event loop. Unlike 2352an 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 2353C<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 2354similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297section below on what exactly this means). 2355section below on what exactly this means).
2298 2356
2299This call incurs the overhead of a syscall only once per loop iteration, 2357This 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 2358so while the overhead might be noticeable, it doesn't apply to repeated
2301calls to C<ev_async_send>. 2359calls to C<ev_async_send>.
2302 2360
2303=item bool = ev_async_pending (ev_async *) 2361=item bool = ev_async_pending (ev_async *)
2304 2362
2305Returns a non-zero value when C<ev_async_send> has been called on the 2363Returns a non-zero value when C<ev_async_send> has been called on the
2307event loop. 2365event loop.
2308 2366
2309C<ev_async_send> sets a flag in the watcher and wakes up the loop. When 2367C<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, 2368the 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 2369it 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. 2370quickly check whether invoking the loop might be a good idea.
2313 2371
2314Not that this does I<not> check wether the watcher itself is pending, only 2372Not that this does I<not> check whether the watcher itself is pending, only
2315wether it has been requested to make this watcher pending. 2373whether it has been requested to make this watcher pending.
2316 2374
2317=back 2375=back
2318 2376
2319 2377
2320=head1 OTHER FUNCTIONS 2378=head1 OTHER FUNCTIONS
2331or timeout without having to allocate/configure/start/stop/free one or 2389or timeout without having to allocate/configure/start/stop/free one or
2332more watchers yourself. 2390more watchers yourself.
2333 2391
2334If C<fd> is less than 0, then no I/O watcher will be started and events 2392If 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 2393is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2336C<events> set will be craeted and started. 2394C<events> set will be created and started.
2337 2395
2338If C<timeout> is less than 0, then no timeout watcher will be 2396If C<timeout> is less than 0, then no timeout watcher will be
2339started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 2397started. 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 2398repeat = 0) will be started. While C<0> is a valid timeout, it is of
2341dubious value. 2399dubious value.
2343The callback has the type C<void (*cb)(int revents, void *arg)> and gets 2401The 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 2402passed 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> 2403C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346value passed to C<ev_once>: 2404value passed to C<ev_once>:
2347 2405
2348 static void stdin_ready (int revents, void *arg) 2406 static void stdin_ready (int revents, void *arg)
2349 { 2407 {
2350 if (revents & EV_TIMEOUT) 2408 if (revents & EV_TIMEOUT)
2351 /* doh, nothing entered */; 2409 /* doh, nothing entered */;
2352 else if (revents & EV_READ) 2410 else if (revents & EV_READ)
2353 /* stdin might have data for us, joy! */; 2411 /* stdin might have data for us, joy! */;
2354 } 2412 }
2355 2413
2356 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2414 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357 2415
2358=item ev_feed_event (ev_loop *, watcher *, int revents) 2416=item ev_feed_event (ev_loop *, watcher *, int revents)
2359 2417
2360Feeds the given event set into the event loop, as if the specified event 2418Feeds 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 2419had 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 2424Feed an event on the given fd, as if a file descriptor backend detected
2367the given events it. 2425the given events it.
2368 2426
2369=item ev_feed_signal_event (ev_loop *loop, int signum) 2427=item ev_feed_signal_event (ev_loop *loop, int signum)
2370 2428
2371Feed an event as if the given signal occured (C<loop> must be the default 2429Feed an event as if the given signal occurred (C<loop> must be the default
2372loop!). 2430loop!).
2373 2431
2374=back 2432=back
2375 2433
2376 2434
2405=back 2463=back
2406 2464
2407=head1 C++ SUPPORT 2465=head1 C++ SUPPORT
2408 2466
2409Libev comes with some simplistic wrapper classes for C++ that mainly allow 2467Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410you to use some convinience methods to start/stop watchers and also change 2468you to use some convenience methods to start/stop watchers and also change
2411the callback model to a model using method callbacks on objects. 2469the callback model to a model using method callbacks on objects.
2412 2470
2413To use it, 2471To use it,
2414 2472
2415 #include <ev++.h> 2473 #include <ev++.h>
2416 2474
2417This automatically includes F<ev.h> and puts all of its definitions (many 2475This automatically includes F<ev.h> and puts all of its definitions (many
2418of them macros) into the global namespace. All C++ specific things are 2476of them macros) into the global namespace. All C++ specific things are
2419put into the C<ev> namespace. It should support all the same embedding 2477put into the C<ev> namespace. It should support all the same embedding
2420options as F<ev.h>, most notably C<EV_MULTIPLICITY>. 2478options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
2487your compiler is good :), then the method will be fully inlined into the 2545your compiler is good :), then the method will be fully inlined into the
2488thunking function, making it as fast as a direct C callback. 2546thunking function, making it as fast as a direct C callback.
2489 2547
2490Example: simple class declaration and watcher initialisation 2548Example: simple class declaration and watcher initialisation
2491 2549
2492 struct myclass 2550 struct myclass
2493 { 2551 {
2494 void io_cb (ev::io &w, int revents) { } 2552 void io_cb (ev::io &w, int revents) { }
2495 } 2553 }
2496 2554
2497 myclass obj; 2555 myclass obj;
2498 ev::io iow; 2556 ev::io iow;
2499 iow.set <myclass, &myclass::io_cb> (&obj); 2557 iow.set <myclass, &myclass::io_cb> (&obj);
2500 2558
2501=item w->set<function> (void *data = 0) 2559=item w->set<function> (void *data = 0)
2502 2560
2503Also sets a callback, but uses a static method or plain function as 2561Also 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 2562callback. The optional C<data> argument will be stored in the watcher's
2508 2566
2509See the method-C<set> above for more details. 2567See the method-C<set> above for more details.
2510 2568
2511Example: 2569Example:
2512 2570
2513 static void io_cb (ev::io &w, int revents) { } 2571 static void io_cb (ev::io &w, int revents) { }
2514 iow.set <io_cb> (); 2572 iow.set <io_cb> ();
2515 2573
2516=item w->set (struct ev_loop *) 2574=item w->set (struct ev_loop *)
2517 2575
2518Associates a different C<struct ev_loop> with this watcher. You can only 2576Associates a different C<struct ev_loop> with this watcher. You can only
2519do this when the watcher is inactive (and not pending either). 2577do this when the watcher is inactive (and not pending either).
2520 2578
2521=item w->set ([args]) 2579=item w->set ([arguments])
2522 2580
2523Basically the same as C<ev_TYPE_set>, with the same args. Must be 2581Basically 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 2582called at least once. Unlike the C counterpart, an active watcher gets
2525automatically stopped and restarted when reconfiguring it with this 2583automatically stopped and restarted when reconfiguring it with this
2526method. 2584method.
2527 2585
2528=item w->start () 2586=item w->start ()
2552=back 2610=back
2553 2611
2554Example: Define a class with an IO and idle watcher, start one of them in 2612Example: Define a class with an IO and idle watcher, start one of them in
2555the constructor. 2613the constructor.
2556 2614
2557 class myclass 2615 class myclass
2558 { 2616 {
2559 ev::io io; void io_cb (ev::io &w, int revents); 2617 ev::io io; void io_cb (ev::io &w, int revents);
2560 ev:idle idle void idle_cb (ev::idle &w, int revents); 2618 ev:idle idle void idle_cb (ev::idle &w, int revents);
2561 2619
2562 myclass (int fd) 2620 myclass (int fd)
2563 { 2621 {
2564 io .set <myclass, &myclass::io_cb > (this); 2622 io .set <myclass, &myclass::io_cb > (this);
2565 idle.set <myclass, &myclass::idle_cb> (this); 2623 idle.set <myclass, &myclass::idle_cb> (this);
2566 2624
2567 io.start (fd, ev::READ); 2625 io.start (fd, ev::READ);
2568 } 2626 }
2569 }; 2627 };
2570 2628
2571 2629
2572=head1 OTHER LANGUAGE BINDINGS 2630=head1 OTHER LANGUAGE BINDINGS
2573 2631
2574Libev does not offer other language bindings itself, but bindings for a 2632Libev 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 2633number 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 2634any interesting language binding in addition to the ones listed here, drop
2577me a note. 2635me a note.
2578 2636
2579=over 4 2637=over 4
2580 2638
2584libev. EV is developed together with libev. Apart from the EV core module, 2642libev. EV is developed together with libev. Apart from the EV core module,
2585there are additional modules that implement libev-compatible interfaces 2643there are additional modules that implement libev-compatible interfaces
2586to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the 2644to 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>). 2645C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
2588 2646
2589It can be found and installed via CPAN, its homepage is found at 2647It can be found and installed via CPAN, its homepage is at
2590L<http://software.schmorp.de/pkg/EV>. 2648L<http://software.schmorp.de/pkg/EV>.
2591 2649
2650=item Python
2651
2652Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2653seems to be quite complete and well-documented. Note, however, that the
2654patch they require for libev is outright dangerous as it breaks the ABI
2655for everybody else, and therefore, should never be applied in an installed
2656libev (if python requires an incompatible ABI then it needs to embed
2657libev).
2658
2592=item Ruby 2659=item Ruby
2593 2660
2594Tony Arcieri has written a ruby extension that offers access to a subset 2661Tony Arcieri has written a ruby extension that offers access to a subset
2595of the libev API and adds filehandle abstractions, asynchronous DNS and 2662of 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 2663more on top of it. It can be found via gem servers. Its homepage is at
2597L<http://rev.rubyforge.org/>. 2664L<http://rev.rubyforge.org/>.
2598 2665
2599=item D 2666=item D
2600 2667
2601Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to 2668Leandro 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>. 2669be found at L<http://proj.llucax.com.ar/wiki/evd>.
2603 2670
2604=back 2671=back
2605 2672
2606 2673
2607=head1 MACRO MAGIC 2674=head1 MACRO MAGIC
2608 2675
2609Libev can be compiled with a variety of options, the most fundamantal 2676Libev can be compiled with a variety of options, the most fundamental
2610of which is C<EV_MULTIPLICITY>. This option determines whether (most) 2677of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611functions and callbacks have an initial C<struct ev_loop *> argument. 2678functions and callbacks have an initial C<struct ev_loop *> argument.
2612 2679
2613To make it easier to write programs that cope with either variant, the 2680To make it easier to write programs that cope with either variant, the
2614following macros are defined: 2681following macros are defined:
2619 2686
2620This provides the loop I<argument> for functions, if one is required ("ev 2687This 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, 2688loop 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: 2689C<EV_A_> is used when other arguments are following. Example:
2623 2690
2624 ev_unref (EV_A); 2691 ev_unref (EV_A);
2625 ev_timer_add (EV_A_ watcher); 2692 ev_timer_add (EV_A_ watcher);
2626 ev_loop (EV_A_ 0); 2693 ev_loop (EV_A_ 0);
2627 2694
2628It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, 2695It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629which is often provided by the following macro. 2696which is often provided by the following macro.
2630 2697
2631=item C<EV_P>, C<EV_P_> 2698=item C<EV_P>, C<EV_P_>
2632 2699
2633This provides the loop I<parameter> for functions, if one is required ("ev 2700This 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, 2701loop 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: 2702C<EV_P_> is used when other parameters are following. Example:
2636 2703
2637 // this is how ev_unref is being declared 2704 // this is how ev_unref is being declared
2638 static void ev_unref (EV_P); 2705 static void ev_unref (EV_P);
2639 2706
2640 // this is how you can declare your typical callback 2707 // this is how you can declare your typical callback
2641 static void cb (EV_P_ ev_timer *w, int revents) 2708 static void cb (EV_P_ ev_timer *w, int revents)
2642 2709
2643It declares a parameter C<loop> of type C<struct ev_loop *>, quite 2710It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644suitable for use with C<EV_A>. 2711suitable for use with C<EV_A>.
2645 2712
2646=item C<EV_DEFAULT>, C<EV_DEFAULT_> 2713=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2662 2729
2663Example: Declare and initialise a check watcher, utilising the above 2730Example: Declare and initialise a check watcher, utilising the above
2664macros so it will work regardless of whether multiple loops are supported 2731macros so it will work regardless of whether multiple loops are supported
2665or not. 2732or not.
2666 2733
2667 static void 2734 static void
2668 check_cb (EV_P_ ev_timer *w, int revents) 2735 check_cb (EV_P_ ev_timer *w, int revents)
2669 { 2736 {
2670 ev_check_stop (EV_A_ w); 2737 ev_check_stop (EV_A_ w);
2671 } 2738 }
2672 2739
2673 ev_check check; 2740 ev_check check;
2674 ev_check_init (&check, check_cb); 2741 ev_check_init (&check, check_cb);
2675 ev_check_start (EV_DEFAULT_ &check); 2742 ev_check_start (EV_DEFAULT_ &check);
2676 ev_loop (EV_DEFAULT_ 0); 2743 ev_loop (EV_DEFAULT_ 0);
2677 2744
2678=head1 EMBEDDING 2745=head1 EMBEDDING
2679 2746
2680Libev can (and often is) directly embedded into host 2747Libev can (and often is) directly embedded into host
2681applications. Examples of applications that embed it include the Deliantra 2748applications. Examples of applications that embed it include the Deliantra
2688libev somewhere in your source tree). 2755libev somewhere in your source tree).
2689 2756
2690=head2 FILESETS 2757=head2 FILESETS
2691 2758
2692Depending on what features you need you need to include one or more sets of files 2759Depending on what features you need you need to include one or more sets of files
2693in your app. 2760in your application.
2694 2761
2695=head3 CORE EVENT LOOP 2762=head3 CORE EVENT LOOP
2696 2763
2697To include only the libev core (all the C<ev_*> functions), with manual 2764To include only the libev core (all the C<ev_*> functions), with manual
2698configuration (no autoconf): 2765configuration (no autoconf):
2699 2766
2700 #define EV_STANDALONE 1 2767 #define EV_STANDALONE 1
2701 #include "ev.c" 2768 #include "ev.c"
2702 2769
2703This will automatically include F<ev.h>, too, and should be done in a 2770This 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 2771single 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 2772it, 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 2773done by writing a wrapper around F<ev.h> that you can include instead and
2707where you can put other configuration options): 2774where you can put other configuration options):
2708 2775
2709 #define EV_STANDALONE 1 2776 #define EV_STANDALONE 1
2710 #include "ev.h" 2777 #include "ev.h"
2711 2778
2712Both header files and implementation files can be compiled with a C++ 2779Both header files and implementation files can be compiled with a C++
2713compiler (at least, thats a stated goal, and breakage will be treated 2780compiler (at least, thats a stated goal, and breakage will be treated
2714as a bug). 2781as a bug).
2715 2782
2716You need the following files in your source tree, or in a directory 2783You need the following files in your source tree, or in a directory
2717in your include path (e.g. in libev/ when using -Ilibev): 2784in your include path (e.g. in libev/ when using -Ilibev):
2718 2785
2719 ev.h 2786 ev.h
2720 ev.c 2787 ev.c
2721 ev_vars.h 2788 ev_vars.h
2722 ev_wrap.h 2789 ev_wrap.h
2723 2790
2724 ev_win32.c required on win32 platforms only 2791 ev_win32.c required on win32 platforms only
2725 2792
2726 ev_select.c only when select backend is enabled (which is enabled by default) 2793 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) 2794 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) 2795 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) 2796 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) 2797 ev_port.c only when the solaris port backend is enabled (disabled by default)
2731 2798
2732F<ev.c> includes the backend files directly when enabled, so you only need 2799F<ev.c> includes the backend files directly when enabled, so you only need
2733to compile this single file. 2800to compile this single file.
2734 2801
2735=head3 LIBEVENT COMPATIBILITY API 2802=head3 LIBEVENT COMPATIBILITY API
2736 2803
2737To include the libevent compatibility API, also include: 2804To include the libevent compatibility API, also include:
2738 2805
2739 #include "event.c" 2806 #include "event.c"
2740 2807
2741in the file including F<ev.c>, and: 2808in the file including F<ev.c>, and:
2742 2809
2743 #include "event.h" 2810 #include "event.h"
2744 2811
2745in the files that want to use the libevent API. This also includes F<ev.h>. 2812in the files that want to use the libevent API. This also includes F<ev.h>.
2746 2813
2747You need the following additional files for this: 2814You need the following additional files for this:
2748 2815
2749 event.h 2816 event.h
2750 event.c 2817 event.c
2751 2818
2752=head3 AUTOCONF SUPPORT 2819=head3 AUTOCONF SUPPORT
2753 2820
2754Instead of using C<EV_STANDALONE=1> and providing your config in 2821Instead 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 2822whatever 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 2823F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757include F<config.h> and configure itself accordingly. 2824include F<config.h> and configure itself accordingly.
2758 2825
2759For this of course you need the m4 file: 2826For this of course you need the m4 file:
2760 2827
2761 libev.m4 2828 libev.m4
2762 2829
2763=head2 PREPROCESSOR SYMBOLS/MACROS 2830=head2 PREPROCESSOR SYMBOLS/MACROS
2764 2831
2765Libev can be configured via a variety of preprocessor symbols you have to 2832Libev 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 2833define before including any of its files. The default in the absence of
2767autoconf is noted for every option. 2834autoconf is noted for every option.
2768 2835
2769=over 4 2836=over 4
2770 2837
2771=item EV_STANDALONE 2838=item EV_STANDALONE
2777F<event.h> that are not directly supported by the libev core alone. 2844F<event.h> that are not directly supported by the libev core alone.
2778 2845
2779=item EV_USE_MONOTONIC 2846=item EV_USE_MONOTONIC
2780 2847
2781If defined to be C<1>, libev will try to detect the availability of the 2848If 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 2849monotonic clock option at both compile time and runtime. Otherwise no use
2783of the monotonic clock option will be attempted. If you enable this, you 2850of the monotonic clock option will be attempted. If you enable this, you
2784usually have to link against librt or something similar. Enabling it when 2851usually have to link against librt or something similar. Enabling it when
2785the functionality isn't available is safe, though, although you have 2852the functionality isn't available is safe, though, although you have
2786to make sure you link against any libraries where the C<clock_gettime> 2853to make sure you link against any libraries where the C<clock_gettime>
2787function is hiding in (often F<-lrt>). 2854function is hiding in (often F<-lrt>).
2788 2855
2789=item EV_USE_REALTIME 2856=item EV_USE_REALTIME
2790 2857
2791If defined to be C<1>, libev will try to detect the availability of the 2858If defined to be C<1>, libev will try to detect the availability of the
2792realtime clock option at compiletime (and assume its availability at 2859real-time clock option at compile time (and assume its availability at
2793runtime if successful). Otherwise no use of the realtime clock option will 2860runtime if successful). Otherwise no use of the real-time clock option will
2794be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2861be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2795(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the 2862(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2796note about libraries in the description of C<EV_USE_MONOTONIC>, though. 2863note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2797 2864
2798=item EV_USE_NANOSLEEP 2865=item EV_USE_NANOSLEEP
28092.7 or newer, otherwise disabled. 28762.7 or newer, otherwise disabled.
2810 2877
2811=item EV_USE_SELECT 2878=item EV_USE_SELECT
2812 2879
2813If undefined or defined to be C<1>, libev will compile in support for the 2880If 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 2881C<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 2882other method takes over, select will be it. Otherwise the select backend
2816will not be compiled in. 2883will not be compiled in.
2817 2884
2818=item EV_SELECT_USE_FD_SET 2885=item EV_SELECT_USE_FD_SET
2819 2886
2820If defined to C<1>, then the select backend will use the system C<fd_set> 2887If 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 2888structure. 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 2889C<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 2890exotic systems. This usually limits the range of file descriptors to some
2824low limit such as 1024 or might have other limitations (winsocket only 2891low limit such as 1024 or might have other limitations (winsocket only
2825allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might 2892allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2826influence the size of the C<fd_set> used. 2893influence the size of the C<fd_set> used.
2827 2894
2876otherwise another method will be used as fallback. This is the preferred 2943otherwise another method will be used as fallback. This is the preferred
2877backend for Solaris 10 systems. 2944backend for Solaris 10 systems.
2878 2945
2879=item EV_USE_DEVPOLL 2946=item EV_USE_DEVPOLL
2880 2947
2881reserved for future expansion, works like the USE symbols above. 2948Reserved for future expansion, works like the USE symbols above.
2882 2949
2883=item EV_USE_INOTIFY 2950=item EV_USE_INOTIFY
2884 2951
2885If defined to be C<1>, libev will compile in support for the Linux inotify 2952If 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 2953interface to speed up C<ev_stat> watchers. Its actual availability will
2893access is atomic with respect to other threads or signal contexts. No such 2960access 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 2961type 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" 2962that 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. 2963as well as for signal and thread safety in C<ev_async> watchers.
2897 2964
2898In the absense of this define, libev will use C<sig_atomic_t volatile> 2965In 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. 2966(from F<signal.h>), which is usually good enough on most platforms.
2900 2967
2901=item EV_H 2968=item EV_H
2902 2969
2903The name of the F<ev.h> header file used to include it. The default if 2970The 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 3009When doing priority-based operations, libev usually has to linearly search
2943all the priorities, so having many of them (hundreds) uses a lot of space 3010all 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 3011and time, so using the defaults of five priorities (-2 .. +2) is usually
2945fine. 3012fine.
2946 3013
2947If your embedding app does not need any priorities, defining these both to 3014If your embedding application does not need any priorities, defining these both to
2948C<0> will save some memory and cpu. 3015C<0> will save some memory and CPU.
2949 3016
2950=item EV_PERIODIC_ENABLE 3017=item EV_PERIODIC_ENABLE
2951 3018
2952If undefined or defined to be C<1>, then periodic timers are supported. If 3019If 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 3020defined to be C<0>, then they are not. Disabling them saves a few kB of
2980defined to be C<0>, then they are not. 3047defined to be C<0>, then they are not.
2981 3048
2982=item EV_MINIMAL 3049=item EV_MINIMAL
2983 3050
2984If you need to shave off some kilobytes of code at the expense of some 3051If you need to shave off some kilobytes of code at the expense of some
2985speed, define this symbol to C<1>. Currently only used for gcc to override 3052speed, define this symbol to C<1>. Currently this is used to override some
2986some inlining decisions, saves roughly 30% codesize of amd64. 3053inlining decisions, saves roughly 30% code size on amd64. It also selects a
3054much smaller 2-heap for timer management over the default 4-heap.
2987 3055
2988=item EV_PID_HASHSIZE 3056=item EV_PID_HASHSIZE
2989 3057
2990C<ev_child> watchers use a small hash table to distribute workload by 3058C<ev_child> watchers use a small hash table to distribute workload by
2991pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more 3059pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2998inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 3066inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2999usually more than enough. If you need to manage thousands of C<ev_stat> 3067usually more than enough. If you need to manage thousands of C<ev_stat>
3000watchers you might want to increase this value (I<must> be a power of 3068watchers you might want to increase this value (I<must> be a power of
3001two). 3069two).
3002 3070
3071=item EV_USE_4HEAP
3072
3073Heaps are not very cache-efficient. To improve the cache-efficiency of the
3074timer and periodics heap, libev uses a 4-heap when this symbol is defined
3075to C<1>. The 4-heap uses more complicated (longer) code but has
3076noticeably faster performance with many (thousands) of watchers.
3077
3078The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3079(disabled).
3080
3081=item EV_HEAP_CACHE_AT
3082
3083Heaps are not very cache-efficient. To improve the cache-efficiency of the
3084timer and periodics heap, libev can cache the timestamp (I<at>) within
3085the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3086which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3087but avoids random read accesses on heap changes. This improves performance
3088noticeably with with many (hundreds) of watchers.
3089
3090The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3091(disabled).
3092
3093=item EV_VERIFY
3094
3095Controls how much internal verification (see C<ev_loop_verify ()>) will
3096be done: If set to C<0>, no internal verification code will be compiled
3097in. If set to C<1>, then verification code will be compiled in, but not
3098called. If set to C<2>, then the internal verification code will be
3099called once per loop, which can slow down libev. If set to C<3>, then the
3100verification code will be called very frequently, which will slow down
3101libev considerably.
3102
3103The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3104C<0.>
3105
3003=item EV_COMMON 3106=item EV_COMMON
3004 3107
3005By default, all watchers have a C<void *data> member. By redefining 3108By default, all watchers have a C<void *data> member. By redefining
3006this macro to a something else you can include more and other types of 3109this macro to a something else you can include more and other types of
3007members. You have to define it each time you include one of the files, 3110members. You have to define it each time you include one of the files,
3008though, and it must be identical each time. 3111though, and it must be identical each time.
3009 3112
3010For example, the perl EV module uses something like this: 3113For example, the perl EV module uses something like this:
3011 3114
3012 #define EV_COMMON \ 3115 #define EV_COMMON \
3013 SV *self; /* contains this struct */ \ 3116 SV *self; /* contains this struct */ \
3014 SV *cb_sv, *fh /* note no trailing ";" */ 3117 SV *cb_sv, *fh /* note no trailing ";" */
3015 3118
3016=item EV_CB_DECLARE (type) 3119=item EV_CB_DECLARE (type)
3017 3120
3018=item EV_CB_INVOKE (watcher, revents) 3121=item EV_CB_INVOKE (watcher, revents)
3019 3122
3026avoid the C<struct ev_loop *> as first argument in all cases, or to use 3129avoid the C<struct ev_loop *> as first argument in all cases, or to use
3027method calls instead of plain function calls in C++. 3130method calls instead of plain function calls in C++.
3028 3131
3029=head2 EXPORTED API SYMBOLS 3132=head2 EXPORTED API SYMBOLS
3030 3133
3031If you need to re-export the API (e.g. via a dll) and you need a list of 3134If you need to re-export the API (e.g. via a DLL) and you need a list of
3032exported symbols, you can use the provided F<Symbol.*> files which list 3135exported symbols, you can use the provided F<Symbol.*> files which list
3033all public symbols, one per line: 3136all public symbols, one per line:
3034 3137
3035 Symbols.ev for libev proper 3138 Symbols.ev for libev proper
3036 Symbols.event for the libevent emulation 3139 Symbols.event for the libevent emulation
3037 3140
3038This can also be used to rename all public symbols to avoid clashes with 3141This can also be used to rename all public symbols to avoid clashes with
3039multiple versions of libev linked together (which is obviously bad in 3142multiple versions of libev linked together (which is obviously bad in
3040itself, but sometimes it is inconvinient to avoid this). 3143itself, but sometimes it is inconvenient to avoid this).
3041 3144
3042A sed command like this will create wrapper C<#define>'s that you need to 3145A sed command like this will create wrapper C<#define>'s that you need to
3043include before including F<ev.h>: 3146include before including F<ev.h>:
3044 3147
3045 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h 3148 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
3062file. 3165file.
3063 3166
3064The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 3167The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3065that everybody includes and which overrides some configure choices: 3168that everybody includes and which overrides some configure choices:
3066 3169
3067 #define EV_MINIMAL 1 3170 #define EV_MINIMAL 1
3068 #define EV_USE_POLL 0 3171 #define EV_USE_POLL 0
3069 #define EV_MULTIPLICITY 0 3172 #define EV_MULTIPLICITY 0
3070 #define EV_PERIODIC_ENABLE 0 3173 #define EV_PERIODIC_ENABLE 0
3071 #define EV_STAT_ENABLE 0 3174 #define EV_STAT_ENABLE 0
3072 #define EV_FORK_ENABLE 0 3175 #define EV_FORK_ENABLE 0
3073 #define EV_CONFIG_H <config.h> 3176 #define EV_CONFIG_H <config.h>
3074 #define EV_MINPRI 0 3177 #define EV_MINPRI 0
3075 #define EV_MAXPRI 0 3178 #define EV_MAXPRI 0
3076 3179
3077 #include "ev++.h" 3180 #include "ev++.h"
3078 3181
3079And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 3182And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3080 3183
3081 #include "ev_cpp.h" 3184 #include "ev_cpp.h"
3082 #include "ev.c" 3185 #include "ev.c"
3083 3186
3084 3187
3085=head1 THREADS AND COROUTINES 3188=head1 THREADS AND COROUTINES
3086 3189
3087=head2 THREADS 3190=head2 THREADS
3088 3191
3089Libev itself is completely threadsafe, but it uses no locking. This 3192Libev itself is completely thread-safe, but it uses no locking. This
3090means that you can use as many loops as you want in parallel, as long as 3193means that you can use as many loops as you want in parallel, as long as
3091only one thread ever calls into one libev function with the same loop 3194only one thread ever calls into one libev function with the same loop
3092parameter. 3195parameter.
3093 3196
3094Or put differently: calls with different loop parameters can be done in 3197Or put differently: calls with different loop parameters can be done in
3095parallel from multiple threads, calls with the same loop parameter must be 3198parallel from multiple threads, calls with the same loop parameter must be
3096done serially (but can be done from different threads, as long as only one 3199done serially (but can be done from different threads, as long as only one
3097thread ever is inside a call at any point in time, e.g. by using a mutex 3200thread ever is inside a call at any point in time, e.g. by using a mutex
3098per loop). 3201per loop).
3099 3202
3100If you want to know which design is best for your problem, then I cannot 3203If you want to know which design (one loop, locking, or multiple loops
3101help you but by giving some generic advice: 3204without or something else still) is best for your problem, then I cannot
3205help you. I can give some generic advice however:
3102 3206
3103=over 4 3207=over 4
3104 3208
3105=item * most applications have a main thread: use the default libev loop 3209=item * most applications have a main thread: use the default libev loop
3106in that thread, or create a seperate thread running only the default loop. 3210in that thread, or create a separate thread running only the default loop.
3107 3211
3108This helps integrating other libraries or software modules that use libev 3212This helps integrating other libraries or software modules that use libev
3109themselves and don't care/know about threading. 3213themselves and don't care/know about threading.
3110 3214
3111=item * one loop per thread is usually a good model. 3215=item * one loop per thread is usually a good model.
3112 3216
3113Doing this is almost never wrong, sometimes a better-performance model 3217Doing this is almost never wrong, sometimes a better-performance model
3114exists, but it is always a good start. 3218exists, but it is always a good start.
3115 3219
3116=item * other models exist, such as the leader/follower pattern, where one 3220=item * other models exist, such as the leader/follower pattern, where one
3117loop is handed through multiple threads in a kind of round-robbin fashion. 3221loop is handed through multiple threads in a kind of round-robin fashion.
3118 3222
3119Chosing a model is hard - look around, learn, know that usually you cna do 3223Choosing a model is hard - look around, learn, know that usually you can do
3120better than you currently do :-) 3224better than you currently do :-)
3121 3225
3122=item * often you need to talk to some other thread which blocks in the 3226=item * often you need to talk to some other thread which blocks in the
3123event loop - C<ev_async> watchers can be used to wake them up from other 3227event loop - C<ev_async> watchers can be used to wake them up from other
3124threads safely (or from signal contexts...). 3228threads safely (or from signal contexts...).
3125 3229
3126=back 3230=back
3127 3231
3128=head2 COROUTINES 3232=head2 COROUTINES
3129 3233
3130Libev is much more accomodating to coroutines ("cooperative threads"): 3234Libev is much more accommodating to coroutines ("cooperative threads"):
3131libev fully supports nesting calls to it's functions from different 3235libev fully supports nesting calls to it's functions from different
3132coroutines (e.g. you can call C<ev_loop> on the same loop from two 3236coroutines (e.g. you can call C<ev_loop> on the same loop from two
3133different coroutines and switch freely between both coroutines running the 3237different coroutines and switch freely between both coroutines running the
3134loop, as long as you don't confuse yourself). The only exception is that 3238loop, as long as you don't confuse yourself). The only exception is that
3135you must not do this from C<ev_periodic> reschedule callbacks. 3239you must not do this from C<ev_periodic> reschedule callbacks.
3176correct watcher to remove. The lists are usually short (you don't usually 3280correct watcher to remove. The lists are usually short (you don't usually
3177have many watchers waiting for the same fd or signal). 3281have many watchers waiting for the same fd or signal).
3178 3282
3179=item Finding the next timer in each loop iteration: O(1) 3283=item Finding the next timer in each loop iteration: O(1)
3180 3284
3181By virtue of using a binary heap, the next timer is always found at the 3285By virtue of using a binary or 4-heap, the next timer is always found at a
3182beginning of the storage array. 3286fixed position in the storage array.
3183 3287
3184=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 3288=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3185 3289
3186A change means an I/O watcher gets started or stopped, which requires 3290A change means an I/O watcher gets started or stopped, which requires
3187libev to recalculate its status (and possibly tell the kernel, depending 3291libev to recalculate its status (and possibly tell the kernel, depending
3188on backend and wether C<ev_io_set> was used). 3292on backend and whether C<ev_io_set> was used).
3189 3293
3190=item Activating one watcher (putting it into the pending state): O(1) 3294=item Activating one watcher (putting it into the pending state): O(1)
3191 3295
3192=item Priority handling: O(number_of_priorities) 3296=item Priority handling: O(number_of_priorities)
3193 3297
3200 3304
3201=item Processing ev_async_send: O(number_of_async_watchers) 3305=item Processing ev_async_send: O(number_of_async_watchers)
3202 3306
3203=item Processing signals: O(max_signal_number) 3307=item Processing signals: O(max_signal_number)
3204 3308
3205Sending involves a syscall I<iff> there were no other C<ev_async_send> 3309Sending involves a system call I<iff> there were no other C<ev_async_send>
3206calls in the current loop iteration. Checking for async and signal events 3310calls in the current loop iteration. Checking for async and signal events
3207involves iterating over all running async watchers or all signal numbers. 3311involves iterating over all running async watchers or all signal numbers.
3208 3312
3209=back 3313=back
3210 3314
3211 3315
3212=head1 Win32 platform limitations and workarounds 3316=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3213 3317
3214Win32 doesn't support any of the standards (e.g. POSIX) that libev 3318Win32 doesn't support any of the standards (e.g. POSIX) that libev
3215requires, and its I/O model is fundamentally incompatible with the POSIX 3319requires, and its I/O model is fundamentally incompatible with the POSIX
3216model. Libev still offers limited functionality on this platform in 3320model. Libev still offers limited functionality on this platform in
3217the form of the C<EVBACKEND_SELECT> backend, and only supports socket 3321the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3224way (note also that glib is the slowest event library known to man). 3328way (note also that glib is the slowest event library known to man).
3225 3329
3226There is no supported compilation method available on windows except 3330There is no supported compilation method available on windows except
3227embedding it into other applications. 3331embedding it into other applications.
3228 3332
3333Not a libev limitation but worth mentioning: windows apparently doesn't
3334accept large writes: instead of resulting in a partial write, windows will
3335either accept everything or return C<ENOBUFS> if the buffer is too large,
3336so make sure you only write small amounts into your sockets (less than a
3337megabyte seems safe, but thsi apparently depends on the amount of memory
3338available).
3339
3229Due to the many, low, and arbitrary limits on the win32 platform and 3340Due to the many, low, and arbitrary limits on the win32 platform and
3230the abysmal performance of winsockets, using a large number of sockets 3341the abysmal performance of winsockets, using a large number of sockets
3231is not recommended (and not reasonable). If your program needs to use 3342is not recommended (and not reasonable). If your program needs to use
3232more than a hundred or so sockets, then likely it needs to use a totally 3343more than a hundred or so sockets, then likely it needs to use a totally
3233different implementation for windows, as libev offers the POSIX readyness 3344different implementation for windows, as libev offers the POSIX readiness
3234notification model, which cannot be implemented efficiently on windows 3345notification model, which cannot be implemented efficiently on windows
3235(microsoft monopoly games). 3346(Microsoft monopoly games).
3347
3348A typical way to use libev under windows is to embed it (see the embedding
3349section for details) and use the following F<evwrap.h> header file instead
3350of F<ev.h>:
3351
3352 #define EV_STANDALONE /* keeps ev from requiring config.h */
3353 #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354
3355 #include "ev.h"
3356
3357And compile the following F<evwrap.c> file into your project (make sure
3358you do I<not> compile the F<ev.c> or any other embedded soruce files!):
3359
3360 #include "evwrap.h"
3361 #include "ev.c"
3236 3362
3237=over 4 3363=over 4
3238 3364
3239=item The winsocket select function 3365=item The winsocket select function
3240 3366
3241The winsocket C<select> function doesn't follow POSIX in that it requires 3367The winsocket C<select> function doesn't follow POSIX in that it
3242socket I<handles> and not socket I<file descriptors>. This makes select 3368requires socket I<handles> and not socket I<file descriptors> (it is
3243very inefficient, and also requires a mapping from file descriptors 3369also extremely buggy). This makes select very inefficient, and also
3244to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, 3370requires a mapping from file descriptors to socket handles (the Microsoft
3245C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor 3371C runtime provides the function C<_open_osfhandle> for this). See the
3246symbols for more info. 3372discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3373C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3247 3374
3248The configuration for a "naked" win32 using the microsoft runtime 3375The configuration for a "naked" win32 using the Microsoft runtime
3249libraries and raw winsocket select is: 3376libraries and raw winsocket select is:
3250 3377
3251 #define EV_USE_SELECT 1 3378 #define EV_USE_SELECT 1
3252 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ 3379 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3253 3380
3254Note that winsockets handling of fd sets is O(n), so you can easily get a 3381Note that winsockets handling of fd sets is O(n), so you can easily get a
3255complexity in the O(n²) range when using win32. 3382complexity in the O(n²) range when using win32.
3256 3383
3257=item Limited number of file descriptors 3384=item Limited number of file descriptors
3258 3385
3259Windows has numerous arbitrary (and low) limits on things. 3386Windows has numerous arbitrary (and low) limits on things.
3260 3387
3261Early versions of winsocket's select only supported waiting for a maximum 3388Early versions of winsocket's select only supported waiting for a maximum
3262of C<64> handles (probably owning to the fact that all windows kernels 3389of C<64> handles (probably owning to the fact that all windows kernels
3263can only wait for C<64> things at the same time internally; microsoft 3390can only wait for C<64> things at the same time internally; Microsoft
3264recommends spawning a chain of threads and wait for 63 handles and the 3391recommends spawning a chain of threads and wait for 63 handles and the
3265previous thread in each. Great). 3392previous thread in each. Great).
3266 3393
3267Newer versions support more handles, but you need to define C<FD_SETSIZE> 3394Newer versions support more handles, but you need to define C<FD_SETSIZE>
3268to some high number (e.g. C<2048>) before compiling the winsocket select 3395to some high number (e.g. C<2048>) before compiling the winsocket select
3269call (which might be in libev or elsewhere, for example, perl does its own 3396call (which might be in libev or elsewhere, for example, perl does its own
3270select emulation on windows). 3397select emulation on windows).
3271 3398
3272Another limit is the number of file descriptors in the microsoft runtime 3399Another limit is the number of file descriptors in the Microsoft runtime
3273libraries, which by default is C<64> (there must be a hidden I<64> fetish 3400libraries, which by default is C<64> (there must be a hidden I<64> fetish
3274or something like this inside microsoft). You can increase this by calling 3401or something like this inside Microsoft). You can increase this by calling
3275C<_setmaxstdio>, which can increase this limit to C<2048> (another 3402C<_setmaxstdio>, which can increase this limit to C<2048> (another
3276arbitrary limit), but is broken in many versions of the microsoft runtime 3403arbitrary limit), but is broken in many versions of the Microsoft runtime
3277libraries. 3404libraries.
3278 3405
3279This might get you to about C<512> or C<2048> sockets (depending on 3406This might get you to about C<512> or C<2048> sockets (depending on
3280windows version and/or the phase of the moon). To get more, you need to 3407windows version and/or the phase of the moon). To get more, you need to
3281wrap all I/O functions and provide your own fd management, but the cost of 3408wrap all I/O functions and provide your own fd management, but the cost of
3288 3415
3289In addition to a working ISO-C implementation, libev relies on a few 3416In addition to a working ISO-C implementation, libev relies on a few
3290additional extensions: 3417additional extensions:
3291 3418
3292=over 4 3419=over 4
3420
3421=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422calling conventions regardless of C<ev_watcher_type *>.
3423
3424Libev assumes not only that all watcher pointers have the same internal
3425structure (guaranteed by POSIX but not by ISO C for example), but it also
3426assumes that the same (machine) code can be used to call any watcher
3427callback: The watcher callbacks have different type signatures, but libev
3428calls them using an C<ev_watcher *> internally.
3293 3429
3294=item C<sig_atomic_t volatile> must be thread-atomic as well 3430=item C<sig_atomic_t volatile> must be thread-atomic as well
3295 3431
3296The type C<sig_atomic_t volatile> (or whatever is defined as 3432The type C<sig_atomic_t volatile> (or whatever is defined as
3297C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different 3433C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
3319is still at least 31 bits everywhere, which is enough for hundreds of 3455is still at least 31 bits everywhere, which is enough for hundreds of
3320millions of watchers. 3456millions of watchers.
3321 3457
3322=item C<double> must hold a time value in seconds with enough accuracy 3458=item C<double> must hold a time value in seconds with enough accuracy
3323 3459
3324The type C<double> is used to represent timestamps. It is required to have 3460The type C<double> is used to represent timestamps. It is required to
3325at least 51 bits of mantissa, which is good enough for at least into the 3461have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3326year 4000. This requirement is fulfilled by implementations implementing 3462enough for at least into the year 4000. This requirement is fulfilled by
3327IEEE 754 (basically all existing ones). 3463implementations implementing IEEE 754 (basically all existing ones).
3328 3464
3329=back 3465=back
3330 3466
3331If you know of other additional requirements drop me a note. 3467If you know of other additional requirements drop me a note.
3332 3468
3333 3469
3470=head1 COMPILER WARNINGS
3471
3472Depending on your compiler and compiler settings, you might get no or a
3473lot of warnings when compiling libev code. Some people are apparently
3474scared by this.
3475
3476However, these are unavoidable for many reasons. For one, each compiler
3477has different warnings, and each user has different tastes regarding
3478warning options. "Warn-free" code therefore cannot be a goal except when
3479targeting a specific compiler and compiler-version.
3480
3481Another reason is that some compiler warnings require elaborate
3482workarounds, or other changes to the code that make it less clear and less
3483maintainable.
3484
3485And of course, some compiler warnings are just plain stupid, or simply
3486wrong (because they don't actually warn about the condition their message
3487seems to warn about).
3488
3489While libev is written to generate as few warnings as possible,
3490"warn-free" code is not a goal, and it is recommended not to build libev
3491with any compiler warnings enabled unless you are prepared to cope with
3492them (e.g. by ignoring them). Remember that warnings are just that:
3493warnings, not errors, or proof of bugs.
3494
3495
3496=head1 VALGRIND
3497
3498Valgrind has a special section here because it is a popular tool that is
3499highly useful, but valgrind reports are very hard to interpret.
3500
3501If you think you found a bug (memory leak, uninitialised data access etc.)
3502in libev, then check twice: If valgrind reports something like:
3503
3504 ==2274== definitely lost: 0 bytes in 0 blocks.
3505 ==2274== possibly lost: 0 bytes in 0 blocks.
3506 ==2274== still reachable: 256 bytes in 1 blocks.
3507
3508Then there is no memory leak. Similarly, under some circumstances,
3509valgrind might report kernel bugs as if it were a bug in libev, or it
3510might be confused (it is a very good tool, but only a tool).
3511
3512If you are unsure about something, feel free to contact the mailing list
3513with the full valgrind report and an explanation on why you think this is
3514a bug in libev. However, don't be annoyed when you get a brisk "this is
3515no bug" answer and take the chance of learning how to interpret valgrind
3516properly.
3517
3518If you need, for some reason, empty reports from valgrind for your project
3519I suggest using suppression lists.
3520
3521
3334=head1 AUTHOR 3522=head1 AUTHOR
3335 3523
3336Marc Lehmann <libev@schmorp.de>. 3524Marc Lehmann <libev@schmorp.de>.
3337 3525

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