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Revision 1.154 by root, Sun May 11 11:47:27 2008 UTC vs.
Revision 1.175 by root, Mon Sep 8 16:36:14 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
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
1092C<EVBACKEND_POLL>. 1134C<EVBACKEND_POLL>.
1093 1135
1094=head3 The special problem of SIGPIPE 1136=head3 The special problem of SIGPIPE
1095 1137
1096While not really specific to libev, it is easy to forget about SIGPIPE: 1138While not really specific to libev, it is easy to forget about SIGPIPE:
1097when reading from a pipe whose other end has been closed, your program 1139when writing to a pipe whose other end has been closed, your program gets
1098gets send a SIGPIPE, which, by default, aborts your program. For most 1140send a SIGPIPE, which, by default, aborts your program. For most programs
1099programs this is sensible behaviour, for daemons, this is usually 1141this is sensible behaviour, for daemons, this is usually undesirable.
1100undesirable.
1101 1142
1102So when you encounter spurious, unexplained daemon exits, make sure you 1143So when you encounter spurious, unexplained daemon exits, make sure you
1103ignore SIGPIPE (and maybe make sure you log the exit status of your daemon 1144ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104somewhere, as that would have given you a big clue). 1145somewhere, as that would have given you a big clue).
1105 1146
1111=item ev_io_init (ev_io *, callback, int fd, int events) 1152=item ev_io_init (ev_io *, callback, int fd, int events)
1112 1153
1113=item ev_io_set (ev_io *, int fd, int events) 1154=item ev_io_set (ev_io *, int fd, int events)
1114 1155
1115Configures an C<ev_io> watcher. The C<fd> is the file descriptor to 1156Configures 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 1157receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1117C<EV_READ | EV_WRITE> to receive the given events. 1158C<EV_READ | EV_WRITE> to receive the given events.
1118 1159
1119=item int fd [read-only] 1160=item int fd [read-only]
1120 1161
1121The file descriptor being watched. 1162The file descriptor being watched.
1130 1171
1131Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1172Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132readable, but only once. Since it is likely line-buffered, you could 1173readable, but only once. Since it is likely line-buffered, you could
1133attempt to read a whole line in the callback. 1174attempt to read a whole line in the callback.
1134 1175
1135 static void 1176 static void
1136 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1177 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1137 { 1178 {
1138 ev_io_stop (loop, w); 1179 ev_io_stop (loop, w);
1139 .. read from stdin here (or from w->fd) and haqndle any I/O errors 1180 .. read from stdin here (or from w->fd) and haqndle any I/O errors
1140 } 1181 }
1141 1182
1142 ... 1183 ...
1143 struct ev_loop *loop = ev_default_init (0); 1184 struct ev_loop *loop = ev_default_init (0);
1144 struct ev_io stdin_readable; 1185 struct ev_io stdin_readable;
1145 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1186 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146 ev_io_start (loop, &stdin_readable); 1187 ev_io_start (loop, &stdin_readable);
1147 ev_loop (loop, 0); 1188 ev_loop (loop, 0);
1148 1189
1149 1190
1150=head2 C<ev_timer> - relative and optionally repeating timeouts 1191=head2 C<ev_timer> - relative and optionally repeating timeouts
1151 1192
1152Timer watchers are simple relative timers that generate an event after a 1193Timer watchers are simple relative timers that generate an event after a
1153given time, and optionally repeating in regular intervals after that. 1194given time, and optionally repeating in regular intervals after that.
1154 1195
1155The timers are based on real time, that is, if you register an event that 1196The 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 1197times 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 1198year, it will still time out after (roughly) and hour. "Roughly" because
1158detecting time jumps is hard, and some inaccuracies are unavoidable (the 1199detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159monotonic clock option helps a lot here). 1200monotonic clock option helps a lot here).
1201
1202The callback is guaranteed to be invoked only after its timeout has passed,
1203but if multiple timers become ready during the same loop iteration then
1204order of execution is undefined.
1205
1206=head3 The special problem of time updates
1207
1208Requesting the current time is a costly operation (it usually takes at
1209least two syscalls): EV therefore updates it's idea of the current time
1210only before and after C<ev_loop> polls for new events, which causes the
1211difference between C<ev_now ()> and C<ev_time ()>.
1160 1212
1161The relative timeouts are calculated relative to the C<ev_now ()> 1213The relative timeouts are calculated relative to the C<ev_now ()>
1162time. This is usually the right thing as this timestamp refers to the time 1214time. This is usually the right thing as this timestamp refers to the time
1163of the event triggering whatever timeout you are modifying/starting. If 1215of the event triggering whatever timeout you are modifying/starting. If
1164you suspect event processing to be delayed and you I<need> to base the timeout 1216you suspect event processing to be delayed and you I<need> to base the
1165on the current time, use something like this to adjust for this: 1217timeout on the current time, use something like this to adjust for this:
1166 1218
1167 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1219 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168 1220
1169The callback is guarenteed to be invoked only when its timeout has passed,
1170but if multiple timers become ready during the same loop iteration then
1171order of execution is undefined.
1172
1173=head3 Watcher-Specific Functions and Data Members 1221=head3 Watcher-Specific Functions and Data Members
1174 1222
1175=over 4 1223=over 4
1176 1224
1177=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1225=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178 1226
1179=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) 1227=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180 1228
1181Configure the timer to trigger after C<after> seconds. If C<repeat> is 1229Configure 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 1230is C<0.>, then it will automatically be stopped once the timeout is
1183timer will automatically be configured to trigger again C<repeat> seconds 1231reached. If it is positive, then the timer will automatically be
1184later, again, and again, until stopped manually. 1232configured to trigger again C<repeat> seconds later, again, and again,
1233until stopped manually.
1185 1234
1186The timer itself will do a best-effort at avoiding drift, that is, if you 1235The 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 1236you configure a timer to trigger every 10 seconds, then it will normally
1188exactly 10 second intervals. If, however, your program cannot keep up with 1237trigger at exactly 10 second intervals. If, however, your program cannot
1189the timer (because it takes longer than those 10 seconds to do stuff) the 1238keep up with the timer (because it takes longer than those 10 seconds to
1190timer will not fire more than once per event loop iteration. 1239do stuff) the timer will not fire more than once per event loop iteration.
1191 1240
1192=item ev_timer_again (loop, ev_timer *) 1241=item ev_timer_again (loop, ev_timer *)
1193 1242
1194This will act as if the timer timed out and restart it again if it is 1243This will act as if the timer timed out and restart it again if it is
1195repeating. The exact semantics are: 1244repeating. The exact semantics are:
1196 1245
1197If the timer is pending, its pending status is cleared. 1246If the timer is pending, its pending status is cleared.
1198 1247
1199If the timer is started but nonrepeating, stop it (as if it timed out). 1248If the timer is started but non-repeating, stop it (as if it timed out).
1200 1249
1201If the timer is repeating, either start it if necessary (with the 1250If the timer is repeating, either start it if necessary (with the
1202C<repeat> value), or reset the running timer to the C<repeat> value. 1251C<repeat> value), or reset the running timer to the C<repeat> value.
1203 1252
1204This sounds a bit complicated, but here is a useful and typical 1253This 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 1254example: 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 1255timeout, 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 1256seconds 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 1257configure 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 1258C<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 1259you go into an idle state where you do not expect data to travel on the
1236 1285
1237=head3 Examples 1286=head3 Examples
1238 1287
1239Example: Create a timer that fires after 60 seconds. 1288Example: Create a timer that fires after 60 seconds.
1240 1289
1241 static void 1290 static void
1242 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1291 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1243 { 1292 {
1244 .. one minute over, w is actually stopped right here 1293 .. one minute over, w is actually stopped right here
1245 } 1294 }
1246 1295
1247 struct ev_timer mytimer; 1296 struct ev_timer mytimer;
1248 ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1297 ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249 ev_timer_start (loop, &mytimer); 1298 ev_timer_start (loop, &mytimer);
1250 1299
1251Example: Create a timeout timer that times out after 10 seconds of 1300Example: Create a timeout timer that times out after 10 seconds of
1252inactivity. 1301inactivity.
1253 1302
1254 static void 1303 static void
1255 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1304 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1256 { 1305 {
1257 .. ten seconds without any activity 1306 .. ten seconds without any activity
1258 } 1307 }
1259 1308
1260 struct ev_timer mytimer; 1309 struct ev_timer mytimer;
1261 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ 1310 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262 ev_timer_again (&mytimer); /* start timer */ 1311 ev_timer_again (&mytimer); /* start timer */
1263 ev_loop (loop, 0); 1312 ev_loop (loop, 0);
1264 1313
1265 // and in some piece of code that gets executed on any "activity": 1314 // and in some piece of code that gets executed on any "activity":
1266 // reset the timeout to start ticking again at 10 seconds 1315 // reset the timeout to start ticking again at 10 seconds
1267 ev_timer_again (&mytimer); 1316 ev_timer_again (&mytimer);
1268 1317
1269 1318
1270=head2 C<ev_periodic> - to cron or not to cron? 1319=head2 C<ev_periodic> - to cron or not to cron?
1271 1320
1272Periodic watchers are also timers of a kind, but they are very versatile 1321Periodic watchers are also timers of a kind, but they are very versatile
1273(and unfortunately a bit complex). 1322(and unfortunately a bit complex).
1274 1323
1275Unlike C<ev_timer>'s, they are not based on real time (or relative time) 1324Unlike 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 1325but 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 1326to 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 () 1327periodic 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 1328+ 10.>, that is, an absolute time not a delay) and then reset your system
1329clock 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 1330to trigger the event (unlike an C<ev_timer>, which would still trigger
1281roughly 10 seconds later). 1331roughly 10 seconds later as it uses a relative timeout).
1282 1332
1283They can also be used to implement vastly more complex timers, such as 1333C<ev_periodic>s can also be used to implement vastly more complex timers,
1284triggering an event on each midnight, local time or other, complicated, 1334such as triggering an event on each "midnight, local time", or other
1285rules. 1335complicated, rules.
1286 1336
1287As with timers, the callback is guarenteed to be invoked only when the 1337As 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 1338time (C<at>) has passed, but if multiple periodic timers become ready
1289during the same loop iteration then order of execution is undefined. 1339during the same loop iteration then order of execution is undefined.
1290 1340
1291=head3 Watcher-Specific Functions and Data Members 1341=head3 Watcher-Specific Functions and Data Members
1292 1342
1293=over 4 1343=over 4
1301 1351
1302=over 4 1352=over 4
1303 1353
1304=item * absolute timer (at = time, interval = reschedule_cb = 0) 1354=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305 1355
1306In this configuration the watcher triggers an event at the wallclock time 1356In 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, 1357time 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 1358jump occurs, that is, if it is to be run at January 1st 2011 then it will
1309system time reaches or surpasses this time. 1359run when the system time reaches or surpasses this time.
1310 1360
1311=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) 1361=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312 1362
1313In this mode the watcher will always be scheduled to time out at the next 1363In 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) 1364C<at + N * interval> time (for some integer N, which can also be negative)
1315and then repeat, regardless of any time jumps. 1365and then repeat, regardless of any time jumps.
1316 1366
1317This can be used to create timers that do not drift with respect to system 1367This can be used to create timers that do not drift with respect to system
1318time: 1368time, for example, here is a C<ev_periodic> that triggers each hour, on
1369the hour:
1319 1370
1320 ev_periodic_set (&periodic, 0., 3600., 0); 1371 ev_periodic_set (&periodic, 0., 3600., 0);
1321 1372
1322This doesn't mean there will always be 3600 seconds in between triggers, 1373This 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 1374but 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 1375full hour (UTC), or more correctly, when the system time is evenly divisible
1325by 3600. 1376by 3600.
1326 1377
1327Another way to think about it (for the mathematically inclined) is that 1378Another 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 1379C<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. 1380time where C<time = at (mod interval)>, regardless of any time jumps.
1330 1381
1331For numerical stability it is preferable that the C<at> value is near 1382For 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 1383C<ev_now ()> (the current time), but there is no range requirement for
1333this value. 1384this value, and in fact is often specified as zero.
1385
1386Note also that there is an upper limit to how often a timer can fire (CPU
1387speed for example), so if C<interval> is very small then timing stability
1388will of course deteriorate. Libev itself tries to be exact to be about one
1389millisecond (if the OS supports it and the machine is fast enough).
1334 1390
1335=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) 1391=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336 1392
1337In this mode the values for C<interval> and C<at> are both being 1393In this mode the values for C<interval> and C<at> are both being
1338ignored. Instead, each time the periodic watcher gets scheduled, the 1394ignored. Instead, each time the periodic watcher gets scheduled, the
1339reschedule callback will be called with the watcher as first, and the 1395reschedule callback will be called with the watcher as first, and the
1340current time as second argument. 1396current time as second argument.
1341 1397
1342NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, 1398NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1343ever, or make any event loop modifications>. If you need to stop it, 1399ever, 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 1400
1401If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1402it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1403only event loop modification you are allowed to do).
1404
1347Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1405The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1348ev_tstamp now)>, e.g.: 1406*w, ev_tstamp now)>, e.g.:
1349 1407
1350 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1408 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1351 { 1409 {
1352 return now + 60.; 1410 return now + 60.;
1353 } 1411 }
1355It must return the next time to trigger, based on the passed time value 1413It 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 1414(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 1415will usually be called just before the callback will be triggered, but
1358might be called at other times, too. 1416might be called at other times, too.
1359 1417
1360NOTE: I<< This callback must always return a time that is later than the 1418NOTE: 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. 1419equal to the passed C<now> value >>.
1362 1420
1363This can be used to create very complex timers, such as a timer that 1421This 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 1422triggers 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 1423next 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 1424you do this is, again, up to you (but it is not trivial, which is the main
1367reason I omitted it as an example). 1425reason I omitted it as an example).
1368 1426
1369=back 1427=back
1404 1462
1405=head3 Examples 1463=head3 Examples
1406 1464
1407Example: Call a callback every hour, or, more precisely, whenever the 1465Example: Call a callback every hour, or, more precisely, whenever the
1408system clock is divisible by 3600. The callback invocation times have 1466system clock is divisible by 3600. The callback invocation times have
1409potentially a lot of jittering, but good long-term stability. 1467potentially a lot of jitter, but good long-term stability.
1410 1468
1411 static void 1469 static void
1412 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1470 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1413 { 1471 {
1414 ... its now a full hour (UTC, or TAI or whatever your clock follows) 1472 ... its now a full hour (UTC, or TAI or whatever your clock follows)
1415 } 1473 }
1416 1474
1417 struct ev_periodic hourly_tick; 1475 struct ev_periodic hourly_tick;
1418 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1476 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419 ev_periodic_start (loop, &hourly_tick); 1477 ev_periodic_start (loop, &hourly_tick);
1420 1478
1421Example: The same as above, but use a reschedule callback to do it: 1479Example: The same as above, but use a reschedule callback to do it:
1422 1480
1423 #include <math.h> 1481 #include <math.h>
1424 1482
1425 static ev_tstamp 1483 static ev_tstamp
1426 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1484 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1427 { 1485 {
1428 return fmod (now, 3600.) + 3600.; 1486 return fmod (now, 3600.) + 3600.;
1429 } 1487 }
1430 1488
1431 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1489 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432 1490
1433Example: Call a callback every hour, starting now: 1491Example: Call a callback every hour, starting now:
1434 1492
1435 struct ev_periodic hourly_tick; 1493 struct ev_periodic hourly_tick;
1436 ev_periodic_init (&hourly_tick, clock_cb, 1494 ev_periodic_init (&hourly_tick, clock_cb,
1437 fmod (ev_now (loop), 3600.), 3600., 0); 1495 fmod (ev_now (loop), 3600.), 3600., 0);
1438 ev_periodic_start (loop, &hourly_tick); 1496 ev_periodic_start (loop, &hourly_tick);
1439 1497
1440 1498
1441=head2 C<ev_signal> - signal me when a signal gets signalled! 1499=head2 C<ev_signal> - signal me when a signal gets signalled!
1442 1500
1443Signal watchers will trigger an event when the process receives a specific 1501Signal watchers will trigger an event when the process receives a specific
1451as you don't register any with libev). Similarly, when the last signal 1509as 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 1510watcher for a signal is stopped libev will reset the signal handler to
1453SIG_DFL (regardless of what it was set to before). 1511SIG_DFL (regardless of what it was set to before).
1454 1512
1455If possible and supported, libev will install its handlers with 1513If possible and supported, libev will install its handlers with
1456C<SA_RESTART> behaviour enabled, so syscalls should not be unduly 1514C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457interrupted. If you have a problem with syscalls getting interrupted by 1515interrupted. 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 1516signals you can block all signals in an C<ev_check> watcher and unblock
1459them in an C<ev_prepare> watcher. 1517them in an C<ev_prepare> watcher.
1460 1518
1461=head3 Watcher-Specific Functions and Data Members 1519=head3 Watcher-Specific Functions and Data Members
1462 1520
1477 1535
1478=head3 Examples 1536=head3 Examples
1479 1537
1480Example: Try to exit cleanly on SIGINT and SIGTERM. 1538Example: Try to exit cleanly on SIGINT and SIGTERM.
1481 1539
1482 static void 1540 static void
1483 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1541 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1484 { 1542 {
1485 ev_unloop (loop, EVUNLOOP_ALL); 1543 ev_unloop (loop, EVUNLOOP_ALL);
1486 } 1544 }
1487 1545
1488 struct ev_signal signal_watcher; 1546 struct ev_signal signal_watcher;
1489 ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1547 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490 ev_signal_start (loop, &sigint_cb); 1548 ev_signal_start (loop, &sigint_cb);
1491 1549
1492 1550
1493=head2 C<ev_child> - watch out for process status changes 1551=head2 C<ev_child> - watch out for process status changes
1494 1552
1495Child watchers trigger when your process receives a SIGCHLD in response to 1553Child watchers trigger when your process receives a SIGCHLD in response to
1497is permissible to install a child watcher I<after> the child has been 1555is 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 1556forked (which implies it might have already exited), as long as the event
1499loop isn't entered (or is continued from a watcher). 1557loop isn't entered (or is continued from a watcher).
1500 1558
1501Only the default event loop is capable of handling signals, and therefore 1559Only the default event loop is capable of handling signals, and therefore
1502you can only rgeister child watchers in the default event loop. 1560you can only register child watchers in the default event loop.
1503 1561
1504=head3 Process Interaction 1562=head3 Process Interaction
1505 1563
1506Libev grabs C<SIGCHLD> as soon as the default event loop is 1564Libev grabs C<SIGCHLD> as soon as the default event loop is
1507initialised. This is necessary to guarantee proper behaviour even if 1565initialised. This is necessary to guarantee proper behaviour even if
1508the first child watcher is started after the child exits. The occurance 1566the first child watcher is started after the child exits. The occurrence
1509of C<SIGCHLD> is recorded asynchronously, but child reaping is done 1567of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510synchronously as part of the event loop processing. Libev always reaps all 1568synchronously as part of the event loop processing. Libev always reaps all
1511children, even ones not watched. 1569children, even ones not watched.
1512 1570
1513=head3 Overriding the Built-In Processing 1571=head3 Overriding the Built-In Processing
1517handler, you can override it easily by installing your own handler for 1575handler, you can override it easily by installing your own handler for
1518C<SIGCHLD> after initialising the default loop, and making sure the 1576C<SIGCHLD> after initialising the default loop, and making sure the
1519default loop never gets destroyed. You are encouraged, however, to use an 1577default loop never gets destroyed. You are encouraged, however, to use an
1520event-based approach to child reaping and thus use libev's support for 1578event-based approach to child reaping and thus use libev's support for
1521that, so other libev users can use C<ev_child> watchers freely. 1579that, so other libev users can use C<ev_child> watchers freely.
1580
1581=head3 Stopping the Child Watcher
1582
1583Currently, the child watcher never gets stopped, even when the
1584child terminates, so normally one needs to stop the watcher in the
1585callback. Future versions of libev might stop the watcher automatically
1586when a child exit is detected.
1522 1587
1523=head3 Watcher-Specific Functions and Data Members 1588=head3 Watcher-Specific Functions and Data Members
1524 1589
1525=over 4 1590=over 4
1526 1591
1555=head3 Examples 1620=head3 Examples
1556 1621
1557Example: C<fork()> a new process and install a child handler to wait for 1622Example: C<fork()> a new process and install a child handler to wait for
1558its completion. 1623its completion.
1559 1624
1560 ev_child cw; 1625 ev_child cw;
1561 1626
1562 static void 1627 static void
1563 child_cb (EV_P_ struct ev_child *w, int revents) 1628 child_cb (EV_P_ struct ev_child *w, int revents)
1564 { 1629 {
1565 ev_child_stop (EV_A_ w); 1630 ev_child_stop (EV_A_ w);
1566 printf ("process %d exited with status %x\n", w->rpid, w->rstatus); 1631 printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567 } 1632 }
1568 1633
1569 pid_t pid = fork (); 1634 pid_t pid = fork ();
1570 1635
1571 if (pid < 0) 1636 if (pid < 0)
1572 // error 1637 // error
1573 else if (pid == 0) 1638 else if (pid == 0)
1574 { 1639 {
1575 // the forked child executes here 1640 // the forked child executes here
1576 exit (1); 1641 exit (1);
1577 } 1642 }
1578 else 1643 else
1579 { 1644 {
1580 ev_child_init (&cw, child_cb, pid, 0); 1645 ev_child_init (&cw, child_cb, pid, 0);
1581 ev_child_start (EV_DEFAULT_ &cw); 1646 ev_child_start (EV_DEFAULT_ &cw);
1582 } 1647 }
1583 1648
1584 1649
1585=head2 C<ev_stat> - did the file attributes just change? 1650=head2 C<ev_stat> - did the file attributes just change?
1586 1651
1587This watches a filesystem path for attribute changes. That is, it calls 1652This 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 1653C<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. 1654compared to the last time, invoking the callback if it did.
1590 1655
1591The path does not need to exist: changing from "path exists" to "path does 1656The 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 1657not exist" is a status change like any other. The condition "path does
1620will be no polling. 1685will be no polling.
1621 1686
1622=head3 ABI Issues (Largefile Support) 1687=head3 ABI Issues (Largefile Support)
1623 1688
1624Libev by default (unless the user overrides this) uses the default 1689Libev by default (unless the user overrides this) uses the default
1625compilation environment, which means that on systems with optionally 1690compilation environment, which means that on systems with large file
1626disabled large file support, you get the 32 bit version of the stat 1691support disabled by default, you get the 32 bit version of the stat
1627structure. When using the library from programs that change the ABI to 1692structure. 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 1693use 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 1694compile 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 1695obviously the case with any flags that change the ABI, but the problem is
1631most noticably with ev_stat and largefile support. 1696most noticeably disabled with ev_stat and large file support.
1697
1698The solution for this is to lobby your distribution maker to make large
1699file interfaces available by default (as e.g. FreeBSD does) and not
1700optional. Libev cannot simply switch on large file support because it has
1701to exchange stat structures with application programs compiled using the
1702default compilation environment.
1632 1703
1633=head3 Inotify 1704=head3 Inotify
1634 1705
1635When C<inotify (7)> support has been compiled into libev (generally only 1706When 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 1707available on Linux) and present at runtime, it will be used to speed up
1646implement this functionality, due to the requirement of having a file 1717implement this functionality, due to the requirement of having a file
1647descriptor open on the object at all times). 1718descriptor open on the object at all times).
1648 1719
1649=head3 The special problem of stat time resolution 1720=head3 The special problem of stat time resolution
1650 1721
1651The C<stat ()> syscall only supports full-second resolution portably, and 1722The C<stat ()> system call only supports full-second resolution portably, and
1652even on systems where the resolution is higher, many filesystems still 1723even on systems where the resolution is higher, many file systems still
1653only support whole seconds. 1724only support whole seconds.
1654 1725
1655That means that, if the time is the only thing that changes, you can 1726That 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 1727easily miss updates: on the first update, C<ev_stat> detects a change and
1657calls your callback, which does something. When there is another update 1728calls 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 1729within the same second, C<ev_stat> will be unable to detect it as the stat
1659data does not change. 1730data does not change.
1660 1731
1661The solution to this is to delay acting on a change for slightly more 1732The 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 1733than 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); 1734a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664ev_timer_again (loop, w)>). 1735ev_timer_again (loop, w)>).
1665 1736
1666The C<.02> offset is added to work around small timing inconsistencies 1737The C<.02> offset is added to work around small timing inconsistencies
1667of some operating systems (where the second counter of the current time 1738of some operating systems (where the second counter of the current time
1717 1788
1718The specified interval. 1789The specified interval.
1719 1790
1720=item const char *path [read-only] 1791=item const char *path [read-only]
1721 1792
1722The filesystem path that is being watched. 1793The file system path that is being watched.
1723 1794
1724=back 1795=back
1725 1796
1726=head3 Examples 1797=head3 Examples
1727 1798
1728Example: Watch C</etc/passwd> for attribute changes. 1799Example: Watch C</etc/passwd> for attribute changes.
1729 1800
1730 static void 1801 static void
1731 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1802 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732 { 1803 {
1733 /* /etc/passwd changed in some way */ 1804 /* /etc/passwd changed in some way */
1734 if (w->attr.st_nlink) 1805 if (w->attr.st_nlink)
1735 { 1806 {
1736 printf ("passwd current size %ld\n", (long)w->attr.st_size); 1807 printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737 printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); 1808 printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738 printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); 1809 printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739 } 1810 }
1740 else 1811 else
1741 /* you shalt not abuse printf for puts */ 1812 /* you shalt not abuse printf for puts */
1742 puts ("wow, /etc/passwd is not there, expect problems. " 1813 puts ("wow, /etc/passwd is not there, expect problems. "
1743 "if this is windows, they already arrived\n"); 1814 "if this is windows, they already arrived\n");
1744 } 1815 }
1745 1816
1746 ... 1817 ...
1747 ev_stat passwd; 1818 ev_stat passwd;
1748 1819
1749 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); 1820 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750 ev_stat_start (loop, &passwd); 1821 ev_stat_start (loop, &passwd);
1751 1822
1752Example: Like above, but additionally use a one-second delay so we do not 1823Example: Like above, but additionally use a one-second delay so we do not
1753miss updates (however, frequent updates will delay processing, too, so 1824miss updates (however, frequent updates will delay processing, too, so
1754one might do the work both on C<ev_stat> callback invocation I<and> on 1825one might do the work both on C<ev_stat> callback invocation I<and> on
1755C<ev_timer> callback invocation). 1826C<ev_timer> callback invocation).
1756 1827
1757 static ev_stat passwd; 1828 static ev_stat passwd;
1758 static ev_timer timer; 1829 static ev_timer timer;
1759 1830
1760 static void 1831 static void
1761 timer_cb (EV_P_ ev_timer *w, int revents) 1832 timer_cb (EV_P_ ev_timer *w, int revents)
1762 { 1833 {
1763 ev_timer_stop (EV_A_ w); 1834 ev_timer_stop (EV_A_ w);
1764 1835
1765 /* now it's one second after the most recent passwd change */ 1836 /* now it's one second after the most recent passwd change */
1766 } 1837 }
1767 1838
1768 static void 1839 static void
1769 stat_cb (EV_P_ ev_stat *w, int revents) 1840 stat_cb (EV_P_ ev_stat *w, int revents)
1770 { 1841 {
1771 /* reset the one-second timer */ 1842 /* reset the one-second timer */
1772 ev_timer_again (EV_A_ &timer); 1843 ev_timer_again (EV_A_ &timer);
1773 } 1844 }
1774 1845
1775 ... 1846 ...
1776 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); 1847 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777 ev_stat_start (loop, &passwd); 1848 ev_stat_start (loop, &passwd);
1778 ev_timer_init (&timer, timer_cb, 0., 1.02); 1849 ev_timer_init (&timer, timer_cb, 0., 1.02);
1779 1850
1780 1851
1781=head2 C<ev_idle> - when you've got nothing better to do... 1852=head2 C<ev_idle> - when you've got nothing better to do...
1782 1853
1783Idle watchers trigger events when no other events of the same or higher 1854Idle watchers trigger events when no other events of the same or higher
1814=head3 Examples 1885=head3 Examples
1815 1886
1816Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1887Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817callback, free it. Also, use no error checking, as usual. 1888callback, free it. Also, use no error checking, as usual.
1818 1889
1819 static void 1890 static void
1820 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1891 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1821 { 1892 {
1822 free (w); 1893 free (w);
1823 // now do something you wanted to do when the program has 1894 // now do something you wanted to do when the program has
1824 // no longer anything immediate to do. 1895 // no longer anything immediate to do.
1825 } 1896 }
1826 1897
1827 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1898 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1828 ev_idle_init (idle_watcher, idle_cb); 1899 ev_idle_init (idle_watcher, idle_cb);
1829 ev_idle_start (loop, idle_cb); 1900 ev_idle_start (loop, idle_cb);
1830 1901
1831 1902
1832=head2 C<ev_prepare> and C<ev_check> - customise your event loop! 1903=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833 1904
1834Prepare and check watchers are usually (but not always) used in tandem: 1905Prepare and check watchers are usually (but not always) used in tandem:
1853 1924
1854This is done by examining in each prepare call which file descriptors need 1925This 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 1926to 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 1927them and starting an C<ev_timer> watcher for any timeouts (many libraries
1857provide just this functionality). Then, in the check watcher you check for 1928provide just this functionality). Then, in the check watcher you check for
1858any events that occured (by checking the pending status of all watchers 1929any 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 1930and stopping them) and call back into the library. The I/O and timer
1860callbacks will never actually be called (but must be valid nevertheless, 1931callbacks will never actually be called (but must be valid nevertheless,
1861because you never know, you know?). 1932because you never know, you know?).
1862 1933
1863As another example, the Perl Coro module uses these hooks to integrate 1934As another example, the Perl Coro module uses these hooks to integrate
1906and in a check watcher, destroy them and call into libadns. What follows 1977and 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 1978is 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 1979priority 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. 1980the callbacks for the IO/timeout watchers might not have been called yet.
1910 1981
1911 static ev_io iow [nfd]; 1982 static ev_io iow [nfd];
1912 static ev_timer tw; 1983 static ev_timer tw;
1913 1984
1914 static void 1985 static void
1915 io_cb (ev_loop *loop, ev_io *w, int revents) 1986 io_cb (ev_loop *loop, ev_io *w, int revents)
1916 { 1987 {
1917 } 1988 }
1918 1989
1919 // create io watchers for each fd and a timer before blocking 1990 // create io watchers for each fd and a timer before blocking
1920 static void 1991 static void
1921 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1992 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1922 { 1993 {
1923 int timeout = 3600000; 1994 int timeout = 3600000;
1924 struct pollfd fds [nfd]; 1995 struct pollfd fds [nfd];
1925 // actual code will need to loop here and realloc etc. 1996 // actual code will need to loop here and realloc etc.
1926 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 1997 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927 1998
1928 /* the callback is illegal, but won't be called as we stop during check */ 1999 /* the callback is illegal, but won't be called as we stop during check */
1929 ev_timer_init (&tw, 0, timeout * 1e-3); 2000 ev_timer_init (&tw, 0, timeout * 1e-3);
1930 ev_timer_start (loop, &tw); 2001 ev_timer_start (loop, &tw);
1931 2002
1932 // create one ev_io per pollfd 2003 // create one ev_io per pollfd
1933 for (int i = 0; i < nfd; ++i) 2004 for (int i = 0; i < nfd; ++i)
1934 { 2005 {
1935 ev_io_init (iow + i, io_cb, fds [i].fd, 2006 ev_io_init (iow + i, io_cb, fds [i].fd,
1936 ((fds [i].events & POLLIN ? EV_READ : 0) 2007 ((fds [i].events & POLLIN ? EV_READ : 0)
1937 | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 2008 | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938 2009
1939 fds [i].revents = 0; 2010 fds [i].revents = 0;
1940 ev_io_start (loop, iow + i); 2011 ev_io_start (loop, iow + i);
1941 } 2012 }
1942 } 2013 }
1943 2014
1944 // stop all watchers after blocking 2015 // stop all watchers after blocking
1945 static void 2016 static void
1946 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 2017 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1947 { 2018 {
1948 ev_timer_stop (loop, &tw); 2019 ev_timer_stop (loop, &tw);
1949 2020
1950 for (int i = 0; i < nfd; ++i) 2021 for (int i = 0; i < nfd; ++i)
1951 { 2022 {
1952 // set the relevant poll flags 2023 // set the relevant poll flags
1953 // could also call adns_processreadable etc. here 2024 // could also call adns_processreadable etc. here
1954 struct pollfd *fd = fds + i; 2025 struct pollfd *fd = fds + i;
1955 int revents = ev_clear_pending (iow + i); 2026 int revents = ev_clear_pending (iow + i);
1956 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; 2027 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; 2028 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958 2029
1959 // now stop the watcher 2030 // now stop the watcher
1960 ev_io_stop (loop, iow + i); 2031 ev_io_stop (loop, iow + i);
1961 } 2032 }
1962 2033
1963 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 2034 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964 } 2035 }
1965 2036
1966Method 2: This would be just like method 1, but you run C<adns_afterpoll> 2037Method 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. 2038in the prepare watcher and would dispose of the check watcher.
1968 2039
1969Method 3: If the module to be embedded supports explicit event 2040Method 3: If the module to be embedded supports explicit event
1970notification (adns does), you can also make use of the actual watcher 2041notification (libadns does), you can also make use of the actual watcher
1971callbacks, and only destroy/create the watchers in the prepare watcher. 2042callbacks, and only destroy/create the watchers in the prepare watcher.
1972 2043
1973 static void 2044 static void
1974 timer_cb (EV_P_ ev_timer *w, int revents) 2045 timer_cb (EV_P_ ev_timer *w, int revents)
1975 { 2046 {
1976 adns_state ads = (adns_state)w->data; 2047 adns_state ads = (adns_state)w->data;
1977 update_now (EV_A); 2048 update_now (EV_A);
1978 2049
1979 adns_processtimeouts (ads, &tv_now); 2050 adns_processtimeouts (ads, &tv_now);
1980 } 2051 }
1981 2052
1982 static void 2053 static void
1983 io_cb (EV_P_ ev_io *w, int revents) 2054 io_cb (EV_P_ ev_io *w, int revents)
1984 { 2055 {
1985 adns_state ads = (adns_state)w->data; 2056 adns_state ads = (adns_state)w->data;
1986 update_now (EV_A); 2057 update_now (EV_A);
1987 2058
1988 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); 2059 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); 2060 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990 } 2061 }
1991 2062
1992 // do not ever call adns_afterpoll 2063 // do not ever call adns_afterpoll
1993 2064
1994Method 4: Do not use a prepare or check watcher because the module you 2065Method 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 2066want to embed is too inflexible to support it. Instead, you can override
1996their poll function. The drawback with this solution is that the main 2067their 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 2068loop is now no longer controllable by EV. The C<Glib::EV> module does
1998this. 2069this.
1999 2070
2000 static gint 2071 static gint
2001 event_poll_func (GPollFD *fds, guint nfds, gint timeout) 2072 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002 { 2073 {
2003 int got_events = 0; 2074 int got_events = 0;
2004 2075
2005 for (n = 0; n < nfds; ++n) 2076 for (n = 0; n < nfds; ++n)
2006 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events 2077 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007 2078
2008 if (timeout >= 0) 2079 if (timeout >= 0)
2009 // create/start timer 2080 // create/start timer
2010 2081
2011 // poll 2082 // poll
2012 ev_loop (EV_A_ 0); 2083 ev_loop (EV_A_ 0);
2013 2084
2014 // stop timer again 2085 // stop timer again
2015 if (timeout >= 0) 2086 if (timeout >= 0)
2016 ev_timer_stop (EV_A_ &to); 2087 ev_timer_stop (EV_A_ &to);
2017 2088
2018 // stop io watchers again - their callbacks should have set 2089 // stop io watchers again - their callbacks should have set
2019 for (n = 0; n < nfds; ++n) 2090 for (n = 0; n < nfds; ++n)
2020 ev_io_stop (EV_A_ iow [n]); 2091 ev_io_stop (EV_A_ iow [n]);
2021 2092
2022 return got_events; 2093 return got_events;
2023 } 2094 }
2024 2095
2025 2096
2026=head2 C<ev_embed> - when one backend isn't enough... 2097=head2 C<ev_embed> - when one backend isn't enough...
2027 2098
2028This is a rather advanced watcher type that lets you embed one event loop 2099This is a rather advanced watcher type that lets you embed one event loop
2084 2155
2085Configures the watcher to embed the given loop, which must be 2156Configures the watcher to embed the given loop, which must be
2086embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be 2157embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087invoked automatically, otherwise it is the responsibility of the callback 2158invoked automatically, otherwise it is the responsibility of the callback
2088to invoke it (it will continue to be called until the sweep has been done, 2159to 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). 2160if you do not want that, you need to temporarily stop the embed watcher).
2090 2161
2091=item ev_embed_sweep (loop, ev_embed *) 2162=item ev_embed_sweep (loop, ev_embed *)
2092 2163
2093Make a single, non-blocking sweep over the embedded loop. This works 2164Make a single, non-blocking sweep over the embedded loop. This works
2094similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most 2165similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095apropriate way for embedded loops. 2166appropriate way for embedded loops.
2096 2167
2097=item struct ev_loop *other [read-only] 2168=item struct ev_loop *other [read-only]
2098 2169
2099The embedded event loop. 2170The embedded event loop.
2100 2171
2102 2173
2103=head3 Examples 2174=head3 Examples
2104 2175
2105Example: Try to get an embeddable event loop and embed it into the default 2176Example: 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 2177event 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 2178loop 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 2179C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109used). 2180used).
2110 2181
2111 struct ev_loop *loop_hi = ev_default_init (0); 2182 struct ev_loop *loop_hi = ev_default_init (0);
2112 struct ev_loop *loop_lo = 0; 2183 struct ev_loop *loop_lo = 0;
2113 struct ev_embed embed; 2184 struct ev_embed embed;
2114 2185
2115 // see if there is a chance of getting one that works 2186 // see if there is a chance of getting one that works
2116 // (remember that a flags value of 0 means autodetection) 2187 // (remember that a flags value of 0 means autodetection)
2117 loop_lo = ev_embeddable_backends () & ev_recommended_backends () 2188 loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) 2189 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119 : 0; 2190 : 0;
2120 2191
2121 // if we got one, then embed it, otherwise default to loop_hi 2192 // if we got one, then embed it, otherwise default to loop_hi
2122 if (loop_lo) 2193 if (loop_lo)
2123 { 2194 {
2124 ev_embed_init (&embed, 0, loop_lo); 2195 ev_embed_init (&embed, 0, loop_lo);
2125 ev_embed_start (loop_hi, &embed); 2196 ev_embed_start (loop_hi, &embed);
2126 } 2197 }
2127 else 2198 else
2128 loop_lo = loop_hi; 2199 loop_lo = loop_hi;
2129 2200
2130Example: Check if kqueue is available but not recommended and create 2201Example: Check if kqueue is available but not recommended and create
2131a kqueue backend for use with sockets (which usually work with any 2202a kqueue backend for use with sockets (which usually work with any
2132kqueue implementation). Store the kqueue/socket-only event loop in 2203kqueue implementation). Store the kqueue/socket-only event loop in
2133C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). 2204C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134 2205
2135 struct ev_loop *loop = ev_default_init (0); 2206 struct ev_loop *loop = ev_default_init (0);
2136 struct ev_loop *loop_socket = 0; 2207 struct ev_loop *loop_socket = 0;
2137 struct ev_embed embed; 2208 struct ev_embed embed;
2138 2209
2139 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) 2210 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) 2211 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141 { 2212 {
2142 ev_embed_init (&embed, 0, loop_socket); 2213 ev_embed_init (&embed, 0, loop_socket);
2143 ev_embed_start (loop, &embed); 2214 ev_embed_start (loop, &embed);
2144 } 2215 }
2145 2216
2146 if (!loop_socket) 2217 if (!loop_socket)
2147 loop_socket = loop; 2218 loop_socket = loop;
2148 2219
2149 // now use loop_socket for all sockets, and loop for everything else 2220 // now use loop_socket for all sockets, and loop for everything else
2150 2221
2151 2222
2152=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2223=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153 2224
2154Fork watchers are called when a C<fork ()> was detected (usually because 2225Fork watchers are called when a C<fork ()> was detected (usually because
2207 2278
2208=item queueing from a signal handler context 2279=item queueing from a signal handler context
2209 2280
2210To implement race-free queueing, you simply add to the queue in the signal 2281To 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 2282handler but you block the signal handler in the watcher callback. Here is an example that does that for
2212some fictitiuous SIGUSR1 handler: 2283some fictitious SIGUSR1 handler:
2213 2284
2214 static ev_async mysig; 2285 static ev_async mysig;
2215 2286
2216 static void 2287 static void
2217 sigusr1_handler (void) 2288 sigusr1_handler (void)
2291=item ev_async_send (loop, ev_async *) 2362=item ev_async_send (loop, ev_async *)
2292 2363
2293Sends/signals/activates the given C<ev_async> watcher, that is, feeds 2364Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294an C<EV_ASYNC> event on the watcher into the event loop. Unlike 2365an 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 2366C<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 2367similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297section below on what exactly this means). 2368section below on what exactly this means).
2298 2369
2299This call incurs the overhead of a syscall only once per loop iteration, 2370This 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 2371so while the overhead might be noticeable, it doesn't apply to repeated
2301calls to C<ev_async_send>. 2372calls to C<ev_async_send>.
2302 2373
2303=item bool = ev_async_pending (ev_async *) 2374=item bool = ev_async_pending (ev_async *)
2304 2375
2305Returns a non-zero value when C<ev_async_send> has been called on the 2376Returns a non-zero value when C<ev_async_send> has been called on the
2307event loop. 2378event loop.
2308 2379
2309C<ev_async_send> sets a flag in the watcher and wakes up the loop. When 2380C<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, 2381the 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 2382it 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. 2383quickly check whether invoking the loop might be a good idea.
2313 2384
2314Not that this does I<not> check wether the watcher itself is pending, only 2385Not that this does I<not> check whether the watcher itself is pending, only
2315wether it has been requested to make this watcher pending. 2386whether it has been requested to make this watcher pending.
2316 2387
2317=back 2388=back
2318 2389
2319 2390
2320=head1 OTHER FUNCTIONS 2391=head1 OTHER FUNCTIONS
2331or timeout without having to allocate/configure/start/stop/free one or 2402or timeout without having to allocate/configure/start/stop/free one or
2332more watchers yourself. 2403more watchers yourself.
2333 2404
2334If C<fd> is less than 0, then no I/O watcher will be started and events 2405If 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 2406is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2336C<events> set will be craeted and started. 2407C<events> set will be created and started.
2337 2408
2338If C<timeout> is less than 0, then no timeout watcher will be 2409If C<timeout> is less than 0, then no timeout watcher will be
2339started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 2410started. 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 2411repeat = 0) will be started. While C<0> is a valid timeout, it is of
2341dubious value. 2412dubious value.
2343The callback has the type C<void (*cb)(int revents, void *arg)> and gets 2414The 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 2415passed 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> 2416C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346value passed to C<ev_once>: 2417value passed to C<ev_once>:
2347 2418
2348 static void stdin_ready (int revents, void *arg) 2419 static void stdin_ready (int revents, void *arg)
2349 { 2420 {
2350 if (revents & EV_TIMEOUT) 2421 if (revents & EV_TIMEOUT)
2351 /* doh, nothing entered */; 2422 /* doh, nothing entered */;
2352 else if (revents & EV_READ) 2423 else if (revents & EV_READ)
2353 /* stdin might have data for us, joy! */; 2424 /* stdin might have data for us, joy! */;
2354 } 2425 }
2355 2426
2356 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2427 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357 2428
2358=item ev_feed_event (ev_loop *, watcher *, int revents) 2429=item ev_feed_event (ev_loop *, watcher *, int revents)
2359 2430
2360Feeds the given event set into the event loop, as if the specified event 2431Feeds 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 2432had 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 2437Feed an event on the given fd, as if a file descriptor backend detected
2367the given events it. 2438the given events it.
2368 2439
2369=item ev_feed_signal_event (ev_loop *loop, int signum) 2440=item ev_feed_signal_event (ev_loop *loop, int signum)
2370 2441
2371Feed an event as if the given signal occured (C<loop> must be the default 2442Feed an event as if the given signal occurred (C<loop> must be the default
2372loop!). 2443loop!).
2373 2444
2374=back 2445=back
2375 2446
2376 2447
2405=back 2476=back
2406 2477
2407=head1 C++ SUPPORT 2478=head1 C++ SUPPORT
2408 2479
2409Libev comes with some simplistic wrapper classes for C++ that mainly allow 2480Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410you to use some convinience methods to start/stop watchers and also change 2481you to use some convenience methods to start/stop watchers and also change
2411the callback model to a model using method callbacks on objects. 2482the callback model to a model using method callbacks on objects.
2412 2483
2413To use it, 2484To use it,
2414 2485
2415 #include <ev++.h> 2486 #include <ev++.h>
2416 2487
2417This automatically includes F<ev.h> and puts all of its definitions (many 2488This automatically includes F<ev.h> and puts all of its definitions (many
2418of them macros) into the global namespace. All C++ specific things are 2489of them macros) into the global namespace. All C++ specific things are
2419put into the C<ev> namespace. It should support all the same embedding 2490put into the C<ev> namespace. It should support all the same embedding
2420options as F<ev.h>, most notably C<EV_MULTIPLICITY>. 2491options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
2487your compiler is good :), then the method will be fully inlined into the 2558your compiler is good :), then the method will be fully inlined into the
2488thunking function, making it as fast as a direct C callback. 2559thunking function, making it as fast as a direct C callback.
2489 2560
2490Example: simple class declaration and watcher initialisation 2561Example: simple class declaration and watcher initialisation
2491 2562
2492 struct myclass 2563 struct myclass
2493 { 2564 {
2494 void io_cb (ev::io &w, int revents) { } 2565 void io_cb (ev::io &w, int revents) { }
2495 } 2566 }
2496 2567
2497 myclass obj; 2568 myclass obj;
2498 ev::io iow; 2569 ev::io iow;
2499 iow.set <myclass, &myclass::io_cb> (&obj); 2570 iow.set <myclass, &myclass::io_cb> (&obj);
2500 2571
2501=item w->set<function> (void *data = 0) 2572=item w->set<function> (void *data = 0)
2502 2573
2503Also sets a callback, but uses a static method or plain function as 2574Also 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 2575callback. The optional C<data> argument will be stored in the watcher's
2508 2579
2509See the method-C<set> above for more details. 2580See the method-C<set> above for more details.
2510 2581
2511Example: 2582Example:
2512 2583
2513 static void io_cb (ev::io &w, int revents) { } 2584 static void io_cb (ev::io &w, int revents) { }
2514 iow.set <io_cb> (); 2585 iow.set <io_cb> ();
2515 2586
2516=item w->set (struct ev_loop *) 2587=item w->set (struct ev_loop *)
2517 2588
2518Associates a different C<struct ev_loop> with this watcher. You can only 2589Associates a different C<struct ev_loop> with this watcher. You can only
2519do this when the watcher is inactive (and not pending either). 2590do this when the watcher is inactive (and not pending either).
2520 2591
2521=item w->set ([args]) 2592=item w->set ([arguments])
2522 2593
2523Basically the same as C<ev_TYPE_set>, with the same args. Must be 2594Basically 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 2595called at least once. Unlike the C counterpart, an active watcher gets
2525automatically stopped and restarted when reconfiguring it with this 2596automatically stopped and restarted when reconfiguring it with this
2526method. 2597method.
2527 2598
2528=item w->start () 2599=item w->start ()
2552=back 2623=back
2553 2624
2554Example: Define a class with an IO and idle watcher, start one of them in 2625Example: Define a class with an IO and idle watcher, start one of them in
2555the constructor. 2626the constructor.
2556 2627
2557 class myclass 2628 class myclass
2558 { 2629 {
2559 ev::io io; void io_cb (ev::io &w, int revents); 2630 ev::io io; void io_cb (ev::io &w, int revents);
2560 ev:idle idle void idle_cb (ev::idle &w, int revents); 2631 ev:idle idle void idle_cb (ev::idle &w, int revents);
2561 2632
2562 myclass (int fd) 2633 myclass (int fd)
2563 { 2634 {
2564 io .set <myclass, &myclass::io_cb > (this); 2635 io .set <myclass, &myclass::io_cb > (this);
2565 idle.set <myclass, &myclass::idle_cb> (this); 2636 idle.set <myclass, &myclass::idle_cb> (this);
2566 2637
2567 io.start (fd, ev::READ); 2638 io.start (fd, ev::READ);
2568 } 2639 }
2569 }; 2640 };
2570 2641
2571 2642
2572=head1 OTHER LANGUAGE BINDINGS 2643=head1 OTHER LANGUAGE BINDINGS
2573 2644
2574Libev does not offer other language bindings itself, but bindings for a 2645Libev 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 2646number 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 2647any interesting language binding in addition to the ones listed here, drop
2577me a note. 2648me a note.
2578 2649
2579=over 4 2650=over 4
2580 2651
2584libev. EV is developed together with libev. Apart from the EV core module, 2655libev. EV is developed together with libev. Apart from the EV core module,
2585there are additional modules that implement libev-compatible interfaces 2656there are additional modules that implement libev-compatible interfaces
2586to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the 2657to 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>). 2658C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
2588 2659
2589It can be found and installed via CPAN, its homepage is found at 2660It can be found and installed via CPAN, its homepage is at
2590L<http://software.schmorp.de/pkg/EV>. 2661L<http://software.schmorp.de/pkg/EV>.
2591 2662
2663=item Python
2664
2665Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2666seems to be quite complete and well-documented. Note, however, that the
2667patch they require for libev is outright dangerous as it breaks the ABI
2668for everybody else, and therefore, should never be applied in an installed
2669libev (if python requires an incompatible ABI then it needs to embed
2670libev).
2671
2592=item Ruby 2672=item Ruby
2593 2673
2594Tony Arcieri has written a ruby extension that offers access to a subset 2674Tony Arcieri has written a ruby extension that offers access to a subset
2595of the libev API and adds filehandle abstractions, asynchronous DNS and 2675of 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 2676more on top of it. It can be found via gem servers. Its homepage is at
2597L<http://rev.rubyforge.org/>. 2677L<http://rev.rubyforge.org/>.
2598 2678
2599=item D 2679=item D
2600 2680
2601Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to 2681Leandro 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>. 2682be found at L<http://proj.llucax.com.ar/wiki/evd>.
2603 2683
2604=back 2684=back
2605 2685
2606 2686
2607=head1 MACRO MAGIC 2687=head1 MACRO MAGIC
2608 2688
2609Libev can be compiled with a variety of options, the most fundamantal 2689Libev can be compiled with a variety of options, the most fundamental
2610of which is C<EV_MULTIPLICITY>. This option determines whether (most) 2690of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611functions and callbacks have an initial C<struct ev_loop *> argument. 2691functions and callbacks have an initial C<struct ev_loop *> argument.
2612 2692
2613To make it easier to write programs that cope with either variant, the 2693To make it easier to write programs that cope with either variant, the
2614following macros are defined: 2694following macros are defined:
2619 2699
2620This provides the loop I<argument> for functions, if one is required ("ev 2700This 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, 2701loop 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: 2702C<EV_A_> is used when other arguments are following. Example:
2623 2703
2624 ev_unref (EV_A); 2704 ev_unref (EV_A);
2625 ev_timer_add (EV_A_ watcher); 2705 ev_timer_add (EV_A_ watcher);
2626 ev_loop (EV_A_ 0); 2706 ev_loop (EV_A_ 0);
2627 2707
2628It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, 2708It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629which is often provided by the following macro. 2709which is often provided by the following macro.
2630 2710
2631=item C<EV_P>, C<EV_P_> 2711=item C<EV_P>, C<EV_P_>
2632 2712
2633This provides the loop I<parameter> for functions, if one is required ("ev 2713This 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, 2714loop 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: 2715C<EV_P_> is used when other parameters are following. Example:
2636 2716
2637 // this is how ev_unref is being declared 2717 // this is how ev_unref is being declared
2638 static void ev_unref (EV_P); 2718 static void ev_unref (EV_P);
2639 2719
2640 // this is how you can declare your typical callback 2720 // this is how you can declare your typical callback
2641 static void cb (EV_P_ ev_timer *w, int revents) 2721 static void cb (EV_P_ ev_timer *w, int revents)
2642 2722
2643It declares a parameter C<loop> of type C<struct ev_loop *>, quite 2723It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644suitable for use with C<EV_A>. 2724suitable for use with C<EV_A>.
2645 2725
2646=item C<EV_DEFAULT>, C<EV_DEFAULT_> 2726=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2662 2742
2663Example: Declare and initialise a check watcher, utilising the above 2743Example: Declare and initialise a check watcher, utilising the above
2664macros so it will work regardless of whether multiple loops are supported 2744macros so it will work regardless of whether multiple loops are supported
2665or not. 2745or not.
2666 2746
2667 static void 2747 static void
2668 check_cb (EV_P_ ev_timer *w, int revents) 2748 check_cb (EV_P_ ev_timer *w, int revents)
2669 { 2749 {
2670 ev_check_stop (EV_A_ w); 2750 ev_check_stop (EV_A_ w);
2671 } 2751 }
2672 2752
2673 ev_check check; 2753 ev_check check;
2674 ev_check_init (&check, check_cb); 2754 ev_check_init (&check, check_cb);
2675 ev_check_start (EV_DEFAULT_ &check); 2755 ev_check_start (EV_DEFAULT_ &check);
2676 ev_loop (EV_DEFAULT_ 0); 2756 ev_loop (EV_DEFAULT_ 0);
2677 2757
2678=head1 EMBEDDING 2758=head1 EMBEDDING
2679 2759
2680Libev can (and often is) directly embedded into host 2760Libev can (and often is) directly embedded into host
2681applications. Examples of applications that embed it include the Deliantra 2761applications. Examples of applications that embed it include the Deliantra
2688libev somewhere in your source tree). 2768libev somewhere in your source tree).
2689 2769
2690=head2 FILESETS 2770=head2 FILESETS
2691 2771
2692Depending on what features you need you need to include one or more sets of files 2772Depending on what features you need you need to include one or more sets of files
2693in your app. 2773in your application.
2694 2774
2695=head3 CORE EVENT LOOP 2775=head3 CORE EVENT LOOP
2696 2776
2697To include only the libev core (all the C<ev_*> functions), with manual 2777To include only the libev core (all the C<ev_*> functions), with manual
2698configuration (no autoconf): 2778configuration (no autoconf):
2699 2779
2700 #define EV_STANDALONE 1 2780 #define EV_STANDALONE 1
2701 #include "ev.c" 2781 #include "ev.c"
2702 2782
2703This will automatically include F<ev.h>, too, and should be done in a 2783This 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 2784single 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 2785it, 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 2786done by writing a wrapper around F<ev.h> that you can include instead and
2707where you can put other configuration options): 2787where you can put other configuration options):
2708 2788
2709 #define EV_STANDALONE 1 2789 #define EV_STANDALONE 1
2710 #include "ev.h" 2790 #include "ev.h"
2711 2791
2712Both header files and implementation files can be compiled with a C++ 2792Both header files and implementation files can be compiled with a C++
2713compiler (at least, thats a stated goal, and breakage will be treated 2793compiler (at least, thats a stated goal, and breakage will be treated
2714as a bug). 2794as a bug).
2715 2795
2716You need the following files in your source tree, or in a directory 2796You need the following files in your source tree, or in a directory
2717in your include path (e.g. in libev/ when using -Ilibev): 2797in your include path (e.g. in libev/ when using -Ilibev):
2718 2798
2719 ev.h 2799 ev.h
2720 ev.c 2800 ev.c
2721 ev_vars.h 2801 ev_vars.h
2722 ev_wrap.h 2802 ev_wrap.h
2723 2803
2724 ev_win32.c required on win32 platforms only 2804 ev_win32.c required on win32 platforms only
2725 2805
2726 ev_select.c only when select backend is enabled (which is enabled by default) 2806 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) 2807 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) 2808 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) 2809 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) 2810 ev_port.c only when the solaris port backend is enabled (disabled by default)
2731 2811
2732F<ev.c> includes the backend files directly when enabled, so you only need 2812F<ev.c> includes the backend files directly when enabled, so you only need
2733to compile this single file. 2813to compile this single file.
2734 2814
2735=head3 LIBEVENT COMPATIBILITY API 2815=head3 LIBEVENT COMPATIBILITY API
2736 2816
2737To include the libevent compatibility API, also include: 2817To include the libevent compatibility API, also include:
2738 2818
2739 #include "event.c" 2819 #include "event.c"
2740 2820
2741in the file including F<ev.c>, and: 2821in the file including F<ev.c>, and:
2742 2822
2743 #include "event.h" 2823 #include "event.h"
2744 2824
2745in the files that want to use the libevent API. This also includes F<ev.h>. 2825in the files that want to use the libevent API. This also includes F<ev.h>.
2746 2826
2747You need the following additional files for this: 2827You need the following additional files for this:
2748 2828
2749 event.h 2829 event.h
2750 event.c 2830 event.c
2751 2831
2752=head3 AUTOCONF SUPPORT 2832=head3 AUTOCONF SUPPORT
2753 2833
2754Instead of using C<EV_STANDALONE=1> and providing your config in 2834Instead 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 2835whatever 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 2836F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757include F<config.h> and configure itself accordingly. 2837include F<config.h> and configure itself accordingly.
2758 2838
2759For this of course you need the m4 file: 2839For this of course you need the m4 file:
2760 2840
2761 libev.m4 2841 libev.m4
2762 2842
2763=head2 PREPROCESSOR SYMBOLS/MACROS 2843=head2 PREPROCESSOR SYMBOLS/MACROS
2764 2844
2765Libev can be configured via a variety of preprocessor symbols you have to 2845Libev 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 2846define before including any of its files. The default in the absence of
2767autoconf is noted for every option. 2847autoconf is noted for every option.
2768 2848
2769=over 4 2849=over 4
2770 2850
2771=item EV_STANDALONE 2851=item EV_STANDALONE
2777F<event.h> that are not directly supported by the libev core alone. 2857F<event.h> that are not directly supported by the libev core alone.
2778 2858
2779=item EV_USE_MONOTONIC 2859=item EV_USE_MONOTONIC
2780 2860
2781If defined to be C<1>, libev will try to detect the availability of the 2861If 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 2862monotonic clock option at both compile time and runtime. Otherwise no use
2783of the monotonic clock option will be attempted. If you enable this, you 2863of the monotonic clock option will be attempted. If you enable this, you
2784usually have to link against librt or something similar. Enabling it when 2864usually have to link against librt or something similar. Enabling it when
2785the functionality isn't available is safe, though, although you have 2865the functionality isn't available is safe, though, although you have
2786to make sure you link against any libraries where the C<clock_gettime> 2866to make sure you link against any libraries where the C<clock_gettime>
2787function is hiding in (often F<-lrt>). 2867function is hiding in (often F<-lrt>).
2788 2868
2789=item EV_USE_REALTIME 2869=item EV_USE_REALTIME
2790 2870
2791If defined to be C<1>, libev will try to detect the availability of the 2871If defined to be C<1>, libev will try to detect the availability of the
2792realtime clock option at compiletime (and assume its availability at 2872real-time clock option at compile time (and assume its availability at
2793runtime if successful). Otherwise no use of the realtime clock option will 2873runtime if successful). Otherwise no use of the real-time clock option will
2794be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2874be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2795(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the 2875(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2796note about libraries in the description of C<EV_USE_MONOTONIC>, though. 2876note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2797 2877
2798=item EV_USE_NANOSLEEP 2878=item EV_USE_NANOSLEEP
28092.7 or newer, otherwise disabled. 28892.7 or newer, otherwise disabled.
2810 2890
2811=item EV_USE_SELECT 2891=item EV_USE_SELECT
2812 2892
2813If undefined or defined to be C<1>, libev will compile in support for the 2893If 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 2894C<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 2895other method takes over, select will be it. Otherwise the select backend
2816will not be compiled in. 2896will not be compiled in.
2817 2897
2818=item EV_SELECT_USE_FD_SET 2898=item EV_SELECT_USE_FD_SET
2819 2899
2820If defined to C<1>, then the select backend will use the system C<fd_set> 2900If 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 2901structure. 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 2902C<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 2903exotic systems. This usually limits the range of file descriptors to some
2824low limit such as 1024 or might have other limitations (winsocket only 2904low limit such as 1024 or might have other limitations (winsocket only
2825allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might 2905allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2826influence the size of the C<fd_set> used. 2906influence the size of the C<fd_set> used.
2827 2907
2876otherwise another method will be used as fallback. This is the preferred 2956otherwise another method will be used as fallback. This is the preferred
2877backend for Solaris 10 systems. 2957backend for Solaris 10 systems.
2878 2958
2879=item EV_USE_DEVPOLL 2959=item EV_USE_DEVPOLL
2880 2960
2881reserved for future expansion, works like the USE symbols above. 2961Reserved for future expansion, works like the USE symbols above.
2882 2962
2883=item EV_USE_INOTIFY 2963=item EV_USE_INOTIFY
2884 2964
2885If defined to be C<1>, libev will compile in support for the Linux inotify 2965If 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 2966interface to speed up C<ev_stat> watchers. Its actual availability will
2893access is atomic with respect to other threads or signal contexts. No such 2973access 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 2974type 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" 2975that 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. 2976as well as for signal and thread safety in C<ev_async> watchers.
2897 2977
2898In the absense of this define, libev will use C<sig_atomic_t volatile> 2978In 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. 2979(from F<signal.h>), which is usually good enough on most platforms.
2900 2980
2901=item EV_H 2981=item EV_H
2902 2982
2903The name of the F<ev.h> header file used to include it. The default if 2983The 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 3022When doing priority-based operations, libev usually has to linearly search
2943all the priorities, so having many of them (hundreds) uses a lot of space 3023all 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 3024and time, so using the defaults of five priorities (-2 .. +2) is usually
2945fine. 3025fine.
2946 3026
2947If your embedding app does not need any priorities, defining these both to 3027If your embedding application does not need any priorities, defining these both to
2948C<0> will save some memory and cpu. 3028C<0> will save some memory and CPU.
2949 3029
2950=item EV_PERIODIC_ENABLE 3030=item EV_PERIODIC_ENABLE
2951 3031
2952If undefined or defined to be C<1>, then periodic timers are supported. If 3032If 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 3033defined to be C<0>, then they are not. Disabling them saves a few kB of
2981 3061
2982=item EV_MINIMAL 3062=item EV_MINIMAL
2983 3063
2984If you need to shave off some kilobytes of code at the expense of some 3064If you need to shave off some kilobytes of code at the expense of some
2985speed, define this symbol to C<1>. Currently this is used to override some 3065speed, define this symbol to C<1>. Currently this is used to override some
2986inlining decisions, saves roughly 30% codesize of amd64. It also selects a 3066inlining decisions, saves roughly 30% code size on amd64. It also selects a
2987much smaller 2-heap for timer management over the default 4-heap. 3067much smaller 2-heap for timer management over the default 4-heap.
2988 3068
2989=item EV_PID_HASHSIZE 3069=item EV_PID_HASHSIZE
2990 3070
2991C<ev_child> watchers use a small hash table to distribute workload by 3071C<ev_child> watchers use a small hash table to distribute workload by
3003 3083
3004=item EV_USE_4HEAP 3084=item EV_USE_4HEAP
3005 3085
3006Heaps are not very cache-efficient. To improve the cache-efficiency of the 3086Heaps are not very cache-efficient. To improve the cache-efficiency of the
3007timer and periodics heap, libev uses a 4-heap when this symbol is defined 3087timer and periodics heap, libev uses a 4-heap when this symbol is defined
3008to C<1>. The 4-heap uses more complicated (longer) code but has a 3088to C<1>. The 4-heap uses more complicated (longer) code but has
3009noticable after performance with many (thousands) of watchers. 3089noticeably faster performance with many (thousands) of watchers.
3010 3090
3011The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 3091The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3012(disabled). 3092(disabled).
3013 3093
3014=item EV_HEAP_CACHE_AT 3094=item EV_HEAP_CACHE_AT
3015 3095
3016Heaps are not very cache-efficient. To improve the cache-efficiency of the 3096Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017timer and periodics heap, libev can cache the timestamp (I<at>) within 3097timer and periodics heap, libev can cache the timestamp (I<at>) within
3018the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), 3098the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3019which uses 8-12 bytes more per watcher and a few hundred bytes more code, 3099which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3020but avoids random read accesses on heap changes. This noticably improves 3100but avoids random read accesses on heap changes. This improves performance
3021performance noticably with with many (hundreds) of watchers. 3101noticeably with with many (hundreds) of watchers.
3022 3102
3023The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 3103The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3024(disabled). 3104(disabled).
3105
3106=item EV_VERIFY
3107
3108Controls how much internal verification (see C<ev_loop_verify ()>) will
3109be done: If set to C<0>, no internal verification code will be compiled
3110in. If set to C<1>, then verification code will be compiled in, but not
3111called. If set to C<2>, then the internal verification code will be
3112called once per loop, which can slow down libev. If set to C<3>, then the
3113verification code will be called very frequently, which will slow down
3114libev considerably.
3115
3116The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3117C<0.>
3025 3118
3026=item EV_COMMON 3119=item EV_COMMON
3027 3120
3028By default, all watchers have a C<void *data> member. By redefining 3121By default, all watchers have a C<void *data> member. By redefining
3029this macro to a something else you can include more and other types of 3122this macro to a something else you can include more and other types of
3030members. You have to define it each time you include one of the files, 3123members. You have to define it each time you include one of the files,
3031though, and it must be identical each time. 3124though, and it must be identical each time.
3032 3125
3033For example, the perl EV module uses something like this: 3126For example, the perl EV module uses something like this:
3034 3127
3035 #define EV_COMMON \ 3128 #define EV_COMMON \
3036 SV *self; /* contains this struct */ \ 3129 SV *self; /* contains this struct */ \
3037 SV *cb_sv, *fh /* note no trailing ";" */ 3130 SV *cb_sv, *fh /* note no trailing ";" */
3038 3131
3039=item EV_CB_DECLARE (type) 3132=item EV_CB_DECLARE (type)
3040 3133
3041=item EV_CB_INVOKE (watcher, revents) 3134=item EV_CB_INVOKE (watcher, revents)
3042 3135
3049avoid the C<struct ev_loop *> as first argument in all cases, or to use 3142avoid the C<struct ev_loop *> as first argument in all cases, or to use
3050method calls instead of plain function calls in C++. 3143method calls instead of plain function calls in C++.
3051 3144
3052=head2 EXPORTED API SYMBOLS 3145=head2 EXPORTED API SYMBOLS
3053 3146
3054If you need to re-export the API (e.g. via a dll) and you need a list of 3147If you need to re-export the API (e.g. via a DLL) and you need a list of
3055exported symbols, you can use the provided F<Symbol.*> files which list 3148exported symbols, you can use the provided F<Symbol.*> files which list
3056all public symbols, one per line: 3149all public symbols, one per line:
3057 3150
3058 Symbols.ev for libev proper 3151 Symbols.ev for libev proper
3059 Symbols.event for the libevent emulation 3152 Symbols.event for the libevent emulation
3060 3153
3061This can also be used to rename all public symbols to avoid clashes with 3154This can also be used to rename all public symbols to avoid clashes with
3062multiple versions of libev linked together (which is obviously bad in 3155multiple versions of libev linked together (which is obviously bad in
3063itself, but sometimes it is inconvinient to avoid this). 3156itself, but sometimes it is inconvenient to avoid this).
3064 3157
3065A sed command like this will create wrapper C<#define>'s that you need to 3158A sed command like this will create wrapper C<#define>'s that you need to
3066include before including F<ev.h>: 3159include before including F<ev.h>:
3067 3160
3068 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h 3161 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
3085file. 3178file.
3086 3179
3087The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 3180The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3088that everybody includes and which overrides some configure choices: 3181that everybody includes and which overrides some configure choices:
3089 3182
3090 #define EV_MINIMAL 1 3183 #define EV_MINIMAL 1
3091 #define EV_USE_POLL 0 3184 #define EV_USE_POLL 0
3092 #define EV_MULTIPLICITY 0 3185 #define EV_MULTIPLICITY 0
3093 #define EV_PERIODIC_ENABLE 0 3186 #define EV_PERIODIC_ENABLE 0
3094 #define EV_STAT_ENABLE 0 3187 #define EV_STAT_ENABLE 0
3095 #define EV_FORK_ENABLE 0 3188 #define EV_FORK_ENABLE 0
3096 #define EV_CONFIG_H <config.h> 3189 #define EV_CONFIG_H <config.h>
3097 #define EV_MINPRI 0 3190 #define EV_MINPRI 0
3098 #define EV_MAXPRI 0 3191 #define EV_MAXPRI 0
3099 3192
3100 #include "ev++.h" 3193 #include "ev++.h"
3101 3194
3102And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 3195And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3103 3196
3104 #include "ev_cpp.h" 3197 #include "ev_cpp.h"
3105 #include "ev.c" 3198 #include "ev.c"
3106 3199
3107 3200
3108=head1 THREADS AND COROUTINES 3201=head1 THREADS AND COROUTINES
3109 3202
3110=head2 THREADS 3203=head2 THREADS
3111 3204
3112Libev itself is completely threadsafe, but it uses no locking. This 3205Libev itself is completely thread-safe, but it uses no locking. This
3113means that you can use as many loops as you want in parallel, as long as 3206means that you can use as many loops as you want in parallel, as long as
3114only one thread ever calls into one libev function with the same loop 3207only one thread ever calls into one libev function with the same loop
3115parameter. 3208parameter.
3116 3209
3117Or put differently: calls with different loop parameters can be done in 3210Or put differently: calls with different loop parameters can be done in
3118parallel from multiple threads, calls with the same loop parameter must be 3211parallel from multiple threads, calls with the same loop parameter must be
3119done serially (but can be done from different threads, as long as only one 3212done serially (but can be done from different threads, as long as only one
3120thread ever is inside a call at any point in time, e.g. by using a mutex 3213thread ever is inside a call at any point in time, e.g. by using a mutex
3121per loop). 3214per loop).
3122 3215
3123If you want to know which design is best for your problem, then I cannot 3216If you want to know which design (one loop, locking, or multiple loops
3124help you but by giving some generic advice: 3217without or something else still) is best for your problem, then I cannot
3218help you. I can give some generic advice however:
3125 3219
3126=over 4 3220=over 4
3127 3221
3128=item * most applications have a main thread: use the default libev loop 3222=item * most applications have a main thread: use the default libev loop
3129in that thread, or create a seperate thread running only the default loop. 3223in that thread, or create a separate thread running only the default loop.
3130 3224
3131This helps integrating other libraries or software modules that use libev 3225This helps integrating other libraries or software modules that use libev
3132themselves and don't care/know about threading. 3226themselves and don't care/know about threading.
3133 3227
3134=item * one loop per thread is usually a good model. 3228=item * one loop per thread is usually a good model.
3135 3229
3136Doing this is almost never wrong, sometimes a better-performance model 3230Doing this is almost never wrong, sometimes a better-performance model
3137exists, but it is always a good start. 3231exists, but it is always a good start.
3138 3232
3139=item * other models exist, such as the leader/follower pattern, where one 3233=item * other models exist, such as the leader/follower pattern, where one
3140loop is handed through multiple threads in a kind of round-robbin fashion. 3234loop is handed through multiple threads in a kind of round-robin fashion.
3141 3235
3142Chosing a model is hard - look around, learn, know that usually you cna do 3236Choosing a model is hard - look around, learn, know that usually you can do
3143better than you currently do :-) 3237better than you currently do :-)
3144 3238
3145=item * often you need to talk to some other thread which blocks in the 3239=item * often you need to talk to some other thread which blocks in the
3146event loop - C<ev_async> watchers can be used to wake them up from other 3240event loop - C<ev_async> watchers can be used to wake them up from other
3147threads safely (or from signal contexts...). 3241threads safely (or from signal contexts...).
3148 3242
3149=back 3243=back
3150 3244
3151=head2 COROUTINES 3245=head2 COROUTINES
3152 3246
3153Libev is much more accomodating to coroutines ("cooperative threads"): 3247Libev is much more accommodating to coroutines ("cooperative threads"):
3154libev fully supports nesting calls to it's functions from different 3248libev fully supports nesting calls to it's functions from different
3155coroutines (e.g. you can call C<ev_loop> on the same loop from two 3249coroutines (e.g. you can call C<ev_loop> on the same loop from two
3156different coroutines and switch freely between both coroutines running the 3250different coroutines and switch freely between both coroutines running the
3157loop, as long as you don't confuse yourself). The only exception is that 3251loop, as long as you don't confuse yourself). The only exception is that
3158you must not do this from C<ev_periodic> reschedule callbacks. 3252you must not do this from C<ev_periodic> reschedule callbacks.
3206 3300
3207=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 3301=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3208 3302
3209A change means an I/O watcher gets started or stopped, which requires 3303A change means an I/O watcher gets started or stopped, which requires
3210libev to recalculate its status (and possibly tell the kernel, depending 3304libev to recalculate its status (and possibly tell the kernel, depending
3211on backend and wether C<ev_io_set> was used). 3305on backend and whether C<ev_io_set> was used).
3212 3306
3213=item Activating one watcher (putting it into the pending state): O(1) 3307=item Activating one watcher (putting it into the pending state): O(1)
3214 3308
3215=item Priority handling: O(number_of_priorities) 3309=item Priority handling: O(number_of_priorities)
3216 3310
3223 3317
3224=item Processing ev_async_send: O(number_of_async_watchers) 3318=item Processing ev_async_send: O(number_of_async_watchers)
3225 3319
3226=item Processing signals: O(max_signal_number) 3320=item Processing signals: O(max_signal_number)
3227 3321
3228Sending involves a syscall I<iff> there were no other C<ev_async_send> 3322Sending involves a system call I<iff> there were no other C<ev_async_send>
3229calls in the current loop iteration. Checking for async and signal events 3323calls in the current loop iteration. Checking for async and signal events
3230involves iterating over all running async watchers or all signal numbers. 3324involves iterating over all running async watchers or all signal numbers.
3231 3325
3232=back 3326=back
3233 3327
3234 3328
3235=head1 Win32 platform limitations and workarounds 3329=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3236 3330
3237Win32 doesn't support any of the standards (e.g. POSIX) that libev 3331Win32 doesn't support any of the standards (e.g. POSIX) that libev
3238requires, and its I/O model is fundamentally incompatible with the POSIX 3332requires, and its I/O model is fundamentally incompatible with the POSIX
3239model. Libev still offers limited functionality on this platform in 3333model. Libev still offers limited functionality on this platform in
3240the form of the C<EVBACKEND_SELECT> backend, and only supports socket 3334the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3247way (note also that glib is the slowest event library known to man). 3341way (note also that glib is the slowest event library known to man).
3248 3342
3249There is no supported compilation method available on windows except 3343There is no supported compilation method available on windows except
3250embedding it into other applications. 3344embedding it into other applications.
3251 3345
3346Not a libev limitation but worth mentioning: windows apparently doesn't
3347accept large writes: instead of resulting in a partial write, windows will
3348either accept everything or return C<ENOBUFS> if the buffer is too large,
3349so make sure you only write small amounts into your sockets (less than a
3350megabyte seems safe, but thsi apparently depends on the amount of memory
3351available).
3352
3252Due to the many, low, and arbitrary limits on the win32 platform and 3353Due to the many, low, and arbitrary limits on the win32 platform and
3253the abysmal performance of winsockets, using a large number of sockets 3354the abysmal performance of winsockets, using a large number of sockets
3254is not recommended (and not reasonable). If your program needs to use 3355is not recommended (and not reasonable). If your program needs to use
3255more than a hundred or so sockets, then likely it needs to use a totally 3356more than a hundred or so sockets, then likely it needs to use a totally
3256different implementation for windows, as libev offers the POSIX readyness 3357different implementation for windows, as libev offers the POSIX readiness
3257notification model, which cannot be implemented efficiently on windows 3358notification model, which cannot be implemented efficiently on windows
3258(microsoft monopoly games). 3359(Microsoft monopoly games).
3360
3361A typical way to use libev under windows is to embed it (see the embedding
3362section for details) and use the following F<evwrap.h> header file instead
3363of F<ev.h>:
3364
3365 #define EV_STANDALONE /* keeps ev from requiring config.h */
3366 #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3367
3368 #include "ev.h"
3369
3370And compile the following F<evwrap.c> file into your project (make sure
3371you do I<not> compile the F<ev.c> or any other embedded soruce files!):
3372
3373 #include "evwrap.h"
3374 #include "ev.c"
3259 3375
3260=over 4 3376=over 4
3261 3377
3262=item The winsocket select function 3378=item The winsocket select function
3263 3379
3264The winsocket C<select> function doesn't follow POSIX in that it requires 3380The winsocket C<select> function doesn't follow POSIX in that it
3265socket I<handles> and not socket I<file descriptors>. This makes select 3381requires socket I<handles> and not socket I<file descriptors> (it is
3266very inefficient, and also requires a mapping from file descriptors 3382also extremely buggy). This makes select very inefficient, and also
3267to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, 3383requires a mapping from file descriptors to socket handles (the Microsoft
3268C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor 3384C runtime provides the function C<_open_osfhandle> for this). See the
3269symbols for more info. 3385discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3386C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3270 3387
3271The configuration for a "naked" win32 using the microsoft runtime 3388The configuration for a "naked" win32 using the Microsoft runtime
3272libraries and raw winsocket select is: 3389libraries and raw winsocket select is:
3273 3390
3274 #define EV_USE_SELECT 1 3391 #define EV_USE_SELECT 1
3275 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ 3392 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3276 3393
3277Note that winsockets handling of fd sets is O(n), so you can easily get a 3394Note that winsockets handling of fd sets is O(n), so you can easily get a
3278complexity in the O(n²) range when using win32. 3395complexity in the O(n²) range when using win32.
3279 3396
3280=item Limited number of file descriptors 3397=item Limited number of file descriptors
3281 3398
3282Windows has numerous arbitrary (and low) limits on things. 3399Windows has numerous arbitrary (and low) limits on things.
3283 3400
3284Early versions of winsocket's select only supported waiting for a maximum 3401Early versions of winsocket's select only supported waiting for a maximum
3285of C<64> handles (probably owning to the fact that all windows kernels 3402of C<64> handles (probably owning to the fact that all windows kernels
3286can only wait for C<64> things at the same time internally; microsoft 3403can only wait for C<64> things at the same time internally; Microsoft
3287recommends spawning a chain of threads and wait for 63 handles and the 3404recommends spawning a chain of threads and wait for 63 handles and the
3288previous thread in each. Great). 3405previous thread in each. Great).
3289 3406
3290Newer versions support more handles, but you need to define C<FD_SETSIZE> 3407Newer versions support more handles, but you need to define C<FD_SETSIZE>
3291to some high number (e.g. C<2048>) before compiling the winsocket select 3408to some high number (e.g. C<2048>) before compiling the winsocket select
3292call (which might be in libev or elsewhere, for example, perl does its own 3409call (which might be in libev or elsewhere, for example, perl does its own
3293select emulation on windows). 3410select emulation on windows).
3294 3411
3295Another limit is the number of file descriptors in the microsoft runtime 3412Another limit is the number of file descriptors in the Microsoft runtime
3296libraries, which by default is C<64> (there must be a hidden I<64> fetish 3413libraries, which by default is C<64> (there must be a hidden I<64> fetish
3297or something like this inside microsoft). You can increase this by calling 3414or something like this inside Microsoft). You can increase this by calling
3298C<_setmaxstdio>, which can increase this limit to C<2048> (another 3415C<_setmaxstdio>, which can increase this limit to C<2048> (another
3299arbitrary limit), but is broken in many versions of the microsoft runtime 3416arbitrary limit), but is broken in many versions of the Microsoft runtime
3300libraries. 3417libraries.
3301 3418
3302This might get you to about C<512> or C<2048> sockets (depending on 3419This might get you to about C<512> or C<2048> sockets (depending on
3303windows version and/or the phase of the moon). To get more, you need to 3420windows version and/or the phase of the moon). To get more, you need to
3304wrap all I/O functions and provide your own fd management, but the cost of 3421wrap all I/O functions and provide your own fd management, but the cost of
3311 3428
3312In addition to a working ISO-C implementation, libev relies on a few 3429In addition to a working ISO-C implementation, libev relies on a few
3313additional extensions: 3430additional extensions:
3314 3431
3315=over 4 3432=over 4
3433
3434=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3435calling conventions regardless of C<ev_watcher_type *>.
3436
3437Libev assumes not only that all watcher pointers have the same internal
3438structure (guaranteed by POSIX but not by ISO C for example), but it also
3439assumes that the same (machine) code can be used to call any watcher
3440callback: The watcher callbacks have different type signatures, but libev
3441calls them using an C<ev_watcher *> internally.
3316 3442
3317=item C<sig_atomic_t volatile> must be thread-atomic as well 3443=item C<sig_atomic_t volatile> must be thread-atomic as well
3318 3444
3319The type C<sig_atomic_t volatile> (or whatever is defined as 3445The type C<sig_atomic_t volatile> (or whatever is defined as
3320C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different 3446C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
3352=back 3478=back
3353 3479
3354If you know of other additional requirements drop me a note. 3480If you know of other additional requirements drop me a note.
3355 3481
3356 3482
3483=head1 COMPILER WARNINGS
3484
3485Depending on your compiler and compiler settings, you might get no or a
3486lot of warnings when compiling libev code. Some people are apparently
3487scared by this.
3488
3489However, these are unavoidable for many reasons. For one, each compiler
3490has different warnings, and each user has different tastes regarding
3491warning options. "Warn-free" code therefore cannot be a goal except when
3492targeting a specific compiler and compiler-version.
3493
3494Another reason is that some compiler warnings require elaborate
3495workarounds, or other changes to the code that make it less clear and less
3496maintainable.
3497
3498And of course, some compiler warnings are just plain stupid, or simply
3499wrong (because they don't actually warn about the condition their message
3500seems to warn about).
3501
3502While libev is written to generate as few warnings as possible,
3503"warn-free" code is not a goal, and it is recommended not to build libev
3504with any compiler warnings enabled unless you are prepared to cope with
3505them (e.g. by ignoring them). Remember that warnings are just that:
3506warnings, not errors, or proof of bugs.
3507
3508
3509=head1 VALGRIND
3510
3511Valgrind has a special section here because it is a popular tool that is
3512highly useful, but valgrind reports are very hard to interpret.
3513
3514If you think you found a bug (memory leak, uninitialised data access etc.)
3515in libev, then check twice: If valgrind reports something like:
3516
3517 ==2274== definitely lost: 0 bytes in 0 blocks.
3518 ==2274== possibly lost: 0 bytes in 0 blocks.
3519 ==2274== still reachable: 256 bytes in 1 blocks.
3520
3521Then there is no memory leak. Similarly, under some circumstances,
3522valgrind might report kernel bugs as if it were a bug in libev, or it
3523might be confused (it is a very good tool, but only a tool).
3524
3525If you are unsure about something, feel free to contact the mailing list
3526with the full valgrind report and an explanation on why you think this is
3527a bug in libev. However, don't be annoyed when you get a brisk "this is
3528no bug" answer and take the chance of learning how to interpret valgrind
3529properly.
3530
3531If you need, for some reason, empty reports from valgrind for your project
3532I suggest using suppression lists.
3533
3534
3357=head1 AUTHOR 3535=head1 AUTHOR
3358 3536
3359Marc Lehmann <libev@schmorp.de>. 3537Marc Lehmann <libev@schmorp.de>.
3360 3538

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