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Revision 1.334 by root, Mon Oct 25 10:30:23 2010 UTC

43 43
44 int 44 int
45 main (void) 45 main (void)
46 { 46 {
47 // use the default event loop unless you have special needs 47 // use the default event loop unless you have special needs
48 struct ev_loop *loop = ev_default_loop (0); 48 struct ev_loop *loop = EV_DEFAULT;
49 49
50 // initialise an io watcher, then start it 50 // initialise an io watcher, then start it
51 // this one will watch for stdin to become readable 51 // this one will watch for stdin to become readable
52 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); 52 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53 ev_io_start (loop, &stdin_watcher); 53 ev_io_start (loop, &stdin_watcher);
77on event-based programming, nor will it introduce event-based programming 77on event-based programming, nor will it introduce event-based programming
78with libev. 78with libev.
79 79
80Familiarity with event based programming techniques in general is assumed 80Familiarity with event based programming techniques in general is assumed
81throughout this document. 81throughout this document.
82
83=head1 WHAT TO READ WHEN IN A HURRY
84
85This manual tries to be very detailed, but unfortunately, this also makes
86it very long. If you just want to know the basics of libev, I suggest
87reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
88look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
89C<ev_timer> sections in L<WATCHER TYPES>.
82 90
83=head1 ABOUT LIBEV 91=head1 ABOUT LIBEV
84 92
85Libev is an event loop: you register interest in certain events (such as a 93Libev is an event loop: you register interest in certain events (such as a
86file descriptor being readable or a timeout occurring), and it will manage 94file descriptor being readable or a timeout occurring), and it will manage
165 173
166=item ev_tstamp ev_time () 174=item ev_tstamp ev_time ()
167 175
168Returns the current time as libev would use it. Please note that the 176Returns the current time as libev would use it. Please note that the
169C<ev_now> function is usually faster and also often returns the timestamp 177C<ev_now> function is usually faster and also often returns the timestamp
170you actually want to know. Also interetsing is the combination of 178you actually want to know. Also interesting is the combination of
171C<ev_update_now> and C<ev_now>. 179C<ev_update_now> and C<ev_now>.
172 180
173=item ev_sleep (ev_tstamp interval) 181=item ev_sleep (ev_tstamp interval)
174 182
175Sleep for the given interval: The current thread will be blocked until 183Sleep for the given interval: The current thread will be blocked until
193as this indicates an incompatible change. Minor versions are usually 201as this indicates an incompatible change. Minor versions are usually
194compatible to older versions, so a larger minor version alone is usually 202compatible to older versions, so a larger minor version alone is usually
195not a problem. 203not a problem.
196 204
197Example: Make sure we haven't accidentally been linked against the wrong 205Example: Make sure we haven't accidentally been linked against the wrong
198version (note, however, that this will not detect ABI mismatches :). 206version (note, however, that this will not detect other ABI mismatches,
207such as LFS or reentrancy).
199 208
200 assert (("libev version mismatch", 209 assert (("libev version mismatch",
201 ev_version_major () == EV_VERSION_MAJOR 210 ev_version_major () == EV_VERSION_MAJOR
202 && ev_version_minor () >= EV_VERSION_MINOR)); 211 && ev_version_minor () >= EV_VERSION_MINOR));
203 212
225probe for if you specify no backends explicitly. 234probe for if you specify no backends explicitly.
226 235
227=item unsigned int ev_embeddable_backends () 236=item unsigned int ev_embeddable_backends ()
228 237
229Returns the set of backends that are embeddable in other event loops. This 238Returns the set of backends that are embeddable in other event loops. This
230is the theoretical, all-platform, value. To find which backends 239value is platform-specific but can include backends not available on the
231might be supported on the current system, you would need to look at 240current system. To find which embeddable backends might be supported on
232C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for 241the current system, you would need to look at C<ev_embeddable_backends ()
233recommended ones. 242& ev_supported_backends ()>, likewise for recommended ones.
234 243
235See the description of C<ev_embed> watchers for more info. 244See the description of C<ev_embed> watchers for more info.
236 245
237=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] 246=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
238 247
292 ... 301 ...
293 ev_set_syserr_cb (fatal_error); 302 ev_set_syserr_cb (fatal_error);
294 303
295=back 304=back
296 305
297=head1 FUNCTIONS CONTROLLING THE EVENT LOOP 306=head1 FUNCTIONS CONTROLLING EVENT LOOPS
298 307
299An event loop is described by a C<struct ev_loop *> (the C<struct> is 308An event loop is described by a C<struct ev_loop *> (the C<struct> is
300I<not> optional in this case unless libev 3 compatibility is disabled, as 309I<not> optional in this case unless libev 3 compatibility is disabled, as
301libev 3 had an C<ev_loop> function colliding with the struct name). 310libev 3 had an C<ev_loop> function colliding with the struct name).
302 311
303The library knows two types of such loops, the I<default> loop, which 312The library knows two types of such loops, the I<default> loop, which
304supports signals and child events, and dynamically created event loops 313supports child process events, and dynamically created event loops which
305which do not. 314do not.
306 315
307=over 4 316=over 4
308 317
309=item struct ev_loop *ev_default_loop (unsigned int flags) 318=item struct ev_loop *ev_default_loop (unsigned int flags)
310 319
311This will initialise the default event loop if it hasn't been initialised 320This returns the "default" event loop object, which is what you should
312yet and return it. If the default loop could not be initialised, returns 321normally use when you just need "the event loop". Event loop objects and
313false. If it already was initialised it simply returns it (and ignores the 322the C<flags> parameter are described in more detail in the entry for
314flags. If that is troubling you, check C<ev_backend ()> afterwards). 323C<ev_loop_new>.
324
325If the default loop is already initialised then this function simply
326returns it (and ignores the flags. If that is troubling you, check
327C<ev_backend ()> afterwards). Otherwise it will create it with the given
328flags, which should almost always be C<0>, unless the caller is also the
329one calling C<ev_run> or otherwise qualifies as "the main program".
315 330
316If you don't know what event loop to use, use the one returned from this 331If you don't know what event loop to use, use the one returned from this
317function. 332function (or via the C<EV_DEFAULT> macro).
318 333
319Note that this function is I<not> thread-safe, so if you want to use it 334Note that this function is I<not> thread-safe, so if you want to use it
320from multiple threads, you have to lock (note also that this is unlikely, 335from multiple threads, you have to employ some kind of mutex (note also
321as loops cannot be shared easily between threads anyway). 336that this case is unlikely, as loops cannot be shared easily between
337threads anyway).
322 338
323The default loop is the only loop that can handle C<ev_signal> and 339The default loop is the only loop that can handle C<ev_child> watchers,
324C<ev_child> watchers, and to do this, it always registers a handler 340and to do this, it always registers a handler for C<SIGCHLD>. If this is
325for C<SIGCHLD>. If this is a problem for your application you can either 341a problem for your application you can either create a dynamic loop with
326create a dynamic loop with C<ev_loop_new> that doesn't do that, or you 342C<ev_loop_new> which doesn't do that, or you can simply overwrite the
327can simply overwrite the C<SIGCHLD> signal handler I<after> calling 343C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
328C<ev_default_init>. 344
345Example: This is the most typical usage.
346
347 if (!ev_default_loop (0))
348 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
349
350Example: Restrict libev to the select and poll backends, and do not allow
351environment settings to be taken into account:
352
353 ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
354
355=item struct ev_loop *ev_loop_new (unsigned int flags)
356
357This will create and initialise a new event loop object. If the loop
358could not be initialised, returns false.
359
360Note that this function I<is> thread-safe, and one common way to use
361libev with threads is indeed to create one loop per thread, and using the
362default loop in the "main" or "initial" thread.
329 363
330The flags argument can be used to specify special behaviour or specific 364The flags argument can be used to specify special behaviour or specific
331backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). 365backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
332 366
333The following flags are supported: 367The following flags are supported:
551If one or more of the backend flags are or'ed into the flags value, 585If one or more of the backend flags are or'ed into the flags value,
552then only these backends will be tried (in the reverse order as listed 586then only these backends will be tried (in the reverse order as listed
553here). If none are specified, all backends in C<ev_recommended_backends 587here). If none are specified, all backends in C<ev_recommended_backends
554()> will be tried. 588()> will be tried.
555 589
556Example: This is the most typical usage.
557
558 if (!ev_default_loop (0))
559 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
560
561Example: Restrict libev to the select and poll backends, and do not allow
562environment settings to be taken into account:
563
564 ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
565
566Example: Use whatever libev has to offer, but make sure that kqueue is
567used if available (warning, breaks stuff, best use only with your own
568private event loop and only if you know the OS supports your types of
569fds):
570
571 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
572
573=item struct ev_loop *ev_loop_new (unsigned int flags)
574
575Similar to C<ev_default_loop>, but always creates a new event loop that is
576always distinct from the default loop.
577
578Note that this function I<is> thread-safe, and one common way to use
579libev with threads is indeed to create one loop per thread, and using the
580default loop in the "main" or "initial" thread.
581
582Example: Try to create a event loop that uses epoll and nothing else. 590Example: Try to create a event loop that uses epoll and nothing else.
583 591
584 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 592 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
585 if (!epoller) 593 if (!epoller)
586 fatal ("no epoll found here, maybe it hides under your chair"); 594 fatal ("no epoll found here, maybe it hides under your chair");
587 595
596Example: Use whatever libev has to offer, but make sure that kqueue is
597used if available.
598
599 struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
600
588=item ev_default_destroy () 601=item ev_loop_destroy (loop)
589 602
590Destroys the default loop (frees all memory and kernel state etc.). None 603Destroys an event loop object (frees all memory and kernel state
591of the active event watchers will be stopped in the normal sense, so 604etc.). None of the active event watchers will be stopped in the normal
592e.g. C<ev_is_active> might still return true. It is your responsibility to 605sense, so e.g. C<ev_is_active> might still return true. It is your
593either stop all watchers cleanly yourself I<before> calling this function, 606responsibility to either stop all watchers cleanly yourself I<before>
594or cope with the fact afterwards (which is usually the easiest thing, you 607calling this function, or cope with the fact afterwards (which is usually
595can just ignore the watchers and/or C<free ()> them for example). 608the easiest thing, you can just ignore the watchers and/or C<free ()> them
609for example).
596 610
597Note that certain global state, such as signal state (and installed signal 611Note that certain global state, such as signal state (and installed signal
598handlers), will not be freed by this function, and related watchers (such 612handlers), will not be freed by this function, and related watchers (such
599as signal and child watchers) would need to be stopped manually. 613as signal and child watchers) would need to be stopped manually.
600 614
601In general it is not advisable to call this function except in the 615This function is normally used on loop objects allocated by
602rare occasion where you really need to free e.g. the signal handling 616C<ev_loop_new>, but it can also be used on the default loop returned by
617C<ev_default_loop>, in which case it is not thread-safe.
618
619Note that it is not advisable to call this function on the default loop
620except in the rare occasion where you really need to free it's resources.
603pipe fds. If you need dynamically allocated loops it is better to use 621If you need dynamically allocated loops it is better to use C<ev_loop_new>
604C<ev_loop_new> and C<ev_loop_destroy>. 622and C<ev_loop_destroy>.
605 623
606=item ev_loop_destroy (loop) 624=item ev_loop_fork (loop)
607 625
608Like C<ev_default_destroy>, but destroys an event loop created by an
609earlier call to C<ev_loop_new>.
610
611=item ev_default_fork ()
612
613This function sets a flag that causes subsequent C<ev_run> iterations 626This function sets a flag that causes subsequent C<ev_run> iterations to
614to reinitialise the kernel state for backends that have one. Despite the 627reinitialise the kernel state for backends that have one. Despite the
615name, you can call it anytime, but it makes most sense after forking, in 628name, you can call it anytime, but it makes most sense after forking, in
616the child process (or both child and parent, but that again makes little 629the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
617sense). You I<must> call it in the child before using any of the libev 630child before resuming or calling C<ev_run>.
618functions, and it will only take effect at the next C<ev_run> iteration.
619 631
620Again, you I<have> to call it on I<any> loop that you want to re-use after 632Again, you I<have> to call it on I<any> loop that you want to re-use after
621a fork, I<even if you do not plan to use the loop in the parent>. This is 633a fork, I<even if you do not plan to use the loop in the parent>. This is
622because some kernel interfaces *cough* I<kqueue> *cough* do funny things 634because some kernel interfaces *cough* I<kqueue> *cough* do funny things
623during fork. 635during fork.
628call it at all (in fact, C<epoll> is so badly broken that it makes a 640call it at all (in fact, C<epoll> is so badly broken that it makes a
629difference, but libev will usually detect this case on its own and do a 641difference, but libev will usually detect this case on its own and do a
630costly reset of the backend). 642costly reset of the backend).
631 643
632The function itself is quite fast and it's usually not a problem to call 644The function itself is quite fast and it's usually not a problem to call
633it just in case after a fork. To make this easy, the function will fit in 645it just in case after a fork.
634quite nicely into a call to C<pthread_atfork>:
635 646
647Example: Automate calling C<ev_loop_fork> on the default loop when
648using pthreads.
649
650 static void
651 post_fork_child (void)
652 {
653 ev_loop_fork (EV_DEFAULT);
654 }
655
656 ...
636 pthread_atfork (0, 0, ev_default_fork); 657 pthread_atfork (0, 0, post_fork_child);
637
638=item ev_loop_fork (loop)
639
640Like C<ev_default_fork>, but acts on an event loop created by
641C<ev_loop_new>. Yes, you have to call this on every allocated event loop
642after fork that you want to re-use in the child, and how you keep track of
643them is entirely your own problem.
644 658
645=item int ev_is_default_loop (loop) 659=item int ev_is_default_loop (loop)
646 660
647Returns true when the given loop is, in fact, the default loop, and false 661Returns true when the given loop is, in fact, the default loop, and false
648otherwise. 662otherwise.
1106=item C<EV_FORK> 1120=item C<EV_FORK>
1107 1121
1108The event loop has been resumed in the child process after fork (see 1122The event loop has been resumed in the child process after fork (see
1109C<ev_fork>). 1123C<ev_fork>).
1110 1124
1125=item C<EV_CLEANUP>
1126
1127The event loop is about to be destroyed (see C<ev_cleanup>).
1128
1111=item C<EV_ASYNC> 1129=item C<EV_ASYNC>
1112 1130
1113The given async watcher has been asynchronously notified (see C<ev_async>). 1131The given async watcher has been asynchronously notified (see C<ev_async>).
1114 1132
1115=item C<EV_CUSTOM> 1133=item C<EV_CUSTOM>
3074disadvantage of having to use multiple event loops (which do not support 3092disadvantage of having to use multiple event loops (which do not support
3075signal watchers). 3093signal watchers).
3076 3094
3077When this is not possible, or you want to use the default loop for 3095When this is not possible, or you want to use the default loop for
3078other reasons, then in the process that wants to start "fresh", call 3096other reasons, then in the process that wants to start "fresh", call
3079C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying 3097C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3080the default loop will "orphan" (not stop) all registered watchers, so you 3098Destroying the default loop will "orphan" (not stop) all registered
3081have to be careful not to execute code that modifies those watchers. Note 3099watchers, so you have to be careful not to execute code that modifies
3082also that in that case, you have to re-register any signal watchers. 3100those watchers. Note also that in that case, you have to re-register any
3101signal watchers.
3083 3102
3084=head3 Watcher-Specific Functions and Data Members 3103=head3 Watcher-Specific Functions and Data Members
3085 3104
3086=over 4 3105=over 4
3087 3106
3088=item ev_fork_init (ev_signal *, callback) 3107=item ev_fork_init (ev_fork *, callback)
3089 3108
3090Initialises and configures the fork watcher - it has no parameters of any 3109Initialises and configures the fork watcher - it has no parameters of any
3091kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, 3110kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3092believe me. 3111really.
3093 3112
3094=back 3113=back
3114
3115
3116=head2 C<ev_cleanup> - even the best things end
3117
3118Cleanup watchers are called just before the event loop is being destroyed
3119by a call to C<ev_loop_destroy>.
3120
3121While there is no guarantee that the event loop gets destroyed, cleanup
3122watchers provide a convenient method to install cleanup hooks for your
3123program, worker threads and so on - you just to make sure to destroy the
3124loop when you want them to be invoked.
3125
3126Cleanup watchers are invoked in the same way as any other watcher. Unlike
3127all other watchers, they do not keep a reference to the event loop (which
3128makes a lot of sense if you think about it). Like all other watchers, you
3129can call libev functions in the callback, except C<ev_cleanup_start>.
3130
3131=head3 Watcher-Specific Functions and Data Members
3132
3133=over 4
3134
3135=item ev_cleanup_init (ev_cleanup *, callback)
3136
3137Initialises and configures the cleanup watcher - it has no parameters of
3138any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
3139pointless, I assure you.
3140
3141=back
3142
3143Example: Register an atexit handler to destroy the default loop, so any
3144cleanup functions are called.
3145
3146 static void
3147 program_exits (void)
3148 {
3149 ev_loop_destroy (EV_DEFAULT_UC);
3150 }
3151
3152 ...
3153 atexit (program_exits);
3095 3154
3096 3155
3097=head2 C<ev_async> - how to wake up an event loop 3156=head2 C<ev_async> - how to wake up an event loop
3098 3157
3099In general, you cannot use an C<ev_run> from multiple threads or other 3158In general, you cannot use an C<ev_run> from multiple threads or other
4706structure (guaranteed by POSIX but not by ISO C for example), but it also 4765structure (guaranteed by POSIX but not by ISO C for example), but it also
4707assumes that the same (machine) code can be used to call any watcher 4766assumes that the same (machine) code can be used to call any watcher
4708callback: The watcher callbacks have different type signatures, but libev 4767callback: The watcher callbacks have different type signatures, but libev
4709calls them using an C<ev_watcher *> internally. 4768calls them using an C<ev_watcher *> internally.
4710 4769
4770=item pointer accesses must be thread-atomic
4771
4772Accessing a pointer value must be atomic, it must both be readable and
4773writable in one piece - this is the case on all current architectures.
4774
4711=item C<sig_atomic_t volatile> must be thread-atomic as well 4775=item C<sig_atomic_t volatile> must be thread-atomic as well
4712 4776
4713The type C<sig_atomic_t volatile> (or whatever is defined as 4777The type C<sig_atomic_t volatile> (or whatever is defined as
4714C<EV_ATOMIC_T>) must be atomic with respect to accesses from different 4778C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4715threads. This is not part of the specification for C<sig_atomic_t>, but is 4779threads. This is not part of the specification for C<sig_atomic_t>, but is
4821=back 4885=back
4822 4886
4823 4887
4824=head1 PORTING FROM LIBEV 3.X TO 4.X 4888=head1 PORTING FROM LIBEV 3.X TO 4.X
4825 4889
4826The major version 4 introduced some minor incompatible changes to the API. 4890The major version 4 introduced some incompatible changes to the API.
4827 4891
4828At the moment, the C<ev.h> header file tries to implement superficial 4892At the moment, the C<ev.h> header file provides compatibility definitions
4829compatibility, so most programs should still compile. Those might be 4893for all changes, so most programs should still compile. The compatibility
4830removed in later versions of libev, so better update early than late. 4894layer might be removed in later versions of libev, so better update to the
4895new API early than late.
4831 4896
4832=over 4 4897=over 4
4898
4899=item C<EV_COMPAT3> backwards compatibility mechanism
4900
4901The backward compatibility mechanism can be controlled by
4902C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4903section.
4904
4905=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4906
4907These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4908
4909 ev_loop_destroy (EV_DEFAULT_UC);
4910 ev_loop_fork (EV_DEFAULT);
4833 4911
4834=item function/symbol renames 4912=item function/symbol renames
4835 4913
4836A number of functions and symbols have been renamed: 4914A number of functions and symbols have been renamed:
4837 4915
4856ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme 4934ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4857as all other watcher types. Note that C<ev_loop_fork> is still called 4935as all other watcher types. Note that C<ev_loop_fork> is still called
4858C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> 4936C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4859typedef. 4937typedef.
4860 4938
4861=item C<EV_COMPAT3> backwards compatibility mechanism
4862
4863The backward compatibility mechanism can be controlled by
4864C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4865section.
4866
4867=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> 4939=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4868 4940
4869The preprocessor symbol C<EV_MINIMAL> has been replaced by a different 4941The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4870mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile 4942mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4871and work, but the library code will of course be larger. 4943and work, but the library code will of course be larger.
4945 5017
4946=back 5018=back
4947 5019
4948=head1 AUTHOR 5020=head1 AUTHOR
4949 5021
4950Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. 5022Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5023Magnusson and Emanuele Giaquinta.
4951 5024

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